In the antireflection filter which possesses the antireflection formation which at least consists of the dielectric thin film

摘要

PROBLEM TO BE SOLVED: To obtain an antireflection filter having improved contamination resistance and scratching resistance by forming a film containing an alkoxysilane compd. having specified perfluoropolyether groups and an alkoxysilane compd. having specified long-chain hydrocarbon groups on the surface of an antireflection layer. SOLUTION: This antireflection filter has an antireflection layer comprising a dielectric thin film on the surface of a transparent base body. Further, the filter has a coating film on the surface is the antireflection layer, and the coating film contains an alkoxysilane compd. having perfluoropolyether groups expressed by Rf(CO-X-R1 -Si(OR2 )3 )n and an alkoxysilane compd. having long- chain hydrocarbon groups expressed by formula R3 -Si(OR2 )3 . In formulae, Rf is a perfluoropolyether group, R1 is an alkylene group, R2 is an alkyl group, R3 is a long-chain hydrocarbon group having =10 carbon atoms, X is a group selected from among -O-, -NH- and -S- and (n) is a natural number =2.