Abstract: The invention provides a polytetrafluoroethylene composition having high flowability. The polytetrafluoroethylene composition contains a particulate polytetrafluoroethylene having fibrillability and a particulate synthetic amorphous silica. The particulate polytetrafluoroethylene is a polytetrafluoroethylene fine powder or a polytetrafluoroethylene molding powder. The particulate synthetic amorphous silica is obtained by a dry process and has an average primary particle size smaller than 200 nm. The particulate synthetic amorphous silica is attached to the surface of the particulate polytetrafluoroethylene.

Abstract: The invention provides a polytetrafluoroethylene composition having high flowability. The polytetrafluoroethylene composition contains a particulate polytetrafluoroethylene having fibrillability and a particulate synthetic amorphous silica. The particulate polytetrafluoroethylene is a polytetrafluoroethylene fine powder or a polytetrafluoroethylene molding powder. The particulate synthetic amorphous silica is obtained by a dry process and has an average primary particle size smaller than 200 nm. The particulate synthetic amorphous silica is attached to the surface of the particulate polytetrafluoroethylene.

Abstract: A method of splicing optical fibers is provided to reduce the splicing loss of the first and second optical fibers having different MFDs from each other. In a pre-fusion heating step, the MFD at the adjacent end face of the optical fiber having larger MFD is enlarged by heating a portion including the adjacent end face thereof so as to diffuse a dopant. After the pre-fusion heating step, fusion-splicing of the first and the second optical fibers is performed. Thereafter, during the post-fusion heating step, the dopant is diffused by heating a portion including the fusion-spliced part between the first and the second optical fibers.

Abstract: The present invention relates to an optical fiber transmission line having a structure offering superior connection loss characteristics at the fusion-spliced position between optical fibers. This optical fiber transmission line has at least first and second optical fibers that are fusion-spliced. Each of these first and second optical fibers has a core region doped with 10 mol % or more of Ge and has a mode field diameter with a minimum value of 7 &mgr;m or less at the wavelength of 1550 nm. The difference between the minimum mode diameter of the first optical fiber and that of the second optical fiber is 1 &mgr;m or less.

Abstract: The present invention relates to an optical fiber transmission line having a structure offering superior connection loss characteristics at the fusion-spliced position between optical fibers. This optical fiber transmission line has at least first and second optical fibers that are fusion-spliced. Each of these first and second optical fibers has a core region doped with 10 mol % or more of Ge and has a mode field diameter with a minimum value of 7 &mgr;m or less at the wavelength of 1550 nm. The difference between the minimum mode diameter of the first optical fiber and that of the second optical fiber is 1 &mgr;m or less.

Abstract: A method of splicing optical fibers is provided to reduce the splicing loss of the first and second optical fibers having different MFDs from each other. In a pre-fusion heating step, the MFD at the adjacent end face of the optical fiber having larger MFD is enlarged by heating a portion including the adjacent end face thereof so as to diffuse a dopant. After the pre-fusion heating step, fusion-splicing of the first and the second optical fibers is performed. Thereafter, during the post-fusion heating step, the dopant is diffused by heating a portion including the fusion-spliced part between the first and the second optical fibers.

Abstract: An optical fiber 2 is spliced to an optical fiber 1 in a state that those optical fibers are axially shifted away from each other by an offset quantity D. With this splicing of the optical fibers, a coupling loss arises at a fusion splicing part 1c. A plurality of fusion splicing parts 1c are provided. The terminal part of the final optical fiber of serially spliced optical fibers is a non-reflection treating part 10. Light propagating through the optical fiber 1 is attenuated at the fusion splicing part, whereby non-reflection of light is realized. The back reflection light is also attenuated at the fusion splicing part, thereby reducing the amount of the back reflection light traveling back to the core 1a of the optical fiber 1.

Abstract: A water-absorptive soft contact lens comprising a polymer prepared by polymerizing a monomer mixture comprising (A) a fluorine-containing styrene derivative represented by the general formula (I): ##STR1## wherein R.sup.1 is hydrogen atom or methyl group, m is an integer of 1 to 3 and n is 0 or an integer of 1 to 7, and (B) N, N-dimethyl(meth)acrylamide. The water-absorptive soft contact lens has excellent oxygen permeability, high mechanical strength and excellent flexibility independent of water content.

Abstract: A process for producing a tinted contact lens, which includes dissolving a soluble vat dye in a monomer capable of dissolving the soluble vat dye therein, mixing the monomer having the soluble vat dye dissolved therein and other monomers, polymerizing the monomer mixture and processing the resulting polymer into a shape of a contact lens.

Abstract: 1. A water-absorptive contact lens obtained by saponification of a copolymer composed essentially of:(A) from 1 to 30% by weight of a (meth)acrylate polymer having at least one polymerizable group per molecule on an average obtained by copolymerizing (a) an alkyl (meth)acrylate and (b) a monomer having at least two polymerizable groups per molecule, as the main components;(B) from 1 to 10% by weight of a vinyl monomer selected from the group consisting of maleic acid esters and N-vinyl lactams;(C) from 50 to 98% by weight of a fatty acid vinyl ester; and(D) from 0.02 to 10% by weight of a cross linking monomer.

Abstract: An ocular lens material made of a copolymer consisting essentially of (A) a polysiloxane macromonomer having polymerizable groups bonded by one or more urethane bonds to the siloxane main chain and (B) an alkyl (meth)acrylamide, wherein the weight ratio of the polysiloxane macromonomer to the alkyl (meth)acrylamide ranges from 10:90 to 90:10.

Abstract: A soft ocular lens material obtained by copolymerizing polymerizable components comprising (A) a fluorine-containing (meth)acrylate having a hydroxyl group of the formula (I): ##STR1## wherein R.sup.1 is a hydrogen atom or a methyl group, R.sup.2 is a C.sub.5-15 perfluoroalkyl group, and n is 0 or 1, (B) a hydrophilic monomer, and (C) at least one monomer selected from the group consisting of silicon-containing (meth)acrylates and siloxane-containing styrene derivatives, wherein the ratio of the amount of the fluorine-containing (meth)acrylate (A) to the amount of the hydrophilic monomer (B) is from 20/80 to 70/30 by weight ratio, and the ratio of the total amount of the fluorine-containing (meth)acrylate (A) and the hydrophilic monomer (B) to the amount of the monomer (C) is from 30/70 to 90/10 by weight ratio.

Abstract: An ocular lens material made of a copolymer comprising, as main copolymerizable components, (A) a polysiloxane macromonomer having polymerizable groups bonded via one or more urethane bonds to the siloxane main chain and (B) an alkyl (meth)acrylamide, wherein the weight ratio of the polysiloxane macromonomer to the alkyl (meth)acrylamide is from 5/95 to 90/10.

Abstract: A soft ocular lens material is formed of a copolymer consisting essentially of:(A) from 5 to 70 parts by weight of a fluorine containing (meth)acrylate;(B) from 5 to 60 parts by weight of an alkyl (meth)acrylate;(C) from 3 to 45 parts by weight of a polysiloxane macromonomer having pllymerizable groups at both terminals; and(D) from 3 to 40 parts by weight of a polysiloxane macromonomer having polymerizable groups bonded via one or two urethane bonds to the siloxane main chain.