U.S. patent application number 11/017778 was filed with the patent office on 2005-07-21 for metal-containing resin particle, resin particle, electronic circuit substrate, and method of producing electronic circuit.
Invention is credited to Aoki, Hideo, Takubo, Chiaki, Yamaguchi, Naoko.
Application Number | 20050158527 11/017778 |
Document ID | / |
Family ID | 34746913 |
Filed Date | 2005-07-21 |
United States Patent
Application |
20050158527 |
Kind Code |
A1 |
Yamaguchi, Naoko ; et
al. |
July 21, 2005 |
Metal-containing resin particle, resin particle, electronic circuit
substrate, and method of producing electronic circuit
Abstract
According to one mode of the present invention, metal-containing
resin particles comprising a resin containing a thermosetting resin
at 50 wt % or more and having a rate of moisture absorption from
500 to 14500 ppm, and fine metal particles contained in the resin,
is provided.
Inventors: |
Yamaguchi, Naoko;
(Yokohama-shi, JP) ; Aoki, Hideo; (Yokohama-shi,
JP) ; Takubo, Chiaki; (Tokyo, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER
LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
34746913 |
Appl. No.: |
11/017778 |
Filed: |
December 22, 2004 |
Current U.S.
Class: |
428/209 ;
257/E23.075; 428/558; 428/559; 428/560 |
Current CPC
Class: |
H05K 2201/0212 20130101;
H05K 2201/0347 20130101; Y10T 428/24917 20150115; H01L 2924/0002
20130101; Y10T 29/4916 20150115; H05K 2203/0517 20130101; Y10T
428/12111 20150115; H01L 2924/0002 20130101; Y10T 428/12097
20150115; Y10T 29/49158 20150115; Y10T 428/12104 20150115; G03G
15/6585 20130101; H01L 2924/00 20130101; Y10T 29/49128 20150115;
H05K 3/4664 20130101; H05K 3/246 20130101; Y10T 29/49155 20150115;
H05K 3/1266 20130101; H01L 23/49883 20130101; H05K 1/095
20130101 |
Class at
Publication: |
428/209 ;
428/558; 428/559; 428/560 |
International
Class: |
B32B 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 26, 2003 |
JP |
P2003-435758 |
Claims
What is claimed is:
1. A metal-containing resin particle, comprising: a resin
containing 50 wt % or more of a thermosetting resin, and having a
rate of moisture absorption from 500 to 14500 ppm; and a fine metal
particle contained in said resin.
2. The metal-containing resin particle according to claim 1,
wherein said resin has the rate of moisture absorption from 4000 to
8000 ppm.
3. The metal-containing resin particle according to claim 1,
wherein the thermosetting resin comprises a B-stage thermosetting
resin.
4. The metal-containing resin particle according to claim 1,
wherein said fine metal particle is at least one kind of the fine
metal particles selected from the group consisting of platinum
(Pt), palladium (Pd), copper (Cu), gold (Au), nickel (Ni), and
silver (Ag).
5. A resin particle comprising: a resin containing 50 wt % or more
of a thermosetting resin, and having the rate of moisture
absorption from 500 to 14500 ppm.
6. The resin particle according to claim 5, wherein said resin has
the rate of moisture absorption from 4000 to 8000 ppm.
7. The resin particle according to claim 5, wherein said
thermosetting resin comprises a B-stage thermosetting resin.
8. An electronic circuit substrate, comprising: a substrate; a
metal-containing resin layer formed on said substrate, and formed
by using the metal-containing resin particle according to claim 1;
and a plating layer formed on said metal-containing resin layer by
using said fine metal particle as a kernel.
9. The electronic circuit substrate according to claim 8, further
comprising: a resin layer formed on said plating layer and formed
by using the resin particle according to claim 5.
10. An electronic circuit substrate, comprising: a substrate; a
plating layer formed on said substrate; and a resin layer formed on
said plating layer and formed by using the resin particle according
to claim 5.
11. A method of producing an electronic circuit, comprising:
forming a metal-containing resin layer in an environment at 70% or
less of relative humidity, wherein said forming of the
metal-containing resin layer comprises, forming a visible image on
the surface of a photoconductor on which an electrostatic latent
image is formed by electrostatically attaching said
metal-containing resin particles composed of a resin containing 50
wt % or more of a thermosetting resin and having the rate of
moisture absorption from 500 to 14500 ppm, and fine metal particles
contained in said resin; and transferring the visible image
composed of said metal-containing resin particles and formed on the
surface of said photoconductor onto a substrate.
12. The method of producing an electronic circuit according to
claim 11, wherein said resin has the rate of moisture absorption
from 4000 to 8000 ppm.
13. The method of producing the electronic circuit according to
claim 11, wherein said thermosetting resin comprises a B-stage
thermosetting resin.
14. The method of producing the electronic circuit according to
claim 11, wherein said fine metal particle is at least one kind of
the fine metal particles selected from the group consisting of
platinum (Pt), palladium (Pd), copper (Cu), gold (Au), nickel (Ni),
and silver (Ag).
15. The method of producing the electronic circuit according to
claim 11, further comprising: forming a plating layer on the
metal-containing resin layer by using the fine metal particle as a
kernel; and forming a resin layer to be performed in an environment
at 70% or less of relative humidity, wherein said forming of the
resin layer comprises: forming the visible image on the surface of
the photoconductor on which the electrostatic latent image is
formed by electrostatically attaching resin particles composed of
the resin containing 50 wt % or more of a thermosetting resin and
having a rate of moisture absorption from 500 to 14500 ppm; and
transferring the visible image composed of the resin particles and
formed on the surface of the photoconductor onto the plating
layer.
16. The method of producing the electronic circuit according to
claim 15, wherein the resin in the resin particle has a rate of
moisture absorption from 4000 to 8000 ppm.
17. The method of producing the electronic circuit according to
claim 15, wherein the thermosetting resin in the resin particle
comprises a B-stage thermosetting resin.
18. A method of producing the electronic circuit, comprising:
forming a resin layer to be performed in an environment at 70% or
less of relative humidity, wherein said forming of resin layer
comprises, forming a visible image on a surface of a photoconductor
on which an electrostatic latent image is formed by
electrostatically attaching resin particles composed of a resin
containing 50 wt % or more of a thermosetting resin and having a
rate of moisture absorption from 500 to 14500 ppm; and transferring
the visible image composed of the resin particles and formed on the
surface of the photoconductor onto a substrate.
19. The method of producing the electronic circuit according to
claim 18, wherein the resin has a rate of moisture absorption from
4000 to 8000 ppm.
20. The method of producing the electronic circuit according to
claim 18, wherein the thermosetting resin comprises a B-stage
thermosetting resin.
Description
CROSS-REFERENCE TO THE INVENTION
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2003-435758, filed on Dec. 26, 2003; the entire contents of which
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a metal-containing resin
particle, a resin particle, an electronic circuit substrate, and a
method of producing the electronic circuit.
[0004] 2. Description of the Related Art
[0005] Conventionally, when producing an electronic circuit
substrate, a conductor pattern is formed by performing resist
coating on a thin metal film, exposure, development, etching, and
the like (refer to Japanese Patent Laid-open Application No. Hei
7-263841). However, this method requires exposure masks for
respective layers, the design and production thereof require a
plenty of time and cost. Besides, when alternation, modification or
the like of the exposure masks becomes necessary, a great influence
is exerted upon the time of delivery or costs of the electronic
circuit substrate.
[0006] Because of these disadvantages, a method of forming an
electronic circuit substrate by printing using electrophotography
is proposed instead of the above method. In this method, an
underlying layer for electroless plating having an arbitrary
pattern is first prepared by using electrophotography with a
metal-containing resin particle. A plating layer is formed on the
underlying layer by electroless plating, and an insulating layer is
formed by electrophotography using resin particles made of resin
only, so that an electronic circuit substrate is formed.
[0007] Incidentally, in order to accurately form an underlying
layer and an insulating layer by electrophotography, it is
necessary to control the amount of electrostatic charge of
metal-containing resin particles and resin particles. Here,
considering heat resistance, thermosetting resin mainly composed of
an epoxy resin is used for both the resin of the metal-containing
resin particles and the resin particles containing resin only.
However, since epoxy radicals are easy to absorb moisture due to
its high hydrophilic nature, there is a problem in that the
electrical resistance of the surfaces of the metal-containing resin
particles and the resin particles is lowered, and the desired
amount of electrostatic charge is difficult to obtain.
BRIEF SUMMARY OF THE INVENTION
[0008] According to one mode of the present invention,
metal-containing resin particles comprising a resin containing a
thermosetting resin at 50 wt % or more and having a rate of
moisture absorption from 500 to 14500 ppm, and fine metal particles
contained in the resin, is provided.
[0009] According to another mode of the present invention, resin
particles comprising a resin containing a thermosetting resin at 50
wt % or more and having a rate of moisture absorption of 500 to
14500 ppm, is provided.
[0010] According to still another mode of the present invention, an
electronic circuit substrate comprising a substrate, a
metal-containing resin layer formed on said substrate and formed by
using the metal-containing resin particles according to claim 1,
and a plating layer formed on said metal-containing resin layer by
using metal particles of said metal-containing resin layer as
kernels is provided.
[0011] According to yet another mode of the present invention, an
electronic circuit substrate comprising a substrate, a plating
layer formed on said substrate, and a resin layer formed on said
plating layer, and formed by using the resin particles according to
claim 5 is provided.
[0012] According to another mode of the present invention, a method
of producing an electronic circuit, comprising forming a
metal-containing resin layer in an environment at 70% or less of
relative humidity, wherein said forming of the metal-containing
resin layer comprises forming a visible image on a surface of a
photoconductor on which an electrostatic latent image is formed, by
electrostatically attaching metal-containing resin particles
composed of a resin containing 50 wt % or more of a thermosetting
resin and having a rate of moisture absorption from 500 to 14500
ppm, and fine metal particles contained in the resin, and
transferring the visible image composed of the metal-containing
resin particles and formed on the surface of the photoconductor on
a substrate, is provided.
[0013] According to still another mode of the present invention, a
method of producing an electronic circuit, comprising forming a
metal-containing resin layer in an environment of 70% or less in
relative humidity, wherein said forming of the resin layer
comprises forming a visible image on a surface of a photoconductor
on which an electrostatic latent image is formed, by
electrostatically attaching resin particles composed of a resin
containing 50 wt % or more of a thermosetting resin and having 500
to 14500 ppm in rate of moisture absorption, and transferring the
visible image composed of the resin particles and formed on the
surface of the photoconductor on the substrate, is provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a flow chart showing a flow of production process
of an electronic circuit substrate relating to an embodiment of the
present invention.
[0015] FIG. 2A to FIG. 2D are schematic diagrams of production
process of the electronic circuit substrate relating to an
embodiment of the present invention.
[0016] FIG. 3 is a view showing the operation of an underlying
layer forming apparatus relating to an embodiment of the present
invention.
[0017] FIG. 4 is a view showing the operation of an insulating
layer forming apparatus relating to an embodiment of the present
invention.
[0018] FIG. 5 is a graph showing relations between a rate of
moisture absorption of metal-containing resin particles and the
amount of electrostatic charge of the metal-containing resin
particles relating to example 1.
[0019] FIG. 6 is a graph showing relations between a rate of
moisture absorption of resin particles and the amount of
electrostatic charge of the resin particles relating to example
2.
[0020] FIG. 7 is a graph showing relations between time for
standing still and a rate of moisture absorption of the resin
particles relating to example 3.
DETAILED DESCRIPTION OF THE INVENTION
[0021] Hereinafter, embodiments will be explained. FIG. 1 is a flow
chart showing a flow of production process of an electronic circuit
substrate relating to an embodiment of the present invention, and
FIG. 2A to FIG. 2D are schematic process drawings of the electronic
circuit substrate relating to an embodiment of the present
invention. FIG. 3 is a view showing operations of an underlying
layer forming apparatus relating to an embodiment of the present
invention, and FIG. 4 is a view showing operations of an insulating
layer forming apparatus relating to an embodiment of the present
invention.
[0022] First, as shown in FIG. 1 and FIG. 2A, an underlying layer 2
for electroless plating is formed by printing using
electrophotography (step 1). The underlying layer 2 can be formed
by using an underlying layer forming apparatus 10 as shown in FIG.
3. Concretely, the underlying layer forming apparatus 10 mainly
comprises a photoconductor drum 11, an electrostatic charger 12, a
laser generator and scanner 13, a developing machine 14, a transfer
printing machine 15, and a fixing apparatus 16. The underlying
layer forming apparatus 10 is placed in a room R where the relative
humidity is 70% or lower.
[0023] In order to form the underlying layer 2, while the
photoconductive drum 11 is turned along the arrow direction first,
a surface potential of the photoconductive drum 11 is uniformly
charged at a fixed potential (for instance, a minus charge) by the
electrostatic charger 12. As a concrete method of charging, a
Scorotron method of charging, a roller method of charging, and a
brush method of charging can be cited.
[0024] Next, a laser beam 13A is irradiated to the photoconductive
drum 11 in response to an image signal by a laser generator and
scanner 13 removing the minus charge in the irradiated portion to
form a charged image (electrostatic latent image) of a prescribed
pattern on the surface of the photoconductive drum 11.
[0025] Then, charged metal-containing resin particles 2A stored in
a developing machine 14 are electrostatically attached on the
electrostatic latent image on the photoconductive drum 11 by means
of a feeder to obtain a visible image. A dry or wet toner transfer
technology in a well known electrophotography type copy system can
be applied to the developing machine 14.
[0026] When the developing machine is a dry type, the
metal-containing resin particles having a particle size from 3 to
50 .mu.m are stored in the developing machine 14. More desirable
particle size of the metal-containing resin particles 2A is from 5
to 10 .mu.m. On the other hand, when the developing machine 14 is a
wet type, the metal-containing resin particles 2A having a particle
size of 3 .mu.m or less are stored in the developing machine 14
together with a liquid which serves as a solvent.
[0027] The metal-containing resin particles 2A stored in the
developing machine 14 are supplied to the photoconductive drum 11
by means of the feeder to develop. At this time, a charged area
development or a discharged area development can be used.
[0028] The metal-containing resin particles 2A are composed of a
resin containing 50 wt % or more of a thermosetting resin having a
rate of moisture absorption from 500 to 14500 ppm and fine metal
particles contained in this resin. A rate of moisture absorption of
the resin is desirably from 4000 to 8000 ppm. The reason for
determining the rate of moisture absorption of the resin to be from
500 to 14500 ppm is as follows. If the rate of moisture absorption
of the resin is less than 500 ppm or more than 14500 ppm, the
amount of electrostatic charge is below 5 .mu.C/g being a lower
limit of the electrostatic charge with which an ordinary dry type
copier is able to develop.
[0029] A thermosetting resin in a B-stage solid at room
temperatures is used as a thermosetting resin to be contained in
the resin. The B-stage refers to a state in which at least one
portion of the thermosetting resin is not hardened but melted when
prescribed heat is applied. As the thermosetting resin in B-stage,
epoxy resin, polyimide resin, phenol resin, bismaleimide resin,
cyanate ester resin, bismaleimide-triazine resin, benzicyclobutene
resin, polyimide resin, polybenzoxazol resin, butadiene resin,
silicone resin, polycarbo-di-imide resin, polyurethane resin and so
on can be used.
[0030] For the fine metal particles, at least one kind of fine
metal particles selected from the group consisting of platinum
(Pt), palladium (Pd), copper (Cu), gold (Au), nickel (Ni), and
silver (Ag) is desirably used. These fine metal particles serve as
kernels for electroless plating and have a catalytic function for
progress of a plating reaction. Among these metal elements,
especially lead or copper is desirably used.
[0031] Then, the visible image (pattern) formed with the
metal-containing resin particles 2A on the surface of the
photoconductive drum 11 is electrostatically transferred onto a
desired substrate 1 from the photoconductive drum 11 by the copier
15. The photoconductive drum 11 is recovered after the transfer by
removing the metal-containing resin particles 2A left on the
surface of the photoconductive drum 11 with a cleaning apparatus
(not shown).
[0032] Then, the metal-containing resin particles 2A in B-stage,
which are transferred onto the substrate 1, are passed through the
fixing apparatus 16 which emits heat or light, so that a
thermosetting resin composing the metal-containing resin particles
2A is melted to form a metal-containing resin layer 2B. Thereafter,
the metal-containing resin layer 2B is heated or irradiated with
light by the fixing apparatus 16 to be hardened so that the
metal-containing resin layer 2B is fixed on the substrate 1.
Through these processes, an underlying layer 2 is formed.
[0033] After forming the underlying layer 2 on the substrate 1, a
plating layer 3 is formed on the underlying layer 2 by electroless
plating using the fine metal particles contained in the underlying
layer 2 as kernels as shown in FIG. 2B(step 2). It should be noted
that though the plating layer 3 is formed by electroless plating in
the present embodiment, the plating layer 3 can be formed by both
of electroless plating and electroplating.
[0034] In order to effectively perform the electroless plating, it
is recommendable to treat at least some of the fine metal particles
to project on the surface of the underlying layer 2 before
performing the electroless plating to the underlying layer. As such
a treatment, for instance, etching with a solvent such as aceton,
isopropanol acid or alkali or the like, or shot blasting,
airblasting and so on can be cited.
[0035] After forming the plating layer 3 on the substrate 1, an
electrically insulative insulating layer 4 is formed on the
substrate 1 as shown in FIG. 2C by printing using the
electrophotography (step 3). The insulating layer 3 can be formed
using an insulating layer forming apparatus 20 nearly similar in
structure to the underlying layer forming apparatus 10. Here, the
insulating layer forming apparatus 20 is placed in the room R
having relative humidity of 70% or lower. A resin particle 4A is
stored in the developing machine 14 in place of the
metal-containing resin particle 2A as shown in FIG. 4.
[0036] In order to form the insulating layer 4, first, while a
photoconductive drum 11 is turned along the arrow direction, a
surface potential of the photoconductive drum 11 is uniformly
charged at a fixed potential (for instance, minus charge) by an
electrostatic charger 12.
[0037] Next, after charging the surface of the photoconductive drum
11, a laser beam 13A is irradiated to the photoconductive drum 11
in response to an image signal by a laser generator 13 removing the
minus charge in the irradiated portion to form a charged image
(electrostatic latent image) of a prescribed pattern on the surface
of the photoconductive drum 11.
[0038] After the electrostatic latent image is formed on the
surface of the photoconductive drum 11, the resin particles 4A
which are charged by the developing machine 14, are
electrostatically attached on the surface of the photoconductive
drum 11 to form a visible image on the surface of the
photoconductive drum 11 (step 33). A dry or wet toner transfer
technology in a well-known electrophotography copying system can be
applied to the developing machine 14.
[0039] When the developing machine 14 is a dry type, the resin
particles 4A having an average particle size from 3 to 50 .mu.m are
stored in the developing machine 14. The more desirable particle
size of the resin particle 4A is from 8 to 15 .mu.m. On the other
hand, when it is a wet type, the resin particles having a particle
size of 3 .mu.m or less are stored together with a liquid being the
solvent in the developing machine 14. When forming the insulating
layer 4, it is desirable for the insulation layer to have a
thickness to some extent in terms of electric insulation, and
therefore, the particle size of the resin particle 4A is desirably
larger than that of the metal-containing resin particle 2A.
[0040] The resin particles 4A stored in the developing machine 14
are supplied to the photoconductive drum 11 by a feeder to be
developed. At this time, a charged area development or a discharged
area development can be used.
[0041] The resin particles 4A are composed of resin containing 50
wt % or more of a thermosetting resin, having the rate of moisture
absorption from 500 to 14500 ppm. The rate of moisture absorption
of the resin is desirably from 4000 to 8000 ppm. The reason for
determining the rate of moisture absorption of the resin to be from
500 to 14500 ppm is as follows. If the rate of moisture absorption
of the resin is less than 500 ppm or more than 14500 ppm, the
amount of electrostatic charge comes to be below 5 .mu.C/g being a
lower limit of the electrostatic charge with which an ordinary dry
type copier is able to develop.
[0042] A thermosetting resin in a B-stage solid state at room
temperatures can be used as a thermosetting resin to be contained
in the resin. As the thermosetting resin in B-stage, epoxy resin,
polyimide resin, phenol resin, bismaleimide resin, cyanate ester
resin, bismaleimide-triazine resin, benzicyclobutene resin,
polyimide resin, polybenzoxazol resin, butadiene resin, silicone
resin, polycarbo-di-imide resin, polyurethane resin and so on can
be used. It is also recommendable to disperse fine particles of
silica or the like contained in the resin particles 4A at a
prescribed ratio, thereby enabling to control the characteristics
such as stiffness, coefficient of thermal expansion and the like
especially in a multilayer wiring substrate, so that improvement in
reliability of substrate can be realized.
[0043] After the visible image (pattern) is formed on the surface
of the photoconductive drum 11, it is electrostatically transferred
onto the desired substrate 1 from the photoconductive drum 11 by
the copier 15. The photoconductive drum 11 after the transfer is
recovered by removing the resin particles 4A left on the surface of
the photoconductive drum 11 with a cleaning apparatus (not
shown).
[0044] After the visible image is transferred onto the substrate 1,
the visible image is heated by the fixing apparatus 16 to soften
the resin particles 4A composing the visible image so that a resin
layer 4B is formed. Then, the resin layer 4B is hardened by heat or
light irradiation with the fixing apparatus 16 to fix the resin
layer 4B on the substrate 1 (step 35). Through the above process,
the insulating layer 4 composed of the resin layer 4B is
formed.
[0045] After forming the insulating layer 4 on the substrate 1, the
electronic circuit forming process from step 1 to step 3 is
repeated to form a multilayered electronic circuit substrate 5 such
as shown in FIG. 2D.
[0046] Since the metal-containing resin particles 2A composed of a
resin containing 50 wt % or more of a thermosetting resin and
having the rate of moisture absorption from 500 to 14500 ppm, and
fine metal particles contained in this resin, are used in the
present embodiment, the amount of charge of the metal-containing
resin particles 2A can be controlled in an optimum range, so that
the underlying layer 2 (metal-containing resin layer 2B) can be
accurately formed.
[0047] Since the resin particles 4A composed of a resin containing
50 wt % or more of a thermosetting resin and having the rate of
moisture absorption from 500 to 14500 ppm are used in the present
embodiment, the amount of charge of the resin particles 4A can be
controlled in an optimum range, so that the insulating layer
4(resin layer 4B) can be accurately formed.
[0048] Since the underlying layer 2 is formed in the room R where
the relative humidity is 70% or less in the present embodiment, the
rate of moisture absorption of the resin in the metal-containing
resin particle 2A can be kept at 14500 ppm or less, so that the
underlying layer 2 (metal-containing resin layer 2B) can be
accurately formed.
[0049] Since the insulating layer 4 is formed in the room R where
the relative humidity is 70% or less in the present embodiment, the
rate of moisture absorption of the resin particle 4A can be kept at
14500 ppm or less, so that the insulating layer 4(resin layer 4B)
can be accurately formed.
(EXAMPLE 1)
[0050] Hereinafter, example 1 will be explained. An optimum range
of the rate of moisture absorption in the resin of the
metal-containing resin particle is studied in the present example
1.
[0051] In the present example, metal-containing resin particles
composed of 50 wt % resin and 50 wt % fine metal particles, having
an average particle size of 7.9 .mu.m are used. Here, the resin is
composed of epoxy resin only and the fine metal particles are
composed of copper (Cu). A plurality of metal-containing resin
particles different in rate of moisture absorption are prepared and
the amount of electrostatic charge at the time when these
metal-containing resin particles are charged is measured. Here, the
rate of moisture absorption of the resin in the metal-containing
resin particles is a value obtained by a calculation in such a
manner that the metal-containing resin particle is kept standing
still for two days in a vacuum environment while weighing the resin
particle. A state at which nearly no change of weight is recognized
is taken as a dry state of the resin particle, and the rate of
moisture absorption is calculated by dividing a change in weight of
the resin since then with the weight of the resin in the dry
state.
[0052] The result of the study will be described below. FIG. 5 is a
graph showing relations between the rate of moisture absorption of
the resin in the metal-containing resin particle and the amount of
electrostatic charge of the metal-containing resin particle
relating to the present example. As shown in FIG. 5, when the rate
of moisture absorption is 458 ppm, the amount of the electrostatic
charge is 4.76 .mu.C/g. This is due to existence of a
metal-containing resin particle which causes reverse charging. On
the other hand, when the rate of moisture absorption is 15424 ppm,
the amount of charge is 3.52 .mu.C/g. This is because the
electrical resistance on the surface of the metal-containing resin
particle is lowered, which makes the charging thereon difficult.
The amounts of electrostatic charge in either cases are below 5
.mu.C/g, the value being a lower limit of the electrostatic charge
with which an ordinary dry type copier is able to develop. When
determining the range of rate of moisture absorption to be 5
.mu.C/g or more from this graph, it is found that when the rate of
moisture absorption is from 500 ppm to 14500 ppm, the amount of
electrostatic charge becomes 5 .mu./g or more. From this result,
the optimum range in rate of moisture absorption of the resin in
the metal-containing resin particle is confirmed to be from 500 ppm
to 14500 ppm.
(EXAMPLE 2)
[0053] Hereinafter, example 2 will be explained. In the present
example, an optimum range of the rate of moisture absorption in the
resin particle is studied.
[0054] In the present example, resin particles composed of epoxy
resin only, having an average particle size of 7.9 .mu.m are used.
A plurality of resin particle samples different in rate of moisture
absorption are prepared, and the amount of electrostatic charge at
the time when these resin particles are charged is measured. Here,
the rate of moisture absorption of the resin is a value obtained by
a calculation in such a manner that the resin particle is kept
standing still for two days in a vacuum environment while weighing
the resin particle. A state at which nearly no change of weight is
recognized is taken as a dry state of the resin particle, and the
rate of moisture absorption is calculated by dividing a change in
weight of the resin since then with the weight of resin particle in
the dry state.
[0055] The result of the study will be described below. FIG. 6 is a
graph showing relations between the rate of moisture absorption of
the resin particle and the amount of electrostatic charge of the
resin particle relating to the present example. As shown in FIG. 6,
when the rate of moisture absorption is 443 ppm, the amount of the
electrostatic charge is 4.82 .mu.C/g. This is due to existence of a
resin particle which causes reverse charging. On the other hand,
when the rate of moisture absorption is 15320 ppm, the amount of
charge is 4.10 .mu.C/g. This is because the electrical resistance
on the surface of the resin particle is lowered, which makes the
charging thereon difficult. The amounts of electrostatic charge in
either cases are below 5 .mu.C/g, the value being a lower limit of
the electrostatic charge with which an ordinary dry type copier is
able to develop. When determining the range of rate of moisture
absorption to be 5 .mu.C/g or more from this graph, it is found
that when the rate of moisture absorption is from 500 ppm to 14500
ppm, the amount of electrostatic charge becomes 5 .mu./g or more.
From this result, the optimum range in rate of moisture absorption
of the resin particle is confirmed to be from 500 ppm to 14500 ppm.
The reason for that the optimum range in the rate of moisture
absorption of the resin of the metal-containing resin particle is
the same as that of the resin particle is as follows. Since 89% in
volume of the metal-containing resin particle containing 50 wt % of
copper (Cu) is resin, the surfaces of both resin are nearly equal,
as long as the average particle size of the metal-containing resin
particles is the same as that of the resin particles.
(EXAMPLE 3)
[0056] Hereinafter, example 3 will be explained. In the present
example, the relative humidity of an environment, at which the rate
of moisture absorption of the resin particle is 14500 ppm or less
is studied.
[0057] In the present example, two kinds of resin particle samples
composed of epoxy resin only, having average particle sizes of 8.5
.mu.m and 11.4 .mu.m respectively, are prepared, and the rates of
moisture absorption of the resin particles when these resin
particles are kept standing still in the environment having
relative humidity (R.H.) of 70% and 80% respectively are
measured.
[0058] The result will be described below. FIG. 7 is a graph
showing relations between the time for standing still and the rate
of moisture absorption of the resin particle relating to the
present example. As shown in FIG. 7, it is confirmed that the rate
of moisture absorption of the resin particle is nearly saturated
for about six hours without depending on the average particle size,
and becomes constant thereafter. Also confirmed is that the rate of
moisture absorption of the resin particle differs depending on the
relative humidity of the environment where the resin particle is
kept standing still. More concretely, when the resin particle is
kept standing still in an environment at 70% R.H., the rate of
moisture absorption becomes constant at around 14400 ppm, and when
the resin particle is kept standing still in an environment at 80%
R.H., the rate of moisture absorption becomes constant at around
17300 ppm. From this result, it is confirmed that a resin particle
having the rate of moisture absorption of 14500 ppm or less can be
obtained when the resin particle is kept standing still in an
environment at 70% R.H. The smaller the average particle size of
the resin particles, the greater the surface area per unit mass
becomes. Accordingly, though the resin particles having an average
particle size of 8.5 .mu.m have the rate of moisture absorption
about 50 ppm larger than the resin particles having an average
particle size of 11.4 .mu.m, it is considered that an environmental
relative humidity has a larger influence upon the rate of moisture
absorption than the average particle size, there is no significant
difference within a range of actual average particle sizes of the
resin particles.
[0059] It should be noted that the present invention is not limited
to the content of description in the above-described embodiment,
structures, materials, arrangements of respective members, and the
like can be appropriately modified within the meaning and range of
equivalency of the present invention.
* * * * *