JPS6355550B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a coating composition capable of forming a coating film with excellent conductivity and transparency. [Prior Art] Semiconductor wafer storage containers, electronic and electrical components, floor materials and wall materials of semiconductor manufacturing factories, etc., are required to have an antistatic effect depending on their use. To this end, these members have conventionally been coated with paint containing carbon powder or metal powder, or molded by kneading carbon powder, carbon fibers, metal fibers, etc. into resin. Further, as described in Japanese Patent Application Laid-Open No. 57-85866, a paint containing conductive fine powder containing tin oxide as a main component in a paint binder has been studied. [Problems to be Solved by the Invention] In the method of coating with paint containing carbon powder or metal powder, or the method of kneading carbon powder, carbon fiber, metal fiber, etc. into resin and molding, the coating film and molded product itself are Because it is colored, it is opaque and the contents cannot be seen through. Therefore, it is not possible to use a window portion as a portion that requires antistatic protection. In addition, in the invention described in Japanese Patent Application Laid-open No. 57-85866,
Although it is possible to 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 does not exhibit sufficient scratch resistance and solvent resistance. The present invention aims to eliminate the above-mentioned conventional drawbacks and provide a coating composition in which conductive powder has excellent dispersibility in the coating material and can form a coating film with excellent transparency and conductivity. It is something. [Means for Solving the Problems] The present invention provides a paint binder containing as a main component one or more (meth)acrylic oligomers having at least two or more acryloyl groups or methacryloyl groups in the molecule, and tin oxide. A conductive powder whose main component is 0.2 μm or less in particle size, and methyl methacrylate and the general formula (wherein, R ₁ is H or CH ₃ group, R ₂ is H or CH ₃ group, and n = 1 to 10) (hereinafter referred to as acrylic polymer with hydroxyl group) The purpose is to contain. In the present invention, (meth)acrylic oligomers include bifunctional acrylates such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, tetraethylene glycol diacrylate, and tetraethylene glycol dimethacrylate. Alternatively, methacrylate oligomers and the like 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) ) Oligomers of trifunctional or higher functional acrylates or methacrylates such as isocyanuric acid ester methacrylate. In the present invention, the (meth)acrylic oligomer has a urethane bond in its molecular skeleton, that is, the urethane oligomer having an acryloyl group or a methacryloyl group at the molecular end is prepared using a polyol and a compound having two or more isocyanate groups per molecule. This can be carried out by polymerizing the above molecules, and then acting on the isocyanate group at the end of the molecule with an acrylate or methacrylate having active hydrogen. Examples of the above polyol 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, and trimethylolpropane. 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, methylene dicyclohexyl diisocyanate, and the like. 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 conductive paint composition of the present invention contains, as a paint binder, one or more compounds of these difunctional or higher-functional (meth)acrylic oligomers or difunctional or higher-functional (meth)acrylic oligomers having a urethane bond in the molecular skeleton. Contains. The conductive powder containing tin oxide as a main component contained in the conductive 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, which reduces the photocurability of the paint binder and sometimes does not cure it properly. The content thereof is preferably 50 to 400 parts by weight based on 100 parts by weight of the paint binder in order to ensure the transparency of the coating film. If the amount of this conductive powder is less than 50 parts 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 objectives of the present invention, will not be exhibited. Not done. If the amount exceeds 400 parts by weight, the powder becomes overcrowded, resulting in poor dispersion of the powder, and as a result, the transparency of the resulting coating film is impaired. Scuff resistance is also reduced. In the present invention, an acrylic polymer having hydroxyl groups is further added. The addition of such an acrylic polymer having hydroxyl groups significantly improves the sedimentation and redispersibility of the paint. Furthermore, the resulting coating film has excellent transparency while retaining electrical conductivity, and its scratch resistance is also improved. In order to obtain such excellent results, the amount of the acrylic polymer having hydroxyl groups added is preferably 0.1 parts by weight or more based on 100 parts by weight of the paint binder. Further, in the present invention, 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-phenylbenzoinbenzyl, α-methylbenzoin, diacetylmethylanthraquinone, chloranthraquinone, benzophenone, anthraquinone, mifilatitone, 4. 4'-Bis (N・N'-
Carbonyl compounds such as diethylamino)benzophenone and acetophenone, sulfur compounds such as diphenylsulfidiphenyl disulfide and dithiocarbamates, α-chloromethylnaphthalene,
Naphthalene such as anthracene, anthracene-based compounds, halogenated hydrocarbons such as dimethyl tetrachlorophthalate, hexachlorobutadiene, metal salts such as uranyl sulfate, iron chloride, silver chloride, pigments such as acriflavine, fluorescein, ribofuran, rhodamine B, etc. Examples include: The amount of these photosensitizers added is based on the photocurable oligomer.
It is preferably 0.01% by weight or more. Amines can be used as auxiliaries for the photocuring reaction. Examples of amines include triethylamine, tributylamine, and diethylaminoethyl methacrylate. The conductive 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 conductive powder in the coating material, equipment commonly used for dispersing and compounding coating materials, such as a sand mill, a ball mill, a high-speed rotating stirring device, a triple roll, etc., can be used. In order to further enhance the dispersion of the conductive powder, dispersion aids such as silane coupling agents, titanate coupling agents, surfactants, oleic acid, and lecithin may also 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. The object may be, for example, a plastic plate or film made of vinyl chloride, polycarbonate, polymethacrylate, ABS resin, or the like. It may also be an inorganic material such as a glass plate. In order to further increase the transparency of the coating film obtained by applying it to the object, it is recommended to buff the coating film. [Function] According to the present invention, an acrylic polymer having hydroxyl groups is added to the acrylic oligomer and the conductive powder, and the acrylic polymer having hydroxyl groups adsorbs to the surface of each particle of the conductive powder and spreads around the particles. It covers the conductive powder to prevent it from coalescing and re-agglomerating, and is also well compatible with the acrylic oligomer, which is the paint binder, to prevent the conductive powder from settling due to the difference in specific gravity with the acrylic oligomer. Therefore, it is assumed that it improves the dispersibility of the conductive powder in the paint, prevents reaggregation and sedimentation even if it is left standing, and significantly improves the transparency of the formed paint film. . [Examples] Hereinafter, the present invention will be described in detail based on Examples. Example 1 (A) Synthesis of photocurable binder resin: 530 g of ε-caprolactone ring-opening polymer (average molecular weight 530) was charged into a separable flask reactor equipped with a cooling tube, a stirrer, and a dropping funnel, and nitrogen gas was introduced. The temperature was raised to 80°C while flowing water. To this was added 1 g of dibutyltin laurate as a urethane production catalyst. 334 g of hexamethylene diisocyanate was placed in a dropping funnel and added dropwise over 1 hour, and stirring was continued for 1 hour at 80°C. Next, 1 g of hydroquinone, a polymerization inhibitor, was added to this reaction system, and then 232 g of 2-hydroxyethyl acrylate was added.
and stirring continued for 2 hours. The weight average molecular weight of the obtained oligomer was 1500. (B) Synthesis of non-photocurable binder resin: cooling tube,
250 g of toluene was charged into a separable flask reactor equipped with a stirrer and a dropping funnel, and the temperature was raised to 110° C. while flowing nitrogen gas. On the other hand, a mixed solution of 112.5 g of methyl methacrylate, 12.5 g of β-hydroxyethyl methacrylate, and 0.5 g of azobisisobutyronitrile as a polymerization initiator was prepared and charged into a dropping funnel. When the temperature inside the reactor reached 110°C, a mixed solution of monomer and polymerization initiator was added dropwise from the dropping funnel over a period of 2 hours to carry out polymerization. Next, the temperature inside the reactor was brought to 90° C., and a solution of 2 g of azobisisobutyronitrile dissolved in 20 g of toluene was charged into the dropping funnel and added dropwise over 2 hours. After completion of the dropwise addition, polymerization was further continued at 90°C for 2 hours. The weight average molecular weight of the obtained copolymer was 4,500. The polymerization rate was 99%. (C) Preparation of paint: 20 g of photocurable binder resin synthesized in Section A above, 20 g of binder resin synthesized in Section B, 10 g of trimethylolpropane triacrylate and tetrahydrofurfuryl acrylate, 10 g of tetraethylene glycol diacrylate, pentaerythritol. 100 g of tetraacrylate, 200 g of tin oxide containing antimony trioxide with a particle size of 0.2 μm or less, 20 g of benzophenone, and 20 g of Mifilar ketone were mixed with methyl ethyl ketone.
Added to 560g. Put this into a ball mill 24
The desired paint was prepared by time dispersion. (D) Preparation of coating film and performance evaluation: The above coating material was applied onto a transparent vinyl chloride plate to a thickness of 5 μm (when dry). After drying the solvent, a high-pressure mercury lamp (output 2KW, effective lamp length 12.5cm) was used in a nitrogen atmosphere from a distance of 10cm.
Timed light irradiation was performed. The coating film after irradiation was tack-free. The surface of the obtained coating film is 30cm in diameter.
Buffed at 3000 rpm using a wool buff. The measurement results of the surface resistivity, total light transmittance, haze value, pencil hardness, and increase in haze value after the taper test of the resulting coating film, and the test results of tetrahydrofuran (THF) solubility resistance are shown in the table below.
Surface resistivity is ASTM D257, total light transmittance and haze value are ASTM D1003, and pencil hardness is JIS K.
−5400, the increase in haze value after the taper test is
Measured using a test method based on ASTM D1044. Regarding THF solubility resistance, the state of the coating film is shown after the weather-resistant object is immersed for 24 hours at 20℃, where 〇 means no change is observed, ×
represents a state in which the coating film has melted and peeled off. Comparative example 1 200g of polyester resin as binder resin
Using this method, 200 g of tin oxide containing antimony trioxide with a particle size of 0.2 μm or less was added to 600 g of methyl ethyl ketone, and the mixture was placed in a ball mill and dispersed for 24 hours to prepare a paint. It was applied onto a transparent PVC plate to a thickness of 5 μm (when dry), and the solvent was dried.
This was subjected to a performance test in the same manner as in Example 1. The results are shown in the table below. Comparative Example 2 A performance test was conducted on the vinyl chloride base material itself. The results are shown in the table below. Example 2 Binder resin 25 synthesized in Section A of Example 1
g, 20 g of binder resin synthesized in Section B, 35 g of trimethylolpropane triacrylate, 5 g of 2-hydroxyethyl acrylate, 15 g of neopentyl glycol diacrylate, 40 g of pentaerythritol tetraacrylate, 60 g of dipentaerythritol hexaacrylate, particle size 0.2 μm or less 200 g of tin oxide containing antimony trioxide, 20 g of benzophenone and 20 g of Mifilar ketone were added to 560 g of methyl ethyl ketone. This was placed in a ball mill and dispersed for 24 hours to produce the desired paint. A coating film was prepared in the same manner as in Example 1,
After buffing, it was subjected to a performance test. The results are shown in the table below.

【table】

[Table] *Note: All paint films were worn away.
[Effects] As described above, the conductive paint composition of the present invention is a paint whose main component is one or more (meth)acrylic oligomers having at least two or more acryloyl groups or methacryloyl groups in the molecule. The binder is mainly composed of tin oxide and its particle size is
Contains conductive powder with a diameter of 0.2 μm or less and an acrylic polymer with hydroxyl groups, and the acrylic polymer with hydroxyl groups significantly increases the dispersibility of the conductive powder and prevents reagglomeration and sedimentation. As a result, the coating film formed has excellent transparency, and has the effect of being excellent not only in conductivity but also in abrasion resistance, hardness, strength, and solvent resistance. Furthermore, since it contains a (meth)acrylic oligomer with excellent photocurability or radiation curability as a binder, it can be easily cured with ultraviolet rays, visible light, or radiation without significantly increasing the temperature of the base material. Therefore, the conductive paint composition of the present invention can be applied to a wider range of fields than conventional conductive paints.

Claims (1)

[Scope of Claims] 1. A paint binder whose main component is one or more (meth)acrylic oligomers having at least two or more acryloyl groups or methacryloyl groups in the molecule, particles of which are mainly composed of tin oxide. Conductive powder with a diameter of 0.2μm or less, methyl methacrylate and general formula (However, R ₁ is H or CH ₃ group, R ₂ is H or CH ₃ group, and n = 1 to 10) A conductive coating composition characterized by containing a copolymer with a monomer represented by thing. 2. The conductive coating composition according to claim 1, wherein at least one of the (meth)acrylic oligomers has a urethane bond. 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.