Patent ID: 8617711

Claim:
A single layer film comprising at least one anionic hydrophilic group selected from a sulfonic acid group, a carboxyl group and a phosphate group, the single layer film having an anion concentration ratio (Sa/Da) of an anion concentration at a surface (Sa) to an anion concentration at a deep part (Da) of 1.1 or more, which is obtained by coating a composition containing a compound (I) represented by the general formula (1) mentioned below, a compound (II) having two or more (meth)acryloyl groups, and a solvent having a solubility parameter of 9.5 (cal/cm 3 ) 1/2 or more, drying the composition whereby the amount of the residual solvent in the composition just before polymerizing is 10% or less, and then polymerizing the composition, [Formula I] [X]s[M1]1[M2]mâ€ƒâ€ƒ(1) wherein, s represents 1 or 2; 1 represents 1 or 2; m represents 0 or 1, M1 and M2 may be the same or different, and represent a hydrogen ion, an ammonium ion, an alkali metal ion, or an alkaline earth metal ion, X represents one kind selected from the hydrophilic groups represented by the following general formulae (1-1) to (1-4), wherein, J and Jâ€² may be the same or different and represent H or CH 3 ; n represents 0 or 1; R and Râ€² may be the same or different, represent an aliphatic hydrocarbon group having 1 to 600 carbon atoms and may contain an aromatic ring, an alicyclic group, an ether group or an ester group.