Anti-reflection coating and optical member comprising same

Patent metadata

Field	Value
Publication number	US-9581733-B2
Application number	US-201414453193-A
Country	US
Kind code	B2
Filing date	Aug 6, 2014
Priority date	Aug 23, 2013
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

An anti-reflection coating having an three-layer structure comprising first to third layers formed in this order on a substrate, the substrate having a refractive index of 1.6-1.9, the first layer having a refractive index of 1.37-1.57, the second layer having a refractive index of 1.75-2.5, and the third layer having a refractive index of 1.18-1.32, to light in a wavelength range of 550 nm; the third layer being formed by silica aerogel; and the first and second layers containing no Al 2 O 3 .

First claim

What is claimed is:

1. An anti-reflection coating having:
a four-layer structure comprising first to fourth layers formed in this order on a substrate;
said substrate having a refractive index of 1.6-1.9, said first layer having a refractive index of 1.37-1.57, said second layer having a refractive index of 1.75-2.5, said third layer having a refractive index of 1.37-1.57, and said fourth layer having a refractive index of 1.18-1.32, to light in a wavelength range of 550 nm;
said fourth layer being formed by silica aerogel; and
said first to third layers containing no Al 2 O 3 .

2. The anti-reflection coating according to claim 1 ;
wherein said first to third layers are formed by a dry process;
wherein said fourth layer is formed by a wet process; and
wherein said wet process includes a sol-gel method.

3. An optical member comprising:
the anti-reflection coating recited in claim 1 on a lens substrate, whose effective diameter D and radius R of curvature meet the condition of 0.1≦D/R≦2.

4. The optical member according to claim 3 ;
wherein said first to third layers are formed by a dry process;
wherein said fourth layer is formed by a wet process; and
wherein said wet process includes a sol-gel method.

5. The optical member according to claim 3 ;
wherein said lens substrate has a maximum inclination angle of 30-65°.

6. The optical member according to claim 3 ;
wherein an optical thickness D1(θ t ) of the first layer, an optical thickness D2(θ t ) of the second layer, and an optical thickness D3(θ t ) of the third layer at an arbitrary inclination angle θ t of said lens substrate are expressed by the following formulae (1) to (3):
D 1(θ t )= D 1 0 ×(cos θ t ) α   (1);

D 2(θ t )= D 2 0 ×(cos θ t ) β   (2); and

D 3(θ t )= D 3 0 ×(cos θ t ) γ   (3);

wherein:
D1 0 , D2 0 , and D3 0 respectively represent optical thicknesses of said first to third layers at a center of said lens substrate; and
α, β and γ are numbers independently in a range of 0-1.

7. The optical member according to claim 3 ;
wherein a thickness of said fourth layer is constant regardless of the inclination angle of said lens substrate, or larger in a peripheral portion of the lens substrate than at a center of the lens substrate.

Assignees

• Ricoh Imaging Co Ltd

Inventors

• Tamada Takaaki
• Sasaki Naohito
• Nakayama Hiroyuki

Classifications

• G02B1/11

  Anti-reflection coatings · CPC title

• G02B5/286

  having four or fewer layers, e.g. for achieving a colour effect · CPC title

• G02B1/115 Primary

  Multilayers · CPC title