Abstract: A composition for a resin which comprises (a) a compound having one or more structures represented by the following formula in one molecule: wherein R1 represents a hydrocarbon group having 1 to 10 carbon atoms, R2, R3 and R4 each represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, X represents S or O, and an average number of S represented by X is about 50% or more of a total number of S and O constituting the three-member ring, and (b) a compound having one or more active hydrogen atoms in one molecule and which is an alcohol having an acryloyloxy group or a methacryloyloxy group, or a mercaptoalcohol.

Abstract: A process for producing a resin used for preparing an optical material. The process comprises curing a composition comprising an ultraviolet light absorbent and an epithio compound by polymerization in the presence of a catalyst, wherein the ultraviolet light absorbent and the catalyst are in amounts, each expressed as parts by weight per 100 parts by weight of the total amount of the epithio compound, which satisfy both of the following relationships (a) and (b): (a) 0.001≦ultraviolet light absorbent≦1,000, and (b) 0.001≦catalyst≦5,000. The process prevents coloration and clouding of optical material for a lens obtained by polymerization of an epithio compound caused by addition of an ultraviolet light absorbent.

Abstract: A process for tinting a resin and a tinted optical material produced by the process. The process comprising dipping a resin into a liquid containing at least one compound selected from the group consisting of polar inorganic compounds and polar organic compounds and subsequently tinting the resin, wherein the resin is obtained by curing by polymerization of a sulfur-containing compound alone or a composition comprising the sulfur-containing compound, the sulfur-containing compound having in the molecule thereof one or more structures represented by the following formula hydrocarbon group having 1 to 10 carbon atoms, R2, R3 and R4 each represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, Y represents S or O and n represents 0 or 1.

Abstract: A composition for a resin comprising (a) a sulfur-containing compound having in one molecule one or more episulfide groups and/or epoxy groups and (b) a compound having in one molecule one or more isocyanate groups and/or thioisocyanate groups. The composition is useful as an optical material such for a plastic lens for glasses, since the composition exhibits an excellent balance between refractivity index and Abbe number and has a high impact resistance.

Abstract: A resinous composition which comprises a compound having, in one molecule, one or more structures of the formula (1) ##STR1## wherein R.sup.1 is a hydrocarbon having 1 to 10 carbon atoms; R.sup.2, R.sup.3 and R.sup.4 are each hydrogen or a hydrocarbon group having 1 to 10 carbon atoms; and X is S or O, and a ratio of S to the total of S and O constituting the three-membered ring is 50% or more on the average; and another compound having one or more SH groups in one molecule. The resinous composition can be used for an optical material having improved oxidation resistance.