Radical cured silicone pressure sensitive adhesive and composition and method for its preparation and use in a flexible display device

Patent metadata

Field	Value
Publication number	US-11773305-B2
Application number	US-202117918010-A
Country	US
Kind code	B2
Filing date	Apr 27, 2021
Priority date	Apr 27, 2021
Publication date	Oct 3, 2023
Grant date	Oct 3, 2023

Abstract

A silicone pressure sensitive adhesive is prepared by curing a radical reaction curable composition. The silicone pressure sensitive adhesive adheres to various silicone elastomers and is useful in preparation of components of flexible display devices.

First claim

What is claimed is:

1. A radical reaction curable composition for forming a silicone pressure sensitive adhesive, where the composition comprises:
(A) a polydiorganosiloxane gum component comprising
0 weight % to 16.3 weight %, based on combined weights of starting materials (A) to (D), of (A-1) an aliphatically unsaturated polydiorganosiloxane gum of unit formula (R M 2 R U SiO 1/2 ) 2 (R M 2 SiO 2/2 ) a , where each R M is an independently selected monovalent hydrocarbon group of 1 to 30 carbon atoms that is free of aliphatic unsaturation; each R U is an independently selected monovalent aliphatically unsaturated hydrocarbon group of 2 to 30 carbon atoms; and subscript a has a value sufficient to give the aliphatically unsaturated polydiorganosiloxane gum a plasticity of 20 mil (0.51 mm) to 80 mil (2.03 mm), where plasticity is measured based on ASTM D926 by applying 1 kg load to a spherical sample of 4.2 g in weight for 3 minutes at 25° C. and the results are measured in thousandths of an inch (mil) and the procedure is based on ASTM D926; and
34.7 to 51.8 weight % of (A-2) a hydroxyl-terminated polydiorganosiloxane gum of unit formula ((HO)R M 2 SiO 1/2 ) 2 (R M 2 SiO 2/2 ) a′ , where each R M is an independently selected monovalent hydrocarbon group of 1 to 30 carbon atoms that is free of aliphatic unsaturation; each subscript a′ has a value sufficient to give the polydiorganosiloxane gum a number average molecular weight of ≥200,000 g/mol;
with the proviso that a weight ratio of (A-1) the aliphatically unsaturated polydiorganosiloxane gum : (A-2) the hydroxyl-terminated polydiorganosiloxane gum {(A-1):(A-2) ratio} <0.47:1;
39.3 weight % to 45.4 weight % of (B) a polyorganosilicate resin comprising unit formula (R M 3 SiO 1/2 ) z′ (SiO 4/2 ) o′ Z p′ , where each R M is an independently selected monovalent hydrocarbon group of 1 to 30 carbon atoms that is free of aliphatic unsaturation, Z is a hydrolyzable group, subscript p′ has a value sufficient to give the resin a hydrolyzable group content of >3% to 10%, subscripts z′ and o′ have values such that z′ >4, o′ >1, and a quantity (z′ +o′) has a value sufficient to provide the resin with a number average molecular weight of 500 g/mol to 5,000 g/mol;
where (A) the polydiorganosiloxane gum component and (B) the polyorganosilicate resin are present in a weight ratio of (B):(A) (Resin: Gum Ratio) <1.1:1;
0.01 weight % to 5 weight %, based on combined weights of starting materials (A) to (D), of (C) a radical initiator;
0. 3 weight % to 7.1 weight %, based on combined weights of starting materials (A) to (D), of (D) a trialkyl borate;
0 weight % to 90 weight %, based on combined weights of all starting materials in the composition, of (E) a solvent.

2. The composition of claim 1 , wherein (A) the polydiorganosiloxane gum component, each R M is an independently selected alkyl group of 1 to 6 carbon atoms;
and each R U is independently selected from the group consisting of vinyl, allyl, and hexenyl, and subscript a is sufficient to provide a plasticity of 30 mil (0.76 mm) to 70 mil (1.78 mm) to (A-1) the aliphatically unsaturated polydiorganosiloxane gum; and subscript a′ is sufficient to provide a plasticity of 30 mil (0.76 mm) to 70 mil (1.78 mm) to (A-2) the hydroxyl-terminated polydiorganosiloxane gum.

3. The composition of claim 1 , wherein the polyorganosilicate resin (B), each R M is an independently selected alkyl group of 1 to 6 carbon atoms; each Z is OH;
and the quantity (z′ +o′) has a value sufficient to provide (B) the polyorganosilicate resin with a number average molecular weight of 3,800 g/mol to 4,300 g/mol.

4. The composition of claim 1 , where the radical initiator (C) comprises dibenzoyl peroxide.

5. The composition of claim 1 , where the trialkyl borate (D) comprises triethyl borate.

6. A wet casting method comprising
1) applying the composition according to claim 1 to a substrate, and
2) curing the composition to form the silicone pressure sensitive adhesive on the substrate.

7. The method of claim 6 , where the substrate is a silicone elastomer.

8. An article prepared by the method of claim 6 .

9. The article of claim 8 , where the article is a component of a lens(frame) mounting layer in a flexible display device.

10. The article of claim 8 , where the article is a component of a silicone hinge and bonding layer in a flexible display device.

11. The article of claim 8 , where the article is an optical component of a flexible display device and the substrate is an optical silicone elastomer.

12. A dry casting method comprising
1) applying the composition according to claim 1 to a release liner, 2) curing the composition to form the silicone pressure sensitive adhesive on the release liner, and
3) applying the silicone pressure sensitive adhesive to a substrate.

13. The method of claim 12 , where the substrate is a silicone elastomer.

14. An article prepared by the method of claim 13 .

15. The article of claim 14 , where the article is a component of a lens(frame) mounting layer in a flexible display device.

16. The article of claim 14 , where the article is a component of a silicone hinge and bonding layer in a flexible display device.

17. The article of claim 14 , where the article is an optical component of a flexible display device and the substrate is an optical silicone elastomer.

18. A component of foldable display device comprising:
I) a silicone elastomer layer, and
II) a silicone pressure sensitive adhesive layer adhered to the silicone elastomer layer, wherein the silicone pressure sensitive adhesive layer is a product of the radical reaction curable composition of claim 1 .

Assignees

• Dow Silicones Corp

Inventors

• Cao Qing
• Zhou Yan
• Xu Bochi

Classifications

• C09J183/04 Primary

  Polysiloxanes · CPC title

• C09J7/38 Primary

  Pressure-sensitive adhesives [PSA] · CPC title

• C09J11/06

  organic · CPC title

• C09J2301/302

  the adhesive being pressure-sensitive, i.e. tacky at temperatures inferior to 30°C · CPC title

• C09J2301/408

  additives as essential feature of the adhesive layer · CPC title