JPH0956549A - Anti-fogging mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of mirror images, such as the double images and darkening of a mirror finished surface occurring in the presence of an optical semiconductor layer by providing the subject mirror with a base material having a light reflection surface and a front surface layer including the optical semiconductor formed on the light reflection surface of this base material and forming the mirror in such a manner that its front surface exhibits hydrophilicity in correspondence to the photoexcitation of the optical semiconductor. SOLUTION: This anti-fogging mirror used as dressing mirrors, bath room mirrors, mirrors for vehicles, road mirrors, etc., has the transparent base material having the reflection coating layer on its rear surface and the front surface layer contg. the optical semiconductor formed on the front surface of the transparent base material. The thickness of the transparent base material is set at <=0.5mm and the refractive index of front surface layer at <=2. The front surface layer is formed by incorporating titanium oxide particles and another material (low- refractive index material) in order to confine the refractive index of this layer to <=2 into the front surface layer. Silica, silicone or the mixture composed thereof is used for the low- refractive index material. The optical semiconductor particles, the titanium oxide particles and the particles of the low-refractive index material respectively having grain sizes of <=0.1μm are used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-fog mirror having an anti-fog treatment. In particular, the present invention relates to an antifogging mirror which has an optical semiconductor layer on its surface and is designed so as to prevent deterioration of the mirror image such as double image and darkening of the mirror surface due to the presence of this optical semiconductor layer.

[0002]

2. Description of the Related Art In Japanese Patent Application No. 7-182020, the inventor of the present invention forms a surface layer containing an optical semiconductor on a mirror to make the surface of the mirror superhydrophilic, and uses water droplets to form dew on the same surface. Therefore, we proposed an anti-fogging method whose main point is to eliminate fogging.

[0003]

However, it has been found that the above technique has the following problems. That is, when TiO _{2 of} an optical semiconductor is formed on the mirror surface, the reflection on the surface is large due to the high refractive index, and a double image and a reflection image from the silver mirror surface are seen. The normal mirror image is
This occurs because the image due to the reflection on the surface and the image reflected on the silver mirror surface are deviated when the glass is viewed obliquely, and it is about 4% in the case of ordinary glass. However, in the case of TiO ₂ having a high refractive index, it is several tens of percent, so that the image shift becomes noticeable. The double image is a double image in the eye when the image of light reflected on the surface of the titanium oxide film and the image of light reflected on the silver mirror surface are deviated when the mirror is viewed obliquely.

[0004] reflectance R is the ratio of light reflected at the interface of both materials when the light in the material B having a refractive index n ₂ of a material A having a refractive index n ₁ enters is, R = ((n ₁ -n ₂ ) / (n ₁ + n ₂ )) ² . In the case of an ordinary mirror, since the light enters from the air (n ₁ = 1.00) into the glass (n ₂ = 1.52), the reflectance of the interface is only 4%. On the other hand, titanium oxide (TiO
₂ ) In the case of an anti-fog mirror having a film, air (n ₁ = 1.0
The reflectance of the interface incident on TiO ₂ (n ₂ = 2.51) from 0) reaches 18.5%. Therefore, a double image, which is not noticeable in the case of a normal mirror, is conspicuous in the antifogging mirror having the titanium oxide film.

The present invention, in an anti-fog mirror which has been subjected to anti-fog treatment with a hydrophilic optical semiconductor layer, prevents deterioration of the mirror image such as double image and darkening of the mirror surface due to the presence of the optical semiconductor layer. It is an object of the present invention to provide an anti-fog mirror with such consideration.

[0006]

In order to solve the above problems, the present invention uses the following four solutions individually or in combination. (1) An optical semiconductor layer is formed directly on a light reflecting surface (without providing a substantial intervening layer) (front surface mirror). This shortens the distance between the two reflecting surfaces that causes a double image. With a normal mirror, only the glass thickness (standard 5 mm),
The surface of the mirror and its reflection surface (silver mirror surface) are separated from each other, and this is multiplied by the sine of the oblique angle θ of the light, and doubled to obtain the double image shift (5 × sin θ × 2) . However, if the optical semiconductor layer is formed directly on the light-reflecting surface, the distance between the two reflecting surfaces can be set only to the thickness of the light-reflecting surface (on the order of μm or less). Double images do not occur.

(2) In the case of a backside mirror, the thickness of the transparent substrate (glass or the like) is reduced to 0.5 mm or less. For the same reason as (1), if the shift of the double image is made as small as possible, the viewer's discomfort can be eliminated as much as possible.
If the thickness of the transparent substrate is 0.5 mm or less, the image shift becomes about 1/10 of the current standard.

(3) The refractive index of the surface layer containing an optical semiconductor is lowered. For example, low refractive index silica (SiO ₂ , refractive index 1.48), magnesium fluoride (MgF ₂ , refractive index 1.378), tin oxide (1.90), alumina (1.
If 63) is mixed with titanium oxide to lower the refractive index of the optical semiconductor layer, the reflectance of the light on the surface of the optical semiconductor layer decreases due to the above reason, and one of the double images becomes weak. From this point of view, rutile type (2.
It is preferable to use anatase type (2.5) having a lower refractive index than 7). Silica and silicone have a refractive index of 1.
Addition of silicone, which is as small as about 5 and in which at least a part of the organic groups bonded to silica and silicon atoms is replaced with hydroxyl groups, also improves the hydrophilicity maintaining performance in the dark place, which also has a favorable effect on the antifogging property. .

(4) The particle diameter of the optical semiconductor and the low refractive index substance contained in the surface layer is reduced to 0.1 μm or less. Then, light scattering by particles is less likely to occur, and thus the mirror image is less likely to be dark.

[0010]

Embodiments of the present invention will be described below. Example 1: Surface mirror by siloxane method A light reflecting surface was formed on a surface of a polycarbonate plate (substrate) having a thickness of 5 mm by aluminum vapor deposition. Next, in order to smooth the surface of the substrate, it was previously coated with a silicone layer. For this reason, the coating composition “GLASCA” of Japan Synthetic Rubber (Tokyo)
Solution A (silica sol) and solution B (trimethoxymethylsilane) are mixed in a weight ratio of 3, and the mixed solution is applied to a substrate and cured at a temperature of 150 ° C. to a film thickness of 3 μm.
Multiple substrates coated with a m 2 silicone base coat were obtained.

Next, the substrate was coated with a polymer coating containing a photocatalyst. Silicone was selected as the film-forming element in order to prevent the film-forming elements of the paint from deteriorating due to the photooxidative action of the photocatalyst. More specifically, 56 parts by weight of anatase-type titania sol (Nissan Chemical Co., Ltd., TA-15) and 33 parts by weight of A liquid (silica sol) of the above "grasca" are mixed and diluted with ethanol, and then B liquid 11 of "grasca". A part by weight was added to prepare a titania-containing coating composition. Apply this coating composition to the surface of the substrate and
It was cured at a temperature of 50 ° C. to form a top coat in which anatase-type titania particles were dispersed in a silicone coating film.

Example 2: Backside mirror by alkoxide method A 0.5 mm thick soda lime glass plate (substrate) was prepared. Next, in 86 parts by weight of an ethanol solvent, 6 parts by weight of tetraethoxysilane Si (OC ₂ H ₅ ) ₄ (Wako Pure Chemical Industries, Osaka), 6 parts by weight of pure water, and 36% as a hydrolysis inhibitor of tetraethoxysilane. 2 parts by weight of hydrochloric acid was added and mixed to prepare a silica coating solution. Since the solution generated heat by mixing, the mixed solution was left to cool for about 1 hour. This solution is applied to the surface of the substrate by the flow coating method,
Dried at a temperature of ° C. Upon drying, tetraethoxysilane was first hydrolyzed to silanol Si (OH) ₄ , and then a thin film of amorphous silica was formed on the surface of the substrate by dehydration polycondensation of silanol.

Next, tetraethoxy titanium Ti (OC ₂
A titania coating solution was prepared by adding 0.1 part by weight of 36% hydrochloric acid as a hydrolysis inhibitor to a mixture of 1 part by weight of H ₅ ) ₄ (Merck) and 9 parts by weight of ethanol, and applying this solution to the surface of the substrate. It was applied by a flow coating method in dry air. The coating amount was 45 μg / cm ² in terms of titania. Since the hydrolysis rate of tetraethoxytitanium is extremely fast, a part of tetraethoxytitanium was hydrolyzed at the coating stage, and titanium hydroxide Ti (OH) ₄ began to be produced.

Next, this substrate is heated at about 150 ° C. for 1 to 10 minutes.
By maintaining the temperature at 1, the hydrolysis of tetraethoxytitanium was completed, and the produced titanium hydroxide was subjected to dehydration polycondensation to produce amorphous titania. Thus, a glass plate in which amorphous titania was coated on amorphous silica was obtained.

This sample was calcined at a temperature of 500 ° C. to convert the amorphous titania into anatase type titania. The amorphous silica coating underlies the amorphous titania coating, so that alkali network modifying ions such as sodium in the glass plate do not diffuse from the glass substrate into the titania coating during firing. it is conceivable that. Next, a silver reflective coating was formed on the back surface of this glass plate by a silver mirror reaction to manufacture a mirror.

Example 3: Backside mirror by TEOS method An amorphous silica thin film was formed on the surface of a mirror (MFL3) (glass thickness: 5 mm) made of Nippon Sheet Glass by the same method as in Example 2.

Next, 0.69 g of tetraethoxysilane
(Wako Pure Chemicals) and anatase titania sol 1.07g
(NISSAN CHEMICAL, TA-15, average particle size 0.01 μm, Ti
O ₂ concentration 15%) means that TiO ₂ : SiO ₂ = 20: 80
(Weight ratio) was mixed. Then, 29.88 g of ethanol and 0.36 g of pure water were mixed to prepare a coating solution. This coating solution was applied to the mirror surface by the flow coating method. By holding this mirror at a temperature of about 150 ° C. for about 20 minutes, tetraethoxysilane is subjected to hydrolysis and dehydration polycondensation, and a coating in which anatase-type titania particles are bound with an amorphous silica binder is applied to the mirror. Formed on the surface.

After leaving this mirror in the dark for several days, the BLB
It was irradiated with ultraviolet rays using a fluorescent lamp at an illuminance of 0.5 mW / cm ² for about 1 hour. When the contact angle of the surface of this mirror with water was measured with a contact angle measuring device, the contact angle reading was 0 °. The refractive index of the optical semiconductor layer was 1.69.

Example 4 An amorphous silica thin film is formed in the same manner as in Example 2. Next, 0.1 part by weight of 36% HCl as a hydrolysis inhibitor was added to a mixed solution of 1 part by weight of tetraethoxy titanium and 9 parts by weight of ethanol to prepare a titania solution. Further, as a silica solution, 16.7 parts by weight of Nissan Chemical Industries methanol silica sol (SiO ₂ concentration 30%) and 83.3 parts by weight of ethanol were mixed to prepare a silica solution having a SiO ₂ concentration of 5 wt%. 5 g of these titania solution and 0.21 g of silica solution were mixed with 23 g of ethanol to prepare a coating solution, which was then applied by a flow coating method. Next, in the same manner as in Example 2, 150 ° C., 5
After heat treatment at 00 ℃ and silver mirror reaction, anatase type TiO 2
A coated mirror having silica particles dispersed in ₂ was obtained.

After leaving this mirror in the dark for several days, the BLB
It was irradiated with ultraviolet rays using a fluorescent lamp at an illuminance of 0.5 mW / cm ² for about 1 hour. When the contact angle of the surface of this mirror with water was measured with a contact angle measuring device, the contact angle reading was 0 °. The refractive index of the optical semiconductor layer was 1.69.

Example 5: 0.5 mm by the same method as in Example 2
An amorphous silica thin film was formed on a thick glass substrate. Then, a TiO ₂ target was used to form a thin film of amorphous TiO _{2 having} a film thickness of 50 μm by a sputtering method in an oxygen atmosphere. The contact angle with water measured at this stage was 47 °. Then the ultraviolet illuminance 0.15
Irradiation with a mW / cm ² BLB lamp for 2 days was still 42 °. In addition, at this stage, when the presence or absence of fogging by the exhalation method was examined, it was apparently fogging. Next, this sample is 400 ℃,
The amorphous TiO ₂ was crystallized into anatase type by heat treatment at 450 ° C and 500 ° C. After leaving these samples in the dark for 1 day, they were irradiated with a BLB lamp having an ultraviolet illuminance of 0.15 mW / cm ² for 2 days. When the contact angle with water was then measured, it was 4.6 ° for the 400 ° C. calcined product, 4.5 ° for the 450 ° C. calcined product, and 4.1 ° for the 500 ° C. calcined product. Further, as a result of measuring the presence or absence of fogging by the exhalation method, the fogging was quickly scratched off and did not remain. Furthermore, no double image was observed due to the influence of the glass thickness.

Comparative Example: An optical semiconductor layer and a silver reflective coating were formed on the front and back surfaces of a soda-lime glass plate having a thickness of 5 mm in the same manner as in Example 2, respectively.

Performance test : The antifogging property was excellent in all of Examples 1, 2, 3, 4, 5 and Comparative Example. For the double image, the comparative example was very noticeable. Regarding Example 2, there was a double image, but it was not very noticeable. For Examples 1, 3, 4, and 5, almost no double image was observed, and very good mirror images were obtained.

[0024]

As is clear from the above description, the antifogging mirror of the present invention has an optical semiconductor layer on its surface. However, due to the presence of this optical semiconductor layer, a double image or darkening of the mirror surface occurs. A good mirror image can be obtained without deterioration of the mirror image.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B32B 27/18 B32B 27/18 Z C03C 17/30 C03C 17/30 Z E01F 9/00 E01F 9 / 00 G02B 5/08 G02B 5/08 F // B60S 1/60 B60S 1/60 E (72) Inventor Shin Hayakawa 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka Prefecture Totoki Equipment Co., Ltd. (72 ) Inventor Toshiya Watanabe 2-1, 1-1 Nakajima, Kokurakita-ku, Kitakyushu City, Fukuoka Prefecture Totoki Equipment Co., Ltd. (72) Atsushi Kitamura 2-1-1, Nakajima, Kokurakita-ku, Kitakyushu, Kitakyushu, Fukuoka Prefecture In the company

Claims (9)

[Claims] 1. A base material having a light-reflecting surface, and a surface layer containing an optical semiconductor formed on the light-reflecting surface of the base material.
An antifogging mirror characterized in that the surface thereof exhibits hydrophilicity in response to photoexcitation of the optical semiconductor. 2. A transparent base material having a reflective coating layer on the back surface, and a surface layer containing an optical semiconductor formed on the surface of the transparent base material, wherein the surface is hydrophilic in response to photoexcitation of the optical semiconductor. An anti-fogging mirror showing the property; wherein the transparent substrate has a thickness of 0.5 mm or less. 3. A transparent base material having a reflective coating layer on the back surface, and a surface layer containing an optical semiconductor formed on the surface of the transparent base material, wherein the surface is hydrophilic in response to photoexcitation of the optical semiconductor. An antifogging mirror having the property of having a refractive index of 2 or less in the surface layer. 4. The antifogging mirror according to claim 3, wherein the surface layer contains titanium oxide particles and another substance (low-refractive index substance) for making the refractive index of the layer 2 or less. 5. The anti-fogging mirror according to claim 4, wherein the low refractive index substance is silica, silicone, or a mixture thereof. 6. The antifogging mirror according to claim 4, wherein the titanium oxide particles are of anatase type. 7. The surface layer contains optical semiconductor particles, and the particle diameter of the optical semiconductor particles is 0.1 μm or less.
6. The antifogging mirror according to any one of 6 to 6. 8. The anti-fogging mirror according to claim 4, wherein the titanium oxide particles and the particles of the low refractive index substance have a particle size of 0.1 μm or less. 9. The mirror is a makeup mirror, a bathroom mirror, a vehicle mirror,
The antifogging mirror according to claim 1, which is either a reflecting mirror or a road mirror.