JPH06148409A - Rear surface reflection mirror - Google Patents

Abstract

PURPOSE:To obtain excellent practicable durability, such as moisture resistance and weatherability, by successively laminating a metallic film, two layers of dielectric substance films, a metallic film and a dielectric substance film on the rear surface of a transparent substrate, thereby forming the rear surface reflection mirror. CONSTITUTION:This rear surface reflection mirror is formed by laminating the metallic film 11, two layers of the dielectric substance films 13, 15, the metallic film 17 and the dielectric substance film 19 in this order on the rear surface of the transparent substrate 10. The reflection mirror is formed by determining the materials and thicknesses of the respective films 11, 13, 15, 17, 19 so as to obtain the desired spectral reflectivity. The front surface side of the transparent substrate 10 is formed as a light incident side. Five layers of the thin films formed on the rear surface of the transparent substrate 10 are formed as the thin films consisting of of Cr, Yb2O3, TiO2, Al, SiO successively from the side of the transparent substrate. Then, the laminated thin films 11, 13, 15, 17, 19 constituting the actual parts of the reflection function are formed on the rear surface side of the transparent substrate 10 and since light is made incident from the front surface side of the transparent base body 10, the laminated thin films are not 'exposed' into the atm. in the condition where the reflection film is used. Five layers of the thin films are therefore protected against the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a back reflector.
The back reflector of the present invention can be used for automobile mirrors and the like.

[0002]

2. Description of the Related Art A reflecting mirror as an optical element is often required to have a specific spectral reflectance depending on the purpose of use. Further, the reflecting mirror is often used in a natural environment, and it is desirable that the reflecting mirror has excellent moisture resistance and weather resistance.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a rear surface reflecting mirror having excellent practical durability such as moisture resistance and weather resistance.

[0004]

As shown in FIG. 1, the rear surface reflecting mirror of the present invention has a structure in which "a metal film 11, two layers of dielectric films 13 and 15, a metal film 17 and a dielectric film are provided on the back surface of a transparent substrate 10. The body films 19 are laminated in this order from the transparent substrate 10 side, and each of the films 11, 13, 1 is provided so as to obtain a desired spectral reflectance.
5, 17 and 19 are defined in material and thickness, and the front surface side of the transparent substrate 10 is set as a light incident side ”(claim 1).

The five layers of thin films formed on the back surface of the transparent substrate 10 are Cr, Yb ₂ O ₃ and T sequentially from the transparent substrate 10 side.
It can be formed as a thin film made of iO ₂ , Al, and SiO (claim 2). In addition, the thin film of the above five layers,
In order from the transparent substrate 10 side, Cr, Yb ₂ O ₃ , Ti
O _2, Al, Yb to the ₂ O ₃ may be formed as a thin film to the material (claim 3), further, a thin film of the five layers in sequence from the side of the transparent substrate 10, Cr, Al ₂ O ₃ , TiO ₂ ,
You may form using Al and SiO as a material (Claim 4). Various transparent glass plates can be preferably used as the transparent substrate 10.

[0006]

As described above, in the back surface reflecting mirror of the present invention, the laminated thin film forming the actual part of the reflection function is formed on the rear surface side of the transparent substrate, and light is incident from the front surface side of the transparent substrate. Does not "bare" into the atmosphere when the reflector is used. Therefore, the five-layer thin film is protected from the outside.

The desired spectral reflectance can be obtained by adjusting the material and thickness of each film, but at that time, the thickness of the two-layer dielectric film sandwiched between the two-layer metal film. By adjusting, the “center wavelength” in the spectral reflectance characteristic can be set.

By adjusting the film thickness of the dielectric film, it is possible to give a desired phase difference between the P-polarized component and the S-polarized component of the reflected light.

[0009]

Example 1 A glass substrate was used as the transparent substrate 10 in FIG.
The inside of the vacuum chamber was evacuated to 4.0 × 10 to ³ Pa or less, a glass substrate with a sufficiently clean and smooth surface was placed, and the backside (the surface opposite to the incident side) had a thickness of metal: Cr. : 0.13λ ₀
The metal film 11 was formed by vacuum deposition on (λ ₀ = ND / RAMD).

On the metal film 11 made of Cr, a dielectric material: Yb ₂ O ₃ (refractive index: 1.83) was formed in a vacuum chamber in which oxygen gas was introduced at a pressure of 1.7 × 10 ² Pa. : 0.290
It is vapor-deposited on 8λ ₀ to form the dielectric film 13, and the dielectric film:
TiO ₂ (refractive index: 2.33) was vapor-deposited under the same oxygen gas pressure as that of the dielectric layer 13 to a thickness of 0.28889λ ₀ to form a dielectric film 15.

Then, the inside of the vacuum chamber was evacuated to 4.0 × 10 to ³ Pa or less, and metal: Al was vapor-deposited to a thickness of 0.06372λ ₀ to form a metal film 17, and a dielectric: SiO (refractive index). : 1.63) was evaporated to a thickness of 0.10373λ ₀ to form a dielectric film 19.

FIG. 2 shows the spectral reflectance characteristics of the back reflecting mirror thus formed. The incident angle is 30 degrees. Due to the spectral reflection characteristics, the mirror image reflected on the mirror surface looks pale yellow (so-called gold).

Example 2 A glass substrate was used as the transparent substrate 10 in FIG.
The inside of the vacuum chamber was evacuated to 4.0 × 10 to ³ Pa or less, a glass substrate having a sufficiently clean and smooth surface was provided, and metal: Cr was vacuum-deposited to a thickness of 0.02599λ ₀ on the back surface side. Then, the metal film 11 is formed.

On the metal film 11 made of Cr, a dielectric material: Yb ₂ O ₃ was vapor-deposited to a thickness of 0.2908λ ₀ in a vacuum chamber in which oxygen gas was introduced at a pressure of 1.7 × 10 ² Pa. To form a dielectric film 13, and a dielectric: TiO ₂ is formed on the dielectric film 13 under the same oxygen gas pressure as that of the dielectric layer 13 to have a thickness of 0.28889λ _0.
Was vapor-deposited to form a dielectric film 15.

Then, the inside of the vacuum chamber was evacuated to 4.0 × 10 to ³ Pa or less, metal: Al was vapor-deposited to a thickness of 0.11635λ ₀ to form a metal film 17, and a dielectric: SiO was further formed. : 0.105λ ₀ to form a dielectric film 19.

FIG. 3 shows the spectral reflectance characteristics of the back reflecting mirror thus formed. The incident angle is 30 degrees. Due to the spectral reflection characteristic, the mirror image reflected on the mirror surface looks like gold as in the back reflecting mirror of the first embodiment.

Example 3 A glass substrate was used as the transparent substrate 10 in FIG.
The inside of the vacuum chamber was evacuated to 4.0 × 10 to ³ Pa or less, and a glass substrate having a sufficiently clean and smooth surface was provided, and metal: Cr was vacuumed to a thickness: 0.013λ ₀ on the back surface side. It vapor-deposited and it was set as the metal film 11.

Dielectric material: Yb ₂ O ₃ is vapor-deposited on the metal film 11 made of Cr to a thickness of 0.2908 λ ₀ in a vacuum chamber in which oxygen gas is introduced at a pressure of 1.7 × 10 ² Pa. To form a dielectric film 13, and a dielectric: TiO ₂ is formed on the dielectric film 1
Under the same oxygen gas pressure as in Example ₃ , vapor deposition was performed to a thickness of 0.28889λ ₀ to form a dielectric film 15.

Then, the inside of the vacuum chamber was evacuated to 4.0 × 10 to ³ Pa or less, metal: Al was vapor-deposited to a thickness of 0.11635λ ₀ to form a metal film 17, and a dielectric: SiO was further formed. : 0.105λ ₀ to form a dielectric film 19.

FIG. 4 shows the spectral reflectance characteristics of the back reflecting mirror thus formed. The incident angle is 30 degrees. Due to the spectral reflection characteristic, the mirror image reflected on the mirror surface looks gold like the back surface reflecting mirrors of Examples 1 and 2.

Example 4 A glass substrate was used as the transparent substrate 10 in FIG.
The inside of the vacuum chamber was evacuated to 4.0 × 10 to ³ Pa or less, a glass substrate having a sufficiently clean and smooth surface was provided, and metal: Cr was vacuum-deposited to a thickness of 0.02599λ ₀ on the back surface side. Then, the metal film 11 is formed.

On the metal film 11 made of Cr, a dielectric material: Yb ₂ O ₃ was vapor-deposited to a thickness of 0.2908λ ₀ in a vacuum chamber in which oxygen gas was introduced at a pressure of 1.7 × 10 ² Pa. To form a dielectric film 13, and a dielectric: TiO ₂ is formed on the dielectric film 1
Under the same oxygen gas pressure as in Example ₃ , vapor deposition was performed to a thickness of 0.28889λ ₀ to form a dielectric film 15.

Then, the inside of the vacuum chamber was evacuated to 4.0 × 10 ³ Pa or less, metal: Al was vapor-deposited to a thickness of 0.06372λ ₀ to form a metal film 17, and a dielectric: SiO was further formed. : 0.10373 λ ₀ to form a dielectric film 19.

FIG. 5 shows the spectral reflectance characteristics of the back reflecting mirror thus formed. The incident angle is 30 degrees. Due to the spectral reflection characteristics, the mirror image on the mirror surface looks pink.

Example 5 A glass substrate was used as the transparent substrate 10 in FIG.
The inside of the vacuum chamber was evacuated to 4.0 × 10 to ³ Pa or less, and a glass substrate having a sufficiently clean and smooth surface was provided, and metal: Cr was vacuumed to a thickness of 0.130λ ₀ on the back surface side. It vapor-deposited and it was set as the metal film 11.

On the metal film 11 made of Cr, the dielectric material: Yb ₂ O ₃ was vapor-deposited to a thickness of 0.32275λ ₀ in a vacuum chamber in which oxygen gas was introduced at a pressure of 1.7 × 10 ² Pa. To form a dielectric film 13, and a dielectric: TiO ₂ is formed on the dielectric film 13 under the same oxygen gas pressure as the dielectric layer 13 and a thickness: 0.32071λ ₀
Was vapor-deposited to form a dielectric film 15.

Next, the inside of the vacuum chamber was evacuated to 4.0 × 10 ³ Pa or less, and metal: Al was vapor-deposited to a thickness of 0.06372λ ₀ to form a metal film 17, and a dielectric: Yb ₂ O ₃ To a thickness of 0.11645λ ₀ to form a dielectric film 19.

FIG. 6 shows the spectral reflectance characteristics of the back reflecting mirror thus formed. The incident angle is 30 degrees. Due to the spectral reflection characteristics, the mirror image reflected on the mirror surface looks violet.

Example 6 A glass substrate was used as the transparent substrate 10 in FIG.
The inside of the vacuum chamber was evacuated to 4.0 × 10 to ³ Pa or less, a glass substrate having a sufficiently clean and smooth surface was provided, and metal: Cr was vacuum-deposited to a thickness of 0.00433λ ₀ on the back surface side. Then, the metal film 11 is formed. A dielectric: Al ₂ O ₃ (refractive index: 1.65) has a thickness of 0.102 on the metal film 11 made of Cr.
The dielectric film 13 was formed by vapor deposition at λ ₀ .

Then, a dielectric: TiO ₂ was formed in a vacuum chamber in which oxygen gas was introduced at a pressure of 1.7 × 10 to ² Pa to a thickness of:
The dielectric film 15 was formed by vapor deposition on 0.12727λ ₀ .

Next, the inside of the vacuum chamber was evacuated to 4.0 × 10 to ³ Pa or less, metal: Al was vapor-deposited to a thickness of 0.06233λ ₀ to form a metal film 17, and a dielectric: SiO was further thickened. Depth: 0.114314 λ ₀ was evaporated to form the dielectric film 19.

FIG. 7 shows the spectral reflectance characteristic of the back reflecting mirror thus formed. The incident angle is 30 degrees. The spectral reflectance is substantially constant in the visible region regardless of the wavelength, and the mirror image reflected on the mirror surface has a silver color.

The back reflecting mirrors of Examples 1 to 6 are all
Since the film having the reflection function is protected from the outside by the transparent substrate in use, it has excellent environment resistance. Further, the back surface reflecting mirrors of Examples 1 to 5 were found to have extremely good anti-glare properties suitable for inner mirrors and outer mirrors of automobiles. In the spectral reflectance diagrams of FIGS. 2 to 7, Rs and Rp are reflectances with respect to the S and P polarized components, respectively, and RH is a reflectance with respect to the average thereof.

[0034]

As described above, according to the present invention, a novel back reflector can be provided. Since the back surface reflecting mirror of the present invention has the above-mentioned structure, it is possible to easily realize a back surface reflecting mirror having a desired spectral reflectance and also have extremely good practical durability.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a configuration of a back reflector of the present invention.

FIG. 2 is a diagram showing the spectral reflectance of the back surface reflecting mirror of Example 1.

FIG. 3 is a diagram showing a spectral reflectance of a back surface reflecting mirror of Example 2.

FIG. 4 is a diagram showing a spectral reflectance regarding a back surface reflecting mirror of Example 3;

FIG. 5 is a diagram showing a spectral reflectance regarding a back surface reflecting mirror of Example 4;

FIG. 6 is a diagram showing a spectral reflectance regarding a back surface reflecting mirror of Example 5;

FIG. 7 is a diagram showing the spectral reflectance of the back surface reflecting mirror of Example 6;

[Explanation of symbols]

10 Substrate 11 Metal Film 13 Dielectric Film 15 Dielectric Film 17 Metal Film 19
Dielectric film

Claims (4)

[Claims] 1. A transparent substrate, on the back surface of which a metal film, a two-layer dielectric film, a metal film, and a dielectric film are laminated in the above-mentioned order, and each of the above films is provided so as to obtain a desired spectral reflectance. And a thickness of the transparent substrate, wherein the front side of the transparent substrate is the light incident side. 2. The backside reflecting mirror according to claim 1, wherein the five layers of thin films formed on the backside of the transparent substrate are made of Cr, Yb ₂ O ₃ , TiO ₂ , Al and SiO sequentially from the transparent substrate side. A back reflector, which is a thin film. 3. The back reflector of claim 1, wherein the five layers of thin films formed on the back surface of the transparent substrate are Cr, Yb ₂ O ₃ , TiO ₂ , Al, and Yb ₂ O _{3 in} order from the transparent substrate side. A backside reflecting mirror characterized by being a thin film made of. 4. The back surface reflecting mirror according to claim 1, wherein the five layers of thin films formed on the back surface of the transparent substrate are made of Cr, Al ₂ O ₃ , TiO ₂ , Al, and SiO in order from the transparent substrate side. A back reflector, which is a thin film.