Patent ID: 6939901

Claim:
An adhesive composition comprising: (a) at least one acidic group-containing polymerizable monomer selected from the group consisting of a phosphate group-containing polymerizable monomer, a pyrophosphate group-containing polymerizable monomer, a thiophosphate group-containing polymerizable monomer and a sulfonate group-containing polymerizable monomer; (b) a polymerizable monomer represented by the general formula (I): wherein R 1 is hydrogen atom or methyl group; R 2 is a halogen atom, hydroxyl group, mercapto group or —O—R 3 —OH group, wherein R 3 is an alkylene group having 6 to 25 carbon atoms; and Y is oxygen atom or sulfur atom; and (c) at least one hydrophilic polymerizable monomer selected from the group consisting of hydroxyalkyl (meth)acrylates having an alkylene group of 2 or 3 carbon atoms; di-, tri- or tetra-hydroxy (meth)acrylates having an alkylene group of 3 to 5 carbon atoms; mono-, di- or tri-hydroxy di(meth)acrylates having an alkylene group of 3 to 5 carbon atoms; (meth)acryloyloxyalkyl trialkylammonium halides having an alkylene group of 2 to 20 carbon atoms; (meth)acrylamides; mono- or di(hydroxyalkyl) (meth)acrylates having 2 or 3 carbon atoms; and polyethylene glycol di(meth)acrylates having at least 9 oxyethylene groups, wherein the weight ratio of the polymerizable monomer (b)/acidic group-containing polymerizable monomer (a) is 0.001 to 0.5.