Protective coating for low index material

Patent metadata

Field	Value
Publication number	US-9505028-B2
Application number	US-201314387873-A
Country	US
Kind code	B2
Filing date	Mar 19, 2013
Priority date	Mar 30, 2012
Publication date	Nov 29, 2016
Grant date	Nov 29, 2016

Abstract

The present disclosure describes a protective coating for a low index material, and a process for preparing a protected low index material. The protective coating partially penetrates the pores of a low index material, providing a seal protecting the pores, and can strengthen the construction by forming a gradient in properties of the protected low index material. The present disclosure further provides a diffusing low index optical element having a protected low index material and a diffusing layer disposed on the low index material.

First claim

What is claimed is:

1. A method, comprising:
coating a first solution on a major surface of an optical element, the first solution comprising a plurality of fumed metal oxide particles, a binder, and a solvent, wherein the binder has a first concentration in the solvent;
coating a second solution on the first solution, the second solution comprising the binder at a second concentration in the solvent, the second concentration different from the first concentration; and
removing the solvent from the first solution and the second solution to form a protected film, wherein the protected film comprises:
a low refractive index layer disposed on the major surface of the optical element, wherein the low refractive index layer comprises a plurality of interconnected voids and an effective refractive index of 1.3 or less, and
a polymeric protective layer on the low refractive index layer, and wherein a weight ratio of the binder to the metal oxide particles increases in a thickness direction of the protected film.

2. The method of claim 1 , wherein coating the first solution and the second solution occurs simultaneously using a slide coater, a multilayer slot coater, or a combination thereof.

3. The method of claim 1 , wherein coating the first solution and the second solution occurs sequentially using a curtain coater.

4. The method of claim 1 , wherein the first concentration is lower than the second concentration.

5. The method of claim 1 , wherein the weight ratio of the binder to the metal oxide particles increases from less than 1:2 proximate the substrate to greater than 1:1 proximate an exterior surface of the protected film.

6. The method of claim 1 , wherein the substrate comprises a third solution coated thereupon, the third solution comprising a second plurality of metal oxide particles, the binder, and the solvent, wherein the binder has a third concentration in the solvent, and the first solution is coated on the third solution.

7. The method of claim 6 , wherein the third concentration is lower than the first concentration.

8. The method of claim 1 , further comprising diffuser particles dispersed in at least one of the first solution or the second solution.

9. The method of claim 1 , further comprising:
coating a fourth solution on the protected film, the fourth solution comprising a second binder, and a second solvent, wherein the second binder has a fourth concentration in the second solvent;
coating a fifth solution on the fourth solution, the fifth solution comprising a third binder at a fifth concentration in the second solvent and a plurality of diffuser particles; and
removing the solvent from the fourth solution and the fifth solution to form a diffusing film.

10. The method of claim 9 , wherein the second binder and the third binder are each selected independently from polymers comprising polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone, polyvinyl acetate, vinyl acetate/ethylene copolymers, polyethylene oxide, polypropylene oxide, or a combination thereof.

11. The method of claim 9 , wherein the diffuser particles comprise beads having a diameter between about 0.5 microns and about 10 microns.

Assignees

• 3M Innovative Properties Co

Inventors

• Steiner Michael L
• Coggio William D
• Ludemann Thomas J
• Rexeisen Emilie L
• Dudley William R
• Mcman Steven J
• Ruegsegger Michael L

Classifications

• Y10T428/249986

  Void-containing component contains also a solid fiber or solid particle · CPC title

• Y10T428/249981

  Plural void-containing components · CPC title

• G02B5/0247

  by means of voids or pores · CPC title

• B05D2490/50

  compositions varying with a gradient perpendicular to the surface · CPC title

• B05D7/5883

  No curing step for any layer · CPC title