Antireflection coating

• US 6,280,848 B1
• Filed: 10/06/1999
• Issued: 08/28/2001
• Est. Priority Date: 10/06/1998
• Status: Expired due to Term

• Current Assignee: Minolta Corporation Limited (Konica Minolta Inc.)
• Original Assignee: Minolta Corporation Limited (Konica Minolta Inc.)
• Inventors: Okumura, Masaru, Tani, Hakuzo
• Primary Examiner(s): Jones, Deborah
• Assistant Examiner(s): Miranda, Lymarie
• Application Number:
  US09/413,736
• Time in Patent Office: 692 Days
• Field of Search: 359/359, 359/360, 359/580, 359/588, 359/589, 428/212, 428/216, 428/336, 428/343, 428/344, 428/426, 428/432, 428/697, 428/701, 428/702
• US Class Current: 428/426
• CPC Class Codes: C03C 17/3417 all coatings being oxide coatings
• CPC Class Codes: C03C 17/3452 comprising a fluoride
• CPC Class Codes: G02B 1/115 Multilayers
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/24975 No layer or component greater than 5 mils thick
• CPC Class Codes: Y10T 428/265 1 mil or less
• CPC Class Codes: Y10T 428/28 Web or sheet containing structurally defined element or component and having an adhesive outermost layer
• CPC Class Codes: Y10T 428/2804 Next to metal

Abstract

Four and five-layer antireflection coatings are disclosed suitable for use on optical parts such as lenses and prisms in which layers of thin films are formed on the surfaces of the optical parts by a process such as vacuum evaporation. By selecting the materials for the layers based on the refractive index of the materials, as well as based on the refractive index of the substrate, reflectance of the s-polarized component of incident light can be reduced over a large range of incident angle up to a range of approximately 45 degrees.

Claims

1. An antireflection coating for a substrate comprising:

a first layer for placement on said substrate either directly or through another layer, said first layer having a thickness d1 and a refractive index n1;

a second layer in contact with said first layer, said second layer having a thickness d2 and a refractive index n2;

a third layer in contact with said second layer, said third layer having a thickness d3 and a refractive index n3; and

a fourth layer in contact with said third layer, said fourth layer having a thickness d4 and a refractive index n4;

wherein, for a dominant wavelength λ

₀, the following relationships are satisfied;

n3>

n2>

n1>

n4;

0<

(n1*d1)≦

0.75*λ

₀;

0.20*λ

₀≦

(n2*d2)≦

0.43*λ

₀;

0.07*λ

₀≦

(n3*d3)≦

1.10*λ

₀; and

0.28*λ

₀≦

(n4*d4)≦

0.35*λ

₀.

2. An antireflection coating in accordance with claim 1, wherein, for a substrate having a refractive index ns, each of the following conditions is satisfied:

1.50≦

ns≦

1.85;

1.35≦

n1≦

1.48;

1.47≦

n2≦

1.80;

2.30≦

n3≦

2.60; and

1.35≦

n4≦

1.48.

3. An antireflection coating in accordance with claim 2, wherein said first layer comprises MgF₂.

4. An antireflection coating in accordance with claim 1, wherein said first layer comprises SiO₂;

and

wherein the following condition is satisfied;

0.15*λ

₀≦

(n1*d1)≦

0.75*λ

₀.

5. An antireflection coating in accordance with claim 1, wherein:

said first layer comprises at least one of MgF₂, Na₅Al₃F₁₄, and SiO₂;

said second layer comprises at least one of SiO₂, YF₃, Al₂O₃, Y₂O₃, and MgO;

said third layer comprises at least one of TiO₂, and ZnS; and

said fourth layer comprises at least one of MgF₂, Na₅Al₃F₁₄, and SiO₂.

6. An antireflection coating in accordance with claim 1, wherein:

adjacent layers of said first, second, third and fourth layers are comprised of different materials; and

wherein said first, second, third and fourth layers are configured so that, when said coating is in contact with said substrate, for light incident on said coating, from a side opposing said substrate, at an angle of incidence of approximately 45 degrees, an amount of s-polarized light reflected therefrom, as a percentage of an amount of s-polarized light incident thereon, is lower than an amount of p-polarized light reflected therefrom, as a percentage of an amount of p-polarized light incident thereon.

7. An antireflection coating for a substrate comprising:

a first layer for placement on said substrate either directly or through another layer, said first layer having a thickness d1 and a refractive index n1;

a second layer in contact with said first layer, said second layer having a thickness d2 and a refractive index n2;

a third layer in contact with said second layer, said third layer having a thickness d3 and a refractive index n3;

a fourth layer in contact with said third layer, said fourth layer having a thickness d4 and a refractive index n4; and

a fifth layer in contact with said fourth layer, said fifth layer having a thickness d5 and a refractive index n5

wherein, for a dominant wavelength λ

₀, the following relationships are satisfied;

n2 or n3≦

1.56;

n4≧

n2>

n1≧

n5;

n2>

n3;

0<

(n1*d1)≦

0.06*λ

₀;

0.03*λ

₀≦

(n2*d2)≦

0.15*λ

₀;

0.02*λ

₀≦

(n3*d3)≦

0.19*λ

₀;

0.09*λ

₀≦

(n4*d4)≦

1.30*λ

₀; and

0.24*λ

₀≦

(n5*d5)≦

0.36*λ

₀.

8. An antireflection coating in accordance with claim 7, wherein, for a substrate having a refractive index ns, each of the following conditions is satisfied:

1.50≦

ns≦

1.85;

1.35≦

n1≦

1.80;

2.00≦

n2≦

2.60;

1.35≦

n3≦

1.80;

2.00≦

n4≦

2.60; and

1.38≦

n5≦

1.48.

10. An antireflection coating in accordance with claim 7, wherein:

said first layer comprises at least one of MgF₂, Na₅Al₃F₁₄, SiO₂, Al₂O₃, and MgO;

said second layer comprises at least one of TiO₂, Zn₂, ZrTiO₄, and Ta₂O₅;

said third layer comprises at least one of MgF₂, SiO₂, Al₂O₃, and MgO;

said fourth layer comprises at least one of TiO₂, ZnS, ZrTiO₄, and Ta₂O₅; and

said fifth layer comprises at least one of MgF₂, and SiO₂.

11. An antireflection coating in accordance with claim 7, wherein:

adjacent layers of said first, second, third, fourth and fifth layers are comprised of different materials; and

wherein said first, second, third, fourth and fifth layers are configured so that, when said coating is in contact with said substrate, for light incident on said coating, from a side opposing said substrate, at an angle of incidence of approximately 45 degrees, an amount of s-polarized light reflected therefrom, as a percentage of an amount of s-polarized light incident thereon, is lower than an amount of p-polarized light reflected therefrom, as a percentage of an amount of p-polarized light incident thereon.

9. An antireflection coating for a substrate comprising:

a first layer for placement on said substrate either directly or through another layer, said first layer having a thickness d1 and a refractive index n1;

a second layer in contact with said first layer, said second layer having a thickness d2 and a refractive index n2;

a third layer in contact with said second layer, said third layer having a thickness d3 and a refractive index n3;

a fourth layer in contact with said third layer, said fourth layer having a thickness d4 and a refractive index n4;

a fifth layer in contact with said fourth layer, said fifth layer having a thickness d5 and a refractive index n5

wherein, for a dominant wavelength λ

₀, the following relationships are satisfied;

n2 or n3≦

1.56;

n4≧

n2>

n1≧

n5;

n2>

n3;

1.50≦

ns≦

1.85;

1.35≦

n1≦

1.80;

2.00≦

n2≦

2.60;

1.35≦

n3≦

1.80;

2.00≦

n4≦

2.60; and

1.38≦

n5≦

1.48

0.20≦

(n1*d1)≦

1.25*λ

₀;

0.03*λ

₀≦

(n2*d2)≦

1.15*λ

₀;

0.02*λ

₀≦

(n3*d3)≦

1.19*λ

₀;

0.09*λ

₀≦

(n4*d4)≦

1.30*λ

₀; and

0.24*λ

₀≦

(n5*d5)≦

0.36*λ

₀.

12. An antireflection coating for a substrate comprising:

a laminate of at least four layers, a first of said four layers for contact with said substrate either directly or through another layer, adjacent layers of said at least four layers being comprised of different materials;

wherein said at least four layers are configured so that, when said laminate is in contact with said substrate, either directly or through another layer, for light incident on said laminate, from a side opposing said substrate, at an angle of incidence of approximately 45 degrees, an amount of s-polarized light reflected therefrom, as a percentage of an amount of s-polarized light incident thereon, is lower than an amount of p-polarized light reflected therefrom, as a percentage of an amount of p-polarized light incident thereon.

13. A process for forming an anti-reflection coating on an article, comprising the steps of:

disposing an anti-reflection coating including a plurality of layers on said article, said disposing step including the steps of;

forming a first layer on said article either directly or through another layer;

forming a second layer on said first layer;

forming a third layer on said second layer; and

forming a fourth layer on said third layer, adjacent layers of said first, second, third and fourth layers being composed of different materials;

wherein said plurality of layers are configured so that, for light incident on said anti-reflection coating, from a side op-posing said article, at an angle of incidence of approximately 45 degrees, an amount of s-polarized light reflected therefrom, as a percentage of an amount of s-polarized light incident thereon, is lower than an amount of p-polarized light reflected therefrom, as a percentage of an amount of p-polarized light incident thereon.

14. An article comprising:

a substrate;

a first layer arranged on said substrate either directly or through another layer, said first layer having a thickness d1 and a refractive index n1;

a second layer arranged on said first layer, said second layer having a thickness d2 and a refractive index n2;

a third layer arranged on said second layer, said third layer having a thickness d3 and a refractive index n3; and

a fourth layer arranged on said third layer, said fourth layer having a thickness d4 and a refractive index n4;

wherein, for a dominant wavelength λ

₀, the following relationships are satisfied;

n3>

n2>

n1≧

n4;

0<

(n1*d1)≦

0.75*λ

₀;

0.20*λ

₀≦

(n2*d2)≦

0.43*λ

₀;

0.07*λ

₀≦

(n3*d3)≦

1.10*λ

₀; and

0.28*λ

₀≦

(n4*d4)≦

0.35*λ

₀.