JPH03227376A - Production of inorganic electrically conductive coating material - Google Patents

Abstract

PURPOSE:To obtain the subject coating material having excellent precipitation property of electrically conductive powder and giving a cured coating film having excellent transparency and conductivity by mixing an inorganic binder and a solvent to a liquid dispersion composed of antimony-doped tin oxide powder. CONSTITUTION:The objective coating material is effective in imparting a substrate with antistaticity when applied to the surface of a transparent substrate such as glass or plastics. It can be produced by mixing (A) a liquid dispersion produced by dispersing (i) 1-10wt.% of antimony-doped tin oxide powder having particle diameter of <=0.2mum, (ii) 99-90wt.% of a solvent such as ethanol and (iii) 1-10wt.% (based on the component i) of a surfactant with a dispersing machine such as homo-mixer and separating the precipitate by centrifugal separation decantation after leaving at rest for several days, (B) an inorganic binder such as tetraethoxysilane and (C) a solvent.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for producing an inorganic conductive paint to be applied to a transparent substrate such as glass or plastic. The present invention relates to a method for producing an inorganic conductive paint having excellent properties and good sedimentation properties of conductive powder.

[Conventional technology]

In recent years, it has become common to prevent static electricity on transparent substrates such as glass or plastic by imparting conductivity to them.

Conventionally, to impart conductivity to a transparent substrate such as glass or plastic, the surface of the substrate is coated with a paint that is made conductive by mixing carbon powder, metal powder, carbon fiber, or metal fiber. has been carried out. However, this paint has a problem in that the paint film exhibits a black or gray color, which impairs the color tone of the base material. Furthermore, even if tin oxide, indium oxide, etc. are used as metal oxides to achieve transparency, there are problems such as clouding of the substrate surface, and transparency cannot always be satisfied.Also, tin oxide has poor conductivity. The problem was that it wasn't enough. Furthermore, if this paint is left to stand, metal oxides will precipitate in a short period of time, which poses a problem in the application process.

In order to solve such problems regarding the transparency, conductivity and sedimentation of coating films, for example, Japanese Patent Publication No. 61-9343 discloses a conductive powder using conductive powder made of tin oxide doped with antimony. Paint is disclosed. However, in this conductive paint, an aqueous solution in which specific amounts of tin chloride and antimony chloride are dissolved is poured into heated water to hydrolyze the chloride, and the precipitate is washed separately, followed by heat treatment. In order to produce conductive powder with a diameter of 0.2 μm or less, the following problems have arisen. That is, when a conductive fine powder precursor is precipitated in a liquid by hydrolyzing a halide as disclosed in the above publication, the resulting precipitate is in a state where extremely fine primary particles aggregate. . For this reason, even if this precipitate is washed door-to-door, then heat-treated and further crushed, it still contains secondary agglomerated particles, which are agglomerated primary particles, and even if these are dispersed in a binder resin, they easily settle out Furthermore, there was a problem with G. et al. that the coating film coated with this coating had poor transparency.

In addition to this, even if the particles were further pulverized by powerful pulverization, the particles would quickly re-agglomerate due to their inherently strong cohesive force, resulting in the same problem as above.

[Problems to be Solved by the Invention] The present invention solves the problems associated with the prior art as described above, and it is possible to solve the problems associated with the prior art as described above. The cured coating film has good conductivity and transparency, and the curing temperature is 1.
It is an object of the present invention to provide a method for producing an inorganic conductive paint that can arbitrarily select a temperature of 00°C or higher and does not have a negative effect on the base material.

[Means to solve the problem]

The present invention is characterized in that (A) antimony-doped particles with a diameter of 0.2
1-10% by weight of tin oxide powder less than μm, solvent 99-9
After removing the precipitate by dispersing a surfactant in an amount of 0% by weight and 1 to 10% by weight based on the weight of the antimony-topped tin oxide powder, (B) an inorganic binder and (
C) A method for producing an inorganic conductive paint characterized by adding and mixing a solvent.

Next, materials used in the present invention will be described.

First, regarding component (A), the antimony-doped tin oxide (hereinafter referred to as antimony-doped tin oxide) powder used is, for example, a solution of tin chloride and antimony chloride in an aqueous solution of hydrochloric acid, an alcohol solution, or a mixed solution thereof. It can be produced by adding a solution obtained by dissolving these into heated water to precipitate a precipitate, which is then washed door to door, then calcined and pulverized. The particle size of this powder is 0.2
Must be less than μm, preferably 0.05 μm
m or less. When the particle size exceeds 0.2 μm, the particles become coarse, cannot form a thin film, have poor transparency, and tend to cause sedimentation. A suitable example of antimony-doped tin oxide is T1 manufactured by Mitsubishi Metals.

Examples of solvents include alcohols such as methanol, ethanol, isopropyl alcohol, butanol, octyl alcohol, and diacetone alcohol, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether. ,Ethyl acetate,
Solvents such as esters such as butyl acetate are used alone or in combination.

As the surfactant, various cationic, anionic, or nonionic surfactants can be used, but it is particularly preferable to use a cationic surfactant from the viewpoint of dispersibility. As a suitable example of surfactant, Bicchem
Anti-Terby made in Japan
ra-P), Disperbyk
) 130 (all product names).

Regarding the formulation, the antimony-doped tin oxide powder is used in an amount of 1-10% by weight, and the solvent is used in an amount of 99-90% by weight.
Used in amounts of % by weight. If it is less than 1% by weight, the concentration will be too low, and the concentration of the inorganic conductive paint described below will also be too low, causing a practical problem. Moreover, if it exceeds 10% by weight, the viscosity increases and the dispersibility deteriorates.

The amount of surfactant added is 1 to 10% by weight of the antimony-doped tin oxide powder. If the amount is less than 1% by weight, the effect of the surfactant will not be expressed and the dispersibility will be poor. 10% by weight
If it exceeds this, permeability and conductivity will deteriorate, and some surfactants may exhibit an aggregation effect rather than a dispersion effect.
Sedimentability deteriorates.

Further, as a dispersing machine, a homomixer, a homogenizer, an attritor, a ball mill, a sand mill, a roll, an ultrasonic wave, etc. are used. Among these, homomixers, homogenizers, ball mills, and sand mills are preferred from the viewpoint of dispersibility.

After processing with a dispersion machine, if centrifugation is performed or left to stand for several hours to several days, it will separate into an upper layer of antimony-doped tin oxide dispersion and a lower layer of precipitate. remove things. When the particles of the dispersion treated in this manner were observed under an electron microscope, it was confirmed that the number of secondary agglomerated particles was considerably reduced compared to before treatment.

Next, as the inorganic binder of component (B), there are silica-based inorganic binders, such as tetraethoxysilane and tetramethoxysilane, which can be used.Also, these can be dissolved in alcohol, ketone, etc., and water and acid are dissolved. In addition,
Polymers obtained by reaction, commercially available silica-based polymers, etc. can be used. Examples of this include ethyl silicate 28 and ethyl silicate 40 (both trade names) manufactured by Tama Chemical Industry (2).

The solvent of component (C) can be any of various solvents as long as it can dissolve the inorganic binder of component (B).
) The solvent used for the component can be used. Furthermore, in order to improve the curability of the inorganic binder, it is also possible to add water, and acids such as nitric acid, hydrochloric acid, and sulfuric acid.

Next, antimony-doped tin oxide powder in component (A),
The blending ratio of components (B) and (C) will be described. In view of the permeability and conductivity of the coating film, the weight ratio of antimony-doped tin oxide powder/inorganic binder is preferably in the range of 1/9 to 6/4. If it exceeds 6/4, the transmittance will be poor, and if it is less than 1/9, the conductivity will be poor.

The amount of solvent is 200 to 500 parts by weight per 10 parts by weight of the antimony-doped tin oxide powder and the inorganic binder.
0 parts by weight is preferred.

The inorganic conductive paint obtained by the method of the present invention can be applied by general coating methods such as spin coating, dip coating, and spray coating.
After drying the solvent at about 100"C from room temperature,
It can be cured at a temperature of 130 to 200 C or higher, but considering cracks and melting of the base material, the curing temperature should be 130 to 200 C.
°C is preferred.

[Example] Next, the present invention will be explained in more detail with reference to Examples. In the Examples and Comparative Examples, "parts" and "%" mean "parts by weight" and "% by weight," respectively, unless otherwise specified.

Example I T-1 (trade name of antimony-doped tin oxide powder manufactured by Mitsubishi Metals ■, antimony doping amount 10%, particle size of formed particles 0.
05 μm) 50 parts, 950 parts of ethanol, and Anti-Terra-P (trade name of a cationic surfactant manufactured by Bi-7 Kemi-Jiyaban) 3.5
The mixture was dispersed in a homomixer for 5 hours. After leaving this for 24 hours, the precipitate was removed by decantation,
Dispersion A was obtained.

When the concentration of the antimony-doped tin oxide powder in this dispersion A was measured, it was 3.0%. 100 parts of this dispersion A, ethyl silicate 40 (trade name of silica-based inorganic binder manufactured by Tama Chemical Industry ■, effective silica amount 40%) 7.5
1 part and 200 parts of ethanol were mixed and stirred for 10 hours to obtain an inorganic conductive paint.

Example 2 100 parts of dispersion A obtained in Example 1, 2 ethyl silicate
8 (trade name of a silica-based inorganic binder manufactured by Tama Chemical Industry Co., Ltd., effective silica content 28%), 25 parts of ethanol, 200 parts of ethanol, and 0.2 part of nitric acid were mixed and stirred for 10 hours to obtain an inorganic conductive paint.

Example 3 50 parts of T-1 used in Example 1, 950 ethanol
1 part and 2.5 parts of Antitelabi used in Example 1 were dispersed in a homomixer for 10 hours. After allowing this to stand for 24 hours, the precipitate was removed by decantation to obtain dispersion B. When the concentration of tin oxide powder in this dispersion B was measured, it was 2.8%. 200 parts of this dispersion B,
10 parts of ethyl silicate 40 and 280 parts of ethanol were mixed and stirred for 10 hours to obtain an inorganic conductive paint.

Comparative Example 50 parts of T-1 used in Example 1 and 95 ethanol
0 parts was dispersed in a homomixer for 10 hours. This is 24
When the mixture was allowed to stand for a period of time, almost all of the T1 precipitated, and the upper layer became a transparent liquid, making it impossible to form a dispersion. Therefore, after uniformly dispersing the above solution again, 100 parts of the solution taken out before precipitation was mixed with 100 parts of ethyl silicate 40.
2.5 parts and 200 parts of ethanol were mixed and stirred for 10 hours to obtain an inorganic conductive paint.

Table 1 shows the properties of the paints obtained in Examples 1 to 3 and Comparative Examples.

Properties of Examples and Comparative Examples in Table: The paint was placed in a 100 d Erlenmeyer flask and sealed tightly, and the presence or absence of sedimentation was determined by visual observation.

*2 Spin code (25 Orpm) the paint on the glass substrate.
), then dried at 80°C for 30 minutes and cured at 180''C for 60 minutes.The surface resistance of the test piece was measured using a surface resistance meter (High Resistance Meter, manufactured by Yokogawa Hewlett Buckard). It was measured.

*3: The transmittance of the glass substrate prepared in *2 at a wavelength of 600 nm was measured using a spectrophotometer (Hitachi 150-20 Model Double Beam Spectrophotometer).

As shown in Table 1, the inorganic conductive paints of Examples have good sedimentation properties and excellent conductivity and transparency.

〔Effect of the invention〕

The inorganic conductive paint obtained by the manufacturing method of the present invention has good settling properties of the conductive powder, excellent transparency and conductivity of the cured coating film,
It is suitable for application to the surface of a transparent substrate such as glass or plastic to impart an antistatic effect to the substrate.

Claims (1)

[Claims] 1. (A) 1 to 10% by weight of antimony-doped tin oxide powder with a particle size of 0.2 μm or less, 99 to 90% by weight of a solvent, and the weight of antimony-doped tin oxide powder. A method for producing an inorganic conductive paint, which comprises dispersing 1 to 10% by weight of a surfactant using a dispersing machine to remove precipitates, and then adding and mixing (B) an inorganic binder and (C) a solvent. 2. Claim 1, wherein the surfactant is a cationic surfactant.
The method for producing the inorganic conductive paint described above.