U.S. patent application number 15/506574 was filed with the patent office on 2017-09-07 for metallic copper particles, and production method therefor.
The applicant listed for this patent is ISHIHARA SANGYO KAISHA, LTD.. Invention is credited to Kiyonobu IDA, Masanori TOMONARI, Mitsuru WATANABE.
Application Number | 20170252801 15/506574 |
Document ID | / |
Family ID | 55399746 |
Filed Date | 2017-09-07 |
United States Patent
Application |
20170252801 |
Kind Code |
A1 |
IDA; Kiyonobu ; et
al. |
September 7, 2017 |
METALLIC COPPER PARTICLES, AND PRODUCTION METHOD THEREFOR
Abstract
Provided are: metallic copper particles exhibiting excellent
low-temperature sintering properties at temperatures equal to or
lower than 300.degree. C.; and a production method therefor. In
these metallic copper particles, metallic copper fine particles are
adhered to the surfaces of large-diameter metallic copper
particles. With regard to the metallic copper particles to be
produced, copper oxide and hypophosphoric acid and/or a salt
thereof are mixed and reduced, preferably in the presence of 1-500
mass % of gelatin and/or collagen peptide. The reduction reaction
temperature is preferably in the range of 20-100.degree. C. The
produced metallic copper particles have a volume resistivity value
when heated to a temperature of 300.degree. C. under a nitrogen
atmosphere of 1.times.10-2 .OMEGA.cm or less.
Inventors: |
IDA; Kiyonobu; (Osaka,
JP) ; WATANABE; Mitsuru; (Osaka, JP) ;
TOMONARI; Masanori; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ISHIHARA SANGYO KAISHA, LTD. |
Osaka-shi, Osaka |
|
JP |
|
|
Family ID: |
55399746 |
Appl. No.: |
15/506574 |
Filed: |
August 26, 2015 |
PCT Filed: |
August 26, 2015 |
PCT NO: |
PCT/JP2015/074025 |
371 Date: |
February 24, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 1/025 20130101;
B22F 1/0007 20130101; B22F 2301/10 20130101; B22F 1/007 20130101;
B22F 1/0055 20130101; B22F 2009/245 20130101; H01B 13/00 20130101;
B22F 9/24 20130101; B22F 2998/10 20130101; H01B 5/00 20130101; B22F
1/0014 20130101; B22F 1/0062 20130101 |
International
Class: |
B22F 1/00 20060101
B22F001/00; B22F 9/24 20060101 B22F009/24 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 28, 2014 |
JP |
2014-174251 |
Apr 10, 2015 |
JP |
2015-081081 |
Claims
1. A metallic copper particle comprising a large diameter metallic
copper particle and at least one fine metallic copper particle
wherein the at least one fine metallic copper particle is adhered
on a surface of the large diameter metallic copper particle.
2. The metallic copper particle according to claim 1, wherein an
aggregate of the fine metallic copper particles is adhered on the
surface of the large diameter metallic copper particle.
3. The metallic copper particle according to claim 1, further
comprising a small metallic copper particle in a mixed state.
4. The metallic copper particle according to claim 1, wherein a
gelatin and/or a collagen peptide exist on at least one selected
from the group consisting of the metallic copper particle, the
large diameter metallic copper particle, and the at least one fine
metallic copper particle.
5. The metallic copper particle according to claim 3, wherein a
gelatin and/or a collagen peptide exist on at least one selected
from the group consisting of the metallic copper particle, the
large diameter metallic copper particle, the at least one fine
metallic copper particle e, and the small metallic copper
particle.
6. The metallic copper particle according to claim 1, wherein at
least one selected from the group consisting of the metallic copper
particle, the large diameter metallic copper particle, and the at
least one fine metallic copper particle comprises an organic acid
and/or a salt thereof.
7. The metallic copper particle according to claim 3, wherein at
least one selected from the group consisting of the metallic copper
particle, the large diameter metallic copper particle, the at least
one fine metallic copper particle, and the small metallic copper
particle comprises an organic acid and/or a salt thereof.
8. The metallic copper particle according to claim 1, having a
specific surface area of 0.1 to 10 m2/g.
9. A process for producing a metallic copper particle having a
volume resistance value of 1.times.10-2 .OMEGA.cm or less after
heating the metallic copper particle at a temperature of
300.degree. C. under a nitrogen atmosphere, the process comprising
mixing a copper oxide and a hypophosphorous acid and/or a salt
thereof in a solvent in the presence of a gelatin and/or a collagen
peptide, thereby reducing the copper oxide.
10. The process for producing a metallic copper particle according
to claim 9, wherein the gelatin and/or the collagen peptide exist
in 1 to 500 parts by mass with regard to 100 parts by mass of the
metallic copper particle.
11. The process for producing a metallic copper particle according
to claim 9, wherein the reduction reaction is performed in a
temperature range of 40 to 95.degree. C.
12. The process for producing a metallic copper particle according
to claim 9, comprising mixing the copper oxide and the
hypophosphorous acid and/or the salt thereof in the solvent in the
presence of the gelatin and/or the collagen peptide, and an amine
complexing agent, thereby reducing the copper oxide.
13. The process for producing a metallic copper particle according
to claim 9, comprising mixing the copper oxide and the
hypophosphorous acid and/or the salt thereof in the solvent in the
presence of the gelatin and/or the collagen peptide, and an organic
acid, thereby reducing the copper oxide.
14. The process for producing a metallic copper particle according
to claim 9, comprising mixing the copper oxide and hypophosphorous
acid and/or the salt thereof in the solvent in the presence of the
gelatin and/or the collagen peptide, an amine complexing agent, and
an organic acid, thereby reducing the copper oxide.
15. The process for producing a metallic copper particle according
to claim 9, wherein the reduction reaction is performed at a pH of
3 or lower.
16. A metallic copper dispersion comprising the metallic copper
particle according to claim 8.
Description
TECHNICAL FIELD
[0001] The present invention relates to a metallic copper particle
and a process for producing the metallic copper particle. The
present invention also relates to a dispersion in which the
metallic copper particle is blended and a process for producing the
dispersion. The present invention further relates to an electrode,
a wiring pattern, and a film coating formed by using the metallic
copper dispersion, and still further relates to a decorative
article with the film coating formed thereon, an antimicrobial
article with the film coating formed thereon, and a process for
producing a metallic copper-containing film for use in them.
BACKGROUND ART
[0002] Metallic copper particle is an inexpensive material having a
good electrical conductivity, and has been widely used as a
material for securing electrical conduction, such as a member for
forming a circuit of a printed wiring board, various electrical
contact members, an external electrode member for a capacitor or
the like, and the metallic copper particle has been also used in an
internal electrode for a multilayer ceramic capacitor in recent
years.
[0003] Dispersion blending metallic copper particles is a general
term that usually includes compositions, such as coating materials,
paints, pastes, and inks, which is obtained by dispersing a
metallic copper particle in a solvent, and further blending one or
more additives such as a binder, a dispersant, and a viscosity
modifier therein when necessary. Such a dispersion is used, by
taking advantage of characteristics of the metallic copper
particles, in various uses such as uses to secure electrical
conduction, antistatic uses, uses to shield electromagnetic waves,
and uses to give metallic luster or antibacterial properties.
Specifically, the metallic copper particles are used, by taking
advantage of characteristics thereof, for shielding electromagnetic
wave in transparent members of a liquid crystal display or the
like. Moreover, the technique for forming a fine electrode or a
fine circuit-wiring pattern has been proposed. This technique is as
follows: a dispersion blending metallic copper particles is applied
on a substrate to form an electrode pattern or circuit-wiring
pattern by a coating method such as screen printing or inkjet
printing, and thereafter the metallic copper particles are fused by
heating at a relatively low temperature. This has been being
applied particularly to the production of printed wiring boards.
Furthermore, the fusion between the metallic copper particles
easily progresses even under a mild heating condition to exhibit
metallic luster, and thus such a simple technique for preparing a
mirror surface has been attracting attention in design and
decoration uses. In recent years, its applications as a joining
material in a device that is used at high temperatures, such as a
power semiconductor, has been also studied.
[0004] As for metallic copper particle and dispersion dispersing
the metallic copper particles, for example, Patent Literature 1
discloses that a metallic copper particle is generated by mixing a
divalent copper oxide and a reducing agent in a solvent in the
presence of a complexing agent and protective colloid to reduce the
divalent copper oxide, and that the metallic copper particles
obtained there are dispersed in a dispersion medium to prepare a
fluid composition. Further, in Patent Literature 1, as the
protective colloid, a gelatin is illustrated, and as the reducing
agent, hydrazine reducing agents such as hydrazine and hydrazine
compounds like hydrazine hydrochloride, hydrazine sulfate, and
hydrazine hydrate; sodium borohydride, sodium sulfite, sodium
hydrogen sulfite, sodium thiosulfate, sodium nitrite, and sodium
hyponitrite; phosphorous acid and salts thereof such as sodium
phosphite; and hypophosphorous acid and salts thereof such as
sodium hypophosphite are listed.
[0005] Moreover, Patent Literature 2 discloses a dispersion
including: a metallic copper particle having a gelatin on the
surface of the particle; a polymeric dispersant; and an organic
solvent in which the gelatin has a difference between an amine
value and an acid value (amine value--acid value) of 0 or less, and
the polymeric dispersant has a difference between an amine value
and an acid value (amine value--acid value) of 0 to 50.
[0006] Furthermore, Patent Literature 3 discloses that a nano size
metallic particle is mixed with a micron size metallic particle
while performing the treatment to adsorb it on the surface of the
micron size metallic particle, thereby forming a fine particle
adsorbed mixed body in which the nano size metallic particle is
adsorbed on the surface of the micron size metallic particle.
CITATION LIST
Patent Literature
[0007] Patent Literature 1: WO 2006/019144 A1 [0008] Patent
Literature 2: WO 2010/024385 A1 [0009] Patent Literature 3: JP
4848674 B
SUMMARY OF INVENTION
Technical Problem
[0010] Patent Literatures 1 and 2 disclose the following: the
metallic copper particle is obtained by reducing copper oxide with
hydrazine in the presence of a gelatin are excellent in the
dispersion stability and are heat-meltable at a relatively low
temperature, and thus the metallic copper particles are fired under
a reducing atmosphere and are suitably used in various uses such as
uses to secure electrical conduction, antistatic uses, uses to
shield electromagnetic waves, and uses to give metallic luster or
antibacterial properties. However, in the methods disclosed in
these Patent Literatures, there is the problem that the metallic
copper particle cannot be easily produced for the reasons such as
that a closed firing facility is required to perform a firing under
a reducing atmosphere. Moreover, Patent Literature 3 discloses that
a high electrical conductivity is exhibited through the heat
treatment at a low temperature. In this case, however, it is
considered to be difficult to sufficiently reduce the resistance of
an easily oxidized metal like copper. Therefore, a metallic copper
particle which can be fired under a nonreducing atmosphere such as
nitrogen and which can provide an excellent sinterability at a
lower temperature and a sufficiently low volume resistance value
has been desired.
Solution Problem
[0011] In order to solve the above problems, the present inventors
have searched for a metallic copper particle having a volume
resistance value of 1.times.10.sup.-2 .OMEGA.cm or less after
heating the metallic copper particle at a temperature of
300.degree. C. under a nitrogen atmosphere. As a result, the
inventors have found, for example, that the above problems can be
solved by a metallic copper particle in which at least one fine
metallic copper particle is adhered on the surface of a large
diameter metallic copper particle, and that when copper oxide and
hypophosphorous acid and/or a salt thereof are mixed in a solvent
in the presence of a gelatin and/or a collagen peptide to reduce
the copper oxide, the desired metallic copper particle having a
volume resistance value of 1.times.10.sup.-2 .OMEGA.cm or less
after the metallic copper particle is heated at a temperature of
300.degree. C. under a nitrogen atmosphere can be unexpectedly
obtained, and thus have completed the present invention. In the
present invention, the "metallic copper particle" is a
superordinate concept including a large diameter metallic copper
particle; at least one fine metallic copper particle and an
aggregate thereof; and further includes the case where a small
metallic copper particle is mixed therewith.
[0012] Namely, one embodiment according to the present invention
relates to (1) a metallic copper particle including at least one
fine metallic copper particle and a large diameter metallic copper
particle wherein the at least one fine metallic copper particle are
adhered on the surface of the large diameter metallic copper
particle, and another embodiment according to the present invention
relates to (2) a process for producing a metallic copper particle
having a volume resistance value of 1.times.10.sup.-2 .OMEGA.cm or
less after heating the metallic copper particle at a temperature of
300.degree. C. under a nitrogen atmosphere, the process comprising
mixing copper oxide and hypophosphorous acid and/or a salt thereof
in a solvent in the presence of a gelatin and/or a collagen
peptide, thereby reducing the copper oxide.
[0013] Specifically, the present invention is as follows.
[0014] (1) A metallic copper particle including at least one fine
metallic copper particle and a large diameter metallic copper
particle wherein the at least one fine metallic copper particle is
adhered on a surface of the large diameter metallic copper
particle.
[0015] (2) The metallic copper particle according to (1), wherein
an aggregate of the fine metallic copper particles is adhered on
the surface of the large diameter metallic copper particle.
(Hereinafter, the metallic copper particle defined in each of (1)
and (2) is sometimes referred to as a "composite particle".)
[0016] (3) The metallic copper particle according to (1) or (2),
further including a small metallic copper particle in a mixed
state. (Hereinafter, the metallic copper particle defined in (3) is
sometimes referred to as a "mixed particle" in contrast with the
"composite particle".)
[0017] (4) The metallic copper particle according to (1) or (2),
wherein a gelatin and/or a collagen peptide exist on at least one
selected from the group consisting of the metallic copper particle,
the large diameter metallic copper particle, and the at least one
fine metallic copper particle.
[0018] (5) The metallic copper particle according to (3), wherein a
gelatin and/or a collagen peptide exist on at least one selected
from the group consisting of the metallic copper particle, the
large diameter metallic copper particle, the at least one fine
metallic copper particle, and the small metallic copper
particle.
[0019] (6) The metallic copper particle according to (1), (2), or
(4), wherein at least one selected from the group consisting of the
metallic copper particle, the large diameter metallic copper
particle, and the at least one fine metallic copper particle
includes an organic acid and/or a salt thereof.
[0020] (7) The metallic copper particle according to (3) or (5),
wherein at least one selected from the group consisting of the
metallic copper particle, the large diameter metallic copper
particle, the at least one fine metallic copper particle, and the
small metallic copper particle includes an organic acid and/or a
salt thereof.
[0021] (8) The metallic copper particle according to any one of (1)
to (7), having a specific surface area of 0.1 to 10 m.sup.2/g.
[0022] (9) A process for producing a metallic copper particle
having a volume resistance value of 1.times.10.sup.-2 .OMEGA.cm or
less after heating the metallic copper particle at a temperature of
300.degree. C. under a nitrogen atmosphere, the process comprising
mixing a copper oxide and hypophosphorous acid and/or a salt
thereof in a solvent in the presence of a gelatin and/or a collagen
peptide, thereby reducing the copper oxide.
[0023] (10) The process for producing a metallic copper particle
according to (9), wherein the gelatin and/or the collagen peptide
exist in 1 to 500 parts by mass with regard to 100 parts by mass of
the metallic copper particle.
[0024] (11) The process for producing a metallic copper particle
according to (9) or (10), wherein the reduction reaction is
performed in a temperature range of 40 to 95.degree. C.
[0025] (12) The process for producing a metallic copper particle
according to any one of (9) to (11) comprising mixing the copper
oxide and the hypophosphorous acid and/or the salt thereof in the
solvent in the presence of the gelatin and/or the collagen peptide,
and an amine complexing agent, thereby reducing the copper
oxide.
[0026] (13) The process for producing a metallic copper particle
according to any one of (9) to (12) comprising mixing the copper
oxide and the hypophosphorous acid and/or the salt thereof in the
solvent in the presence of the gelatin and/or the collagen peptide,
and an organic acid, thereby reducing the copper oxide.
[0027] (14) The process for producing a metallic copper particle
according to any one of (9) to (13) comprising mixing the copper
oxide and the hypophosphorous acid and/or the salt thereof in the
solvent in the presence of the gelatin and/or the collagen peptide,
an amine complexing agent, and an organic acid, thereby reducing
the copper oxide.
[0028] (15) The process for producing a metallic copper particle
according to any one of (9) to (14), wherein the reduction reaction
is performed at a pH of 3 or lower.
[0029] (16) A metallic copper dispersion including the metallic
copper particle according to any one of (1) to (8).
Advantageous Effects of Invention
[0030] The metallic copper particle according to the present
invention can be fired under a nonreducing atmosphere such as
nitrogen, is excellent in sinterability at lower temperatures, and
exhibits a sufficiently low volume resistance value even in the
case of a low temperature heating. Moreover, by using the process
for producing a metallic copper particle according to the present
invention, the metallic copper particle that is excellent in
sinterability at low temperatures and that exhibits a sufficiently
low volume resistance value even when heated under a nonreducing
atmosphere can simply be produced. Therefore, the metallic
copper-containing film that is excellent in electrical conductivity
and metallic color tone can be simply produced by applying a
dispersion including the metallic copper particles according to the
present invention on the surface of a base material or by heating
the dispersion under a nonreducing atmosphere after the
application. Moreover, the dispersion can be also used for joining
members. Furthermore, the metallic copper-containing film can be
also produced by performing heating, light irradiation, plasma
irradiation, or the like under a reducing atmosphere in place of or
together with heating under a nonreducing atmosphere.
[0031] For these reasons, in the present invention, metallic copper
particle(s) and the dispersion including them can be used in
materials for securing electrical conduction, materials for
antistatic, materials for shielding electromagnetic waves,
materials for giving metallic luster or antibacterial properties,
and the like, and can be used particularly in uses for forming a
fine electrode and a fine circuit-wiring pattern, such as a print
wiring board making use of the electrical conductivity of the
metallic copper-containing film, in uses for joining chips and
substrates, in design and decoration uses making use of metallic
color tone of the metallic copper-containing film, and the
like.
BRIEF DESCRIPTION OF DRAWINGS
[0032] FIG. 1 shows an X-ray diffraction chart for sample A
produced in Example 1.
[0033] FIG. 2 shows an electron micrograph for sample A produced in
Example 1.
[0034] FIG. 3 shows an electron micrograph (enlarged photograph)
for sample A produced in Example 1.
[0035] FIG. 4 shows an electron micrograph for sample B produced in
Example 2.
[0036] FIG. 5 shows an electron micrograph (enlarged photograph)
for sample B produced in Example 2.
[0037] FIG. 6 shows an electron micrograph for sample C produced in
Example 3.
[0038] FIG. 7 shows an electron micrograph (enlarged photograph)
for sample C produced in Example 3.
[0039] FIG. 8 shows an electron micrograph for sample D produced in
Example 4.
[0040] FIG. 9 shows an electron micrograph (enlarged photograph)
for sample D produced in Example 4.
[0041] FIG. 10 shows an electron micrograph for sample E produced
in Example 5.
[0042] FIG. 11 shows an electron micrograph (enlarged photograph)
for sample E produced in Example 5.
[0043] FIG. 12 shows an electron micrograph for sample F produced
in Example 6.
[0044] FIG. 13 shows an electron micrograph (enlarged photograph)
for sample F produced in Example 6.
[0045] FIG. 14 shows an electron micrograph for sample G produced
in Example 7.
[0046] FIG. 15 shows an electron micrograph (enlarged photograph)
for sample G produced in Example 7.
[0047] FIG. 16 shows an electron micrograph for sample H produced
in Example 8.
[0048] FIG. 17 shows an electron micrograph (enlarged photograph)
for sample H produced in Example 8.
[0049] FIG. 18 shows an electron micrograph for sample I produced
in Example 9.
[0050] FIG. 19 shows an electron micrograph (enlarged photograph)
for sample Iproduced in Example 9.
[0051] FIG. 20 shows an electron micrograph for sample J produced
in Example 10.
[0052] FIG. 21 shows an electron micrograph (enlarged photograph)
for sample J produced in Example 10.
[0053] FIG. 22 shows an electron micrograph for sample K produced
in Example 11.
[0054] FIG. 23 shows an electron micrograph (enlarged photograph)
for sample K produced in Example 11.
[0055] FIG. 24 shows an electron micrograph for sample L produced
in Example 12.
[0056] FIG. 25 shows an electron micrograph (enlarged photograph)
for sample L produced in Example 12.
[0057] FIG. 26 shows an electron micrograph for sample M produced
in Example 13.
[0058] FIG. 27 shows an electron micrograph (enlarged photograph)
for sample M produced in Example 13.
[0059] FIG. 28 shows an electron micrograph for sample Z produced
in Example 26.
[0060] FIG. 29 shows an electron micrograph (enlarged photograph)
for sample Z produced in Example 26.
[0061] FIG. 30 shows an electron micrograph for sample AE produced
in Comparative Example 1.
[0062] FIG. 31 shows an electron micrograph (enlarged photograph)
for sample AE produced in Comparative Example 1.
[0063] FIG. 32 shows an electron micrograph for sample AF produced
in Comparative Example 2.
[0064] FIG. 33 shows an electron micrograph (enlarged photograph)
for sample AF produced in Comparative Example 2.
[0065] FIG. 34 shows an electron micrograph for sample AG produced
in Comparative Example 3.
[0066] FIG. 35 shows an electron micrograph (enlarged photograph)
for sample AG produced in Comparative Example 3.
[0067] FIG. 36 shows an electron micrograph of a cross section of a
metallic copper-containing film produced by heating, at 120.degree.
C. in the air, sample Q produced in Example 17.
[0068] FIG. 37 shows an electron micrograph (enlarged photograph)
of a cross section of a metallic copper-containing film produced by
heating, at 120.degree. C. in the air, sample Q produced in Example
17.
DESCRIPTION OF EMBODIMENTS
[0069] In the present invention, the "metallic copper particle" is
a composite particle in which two kinds of particles each having a
relatively different particle diameter are composited. Herein, the
particle having a larger particle diameter is referred to as the
"large diameter metallic copper particle", and the particle having
a smaller particle diameter are referred to as the "fine metallic
copper particle". The "particle diameter" does not necessarily mean
the average primary particle diameter, and is appropriately defined
in consideration of the shape, distribution, and the like.
Specifically, the metallic copper particle according to the present
invention is a metallic copper particle which includes a large
diameter metallic copper particle and at least one fine metallic
copper particle adhered on the surface of the large diameter
metallic copper particle, and is a particle in which the at least
one fine metallic copper particle and the large diameter metallic
copper particle are composited and not merely mixed. It is
preferable that an aggregate of the fine metallic copper particles
is adhered on the surface of the large diameter metallic copper
particle. The metallic copper particle according to the present
invention also includes one in which a "small metallic copper
particle" of a different type from the above composite particle is
mixed in addition to the above composite particle.
[0070] The "metallic copper" in the present invention is a
substance having metallic property, the substance including at
least metal copper, metal copper alloy, or copper hydride, and the
"metallic copper" may be metal copper or an alloy including metal
copper as the main component, such as a copper-tin, copper-zinc,
copper-bismuth, copper-nickel, copper-lead, or copper-phosphorus
alloy. Copper hydride is classified as a copper compound, but is
converted to metal copper by heating, and thus is defined herein as
included in the metallic copper. Moreover, the metallic copper
particle may be a particle of which the surface is coated with a
metal such as silver or tin, a metallic copper alloy, or a metal
oxide such as silica or alumina, and may also include an impurity,
a copper compound, a copper alloy, a stabilizer against oxidation,
or the like on the surface or inside of the metallic copper
particle as long as the inclusion of them does not affect its uses.
For example, phosphorus of a component of a reducing agent is
liable to remain in the metallic copper particle. The content of
phosphorus can be adjusted by the amount of phosphorus to be used
during the reduction reaction, washing after the reduction
reaction, or the like, and is preferably about 0 to about 5 parts
by mass with regard to 100 parts by mass of the metallic copper
particle, more preferably 0 to 2 parts by mass, still more
preferably 0 to 1 part by mass. The gelatin and/or the collagen
peptide which act as a protective colloid also remain on the
surface or the like of the metallic copper particle, but the
content thereof can be adjusted by the amount of the gelatin and/or
the collagen peptide to be used or by removing the gelatin and/or
the collagen peptide after the reduction reaction. Moreover, in the
case where a complexing agent is used, the complexing agent is
included in the metallic copper particle according to the amount of
the complexing agent to be used.
[0071] In the present invention, the "large diameter metallic
copper particle" refers to a coarser particle compared with the
fine metallic copper particle described below. The shape of the
large diameter metallic copper particle is not particularly
limited, and the large diameter metallic copper particle having an
arbitrary shape can be used. For example, a particle having a shape
constituted by a curved surface such as a spherical shape or an
elliptical shape, a particle having a shape constituted by a
polyhedron such as a flat shape, a granular shape, a rectangular
parallelepiped shape, a cubic shape, a rod shape, a needle-shaped
particle, or a wire shape, a particle having such a shape as flat
plates are combined, and a particle having an irregular shape which
cannot be specified in shape can be used, and these particles may
be mixed. With respect to the particle having such a shape as flat
plates are combined, it can be confirmed that such a particle
partially exists in the electron micrographs shown in, for example,
FIGS. 2, 4, and 6. In the present invention, the shape of the
metallic copper particle, the large diameter metallic copper
particle, the fine metallic copper particles and an aggregate
thereof can be observed with a scanning electron microscope (which
is sometimes written as "SEM" hereinafter). The particle having a
flat shape refers to a particle of which the thickness is thinner
with regard to the flat surfaces of the particle. It is preferable
that in view of the volume resistivity after heating, the large
diameter metallic copper particle is a particle having such a shape
as flat plates are combined, a particle having a flat shape, or a
particle having a granular shape, or the like.
[0072] The particle diameter of the large diameter metallic copper
particle can be appropriately selected according to its uses (e.g.
film thickness, film width, and the like). In the case where the
particle diameter can be specified by the average primary particle
diameter, it is preferable that the average primary particle
diameter is generally 0.1 to 100 .mu.m, and the range of 1.0 to 30
.mu.m is more preferable. The average primary particle diameter is
preferably at least 5 times as large as that of the fine metallic
copper particles described below. The average primary particle
diameter is determined by measuring the particle diameters of 100
or more particles that are randomly selected from an SEM image and
calculating the number average of the measured particle diameters.
In the case of a highly anisotropic particle, the maximum diameter
of the particle is defined as a particle diameter of the particle.
For example, in the case of particles having a flat shape, the
average width of the flat surfaces of the particles (specifically,
average value of maximum diameters of the flat surfaces of the
particles) is defined as the average primary particle diameter, and
the average primary particle diameter thereof is preferably in a
range of 0.1 to 100 .mu.m, more preferably in a range of 0.5 to 50
.mu.m, and still more preferably in a range of 1.0 to 30 .mu.m. The
average thickness of the particles having a flat shape can be
appropriately set, and the average thickness thereof is preferably
0.005 to 10 .mu.m, more preferably 0.01 to 10 .mu.m, and still more
preferably 0.05 to 5.mu.m. In the case of particles having a
granular shape or the like, the average primary particle diameter
of the particles (specifically, average value of maximum diameters
of the particles) is preferably in a range of 0.1 to 100 .mu.m,
more preferably in a range of 0.5 to 50 .mu.m, and still more
preferably in a range of 1.0 to 30 .mu.m.
[0073] The "fine metallic copper particle" in the present invention
refer to a finer particle than the large diameter metallic copper
particle (, namely, a particle having smaller particle diameter
than the large diameter metallic copper particle), and the
component composition thereof may be the above metallic copper
having the same quality as the large diameter metallic copper
particle, or may be the above metallic copper having the different
quality from the large diameter metallic copper particle. The shape
of the fine metallic copper particle is not particularly limited,
and the fine metallic copper particle having an arbitrary shape can
be used. In the case where the particle diameter is specified by
the average primary particle diameter, the average primary particle
diameter of the fine metallic copper particles is preferably in a
range of 2 to 500 nm, more preferably 5 to 300 nm, and still more
preferably in a range of 10 to 250 nm. The average primary particle
diameter of the fine metallic copper particles is also determined
by measuring each maximum particle diameter of the 100 or more fine
metallic copper particles that are randomly selected from an SEM
image and calculating the number average of the measured maximum
particle diameters. In the case where the particle shape in the
aggregated interface between the adjacent particles may be unclear
because at least part of the fine metallic copper particles in the
present invention form an aggregate as described below. In this
case, however, the particle shape may be estimated from its
outline.
[0074] In the case where the particle diameter can be specified by
the average primary particle diameter, when the average primary
particle diameter of the fine metallic copper particles is, for
example, 400 nm within the preferable range of 2 to 500 nm
described above, the range of 0.1 to 100 .mu.m which is described
above as a generally preferable range of the average primary
particle diameter of the large diameter metallic copper particle
means a range larger than 0.4 .mu.m to 100 .mu.m or smaller (a
range of 2 .mu.m to 100 .mu.m when it is further required
considering that the average primary particle diameter of the large
diameter metallic copper particles is preferably at least 5 times
as large as that of the fine metallic copper particles) within the
range. When the average primary particle diameter of the fine
metallic copper particles is, for example, 10 nm, it is meant that
the range of 0.1 to 100 .mu.m which is described above as a
generally preferable range of the average primary particle diameter
of the large diameter metallic copper particles is preferable. The
average primary particle diameter of the fine metallic copper
particles is preferably 1/5 or smaller of the average particle
diameter of the large diameter metallic copper particles, more
preferably 1/7 or smaller, and still more preferably 1/10 or
smaller.
[0075] Regarding the fine metallic copper particle, it is
preferable that an aggregate is formed by the aggregation of a
plurality of the fine metallic copper particles. The "aggregation"
herein is distinguished from "agglomeration" referring to a state
where adjacent particles are in contact with each other at a
point(s), and refers to a state where adjacent particles are bound
each other through necking or fusion or a state where adjacent
particles share a face(s) each other. It can be confirmed through
the observation of a SEM image whether the aggregate is formed by
the aggregation of a plurality of the fine metallic copper
particles. In the case where the particles share a face(s) each
other even when an interface is observed between the particles, the
particles are considered as forming an aggregate. A plurality of
the fine metallic copper particles may aggregate to form a particle
having an irregular shape. The aggregate is formed by the
aggregation of the two or more fine metallic copper particles,
preferably the three or more fine metallic copper particles, and
more preferably the four or more fine metallic copper
particles.
[0076] The metallic copper particle of the present invention is a
composite particle in which at least one fine metallic copper
particle is adhered on the surface of the large diameter metallic
copper particle, and preferably, an aggregate formed by the
aggregation of the fine metallic copper particles are adhered on
the surface of the large diameter metallic copper particle. The
adhesion may be performed by aggregation, adsorption, or
combination thereof. It can be confirmed through the observation of
a SEM image whether at least one fine metallic copper particle
and/or the aggregate of the fine metallic copper particles is
adhered on the surface of the large diameter metallic copper
particle. When the large diameter metallic copper particle and at
least one fine metallic copper particle are merely mixed, the
adhesion state of them cannot be obtained, and the state where a
plurality of the fine metallic copper particles aggregate cannot be
also obtained. Additionally, in this case, the large diameter
metallic copper particle and the fine metallic copper particle(s)
exist individually. Thus, the large diameter metallic copper
particle and the fine metallic copper particle(s) can be clearly
distinguished from the metallic copper particle according to the
present invention. Also, all of the fine metallic copper particles
do not necessarily form the aggregate, and some of the fine
metallic copper particles may be adhered as an agglomerate or
single particle on the surface of the large diameter metallic
copper particle. It is preferable that the aggregation between the
large diameter metallic copper particles less frequently occurs. As
described below, the particle which constitutes the above metallic
copper particle, namely, the particle having a flat shape; the
particle having a granular shape or the like; the particle having
such a shape as flat plates are combined; or the particle having an
irregular shape can be produced by adjusting the amount of the
gelatin and/or the collagen peptide, or the complexing agent to be
used at the time of the reduction reaction and the condition of the
reduction reaction, and further the metallic copper particles in
the states where these particles are mixed can be also produced
thereby.
[0077] It is preferable that one embodiment of the metallic copper
particle according to the present invention is a mixed particle
including the above metallic copper particle (i.e. composite
particle) in a mixed state with a small metallic copper particle of
a different type from it. The "the small metallic copper particle"
refer to, in the state of being mixed with the above metallic
copper particle (i.e. the composite particle in which the at least
one fine metallic copper particle and/or an aggregate thereof are
adhered on the surface of the large diameter metallic copper
particle), a particle(s) other than the above composite particle.
In this case, the component composition thereof may be the above
metallic copper having the same quality as the composite particle
or may be the above metallic copper having the different quality
from it. It is preferable that the particle diameter of the small
metallic copper particle is smaller than that of the above large
diameter metallic copper particle (in other words, the particle
diameter of the above large diameter metallic copper particle is
larger than that of the small metallic copper particle). In the
case where the particle diameter can be specified by the average
primary particle diameter, the average primary particle diameter of
the small metallic copper particles is, for example, preferably in
a range of 2 to 1000 nm, more preferably in a range of 5 to 500 nm,
and still more preferably 10 to 400 nm. The average primary
particle diameter of the small metallic copper particles is also
determined by measuring the maximum particle diameter of each of
100 or more particles that are randomly selected from an SEM image
and calculating the number average of the measured maximum particle
diameters. The shape of the small metallic copper particle is not
particularly limited, and the small metallic copper particle having
an arbitrary shape can be used.
[0078] The state where the composite particle and the small
metallic copper particle are mixed is obtained by simultaneously
producing the composite particle and the small metallic copper
particle as well as by separately adding the small metallic copper
particle to the produced composite particle. By employing such a
state, sinterability thereof at a further lower temperature becomes
excellent, and a much lower volume resistance value is provided
even in the case of a low temperature heating, compared with the
case where the metallic copper particle (i.e. composite particle)
is singularly used. The reason is not necessarily clear, but it is
considered that a large number of the small metallic copper
particles exist in spaces between the metallic copper particles
(i.e. composite particles) during the film formation, thereby
enhancing the conduction among the metallic copper particles. It is
favorable that the small metallic copper particle exists
independently from the metallic copper particle, namely, a state
where the small metallic copper particle is not adhered on the
surface of the large diameter metallic copper particle but exist
individually from the metallic copper particle is preferable. The
state of the small metallic copper particle is not particularly
limited, and the small metallic copper particle may exist in the
state of a single particle, may exist in the state of an
agglomerate formed by gathering a plurality of the small metallic
copper particles, may exist in the state of an aggregate of the
small metallic copper particles as in the case of the fine metallic
copper particles, or may exist in the state of the mixture of them.
The mixing ratio of the metallic copper particle (i.e. composite
particle) and the small metallic copper particle can be
appropriately set, but the amount of the small metallic copper
particle is preferably in a range of 1 to 50% by mass with regard
to the metallic copper particle (i.e. composite particle), more
preferably in a range of 2 to 30% by mass, and still more
preferably in a range of 3 to 20% by mass.
[0079] As an index of the volume resistance value of the metallic
copper particle according to the present invention, the volume
resistance value of a metallic copper-containing film prepared by
heating and firing the metallic copper particles at a temperature
of 300.degree. C. under a nitrogen atmosphere is used.
Specifically, the volume resistance value measured according to the
"<Method 1 for Measuring Volume Resistance Value>" described
below is 1.times.10.sup.-2 .OMEGA.cm or less, preferably
1.times.10.sup.-3 .OMEGA.cm or less, and more preferably
1.times.10.sup.-4 .OMEGA.cm or less. In this way, when using the
metallic copper particle according to the present invention, its
sintering occurs even when being heated at a temperature of
300.degree. C. under a nitrogen atmosphere, and thus has a low
volume resistance value and a high electrical conductivity.
<Method 1 for Measuring Volume Resistance Value>
[0080] A copper paste is prepared by: mixing 10 g of a metallic
copper powder, 3.5 g of a vehicle (resin: 20% by mass of ethyl
cellulose N200 and solvent: terpineol), and 6.5 g of terpineol; and
then kneading the mixture with a three-roll mill The prepared
copper paste is applied to an alumina substrate and fired, using an
atmosphere tube furnace, at 300.degree. C. for one hour under a
nitrogen atmosphere to prepare a metallic copper-containing film.
The specific resistance value of the prepared metallic
copper-containing film is measured using MCP-T610 Loresta GP
manufactured by Mitsubishi Chemical Analytech Co., Ltd. by a direct
current four-terminal method. Thereafter, the cross section is
observed with a scanning electron microscope to measure the film
thickness, and the volume resistance value is calculated with
regard to the specific resistance value.
[0081] The metallic copper particle according to the present
invention has a low volume resistance value after heating it at a
temperature of 300.degree. C. under a nitrogen atmosphere.
Therefore, a copper-containing film or joined body having a low
volume resistance value can be produced even at a temperature of
300.degree. C. or lower under a nonreducing atmosphere (namely,
under an inert atmosphere) such as nitrogen or argon, and a
copper-containing film or joined body having a low volume
resistance value can be also produced even at a temperature of
300.degree. C. or lower under a reducing atmosphere such as
hydrogen. It is preferable that the heating temperature of the
metallic copper particle according to the present invention is a
lower temperature in the case where plastic is used as a base
material. For example, a temperature of 200.degree. C. or lower is
more preferable, and a temperature of 150.degree. C. or lower is
still more preferable. Furthermore, a copper-containing film having
a low volume resistance value can be also produced by performing
light irradiation, plasma irradiation, or the like in place of or
together with the heating under the above non-reducing atmosphere
(i.e. under an inert atmosphere) or under the above reducing
atmosphere.
[0082] In this way, the metallic copper particle according to the
present invention can be fired under a nonreducing atmosphere such
as nitrogen, is excellent in sinterability at a lower temperature,
and exhibits a sufficiently low volume resistance value even in the
case of a low temperature heating. The reason is not necessarily
clear, but it is considered that the sinterablity at a low
temperature and the reduction in the volume resistivity are
provided, for example, by the following: the melting point of the
fine metallic copper particle is dominantly low; the increase in
the melting point due to aggregation when the fine metallic copper
particles form an aggregate thereof is unexpectedly small; it is
presumed that the contact area with the air outside becomes small
to suppress the oxidation of the fine metallic copper particles by
forming the aggregate; and further, the gaps between the large
diameter metallic copper particles having a volume resistance value
comparable to that of the bulk are efficiently connected by the
fine metallic copper particle(s) (and/or an aggregate thereof) or
the small metallic copper particle mixed therewith during
heating.
[0083] The metallic copper particle according to the present
invention is, as described above, the following: a composite
particle in which at least one fine metallic copper particle and/or
an aggregate thereof are adhered on the surface of a large diameter
metallic copper particle; or a mixed particle including the
composite particle in which the at least one fine metallic copper
particle and/or the aggregate thereof are adhered on the surface of
the large diameter metallic copper particle, in a mixed state with
a small metallic copper particle.
[0084] In the metallic copper particle according to the present
invention, it is preferable that at least one selected from the
group consisting of the metallic copper particle, the large
diameter metallic copper particle, the at least one fine metallic
copper particle, and the small metallic copper particle has a
gelatin and/or a collagen peptide, and it is more preferable that
the surface of the metallic copper particle and/or the surface of
the at least one fine metallic copper particle have a gelatin
and/or a collagen peptide. In addition, the meaning of "the at
least one fine metallic copper particle has a gelatin and/or a
collagen peptide" is not only that non-aggregated fine metallic
copper particles have the gelatin or the like but also that at
least one fine metallic copper particle constituting an aggregate
has the gelatin or the like.
[0085] Namely, in the metallic copper particle according to the
present invention, it is preferable that the gelatin and/or the
collagen peptide exist on at least one selected from the group
consisting of the metallic copper particle (i.e. the composite
particle in which the at least one fine metallic copper particle
and/or an aggregate thereof are adhered on the surface of the large
diameter metallic copper particle), the large diameter metallic
copper particle and the at least one fine metallic copper particle
which constitute the above composite particle. In the case of the
mixed particle in which the small metallic copper particle is mixed
with the above composite particle, it is preferable that the
gelatin and/or the collagen peptide exist on at least one selected
from the group consisting of the metallic copper particle (i.e.
composite particle), the large diameter metallic copper particle,
the at least one fine metallic copper particle, and the small
metallic copper particle. Among others, it is more preferable that
the gelatin and/or the collagen peptide exist on the surface of the
composite particle and/or the surface of the at least one fine
metallic copper particle constituting the composite particle. As a
result, the oxidation of the metallic copper particle in the
presence of oxygen can be suppressed, and thus the volume
resistivity after heating can be further reduced. Moreover, the
gelatin and the collagen peptide serve as protective colloid, and
can suppress the agglomeration of the metallic copper particles in
an aqueous solvent. It is preferable that the gelatin and/or the
collagen peptide exist in a range of about 0.1 to about 15 parts by
mass with regard to 100 parts by mass of the metallic copper
particle and the like (namely, at least one particle selected from
the above group wherein the at least one particle has the gelatin
and/or the collagen peptide) because desired effects are obtained,
and the more preferable range is about 0.1 to about 10 parts by
mass. The details about the gelatin and/or the collagen peptide
that can be used will be described in the paragraphs related to the
production process. The content of the gelatin is determined by
performing CHN analysis of the metallic copper particle based on
the assumption that the total amounts of C, H, and N in % by mass
satisfying the ratio of C, H, and N in the used gelatin originates
in the gelatin.
[0086] In the metallic copper particle according to the present
invention, it is preferable that at least one selected from the
group consisting of the metallic copper particle, the large
diameter metallic copper particle, the at least one fine metallic
copper particle, and the small metallic copper particle includes an
organic acid and/or a salt thereof. In addition, the meaning of
"the at least one fine metallic copper particle includes an organic
acid and/or a salt thereof" is not only that non-aggregated fine
metallic copper particles include an organic acid or the like but
also that the at least one fine metallic copper particle
constituting an aggregate includes an organic acid or the like.
[0087] Namely, in the metallic copper particle according to the
present invention, it is preferable that the organic acid and/or a
salt thereof exist on at least one selected from the group
consisting of the metallic copper particle (i.e. the composite
particle in which the at least one fine metallic copper particle
and/or an aggregate thereof are adhered on the surface of the large
diameter metallic copper particle), the large diameter metallic
copper particle and the at least one fine metallic copper particle
which constitute the above composite particle. In the case of the
mixed particle in which the small metallic copper particle is mixed
with the above composite particle, it is preferable that the
organic acid and/or a salt thereof exist on at least one selected
from the group consisting of the metallic copper particle (i.e.
composite particle), the large diameter metallic copper particle,
the at least one fine metallic copper particle, and the small
metallic copper particle. The organic acid and/or a salt thereof
may exist in a mixed state with the metallic copper particle, or
may be adsorbed on the surface of the metallic copper particle. In
particular, it is preferable that the organic acid and/or a salt
thereof are adsorbed on the surface of the metallic copper
particle. It is considered that the organic acid and/or a salt
thereof facilitate the sintering between the metallic copper
particles at a low temperature during heating, and the volume
resistivity after heating the metallic copper particle at a low
temperature can be much more reduced. Specifically, the volume
resistance value of a metallic copper-containing film prepared by
heating and firing the metallic copper particles at a temperature
of 120.degree. C. under an air atmosphere is used as an index, and
a volume resistance value of 1.times.10.sup.-1 .OMEGA.cm or less
can be achieved in terms of the volume resistance value measured
according to the "<Method 2 for Measuring Volume Resistance
Value>" described below, and further a metallic
copper-containing film having a volume resistance value in the
order of 1.times.10.sup.-3.OMEGA.cm can be also obtained. Examples
of the organic acid and/or a salt thereof include carboxylic acids,
amino acids, aminocarboxylic acids and salts thereof. Among them,
carboxylic acids are preferable, and formic acid is more
preferable. In the case where the metallic copper particle and the
like include the organic acid and/or a salt thereof, the content
thereof can be appropriately set, but is preferably set to 0.01 to
1% by mass in the metallic copper particle and the like.
[0088] The specific surface area of the metallic copper particle
according to the present invention, which is measured by a nitrogen
adsorption BET method is preferably about 0.1 to about 10
m.sup.2/g, more preferably about 0.2 to about 8 m.sup.2/g, still
more preferably about 0.3 to about 7 m.sup.2/g, and much more
preferably about 1 to about 6 m.sup.2/g. It is considered that the
specific surface area of the metallic copper particle reflects an
abundance ratio of the large diameter metallic copper particle and
the at least one fine metallic copper particle (In this regard, in
the case where the small metallic copper particle is mixed
therewith, the above abundance ratio further includes them.). In
the case where the BET specific surface area is within the above
range, the metallic copper particle is excellent in sinterability
at a further lower temperature and exhibits a much lower volume
resistance value even in the case of a low temperature heating.
[0089] Among others, the metallic copper particle having a specific
surface area in a range of 1 to 5 m.sup.2/g provides a metallic
copper-containing film exhibiting electrical conductivity when
being heated at a temperature of 120.degree. C. under an air
atmosphere. Specifically, the volume resistance value is used as an
index, and a volume resistance value in the order of
1.times.10.sup.+1 .OMEGA.cm can be achieved in terms of the volume
resistance value measured according to the "<Method 2 for
Measuring Volume Resistance Value>" described below, and further
a metallic copper-containing film that exhibits a volume resistance
value of 1.times.10.sup.-1 .OMEGA.cm or less is obtained. In this
way, the metallic copper particle according to the present
invention has a low volume resistance value and a high electrical
conductivity because the sinterability or the contact property
between the particles are improved even when heating the metallic
copper particle at a temperature of 120.degree. C. under an air
atmosphere. Therefore, the metallic copper particle according to
the present invention can be used with a base material having a low
heat resistance temperature, and can be employed in a wide range of
uses. Moreover, the firing in the air can be performed, and thus
constraints on facilities such as control of an atmosphere can be
avoided.
<Method 2 for Measuring Volume Resistance Value>
[0090] A copper paste is prepared by: mixing 5 g of a metallic
copper powder, a phenol resin (0.62 g of Resitop: PL-5208
(containing 59% by weight of phenol resin as active ingredient)),
and 0.26 g of ethylene glycol monobutyl ether acetate using a
deaerating stirrer; and then kneading the mixture with a three-roll
mill. The prepared copper paste is applied to an alumina substrate
and fired at 120.degree. C. for 10 minutes in a natural convection
type drier to prepare a metallic copper-containing film. The
specific resistance value of the obtained metallic
copper-containing film is measured using MCP-T610 Loresta GP
manufactured by Mitsubishi Chemical Analytech Co., Ltd. by a direct
current four-terminal method. Thereafter, the cross section is
observed with a scanning electron microscope to measure the film
thickness, and the volume resistance value is calculated based on
the above specific resistance value.
[0091] The metallic copper particle according to the present
invention, when being blended with a solvent, a resin, and the like
to prepare a dispersion, exhibits a high fluidity even in the case
where the concentration is high. Dispersion including metallic
particles in a nano order is generally liable to lose fluidity when
the concentration thereof becomes high. Micronization of a metallic
copper particle, which is a general method for improving the
sinterability at a low temperature, is in a trade-off relation with
fluidity of the dispersion, and thus it is difficult to make the
concentration of the dispersion high. To the contrary, when using
the metallic copper particle according to the present invention,
the dispersion which has such an excellent sinterability at a low
temperature that the sintering can be performed even by heating at
120.degree. C. in the air and which maintains a sufficient fluidity
even when the concentration of the metallic copper particle is made
to be 50% by mass or more can be prepared. The reason is not clear,
but it is considered that the capture of a solvent and the like can
be reduced because the at least one fine metallic copper particle
is adhered on the large diameter metallic copper particle or
because the fine metallic copper particles in a state of
aggregation thereof are adhered on the large diameter metallic
copper particle. Due to this characteristic, the metallic copper
dispersion according to the present invention can be suitably used
in joining materials and the like for which a high concentration
dispersion is required.
[0092] The metallic copper particle according to the present
invention can be applied to various kinds of dispersions (coating
materials, paints, metallic pastes, inks, and the like), and is
suitable for the application in metallic pastes among others. The
metallic paste herein is a paste including a metallic copper
particle, a binder resin, a solvent, and the like as main
components, in which a surfactant, a crosslinking agent, a
polymeric dispersant, or the like are appropriately blended,
thereby providing suitable fluidity and viscosity. The metallic
paste can be used for various kinds of printing, and can be
suitably used for printing by a platemaking, particularly. Examples
of the printing by a platemaking include screen printing, offset
printing, and gravure printing, and the screen printing is
preferable in view of thick-film formation. The screen printing is
a method of placing a paste on a screen in which holes
corresponding to a wiring or electrode pattern are formed, followed
by rubbing off the paste with a squeegee to print the wiring or
electrode pattern on a substrate. By the screen printing, printing
to form a thick film having a thickness of several .mu.m to several
tens .mu.m can be easily performed, and thus the screen printing is
often utilized in a production process of printed wiring boards,
electronic parts, or flat panel displays. It is desirable that the
metallic paste has a certain degree of viscosity in view of
thick-film formation, and a metallic paste having a viscosity of
2000 mPas or higher is generally used.
[0093] The metallic copper particle according to the present
invention has a characteristic that the thixotropy index value is
relatively high when a metallic paste is prepared by blending the
metallic copper particle with a solvent, a resin, and the like. The
thixotropy index (which is referred to as TI value, hereinafter)
herein is a value calculated from a viscosity ratio of the
viscosity (.eta.a) of the metallic paste when the metallic paste is
stirred at a predetermined low shear rate to the viscosity (.eta.b)
of the metallic paste when the metallic paste is stirred at a
predetermined high shear rate, and is specifically calculated from
the following expression.
TI=.eta.a/.eta.b
[0094] The measurement of the viscosity .eta.a and the viscosity
.eta.b that are needed for calculation of the TI value is performed
under the following condition.
<Method for Preparing Metallic Paste>
[0095] A metallic paste (Cu solid content of 75% by mass) is
prepared by: mixing 9 g of a metallic copper powder, 1 g of a
vehicle (resin: 20% by mass of ethyl cellulose N200, and solvent:
terpineol), and 2 g of terpineol; and kneading the mixture with a
three-roll mill
<Method for Measuring Viscosity of Metallic Paste>
[0096] The viscosity of the metallic paste is measured using a B
type viscometer (model HB DV-I+) manufactured by Brookfield AMETEK.
The measurement temperature is set at 20.degree. C., and CPE-52 is
used as a corn spindle. The viscosity (.eta.a) at a shear rate of
10 [1/sec] and the viscosity (.eta.b) at a shear rate of 100
[1/sec] are measured, and the TI value is calculated by applying
the measured .eta.a and .eta.b to the above expression.
[0097] The fact that the TI value is high means that although the
viscosity of a paste is suitably maintained in a normal state, when
a high shear force is applied to the paste, the viscosity thereof
is easily lowered. In a metallic paste using the metallic copper
particle according to the present invention, the TI value can be
set to be dominantly high value, and specifically, the TI value can
be set to be 3.0 or more, preferably 3.5 or more, and more
preferably 4.0 or more. Therefore, for example, in the screen
printing, the fluidity of the metallic paste during continuous
printing becomes favorable, and a thick film can be obtained after
completion of patterning on a substrate. Moreover, cracks,
disconnection, short-circuits, bleeding, and the like are
suppressed, and thus the thick film can be reproducibly obtained
during continuous printing. Furthermore, in printing such as inkjet
printing in which a high shear force is applied to the metallic
paste, ejection of the metallic paste from holes can be made
smooth, and fixing of the metallic paste to a printing medium can
be made favorable.
[0098] The reason that the TI value of the metallic copper
dispersion (i.e. metallic paste) as an embodiment according to the
present invention is high is not necessarily clear, but it is
considered that the at least one fine metallic copper particle
(and/or an aggregate of the fine metallic copper particles) adhered
on the large diameter metallic copper particle or (in the case
where the small metallic copper particle is mixed therewith,) the
small metallic copper particle serves such a function as a
lubricant so as to contribute to the improvement of the TI
value.
[0099] Next, the present invention relates to a method for
producing the metallic copper particle, and in the method, a copper
compound and hypophosphorous acid and/or a salt thereof are mixed
in a solvent in the presence of a gelatin and/or a collagen peptide
to reduce the copper compound, thereby producing the metallic
copper particle. In the present invention, it is preferable to use
a gelatin and/or a collagen peptide, copper oxide, and
hypophosphorous acid and/or a salt thereof. By using these three
compounds, the metallic copper particle having a volume resistance
value of 1.times.10.sup.-2 .OMEGA.cm or less after the metallic
copper particle is heated at a temperature of 300.degree. C. under
a nitrogen atmosphere can be easily produced. Particularly,
according to this method, the large diameter metallic copper
particle and the at least one fine metallic copper particle each of
which has a different average particle diameter can be produced by
a single reduction operation, and thus there is no need to perform
a complicated treatment that powders each of which has a different
average particle diameter are mixed. Moreover, a metallic copper
particle including a large diameter metallic copper particle and at
least one fine metallic copper particle wherein the at least one
fine metallic copper particle is adhered on the surface of the
large diameter metallic copper particle can be also prepared.
Further, the metallic copper particle in which an aggregate of a
plurality of the fine metallic copper particles is adhered on the
surface of the large diameter metallic copper particle can be also
prepared. Furthermore, when a mixed particle in which the small
metallic copper particle is mixed with the composite particle
adhering the at least one fine metallic copper particle and/or an
aggregate thereof on the surface of the large diameter metallic
copper particle, the metallic copper particle (i.e. composite
particle) and the small metallic copper particle each of which has
a different shape and particle diameter can be easily produced by a
single reduction operation.
[0100] The gelatin includes the following: a gelatin in a state as
extracted; a gelatin obtained by hydrolyzing the above gelatin in a
state as extracted so as to become lower the molecular weight (,
which is sometimes referred to as a "collagen peptide",
hereinafter); and a gelatin obtained by chemically modifying these
gelatins (, which is sometimes referred to as a "modified gelatin",
hereinafter). In general, a gelatin is an animal protein obtained
from a collagen as a parental material. In the production process
of a gelatin, a pretreatment of raw materials is performed with an
inorganic acid such as hydrochloric acid or sulfuric acid, or lime
in order to efficiently extract a high-quality gelatin from raw
materials such as cattle bones, cattle hides, and pig hides. The
gelatin obtained through the pretreatment with the inorganic acid
is called an "acid-treated gelatin" and the gelatin obtained from
the pretreatment with the lime is called an "alkali-treated
gelatin" (or "lime-treated gelatin"). During the process of
extracting a gelatin, an acid amide in a collagen is hydrolyzed,
and releases ammonia to change into a carboxyl group, and thus the
isoionic point of the gelatin is lowered. Because particularly the
alkali-treated gelatin is deamidized to nearly 100% in a liming
process, the isoionic point is in an acidic region, and the pH
thereof is nearly 5. On the other hand, the acid-treated gelatin
has a low deamidization ratio because of a short raw material
treatment period, and thus has an isoionic point in an alkaline
region, and the pH thereof is about 8 to about 9 near the isoionic
point of a collagen. For these reasons, a gelatin has an amine
value because of having a basic group and a hydroxy group, and
further has an acid value because of having an acidic group. In the
present invention, it is preferable that the gelatin exists on the
surface of the metallic copper. More preferably, the gelatin is the
alkali-treated gelatin. Also, the gelatin having a difference
between the amine value and the acid value measured according to
the method described below, namely "(amine value--acid value)", of
0 or less is preferable. More preferably, the difference between
the amine value and the acid value is in a range of -50 to 0.
Compared with the acid-treated gelatin, the alkali-treated gelatin
exhibits excellent effects as a protective colloid of the metallic
copper particle, and thus is preferable.
[0101] Moreover, the collagen peptide (i.e. hydrolyzed gelatin) is,
directly or through a gelatin, obtained by hydrolyzing a collagen
(specifically, collagen protein) included in animal bones and hides
by means of an enzyme, acid, alkali, or the like. As a hydrolysis
method for obtaining the collagen peptide (i.e. hydrolyzed
gelatin), conventionally known methods can be used. For example,
the hydrolysis can be performed according to a method of using an
enzyme, a method of using chemical treatment with an acid or
alkali, or the like. As the enzyme, any enzyme may be used as long
as the enzyme has a function of cleaving a peptide bond of a
gelatin. The enzyme is usually called a proteolytic enzyme or
protease. Specific examples of the enzyme include a collagenase, a
thiol protease, a serine protease, an acidic protease, an alkaline
protease, a metal protease, or the like, and one of them may be
singularly used, or two or more thereof may be used in combination.
Examples of the thiol protease include plant-derived thiol
proteases such as a chymopapain, papain, a promelain, and a ficin
and animal-derived thiol proteases such as a cathepsin, and
calcium-dependent proteases. Examples of the serine proteases
include trypsin, cathepsin D, or the like. Examples of the acid
protease include hepsin, chymosin, or the like. When the enzyme is
used, it is preferable to use 0.01 to 5 parts by mass of the enzyme
with regard to 100 parts by mass of the gelatin before the
hydrolysis treatment, and it is preferable that the temperature
condition of the hydrolysis is 30 to 70.degree. C. and the
treatment time is 0.5 to 24 hours. When the hydrolysis is performed
using the enzyme, deactivation of the enzyme is performed after the
treatment. The deactivation of enzyme is performed by heating, and
the heating temperature is, for example, 70 to 100.degree. C.
[0102] When the acid or alkali is used, it is preferable to set the
pH of the gelatin solution to be 3 or less, or 10 or more, and it
is preferable that the temperature condition of the hydrolysis is
50 to 90.degree. C. and the treatment time is 1 to 8 hours.
Examples of the acid include hydrochloric acid, sulfuric acid, and
nitric acid. Examples of the alkali include sodium hydroxide and
calcium hydroxide. When the hydrolysis is performed with the acid
or alkali, desalting is performed by neutralization with a
neutralizing agent or by an ion exchange resin. At the time when
the hydrolysis treatment is completed, the hydrolyzed gelatin is
dissolved or dispersed in the hydrolysis treatment liquid. Various
purification treatments which are usually used can be applied to
this solution. The purification treatment is not particularly
limited. For example, activated carbon can be added to improve tone
of color or textures, or remove impurities, or conventionally known
solid-liquid separation treatment such as filtration or centrifugal
separation can be applied to remove impurities.
[0103] The modified gelatin may be obtained by chemically modifying
gelatin, namely, by chemically modifying a side chain of each amino
acid residue, a terminal amino group, a terminal carboxyl group, or
the like, included in a gelatin. For example, by chemically
modifying the side chain of amino acid residues included in the
gelatin to introduce the following: a functional group including a
nitrogen element, such as an amino group, an imino group, a cyano
group, an azo group, an azi group, a nitrile group an isonitrile
group, a diimide group, a cyano group, an isocyanate group, and a
nitro group; a functional group including a sulfur element, such as
a thiol group, sulfone group, a sulfide group, and a disulfide
group; and a functional group including both the nitrogen element
and the sulfur element, such as a thioisocyanate group and a
thioamide group, the average particle diameter of the metallic
copper particle to be obtained can be controlled to various levels
according to the kind and amount of the above functional
groups.
[0104] As a general chemical modification method, for example, the
method having the steps of: adding a water-soluble carbodiimide to
a gelatin solution so as to activate a carboxyl group included in a
gelatin; and then reacting an arbitrary amino compound with the
activated carboxyl group to amidate the gelatin can be used.
According to this method, for example, an amino acid such as
methionine, which includes a sulfur element or an amino acid such
as lysine, which includes a nitrogen element can be simply
introduced. Examples of the water-soluble carbodiimide include
1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC),
1-cyclohexyl-3-(2-morpholinyl-4-ethyl)carbodiimide.cndot.p-toluenesulfoni-
c acid salt (CMC), N,N'-dicyclohexylcarbodiimide (DCC), and the
like. The gelatin that is applicable to the present invention may
be gelatin obtained by performing the hydrolysis treatment and the
chemical modification. In this case, the chemical modification may
be performed after the hydrolysis treatment, or the hydrolysis
treatment may be performed after the chemical modification.
[0105] In the present invention, the average particle diameter of
the metallic copper particle can be controlled by selecting whether
the size of the average molecular weight of the gelatin is large or
small In this case, regardless of the measurement methods of the
average molecular weight such as the mass average molecular weight
and the number average molecular weight, any measurement methods
can be used as the judgment standard on whether the size of the
average molecular weight of the gelatin is large or small
Specifically, taking the mass average molecular weight as an
example, the mass average molecular weight of the gelatin to be
used is preferably 2000 to 300000. Moreover, it is preferable that
the number average molecular weight of the gelatin is 200 to 60000.
When the average molecular weight is too small, there is a risk
that the gelatin does not sufficiently function as protective
colloid. Also, when the average molecular weight is too large,
there is a risk that it becomes difficult to control the average
particle diameter, and there is also a risk that the content of
organic components in the protective colloid becomes too large. The
mass average molecular weight of the gelatin is more preferably
250000 or less, still more preferably 200000 or less, and
particularly preferably 2000 to 200000. Moreover, the number
average molecular weight of the gelatin is more preferably 50000 or
less, still more preferably 30000 or less, and particularly
preferably 500 to 20000. In this way, the reason why the hydrolyzed
gelatin of which the molecular weight is lowered by the hydrolysis
is preferable is because by using such a gelatin, the variation of
the particle diameter distribution of the metallic copper particles
to be obtained becomes small, and is also because the sintering at
a lower temperature in preparing a metallic copper-containing film
becomes possible.
(Measurement of Molecular Weight of Gelatin)
[0106] The "average molecular weight" in the present invention is a
value measured by a "PAGI method". The "PAGI method" herein is a
method for estimating the molecular weight distribution by
determining a chromatogram of a sample solution by a gel filtration
technique using a high-performance liquid chromatography.
Specifically, the average molecular weight was measured according
to the following method. In a 100 mL measuring flask, 2.0 g of a
sample was placed, an eluent consisting of an equal amount mixed
solution of 0.1 mol/L potassium dihydrogen phosphate, and 0.1 mol/L
disodium hydrogen phosphate was added thereto, and then the sample
was expanded for 1 hour, the resultant was heated at 40.degree. C.
for 60 minutes to dissolve the sample, then the resulting eluent
was diluted accurately 10 times after cooling to room temperature,
and the resultant solution was used as a test liquid. The
chromatogram of the test liquid was determined by the following gel
filtration method. Columns: Shodex Asahipak GS 620 7G installed in
tandem with another one was used. By using flow rate: 1.0 mL/min,
column temperature: 50.degree. C., measurement wavelength: 230 nm,
and pullulan (P-82, manufactured by SHOWA DENKO K.K.) of which the
molecular weight is known, the elution time was determined, and
thereby a calibration curve was made. Thereafter, the gelatin was
analyzed, and the mass average molecular weight and number average
molecular weight of this specimen were determined using the
following equation. In the following equation, Si represents
absorbance at each point, and Mi represents a molecular weight at
elution time Ti.
Mass average molecular weight=(.SIGMA..times.Mi)/.SIGMA.Si
Number average molecular weight=.SIGMA.Si/(.SIGMA.Si/Mi)
[0107] It is preferable that the amount of the gelatin and/or the
collagen peptide to be used is 1 to 500 parts by mass with regard
to 100 parts by mass of the metallic copper particle to be
produced, more preferably 5 to 500 parts by mass, still more
preferably 5 to 300 parts by mass, most preferably 5 to 200 parts
by mass. The reason why the above range is preferable is because in
the case where the amount of the gelatin and/or the collagen
peptide to be used is in the above range, a metallic copper
particle having a desired volume resistance value after the
metallic copper particle is heated at a temperature of 300.degree.
C. under a nitrogen atmosphere can be produced. The other
protective colloids may be used in addition to the gelatin and/or
the collagen peptide as long as the volume resistance value of the
metallic copper particle is not impaired. The degree of aggregation
of the fine metallic copper particles can be controlled according
to the amount of the gelatin and/or the collagen peptide to be
used, and the fine metallic copper particles more easily aggregate
when the amount of the gelatin and/or the collagen peptide to be
used is smaller.
[0108] Next, a copper compound is used as a raw material for a
metallic copper particle. As the copper compound, the following:
hardly soluble (or insoluble) copper compounds such as copper
oxides; water soluble copper compounds such as copper sulfate,
copper nitrate, copper formate, copper acetate, copper chloride,
copper bromide, and copper iodide; and one or more copper compounds
selected from these compounds can be used. Particularly, copper
oxides, copper sulfate, copper nitrate, and copper formate are
preferable, and copper oxides are more preferable among them. With
respect to copper oxides, when a divalent copper oxide such as
copper oxide (copper (II) oxide) or copper hydroxide (copper (II)
hydroxide) or a monovalent copper oxide such as cuprous oxide
(copper (I) oxide) or copper hydroxide (copper (I) hydroxide) is
used, a metallic copper particle having a desired volume resistance
value can be produced. Among them, the "divalent copper oxides" are
more preferable than the "monovalent copper oxides". In the
"divalent copper oxide", the atomic valence of the copper oxide is
divalent (Cu.sup.2+), and includes copper (II) oxide, copper (II)
hydroxide, and a mixture thereof. The divalent copper oxide may
appropriately include an impurity such as another metal, a metal
compound, or a nonmetallic compound, but it is preferable that the
monovalent copper oxide is substantially free of impurities except
for those in an inevitable amount. Moreover, a divalent copper
oxide having X-ray diffraction peaks assigned to copper (II) oxide
is preferably used. It is preferable to use the copper (II) oxide
having an average crystallite diameter in a range of 20 to 500 nm,
the average crystallite diameter calculated from the following
expression 1 based on an X-ray diffraction peak of (110) plane of
the copper (II) oxide, and a range of 50 to 200 nm is still more
preferable. When the average crystallite diameter of the divalent
copper oxide is at least in the range, a desired metallic copper
particle can be produced. When the average crystallite diameter is
smaller than the above range, the copper (II) oxide has a small
particle diameter and low crystallinity. As a result, a dissolution
rate of the copper (II) oxide accelerates, and thus the reduction
reaction rate is difficult to be controlled unless a large amount
of a complexing agent is used. On the other hand, when the average
crystallite diameter is larger than the above range, the particle
diameter is large and its crystallinity is favorable. As a result,
a dissolution rate decelerates, and thus unreacted copper (II)
oxide is liable to remain in the metallic copper particle unless
the reduction reaction time is long. Therefore, the above range is
preferable. The process for producing the copper oxide is not
limited, and a copper oxide industrially produced, for example,
through an electrolytic process, a chemical conversion process, an
oxidation-by-heating process, a thermal decomposition process, an
indirect wet process, or the like can be used. Another copper
compound may be used in addition to the copper oxide as long as the
volume resistance value of the metallic copper particle is not
impaired.
DHKL=K*.lamda..beta.cos0 Expression 1
[0109] DHKL: average crystallite diameter (.ANG.)
[0110] .lamda.: wavelength of X-ray
[0111] .beta.: half-width value of diffraction peak
[0112] .theta.: Bragg's angle
[0113] K: constant (=0.9)
[0114] Next, when hypophosphorous acid (i.e. phosphinic acid)
and/or a salt thereof are used as a reducing agent, a metallic
copper particle having a desired volume resistance value after the
metallic copper particle is heated at a temperature of 300.degree.
C. under a nitrogen atmosphere can be produced compared with the
case where a reducing agent such as hydrazine is used. Examples of
the hypophosphite include salts such as a sodium salt and a
potassium salt, and when the hypophosphite is used, the reaction
easily progresses by adjusting on an acidic side the pH in the
reduction reaction. The amount of the reducing agent to be used can
be appropriately set as long as it is an amount capable of reducing
a copper compound to a metallic copper particle, and the range of
0.33 to 5 mol with regard to 1 mol of copper included in the copper
compound is preferable. When the amount of the reducing agent is
smaller than the above range, the reaction is hard to progress, so
that the metallic copper particle is not sufficiently produced.
Also, when the amount of the reducing agent is larger than the
above range, the reaction excessively progresses, so that the
desired metallic copper particle is hard to obtain. Therefore, the
above range is preferable. The amount of the reducing agent to be
used is more preferably in a range of 0.4 to 4 mol, and still more
preferably 0.5 to 4 mol. Also, another reducing agent may be used
in addition hypophosphorous acid and/or a salt thereof in a range
where there is no problem in terms of the volume resistance value
of the metallic copper particle.
[0115] It is preferable that the reduction reaction is performed at
a pH of 3 or lower. The above reduction reaction performed at a pH
of 3 or lower does not mean that the reaction is constantly
performed at a pH of 3 or lower but that the reduction reaction has
only to pass through a state where the pH is 3 or lower. In
particular, it is preferable that aging at the time of and after
the completion of the reduction reaction is performed at a pH of 3
or lower. It is considered that a balance among the elution of a
copper ion, the nuclear generation rate of copper, and the nuclear
growth rate of copper can be kept by using, as a raw material, a
copper compound including at least copper oxide which is hardly
soluble and reducing it in a liquid medium having a pH of 3 or
lower by using hypophosphorous acid and/or a salt thereof as a
reducing agent in the presence of gelatin and/or a collagen
peptide. Therefore, a metallic copper particle including a large
diameter metallic copper particle and at least one fine metallic
copper particle wherein the at least one fine metallic copper
particle is adhered on the large diameter metallic copper particle
can be produced, and further the metallic copper particle
specifically characterized as one embodiment of the present
invention, in which an aggregate of a plurality of the fine
metallic copper particles are adhered on the surface of the large
diameter metallic copper particle can be also produced. Moreover, a
mixed particle in which the metallic copper particle (i.e.
composite particle) and a small metallic copper particle are mixed
can be also produced by selecting a reduction condition.
[0116] Next, in the present invention, a complexing agent may be
added at the time of the reduction reaction when necessary, and it
is preferable to use the amine complexing agent such as the amines
or the alkanol amines, described below. It is considered that the
"complexing agent" in the present invention acts in a process
eluting copper ions from the copper compound or in a process
reducing the copper compound to produce metallic copper. The
"complexing agent" in the present invention means a compound
capable of forming a copper complex compound by binding of donor
atoms in a ligand included in the complexing agent with copper ions
or metallic copper, and examples of the donor atom include
nitrogen, oxygen, and sulfur. Specifically, as examples thereof,
the complexing agents described in the following (1) to (5) are
included.
[0117] (1) The complexing agents having nitrogen as the donor atom
include, for example, (a) amines (for example, primary amines such
as butylamine, ethylamine, propylamine, and ethylenediamine;
secondary amines such as dibutylamine, diethylamine, dipropylamine
and imines such as piperidine and pyrrolidine; tertiary amines such
as tributylamine, triethylamine, and tripropylamine; and those
having two or more kinds of the primary to tertiary amines in one
molecule of diethylenetriamine or triethylenetetramine), (b)
nitrogen-containing heterocyclic compounds (for example, imidazole,
pyridine, and bipyridine), (c) nitriles (for example, acetonitrile,
and benzonitrile) and cyanides, (d) ammonia and ammonium compounds
(for example, ammonium chloride, and ammonium sulfate), and (e)
oximes.
[0118] (2) The complexing agents having oxygen as the donor atom
include, for example, (a) carboxylic acids (for example,
oxycarboxylic acids such as citric acid, malic acid, tartaric acid,
and lactic acid; monocarboxylic acids such as acetic acid and
formic acid; dicarboxylic acids such as oxalic acid and malonic
acid; aromatic carboxylic acids such as benzoic acid), (b) ketones
(for example, monoketones such as acetone, and diketones such as
acetylacetone and benzoylacetone), (c) aldehydes, (d) alcohols (for
example, monohydric alcohols, glycols, and glycerols), (e)
quinones, (f) ethers, (g) phosphoric acid (for example,
orthophosphoric acid) and phosphoric acid compounds (for example,
hexametaphosphoric acid, pyrophosphoric acid, and phosphorous
acid), and (h) sulfonic acid or sulfonic acid compounds.
[0119] (3) The complexing agents having sulfur as the donor atom
include, for example, (a) aliphatic thiols (for example, methyl
mercaptan, ethyl mercaptan, propyl mercaptan, isopropyl mercaptan,
n-butyl mercaptan, allyl mercaptan, and dimethyl mercaptan), (b)
alicyclic thiols (such as cyclohexyl thiol), (c) aromatic thiols
(for example, thiophenol), (d) thioketones, (e) thioethers, (f)
polythiols, (g) thiocarbonic acids (for example, trithiocarbonic
acids), (h) sulfur-containing heterocyclic compounds (for example,
dithiol, thiophene, and thiopyran), (i) thiocyanates and
isothiocyanates, and (j) inorganic sulfur compounds (for example,
sodium sulfide, potassium sulfide, and hydrogen sulfide).
[0120] (4) The complexing agents having two or more kinds of donor
atoms include, for example, (a) amino acids (where the donor atoms
are nitrogen and oxygen: for example, neutral amino acids such as
glycine and alanine; basic amino acids such as histidine and
arginine; and acidic amino acids such as aspartic acid and glutamic
acid), (b) amino polycarboxylic acids (where the donor atoms are
nitrogen and oxygen: for example, ethylenediaminetetraacetate
(EDTA), nitrilotriacetate (NTA), iminodiacetate (IDA),
ethylenediaminediacetate (EDDA),
ethyleneglycoldiethyletherdiaminetetraacetate (GEDA)), (c)
alkanolamines (where the donor atoms are nitrogen and oxygen: for
example, ethanolamine, diethanolamine, and triethanolamine), (d)
nitroso compounds and nitrosyl compounds (where donor atoms are
nitrogen and oxygen), (e) mercaptocarboxylic acids (where donors
are sulfur and oxygen: for example, mercaptopropionic acid,
mercaptoacetic acid, thiodipropionic acid, mercaptosuccinic acid,
dimercaptosuccinic acid, thioacetic acid, and thiodiglycolic acid),
(f) thioglycols (donors are sulfur and oxygen: for example,
mercaptoethanol, and thiodiethylene glycol), (g) thionic acids
(where the donors are sulfur and oxygen), (h) thiocarbonic acids
(where the donor atoms are sulfur and oxygen: for example,
monothiocarbonic acid, dithiocarbonic acid, and thione carbonic
acid), (i) aminothiols (where the donors are sulfur and nitrogen:
for example, aminoethylmercaptan and thiodiethylamine), (j)
thioamides (where the donor atoms are sulfur and nitrogen: for
example, thioformamide), (k) thioureas (where the donor atoms are
sulfur and nitrogen), (1) thiazoles (where the donor atoms are
sulfur and nitrogen: for example, thiazole, and benzothiazole), (m)
sulfur-containing amino acids (where the donors are sulfur,
nitrogen and oxygen: for example, cysteine, methionine).
[0121] (5) Examples of salts of the above compounds and derivatives
thereof include alkali metal salts such as trisodium citrate,
potassium sodium tartrate, sodium hypophosphite, and disodium
ethylenediaminetetraacetate; and esters of carboxylic acid,
phosphoric acid, and sulfonic acid.
[0122] Among these complexing agents, at least one thereof can be
used. The amount of the complexing agent to be used can be
appropriately set, but it is preferable to set the amount of the
complexing agent to be used in a range of 0.01 to 500 parts by mass
with regard to 1000 parts by mass of the copper compound because
the effects of the present invention are easily obtained. By
reducing the amount of the complexing agent to be used within the
above range, primary particles of the metallic copper particle can
be made smaller, and by increasing the amount of the complexing
agent to be used, primary particles thereof can be made larger. The
amount of the complexing agent to be used is preferably in a range
of 0.1 to 500 parts by mass, still more preferably in a range of
0.5 to 250 parts by mass.
[0123] In the present invention, the complexing agent including at
least one selected from nitrogen and oxygen as the donor atom is
preferable because the effects of the present invention are easily
obtained. Specifically, at least one complexing agent selected from
amines, nitrogen-containing heterocyclic compounds, nitriles,
cyanides, carboxylic acids, ketones, phosphoric acid and phosphoric
acid compounds, amino acids, aminopolycarboxylic acids,
alkanolamines, salts thereof, or derivatives thereof is more
preferable. Among the carboxylic acids, oxycarboxylic acids are
preferable; among the ketones, diketones are preferable; and among
the amino acids, basic or acidic amino acids are preferable.
Further, it is preferable that the complexing agent is at least one
complexing agent selected from butylamine, ethylamine, propylamine,
dibutylamine, diethylamine, dipropylamine, tributylamine,
triethylamine, tripropylamine, imidazole, citric acid or alkali
metal salts thereof, acetylacetone, hypophosphorous acid or alkali
metal salts thereof, histidine, arginine,
ethylenediaminetetraacetate or alkali metal salts thereof,
ethanolamine, and acetonitrile. As described above, the amount of
the oxygen or nitrogen complexing agent to be used is preferably in
a range of 0.01 to 500 parts by mass with regard to 1000 parts by
mass of the copper compound, more preferably in a range of 0.1 to
500 parts by mass, and still more preferably in a range of 0.5 to
250 parts by mass.
[0124] In the present invention, it is preferable to use the
complexing agent including oxygen as the donor atom, and among
others, it is more preferable to use the complexing agent
corresponding to an organic acid. As described above, it is
preferable to perform the reduction reaction in a region of a pH of
3 or lower. In this regard, it is considered that the use of the
organic acid as the complexing agent can be lower the initial pH of
the reaction liquid and have, in the reduction reaction, some
effect on the elution of copper ions and the nuclear generation and
nuclear growth rate of copper. Therefore, the metallic copper
particle including a large diameter metallic copper particle and at
least one fine metallic copper particle wherein the at least one
fine metallic copper particle is adhered on the large diameter
metallic copper particle can be produced more effectively, and the
metallic copper particle specifically characterized as one
embodiment of the present invention, in which an aggregate of a
plurality of the fine metallic copper particles is adhered on the
surface of the large diameter metallic copper particle can be also
produced more effectively. Moreover, by selecting a reduction
condition, the mixed particle in which the composite particle and
the small metallic copper particle are mixed can be also produced,
and thus a mixture (i.e. mixed particle) of the large diameter
metallic copper particle on which the partially aggregated fine
metallic copper particles are adhered and the small metallic copper
particle is easily obtained. Further, in the state where the
metallic copper particle (i.e. composite particle) and the small
metallic copper particle are mixed, the specific surface area
easily falls within the range of 1 to 6 m.sup.2/g, and in this
case, the ratio of both particles (the metallic copper particle
(i.e. composite particle) and the small metallic copper particle)
is a ratio in the case of exhibiting particularly excellent
sinterability at low temperature. Furthermore, it is presumed that
an organic acid remains adsorbed on the surface of the produced
metallic copper particle, and the organic acid disappears even at a
relatively low temperature during heating to make it easy to sinter
the metallic copper particles, so that the volume resistance value
at the time of a low temperature heating can remarkably be reduced.
Examples of the organic acid include carboxylic acids, amino acids,
and aminocarboxylic acids. Among these organic acids, carboxylic
acids are more preferable, and formic acid is most preferable
therein.
[0125] In the production methods according to the present
invention, in the case of using the complexing agent corresponding
to the organic acid, the volume resistance value of a metallic
copper-containing film prepared by performing heating and firing at
a temperature of 120.degree. C. under an air atmosphere is used as
an index, and a volume resistance value of 1.times.10.sup.-1
.OMEGA.cm or less can be achieved in terms of the volume resistance
value measured according to the <Method 2 for Measuring Volume
Resistance Value> described above, and further a metallic
copper-containing film that exhibits a volume resistance value of
1.times.10.sup.-1 .OMEGA.cm or less can be obtained. In this way,
the metallic copper particle according to the present invention has
a low volume resistance value and a high electrical conductivity
because the sinterability or the contact property between the
particles are improved even when heating the metallic copper
particle at a temperature of 120.degree. C. under an air
atmosphere. Therefore, the metallic copper particle according to
the present invention can be used with a base material having a low
heat resistance temperature, and can be employed in a wide range of
uses. Moreover, the firing in the air can be performed, and thus
constraints on facilities such as control of an atmosphere can be
avoided.
[0126] In the present invention, in the case where the gelatin
and/or the collagen peptide and, when necessary, the complexing
agent exist at the time of mixing the copper oxide and the reducing
agent, the order to add each raw material is not limited. Examples
of adding each raw material include (1) a method for performing the
concurrent addition of the copper oxide and the reducing agent to a
solvent including the gelatin and/or the collagen peptide, and,
when necessary, the complexing agent, (2) a method for adding the
reducing agent to a solvent including the gelatin and/or the
collagen peptide, the copper compound, and, when necessary, the
complexing agent, (3) a method for performing the concurrent
addition of the reducing agent and the complexing agent to a
solvent including the gelatin and/or the collagen peptide, and the
copper compound, and (4) a method for adding a mixed solution of
the reducing agent and the complexing agent to a solvent including
the gelatin and/or the collagen peptide, and the copper compound.
Among these, methods (3) and (4) are preferable because the
reaction is easily controlled, and method (4) is particularly
preferable. The copper compound, the reducing agent, the complexing
agent, and the gelatin and/or the collagen peptide may be suspended
or dissolved in a solvent in advance before these are used in the
reduction reaction. In addition, the "concurrent addition" means a
method for separately adding the copper compound and the reducing
agent, or the complexing agent and the reducing agent at the same
time during the reaction or at the same time period during the
reaction, and includes not only continuous addition of both
materials during the reaction but also intermittent addition of one
or both materials.
[0127] As a solvent, for example, an aqueous solvent or an organic
solvent such as an alcohol is used, and the aqueous solvent is
preferably used. It is preferable that the reaction temperature is
in a range of 10.degree. C. to a boiling point of the used solvent
because the reaction easily progresses, more preferably in a range
of 20 to 100.degree. C. because a fine metallic copper particle is
obtained, still more preferably in a range of 30 to 95.degree. C.,
particularly preferably 40 to 95.degree. C. As described above, the
pH of the reaction liquid may be 3 or less during the reduction
reaction. In the case where hypophosphorous acid is used as a
reducing agent, the initial pH of the reaction liquid is not
particularly limited and may be appropriately set because the pH
can be lowered by the addition of hypophosphorous acid. In the case
where the hypophosphite is used as a reducing agent, it is
preferable to adjust the initial pH of the reaction liquid to 3 or
lower by adding an arbitrary acid in advance. It is preferable to
add an organic acid to the reaction liquid in advance as described
above irrespective of whichever reducing agent is used. In
addition, the pH may be lowered with only an organic acid, and the
pH may be also set at 3 or lower using an organic acid in
combination with hypophosphorous acid as a reducing agent. An
inorganic acid other than hypophosphorous acid, such as phosphoric
acid, a phosphate, pyrophosphoric acid, or pyrophosphate, may be
used for the pH adjustment. In particular, by the use of
pyrophosphoric acid for the pH adjustment, the reduction reaction
of copper oxide using hypophosphorous acid (i.e. phosphinic acid)
and/or a salt thereof can be softly progressed, and thus the heat
generation at the time of the reaction can be suppressed.
Furthermore, by making it easy to control the reaction rate, the
adjustment of the particle size becomes easy. Moreover, a defoaming
agent may be used in order to suppress foaming during reaction. The
reaction time can be controlled and set by the time for adding raw
materials such as a reducing agent, and about 10 minutes to six
hours is appropriate, for example. After the completion of adding
raw materials such as a reducing agent, the reaction liquid may be
subjected to aging as it is. The aging temperature or time can be
appropriately set. The aging temperature at the same level as the
above reaction temperature is appropriate, and the aging time of
about 10 minutes to about six hours is appropriate.
[0128] The production of a particle having a flat shape becomes
easy by adding 10% by mass or more of polymer gelatin with regard
to the produced metallic copper particle. Also, the above
production becomes easy when the temperature of the reduction
reaction is 50.degree. C. or higher. The production of a particle
having a granular shape or the like becomes easy by adding 10% by
mass or more of the collagen peptide with regard to the produced
metallic copper particle. Moreover, the production of a particle
having a granular shape or the like becomes easy when the
temperature of the reduction reaction is set at 20 to 90.degree. C.
in the presence of the gelatin and/or the collagen peptide. The
production of the particle having an irregular shape becomes easy
when the temperature of the reduction reaction is set at 90.degree.
C. or higher. The average particle diameter of the large diameter
metallic copper particle and the abundance ratio of the large
diameter metallic copper particle and the at least one fine
metallic copper particle can be adjusted according to the reaction
temperature or aging temperature, and the average particle diameter
and the abundance ratio of the large diameter metallic copper
particle become larger as the temperature becomes higher. The
average particle diameter and shape of the large diameter metallic
copper particle and the abundance ratio of the large diameter
metallic copper particle and the at least one fine metallic copper
particle can be also adjusted according to the reaction time or
aging time. Moreover, the average particle diameter and shape of
the small metallic copper particle, and the abundance ratio of the
metallic copper particle (i.e. composite particle) and the small
metallic copper particle can be also adjusted according to the
reaction time or aging time.
[0129] In the present invention, the mixed particle including the
metallic copper particle (specifically, the composite particle in
which the at least one fine metallic copper particle and/or an
aggregate thereof are adhered on the surface of the large diameter
metallic copper particle) in a mixed state with the small metallic
copper particle can be produced at once without undergoing a mixing
process of particles, according to the above production methods.
According to the above production methods, the metallic copper
particle in which the size or particle shape of the large diameter
metallic copper particle, the size or particle shape of the at
least one fine metallic copper particle, or the size or particle
shape of the small metallic copper particle is different, and the
metallic copper particle in which the abundance ratio of them is
different can be produced. Moreover, the above mixed particle
including the small metallic copper particle in the mixed state can
be also obtained by mixing the above metallic copper particle
(specifically, the composite particle in which the at least one
fine metallic copper particle and/or an aggregate thereof are
adhered on the surface of the large diameter metallic copper
particle) and the small metallic copper particle separately
prepared.
[0130] According to the above methods, the metallic copper
particles, in the presence of the gelatin and/or the collagen
peptide and the complexing agent when necessary, are produced, and
then fractionation and washing are performed when necessary.
Moreover, the gelatin and/or the collagen peptide, adhered on the
surface of the metallic copper particles are decomposed by adding a
protective colloid remover to the solvent after the reaction,
thereby agglomerating the metallic copper particles, and
subsequently, the resultant can be fractionated. The "protective
colloid remover" is a compound that decomposes or dissolves
protective colloid to suppress the action of the protective
colloid, and when part, if not all, of the protective colloid can
be removed from the solvent, the effects according to the present
invention are obtained. The kind of protective colloid remover is
appropriately selected according to the protective colloid to be
used. Specifically, for removing the protein protective colloid,
proteases such as serine proteases (for example, trypsin and
chymotrypsin), thiol proteases (for example, papain), acid
proteases (for example, pepsin), and metalloproteases can be used.
The additive amount of the protective colloid remover may be an
amount which protective colloid can be removed to such an extent
that the metallic copper particles can be agglomerated and
fractionated. Although the additive amount of the protective
colloid remover is different depending on the kind thereof, in the
case of a protease, with regard to 1000 parts by mass of protein
protective colloid, a range of 0.001 to 1000 parts by mass is
preferable, 0.01 to 200 parts by mass is more preferable, and 0.01
to 100 parts by mass is still more preferable. The temperature of
the solvent at the time of adding the protective colloid remover
can be appropriately set, and may be in the state where the
temperature of the reduction reaction is retained, or a range of
10.degree. C. to the boiling point of the used solvent is
preferable because the removal of the protective colloid easily
progresses, and a range of 40 to 95.degree. C. is more preferable.
When the protective colloid remover is added and then the resultant
state is appropriately retained, the protective colloid can be
decomposed, and for example, about 10 minutes to about 10 hours of
the retention time is appropriate. After removing the protective
colloid to agglomerate the metallic copper particles, fractionation
is performed by an ordinary method. The method for performing the
fractionation is not particularly limited, and methods such as
gravity filtration, pressure filtration, vacuum filtration, suction
filtration, centrifugal filtration, and natural sedimentation can
be used. However, from the industrial viewpoint, the pressure
filtration, the vacuum filtration, and the suction filtration are
preferable, and it is preferable to use a filter machine such as a
filter press and a roll press because the dehydration ability is
high and the treatment of a large amount is possible.
[0131] As an embodiment of the above method, it is preferable to
further add a flocculant agent after adding the protective colloid
remover because the yield is much more improved. The publicly known
flocculants can be used, and specific examples thereof include
anionic flocculants (for example, partially hydrolyzed products of
polyacrylamide, acrylamide-sodium acrylate copolymers, and sodium
alginate), cationic flocculants (for example, polyacrylamide,
dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate,
polyamidine, and chitosan), and amphoteric flocculants (for
example, acrylamide-dimethylaminoethyl acrylate-acrylic acid
copolymers). The additive amount of the flocculants can be
appropriately set according to a required amount, and is preferably
in a range of 0.5 to 100 parts by mass with regard to 1000 parts by
mass of the metallic copper particle, and more preferably in a
range of 1 to 50 parts by mass.
[0132] Alternatively, a similar effect of improving the yield is
also obtained by adding a protective colloid remover after
adjusting the pH of the solvent in a range of 1 to 8 using an
alkali in place of the use of the flocculant. When the pH is lower
than 1, the metallic copper particle corrodes or dissolves, and
thus a range of 1 to 7 is a preferable pH region. It is more
preferable that the pH be in a range of 1 to 6 because the amount
of the alkali to be used is reduced.
[0133] After the metallic copper particles are subjected to a
solid-liquid separation and washed when necessary, the solid of the
metallic copper particles obtained thereby can be used by
dispersing it in an aqueous solvent or an organic solvent such as
an alcohol, preferably in the aqueous solvent. Alternatively, the
solid of the metallic copper particles may be dried by an ordinary
method, and further the solid can be used by dispersing it in an
aqueous solvent or an organic solvent such as an alcohol,
preferably in the aqueous solvent after drying. The metallic copper
particle is easily oxidized, and thus it is preferable that drying
is performed under an atmosphere of an inert gas such as nitrogen
or argon in order to suppress oxidization. After drying, grinding
may be performed when necessary.
[0134] Next, the present invention relates to a metallic copper
dispersion including the above metallic copper particle. Any
aqueous solvent and/or any organic solvent can be used as a
dispersion medium, and a polymeric dispersant may be used when
necessary. Moreover, another metallic particle such as a silver,
nickel, copper, or tin particle or an alloy particle such as a
copper-tin alloy particle may be mixed with the metallic copper
particle when necessary. The mixing ratio of the metallic particle
or the alloy particle can be appropriately set.
[0135] In the present invention, the gelatin and/or the collagen
peptide suitably exist on the surface of the metallic copper
particle. However, the gelatin and/or the collagen peptide have a
high acid value, and thus the metallic copper particle having the
gelatin and/or the collagen peptide on the surface thereof
dissociates in a solvent to be electrically negative and is easy to
agglomerate in an organic solvent. Thus, it is preferable to mix a
polymeric dispersant in order to neutralize acid sites which are
the cause of an acid value of the gelatin and/or the collagen
peptide. The polymeric dispersant as well as the gelatin and/or the
collagen peptide includes a hydroxyl group, an acidic group, a
basic group, and the like, and thus has an amine value and an acid
value, and the polymeric dispersant having an amine value of 10 to
150 mgKOH/g is preferable, more preferably 10 to 130 mgKOH/g, still
more preferably 10 to 90 mgKOH/g, particularly preferably 15 to 80
mgKOH/g, and most preferably 15 to 50 mgKOH/g. The amine value in
the above range can contribute to the dispersion stability of the
metallic copper particle in an organic solvent, and thus is
preferable. Moreover, with respect to the amine value and acid
value of the polymeric compound, it is preferable that the
polymeric compound has an amine value (i.e. base site) and an acid
value (i.e. acid site) in an amount which is almost equal to or
more than the amount to compensate (i.e. neutralize) the amine
value and acid value of the gelatin and/or the collagen peptide
that exist on the surface of the metallic copper particle, and it
is preferable that the difference between the amine value and the
acid value, namely (i.e. "(amine value--acid value)") is in a range
of 0 to 50, and more preferably in a range of 1 to 30. The
polymeric dispersant may be electrostatically bound to the acid
sites or base sites of the gelatin and/or the collagen peptide
through the base sites or acid sites thereof. For these reasons, it
is considered that (amine value of polymeric dispersant.times.mass
of polymeric dispersant)-(acid value of gelatin.times.mass of
gelatin) is preferably 0 or more.
[0136] It is preferable that the polymeric dispersant has a
specific heat capacity of 1.0 to 2.0 J/(gK) at the glass transition
point. This is because the heat accumulation amount of the
polymeric dispersant is so small that the heat amount necessary for
raising a temperature by 1 K can be small and the heat amount added
for the purpose of decomposition can be small. The specific heat
capacity is more preferably in a range of 1.2 to 1.9 J/(gK), and
still more preferably in a range of 1.3 to 1.8 J/(gK). Moreover, it
is preferable that the polymeric dispersant has a glass transition
point in a range of -70 to 10 .degree. C. because the glass
transition occurs at a low temperature to make the heat amount
added for the purpose of decomposition small. The glass transition
point is preferably in a range of -70 to 7.degree. C., still more
preferably in a range of -70 to 5.degree. C., and still more
preferably in a range of -70 to 0.degree. C. For these reasons, in
the present invention, a more preferable polymeric dispersant has
an amine value of 10 to 90 mgKOH/g and a glass transition point in
a range of -70 to 10.degree. C., and a still more preferable
polymeric dispersant has an amine value of 10 to 90 mgKOH/g, a
glass transition point in a range of -70 to 10.degree. C., and a
specific heat capacity of 1.0 to 2.0 J/(gK) at the glass transition
point.
(Measurement of Specific Heat Capacity at Glass Transition
Point)
[0137] According to JIS K 7123-1987 "Testing Methods for Specific
Heat Capacity of Plastics", the specific heat capacity was measured
with DSC Q 100 Type manufactured by TA Instruments. With respect to
a temperature-raising pattern, the temperature was held at
-90.degree. C. for 5 minutes, then raised to 40.degree. C. at
5.degree. C./min, and held at 40.degree. C. for 5 minutes. As
analytical software, option software "Thermal Specialty Library"
manufactured by TA Instruments was used.
(Measurement of Glass Transition Point)
[0138] According to JIS K 7121-1987 "Testing Methods for Transition
Temperatures of Plastics", the glass transition point was measured
with DSC Q 100 Type manufactured by TA
[0139] Instruments. With respect to a temperature-raising pattern,
the temperature was held at -90.degree. C. for 5 minutes, then
raised to 40.degree. C. at 5.degree. C./min, and held at 40.degree.
C. for 5 minutes.
[0140] The polymeric dispersant is, for example, a polymer or
copolymer having a tertiary amino group, quaternary ammonium group,
heterocyclic group having a basic nitrogen atom, or a basic group
such as a hydroxyl group, and may have an acidic group such as a
carboxyl group, and thus the amine value and acid value of the
polymeric dispersant are compensated, so that (amine value--acid
value) may be 0. The polymeric dispersant having an amine value
higher than the acid value is preferable, and (amine value--acid
value) is in a range of 0 to 50, and more preferably in a range of
1 to 30. Because the basic group or acidic group of the polymeric
dispersant is a functional group affinitive to the metallic copper
particle covered with the gelatin, the polymeric dispersant having
one or more basic or acidic groups in the main chain and/or the
side chain is preferable, and the polymeric dispersant having
several basic or acidic groups in the main chain and/or the side
chain is more preferable. The basic or acidic groups may be
included at one terminal of the main chain of the polymer and/or
one terminal of the side chain of the polymer. The straight-chain
polymers such as A-B block type polymers; polymers having a
comb-shaped structure with a plurality of side chains; and the like
can be used as the polymeric dispersant. The mass average molecular
weight of the polymeric dispersant is not limited, but it is
preferable that the mass average molecular weight measured by a gel
permeation chromatography method is in a range of 2000 to 1000000
g/mol. When the mass average molecular weight is less than 2000
g/mol, the dispersion stability is not sufficient, and when the
mass average molecular weight exceeds 1000000 g/mol, the viscosity
is too high and the handling is likely to be difficult. Thus, the
mass average molecular weight is more preferably in a range of 4000
to 1000000 g/mol, still more preferably in a range of 10000 to
1000000 g/mol, and further more preferably in a range of 1000 to
100000 g/mol. Moreover, the polymeric dispersant including a small
amount of elements of phosphorus, sodium, and potassium is
preferable, and the polymeric dispersant not including these
elements is more preferable. When the elements of phosphorus,
sodium, and potassium are included in the polymeric dispersant, the
elements remain as ash in producing an electrode, a wiring pattern,
or the like by heating and firing, and thus the polymeric
dispersant not including these elements is preferable. One or more
of such polymeric dispersants can be appropriately selected and
used.
[0141] Specifically, the polymeric dispersant includes polymers
having a basic group such as salts of long-chain polyaminoamides
and polar acid esters, unsaturated polycarboxylic acid
polyaminoamides, polycarboxylic acid salts of polyaminoamides, and
salts of long-chain polyaminoamides and acid polymers. Moreover,
the polymeric dispersant includes alkylammonium salts, amine salts,
and amide amine salts of polymers such as acrylic polymers, acrylic
copolymers, modified polyester acids, polyether ester acids,
polyether carboxylic acids, and polycarboxylic acids, and
straight-chain type acrylic polymers or straight-chain type acrylic
copolymers are preferable. Commercially available polymeric
dispersants can be also used as such a polymeric dispersant.
Examples of the commercially available polymeric dispersant include
DISPERBYK (which is a registered trade-mark)-106, DISPERBYK-109,
DISPERBYK-110, DISPERBYK-111, DISPERBYK-130, DISPERBYK-161,
DISPERBYK-162, DISPERBYK-163, DISPERBYK-167, DISPERBYK-168,
DISPERBYK-180, DISPERBYK-182, DISPERBYK-183, DISPERBYK-184,
DISPERBYK-185, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2013,
DISPERBYK-2163, DISPERBYK-2164, BYK-4512, BYK-P105, LPN-21854, and
LPC-22124 (, all of which are manufactured by BYK-Chemie GmbH),
FLOWLEN DOPA-15B, FLOWLEN DOPA-15BHFS, FLOWLEN 17HF, FLOWLEN
DOPA-22, FLOWLEN DOPA-33, and FLOWLEN DOPA-44 (, all of which are
manufactured by Kyoeisha Chemical Co., Ltd.), and ED-212 and ED-213
(, all of which are manufactured by Kusumoto Chemicals, Ltd.).
[0142] The amine values of the gelatin and/or the collagen peptide,
and the polymeric dispersant denote the total amount of free bases
and bases, and expressed by an equivalent amount of potassium
hydroxide in mg to the amount of hydrochloric acid needed to
neutralize 1 g of a sample. Moreover, the acid value denotes the
total amount of free fatty acids and fatty acids, and expressed by
an amount of potassium hydroxide in mg needed to neutralize 1 g of
a sample. Specifically, the amine value and the acid value are
measured by the following method according to JIS K7700 or ASTM
D2074 below.
(Method for Measuring Amine Value)
[0143] In 300 mL of a mixed solvent of ethanol and pure water, 5 g
of the gelatin and/or the collagen peptide, or the polymeric
dispersant, and several drops of a bromocresol green ethanol
solution are dissolved. Then, to the resultant mixed solution a 0.1
M HCl ethanol solution whose factor (correction coefficient) has
been calculated is added, and the amine value is calculated from
the titer of the 0.1M HCl ethanol solution when yellow of a
bromocresol green indicator continues for 30 seconds.
(Method for Measuring Acid Value)
[0144] In 300 mL of pure water, 5 g of the gelatin and/or the
collagen peptide, or the polymeric dispersant, and several drops of
a phenolphthalein solution are dissolved. Then, to the resultant
mixed solution a 0.1M KOH ethanol solution whose factor (correction
coefficient) has been calculated is added. The acid value is
calculated from the titer of the 0.1M KOH ethanol solution when
light red of a phenolphthalein indicator continues for 30
seconds.
[0145] The organic solvent can appropriately be selected, and
specifically, at least one selected from hydrocarbon solvents such
as toluene, xylene, solvent naphtha, normal hexane, isohexane,
cyclohexane, methylcyclohexane, normal heptane, tridecane,
tetradecane, and pentadecane; alcoholic solvents such as methanol,
ethanol, butanol, IPA (isopropyl alcohol), normal propyl alcohol,
2-butanol, TBA (tertiary butanol), butanediol, ethylhexanol, benzyl
alcohol, and terpineol; ketone solvents such as acetone, methyl
ethyl ketone, methyl isobutyl ketone, DIBK (diisobutyl ketone),
cyclohexanone, and DAA (diacetone alcohol); ester solvents such as
ethyl acetate, butyl acetate, methoxybutyl acetate, cellosolve
acetate, amyl acetate, normal propyl acetate, isopropyl acetate,
methyl lactate, ethyl lactate, and butyl lactate; ether solvents
such as methyl cellosolve, cellosolve, butyl cellosolve, dioxane,
MTBE (methyl tertiary butyl ether), and butyl carbitol; glycol
solvents such as ethylene glycol, diethylene glycol, triethylene
glycol, and propylene glycol; glycol ether solvents such as
diethylene glycol monomethyl ether, triethylene glycol monomethyl
ether, propylene glycol monomethyl ether, and
3-methoxy-3-methyl-1-butanol; and glycol ester solvents such as
ethylene glycol monomethyl ether acetate, PMA (propylene glycol
monomethyl ether acetate), diethylene glycol monobutyl ether
acetate, and diethylene glycol monoethyl ether acetate can be used
for the organic solvent. The organic solvent having a low viscosity
is preferable for adaptation reduction in viscosity of the metallic
copper dispersion, and the organic solvent having a viscosity in a
range of 1 to 20 mPas is preferable. As such an organic solvent,
toluene, butyl carbitol, butanol, propylene glycol-l-monomethyl
ether-2-acetate, butyl cellosolve, tetradecane, and the like are
suitably used. Also, the aqueous solvent can be appropriately
selected, and specifically, water, and water and water-soluble
solvents can be used.
[0146] It is preferable that the gelatin and/or the collagen
peptide exist in an amount within a range of about 0.1 to about 15
parts by mass with regard to 100 parts by mass of the metallic
copper particle because a desired effect is obtained. The more
preferable range is about 0.1 to about 10 parts by mass. It is
preferable that the polymeric dispersant be in a range of 0.1 to 20
parts by mass with regard to 100 parts by mass of the metallic
copper particle because a desired effect is obtained. The above
range is preferable because when the amount of the polymeric
dispersant is too much smaller than the above range, it is
difficult to obtain the effects of the present invention, and when
the amount of the polymeric dispersant is too much larger than the
above range, the electrical conductivity may be obstructed in
electrode material uses and cloudiness or the like may occur to
deteriorate an appearance in decorative article uses. The more
preferable range is 0.1 to 10 parts by mass. The concentration of
the metallic copper particle in the dispersion can be appropriately
adjusted, and specifically, the concentration of the metallic
copper particle can be adjusted to 10% by mass or more, preferably
10 to 99% by mass, and more preferably about 20 to about 95% by
mass.
[0147] The metallic copper dispersion according to the present
invention can maintain a sufficient fluidity even when the
concentration of the metallic copper particle is made 50% by mass
or more. Therefore, the metallic copper dispersion according to the
present invention can be suitably used for joining materials and
the like for which a high-concentration paste is required.
Moreover, in the metallic copper dispersion according to the
present invention, the metallic copper particle is sufficiently
dispersed, and thus even if the metallic copper particle is in a
high concentration, viscosity of the dispersion can be adjusted to
be relatively low. For example, the viscosity of the dispersion can
be set to preferably 100 mPas or less, more preferably 1 to 30
mPas, and still more preferably 1 to 20 mPas. Furthermore, the
dispersion according to the present invention can be suitably used
for ink jet printing, spray coating, and the like by setting the
concentration of the metallic copper particle to an appropriate
concentration of 15% by mass or more.
[0148] In the metallic copper dispersion according to the present
invention, in addition to the above metallic copper particle, the
above aqueous solvent and/or the above organic solvent, and the
above polymeric dispersant when necessary, a curable resin, a
thickener, a plasticizer, an antifungal agent, a surfactant, a
non-surfactant type dispersant, a surface control agent (leveling
agent), and the like can be appropriately blended when necessary.
The curable resin can further improve adhesion of a coating product
to a base material. As the curable resin, resins of a dissolved
type in a low-polar and non-aqueous solvent, an emulsion type, a
colloidal dispersion type, and the like can be used without
limitation. Moreover, as for the kind of the curable resin, known
resins such as protein polymers, acrylic resins, polyester resins,
urethane resins, phenol resins, epoxy resins, and cellulose can be
used without limitation. It is preferable that the blending amount
of the curable resin component is 10 parts by mass or less with
regard to 100 parts by mass of the metallic copper particle, the
more preferable range is 8 parts by mass or less, and a range of 5
parts by mass or less is still more preferable. As the surfactant,
a cationic surfactant is preferable, and is a compound having
surface activity in a portion showing positive electric charge by
the dissociation in an aqueous solvent. Examples thereof include
(1) quaternary ammonium salts ((a) aliphatic quaternary ammonium
salts (such as [RN(CH.sub.3).sub.3].sup.+X.sup.-,
[RR'N(CH.sub.3).sub.2].sup.+X.sup.-,
[RR'R''N(CH.sub.3)].sup.+X.sup.-, and [RR'R''R'''N].sup.30 X.sup.-
wherein R, R', R'', and R''' represent a same or different alkyl
group and X represents a halogen atom such as Cl, Br, and I, and
the same shall apply hereinafter), and (b) aromatic quaternary
ammonium salts (such as [R.sub.3N(CH.sub.2Ar)].sup.+X.sup.- and
[RR'N(CH.sub.2Ar).sub.2].sup.+X.sup.- wherein Ar represents an aryl
group), and (c) heterocyclic quaternary ammonium salts (such as
pyridinium salts ([C.sub.6H.sub.5N--R].sup.+X.sup.-) and
imidazolinium salts ([R--CN(CNR'R'')C.sub.2H.sub.4].sup.+X.sup.-)),
and (2) alkylamine salts (such as RH.sub.2NY, RR'HNY, and RR'R''NY
wherein Y represents an organic acid, an inorganic acid, or the
like), and one of these may be used, or two or more thereof may be
used. Specifically, the aliphatic quaternary ammonium salts include
octyltrimethylammonium chloride, stearyltrimethylammonium chloride,
cetyltrimethylammonium chloride, cetyltrimethylammonium bromide,
lauryltrimethylammonium chloride, dioctyldimethylammonium chloride,
distearyldimethylammonium chloride, trioctylmethylammonium
chloride, tristearylmethylammonium chloride, tetraoctylammonium
chloride, and the like. The aromatic quaternary ammonium salts
include decyldimethylbenzylammonium chloride,
lauryldimethylbenzylammonium chloride,
stearyldimethylbenzylammonium chloride, benzethonium chloride, and
the like. The heterocyclic quaternary ammonium salts include
cetylpyridinium chloride, an alkyl isoquinolinium bromide, and the
like. The alkylamine salts include neutralized products of
octylamine, decylamine, laurylamine, stearylamine, coconut oil
amine, dioctylamine, distearylamine, trioctylamine,
tristearylamine, and dioctylmethylamine neutralized with an
inorganic acid such as hydrochloric acid, nitric acid, and sulfuric
acid, or a carboxylic acid such as acetic acid. Alternatively, a
neutralized product obtained by reacting a mercapto carboxylic acid
on the surface of the metallic copper particle and/or a salt
thereof with alkylamine may be used as the alkylamine salt. Among
the quaternary ammonium salts, those having at least one alkyl
group with a number of carbon atoms of 8 or more or benzyl group
are particularly preferable, and such quaternary ammonium salts
include stearyltrimethylammonium chloride (number of carbon atoms
of alkyl group: 18), octyltrimethylammonium chloride (number of
carbon atoms of alkyl group: 8), lauryltrimethylammonium chloride
(number of carbon atoms of alkyl group: 12), cetyltrimethylammonium
chloride (number of carbon atoms of alkyl group: 16),
cetyltrimethylammonium bromide (number of carbon atoms of alkyl
group: 16), tetraoctylammonium bromide (number of carbon atoms of
alkyl group: 8), dimethyltetradecylbenzylammonium chloride (number
of carbon atoms of alkyl group: 14),
distearyldimethylbenzylammonium chloride (number of carbon atoms of
alkyl group: 18), stearyldimethylbenzylammonium chloride (number of
carbon atoms of alkyl group: 18), and benzalkonium chloride (number
of carbon atoms of alkyl group: 12 to 18). Moreover, among the
alkylamines of the alkylamine salts, those having at least one
alkyl group with a number of carbon atoms of 8 or more are
preferable, and such alkylamines include octylamine (number of
carbon atoms of alkyl group: 8), laurylamine (number of carbon
atoms of alkyl group: 12), stearylamine (number of carbon atoms of
alkyl group: 18), dioctylamine (number of carbon atoms of alkyl
group: 8), dilaurylamine (number of carbon atoms of alkyl group:
12), distearylamine (number of carbon atoms of alkyl group: 18),
trioctylamine (number of carbon atoms of alkyl group: 8), and
trilaurylamine (number of carbon atoms of alkyl group: 12).
Moreover, the surface control agent controls surface tension of an
organic solvent dispersion prevent defects such as cissing and
craters, and the surface control agents include acrylic surface
control agents, vinyl surface control agents, silicone surface
control agents, fluorine surface control agents, and the like. The
additive amounts of the surfactant and the surface control agent
can be appropriately adjusted, and it is preferable that the amount
is, for example, 2.0 parts by mass or less with regard to 100 parts
by mass of the metallic copper particle, and more preferably 0.2
parts by mass or less.
[0149] Furthermore, in the metallic copper dispersion according to
the present invention, a fine metal particle other than the
metallic copper may be appropriately blended according to the
purpose of use in a range where the characteristics of the metallic
copper of the present invention are not obstructed. For example, a
fine metal particle such as gold, silver, nickel, or tin may be
blended in the metallic copper dispersion.
[0150] The metallic paste according to the present invention
includes a metallic copper particle, a binder resin, a solvent, and
the like as main components, and appropriately including a
surfactant, a cros slinking agent, a polymer dispersant, and the
like blended therein. The metallic paste has a characteristic of
having a relatively high thixotropy index (TI) value measured by
the method described above, and specifically, the TI value can be
set to 3.0 or more, preferably 3.5 or more, and more preferably 4.0
or more. The metallic paste actually used is prepared by
appropriately blending the metallic copper particle and the like,
and is desirable to have a certain degree of viscosity in view of a
thick film formation, and generally, a metallic paste having a
viscosity of 2000 mPas or higher is preferable.
[0151] Next, one embodiment according to the present invention is a
process for producing a metallic copper dispersion including:
mixing a copper compound and hypophosphorous acid and/or a salt
thereof in a solvent in the presence of gelatin and/or a collagen
peptide to reduce the copper compound; thereafter performing
solid-liquid separation; and subsequently mixing and dispersing an
obtained metallic copper particle in an aqueous solvent and/or an
organic solvent. Moreover, preferably, one embodiment according to
the present invention is a process for producing a metallic copper
dispersion including: reducing a copper compound in the presence of
gelatin and/or a collagen peptide in an aqueous solvent; thereafter
performing solid-liquid separation; and subsequently mixing and
dispersing: an obtained metallic copper particle having the gelatin
and/or the collagen peptide on a surface of the particle; and a
polymeric dispersant in an organic solvent.
[0152] A wet mixer is used for mixing the metallic copper particle
and the aqueous solvent and/or the organic solvent, and, for
example, fixed mixers such as stirrers, spiral mixers, ribbon
mixers, and fluidizing mixers, rotary mixers such as cylindrical
mixers and twin cylindrical mixers, wet grinding mills such as sand
mills, ball mills, bead mills, colloid mills, and sand grinder
mills, shakers such as paint shakers, and dispersion machines such
as ultrasonic dispersion machines can be used. After appropriately
selecting the mixer and the like from among those described above,
mixing conditions thereof, mixing time thereof, and a dispersion
media thereof are appropriately set. In this way, a metallic copper
dispersion including the metallic copper particle dispersed in the
organic solvent is obtained. Moreover, the metallic copper particle
may be ground before mixing when necessary using a grinding mill
such as a compression grinding type mill, an impact compression
grinding type mill, a shearing grinding type mill, and a friction
grinding type mill. Also, the metallic copper particle may be mixed
at the same time when the metallic copper particle is ground.
[0153] Next, a metallic copper-containing film for an electrode, a
wiring pattern, a design or decorative film coating, and the like,
which use the metallic copper dispersion as one embodiment
according to the present invention will be described. The metallic
copper-containing film is a film in which a metallic copper is
fixed on a base material. In addition, a metallic copper-containing
film in which the metallic copper particle is more firmly fixed can
be obtained by adding a curable resin to the dispersion. Moreover,
by applying heat to the film coating or irradiating the film
coating with light or plasma, the metallic copper particle is
molten and bonded, and can be fixed still more firmly. In such a
metallic copper-containing film, the thickness, size, shape, and
the like are not limited, the film thickness may be thin or thick,
and the whole surface of the base material or part thereof may be
covered with the metallic copper-containing film. Alternatively,
the metallic copper-containing film may have a fine line shape
formed on part of the base material, a broad line shape, or a fine
dot shape. As to the specific uses, the metallic copper-containing
film can be used for an electrode and a wiring pattern by making
use of conductivity of metallic copper, and can be also used for
decoration uses and antimicrobial uses by making use of tone of
color and antimicrobial action of metallic copper. Moreover, the
metallic dispersion can be used for joining uses.
[0154] A decorative article or an antimicrobial article which are
one embodiment according to the present invention is obtained by
forming the metallic copper-containing film on at least part of the
surface of a base material, and a metal color tone or antibacterial
properties of the metallic copper particle are given on the surface
of the base material of the decorative article or the antimicrobial
article. The whole surface of the base material can be colored to
give a metal color tone or antibacterial properties, and
additionally, design, a mark, and a logo mark can be formed on part
of the surface of the base material, or other characters, figures,
and symbols can be also formed. As the base material, an inorganic
material such as metal, glass, ceramics, rock, and concrete, an
organic material such as rubber, plastics, paper, wood, leather,
fabric, and fiber, and a material in which the inorganic material
and the organic material are used in combination or are compounded
can be used. The metallic copper-containing film can be formed on a
raw material before processing the base material having such a
material quality into an article to be used to give a decoration or
antibacterial properties, or in all articles after processing the
base material, a decoration or antibacterial properties can be
given. In this case, the case where a decoration or antibacterial
properties is given on the surfaces of articles coated in advance
on the surfaces of these base materials is also included.
[0155] Specific examples of articles giving the decoration or
antibacterial properties include the following:
[0156] (1) exterior and interior of transportation such as
automobiles, tracks, and buses, a bumper, a doorknob, a rearview
mirror, a front grille, a reflecting plate of a lamp, a display
instrument, and the like;
[0157] (2) exterior of electric appliances such as a television
set, a refrigerator, a microwave oven, a personal computer, a
mobile phone, and a camera, a remote control, a touch panel, a
front panel, and the like;
[0158] (3) exterior of buildings such as houses, buildings,
department stores, stores, shopping malls, pachinko parlors,
wedding halls, funeral halls, shrines, and temples, window glass,
an entrance, a doorplate, a gate, a door, a doorknob, a show
window, interior, and the like;
[0159] (4) house facilities such as lighting equipment, furniture,
furnishings, toilet equipment, Buddhist altars and fittings, a
Buddha statue, and the like;
[0160] (5) utensils such as hardware and tableware;
[0161] (6) vending machines of beverage, tobacco, and the like;
[0162] (7) containers for synthetic detergents, skin care products,
soft drinks, alcoholic beverages, confectionery, food products,
tobacco, and pharmaceuticals;
[0163] (8) packing materials such as wrapping paper and a carton
box;
[0164] (9) outfits and accessories such as clothes, shoes, bags,
glasses, artificial nails, artificial hair, and jewels;
[0165] (10) sporting goods such as a baseball bat, and a golf club,
and products for hobbies such as fishing tools;
[0166] (11) stationery such as pencils, colored paper, notebooks,
and postcards for New Year's greetings, and business equipment such
as desks and chairs; and
[0167] (12) covers and bands for books, toys such as dolls and
small toy cars, cards such as a commuter pass, and recording media
such as CDs and DVDs. Moreover, human nails, skin, eyebrows, hair,
and the like can be used as a base material.
[0168] Next, one embodiment according to the present invention is a
process for producing a metallic copper-containing film wherein the
above metallic copper dispersion is used. A step (a) in the
production process according to the present invention is a step of
adhering the metallic copper dispersion on the surface of the base
material. A step (b) is a step of heating the metallic
copper-containing film produced in the above step (a) under a
nonreducing gas atmosphere or under a reducing gas atmosphere. A
step (c) is a step of irradiating the whole or partial region of
the metallic copper-containing film with light after the above step
(a). Moreover, a step (d) is a step of irradiating the whole or
partial region of the metallic copper-containing film with plasma
after the step (a). Further, a step (e) is a step of removing the
metallic copper-containing film in the region not irradiated after
the above step (c) or (d). Furthermore, a step (f) is a step of
transferring the metallic copper-containing film obtained through
the above steps (a) to (d) on another base material. The metallic
copper-containing film can be also produced in the above step (a),
and the subsequent steps (b) to (f) are a step performed when
necessary. A firm metallic copper-containing film can be produced
by performing any one of the steps (b) to (e), and moreover, by
performing the step (f), a metallic copper-containing film can be
simply produced on a base material which is difficult to directly
form the metallic copper-containing film. Moreover, when an
electrode and a wiring pattern are produced, it is also possible to
perform any combination of steps (b) to (f) after the step (a).
Step (a)
[0169] The metallic copper dispersion according to the present
invention is adhered (which is typically expressed by "applied"
hereinafter) on the base material. As for application of the
metallic copper dispersion, a general printing method or transfer
method, such as screen printing, gravure printing, flexographic
printing, ink jet printing, or offset printing, or a general
application method using a spray, a slit coater, a curtain coater,
a bar coater, a brush, a pen brush, or a spin coater can be used.
The thickness of the coated layer is not particularly limited, and
can be appropriately selected according to the purpose of use and
uses, however, a thickness of 0.001 to 100 .mu.m is preferable, and
a thickness of 0.005 to 70 .mu.m is more preferable. An application
pattern at this time can be applied on the whole surface of the
base material, and can be also applied in pattern or figuratus
form. According to the application method, the purpose of use, and
uses, the particle diameter of the metallic copper particle, the
kind of the polymeric dispersant, the organic solvent, and other
compounds can be appropriately selected. Similarly, viscosity of
the dispersion and the concentration of metallic copper can be
appropriately selected.
[0170] As the base material, glasses such as alkali-free glass,
quartz glass, crystallized transparent glass, Pyrex (which is a
registered trade-mark) glass, and sapphire glass; inorganic
materials such as Al.sub.2O.sub.3, MgO, BeO, ZrO2, Y.sub.2O.sub.3,
CaO, and GGG (gadolinium-gallium-garnet); acrylic resins such as
PET (polyethylene terephthalate), PEN (polyethylene naphthalate),
polypropylene, polycarbonate, and polymethyl methacrylate; vinyl
chloride resins such as polyvinyl chloride and vinyl chloride
copolymers; organic materials such as epoxy resins, polyarylates,
polysulfones, polyethersulfones, polyimides, fluororesins, phenoxy
resins, polyolefin resins, nylons, styrene resins, and ABS resins;
and a substrate formed by using a composite material in which
inorganic particles having a diameter of several nanometers are
dispersed in the organic material; a silicon wafer; and a metal
plate, and the like can be used. The base material can be
appropriately selected from these materials according to uses, and
used as a flexible base material in a film form and the like or a
rigid base material. In addition, the size of the base material is
not limited, the shape of the base material may be any shape such
as a disc shape, a card shape, and a sheet-like shape, and the
surface of the base material does not need to be planar, and may
have depressions and projections, or may have a curved surface.
[0171] On the base material, a foundation layer may be provided in
order to improve planarity of the surface of the base material and
adhesive strength and in order to prevent deterioration of the
metallic copper-containing film. Examples of materials for the
foundation layer include polymer materials such as polymethyl
methacrylate, acrylic acid-methacrylic acid copolymers,
styrene-maleic anhydride copolymers, polyvinyl alcohols,
N-methylolacrylamide, styrene-vinyltoluene copolymers,
chlorosulfonated polyethylenes, nitrocellulose, polyvinyl chloride,
polyvinylidene chloride, chlorinated polyolefins, polyesters,
polyimides, vinyl acetate-vinyl chloride copolymers, ethylene-vinyl
acetate copolymers, polyethylenes, polypropylenes, and
polycarbonates; thermosetting resins, photocurable or electron beam
curable resins; and surface modifiers such as coupling agents. As
the material of the foundation layer, materials having high
adhesion between the base material and the metallic
copper-containing film are preferable. Specifically, thermosetting,
photocurable or electron beam curable resins, and surface modifiers
such as coupling agents (for example, silane coupling agents,
titanate coupling agents, germanium coupling agents, and aluminum
coupling agents), colloidal silica, and the like are
preferable.
[0172] The foundation layer can be formed by dissolving or
dispersing the above material in an appropriate solvent to prepare
a coating liquid, applying the coating liquid on the surface of the
base material using a coating method such as spin coating, dip
coating, extrusion coating, and bar coating. It is preferable that
the layer thickness (at the drying) of the foundation layer is
generally 0.001 to 20 .mu.m, and more preferably 0.005 to 10
.mu.m.
[0173] When necessary, a film after the metallic copper dispersion
is applied thereon may be heated at an appropriate temperature to
evaporate and remove (which is described as "drying by heating"
hereinafter) the organic solvent or the aqueous solvent (in this
case, depending on the kind thereof, other compounds having
low-boiling point are included) in the metallic copper-containing
film. The temperature for drying by heating can be appropriately
set, but in order to suppress oxidization of metallic copper, the
temperature of 150.degree. C. or less is preferable, and the
temperature of 120.degree. C. or less is more preferable. The
heating time can also be set appropriately. Also, an atmosphere can
be appropriately set, and further, heating can be performed under a
nonreducing gas atmosphere (i.e. inert gas atmosphere (for example,
nitrogen or argon) or oxygen gas-containing atmosphere (for
example, in the air)) or a reducing gas atmosphere. Nitrogen gas,
argon gas, helium gas, and the like can be used as an inert gas. In
addition, evaporation and removal of the organic solvent or the
like is not limited to drying by heating, and a natural drying
method or a reduced pressure drying method may be used. In the case
of reduced pressure drying, it is performed under pressure lower
than atmospheric pressure, and specifically, the reduced pressure
drying may be performed under vacuum pressure and ultra-vacuum
pressure.
Step (Preliminary Step for Step (b))
[0174] After the step (a), it is preferable to heat the metallic
copper-containing film at an appropriate temperature when
necessary. By heating, organic compounds included in the metallic
copper-containing film, such as the gelatin and/or the collagen
peptide, and the polymeric dispersant can be decomposed and/or
vaporized (which is described as "oxidization firing by heating"
hereinafter). It is preferable that the heating is performed under
an oxygen-containing atmosphere in order to accelerate
decomposition and/or vaporization of the organic compounds, and
more preferably in an oxygen-containing gas stream. It is
preferable that the concentration of oxygen in the atmosphere is 10
to 10000 ppm because oxidization of the metallic copper particle
does not progress so fast. The temperature for oxidization firing
by heating can be appropriately set according to the kind of the
base material or the like, and the temperature of 100 to
500.degree. C. is preferable, and the temperature of 120 to
300.degree. C. is more preferable. The heating time can be also set
appropriately, and can be set to, for example, about one minute to
about 48 hours, and the heating time of about 10 minutes to about
48 hours is preferable.
Step (b)
[0175] A copper-containing film is heated at an appropriate
temperature under a nonreducing gas atmosphere (i.e. under inert
gas atmosphere or oxygen gas-containing atmosphere (for example, in
the air)) or under a reducing gas atmosphere (which is described as
"firing by heating" hereinafter). The inert gas atmosphere is
preferable, and nitrogen gas, argon gas, helium gas, and the like
can be used as an inert gas. In the present step, fusion between
the metallic copper particles formed in the previous step such as
"Preliminary Step for Step (b)" is made to occur, and, when
necessary, a reduction reaction of the copper compound or the like
to metallic copper is made to occur. This is because the melting
point of the nano-size particle (i.e. the fine metallic copper
particle or the small metallic copper particle) included in the
metallic copper particle according to the present invention becomes
lower than that of a bulk due to a size effect thereof, and thus
this nano size particle is molten even in a relatively low
temperature range. As a result, electric resistance can be
remarkably reduced and a metal color tone can be improved through
the step in a short time. For example, hydrogen gas, carbon
monoxide gas, and the like can be used as a reducing gas, and the
nitrogen gas including about 0.1 to about 5% of hydrogen gas is
preferable in view of safety and availability. The heating
temperature can be appropriately set according to the kind of the
base material or the like, and the heating temperature of 50 to
500.degree. C. is preferable, the heating temperature of 80 to
300.degree. C. is more preferable, and a temperature from the
heating temperature in the step (i.e. "Preliminary Step for Step
(b)") to 300.degree. C. is still more preferable. The heating time
can be also set appropriately, and can be set to, for example,
about one minute to about 48 hours, and the heating time of about
10 minutes to about 48 hours is preferable. By this heating step, a
volume resistance value of the obtained metallic copper-containing
film can be made at 1.times.10.sup.-2 .OMEGA.cm or less, preferably
1.times.10.sup.-3 .OMEGA.cm or less, more preferably
1.times.10.sup.-4 .OMEGA.cm or less, and still more preferably
1.times.10.sup.-5 .OMEGA.cm or less.
[0176] The step for evaporation and removal of the organic solvent,
which is performed when necessary, the step for the oxidization
firing by heating (i.e. "Preliminary Step for Step (b)"), and the
step for the firing by heating (i.e. "Step (b)") may be performed
separately, or may be performed continuously. Moreover, these steps
are not limited to the case of performing the step for the
oxidization firing by heating after the drying by heating, and the
step for the oxidization firing by heating can be performed after a
natural drying or reduced pressure drying is performed without
performing the drying by heating, or the organic solvent can be
evaporated and removed in the step for the oxidization firing by
heating, which also serves as the step for the drying by heating,
and these steps do not need to be clearly distinguished.
Step (c)
[0177] The whole or partial region of the metallic
copper-containing film produced in the step (a) is irradiated with
light. The light may be infrared rays, visible rays, ultraviolet
rays, X-rays (soft X-rays to hard X-rays), a laser beam that
radiates by amplifying light, or sunlight. A pattern is drawn on
the base material by moving a light source or the base material
while irradiating the metallic copper-containing film with the
light. A pattern can be also drawn on the base material by
converging a laser beam oscillated with a laser oscillator, setting
a diameter of irradiation appropriately, and moving a laser mount
section or the base material while irradiating the metallic
copper-containing film with the laser beam. The light is absorbed
by the metallic copper-containing film, and along with the
decomposition and/or vaporization of the organic compounds such as
the gelatin and/or the collagen peptide and the polymeric
dispersant by the heat generated thereby, the fusion between the
metallic copper particles occurs, and thus the reduction of
electric resistance of an irradiated portion of the metallic
copper-containing film and the improvement of a metal color tone
thereof can be provided. The nano size particle (the fine metallic
copper particle or the small metallic copper particle) according to
the present invention has the melting point lower than the melting
point of a bulk due to a size effect thereof, and thus the pattern
can be drawn with a relatively low energy and at a high speed.
[0178] According to kinds and blending amounts of the gelatin
and/or the collagen peptide, the polymeric dispersant, the
complexing agent and the like which are used, a wavelength of the
light can be arbitrarily selected in a range where the metallic
copper-containing film can absorb the light, and the light with a
wavelength in an ultraviolet region, a visible light region, an
infrared region, or the like is preferable because it is easy to
use. Light sources that emit incandescent light, discharge light,
electroluminescence, or the like can be used as the light source,
and an incandescent lamp, light sources that make use of
luminescence by discharge such as an infrared lamp, a visible light
lamp, an ultraviolet lamp, a mercury lamp, and xenon lamp,
semiconductor devices (e.g. light emitting diodes) and the like
that emit light when a voltage is applied, such as LED can be used
as the light source. Typical lasers include: semiconductor lasers
using GaN, GaAsAl, InGaAsP, or the like; excimer lasers using ArF,
KrF, XeCl, or the like; dye lasers using rhodamine, or the like;
gas lasers using He--Ne, He--Cd, CO.sub.2, Ar ion, or the like;
free electron lasers; solid state lasers such as ruby lasers and
Nd: YAG lasers; and so on. Moreover, a higher order harmonic wave
such as a second harmonic wave and third harmonic wave of these
lasers may be also used, and a laser beam at any wavelength in the
ultraviolet region, the visible light region, and the infrared
region can be used. Further, irradiation of a continuous wave or
irradiation of a pulse wave may be used. Conditions on applied
energy such as a diameter of irradiation of the light, a scan
speed, and an output can be appropriately set in a range in which
oxidization of metallic copper, and ablation and peening of the
metallic copper-containing film do not occur. The diameter of
irradiation can be appropriately set in accordance with a pattern
or figure to be drawn, and the diameter of irradiation of 10 .mu.m
to 5 mm is suitable. The scan speed can be also set appropriately
according to other parameters, required accuracy, manufacturing
capacity, and the like.
[0179] An atmosphere performing light irradiation such as an inert
gas atmosphere, a reducing gas atmosphere, and an oxygen
gas-containing atmosphere (e.g. air atmosphere) can be
appropriately set. By using the metallic copper dispersion
according to the present invention, a metallic copper-containing
film having a low resistance and a good metal color tone can be
formed without causing the oxidation of copper in the metallic
copper-containing film even under the oxygen gas-containing
atmosphere (e.g. air atmosphere), which is expected to be
attributed to the presence of the gelatin. Specifically, this can
be achieved by irradiation with a continuous wave laser beam having
a wavelength in the infrared region at a scan speed of 1 to 500
mm/s and at an output range of 1 to 140 W under the oxygen
gas-containing atmosphere (e.g. air atmosphere). At this time,
conditions on laser irradiation are adjusted so that main peak
strength in a Cu.sub.2O (111) plane may be 20 or less when main
peak strength in a metallic copper (111) plane is assumed to be 100
in X-ray diffraction of the metallic copper-containing film at a
portion irradiated with the laser beam. It is more preferable to
set an output of the laser beam to be 10 to 100 W, and an output of
the laser beam in a range of 20 to 50W is still more preferable.
The semiconductor lasers are preferable because the semiconductor
lasers are generally suitable for irradiation with a continuous
laser beam having a wavelength in the infrared region.
Step (d)
[0180] Next, the whole or partial region of the metallic
copper-containing film produced in the step (a) is irradiated with
plasma to produce a metallic copper-containing film. In this step,
organic compounds included in the metallic copper-containing film,
such as the gelatin and/or the collagen peptide, and the polymeric
dispersant are decomposed or vaporized, and fusion of metallic
copper particles is made to occur. Plasma irradiation can be
appropriately selected from among publicly known methods. For
example, a metallic copper-containing film is placed in a plasma
treatment apparatus, a gas is introduced, and energy is applied to
ionize the gas to be in a plasma state. Excitation energy that is
supplied to the gas is, for example, electric discharge, direct
current, radio frequency, microwave, or electromagnetic radiation.
Moreover, in general, plasma can be also generated by applying
voltage between two electrodes to form an electric field. Gases
suitable for plasma treatment include helium, argon, hydrogen,
nitrogen, air, nitrous oxide, ammonia, carbon dioxide, oxygen, and
the like, and the oxygen gas, the hydrogen gas, a mixed gas of
oxygen and helium or argon, and a mixed gas of hydrogen and helium
or argon are more preferable. The plasma treatment can be performed
under atmospheric conditions, or the plasma treatment may be
performed in an apparatus capable of retaining plasma under a
reduced pressure or a vacuum condition. It is preferable that the
pressure is in a range of about 10 mTorr to about 760 Torr (about
1.333 to about 101325 Pa).
[0181] Specifically, the plasma treatment can be performed as
described in the following example. First of all, the metallic
copper-containing film is placed in a plasma treatment apparatus,
and the base material is heated in the atmospheric air when
necessary. The heating temperature can be set according to the
material quality of the base material, and the heating temperature
is preferably 180.degree. C. or less when a plastic having a low
heat resistance is used, and more preferably 120.degree. C. or
less. As the lower limit value of the heating temperature, a
temperature of about 20.degree. C. is practical. Next, it is
preferable that heating be performed under a reduced pressure or a
vacuum condition, and the heating temperature is preferably
180.degree. C. or less, and still more preferably 120.degree. C. or
less. The heating time can be appropriately set. And a gas is
introduced in the plasma treatment apparatus to generate plasma
while heating is continuously performed, and the whole or partial
region of the metallic copper-containing film is irradiated with
its plasma. It is preferable that microwave energy having a
frequency of 2450 MHz is supplied to generate microwave surface
wave plasma. When a partial region is irradiated with plasma, the
other region can be protected so as not to be irradiated with
plasma by putting a mask pattern on the metallic copper-containing
film. The plasma irradiation time can be appropriately set, and is,
for example, about 0.01 to about 30 minutes, and a plasma
irradiation time of about 0.01 to about 10 minutes is suitable. The
plasma irradiation can be also performed in two stages. In the
first step thereof, the metallic copper-containing film is
irradiated with plasma in the presence of oxygen gas to decompose
an organic compound such as the gelatin, and thereafter in the
second step thereof, the metallic copper-containing film is
irradiated in the presence of a reducing gas, thereby making it
possible to sinter the metallic copper particle.
Step (e)
[0182] Further, an unnecessary portion of the metallic
copper-containing film, a portion of the metallic copper-containing
film, not irradiated with the light in the above step (c), or a
portion of the metallic copper-containing film, not irradiated with
the plasma in the above step (d) may be removed using an
appropriate solvent when necessary. As the solvent, various
solvents such as alcohol solvents, glycol ether solvents, and
aromatic solvents can be used. The unnecessary portion or the like
can be removed by immersing the base material in such a solvent or
wiping off the portion with fabric or paper dipped in the
solvent.
Step (f)
[0183] Next, the whole or partial region of the metallic
copper-containing film produced on the base material can be also
transferred on another base material after the step (a), the step
(b), the step (c), the step (d), or the step (e).
[0184] In addition, the steps (b) to (e) after the step (a) can be
arbitrarily combined and performed. For example, the step (b) can
be performed after the step (a), and the step (c) can further be
performed. Also, the step (c), the step (d), or the step (e) can be
performed after the step (a), and the step (b) can further be
performed. Moreover, in the step (b), only the "Preliminary Step
for Step (b)" of the step (b) or only the step (b) can be combined
and performed. For example, the step (c) can be performed after the
step (a), and the step (b) can further be performed.
[0185] It is preferable that the whole of the metallic
copper-containing film produced by any one of (a) to (f) in the
present invention is sintered because the resistance value is low.
Thus, it is preferable to perform heating, light irradiation, or
plasma irradiation with sufficient time and strength for sintering
the whole of the metallic copper-containing film. However, only the
surface portion of the metallic copper-containing film may be
sintered and the inside thereof may not be sintered, and there is
no problem even when only part of the surface is sintered, as long
as the performance of the resistance value or the like, necessary
for uses can be obtained. The volume resistance value of the
metallic copper-containing film is preferably 50 .mu..OMEGA.cm or
less, more preferably 20 .mu..OMEGA.cm or less, and still more
preferably 10 .mu..OMEGA.cm or less. The thickness, size, shape,
and the like of such a metallic copper-containing film are not
limited, and the metallic copper-containing film may be a thin film
or a thick film, and the film may cover the whole or part of the
base material. Alternatively, the metallic copper-containing film
may have a fine wire-like shape or wide wire-like shape formed on
part of the base material, or may have a fine dotted shape. It is
preferable that the thickness be, for example, 1 .mu.m or less,
more preferably 0.5 .mu.m or less. As specific uses, the metallic
copper-containing film can be used for an electrode and a wiring
pattern, for joining chips and substrates, and for other uses
making use of the electrical conductivity of metallic copper, and
can be also used for decoration uses and antibacterial uses making
use of color tone or antibacterial properties of metallic
copper.
EXAMPLES
[0186] Hereinafter, the present invention will be described in more
detail giving Examples, however the present invention is not
limited to these Examples.
Example 1
[0187] To 150 ml of pure water, 24 g of industrial copper(II) oxide
(N-120 manufactured by NC-Tech Co., Ltd.) and 9.55 g of gelatin
(amine value of 23, acid value of 29, amine value -acid value=-6,
and mass average molecular weight of 200000) as protective colloid
were added and mixed, and the temperature of the mixed solution was
raised to 80.degree. C. After the temperature was raised, a
solution prepared by mixing 1.2 g of aminoethanol as a complexing
agent and 99 g of 50% hypophosphorous acid in 150 ml of pure water
was added to the mixed solution under stirring, the resultant
mixture was reacted with copper oxide for one hour, and then the
reaction solution was subjected to aging for two hours to produce a
copper particle coated with the gelatin. Thereafter, the copper
particle was subjected to filtration and washing until a specific
conductivity of a filtrate reached 100 .mu.S/cm or less, and dried
for 10 hours at a temperature of 60.degree. C. under an atmosphere
of nitrogen gas to obtain a metallic copper particle coated with
the gelatin (sample A).
Examples 2 to 5
[0188] Metallic copper particles (samples B to E) according to the
present invention were obtained in the same manner as in Example 1
except that the amount of the gelatin in Example 1 was changed to
the amounts described in Table 1.
Examples 6 to 7
[0189] Metallic copper particles (samples F to G) according to the
present invention were obtained in the same manner as in Example 1
except that the reaction temperature set at 80.degree. C. in
Example 1 was changed to 60.degree. C. or 70.degree. C.
Example 8
[0190] A metallic copper particle (sample H) according to the
present invention was obtained in the same manner as in Example 1
except that the aminoethanol in Example 1 was not added.
Example 9
[0191] A metallic copper particle (sample I) according to the
present invention was obtained in the same manner as in Example 1
except that the aminoethanol in Example 1 was added in an amount of
4.86 g.
Example 10
[0192] A metallic copper particle (sample J) according to the
present invention was obtained in the same manner as in Example 1
except that the gelatin in Example 1 had a mass average molecular
weight of 10000.
Example 11
[0193] A metallic copper particle (sample K) according to the
present invention was obtained in the same manner as in Example 1
except that the gelatin in Example 1 was 19.11 g of gelatin having
a mass average molecular weight of 10000.
Example 12
[0194] A metallic copper particle (sample L) according to the
present invention was obtained in the same manner as in Example 1
except that a collagen peptide having a mass average molecular
weight of 5000 was further used.
Example 13
[0195] A metallic copper particle (sample M) according to the
present invention was obtained in the same manner as in Example 1
except that 19.11 g of a collagen peptide having a mass average
molecular weight of 5000 was further used.
Examples 14 to 15
[0196] Metallic copper particles (samples N to O) according to the
present invention were obtained in the same manner as in Example 7
except that the aging time in Example 7 was changed to one hour or
three hours.
Examples 16 to 18
[0197] Metallic copper particles (samples P to R) according to the
present invention were obtained in the same manner as in Example 7
except that to the mixed solution of industrial copper (II) oxide,
gelatin, and pure water in Example 7, citric acid, formic acid, or
lactic acid was further added as an organic acid.
Examples 19 to 20
[0198] Metallic copper particles (sample S to T) according to the
present invention were obtained in the same manner as in Example 1
except that the time for adding hypophosphorous acid in Example 1
was changed to two hours or three hours.
Examples 21 to 24
[0199] Metallic copper particles (samples U to X) according to the
present invention were obtained in the same manner as in Example 17
except that the amount of the gelatin in
Example 17 was changed.
Examples 25 to 27
[0200] Metallic copper particles (samples Y to AA) according to the
present invention were obtained in the same manner as in Example 17
except that the amount of the organic acid in Example 17 was
changed to the amounts described in Table 1.
Example 28
[0201] A metallic copper particle (sample AB) according to the
present invention was obtained in the same manner as in Example 17
except that the reaction temperature in Example 17 was changed to
40.degree. C.
Example 29
[0202] A metallic copper particle (sample AC) according to the
present invention was obtained in the same manner as in Example 17
except that the aminoethanol in Example 17 was not added.
Example 30
[0203] A metallic copper particle (sample AD) according to the
present invention was obtained in the same manner as in Example 29
except that 9.62 g of pyrophosphoric acid was added as a
pH-adjusting agent to the mixed solution of industrial copper (II)
oxide, gelatin, and pure water in Example 29.
Comparative Example 1
[0204] A metallic copper particle (sample AE) was obtained in the
same manner as in Example 1 except that the gelatin in Example 1
was not used.
Comparative Example 2
[0205] To 350 ml of pure water, 24 g of industrial copper (II)
oxide (N-120: manufactured by NC-Tech Co., Ltd.) and 9.55 g of
gelatin (amine value of 23, acid value of 29, amine value--acid
value =-6, and mass average molecular weight of 200,000) as
protective colloid were added and mixed, and after the pH of the
mixed solution was adjusted at 9 using 15% ammonia water, the
temperature of the mixed solution was raised from room temperature
to 90.degree. C. in 30 minutes. After the temperature was raised, a
solution prepared by mixing 1.2 g of an aminoethanol solution and
38 g of 80% hydrazine monohydrate to 15 ml of pure water was added
to the mixed solution in 60 minutes under stirring, and the
resultant mixture was reacted with the copper (II) oxide for one
hour to produce a copper particle. After producing the fine copper
particle, 5 mL of a serine protease (Ptoteinase K: manufactured by
Worthington Biochemical Corporation) was added as a protective
colloid remover, and the resultant mixture was held for one hour.
Thereafter, the mixture was subjected to filtration and washing
until a specific conductivity of a filtrate reached 100 .mu.S/cm or
less, and dried for 10 hours at a temperature of 60.degree. C.
under an atmosphere of nitrogen gas to obtain a metallic copper
particle (sample AF).
Comparative Example 3
[0206] A metallic copper particle having a flat shape (sample AG)
was obtained by mixing and suspending 10 g of the copper particle
which is coated with the gelatin and which has an average particle
diameter of 500 nm, synthesized in Comparative Example 2, 30 g of
ethanol, and 50 g of zircon beads; shaking the suspension with a
paint shaker for three hours;
[0207] subsequently separating and removing the beads; and then
filtrating the resultant.
Comparative Example 4
[0208] A metallic copper particle (sample AH) was obtained in the
same manner as in Example 1 except that the copper oxide in Example
1 was changed to copper sulfate.
[0209] Production conditions described above are listed together in
Table 1. Moreover, the pH before adding a reducing agent and the pH
after aging are shown in Table 2 for some samples.
TABLE-US-00001 TABLE 1 Amount of Mass reducing agent average Amount
of Amount (g) molecular Amount Kind of complexing Kind of of
organic (50 wt % Reaction weight of of gelatin complexing agent
organic acid Hypophosphorous temperature Sample gelatin (g) agent
(g) acid (g) acid) [.degree. C.] Example 1 A 200000 9.55
Aminoethanol 1.2 Not added 0 99 80 Example 2 B 200000 4.78
Aminoethanol 1.2 Not added 0 99 80 Example 3 C 200000 5.73
Aminoethanol 1.2 Not added 0 99 80 Example 4 D 200000 14.33
Aminoethanol 1.2 Not added 0 99 80 Example 5 E 200000 19.11
Aminoethanol 1.2 Not added 0 99 80 Example 6 F 200000 9.55
Aminoethanol 1.2 Not added 0 99 60 Example 7 G 200000 9.55
Aminoethanol 1.2 Not added 0 99 70 Example 8 H 200000 9.55 Not
added 0 Not added 0 99 80 Example 9 I 200000 9.55 Aminoethanol 4.86
Not added 0 99 80 Example 10 J 10000 9.55 Aminoethanol 1.2 Not
added 0 99 80 Example 11 K 10000 19.11 Aminoethanol 1.2 Not added 0
99 80 Example 12 L 5000 9.55 Aminoethanol 1.2 Not added 0 99 80
Example 13 M 5000 19.11 Aminoethanol 1.2 Not added 0 99 80 Example
14 N 200000 9.55 Aminoethanol 1.2 Not added 0 99 70 Example 15 O
200000 9.55 Aminoethanol 1.2 Not added 0 99 70 Example 16 P 200000
9.55 Aminoethanol 1.2 Citric acid 11.5 99 70 Example 17 Q 200000
9.55 Aminoethanol 1.2 Formic acid 3.1 99 70 Example 18 R 200000
9.55 Aminoethanol 1.2 Lactic acid 5.4 99 70 Example 19 S 200000
9.55 Aminoethanol 1.2 Not added 0 99 80 Example 20 T 200000 9.55
Aminoethanol 1.2 Not added 0 99 80 Example 21 U 200000 1.91
Aminoethanol 1.2 Formic acid 3.1 99 70 Example 22 V 200000 3.82
Aminoethanol 1.2 Formic acid 3.1 99 70 Example 23 W 200000 5.73
Aminoethanol 1.2 Formic acid 3.1 99 70 Example 24 X 200000 7.64
Aminoethanol 1.2 Formic acid 3.1 99 70 Example 25 Y 200000 9.55
Aminoethanol 1.2 Formic acid 1.6 99 70 Example 26 Z 200000 9.55
Aminoethanol 1.2 Formic acid 4.8 99 70 Example 27 AA 200000 9.55
Aminoethanol 1.2 Formic acid 6.2 99 70 Example 28 AB 200000 9.55
Aminoethanol 1.2 Formic acid 3.1 99 40 Example 29 AC 200000 9.55
Not added 0 Formic acid 3.1 99 70 Example 30 AD 200000 9.55 Not
added 0 Formic acid 3.1 99 70 Comparative AE -- 0 Aminoethanol 1.2
Not added 0 99 80 Example 1 Comparative AF 200000 9.55 Aminoethanol
1.2 Not added 0 38 g of 90 Example 2 Hydrazine Comparative AH
200000 9.55 Aminoethanol 1.2 Not added 0 99 80 Example 4
TABLE-US-00002 TABLE 2 Sample Initial pH pH after aging Example 1 A
8.4 0.8 Example 16 P 3.5 0.7 Example 17 Q 3.4 0.7 Example 18 R 3.5
0.7 Example 25 Y 3.7 0.7 Example 26 Z 3.0 0.6 Example 27 AA 2.8 0.6
Example 30 AD 1.4 0.6 Comparative AE 8.6 0.8 Example 1 Comparative
AF 9.0 9.8 Example 2
[0210] As a result of X-ray diffraction of the samples (A to AH)
obtained in the Examples and the Comparative Examples, peaks of
metallic copper were confirmed for all the samples, and thus it was
found that all the samples were metallic copper. FIG. 1 shows an
X-ray diffraction chart of sample A. Moreover, the specific surface
areas (according to nitrogen adsorption BET method) and the amounts
of phosphorus (according to XRF analysis) included in these samples
are shown in Table 3. It was found that the samples of the Examples
include phosphorus in an amount of about 0.2 to about 0.4% by mass.
Further, it was found from these electron micrographs that in the
samples of the Examples, fine metallic copper particles were
adhered on the surface of a large diameter metallic copper
particle, and partially aggregated fine metallic copper particles
were adhered on the surface of the large diameter metallic copper
particle. Furthermore, it was also found that the metallic copper
particles (i.e. composite particles) and the small metallic copper
particles coexisted. On the other hand, it was found that in the
samples of the Comparative Examples, particles having one kind of
shape and almost uniform size existed. As one example, in FIG. 2 to
FIG. 35, electron micrograph (SEM photograph) of each of the
samples (A to M, Z, AE, AF, AND AG) is shown. Moreover, the primary
particle diameters of the samples (A to AH) are shown in Table
3.
TABLE-US-00003 TABLE 3 Specific Average primary Average primary
surface particle diameter particle diameter area Amount of P of
fine particles of large diameter Sample [m.sup.2/g] [% by mass]
[nm] particles [.mu.m] Example 1 A 1.9 0.26 128 15.9 Example 2 B
1.9 0.27 47 13.2 Example 3 C 1.1 0.26 103 13.5 Example 4 D 1.7 0.25
154 15.1 Example 5 E 1.9 0.26 70 12.3 Example 6 F 5.3 0.32 88 4.1
Example 7 G 2.7 0.26 114 9.8 Example 8 H 1.8 0.24 111 9.8 Example 9
I 1.8 0.25 121 9.8 Example 10 J 1.5 0.25 123 2.3 Example 11 K 1.5
0.25 148 2.3 Example 12 L 1.2 0.25 161 6.3 Example 13 M 2.0 0.25 93
12.1 Example 14 N 4.2 0.21 179 6.26 Example 15 O 3.8 0.21 134 11.02
Example 16 P 3.2 0.25 45 3.7 Example 17 Q 3.3 0.24 186 4.5 Example
18 R 3.4 0.23 134 5.5 Example 19 S 3.2 0.25 125 5.5 Example 20 T
3.1 0.25 143 6.2 Example 21 U 2.9 0.21 164 16.9 Example 22 V 2.7
0.25 173 14.5 Example 23 W 3.8 0.25 202 9.1 Example 24 X 3.7 0.26
211 10.4 Example 25 Y 3.1 0.28 173 10.0 Example 26 Z 3.0 0.26 203
9.4 Example 27 AA 3.2 0.24 155 18.2 Example 28 AB 5.9 0.25 149 2.2
Example 29 AC 3.5 0.25 140 15.2 Example 30 AD 3.5 0.30 60 10.2
Comparative AE 0.5 0.24 Not exist 3.8 Example 1 Comparative AF 1.5
-- Not exist 0.5 Example 2 Comparative AG 2.5 -- Not exist 2.4
Example 3 Comparative AH 3.1 0.25 129 Not exist Example 4
[0211] The CHN analysis was performed for the metallic copper
powders of samples N and Q to estimate the amounts of gelatin and
of formic acid. Specifically, the amount of gelatin was calculated
from the ratio of CHN components in the gelatin, and the residual
organic content was estimated as the amount of formic acid and the
like. The results are shown in Table 4. In the sample Q in which
formic acid was added, the organic content originating in formic
acid and the like was large, and it is suggested that formic acid
is adsorbed on the surface. The CHN analysis was performed using
Vario III CHN Elemental Analyzer manufactured by Elementar
Analysensysteme GmbH, capable of analyzing the amount of C, H, and
N with a TCD (Thermal conductivity detector) by burning and
gasifying an organic component on the surface of each powder and
separating the gas with a column.
TABLE-US-00004 TABLE 4 Formic acid and Total amount Sam- Gelatin
[wt %] the like [wt %] of CHN [wt %] ple C H N C H N C H N N 0.50
0.08 0.18 0.01 0.00 0.00 0.51 0.08 0.18 Q 0.37 0.06 0.13 0.14 0.02
0.00 0.51 0.08 0.13
Production 1 of Metallic Copper-Containing Film (Heating at
300.degree. C. under Nitrogen Atmosphere)
[0212] Copper pastes were prepared by mixing 10 g of each of the
samples (A to AG) obtained in the Examples and the Comparative
Examples, 3.5 g of a vehicle (resin: 20% by mass of ethyl cellulose
N200 and solvent: terpineol), and 6.5 g of terpineol, and then
kneading the resultant mixture with a three-roll mill. Each of the
prepared copper pastes was applied on an alumina substrate with an
applicator and fired using an atmosphere tube furnace at
300.degree. C. for one hour under a nitrogen atmosphere to prepare
metallic copper-containing films. The specific resistance values of
the obtained metallic copper-containing films were measured using
MCP-T610 Loresta GP manufactured by Mitsubishi Chemical Analytech
Co., Ltd. by a direct current four-terminal method. Thereafter, the
cross sections were observed with a scanning electron microscope to
measure the film thicknesses, and the volume resistance values were
calculated. The results are shown in Table 5. The volume resistance
values are 1.times.10.sup.-2 .OMEGA.cm or less in all the samples
of the Examples. And, it is presumed that the existence state, the
ratio, the particle diameter, the aggregation state, and the like
of the fine metallic copper particles and the large diameter
metallic copper particle give an influence on the results.
Moreover, it is presumed that the existence state, the ratio, the
particle diameter, the aggregation state, and the like of the
metallic copper particle (i.e. composite particle) and the small
metallic copper particles give an influence on the results.
Alternatively, it is presumed that because formic acid existing on
the surface is easy to disappear at low temperatures, the sintering
was facilitated. On the other hand, in all the samples of the
Comparative Examples, the volume resistance values were
1.times.10.sup.2 .OMEGA.cm or more.
TABLE-US-00005 TABLE 5 Volume Film resistance value thickness
Sample [.OMEGA. cm] [.mu.m] Example 1 A 9.20E-05 10.1 Example 2 B
2.40E-03 11.7 Example 3 C 5.70E-04 11.1 Example 4 D 4.40E-04 17.1
Example 5 E 1.00E-04 7.4 Example 6 F 2.10E-04 11.8 Example 7 G
1.50E-04 9.5 Example 8 H 6.60E-03 10.1 Example 9 I 1.60E-03 15.5
Example 10 J 6.10E-03 9.9 Example 11 K 7.40E-03 10.5 Example 12 L
3.70E-03 12.4 Example 13 M 3.90E-03 11.2 Example 14 N 4.50E-05 12.0
Example 15 O 6.52E-05 11.1 Example 16 P 1.10E-04 10.5 Example 17 Q
5.00E-05 11.3 Example 18 R 5.80E-05 11.8 Example 19 S 1.90E-03 10.5
Example 20 T 1.10E-04 8.5 Example 21 U 2.20E-05 9.8 Example 22 V
3.50E-05 11.6 Example 23 W 4.20E-05 11.4 Example 24 X 2.30E-05 11.5
Example 25 Y 1.10E-04 10.8 Example 26 Z 3.60E-05 10.2 Example 27 AA
5.10E-05 11.2 Example 28 AB 1.20E-04 11.0 Example 29 AC 8.00E-05
10.9 Example 30 AD 6.55E-05 11.2 Comparative AE 8.60E+04 14.6
Example 1 Comparative AF 1.10E+04 15.1 Example 2 Comparative AG
5.50E+02 11.5 Example 3
[0213] Next, metallic copper-containing films were prepared in the
same manner as "Production 1 of Metallic Copper-Containing Film"
described above, except that the metallic copper particles each of
which was prepared by mixing the sample W and the sample X in a
ratio as shown in Table 6 were used, and the volume resistance
values were measured for the metallic copper-containing films. The
results are shown in Table 6. The volume resistance values can be
further reduced by mixing the sample W and the sample X in a manner
as described in the
[0214] Table and preparing pastes thereof. The similar effect can
be also expected by mixing the metallic copper particle according
to the present invention and a commercially available copper
powder.
TABLE-US-00006 TABLE 6 Sample Sample Volume resistance W[g] X[g]
value [.OMEGA. cm] Example 31 5 0 5.10E-05 Example 32 4 1 2.15E-05
Example 33 3 2 2.20E-05 Example 34 2 3 5.30E-05 Example 35 1 4
6.40E-05 Example 36 0 5 1.20E-04
Production 2 of Metallic Copper-Containing Film (Sintering with
Plasma)
[0215] Copper pastes were prepared using sample A obtained in the
Examples and sample AF obtained in the Comparative Examples
according to the above method. Each copper paste was applied on a
PET film with an applicator to prepare each metallic
copper-containing film. Thereafter, plasma treatment was performed
using Micro Labo-PS manufactured by Nissin Inc. under the following
condition, and thereby each metallic copper-sintered film was
obtained.
[0216] First of all, the metallic copper-containing film was placed
on a stage heated at 100.degree. C. in the plasma apparatus to
perform heating at a predetermined time of 180 seconds or 30
seconds. Thereafter, the pressure inside the apparatus was reduced
for 60 seconds, 3% H.sub.2--He gas was introduced to the apparatus
for 30 seconds, and plasma irradiation was performed for 180
seconds. After performing the plasma treatment, cooling was
performed by purging N2 gas for 90 seconds to obtain a metallic
copper-sintered film (film thickness of 10 .mu.m). The results are
shown in Table 7. It has been found that a metallic
copper-containing film having a low resistance can be produced,
even through plasma treatment is performed, by the use of the
metallic copper particle according to the present invention.
TABLE-US-00007 TABLE 7 Treated base Heater Volume resistance Sample
material temperature value [.OMEGA. cm] Example 1 A PET 100.degree.
C. 2.26E-04 Comparative AF PET 100.degree. C. O.L. Example 2 * In
the table, O.L. represents a value equal to or more than the upper
limit of measurement of the measurement apparatus. The value is
roughly 1 .times. 10.sup.+4 .OMEGA. cm or more, while it depends on
the film thickness.
Production 3 of Metallic Copper-Containing Film (Heating at
120.degree. C. in the Air)
[0217] Copper pastes were prepared by mixing 5 g of each of the
samples (A to AH) obtained in the Examples and the Comparative
Examples, a phenol resin (0.62 g of Resitop: PL-5208 (containing
59% by weight of phenol resin as an active ingredient)), and 0.26 g
of ethylene glycol monobutyl ether acetate using a deaerating
stirrer, and then kneading the resultant mixture with a three-roll
mill. Each of the prepared copper pastes was applied on an alumina
substrate with an applicator, and fired at 120.degree. C. for 10
minutes in a natural convection type drier to prepare metallic
copper-containing films each of which has a film thickness of about
25 .mu.m. The specific resistance values of the obtained metallic
copper-containing films were measured using MCP-T610 Loresta GP
manufactured by Mitsubishi Chemical Analytech Co., Ltd. by a direct
current four-terminal method. Thereafter, the cross sections were
observed with a scanning electron microscope to measure the film
thicknesses, and the volume resistance values were calculated based
on the specific resistance values. The results are shown in Table
8. From the fact that low volume resistance values are obtained by
firing at a low temperature of 120.degree. C., it can be said that
the material according to the present invention is excellent in
sinterability at a low temperature. Moreover, FIGS. 36 and 37 show
an SEM image of the cross section in the metallic copper-containing
film of the sample Q produced in Example 17. It was confirmed from
these SEM images that the metallic copper particles according to
the present invention are sintered by firing at a low temperature
of 120.degree. C. in the air.
TABLE-US-00008 TABLE 8 Volume resistance value Sample [.OMEGA. cm]
Example 1 A 1.90E-02 Example 2 B 5.00E-02 Example 3 C 8.20E-02
Example 4 D 7.50E-02 Example 5 E 9.80E-02 Example 7 G 1.30E-01
Example 8 H 2.50E-01 Example 9 I 2.50E-01 Example 10 J 3.10E-01
Example 11 K 9.50E-02 Example 12 L 9.20E-02 Example 13 M 8.30E-02
Example 14 N 4.40E+01 Example 15 O 5.90E-02 Example 16 P 4.80E-02
Example 17 Q 2.10E-03 Example 18 R 3.70E-01 Example 19 S 1.60E-01
Example 20 T 2.80E+00 Example 21 U 6.70E-02 Example 22 V 7.40E-03
Example 23 W 5.10E-03 Example 24 X 2.00E-03 Example 25 Y 2.00E-03
Example 26 Z 3.10E-03 Example 27 AA 5.00E-03 Example 29 AC 8.05E-03
Example 30 AD 1.20E-02 Comparative AE O.L. Example 1 Comparative AF
O.L. Example 2 Comparative AG O.L. Example 3 Comparative AH O.L.
Example 4 * In the table, O.L. represents a value equal to or more
than the upper limit of measurement of the measurement apparatus.
The value is roughly 1 .times. 10.sup.+4 .OMEGA. cm or more, while
it depends on the film thickness.
Production of Metallic Paste
[0218] Metallic pastes (Cu solid content of 75% by mass) were
prepared by mixing 9 g of each of the samples (A, C, E, J, N, Q,
AB, AF, AG) obtained in the Examples and the Comparative Examples,
1 g of a vehicle (resin: 20% by mass of ethyl cellulose N200 and
solvent: terpineol), and 2 g of terpineol and kneading the
resultant mixture with a three-roll mill. The viscosity of the
metallic paste was measured for each paste produced with a B type
viscometer (model HB DV-I+) manufactured by Brookfield AMETEK
setting the measurement temperature at 20.degree. C. and using
CPE-52 as a corn spindle. The viscosity (.eta.a) at a low shear
rate (10 [1/sec]) and the viscosity (.eta.b) at a high shear rate
(100 [1/sec]) were measured, and the value of the viscosity
(.eta.a) was divided by the value of the viscosity (.eta.b) to
calculate a thixotropy index (TI) value. These results are shown in
Table 9.
[0219] In the pastes (i.e. metallic pastes) using the metallic
copper particles of the Examples according to the present
invention, the TI values are dominantly higher (specifically, TI
values are 3.0 or more) than those in the Comparative Examples. For
this reason, for example, in the screen printing, the fluidity of
the metallic paste during continuous printing becomes favorable,
and a thick film can be obtained after completion of patterning on
a substrate. Moreover, cracks, disconnection, short-circuits,
bleeding, and the like are suppressed, and thick films are
reproducibly obtained during continuous printing. Furthermore, in
printing, such as inkjet printing, during which a high shear force
is applied to the metallic paste, ejection of the metallic paste
from holes can be made smooth, and fixing of the metallic paste to
a printing medium becomes favorable.
TABLE-US-00009 TABLE 9 Viscosity [mPa s] TI Sample .eta. a .eta. b
(.eta. a/.eta. b) Example 1 A 31500 6415 4.91 Example 3 C 26500
6000 4.42 Example 5 E 28500 5500 5.18 Example 10 J 35146 5015 7.01
Example 14 N 25152 7055 3.57 Example 17 Q 22700 5159 4.40 Example
28 AB 58260 10820 5.38 Comparative AF 23300 8200 2.84 Example 2
Comparative AG 35688 12000 2.97 Example 3
Industrial Applicability
[0220] According to the present invention, a metallic copper
particle which can be fired under a nonreducing atmosphere such as
nitrogen and which is excellent in sinterability at a lower
temperature can be simply produced. The metallic copper particle
can be used in materials for securing electrical conduction,
materials for antistatic, materials for shielding electromagnetic
waves, materials for giving metallic luster or antibacterial
properties, and other materials, and can be used particularly in
uses for forming a fine electrode and a fine circuit-wiring pattern
such as a printed wiring board, making use of the electrical
conductivity of the metallic copper-containing film, in uses for
joining chips and substrates, and in design and decoration uses
making use of metallic color tone of the metallic copper-containing
film.
* * * * *