Optical stack comprising adhesive

Patent metadata

Field	Value
Publication number	US-9791603-B2
Application number	US-201214005912-A
Country	US
Kind code	B2
Filing date	Mar 26, 2012
Priority date	Apr 4, 2011
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

Presently described are optical stacks comprising a first optical film comprising a plurality of structures comprising an optically active portion designed primarily to provide optical gain and optionally an optically in-active bonding portion disposed on a first surface bonded to a second optical film with a light-transmissive adhesive layer such that a portion of the structures penetrate the adhesive layer and a separation is provided between the adhesive layer and the first surface. In one embodiment, the optical stacks exhibit a combination of high peel strength and high retained brightness, particularly after aging. The adhesive layer preferably comprises an interpenetrating network of the reaction product of a polyacrylate component and a polymerizable monomer and the adhesive layer has an elastic modulus ranging from 100 to 2000 MPa at 25° C.

First claim

What is claimed is:

1. An optical stack comprising a first optical film comprising a plurality of structures comprising an optically active portion designed primarily to provide optical gain and an optically in-active bonding portion disposed on a first surface wherein the optically in-active portion of the structures is bonded to a second optical film with a light-transmissive adhesive layer such that a portion of the structures penetrate the adhesive layer and a separation is provided between the adhesive layer and the first surface, wherein the adhesive layer comprises an interpenetrating network of the reaction product of a polyacrylate component and a polymerizable monomer having functional groups and a molecular weight less than 150 g/mole per functional group, the peel strength of the optical stack is at least 50 grams force/inch and the stack exhibits a decrease in optical gain of no greater than 5% when the optical stack is conditioned at 65° C. and 95% relative humidity for 200 hours.

2. The optical stack of claim 1 wherein the structures that penetrate the adhesive layer define an average penetration that increases by no more than 50% when the optical stack is conditioned at 65° C. and 95% relative humidity for 200 hours.

3. The optical stack of claim 1 wherein the adhesive layer has an elastic modulus ranging from 100 to 2000 MPa at 25° C.

4. The optical stack of claim 1 wherein at least a portion of the first optical film or structures comprise a bonding portion that penetrates the adhesive layer.

5. The optical stack of claim 4 wherein optically active portions of the structures do not penetrate the adhesive layer.

6. The optical stack of claim 1 wherein the structures comprise prism microstructures.

7. The optical stack of claim 6 wherein at least a portion of the prisms comprise a post extending from an apex of the prisms that functions as an optically non-active bonding portion.

8. The optical stack of claim 1 wherein the optical stack has an optical gain of at least 2.1.

9. The optical stack of claim 1 wherein the separation between the adhesive layer and the first surface provides an air interface.

10. The method of claim 1 wherein the substrate is an optical film or a release liner.

11. The optical film of claim 1 wherein the adhesive comprises about 35 wt-% to about 75 wt-% polyacrylate.

12. The optical film of claim 1 wherein the polyacrylate is a pressure sensitive adhesive comprising monomeric repeat units comprising branched C4-C12 alkyl groups.

13. The optical film of claim 1 wherein the polymerizable monomer is an epoxy component and the adhesive composition further comprises a photoactivated cationic initiator.

14. The optical film of claim 1 wherein the polymerizable monomer comprises at least three (meth)acrylate groups and the adhesive composition further comprises a free-radical photoinitiator.

15. The optical film of claim 1 wherein the adhesive further comprises a light transmissive filler.

Assignees

• Edmonds William F
• Carter Brandt K
• Petaja Jason S
• 3M Innovative Properties Co

Inventors

• Edmonds William F
• Carter Brandt K
• Petaja Jason S

Classifications

• C09J133/08 Primary

  Homopolymers or copolymers of acrylic acid esters · CPC title

• C09J7/0207

  Chemistry & Metallurgy · mapped topic

• G02B5/045 Primary

  Prism arrays · CPC title

• C09J151/06

  grafted on to homopolymers or copolymers of aliphatic hydrocarbons containing only one carbon-to-carbon double bond · CPC title

• C08L2205/04

  containing interpenetrating networks · CPC title