Multi-layered surface reflecting mirror

• US 5,007,710 A
• Filed: 10/23/1989
• Issued: 04/16/1991
• Est. Priority Date: 10/31/1988
• Status: Expired due to Fees

• Current Assignee: Hoya Corporation
• Original Assignee: Hoya Corporation
• Inventors: Nakajima, Yuji, Mochizuki, Masashi
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): PARSONS, DAVID
• Application Number:
  US07/425,119
• Time in Patent Office: 540 Days
• Field of Search: 350/164, 350/166, 350/163, 350/600, 350/642, 350/278, 350/311, 428/912.2
• US Class Current: 359/589
• CPC Class Codes: G02B 5/0833 comprising inorganic materials only
• CPC Class Codes: G02B 5/0858 the reflecting layers comprising a single metallic layer with one or more dielectric layers

Abstract

A multi-layered surface reflecting mirror comprises a substrate, a metal or semiconductor film formed on one side of the substrate and a dielectric multi-layered film formed on the metal or semiconductor film. The dielectric multi-layered film consisting of a low refractive index material layer having an optical thickness of 0.05λo (λo/20)-0.4λo (2/5λo) (λo is the wavelength of a light used as the reference measurement for design purposes) and a high refractive index material layer having an optical thickness of λo/2. The low refractive index material layer existing closer to the metal or semiconductor film relative to the high refractive index material layer, and the high refractive index material layer existing closer to the atmosphere relative to the low refractive index material layer. The multi-layered surface reflecting mirror is used mainly as a rearview mirror for automobiles, a mirror with a convex surface that warns drivers against hazards on the road, an ornamental mirror, etc.

Claims

1. A multi-layered surface reflecting mirror comprising a substrate, a metal or semiconductor film formed on one side of the substrate and a dielectric multi-layered film formed on the metal or semiconductor film, said dielectric multi-layered film consisting of a low refractive index material layer having an optical thickness in the range of 0.05 λ

o (λ

o/20)-0.4 λ

o (2/5 λ

o), where λ

o is the wavelength of a light used as the reference measurement for design purposes, and a high refractive index material layer having an optical thickness of λ

o/2, said low refractive index material layer being closer to the metal or semiconductor film relative to said high refractive index material layer, and said high refractive index material layer being closer to the atmosphere relative to said low refractive index material layer.

2. A multi-layered surface reflecting mirror according to claim 1, wherein the optical thickness of the low refractive index material layer is λ

o/8.

3. A multi-layered surface reflecting mirror according to claim 1, wherein the high refractive index material layer having an optical thickness of λ

o/2 is constituted by a high refractive index material layer having an optical thickness of λ

o/4 and another high refractive index material layer having an optical thickness of λ

o/4, said two high refractive index material layers being adjacent to each other.

4. A multi-layered surface reflecting mirror according to claim 1, wherein the low refractive index material layer is made of a low refractive index material having a refractive index in the range of 1.3-1.5.

5. A multi-layered surface reflecting mirror according to claim 4, wherein the low refractive index material is silicon oxide a metal fluoride or both.

6. A multi-layered surface reflecting mirror according to claim 1, wherein the high refractive index material layer is made of a high refractive index material having a refractive index in the range of 1.5-2.4.

7. A multi-layered surface reflecting mirror according to claim 6, wherein the high refractive index material is at least one member selected from the group consisting of a silicon or metal oxide, a metal fluoride and a metal sulfide.

8. A multi-layered surface reflecting mirror according to claim 1, wherein the substrate is made of glass or plastic.

9. A multi-layered surface reflecting mirror according to claim 1, wherein the metal or semiconductor film is made of at least one member selected from the group consisting of Cr, Ni, Al, Ag, Co, Fe, Si, Ge and an alloy containing at least one of the above mentioned metals, semiconductors or both.

10. A multi-layered surface reflecting mirror according to claim 1, wherein the optical thickness of the low refractive index material layer is λ

o/4.