JP2000262367A - Antifogging mirror and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extremely improve an antifogging property by coating the opposite side surface of a mirror subjected to a mirror finishing surface treatment on one surface of a substrate with a metal oxide film having a rugged shape on the surface uniformly dispersed with specific weight % of water absorptive particulates in a metal oxide for matrix formation and specifying the cloud value of this film. SOLUTION: An antifogging mirror is formed by coating the one side surface of the substrate with the metal oxide film, into which 10 to 30 wt.% superfine particles having a cloud value of >=1 to <=20% are incorporated, and subjecting the surface on the other side to the mirror finishing surface treatment. The representative process for production consists in uniformly mixing the water absorptive particulates, raw material for the metal oxide for matrix formation and a solvent, applying the solution prepared in this manner on the opposite side surface of the mirror subjected to the mirror finishing surface treatment on the one surface side of the substrate, then baking the coating to fix the metal oxide film, thereby producing the mirror. As a result, the antifogging mirror which is capable of maintaining the excellent antifogging property for a long period of time in spite of repetitive use, is highly durable and is free of problems in practicable use in wear resistance and chemical resistance.

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 mainly used for bathroom mirrors.

[0002]

2. Description of the Related Art Recently, a film having a photocatalytic function has been formed on the surface of a substrate in order to impart hydrophilicity, antifogging property or antifouling property to the substrate. For example, a plate-like member in which a photocatalyst fine powder mainly composed of anatase type titania described in JP-A-5-253544 is partially exposed from the surface of the binder layer is disclosed in JP-A-7-23080.
The photocatalyst fine particles described in the publication are titania, zinc oxide, strontium titanate, iron oxide, tungsten oxide, iron titanate, bismuth oxide, tin oxide and the like, and the gap filling particles of the photocatalyst particles are tin, titanium, silver, and copper. A multifunctional material having a photocatalytic function, which is a metal or oxide of zinc, iron, platinum, cobalt, nickel, or titania having a photocatalytic average crystal particle diameter of about 0.1 μm or less described in JP-A-9-59042. Transparent substrates and the like covered with a hydrophilic coating containing particles are known.

Conventionally, it has been known for a long time that a surfactant is applied to the surface of a base material to modify the surface to be hydrophilic, and a water-soluble organic solvent such as polyacrylic acid or polyvinyl alcohol is used as the surfactant. It is known that the persistence of hydrophilicity is increased by adding and blending a polymer (Japanese Patent Application Laid-Open No. 52-101680).

Further, a method of immobilizing a hydrophilic polymer such as cellulose, glycols and glycerin on the surface and inside of a porous membrane made of a hydrophobic polymer through a coating of a copolymer of polyvinyl alcohol and vinyl acetate. Is known (Japanese Patent Publication No. 5-67330).

Further, in the physical method, a hydrophilic treatment such as a plasma treatment and a laser irradiation treatment has been put to practical use.

Further, chemical methods include a method of generating radicals on the surface and graft-polymerizing a polymerizable compound having a hydrophilic residue, and a method of cutting a bond of a surface such as an acid or a basic substance to obtain a hydrophilic compound. And the like.

[0007]

In the above-mentioned hydrophilicity and anti-fogging property utilizing the photocatalytic function, it is essential to irradiate with ultraviolet rays, and in a bathroom without irradiating ultraviolet rays, the hydrophilicity and anti-fogging property are extremely high. Have difficulty. Therefore, it is necessary to newly install a light source so that the mirror in the bathroom is irradiated with ultraviolet rays. In addition, even if the surface is once hydrophilic and anti-fog when exposed to ultraviolet light, its performance can be maintained for a short time, and is lost after several hours. Therefore, it is necessary to frequently perform operations such as irradiation with ultraviolet rays. In order to further exhibit anti-fogging properties, it is not limited solely to the water contact angle. Fogging is lost.
In addition, when a photocatalytic film is coated on a substrate, titania exhibiting a photocatalytic function is a high-refractive-index film and thus has high reflectivity and is colored. May occur, impairing the original function as a mirror or impairing the design.

On the other hand, the antifogging property by physical treatment can be maintained only for a short period of time, and the polyethylene oxide organic polymer film has low water resistance and low mechanical strength, so that it may be practically used depending on the application. Not enough.

Also, for example, in a method of immobilizing a film such as cellulose on the surface and the inside of a porous film via a film of a copolymer of polyvinyl alcohol and vinyl acetate, the film is extremely soft, It is also difficult to expect good durability, and the use to be used is limited.

Further, for example, a coating made of an inorganic substance
Substances having relatively high film strength but exhibiting hydrophilicity have high solubility in water and the coating easily disappears, which limits the practical use thereof.

For example, as an anti-fog mirror, a type with a built-in heater has already been commercialized, but also in this case, the fogging does not clear instantaneously, and it takes several minutes after the switch is turned on until the fogging clears. It is hard to say that it has versatility because of its high cost.

[0012] In each of the above methods, the antifogging property is imparted only temporarily or for a relatively short period of time, and it is difficult to expect sufficient durability of the antifogging effect. The cost was high and it was difficult to adopt it for practical use.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in consideration of the above-described circumstances, and has a metal oxide film formed on a surface of a mirror (an opposite side is a mirror surface). The water-absorbing ultrafine particles are evenly dispersed in the matrix of the membrane, and once wetted with water, the haze is eliminated and the film becomes transparent, and also excellent water retention is provided by a synergistic effect with the structure shown in FIG. Therefore, for example, when used in an environment with a high relative humidity in a bathroom, the present invention provides an antifogging mirror having extremely excellent antifogging properties and a method for manufacturing the same.

That is, in the antifogging mirror of the present invention, 10 to 30% by weight of water-absorbing ultrafine particles in a metal oxide for forming a matrix is provided on the opposite surface of the mirror having one surface of the substrate subjected to mirror finishing. A metal oxide film having a uniformly dispersed surface with an uneven shape is coated, and the haze of the film is 1% to 20%.

The visible light transmittance of the transparent substrate coated with the metal oxide film is preferably 80% to 94%.

Further, the anti-fog mirror of the present invention can maintain the anti-fog property in a state of being wetted by water without ultraviolet rays for a bathroom, and can not form a double image.

Further, in the method for manufacturing an anti-fog mirror according to the present invention, a solution prepared by uniformly mixing water-absorbing fine particles, a raw material for a metal oxide for forming a matrix, and a solvent is subjected to mirror finishing on one side of a substrate. The method is characterized in that a metal oxide film is fixed after being applied to the opposite surface of the mirror to be applied and then baked.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION In the anti-fog mirror of the present invention, ultrafine particles having a haze of 1% or more and 20% or less are formed on one surface of a substrate.
３０30% by weight of a metal oxide film, and the other surface is mirror-finished. Typical manufacturing methods include water-absorbing fine particles and a raw material for a metal oxide for forming a matrix. , And a solvent prepared by uniformly mixing the solvent with the solution, and then applying the solution to the opposite surface of the mirror, which has been subjected to mirror finishing on one side of the substrate, and then sintering to fix the metal oxide film. be able to.

The metal oxide film is formed by uniformly dispersing water-absorbing ultrafine particles in a metal oxide for forming a matrix. The main raw material of the metal oxide for forming a matrix is, for example, a main material of silica. As raw materials, metal alkoxides, silica alkoxides, tetraethoxysilane, tetramethoxysilane, monomethyltriethoxysilane, monomethyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, other tetraalkoxysilane compounds, other Alkoxysilane compounds of the above, the main raw materials of titania include alkoxides such as tetraisopropoxytitanium, tetranormal butoxytitanium, triisopropoxytitanium monoacetylacetonate, and the main raw materials of alumina include alcohol In the case of SIDs, aluminum butoxide, in the case of aluminum acetates, there are organometallic compounds such as aluminum acetylacetonate, and in the main raw materials of zirconia, in the case of alkoxides, there are zirconium butoxide; in the case of zirconia acetates, such as zirconium acetylacetonate. Organometallic compounds can be used.

As the water-absorbing ultrafine particles, for example, the silica may be crystalline silica or amorphous, glassy or colloidal silica, but colloidal silica is particularly preferred. Is preferably alumina of boehmite type crystal.
The titania fine particles may be crystalline or colloidal amorphous such as anatase or rutile, but crystalline fine particles are particularly preferable. The superabsorbent ultrafine particles are
The particle size is not particularly limited, but those having a particle size of 50 nm or less are particularly preferred.

The diluting solvent is preferably an alcoholic solvent, and specific examples thereof include methanol, ethanol and the like.
, Propanol, butanol, ethylene glycol,
Propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, esters such as ethyl acetate, butyl acetate, and amyl acetate; and cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and a mixture thereof. Then, an appropriate amount of a methyl silicone such as dimethyl silicone or a fluorine-based leveling agent may be added as a leveling agent. Alcohols or cellosolves which are originally contained in the solution may be selected alone or in a mixture in consideration of the evaporation rate of the solution and the film viscosity.

When the metal oxide film is formed on clear float glass without coloring, the visible light transmittance is 8%.
The haze is preferably from 0% to 94%, and the haze is preferably from 5% to 20%. If the visible light transmittance is less than 80%, the transparency will be insufficient even if the film is wet with water, the image will be insufficiently clear, and it will be difficult to say that it has a sufficient mirror function. The haze of the film is less than 1%, and even when the film is once wet, the portion that dries quickly and becomes dry may become cloudy, and the antifogging property becomes insufficient. Further, if the haze is less than 5%, as in the case of the visible light transmittance, even if the water gets wet, the dried portion may quickly become dry and become cloudy, and the antifogging property may become insufficient. However, even if it gets wet, the transparency is insufficient, the sharpness of the image becomes insufficient, and the function as a mirror is hardly sufficient. In addition, more preferably, the visible light transmittance is 85 to 85.
The haze is preferably 90% and the haze is preferably 8% to 15%.

The content ratio of the metal oxide for forming a matrix contained in the metal oxide film is preferably from 70 to 90% by weight based on the composition of the metal oxide film. The effect of the ultrafine particles is not sufficiently exhibited, and the structure of the film is hardly as shown in FIG. On the other hand, if it is less than 70% by weight, the durability and abrasion strength of the film such as water resistance and chemical resistance are reduced, and it is difficult to practically use the film as a bathroom mirror.

The thickness of the film is not particularly limited, but is preferably in the range of 10 to 400 nm, and if it is less than 10 nm, the image is not distorted immediately after wetting once with water and the anti-fog property is good. However, under high humidity in the bathroom, the water absorption in the thickness direction of the film is small, so that the thickness of the water film becomes uneven and the image is gradually distorted, and the function of the mirror becomes insufficient. If the thickness exceeds 400 nm, cracks are likely to occur during firing, so that multi-stage firing is required to prevent the cracks, resulting in poor productivity and increased cost. Preferably, it is in the range of 150 to 270 nm, more preferably in the range of 180 to 220 nm.

The baking temperature after coating the coating solution on the substrate is preferably 400 to 600 ° C. If it is less than 400 ° C., the mechanical strength of the film and the chemical resistance such as acid resistance and alkali resistance are insufficient. If it exceeds, the glass warps,
The image is distorted and the original function as a mirror cannot be exhibited. In addition, more preferably, it is the range of 500-550 degreeC.

The coating method is not particularly limited, but from the viewpoint of productivity and the like, for example, a spin coating method or a dip coating method, a reverse coating method, a flexographic printing method, and other roll coating methods. And a curtain coating method, and further, a nozzle coating method, a spray coating method, a bar coating method, a screen printing method and the like can be appropriately employed. The concentration of the total solid content in the coating liquid when forming a film by coating with these coating methods is preferably about 0.1 to 5% by weight, and the viscosity of the coating liquid is preferably about 2 to 10 cp.

As the drying treatment after the coating, the drying temperature is 1
The drying time is preferably about 00 to 200 ° C. and about 5 to 30 minutes, more preferably the drying temperature is 140 to 16
The drying time is about 10 to 20 minutes at about 0 ° C.

As the baking treatment after drying, a baking temperature of 4
The firing time at about 00 to 600 ° C. is preferably about 1 to 30 minutes, and more preferably the firing time is 5 to 20 minutes.

The substrate used in the present invention is not particularly limited as long as it is transparent, and glass, plastic and the like can be used. For example, as a bathroom mirror, clear float glass with a thickness of about 5.0 mm is suitable, but it can be appropriately selected and used depending on the size of the mirror and the like. In addition, although the environmental conditions of a bathroom are not specifically limited, In order to exhibit the function of the anti-fog mirror of this invention more effectively, room temperature 10-40 degreeC, humidity 70-95.
% RH environments are preferred.

The coating of the metal oxide film is preferably carried out on a mirror which has been subjected to a mirror finish.
After forming the metal oxide film on the substrate surface, it is possible to form a mirror surface on the opposite surface.

[0031]

The physical properties relating to hydrophilicity and anti-fogging property are extremely highly dependent on the amount of hydroxyl groups on the film surface, the water retention from the surface to the inside and the shape of the film surface capable of uniformly forming a water film.
That is, if the contact angle of water with the film surface is small and as much water as possible is absorbed or adsorbed and a uniform water film can be formed at this time, the hydrophilic effect and the antifogging effect can be maintained for a long time. According to the present invention, a metal oxide film formed on a glass substrate and having a surface texture as shown in FIG. 1 can maintain hydrophilicity and antifogging properties for a long time once it is wet with water because the film texture Are dispersed with water-absorbing substances. Since these have hydroxyl groups on their surface, they are easily adsorbed with water and also exhibit water retention. Due to this effect and the membrane structure shown in FIG. 1, the adsorbed water becomes a uniform water film, and the water does not easily run out. Furthermore, because the environment of use is a bathroom under high humidity, the water adsorbed on the membrane surface is difficult to desorb, so once wetted with water, it can exhibit anti-fog properties for a long time and there is no double image Looks very clear. In addition, since the film surface is covered with a uniform water film, dirt such as oils is hardly attached, and antifouling property is provided.

In order to exhibit the anti-fogging property due to hydrophilicity, it is not limited solely to the water contact angle. However, the contact angle of water when the anti-fogging property is obtained is generally 5 # or less. Since the antifogging property is lost around 10 #, in the present invention, a water contact angle of 5 # or less was accepted in the following hydrophilicity evaluation test.

[0033]

The present invention will be described below in detail with reference to examples. However, the present invention is not limited to these examples.

The performance of the hydrophilic coating was evaluated by the following method. ■ Hydrophilicity evaluation: Evaluated by measuring the contact angle of water (Measurement equipment) CA-A type manufactured by Kyowa Interface Science (Measurement environment) Room temperature / in the air (Water drop volume) 20 μl (1) The anti-fogging property was evaluated: the entire membrane was once wetted with tap water, and the state of formation of the water membrane and the time for maintaining the water membrane were evaluated (measurement environment): temperature; 80-90%
RH [Pass / fail judgment] Water film formation state: Visually, a water film was uniformly formed. Passed water film maintenance time; Wet the surface once with water to form a water film. ■ Evaluation of image clarity and double image was visually evaluated. [Pass / Fail] Judged as acceptable if it looks like a normal mirror. ■ Film hardness Evaluation: Pencil hardness test (JIS K5400) [Pass / Fail] Pencil hardness of 5H or more was accepted. ■ Acid resistance test: After immersion in 25 ° C and 1N hydrochloric acid for 24 hours, it was strongly rubbed with a gauze cloth under running water and scratches and film were observed. The presence or absence of peeling was checked. [Pass / Fail] Those without scratches and film peeling were accepted. ■ Alkali resistance test: 25 ° C, 2N in 1N sodium hydroxide
After immersion for 4 hours, it was strongly rubbed with a gauze cloth under running water, and the presence or absence of scratches and film peeling was examined.

Table 1 shows the results of the above performance evaluations in the following Examples and Comparative Examples.

[0036]

Example 1 Preparation of sol solution: As a starting material, a silica sol for matrix formation (Rixon coat CSG-D
I-0600, manufactured by Chisso), a self-made solution obtained by chelating tetraisopropyl titanate with acetylacetone,
Ultrafine particle colloidal silica (IPA-ST-S, manufactured by Nissan Chemical Industries, Ltd.) was used, and denatured alcohol (Ekinen F-1) was used as a diluting solvent. The solution was prepared according to the following procedure.

The sol solution composition is silica: titania: ultrafine silica = 40: 40: 20% by weight in terms of oxide, and a predetermined amount of Rixon coat, a self-made titania sol and colloidal silica, and a predetermined amount of Echinen F-1 Were added sequentially to a beaker and stirred at room temperature to obtain a coating solution. The solid content of the solution was 4 in terms of total oxides.
% By weight.

Coating and firing: 10 for substrate
Using a float glass having a size of 5 cm and a thickness of 5 mm, the coated surface was sufficiently polished with cerium oxide, washed with a brush pre-cleaner, and then wiped with isopropyl alcohol to obtain a substrate. The back side was masked with a curing tape. The glass substrate prepared in this way was coated with the above solution at a rate of 2 mm / sec by a dipping method, and after the coating was completed, the curing tape on the back side was peeled off.
After drying for 0 minutes and cooling to room temperature, it was baked at 550 ° C. for 30 minutes. The resulting film has a neutral color tone for both reflection and transmission, and has a thickness of a stylus type surface roughness meter (DEKTAK303).
0, manufactured by SLOAN Co., Ltd.). The structure of the film surface was as shown in FIG. 1, and the visible light transmittance was 88% and the haze was 5.7%. In addition, FIG. 1 is a micrograph (400 times) showing the structure of the surface shape of the film. As a result of the hydrophilicity evaluation, the contact angle of the coating film with water was as good as 2 to 3 °, and other characteristics were obtained. The performance evaluation results were all good as shown in Table 1. In order to evaluate the anti-fogging property, a metal titanium film having a thickness of 70 nm was formed by sputtering on the back side on which the metal oxide was formed, and mirror-finished.

[0039]

[Table 1]

[0040]

Example 2 The same procedure as in Example 1 was conducted except that the sol solution composition was changed to silica: titania: ultrafine alumina = 40: 40: 20% by weight, and the film thickness after firing was 180 nm. The structure of the film surface was as shown in FIG. 1, and the visible light transmittance was 87% and the haze was 6.4%. As a result of the hydrophilicity evaluation, the contact angle of the coating film with water was 1-2.
°, and other performance evaluation results are shown in Table 1.
All were good as shown in FIG.

[0041]

EXAMPLE 3 The sol solution composition was silica: titania: ultrafine silica: ultrafine alumina = 40: 40: 10: 10
All were the same as Example 1 except that the weight% was used, and the film thickness after firing was 150 nm. The structure of the film surface was as shown in FIG. 1, and the visible light transmittance was 89% and the haze was 11.8%. As a result of the hydrophilicity evaluation, the contact angle of the coating film with water was good at 2-3 °, and the performance evaluation results were all good as shown in Table 1.

[0042]

Example 4 The sol solution composition was silica: titania: zirconia: ultrafine silica = 30: 30: 30: 10% by weight.
Except for the above, all were the same as in Example 1, and the film thickness after firing was 220 nm. The structure of the film surface was as shown in FIG. 1, and the visible light transmittance was 87% and the haze was 12.3%. As a result of the hydrophilicity evaluation, the contact angle of the coating film with water was 3 to 4 °, which was good, and the performance evaluation results were all good as shown in Table 1. Note that zirconium-n-butoxide (reagent, manufactured by Kishida Chemical) was used as a raw material for zirconia.

[0043]

Comparative Example 1 The same procedure as in Example 1 was carried out except that the sol solution composition was changed to silica: titania: ultrafine silica = 30: 30: 40% by weight in terms of oxide, and the film thickness after firing was 140.
nm. The structure of the film surface is as shown in FIG. 1, the visible light transmittance is 90%, and the haze is 11.
1%. As a result of the performance evaluation, the initial contact angle of the coating film with water was as good as 2 to 3 [deg.], But the pencil hardness was H or less and the film was peeled off in the alkali resistance test.

[0044]

Comparative Example 2 The same procedure as in Example 1 was carried out except that the sol solution composition was changed to silica: titania: ultrafine silica = 45: 45: 5% by weight in terms of oxide, and the film thickness after firing was 160 n.
m. The structure of the film surface was not as shown in FIG. 1 and was a flat surface. The visible light transmittance was 82% and the haze was 0.7%. As a result of the performance evaluation, the initial contact angle of the coating with water was 8 to 9
° is not preferable, and in the evaluation of the anti-fogging property, a uniform water film was formed by wetting once with water, but the time during which the water film could be maintained was not preferable within 1 minute.

[0045]

Comparative Example 3 The same procedure as in Example 1 was carried out except that the sol solution composition was changed to silica: titania: ultrafine silica = 20: 70: 10% by weight in terms of oxide, and the film thickness after firing was 200.
nm. The structure of the film surface is as shown in FIG. 1, the visible light transmittance is 73%, and the haze is 6.4.
%Met. In addition, as a result of performance evaluation, the initial contact angle of the coating film to water was preferably 2-3 °,
Due to the high reflectivity of the film surface, the image appeared double and did not have the function as a mirror.

[0046]

Comparative Example 4 A glass (hario) having one surface of a glass substrate subjected to non-glare treatment (glass surface treated to a frosted glass) and having a glare degree of # 80 and having a surface structure as shown in FIG. 1 was used as a sample. . Visible light transmittance is 8
At 7%, the haze was 8.7%. The performance evaluation results
Although the contact angle with water was preferably 4-5 °, a uniform water film was formed by wetting once with water in the evaluation of antifogging property, but the time during which the water film could be maintained was within 2 minutes. It was not a good thing.

[0047]

According to the antifogging mirror for bathrooms and the method of manufacturing the same of the present invention, excellent antifogging property can be obtained even by repeated use with a specific means which is stable, reliable and easy without any troublesome steps and easily. In addition to being able to be maintained for a long time, a metal oxide thin film can be obtained inexpensively and efficiently with high productivity, has no defects such as cracks, and has excellent durability without impairing the function as a mirror. A material having no practical problem in abrasion and chemical resistance can be provided.

[Brief description of the drawings]

FIG. 1 is a photomicrograph (× 400) showing the structure of the surface shape of a metal oxide film.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yoshihiro Nishida 1510 Oguchi-cho, Matsusaka-shi, Mie Central Glass Laboratory Co., Ltd. (72) Inventor Keiji Honjo 1510 Oguchi-cho, Matsusaka-shi, Mie Central Glass Co., Ltd. F term (reference) 3B111 AA01 AC01 AC03 AD01 BC01 BC03 BD01 CA03 CC01 CD01 CE01 4G059 AA11 AC01 AC21 EA01 EA04 EA05 EA18 EB05

Claims (4)

[Claims] 1. A method according to claim 1, wherein one side of the substrate is mirror-finished and the other side of the mirror is covered with a metal oxide for matrix formation.
A metal oxide film having a surface with irregularities in which about 30% by weight of water-absorbing ultrafine particles are uniformly dispersed, and a haze value of the film is 1% or more and 20% or less. Cloudy mirror. 2. The anti-fog mirror according to claim 1, wherein the visible light transmittance of the substrate coated with the metal oxide film is 80% to 94%. 3. The anti-fog mirror according to claim 1, wherein the anti-fog mirror maintains the anti-fogging property in a state of being wetted by water without ultraviolet rays for a bathroom and does not form a double image. 4. A solution prepared by uniformly mixing and adjusting water-absorbing fine particles, a raw material for a matrix-forming metal oxide, and a solvent is applied to the opposite surface of a mirror having one surface of a substrate subjected to mirror finishing. A method for manufacturing an anti-fog mirror, comprising applying and firing to fix a metal oxide film.