JPH0959536A - Production of antistatic plastic plate or sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antistatic plastic plate-producing method capable of producing a transparent antistatic plastic plate excellent in antistatic property, transparency, abrasion resistance and appearance beauty by a simple facility and man-hour. SOLUTION: An antistatic coating containing a coating binder consisting essentially of a (meth)acrylate compound having at least two or more acryloyl groups or methacryloyl goups in the molecule, an electroconducting filler containing tin oxide and a photopolymerization initiator is applied to a plastic plate and dried and irradiated with ultraviolet rays to form a cured coating layer and the cured coating layer is exposed to vapor atmosphere of hydrogen peroxide.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing an antistatic plastic plate or sheet.

[0002]

2. Description of the Related Art A device for storing or carrying devices such as semiconductor wafer storage containers which are damaged by static electricity.
Antistatic performance is required for the materials of walls and windows such as clean rooms, clean zones, and clean process units in the production plants of these electronic and electric parts, and these materials are electrically conductive including carbon powder, metal powder, etc. It has been carried out by coating with a paint or by compounding carbon powder, carbon fiber, metal fiber or the like with a plastic material to impart antistatic performance.

However, as the antistatic performance of these plastic materials, if the surface resistance is a low level antistatic measure of about 10 ⁹ Ω or more, a surfactant which increases hydrophilicity or ionic conductivity is kneaded into the plastic material. Antistatic performance can be imparted without impairing the transparency of plastic materials by methods such as the above, but in the case of the aforementioned semiconductor materials, semi-finished products or storage containers such as semiconductor devices, clean room materials, etc. It is extremely difficult to maintain the transparency of plastic materials because of the demand for prevention performance.

On the other hand, with the development of the semiconductor industry, the degree of circuit integration of semiconductor devices is increasing more and more, and it is necessary to see through the interior from a transparent protective wall in each process from the production of these semiconductor devices to the semi-finished products and the storage of the products. However, the above-mentioned demand for a highly antistatic transparent plastic material is only increasing. With the above background,
For example, Japanese Unexamined Patent Publication (Kokai) No. 58-91777 discloses a conductive transparent coating material in which a conductive fine powder made of tin oxide containing antimony is mixed with a synthetic resin binder.

However, in the conductive transparent paint disclosed in the above-mentioned Japanese Patent Laid-Open No. 58-91777, the light refractive index of the synthetic resin binder, which is the main element of the paint, is from 1.6 to 1.6.
By setting the average particle size of the conductive fine powder to be close to 1.7 or 0.4 μm or less, which is smaller than the wavelength of visible light, transparency can be secured to some extent, but abrasion resistance and It had a defect of low solvent property.

Particularly, plastic plates used for windows in clean rooms, windows of clean benches, etc. are required to have antistatic properties, transparency, abrasion resistance and chemical resistance. However, the conductive fine powder containing tin oxide has a property of being colored by irradiation with ultraviolet rays. Furthermore, when it is applied to a white or ivory plastic plate or a plastic plate having a color tone different from that of the above coloring, the conventional technique is used. However, it is almost impossible to apply to these opaque plastic plates because uneven coloring is noticeable.

[0007]

DISCLOSURE OF THE INVENTION The inventor of the present invention has made a plastic plate coated with a conductive transparent paint prepared by mixing conductive fine powder containing tin oxide as a main component with a synthetic resin binder in an aqueous solution containing an oxidizing agent. Although it was found that the transparency of the coating film of the coated plastic plate is improved by doing, in an oxidizing agent aqueous solution other than hydrogen peroxide, it takes a long time to develop the effect of improving the transparency, The above-mentioned coated plastic plate immersed in hydrogen peroxide water has a trouble that the odor of hydrogen peroxide does not come off easily and must be sufficiently washed with water.

Further, as a plastic plate used for a window in a clean room, a window of a clean bench, etc.,
Acrylic resin plate with excellent transparency has been used,
Since the acrylic resin plate has a relatively high water absorbency, there is a problem that the acrylic resin plate warps or bends due to water absorption when the above-mentioned aqueous solution immersion treatment time becomes long.

The present invention has been made in view of the above facts, and an object thereof is to provide a transparent antistatic plastic excellent in antistatic property, transparency, abrasion resistance and beautiful appearance. It is an object of the present invention to provide a method for producing an antistatic plastic plate that can be produced with simple equipment and man-hours.

[0010]

SUMMARY OF THE INVENTION The present invention is directed to a coating binder containing a (meth) acrylate compound having at least two or more acryloyl groups or methacryloyl groups in its molecule as a main component, a conductive filler containing tin oxide, and an optical material. Applying an antistatic coating containing a polymerization initiator to a plastic plate, drying it, and irradiating it with ultraviolet rays to form a cured coating layer, and then exposing the cured coating layer to a vapor atmosphere of hydrogen peroxide. The gist is a method of manufacturing a characteristic antistatic plastic plate or sheet.

The (meth) acrylate compound having at least two acryloyl groups or methacryloyl groups in the molecule is cured to have a highly crosslinked structure. Examples of the (meth) acrylate compound having at least two acryloyl groups or methacryloyl groups in the molecule include ethylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, and tetraethylene glycol dimethacrylate. Bifunctional acrylates or methacrylates such as acrylate and tetraethylene glycol dimethacrylate may be mentioned. Further, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, glycerol triacrylate, glycerol trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, tris (2-hydroxyethyl) isocyanuric acid ester acrylate, tris (2-hydroxyethyl) ) Trifunctional acrylates or methacrylates such as isocyanuric acid ester methacrylates.

When the (meth) acrylate compound having at least two acryloyl groups or methacryloyl groups in the molecule has a urethane bond in its molecular skeleton, the hardness and scuff resistance of the resulting coating film are further improved. .

The preparation of the (meth) acrylate compound having at least two acryloyl groups or methacryloyl groups in the molecule is not particularly limited. For example, a polyol and two or more isocyanates in one molecule are used. It is carried out by polymerizing a compound having a group, and reacting an acrylate or methacrylate having active hydrogen with an isocyanate group at the molecular end thereof. Examples of the polyol 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- Pentanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, trimethylolpropane, polyethylene glycol, polypropylene glycol, polyoxytetramethylene glycol, adipic acid and ethylene glycol, adipic acid and propylene glycol, adipic acid and neo. Examples thereof include pentyl glycol, adipic acid and butanediol, adipic acid and pentanediol, condensed polyester glycol of adipic acid and hexanediol, and ε-caprolactone ring-opening polymer.

Examples of the compound 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 the acrylate or methacrylate having active hydrogen include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, acrylic acid and the like.

The antistatic coating used in the present invention contains, as a coating binder, one or more of (meth) acrylate compounds having at least two acryloyl groups or methacryloyl groups in the molecule. It

The antistatic coating material contains a conductive filler containing tin oxide. The shape of the conductive filler containing tin oxide is preferably a fine particle having a particle size of 0.2 μm or less. . The particle size of the conductive filler is 0.2 μm
If it exceeds, the incident visible light is scattered and the transparency of the obtained coating film is lowered. At the same time, since a part of ultraviolet rays is also scattered, the photocurability of the coating binder is lowered, and sometimes it is not cured at all.

The conductive filler containing tin oxide may be fine particles of a metal oxide mainly composed of tin oxide, but fine particles of tin oxide doped with antimony or tin oxide doped with antimony are used as the surface. The use of the barium sulfate fine particles coated on the surface improves the transparency of the coating film and can be suitably used for a transparent antistatic plastic plate. Further, for light-colored opaque plates such as white, barium sulfate fine particles coated with the above-mentioned antimony-doped tin oxide or potassium titanate whiskers coated with antimony-doped tin oxide on the surface can be used. It can be preferably used. The content of the conductive filler containing tin oxide is 100% in order to secure the transparency of the coating film, the color unevenness prevention property of the plate surface and the conductivity.
It is 50 to 400 parts by weight with respect to parts by weight. If the content is less than 50 parts by weight, sufficient conductivity cannot be ensured, and
If it exceeds 0 parts by weight, the dispersibility of the conductive filler containing tin oxide is lowered, and the transparency of the resulting coating film, the prevention of color unevenness on the plate surface, the hardness and scratch resistance of the coating film are impaired.

A photosensitizer may be added to the antistatic coating for the purpose of improving the photocurability of the coating binder. Examples of the photosensitizer include benzoin, benzyl, benzoin isopropyl ether, benzoin methyl ether, α-methylbenzoin: α-phenylbenzoinbenzyl, diacetylmethylanthraquinone, benzophenone, anthraquinone, 4,4′-
Carbonyl compounds such as bis (N, N′-diethylamino) benzophenone and acetophenone, sulfur compounds such as diphenyl disulfide and dithiocarbamate, α-chloromethylnaphthalene, naphthalene such as anthracene, anthracene compounds, dimethyl tetrachlorophthalate,
Examples thereof include halogenated hydrocarbons such as hexaurobutadiene, metal salts such as uranyl sulfate, iron chloride and silver chloride, and dyes such as acriflavine, fluorescein, riboflavin and rhodamine B. The amount of the photosensitizer added is 0.01 parts by weight or more based on 100 parts by weight of the coating binder.

Further, amines may be used as an auxiliary agent for the photo-curing reaction. Examples of the amines include triethylamine, tributylamine, diethylaminoethyl methacrylate and the like. Further, in order to improve the dispersion of the conductive filler containing tin oxide, an acrylic polymer having a hydroxyl group may be added as a dispersant. The addition amount of the acrylic polymer having a hydroxyl group is 0.1 part by weight or more based on 100 parts by weight of the coating binder. In addition to the above dispersants, or alone, a dispersion aid such as a silane coupling agent, a titanate coupling agent, a surfactant, oleic acid, and lecithin may be used.

The preparation of the antistatic coating is not particularly limited, but, for example, the coating binder is dissolved in an organic solvent, and a conductive filler containing tin oxide and a photopolymerization initiator are mixed therein. Is done. For the above mixing, equipment normally used for dispersing or blending the coating material, for example, a sand mill, a ball mill, a high-speed rotary stirring device, or a triple roll is appropriately selected and used.

The antistatic paint prepared as described above is
An appropriate coating method such as a spray method, a bar coating method, a doctor blade method, a dipping method, etc. is selected and applied to a plastic plate or sheet of an object and dried to form a coating film. As the plastic plate or sheet of the above object, those made of vinyl chloride resin, polycarbonate, acrylic resin, etc. are used for clean room construction materials and electrostatic protection storage or transportation containers, but are not limited to these. Widely applied to plastic rate or sheet.

The plastic plate or sheet coated as described above is then irradiated with ultraviolet rays to form a cured coating layer. By buffing the cured coating surface of the plastic plate or sheet coated as described above, the transparency of the coated plastic plate or sheet can be further increased. The cured coating film layer is further exposed to a hydrogen peroxide vapor atmosphere, and the method of exposure is not particularly limited as long as the cured coating film layer is exposed to the hydrogen peroxide vapor atmosphere. .
As the exposure condition, for example, an atmospheric temperature of 20 to 60 ° C. and a treatment time of about 10 minutes to 2 hours are appropriately set in consideration of various conditions.

As described above, when an ultraviolet curable antistatic coating material containing a conductive filler containing tin oxide is applied and cured by ultraviolet light, radicals during polymerization photoreduce the metal. Although the absorption is increased and the coloring and the transparency are deteriorated, the vapor atmosphere treatment of the hydrogen peroxide prevents or eliminates the deterioration of the coloring and the transparency. This is because the hydrogen peroxide vapor sufficiently penetrates into the cured coating film by the treatment with the hydrogen peroxide vapor atmosphere, and the conductive filler containing tin oxide once photoreduced is reoxidized to obtain the original color tone. It is presumed that this is due to returning to.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 Preparation of Antistatic Coating 100 parts by weight of antimony oxide-containing tin oxide powder (manufactured by Mitsubishi Materials, trade name: T-1) having a primary particle size of 0.02 μm, hydroxyethyl methacrylate / methacryl 20 parts by weight of methyl acid copolymer (molar ratio 2: 8), 40 parts by weight of pentaerythritol tetraacrylate, 300 parts by weight of ethyl cellosolve, 1 part by weight of benzophenone, and 1 part by weight of Michler's ketone were charged into an attritor and dispersed for 10 hours. Then, an antistatic paint was prepared.

The above antistatic paint is applied in a size of 1 m × 1 m × 3 mm
Was coated on a transparent acrylic resin plate of No. 3 using a roll coater so that the film thickness after drying would be 3 μm, dried at room temperature for 30 minutes, and then dried at 50 ° C. for 10 minutes with hot air. The coating surface of the obtained coated transparent acrylic resin plate is 120
Using a high-pressure mercury lamp of W / cm, 200
Ultraviolet rays were irradiated from the position of mm so that the integrated light quantity would be 1500 mJ / cm ² , and the coating film was cured, and then buffing was performed. Further, the transparent acrylic resin plate on which the above-mentioned cured coating film was formed was fixed in a sealed treatment chamber at a position 10 cm above the 30% hydrogen peroxide solution water tank with the coating surface facing the above water tank, and then peroxide-oxidized for 30 minutes. An antistatic transparent acrylic resin plate was manufactured by exposure to hydrogen vapor.

Obtained antistatic transparent acrylic resin play
The obtained antistatic transparent acrylic resin plate had no odor of hydrogen peroxide and did not need to be washed with water, and could be used for various applications as it was. Antistatic performance is
The surface specific resistance value was measured and evaluated according to ASTM-D257. The total light transmittance and haze value are AST
It measured based on M-D1003. Regarding the warp of the plate, the obtained antistatic transparent acrylic resin plate was placed on a flat plate, the maximum value floating from the flat plate was measured, and the maximum value was evaluated as the size of the warp. The measured values are shown in Table 1.

Comparative Example 1 Instead of the hydrogen peroxide vapor treatment of Example 1, a transparent acrylic resin plate having a cured coating film formed thereon was immersed in a 5% hydrogen peroxide aqueous solution for 5 minutes to perform the hydrogen peroxide treatment. went. Since the treated transparent acrylic resin plate had a strong hydrogen peroxide odor and needed to be washed with water, it was washed with water for 10 minutes for deodorization and dried with hot air to prepare an antistatic transparent acrylic resin plate. The performance of the obtained antistatic transparent acrylic resin plate was tested in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 An antistatic transparent acrylic resin plate was produced in the same manner as in Example 1 except that the hydrogen peroxide vapor treatment of Example 1 was not carried out. The performance of the obtained antistatic transparent acrylic resin plate was tested in the same manner as in Example 1, and the results are shown in Table 1.

Example 2 Preparation of Antistatic Coating 60 parts by weight of conductive potassium titanate whiskers (trade name: Dentol WK-200, manufactured by Otsuka Chemical Co., Ltd.), 100 parts by weight of dipentaerythreisylitol hexaacrylate,
2 parts by weight of thioxanthone, 1 part by weight of dimethylaminoacetophenone, and 300 parts by weight of ethyl cellosolve were charged into a dissolver and stirring was continued for 5 hours to prepare an antistatic coating material.

An antistatic transparent acrylic resin plate was produced in the same manner as in Example 1 using the above antistatic paint. The performance of the obtained antistatic transparent acrylic resin plate was tested in the same manner as in Example 1, and the results are shown in Table 1.

(Comparative Example 3) An antistatic transparent acrylic resin plate was produced in the same manner as in Example 2 except that the hydrogen peroxide vapor treatment of Example 2 was not carried out. The performance of the obtained antistatic transparent acrylic resin plate was tested in the same manner as in Example 1, and the results are shown in Table 1.

[0033]

[Table 1]

From the test results shown in Table 1, the total light transmittance of the antistatic transparent acrylic resin plate which was not treated with hydrogen peroxide clearly showed a difference from that of the one which was treated with hydrogen peroxide. The antistatic transparent acrylic resin plate of Example 3 was entirely blackish, had color unevenness along the coating direction, became unsightly in appearance, and markedly reduced the commercial value. Further, the warpage of the antistatic transparent acrylic resin plate of Comparative Example 1 which was brought into contact with a large amount of water (hydrogen peroxide aqueous solution) was large, clearly showing a difference from the antistatic transparent acrylic resin plate of the Example, and the commercial value was significantly reduced. It was something that caused it.

[0035]

Since the method for producing an antistatic plastic plate or sheet of the present invention is constructed as described above, an ultraviolet curable antistatic paint containing a conductive filler containing tin oxide is applied, When UV-cured, the absorption of visible light becomes large, and the coloring and the transparency are reduced, but by the vapor atmosphere treatment of the hydrogen peroxide, the coloring and the reduction in the transparency are prevented or eliminated. It is possible to obtain an antistatic plastic plate or sheet having both conductivity and transparency that cannot be obtained. .

In the method for producing an antistatic plastic plate or sheet according to the present invention, even a plastic plate or sheet having a high hygroscopic property does not come into direct contact with a large amount of aqueous hydrogen peroxide solution or water. It is possible to provide a highly productive method for producing an antistatic plastic plate or sheet, which does not require washing with water for deodorizing odors or a drying step accompanying it.

In the method for producing an antistatic plastic plate or sheet of the present invention, the treatment with hydrogen peroxide does not cause deformation such as warpage on the plastic plate or sheet as the article to be coated, and (EN) Provided is an antistatic plastic plate or sheet having excellent performance without affecting the conductivity, scratch resistance, and abrasion resistance of a cured coating film that has been processed.

Claims (1)

[Claims] 1. An antistatic agent containing a paint binder containing as a main component a (meth) acrylate compound having at least two or more acryloyl groups or methacryloyl groups in the molecule, a conductive filler containing tin oxide and a photopolymerization initiator. Apply paint for plastic to plastic plate, dry,
A method for producing an antistatic plastic plate or sheet, which comprises irradiating ultraviolet rays to form a cured coating film layer, and then exposing the cured coating film layer to a vapor atmosphere of hydrogen peroxide.