| abstract |
Provided is a coating composition which can form a film having a low refractive index in a short wavelength band and excellent in solubility in an alkaline aqueous solution and is excellent in storage stability. The unit has a unit represented by-[CX1X2-CY (Rf1-COOM)]-, and the content of a -COOM group is 1.5 x 10-3 to 1.9 x 10-3 mol / g. A coating composition containing the fluoropolymer (A). X1 and X2 are each independently a hydrogen atom, a fluorine atom or a chlorine atom, Y is a hydrogen atom, a fluorine atom, a chlorine atom, a methyl group or a trifluoromethyl group, and Rf1 is an etheric oxygen atom between carbon-carbon atoms. A linear perfluoroalkylene group which may contain, or a linear oxyperfluoroalkylene group which may contain an etheric oxygen atom between carbon-carbon atoms, -COOM is -COOH, or -COOZ1 (Z1 is substituted) May be an ammonium ion). [Selection figure] None |