Anti-reflection film and method for manufacturing anti-reflection film

Patent metadata

Field	Value
Publication number	US-9709704-B2
Application number	US-201213647510-A
Country	US
Kind code	B2
Filing date	Oct 9, 2012
Priority date	Oct 12, 2011
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

An object of the present invention is to provide an anti-reflection film excellent in high-temperature and high-humidity environment resistance and scratch resistance in addition to improved anti-reflection performance of a concave-convex nanostructure. To achieve the object, an anti-reflection film 10 comprises: a base layer 11 as a first optical thin film that is provided on an optical surface 21 a of an optical element 21 ; a concave-convex nanostructure layer that is provided on a surface of the base layer 11 and is composed of a concave-convex nanostructure 12 formed so as to have a pitch width p between the convex parts 12 b of shorter than an incident light wavelength; and a cover layer 13 as a second optical thin film that covers peaks of the convex part 12 b with a void 14 being provided between the cover layer 13 and concave part 12 a constituting the concave-convex nanostructure 12.

First claim

What is claimed is:

1. An anti-reflection film to be provided on an optical surface of an optical element to reduce reflection of incident light, comprising:
a base layer as a first optical thin film that is to be provided on the optical surface;
a concave-convex nanostructure layer that is provided on a surface of the base layer and is composed of a concave-convex nanostructure formed so as to have pitch width between the convex parts of shorter than an incident light wavelength;
wherein the concave-convex nanostructure comprises a plurality of convex portions;
wherein the convex portions of the concave-convex nanostructure are tapered, wherein a peak of each convex portion is narrower than a base end of each convex portion; and
wherein the base ends are provided closer to the base layer than the peaks; and
the anti-reflection film further comprising a cover layer as a second optical thin film that covers the peaks of the convex part constituting the concave-convex nanostructure with a void being provided between the cover layer and concave part of the concave-convex nanostructure;
wherein the cover layer contacts the concave-convex nanostructure at a plurality of the peaks;
wherein the cover layer is a film including pores, wherein the pores are dispersed in the cover layer;
wherein the cover layer is composed of an inorganic light-transmitting material; and
wherein an optical thickness (n c ×d c ) of the cover layer satisfies a following expression (1):
[Expression 1]
0.05×(λ 0 /4)< n c ×d c <0.75×(λ 0 /4)  (1)

where,
n c : refractive index of the cover layer
d c : physical thickness of the cover layer
λ 0 : reference wavelength in the range 400 nm≦λ 0 ≦700 nm.

2. The anti-reflection film according to claim 1 , wherein the refractive index n c of the cover layer at a reference wavelength λ 0 in the range 400 nm≦λ 0 ≦700 nm is 1.15 to 1.8 inclusive.

3. The anti-reflection film according to claim 1 , wherein the refractive index of the cover layer at the reference wavelength λ 0 in the range 400 nm≦λ 0 ≦700 nm is lower than a refractive index of the light-transmitting material itself.

4. The anti-reflection film according to claim 1 , wherein the base layer is an optical thin film composed of a single layer, and a value of a refractive index n b of the base layer is between a value of a refractive index of the optical element and a value of a refractive index of a material constituting the concave-convex nanostructure.

5. The anti-reflection film according to claim 4 , wherein an optical thickness (n b ×d b ) of the base layer satisfies a following expression (2):
[Expression 2]
0.1×(λ 0 /4)< n b ×d b <1.5×(λ 0 /4)  (2)

where,
n b : refractive index of the base layer
d b : physical thickness of the base layer
λ 0 : reference wavelength in the range 400 nm 700 nm.

6. The anti-reflection film according to claim 1 , wherein the base layer is an optical thin film composed of at least two layers obtained by alternately stacking a layer having a refractive index of 2.0 or more at the reference wavelength λ 0 in the range 400 nm≦λ 0 ≦700 nm and a layer having a refractive index of 1.38 to 1.7 at the reference wavelength λ 0 .

7. The anti-reflection film according to claim 1 , wherein the concave-convex nanostructure is made of a resin material, and the pitch width is 200 nm or less.

8. The anti-reflection film according to claim 1 , wherein the anti-reflection film is provided on the optical element which has a refractive index at d-line of 1.4 to 2.1 inclusive.

9. The anti-reflection film according to claim 1 , wherein the cover layer is formed by depositing a light-transmitting material on peaks of the convex part constituting the concave-convex nanostructure by physical vapor deposition method while rotating the optical element which is held by dome-like or planet-like substrate holder.

10. A method for manufacturing an anti-reflection film according to claim 1 , comprising the steps of:
formation of the base layer on an optical surface of an optical element;
formation of the concave-convex nanostructure on a surface of the base layer; and
formation of the cover layer by depositing a light-transmitting material on peaks of the convex part constituting the concave-convex nanostructure by physical vapor deposition method while rotating the optical element held by dome-like or planet-like substrate holder in which the base layer and the concave-convex nanostructure are formed.

11. The anti-reflection film according to claim 1 , wherein a refractive index of the concave-convex nanostructure layer increases along a depth direction of the concave-convex nanostructure from the peaks of the convex parts toward the concave parts.

12. The anti-reflection film according to claim 1 , wherein the base layer is an optical thin film composed of more than one layer, wherein an optical thickness (n b ×d b ) of the base layer satisfies a following expression (2):
[Expression 2]
0.1×(λ 0 /4)< n b ×d b <1.5×(λ 0 /4)  (2)

where,
n b : effective refractive index of the base layer
d b : physical thickness of the base layer
λ 0 : reference wavelength in the range 400 nm≦λ 0 ≦700 nm.

13. The optical element as in claim 1 , wherein:
the anti-reflection film is situated on the optical surface;
wherein the base layer of the anti-reflection film is an optical thin film composed of more than one layer; and
wherein the base layer has a value of an effective refractive index n b between a value of a refractive Index of the optical element and a value of a refractive index of a material constituting the concave-convex nanostructure of the anti-reflection film at the reference wavelength λ 0 in a range 400 nm≦λ 0 ≦700 nm.

14. The anti-reflection film of claim 1 , wherein the cover layer is a physical vapor deposition film.

Assignees

• Tamron Kk

Inventors

• Miyahara Masaaki
• Shibuya Minoru
• Kunisada Terufusa

Classifications

• G02B1/11 Primary

  Anti-reflection coatings · CPC title

• G02B1/118 Primary

  having sub-optical wavelength surface structures designed to provide an enhanced transmittance, e.g. moth-eye structures · CPC title

• G02B1/115

  Multilayers · CPC title