JPH07181302A - Coating liquid for forming reflection preventive overcoat film - Google Patents

Abstract

PURPOSE:To form a film which is excellent in waterproof on a transparent conductive oxide film by carrying out hydrolysis and condensation polymerization of alcohol solution mainly consisting of alkyl silicate under the specific condition. CONSTITUTION:A coating liquid, which is applied on a base board on which a transparent conductive oxide film consisting of ITO particles using alkyl silicate as a binder is formed, consists of l-25% by weight of alkyl silicate and an organic solvent at least containing 60% by weight or more of ethanol. An alkyl group in alkyl silicate is one or a mixture consisting of two kinds or more of groups selected from a methyl group, an ethyl group, a propyl group, and a butyl group. Moreover, for the organic solvent, ethanol alone or a mixture solvent consisting of ethanol and one or more kind of substance selected from methanol, propanol, butanol, diacetone alcohol, acetone, and dimethylformamide is used. In terms of a film thickness controlling property, uniformity, a smooth application property, and the like, spin coating is desirable for an application method.

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 an overcoat film having excellent water resistance on a transparent conductive film for electric field shielding formed on the surface of a display or cathode ray tube of an office automation equipment.

[0002]

2. Description of the Related Art Since dust due to static electricity is easily attached to the surface of a cathode ray tube, and when a human body is in contact therewith, electric discharge causes an electric shock. There is. In particular, with the recent development of OA, many office automation displays have been introduced into offices, and work is performed in contact with a cathode ray tube (CRT).
When working in contact with a CRT of a computer, not only dust on the surface of the CRT due to static electricity or electric shock, but also the display screen is easy to see, images are easy to read, and visual fatigue is not felt. It is necessary and the effects of leaked X-rays and leaked electromagnetic fields on the human body must meet safety standards.

Generally, the problem with electrostatic charging is CR
The problem can be solved by depositing a conductive film on the surface of T for grounding. However, since the CRT is on the surface of the transmission image, the conductive film is preferably excellent in transparency. That is,
For a practical CRT, the haze value defined by the percentage of the ratio of the diffuse transmitted light amount to the total transmitted light amount is required to be as small as possible, about 5% or less. In order to reduce the haze, it is necessary that the light scattering source in the film is small and the film thickness is as thin as possible. Further, in order to make the screen easy to see, it is achieved by performing anti-glare (non-glare) treatment on the surface of the CRT or AR (Anti Reflection) treatment by forming a multilayer film to suppress the reflection of the image by diffuse reflection of extraneous light. . Further, the selection of the emission color is an important factor for making the image easy to read. In addition, since X-ray shielding is generated near the shadow mask, Pb,
A heavy element such as Ba or Sr may be added to provide a shielding effect. In addition, the electromagnetic field is generated around the electron gun,
Larger electromagnetic waves tend to leak to the surroundings as they become larger. Leakage of magnetic field can be prevented by applying reverse magnetic field,
Leakage of the electric field can be prevented by forming a conductive transparent film on the surface of the CRT glass and shielding the electric field, as in the case of preventing electrification.

However, in the electric field shield and the antistatic,
There is a large difference in the level of conductivity formed on the film, and a low resistance transparent conductive film with a surface resistance of about 10 ⁸ Ω / □ and an electric field shield of less than about 10 ⁵ Ω / □ is formed to prevent electrification. There is a need. Various proposals have hitherto been made to meet the above demands. 10 ⁶ Pa inside the CRT
Because it is a high vacuum, it is designed to increase the wall thickness of glass and to be curved to withstand atmospheric pressure. Since the cathode ray tube in this state cannot be heated to a high temperature, substantial surface film formation must be performed at a temperature of 200 ° C. or lower. As a method capable of forming a film at such a low temperature, for example, there is a method of forming a film of a conductive oxide such as tin oxide or indium oxide on the front surface of a CRT by vacuum vapor deposition and CVD.

Since the film formed by this method is composed of a single composition of tin oxide or indium oxide, the conductivity of the material is directly exhibited and a resistance value sufficiently low for the electric field shielding effect is obtained. Further, the film thickness is sufficiently thin and easy to control uniformly, and the antireflection treatment is easy to perform without impairing the resolution of the CRT. However, although a resistance value satisfying the electric field shielding effect can be obtained by this method, the atmosphere must be controlled and processed for each cathode ray tube, and the film formation requires a large cost, which is extremely difficult for practical CRT manufacturing. Inconvenient and less expensive coating methods are desired.

As an inexpensive coating method, a method of spraying or coating an ink composition is known. For example, as disclosed in Japanese Patent Laid-Open No. 1-29887,
There is a method in which an antistatic treatment liquid composed of fine particles of tin oxide, silica sol and an organic solvent can be formed into a film by spin coating at a low temperature of 200 ° C. or lower. However, the surface resistance of the transparent conductive film formed by this method is about 10 ⁷ to 10 ⁸ Ω / □, and only the conductivity satisfying the antistatic function is obtained, and the conductivity required to shield the leakage electric field is reduced. Is far behind.

From this point of view, the present inventors have previously proposed a treatment liquid for electric field shield which is excellent in transparency and coatability, and in particular provides sufficient electric conductivity for a leakage electric field shield of a CRT (Japanese Patent Application No. Hei 10 (1999) -135242). 4-307189). That is, 1 to 15% by weight of indium tin oxide (hereinafter referred to as ITO) fine particle powder having a tin content of 1 to 10% by weight and an average particle size of 50 nm or less is contained, and the binder has an alkyl group of methyl, ethyl, propyl, Butyl is an alkyl silicate, and the mixing ratio with respect to the ITO powder is 0.1 to 0.6 by weight, and the polar solvent is N-methyl-2pyrrolidinone (NMP) and ethanol, acetone, tetrahydroxyfuran, isopropyl alcohol, It contains one or more of diacetone alcohol and dimethylformamide (DMF).
The content of alkyl silicate is 0.1 to 6% by weight. The polar solvent contains N-methyl-2pyrrolidinone (NMP) and ethanol, and N-
The treatment liquid for electric field shielding is composed of 1 to 20% by weight of methyl-2 pyrrolidinone and 25 to 90% by weight of ethanol.

[0008]

However, there is a problem that the resistance of ITO fine particles increases due to the presence of water.
When the environment in which the CRT is placed is high temperature and high humidity, there is a concern that the infiltration of water will increase the resistance of the film and deteriorate it. Also regarding the film strength, the pencil hardness of the ITO layer film itself is about 3 to 4H at most, and the hardness of the CRT surface is insufficient. From this point of view I
It is important to form an antireflection overcoat film excellent in water resistance by taking advantage of the low resistance of TO. An object of the present invention is to solve the above problems and provide a coating liquid for forming an antireflection film having both surface protection and water resistance of a transparent conductive oxide film made of ITO fine particles capable of shielding a leakage electric field. .

[0009]

DISCLOSURE OF THE INVENTION The inventors of the present invention have been keen on a coating liquid for forming an antireflection overcoat film which is excellent in water resistance and protects a transparent conductive oxide film composed of ITO fine particles capable of shielding a leakage electric field. As a result of repeated studies, the inventors have found a coating liquid capable of forming a film that achieves the above-mentioned object by carrying out hydrolysis and polycondensation of alkyl silicate under appropriate conditions, and completed the present invention.

That is, the present invention is applied on a substrate on which a transparent conductive oxide film composed of ITO fine particles having an alkyl silicate as a binder is formed, wherein the alkyl silicate is 1 to 25% by weight and the ethanol is at least 60% by weight. A coating liquid consisting of the organic solvent contained above,
The alkyl group of the alkyl silicate is one or a mixture of two or more selected from methyl, ethyl, propyl and butyl, and the organic solvent is ethanol alone or ethanol and methanol, propanol, butanol, diacetone. It is characterized by being a mixed solvent of at least one selected from alcohol, acetone and dimethylformamide.

[0011]

The coating liquid for forming an antireflection overcoat film of the present invention contains an alkyl silicate as a main component on a transparent conductive oxide film made of ITO fine particles having an alkyl silicate as a binder, which is undercoated on a substrate. By hydrolyzing and polycondensing an alcohol solution under appropriate conditions, an antireflection overcoat film having excellent water resistance can be formed. The ITO fine particles used in the present invention have an average particle size of 50 nm or less from the viewpoint of the transparency of the coating film. The coating of the overcoat liquid on the substrate on which the transparent conductive oxide film made of ITO fine particles having an alkyl silicate as a binder is formed is preferably performed at a substrate temperature of 30 to 60 ° C. If the substrate temperature is too low, it takes a long time to form a coating film, dust is attached and a coating liquid flows after coating, resulting in unevenness of the film. Further, if it is too high, the leveling is deteriorated and the film becomes uneven.

The alkyl silicate may be appropriately selected depending on the alkyl silicate used as the binder for forming the transparent conductive oxide film composed of ITO fine particles, and is selected from methyl silicate, ethyl silicate, propyl silicate and butyl silicate. It is preferable that it is one kind or a mixture of two or more kinds. If the amount of alkyl silicate is less than 1% by weight, a film satisfying the water resistance cannot be obtained. If it exceeds 25% by weight, the film becomes too thick and the film is cracked after firing. Is good.

The catalyst is one selected from hydrochloric acid, sulfuric acid, nitric acid, acetic acid, hydrofluoric acid and ammonia. The amount of catalyst and water are not particularly limited, and may be added so that hydrolysis and polycondensation of the alkyl silicate proceed sufficiently and a film satisfying water resistance is obtained. Considering the compatibility with the alkyl silicate and water and the film forming state, the organic solvent is ethanol alone or ethanol and methanol, propanol,
A mixed solvent containing at least one solvent selected from butanol, acetone and dimethylformamide is preferable. Ethanol is contained in an amount of at least 60% by weight or more because if it is less than 60% by weight, the film after forming the coating film becomes non-uniform and satisfactory optical characteristics such as light transmittance and Haze value cannot be obtained.

ITO using an alkyl silicate as a binder
On a substrate on which a transparent conductive oxide coating composed of fine particles is formed, an alkyl silicate sol solution prepared from the above alkyl silicate, catalyst, water and organic solvent is applied by spin coating, spray coating or dip coating. Any method can be applied as long as it can be uniformly applied, but in terms of film thickness controllability, uniformness, smooth coating property, etc.,
Spin coating is particularly preferable. When spin coating,
Spin coating is performed at a substrate temperature of 30 to 60 ° C. and a rotation speed of 100 to 180 rpm. The rotation speed is one factor for controlling the film thickness, and thus may be appropriately changed to obtain a desired film thickness, but the rotation speed is preferable for the purpose of the present invention. The formed overcoat dry coating film is preferably baked at 120 to 200 ° C. in order to form a film having excellent water resistance. The baking time may be appropriately selected depending on the composition of the coating liquid and the baking temperature, but is usually 10 to 6
0 minutes is sufficient. As described above, the antireflection overcoat film having excellent water resistance can be formed.

[0015]

EXAMPLES Examples of the present invention will be specifically described below. A glass substrate (20 × 10 cm, thickness 3 mm) is washed with acetone and then heated to 30 to 60 ° C. After setting the heated substrate on the spin coater, Sn at 180 rpm.
ITO powder with a content of 4.3% [Made by Sumitomo Metal Mining Co., Ltd.]
Ethyl silicate 40 [manufactured by Tama Chemical Industry Co., Ltd.] 0.5% by weight, H ₂ O 0.1% by weight, 5%
HCl 0.1% by weight, ethanol 86.3% by weight, diacetone alcohol 6.0% by weight, DMF 4.3% by weight
And an antistatic liquid consisting of 1.2% by weight of NMP were coated while moving from the central part to the end part, and 120 sccc was held in this state to form an ITO transparent conductive oxide film. The following examples and comparative examples were performed using a substrate coated with an ITO transparent conductive oxide film formed as described below. All percentages below are weight percentages.

Example 1 Ethyl silicate 40 3.0% Water 0.9% 6% HCl 0.2% Ethanol 95.9% Film forming conditions were as follows: substrate temperature 43 ° C., rotation speed 180 rpm, baking temperature 160 ° C. -30 minutes. (Example 2) Methyl silicate 51 4.7% [manufactured by Tama Chemical Industry Co., Ltd.] Water 1.4% 6% HCl 0.1% Diacetone alcohol 7.3% Acetone 16.8% Ethanol 69.7% The film forming conditions are a substrate temperature of 40 ° C., a rotation speed of 180 rpm, and a baking temperature of 160 ° C. for 30 minutes.

(Example 3) Methyl silicate 7.0% Water 5.0% 6% HNO ₃ 0.3% Methanol 8.7% Ethanol 79.0% Film forming conditions are: substrate temperature 54 ° C., rotation speed 180 rpm. The firing temperature is 190 ° C.-80 minutes. (Example 4) Ethyl silicate 4.6% Butyl silicate 0.4% Water 0.6% 6% HCl 0.7% Methanol 86.0% Butanol 7.7% Film formation conditions were a substrate temperature of 47 ° C. and rotation. It is several 160 rpm and the firing temperature is 180 ° C.-40 minutes.

(Example 5) Propyl silicate 2.0% Water 0.3% 5% H ₂ SO ₄ 0.4% Ethanol 89.5% Isopropanol 7.8% Film formation conditions were a substrate temperature of 38 ° C. and rotation. It is several 150 rpm and the firing temperature is 170 ° C. for 30 minutes. (Example 6) Ethyl silicate 40 25.0% water 60. % 6% HCl 1.5% ethanol 67.5% The film forming conditions are a substrate temperature of 47 ° C., a rotation speed of 180 rpm, and a firing temperature of 180 ° C. for 30 minutes. (Example 7) Ethyl silicate 40 15.0% Water 3.6 6% HCl 0.9% Ethanol 80.5% The film forming conditions are a substrate temperature of 50 ° C, a rotation speed of 180 rpm, and a baking temperature of 160 ° C for 30 minutes. is there.

(Comparative Example 1) 0.8% ethyl silicate,
A coating solution similar to that in Example 5 was prepared except that ethanol was changed to 90.7% to form a film. (Comparative Example 2) A coating solution similar to that in Example 3 was prepared except that methyl silicate 51 27.0% water 6.4 6% HCl 1.6% ethanol 65.0% was used.

Comparative Example 3 A coating solution similar to that of Example 4 was prepared except that the organic solvent was ethanol 50% and isopropanol 43.7%. (Comparative Example 4) A coating solution similar to that in Example 7 was prepared except that propanol was used instead of ethanol, and a film was formed. (Comparative Example 5) A coating liquid similar to that in Example 7 was prepared except that methanol was used instead of ethanol,
The film was formed.

The coating solutions prepared as in Examples 1 to 7 and Comparative Examples 1 to 5 were continuously coated on a substrate coated with the ITO transparent conductive oxide film formed as described above. Hold for 60 seconds. After that, the antireflection overcoat film was formed by baking under the above respective conditions. The evaluation results of the obtained overcoat film are shown in Table 1. The haze value is HR-1 manufactured by Murakami Color Research Laboratory.
00, the film strength was measured using a scratch film hardness tester manufactured by Toyo Seiki Seisaku-sho, Ltd. The boiling water resistance was examined by immersing the film in boiling water for 30 minutes and then checking for film peeling. The film that did not change was represented by O, the film that peeled slightly was represented by Δ, and the film that completely peeled was represented by X. For the film unevenness, a visual appearance test was conducted. A for a clear film, B for a slightly uneven film,
The non-uniform film was ranked C.

[0022]

[Table 1]

From the results shown in Table 1, the coating liquid composition of the present invention can form an overcoat film sufficiently satisfying the water resistance, uniformity and film strength of the film. If the amount of alkyl silicate is too small (Comparative Example 1) or too much (Comparative Example 2), the film strength satisfying the water resistance cannot be obtained, or a large amount of unreacted alkyl silicate remains, causing the deterioration of resistance with time. And film cracking. When the amount of ethanol contained is small (Comparative Example 3) or ethanol is not contained at all (Comparative Examples 4 and 5), the film has a high haze value and lacks transparency.

[0024]

As described above, according to the coating solution for forming an antireflection overcoat film according to the present invention, a transparent conductive oxide composed of indium tin oxide particles containing an alkyl silicate as a binder and capable of shielding a leakage electric field is used. It is possible to form an antireflection film having both surface protection and water resistance of a physical film.

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Claims (3)

[Claims] 1. An alkyl silicate is coated on a substrate on which a transparent conductive oxide film made of indium tin oxide fine particles having an alkyl silicate as a binder is formed.
A coating liquid for forming an antireflection overcoat film, which comprises 25% by weight and an organic solvent containing at least 60% by weight of ethanol. 2. The alkyl group of the alkyl silicate is one kind or a mixture of two or more kinds selected from methyl, ethyl, propyl and butyl.
The coating liquid for forming the antireflection overcoat film as described above. 3. The organic solvent is ethanol alone or a mixed solvent of ethanol and one or more kinds selected from methanol, propanol, butanol, diacetone alcohol, acetone and dimethylformamide. Alternatively, the coating liquid for forming the antireflection overcoat film according to item 2.