Hybrid gradient-interference hardcoatings

Patent metadata

Field	Value
Publication number	US-11520082-B2
Application number	US-201816643368-A
Country	US
Kind code	B2
Filing date	Aug 31, 2018
Priority date	Aug 31, 2017
Publication date	Dec 6, 2022
Grant date	Dec 6, 2022

Abstract

Durable and scratch resistant articles including an optical coating with a gradient. An article comprises: a substrate; and an optical coating having a thickness and a first gradient portion. A refractive index of the optical coating varies along a thickness of the optical coating. The difference between the maximum refractive index of the first gradient portion and the minimum refractive index of the first gradient portion is 0.1 or greater. The absolute value of the slope of the refractive index of the first gradient portion is 0.1/nm or less everywhere along the thickness of the first gradient portion. The article exhibits an average single-surface reflectance of 15% to 98% over the wavelength range 400 nm-700 nm. The article also exhibits a maximum hardness in the range from about 10 GPa to about 30 GPa.

First claim

The invention claimed is:

1. An article comprising:
a substrate comprising a first major surface; and
an optical coating disposed over the first major surface, the optical coating comprising:
a second major surface opposite the first major surface,
a thickness in a direction normal to the second major surface, and
a first gradient portion,

wherein:
a refractive index of the optical coating varies along a thickness of the optical coating between the first major surface and the second major surface;
the difference between the maximum refractive index of the first gradient portion and the minimum refractive index of the first gradient portion is 0.1 or greater;
the absolute value of the slope of the refractive index of the first gradient portion is 0.1/nm or less everywhere along the thickness of the first gradient portion;

wherein the article exhibits:
an average single-surface reflectance of 15% to 98% over the wavelength range 400 nm-700 nm, measured at the second major surface; and
a maximum hardness in the range from about 10 GPa to about 30 GPa, wherein maximum hardness is measured on the second major surface by indenting the second major surface with a Berkovich indenter to form an indent comprising an indentation depth of about 100 nm or more from the surface of the second major surface;

wherein slope is measured along the thickness over a refractive index change of 0.04.

2. The article of claim 1 , wherein the difference between the maximum refractive index of the first gradient portion and the minimum refractive index of the first gradient portion is 0.3 or greater.

3. The article of claim 1 , wherein the article exhibits an average transmittance of 5% to 90%, measured at the second major surface.

4. The article of claim 1 , wherein:
everywhere along the thickness of the first gradient portion, the absolute value of the slope of the refractive index of the optical coating is 0.001/nm to 0.02/nm.

5. The article of claim 1 , wherein the optical coating further comprises a high hardness portion, wherein:
the thickness of the high hardness portion is 200 nm or more;
the average index of refraction in the high hardness portion is 1.6 or more; and
the maximum hardness of the high hardness portion is 10 GPa or more, wherein maximum hardness is measured by indenting the thick high hardness portion with a Berkovich indenter to form an indent comprising an indentation depth of about 100 nm or more.

6. The article of claim 5 , wherein for 95% or more of the thickness of the high hardness portion, the difference between the maximum refractive index of the high hardness portion and the minimum refractive index of the high hardness portion is 0.05 or less.

7. The article of claim 5 , wherein:
everywhere along the thickness of the high hardness portion, the difference between the maximum refractive index of the high hardness portion and the minimum refractive index of the high hardness portion is 0.05 or less.

8. The article of claim 5 , wherein the optical coating comprises, in order, along the direction of the thickness from the second major surface toward the first major surface:
the first gradient portion; and
the high hardness portion in contact with the first gradient portion;
wherein, where the high hardness portion contacts the first gradient portion, the difference between the refractive index of the high hardness portion and the maximum refractive index of the first gradient portion is 0.05 or less.

9. The article of claim 5 , wherein the optical coating further comprises a second gradient portion disposed between the high hardness portion and the substrate, wherein the second gradient portion is in contact with the high hardness portion, and wherein:
the difference between the maximum refractive index of the second gradient portion and the minimum refractive index of the second gradient portion is 0.05 or greater;
everywhere along the thickness of the second gradient portion, the absolute value of the slope of the refractive index of the optical coating is 0.1/nm or less.

10. The article of claim 5 , wherein:
the refractive index of the first gradient portion monotonically increases along the thickness in a direction moving away from the second major surface;
the optical coating further comprises a multilayer interference stack comprising discrete layers disposed between the high hardness portion and the substrate.

11. The article of claim 5 , wherein:
the refractive index of the first gradient portion monotonically increases along the thickness in a direction moving away from the second major surface;
the optical coating further comprises a second gradient portion that oscillates across the thickness of the gradient portion as a function of distance from the substrate.

12. The article of claim 5 , wherein the optical coating comprises, in order, along the direction of the thickness from the second major surface toward the first major surface:
a multilayer interference stack comprising discrete layers;
the high hardness portion in contact with the multilayer interference stack;
the first gradient portion in contact with the high hardness portion;
wherein:
where the high hardness portion contacts the first gradient portion, the difference between the refractive index of the high hardness portion and the maximum refractive index of the first gradient portion is 0.05 or less;
the refractive index of the first gradient portion monotonically decreases along the thickness in a direction moving away from the second major surface.

13. The article of claim 1 , wherein the article exhibits a single side reflected color range for all viewing angles from 0 to 60 degrees, measured at the second major surface, that comprises all a* points and all b* points comprising values of 5 or less.

14. The article of claim 1 , wherein the article exhibits a maximum visible reflectance between 30% to 80%.

15. The article of claim 1 , wherein the article exhibits an average photopic reflectance between 15% to 50%.

16. The article of claim 1 , wherein the article exhibits an average transmittance or average reflectance comprising an average oscillation amplitude of 20 percentage points or less, over the optical wavelength regime.

17. The article of claim 1 , wherein optical coating comprises a thickness in the range from about 0.5 μm to about 3 μm.

18. The article of claim 5 , wherein the cumulative thickness of any parts of the optical coating between the high hardness portion and the second major surface comprising a RI of 1.6 or less is 200 nm or less.

19. The article of claim 1 , wherein the optical coating comprises a compositional gradient, the compositional gradient comprising at least two of Si, Al, N, and O.

20. A method of forming an article comprising:
obtaining a substrate comprising a first major surface and comprising an amorphous substrate or a crystalline substrate;
disposing an optical coating on the first major surface, the optical coating comprising a second major surface opposite the first major surface and a thickness in a direction normal to the second major surface,
creating a refractive index gradient along at least a first gradient portion of the thickness of the optical coating,
wherein:
a refractive index of the optical coating varies along a thickness of the optical coating between the first major surface and the second major surface;
the difference between the maximum refractive index of the first gradient portion and the minimum refra

Assignees

• Corning Inc

Inventors

• Bellman Robert Alan
• Hart Shandon Dee
• Koch Iii Karl William
• Kosik Williams Carlo Anthony
• Paulson Charles Andrew
• Price James Joseph

Classifications

• G02B5/289

  Rugate filters · CPC title

• C03C2217/734

  comprising an alternation of high and low refractive indexes · CPC title

• G02B5/0883

  with a refractive index gradient (rugate filters G02B5/289) · CPC title

• C03C17/3435

  comprising a nitride, oxynitride, boronitride or carbonitride · CPC title

• G02B1/14 Primary

  Protective coatings, e.g. hard coatings · CPC title