Pressure-sensitive adhesive sheet and pressure-sensitive adhesive composition

Abstract

A pressure-sensitive adhesive composition according to an embodiment includes: 100 parts by mass of a polymer (A) having a glass transition temperature lower than 0° C.; and 0.1 to 20 parts by mass of a polymer (B) that contains, as monomer units, both a monomer having a functional group equivalent (Fge) of 1000 g/mol≤Fge<15000 g/mol and having a polyorganosiloxane skeleton and a monomer whose homopolymer has a glass transition temperature of 40° C. or higher, and that has a weight average molecular weight (MwB) of 10000≤MwB≤100000.

What is claimed is: 
     
       1. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive composition, wherein
 the pressure-sensitive adhesive composition includes: 
 100 parts by mass of an acrylic polymer (A) having an acrylic acid and having a glass transition temperature lower than 0° C.; and 
 0.1 to 20 parts by mass of a polymer (B) that contains, as monomer units, a monomer (B1) having a functional group equivalent (Fge) of 1000 g/mol≤Fge<2990 g/mol and having a polyorganosiloxane skeleton and 30% by mass to 50% by mass of a (meth)acrylic monomer (B2) whose homopolymer has a glass transition temperature of 80° C. or higher, and that has a weight average molecular weight (MwB) of 10000≤MwB<100000, 
 wherein the (meth)acrylic monomer (B2) is at least one monomer selected from the group consisting of dicyclopentanyl methacrylate, dicyclopentanyl acrylate, isobornyl methacrylate, isobornyl acrylate, methyl methacrylate, 1-adamantyl methacrylate, and 1-adamantyl acrylate, and 
 wherein pressure-sensitive adhesive force to each of a stainless plate, an ABS plate, and a glass plate, occurring in an initial condition of 23° C. for 30 minutes, is smaller than 3.0 N/25 mm, and wherein 
 pressure-sensitive adhesive force to each of the plates, occurring in an ordinary condition of 48 hours at 40° C., followed by 23° C. for 30 minutes, is 5.7 times or more larger than the pressure-sensitive adhesive force occurring in the initial condition. 
 
     
     
       2. The pressure-sensitive adhesive sheet according to  claim 1 , wherein the pressure-sensitive adhesive layer is formed on at least one surface of a supporting body. 
     
     
       3. The pressure-sensitive adhesive sheet according to  claim 1 , wherein the monomer having a polyorganosiloxane skeleton is one or more monomers selected from the group consisting of monomers represented by the following general formula (1) or (2): 
       
         
           
           
               
               
           
         
         [wherein, R 3  is hydrogen or methyl; R 4  is methyl or a monovalent organic group; and each of m and n is an integer of 0 or more.]