JPH1045427A - Coating liquid for forming dark color transparent conductive film and dark color transparent conductive film formed by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating liquid for forming a dark color transparent conductive film for easily manufacturing a film which lowers transmittance without scattering the visible light of a CRT screen, has the better electrical conductivity than heretofore and has an effect in shielding a low-frequency electric field at a low cost by using a coating method and the dark color transparent conductive film formed by using this liquid. SOLUTION: This coating liquid for forming the dark color transparent conductive film is prepd. by dispersing ruthenium oxide particulates as conductive particulates into a polar solvent and coating these ruthenium oxide particulates with coating layers of silver in part or the whole of the particle surfaces and the grain size thereof is <=50nm. The polar solvent in the constitution described above further contains the partial hydrolyzed polymer of alkyl silicate. The dark color transparent conductive film is obtd. by coating a base material with the coating liquid for forming the dark color transparent conductive film and further coating the film described above with a soln. of the partial hydrolyzed polymer of alkyl silicate, then baking the coating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating liquid for forming a dark-colored transparent conductive film for imparting an electric field shielding effect to a front glass of a cathode ray tube such as a display of an OA apparatus and a cathode ray tube of a television, and the like. For the dark transparent conductive film, more specifically, ruthenium oxide fine particles were used as conductive fine particles in a polar solvent to form a film having better conductivity than before and suitable for shielding low-frequency electric fields. The present invention relates to a dispersion liquid for forming a dark-colored transparent conductive film and a dark-colored transparent conductive film using the same.

[0002]

2. Description of the Related Art In recent years, many OA have been developed due to the digitization of office equipment.
It is not uncommon for devices to be installed and faced with displays to work all day. A computer, which is a typical OA device, is required to have a display screen that is easy to see and does not cause visual fatigue, and that the surface of the computer is free from dust and electric shock. In addition, recently, there is a concern that a low-frequency electromagnetic wave generated from a cathode ray tube (CRT) may have an adverse effect on a human body. Therefore, it is desired that the electromagnetic wave does not leak to the outside.

In a CRT, electromagnetic waves are generated from a deflection coil and a flyback transformer. As the size of the display increases, more and more electromagnetic waves tend to leak to the surroundings. An electromagnetic wave is composed of a magnetic field and an electric field.
Most can be prevented by changing the shape of the RT deflection coil. On the other hand, the leakage of the electric field of the electromagnetic wave can be prevented by forming a conductive transparent film on the surface of the CRT front glass (electric field shielding effect). This is the same in principle as the countermeasure that has been conventionally taken for antistatic, but the conductivity of the conductive film required for preventing the leakage electric field is the same as the conductive film for preventing antistatic. A value much higher than the conductivity is required. Specifically, it is considered that a surface resistance of about 10 ⁸ Ω / □ is sufficient for antistatic, but at least one surface resistance is required for preventing leakage electric field.
0 ⁶ Ω / □ or less, preferably required 10 ² ~10 ³ Ω / □ pedestal low resistance.

[0004] In order to meet this demand, several proposals have been made conventionally. One of them is vacuum deposition, C
There is a method of forming a conductive oxide film such as tin oxide or indium oxide on the surface of a CRT front glass by VD, sputtering, or the like. Since the film formed by this method is composed of a continuous film having a single composition of tin oxide or indium oxide, the conductivity inherent in the conductive oxide appears as it is, and a sufficiently low resistance value for the electric field shielding effect can be obtained. Further, the film thickness can be controlled to be sufficiently thin and uniform, and antireflection processing can be performed without impairing the resolution of the CRT.

However, in this method, it is necessary to control the atmosphere for each CRT and to perform the treatment, and it requires a great deal of cost to form a film, which is inconvenient for manufacturing a practical CRT. It is inappropriate except for. For this reason, a less expensive and faster film forming method has been desired.

To realize a low surface resistance value at low cost, ultrafine indium tin oxide (ITO) powder is mixed with an alkyl silicate binder in a polar solvent containing N-methyl-2-pyrrolidone as a main component. A dispersed treatment solution for electric field shielding has been proposed (Japanese Patent Application No. 4-30711).
No. 05). This treatment liquid is applied to the front glass of the CRT.
After drying, by firing at a temperature of 200 ° C. or less, a surface resistance value of 10 ³ to 10 ⁵ Ω / □ is obtained depending on the film thickness. According to the application of the ink, the method is much simpler and the manufacturing cost is lower than other methods of forming a dark-colored transparent conductive film such as a vacuum evaporation method and a sputtering method, and is an advantageous method for coping with a CRT electric field shield. It is. However, the obtained surface resistance has a limit that can be reduced.
0 and ^{2 ~10 3 Ω} / □ die was good enough difficult.

On the other hand, a transparent conductive film used for a CRT is
The transparency and resolution of the screen must not be impaired,
Further, it is preferable that the transmittance can be controlled to some extent. That is, in order to improve the image contrast, the transmittance of the front glass of the CRT is limited to a moderate level. However, since the thickness of the glass varies depending on the position of the screen, the transmittance becomes non-uniform. Is desired to be able to be adjusted by about 10 to 20%. In this case, of course, it is possible to uniformly darken the screen, but in order to reduce the light transmittance without lowering the resolution, diffuse scattered light by the surface forming film is as small as possible.
It is desirable to lower the transmittance by light absorption by the film material itself. However, when the above-mentioned ITO is used, since the ITO powder essentially having the visible light transmittance is used, the low transmittance of the dark-colored transparent conductive film whose luminance can be adjusted is not realized.

[0008] As described above, the film in which the ITO fine particles are dispersed was not sufficient in both the film conductivity and the visible light transmittance controllability.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a function of reducing the transmittance without scattering visible light on a CRT screen, and to have an effect on the human body by having a conductivity superior to that of the conventional art. A coating solution for forming a dark-colored transparent conductive film for easily and inexpensively producing a film having a sufficient effect for shielding a low-frequency electric field that may be exerted, and a dark-colored coating solution using the same. It is to provide a transparent conductive film.

[0010]

In order to achieve the above-mentioned object, a coating liquid for forming a dark-colored transparent conductive film according to the present invention comprises fine particles of ruthenium oxide as conductive fine particles dispersed in a polar solvent. The fine particles are partially or entirely covered with a silver coating layer and have a particle size of 50 n.
m or less.

In another coating liquid for forming a dark-colored transparent conductive film according to the present invention, ruthenium oxide fine particles are dispersed in a polar solvent as conductive fine particles, and the ruthenium oxide fine particles are partially or wholly part of the particle surface. Is coated with a silver film layer and has a particle size of 50 nm or less, and the polar solvent contains an alkyl silicate partially hydrolyzed polymer.

Further, the dark-colored transparent conductive film of the present invention is obtained by coating a substrate with any one of the above-mentioned dark-colored transparent conductive film forming coating solutions.

Further, another dark transparent conductive film of the present invention comprises:
It is obtained by coating a base material with any one of the above-mentioned coating solutions for forming a dark-colored transparent conductive film, coating a solution of the alkyl silicate partially hydrolyzed polymer thereon, and then firing.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The conductive fine particles used in the present invention are:
Ruthenium oxide fine particles are the main component, and a part or the whole of the particle surface is covered with a silver coating layer, and the particle size is 50 nm or less. As ruthenium oxides, ruthenium dioxide (RuO ₂ ), bismuth ruthenate (Bi ₂ Ru ₂ O ₇ ), lead ruthenate (Pb ₂ Ru)
₂ O _6.5 ), strontium ruthenate (SrRu
O ₃ ) and the like, and are not limited to these.

The specific resistance of these ruthenium oxides is 10 ^-4.
~10 ^-5 Ω · cm on the order of, and because the specific resistance of the silver is in the order of 10 ^-6 Ω · cm, the specific resistance of the ruthenium oxide silver was coated obviously indium tin oxide (ITO) , And two to three orders of magnitude lower than transparent conductive oxides such as antimony-added tin oxide (ATO) and aluminum-added zinc oxide (AZO). Therefore, the conductive fine particles made of silver-coated ruthenium oxide form conductive paths in contact with each other in the film, and realize a lower resistance value than a film or the like using ITO fine particles.

When the conductive fine particles of the silver-coated ruthenium oxide are contained in the coating solution in an amount of 0.1% by weight or more, the effect of high conductivity is obtained. As the content of the conductive fine particles increases, the thickness of the conductive layer formed also increases and the surface resistance decreases, but when the content exceeds 10% by weight in the coating solution, it is difficult to form a film having a smooth interface. At the same time, the dispersion stability of the conductive particles in the coating liquid is lowered, and a non-negligible precipitation is generated, which is not preferable. 10 ² to 10 ³ Ω / □
In order to obtain a surface resistance value of the base, a content of about 7% by weight or less is sufficient when a film is formed under ordinary coating conditions.

When the conductive fine particles have too large a particle size or strong agglomeration, the formed film becomes cloudy and the resolution of the CRT screen is undesirably reduced. The haze of the transparent film is represented by a haze value defined as a percentage of the amount of scattered transmitted light with respect to the total transmitted light amount. In general, it is necessary to suppress the haze to 5% or less so as not to impair the resolution of the CRT screen.

Although the haze is almost proportional to the film thickness, as a result of examination using fine particles having various particle sizes, it is preferable that the particle size of the conductive fine particles is smaller, and when the film thickness is about 0.1 μm, the haze is 5% or less. It has been clarified that it is important to keep the average particle diameter of the conductive fine particles to about 50 nm or less in order to suppress them. When the average particle diameter is 50 nm or less, most of the scattering modes of the incident visible light are so-called Rayleigh scattering or Mie scattering modes, and scattering due to the shape of the object is extremely reduced. Conversely, when particles having an average particle size of 50 nm or more are used, scattering of the particles themselves or scattering due to an increase in the roughness of the film surface increases, and the haze easily exceeds 5%.

The thickness of the film using the coating solution of the present invention is 0.1.
The thickness is preferably about 0.05 to 0.6 μm. The reason why the thickness is preferably 0.6 μm or less is to suppress the haze within 5%. The reason why the thickness is preferably 0.05 μm or more is that it is difficult to obtain a uniform film of less than 0.05 μm by the ink method.

The coating liquid of the present invention can be produced by highly dispersing conductive fine particles having an average particle diameter of 50 nm or less in a polar solvent for dispersion, and mixing this with a polar solvent for dilution. This means that, for example, a silver-coated average particle size of 50 nm
The following ruthenium oxide microparticles can be obtained by preparing them, dispersing them in a polar solvent for high dispersion, and further mixing this with a diluting polar solvent.

There are various methods for producing ruthenium oxide fine particles coated with silver, for example, a CVD method, an ion plating method, and a thermal plasma method. Method can be used.

In the dispersion treatment step, the conductive fine particles are mixed in a polar solvent for dispersion, and pulverized using a powerful disperser until the aggregated particles become mostly primary particles. It is preferable to obtain. As the disperser, a ball mill, an attritor, a sand mill, or the like can be used.

As the polar solvent for dispersion, one having an appropriate boiling point not higher than the firing temperature and capable of efficiently dispersing the conductive fine particles is preferable. For example, water, N-methyl-2-pyrrolidone (NMP), ethanol, 4-hydroxy-4-methyl-
2-pentanone (diacetone alcohol), isopropyl alcohol, N, N-dimethylformamide (DM
F), dimethylacetamide, methyl cellosolve, acetone, tetrahydroxyfuran and the like. At this time, in order to enhance dispersibility, a small amount of a dispersing agent such as a silane-based, titanate-based, zirconate-based, aluminate-based coupling agent, a polycarboxylic acid-based, phosphate-based, or silicone-based surfactant is used. It may be added. In the present invention, there is no problem as long as it does not affect the conductivity, and there is no problem if a small amount of 0 to 1% by weight is added.

The diluting polar solvent is selected from solvents which are compatible with the dispersing solvent and the dispersant and have a boiling point below the calcination temperature. The polar solvent for dilution is used for the purpose of improving coatability on a substrate at the time of film formation, in particular, to obtain a smooth film without unevenness at the time of coating, and those skilled in the art can easily prepare an appropriate solvent by a known technique. You can choose.

The partially hydrolyzed alkyl silicate polymer is used to bond and fix the conductive fine particles on the glass surface. Examples of such partially hydrolyzed alkyl silicate polymer include hydrolyzing orthoalkyl silicate. For example, those in which dehydration condensation polymerization has progressed to some extent are used. As orthoalkyl silicate,
For example, ortho-methyl silicate Si (OCH ₃ ) ₄ , ortho-ethyl silicate Si (OC ₂ H ₅ ), ortho-propyl silicate Si (OC ₃ H ₇ ) ₄ , ortho-butyl silicate Si (OC ₄ H ₉ ) _{4 and the} like can be used. Yes, 2
Orthoalkyl silicate having at least one kind of alkyl group in the same molecule may be used. Further, two or more kinds of alkyl orthosilicates may be used as a mixture.

Orthoalkyl silicate is easily hydrolyzed in the presence of moisture to convert an alkoxyl group into a hydroxyl group, and water is removed from the hydroxyl groups to cause dehydration polycondensation. Those having advanced polycondensation can be used. In short, it suffices if it has the ability to promote dehydration-condensation polymerization by heating and ultimately fix the conductive fine particles on the glass surface in the form of silica gel or silica. In order to promote the dehydration-condensation polymerization reaction, a small amount of water or an acid such as hydrochloric acid or sulfuric acid as a reaction accelerator may be allowed to coexist.

The alkyl silicate partially hydrolyzed polymer can be prepared using orthoalkyl silicate as a starting material as described above, but if the same alkyl silicate partially hydrolyzed polymer is obtained, the raw material is not necessarily orthoalkyl. It is not limited to silicate. For example, ethyl silicate 40 or methyl silicate 51 (Tama Chemical Industry) can be obtained as a commercially available product, and such a compound is used as it is or after being subjected to further hydrolysis-condensation polymerization and diluted to a predetermined amount. be able to. Further, for example, titanium, zirconium,
A hydrolyzate of an alkoxide such as aluminum can be added as needed.

The addition amount of the above-mentioned alkyl silicate partially hydrolyzed polymer is preferably such that the amount of the solidified SiO ₂ is equal to or less than the amount of the conductive fine particles or is not contained at all. That is, the conductive fine particles are contained in the coating solution in an amount of 0.1%.
It is preferably contained in an amount of 1 to 10% by weight, but it is desirable to suppress the maximum amount of the alkyl silicate partially hydrolyzed polymer to 10% by weight. The reason is that when the content of the alkyl silicate partially hydrolyzed polymer is increased to an appropriate amount or more, the film interface becomes rough or the filling state of the conductive particles deteriorates,
This is because haze and resistance value increase. The addition of the alkyl silicate partially hydrolyzed polymer has the advantage of contributing to the improvement of the adhesion to the substrate and the applicability of the film. However, when the overcoat is applied and the film surface strength can be secured as a two-layer film, May not be contained at all in the coating liquid for the first layer.

The coating solution of the present invention is applied and dried on the surface of a completed CRT sphere or on the surface of a front glass for CRT before sealing, and then baked in the air to form a dark transparent conductive film having an electric field shielding effect. Can be manufactured simply and at low cost. The baking after applying the application liquid to the CRT face panel is performed at a temperature of 150 to 450 ° C. in the air. When a film is formed on the front glass of a CRT before vacuum sealing, the temperature can be raised to just below the glass softening point. However, when forming a film of a completed CRT ball after sealing, a high heating temperature may cause rupture. Therefore, it is preferable to carry out at 200 ° C. or lower.

During the firing, polycondensation of the silicate and evaporation of the solvent component occur, and the coating film shrinks, dries and hardens. The completion of the silicate polycondensation reaction is 200-250 ° C
Therefore, a small amount of unreacted
Unevaporated ink components remain unavoidable. Therefore, even if the sintering temperature is 200 ° C. or less, a very strong film is formed, but if circumstances permit, a higher temperature is generally preferred. When the firing temperature is 250 ° C. or higher, the gel condensation reaction and drying of the silicate are completed, and this further shrinks the film, so that the packing density of the conductive fine particles increases and the surface resistance value decreases. Also, the contact state between the conductive fine particles is improved with the evaporation of the solvent component, and the stability of the resistance value and the change with time are improved.

The coating liquid according to the present invention is obtained by dispersing conductive fine particles, and does not form a thin film of the desired conductive fine particles by utilizing decomposition or chemical reaction of the coating liquid components due to heat during baking. Therefore, it is possible to form a thin film having stable characteristics and a uniform thickness. Further, the firing temperature may be a temperature at which the evaporation of the solvent component and the dispersant component or the polymerization and solidification of the alkyl silicate partial hydrolyzate can be promoted, so that the low-temperature film formation as described above is possible.

In order to supplement the strength of the single-layer film by the coating solution,
When a coating solution containing the alkyl silicate partially hydrolyzed polymer is further applied and then fired, the firing temperature may be, for example, 150 to 450 ° C.

[0033]

Embodiments of the present invention will be described below. As a solution containing an alkyl silicate partially hydrolyzed polymer used in the following examples (hereinafter, referred to as “silicate solution”), 30 parts of Tama Chemical Industries ethyl silicate 40 having an average degree of polymerization of 4 to pentamer was used. And 44 parts of ethanol are mixed, and stirred with a water-ethanol solution (distilled water 46).
Parts + 20 parts of ethanol), and 1% by weight of HC
A solution prepared by dropping a mixed solution of 10 parts of an aqueous solution and 7 parts of ethanol was used. Before use, this was appropriately diluted with a solvent such as ethanol. Note that this silicate solution is merely an example, and this example does not limit the present invention.

The surface resistance of the formed film was measured using a surface resistance meter MCP-T200 manufactured by Mitsubishi Yuka Corporation. The haze value and the transmittance were measured using a haze meter HR-200 manufactured by Murakami Color Research Laboratory. The particle size of the conductive fine particles was evaluated with a transmission electron microscope manufactured by JEOL.
The powder resistance value of the pellets formed by hydrostatic pressure of 1 ton
It was measured by the UW method.

Example 1 RuO ₂ having an average particle size of 18 nm was added to 100 g of an aqueous solution in which 0.01 g of tin dichloride was dissolved.
The powder was impregnated with 3 g of ultrafine powder for 1 hour, filtered, washed sufficiently with water, and dried at 120 ° C. On the other hand, 100 g of an aqueous solution of Ag / ammonia complex prepared by adding aqueous ammonia to a 3% aqueous solution of silver nitrate until the liquid becomes transparent is prepared.
As a reducing solution, a solution prepared by diluting 9.5 g of a 30% aqueous solution of sodium potassium tartrate tetrahydrate (Rossel salt) with 90.5 g of water was prepared.

The above treated RuO ₂ ultrafine powder was added to the reduced solution, stirred for 10 minutes, and then the above Ag / ammonia complex aqueous solution was added. The silver precipitation reaction was continued for 4 hours with stirring, and then a 1 μm membrane filter was used. Ru, washed with water, dried at 120 ° C. and covered with a silver coating layer
O ₂ powder was obtained.

The powder resistance value of this powder is 6.1 × 10 ⁻⁴ Ω.
Cm, which is one digit lower than the dust resistance of 4.7 × 10 ⁻³ Ω · cm in the case where silver coating is not performed.

(Example 2) 15 parts of RuO ₂ powder coated with a silver coating layer obtained in the same manner as in Example 1, and 25 parts of 4-hydroxy-4-methyl-2-pentanone (diacetone alcohol) as a dispersion solvent And a silane coupling agent as a dispersant (TSL880 manufactured by Toshiba Silicone Co., Ltd.)
2) Stir and mix at a ratio of 5 parts, perform ball mill dispersion using a zirconia ball having a diameter of 5 mm for 100 hours, add ethanol, mix vigorously again, and mix RuO ₂ coated with a silver coating layer. A coating liquid containing 5% by weight of conductive fine particles of powder was prepared.

This coating solution was further subjected to a solid concentration of 0.5,
200 × 200 × 3 m, diluted with ethanol to 1.0, 2.0, 3.0%, and rotated at 160 rpm
m was dropped from a beaker onto a soda lime plate glass, and then baked in the air at 180 ° C. for 30 minutes to form a single-layer film in which conductive fine particles were dispersed. The monolayer film thus formed has a solid content concentration of 0.5, 1.0, 2..
0, 3.0%, respectively.
5 × 10 ⁵ Ω / □, 2.3 × 10 ⁵ Ω / □, 8.6 × 10
³ Ω / □, 3.4 × 10 ³ Ω / □. A film having a surface resistance of 3.4 × 10 ³ Ω / □ has a haze value of 2.1%,
The transmittance was 70%.

(Example 3) The solid concentration of Example 2 was 3.
200 × 20 rotating 0% coating solution at 160 rpm
A 0 × 3 mm soda lime plate glass was dropped from a beaker, followed by dropwise addition of a solution obtained by diluting the above silicate solution with ethanol so that the SiO ₂ concentration became 1.1%. Bake for a minute,
A two-layer film composed of a RuO ₂ dispersion layer and an overcoat layer was prepared. The characteristics of the two-layer film thus formed were such that the surface resistance was 7.6 × 10 ² Ω / □, the haze was 2.1%, and the transmittance was 69%.

Example 4 RuO was used as the conductive fine particles.
_A silver coating treatment was performed in the same manner as in Example 1 except that Pb ₂ RuO _6.5 ultrafine powder having an average particle size of 32 nm was used instead of ₂ . The powder resistance of the obtained powder is 8.3 × 10 ⁻⁴ Ω · c.
m, which is almost two orders of magnitude lower than the dust resistance value of 9.0 × 10 ⁻² Ω · cm when the silver coating treatment is not performed.

Example 5 A silver-coated Pb ₂ RuO _6.5 dispersion coating solution having a solid content of 3.0% was obtained in the same manner as in Example 2 using the silver-coated Pb ₂ RuO _6.5 ultrafine powder obtained in Example 4. This was spin-coated in the same manner as in Example 3 to form a two-layer film using silicate as an overcoat layer. The characteristic of this two-layer film is that the surface resistance value is 8.8 × 10 ² Ω.
/ □, transmittance was 67%, and haze value was 3.5%.

(Comparative Example 1) The conductive fine particles containing silver described in claim 1 were not used as the conductive fine particles, and an ITO ultrafine powder (ITO-) having an average particle diameter of 19 nm manufactured by Sumitomo Metal Mining Co., Ltd. was used. UFP) alone. Other operations were performed in the same manner as in Example 2 to form a two-layer film, and the characteristics were evaluated. In this case, a surface resistance of 8.6 × 10 ³ Ω / □ was obtained, but the transmittance was 96%, and a dark film could not be formed.

Comparative Example 2 A film was formed in the same manner as in Example 2 except that high-conductivity carbon powder manufactured by Mitsubishi Chemical Corporation having an average particle diameter of 8 nm was used as the conductive fine particles, and the characteristics were evaluated. In this case, the transmittance was extremely dark at 46%, and the surface resistance was very high at 3.9 × 10 ⁸ Ω / □.

(Comparative Example 3) A silver coating treatment was performed in the same manner as in Example 1 using RuO ₂ powder having an average particle size of 55 nm as the conductive fine particles. % Of a silver-coated RuO ₂ dispersion coating liquid was prepared and spin-coated in the same manner as in Example 3 to prepare a two-layer film having silicate as an overcoat layer. Regarding the characteristics of this two-layer film, the surface resistance was 5.8 × 10 ² Ω / □, which was a low value, but the transmittance dropped to 47% and the haze value was 5.5.
%.

As is clear from the comparison with the above Examples and Comparative Examples, when a processing solution containing only a transparent oxide such as ITO or a black conductive material such as carbon was used as the conductive powder, the surface resistance value and Desired characteristics such as transmittance and reflectivity cannot be obtained, but by using a coating solution in which silver-coated ruthenium oxide fine particles are dispersed, transmittance can be reduced appropriately without increasing haze, and electric field shielding A film having high conductivity required for the above can be obtained.

[0047]

As described above, the CRT screen has the function of reducing the transmittance without scattering the visible light, and has a higher conductivity than the conventional one, which may affect the human body. Provided is a coating solution for forming a dark-colored transparent conductive film and a dark-colored transparent conductive film using the same, which can easily and inexpensively produce a film having a sufficient effect of shielding a low-frequency electric field using a coating method. Was done.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H01B 13/00 503 H01B 13/00 503C

Claims (4)

[Claims] 1. Ruthenium oxide fine particles as conductive fine particles are dispersed in a polar solvent, and the ruthenium oxide fine particles are partially or entirely covered with a silver film layer,
A coating liquid for forming a dark-colored transparent conductive film, which has a particle size of 50 nm or less. 2. Ruthenium oxide fine particles are dispersed in a polar solvent as conductive fine particles, and the ruthenium oxide fine particles are partially or entirely coated with a silver film layer,
A coating liquid for forming a dark-colored transparent conductive film, wherein the particle diameter is 50 nm or less, and the polar solvent contains an alkyl silicate partially hydrolyzed polymer. 3. A dark-colored transparent conductive film obtained by coating a substrate with the coating solution for forming a dark-colored transparent conductive film according to claim 1. 4. A base material is coated with the coating liquid for forming a dark-colored transparent conductive film according to claim 1 or 2,
A dark-colored transparent conductive film obtained by coating a solution of the alkyl silicate partially hydrolyzed polymer thereon and then baking it.