JPH0522740B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a paint that can be applied to floors, walls, ceilings, etc. of hospitals, electronics factories, chemical laboratories, etc. to prevent static electricity. In recent years, with the rapid spread of electronic equipment, IC,
Demand for electronic components such as LSI and VLSI is also increasing significantly. In production factories and assembly factories for these electronic components, attempts are being made to make the floors, walls, ceilings, etc. of the production site conductive in order to eliminate static electricity and charge. In other words, if the floor surface becomes electrically charged due to the frictional contact of workers' coverings, or if the walls or ceiling become electrically charged due to indoor airflow, this static electricity may discharge to electronic components and damage them. This is because it makes it difficult to remove fine dust. Taking the case of a dry coating film as an example, it is generally said that the effective surface resistance value for preventing static electricity is 10 ⁵ to 10 ⁹ Ω. In addition, highly flammable chemicals and solvents are often used in hospital operating rooms and chemical laboratories, so in order to prevent fires and explosions, the floors must be made conductive to discharge static electricity that inevitably occurs. It is hoped that this will happen. On the other hand, if the resistance is reduced excessively when making it conductive, it may cause an electric shock accident, so it is said that a surface resistance value of about 10 ⁵ to 10 ⁶ Ω for the dry coating film is desirable. By the way, the US NFPA (National
According to the Fire Protection Association standard, 2.5×
It is 10 ⁴ to 1×10 ⁶ Ω. In addition, antistatic applications can be considered in a wide variety of applications, such as meter display glass, television cathode ray tubes, clean room window glass, and semiconductor packaging materials. Conventionally, dielectric powders and conductive polymers have been used to prevent or remove static electricity. However, metals such as nickel and aluminum have oxidation problems, precious metals such as silver are too expensive to use, and carbon black is black, so
There are restrictions on where it can be used, and metal oxides have high resistance, making it impossible to obtain a sufficiently low resistance. Furthermore, since dielectric polymers have strong humidity dependence, they have little effect in low humidity environments. As described above, the reality is that there is no inexpensive and fully satisfactory material for preparing dielectric paints. The present inventors focused on conductive zinc oxide, which is a white powder and is available at a relatively low cost, and considered dispersing it in a binder solution to make an antistatic paint. In order to obtain the target resistance value, it is necessary to increase the ratio of conductive zinc oxide to the binder, which results in the conductive zinc oxide being exposed on the coating surface and the coating strength being insufficient. peeling was likely to occur. Moreover, if the target resistance value is less than 10 ⁶ Ω, it will be difficult to achieve this using conductive zinc oxide. In this regard, if conductive tin oxide is used, it is possible to obtain a surface resistance value of 10 ⁶ Ω or less;
It was 50 times more expensive, and there were cost constraints. In view of the current situation, the present inventors have conducted intensive research and found that when the following component (b) or (c) is mixed with the conductive zinc oxide or tin oxide, which is the component (a), The present invention was completed based on the knowledge that the electrical conductivity is significantly improved and the resistance value of the coating film surface is reduced. (b) Ingredients: Ascorbic acid, its optical isomers, or metal salts or basic salts thereof (c) Ingredients: Reducing sugars Conductive zinc oxide contains a small amount of aluminum, gallium, and tin equivalent to zinc oxide. It is an N-type semiconductor obtained by adding an impurity metal as a doping agent and firing it.
By appropriately selecting processing conditions such as temperature and time, particles with various particle sizes and resistances can be obtained. The same applies to conductive tin oxide, and its performance is generally determined by using antimony as a doping agent and controlling various processing conditions. These conductive zinc oxides and tin oxides are effective in improving conductivity because the finer the particle size, the better the mutual contact within the coating film.
Below, those of 0.5μ or less are particularly preferred. Particularly, fine powder having a particle size of 0.1 μm or less is useful because a transparent coating film can be obtained. When electrophilic molecules such as oxygen are adsorbed to the surface of the conductive zinc oxide and tin oxide described above, conduction electrons are driven inside, resulting in a decrease in electrical conductivity. In the present invention, as a result of incorporating component (b) such as ascorbic acid or component (c) such as reducing sugars into the paint, electrical conductivity is improved.
The reason is that component (b) or (c) reduces oxygen adsorbed on the surface of component (a), and at the same time, component (b) or (c)
This is thought to be due to the fact that as a result of the component adsorbing to the surface of component (a), charge transfer occurs between component (a) and component (b) or component (c) adsorbed to the surface. Furthermore, when a reducing substance such as phosphite or hypophosphite is added to the metallic copper powder and copper compound as a conductive paint used to form circuits on printed wiring boards, the conductive effect can be improved. Are known.
Since the paint used for forming these circuits is mainly composed of metallic copper powder, its unique color tone limits its uses. In addition, phosphites etc. reduce and precipitate the copper content in the copper compound as metallic copper, and fill the interparticle gaps of metallic copper powder with this precipitated copper.
As a result, conductivity is improved. Therefore, phosphites, sulfites, thiosulfates, etc. do not have a conductivity-improving effect on semiconductor materials known as conductive zinc oxide and tin oxide, which are component (a) of the present invention. . To explain the component (b) used in the present invention, ascorbic acid is a strongly reducing substance with an enediol group represented by L-ascorbic acid [the following general formula ()], and its optical isomer erythorbine Together with the acid [the following general formula ()], it increases the conductivity of the conductive zinc oxide and tin oxide as described above. Similarly, metal salts and basic salts of the above-mentioned ascorbic acid and its optical isomers, such as sodium ascorbic acid, can also be effectively used.

【formula】

[Formula] On the other hand, the reducing sugars serving as component (c) include reducing disaccharides such as meltose, lactose, and melbiose; aldose-based glycolaldehyde, glycose, xylose, galactose, arabinose, and mannose; ketose-based fructose;
Examples include sorbose, dihydroxyacetone, etc., 2-ketoaldonic acid-based 2-ketogluconic acid, and uronic acid-based glucuronic acid. In particular, aldose-based, ketose-based, and uronic acid-based materials have strong reducing properties and have a remarkable effect of improving conductivity. The blending ratio of component (b) and component (c) above to component (a) is 10 parts by weight or less per 100 parts by weight of component (a).
Preferably it is 0.005 to 5 parts by weight. At the end of 0.005 parts by weight, the effect of improving conductivity is small, and when it exceeds 5 parts by weight, the conductivity tends to decrease. Component (b) or (c) is usually added at the time of dispersing component (a) or mixing to prepare a paint, but it may be mixed with component (a) in advance. On the other hand, whether the binder of the paint is water-based or organic solvent-based, and which binder to use specifically is selected mainly depending on the situation and environment of the object to be coated. In aqueous systems, water-soluble binders such as polyvinyl alcohol, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, starch, modified starch, vinegar-based acrylic, acrylic acid,
Examples include emulsion binders such as styrene-butadiene and polyester. In addition, polymer electrolytes such as sodium polystyrene sulfonate and sodium polyacrylate having binding strength may be used as the binder. Organic solvent types include acrylic acid, styrene,
Examples include polymers or copolymers of butadiene, ethylene, acrylic esters, and methacrylic acid, silicone resins, polyester resins, polyurethane resins, alkyd resins, and epoxy resins. The present invention is not limited to the above-mentioned binders, and two or more binders may be used in combination as appropriate. In addition, if necessary, auxiliary agents, inorganic pigments, dyes, dispersants, ultraviolet absorbers, etc. are added to prepare the paint. The blending ratio of component (a) and binder varies depending on the target resistance value and strength of the coating film, or if too much binder is used, the distance between components (a) increases, resulting in higher resistance. The weight ratio is approximately 40:60 to 95:5. The paint thus obtained is applied using a bar, spray, doctor, blade, roll, brush, etc. onto ceilings, walls, wallpaper, floors, etc. that require conductive treatment, and For small items, a surface coating is formed by dipping. Further, by applying the above-mentioned paint to a synthetic resin film, an antistatic film that can be used extremely easily can be obtained. The film used as the support in this case may have a thickness of several mm, but from the viewpoint of processability, it is generally desirable to use a thin film of 0.2 mm or less. In particular, the antistatic film obtained by coating a transparent synthetic resin film with a paint that uses conductive tin oxide as component (a) is prepared by selecting fine particles of tin oxide and reducing the amount of tin oxide applied. By doing so, transparent products can be manufactured. As described above, according to the present invention, a paint comprising at least one component (a) and at least one component (b) or (c) dispersed in a binder can be applied by applying the paint. The advantage is that the surface resistance of the dried coating film obtained is extremely low. For this reason, it is possible to reduce costs by reducing the amount of coating, and if the amount of coating is the same, the ratio of binder can be increased.
The strength of the dried coating film can be improved. Furthermore, paints containing conductive zinc oxide with an average particle size of about 0.2μ produce a white coating, and in the case of conductive tin oxide, ultrafine powder produces a slightly grayish transparent coating. If the powder is larger than about 0.1μ, it will be a white coating. Therefore, after considering the target resistance value, add dyes and pigments as appropriate.
It is also easy to adjust the color. Furthermore, the antistatic film using the above-mentioned paint has the above-mentioned features as is, and can be cut into any shape and size depending on the intended object, making it easy to use. This antistatic film can be applied as long as the object is substantially flat. In particular, transparent antistatic films have high utility value because they can be used as they are by being attached to clean room window glass or meter display glass. Next, the present invention will be specifically described with reference to Examples. Note that parts in the description mean parts by weight. Comparative example 1 Specific resistance 192Ω (150Kg/ ^cm3 pressurized), pressurized specific gravity 1.530
(70Kg/cm ³ ) of conductive zinc oxide (manufactured by Hakusui Chemical Co., Ltd., average particle size 0.2μ) and 100 parts of a saturated polyester resin (Vylon 20SS, manufactured by Toyobo Co., Ltd., 30% solids concentration) were mixed in advance to create an attritor. The mixture was dispersed for 20 minutes to obtain a paint. This paint was applied onto a hard vinyl chloride floor tile using a wire bar so that the dry coating film had a thickness of 20 μm, and after drying and hardening,
The resistance value of the coating film surface was measured. Example 1 0.7 parts of fructose was added to the paint of Comparative Example 1 and well dispersed to form a paint. A coating film was formed on a floor tile in the same manner as in Comparative Example 1 except that this coating material was used, and its surface resistance value was measured. Examples 2 and 3 The same procedure as Comparative Example 1 was carried out except that Vylon 20SS was added to the paint of Comparative Example 1 so that the conductive zinc oxide, binder, and solid ratios were 6:4 and 5:5. A paint was prepared and a coating test was conducted. Examples 2 and 3 Comparative Examples 2 and 3 were carried out in the same manner except that the paint of Example 1 was used instead of the paint of Comparative Example 1. Comparative Example 4 100 parts of the same conductive zinc oxide as in Example 1 was mixed with 400 parts of a 20% concentration styrene-butadiene copolymer (Califlex TR-1102 manufactured by Ciel Chemical Co., Ltd.) dissolved in advance, and dispersed with an attritor for 15 minutes. I got the paint. This paint was applied onto floor tiles using a wire bar to form a film with a dry thickness of 12μ, and the surface resistance value was measured. Example 4 A paint was obtained in the same manner as in Comparative Example 4, except that 1 part of dihydroxyacetone was added prior to the attritor treatment. A coating test was conducted in the same manner as in Comparative Example 1 using this paint. Comparative Example 5 100 parts of the same conductive zinc oxide as in Example 1 and 400 parts of a 2.5% methyl cellulose solution were mixed in advance and dispersed for 40 minutes using an attritor to obtain a paint. This paint was applied onto coated paper using a wire bar so that the dried paint film had a thickness of 6μ and 11μ respectively, and after being conditioned for 24 hours in an atmosphere of 20°C and 50%RH, the paint film was removed. The surface resistance value was measured. Examples 5- to 5- Paints were prepared in the same manner as in Comparative Example 5, except that 0.1 part of galactose, xylose, melibiose, or glucuronic acid was added before the attritor treatment and the attritor was used for dispersion treatment. A coating film similar to Comparative Example 5 was obtained using these paints,
Its surface resistance value was measured. Comparative Example 6 90 parts of water-dispersed polyester resin (MD-1200, manufactured by Toyobo Co., Ltd., 34% solid content concentration) per 100 parts of conductive oxidation-resistant tin (T-1 manufactured by Mitsubishi Metals, Sb-doped product, particle size 0.1μ or less) was added and dispersed for 30 minutes using an attritor to obtain a paint. Apply this paint to a 27μ thick polyester film using a wire bar.
An antistatic film was obtained by coating to obtain a dry coating film of . Examples 6- to 6- In Comparative Example 6, L- before the attritor treatment
Ascorbic acid, erythorbic acid or sodium ascorbic acid was added 1.5 times as much and well dispersed with an attritor to obtain a paint. These paints were applied to a polyester film in the same manner as in Comparative Example 6 to obtain an antistatic film. The color tone of the coating film obtained in this example was transparent with a slight gray tinge. When this film was pasted on the display glass of a measuring instrument, an excellent antistatic effect was obtained. In addition, when looking at the paint stage, the viscosity was higher and the film forming property was better than that of the paint of Comparative Example 6. Examples 7- to 7- The same procedure as in Example 6- was carried out except that fructose, galactose, xylose, melibiose, or glucuronic acid was used instead of L-ascorbic acid. Comparative Example 8 For 100 parts of conductive zinc oxide used in Comparative Example 1,
90 parts of the water-dispersible polyester resin used in Comparative Example 6 was added and dispersed for 30 minutes using an attritor to obtain a paint. This paint was applied onto a hard vinyl chloride floor tile using a wire bar so that the dried paint film had a thickness of 11μ, and was dried and solidified. Examples 8- to 8- In Comparative Example 8, L- before the attritor treatment.
The same procedure was carried out except that 1.5 parts of ascorbic acid, erythorbic acid, or sodium ascorbic acid was added and the mixture was dispersed with an attritor. The test results of the above Examples and Comparative Examples are summarized in a table. The surface electrical resistance was measured by placing two electrodes at a distance of 90 mm and measuring the electrical resistance between them.

[Table] From the above table, it can be seen that by adding component (b) or (c) to the paint, the surface resistance value of the obtained dry coating film is significantly reduced. Therefore, in each example, if a relatively low resistance value, that is, a surface resistance value comparable to that of the corresponding comparative example, is sufficient,
Since it is possible to increase the proportion of binder in the paint, a stronger dry coating can be obtained than in the comparative example.

Claims (1)

[Scope of Claims] 1. It is characterized by comprising at least one of the following components (a) and at least one component (b) or (c) as essential components dispersed in a binder solution. Antistatic paint. (a) Component; conductive zinc oxide or conductive tin oxide; (b) component; ascorbic acid, its optical isomer, or a metal salt or basic salt thereof; (c) component; reducing saccharide. 2. The antistatic paint according to claim 1, wherein 0.005 to 5 parts by weight of component (b) or (c) is blended with respect to 100 parts by weight of component (a).