Pressure-sensitive adhesive sheet for portable electronics

Patent metadata

Field	Value
Publication number	US-10550298-B2
Application number	US-201515327408-A
Country	US
Kind code	B2
Filing date	Jul 14, 2015
Priority date	Jul 23, 2014
Publication date	Feb 4, 2020
Grant date	Feb 4, 2020

Abstract

Provided is a PSA sheet that provides highly reliable adhesion and great stretch removability from adherends. This invention provides a PSA sheet. The PSA sheet exhibits a shear adhesive strength of 0.5 MPa or greater, a tensile strength at break of 10 MPa or greater, and an elongation at break of 300% or greater.

First claim

The invention claimed is:

1. A pressure-sensitive adhesive sheet for portable electronics, with the pressure-sensitive adhesive sheet exhibiting a shear adhesive strength of 0.5 MPa or greater, a tensile strength at break of 10 MPa or greater, an elongation at break of 500% or greater, and a tensile recovery of 50% or greater when measured by the following method for measuring the tensile recovery:
the pressure-sensitive adhesive sheet is subjected to a tensile test in which a designated segment of a length L 0 in the pressure-sensitive adhesive sheet is stretched by 100%; when stretched by 100%, the pressure-sensitive adhesive sheet is released; when the designated segment has a length L 1 at five minutes after released, the tensile recovery is determined by an equation: tensile recovery (%)=L 0 /L 1 ×100.

2. The pressure-sensitive adhesive sheet for portable electronics according to claim 1 , wherein the pressure-sensitive adhesive sheet comprises a pressure-sensitive adhesive layer and a substrate film supporting the pressure-sensitive adhesive layer.

3. The pressure-sensitive adhesive sheet according to claim 2 , comprising, as the pressure-sensitive adhesive layer, a first pressure-sensitive adhesive layer placed on a first face of the substrate film and a second pressure-sensitive adhesive layer placed on a second face of the substrate film with the first pressure-sensitive adhesive layer having a thickness of 3 μm to 200 μm, the second pressure-sensitive adhesive layer having a thickness of 3 μm to 200 μm, and the first and second pressure-sensitive adhesive layers may be different in thickness.

4. The pressure-sensitive adhesive sheet according to claim 1 -exhibiting a tensile recovery of 80% or greater.

5. The pressure-sensitive adhesive sheet according to claim 1 provided with a tab.

6. The pressure-sensitive adhesive sheet according to claim 1 comprising a pressure-sensitive adhesive layer, wherein
the pressure-sensitive adhesive layer comprises an acrylic polymer in an amount accounting for more than 50% by weight of polymers in the pressure-sensitive adhesive layer,
the acrylic polymer comprises, as a monomeric component, an alkyl (meth)acrylate represented by a formula (1):
CH 2 ═C(R 1 )COOR 2   (1)

in which R 1 is a hydrogen atom or a methyl group; R 2 is an acyclic alkyl group having 1 to 20 carbon atoms, and the alkyl (meth)acrylate is present in an amount of 70% by weight or higher.

7. The pressure-sensitive adhesive sheet according to claim 6 , wherein the alkyl (meth)acrylate comprises either n-butyl acrylate or 2-ethylhexyl acrylate.

8. The pressure-sensitive adhesive sheet according to claim 6 , wherein the acrylic polymer further comprises a functional group-containing monomer as a monomeric component, wherein the functional group-containing monomer is at least one species selected from the group consisting of a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an acid anhydride group-containing monomer, an amide group-containing monomer, an amino group-containing monomer, a keto group-containing monomer, a monomer having a nitrogen atom-containing ring, an alkoxysilyl group-containing monomer, an imide group-containing monomer, and an epoxy group-containing monomer.

9. The pressure-sensitive adhesive sheet according to claim 6 , wherein the pressure-sensitive adhesive layer comprises a tackifier resin having a softening point of 100° C. or higher, with the tackifier resin comprising at least either a rosin-based tackifier resin or a terpene-based tackifier resin.

10. The pressure-sensitive adhesive sheet according to claim 6 , wherein the pressure-sensitive adhesive layer comprises 10 parts to 60 parts by weight of a tackifier to 100 parts by weight of the acrylic polymer.

11. The pressure-sensitive adhesive sheet according to claim 6 , wherein a pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer comprises at least one species of crosslinking agent selected from the group consisting of an isocyanate-based crosslinking agent, epoxy-based crosslinking agent, oxazoline-based crosslinking agent, aziridine-based crosslinking agent, melamine-based crosslinking agent, peroxide-based crosslinking agent, and metal chelate-based crosslinking agent.

12. The pressure-sensitive adhesive sheet according to claim 1 comprising a substrate film, wherein
the substrate film comprises an urethane (meth)acrylate-based polymer.

13. The pressure-sensitive adhesive sheet according to claim 1 comprising a substrate film, wherein the substrate film comprises 70% or more polyurethane by weight, and the polyurethane is an ether-based polyurethane, an ester-based polyurethane or a carbonate-based polyurethane.

14. The pressure-sensitive adhesive sheet according to claim 1 , comprising a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is formed of a rubber-based pressure-sensitive adhesive that comprises a base polymer which is a block copolymer of a monovinyl-substituted aromatic compound and a conjugated diene compound.

15. The pressure-sensitive adhesive sheet according to claim 14 , wherein the block copolymer has a diblock fraction of 30% by weight or higher.

16. The pressure-sensitive adhesive sheet according to claim 14 , wherein the block copolymer is a styrene-based block copolymer including 5% to 40% by weight of styrene.

17. The pressure-sensitive adhesive sheet according to claim 14 , wherein the pressure-sensitive adhesive layer comprises:
a high softening point resin having a softening point of 120° C. or higher; and
a low softening point resin having a softening point of lower than 120° C.,
the high softening point resin comprises:
a terpene-phenol resin A having a hydroxyl value of 40 mg KOH/g or higher, and lower than 80 mg KOH/g; and
a terpene-phenol resin B having a hydroxyl value of 80 mg KOH/g or higher, and the low softening point resin comprises a terpene resin.

18. A pressure-sensitive adhesive sheet for portable electronics, the pressure-sensitive adhesive sheet comprising:
a pressure-sensitive adhesive layer;
a substrate film supporting the pressure-sensitive adhesive layer; and
a tab, wherein
the pressure-sensitive adhesive sheet exhibits a shear adhesive strength of 1.0 MPa or greater, a tensile strength at break of 20 MPa or greater, and an elongation at break of 500% or greater, with the tensile strength (MPa) at break being at least 10 times the shear adhesive strength (MPa);
the pressure-sensitive adhesive sheet exhibits a tensile recovery of 80% or greater, wherein the tensile recovery is determined as follows: the pressure-sensitive adhesive sheet is subjected to a tensile test in which a designated segment of a length L 0 in the pressure-sensitive adhesive sheet is stretched by 100%; when stretched by 100%, the pressure-sensitive adhesive sheet is released; when the designated segment has a length L 1 at five minutes after released, the tensile recovery is determined by an equation: tensile recovery (%)=L 0 /L 1 ×100;
the pressure-sensitive adhesive layer comprises an acrylic polymer in an amount accounting for more than 50% by weight of polymers in the pressure-sensitive adhesive layer;
the acrylic polymer comprises, as a monomeric component, an alkyl (meth)acrylate represented by a formula (1):
CH 2 ═C(R 1 )COOR 2   (1)

in which R 1 is a hydrogen atom or a methyl group; R 2 is an acyclic alkyl group having 1 to 20 carbon atoms, and the alkyl (meth)acrylate is present in an amount of 70% by weight or hig

Assignees

• Nitto Denko Corp

Inventors

• Jozuka Kenta
• Nakayama Naoki
• Soeda Yoshikazu
• Buzojima Yasushi
• Higuchi Naoaki

Classifications

• C09J2475/006

  in the substrate · CPC title

• C09J133/06

  of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical · CPC title

• C08L93/00 Primary

  Compositions of natural resins; Compositions of derivatives thereof (of polysaccharides C08L1/00 - C08L5/00; of natural rubber C08L7/00) · CPC title

• C09J201/00

  Adhesives based on unspecified macromolecular compounds · CPC title

• C09J7/22

  Plastics; Metallised plastics · CPC title