Optical stack comprising adhesive

• US 9,791,603 B2
• Filed: 03/26/2012
• Issued: 10/17/2017
• Est. Priority Date: 04/04/2011
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Edmonds, William F., Carter, Brandt K., Petaja, Jason S.
• Primary Examiner(s): Pinkney, Dawayne A
• Application Number:
  US14/005,912
• Publication Number:
  US 20140016208A1
• Time in Patent Office: 2,031 Days
• Field of Search: 359625, 359618, 359619, 359629, 359631, 359640, 359443, 359454-455, 359459, 362 26- 27, 362 31, 362 19, 362559-560, 349 19, 349 61- 65
• CPC Class Codes: C08L 2205/04 containing interpenetrating networks
• CPC Class Codes: C09J 133/08 Homopolymers or copolymers of acrylic acid esters
• CPC Class Codes: C09J 151/06 grafted on to homopolymers or copolymers of aliphatic hydrocarbons containing only one carbon-to-carbon double bond
• CPC Class Codes: C09J 7/38 Pressure-sensitive adhesives [PSA]
• CPC Class Codes: G02B 5/045 Prism arrays

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.

Claims

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.