To provide a coating agent composition which is suitable for protective films for display screens such as liquid crystal touch panels and cellular phones and for coating the surface of optical articles such as an optical lens and an optical prism, and which can form low-refractive-index coatings having the repellency to water and oil and stain resistance and excellent in adhesion to optical substrates and abrasion resistance .

The low-refractive-index coating agent comprises a copolymer consisting of (1) 70-98.9 pts. wt. of an acrylate or a methacrylate having a perfluoroalkyl group (wherein an ether-oxygen atom may be contained), (2) 1-20 pts. wt. of a polysiloxane having a perfluoroalkyl group (wherein an ether-oxygen atom may be contained) and a (meth)aryloxy group, and (3) 0.1-10 pts. wt. of a monomer having a reactive group bonded to a silicon atom and a free-radically polymerizable group, wherein the sum of the above (1) to (3) is 100 pts. wt. The low-refractive-index coating agent forms coatings having a refractive index nD at 25°C of 1.400 or less.