FOUR LAYER ANTI-REFLECTION COATING

• US 3,781,090 A
• Filed: 11/06/1972
• Issued: 12/25/1973
• Est. Priority Date: 11/06/1972
• Status: Expired due to Term

• Current Assignee: Haruki Sumita
• Original Assignee: Haruki Sumita
• Inventors: Sumita, Haruki
• Primary Examiner(s): Wibert, Ronald L.
• Application Number:
  US05/304,140
• Time in Patent Office: 414 Days
• Field of Search: 350/164,166 117/33.3
• US Class Current: 359/588
• CPC Class Codes: C03C 17/3411 with at least two coatings of inorganic materials C03C17/36, C03C17/42 take precedence
• CPC Class Codes: C03C 17/3417 all coatings being oxide coatings
• CPC Class Codes: C03C 17/3429 at least one of the coatings being a non-oxide coating
• CPC Class Codes: C03C 17/3452 comprising a fluoride
• CPC Class Codes: C03C 17/347 comprising a sulfide or oxysulfide
• CPC Class Codes: C03C 17/3494 comprising other salts, e.g. sulfate, phosphate
• CPC Class Codes: G02B 1/115 Multilayers

Abstract

A multi-layered anti-reflection coating for use with a glass substrate includes four layers of material, the first layer furthest from the substrate having an optical thickness of a preselected design wavelength, lambda o in the range of 0.260 lambda o > Nld1 > 0.230 lambda o and an index of refraction in the range of 1.35 to 1.62. The second layer having an optical thickness in the range of 0.520 lambda o > N2d2 > 0.400 lambda o and an index of refraction in the range of 2.00 to 2.30. The optical thickness of one of the third and fourth layers is in the range of 0.500 Tau o > N d > 0.250 lambda o while the optical thickness of the other layer of the third and fourth layers is in the range of 0.250 lambda o > N d > 0.060 lambda o. The third layer has an index of refraction in the range of 1.56 to 1.72 and the fourth layer closest to the substrate has an index or refraction in the range of 1.35 to 1.62. The optical thicknesses of the layers can be varied to compensate for any variations from the theoretical design index of refractions.

Claims

2. A multi-layered anti-reflection coating as in claim 1 wherein the substrate has an index of refraction of Ns and the indices of refraction are related as follows, N1 equals N4 and N2 is greater than N3 and Ns.

3. A multi-layered anti-reflection coating as in claim 1 wherein the first and fourth coating layers are selected from the group consisting of MgF2, SiO2, ThF4, LaF2, Na3(AlF4), Al2O3, and CeF3.

4. A multi-layered anti-reflection coating as in claim 1 wherein the second coating layer is selected from the group consisting of CeO2, ZrO2, TiO2, Ta2O5, ZnS and ThO2.

5. A multi-layered anti-reflection coating as in claim 1 wherein the third coating layer is selected from the group consisting of Al2O3, MgO, CeF3, LaF3, NdF3, BeO, InO2, ThOH2 and a mixture of MgO and Al2O3.

6. A multi-layered anti-reflection coating as in claim 1 wherein the first and fourth coating layer are selected from the group consisting of MgF2, SiO2, ThF4, LaF2, Na3(AlF4), Al2O3, and CeF3;

the second coating layer is selected from the group consisting of CeO2, ZrO2, TiO2, Ta2O5, ZnS and ThO2, and the third coating layer is selected from the group consisting of Al2O3, MgO, CeF3, LaF3, NdF3, BeO, InO2, ThOH2 and a mixture of MgO and Al2O3.

7. A multi-layered anti-reflection coating as in claim 6 wherein the substrate is a glass having an index of refraction Ns in the range of 1.42 to 1.72.

8. A multi-layered anti-reflection coating for use with a substrate to reduce reflection of energy comprising four layers of material, each layer having an optical thickness of a preselected design wavelength lambda o as follows:

0.260 lambda o >

N1d1 >

0.230 lambda o 0.520 lambda o >

N2d2 >

0.400 lambda o 0.500 lambda o >

N3d3 >

0.060 lambda o 0.500 lambda o >

N4d4 >

0.060 lambda o wherein N refers to the index of refraction and d refers to the physical thickness of the layer, the subnumbers corresponding to the layers with N1d1 being the layer furthest from the substrate, the optical thickness of the layers being adjustable to compensate for variations from any design N whereby the design reflectance is maintained.

9. A multi-layered anti-reflection coating as in claim 8 wherein the substrate has an index of refraction of Ns and the indices of refraction are related as follows, N1 equals N4 and N2 is greater than N3 and Ns.

10. A multi-layered anti-reflection coating as in claim 8 wherein the substrate has an index of refraction of Ns and the indices of refraction are related as follows:

N1 N4 <

Ns >

N3 <

N2.

11. A multi-layered anti-reflection coating as in claim 8 wherein the first layer furtherest from the substrate and the fourth layer adjacent the substrate have an index of refraction in the range of 1.35 to 1.62, the second layer has an index of refraction in the range of 2.00 to 2.30 and the third layer has an index of refraction in the range of 1.56 to 1.72.

12. A multi-layered anti-reflection coating as in claim 8 wherein the optical thickness of the third and fourth layers are as follows:

0.500 lambda o >

N3d3 >

0.250 lambda o 0.250 lambda o >

N4d4 >

0.060 lambda o.

13. A multi-layered anti-reflection coating as in claim 8 wherein the optical thickness of the third and fourth layers are as follows:

0.250 lambda o >

N3d3 >

0.060 lambda o 0.500 lambda o >

N4d4 >

0.250 lambda o.

14. A multi-layered anti-reflection coating as in claim 8 wherein the optical thickness of the third and fourth layers are as follows:

0.360 lambda o >

N3d3 >

0.150 lambda o 0.470 lambda o >

N4d4 >

0.060 lambda o.

15. multi-layered anti-reflection coating as in claim 8 wherein the first and fourth layers are magnesium fluoride.

16. A multi-layered anti-reflection coating as in claim 8 wherein the first and fourth coating layers are selected from the group consisting of MgF2, SiO2, ThF4, LaF2, Na3(AlF4), Al2O3, and CeF3.

17. A multi-layered anti-reflection coating as in claim 8 wherein the second coating layer is selected from the group consisting of CeO2, ZrO2, TiO2, Ta2O5, ZnS and ThO2.

18. A multi-layered anti-reflection coating as in claim 8 wherein the third coating layer is selected from the group consisting of Al2O3, MgO, CeF3, LaF3, NdF3, BeO, InO2, ThOH2 and a mixture of MgO and Al2O3.

19. A multi-layered anti-reflection coating as in claim 8 wherein the first and fourth coating layers are selected from the group consisting of MgF2, SiO2, ThF4, LaF2, Na3(AlF4), Al2O3, and CeF3;

the second coating layer is selected from the group consisting of CeO2, ZrO2, TiO2, Ta2O5, ZnS and ThO2, and the third coating layer is selected from the group consisting of Al2O3, MgO, CeF3, LaF3, NdF3, BeO, InO2, ThOH2 and a mixture of MgO and Al2O3.

20. A multi-layered anti-reflection coating as in claim 8 wherein the substrate is a glass having an index of refraction Ns in the range of 1.42 to 1.72.