JPH0959042A - Transparent base material having anti-mist coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a transparent base material capable of reducing reflection of light, avoiding lowering of light transmittance and securing the field of vision by covering a transparent base material with an anti-mist coating composed of a mixture of a specific medium and prescribed titania particles. SOLUTION: A transparent base material (e.g.; window glass of a building) is covered with an anti-mist coating composed of a medium having <2 refractive index and preferably selected from silica, silicone, magnesium fluoride, alumina, tin oxide and their mixture and photocatalytic titania particles (e.g.; anatase-type titania particles) having about <=0.1μm average crystallite diameter and having transparency and preferably <=2 refractive index.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a transparent substrate provided with an antifogging coating.

[0002]

2. Description of the Related Art It is often experienced that in cold weather, windshields and windows of automobiles and other vehicles, window glasses of buildings, lenses of glasses, and cover glasses of various instrument panels are fogged by condensed moisture. In addition, the lenses of mirrors and glasses in bathrooms and washrooms are often fogged by steam.

The occurrence of fogging has a profound effect on safety and efficiency of various operations. For example, if the windshield, the window glass, or the rearview mirror of the vehicle becomes cloudy, the safety of the vehicle or the traffic is impaired. Fogging of the endoscopic lens or the dental ophthalmoscope is an obstacle to accurate diagnosis, surgery and treatment. If the cover glass of the instrument panel becomes cloudy, it will be difficult to read the data. Conventionally used antifogging compositions consist of hydrophilic compounds such as polyethylene glycol. However, this kind of anti-fogging composition is only a temporary one, and it is easily removed by water or contact, and there is a drawback that the effect is lost early.

The present inventor has discovered that when a semiconductor photocatalyst is photoexcited, its surface is highly hydrophilized. Applying this finding and coating the surface of a transparent substrate such as glass or lens with a transparent coating containing photocatalyst particles, a high degree of antifogging effect is permanently obtained. As a photocatalyst used for anti-fog coating, titania
O ₂ ) is most preferred. Titania is harmless and chemically stable. Furthermore, since titania has a high band gap energy and therefore requires ultraviolet light for photoexcitation and does not absorb visible light in the process of photoexcitation, color development by a complementary color component does not occur. Therefore, it is particularly suitable for coating transparent members such as glass, lenses and mirrors.

[0005]

However, since the refractive index of titania is much higher than that of glass or plastic, when a transparent substrate is coated with an antifogging coating containing titania, the interface between the antifogging coating and air is increased. In addition, the reflection of light at the interface between the antifogging coating and the substrate becomes remarkable.

An object of the present invention is to reduce the reflection of light by an antifogging coating containing titania.

[0007]

SUMMARY OF THE INVENTION The present invention is a transparent substrate coated with a transparent antifogging coating containing particles of photocatalytic titania, wherein the antifogging coating is on a medium having a refractive index of less than about 2. Made of titania particles,
Average crystallite size of titania particles (2 in powder X-ray diffraction of particles)
The value obtained from the integral width of the strongest peak around θ = 25.3 ° by the Scherrer equation) is about 0.1 μm or less. Preferably, the antifogging coating has a refractive index of about 2 or less, and the medium having a refractive index of less than 2 is selected from silica, silicone, magnesium fluoride, alumina and tin oxide.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The surface of building window glass, vehicle window glass, lens, mirror, transparent film, instrument panel cover glass, and other transparent base materials that require antifogging treatment contain titania particles. Covered by coating. As titania, either anatase or rutile can be used. The advantages of anatase titania are:
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 has a lower conduction band level than the anatase type, but has an advantage that it can be sintered at high temperature and a coating excellent in strength and wear resistance can be obtained.

In addition to titania, the anti-fog coating incorporates silica, silicone, magnesium fluoride, alumina, tin oxide, or mixtures thereof as a medium with a refractive index of less than about 2. The refractive indexes of these media, titania, and transparent substrate are shown below. Material Refractive index Anatase 2.52 Rutile 2.76 Magnesium fluoride 1.38 Silica 1.48 Alumina 1.63 Tin oxide 1.90 Silicone 1.4-1.6 Glass 1.45-1.96 PET 1. 62 acrylic resin 1.49

By mixing a medium having a refractive index of less than about 2 such as silica, silicone, magnesium fluoride, alumina and tin oxide into the antifogging coating, the refractive index of the antifogging coating is made to be similar to that of glass or plastic. The refractive index of the transparent substrate can be made close to that of the transparent substrate, and the reflection of light at the interface between the antifogging coating and the air and the interface between the antifogging coating and the substrate can be reduced. Dispersing high-refractive-index titania in a low-refractive-index medium such as silica, silicone, magnesium fluoride, alumina, or tin oxide makes the anti-fog coating white due to light scattering, and makes the anti-fog coating transparent. May deteriorate. However, when the average crystallite size of the titania particles is set to about 0.1 μm or less according to the present invention, light scattering by the titania particles can be prevented.

When a material having a high refractive index such as titania is coated on the surface of a transparent substrate, interference fringes due to light interference appear, but the occurrence of interference fringes is reduced by reducing the refractive index of the antifogging coating. can do.

The antifogging coating can be formed on the surface of the substrate by various methods. When the base material is made of a heat-resistant material such as glass, the surface of the base material exhibits superhydrophilicity such that the contact angle with water is 10 ° or less, and the anti-fogging property and abrasion resistance are excellent. A preferred way to form a cloudy coating is to mix silica sol, magnesium fluoride sol, alumina sol, or tin oxide sol with titania sol and apply the mixture to the surface of the substrate and then at a temperature below the softening point of the substrate. Sintering the mixture.

Alternatively, when the substrate is made of a heat-resistant material such as glass, a precursor of amorphous titania (organic titanium compound such as titanium alkoxide, chelate or acetate, or TiCl ₄ or Ti ( sO ₄₎ silica sol solution of an inorganic titanium compound such as _2), magnesium fluoride sol, alumina sol, or a tin oxide sol is mixed, the mixture was applied to a substrate surface, the amorphous titania precursor from room 200 By subjecting to hydrolysis and dehydration polycondensation at a temperature of ° C, a thin film of amorphous titania in which particles of silica, magnesium fluoride, alumina, or tin oxide are dispersed is formed. Then, the amorphous titania is phase-changed into crystalline titania by heating the titania to a temperature above the crystallization temperature and below the softening point of the substrate.

When the base material is made of a non-heat-resistant material such as plastic, the surface of the base material exhibits superhydrophilicity such that the contact angle with water is 10 ° or less. A preferred way to form a good anti-fog coating is to use precursors of amorphous silica (e.g. tetraalkoxysilanes such as tetraethoxysilane, tetraisopropoxysilane, tetra-n-propoxysilane, tetrabutoxysilane, tetramethoxysilane, etc. Silane; a silanol which is a hydrolyzate thereof; or a mixture of a polysiloxane having an average molecular weight of 3000 or less) and a crystalline titania sol is applied to the surface of a base material, and if necessary hydrolyzed to form silanol, A photocatalyst in which titania is bound with amorphous silica by subjecting silanol to dehydration polycondensation by heating at a temperature of about 100 ° C or higher. It is to form a coating.

Further, when the base material is made of a non-heat-resistant material such as plastic, the surface of the base material exhibits superhydrophilicity such that the contact angle with water is 10 ° or less and the anti-fogging property and resistance A preferred method of forming an abrasion resistant anti-fog coating is to disperse the titania particles in a film-forming element consisting of uncured or partially cured silicone (organopolysiloxane) or a precursor of the silicone. It is to use the coating composition.

As the 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; their partial hydrolysates; and their mixtures can be used.

The antifogging coating thus formed on the surface of the transparent substrate is irradiated with ultraviolet rays before use to photoexcite the photocatalytic titania. For photoexcitation of the photocatalytic titania, it is advantageous to use the ultraviolet rays contained in the sunlight under the condition where the sunlight hits. Indoors and at night,
Sterilization lamps, mercury lamps, metal halide lamps, xenon lamps and other UV light sources can be used. The photocatalyst can be photoexcited by the weak ultraviolet rays contained in fluorescent lamps and incandescent lamps. Upon photoexcitation of the photocatalytic titania, the surface of the antifogging coating is hydrophilized to a degree that the contact angle with water is 10 ° or less, and exhibits a high antifogging property. When the anti-fog coating is made by mixing photocatalytic titania with silicone, when photocatalytic titania is photoexcited by ultraviolet rays, the organic group bonded to the silicon atom of the silicone molecule is replaced by the hydroxyl group by the photocatalytic action of the photocatalyst, and the coating The surface of is made super-hydrophilic so that the contact angle with water is 10 ° or less, and exhibits a high degree of antifogging property.

When the transparent substrate is made of plastic, in order to prevent the substrate from deteriorating due to the photooxidation action of the photocatalyst, the surface of the substrate is previously coated with silicone, fluororesin, silica or the like. It is preferably covered.

The superhydrophilic phenomenon by the photocatalyst can be realized by a photocatalytic action weaker than the photooxidation action by the photocatalyst. Therefore, another way to prevent the deterioration of the plastic substrate is to suppress the photooxidation action of the photocatalyst. Therefore, a photooxidation inhibitor such as an alkali metal, an alkaline earth metal, alumina, silica, zirconia, antimony oxide, amorphous titania, or hydrous titania can be added to the coating composition.
Furthermore, it is preferable that the antifogging coating is made as thin as possible so that the film thickness becomes 0.1 μm or less.

[0020]

Example 1 Anatase-type titania sol (Nissan Kagaku, TA-15, average crystallite diameter 12 nm) was mixed with liquid B (trimethoxymethylsilane) of coating composition "GLASCA" of Japan Synthetic Rubber, and ethanol was mixed. A titania-containing coating composition was prepared by diluting with. The weight ratio of titania to trimethoxymethylsilane was 20:80. This coating composition is applied to a polyethylene terephthalate (PET) film (Fuji Xerox, OHP film for monochrome PPC, JF-001) and cured at a temperature of 110 ° C to disperse the anatase-type titania particles in the silicone coating film. Formed an antifogging coating. The film thickness of the coating was 0.1 μm. The antifogging coating had a refractive index of 1.69. After irradiating this sample with ultraviolet rays for 5 days at a illuminance of 0.5 mW / cm ² using a 20 W black light blue (BLB) fluorescent lamp (Sankyo Denki, FL20BLB), the contact angle of the surface of this sample with water was measured. Contact angle measuring device (Kyowa Interface Science Co., Ltd., Model CA-X15
The contact angle reading was less than 3 ° when measured at 0, the detection limit of 1 ° on the low angle side. No cloudiness was observed when the sample was blown. When the light reflection due to the anti-fog coating was observed with the naked eye, no reflection occurred.

Example 2 Anatase-type titania sol (TA-15), the above-mentioned "grasca" solution B (trimethoxymethylsilane) and magnesium fluoride were mixed in a weight ratio of 30:40:30 and diluted with ethanol. Thus, a coating composition was prepared. This coating composition was applied to a polyethylene terephthalate film (JF-001) and cured at a temperature of 110 ° C to form an antifogging coating in which anatase-type titania particles and magnesium fluoride were dispersed in a silicone coating film. . The film thickness of the coating was 0.1 μm. The refractive index of this coating was 1.76. 0.5mW / for this sample
After irradiating with ultraviolet rays for 5 days at an illuminance of cm ² , the contact angle of the surface of this sample with water was measured with a contact angle measuring instrument (CA-X150), and the contact angle reading was less than 3 °. No cloudiness was observed when the sample was blown. When the light reflection due to the anti-fog coating was observed with the naked eye, no reflection occurred.

Comparative Example Anatase-type titania sol (TA-15) and the above-mentioned "Glaska" solution B (trimethoxymethylsilane) were mixed and diluted with ethanol to prepare a titania-containing coating composition. The weight ratio of titania to trimethoxymethylsilane was 90:10. This coating composition was applied to a polyethylene terephthalate film (JF-001) and cured at a temperature of 110 ° C to form an antifogging coating in which anatase type titania particles were dispersed in a silicone coating film. The film thickness of the coating was 0.1 μm. The refractive index of this coating was 2.42. After irradiating this sample with ultraviolet light at an illuminance of 0.5 mW / cm ² for 5 days, the contact angle of the surface of this sample with water was measured with a contact angle measuring device (CA
-X150), the contact angle reading was less than 3 °. No cloudiness was observed when the sample was blown. However, when the anti-fog coating was visually observed, it reflected glare.

[0023]

As can be seen from the above, according to the present invention, the reflection of light by the titania-containing antifogging coating can be reduced. Therefore, when a building window glass, a vehicle window glass, a lens, a mirror, or a cover glass of an instrument panel is coated with an anti-fog coating, it is possible to prevent them from glare. In addition, it is possible to avoid a decrease in light transmittance due to the antifogging coating and to secure the visibility.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location B32B 27/00 101 B32B 27/00 101 27/18 27/18 F C03C 17/38 C03C 17/38 C08J 7/04 C08J 7/04 S // B32B 27/16 B32B 27/16 (72) Inventor Toshiya Watanabe 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka Prefecture (72) Invention Atsushi Kitamura 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu City, Fukuoka Prefecture Totoki Equipment Co., Ltd.

Claims (4)

[Claims] 1. A transparent substrate coated with a transparent anti-fog coating containing particles of photocatalytic titania,
The coating comprises a medium having a refractive index of less than 2 and titania particles, and the titania particles have an average crystallite size of about 0.1 μm or less. 2. The transparent substrate according to claim 1, wherein the coating has a refractive index of about 2 or less. 3. The medium is one selected from the group consisting of silica, silicone, magnesium fluoride, alumina, tin oxide, and a mixture thereof.
Based transparent substrates. 4. The transparent substrate according to any one of claims 1 to 3, wherein the substrate is a building window glass, a vehicle window glass, a lens, a mirror, a transparent film, or a cover glass for an instrument panel.