Multi-layered mirror

• US 4,921,331 A
• Filed: 12/28/1987
• Issued: 05/01/1990
• Est. Priority Date: 12/27/1986
• Status: Expired due to Term

• Current Assignee: Hoya Corporation
• Original Assignee: Hoya Corporation
• Inventors: Nakajima, Yuji
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US07/138,108
• Time in Patent Office: 855 Days
• Field of Search: 350/164, 350/600, 350/166, 350/642, 350/278, 350/276 R, 350/276 SL, 428/333
• US Class Current: 359/584
• CPC Class Codes: A47G 1/02 Mirrors used as equipment hand, pocket, or shaving mirrors A45D42/00; optical viewing means for vehicles B60R1/00
• CPC Class Codes: B60R 1/083 Anti-glare mirrors, e.g. "day-night" mirrors
• CPC Class Codes: C03C 17/3417 all coatings being oxide coatings
• CPC Class Codes: G02B 5/0825 the reflecting layers comprising dielectric materials only
• CPC Class Codes: G02B 5/0833 comprising inorganic materials only
• CPC Class Codes: G02B 5/26 Reflecting filters G02B5/28 takes precedence

Abstract

An improved mirror of a type especially advantageous for use as a rearview mirror for automotive applications. The inventive mirror employs a dielectric multi-layered coating formed on the front side of a glass or plastic transparent substract, the back side of which is provided with a light-absorbing layer. The dielectric coating is composed of three to six dielectric layers laminated one on top of another and having alternately differing refractive indices. At least one of the laminated dielectric layers has an optical thickness of λ₀ /2, where λ₀ is a wavelength of light used as a reference for design purposes and which is in a range of 500 to 580 nm for an incident angle of 0°, with each of the remaining dielectric layers having a thickness of λ₀ /4.

Claims

1. A multi-layered mirror comprising:

a substrate made of one of glass and transparent plastic;

a dielectric multi-layered coating disposed on the front side of said substrate; and

a light-absorbing layer formed on the backside of said substrate,

said dielectric multi-layered coating comprising three to six dielectric layers laminated one on top of another and having alternately differing refractive indices, one of said dielectric layers being one of a single high-refractive index layer and single low-refractive index layer having an optical thickness of λ

₀ /2, where λ

₀ is a wavelength of light used as a reference measurement for design purposes, and each of the remaining layers has an optical thickness of λ

₀ /4.

2. A multi-layered mirror according to claim 1, wherein said three to six layers are selected from L, H, 2L and 2H layers, wherein said H layer is a layer made of a material having a high refractive index of 1.9 to 2.4 and an optical thickness of λ

₀ /4, said 2H layer is made of a material having a high refractive index of 1.9 to 2.4 and an optical thickness of λ

₀ /2, said L layer is made of a material having a low refractive index of 1.3 to 1.8 and an optical thickness of λ

₀ /4, and said 2L layer is made of a material having a low refractive index of 1.3 to 1.8 and an optical thickness of λ

₀ /2.

3. A multi-layered mirror according to claim 2, wherein said dielectric multi-layered coating is composed of three dielectric layers.

4. A multi-layered mirror according to claim 3, wherein said dielectric multi-layered coating comprises:

a plurality of dielectric layers formed on a front side of said substrate in the order from the substrate side, of a 2H layer, an L layer and an H layer.

5. A multi-layered mirror according to claim 3, wherein said dielectric multi-layered coating comprises:

a plurality of dielectric layers formed on a front side of said substrate in the order from the substrate side, of an H layer, an L layer and a 2H layer.

6. A multi-layered mirror according to claim 2, wherein said dielectric multi-layered coating consists of four dielectric layers.

7. A multi-layered mirror according to claim 6, wherein said dielectric multi-layered coating consists of dielectric layers formed on the front side of the transparent substrate in the order from the substrate side, of an L layer, a 2H layer, an L layer and an H layer.

8. A multi-layered mirror according to claim 6, wherein said dielectric multi-layered coating consists of dielectric layers formed on the front side of the transparent substrate in the order from the substrate side, of a 2L layer, a 2H layer, an L layer and an H layer.

9. A multi-layered mirror according to claim 6, wherein said dielectric multi-layered coating consists of dielectric layers formed on the front side of the transparent substrate in the order from the substrate side, of an L layer, an H layer, an L layer and a 2H layer.

10. A multi-layered mirror according to claim 2, wherein said dielectric multi-layered coating consists of five dielectric layers.

11. A multi-layered mirror according to claim 10, wherein said dielectric multi-layered coating consists of dielectric layers formed on the front side of said transparent substrate in the order from the substrate side, of a 2H layer, an L layer, an H layer, an L layer and an H layer.

12. A multi-layered mirror according to claim 10, wherein said dielectric multi-layered coating consists of dielectric layers formed on the front side of said transparent substrate in the order from the substrate side, of an H layer, a 2L layer, an H layer, an L layer and an H layer.

13. A multi-layered mirror according to claim 10, wherein said dielectric multi-layered coating consists of dielectric layers formed on the front side of said transparent substrate in the order from the substrate side, of an H layer, an L layer, an H layer, an L layer and a 2H layer.

14. A multi-layered mirror according to any one of claims 4, 5 or 7-13, wherein said 2H layer comprises a pair of H layers.

15. A multi-layered mirror according to any one of claims 7 to 9 and 11 to 13, wherein said 2L layer comprises a pair of L layers.

16. A multi-layered mirror comprising:

a substrate made of one of glass and transparent plastic;

a dielectric multi-layered coating disposed on the front side of said substrate; and

a light-absorbing layer formed on the backside of said substrate,

said dielectric multi-layered coating comprising three to six dielectric layers laminated one on top of another and having alternately differing refractive indices, one of said dielectric layers being a single high-refractive index layer and another layer being a single low-refractive index layer, said high-refractive index layer and said low-refractive index layer both having an optical thickness of λ

₀ /2, where λ

₀ is a wavelength of light used as a reference measurement for design purposes, and each of the remaining layers has an optical thickness of λ

₀ /4.