JPH0148874B2 - - Google Patents

Description

[Detailed description of the invention]

Technical field: The present invention relates to a conductive plastic sheet, particularly a conductive plastic sheet in which a two-layer coating is laminated on a transparent plastic sheet substrate, and the coating has excellent transparency, hardness, strength, and scratch resistance. Regarding plastic sheets. Prior Art: Semiconductor wafer storage containers, electronic/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. This paint can form a film that is transparent and has an antistatic function, but since the paint binder is a thermoplastic resin, the resulting paint film generally cannot exhibit not only scratch resistance but also solvent resistance. . When a photocurable resin is used as a paint binder, when a conductive powder is added, the powder absorbs light, especially ultraviolet rays, so a large amount of ultraviolet rays must be irradiated to cure the paint. Object of the invention: An object of the invention is to provide a conductive plastic sheet with excellent hardness, strength and scratch resistance. Another object of the present invention is to provide a conductive plastic sheet having a coating film with high transparency, hardness, and scratch resistance, the surface of which is coated with a conductive paint that can be easily photocured or radiation cured at low doses. It is in. Summary of the invention: In the present invention, a hard coat layer is formed as a first layer on a transparent plastic sheet base material, and a photo-curable or radiation-curable resin layer containing conductive fine powder is formed as a second layer thereon. The inventor believes that if this is done, the characteristics of the highly hard first layer will be utilized even when the second layer is relatively thin, resulting in a transparent conductive plastic sheet with excellent hardness, strength, and scratch resistance. It was completed based on new knowledge. Therefore, the conductive plastic sheet of the present invention has a hard coat layer mainly made of a photocurable, radiation-curable or thermosetting resin on a transparent plastic substrate, and a 0.2 μm thick hard coat layer on the hard coat layer.
The above object is achieved by sequentially laminating layers containing the following conductive powder containing tin oxide as a main component and a photo-curable acrylate resin or methacrylate resin or a radiation-curable acrylate resin or methacrylate resin. Ru. The hard coat layer formed on the sheet base material of the conductive plastic sheet of the present invention is thermosetting,
Obtained by applying a photo-curable or radiation-curable paint. Examples of thermosetting paints include melamine resin paints and organosilane resin paints. A melamine resin-based paint is obtained, for example, by mixing a melamine resin, nitrified cotton, and an allyl or vinyl compound having two or more crosslinkable functional groups. It can also be obtained, for example, by mixing etherified methylolmelamine, nitrified cotton and a suitable acid catalyst. Organosilane resin-based paints are, for example, reaction mixtures of methyltriethoxysilane and phenyltriethoxysilane. A coating film obtained by thermosetting an organosilane resin coating has particularly excellent scratch resistance. Photo-curable or radiation-curable coatings include acrylic acid, methacrylic acid, ester derivatives thereof, and vinyl monomers. Among photo-curable paints, ultraviolet-curable paints are particularly superior in terms of workability, productivity, and the ability to suppress thermal deformation of sheet substrates. The photo-curable or radiation-curable surface hardening coating used in the present invention includes (meth)acrylic oligomers. It has two or more acryloyl or methacryloyl groups. This (meta)
Acrylic oligomers have a highly crosslinked structure when cured, and examples include ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, tetraethylene glycol diacrylate,
Difunctional acrylates or methacrylates such as tetraethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, glycerol triacrylate, glycerol trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, tris(2- hydroxyethyl) isocyanurate acrylate, tris(2
There are also trifunctional or higher functional acrylates or methacrylates such as -hydroxyethyl) isocyanurate ester methacrylate. Reactive monofunctional acrylates or methacrylates can be added when it is desired to reduce the viscosity of the coating or to obtain desired properties of the coating. When the (meth)acrylic oligomer has a urethane bond in its molecular skeleton, the abrasion resistance of the coating film increases, and the abrasion 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. Examples of the above polyols include ethylene glycol, 1,2-propanediol,
1,3-propanediol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-heptanediol, 1,6
- Short-chain diols such as hexanediol, diethylene glycol, dipropylene glycol, and trimethylolpropane. There are also polyethylene glycol, polypropylene glycol, polyoxytetramethylene glycol, etc. 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, and adipic acid and hexanediol. Ring-opened ε-caprolactone polymers can also be used as polyols. Examples of compounds having two or more isocyanate groups in one molecule include hexamethylene diisocyanate, methylene diphenyl diisocyanate, toluene diisocyanate, xylene diisocyanate, and methylene dicyclohexyl diisocyanate.
Examples of active hydrogen-containing acrylates or methacrylates include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, and 3-hydroxyethyl acrylate.
Examples include hydroxypropyl methacrylate and acrylic acid. As described above, the photo-curable or radiation-curable paint used in the hard coat layer constituting the plastic sheet of the present invention contains a difunctional or more functional (meth)acrylic oligomer or an acryloyl group or methacryloyl group at the molecular end as a paint binder. Contains one or more urethane oligomer compounds having the following. As the conductive fine powder-containing resin paint coated on the hard coat layer, the same photo-curable or radiation-curable paint as used for the hard coat layer is used. Since this conductive fine powder-containing layer is located on the outermost surface of the plastic sheet of the present invention and is easily damaged by direct external force, a photocurable paint containing the above-mentioned urethane oligomer, which has excellent scratch resistance, is preferably used. . The conductive fine powder contained in this outermost layer is mainly composed of tin oxide and has a particle size of 0.2 μm or less. When the particle size exceeds 0.2 μm, visible light is 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 50 to 400 parts by weight per 100 parts by weight of the paint binder in order to ensure transparency and conductivity of the coating film. If the amount of this conductive fine 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 achieved. cannot be fully demonstrated. If it exceeds 400 parts 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. For the purpose of improving the photocurability of the paint binder used in the hard coat layer and the conductive powder-containing layer laminated thereon, a photosensitizer is appropriately added as necessary. Examples of the photosensitizer include benzoin, benzyl, benzoin isopropyl ether, benzoin isomethyl ether,
α-Methylbenzoin, α-phenylbenzoinbenzyl, diacetylmethylanthraquinone, chloranthraquinone, benzophenone, anthraquinone, Mifilarketone, 4,4′-bis(N.
Carbonyl compounds such as N'-diethylamino)benzophenone and acetophenone; Sulfur compounds such as diphenyl sulfide, diphenyl disulfide, and dithiocarbamate; Naphthalene and anthracene compounds such as α-chloromethylnaphthalene and anthracene; Tetrachlorphthal Examples include halogenated hydrocarbons such as dimethyl acid and hexachlorobutadiene; metal salts such as uranyl sulfate, iron chloride, and silver chloride; and dye acids such as acriflavin, fluorescein, riboflavin, and rhodamine B. The amount of these sensitizers added is preferably 0.01% by weight or more based on the photocurable oligomer. For example, amines can be used as an auxiliary agent for the photocuring reaction. Examples of amines include triethylamine, tributylamine, and diethylaminoethyl methacrylate. It is obtained by dissolving the above-mentioned hard coat layer coating binder and photosensitizer in an organic solvent. The paint for the conductive fine powder-containing layer is obtained by dissolving the corresponding binder, conductive fine powder containing tin oxide as a main component, and a photosensitizer in an organic solvent. When preparing a paint for this conductive fine powder-containing layer, use equipment normally used for dispersing and compounding paints, such as a sand mill, a ball mill, a high-speed rotating stirring device, and a three-roll mill, in order to sufficiently disperse the fine powder in the paint. etc. may be used. In order to further enhance the dispersion of this fine powder, dispersion aids such as silane coupling agents, titanate coupling agents, surfactants, oleic acid, and lecithin may also be used. The conductive plastic sheet of the present invention is produced by coating the thus prepared hard coat layer coating material on a transparent plastic substrate and curing it, and then applying the conductive fine powder-containing layer coating material onto the hard coat layer obtained by applying the coating material for the hard coat layer prepared in this way onto a transparent plastic base material and curing it. It is obtained by coating and curing. General coating methods such as a spray method, a bar coating method, a doctor blade method, and a dipping method are used to apply the paint. Examples of plastic sheet base materials include vinyl chloride, polycarbonate, polymethacrylate, and ABS resin. In order to further increase the transparency of the resulting coating film, 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. Pour 334g of hexamethylene diisocyanate into the dropping funnel 1
The mixture was added dropwise over a period of time, and stirring was continued at 80°C for 1 hour. Next, 1 g of hydroquinone was added as a polymerization inhibitor to this reaction system, and then 232 g of 2-hydroxyethyl acrylate was added, and the stirring was continued for 2 hours.
It lasted for hours. The weight average molecular weight of the obtained oligomer was 1500. (B) Preparation of paint for hard coat layer: 20 g of binder resin prepared in Section A, 40 g of trimethylolpropane triacrylate, 20 g of tetrahydrofurfuryl acrylate, 20 g of tetraethylene glycol diacrylate, 100 g of pentaerythritortetraacrylate, 6 benzophenone.
g and 6 g of Mifilar ketone were added to and dissolved in 788 g of methyl ethyl ketone. (C) Preparation of paint for layer containing conductive fine powder: A above
20g of binder resin synthesized in Section 4, 40g of trimethylolpropane triacrylate, 20g of tetrahydrofurfuryl acrylate, 20g of tetraethylene glycol diacrylate, 100g of pentaerythritol tetraacrylate, particle size
Tin oxide containing antimony trioxide less than 0.2μm 200
g, 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. (D) Preparation of coating film and evaluation of performance: The hard coat layer coating prepared in Section B above was applied onto a transparent vinyl chloride sheet to a dry thickness of 10 μm. After volatilizing the solvent at 50℃ for 5 minutes and drying it, use a high-pressure mercury lamp (output 2KW) in a nitrogen atmosphere.
30 from a distance of 10cm due to effective lamp length 12.5cm)
Light irradiation was performed for a minute. The coating film after irradiation was tack-free. Furthermore, the dry thickness of the coating material for the conductive fine powder-containing layer synthesized in Section C above is
It was coated to a thickness of 2 μm. After the solvent was volatilized and dried, light irradiation was performed for 30 minutes from a distance of 10 cm using a mercury lamp as in the case of the hard coat layer. 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. Surface specific resistance, total light transmittance, haze value,
The measurement results of pencil hardness and increase in haze value after the taper test 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, pencil hardness is JIS K-
5400, the increase rate of haze value after the taper test is
Measured using a test method based on ASTM D-1044. For THF solubility resistance, the target material is 20
The state of the coating film after being immersed for 24 hours at ℃ is shown, where 〇 indicates a state where no change is observed, and × indicates a state where the coating film has melted and peeled off. Example 2 (A) Synthesis of binder resin: A binder resin was synthesized in the same manner as in Example 1. (B) Preparation of paint for hard coat layer: 25 g of binder resin synthesized in Section A, 35 g of trimethylolpropane triacrylate, 10 g of 2-hydroxyethyl acrylate, 30 g of neopentyl glycol acrylate, 40 g of pentaerythritol tetraacrylate, dipentaerythritol hexa acrylate 60g, benzophenone 6
g, 6 g of Mifilar ketone was dissolved in 788 g of methyl ethyl ketone. (C) Preparation of paint for layer containing conductive fine powder: 25 g of binder resin synthesized in Section A, 35 g of trimethylolpropane triacrylate, 10 g of 2-hydroxyethyl acrylate, 30 g of neopentyl glycol diacrylate, 40 g of pentaerythritol tetraacrylate. , dipentaerythritol hexaacrylate 60g, particle size 0.2μm
200 g of tin oxide containing antimony trioxide, 20 g of benzophenone, and 20 g of mifilar ketone:
g was added to 560 g of methyl ethyl ketone, charged into a ball mill, and dispersed for 24 hours to prepare a paint. (D) Preparation of coating film and evaluation of performance: A coating film was prepared in the same manner as in Example 1(D) and performance evaluation was performed. The results are shown in the table below. Example 3 A partially hydrolyzed condensate of methyltriethoxysilane (manufactured by Owens-Illinois, glass resin) was coated onto a transparent polycarbonate plate so that the thickness after thermosetting was 10 μm. Heat curing is 100
The test was carried out at ℃ for 15 hours. Next, a paint for a conductive fine powder-containing layer was prepared in the same manner as in Example 1 (C), and a coating film was formed on the hard coat layer in the same manner as in Example 1 (D). This was subjected to a performance test in the same manner as in Example 1. The results are shown in the table below. Example 4 30 g of hexakis(methoxymethyl)melamine and 0.1 g of nitrified cotton having a nitrogen content of 13% and an average degree of polymerization of 70 were dissolved in a mixed solution of 98 g of butyl acetate and 2 g of water. A hydrochloric acid catalyst was added to this to prepare a paint for a hard coat layer. This was applied onto a transparent polycarbonate plate so that the thickness after heat curing was 10 μm. Heat curing was carried out at 100°C for 8 hours. Next, a paint containing conductive fine powder was prepared in the same manner as in Example 1 (C), and a coating film was formed on the hard coat layer in the same manner as in Example 1 (D). A performance test was conducted in the same manner as in Example 1. The results are shown in the table below. Comparative Example 1 Everything is the same as in Example 1 except that only the paint for the conductive fine powder-containing layer was directly applied to the transparent vinyl chloride sheet to a dry thickness of 2 μm without applying the paint for the hard coat layer. . The performance evaluation is shown in the table below. Comparative Example 2 Using 200 g of polyester resin (Vylon 200 manufactured by Toyobo Co., Ltd.) as a binder resin, 400 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 charged in a ball mill.
A paint was prepared by dispersing it for 24 hours. After coating on a transparent PVC sheet to a dry thickness of 2 μm and drying, performance evaluation was performed. The results are shown in the table below.

[Table] Effects of the invention: The conductive plastic sheet of the present invention has a hard coat layer obtained by coating and curing a thermosetting, photocuring, or radiation curing paint on a transparent plastic substrate, and further has a conductive layer on the hard coat layer. Because it is obtained by applying and curing a photo-curing or radiation-curing paint containing fine powder, the surface of the coating film has excellent not only conductivity but also excellent transparency, hardness, strength, scratch resistance, and solvent resistance. ing. Even if the conductive fine powder-containing layer located on the outermost surface is relatively thin, the properties of the highly hard hard coat layer located inside it are utilized, so the sheet of the present invention has sufficient transparency, hardness, strength, and May be scratch resistant. Moreover, the amount of expensive metal fine powder that controls the antistatic function of the sheet can be minimized. The sheet of the present invention can therefore be obtained at low cost.

Claims (1)

[Claims] 1. A hard coat layer made of a photo-curable, radiation-curable or thermosetting resin is provided on a transparent plastic sheet base material, and the hard coat layer has a particle size of 0.2μ.
A conductive plastic sheet formed by sequentially laminating layers containing a conductive powder containing tin oxide as a main component and a photocurable acrylate resin, a methacrylate resin, or a radiation-curable acrylate resin or methacrylate resin. 2. The plastic sheet according to claim 1, wherein the photocurable hard cord layer contains a photocurable acrylate resin or a photocurable methacrylate resin as a main component. 3. The plastic sheet according to claim 1, wherein the thermosetting hard coat layer contains a silane resin as a main component. 4. The plastic sheet according to claim 1, wherein the plastic sheet base material is hard vinyl chloride, polyethylene terephthalate, polycarbonate, or acrylate. 5. The plastic sheet according to claim 1, wherein the hard coat layer has a thickness of 5 μm or more. 6. The plastic sheet according to claim 1, wherein the layer containing the conductive powder and photo-curable or radiation-curable resin has a thickness of 10 μm or less. 7. The plastic sheet according to claim 1, wherein the surface of the layer containing the conductive powder and photo-curable or radiation-curable resin is buffed.