Cured fluorine-containing material

A cured fluorine-containing material comprising as the backbone a perfluoropolyether of the following general formula (1):

• —(Rf—O)q— (1)
• wherein Rf is a perfluoroalkylene group of 1 to 6 carbon atoms and q is a number of 1 to 500,
• wherein the cured fluorine-containing material has a refractive index of up to 1.335 at 25° C., and
• wherein the cured fluorine-containing material is obtained by curing a curable composition comprising:
• (A) a linear fluoropolyether compound having at least two alkenyl groups per molecule and a perfluoroalkyl ether structure of the formula (1) in the backbone, wherein said linear fluoropolyether compound is of the following formula (2):
• wherein X is independently —CH2—, —CH2O—, or —Y—NR—CO—,
• Y is —CH2— or
• in the o, m or p position,
• R is hydrogen, methyl, phenyl or allyl,
• p is independently 0 or 1, k is an integer of 2 to 6, and m and n each are an integer of 0 to 200,
• (B) a fluorine-containing organohydrogensiloxane, and
• (C) a platinum group catalyst,
• wherein the fluorine-containing organohydrogensiloxane, (B), having hydrosilyl groups, is provided in an amount such that 0.5 to 5 mol of the hydrosilyl groups are available per mol of alkenyl groups in the linear fluoropolyether compound, (A).