Adhesive sheet
According to the present invention, there can be obtained a pressure sensitive adhesive sheet having an adhesive layer which even when the thickness is reduced to 5 μm or less, exhibits a desired adhesive strength. The pressure sensitive adhesive sheet includes a base material having an adhesive layer provided on at least one surface thereof, wherein a pressure sensitive adhesive constituting the adhesive layer contains (A) an acrylic copolymer having a crosslinkable functional group and (B) a urethane resin, the urethane resin is a product obtained by allowing an isocyanate-terminated urethane prepolymer obtained by a reaction between [b1] a diol and [b2] a polyvalent isocyanate compound to react with [b3] a chain extender, and the chain extender is composed of [b4] a compound having two hydroxyl groups and/or amino groups and [b5] a compound having three or more hydroxyl groups and/or amino groups, in a proportion of [b4] to [b5] of from 7/3 to 10/0 in terms of a mass ratio.
1. A pressure sensitive adhesive sheet, comprising a base material having an adhesive layer provided on at least one surface thereof, wherein:
the adhesive layer comprises a pressure sensitive adhesive comprising (A) an acrylic copolymer having a crosslinkable functional group, and (B) a urethane resin;
wherein
said urethane resin (B) is a product obtained by allowing an isocyanate-terminated urethane prepolymer obtained by a reaction between [b1] a diol and [b2] a polyvalent isocyanate compound to react with [b3] a chain extender comprising [b4] at least one compound selected from the group consisting of an aliphatic diol, an alkanolamine, a bisphenol and a phenolamine, and [b5] a compound having three or more groups selected from hydroxyl groups and amino groups in a proportion of [b4] and [b5] represented by [b4]/[b5] of from 7/3 to 9/1 in terms of a mass ratio,
a proportion of said acrylic copolymer (A) and said urethane resin (B) represented by (A)/(B) is from 40/60 to 1/99 in terms of a mass ratio, and
a sum of hydroxyl groups and amino groups in each compound of [b4] is two groups.
2. The pressure sensitive adhesive sheet according to claim 1 , wherein the diol [b1] is a glycol having a molecular weight of from 1,000 to 3,000.
3. The pressure sensitive adhesive sheet according to claim 1 , wherein the [b4] is a compound having one hydroxyl group and one amino group.
4. The pressure sensitive adhesive sheet according to claim 1 , wherein the crosslinkable functional group is from an ethylenically unsaturated carboxylic acid or a hydroxyalkyl(meth)acrylate.
5. The pressure sensitive adhesive sheet according to claim 1 , wherein a monomer constituting the acrylic copolymer (A) further comprises a nitrogen-containing ethylenically unsaturated monomer as a constituent component.
6. The pressure sensitive adhesive sheet according to claim 1 , further comprising a crosslinking agent.
7. The pressure sensitive adhesive sheet according to claim 1 , wherein a weight average molecular weight (Mw) of the acrylic copolymer (A) is from 300,000 to 1,500,000.
8. The pressure sensitive adhesive sheet according to claim 1 , wherein a thickness of the adhesive layer is from 0.1 to 5 μm.
9. The pressure sensitive adhesive sheet according to claim 2 , wherein the [b4] is a compound having one hydroxyl group and one amino group.
10. The pressure sensitive adhesive sheet according to claim 2 , wherein the crosslinkable functional group is from an ethylenically unsaturated carboxylic acid or a hydroxyalkyl(meth)acrylate.
11. The pressure sensitive adhesive sheet according to claim 2 , wherein a monomer constituting the acrylic copolymer (A) further comprises a nitrogen-containing ethylenically unsaturated monomer as a constituent component.
12. The pressure sensitive adhesive sheet according to claim 2 , further comprising a crosslinking agent.
13. The pressure sensitive adhesive sheet according to claim 2 , wherein a weight average molecular weight (Mw) of the acrylic copolymer (A) is from 300,000 to 1,500,000.
14. The pressure sensitive adhesive sheet according to claim 2 , wherein a thickness of the adhesive layer is from 0.1 to 5 μm.