Amorphous fluoropolymer pellicle films

Claim 2

A pellicle comprising a thin, durable film of substantially uniform thickness which absorbs less than 10% light at wavelengths between 190 and 820 nanometers, tautly adhered to one edge of an enclosed support frame, said thin film comprising amorphous fluoropolymers having a refractive index between 1.24 and 1.41.

Claim 3

A pellicle according to claim 1, wherein said amorphous fluoropolymers are copolymers of 30-99 mole % of perfluoro-2,2-dimethyl-1,3-dioxole with complementary amounts of at least one comonomer selected from the class consisting of the following compounds: a) tetrafluoroethylene, b) chlorotrifluoroethylene, c) vinylidene fluoride, d) hexafluoropropylene, e) trifluoroethylene, f) perfluoro(alkyl vinyl ethers) of the formula CF 2 ═CFOR F , where R F is a normal perfluoroalkyl radical having 1-3 carbon atoms, g) fluorovinyl ethers of the formula CF 2 ═CFOQZ, where Q is a perfluorinated alkylene radical containing 0-5 ether oxygen atoms, wherein the sum of the C and O atoms in Q is 2 to 10; and Z is a group selected from the class consisting of --COOR, --SO 2 F, --CN, --COF, and --OCH 3 , where R is a C 1 -C 4 alkyl, h) vinyl fluoride, and i) (perfluoroalkyl)ethylene, R f CH═CH 2 , where R f is a C 1 -C 8 normal perfluoroalkyl radical; the glass transition temperature of the copolymer being at least 80° C., the maximum mole percentage, M a . . . M i , of the comonomer in the copolymers being as follows: a) for tetrafluoroethylene, M a =70, b) for chlorotrifluoroethylene, M b =70, c) for vinylidene fluoride, M c =70, d) for hexafluoropropylene, M d =15, e) for trifluoroethylene, M e =30, f) for CF 2 ═CFOR F , M f =30, g) for CF 2 ═CFOQZ, M g =20, h) for vinyl fluoride, M h =70, and i) for R f CH═CH 2 , M i =10; and, in the case of copolymers with more than one comonomer, the amount of each comonomer being such that the sum, S, of the ratios of the mole percentages, m a . . . m i , to the corresponding maximum mole percentages, M a . . . M i is no larger than 1, as shown below: S=m.sub.a /M.sub.a +m.sub.b /M.sub.b + . . . +m.sub.i /M.sub.i ≦1.

Claim 4

A pellicle according to claim 2 wherein said amorphous fluoropolymer comprises an amorphous copolymer consisting of 30-99 mole % perfluoro-2,2-dimethyl-1,3-dioxole with complementary amounts of tetrafluoroethylene.

Claim 5

A pellicle according to claim 3 wherein said amorphous fluoropolymer comprises a copolymer consisting of 60-90 mole % perfluoro-2,2-dimethyl-1,3-dioxole with 40-10 mole % tetrafluoroethylene.

Claim 6

A pellicle according to claim 2 wherein said film absorbs less than 6% of incident light in the band of 193 nanometers to 820 nanometers.

Claim 7

A pellicle according to claim 5 wherein said film absorbs less than 3% of incident light in the band of 245 nanometers to 820 nanometers.

Claim 8

A pellicle according to claim 1, wherein said thin film has a thickness of 0.3 to 20 microns.