Optical: systems and elements – Protection from moisture or foreign particle
Reexamination Certificate
2000-10-16
2002-07-30
Shafer, Ricky D. (Department: 2872)
Optical: systems and elements
Protection from moisture or foreign particle
C359S584000, C359S585000, C359S586000, C359S588000, C359S589000, C359S603000, C359S883000
Reexamination Certificate
active
06425670
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a mirror having both an anti-fog property and a dimming property.
It is effective for improving visibility of a mirror for an automobile to improve anti-fog and dimming properties of the mirror. The anti-fog property is a property of removing a waterdrop which is deposited on the surface of a mirror. There is a mirror for an automobile imparted with such anti-fog property by applying a water-repellent treatment on the surface of the mirror thereby to facilitate removal of waterdrop. There is a mirror for an automobile imparted with such anti-fog property by the opposite way that is applying a hydrophilic treatment on the surface of the mirror thereby to spread waterdrops on the mirror in the form of a thin film.
The dimming property is a property of mitigating the glare of the sun light during the day. As a mirror for an automobile having such dimming property, there is a colored mirror (so-called blue mirror) which has a peak of reflection in the blue range (i.e., short wavelength range) and therefore has a mirror surface exhibiting a bluish color. The human spectral luminous efficacy has a peak at a wavelength of about 555 nm in a bright environment at which yellowish green color becomes clear. As the environment becomes darker, the peak of spectral luminous efficacy shifts in the direction of blue and the peak wavelength is shifted to about 505 nm. The blue mirror has a peak of reflectance within a range from 400 nm to 510 nm. Therefore, there is discrepancy between a reflected image from the blue mirror and the peak of the human spectral luminous efficacy during the day and the reflected image looks somewhat dark and the glare of the sun light thereby is mitigated. The reflected image agrees with the human spectral luminous efficacy during the night so that the reflected image looks relatively bright during the night thereby affording good visibility.
There is a prior art mirror for an automobile with improved anti-fog and dimming properties which is proposed in the applicant's copending Japanese Patent Application No. 234981/1998. The structure of this prior art mirror will be-described with reference to
FIG. 2. A
TiO
2
film
4
having a high refractive index is provided on the rear surface of a transparent glass substrate
2
. On the rear surface of the TiO
2
film
4
is provided a SiO
2
film
6
having a low refractive index. Further, on the rear surface of the SiO
2
film
6
is provided a Cr reflecting film
8
as a metal reflecting film. The thickness of the TiO
2
film having a high refractive index and the thickness of the SiO
2
film
6
having a low refractive index are so set that the mirror will exhibit a blue color owing to interference of light. On the front surface of the transparent glass substrate
2
is provided a TiO
2
film
10
having a photocatalytic function. Further on the front surface of the TiO
2
film
10
is provided a porous SiO
2
film
12
having a hydrophilic property.
Light incident from a mirror surface
14
exhibits blue reflected light owing to interference between the TiO
2
film having a high refractive index, the SiO
2
film having a low refractive index and the Cr reflecting film
8
which constitutes the reflecting film whereby the dimming property is afforded. Owing to the action of the porous SiO
2
film, waterdrops deposited on the mirror surface
14
spreads on the mirror in the form of a thin film with a contact angle of 20 degree or below whereby the anti-fog property caused by the hydrophilic property is afforded. Since the mirror for an automobile is exposed to the outside air, contaminants are deposited on the porous SiO
2
film
12
which is provided on the mirror surface and the contaminants reduce the hydrophilic property of the SiO
2
film. The contaminants deposited on the porous SiO
2
film
12
, however, are decomposed and removed owing to the photocatalytic action of the Ti
0
2
film
10
having the photocatalytic function and the hydrophilic function of the SiO
2
film thereby can be maintained.
In the prior art mirror for an automobile shown in
FIG. 2
, the Cr reflecting film
8
is provided as a metal reflecting film on the rear surface of the substrate
2
. Further, on the front surface of the substrate
2
is provided the TiO
2
film
10
having the photocatalytic function. Ti
0
2
inherently has a high refractive index and therefore tends to cause reflection on the surface. This surface reflection and reflection from the Cr reflecting film
9
tend to produce double images in a reflected image. This is particularly so in a mirror of a small radius of curvature and a mirror of a complex radius of curvature.
Moreover, the mirror of
FIG. 2
in which the two layers of the TiO
2
film and the SiO
2
film are respectively provided on both the front and rear surfaces of the transparent glass substrate has a complex structure with resulting high cost of manufacturing.
It is, therefore, an object of the invention to provide a colored anti-fog mirror exhibiting a blue color on the mirror surface which is capable of preventing occurrence of double images with a simple structure and a low manufacturing cost.
SUMMARY OF THE INVENTION
For achieving the object of the invention, there is provided a colored anti-fog mirror comprising a substrate, a metal reflecting film formed on a front surface of the substrate, and a hydrophilic function layer having a hydrophilic function and comprising photocatalytic substance provided on the metal reflecting film, the thickness of the hydrophilic function layer being set in such a manner that wavelength of reflected light has a peak of reflectance within a range from 400 nm to 510 nm and a mirror surface thereby exhibits a bluish color.
According to the invention, owing to the hydrophilic property of the hydrophilic function layer comprising photocatalytic substance, waterdrops deposited on the mirror surface are spread to a thin film and the anti-fog property thereby can be obtained. Further, by setting the thickness of the hydrophilic function layer comprising photocatalytic substance in such a manner that wavelength of reflected light has a peak of reflectance within a range from 400 nm to 510 nm and the mirror surface thereby exhibits a bluish color by interference between reflected light from the metal reflecting film and reflected light from the surface of the hydrophilic function layer comprising photocatalytic substance, the glare of the sun light during the day can be mitigated and excellent visibility can be obtained during the night. Further, when contaminants are deposited on the mirror surface with the result that the hydrophilic function is reduced, the contaminants are decomposed owing to the photocatalytic function of the hydrophilic function layer comprising the photocatalytic substance whereby the hydrophilic function can be restored. Further, since the distance between the metal reflecting layer and the mirror surface which causes double images is so short that occurrence of double images which can be recognized with human eyes can be prevented. Again, by causing the layer for producing interference of light to function also as the layer performing hydrophilic and photocatalytic functions, the process of manufacture can be simplified and the manufacturing cost can be reduced. In the prior art structure in which the reflecting film is provided on the rear surface of the substrate, provision of a hydrophilic function layer on the front surface of the substrate and adjustment of thickness of the layer do not contribute significantly to spectral reflectance. By only providing a hydrophilic function layer on the front surface of a substrate in the structure in which the reflecting film is provided on the front surface of the substrate and adjusting the thickness of the layer as in the present invention, color can be imparted to reflected light from the reflecting film.
The hydrophilic function layer may be made of a laminate of a photocatalytic layer comprising a photocatalytic substance and a hydrophilic la
Kobayashi Masaki
Komatsu Toru
Hedman & Costigan ,P.C.
Murakami Corporation
Shafer Ricky D.
LandOfFree
Colored anti-fog mirror does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Colored anti-fog mirror, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Colored anti-fog mirror will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2833008