Patent ID: 7531604

Claim:
A phospholipid derivative, which is a phospholipid and is a copolymer containing, as essential component units, (A) a component unit A represented by the following formula (1), (B) a component unit B represented by the following formula (2A) and/or the following formula (2B), and (C) a component unit C represented by the following formula (3): wherein, in the formula (1), R 1 and R 2 independently represent hydrogen atom or methyl group, provided that R 1 and R 2 do not simultaneously represent methyl group; R 3 represents a divalent hydrocarbon group having 1 to 3 carbon atoms; AO independently represents an oxyalkylene group having 2 to 4 carbon atoms; m represents an average molar number of the added oxyalkylene groups and is a number in the range represented as 4≦m≦100; and R 4 represents hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms or an acyl group having 1 to 20 carbon atoms; in the formula (2A), X independently represents hydrogen atom, an alkali metal atom, ammonium or an organic ammonium; and in the formula (3), R 5 CO and R 6 CO independently represent an acyl group having 8 to 24 carbon atoms; R 7 represents a divalent hydrocarbon group having 2 to 4 carbon atoms; X represents hydrogen atom, an alkali metal atom, ammonium or an organic ammonium, and Y represents hydrogen atom, an alkali metal atom ammonium or an organic ammonium, wherein a molar ratio of the component unit A relative to a total of the component unit B and the component unit C is from 7/3 to 3/7, and the component unit C is contained at a ratio of from 1 to 5 moles per 1 mole of the copolymer.