JP2005225700A - Indium tin oxide fine particle, coating for forming transparent conductive film, transparent conductive film and display apparatus, and method of manufacturing transparent conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide indium tin oxide fine particles and a coating for forming a transparent conductive film by which the transparent conductive film having a superior conductivity such that the surface resistivity is 10<SP>3</SP>Ω/sq. or lower, a excellent antireflection property such that the lowest reflectance in the visible light region is 1% or smaller, a excellent durability such that the lowering of the conductivity with time is small, can be realized, and a transparent conductive film and a display apparatus, and also a method of manufacturing the transparent conductive film. <P>SOLUTION: The indium tin oxide fine particles have a specific surface area of 15 m<SP>2</SP>/g to 30 m<SP>2</SP>/g, the range of the value of a<SP>*</SP>is -12 to -7 when the color values of transmitting color in the visible light region are expressed with a<SP>*</SP>and b<SP>*</SP>, and the range of the value of b<SP>*</SP>is 15 to 25. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to tin-containing indium oxide fine particles, a coating for forming a transparent conductive film, a transparent conductive film, a display device, and a method for producing the transparent conductive film, and more particularly, a cathode ray tube (CRT), a liquid crystal display (LCD), an electroluminescent It is suitably used for various display devices such as nescent display (EL), plasma display (PDP), and field emission display (FED). It is related with the technique which can provide.

Conventionally, display devices such as a cathode ray tube (CRT), a liquid crystal display (LCD), an electroluminescent display (EL), a plasma display (PDP), and a field emission display (FED) are provided with an electromagnetic shielding property. A transparent conductive film is formed on the display surface.
Furthermore, in order to impart antireflection properties, a low refractive index film mainly composed of silica is laminated on the transparent conductive film.
In such a transparent conductive film, tin-containing indium oxide (ITO) is used as a conductive component particularly when high transparency is required for light in the visible light region. The transparent conductive film using ITO is required to have a surface resistance value of 10 ³ Ω / □ and a minimum reflectance of 1% or less in the visible light region.
As a method for forming a transparent conductive film using ITO, a dry film forming method for forming a film by a sputtering method, a high temperature thermal decomposition method, or the like, or a coating method for forming a film by applying a paint in which ITO fine particles are dispersed ( For example, see Patent Document 1.
JP-A-6-232586

By the way, in the conventional dry film forming method, the formed transparent conductive film can satisfy the required characteristics, but an expensive manufacturing apparatus such as a sputtering apparatus or a high-temperature pyrolysis apparatus is required. The apparatus cannot process a large amount at a time, and the productivity is very inferior. As a result, there is a problem that the transparent conductive film is expensive.
Further, in the conventional coating method, if a transparent conductive film having a surface resistance value of 10 ³ Ω / □ is to be obtained, the thickness of the transparent conductive film must be increased, resulting in poor antireflection properties. There is a problem that the minimum reflectance in the visible light region exceeds 1%.

In addition, attempts have been made to increase the conductivity of the ITO fine particles themselves by increasing the degree of reduction of the ITO fine particles. However, if ITO fine particles having an increased degree of reduction are used, the surface resistance value of the transparent conductive film is reduced after the coating film is formed. There is a problem that it becomes higher due to the change with time, and as a result, the conductivity of the transparent conductive film is lowered.
As described above, the conventional transparent conductive film using ITO fine particles cannot satisfy the characteristics required in terms of conductivity, antireflection properties and durability, and has better conductivity than the transparent conductive film. , Antireflection properties and durability have been demanded.

The present invention has been made in order to solve the above-described problems, and has an excellent conductivity such that the surface resistance value is 10 ³ Ω / □ or less and the minimum reflectance in the visible light region is 1% or less. Tin-containing indium oxide fine particles capable of realizing a transparent conductive film having excellent durability such as high anti-reflection properties and small deterioration in conductivity due to changes over time, and formation of a transparent conductive film using the tin-containing indium oxide fine particles An object of the present invention is to provide a coating material and a transparent conductive film, a display device including the transparent conductive film, and a method for producing the transparent conductive film.

The present inventors are not concerned with the change in the general color tone of tin-containing indium oxide fine particles and the reducibility, but the influence of the color tone and specific surface area of tin-containing indium oxide fine particles on conductivity, antireflection properties, and durability. As a result of earnest research, tin-containing indium oxide fine particles having a specific surface area in a specific range and a color tone in a specific region have excellent conductivity, antireflection properties and durability as fine particles, and in particular, the specific surface area is 15 m ^2. / G to 30 m ² / g and the value range of a ^* when the color value of the transmitted color in the visible light region is represented by a ^* and b ^* is −12 to −7 and b ^* When the value range is 15 or more and 25 or less, the surface resistance value is 10 ³ Ω / □ or less, excellent conductivity, and the minimum reflectance in the visible light region is 1% or less, Decrease in conductivity due to changes over time It found that it is possible to realize the transparent conductive film having excellent durability as small, and have completed the present invention.

That is, the tin-containing indium oxide fine particles of the present invention have a specific surface area of 15 m ² / g or more and 30 m ² / g or less, and the transmitted color values in the visible light region are represented by a ^* and b ^*. The value range of ^* is -12 or more and -7 or less, and the value range of b ^* is 15 or more and 25 or less.

  The transparent conductive film-forming coating material of the present invention comprises the tin-containing indium oxide fine particles of the present invention.

The transparent conductive film of the present invention comprises a transparent conductive layer containing the tin-containing indium oxide fine particles of the present invention.
It is preferable that a transparent layer having a refractive index different from that of the transparent conductive layer is formed on one or both main surfaces of the transparent conductive layer.

  The display device of the present invention is characterized by comprising the transparent conductive film of the present invention on a display surface.

  In the method for producing a transparent conductive film of the present invention, the transparent conductive film-forming coating material of the present invention is applied onto a substrate, and then a transparent layer-forming coating material containing a material that is a raw material for silicon oxide is applied on the coating film. It is characterized by applying and then heat-treating the substrate on which these coating films are formed.

According to the tin-containing indium oxide fine particles of the present invention, a ^* when the specific surface area is 15 m ² / g or more and 30 m ² / g or less and the color value of the transmitted color in the visible light region is represented by a ^* and b ^{* .} The tin-containing indium oxide fine particles having excellent transparency, conductivity, antireflection properties and durability because the value range of −12 and −7 and b ^* value range of 15 and 25 Can be realized.

  According to the coating film for forming a transparent conductive film of the present invention, since the tin-containing indium oxide fine particles of the present invention are contained, a transparent conductive film excellent in transparency, conductivity, antireflection property and durability can be realized. .

According to the transparent conductive film of the present invention, since the transparent conductive layer containing the tin-containing indium oxide fine particles of the present invention is provided, not only the transparency but also the surface resistance value of 10 ³ Ω / □ or less is excellent. It is possible to realize a transparent conductive film having conductivity, excellent antireflection properties such that the minimum reflectance in the visible light region is 1% or less, and excellent durability that the decrease in conductivity due to aging is small.

  Further, if a transparent layer having a refractive index different from that of the transparent conductive layer is formed on one or both main surfaces of the transparent conductive layer, the antireflection property can be further improved.

According to the display device of the present invention, since the transparent conductive film of the present invention is provided on the display surface, the display surface has not only transparency, but also excellent conductivity with a surface resistance value of 10 ³ Ω / □ or less. , Excellent anti-reflection properties such that the minimum reflectance in the visible light region is 1% or less, and excellent durability that the decrease in conductivity due to change over time is small, the transparency of the display surface of the display device, The conductivity, antireflection property and durability can be improved.

According to the method for producing a transparent conductive film of the present invention, the transparent conductive film-forming coating material of the present invention is applied onto a substrate, and then a transparent layer forming material containing a material that is a raw material of silicon oxide on the coating film. Since the coating material is applied and then the base material on which these coating films are formed is heat-treated, the surface resistance value is 10 as well as transparency on the surface of the base material using a simple and inexpensive manufacturing apparatus. Transparent conductive film having excellent conductivity of ³ Ω / □ or less, excellent antireflection property with a minimum reflectance of 1% or less in the visible light region, and excellent durability that the decrease in conductivity due to aging is small Can be formed easily and at low cost.

BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the tin-containing indium oxide fine particles, the transparent conductive film forming paint, the transparent conductive film, the display device, and the method for producing the transparent conductive film of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[Tin-containing indium oxide (ITO) fine particles]
The ITO fine particles of the present invention have a specific surface area of 15 m ² / g or more and 30 m ² / g or less, and the range of the value of a ^* when the color value of the transmitted color in the visible light region is represented by a ^* and b ^*. Is a particle having a value of b ^* of not less than −12 and not more than −7, and b ^* of not less than 15 and not more than 25.

Here, the “specific surface area” is a total surface area per 1 g of ITO fine particles, and is a specific surface area measured by the BET method.
The specific surface area of the ITO fine particles of the present invention needs to be 15 m ² / g or more and 30 m ² / g or less. If the specific surface area is less than 15 m ² / g, a dispersion failure is likely to occur when the coating material is produced, and as a result, the uniformity of the coating film is impaired. This is because, when the film is formed, the contact area between the ITO fine particles is reduced, so that the conductivity of the film is reduced and the surface resistance value is increased. On the other hand, if the specific surface area exceeds 30 m ² / g, the contact resistance between particles increases when the film is formed, and thus the surface resistance value increases.

Further, a visible color value of transparent color in the light region ^{a *} and ^{b *,} by the ^{a *} and ^{b *} values in the ^a * ^{b *} color system standardized by International Certification Commission (CIE) Yes, standardized by Japanese Industrial Standards (JIS Z 8729).
When the color value of the transmitted color in the visible light region of the ITO fine particles of the present invention is represented by a ^* and b ^* , the range of the value of a ^* is −12 or more and −7 or less, and the range of the value of b ^* is 15. It must be above and below 25.

  In general, ITO fine particles have oxygen-deficient conductive properties due to their characteristics, and the conductivity is affected by the degree of oxidation and reduction. The higher the degree of reduction, the better the conductivity. The color tone changes from yellow to blue depending on the degree of reduction. However, since the ITO fine particles cause oxygen deficiency due to reduction, the conductivity of the film when the film is formed using the ITO fine particles changes with time depending on the environment where the oxygen deficiency increases. easy. Furthermore, the properties of the ITO fine particles and the properties of the film formed using the same do not necessarily match, and the ITO fine particles having a very high degree of reduction are likely to cause grain growth. Therefore, the ITO fine particles were used. In the paint, the surface resistance value and the reflectance are increased due to the deterioration of dispersibility in the paint or film. In addition, since the ITO fine particles are oxidized by heating during film formation, the conductivity is likely to decrease.

In the ITO fine particles of the present invention, the specific surface area is 15 m ² / g or more and 30 m ² / g or less, and the range of the value of a ^* when the color value of the transmitted color in the visible light region is represented by a ^* and b ^*. -12 or more and -7 or less, and by the range of b ^* value is 15 or more and 25 or less, by forming the transparent conductive film using the ITO fine particles, the surface resistance of 10 ³ Ω / □ To achieve a transparent conductive film having excellent conductivity of less than a pedestal, excellent anti-reflection property with a minimum reflectance of 1% or less in the visible light region, and excellent durability that a decrease in conductivity due to aging is small. Can do.
A more preferable range of these a ^* and b ^* values is a range of a ^* values of −12 to −7 and a b ^* value range of 21 to 25.

The ITO fine particles of the present invention can be obtained, for example, by hydrolyzing an indium salt and a tin salt in a solution, and heating the resulting oxide or hydroxide product in a reducing atmosphere. . Here, by adjusting the concentration, pH, hydrolysis rate, degree of reduction, etc. of the raw material salt, it is possible to control the specific surface area of the ITO fine particles and the color values a ^* and b ^* of the transmitted color in the visible light region. it can.

[Paint for forming transparent conductive film]
The coating film for forming a transparent conductive film of the present invention has a specific surface area of 15 m ² / g or more and 30 m ² / g or less, and a ^* when the color value of the transmitted color in the visible light region is represented by a ^* and b ^{* .} Is a paint containing ITO fine particles having a value range of −12 to −7 and a b ^* value range of 15 to 25. This paint includes paste-like ones.

This coating material is obtained by dispersing the ITO fine particles of the present invention in a solvent, and may contain a dispersant, a binder component, a colorant, other inorganic particles, organic particles, and the like as necessary.
The solvent is not particularly limited as long as the ITO fine particles can be dispersed, and water and / or an organic solvent is preferable.

  Examples of the organic solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, diacetone alcohol, furfuryl alcohol, cyclohexyl alcohol, tridecyl alcohol, ethylene glycol, diethylene glycol, and hexylene glycol. , Esters such as acetic acid methyl ester and acetic acid ethyl ester, and ketones such as acetone, acetylacetone, diacetone alcohol, methyl ethyl ketone, methyl isobutyl ketone and acetoacetic acid ester are preferably used.

  Further, diethyl ether, β-oxyethyl methyl ether (ethylene glycol monomethyl ether / methyl cellosolve), β-oxyethyl ether (ethylene glycol monoethyl ether / ethyl cellosolve), butyl-β-oxyethyl ether (ethylene glycol monobutyl ether / Butyl cellosolve), β-oxyethylpropyl ether (ethylene glycol monopropyl ether / isopropyl cellosolve), diethylene glycol monomethyl ether, diethylene glycol monoethyl ether (carbitol), ethers such as diethylene glycol monobutyl ether (butyl carbitol) are also preferably used. .

In addition, toluene, cyclohexane, isophorone, methyl acetate, butyl acetate, tetrahydrofuran, terpioneel, cyclohexanone, propylene carbonate, N-methyl-2-pyrrolidone, n-hexane, xylene, butyl-β-oxyethyl ether acetate (butyl cellosolve acetate (Trade name)), butyl carbitol acetate and the like are also preferably used.
These organic solvents may be used alone or in combination of two or more.
Among these organic solvents, ethanol, 2-propanol, β-oxyethyl ether (ethyl cellosolve) and the like are particularly preferable because of excellent dispersibility of ITO fine particles.

The dispersant is not particularly limited. For example, an oily dispersant such as alkyl diamine, lecithin, sorbitan fatty acid ester, polyacrylic acid, alkyl amine fatty acid salt, alkyl triamine, or anionic surfactant, cation Examples thereof include aqueous surfactants such as system surfactants, nonionic surfactants, and pH regulators.
Although the ratio of a dispersing agent changes with kinds of dispersing agent to be used, it is 0.1-100 weight% normally with respect to ITO fine particles.

As the binder component, an inorganic binder or an organic binder can be used.
As the inorganic binder, for example, metal alkoxides such as tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ), tetramethoxysilane (Si (OCH ₃ ) ₄ ), and hydrolysates thereof can be used.

  Examples of the organic binder include melamine acrylate resin, polyester resin, polyvinyl chloride resin, ethyl cellulose resin, nitrocellulose resin, ketone resin, epoxy resin, styrene / maleic acid resin, fluorine resin, polyurethane resin, polypropylene resin, alkyd Resins, polyamide resins, phenol resins, silicone resins, polyvinyl acetate resins, cellulose acetate resins, polyvinyl alcohol resins, silicone monomers, silicone oligomers, and silicone resins are preferably used.

Among these organic binders, acrylic resin, ethyl cellulose resin, and polyester resin are particularly preferable because a film having high transparency and low surface resistance can be obtained.
These resins are preferably one of a thermosetting resin and an ultraviolet curable resin from the viewpoint of film accuracy and workability.
The proportion of the binder component in the coating is usually 1 to 30% by weight, although it varies depending on the type of binder component used.
In addition, when improving the electroconductivity of a film | membrane in particular, it is preferable that the binder component in a coating material is as little as possible or does not contain.

  Examples of the colorant include monoazo pigment, quinacridone, iron oxide yellow, disazo pigment, phthalocyanine green, phthalocyanine blue, cyanine blue, flavanthrone yellow, dianthraquinolyl red, indanthrone blue, thioindigo Bordeaux, perylene orange Organic pigments such as perylene scarlet, perylene red 178, perylylene maroon, dioxazine violet, isoindoline yellow, nickel nitroso yellow, madder lake, copper azomethine yellow, aniline black, and alkali blue are preferably used.

  In addition, zinc white, titanium oxide, petal, chromium oxide, iron black, titanium erotic, cobalt blue, cerulean blue, cobalt green, alumina white, viridian, cadmium yellow, cadmium red, vermilion, lithopone, yellow lead, molybdate orange Inorganic pigments such as zinc chromate, calcium sulfate, barium sulfate, calcium carbonate, lead white, ultramarine, manganese violet, emerald green, bitumen, and carbon black are also preferably used.

Also suitable are azo dyes, anthraquinone dyes, indigoid dyes, phthalocyanine dyes, carbonium dyes, quinone imine dyes, methine dyes, quinoline dyes, nitro dyes, nitroso dyes, benzoquinone dyes, naphthoquinone dyes, naphthalimide dyes, perinone dyes, etc. Used.
These colorants such as organic pigments, inorganic pigments and dyes can be used alone or in combination of two or more. This coloring material is used for improving the contrast of a transmission image and adjusting the colors of transmitted light and reflected light.

  In addition to the above-mentioned various raw material components, this transparent conductive film-forming coating material may contain, for example, metal fine particles such as ruthenium, rhodium, palladium, osmium, iridium, and platinum, for the purpose of improving film strength and conductivity. , Silicon, aluminum, zirconium, cerium, titanium, yttrium, zinc, magnesium, indium, tin, antimony, inorganic particles such as gallium, or inorganic particles such as nitride, or conductive polymers such as polyaniline May be included.

This transparent conductive film forming paint can be produced, for example, as follows.
After weighing various raw material components such as the ITO fine particles, dispersant, binder component, colorant, other inorganic particles, and organic particles of the present invention so as to be in the above composition range, these raw material components are three roll mill, ball mill, Mix and disperse using a mixing device such as a sand grinder.

By producing a transparent conductive film using this paint for forming a transparent conductive film, the haze value is 0.5% or less, the total light transmittance is 90% or more, and the surface resistance value is 9 × 10 ³ Ω / □ or less. A transparent conductive film having a very small change in resistance value due to a change with time can be easily obtained.

[Transparent conductive film]
This transparent conductive film has a specific surface area of 15 m ² / g or more and 30 m ² / g or less, and the range of the value of a ^* when the color value of the transmitted color in the visible light region is represented by a ^* and b ^*. It is a transparent conductive film comprising a transparent conductive layer containing ITO fine particles having a value of −12 or more and −7 or less and a b ^* value of 15 or more and 25 or less.

In this transparent conductive layer, ITO fine particles may be dispersed in a binder component or a matrix component, and almost all of the transparent conductive layer may be composed of ITO fine particles.
Moreover, at least a part of the ITO fine particles may be welded. From the viewpoint of conductivity, it is preferable that the binder component and the matrix component be as small as possible. The content of ITO fine particles in the transparent conductive film is preferably 30% by weight or more, more preferably 70% by weight or more.
This transparent conductive layer may contain the above-described dispersant, binder component, colorant, other inorganic particles, organic particles, and the like, if necessary.

This transparent conductive layer can be produced, for example, by applying the above-described transparent conductive film-forming coating material on a substrate, then drying, and further heat-treating as necessary. The base material is preferably transparent, and the material is not particularly limited, but a glass base material, a plastic base material and the like are preferably used.
Although it does not specifically limit as a glass base material, For example, a glass substrate used for the display part of various display apparatuses, for example, a soda-lime glass substrate, a low alkali glass substrate, a non-alkali glass substrate, a high strain point glass substrate, etc. Can be appropriately selected and used.

The plastic substrate is not particularly limited, but a plastic substrate in the form of a film or a sheet is preferable, and a plastic substrate transparent to visible light is particularly preferable.
The shape of these base materials is not particularly limited, such as a plate shape or a film shape.

  This transparent conductive layer is a coating for forming the transparent conductive film described above, using a coating technique such as a spin coating method, a roll coating method, a spray method, a bar coating method, a dip method, a meniscus coating method, a gravure printing method, It can apply | coat on the base material mentioned above and can obtain by heat-processing as needed.

According to the transparent conductive layer, and a specific surface area of ^{15 m} 2 / g or more and ^{30 m} 2 / g or less, the ^{a *} value when representing the color value of the transparent color in the visible light range ^{a *} and ^{b *} in Since the ITO fine particles having a range of -12 or more and -7 or less and a b ^* value range of 15 or more and 25 or less were contained, the haze value was 0.5% or less, the total light transmittance was 90% or more, A transparent conductive film having a surface resistance value of 9 × 10 ³ Ω / □ or less and a very small change in resistance value due to a change with time can be realized.

In this transparent conductive film, by forming a transparent layer having a refractive index different from that of the transparent conductive layer on one or both main surfaces of the transparent conductive layer, low reflectivity (antireflection property), Functions such as anti-glare properties can be added.
In particular, when producing a transparent conductive film having low reflectivity, conventionally, a multilayer film such as a two-layer or three-layer film having an optical film thickness adjusted by adjusting a refractive index and a film thickness is used. In this case, it is necessary to appropriately adjust the optical film thickness of each layer. However, in the case of a conductive film using conventional ITO fine particles, it is necessary to increase the film thickness in order to improve conductivity. In other words, the range of adjustment of the optical film thickness becomes narrow, and there is a possibility that adjustment with other layers may not be successful. Therefore, it has been difficult to achieve excellent transparency, conductivity and excellent low reflectivity at the same time.

In this transparent conductive film, the specific surface area is 15 m ² / g or more and 30 m ² / g or less, and the range of the value of a ^* when the color value of the transmitted color in the visible light region is represented by a ^* and b ^* is -12 or more and -7 or less, and the range of the value of b ^* is 15 or more and 25 or less. By forming transparent layers having different refractive indexes, excellent conductivity is exhibited even when the film thickness is thin, optical film thickness adjustment is easy, and various combinations with other layers are possible, In addition to excellent transparency and conductivity, excellent low reflectivity can be realized.
Next, a low reflective transparent conductive film obtained by adding a low reflective function to the transparent conductive film of the present invention will be described.

[Low reflective transparent conductive film]
The low-reflectivity transparent conductive film is a specific surface area of ^{15 m} 2 / g or more and ^{30 m} 2 / g or less, ^{a *} value when representing the color value of the transparent color in the visible light range ^{a *} and ^{b *} in A transparent layer containing silica (silicon oxide) is formed on the transparent conductive layer containing ITO fine particles having a range of -12 to -7 and a b ^* value of 15 to 25. It is a configuration.
This transparent layer is preferably formed on the transparent conductive layer.
A transparent layer containing silica has a relatively low refractive index and a high surface hardness of the film, so that it is very preferable when a low-reflective film is formed.

In the case of a conventional transparent conductive film using ITO fine particles, the film thickness must be increased in order to improve the conductivity, and silica is obtained while obtaining a surface resistance value of 9 × 10 ³ Ω / □ or less. It was difficult to achieve low reflectivity in combination with the transparent film contained.

This low-reflectivity transparent conductive film, and a specific surface area of 15 m 2 / ^g or more and 30 m 2 / ^g or less, a ^* value when representing the color value of the transparent color in the visible light range a ^* and b ^* in By combining a transparent conductive layer containing ITO fine particles having a range of -12 to -7 and a b ^* value of 15 to 25 and a transparent film containing silica, Even if it is thin, excellent conductivity can be exhibited, the optical film thickness can be adjusted, and excellent low reflectivity can be exhibited.
In particular, when a transparent layer mainly composed of silica is formed on the transparent conductive layer, a strong film can be formed without a binder in the transparent conductive layer.

Next, the manufacturing method of this low reflective transparent conductive film is demonstrated.
The specific surface area is 15 m ² / g or more and 30 m ² / g or less on a base material such as a glass substrate, a plastic substrate, or a plastic film, and the color value of the transmitted color in the visible light region is represented by a ^* and b ^* . When a transparent conductive film forming coating material containing ITO fine particles having a ^* value range of −12 to −7 and b ^* value of 15 to 25 is applied, and then dried. The coating film of the transparent conductive layer.
Next, a coating material for forming a transparent layer containing a material that is a raw material for silica is applied onto the coating film, and then dried to obtain a coating film for the transparent layer.

Examples of the material that is a raw material of silica contained in the coating material for forming a transparent layer include the following formula (1),
M (OR) _m R _n (1)
(Wherein, M is Si, R is an alkyl group of _C 1 -C _4, m is an integer from 1 to 4, n is an integer of 0 or 1 to 3, and m + n is 4 )
A paint containing one or a mixture of one or more of the compounds represented by the formula (1) or a partial hydrolyzate thereof in a solvent is preferably used.

As the compound represented by the formula (1), for example, a metal alkoxide such as tetraethoxysilane (Si (OC ₂ H ₅ ) ₄ ), tetramethoxysilane (Si (OCH ₃ ) ₄ ) is preferably used. In particular, tetraethoxysilane is suitably used from the viewpoints of thin film formability, transparency, bondability with a transparent conductive layer, film strength, and antireflection performance.

Examples of the solvent for the coating material for forming the transparent layer include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, diacetone alcohol, β-oxyethyl ether (ethylene glycol monoethyl ether / ethyl cellosolve), water, and the like. Etc., and methanol, ethanol, 2-propanol and the like are particularly preferable.
In addition, various resins, metal oxides, composite oxides, nitrides, or the like or precursors thereof may be included as long as the optical film thickness can be adjusted.

As a coating method of the transparent layer forming paint, various coating methods used when applying the above-described transparent conductive film forming paint can be used, for example, spin coating method, roll coating method, spray method, Coating techniques such as bar coating, dip coating, meniscus coating, and gravure printing can be used.
Thereafter, the substrate on which these coating films are formed is heat-treated.

The temperature and time of the heat treatment vary depending on the type of substance used as a silica raw material, but the heat treatment temperature is 100 to 300 ° C.
The reason why the heat treatment temperature is limited to 100 to 300 ° C. is that if the heat treatment temperature is lower than 100 ° C., the paint containing silica cannot be sufficiently baked, and if the heat treatment temperature is higher than 300 ° C. This is because the ITO fine particles are oxidized and the conductivity is deteriorated.
Further, the heat treatment time may be selected so that the paint containing the silica component is sufficiently baked in accordance with the heat treatment temperature, and usually 10 minutes or more is preferable, and in particular, the baking condition of the paint containing the silica component. 20 minutes to 180 minutes is preferable.
As described above, a low reflective transparent conductive film can be produced.

According to this method for producing a low reflective transparent conductive film, the transparent conductive film forming paint and the transparent layer forming paint are heat-treated at the same time. Since the contact resistance between the ITO fine particles in the transparent conductive film is reduced, a highly conductive film can be obtained.
In addition, due to this action, a strong film can be obtained even when the lower transparent conductive layer does not contain a binder component.
Therefore, a low reflective transparent conductive film having high conductivity, transparency and low reflectivity can be easily produced.
In addition, since the transparent conductive film forming paint for forming the lower layer does not need to contain a binder component, the content of the ITO fine particles can be 90% by weight or more.

[Display device]
The display device of the present invention has the above low reflectivity on the display surface of a cathode ray tube (CRT), a liquid crystal display (LCD), an electroluminescent display (EL), a plasma display (PDP), a field emission display (FED) or the like. The transparent conductive film is formed.
According to this display device, since the low-reflective transparent conductive film is formed on the display surface, excellent transparency, excellent conductivity with a surface resistance of 10 ³ Ω / □ or less, and the lowest in the visible light region. Excellent anti-reflective properties with a reflectance of 1% or less, and excellent durability that the decrease in conductivity due to changes over time is small, providing transparency, conductivity, anti-reflective properties and durability of the display surface. Can be increased.

EXAMPLES Hereinafter, although this invention is demonstrated concretely by Examples 1-6 and Comparative Examples 1-7, this invention is not limited by these Examples.
As for the ITO fine particles, ITO fine particles having specific surface areas and color values a ^* and b ^* shown in Table 1 were prepared, respectively, and these ITO fine particles were used for the preparation of a transparent conductive layer forming coating material.

The specific surface area and color evaluation method of the ITO fine particles are as follows.
(1) Specific surface area: MONO SORB (manufactured by Quanta chrome (Yuasa Ionics))
Used, measured by the BET one-point method by the continuous flow method. Carrier gas
Is a measurement equilibrium phase using a 30 v / v% N ₂ -70 v / v% He mixed gas.
The counter pressure (P / P ₀ ) was set to 0.3.
The degassing condition was a gas flow at 250 ° C. for 15 minutes.
(2) Color: Tokyo Denshoku "TOP SCAN TC-1800MK II" (light source: halogen lamp)
The sample was filled into a predetermined colorless and transparent container, and the reflected light was measured.

[Example 1]
(1) Preparation of ITO paint (paint for forming transparent conductive layer) Using yellow-green ITO fine particles having a specific surface area of 20 m ² / g, color value a ^* of −9 and b ^* of +22, 15% by weight of ITO fine particles These were weighed and mixed so that the polymer dispersant was 1% by weight and the ethanol was 84% by weight, and dispersed in a bead mill for 5 hours to obtain a concentrated solution.
Next, N in the above concentrate was added to the above concentrate so that the ITO fine particles as a solid content was 2% by weight, N-methylpyrrolidone 1.5% by weight, β-oxyethyl ether (ethyl cellosolve) 20% by weight, and the balance being ethanol. -Methylpyrrolidone, β-oxyethyl ether and ethanol were added to prepare an ITO paint.

(2) Preparation of Silica Paint (Transparent Layer Forming Paint) Each was weighed and mixed to 25% by weight of tetraethoxysilane, 38% by weight of ethanol, and 12% by weight of 1N hydrochloric acid, and then 60% using an evaporator. Hydrolysis was performed at 0 ° C. for 3 hours to obtain a concentrated solution.
Next, diacetone alcohol, β β-oxyethyl ether (ethyl cellosolve) 20% by weight, silica as solid content, 20% by weight of β-oxyethyl ether (ethyl cellosolve), and the remainder to be ethanol. -Oxyethyl ether and ethanol were added to prepare a silica paint.

(3) Production of low-reflective transparent conductive film An ITO paint was applied on a soda glass substrate by a spin coating method, dried at room temperature (25 ° C.), and then on this coating film by a spin coating method. A silica paint was applied and dried at room temperature (25 ° C.) to prepare a substrate with a coating film.
This coated substrate was heat-treated at 200 ° C. for 30 minutes to produce the low reflective transparent conductive film of Example 1.

[Examples 2 to 6]
Low reflective transparent conductive films of Examples 2 to 4 were produced in the same manner as in Example 1 except that the ITO fine particles used were changed as shown in Table 1.
Moreover, the low reflective transparent conductive film of Examples 5 and 6 was produced like Example 1 except having changed the ITO fine particles to be used and the heat treatment temperature as shown in Table 1.

[Comparative Examples 1 to 7]
Low reflective transparent conductive films of Comparative Examples 1 to 5 were produced in the same manner as in Example 1 except that the ITO fine particles used were changed as shown in Table 2.
Moreover, the low reflective transparent conductive films of Comparative Examples 6 and 7 were produced in the same manner as in Example 1 except that the ITO fine particles used and the heat treatment temperature were changed as shown in Table 2.

[Evaluation of membrane]
The low reflective transparent conductive films in Examples 1 to 6 and Comparative Examples 1 to 7 were evaluated.
Evaluation items and evaluation methods are as follows.
(1) Transmittance: Measured by “Automatic Haze Meter HIII DP” manufactured by Tokyo Denshoku Co., Ltd. (2) Haze: Same as above (3) Minimum reflectance: Measured by “Self-recorded spectrophotometer, U-3500 type” manufactured by Hitachi, Ltd. 4) Surface resistance value: measured by “Loresta AP” manufactured by Mitsubishi Chemical Corporation
Measurement includes initial measurement (initial value) and constant temperature and humidity chamber (23 ° C., 55% RH)
The measurement was carried out after being left for 30 days (after 30 days).

[Evaluation results]
In the low-reflective transparent conductive films of Examples 1 to 6, the transmittance, haze, and minimum reflectance are excellent, and the surface resistance value is 6.3% or less after changing for 30 days. It was confirmed that the surface resistance value was small and the change over time was very small.
On the other hand, in the low reflective transparent conductive films of Comparative Examples 1 to 7, the transmittance is not different from Examples 1 to 6, but the haze is 0.6% or more, and the minimum reflectance is 1% or more. It was inferior to the film | membrane of Examples 1-6. As for the surface resistance value, the rate of change of the surface resistance value after being left for 30 days was as large as 6% or more, and some of them exceeded 50%.

The tin-containing indium oxide fine particles, the transparent conductive film forming paint, the transparent conductive film, the display device, and the method for producing the transparent conductive film of the present invention have excellent conductivity and visible light with a surface resistance value of 10 ³ Ω / □ or less. Since it is possible to realize a transparent conductive film having excellent anti-reflection properties such that the minimum reflectance in the region is 1% or less, and excellent durability that the decrease in conductivity due to aging is small, CRT, LCD, The effect is great not only in display devices such as EL, PDP, and FED, but also in various industrial fields such as windows for automobiles and buildings.

Claims (6)

When the specific surface area is 15 m ² / g or more and 30 m ² / g or less, and the color value of the transmitted color in the visible light region is represented by a ^* and b ^* , the range of the value of a ^* is −12 or more and −7 Tin-containing indium oxide fine particles having a value of b ^* of 15 or more and 25 or less.   A paint for forming a transparent conductive film, comprising the tin-containing indium oxide fine particles according to claim 1.   A transparent conductive film comprising a transparent conductive layer containing the tin-containing indium oxide fine particles according to claim 1.   4. The transparent conductive film according to claim 3, wherein a transparent layer having a refractive index different from that of the transparent conductive layer is formed on one or both main surfaces of the transparent conductive layer.   A display device comprising the transparent conductive film according to claim 3 on a display surface.   3. The transparent conductive film-forming paint according to claim 2 is applied onto a substrate, and then a transparent layer-forming paint containing a substance that is a raw material for silicon oxide is applied onto the coating film, and then these coating films are applied. A method for producing a transparent conductive film, comprising: heat-treating a substrate on which the film is formed.