Patent ID: 8597805

Claim:
A binder composition for a magnetic recording medium, which comprises a vinyl copolymer comprising a structural unit denoted by general formula [G] and a structural unit denoted by general formula [P]: wherein, in general formula [G], R a1 denotes a hydrogen atom, a halogen atom, or a methyl group, L a denotes a single bond or a divalent linking group, and A denotes a repeating unit denoted by general formula [a]: wherein, in general formula [a], each of R a11 , R a12 , and R a13 independently denotes a hydrogen atom, a halogen atom, or a methyl group, each of A 1 and A 2 independently denotes a vinyl monomer residue, n1 denotes an integer of equal to or greater than 1, and * denotes a position of a bond with the group denoted by L a ; wherein, in general formula [P], each of R b1 and R b2 independently denotes a hydrogen atom, a halogen atom, or a methyl group, each of L b1 and L b2 independently denotes a single bond or a divalent linear linking group, each of X b1 and X b2 denotes a hydrogen atom, a halogen atom, a methyl group, or a polar group selected from the group consisting of a sulfonic acid group, a sulfonate group, a carboxylic acid group, a carboxylate group, a phosphoric acid group, a phosphate group, and a salt thereof, wherein at least either X b1 or X b2 is the polar group.