U.S. patent application number 11/127252 was filed with the patent office on 2005-09-29 for process for producing noble-metal type fine-particle dispersion, coating liquid for forming transparent conductive layer, transparent conductive layered structure and display device.
This patent application is currently assigned to Sumitomo Metal Mining Co., Ltd.. Invention is credited to Suekane, Yukiko, Yukinobu, Masaya.
Application Number | 20050214522 11/127252 |
Document ID | / |
Family ID | 28046112 |
Filed Date | 2005-09-29 |
United States Patent
Application |
20050214522 |
Kind Code |
A1 |
Yukinobu, Masaya ; et
al. |
September 29, 2005 |
Process for producing noble-metal type fine-particle dispersion,
coating liquid for forming transparent conductive layer,
transparent conductive layered structure and display device
Abstract
A process for producing a noble-metal type fine-particle
dispersions, having the steps of an agglomeration step of add ing a
hydrazine solution to a dispersion in which primary particles of
noble-metal type fine particles have been made to stand
monodisperse in a solvent, to destabilize the dispersibility of the
noble-metal type fine particles in the dispersion and cause the
plurality of primary particles in the noble-metal type fine
particles to agglomerate in the form of chains to obtain a
dispersion of chainlike agglomerates; and a stabilization step of
adding a hydrogen peroxide solution to the dispersion of the
chainlike agglomerates obtained, to decompose and remove the
hydrazine to stabilize the dispersibility of the chainlike
agglomerates in the dispersion.
Inventors: |
Yukinobu, Masaya; (Chiba,
JP) ; Suekane, Yukiko; (Chiba, JP) |
Correspondence
Address: |
WESTERMAN, HATTORI, DANIELS & ADRIAN, LLP
1250 CONNECTICUT AVENUE, NW
SUITE 700
WASHINGTON
DC
20036
US
|
Assignee: |
Sumitomo Metal Mining Co.,
Ltd.
Tokyo
JP
|
Family ID: |
28046112 |
Appl. No.: |
11/127252 |
Filed: |
May 12, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11127252 |
May 12, 2005 |
|
|
|
10390593 |
Mar 19, 2003 |
|
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Current U.S.
Class: |
428/323 |
Current CPC
Class: |
Y10T 428/2991 20150115;
C09K 2323/06 20200801; Y10T 428/25 20150115; B22F 1/0022 20130101;
Y10T 428/24917 20150115; H01B 1/22 20130101; B22F 1/0096 20130101;
B01J 13/0043 20130101; Y10T 428/12889 20150115; B22F 2998/00
20130101; B82Y 30/00 20130101; Y10T 428/1086 20150115; B22F 2998/00
20130101; B22F 1/0022 20130101 |
Class at
Publication: |
428/323 |
International
Class: |
B32B 005/16 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 25, 2002 |
JP |
083031/2002 |
Jan 21, 2003 |
JP |
011782/2003 |
Feb 24, 2003 |
JP |
045596/2003 |
Claims
1-8. (canceled)
9. A transparent conductive layered structure comprising a
transparent double-layer film constituted of: a transparent
conductive layer formed on a transparent substrate by the use of a
transparent conductive layer forming coating liquid; and a
transparent coat layer formed on the transparent conductive layer
by the use of a transparent coat layer forming coating liquid which
contains an inorganic binder, wherein the coating liquid comprises
a solvent and chainlike agglomerates of noble-metal-coated fine
silver particles, having been dispersed in the solvent, and the
chainlike agglomerates of noble-metal-coated fine silver particles
comprise a plurality of primary particles having an average
particle diameter of from 1 nm to 100 nm which stand agglomerated
in the form of chains, and have an average length of from 5 nm to
500 nm.
10. A display device comprising a device main body and a front
panel provided on the front side of the device main body, wherein;
said front panel comprises the transparent conductive layered
structure according to claim 9, which is incorporated setting the
transparent double-layer film on the outside.
11. The transparent conductive layered structure according to claim
9, wherein the transparent conductive layer further comprises from
1 part by weight to 100 parts by weight of fine color-pigment
particles, based on 100 parts by weight of the noble-metal-coated
fine silver particles.
12. A transparent conductive layered structure according to claim
11, wherein said fine color-pigment particles are fine particles of
at least one pigment selected from carbon, titanium black, titanium
nitride, a compound oxide pigment, cobalt violet, molybdenum
orange, ultramarine blue, iron blue, a quinacridone pigment, a
dioxazine pigment, an anthraquinone pigment, a perylene pigment, an
isoindolinone pigment, an azo pigment and a phthalocyanine pigment,
or fine color-pigment particles whose surfaces have been coated
with silicon oxide.
13. A transparent conductive layered structure according to claim
9, wherein said noble-metal-coated fine silver particles are fine
silver particles surface-coated with gold or platinum alone or a
composite of gold and platinum.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a process for producing a
noble-metal type fine-particle dispersion (liquid dispersion) in
which noble-metal type fine particles have been dispersed in a
solvent. More particularly, it relates to improvements in a process
for producing a noble-metal type fine-particle dispersion in which
the noble-metal type fine particles make up chainlike agglomerates,
and also in a coating liquid for forming transparent conductive
layers (hereinafter "transparent conductive layer forming coating
liquid") which is obtained by this process, a transparent
conductive layered structure which is obtained by using the
transparent conductive layer forming coating liquid, and a display
device incorporated with such a transparent conductive layered
structure.
[0003] 2. Description of the Related Art
[0004] At present, in cathode ray tubes (CRTs; also called Braun
tubes) used as computer displays and so forth, it is required for
their display screens to be easy to watch and not to cause visual
fatigue. Moreover, any ill influence on human bodies by
low-frequency electromagnetic waves generated from CRTs is recently
worried about, and it is desired for such electromagnetic waves not
to leak outside. Against the leakage of such electromagnetic waves,
it can be prevented by forming a transparent conductive layer on
the front-panel surface of a display. For example, for preventing
the leakage of electromagnetic waves (i.e., electric-field
shielding), it is required to form at least a transparent
conductive layer with a low resistance of 10.sup.6 .OMEGA./square
or less, preferably 5.times.10.sup.3 .OMEGA./square or less, and
more preferably 10.sup.3 I/square or less.
[0005] Some proposals have been made on such low-resistance
transparent conductive films. For example, proposed are methods
such as a method in which a transparent conductive layer forming
coating liquid in which fine conductive oxide particles of
indium-tin oxide (ITO) or the like or fine metal particles have
been dispersed in a solvent is coated on the front glass (front
panel) of a CRT by spin coating or the like and the coating formed
is dried, followed by baking at a temperature of about 200.degree.
C. to form the transparent conductive layer, a method in which a
transparent conductive tin oxide film (nesa film) is formed on the
front glass (front panel) by high-temperature chemical vapor
deposition (CVD) of tin chloride, and a method in which a
transparent conductive film is formed on the front glass (front
panel) by sputtering of an indium-tin oxide, titanium nitride or
the like.
[0006] The first-mentioned method making use of the transparent
conductive layer forming coating liquid has been a very
advantageous method because it is far simpler and can enjoy a lower
production cost than the latter methods in which the transparent
conductive film is formed by CVD or sputtering.
[0007] However, where, in the first-mentioned method making use of
the transparent conductive layer forming coating liquid, the fine
conductive oxide particles of indium-tin oxide (ITO) or the like
are used as materials for the transparent conductive layer forming
coating liquid, the transparent conductive layer formed has a
surface resistance of as high as 10.sup.4 to 10.sup.6
.OMEGA./square. Hence, this has not been adequate for shielding the
leaking electric fields.
[0008] Meanwhile, in the case of the transparent conductive
layer-forming coating liquid having fine metal particles used
therein, a transparent conductive layer having a low resistance of
from 10.sup.2 to 10.sup.3 .OMEGA./square can be formed although the
film has a little lower transmittance than the coating liquid
making use of ITO. Hence, this is considered to be a promising
method in future.
[0009] As the fine metal particles used in the transparent
conductive layer forming coating liquid, proposed are, as disclosed
in Japanese Patent Applications Laid-open No. 8-77832 and No.
9-55175, particles of noble metals such as silver, gold, platinum,
palladium, rhodium and ruthenium, which may hardly be oxidized in
air. Incidentally, this publication also discloses that fine
particles of a metal other than noble metals as exemplified by
iron, nickel or cobalt may also be used. In practice, however,
oxide films are necessarily formed on the surfaces of such fine
metal particles in the atmosphere, and hence it is difficult to
attain good conductivity as the transparent conductive layer.
[0010] In order to make display screens easy to watch, in CRTs, the
surface of the front panel is subjected to, e.g., anti-glare
treatment so that the screen can be restrained from reflecting
light.
[0011] This anti-glare treatment can be made by a method in which a
finely rough surface is provided to make diffused reflection on the
surface greater. This method, however, can not be said to be
preferable so much because its employment may bring about a low
resolution, resulting in a low picture quality. Accordingly, it is
preferable to make the anti-glare treatment by an interference
method in which the refractive index and layer thickness of a
transparent film is so controlled that the reflected light may
rather interfere destructively with the incident light.
[0012] In order to attain the effect of low reflection by such an
interference method, it is common to employ a film of double-layer
structure formed of a high-refractive-index film and a
low-refractive-index film each having an optical film thickness set
at 1/4 .lambda. and 1/4 .lambda., or 1/2 .lambda. and 1/4 .lambda.,
respectively (.lambda.: wavelength). The film formed of fine
particles of indium-tin oxide (ITO) as mentioned above is also used
as a high-refractive-index film of this type.
[0013] In metals, among parameters constituting an optical constant
n-ik (n: refractive index; i.sup.2=-1; k: extinction coefficient),
the value of n is small but the value of k is great, and hence,
also when the transparent conductive layer formed of fine metal
particles is used, the effect of low reflection that is
attributable to the interference of light can be attained by the
double-layer structure as in the case of ITO (a
high-refractive-index film).
[0014] In recent years, in addition to the above characteristics
such as good conductivity and low reflectance, as CRT screens are
made flatter, transparent conductive layered structures in which
the transparent conductive layer of this type has been formed are
further demanded to have characteristics by which their
transmittance can be adjusted within a stated range lower than 100%
(stated specifically from 40% to 95%, and commonly from 40% to 75%)
to improve the contrast of images. To meet such a demand, it is
also common to mix fine color-pigment particles or the like in the
transparent conductive layer forming coating liquid.
[0015] Here, the reason why the transparent conductive layer having
a low transmittance is formed in flat-screen CRTs is as follows:
Face panels (front panels) of the flat-screen CRTs have a structure
that the outer surface of the panel is flat and the inner surface
thereof has a curvature. Hence, the face panel differ in thickness
between the screen center and its periphery. This causes in-plane
non-uniformity of brightness when conventional color glass (e.g.,
semi-tinted glass; transmittance: about 53%) is used in panel
glass. Accordingly, a high-transmittance panel glass and a
low-transmittance transparent conductive layer are combined so as
to achieve both the in-plane uniformity of brightness and the
improvement in contrast (the contrast is improved as the
transmittance is lowered).
[0016] However, there has also been a problem that the addition of
fine color-pigment particles or the like tends to make the
transparent conductive layer have a little low conductivity.
[0017] Now, for a conductive layer having fine metal particles used
therein, it is desirable that, since metals are originally not
transparent to visible light rays, fine metal particles in a
quantity as small as possible form conducting paths in the
transparent conductive layer in a good efficiency in order to
achieve both the high transmittance and the low resistance in the
above transparent conductive layer. That is to say, as structure of
a conductive layer formed by coating on a substrate a commonly
available transparent conductive layer forming coating liquid
composed chiefly of a solvent and fine metal particles, and drying
the coating formed, it is necessary for the layer to have a
structure in which microscopic openings (spaces) have been
introduced into a layer of fine metal particles, i.e., a network
structure.
[0018] Formation of such a network structure can provide a
transparent conductive layer having low resistance and high
transmittance. This is because the network part comprised of fine
metal particles functions as conducting paths on the one hand and
the part of openings formed in the network structure has the
function to improve light ray transmittance, as so presumed.
[0019] As methods of forming the network structure of fine metal
particles, they may include, in rough classification, the following
methods.
[0020] (1) Methods of forming the network structure by causing fine
metal particles to agglomerate one another in the course that the
transparent conductive layer forming coating liquid is coated and
the coating formed is dried to form a film.
[0021] More specifically, a method in which, since the fine metal
particles tend to agglomerate compared with fine oxide particles,
the solvent composition and so forth of the transparent conductive
layer forming coating liquid is appropriately selected so that the
fine metal particles may necessarily agglomerate one another to a
certain extent in the course of coating and drying for film
formation to obtain the network structure (see Japanese Patent
Applications Laid-open No. 9-115438, No. 10-1777, No. 10-142401,
No. 10-182191 and so forth); and
[0022] a method in which an agglomeration-inducing agent, an
agglomeration-accelerating high-boiling solvent or the like is
intentionally further added to the transparent conductive layer
forming coating liquid so as to actively accelerate the
agglomeration between fine metal particles in the course of coating
and drying to obtain a network structure (see Japanese Patent
Applications Laid-open No. 10-110123, No. 2002-38053 and so
forth).
[0023] (2) Methods of forming the network structure by coating a
transparent conductive layer forming coating liquid in which
agglomerates of fine metal particles have been dispersed, and
drying the coating formed.
[0024] More specifically, a method in which a dispersion of fine
metal particles having been made to gather in the form they have
minute holes (i.e., in the form of rings), without bringing primary
particles of the fine metal particles into a uniformly monodisperse
state, is used (see Kogyo Zairyo (Industrial Materials), Vol. 44,
No. 9, 1996, pp. 68-71); and
[0025] a method in which a transparent conductive layer forming
coating liquid in which chainlike agglomerates comprised of fine
metal particles having agglomerated in the form of chains have been
dispersed in advance is used (see Japanese Patent Application
Laid-open No. 2000-124662).
[0026] To compare the methods (1) with the methods (2), the methods
(2) have an advantage that a developed network structure can be
formed with ease because the agglomerates of fine metal particles
have been completed in advance in the transparent conductive layer
forming coating liquid.
[0027] On the other hand, there may be other problem that filters
tend to clog at the time of filtering treatment of the transparent
conductive layer forming coating liquid, or that coating film
defects may occur if the agglomeration of fine metal particles has
proceeded in excess.
[0028] However, the above can be said to be preferable methods from
the viewpoint that a transparent conductive layer having good
conductivity can be formed as long as the agglomerates of fine
metal particles that have been formed in advance in the transparent
conductive layer forming coating liquid have sufficiently high
dispersion stability and the size of the agglomerates has been
controlled to be hundreds of micron or less.
[0029] Here, in the methods (2), as methods of forming the
agglomerates of fine metal particles in advance in the transparent
conductive layer forming coating liquid (or a fine-metal-particle
dispersion used in producing the transparent conductive layer
forming coating liquid), the following methods (a) to (e) are known
as disclosed in, e.g., Japanese Patent Applications Laid-open No.
2000-124662, No. 11-329071 and No. 2000-196287.
[0030] (a) A method in which a water-soluble salt such as sodium
salt, potassium salt, calcium salt or ammonium salt, an acid such
as hydrochloric acid, nitric acid, phosphoric acid or acetic acid
or an alkali such as sodium hydroxide or ammonia is added to a
dispersion of fine metal particles to make the dispersibility of
fine metal particles unstable, to form the agglomerates of fine
metal particles.
[0031] (b) A method in which, at the stage where fine metal
particles dispersed in the transparent conductive layer forming
coating liquid are prepared from an aqueous solution of a metal
salt, the pH and so forth of the aqueous solution are controlled
within stated ranges to form the agglomerates of fine metal
particles.
[0032] (c) A method in which a dispersion of fine metal particles
is kept at tens of degree of temperature which is not higher than
the boiling point of a dispersion solvent, for several hours to
tens of hours to form the agglomerates of fine metal particles.
[0033] (d) A method in which an organic compound such as an alcohol
is added to a dispersion of fine metal particles to control the
polarity of a dispersion solvent, to form the agglomerates of fine
metal particles.
[0034] (e) A method in which a dispersion of fine metal particles
is subjected to mechanical dispersion treatment such as sand mill
treatment or impact dispersion treatment to form the agglomerates
of fine metal particles.
[0035] Now, in the above methods (a) to (d), the methods (a) and
(d) are not practical because they are methods in which the
dispersion stability of fine metal particles is made to lower (the
zeta potential of the system lowers and the stability lowers) to
form the agglomerates and hence, if left as it is, the
agglomeration may gradually proceed as the fine metal particles are
kept unstable. Accordingly, in order to make the stability of the
system higher, it is necessary to remove any destabilization
factor(s) [in the method (a), the water soluble salt, the acid or
the alkali; in the method (d), the organic compound such as an
alcohol]. However, this step is so complicate that these methods
have not been preferable methods.
[0036] The method (c) is a simple method because the dispersion of
fine metal particles may only be kept heated. However, such a
transparent conductive layer forming coating liquid of the kind
that originally the agglomerates are formed by heating at tens of
degree of temperature can not be said to ensure high dispersion
stability of the fine metal particles themselves contained therein.
Hence, there has been a problem that the agglomerates formed have
also a low dispersion stability. If on the other hand the fine
metal particles themselves have a high dispersion stability, it
takes a long time to form the agglomerates by heating at tens of
degree of temperature. Thus, this method can not still be said to
be practical.
[0037] The method (b) is a method in which the agglomerates of fine
metal particles are formed at the stage where the fine metal
particles are prepared from an aqueous metal salt solution. Hence,
there is a problem that the agglomerates further agglomerate one
another and settle in, e.g., a concentrating step taken thereafter
for preparing the transparent conductive layer forming coating
liquid, and further it is necessary to determine the state of
agglomeration of fine metal particles in advance. Thus, this method
has been inconvenient in that the state of agglomeration of the
fine metal particles can not be changed at will in the subsequent
stage.
[0038] In addition, the method (e) is a method in which mechanical
dispersion treatment is carried out to form the agglomerates of
fine metal particles, and hence it has had a problem that it
requires an expensive treatment equipment and also the step of
treatment can not be said to be simple.
SUMMARY OF THE INVENTION
[0039] The present invention was made taking note of the above
problems. Accordingly, an object of the present invention is to
provide, presupposing the transparent conductive layer forming
coating liquid in which agglomerates of fine metal particles have
been dispersed [i.e., those in the method (2)], a process for
producing a noble-metal type fine-particle dispersion by which the
noble-metal type fine-particle dispersion used in this transparent
conductive layer forming coating liquid can be produced simply and
at a low cost.
[0040] Another object of the present invention is to provide a
transparent conductive layer forming coating liquid which can form
on a transparent substrate a transparent conductive layer having
superior high-transmittance and low-reflectance characteristics and
good conductivity and also has superior storage stabibility.
[0041] Still another object of the present invention is to provide
a transparent conductive layered structure formed using this
transparent conductive layer forming coating liquid, and a display
device having the transparent conductive layered structure.
[0042] More specifically, the process for producing a noble-metal
type fine-particle dispersion according to the present invention
presupposes a process for producing a noble-metal type
fine-particle dispersion which contains a solvent and noble-metal
type fine particles having an average particle diameter of from 1
nm to 100 nm, having been dispersed in the solvent, and in which a
plurality of primary particles of the noble-metal type fine
particles stand agglomerate in the form of chains to make up
chainlike agglomerates, wherein;
[0043] the process comprising the steps of:
[0044] an agglomeration step of adding a hydrazine solution to a
dispersion in which primary particles of noble-metal type fine
particles have been made to stand monodisperse in a solvent, to
destabilize the dispersibility of the noble-metal type fine
particles in the dispersion and cause the plurality of primary
particles in the noble-metal type fine particles to agglomerate in
the form of chains to obtain a dispersion of chainlike
agglomerates; and
[0045] a stabilization step of adding a hydrogen peroxide solution
to the dispersion of the chainlike agglomerates obtained, to
decompose and remove the hydrazine to stabilize the dispersibility
of the chainlike agglomerates in the dispersion.
[0046] The transparent conductive layer forming coating liquid
according to the present invention also presupposes the transparent
conductive layer forming coating liquid obtained by the above
process for producing a noble-metal type fine-particle dispersion,
wherein;
[0047] the coating liquid comprises a solvent and chainlike
agglomerates of noble-metal-coated fine silver particles, having
been dispersed in the solvent, and the chainlike agglomerates of
noble-metal-coated fine silver particles comprising a plurality of
primary particles having an average particle diameter of from 1 nm
to 100 nm which stand agglomerate in the form of chains, and having
an average length of from 5 nm to 500 nm.
[0048] Then, the transparent conductive layered structure according
to the present invention comprises a transparent double-layer film
constituted of a transparent conductive layer formed on a
transparent substrate by the use of the above transparent
conductive layer forming coating liquid and a transparent coat
layer formed on this transparent conductive layer by the use of a
transparent coat layer forming coating liquid which contains an
inorganic binder.
[0049] The display device according to the present invention also
presupposes a display device having a device main body and a front
panel provided on the front side of the device main body,
wherein;
[0050] the front panel comprises the above transparent conductive
layered structure, which is incorporated setting its transparent
double-layer film on the outside.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0051] The present invention is described below in detail.
[0052] Specifically, the present invention has been accomplished
upon discovery that the addition of a hydrazine (N.sub.2H.sub.4)
solution to a dispersion of noble-metal type fine particles in
which noble-metal type fine particles have been made monodisperse
in a solvent makes the dispersibility of the noble-metal type fine
particles lower (the zeta potential [absolute value] of the system
lowers), so that the noble-metal type fine particles agglomerate in
the form of chains to form chainlike agglomerates of the
noble-metal type fine particles; that further addition of a
hydrogen peroxide (H.sub.2O.sub.2) solution thereto makes the
hydrazine come decomposed and removed by the action of the hydrogen
peroxide, so that the dispersion stability of the chainlike
agglomerates is again improved (the zeta potential [absolute value]
of the system increases) as the state of their agglomeration is
kept unchanged; and also that a series of such reactions bring only
water (H.sub.2O) and nitrogen gas (N.sub.2) as reaction products,
as shown by the following reaction scheme (1), and are free from
any secondary formation of impurity ions.
N.sub.2H.sub.4+2H.sub.2O.sub.2.fwdarw.4H.sub.2O+N.sub.2.Arrow-up
bold. (1)
[0053] As a specific method of preparing the noble-metal type
fine-particle dispersion according to the present invention in
which the noble-metal type fine particles make up the chainlike
agglomerates, the hydrazine solution and the hydrogen peroxide
solution may respectively only be added to a dispersion containing
the noble-metal type fine particles standing monodisperse, which is
held in, e.g., a glass or plastic container; the former being added
stirring the latter by means of a stirrer or the like.
Incidentally, these solutions may preferably be added little by
little, using a syringe, a pump or the like. Especially in respect
of the hydrazine solution, its addition at a time to the dispersion
containing the noble-metal type fine particles standing
monodisperse is undesirable because there is a possibility of
causing excessive agglomeration in some noble-metal type fine
particles.
[0054] Here, the reason why the addition of the hydrazine solution
may cause agglomeration of the noble-metal type fine particles is
unclear. It is considered that the dispersion stability of the
noble-metal type fine particles lowers because of the action of
hydrazine as alkali ions or the action thereof as a reducing agent
to lower the redox potential of the system.
[0055] As the hydrazine solution, an aqueous solution or organic
solution, or a water and organic-solvent mixed solution, of
hydrazine or hydrazine monohydrate (N.sub.2H.sub.4.H.sub.2O) may be
used. Also, as the hydrogen peroxide solution, an aqueous solution
or organic solution, or a water and organic-solvent mixed solution,
of hydrogen peroxide may be used.
[0056] As to the amount of the hydrazine solution to be added, it
may arbitrarily be set in accordance with the concentration of the
noble-metal type fine particles and the intended degree of
agglomeration of the noble-metal type fine particles. For example,
in the case of a dispersion of noble-metal type fine particles in
which the noble-metal type fine particles are in a concentration of
from 1% by weight to 2% by weight, the hydrazine may preferably be
added in an amount of from 10 ppm to 500 ppm, and more preferably
from 20 ppm to 200 ppm, based on the dispersion of noble-metal type
fine particles. If it is less than 10 ppm, the agglomeration of the
noble-metal type fine particles may come insufficient. Its addition
in an amount of more than 500 ppm is not practical because the
agglomeration of the noble-metal type fine particles may proceed in
excess. Meanwhile, as to the amount of the hydrogen peroxide
solution to be added, it may be in an amount which enables
decomposition of the hydrazine added, and may preferably be in a
value which is stoichiometric to the hydrazine in the reaction
shown by the above reaction scheme (1). However, since the hydrogen
peroxide tends to undergo self-decomposition (decomposed into water
and oxygen gas), it may be used in an excess amount of, e.g., about
1.5 times the stoichiometric value, without any hindrance.
[0057] The state of agglomeration of the chainlike agglomerates in
the noble-metal type fine particles obtained by the production
process of the present invention is controllable at will by
regulating the amount of the hydrazine solution as described above.
It is also controllable by regulating the time (retention time) and
temperature (retention temperature) by and at which the hydrogen
peroxide solution is added after the hydrazine solution has been
added. This is because the state in which the dispersion of the
noble-metal type fine particles has been destabilized by the
hydrazine is maintained until the hydrogen peroxide is added.
However, taking account of utility, it is preferable to set the
retention time to from several minutes to about 1 hour (preferably
from several minutes to about 20 minutes) and the retention
temperature to room temperature (e.g., 25.degree. C.), under
conditions of which the state of agglomeration of the chainlike
agglomerates may be controlled by increasing or decreasing the
amount of the hydrazine solution to be added.
[0058] Here, the noble-metal type fine-particle dispersion
according to the present invention presupposes, as its chief use,
the transparent conductive layer forming coating liquid for forming
a transparent conductive layer on a transparent substrate.
Accordingly, the noble-metal type fine particles in the noble-metal
type fine-particle dispersion must have an average particle
diameter of from 1 nm to 100 nm. This is because, if they have an
average particle diameter of less than 1 nm, it is difficult to
produce the fine particles, and at the same time such too fine
particles can not be dispersed with ease when made into a coating
material, and are not practical. If on the other hand they have an
average particle diameter of more than 100 nm, the visible light
rays may greatly scatter in the transparent conductive layer formed
(i.e., the film may have a high haze value). Incidentally, the
average particle diameter herein termed refers to the average
particle diameter of primary particles constituting the
agglomerates observed on a transmission electron microscope
(TEM).
[0059] As the noble-metal type fine particles, they may include
fine particles of a noble metal selected from gold, silver,
platinum, palladium, rhodium and ruthenium; blended fine particles
made up of a blend of two or more kinds of fine noble-metal
particles; fine alloy particles containing two or more kinds of
noble metals; and noble-metal-coated fine silver particles,
surface-coated with any of the above noble metals except the
silver; any of which may be used.
[0060] Here, to compare specific resistance of silver, gold,
platinum, rhodium, ruthenium, palladium and so forth, the platinum,
rhodium, ruthenium and palladium have a resistivity of 10.6, 4.51,
7.6 and 10.8 .mu..OMEGA..multidot.cm, respectively, which are
higher than 1.62 and 2.2 .mu..OMEGA..multidot.cm of silver and
gold, respectively. Hence, it is considered advantageous to use
fine silver particles or fine gold particles in order to form a
transparent conductive layer having a low surface resistance.
[0061] The use of fine silver particles, however, imposes a
limitation to their use in view of the weatherability that it may
cause a great deterioration due to sulfidation or exposure to
brine. On the other hand, the use of fine gold particles, fine
platinum, particles, fine rhodium particles, fine ruthenium
particles or fine palladium particles can eliminate such a problem,
but can not necessarily be said to be the best when the cost is
taken into account.
[0062] Accordingly, as noble-metal type fine particles which
fulfill the both conditions of weatherability and cost, they may
include noble-metal-coated fine silver particles obtained by
coating the surfaces of fine silver particles with noble metal(s)
other than silver, as exemplified by noble-metal-coated fine silver
particles surface-coated with gold or platinum alone or a composite
of gold and platinum. Incidentally, the present inventors have
already proposed a transparent conductive layer forming coating
liquid which contains such noble-metal-coated fine silver
particles, and a process for producing the same (see Japanese
Patent Applications Laid-open No. 11-228872 and No.
2000-268639).
[0063] Now, where the noble-metal type fine-particle dispersion
according to the present invention is used as the transparent
conductive layer forming coating liquid which is the former's chief
use, a difficulty as stated below may arise if, e.g., the blended
fine particles made up of a blend of two or more kinds of fine
noble-metal particles are used as the noble-metal type fine
particles contained in the transparent conductive layer forming
coating liquid.
[0064] That is, where two or more kinds of fine noble-metal
particles are used in combination as the noble-metal type fine
particles contained in the transparent conductive layer forming
coating liquid, the respective kinds of fine noble-metal particles
tend to localize in the agglomerates because the respective primary
particles constituting the agglomerates are comprised of one kind
of noble metal, even when the respective kinds of fine noble-metal
particles are first agglomerated in the form of chains and then
individual dispersions are mixed or the agglomerating treatment is
carried out after dispersions in which the individual kinds of fine
noble-metal particles stand monodisperse respectively have been
mixed.
[0065] For this reason, when the transparent conductive layer is
formed using the transparent conductive layer forming coating
liquid making use of such blended fine particles, the noble metals
constituting the blended fine particles are not uniformly present
in the transparent conductive layer, so that portions where the
respective kinds of fine noble-metal particles have gathered may
form to adversely affect the characteristics of the transparent
conductive layer formed. For example, portions where fine silver
particles have gathered have especially poor weatherability at such
portions only, and may adversely affect the overall evaluation of
weatherability. Any portions where noble metals having higher
specific resistance than silver have gathered also makes the whole
surface resistance high.
[0066] Accordingly, in the case when the noble-metal type
fine-particle dispersion according to the present invention is used
as the transparent conductive layer forming coating liquid which is
the former's chief use, the noble-metal type fine particles
contained in the transparent conductive layer forming coating
liquid must be the noble-metal-coated fine silver particles.
[0067] Incidentally, in the case when the noble-metal type fine
particles contained in the transparent conductive layer forming
coating liquid are the noble-metal-coated fine silver particles,
noble metals may come into an alloy at the interfaces between the
coat layers of noble-metal-coated fine silver particles and the
fine silver particles as a result of the heat treatment in the
course of film formation, so that there is a case in which the coat
layers are not necessarily constituted of only the noble metal
other than silver (e.g., only gold, platinum or the like). Even in
such a case, however, it follows that each coat layer of each
noble-metal-coated fine silver particle is constituted of the
same-component alloy, and hence any difficulty caused by the
localization stated previously by no means arise.
[0068] Then, the noble-metal type fine-particle dispersion
according to the present invention, when used as the transparent
conductive layer forming coating liquid which is the former's chief
use, may be in the state of a coating liquid that the above
dispersion can be coated as it is, on the transparent substrate
(i.e. the concentration, solvent composition and so forth of the
chainlike agglomerates in the noble-metal type fine-particle
dispersion have been adjusted to the coating liquid for forming the
transparent conductive layer, and hence, using this coating liquid,
the transparent conductive layer may directly be formed on the
transparent substrate), or may be in the state of a dispersion
having the chainlike agglomerates in a high concentration. In the
latter case, an organic solvent or the like may be added to the
dispersion having the chainlike agglomerates dispersed therein in a
high concentration, to make component adjustment (the
chainlike-agglomerate concentration, water concentration and
various organic solvent concentration in the noble-metal type
fine-particle dispersion) so that the coating liquid can be
prepared in a concentration which enables direct formation of the
transparent conductive layer on the transparent substrate.
[0069] In the case when the noble-metal type fine-particle
dispersion is used as the transparent conductive layer forming
coating liquid, fine color-pigment particles may also be added to
the transparent conductive layer forming coating liquid. The mixing
of such fine color-pigment particles enables adjustment of the
transmittance of the transparent conductive layered structure
within a stated range lower than 100% (from 40% to 95%, and
commonly from 40% to 75%). Hence, in addition to various
characteristics such as good conductivity and low reflectance, the
contrast of images can be improved to make display screens easy to
watch, or the demand increasing as CRT screens are made flatter as
stated previously can be met.
[0070] In the transparent conductive layer forming coating liquid
making use of the noble-metal type fine-particle dispersion
according to the present invention, the noble-metal type fine
particles form the chainlike agglomerates in that coating liquid.
Thus, in the transparent conductive layer formed using this coating
liquid, a good network structure formed of the noble-metal type
fine particles is materialized. Hence, the addition of such fine
color-pigment particles may cause less hindrance to the
conductivity of the transparent conductive layer.
[0071] As to the mixing proportion of the fine color-pigment
particles, it may be set within the range of from 1 part by weight
to 100 parts by weight based on 100 parts by weight of the
noble-metal type fine particles.
[0072] As the fine color-pigment particles, usable are, e.g., fine
particles of at least one pigment selected from carbon, titanium
black, titanium nitride, a compound oxide pigment, cobalt violet,
molybdenum orange, ultramarine blue, iron blue, a quinacridone
pigment, a dioxazine pigment, an anthraquinone pigment, a perylene
pigment, an isoindolinone pigment, an azo pigment and a
phthalocyanine pigment, or fine color-pigment particles whose
surfaces have been coated with silicon oxide.
[0073] The process for producing the noble-metal type fine-particle
dispersion making use of the noble-metal-coated fine silver
particles as the noble-metal type fine particles is described below
in greater detail.
[0074] First, a colloidal dispersion of fine silver particles is
made up by a known process [e.g., the Carey-Lea process, Am. J.
Sci., 37, 47 (1889), Am. J. Sci., 38 (1889)]. More specifically, a
mixed solution of an aqueous iron (II) sulfate solution and an
aqueous sodium citrate solution are added to an aqueous silver
nitrate solution to carry out reaction, and the resultant sediment
is filtered and washed, followed by addition of pure water, whereby
a colloidal dispersion of fine silver particles (Ag: 0.1 to 10% by
weight) can simply be made up. This colloidal dispersion of fine
silver particles may be made up by any method so long as fine
silver particles having an average particle diameter of from 1 nm
to 100 nm can be dispersed, without any limitation to the above
method.
[0075] Next, to the colloidal dispersion of fine silver particles
thus obtained, a solution containing a reducing agent and a
solution selected from any of the following (A) to (C) are each
separately dropwise added to thereby coat the surfaces of the fine
silver particles with gold or platinum alone or a composite of gold
and platinum. Thus, a colloidal dispersion of noble-metal-coated
fine silver particles can be obtained (a noble-metal-coated fine
silver particle making step).
[0076] (A) An alkali metal aurate solution or an alkali metal
platinate solution.
[0077] (B) An alkali metal aurate solution and an alkali metal
platinate solution.
[0078] (C) A solution of mixture of an alkali metal aurate and an
alkali metal platinate.
[0079] In this step of making the noble-metal-coated fine silver
particles, a dispersant may optionally be added in a small quantity
to at least one of the colloidal dispersion of fine silver
particles, the solution containing a reducing agent and any of the
solutions (A) to (C), or to each of them.
[0080] The colloidal dispersion of noble-metal-coated fine silver
particles thus obtained may thereafter preferably be subjected to
desalting by dialysis, electrodialysis, ion exchange,
ultrafiltration or the like to lower the concentration of the
electrolyte in the dispersion. This is because colloids may
commonly agglomerate when electrolytes are in a high concentration.
This phenomenon is known also as the Schultz-Hardy's rule.
[0081] Next, the colloidal dispersion of noble-metal-coated fine
silver particles which has-been subjected desalting is subjected to
concentrating treatment. Thus, a dispersion containing the
noble-metal-coated fine silver particles standing monodisperse in a
high concentration is obtained.
[0082] To this dispersion containing the noble-metal-coated fine
silver particles standing monodisperse in a high concentration, the
hydrazine solution is added to cause the noble-metal-coated fine
silver particles to agglomerate. Thereafter, this is retained,
e.g., at room temperature for several minutes to about 1 hour, and
then the hydrogen peroxide solution is added thereto. Thus, a
noble-metal type fine-particle dispersion in which the chainlike
agglomerates of noble-metal-coated fine silver particles sand
disperse in a high concentration is obtained.
[0083] In the case when the noble-metal type fine-particle
dispersion according to the present invention is used as the
transparent conductive layer forming coating liquid, the above
chainlike agglomerates must have an average length of from 5 nm to
500 nm. This is because, if they are in an average length of less
than 5 nm, the action to promote the formation of the network
structure of the transparent conductive layer may be insufficient,
and, if they are in an average length of more than 500 nm, the
noble-metal-coated fine silver particles (chainlike agglomerates)
may come unstable to more tend to agglomerate.
[0084] Next, an organic solvent or the like is added to the
noble-metal type fine-particle dispersion in which the chainlike
agglomerates of noble-metal-coated fine silver particles stand
disperse in a high concentration, to make component adjustment
(fine-particle concentration, water concentration,
high-boiling-point organic solvent concentration and so forth).
Thus, the transparent conductive layer forming coating liquid
containing the chainlike agglomerates of noble-metal-coated fine
silver particles is obtained.
[0085] The concentrating treatment in the colloidal dispersion of
the noble-metal-coated fine silver particles may be carried out by
a conventional method such as reduced-pressure evaporation or
ultrafiltration. By controlling the degree of this concentration,
the water concentration in the noble-metal type fine-particle
dispersion can be controlled within a stated range.
[0086] Here, in the case when the noble-metal type fine-particle
dispersion according to the present invention is used as the
transparent conductive layer forming coating liquid, the
transparent conductive layer forming coating liquid may preferably
be component-adjusted so as to contain, as its composition, from
0.1% by weight to 10% by weight of the noble-metal-coated fine
silver particles (chainlike agglomerates) and from 1% by weight to
50% by weight of water. If the noble-metal-coated fine silver
particles (chainlike agglomerates) are in a content of less than
0.1% by weight, any sufficient conducting performance is not
achievable. If on the other hand they are in a content of more than
10% by weight, the noble-metal-coated fine silver particles
(chainlike agglomerates) come unstable to more tend to agglomerate.
Also, if the water concentration is less than 1% by weight, namely,
if the agglomerating treatment is carried out after the degree of
concentration of the dispersion containing the noble-metal-coated
fine silver particles standing monodisperse has been made greatly
higher, the noble-metal-coated fine silver particles (chainlike
agglomerates) come unstable to more tend to agglomerate like the
above, because the concentration of the noble-metal-coated fine
silver particles (chainlike agglomerates) comes too high. If they
are in a content of more than 50% by weight, the transparent
conductive layer forming coating liquid may have greatly poor
coating properties.
[0087] As the organic solvent used in the noble-metal type
fine-particle dispersion according to the present invention, there
are no particular limitations thereon. It may appropriately be
selected according to coating methods and film-forming conditions
when used as the transparent conductive layer forming coating
liquid. It may include, but is not limited to, e.g., alcohol type
solvents such as methanol (MA), ethanol (EA), 1-propanol (NPA),
isopropanol (IPA), butanol, pentanol, benzyl alcohol and diacetone
alcohol; ketone type solvents such as acetone, methyl ethyl ketone
(MEK), methyl propyl ketone, methyl isobutyl ketone (MIBK),
cyclohexanone and isophorone; glycol derivatives such as ethylene
glycol monomethyl ether (MCS), ethylene glycol monoethyl ether
(ECS), ethylene glycol isoproyl ether (IPC), propylene glycol
methyl ether (PGM), propylene glycol ethyl ether (PE), propylene
glycol methyl ether acetate (PGM-AC) and propylene glycol ethyl
ether acetate (PE-AC); and formamide (FA), N-methylformamide,
dimethylformamide (DMF), dimethylacetamide, dimethyl sulfoxide
(DMSO) and N-methyl-2-pyrrolidone (NMP).
[0088] Also where a colloidal dispersion of the fine particles of a
noble metal selected from gold, silver, platinum, palladium,
rhodium and ruthenium, the blended fine particles made up of a
blend of two or more kinds of fine noble-metal particles or the
fine alloy particles containing two or more kinds of noble metals
is used in place of the colloidal dispersion of the
noble-metal-coated fine silver particles, the noble-metal type
fine-particle dispersion (i.e., the noble-metal type fine-particle
dispersion containing the chainlike agglomerates formed of the
noble-metal type fine particles standing agglomerate in the form of
chains) is obtainable by the production process according to the
present invention.
[0089] Then, using the transparent conductive layer forming coating
liquid making use of the noble-metal type fine-particle dispersion
according to the present invention, a transparent conductive
layered structure may be obtained the main part of which is
constituted of a transparent substrate and a transparent
double-layer film consisting of a transparent conductive layer and
a transparent coat layer which have been formed on the transparent
substrate in order.
[0090] To form the transparent double-layer film on the transparent
substrate, it may be done by a method described below. That is, the
transparent conductive layer forming coating liquid containing the
chainlike agglomerates formed of the noble-metal type fine
particles standing agglomerate in the form of chains may be coated
on the transparent substrate, such as a glass substrate or a
plastic substrate, by a coating process such as spin coating, spray
coating, wire bar coating or doctor blade coating, optionally
followed by drying. Thereafter, a transparent coat layer forming
coating liquid containing an inorganic binder such as silica sol
may be over-coated (top-coated) by the coating process described
above, followed by drying.
[0091] Next, the coating formed is subjected to heat treatment at a
temperature of about, e.g., 50.degree. C. to 350.degree. C. to
cause the coating of the transparent coat layer forming coating
liquid to cure to form the transparent double-layer film.
[0092] In the case when the transparent conductive layer forming
coating liquid according to the present invention, containing the
chainlike agglomerates formed of the noble-metal type fine
particles standing agglomerate in the form of chains, the
noble-metal type fine particles can form conducting paths in a good
efficiency in the transparent conductive layer and hence a
transparent conductive layer having a very good conductivity can be
obtained, compared with cases in which conventional transparent
conductive layer forming coating liquids in which individual
noble-metal type fine particles do not stand agglomerate are used.
In other words, in the case of the transparent conductive layer
forming coating liquid containing the chainlike agglomerates formed
of the noble-metal type fine particles standing agglomerate in the
form of chains, a transparent conductive layer having substantially
the same conductivity as the cases in which conventional
transparent conductive layer forming coating liquids are used can
be obtained even when the content of the noble-metal type fine
particles is made vastly low. This makes it possible to vastly
lower the cost of the transparent conductive layer forming coating
liquid.
[0093] Even in the case when the fine color-pigment particles (or a
dispersion having the fine color-pigment particles dispersed
therein) are mixed in the transparent conductive layer forming
coating liquid according to the present invention, it is also
possible to add the fine color-pigment particles in a higher
concentration than the cases in which the conventional transparent
conductive layer forming coating liquids containing noble-metal
type fine particles not standing agglomerate are used. This makes
it easy to adjust transmittance and at the same time makes it
possible to vastly lower the content of the noble-metal type fine
particles and also to vastly lower the cost of the transparent
conductive layer forming coating liquid.
[0094] For the same reason as the reason why the desalting is
carried out when the colloidal dispersion of noble-metal-coated
fine silver particles described previously are produced, it is
preferable that the desalting is thoroughly carried out in advance
also in respect of the dispersion of the fine color-pigment
particles which is to be mixed in the transparent conductive layer
forming coating liquid.
[0095] When the transparent coat layer forming coating liquid
containing the inorganic binder such as silica sol is over-coated
by the above coating process, the silica sol thus over-coated (this
silica sol turns into a binder matrix composed chiefly of silicon
oxide as a result of the heating) soaks into the part of openings
(spaces) of the network structure in the noble-metal type
fine-particle layer formed previously. Thus, an improvement in
transmittance and an improvement in conductivity can simultaneously
be achieved.
[0096] An improvement in strength can also be achieved because the
area of contact between the transparent substrate and the binder
matrix of silicon oxide enlarges via the part of openings of the
network structure and hence the transparent substrate and the
binder matrix combine strongly.
[0097] Moreover, the transparent double-layer film structure
constituted of the transparent conductive layer and the transparent
coat layer can make the reflectance of the transparent double-layer
film greatly low, because the transparent conductive layer having
the noble-metal-coated fine silver particles dispersed in the
binder matrix composed chiefly of silicon oxide has, in its optical
constant (n-ik), a refractive index n which is not so great but has
a great extinction coefficient.
[0098] As the silica sol to be contained in the transparent coat
layer forming coating liquid, usable are a polymeric product
obtained by adding water and an acid catalyst to an
orthoalkyl-silicate to effect hydrolysis followed by
dehydropolycondensation further made to proceed, and a polymeric
product obtained by subjecting a commercially available
alkyl-silicate solution having already been subjected to hydrolysis
and polycondensation made to proceed up to a 4- to 5-mer (tetramer
to pentamer), to hydrolysis and dehydropolycondensation further
made to proceed. Since the solution viscosity increases with
progress of dehydropolycondensation to finally make the product
solidify, the degree of dehydropolycondensation may be so
controlled as to be not higher than the maximum viscosity at which
the coating liquid can be coated on the transparent substrate such
as a glass substrate or a plastic substrate. Here, the degree of
dehydropolycondensation is not particularly specified so long as it
is kept at a level not higher than the maximum viscosity, but may
preferably be from about 500 to about 3,000 as weight-average
molecular weight, taking account of film strength, weatherability
and so forth. Then, the dehydropolycondensation is substantially
completed at the time the transparent double-layer film is heated
and baked, and the alkyl-silicate hydrolyzed polymeric product
turns into a hard silicate film (a film composed chiefly of silicon
oxide).
[0099] To the silica sol, fine magnesium fluoride particles, an
alumina sol, a titania sol or a zirconia sol may be added so that
the refractive index of the transparent coat layer can be
controlled to change the reflectance of the transparent
double-layer film.
[0100] Thus, according to the process for producing the noble-metal
type fine-particle dispersion according to the present invention,
the process has the steps of i) an agglomeration step of adding a
hydrazine solution to a dispersion in which primary particles of
noble-metal type fine particles have been made to stand
monodisperse in a solvent, to destabilize the dispersibility of the
noble-metal type fine particles in the dispersion and cause the
plurality of primary particles in the noble-metal type fine
particles to agglomerate in the form of chains to obtain a
dispersion of chainlike agglomerates, and ii) a stabilization step
of adding a hydrogen peroxide solution to the dispersion of the
chainlike agglomerates obtained, to decompose and remove the
hydrazine to stabilize the dispersibility of the chainlike
agglomerates in the dispersion. In a series of these steps, the
reaction products are only water (H.sub.2O) and nitrogen gas
(N.sub.2) and are free from any secondary formation of impurity
ions.
[0101] Hence, the process has the effect that the noble-metal type
fine-particle dispersion usable as the transparent conductive layer
forming coating liquid which can form the transparent conductive
layer having superior high-transmittance and low-reflectance
characteristics and good conductivity and also has superior storage
stability can be produced simply and at a low cost.
[0102] The transparent conductive layer forming coating liquid
obtained by the production process according to the present
invention also has the effect that, since the noble-metal-coated
fine silver particles formed by coating fine silver particles with
noble metal are used as primary particles and such fine particles
are made to stand agglomerate in the form of chains, the
transparent conductive layer having very good conductivity in
addition to various characteristics such as high transmittance and
low reflectance can be formed even when the noble-metal-coated fine
silver particles in the transparent conductive layer forming
coating liquid are in a small content, and also that the coating
liquid has superior storage stability.
[0103] In addition, since the transparent conductive layer formed
using this transparent conductive layer forming coating liquid has
very good conductivity in addition to various characteristics such
as high transmittance and low reflectance, the transparent
conductive layered structure having this transparent conductive
layer can be used in front panels of display devices such as
cathode ray tubes (CRT), plasma display panels (PDP), fluorescent
display (VFD) devices, field emission display (FED) devices,
electroluminescence display (ELD) devices and liquid-crystal
display (LCD) devices.
[0104] Moreover, in addition to various characteristics such as
good conductivity and low reflectance, the transmittance of the
transparent conductive layer can be adjusted at will by mixing the
fine color-pigment particles in this transparent conductive layer
forming coating liquid, and hence, for example, the contrast of
images can be improved to make display screens easy to watch, or
the demand increasing as CRT screens are made flatter as stated
previously can be met.
[0105] The present invention is described below in greater detail
by giving Examples. The present invention is by no means limited to
these Examples. In the following, "%" refers to "% by weight"
except for "%" of transmittance, reflectance and haze value, and
"part (s)" refers to "part(s) by weight".
EXAMPLE 1
[0106] A colloidal dispersion of fine silver particles was made up
by the Carey-Lea process described previously.
[0107] Stated specifically, to 330 g of an aqueous 9% silver
nitrate solution, a mixed solution of 390 g of an aqueous 23% iron
(II) sulfate solution and 480 g of an aqueous 37.5% sodium citrate
solution was added, and thereafter the sediment formed was filtered
and washed, followed by addition of pure water to make up a
colloidal dispersion of fine silver particles (Ag: 0.15%).
[0108] To 600 g of this colloidal dispersion of fine silver
particles, 80.0 g of an aqueous 1% solution of hydrazine
monohydrate (N.sub.2H.sub.4.H.sub.2O) was added, and a mixed
solution of 4,800 g of an aqueous potassium aurate KAu(OH).sub.4
solution (Au: 0.075%) and 2.0 g of an aqueous 1% polymeric
dispersant solution was further added with stirring to obtain a
colloidal dispersion of noble-metal-coated fine silver particles
coated with gold alone.
[0109] This colloidal dispersion of noble-metal-coated fine silver
particles was desalted With an ion-exchange resin (available from
Mitsubishi Chemical Industries Limited; trade name: DIAION SK1B,
SA20AP), followed by ultrafiltration to effect concentration of the
colloidal dispersion of noble-metal-coated fine silver particles.
To the resultant dispersion, ethanol (EA) were added to obtain a
dispersion containing the noble-metal-coated fine silver particles
standing monodisperse in a high concentration (Ag--Au: 1.6%; water:
20.0%; EA: 78.4%) (liquid B).
[0110] Next, stirring 60 g of the liquid B, 0.8 g of a hydrazine
solution (N.sub.2H.sub.4.H.sub.2O: 0.75%) (0.8 g corresponding to
100 ppm of hydrazine, based on the 1.6% Ag--Au dispersion) was
added thereto over a period of 1 minute. Thereafter, this was
retained at room temperature for 15 minutes, followed by further
addition of 0.6 g of a hydrogen peroxide solution (H.sub.2O.sub.2:
1.5%) over a period of 1 minute to obtain a noble-metal type
fine-particle dispersion according to Example 1 (liquid C), in
which chainlike agglomerates of the noble-metal-coated fine silver
particles stood disperse in a high concentration.
[0111] Incidentally, as to i) the lowering of dispersion stability
in respect of the noble-metal-coated fine silver particles when the
hydrazine solution was added to the dispersion (liquid B)
containing the noble-metal-coated fine silver particles standing
monodisperse in a high concentration and ii) the improvement in
dispersion stability in respect of the chainlike agglomerates when
the hydrogen peroxide solution was added to the dispersion
containing the noble-metal-coated fine silver particles standing
agglomerate, these have scientifically been ascertained from the
measurements of zeta potentials of the respective dispersions.
[0112] Next, to the noble-metal type fine-particle dispersion
according to Example 1 (liquid C), acetone, ethanol (EA), propylene
glycol monomethyl ether (PGM), diacetone alcohol (DAA) and
formamide (FA) were added to obtain a transparent conductive layer
forming coating liquid according to Example 1 (Ag: 0.03%; Au:
0.12%; water: 1.9%; acetone: 40%; EA: 37.9%; PGM: 15%; DAA: 5%; FA:
0.03%), containing the chainlike agglomerates of noble-metal-coated
fine silver particles and prepared in a concentration enabling the
coating liquid to be directly used to form the transparent
conductive layer.
[0113] This transparent conductive layer forming coating liquid was
observed on a transmission electron microscope to reveal that the
chainlike agglomerates of noble-metal-coated fine silver particles
were formed of noble-metal-coated fine silver particles of about 6
nm in primary particle diameter which stood strung in strings of
beads and also had partially branched shapes [length: 100 nm to 300
nm (the maximum value of length in individual chainlike
agglomerates); average length: 200 nm].
[0114] Next, the transparent conductive layer forming coating
liquid containing the chainlike agglomerates of noble-metal-coated
fine silver particles was filtered with a filter of 5 .mu.m in
filtering precision (pore size). Thereafter, this was spin-coated
(at 90 rpm for 10 seconds and 120 rpm for 80 seconds) on a glass
substrate (soda-lime glass of 3 mm thick) heated to 35.degree. C.,
and subsequently a silica sol was spin-coated thereon (at 150 rpm
for 60 seconds), further followed by heat treatment at 180.degree.
C. for 20 minutes to obtain a glass substrate provided with a
transparent double-layer film constituted of a transparent
conductive layer containing the noble-metal-coated fine silver
particles in well-developed network structure and a transparent
coat layer formed of a silicate film composed chiefly of silicon
oxide, i.e., a transparent conductive layered structure according
to Example 1.
[0115] The above glass substrate was polished with a cerium oxide
type polishing agent before use, and was used after the polished
one was cleaned with pure water, dried and thereafter heated to
35.degree. C.
[0116] Here, the above silica sol was made up using 19.6 parts of
Methyl-silicate 51 (trade name; available from Colcoat Co., Ltd.),
57.8 parts of ethanol, 7.9 parts of an aqueous 1% nitric acid
solution and 14.7 parts of pure water, to obtain one having
SiO.sub.2 (silicon oxide) solid content concentration of 10% and a
weight-average molecular weight of 1,050 (silica sol: liquid D),
which was finally diluted with a mixture of isopropyl alcohol (IPA)
and n-butanol (NBA) (IPA/NBA=3/1) so as to have the SiO.sub.2 solid
content concentration of 0.8%.
[0117] Film characteristics (surface resistance, visible light ray
transmittance, haze value, and bottom reflectance/bottom
wavelength) of the transparent double-layer film formed on the
glass substrate are shown in Table 1 below. Here, the bottom
reflectance is meant to be the minimum reflectance in the
reflection profile of the transparent conductive layered structure,
and the bottom wavelength the wavelength at the minimum
reflectance.
[0118] Transmittance shown in Table 1 in respect of only the
transparent double-layer film, excluding the transparent substrate
(glass substrate) is determined in the following way:
Transmittance (%) of only transparent double-layer film, excluding
transparent substrate (glass substrate)=[(transmittance measured on
the whole structure inclusive of transparent
substrate)/(transmittance of transparent substrate)].times.100
[0119] Here, in the present specification, unless particularly
noted, the value obtained by measuring transmittance of only the
transparent double-layer film, excluding that of the transparent
substrate, is used as the transmittance.
[0120] The surface resistance of the transparent double-layer film
was also measured with a surface resistance meter LORESTA AP
(MCP-T400), manufactured by Mitsubishi Chemical Corporation. The
haze value and the visible light ray transmittance was measured
with a haze meter (HR-200, a reflectance-transmittance meter)
manufactured by Murakami Color Research Laboratory. The reflectance
was measured with a spectrophotometer (U-4000) manufactured by
Hitachi Ltd. The shape of chainlike agglomerates and particle size
(length) in respect of the noble-metal-coated fine silver particles
were observed on a transmission electron microscope manufactured by
JEOL, Ltd.
EXAMPLE 2
[0121] 5 g of fine titanium nitride (TiN) particles (available from
Netsuren Co., Ltd.) and 5 g of the silica sol (liquid D) prepared
in Example 1 were mixed with 20 g of pure water and 70 g of
ethanol, and these were subjected to paint shaker dispersion
together with zirconia beads, followed by desalting with the ion
exchange resin used in Example 1, to obtain a dispersion of
silicon-oxide-coated fine titanium nitride particles of 85 nm in
dispersed-particle diameter (liquid E), surface coated with silicon
oxide.
[0122] Next, to the noble-metal type fine-particle dispersion
according to Example 1 (liquid C), the above liquid E, acetone,
ethanol (EA), propylene glycol monomethyl ether (PGM), diacetone
alcohol (DAA) and formamide (FA) were added to obtain a transparent
conductive layer forming coating liquid according to Example 2 (Ag:
0.04%; Au: 0.16%; TiN: 0.15%; water: 3.1%; acetone: 40%; EA: 36.5%;
PGM: 15%; DAA: 5%; FA: 0.03%, containing the chainlike agglomerates
of noble-metal-coated fine silver particles and the fine titanium
nitride particles and prepared in a concentration enabling the
coating liquid to be directly used to form the transparent
conductive layer.
[0123] This transparent conductive layer forming coating liquid was
observed on a transmission electron microscope to reveal that the
fine titanium nitride particles had an average particle diameter of
20 nm.
[0124] Then, the subsequent procedure in Example 1 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles in well-developed network
structure and the fine titanium nitride particles and a transparent
coat layer formed of a silicate film composed chiefly of silicon
oxide, i.e., a transparent conductive layered structure according
to Example 2.
[0125] Film characteristics (surface resistance, visible light ray
transmittance, haze value, and bottom reflectance/bottom
wavelength) of the transparent double-layer film formed on the
glass substrate are shown in Table 1 below.
COMPARATIVE EXAMPLE 1
[0126] To the liquid B in Example 1 (dispersion containing the
noble-metal-coated fine silver particles standing monodisperse in a
high concentration), acetone, ethanol (EA), propylene glycol
monomethyl ether (PGM), diacetone alcohol (DAA) and formamide (FA)
were added to obtain a transparent conductive layer forming coating
liquid according to Comparative Example 1 (Ag: 0.03%; Au: 0.12%;
water: 1.9%; acetone: 40%; EA: 37.9%; PGM: 15%; DAA: 5%; FA:
0.03%), containing noble-metal-coated fine silver particles having
individual fine particles not standing agglomerate, and prepared in
a concentration enabling the coating liquid to be directly used to
form the transparent conductive layer.
[0127] Then, the subsequent procedure in Example 1 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles and a transparent coat
layer formed of a silicate film composed chiefly of silicon oxide,
i.e., a transparent conductive layered structure according to
Comparative Example 1.
[0128] Film characteristics (surface resistance, visible light
ray-transmittance, haze value, and bottom reflectance/bottom
wavelength) of the transparent double-layer film formed on the
glass substrate are shown in Table 1 below.
COMPARATIVE EXAMPLE 2
[0129] The liquid B in Example 1 (dispersion containing the
noble-metal-coated fine silver particles standing monodisperse in a
high concentration) and the liquid E in Example 2 (dispersion of
silicon-oxide-coated fine titanium nitride particles) were used to
obtain a transparent conductive layer forming coating liquid
according to Comparative Example 2 (Ag: 0.04%; Au: 0.16%; TiN:
0.15%; water: 3.1%; acetone: 40%; EA: 36.5%; PGM: 15%; DAA: 5%; FA:
0.03%), containing noble-metal-coated fine silver particles having
individual fine particles not standing agglomerate and the fine
titanium nitride particles, and prepared in a concentration
enabling the coating liquid to be directly used to form the
transparent conductive layer.
[0130] Then, the subsequent procedure in Example 2 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles and the fine titanium
nitride particles and a transparent coat layer formed of a silicate
film composed chiefly of silicon oxide, i.e., a transparent
conductive layered structure according to Comparative Example
2.
[0131] Film characteristics (surface resistance, visible light ray
transmittance, haze value, and bottom reflectance/bottom
wavelength) of the transparent double-layer film formed on the
glass substrate are shown in Table 1 below.
Table 1
[0132] Stability Test on Dispersions:
[0133] In Examples 1 and 2, glass substrates each provided with a
transparent double-layer film constituted of a transparent
conductive layer containing the noble-metal-coated fine silver
particles in well-developed-network structure and a transparent
coat layer formed of a silicate film composed chiefly of silicon
oxide were obtained in the same manner as in these Examples except
that the noble-metal type fine-particle dispersion (liquid C), in
which the chainlike agglomerates of noble-metal-coated fine silver
particles stood disperse in a high concentration, was left at room
temperature for 2 weeks and thereafter prepared in a concentration
suited for the formation of the transparent conductive layer.
[0134] The film characteristics of these transparent double-layer
films formed on the glass substrates were equal to those in
Examples 1 and 2.
[0135] Evaluation:
[0136] 1. The following is ascertained from the results shown in
Table 1.
[0137] First, it is ascertained that, while the transparent
double-layer films according to Comparative Examples 1 and 2,
making use of the transparent conductive layer forming coating
liquid containing noble-metal-coated fine silver particles having
individual fine particles not standing agglomerate, have surface
resistance of 10.sup.6 .OMEGA./square or more, the transparent
double-layer films according to Examples 1 and 2 have surface
resistance of 870 .OMEGA./square to 965 .OMEGA./square, having
superior conductivity, thus a remarkable improvement in film
characteristics has been brought by the present invention.
[0138] From a different point of view, this fact show the
following: In the transparent conductive layer forming coating
liquids of Comparative Examples 1 and 2, containing
noble-metal-coated fine silver particles having individual fine
particles not standing agglomerate, the content of the
noble-metal-coated fine silver particles in the coating liquid must
be vastly high in order to attain practical film resistance value
(several k.OMEGA./square or less). On the other hand, in the
transparent conductive layer forming coating liquids of Examples 1
and 2, in which the chainlike agglomerates of noble-metal-coated
fine silver particles have been dispersed, the content of noble
metal may be set as low as from 0.15% to 0.2%.
[0139] Thus, the process for producing the noble-metal type
fine-particle dispersion according to the present invention not
only has simpler production steps than the conventional methods
discussed previously, but also has an advantage that inexpensive
transparent conductive layer forming coating liquids can be
provided.
[0140] 2. From the results of the stability test on dispersions, it
is also ascertained that the noble-metal type fine-particle
dispersion in which the chainlike agglomerates of
noble-metal-coated fine silver particles stand disperse in a high
concentration does not show any deterioration when used as the
transparent conductive layer forming coating liquid, even though it
has been left at room temperature for 2 weeks, and has superior
storage stability.
[0141] That is, superiority over the conventional methods discussed
previously can be ascertained in the process for producing the
noble-metal type fine-particle dispersion according to the present
invention.
EXAMPLE 3
[0142] A dispersion containing noble-metal-coated fine silver
particles standing monodisperse in a high concentration (Ag--Au:
1.6%; water: 20.0%; EA: 78.4%) (liquid F) was obtained in the same
manner as the manner of obtaining the liquid B in Example 1.
[0143] Next, stirring 60 g of this liquid F, 0.8 g of a hydrazine
solution (N.sub.2H.sub.4.H.sub.2O: 0.5%) (0.8 g corresponding to 67
ppm of hydrazine, based on the 1.6% Ag--Au dispersion) was added
thereto over a period of 1 minute. Thereafter, this was retained at
room temperature for 15 minutes, followed by further addition of
0.6 g of a hydrogen peroxide solution (H.sub.2O.sub.2: 1.0%) over a
period of 1 minute to obtain a noble-metal type fine-particle
dispersion according to Example 3 (liquid G), in which chainlike
agglomerates of the noble-metal-coated fine silver particles stood
disperse in a high concentration.
[0144] To this liquid G, ethanol (EA), propylene glycol monomethyl
ether (PGM), diacetone alcohol (DAA) and formamide (FA) were added
to obtain a transparent conductive layer forming coating liquid
according to Example 3 (Ag: 0.08%; Au: 0.32%; water: 10%; EA:
54.5%; PGM: 25%; DAA: 10%; FA: 0.1%), containing the chainlike
agglomerates of noble-metal-coated fine silver particles and
prepared in a concentration enabling the coating liquid to be
directly used to form the transparent conductive layer.
[0145] This transparent conductive layer forming coating liquid was
observed on a transmission electron microscope to reveal that the
chainlike agglomerates of noble-metal-coated fine silver particles
were formed of noble-metal-coated fine silver particles of about 6
nm in primary particle diameter which stood strung in strings of
beads and also had partially branched shapes [length: 20 nm to 100
nm (the maximum value of length in individual chainlike
agglomerates); average length: 50 nm].
[0146] Next, this coating liquid was spin-coated (at 90 rpm for 10
seconds and 130 rpm for 80 seconds) on a glass substrate (soda-lime
glass of 3 mm thick) heated to 35.degree. C., and subsequently the
silica sol in Example 1 (the one obtained by diluting the liquid D
and finally made to have SiO.sub.2 solid content concentration of
0.8%) was spin-coated thereon (at 150 rpm for 60 seconds). Except
for these, the corresponding procedure in Example 1 was repeated to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles in well-developed network
structure and a transparent coat layer formed of a silicate film
composed chiefly of silicon oxide, i.e., a transparent conductive
layered structure according to Example 3.
[0147] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 2 below.
EXAMPLE 4
[0148] To the liquid G in Example 3 (noble-metal type fine-particle
dispersion in which the chainlike agglomerates of
noble-metal-coated fine silver particles stood disperse in a high
concentration), ethanol (EA), propylene glycol monomethyl ether
(PGM), diacetone alcohol (DAA) and formamide (FA) were added to
obtain a transparent conductive layer forming coating liquid
according to Example 4 (Ag: 0.04%; Au: 0.16%; water: 10%; EA:
54.5%; PGM: 25%; DAA: 10%; FA: 0.1%), containing the chainlike
agglomerates of noble-metal-coated fine silver particles and
prepared in a concentration enabling the coating liquid to be
directly used to form the transparent conductive layer.
[0149] Then, the subsequent procedure in Example 3 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles in well-developed network
structure and a transparent coat layer formed of a silicate film
composed chiefly of silicon oxide, i.e., a transparent conductive
layered structure according to Example 4.
[0150] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 2 below.
EXAMPLE 5
[0151] Stirring 60 g of the liquid F prepared in Example 3
(dispersion containing the noble-metal-coated fine silver particles
standing monodisperse in a high concentration), 0.8 g of a
hydrazine solution (N.sub.2H.sub.4.H.sub.2O: 0.75%) (0.8 g
corresponding to 100 ppm of hydrazine, based on the 1.6% Ag--Au
dispersion) was added thereto over a period of 1 minute.
[0152] Thereafter, this was retained at room temperature for 15
minutes, followed by further addition of 0.6 g of a hydrogen
peroxide solution (H.sub.2O.sub.2: 1.5%) over a period of 1 minute
to obtain a noble-metal type fine-particle dispersion according to
Example 1 (liquid H), in which chainlike agglomerates of the
noble-metal-coated fine silver particles stood disperse in a high
concentration. Incidentally, as to i) the lowering of dispersion
stability in respect of the noble-metal-coated fine silver
particles when the hydrazine solution was added to the dispersion
(liquid F) containing the noble-metal-coated fine silver
particles-standing monodisperse in a high concentration and ii) the
improvement in dispersion stability in respect of the chainlike
agglomerates when the hydrogen peroxide solution was added to the
dispersion containing the noble-metal-coated fine silver particles
standing agglomerate, these have scientifically been ascertained
from the measurements of zeta potentials of the respective
dispersions.
[0153] Next, to this liquid H, ethanol (EA), propylene glycol
monomethyl ether (PGM), diacetone alcohol (DAA) and formamide (FA)
were added to obtain a transparent conductive layer forming coating
liquid according to Example 5 (Ag: 0.08%; Au: 0.32%; water: 10%;
EA: 54.5%; PGM: 25%; DAA: 10%; FA: 0.1%), containing the chainlike
agglomerates of noble-metal-coated fine silver particles and
prepared in a concentration enabling the coating liquid to be
directly used to form the transparent conductive layer.
[0154] This transparent conductive layer forming coating liquid was
observed on a transmission electron microscope to reveal that the
chainlike agglomerates of noble-metal-coated fine silver particles
were formed of noble-metal-coated fine silver particles of about 6
nm in primary particle diameter which stood strung in strings of
beads and also had partially branched shapes [length: 100 nm to 500
nm (the maximum value of length in individual chainlike
agglomerates); average length: 250 nm].
[0155] Next, on a glass substrate (soda-lime glass of 3 mm thick),
the subsequent-procedure in Example 3 was repeated but using this
transparent conductive layer forming coating liquid, to obtain a
glass substrate provided with a transparent double-layer film
constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles in well-developed network
structure and a transparent coat layer formed of a silicate film
composed chiefly of silicon oxide, i.e., a transparent conductive
layered structure according to Example 5.
[0156] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 2 below.
EXAMPLE 6
[0157] To the liquid H in Example 5 (dispersion in which the
chainlike agglomerates of noble-metal-coated fine silver particles
stood disperse in a high concentration), ethanol (EA), propylene
glycol monomethyl ether (PGM), diacetone alcohol (DAA) and
formamide (FA) were added to obtain a transparent conductive layer
forming coating liquid according to Example 6 (Ag: 0.04%; Au:
0.16%; water: 10%; EA: 54.5%; PGM: 25%; DAA: 10%; FA: 0.1%),
containing the chainlike agglomerates of noble-metal-coated fine
silver particles and prepared in a concentration enabling the
coating liquid to be directly used to form the transparent
conductive layer.
[0158] Then, the subsequent procedure in Example 3 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles in well-developed network
structure and a transparent coat layer formed of a silicate film
composed chiefly of silicon oxide, i.e., a transparent conductive
layered structure according to Example 6.
[0159] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 2 below.
COMPARATIVE EXAMPLE 3
[0160] To the liquid F in Example 3 (dispersion containing the
noble-metal-coated fine silver particles standing monodisperse in a
high concentration), ethanol (EA), propylene glycol monomethyl
ether (PGM), diacetone alcohol (DAA) and formamide (FA) were added
to obtain a transparent conductive layer forming coating liquid
according to Comparative Example 3 (Ag: 0.08%; Au: 0.32%; water:
10%; EA: 54.5%; PGM: 25%; DAA: 10%; FA: 0.1%), containing
noble-metal-coated fine silver particles having individual fine
particles not standing agglomerate, and prepared in a concentration
enabling the coating liquid to be directly used to form the
transparent conductive layer.
[0161] Then, the subsequent procedure in Example 3 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles and a transparent coat
layer formed of a silicate film composed chiefly of silicon oxide,
i.e., a transparent conductive layered structure according to
Comparative Example 3.
[0162] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 2 below.
COMPARATIVE EXAMPLE 4
[0163] To the liquid F in Example 3, ethanol (EA), propylene glycol
monomethyl ether (PGM), diacetone alcohol (DAA) and formamide (FA)
were added to obtain a transparent conductive layer forming coating
liquid according to Comparative Example 4 (Ag: 0.04%; Au: 0.16%;
water: 10%; EA: 54.5%; PGM: 25%; DAA: 10%; FA: 0.1%), containing
noble-metal-coated fine silver particles having individual fine
particles not standing agglomerate, and prepared in a concentration
enabling the coating liquid to be directly used to form the
transparent conductive layer.
[0164] Then, the subsequent procedure in Example 3 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles and a transparent coat
layer formed of a silicate film composed chiefly of silicon oxide,
i.e., a transparent conductive layered structure according to
Comparative Example 4.
[0165] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 2 below.
EXAMPLE 7
[0166] To the liquid G in Example 3 (noble-metal type fine-particle
dispersion in which the chainlike agglomerates of
noble-metal-coated fine silver particles stood disperse in a high
concentration), the liquid E in Example 2 (dispersion of
silicon-oxide-coated fine titanium nitride particles), acetone,
ethanol (EA), propyleneglycol monomethyl ether (PGM), diacetone
alcohol (DAA) and formamide (FA) were added to obtain a transparent
conductive layer forming coating liquid according to Example 7 (Ag:
0.072%; Au: 0.288%; TiN: 0.09%; water: 10%; acetone: 40%; EA:
29.52%; PGM: 15%; DAA: 5%; FA: 0.03%), containing the chainlike
agglomerates of noble-metal-coated fine silver particles and the
fine titanium nitride particles and prepared in a concentration
enabling the coating liquid to be directly used to form the
transparent conductive layer.
[0167] Then, the subsequent procedure in Example 3 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent
double-layer-film constituted of a transparent conductive layer
containing the noble-metal-coated fine silver particles in
well-developed network structure and the fine titanium nitride
particles and a transparent coat layer formed of a silicate film
composed chiefly of silicon oxide, i.e., a transparent conductive
layered structure according to Example 7.
[0168] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 3 below.
EXAMPLE 8
[0169] To the liquid G in Example 3, the liquid E in Example 2,
acetone, ethanol (EA), propylene glycol monomethyl ether (PGM),
diacetone alcohol (DAA) and formamide (FA) were added to obtain a
transparent conductive layer forming coating liquid according to
Example 8 (Ag: 0.052%; Au: 0.208%; TiN: 0.13%; water: 10%; acetone:
40%; EA: 29.58%; PGM: 15%; DAA: 5%; FA: 0.03%), containing the
chainlike agglomerates of noble-metal-coated fine silver particles
and the fine titanium nitride particles and prepared in a
concentration enabling the coating liquid to be directly used to
form the transparent conductive layer.
[0170] Then, the subsequent procedure in Example 3 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles in well-developed network
structure and the fine titanium nitride particles and a transparent
coat layer formed of a silicate film composed chiefly of silicon
oxide, i.e., a transparent conductive layered structure according
to Example 8.
[0171] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 3 below.
EXAMPLE 9
[0172] To the liquid H in Example 5 (noble-metal type fine-particle
dispersion in which the chainlike agglomerates of
noble-metal-coated fine silver particles stood disperse in a high
concentration), the liquid E in Example 2, acetone, ethanol (EA),
propylene glycol monomethyl ether (PGM), diacetone alcohol (DAA)
and formamide (FA) were added to obtain a transparent conductive
layer forming coating liquid according to Example 9 (Ag: 0.072%;
Au: 0.288%; TiN: 0.09%; water: 10%; acetone: 40%; EA: 29.52%; PGM:
15%; DAA: 5%; FA: 0.03%), containing the chainlike agglomerates of
noble-metal-coated fine silver particles and the fine titanium
nitride particles and prepared in a concentration enabling the
coating liquid to be directly used to form the transparent
conductive layer.
[0173] Then, the subsequent procedure in Example 3 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles in well-developed network
structure and the fine titanium nitride particles and a transparent
coat layer formed of a silicate film composed chiefly of silicon
oxide, i.e., a transparent conductive layered structure according
to Example 9.
[0174] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 3 below.
EXAMPLE 10
[0175] To the liquid H in Example 5, the liquid E in Example 2,
acetone, ethanol (EA), propylene glycol monomethyl ether (PGM),
diacetone alcohol (DAA) and formamide (FA) were added to obtain a
transparent conductive layer forming coating liquid according to
Example 10 (Ag: 0.052%; Au: 0.208%; TiN: 0.13%; water: 10%;
acetone: 40%; EA: 29.58%; PGM: 15%; DAA: 5%; FA: 0.03%), containing
the chainlike agglomerates of noble-metal-coated fine silver
particles and the fine titanium nitride particles and prepared in a
concentration enabling the coating liquid to be directly used to
form the transparent conductive layer.
[0176] Then, the subsequent procedure in Example 3 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles in well-developed network
structure and the fine titanium nitride particles and a transparent
coat layer formed of a silicate film composed chiefly of silicon
oxide, i.e., a transparent conductive layered structure according
to Example 10.
[0177] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 3 below.
EXAMPLE 11
[0178] To the liquid H in Example 5, the liquid E in Example 2,
acetone, ethanol (EA), propylene glycol monomethyl ether (PGM),
diacetone alcohol (DAA) and formamide (FA) were added to obtain a
transparent conductive layer forming coating liquid according to
Example 11 (Ag: 0.04%; Au: 0.16%; TiN: 0.14%; water: 10%; acetone:
40%; EA: 29.63%; PGM: 15%; DAA: 5%; FA: 0.03%), containing the
chainlike agglomerates of noble-metal-coated fine silver particles
and the fine titanium nitride particles and prepared in a
concentration enabling the coating liquid to be directly used to
form the transparent conductive layer.
[0179] Then, the subsequent procedure in Example 3 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles in well-developed network
structure and the fine titanium nitride particles and a transparent
coat layer formed of a silicate film composed chiefly of silicon
oxide, i.e., a transparent conductive layered structure according
to Example 11.
[0180] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 3 below.
EXAMPLE 12
[0181] 1 g of fine blue-pigment particles with an average particle
diameter of 20 nm (Phthalocyanine Blue #5203, available from
Dainichiseika Color & Chemicals Mfg. Co., Ltd.) and 2 g of the
liquid D (silica sol) prepared in Example 1 were mixed with 97 g of
ethanol, and these were subjected to paint shaker dispersion
together with zirconia beads, followed by desalting with the ion
exchange resin used in Example 1, to obtain a dispersion of
silicon-oxide-coated fine Phthalocyanine Blue particles of 99 nm in
dispersed-particle diameter (liquid I).
[0182] TEM observation of the silicon-oxide-coated fine
Phthalocyanine Blue particles ascertained that the fine
Phthalocyanine Blue particles stood coated with silicon oxide.
[0183] Next, 5 g of fine red-pigment particles (Quinacridone #44,
available from Dainichiseika Color & Chemicals Mfg. Co., Ltd.)
and 0.5 g of a dispersant were mixed with 94.5 g of diacetone
alcohol (DAA), and thereafter these were subjected to paint shaker
dispersion together with zirconia beads to obtain a dispersion of
fine red-pigment particles of 135 nm in dispersed-particle diameter
(liquid J).
[0184] Next, to the liquid H in Example 5 (noble-metal type
fine-particle dispersion in which the chainlike agglomerates of
noble-metal-coated fine silver particles stood disperse in a high
concentration), the above liquid I and liquid J, ethanol (EA),
propylene glycol monomethyl ether (PGM), diacetone alcohol (DAA)
and formamide (FA) were added to obtain a transparent conductive
layer forming coating liquid according to Example 12 (Ag: 0.06%;
Au: 0.24%; Phthalocyanine Blue: 0.04%; Quinacridone: 0.1%; water:
6.5%; EA: 63.0%; PGM: 20%; DAA: 10%; FA: 0.05%), containing the
chainlike agglomerates of noble-metal-coated fine silver particles,
the fine Phthalocyanine Blue particles and the fine Quinacridone
particles and prepared in a concentration enabling the coating
liquid to be directly used to form the transparent conductive
layer.
[0185] Then, the subsequent procedure in Example 3 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver-particles in well-developed network
structure the fine Phthalocyanine Blue particles and the fine
Quinacridone particles and a transparent coat layer formed of a
silicate film composed chiefly of silicon oxide, i.e., a
transparent conductive layered structure according to Example
0.12.
[0186] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 3 below.
COMPARATIVE EXAMPLE 5
[0187] To the liquid F in Example 3 (dispersion containing the
noble-metal-coated fine silver particles standing monodisperse in a
high concentration), the liquid E in Example 2 (dispersion of
silicon-oxide-coated fine titanium nitride particles), acetone,
ethanol (EA), propylene glycol monomethyl ether (PGM), diacetone
alcohol (DAA) and formamide (FA) were added to obtain a transparent
conductive layer forming coating liquid according to Comparative
Example 5 (Ag: 0.072%; Au: 0.288%; TiN: 0.09%; water: 10%; acetone:
40%; EA: 29.52%; PGM: 15%; DAA: 5%; FA: 0.03%), containing
noble-metal-coated fine silver particles having individual fine
particles not standing agglomerate and the fine titanium nitride
particles, and prepared in a concentration enabling the coating
liquid to be directly used to form the transparent conductive
layer.
[0188] Then, the subsequent procedure in Example 3 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles and the fine titanium
nitride particles and a transparent coat layer formed of a silicate
film composed chiefly of silicon oxide, i.e., a transparent
conductive layered structure according to Comparative Example
5.
[0189] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 3 below.
COMPARATIVE EXAMPLE 6
[0190] To the liquid F in Example 3 (dispersion containing the
noble-metal-coated fine silver particles standing monodisperse in a
high concentration), the liquid E in Example 2 (dispersion of
silicon-oxide-coated fine titanium nitride particles), acetone,
ethanol (EA), propylene glycol monomethyl ether (PGM), diacetone
alcohol (DAA) and formamide (FA) were added to obtain a transparent
conductive layer forming coating liquid according to Comparative
Example 6 (Ag: 0.052%; Au: 0.208%; TiN: 0.13%; water: 10%; acetone:
40%; EA: 29.58%; PGM: 15%; DAA: 5%; FA: 0.03%), containing
noble-metal-coated fine silver particles having individual fine
particles not standing agglomerate and the fine titanium nitride
particles, and prepared in a concentration enabling the coating
liquid to be directly used to form the transparent conductive
layer.
[0191] Then, the subsequent procedure in Example 3 was repeated but
transparent conductive layer forming coating liquid, to obtain a
glass substrate provided with a transparent double-layer film
constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles and the fine titanium
nitride particles and a transparent coat layer formed of a silicate
film composed chiefly of silicon-oxide, i.e., a transparent
conductive layered structure according to Comparative Example
6.
[0192] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 3 below.
COMPARATIVE EXAMPLE 7
[0193] To the liquid F in Example 3 (dispersion containing the
noble-metal-coated fine silver particles standing monodisperse in a
high concentration), the liquid E in Example 2 (dispersion of
silicon-oxide-coated fine titanium nitride particles), acetone,
ethanol (EA), propylene glycol monomethyl ether (PGM), diacetone
alcohol (DAA) and formamide (FA) were added to obtain a transparent
conductive layer forming coating liquid according to Comparative
Example 7 (Ag: 0.04%; Au: 0.16%; TiN: 0.14%; water: 10%; acetone:
40%; EA: 29.63%; PGM: 15%; DAA: 5%; FA: 0.03%), containing
noble-metal-coated fine silver particles having individual fine
particles not standing agglomerate and the fine titanium nitride
particles, and prepared in a concentration enabling the coating
liquid to be directly used to form the transparent conductive
layer.
[0194] Then, the subsequent procedure in Example 3 was repeated but
using this transparent conductive layer forming coating liquid, to
obtain a glass substrate provided with a transparent double-layer
film constituted of a transparent conductive layer containing the
noble-metal-coated fine silver particles and the fine titanium
nitride particles and a transparent coat layer formed of a silicate
film composed chiefly of silicon oxide, i.e., a transparent
conductive layered structure according to Comparative Example
7.
[0195] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 3 below.
COMPARATIVE EXAMPLE 8
[0196] In Example 12, in place of the liquid H in Example 5
(noble-metal type fine-particle dispersion in which the chainlike
agglomerates of noble-metal-coated fine silver particles stood
disperse in a high concentration), the liquid F in Example 3
(dispersion containing the noble-metal-coated fine silver particles
standing monodisperse in a high concentration) was used to obtain a
transparent conductive layer forming coating liquid according to
Comparative Example 8 (Ag: 0.06%; Au: 0.24%; Phthalocyanine Blue:
0.04%; Quinacridone: 0.1%; water: 6.5%; EA: 63.0%; PGM: 20%; DAA:
10%; FA: 0.05%), containing noble-metal-coated fine silver
particles having individual fine particles not standing
agglomerate, the fine Phthalocyanine Blue particles and the fine
Quinacridone particles, and prepared in a concentration enabling
the coating liquid to be directly used to form the transparent
conductive layer.
[0197] Then, the subsequent procedure in Example 12 was repeated
but using this transparent conductive layer forming coating liquid,
to obtain a glass substrate provided with a transparent
double-layer film constituted of a transparent conductive layer
containing the noble-metal-coated fine silver particles, the fine
Phthalocyanine Blue particles and the fine Quinacridone particles
and a transparent coat layer formed of a silicate film composed
chiefly of silicon oxide, i.e., a transparent conductive layered
structure according to Comparative Example 8.
[0198] Film characteristics (surface resistance, visible light ray
transmittance and haze value) of the transparent double-layer film
formed on the glass substrate are shown in Table 3 below.
Table 2
Table 3
[0199] Evaluation:
[0200] 1. The following is ascertained from the results shown in
Table 2.
[0201] First, as shown in the transparent double-layer films
according to Comparative Example 3 and Examples 3 and 5, in the
case when the noble-metal-coated fine silver particles in the
transparent conductive layer forming coating liquid are in a
relatively high content (0.4%), the transparent double-layer films
according to Examples 3 and 5 have surface resistance of 250
.OMEGA./square and 190 .OMEGA./square, respectively, in respect to
the surface resistance (280 .OMEGA./square) of the transparent
double-layer film according to Comparative Example 3. The former
clearly has a lower surface resistance than the latter, though not
so remarkable, and is seen to have been improved in
conductivity.
[0202] As also shown in the transparent double-layer films
according to Comparative Example 4 and Examples 4 and 6, in the
case when the noble-metal-coated fine silver particles in the
transparent conductive layer forming coating liquid are in a
content made smaller (0.2%), the transparent double-layer films
according to Comparative Example 4 has surface resistance of
10.sup.6 .OMEGA.K/square or more, whereas the transparent
double-layer films according to Examples 4 and 6 have surface
resistance of 4,000 I/square and 1,000 .OMEGA./square,
respectively, and are seen to have been improved very much.
[0203] As also ascertained from the comparison between Example 3
(67 ppm) and Example 5 (100 ppm) and between Example 4 (67 ppm) and
Example 6 (100 ppm), it is also seen that the surface resistance
can be adjusted by changing the quantity of the hydrazine to be
added at the time of agglomerating treatment.
[0204] These results also show that, in respect of the content of
the noble-metal-coated fine silver particles in coating liquid that
is required to attain practical film resistance value (several
k.OMEGA./square or less), it can be made vastly low by making the
noble-metal-coated fine silver particles stand agglomerate in the
form of chains to make up the chainlike agglomerates, making it
possible to provide inexpensive transparent conductive layer
forming coating liquids.
[0205] 2. Then, the following is ascertained from the results shown
in Table 3.
[0206] That is, in respect to the surface resistance of the
transparent double-layer films according to Comparative Examples 5
to 8, the transparent double-layer films according to Examples 7 to
12 are seen to have attained the practical film resistance value
even though the noble-metal-coated fine silver particles in the
coating liquid are in a small content and also the color pigment is
in a large content.
1 TABLE 1 Bottom Noble-metal-coated Fine reflectance/ fine silver
particles color = pigment Surface Visible = light Haze bottom
Content Chainlike Hydrazine particles resistance transmittance
value wavelength (%) agglomerates (ppm) (%) (.OMEGA./square) (%)
(%) (%)/(nm) Example: 1 0.15 formed 100 none 965 90.7 0.1 1.15/565
2 0.20 formed 100 0.15 (TiN) 870 65.3 0.8 0.87/560 Comparative
Example: 1 0.15 none -- none .sup. >10.sup.6 90.2 0.1 1.18/570 2
0.20 none -- 0.15 (TiN) .sup. >10.sup.6 65.1 0.8 0.86/565
[0207]
2 TABLE 2 Noble-metal-coated fine silver particles Surface Visible
= light Content Chainlike Hydrazine resistance transmittance Haze
value (%) agglomerates (ppm) (.OMEGA./square) (%) (%) Example: 3
0.4 formed 67 250 82.0 0.2 4 0.2 formed 67 4,000 85.1 0.2 5 0.4
formed 100 190 82.3 0.3 6 0.2 formed 100 1,000 87.9 0.2 Comparative
Example: 3 0.4 none -- 280 81.5 0.1 4 0.2 none -- >1 .times.
10.sup.6 84.8 0.1
[0208]
3 TABLE 3 Noble-metal-coated Fine fine silver particles color =
pigment Surface Visible = light Haze Content Chainlike Hydrazine
particles resistance transmittance value (%) agglomerates (ppm) (%)
(.OMEGA./square) (%) (%) Example: 7 0.36 formed 67 0.09 (TiN) 430
67.3 0.6 8 0.26 formed 67 0.13 (TiN) 1,800 64.1 0.7 9 0.36 formed
100 0.09 (TiN) 270 67.4 0.6 10 0.26 formed 100 0.13 (TiN) 470 65.4
0.9 11 0.2 formed 100 0.14 (TiN) 920 66.6 1.0 12 0.3 formed 100
0.04 (*1) 2,100 73.9 1.2 0.1 (*2) Comparative Example: 5 0.36 none
-- 0.09 (TiN) 1,000 64.6 0.7 6 0.26 none -- 0.13 (TiN) 6,000 63.8
0.7 7 0.2 none -- 0.14 (TiN) >1 .times. 10.sup.6 65.2 0.8 8 0.3
none -- 0.04 (*1) >1 .times. 10.sup.6 73.8 1.2 0.1 (*2) *1
Phthalocyanine Blue *2 Quinacridone
* * * * *