JPS6328943B2 - - Google Patents

Description

[Detailed description of the invention]

Technical Field: The present invention relates to a coating composition that can be easily cured by ultraviolet rays, visible light, etc., and can form a coating film with excellent scratch resistance, conductivity, and transparency. Prior Art: Semiconductor wafer storage containers, electronic and electrical components, flooring and wall materials of semiconductor manufacturing factories, etc., need to have an antistatic effect depending on their use. To this end, conventionally these parts were coated with paint containing carbon powder or metal powder, or
Alternatively, carbon powder, carbon fibers, metal fibers, etc. are kneaded into resin and molded. However, in these conventional methods, the coating film and the molded article themselves are colored and are therefore opaque, making it impossible to see through the contents. Therefore, it is not possible to use a window as a portion that requires antistatic protection. JP-A-57-85866 discloses a paint containing a paint binder containing conductive fine powder containing tin oxide as a main component. Although this paint can form a coating film that is transparent and has an antistatic function, since the paint binder is a thermoplastic resin, the resulting coating film generally cannot exhibit scratch resistance or solvent resistance. Furthermore, metal powder such as tin oxide generally has a higher specific gravity than a paint binder, and therefore is difficult to uniformly disperse. Purpose of the invention: The purpose of the present invention is to provide a coating composition that can be easily cured by ultraviolet rays, visible light, etc., and can form a coating film that has excellent scratch resistance and hardness, as well as excellent conductivity and transparency. There is a particular thing. Another object of the present invention is to provide a coating composition that can effectively disperse the conductive powder contained therein, thereby increasing the transparency of the resulting coating film and forming a coating film with uniform conductivity. There is a particular thing. Summary of the invention: The present invention provides a highly cross-linked (meth)acrylic oligomer having at least two acryloyl or methacryloyl groups in its molecule when photocured, resulting in improved abrasion resistance and hardness of the resulting coating film. By adding a conductive fine powder whose main component is tin oxide, excellent transparency can be obtained while maintaining sufficient conductivity; By adding a styrene-maleic acid copolymer derivative, a conductive fine powder can be obtained. It was completed based on the knowledge that it prevents the re-agglomeration of the particles and significantly improves the transparency of the resulting coating film. Therefore, the paint of the present invention has at least two
A paint binder whose main component is one or more (meth)acrylic oligomers having at least one acryloyl or methacryloyl group; a conductive powder whose main component is tin oxide and whose particle size is 0.2 μm or less; and styrene. - Contains a maleic acid copolymer derivative, thereby achieving the above object. The styrene-maleic acid copolymer has a group represented by the following general formula.

[expression] and

[Formula] Here, R is a group containing carbon and hydrogen having 1 to 20 carbon atoms, a group having an unsaturated bond and a hydroxyl group, or hydrogen. However, hydrogen always exists in R in the derivative. The composition of the present invention contains a (meth)acrylic oligomer having two or more acryloyl or methacryloyl groups as a paint binder.
This (meth)acrylic oligomer is cured into a highly crosslinked structure. Examples of (meth)acrylic oligomers include ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol diacrylate, and polyethylene glycol dimethacrylate. methacrylate,
Difunctional acrylates or methacrylates such as polypropylene glycol diacrylate and polypropylene glycol dimethacrylate can be mentioned. In addition, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, glycerol triacrylate, glycerol trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, tris-(2-hydroxyethyl)-isocyanurate acrylate, tris-(2-hydroxyethyl)-isocyanurate acrylate, -Hydroxyethyl)-isocyanurate ester methacrylate and other trifunctional or higher functional acrylates or methacrylates. A reactive monofunctional acrylate or methacrylate may be included for the purpose of lowering the viscosity of the paint. When the (meth)-acrylic oligomer has a urethane bond in its molecular skeleton, the hardness and therefore the scratch resistance of the resulting coating film is further improved.
The preparation of such a urethane oligomer having an acryloyl group or a methacryloyl group at the molecular end involves polymerizing a polyol and a compound having two or more isocyanate groups in one molecule, and then polymerizing the polyol with a compound having two or more isocyanate groups in one molecule, and then polymerizing the polyol with a compound having an active hydrogen in the isocyanate group at the end of the molecule. This can be done by using acrylate or methacrylate. The above polyols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1.
2-butanediol, 1,3-butanediol;
There are short chain diols such as 1,4-butanediol, 2,3-butanediol, 1,5-heptanediol, 1,6-hexanediol, diethylene glycol; dipropylene glycol. Other examples include polyethylene glycol, polypropylene glycol, and polyoxytetramethylene glycol. Furthermore, there are also condensed polyester glycols of adipic acid and ethylene glycol, adipic acid and propanediol, adipic acid and neopentyl glycol, adipic acid and butanediol, or adipic acid and hexanediol. ε
- Ring-opened caprolactone polymers can also be used as polyols. Examples of compounds having two or more isocyanates in one molecule include hexamethylene diisocyanate, methylene diphenyl diisocyanate, toluene diisocyanate, xylene diisocyanate, methylene dicyclohexyl diisocyanate, and the like. As active hydrogen-containing acrylate or methacrylate,
For example, 2-hydroxyethyl acrylate, 2
-Hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, acrylic acid, etc. The coating composition of the present invention contains, as a coating binder, one or more compounds of these bifunctional or more functional (meth)acrylic oligomers or bifunctional or more functional (meth)acrylic oligomers having a urethane bond in the molecular skeleton. be done. The conductive powder containing tin oxide as a main component contained in the coating composition of the present invention has a particle size of 0.2 μm or less.
If it exceeds 0.2 μm, visible light will be scattered, resulting in poor transparency of the resulting coating film. At the same time, it also scatters ultraviolet rays, reducing the photocurability of the paint binder.
Sometimes it does not harden very quickly. The content thereof is preferably 5 to 80% by weight of the entire coating composition in order to ensure transparency and conductivity of the coating film. If the amount of the conductive fine powder is less than 5% by weight, even if the degree of dispersion is sufficient, the resulting coating film will not exhibit sufficient conductivity, and therefore the antistatic effect, which is one of the purposes of the present invention, will not be achieved. It cannot be demonstrated. If it exceeds 80% by weight, it will become overcrowded, resulting in poor dispersion of the fine powder, and as a result, the transparency of the resulting coating film will be impaired. Scuff resistance is also reduced. In the present invention, a styrene-maleic acid copolymer derivative is contained as a dispersant in order to enhance the dispersion of the conductive fine powder. This copolymer derivative has a group represented by the following general formula.

[expression] and

[Formula] Here, R is a group containing 1 to 20 carbon atoms and hydrogen. However, hydrogen always exists in R in the derivative. In the above derivative, the copolymerization ratio of styrene and maleic acid does not need to be 1:1, but 50:
The ratio may be in the range of 1 to 1:1. This copolymerization ratio is
If it is larger than 50, the conductive powder will not be sufficiently dispersed. Therefore, both transparency and photocurability are reduced. If the copolymerization ratio is less than 1:1, the water resistance of the formed coating film will be poor. This copolymer derivative is obtained by reacting a styrene-maleic anhydride copolymer with alcohol. Even if this derivative is not in the form of a complete half-ester, it will produce the same effect as long as the carboxylic acid accounts for 30% to 80% of the whole. Examples of the alcohol include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, t-butanol, pentanol, hexanol, octanol, and lauryl alcohol. Furthermore, if a group having an unsaturated bond and a hydroxyl group is introduced, in other words, if an alcohol having a photocurable double bond is reacted, this dispersant will also participate in the crosslinking structure, resulting in a strong coating film. be able to. Examples of the alcohol having a photocurable double bond include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 1-hydroxypropyl acrylate, 1-hydroxypropyl methacrylate, and 2-hydroxyethyl acrylate.
-Hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, etc. This derivative is preferably contained in an amount of 0.1% by weight or more of the entire coating composition. If it is less than 0.1% by weight, the conductive powder will not be sufficiently dispersed and transparency will decrease.
It also has poor photocurability. A photosensitizer is selectively added for the purpose of improving the photocurability of the paint binder. Examples of the photosensitizer include benzoin, benzyl, benzoin isopropyl ether, benzoin isomethyl ether, α-methylbenzoin, α-phenylbenzoinbenzyl, diacetylmethylanthraquinone, chloranthraquinone, benzophenone, anthraquinone, mifilar ketone, 4.
Carbonyl compounds such as 4′-bis-(N・N′-diethylamino)-benzophenone and acetophenone; Sulfur compounds such as diphenyl sulfide, diphenyl disulfide, and dithiocarbamate; α
- Naphthalene and anthracene compounds such as chloromethylnaphthalene and anthracene; halogenated hydrocarbons such as dimethyl tetrachlorophthalate and hexachlorobutadiene; metal salts such as uranyl sulfate, iron chloride, and silver chloride; acriflavin, fluorescein, riboflavin, Examples include pigments such as rhodamine B. The amount of these sensitizers added is preferably 0.01% by weight or more based on the photocurable oligomer. Amines can be used as auxiliaries for the photocuring reaction. Examples of amines include triethylamine,
Examples include tributylamine and diethylaminoethyl methacrylate. The coating composition of the present invention is prepared by adding the coating binder, the copolymer derivative, and a conductive fine powder containing tin oxide as main components to an organic solvent and mixing them. In order to sufficiently disperse the fine powder in the paint, equipment commonly used for dispersing and compounding paints, such as sand mills, ball mills, etc.
High speed rotating stirrers, triple rolls, etc. may be used. The conductive coating composition of the present invention thus prepared is applied to an object to be coated by a general coating method such as a spray method, a bar coating method, a doctor blade method, or a dipping method.
Examples of objects include plastic plates or plastic films made of vinyl chloride, polycarbonate, polymethacrylate, ABS resin, etc. It may also be an inorganic material such as a glass plate. In order to further increase the transparency of the resulting coating film after it has been applied to an object and photocured, it is recommended that the coating film be buffed. Examples: The present invention will be described below with reference to preferred examples. Example 1 (A) Synthesis of binder resin: 530 g of ε-caprolactone ring-opening polymer (average molecular weight 530: Daicel Plaxel 205) was charged into a separable flask reactor equipped with a cooling tube, a stirrer, and a dropping funnel, and nitrogen was added. The temperature was raised to 80°C while flowing gas. To this was added 1 g of dibutyltin laurate as a urethane production catalyst. 524 g of 4,4'-diphenylmethane diisocyanate was placed in a dropping funnel, added dropwise over 1 hour, and stirring was continued at 80°C for another 1 hour. Next, 1 g of hydroquinone, a polymerization inhibitor, was added to the reaction system.
After that, 232 g of 2-hydroxyethyl acrylate was added and stirring was continued for 2 hours. The weight average molecular weight of the obtained oligomer was 1500. (B) Synthesis of dispersant: In a separable flask equipped with a condenser, a stirrer, and a dropping funnel, add 250 g of methyl ethyl ketone.
Styrene-maleic acid copolymer (average molecular weight
1600, copolymerization 1:1; trade name manufactured by Kawasaki Chemical Co., Ltd.
SMA-1000) 160g and phenothiazine 25mg
was prepared and the temperature was raised to 80℃. On the other hand, 130 g of lauryl alcohol was added dropwise over 2 hours using a dropping funnel. After the dropwise addition was completed, the mixture was stirred at 80°C for 6 hours to obtain a styrene-maleic acid copolymer derivative. It was confirmed that the obtained compound was half-esterified by means such as IR spectroscopy. (C) Preparation of paint: 20g of binder resin synthesized in (A) above, (B)
50 g of the dispersant synthesized in Section 1, 20 g of trimethylolpropane triacrylate, 10 g of tetrahydrofurfuryl acrylate, 20 g of tetraethylene glycol diacrylate, 80 g of pentaerythritol tetraacrylate, average particle size 0.2 μm.
290 g of tin oxide containing antimony trioxide, 18 g of benzophenone and 3.6 g of mifilar ketone:
g was added to 560 g of methyl ethyl ketone. This was placed in a ball mill and dispersed for 24 hours to prepare a desired paint. (D) Preparation of coating film and evaluation of performance: The above coating material was applied onto a transparent acrylic plate (Acrylite manufactured by Mitsubishi Rayon Co., Ltd.; thickness 3 mm) to a thickness of 1.5 μm (when dry). After drying the solvent at 50° C. for 5 minutes, light irradiation was performed for 30 minutes from a distance of 10 cm using a high-pressure mercury lamp (output 2 kW, effective lamp length 12.5 cm) in a nitrogen atmosphere.
The coating film after irradiation was tack-free. The surface of the resulting coating film was buffed at 3000 rpm using a wool buff with a diameter of 30 cm. The measurement results of the surface resistivity, total light transmittance, haze value, pencil hardness, and increase in haze value after the Taber test of the resulting coating film; and the test results of the tetrahydrofuran (THF) solubility resistance are shown in the table below. The surface resistivity is
ASTM D-257, total light transmittance and haze value
ASTM D-1003, pencil hardness is JISK-5400,
The increase in haze value after the Taber test is ASTM D-
Measured using a test method based on 1044. Endurance
For THF solubility, the target material is kept at 20℃.
The state of the coating film after immersion for 24 hours is shown, and 〇 indicates that no change is observed. Example 2 Same as Example 1 except that a styrene-maleic acid copolymer derivative (average molecular weight 1600, copolymerization ratio 1:1; trade name SMA-1440, manufactured by Kawasaki Chemical Co., Ltd.) was used as a dispersant. . Example 3 Same as Example 1 except that the dispersant was synthesized as follows. (B) Synthesis of dispersant: In a separable flask equipped with a condenser, a stirrer, and a dropping funnel, add 250 g of methyl ethyl ketone.
Styrene-maleic acid copolymer (average molecular weight
1600, copolymer ratio 1:1; trade name manufactured by Kawa Yuka Kaisha.
160 g of SMA-1000) and 25 mg of phenothiazine were added, and the temperature was raised to 80°C. On the other hand, 91 g of 2-hydroxyethyl acrylate was added dropwise over 2 hours using a dropping funnel. After the dropwise addition was completed, the mixture was stirred at 80°C for 6 hours. It was confirmed that the obtained compound was half-esterified by means such as IR spectroscopy. Example 4 Same as Example 1 except that the dispersant was synthesized as follows. (B) Synthesis of dispersant: In a separable flask equipped with a cooling tube, a stirrer, and a dropping funnel, add 250 g of toluene and styrene-maleic acid copolymer (average molecular weight 1900, copolymer ratio 3:1; manufactured by Kawasaki Chemical Co., Ltd.) Product name: SMA
3000) and 24 mg of phenothiazine were added and the temperature was raised to 80°C. On the other hand, 53.7 g of 2-hydroxyethyl acrylate was added dropwise over 2 hours using a dropping funnel. 6 at 80℃ after completion of dropping
Stir for hours. It was confirmed that the obtained compound was half-esterified by means such as IR spectroscopy. Comparative Example (A) Synthesis of binder resin: Same as Example 1. (B) Preparation of paint: 27g of photocurable binder synthesized in section (A), 27g of trimethylolpropane triacrylate,
13g of tetrahydrofurfuryl acrylate, 27g of tetraethylene glycol diacrylate,
Pentaerythritol tetraacrylate 106
290 g of tin oxide containing antimony trioxide having an average particle size of 0.2 μm or less, 18 g of benzophenone, and 3.6 g of Mifilar ketone were added to 560 g of methyl ethyl ketone, and the mixture was charged into a ball mill and dispersed for 24 hours to prepare a paint. (C) Preparation of coating film and performance evaluation: Same as Example 1.

[Table] Effects of the invention: The conductive paint composition containing the conductive fine powder of the present invention contains (meth)acrylic oligomer with excellent photocurability or radiation curability as a binder. It can be easily cured by ultraviolet rays, visible light, etc. without significantly increasing the temperature. The formed coating film is not only conductive, but also has transparency, hardness,
It also has outstanding strength, scratch resistance, and melt resistance. Furthermore, since the coating composition contains the styrene-maleic acid copolymer derivative as a dispersant, the dispersion of the conductive fine powder is significantly enhanced, and the transparency of the resulting coating film is further improved. The electrical conductivity of the resulting coating film also becomes uniform. Therefore, the coating composition of the present invention can be applied to a wider range of fields than conventional conductive coatings.

Claims (1)

[Scope of Claims] 1. A paint binder whose main component is one or more types of (meth)acrylic oligomers having at least two or more acryloyl groups or methacryloyl groups in the molecule; particles whose main component is tin oxide; A photocurable conductive coating composition containing a conductive powder having a diameter of 0.2 μm or less; and a styrene-maleic acid copolymer derivative. 2 The styrene-maleic acid copolymer derivative is
The composition according to claim 1, which has a group represented by the following general formula. [Formula] and [Formula] (R is a group consisting mainly of carbon and hydrogen having 1 to 20 carbon atoms, a group having an unsaturated bond and a hydroxyl group, or hydrogen. However, hydrogen is always present in R in derivatives. 3. The composition according to claim 1, wherein at least one of the (meth)acrylic oligomers has a urethane bond. 4 The conductive powder accounts for 5 to 80% of the total coating composition.
A composition according to claim 1, in which the composition is contained in a proportion of % by weight.