Optically clear hot melt adhesives and uses thereof

• US 10,266,733 B2
• Filed: 02/07/2017
• Issued: 04/23/2019
• Est. Priority Date: 08/11/2014
• Status: Active Grant

• Current Assignee: Henkel AG & Co KGaA
• Original Assignee: Henkel AG & Co KGaA, Henkel IP & Holding GmbH (Henkel AG & Co KGaA)
• Inventors: Liu, Yuxia, Paul, Charles W., Palasz, Peter D.
• Primary Examiner(s): Zhang, Ruiyun
• Application Number:
  US15/426,214
• Publication Number:
  US 20170145267A1
• Time in Patent Office: 805 Days
• Field of Search: 428 11, 428 15, 428 154, 428 155, 428345, 257100, 2641711
• CPC Class Codes: B32B 2037/1253 curable adhesive
• CPC Class Codes: B32B 2037/1269 multi-component adhesive
• CPC Class Codes: B32B 2264/10 Inorganic particles
• CPC Class Codes: B32B 2264/101 Glass
• CPC Class Codes: B32B 2264/102 Oxide or hydroxide
• CPC Class Codes: B32B 2264/105 Metal
• CPC Class Codes: B32B 2264/108 Carbon, e.g. graphite particles
• CPC Class Codes: B32B 2270/00 Resin or rubber layer containing a blend of at least two different polymers
• CPC Class Codes: B32B 2307/412 Transparent
• CPC Class Codes: B32B 2307/7244 Oxygen barrier
• CPC Class Codes: B32B 2307/7246 Water vapor barrier
• CPC Class Codes: B32B 2309/02 Temperature
• CPC Class Codes: B32B 2309/12 Pressure
• CPC Class Codes: B32B 2309/68 Vacuum
• CPC Class Codes: B32B 2325/00 Polymers of vinyl-aromatic compounds, e.g. polystyrene
• CPC Class Codes: B32B 2333/08 Polymers of acrylic acid esters, e.g. PMA, i.e. polymethylacrylate
• CPC Class Codes: B32B 2457/00 Electrical equipment
• CPC Class Codes: B32B 2457/12 Photovoltaic modules
• CPC Class Codes: B32B 2457/20 Displays, e.g. liquid crystal displays, plasma displays
• CPC Class Codes: B32B 2457/202 LCD, i.e. liquid crystal displays
• CPC Class Codes: B32B 2457/206 : Organic displays, e.g. OLED
• CPC Class Codes: B32B 2457/208 : Touch screens
• CPC Class Codes: B32B 27/08 : of synthetic resin
• CPC Class Codes: B32B 27/10 : of paper or cardboard
• CPC Class Codes: B32B 27/20 : using fillers, pigments, thixotroping agents
• CPC Class Codes: B32B 27/30 : comprising vinyl (co)polymers; comprising acrylic (co)polymers
• CPC Class Codes: B32B 27/302 : comprising aromatic vinyl (co)polymers, e.g. styrenic (co)polymers
• CPC Class Codes: B32B 27/308 : comprising acrylic (co)polymers
• CPC Class Codes: B32B 27/32 : comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: B32B 27/36 : comprising polyesters
• CPC Class Codes: B32B 27/38 : comprising epoxy resins
• CPC Class Codes: B32B 27/40 : comprising polyurethanes
• CPC Class Codes: B32B 37/003 : to avoid air inclusion
• CPC Class Codes: B32B 37/12 : characterised by using adhesives
• CPC Class Codes: B32B 7/06 : permitting easy separation
• CPC Class Codes: B32B 7/12 : using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: C08F 285/00 : Macromolecular compounds obtained by polymerising monomers on to preformed graft polymers
• CPC Class Codes: C08L 9/00 : Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
• CPC Class Codes: C09J 153/025 : modified
• CPC Class Codes: C09J 2453/00 : Presence of block copolymer
• CPC Class Codes: C09J 4/06 : Organic non-macromolecular compounds having at least one polymerisable carbon-to-carbon unsaturated bond in combination with a macromolecular compound other than an unsaturated polymer of groups C09J159/00 - C09J187/00
• CPC Class Codes: C09J 5/00 : Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
• CPC Class Codes: Y02P 20/582 : Recycling of unreacted starting or intermediate materials

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.

Claims

1. A pressure sensitive adhesive composition comprising:

(A) about 0.5 to about 20 parts by weight of a styrenic block copolymer having fully hydrogenated and saturated soft blocks;

(B) about 10 to about 60 parts by weight of a liquid diluent having a weight average molecular weight (Mw) less than 100,000 g/mol, a tackifier, or mixtures thereof;

(C) about 10 to about 25 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 0.1 to about 5 parts by weight 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,

and wherein the total content of the pressure sensitive adhesive composition totals to 100 parts by weight.

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 by weight of a styrenic block copolymer having fully hydrogenated and saturated soft blocks;

(B) about 10 to about 60 parts by weight of a liquid diluent, a tackifier, or mixtures thereof;

(C) about 10 to about 25 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 0.1 to about 5 parts by weight 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

wherein the adhesive does not have a flow temperature after cure; and

and wherein the total content of the pressure sensitive adhesive composition totals to 100 parts by weight.