Patent ID: 7759442

Claim:
An adhesive composition comprising, as raw monomers, an alkyl (meth)acrylate ester whose alkyl group has 4 to 18 carbon atoms, a carboxyl group-containing vinyl monomer, a phosphoric acid group-containing vinyl monomer represented by the following general formula (1), and a copolymerizable vinyl monomer which is optionally copolymerizable with the above monomers, wherein with respect to a proportion of the raw monomers, an amount of the alkyl (meth) acrylate ester is from 60 to 99 parts by weight based on 100 parts by weight of the total amount of the raw monomers, and a total proportion of the carboxyl group-containing vinyl monomer, the phosphoric acid group-containing vinyl monomer and the copolymerizable vinyl monomer is from 1 to 40 parts by weight based on 100 parts by weight of the total amount of the raw monomers, and a carboxyl group concentration is from 0.05 to 1.50 mmol/g and a phosphoric acid group concentration is from 0.01 to 0.45 mmol/g in the raw monomers: in the general formula (1), R 1 represents a hydrogen atom or a methyl group, R 2 represents a polyoxyalkylene group represented by the following general formula (2), and X represents a phosphoric acid group or a salt thereof represented by the following general formula (3) in the general formula (2), n represents an integer of 1 to 4, and m represents an integer of 2 or more, and in the general formula (3), M 1 and M 2 each independently represents a hydrogen atom or a cation.