JPH1170038A - Defogging mirror - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to irradiate ultraviolet light to an optical catalyst without exposing a human body, activating the optical catalyst, and imparting a satisfactory defogging function to a mirror, by setting a contact angle on one plane of excited light to transmit the light in plate glass by making repeated total reflection between the optical catalyst and an optical reflection metal film. SOLUTION: A light source for optical catalyst excitation is equipped on a place where no light reflection metal film or no optical catalyst film 3 is formed in a peripheral suitable place on one face of a mirror, and therefrom excited light is irradiated into plate glass. To transmit the light in a plate glass by making the light repeatedly reflected between the optical catalyst and the optical reflection metal film, a refractive angle αt in one plane X-X' of the excited light is set to make a defogging mirror. Concretely, a prism 8 is additionally equipped on a light incoming place 1' and thereby easily βi=αt>=40.8 deg. is satisfied, and thereby the light to generate total reflection is not leak out from an opticoel catalyst film 3 to enable a user of the mirror M to be prevented from ultraviolet exposure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photocatalytic film which exhibits a hydrophilic action on a surface of a mirror (sheet glass) when the mirror is used in an environment where water vapor in the air is condensed and fogging is likely to occur on the surface. The photocatalytic substance is provided to prevent the fogging, and even in a place where direct sunlight (excitation light) is hardly incident, such as a washroom or a bathroom, the photocatalytic substance is irradiated by the excitation light of the photocatalytic film arranged in a specific place. And an anti-fog mirror designed such that the light does not adversely affect the human body.

[0002]

2. Description of the Related Art Some antifogging mirrors have a film made of an organic water repellent or hydrophilic agent formed on the surface thereof, but fine water droplets remain on the mirror surface to completely repel water. There is a problem that it cannot be removed, or a uniform water film cannot be formed due to insufficient hydrophilic action, and in any case, the durability is poor and the function is lost after long-term use.

[0003] There is a type in which a resistance heater is attached to the back surface of the mirror to remove dew condensation by heating. However, it is not economical due to the consumption of electric energy, and it is necessary to consider the safety against electric leakage and the like. Challenges remain.

[0004] Unlike the above, the present invention forms a film made of a photocatalytic substance on a mirror surface, activates the photocatalytic substance by photoexcitation, develops an excellent hydrophilic action, and removes fogging due to condensation. is there.

When a photocatalytic substance (for example, TiO2 semiconductor) is excited by high-energy light (ultraviolet light), electron-hole pairs are generated, and these electrons (e-) and holes (h +) are generated on the surface of the substance. Adsorption and redox of adhering substances, for example, organic substances are decomposed, oxidized and reduced and removed, and photocatalytic substances are
Adsorbed organic substances (hydrophobic substances) are decomposed and removed to make them hydrophilic, and water is chemically adsorbed on the photocatalytic substance surface in the form of -OH,
Further, it is considered that the adhering water combines with the water to form a smooth water film and prevent fogging.

Excitation light is necessary to activate the photocatalyst substance, and sunlight (ultraviolet region) is also effective. However, in a bathroom or a washroom where sunlight is hardly incident, ultraviolet light as excitation light is emitted. It becomes necessary to irradiate. However, ultraviolet rays are harmful to human health, such as inflammation and sometimes cancer when they come into contact with human eyes and skin.

[0007] Therefore, it was necessary to take measures such as arranging an ultraviolet light source on the surface of the mirror and stopping the ultraviolet irradiation when a person approaches the mirror, or irradiating the ultraviolet light at night when the mirror is not used. According to the invention, such considerations are useless.

[0008]

According to the present invention, there is provided a mirror having a light reflecting metal film formed on a back surface of a glass sheet and a photocatalytic film formed on a front surface thereof, wherein a mirror is formed at an appropriate position on the one side of the mirror.
A light source for photocatalyst excitation is arranged so as not to leak to the above-mentioned portion, at a portion where the light reflecting metal film or the photocatalyst film is not formed, and excitation light enters the plate glass from the above portion, and the photocatalytic film and the light This is an anti-fog mirror in which the refraction angle αt of the excitation light at the one surface XX ′ is set so that the light is repeatedly totally reflected between the reflective metal film and propagated in the glass sheet.

It is important to adjust the excitation light incident conditions so that the refraction angle αt of the incident excitation light with respect to one surface XX ′ is 40.8 ° or more.

In the above, it is also preferable that the glass surface at the excitation light incident point is a surface inclined with respect to one surface XX ′.

Further, it is preferable that a light-introducing hologram or a prism is additionally provided at the excitation light incident point, and the excitation light is incident through the light-introducing hologram or the prism.

In addition, the haze value of the photocatalytic film is 0.5%
It is better to do the following. Preferably, a transparent oxide film having a lower refractive index than the photocatalytic film is interposed between the photocatalytic film and the plate glass.

[0013]

1A, 1B, and 1C are schematic cross-sectional views of a mirror according to various aspects of the present invention. As the transparent plate-like material constituting the mirror M, a soda-lime-based plate glass 1 made by a float method is employed.

On the back side of the plate glass 1, a film (light reflecting metal film) 4 of a metal having high light reflectivity such as silver, aluminum, stainless steel, chromium or the like is formed, and it faces the front side, that is, faces a person. On the side, a mirror M (so-called backside mirror) is formed by forming a film made of a photocatalytic substance or a film (photocatalytic film) 3 mainly composed of a photocatalytic substance. In a normal mirror, it is common to form a silver film on the rear surface side, a copper film for protecting the silver film, and a backing coating film made of a corrosion-resistant material and a resin binder for protecting the metal film. is there. The plate glass 1 is a glass whose front and back surfaces are parallel to each other, and the photocatalyst film 3 disposed on each of the front and back surfaces.
The light reflecting metal film 4 is also formed in parallel.

In each embodiment of the present invention, for example, the light source 5,
Reference numeral 5 'denotes a surface side of the mirror (that is, the glass sheet 1), which is disposed at a peripheral portion 1' where the photocatalytic film is not formed, is covered with the lamp shade 6, and is made of ultraviolet light having a wavelength of 320 nm to 390 nm. Excitation light (hereinafter simply referred to as light) 2 is prevented from leaking outside.

The light enters from the peripheral edge 1 'on the front side of the sheet glass,
The light 2 propagating in the sheet glass 1 repeatedly enters and reflects between the light reflecting metal film 4 and the photocatalytic film 3 as shown in the figure, and during that time, the light applied to the photocatalytic film 3 excites the photocatalytic film 3 to make it hydrophilic. It acts.

Meanwhile, the light 2 is absorbed by the glass and attenuated to activate the photocatalytic film 3. In order to allow the light 2 to spread over the entire surface of the photocatalytic film 3, the initial light intensity is designed in consideration of the size of the glass sheet 1 and the area of the photocatalytic film 3 provided with a film. This is an appropriate design item.

FIG. 2 is an enlarged partial sectional view showing the path of incidence (refraction) and reflection of light on a mirror.
The incident light 2 on the surface side peripheral portion 1 ′ of the sheet glass
The condition for total reflection in the interior will be described. The symbols in the figure are as follows. αi: Incident angle at the air / sheet glass interface βi: Incident angle at the sheet glass / photocatalytic film interface θi: Incident angle at the photocatalytic film / air interface αt: Refraction angle at the air / sheet glass interface βt: Sheet glass / Refraction angle at the interface of the photocatalytic film θt: Refraction angle at the interface of the photocatalytic film / air n0: Refractive index of air (1.00) n1: Refractive index of plate glass (1.53) n2: Refractive index of photocatalytic film (anatase) (2.15) Note 1: Refractive index is the excitation wavelength range of photocatalytic film (320nm)
390 nm). Note 2: The refractive index of sheet glass is around 1.53, though it depends on the composition of soda-lime glass.

[Regarding the incident angle at which the light is totally reflected at the photocatalytic film / air space interface] The surface side 1 'near the edge of the sheet glass
In order to excite the photocatalyst film 3 without leaking the light 2 out of the front and back surfaces of the glass plate 1, the light 2 is totally reflected at the interface between the photocatalyst film 3 and the air a. There is a need. The incident angle for preventing the light 2 from leaking from the photocatalytic film 3 can be obtained from Snell's equation. In addition,
It is assumed that the interfaces of the air / photocatalyst film, the photocatalyst film / plate glass, and the plate glass / metal reflection (silver) film are all parallel.

The incident angle θi at the photocatalyst film / air interface is
It is represented by the following [Equation 1]. θi = sin-1 [(n0 / n2) sin θt] (Because θt for total reflection at the interface is 90 °) = sin−1 (n0 / n2) −Equation 1 That is, the photocatalytic film / Incident angle at the air interface θi ≧ sin-1
If (n0 / n2), it is totally reflected and does not leak into the air space.

[About the incident angle at the interface between the plate glass and the photocatalytic film for obtaining the above θi] The incident angle βi at the interface between the plate glass and the photocatalytic film is obtained by the following equation. βi = sin−1 [(n2 / n1) sin βt] (Because βt = θi, substitute [Equation 1]) = sin−1 [(n2 / n1) sin θi] = sin−1 [(n2 / n1) (n0 / n2)] = sin-1 (n0 / n1) [Equation 2] = 40.8 That is, regardless of the refractive index of the photocatalyst, the angle of incidence βi at the glass / photocatalyst film interface. If ≧ 40.8 °, total reflection occurs at the photocatalyst film / air space interface, and from the preconditions, βi = αt (the refraction angle at the air / sheet glass interface; (Represented by the line XX ′ in each figure), and if the refraction angle αt ≧ 40.8 °, the light is totally reflected.

[On the incident angle of light on the surface near the edge of the mirror (sheet glass) for obtaining the above αt] The incident angle αi with respect to the sheet glass surface XX 'at the interface of air space / sheet glass
Is obtained from the following equation. αi = sin−1 [(n1 / n0) sin αt] (αt = βi) = sin−1 [(n1 / n0) sin βi] (from the precondition) [Expression 3] By the way, βi ≧ 40.8 °, the incident angle αi> 90 °
And light cannot be incident as it is.

In the embodiment shown in FIG. 1A, a prism 8 is additionally provided at the light incident point 1 ', whereby βi = αt ≧ 40.8 ° can be easily achieved, thereby causing total reflection. Light does not leak from the photocatalytic film. Therefore, the person using the mirror can be prevented from being exposed to ultraviolet rays. The angle φ of the angle of the prism 8 and the refractive index are as follows:
An appropriate design can be made in consideration of the position of the light source 1.

As shown in FIG. 1B, if the light incident portion of the sheet glass 1 is a surface 1 "which is inclined so as to be thinner toward the end surface of the sheet glass, and the light is made incident, an apparent surface X of the sheet glass can be obtained. −X ′ line, the refraction angle αt ≧
Since the angle can be set to 40.8 °, light does not leak from the photocatalytic film as described above.

The light source 5 'may be designed to collect sunlight or light from an ultraviolet light source disposed at another location, transmit the light to the light source 5' by an optical fiber, and make the light incident. It is.

Further, in FIG. 1C, similarly to the above, the light incident portion of the plate glass 1 is made to be an inclined surface 1 ″, and the known reflected light is diffracted at the portion at a desired angle of 40.8 ° or more. If a sheet made of a light-introducing hologram to be adhered is attached, a desired refraction angle can be obtained.

In practice, the surface of the photocatalytic film is not completely parallel to the plate glass of the substrate. A haze value (intensity ratio between scattered light of light perpendicularly incident on the film surface and the total transmitted light) is an obvious physical property value that indicates deviation from parallelism. If the value is large, light may leak to the external space side. There is.

By the way, when the photocatalytic film is completely parallel to the glass sheet and the haze value of the film measured by the perpendicular incident light is 0.5% or less even under the condition where total reflection occurs at the photocatalytic film / air interface. However, as will be described later in the embodiments, the ultraviolet ray detector cannot detect light, and it can be considered that there is no influence on the human body.

As a photocatalytic substance constituting the photocatalytic film, it is known that anatase exhibits the best catalytic activity. However, in order to improve the strength of the film and the adhesiveness to the substrate glass, etc. One or more of silica, alumina, tin oxide, zirconium oxide and the like can be mixed.

Alternatively, between the plate glass and the photocatalytic film,
By interposing a film having a refractive index lower than those of the photocatalytic films and adjusting the film thickness, reflection from the photocatalytic film (a double image) can be reduced by light interference.

In order to form a film of anatase or a complex metal oxide containing anatase in the photocatalyst film, an oxide sol solution using a metal alkoxide such as titanium or a metal acetylacetonate such as titanium as a starting material is used. A sol-gel method in which the metal oxide is applied to a heated substrate and fired by heating, or a CVD method in which a similar metal compound vapor is sprayed on the heated substrate to form an oxide film by thermal decomposition or the like, and the metal oxide is applied to the substrate by physical vapor deposition means. The PVD method or the like for vapor deposition is suitable, and the haze value can be 0.5% or less in any case.

In the above description, suppression of light leakage from the mirror surface has been described. However, the end face 1x which is adjacent to the peripheral edge (indicated by reference numeral 1 'in FIG. 1A) of the plate glass on which light is incident is opposed to the end face 1x. The leakage of light from the end face 1x 'or the side end face of the glass sheet does not cause a serious problem as long as a person faces the mirror. In order to suppress leakage from each of the ends, a film made of a reflective substance (various metals such as stainless steel and aluminum) or an absorbent substance (ceria or titania) may be coated on each end. Good. For example, if the opposing end face 1x 'is coated with a reflective substance as shown by a reference numeral 7 (shown by a broken line) in FIG. This is convenient because it can be used effectively.

[0033]

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

[Example 1] One peripheral edge 1 '(width) of a plate glass 1 having a size of 363 mm x 455 mm to which light is to be incident is provided on one surface.
An anatase type photocatalytic film 3 having a film thickness of 153 ± 20 nm was coated by a sol-gel film forming method except for 10 mm).

As a starting material, titanium isopropoxide is used, dissolved in an isopropyl alcohol solvent, and hydrolyzed to obtain a titania sol solution. One surface on which a reflective metal film is to be formed, and the one peripheral portion 1 '
Is immersed in a glass plate, and then gradually pulled up to form a film, which is dried and heated and fired at about 500 ° C. to form an anatase-type photocatalytic film.

The haze value of this glass was 0.3% as determined by a haze meter. Then, a film thickness of 70 is formed on one side (glass back side) not covered with the photocatalyst film.
A mirror with a photocatalytic film was produced by coating the silver film 4 with a thickness of nm. In the mirror making, a silver nitrate solution and a reducing solution mainly composed of a strong alkali are brought into contact with the glass surface by a conventional method to deposit silver by a so-called silver mirror reaction.

A prism 8 having the same refractive index as that of the sheet glass is attached to one peripheral edge 1 ′ of the mirror having a length of 363 mm and a width of 10 mm, a lamp shade is arranged so as to cover the same, and a high-pressure mercury lamp is arranged inside. And the light intensity on the light incident surface of the prism 8 is
A high-pressure mercury lamp was set at a position of 20 mW / cm2. The emission spectrum of the high-pressure mercury lamp is a bright line spectrum, with a relative intensity of 75% at a wavelength of 305 nm, 95% at 357 nm, and 3%.
It is 67% at 95 nm.

Incidentally, light is incident from the high pressure mercury lamp,
When the amount of light leaking from the photocatalytic film of the mirror to the mirror surface was measured using Otsuka Denki's Photomaru (MCPD-1100), it was not detected.

After the light was incident, leakage of light 2 at the end face 1x 'opposite to the end face 1x of the plate glass was inspected. Light of about 3 mW / cm2 was detected, light energy was absorbed into the glass, and the photocatalytic film caused the light to be absorbed. Even if absorbed and attenuated, surplus light energy was still detected, indicating that the entire photocatalytic film was activated uniformly.

The above-mentioned mirror with a photocatalytic film as Example 1
Both the mirror, not coated with the photocatalytic film as Comparative Example 1 but coated with only the light-reflective metal (silver) film, was brought into contact with saturated steam at about 43 ° C. for about 3 minutes, and then dried in a dryer at about 40 ° C. For about 10 minutes, leave it at room temperature for 1 hour, conduct the fogging test up to 10 cycles, with 1 cycle until the start of the first contact with saturated steam again. The occurrence of fogging during the contact was visually evaluated. During the test, the mirror of Example 1 always received the light of the high-pressure mercury lamp through the prism 8.

As a result, as shown in Table 1, Comparative Example 1
The mirror of Example 1 had fogging from 3 cycles, but the mirror of Example 1 did not show fogging for 10 cycles. [Table 1] Sample judgment 1 2 3 4 5 6 7 8 9 10 Example 1 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Comparative Example 1 ○ ○ × × × × × × × × (Note) ○: No fogging is observed. X: Clouding was observed.

Example 2 A solution obtained by adding octylene glycol to titanium tetraisopropoxide was poured into a stainless steel sealed container (evaporator) heated to about 200 ° C. by a metering pump. Separately, a dry nitrogen gas was passed through the container, and further mixed with dry air at about 200 ° C. at the outlet side to prepare a normal pressure CVD gas.

Example 1 A plate glass similar to that of Example 1 was placed on a peripheral portion to be irradiated with light on the upper surface thereof, and was then transferred into a heating furnace by a transfer conveyor at a maximum temperature of about 620 ° C.
Immediately after the temperature was raised to about the same, and immediately after being carried out of the heating furnace by the transfer conveyor, the prepared gas was sprayed from a CVD nozzle by a previously prepared CVD apparatus to form an anatase type photocatalytic film.

The thickness of this glass was 120 ± 25 nm, and the haze value of the glass was 0.5%. Then, as in Example 1, a film thickness of about 70
A mirror with a photocatalytic film was formed by coating with a nm silver film.

In the same manner as in the first embodiment, a high-pressure mercury lamp with a prism disposed on the periphery and covering the lamp shade is set, and light enters from the prism and leaks from the photocatalytic film of the mirror to the mirror surface. As a result, no light could be detected. Also, as in the first embodiment, the facing end face 1x '
As a result, light was detected in the same manner as in Example 1.

Stearic acid was applied onto the photocatalytic film of the mirror so that the haze value was about 3% as measured by a haze meter, and ultraviolet rays were incident on the high-pressure mercury lamp through a prism for about 20 minutes. When the haze value was measured, the haze value was reduced to 1% or less.

The same mirror as in Comparative Example 1 without a photocatalytic film was coated with stearic acid in the same manner as above, and the haze value after the lapse of the same time was measured.
Did not change at all even after the lapse of time.

Example 3 The same plate glass as in Example 1 was used, except that titanium isopropoxide and silicon tetraethoxide (titania: silica = 70 in terms of oxide weight) were used as starting materials. : 30), dissolved in an isopropyl alcohol solvent, and hydrolyzed to obtain a titania / silica sol solution, and immersed in this solution a plate glass on which one surface on which a reflective metal film is to be formed and one peripheral portion on which light is to be incident are masked. Then, the film was gradually pulled up to form a film, which was dried and heated and fired at about 500 ° C. to form an anatase-silica mixed photocatalyst film. The haze value of this glass was 0.3% as determined by a haze meter.

Thereafter, the glass surface not covered with the photocatalyst film was coated with a silver film in the same manner as in Example 1 to produce a mirror with a photocatalyst film. In the same manner as in the first embodiment, a prism is arranged at the one peripheral edge, a high-pressure mercury lamp covered with a lamp shade is set, and light enters through the prism to leak from the photocatalytic film of the mirror to the mirror surface. When the amount of light was measured, no light could be detected. When the light from the facing end face 1x 'was measured as in Example 1, light was detected as in Example 1.

As in Example 2, stearic acid was applied on the photocatalytic film of the mirror so that the haze value was about 3%, and the end face was irradiated with ultraviolet rays for about 20 minutes by the high-pressure mercury lamp, and the haze value was measured again. As a result, the haze value was reduced to about 1%.

In addition, it was found that the silica was mixed in the photocatalyst film, so that the film was less likely to be peeled off than in the case of only anatase even in a wear test using a wear wheel.

[0052]

According to the present invention, it is possible to activate the photocatalyst film by irradiating the photocatalyst film on the surface of the anti-fog mirror without exposing ultraviolet rays to the human body, and to exhibit a satisfactory anti-fog function. Play.

[Brief description of the drawings]

1A and 1B are schematic sectional views of an anti-fog mirror.

FIG. 2 is an enlarged partial cross-sectional view of the anti-fog mirror.

[Explanation of symbols]

 M mirror 1 sheet glass 1 'light incident point 1 "inclined surface 2 light (excitation ultraviolet light) 3 photocatalytic film 4 light reflecting metal film 8 prism 8' sheet made of light introduction hologram

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI C03C 17/06 C03C 17/06 Z

Claims (5)

[Claims] 1. A mirror having a light-reflective metal film formed on the back side of a plate glass and a photocatalyst film formed on the front side, wherein a light-reflective metal film or a photocatalyst film is provided at an appropriate peripheral portion on the one surface of the mirror. For a portion that is not formed, a light source for photocatalyst excitation is arranged so as not to leak to a portion other than the portion, excitation light is incident on the plate glass from the portion, and between the photocatalytic film and the light reflecting metal film. An anti-fog mirror characterized in that a refraction angle αt of the excitation light at the one surface XX ′ is set so that the light is repeatedly totally reflected and propagated in the glass sheet. 2. The antifogging mirror according to claim 1, wherein the excitation light incidence conditions are adjusted so that the refraction angle αt of the incident excitation light with respect to one surface XX ′ is 40.8 ° or more. 3. The glass surface at the excitation light incident point is connected to one surface X
3. The anti-fog mirror according to claim 2, wherein the surface is inclined with respect to -X '. 4. A light-introducing hologram or a prism is provided at an excitation light incident point, and the excitation light is incident through the light-introducing hologram or the prism. Anti-fog mirror as described. 5. The antifogging mirror according to claim 1, wherein a transparent oxide film having a lower refractive index than the photocatalytic film is interposed between the photocatalytic film and the plate glass.