JPS6098405A - Multi-layered rear reflection mirror - Google Patents

Abstract

PURPOSE:To obtain the stable color tone of a blue base and an anti-dazzling effect by laminating alternately TiO2 films and SiO2 films having specific film thickness into four layers on one side of a glass base plate and forming the final film of the SiO2 film thereby specifying the spectral characteristic of reflected light only in the prescribed wavelength range. CONSTITUTION:TiO2 films 2, 2' having n/4lambda (n is an odd number) film thickness, SiO2 films 3, 3' having n/4lambda (n is an odd number) film thickness and a light absorptive film 4 having a dark black color are laminated on a glass base plate 1 constituting a reflection mirror. The films 2, 2' and the films 3, 3' are formed by vacuum evaporation, etc. on one side of the plate 1. The reflectivity is maintained at 38-60% and the spectral characteristic of the reflected light is maintained within the prescribed wavelength range by the above-mentioned constitution. More specifically, the curve (f) shown in the figure is the spectral characteristic in the case of lambda=410nm and the curve (g) is likewise the spectral characteristic in the case of lambda=480nm. The stable color is thus obtd. on the blue base at about 410-480nm on the short wavelength side and an anti-dazzling effect is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a reflecting mirror used for automobile rearview mirrors, etc. More specifically, the present invention relates to a reflecting mirror used for automobile rearview mirrors, etc., and more specifically, a light interference thin film is formed on the back surface of a glass substrate to reduce dazzle caused by reflected light from the mirror surface. This invention relates to an anti-glare back reflecting mirror.

TECHNICAL BACKGROUND OF THE INVENTION So-called aluminum mirrors and chrome mirrors are commonly used, which have an aluminum film, chrome film, etc. applied to the surface and a protective coating film applied to the upper surface of the film. However, recently, many multilayer reflective mirrors have been proposed to enhance the anti-glare effect, and some of them are already on the market. This multilayer reflector has Ti on the top surface of the glass substrate.
A three-layer film surface mirror in which a three-layer film of 0z-'Sigh-TiO2 is formed and a light-absorbing film is coated on the bottom surface of a glass substrate, and a mirror with a three-layer film of Ti0z-SiO2 on one side of the glass substrate.
2- There is a three-layer film back mirror in which a three-layer film of Ti02 is formed and a light-absorbing film is coated on the top surface of the film. Also, JP-A-5
No. 7-144504 discloses a Ti0z film and a 5lo2 film.
A five-layer film back reflecting mirror is disclosed in which films are alternately stacked as five-layer films and a light-absorbing film is coated on the upper surface of the films.

Problems with the Background Art Figure 1 shows the spectral reflection characteristics of various reflecting mirrors. In the figure, the daylight reflection characteristic of the aluminum mirror is shown by curve a. The reflectance of this aluminum mirror (hereinafter the reflectance using standard illuminant A specified in JTS-D-5705) is very good, but its spectral reflection characteristics cover a wide wavelength range, so it has little anti-glare effect and is extremely harmful to drivers. In addition, the spectral reflection characteristics of the chrome mirror are shown by the curve in Figure 1.The reflectance of this chrome mirror is as low as 38 to 4596, so it has a certain degree of anti-glare effect, but it Visibility is poor, and the spectral wavelength range of the reflected light is wide-ranging, resulting in glare from the light in the wavelength range that is unnecessary for visibility projected from the headlights of the following vehicle and the reflection of strong yellow to red light from sunlight. It has the disadvantage of extremely poor visibility.

In order to improve the above-mentioned drawbacks of aluminum mirrors and chrome mirrors, multilayer mirrors that can attenuate visible light in the long wavelength range have been developed, and three-layer front mirrors and three-layer rear mirrors have been adopted. It became so. The spectral reflection characteristics of the three-layer film surface mirror are shown by curve C in FIG.

This reflector has a reflectance of 48% and meets JIS-I)-5705.
It satisfies the reflectivity of 38% or more for chrome mirrors stipulated by the ``Automobile Mirror Devices'' and has an excellent anti-glare effect, but because it uses a surface mirror system, it can be easily damaged by dust or brush wiping when washing the car. The film formed on the glass substrate is easily damaged and has a durability problem. The spectral reflection characteristics of the three-layer film back mirror are shown by the curves in FIG. Since this reflecting mirror is of the back mirror type, the film will not be damaged, but it has the disadvantage that the reflectance is as low as 36% and does not meet the standards for the above-mentioned "automotive mirror device."

Furthermore, the reflector disclosed in Japanese Patent Application Laid-Open No. 57-144504 has five layers of Ti02 and 5102 films stacked alternately, so the reflectance is improved to 53%. As shown by curve e in the figure, the wavelength range of the spectral reflection characteristics is too narrow, so the film thickness control range for each layer is narrow (and the reflected color tone of the product varies within the range of blue → blue-green → green, making it difficult to stabilize. There are drawbacks.

When a single layer of a thin film having a refractive index higher than that of the glass substrate is deposited, the reflectance becomes maximum at a wavelength position where the film thickness is n/4λ (where n is an odd number).

At this position, a high refractive index TiO2 film (refractive index 2.3)
It is well known that the reflectance increases if a multilayer film is formed by alternately stacking Sio2 films with low refractive index (refractive index 1.4).

The thin film deposited on the glass substrate (refractive index 1.5 to 1.55) is preferably TiO2, and the final film may also be TlO2 because it is a light absorbing film (refractive index 1.5 to 1.6). Considering only the increase in reflectance from the relationship, it can be said that this is preferable. For this reason, conventional products all have an odd number of layers, such as single layer, three layers, or five layers, and are generally formed starting from a Ti (h film on the glass substrate side) and ending with a Ti 02 film.

However, with the exception of surface mirrors, thin films with an odd number of layers as described above have a low reflectance when the number of layers is small, and as the number of layers increases, the spectral wavelength range of the reflected light narrows, so it is difficult to maintain a constant color tone. The disadvantage is that the range of control is narrower. Therefore, the reflectance of the single-layer film and the back mirror of the three-layer film is low, and the five-layer film has difficulty in stabilizing the color tone. Further, two-layer films have low reflectance, and six-layer films or more have the disadvantage that workability is significantly reduced and color tone becomes unstable.

OBJECT OF THE INVENTION The present invention has been made in view of the circumstances described in item 1, and the reflectance of the back reflector of a multilayer film is determined according to the JIS-D standard.
White music nine city Guki batch station 1 Kukoriro left double E blood rate 3896
600nm while satisfying the above requirements and maintaining improvement to around 60%
It is an object of the present invention to provide a reflecting mirror with excellent anti-glare effect and good visibility by reducing visible light in a longer wavelength range to a large rlJ.

SUMMARY OF THE INVENTION The present invention is characterized in that each layer is formed on one side of a glass substrate by n7. By alternately stacking four layers of T i O2 films and 5102 films with a film thickness of λ (n is an odd number) and making the final film a SiO2 film, the spectral characteristics of reflected light are kept constant only within a predetermined wavelength range 6001
It was possible to reduce yellow to red reflected light in the vicinity of m, and obtain a stable blue-based color tone and anti-glare effect.

FIG. 3 is an experimentally determined relationship between the spectral spectrum λ of reflected light and the reflectance in the back reflecting mirror of the four-layer film of the present invention, and shows that the reflectance is 3 within the range of 2410 to 4801 m.
It is 8% to 60%, and the reason for limiting λ in the present invention is based on this fact.

In addition, the reflectance is approximately within the range of 38 to 60% due to the relationship between the refractive index of the final SiO2 film and the dark-black light-absorbing film formed on the two sides of that film, and the relationship between the number of film layers. You could choose any color with the same stable color tone.

EXAMPLES OF THE INVENTION Examples of the present invention will be specifically described below. FIG. 2 is an enlarged cross-sectional view of the main parts of the multilayer film back reflecting mirror of the present invention. (1
) are glass substrates constituting the reflecting mirror, (2) and (2;
゛ is a TiO2 film with a thickness of 1λ (n is an odd number), (3) and (3; are a SiO2 film with a thickness of λ (n is an odd number),
(4) is a dark black light absorbing film. Ti0z film +2)
The +2)' and 5iOz films +3+ taf are formed on one side of the glass substrate (1) by vacuum evaporation, CVD (chemical paper deposition), CLD (chemical liquid deposition), or the like. Next, the above T
The final film 5iO2 (3), which is a 4-layer stack of alternating iO2 and SiOz films, is coated with epoxy, which has good adhesion to the glass substrate (1) and is highly durable, for the purpose of light absorption and protection of the thin film. A light-absorbing film (4) made of a dark black resin such as a silicone resin or a silicone resin is formed to a thickness of about 20 to 100 microns by a method such as painting.

The present invention sets the optimum conditions for the spectral characteristics and stacks four layers of TlO2 film and SiO2 film alternately on a glass substrate to make the final film a 5iOz film, thereby achieving a reflectance of 3896.
~60%, and the spectral characteristics of the reflected light could be kept constant within a predetermined wavelength range. The curve f in FIG. 1 is the spectral characteristic (4'lOnm) of the multilayer mirror of the present invention, and the curve g is the spectral characteristic of the present invention when λ=480 nm.

Figure 4 shows the spectral distribution characteristics of light emitted from the headlights of the following vehicle. The longer the wavelength of the light projected from the headlights of the following vehicle, that is, the yellow to orange-red, the higher the spectral energy value, and the more the light is felt and the more dazzling it becomes.

Therefore, by reducing the reflected light in this wavelength range, 410
It is easy to understand that if a stable color with a blue tone around 4801 m can be obtained, the anti-glare effect will be exhibited.

Effects of the Invention Based on the configuration of the present invention, by adopting a back mirror system, there is no need to worry about surface scratches, the color tone is stable, and reflected light in the long wavelength range unnecessary for visibility is reduced, resulting in an anti-glare effect. Improved to large IJ. Further, the reflectance can be increased to 3896 or more, improving visibility.

[Brief explanation of drawings]

Fig. 1 is a spectral reflection characteristic diagram, Fig. 2 is an enlarged cross-sectional view of the main part of a multilayer back reflecting mirror with four layers of the present invention, and Fig. 3 is a reflected light of the four-layer back reflecting mirror of the present invention. FIG. 4 is a diagram showing the relationship between the spectral spectrum λ and the reflectance, and FIG. 4 is a diagram showing the spectral distribution characteristics of light source A. a-e...Spectral distribution curve of conventional example, f, g・
...Spectral distribution curve of the present invention, I...Glass substrate, 2,2'...Ti0z film, 3,3'...
...SiO2 film, 4...Dark black light absorption film. Patent applicant: Toshiba Glass Corporation Figure 1 Figure 2

Claims (1)

[Claims] In a multilayer back reflecting mirror in which Ti'02 films and Sio2 films are alternately laminated on one side of a glass substrate with each layer having a film thickness of \λ (where n is an odd number), the Ti0z film and the SiO+ film are A multilayer back reflecting mirror characterized in that the spectrum of reflected light obtained by alternately stacking four layers is in the range of 410 to 480 nm, and a light absorbing film is formed on the upper surface of the film.