JPH09232096A - Electrification preventing method, and electrification preventive composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the static electrification of a surface, by radiating light to an optical conductor photocatalyst containing layer, for coating electrically insulating base material, to optically excite a photocatalyst, and the surface of the layer is made hydrophilic, to adsorb humidity in air to the surface. SOLUTION: An electrically insulating base material (a ceramic and a tile, etc.) is coated by a layer, composed of a cilicone composition containing a semiconductive photocatalyst (TiO2 is preferableast), so that the coat thickness can be 0.2μm or less. Light such as the sunlight, etc., is radiated to the base material, to optically excite the photocatalyst; and the surface of the layer is made hydrophilic to about 10 deg. or less calculated in terms of a contact angle with water, to adsorb a moisture content in air into the layer surface. This can prevent the static electrification on the base material surface.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an antistatic technique.

[0002]

2. Description of the Related Art Since plastics are excellent in mechanical properties, processability, moldability, colorability, chemical resistance, and light weight, they are used in many household goods, household appliances, office equipment, automobiles, packaging materials, etc. Used in the field of. In addition, since high-polymer synthetic fibers have excellent durability, they are often used in clothes and carpets. Since many plastics and synthetic fibers are electrically insulating, they are easily electrostatically charged, causing electric shock or spark discharge, or adsorbing dust. Static electricity charged in a copying machine, etc. causes troubles in paper feeding. The electrostatic charge and its discharge may cause electronic devices to malfunction or damage integrated circuits and recording media. Fluorescent lamps, electron-beam-scanned televisions, and cathode ray tubes of computers tend to adsorb dust due to electrostatic charging.

[0003]

As a conventional antistatic technique, there is a method of applying an antistatic agent comprising a surfactant to the surface of an article. However, the antistatic agent is temporary and is lost from the article surface by wiping with cloth, washing with water, etc., and the antistatic effect is reduced at an early stage. There is also a method of applying carbon black to make the surface conductive, but it is troublesome,
The problem is that the surface of the article becomes dirty.

An object of the present invention is to provide an antistatic technique which does not have the above-mentioned inconvenience. Another object of the present invention is to provide an article provided with a semi-permanent antistatic film having excellent abrasion resistance. Another object of the present invention is to provide an antistatic technique that can be easily implemented.

[0005]

The present inventor has discovered that when the photocatalyst is photoexcited, the surface of the photocatalyst is highly hydrophilized, and the electrical conductivity of the surface is increased (surface resistivity is decreased).

The present invention is based on such a discovery, and the present invention provides an antistatic method for an article and an antistatic composite material. According to the present invention, the surface of various articles is coated with a layer containing a semiconductor photocatalyst. When the photocatalyst is photoexcited by irradiating the article with light, the surface of the photocatalyst-containing layer is made superhydrophilic so that the contact angle with water is 10 ° or less, preferably 5 ° or less, and more preferably about 0 °. Photoexcitation of the photocatalyst
It can be performed by various light sources. It is preferable to use sunlight under conditions where it is exposed to sunlight. Indoors, metal halide lamps, mercury lamps, xenon lamps and other light sources can be used. The photocatalyst can be excited by the weak ultraviolet rays contained in fluorescent lamps and incandescent lamps. Once the surface of the article is highly hydrophilized, the superhydrophilicity of the surface lasts for a considerable period of time.

The superhydrophilic surface thus adsorbs moisture in the air and increases the electric conductivity. Static electricity generated by friction and electron beam scanning is easily discharged, so that the surface of the article is less likely to be electrostatically charged.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is directed to daily sundries, household appliances, office equipment, automobile interior and exterior parts, packaging materials,
It is applied to textiles such as clothes and carpets, cathode ray tubes for televisions and computers, fluorescent lamps, and other articles requiring antistatic treatment. The surface of the substrate requiring antistatic treatment is covered with a transparent layer containing a semiconductor photocatalyst.

The most preferable photocatalyst is titania (TiO ₂ ). Titania is harmless, chemically stable, and available at low cost. Further, titania has a high band gap energy, and thus requires ultraviolet light for photoexcitation and does not absorb visible light in the process of photoexcitation, so that coloring by a complementary color component does not occur. Both anatase titania and rutile titania can be used. The advantage of the anatase type titania is that a sol in which very fine particles are dispersed can be easily obtained on the market, and a very thin thin film can be easily formed. On the other hand, rutile-type titania can be sintered at a high temperature, and has an advantage that a film having excellent strength and wear resistance can be obtained. Covering the surface of the substrate with a photocatalytic titania-containing layer, when the titania is photoexcited by UV light, water by photocatalysis hydroxyl (OH ^-) are chemisorbed on the surface in the form of, as a result, the surface becomes superhydrophilic Conceivable. Other photocatalysts that can be used include ZnO, SnO ₂ , SrTiO ₂ .
₃ , metal oxides such as WO ₃ , Bi ₂ O ₃ , and Fe ₂ O ₃ . It is considered that these metal oxides adsorb surface hydroxyl groups (OH ⁻ ), as in the case of titania, because a metal element and oxygen exist on the surface. The photocatalyst-containing layer may be formed by mixing particles of photocatalytic titania with a metal oxide.
In particular, when anatase titania is mixed with silica or tin oxide as described later, the surface can be highly hydrophilized.

The thickness of the photocatalyst containing layer is preferably 0.2 μm or less. With such a film thickness, color formation due to light interference can be prevented. Further, the thinner the photocatalyst containing layer, the more the transparency of the photocatalyst containing layer can be secured. Furthermore, if the film thickness is reduced, the wear resistance of the photocatalyst containing layer is improved.

When the substrate is made of a heat-resistant material such as ceramic, tile, or glass, it exhibits superhydrophilicity such that the contact angle with water is 0 ° and is excellent in abrasion resistance. One of the preferred ways of forming the photocatalyst-containing layer is to first coat the surface of the substrate with amorphous titania and then phase-change the amorphous titania to crystalline titania (anatase or rutile) by firing. Any of the following methods can be used for forming amorphous titania. (1) Hydrolysis and dehydration condensation polymerization of organic titanium compounds Alkoxides of titanium, for example, tetraethoxytitanium, tetraisopropoxytitanium, tetra-n-propoxytitanium, tetrabutoxytitanium, tetramethoxytitanium, and hydrochloride such as hydrochloric acid or ethylamine After adding a decomposition inhibitor and diluting with an alcohol such as ethanol or propanol, after partially or completely promoting hydrolysis, the mixture is spray-coated, flow-coated, spin-coated,
Apply to the substrate surface by dip coating, roll coating or other coating method
Dry at a temperature of 0 ° C. By drying, hydrolysis of the alkoxide of titanium is completed to produce titanium hydroxide, and a layer of amorphous titania is formed on the surface of the substrate by dehydration-condensation polymerization of titanium hydroxide. Instead of titanium alkoxides, other organic titanium compounds such as titanium chelates or titanium acetate may be used. (2) Formation of amorphous titania by inorganic titanium compound Spray coating, flow coating of an acidic aqueous solution of an inorganic titanium compound, for example, TiCl ₄ or Ti (SO ₄ ) ₂ ,
It is applied to the surface of a substrate by spin coating, dip coating, or roll coating. Next, the inorganic titanium compound is subjected to hydrolysis and dehydration-condensation polymerization by drying at a temperature of about 100 ° C to 200 ° C to form a layer of amorphous titania on the surface of the substrate. Alternatively, amorphous titania may be applied to the surface of the substrate by chemical vapor deposition of TiCl ₄ . (3) Formation of Amorphous Titania by Sputtering Amorphous titania is deposited on the surface of a substrate by irradiating an electron beam to a target of titanium metal in an oxidizing atmosphere. (4) Firing temperature The firing of amorphous titania is performed at a temperature of at least the crystallization temperature of anatase. Amorphous titania can be converted to anatase titania by firing at a temperature of 400 ° C to 500 ° C or higher. By firing at a temperature of 600 ° C. to 700 ° C. or higher, amorphous titania can be converted to rutile type titania. (5) Formation of diffusion prevention layer When the base material is glass or glazed tile containing alkali network modifying ions such as sodium, an intermediate layer such as silica is previously formed between the base material and the amorphous titania layer. Good to keep. This prevents the alkali network modifying ions from diffusing from the substrate into the photocatalyst-containing layer during firing of the amorphous titania, and achieves a super-hydrophilic property such that the contact angle with water becomes 0 °. .

Another preferable method for forming a photocatalyst containing layer having superhydrophilicity such that the contact angle with water is 0 ° and having excellent abrasion resistance is to form a photocatalyst containing layer comprising a mixture of titania and silica. It is to form on the surface of the base material. The ratio of silica to the total of titania and silica is 5 to 5.
It can be 90 mol%, preferably 10 to 70 mol%, more preferably 10 to 50 mol%. For forming the photocatalyst-containing layer made of silica-containing titania, any of the following methods can be employed. (1) A suspension containing particles of anatase type or rutile type titania and particles of silica is applied to the surface of a substrate, and sintered at a temperature equal to or lower than the softening point of the substrate. (2) precursors of amorphous silica (for example, tetraalkoxysilanes such as tetraethoxysilane, tetraisopropoxysilane, tetra-n-propoxysilane, tetrabutoxysilane, tetramethoxysilane, etc .; silanol which is a hydrolyzate thereof); Alternatively, a mixture of a polysiloxane having an average molecular weight of 3,000 or less) and crystalline titania sol is applied to the surface of the base material and, if necessary, hydrolyzed to form silanol, and then heated at a temperature of about 100 ° C. or higher to obtain silanol. Is subjected to dehydration-condensation polymerization to form a photocatalyst-containing layer in which titania is bound with amorphous silica. In particular, if the dehydration polycondensation of silanol is performed at a temperature of about 200 ° C. or more,
The polymerization degree of silanol can be increased, and the alkali resistance performance of the photocatalyst-containing layer can be improved. This approach can be applied to non-heat resistant substrates such as plastic. (3) Disperse silica particles in a solution of amorphous titania precursor (organic titanium compound such as titanium alkoxide, chelate, or acetate, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ). The resulting suspension is applied to the surface of the base material, and the titanium compound is subjected to hydrolysis and dehydration polycondensation at a temperature from room temperature to 200 ° C to form a thin film of amorphous titania in which silica particles are dispersed. . Next, the amorphous titania is changed into crystalline titania by heating to a temperature equal to or higher than the crystallization temperature of titania and equal to or lower than the softening point of the substrate. (4) Amorphous silica precursor in a solution of amorphous titania precursor (organic titanium compound such as titanium alkoxide, chelate or acetate, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ). Body (eg, tetraethoxysilane, tetraisopropoxysilane, tetra n
A mixture of tetraalkoxysilanes such as propoxysilane, tetrabutoxysilane, and tetramethoxysilane; silanol which is a hydrolyzate thereof; or polysiloxane having an average molecular weight of 3000 or less), and coating the mixture on the surface of the substrate. Next, these precursors are subjected to hydrolysis and dehydration condensation polymerization to form a thin film composed of a mixture of amorphous titania and amorphous silica. Next, the amorphous titania is changed into crystalline titania by heating to a temperature equal to or higher than the crystallization temperature of titania and equal to or lower than the softening point of the substrate.

Still another preferred method of forming a photocatalyst containing layer having superhydrophilicity such that the contact angle with water is 0 ° and having excellent abrasion resistance is a photocatalyst containing a mixture of titania and tin oxide. Forming a layer on the surface of the substrate. The proportion of tin oxide with respect to the total of titania and tin oxide can be 1 to 95% by weight, preferably 1 to 50% by weight. For forming the photocatalyst-containing layer made of tin oxide-containing titania, any of the following methods can be employed. (1) A suspension containing particles of anatase or rutile type titania and particles of tin oxide is applied to the surface of a substrate, and sintered at a temperature equal to or lower than the softening point of the substrate. (2) Tin oxide particles in a solution of amorphous titania precursor (organic titanium compound such as titanium alkoxide, chelate or acetate, or inorganic titanium compound such as TiCl ₄ or Ti (SO ₄ ) ₂ ) The suspension obtained by dispersing is applied to the surface of the base material, and the titanium compound is subjected to hydrolysis and dehydration condensation polymerization at a temperature of from room temperature to 200 ° C., thereby forming a thin film of amorphous titania in which tin oxide particles are dispersed. Form. Next, the amorphous titania is changed into crystalline titania by heating to a temperature equal to or higher than the crystallization temperature of titania and equal to or lower than the softening point of the substrate.

When the substrate is formed of a non-heat resistant material such as plastic or synthetic fiber, a photocatalyst containing layer having superhydrophilicity such that the contact angle with water is 0 ° is formed. A preferred approach is to use a coating composition comprising photocatalyst particles dispersed in a film-forming element consisting of uncured or partially cured silicone or a silicone precursor. This coating composition is applied to the surface of the substrate, after curing the film-forming element, when the photocatalyst is photoexcited, the organic group bonded to the silicon atom of the silicone molecule is substituted with a hydroxyl group by the photocatalytic action of the photocatalyst, The surface of the photocatalyst containing layer is made superhydrophilic. This approach has several advantages. Since the photocatalyst-containing silicone paint can be cured at room temperature or a relatively low temperature, it can be applied to a substrate formed of a non-heat resistant material such as plastics and synthetic fibers. This coating composition containing a photocatalyst is applied to a substrate requiring antistatic treatment by brush coating, spray coating, dip coating,
It can be applied by roll coating or the like.
Since the photocatalyst-containing silicone coating has a siloxane bond, it has sufficient resistance to the photooxidation action of the photocatalyst. Still another advantage of the photocatalyst-containing layer made of a photocatalyst-containing silicone coating is that it maintains superhydrophilicity even at night after the surface is once made superhydrophilic.

As the coating film forming element, methyltrichlorosilane, methyltribromosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltri-t-butoxysilane; ethyltrichlorosilane, ethyltribromosilane, Ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, ethyltrit-butoxysilane; n-propyltrichlorosilane, n-propyltribromosilane, n-propyltrimethoxysilane,
n-propyltriethoxysilane, n-propyltriisopropoxysilane, n-propyltri-t-butoxysilane; n-hexyltrichlorosilane, n-hexyltribromosilane, n-hexyltrimethoxysilane, n
-Hexyltriethoxysilane, n-hexyltriisopropoxysilane, n-hexyltrit-butoxysilane; n-decyltrichlorosilane, n-decyltribromosilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, n -Decyltriisopropoxysilane, n-decyltri-t-butoxysilane; n-octadecyltrichlorosilane, n-octadecyltribromosilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octadecyltriisopropoxysilane, n-octadecyltri-t-butoxysilane; phenyltrichlorosilane, phenyltribromosilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane, phenyltrisilane -Butoxysilane; tetrachlorosilane, tetrabromosilane, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane; dimethyldichlorosilane, dimethyldibromosilane, dimethyldimethoxysilane, dimethyldiethoxysilane; diphenyldisilane Chlorosilane, diphenyldibromosilane, diphenyldimethoxysilane,
Diphenyldiethoxysilane; phenylmethyldichlorosilane, phenylmethyldibromosilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane; trichlorohydrosilane, tribromohydrosilane, trimethoxyhydrosilane, triethoxyhydrosilane, triisopropoxyhydrosilane, tri-t -Butoxyhydrosilane; vinyltrichlorosilane, vinyltribromosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane,
Vinyltri-t-butoxysilane; trifluoropropyltrichlorosilane, trifluoropropyltribromosilane, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, trifluoropropyltriisopropoxysilane, trifluoropropyltrit-butoxysilane; γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltriisopropoxy Silane, γ-glycidoxypropyltri-t-butoxysilane; γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryl Riloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriisopropoxysilane, γ-methacryloxypropyltri-t-butoxysilane; γ-aminopropylmethyldimethoxysilane, γ- Aminopropylmethyldiethoxysilane, γ
-Aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriisopropoxysilane, γ-aminopropyltri-t-butoxysilane; γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane , Γ-mercaptopropyltrimethoxysilane, γ-
Mercaptopropyltriethoxysilane, γ-mercaptopropyltriisopropoxysilane, γ-mercaptopropyltri-t-butoxysilane; β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β-
(3,4-Epoxycyclohexyl) ethyltriethoxysilane; and their partial hydrolysates; and mixtures thereof can be used.

When the photocatalyst is photoexcited by irradiating the substrate coated with the photocatalyst-containing layer with light having a wavelength not longer than the excitation wavelength of the photocatalyst as described above, the surface of the photocatalyst-containing layer is hydrophilized as described above. Electric conductivity increases (surface resistivity decreases). In the case of a photocatalyst whose excitation wavelength is in the ultraviolet region such as titania, the surface of the photocatalyst containing layer is first made superhydrophilic by sunlight, sterilization lamps, metal halide lamps, mercury lamps, xenon lamps, and other light sources. UV rays can be used. Once the surface of the photocatalyst-containing layer has been made highly hydrophilic, the superhydrophilicity of the surface can be sufficiently maintained or restored even with the weak ultraviolet rays contained in fluorescent lamps and incandescent lamps. The photocatalyst containing layer, Cu,
Metals such as Ag, Pt, Pd, Ir, Os, Ru and Rh can be added. When these metals are added, the electric conductivity of the surface of the base material is improved, so that the antistatic performance can be further improved. Further, since these metals enhance the photooxidation action of the photocatalyst, the functions such as antibacterial property and deodorant property are also improved.

[0017]

Example: Anatase type titania sol (Nissan Chemical, TA-1
5) and trimethoxymethylsilane (liquid B of the silicone coating composition "GLASCA" of Nippon Synthetic Rubber) were mixed and diluted with ethanol to prepare a titania-containing silicone coating composition. The weight ratio of trimethoxymethylsilane to titania was 1. This titania-containing coating composition was applied to a polyethylene terephthalate (PET) film (Fuji Xerox, monochrome PPC OHP film, JF-001), cured at a temperature of 110 ° C, and coated with titania-containing silicone # 1. A sample was obtained. Next, using a 20W black light blue fluorescent lamp (Sankyo Denki, FL20BLB), an ultraviolet illuminance of 0.6 mW / cm ² was irradiated on the surface of this # 1 sample (the illuminance of an ultraviolet ray having a wavelength shorter than the excitation wavelength of 387 nm of anatase-type titania). ) For about 3 days to obtain a # 2 sample.
The contact angle of the surface of # 1 sample and # 2 sample with water was measured with a contact angle measuring instrument (Kyowa Interface Science Co., Ltd., Model CA-X150, low angle side detection limit 1 °). ,
It was 85 ° for the # 1 sample and 10 ° for the # 2 sample.

In addition, static
Using a Honest meter, the # 1 and # 2 samples are positively charged in the corona discharge field in accordance with the A method (half-life measurement method) of the Japanese Industrial Standard "Testing method for electrification of textiles and knits" (JIS L1094). After that, the time taken for the charged voltage to decrease by half was measured. As a result, the half-life of the # 1 sample was 999 seconds or more, while the half-life of the # 2 sample was about 70 seconds.
It was confirmed that the antistatic property was obviously improved with the hydrophilization.

[0019]

The present invention is made of plastic, ceramic,
Articles formed or coated with synthetic fibers, glass, and other electrically insulating materials, such as household goods, household appliances, office equipment, automobiles, packaging materials, clothes and carpets, television and computer cathode ray tubes. , Discharge lamp,
Can be applied to, and electrostatic charging of the surface can be prevented. Therefore, it is possible to prevent failures due to static electricity, such as electric shock and spark discharge, dust adsorption, malfunction of electronic devices, and destruction of integrated circuits and recording media. When used as a copying machine, the paper can be fed smoothly. The photocatalyst-containing layer can be firmly bonded to the surface of the article and has excellent wear resistance, so that the antistatic effect can be permanently obtained. The antistatic effect continues even with the weak UV light contained in fluorescent lamps and incandescent lamps.

Claims (12)

[Claims] 1. An electrically insulating substrate coated with a layer containing a semiconductor photocatalyst is irradiated with light to photoexcite the photocatalyst, whereby the surface of the layer is converted into a contact angle with water of about 10. A method for preventing static electricity, which comprises hydrophilizing to below ℃ and adsorbing moisture in the air on the surface. 2. A surface of a base material made of an electrically insulating material is covered with a layer containing a semiconductor photocatalyst, and the surface of the layer is converted into a contact angle with water by photoexciting the photocatalyst to be about 10 ° or less. A method for preventing electrification, which comprises hydrophilizing to the surface and adsorbing moisture in the air on the surface. 3. A coating composition comprising particles of a semiconductor photocatalyst and a film-forming element comprising uncured or partially cured silicone or a precursor of silicone, and a surface of a substrate comprising an electrically insulating material. To form a layer in which photocatalyst particles are evenly dispersed in silicone by curing the coating film-forming element, and photoexcitation of the photocatalyst binds to the silicon atom of the silicone molecule on the surface of the layer. By substituting the organic group with a hydroxyl group at least partially by the action of a photocatalyst,
An antistatic method comprising hydrophilizing the surface of the layer to a contact angle with water of about 10 ° or less. 4. The antistatic method according to any one of claims 1 to 3, wherein the photocatalyst is photoexcited until the surface of the layer is hydrophilized to a contact angle with water of about 5 ° or less. . 5. An antistatic composite material comprising: a base material made of an electrically insulating material; and a layer bonded to the surface of the base material and containing a semiconductor photocatalyst, wherein the photocatalyst responds to photoexcitation. An antistatic composite material, characterized in that the surface of the layer is hydrophilized to a contact angle with water of about 10 ° or less so that moisture in the air is adsorbed on the surface. 6. The antistatic composite material according to claim 5, wherein the photocatalyst hydrophilizes the surface of the layer to a contact angle with water of about 5 ° or less in response to photoexcitation. 7. The photocatalyst-containing layer has a thickness of about 0.2 μm.
An antistatic composite material according to claim 5 or 6 below. 8. The photocatalyst is TiO ₂ , ZnO, SnO ₂ , SrTiO ₂ .
_The antistatic composite material according to any one of claims 5 to 7, containing one oxide selected from the group consisting of ₃ , WO ₃ , Bi ₂ O ₃ , and Fe ₂ O ₃ . 9. The antistatic composite material according to claim 8, wherein the photocatalyst is composed of anatase type titania. 10. The antistatic composite material according to claim 8, wherein the photocatalyst is made of rutile type titania. 11. The photocatalyst-containing layer further comprises SiO ₂ or SnO ₂
An antistatic composite material according to claim 8 comprising: 12. The photocatalyst-containing layer is formed of silicone in which photocatalyst particles are uniformly dispersed, and the surface of the layer has an organic group bonded to a silicon atom of a silicone molecule at least partially substituted with a hydroxyl group. 11. An antistatic composite material according to any one of claims 5 to 10 formed of a silicone derivative.