Patent ID: 7125926

Claim:
A surface treatment agent comprising: (A) a hydrolyzable metal alkoxide or a hydrolyzate thereof, (B) a fluorocompound containing a perfluoroalkyl group and a functional group reactive with the hydrolyzable metal alkoxide (A), (C) an adhesion improvement agent, and (D) a fluoropolymer having a number-average molecular weight of at least 500, wherein a one-layer film formed from the surface treatment agent has a graded refractive index structure, and the fluoropolymer (D) is a polymer of the general formula (3): -(M) x -(N) y - wherein x and y are from 1 to 500, the structural unit M is derived from a fluorine-containing ethylenic monomer and is a structural unit derived from a fluorine-containing ethylenic monomer of the formula (M): (in which, X 1 and X 2 are, the same or different, H or F, X 3 is H, F, CH 3 or CF 3 , X 4 and X 5 are, the same or different, H, F or CH 3 , Rf 1 is an organic group wherein 1 to 3 Y 3 groups (Y 3 is a hydroxyl group, a glycidyl group, an amino group, an alkoxy group, a carboxyl group, an isocyanate group, or a C 1 –C 10 monovalent organic group having at least one of these reactive groups) are bonded to a C 1 –C 40 fluorine-containing alkyl group or a C 2 –C 100 fluorine-containing alkyl group having an ether linkage, a is an integer of from 0 to 3, and b and c are, the same or different, 0 or 1), and the structural unit N is a structural unit obtained by reacting an unsaturated carboxylic acid of the formula (A): (in which R 1 is a divalent organic group having 1 to 7 carbon atoms, which may be substituted with a fluorine atom, X 6 is H, F, CH 3 or CF 3 , X 7 and X 8 are, the same or different, H or F, and f is 0 or 1), or a derivative thereof, with the Y 3 group in the Rf 1 group of the ethylenic monomer giving the structural unit M.