JPH05239409A - Conductive coating composition and production of conductive coating film - Google Patents

Abstract

PURPOSE:To obtain a composition capable of giving a coating film excellent in conductivity, transparency and pencil hardness. CONSTITUTION:This composition comprises a siloxane polymer obtained by the hydrolytic condensation of a tetraalkoxysilane, a mixture obtained by dispersing an antimony-doped tin oxide powder of a particle diameter of 0.2mum or below in a silane coupling agent, a photosensitizer and a solvent. The process in the title comprises using this composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive coating composition, and more specifically to a conductive coating composition suitable for forming a conductive film having excellent transparency on the surface of a substrate such as glass or ceramics. Relates to a method for producing a conductive coating film.

[0002]

2. Description of the Related Art In recent years, a conductive coating film has been formed on a glass surface of a cathode ray tube of a television or a display of various OA devices for the purpose of preventing static electricity. This method includes a method of applying an organic substance such as a hydroxyl group-containing polymer, a higher alcohol, and a surfactant, but this method has poor solvent resistance and scratch resistance, and therefore has a short life of antistatic effect and is not practical. . As another method, formation of an antistatic film using an inorganic material has been attempted. For example, JP-A-62-187188 discloses a method in which a hydrolyzable tin compound or antimony-doped tin compound is hydrolyzed to obtain fine particles, water is removed, and the particles are dispersed in ethanol and baked. ing. However, this method has a drawback that it is inferior in scratch resistance because it does not contain a binder. Japanese Unexamined Patent Publication (Kokai) No. 62-252481 discloses a composition comprising a conductive powder, a binder and a solvent, but the binder is an organic type, so that the scratch resistance is limited.
Japanese Unexamined Patent Application Publication No. 1-29887 discloses tin oxide fine particles,
An antistatic treatment liquid consisting of silica sol and an organic solvent is disclosed, but since this liquid is a heat-curing type, it is necessary to heat the entire CRT in order to completely cure the thin antistatic film on the surface of the CRT. It is not desirable in efficiency, and it takes a lot of time for heating and cooling.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and a method for producing a conductive coating composition and a conductive coating film having excellent conductivity, transparency, solvent resistance and scratch resistance. Is provided.

[0004]

The present invention provides (A) a siloxane polymer obtained by hydrolyzing and condensing tetraalkoxysilane, and (B) antimony-doped tin oxide powder having a particle size of 0.2 μm or less. Is dispersed in a silane coupling agent, a conductive coating composition containing (C) a photosensitizer and (D) a solvent, and the composition are coated on the surface of a base material and irradiated with ultraviolet rays. The present invention relates to a method for producing a conductive coating film that cures. A method for synthesizing the siloxane-based polymer which is the component (A) of the present invention will be described. Siloxane-based polymer dissolves tetraalkoxysilane in a solvent,
It is obtained by adding water dropwise to this and subjecting it to hydrolysis and condensation. Solvents include methanol, ethanol, isopropanol,
Common siloxane polymer synthesis solvents such as alcohols such as butanol, ketones such as acetone and methyl ethyl ketone, and esters such as ethyl acetate and butyl acetate can be used. The amount of water required for hydrolysis is preferably 1.0 to 10.0 mol with respect to 1 mol of tetraalkoxysilane. If it is less than 1.0 mol, it is difficult to obtain a uniform coating film,
If it exceeds 10.0 mol, the scratch resistance tends to be poor. Inorganic acids such as hydrochloric acid and nitric acid, and organic acids such as maleic acid and acetic acid can be used as a catalyst, if necessary. The synthesis temperature is within a range not exceeding the boiling point of the synthesis solvent of 50 ° C to 100 ° C,
The synthesis time is 10 minutes to 15 from the viewpoint of coating film forming property and film strength.
A range of about time is preferable.

The component (B) antimony-doped tin oxide (hereinafter referred to as antimony-doped tin oxide powder) powder is prepared by dissolving tin chloride and antimony chloride in an aqueous solution of hydrochloric acid, an alcohol solution, or a mixed solution thereof. The resulting solution is added to heated water to precipitate,
It can be produced by filtering and washing this, followed by firing and crushing. Particles having a particle size of 0.2 μm or less can be used, but those having a particle size of 0.05 μm or less are more preferable. If the particle size exceeds 0.2 μm, a thin film cannot be formed, the transparency decreases, and sedimentation easily occurs. Preferable examples of the antimony-doped tin oxide powder include T-1 manufactured by Mitsubishi Materials Corporation. As the silane coupling agent used for producing the component (B), a silane coupling agent represented by the formula (I) is preferable.

Embedded image RnSi (OR ′) _4-n (I) (R is an organic group having 1 to 8 carbon atoms, R ′ is an alkyl group having 1 to 5 carbon atoms, and n is 1 or 2) Is γ−
Examples thereof include methacryloxypropyltrimethoxysilane, vinyltriethoxysilane, and γ-glycidoxypropyltrimethoxysilane.

As a method for obtaining a mixture by dispersing antimony-doped tin oxide powder with a silane coupling agent, the silane coupling agent is sprayed or drip into the tin oxide powder while being well stirred by a Henschel mixer, super mixer, or the like. There is a dry method of adding by, a wet method of stirring tin oxide powder with a silane coupling agent at high speed in the presence of a solvent, a spray method of spray adding a silane coupling agent to tin oxide powder in a high temperature state, and the like. A wet method that can uniformly treat the entire particle is preferable. As a dispersing device by a wet method, a ball mill,
A sand mill, three rolls, etc. are used. Dispersion of the antimony-doped tin oxide powder with a silane coupling agent is preferably roll dispersion with a strong shearing force, but dispersion with a bead mill such as a sand grinder is also possible. When the dispersion liquid of the antimony-doped tin oxide powder and the silane coupling agent is dispersed in the siloxane-based polymer and the solvent, a usual dispersion method such as bead milling or ultrasonic dispersion can be applied.

As the photosensitizer of the component (C), benzyl dimethyl ketal, benzophenone, acetophenone,
Conventional photosensitizers such as benzoin and their derivatives can be used.

Examples of the component (D) solvent include ketone solvents such as acetone and methyl ethyl ketone, alcohol solvents such as methyl alcohol, ethyl alcohol, isopropyl alcohol and diacetone alcohol, ester solvents such as ethyl acetate and butyl acetate, Methylene chloride,
A chlorine-based solvent such as 1,1,1-trichloroethane can be used, but it is preferable to use methyl ethyl ketone as a main component from the viewpoint of film forming property.

The solid content of the conductive coating composition of the present invention is 0.1
It is preferably in the range of 10% by weight. If it is less than 0.1% by weight, the resistance reduction is insufficient, and if it exceeds 10% by weight, the scratch resistance tends to be lowered. The solvent of the component (D) is preferably blended so that the solid content of the composition is 0.1 to 10% by weight. The photosensitizer as the component (C) is preferably used in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the silane coupling agent as the component (B).
If it is less than 0.1 parts by weight, the photocurability tends to decrease, and if it exceeds 10 parts by weight, the scratch resistance tends to decrease. When the antimony-doped tin oxide powder as the component (B) is dispersed with a silane coupling agent, the compounding ratio is 100 silane coupling agent.
Antimony-doped tin oxide is 50 to 20 parts by weight.
A range of 00 parts by weight is preferred. Outside of this range, roll dispersion is difficult. Next, the compounding ratio of the siloxane polymer as the component (A), the antimony-doped tin oxide powder as the component (B), and the silane coupling agent will be described. The antimony-doped tin oxide powder is preferably used in the range of 10 to 400 parts by weight based on 100 parts by weight of the siloxane-based polymer. If it is less than 10 parts by weight, the resistance reduction is insufficient, and if it exceeds 400 parts by weight, the scratch resistance tends to be lowered. The compounding ratio of the silane coupling agent is
The range of 0.1 to 200 parts by weight is preferable with respect to 100 parts by weight of the total amount of the siloxane polymer and the antimony-doped tin oxide powder. If it is less than 0.1 part by weight, the curability tends to decrease, and if it exceeds 200 parts by weight, the scratch resistance tends to decrease.

The conductive coating composition of the present invention is applied on the surface of a substrate such as glass or ceramic by a general coating method such as spin coating, spray coating, roll coating or dip coating to obtain a high pressure mercury lamp or an ultra high pressure mercury lamp. A conductive coating film is obtained by irradiating ultraviolet rays with a general ultraviolet ray irradiating device such as a metal halide lamp and curing.

After the conductive coating composition is coated on the surface of the substrate, it is exposed to 20 mW / cm ^{2 to} 200 mW / c by an ultraviolet irradiation device.
After irradiation with ultraviolet rays having an exposure illuminance of m ² , it is preferable to heat-cure at 60 ° C. to 250 ° C. to obtain a transparent conductive coating film. When the exposure illuminance of ultraviolet rays is less than 20 mW / cm ² , the resistance reduction is insufficient, and when it exceeds 200 mW / cm ² , the temperature is too high, which is not preferable in terms of damage to the substrate and energy efficiency. If heated below 60 ° C, scratch resistance will decrease and 250 ° C
If it exceeds, it is not preferable in terms of damage to the substrate and energy efficiency. The UV irradiation time is usually set to 5 seconds or longer, and it is preferably 20 seconds or longer from the viewpoint of resistance reduction due to UV curing. The heat curing time is not particularly limited, but it is not necessary to heat for 30 minutes or more from the viewpoint of energy loss. UV irradiation and heating may be performed at the same time, but heating after UV irradiation is more economical in terms of energy efficiency. From the viewpoint of crack resistance, the film thickness is preferably 40 μm or less.

[0012]

EXAMPLES The present invention will now be described with reference to examples. In Examples and Comparative Examples, parts and% are based on weight. <Synthesis of Siloxane Polymer Solution A> Using a 500 ml four-neck flask made of glass, tetraethoxysilane 140 was added while passing dry nitrogen at a flow rate of 30 ml / min.
g, and 240 g of ethyl alcohol were charged, while stirring at room temperature, an aqueous maleic acid solution prepared by dissolving 1.5 g of maleic acid in 50 g of water was added dropwise over 1 hour, and then at 70 ° C.
After reacting for a time, a siloxane-based polymer solution A was obtained. As a result of measuring the nonvolatile content, it was 15%. Example 1 50 parts of T-1 (trade name of antimony-doped tin oxide powder manufactured by Mitsubishi Materials Corp., antimony doping amount: 10%, particle size of primary particles: about 0.05 μm), γ-methacryloxypropyltrimethoxysilane 3 rolls of 25 parts
A rounded dispersion mixture was obtained. 1 part of this mixture, 20 parts of siloxane-based polymer solution A, 0.0003 parts of benzyl dimethyl ketal, and 79 parts of methyl ethyl ketone were mixed and stirred with a bead mill (zirconia beads 0.5 mmφ) to obtain a composition A. Place this on a glass substrate at 300 rpm for 3
Spin coat for 0 seconds, then 30mw with ultra high pressure mercury lamp
It was irradiated with an exposure illuminance of / cm ² for 15 minutes to be cured to obtain a cured film.

Example 2 A cured film was obtained in the same manner as in Example 1 except that γ-methacryloxypropyltrimethoxysilane was changed to vinyltriethoxysilane. Comparative Example 1 A composition obtained by removing benzyl dimethyl ketal from the composition A of Example 1 was spin-coated in the same manner as in Example 1 and then cured at 160 ° C. for 30 minutes to obtain a cured film.

Comparative Example 2 20 parts of siloxane polymer solution A and 0.7 parts of T-1
And 79 parts of methyl ethyl ketone were mixed and stirred with a bead mill (zirconia beads, 0.5 mmφ) to obtain a composition B. From this, a cured film was obtained by the same curing method as in Example 1. Using the obtained cured film, surface resistance, transmittance at 550 nm, pencil hardness and ethyl alcohol resistance were evaluated. The results are shown in Table 1.

[0015]

[Table 1] * 1 Measured with a Yokogawa Hewlett-Packard high resistance meter. * 2 Absorbance at 550 nm was measured with a UV spectrophotometer. * 3 Performed according to JIS C3003. * 4 Immersed in ethyl alcohol at room temperature for 24 hours, and visually confirmed changes in appearance. * 5 The appearance of the conductive coating film was visually observed.

Example 3 A mixture of T-1, 50 parts, γ-methacryloxypropyltrimethoxysilane 25 parts and methyl ethyl ketone 25 parts was bead milled (zirconia beads 0.5 mmφ).
To obtain a dispersion mixture. 1 part of this mixture, 20 parts of siloxane polymer solution A, 0.0003 parts of benzyl dimethyl ketal, and 79 parts of methyl ethyl ketone were dispersed by ultrasonic dispersion to obtain a composition B. This was spin-coated on a glass substrate at 300 rpm for 30 seconds and irradiated with an ultrahigh pressure mercury lamp at an exposure illuminance of 30 mw / cm ² for 3 minutes,
A cured film was obtained by heating and curing at 100 ° C. for 10 minutes.

Example 4 A cured film was obtained in the same manner as in Example 3 except that γ-methacryloxypropyltrimethoxysilane was changed to vinyltriethoxysilane.

Comparative Example 3 A composition obtained by removing the benzyl dimethyl ketal from the composition B of Example 3 was spin-coated in the same manner as in Example 3 and then cured at 160 ° C. for 30 minutes to obtain a cured film.

Comparative Example 4 20 parts of siloxane polymer solution A, T-1, 0.7
Parts and 79 parts of methyl ethyl ketone were dispersed by ultrasonic dispersion to obtain a composition. From this, a cured film was obtained by the same curing method as in Example 3.

Comparative Example 5 A cured film was obtained in the same manner as in Example 3 except that the heating temperature was changed to 50 ° C. The obtained conductive coating film was evaluated for surface resistance, transmittance at 550 nm, pencil hardness, ethyl alcohol resistance, and film appearance. The results are shown in Table 2.

[0021]

[Table 2] * 1 Measured with a high resistance meter stack TR-3 manufactured by Tokyo Electronics Co., Ltd. * 2 Absorbance at 550 nm was measured with a UV spectrophotometer. * 3 Performed according to JIS C3003. * 4 Immersed in ethyl alcohol at room temperature for 24 hours, and visually confirmed changes in appearance. * 5 The appearance of the conductive coating film was visually observed.

From Tables 1 and 2, the conductive coating composition and the conductive coating film obtained by the production method of the present invention have low surface resistance, high transparency, and high pencil hardness. Therefore, they are excellent in scratch resistance and solvent resistance. It is shown to be excellent.

[0023]

The conductive coating composition of the present invention is obtained by previously dispersing metal particles with a silane coupling agent and then mixing a siloxane polymer, a solvent and a photosensitizer.
This can be ultraviolet-cured to form a coating film having excellent conductivity, transparency and pencil hardness. Further, when the conductive coating composition of the present invention is cured by being irradiated with ultraviolet rays having an exposure illuminance of ²⁰ mw / cm ² or more and then heated at 60 ° C. or more, this coating film is obtained with good energy efficiency in a short time. be able to.

Claims (3)

[Claims] 1. A siloxane-based polymer obtained by hydrolyzing and condensing tetraalkoxysilane (A), and (B) tin oxide powder doped with antimony and having a particle size of 0.2 μm or less, dispersed with a silane coupling agent. A conductive coating composition comprising the mixture obtained by the above, (C) a photosensitizer and (D) a solvent. 2. A method for producing a conductive coating film, which comprises coating the surface of a substrate with the conductive coating composition according to claim 1 and irradiating with ultraviolet rays to cure the coating film. 3. A coating a conductive coating composition of claim 1 on a substrate surface, after irradiation with ultraviolet rays of exposure illuminance of ^{20mW / cm 2 ~200mW / cm 2} , is cured by heating at 60 ° C. to 250 DEG ° C. Method for producing conductive coating film.