JPH0576505B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical Field) The present invention relates to a conductive coating composition that can be easily cured by irradiation with radiation such as ultraviolet rays or electron beams, and can form a coating film with excellent scratch resistance, conductivity, and transparency. (Prior Art) Semiconductor wafer storage containers, electronic/electrical parts, flooring and wall materials of semiconductor manufacturing factories, etc., need to have an antistatic effect depending on their use. For this reason, conventionally, these members have been coated with paint containing carbon powder or metal powder, or molded by kneading carbon powder, carbon fiber, metal fiber, etc. into resin. 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. (Objective of the Invention) The object of the present invention is to form a paint film that is easily effective against radiation such as ultraviolet rays and electron beams, has excellent scratch resistance and hardness, and has excellent conductivity and transparency. An object of the present invention is to provide a composition.
Another object of the present invention is to provide a coating composition that can effectively disperse the conductive powder contained therein, improve the transparency of the resulting coating film, and form a coating film with uniform conductivity. There is a particular thing. (Summary of the Invention) The gist of the present invention is to provide one or two types of (meth)acrylic oligomers having at least two or more acryloyl groups or methacryloyl groups in the molecule.
A paint binder whose main component is tin oxide or more, a conductive powder whose main component is tin oxide and whose particle size is 0.2 μm or less, and the general formula (1)

[Formula] (R ₁ is hydrogen or methyl group, R ₂ has 1 to 8 carbon atoms
a copolymer mainly composed of one or more monomers selected from the monomers represented by (alkyl group) or styrene monomers and a (meth)acrylic tertiary amine monomer A conductive coating composition containing: (Structure of the Invention) The present invention provides that when a (meth)acrylic oligomer having at least two or more acryloyl groups or methacryloyl groups in its molecule is photocured, it becomes highly crosslinked and the resulting coating film has improved scratch resistance and hardness. improves. General formula (1) that provides excellent transparency while maintaining sufficient conductivity by adding conductive powder containing tin oxide as the main component.

[Formula] (R ₁ is hydrogen or methyl group, R ₂ has 1 to 8 carbon atoms
A copolymer mainly composed of one or more monomers selected from monomers represented by (alkyl group) or styrene monomers and a (meth)acrylic tertiary amine monomer. It was completed based on the knowledge that adding it prevents re-aggregation of the conductive powder and significantly improves the transparency of the resulting coating film. 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 bifunctional acrylates or methacrylates such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, tetraethylene glycol diacrylate, and tetraethylene glycol dimethacrylate. It will be done. Additionally, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, glycerol triacrylate, glycerol trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, tris-(2
-hydroxyethyl)-isocyanurate acrylate, tris-(2-hydroxyethyl)
-Trifunctional or higher functional acrylates or methacrylates such as isocyanuric acid ester methacrylate can be mentioned. 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. To prepare such a urethane oligomer having an acryloyl group or a methacryloyl group at the end of the molecule, a polyol and a compound having two or more isocyanate groups per molecule are polymerized, and the isocyanate group at the end of the molecule is
This can be carried out by using acrylate or methacrylate containing active hydrogen. The polyols include, for example, ethylene glycol; 1,2-propanediol; 1,3-propanediol; neopentyl glycol; 1,2-butanediol;
There are short chain diols such as 1,3-butanediol; 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. Ring-opened ε-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,
Examples include methylene dicyclohexyl diisocyanate. Examples of the active hydrogen-containing acrylate or methacrylate include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, and acrylic acid. 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. Its content is a paint binder in ensuring the transparency and conductivity of the paint film.
The proportion is preferably 50 to 400 parts by weight per 100 parts by weight. If the amount of this conductive powder is less than 50 parts by weight, even if its 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 be reduced. is difficult to express.
If the amount exceeds 400 parts by weight, the powder becomes overcrowded, resulting in poor dispersion of the powder, resulting in poor transparency of the resulting coating film and reduced scratch resistance. In the present invention, in order to enhance the dispersion of the conductive powder, general formula (1) is used as a dispersant.

[Formula] (R ₁ is hydrogen or methyl group, R ₂ has 1 to 8 carbon atoms
A copolymer containing one or more monomers selected from monomers represented by (alkyl group) or styrene monomers and a (meth)acrylic tertiary amine monomer is Contains. Examples of the monomer represented by general formula (1) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isoamyl (meth)acrylate, and hexyl (meth)acrylate. Examples include acrylate, octyl (meth)acrylate, and the like. (Meth)acrylic tertiary amine monomers include N,N'-dimethylaminoethyl methacrylate, N,N'-diethylaminoethyl methacrylate, N,N'-dimethylaminopropyl methacrylate, N,N'-diethylaminopropyl Examples include methacrylate, N,N'-dimethylaminoethyl acrylate, N,N'-diethylaminoethyl acrylate, N,N'-dimethylaminopropyl acrylate, and N,N'-diethylaminopropyl acrylate. In this copolymer, it is preferable that the (meth)acrylic tertiary amine monomer is copolymerized in a proportion of 2 to 30 mol%. If it is less than 2 mol %, the dispersion effect will not be significant, and if it exceeds 30 mol %, the water resistance of the coating film will be significantly reduced, which is not preferable. In this copolymer, vinyl monomers other than the above-mentioned monomers may be copolymerized depending on the purpose and use. In particular, (meth)acrylates having hydroxyl groups, such as 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, 2-
By using in combination hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, polypropylene glycol monomethacrylate, polypropylene glycol monoacrylate, polyethylene glycol monomethacrylate, polyethylene glycol monoacrylate, etc., the dispersion of the powder can be further enhanced. It is also possible to improve the transparency of the coating film. This copolymer is preferably contained in an amount of 2 to 70% by weight, particularly preferably 5 to 50% by weight, of the entire conductive coating composition. If it is less than 2% by weight, the conductive powder will not be sufficiently dispersed and transparency will decrease. If it exceeds 70% by weight, the crosslinking component will decrease and the desired scratch resistance will not be achieved. 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 launyl sulfate, iron chloride, and silver chloride; acriflavin, fluorescene, 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, tributylamine,
Examples include diethylaminoethyl methacrylate. The coating composition of the present invention is prepared by adding the coating binder, the copolymer, and a conductive powder containing tin oxide as main components to an organic solvent and mixing them. In order to sufficiently disperse the powder in the paint, equipment commonly used for dispersing and compounding paints, such as sand mills, ball mills, high-speed rotation stirrers, triple rolls, etc., can be used. The conductive coating composition of the present invention thus prepared can be applied to objects to be coated by general coating methods such as spraying, bar coating, doctor blading, and dipping, such as synthetic resin plates. After being applied to a sheet or the like, it is cured to form a coating film by irradiation with radiation such as ultraviolet rays or electron beams. Examples of materials for the synthetic resin plates, sheets, etc. include polyvinyl chloride, polyethylene terephthalate, polycarbonate, poly(meth)acrylate, acrylonitrile-butadiene-styrene copolymer, polyethylene, polypropylene, and the like. The coating composition of the present invention has almost no charge in the resulting coating film, and is therefore suitable for use in electronic devices that require functions such as preventing dust accumulation, preventing electrostatic damage, and preventing electrostatic malfunction. (Example) The present invention will be explained below with reference to 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. The temperature was raised to 80°C while flowing nitrogen gas. To this was added 1 g of dibutyltin laurate as a urethane production catalyst. 524 g of 4,4'-diphenylmethane diisocyanate was charged into the dropping funnel and added dropwise over 1 hour, and stirring was continued for another 1 hour. The weight average molecular weight of the obtained oligomer was 1500. (B) Synthesis of dispersant: Add methyl ethyl ketone to a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen inlet.
480 g of methyl methacrylate, 465 g of dimethylaminoethyl methacrylate, and 35 g of dimethylaminoethyl methacrylate were charged, and the temperature was raised to 80° C. while passing nitrogen gas. Next, as a polymerization initiator, azobisisobutyronitrile
2.5g was dissolved in 10g of methyl ethyl ketone and added. After continuing the polymerization for 4 hours while keeping the temperature constant, 1.5 g of the polymerization initiator azobisisobutyronitrile was added to 10 ml of methyl ethyl ketone.
The polymerization was continued for an additional 5 hours. The weight average molecular weight of the obtained copolymer is
It was 42,000. (C) 100g of the dispersant copolymer solution prepared in Section B,
320 g of tin oxide containing antimony trioxide with an average particle size of 0.2 μm or less and 500 g of methyl ethyl ketone were placed in a ball mill and dispersed for 24 hours. Next, add 20 g of the binder resin prepared in Section A, 30 g of trimethylolpropane triacrylate, 20 g of tetraethylene glycol diacrylate, 80 g of pentaerythritol tetraacrylate, 18 g of benzophenone, and 3.6 g of Mifilar ketone.
was added and dispersed for 24 hours. (D) Preparation and performance evaluation of coating film: Transparent acrylic plate (Acrylite manufactured by Mitsubishi Rayon Co., Ltd.: thickness 3 mm)
The above paint was applied on top to a thickness of 2 μm (when dry). After drying the solvent at 50° C. for 5 minutes, it was cured by UV irradiation for 12 minutes from a distance of 25 cm using a high-pressure mercury lamp (output 5.6 KW, effective lamp length 70 cm). Table 1 shows 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. The surface resistivity was measured by ASTMD-257, the total light transmittance and haze value by ASTMD-1003, the pencil hardness by JISK-5400, and the increase in haze value after the Taber test was measured by a test method based on ASTMD-1044. Example 2 Dispersant copolymer solution prepared in Section B of Example 1
76 g of tin oxide containing antimony trioxide having an average particle size of 0.2 μm or less, and 512 g of methyl ethyl ketone were charged into a ball mill and dispersed for 24 hours. Next, add the binder resin 30 prepared in Section A of Example 1 to this.
g, trimethylolpropane triacrylate 33
g, tetraethylene glycol diacrylate 21
g, pentaerythritol tetraacrylate 80
g, benzophenone 18g and mifilar ketone
3.6g was added and dispersed for 24 hours to prepare a paint. Apply this paint in the same manner as in Example 1,
Curing was performed by ultraviolet irradiation. The obtained coating film was tested in the same manner as in Example 1,
The measurement results are shown in Table 1. Example 3 Into the same reaction vessel as in Example 1, 480 g of methyl ethyl ketone, 420 g of methyl methacrylate, 40 g of hydroxyethyl methacrylate, and 40 g of diethylaminoethyl methacrylate were charged, and the temperature was raised to 80° C. under a nitrogen stream. After this, azobisisobutyronitrile dissolved in 10g of methyl ethyl ketone
2.5g was charged and reacted for 4 hours. Furthermore, 2.5 g of azobisisobutyronitrile dissolved in 10 g of methyl ethyl ketone was added, and the reaction was continued for 5 hours. The weight average molecular weight of the obtained copolymer was 38,000. A coating film was obtained in the same manner as in Example 1 except that the dispersant copolymer solution in Example 1 was replaced with the above copolymer solution. The obtained coating film was tested in the same manner as in Example 1,
The measurement results are shown in Table 1. Example 4 In a reaction vessel similar to Example 1, 400 g of methyl ethyl ketone, 400 g of methyl methacrylate, 25 g of ethyl methacrylate, and isobutyl methacrylate were added.
15g, dimethylaminoethyl methacrylate 35
g, 2-hydroxypropyl methacrylate 25g
was charged and the temperature was raised to 70°C under a nitrogen stream. On the other hand, 5 g of azobisisobutyronitrile, a polymerization initiator, was dissolved in 100 g of methyl ethyl ketone, and this solution was added dropwise from the dropping funnel over 3 hours. After the dropwise addition was completed, the reaction was continued at 70° C. for an additional 3 hours to prepare a dispersant copolymer solution. 100g of the above dispersant copolymer solution, average particle size 0.2μ
Pour 320 g of tin oxide containing antimony trioxide and 500 g of methyl ethyl ketone into a ball mill.24
Spread out the time. Next, add to this 20 g of the binder resin prepared in Section A of Example 1, 30 g of trimethylolpropane triacrylate, 20 g of tetraethylene glycol diacrylate, 80 g of pentaerythritol tetraacrylate, and benzophenone.
18 g and 3.6 g of Mifilar Ketone were added and dispersed for 24 hours to prepare a paint. Apply this paint in the same manner as in Example 1,
Curing was performed by ultraviolet irradiation. The obtained coating film was tested in the same manner as in Example 1,
The measurement results are shown in Table 1. Comparative Example 1 213 g of tin oxide containing antimony trioxide with an average particle size of 0.2 μm or less, 330 g of methyl ethyl ketone, Example 1
20 g of the binder resin prepared in Section A, 30 g of trimethylolpropane triacrylate, 20 g of tetraethylene glycol diacrylate, 80 g of pentaerythritol tetraacrylate, 18 g of benzophenone, and 3.6 g of Mifilar ketone were placed in a ball mill and dispersed for 24 hours to prepare a paint. Apply this paint in the same manner as in Example 1,
Curing was performed by ultraviolet irradiation. The obtained coating film was tested in the same manner as in Example 1,
The measurement results are shown in Table 1.

[Table] (Effects of the invention) The conductive coating composition of the present invention contains a (meth)acrylic oligomer with excellent photocurability as a binder, so it can be easily cured by radiation such as ultraviolet rays or electron beams. . The formed coating film has outstanding not only electrical conductivity but also transparency, hardness, strength, scratch resistance, and solvent resistance. Furthermore, since the coating composition contains the copolymer as a dispersant,
The dispersion of the conductive powder is significantly improved, and the transparency of the resulting coating film is further improved. The electrical conductivity of the resulting coating film also becomes uniform. Therefore, the conductive coating composition of the present invention is suitably used in electronic equipment applications that require functions such as preventing dust accumulation, preventing electrostatic damage, and preventing electrostatic malfunction.

Claims (1)

[Claims] 1. A paint binder whose main component is one or more (meth)acrylic oligomers having at least two or more acryloyl or methacryloyl groups in the molecule, and a paint binder whose main component is tin oxide. Conductive powder with a particle size of 0.2 μm or less and general formula (1) [Formula] (R ₁ is hydrogen or a methyl group, R ₂ has a carbon number of 1 to 8
a copolymer mainly composed of one or more monomers selected from the monomers represented by (alkyl group) or styrene monomers and a (meth)acrylic tertiary amine monomer A conductive paint composition containing. 2. The conductive coating composition according to claim 1, wherein the copolymer is a copolymer of a (meth)acrylic tertiary amine monomer in a proportion of 2 to 30 mol%. 3. The conductive coating composition according to claim 1, wherein the conductive powder is contained in an amount of 50 to 400 parts by weight based on 100 parts by weight of the coating binder.