Optically clear hot melt adhesives and uses thereof

Patent metadata

Field	Value
Publication number	US-2017145267-A1
Application number	US-201715426214-A
Country	US
Kind code	A1
Filing date	Feb 7, 2017
Priority date	Aug 11, 2014
Publication date	May 25, 2017
Grant date	—

Abstract

Hot melt adhesives with pressure sensitive adhesive properties for electronic devices are described. The hot melt adhesive comprises a styrenic block copolymer with fully hydrogenated and saturated soft blocks, a liquid diluent or a tackifier, a (meth)acrylate monomer or an oligomer having at least two (meth)acrylic functionalities per oligomer chain, and an initiator. The hot melt adhesive is also a reworkable UV curable optically clear adhesive film. The adhesive and film are suitable as a laminating PSA film or encapsulant for LCD display, LED display, touch screen, and flexible thin film photovoltaic module.

First claim

We claim:

1 . A pressure sensitive adhesive composition comprising:
(A) about 0.5 to about 20 parts of a styrenic block copolymer having fully hydrogenated and saturated soft blocks; (B) about 0.5 to about 80 parts by weight of a liquid diluent, a tackifier, or mixtures thereof; (C) about 0.5 to about 50 parts by weight of a (meth)acrylate monomer, an oligomer having at least two (meth)acrylic functionalities per oligomer chain or mixtures thereof; and (D) about 0.01 to about 5 parts of a free radical initiator; wherein the styrenic block copolymer form a crosslinked network with the (meth)acrylate monomer or oligomer upon UV irradiation or heat.

2 . The adhesive of claim 1 , wherein the adhesive has a flow temperature (G′ =G″) of from about 45° C. to about 110° C. prior to cure and wherein the adhesive does not have a flow temperature after cure.

3 . The adhesive of claim 1 , wherein the adhesive has (a) a transmittance, measured in accordance with ASTM E903 at 500 nm, of greater than 90%, (b) a Shore OO value, measured in accordance with ASTM D2240, of about 10 to about 70, and (c) elongation at break, measured in accordance with ASTM D638, of greater than 200%.

4 . The adhesive of claim 1 wherein the fully hydrogenated and saturated soft block of styrenic block copolymer is selected from the groups consisting of ethylene, propylene, butylene, isobutylene, ethylene-propylene, ethylene-butylene, and mixtures thereof.

5 . The adhesive of claim 1 wherein the styrenic block copolymer is a triblock, a diblock, or mixtures thereof.

6 . The adhesive of claim 1 wherein the liquid diluent is white oil or a wax.

7 . The adhesive of claim 1 wherein the liquid diluent is polyisobutylene, polybutene, or a synthetic liquid polymer, having a weight average molecular less than about 100,000 g/mol.

8 . The adhesive of claim 1 wherein the tackifier is a fully or partially hydrogenated soft block and/or hard block modifying tackifier selected from aliphatic resin, and/or aromatic resins.

9 . The adhesive of claim 1 wherein the (meth)acrylic monomer is a multifunctional (meth)acrylate monomer, or mixtures thereof.

10 . The adhesive of claim 1 wherein the (meth)acrylic oligomer is a (meth)acrylic functionalized polyisobutylene, polybutadiene, hydrogenated polybutadiene, and/or other polyolefin having greater than one reactive functional group per oligomer chain, wherein the reactive functional group is selected from the group consisting of terminal methacrylates, pendant methacrylates, terminal acrylates, and/or pendant acrylates; and mixtures thereof.

11 . The adhesive of claim 1 wherein the free radical initiator is a photoinitiator or a thermal initiator.

12 . The adhesive of claim 1 which is a film.

13 . An article comprising the film of claim 12 .

14 . The article of claim 13 which is an electronic device.

15 . The article of claim 14 wherein the electronic device is a LCD display, LED display, touch screen, or flexible thin film photovoltaic.

16 . An electronic device comprising at least one optically clear pressure sensitive adhesive film,
wherein the pressure sensitive adhesive film comprises: (A) about 0.5 to about 20 parts of a styrenic block copolymer having fully hydrogenated and saturated soft blocks; (B) about 0.5 to about 80 parts by weight of a liquid diluent, a tackifier, or mixtures thereof; (C) about 0.5 to about 50 parts by weight of a (meth)acrylate monomer, an oligomer having at least two (meth)acrylic functionalities per oligomer chain or mixtures thereof; and (D) about 0.01 to about 5 parts of a free radical initiator; wherein the styrenic block copolymer form a crosslinked network with the (meth)acrylate monomer or oligomer upon UV irradiation or heat; wherein the pressure sensitive adhesive film is removable before and/or after the UV or heat cure; wherein the adhesive has a flow temperature (G′=G″) of from about 45° C. to about 110° C. prior to curing; and wherein the adhesive does not have a flow temperature after cure.

17 . A method of making an optically clear, reworkable pressure sensitive adhesive film comprising the steps of:
(1) preparing a pressure sensitive adhesive by mixing (A) about 0.5 to about 20 parts of a styrenic block copolymer having fully hydrogenated and saturated soft blocks; (B) about 0.5 to about 80 parts by weight of a liquid diluent, a tackifier, or mixtures thereof; (C) about 0.5 to about 50 parts by weight of a (meth)acrylate monomer, an oligomer having at least two (meth)acrylic functionalities per oligomer chain or mixtures thereof; and (D) about 0.01 to about 5 parts of a free radical initiator at about 50° C. to about 150° C. to form a homogeneous melt; (2) applying the homogeneous melt at about 50° C. to about 150° C. onto a first release liner at a thickness of about 25 to about 250 μm as a film; and (3) laminating the film with a second release liner whereby the adhesive film is interdisposed in between the two release liners.

18 . A method of forming an optically clear electronic device of claim 17 , further comprising the steps of:
(4) preparing a substrate; (5) removing the first release liner; (6) laminating the film onto the substrate at temperature ranging from about −50° C. to about 100° C., under a pressure ranging from about 0.01 to about 0.5 MPa; (7) removing the second release liner; (8) laminating the film onto a cover sheet at temperature ranging from about −50° C. to about 100° C., under a pressure ranging from about 0.01 to about 0.5 MPa; and (9) curing the film with UV radiation ranging from about 280 to about 700 nm or heat ranging from about 60° C. to about 190° C.; whereby the film adheres the first substrate and the second substrate together, wherein the film is removable at after step (8) and/or after step (9).

19 . A method of making an optically clear, reworkable pressure sensitive adhesive film comprising the steps of:
(1) preparing a pressure sensitive adhesive solution in about 50-90wt % heptane and/or xylene solution by dissolving (A) about 0.5 to about 20 parts of a styrenic block copolymer having fully hydrogenated and saturated soft blocks; (B) about 0.5 to about 80 parts by weight of a liquid diluent, a tackifier, or mixtures thereof; (C) about 0.5 to about 50 parts by weight of a (meth)acrylate monomer, an oligomers having at least two (meth)acrylic functionalities per oligomer chain or mixtures thereof; and (D) about 0.01 to about 5 parts of a free radical initiator at about 20° C. to about 90° C. to form a homogeneous solution; (2) applying the solution at about 20° C. to about 30° C. onto a first release liner at a thickness of about 25 to about 250 μm as a dried film; and (3) laminating the fully dried film with a second release liner whereby the adhesive film is interdisposed in between the two release liners.

20 . A method of forming an optically clear electronic device of claim 19 , further comprising the steps of:
(4) preparing a substrate; (5) removing the first release liner; (6) laminating the film onto the substrate at temperature ranging from about −50° C. to about 100° C., under a pressure ranging from about 0.01 to about 0.5 MPa; (7) removing the second release liner; (8) laminating the film onto a cover sheet at temperature ranging from about −50° C. to about 100° C., under a pressure ranging from about 0.01 to about 0.5 MPa; and (9) curing the film with UV radiation ranging from about 280 to about 700 nm or heat ranging from about 60° C. to ab

Assignees

• Henkel IP & Holding GmbH
• Henkel Ag & Co Kgaa

Inventors

• Liu Yuxia
• Paul Charles W
• Palasz Peter D

Classifications

• B32B2264/108

  Carbon, e.g. graphite particles · CPC title

• C08L9/00

  Compositions of homopolymers or copolymers of conjugated diene hydrocarbons · CPC title

• B32B37/003

  to avoid air inclusion · CPC title

• B32B2307/412

  Transparent · CPC title

• B32B2457/206

  Organic displays, e.g. OLED · CPC title