R3 is a hydrogen or chlorine atom or a hydroxyl group; R4 is a carboxylic acid group or a salt, ester or amide thereof; R5 is a hydrogen, chlorine or fluorine atom or a methyl, methoxyl or hydroxyl group or a carboxylic acid group or a salt, ester or amide thereof; R6 is a hydrogen atom or a methyl, or propyl group; X is an oxygen atom or a bond; and Y is an alkylene group of up to 6 carbon atoms