Anti-reflection coating of optical part made of synthetic resin

• US 4,921,760 A
• Filed: 09/25/1987
• Issued: 05/01/1990
• Est. Priority Date: 09/26/1986
• Status: Expired due to Fees

• Current Assignee: Minolta Camera Kabushiki Kaisha
• Original Assignee: Minolta Camera Kabushiki Kaisha
• Inventors: Okumura, Masaru, Tani, Hakuzo
• Primary Examiner(s): Swisher, Nancy A. B.
• Application Number:
  US07/100,953
• Time in Patent Office: 949 Days
• Field of Search: 428/446, 428/701, 428/698, 428/699, 428/432, 428/428, 428/429, 428/448
• US Class Current: 428/446
• CPC Class Codes: G02B 1/115 Multilayers

Abstract

An anti-reflection coating with n layers on an optical part substrate made of synthetic resin wherein n is 3, 4, or 5, and the first layer at the air side comprises silicon dioxide (SiO₂), and the n-th layer on the surface of the synthetic resin comprises ceric oxide (CeO₂) is excellent in reflection reducing effect and does not result in the age-based change of the refractive index. And that the very good adhesion of the reflection reducing coating with the substrate results in hardness of layer stripping.

Further an anti-reflection coating of the invention has reflection reducing effect in the near-infrared region.

Claims

1. An anti-reflection coating of three layers for a synthetic resin substrate having a refractive index in the approximate range of 1.49 to 1.58, comprising:

a first layer, at the air side, of silicon dioxide;

a second layer having an index of refraction of n₂ ;

a third layer, adjacent the substrate, of ceric oxide, having an index of refraction of n₃, and

the second layer and the third layer satisfying the following conditions, respectively;

1.50≦

n₂ ≦

1.62,

0.04λ

₀ ≦

n₂ d₂ ≦

0.15λ

₀,

1.92≦

n₃ ≦

2.10,

0.02λ

₀ ≦

n₃ d₃ ≦

0.50λ

₀,

wherein n₂ d₂ and n₃ d₃ are the optical thickness of the second layer and the third layer, respectively, and λ

₀ is the dominant design wavelength.

2. An anti-reflection coating of claim 1, which further satisfies the below conditions:

1.45≦

n₁ ≦

1.47,

1.92≦

n₃ ≦

2.10,

0.20λ

ο

≦

n₁ d₁ ≦

0.32λ

ο

,

0.02λ

ο

≦

n₃ d₃ ≦

0.50λ

ο

,

wherein

n₁ ;

refractive index of the first layer,

n₃ ;

refractive index of the third layer,

n₁ d₁ ;

optical thickness of the first layer,

n₃ d₃ ;

optical thickness of the third layer,

λ

₀ ;

design dominant wavelength.

3. An anti-reflection coating of four layers for a synthetic resin substrate, comprising:

a first layer, at the air side, of silicon dioxide;

a second layer comprising a material selected from the group consisting of zirconium oxide, titanium dioxide, hafnium dioxide, ceric oxide, tantalum oxide, and a mixture of zirconium oxide and titanium oxide;

a third layer selected from one of aluminum oxide and silicon dioxide, and

a fourth layer, on the surface of the synthetic resin substrate, comprising ceric oxide having an index of refraction of n₄, and the fourth layer satisfying the following equations;

1.92≦

n₄ ≦

2.10,

0<

n₄ d₄ ≦

0.25λ

₀

wherein n₄ d₄ is an optical thickness of the fourth layer and λ

₀ is a dominant design wavelength.

4. An anti-reflection coating of claim 3, which further satisfies the below conditions:

1.45≦

n₁ ≦

1.47,

1.92≦

n₂ ≦

2.10,

1.45≦

n₃ ≦

1.62,

1.92≦

n₄ ≦

2.10,

0.25λ

ο

≦

n₁ d₁ ≦

0.30λ

ο

,

0.25λ

ο

≦

n₂ d₂ ≦

0.60λ

ο

,

0<

n₃ d₃ ≦

0.25λ

ο

,

0<

n₄ d₄ ≦

0.25λ

ο

,

wherein

n₁ ;

refractive index of the first layer,

n₂ ;

refractive index of the second layer,

n₃ ;

refractive index of the third layer,

n₄ ;

refractive index of the fourth layer,

n₁ d₁ ;

optical thickness of the first layer,

n₂ d₂ ;

optical thickness of the second layer,

n₃ d₃ ;

optical thickness of the third layer,

n₄ d₄ ;

optical thickness of the fourth layer,

λ

₀ ;

design dominant wavelength.

5. An anti-reflection coating of five layers for a synthetic resin substrate, comprising:

a first layer, at the air side, of silicon dioxide;

a second layer of aluminum oxide;

a third layer of ceric oxide;

a fourth layer of aluminum oxide, and

a fifth layer, on the surface of the synthetic resin substrate, of ceric oxide having an index of refraction of n₅, and the fifth layer satisfying the following equations;

1.92≦

n₅ ≦

2.10,

0.05λ

₀ ≦

n₅ d₅ ≦

0.20λ

₀,

wherein n₅ d₅ is an optical thickness of the fifth layer and λ

₀ is a dominant design wavelength.