The purpose of the present invention is to appropriately control the rate of polymerization of a composition in which a thiol compound and an isocyanate compound are added to an episulfide compound and thereby provide an optical material which has high transparency. This composition for use as optical material comprises (a) an episulfide compound, (b) an isocyanate compound, (c) a thiol compound, and (d) a benzyl halide compound represented by formula (1):

##STR00001##

wherein: X is a halogen; L is selected from the group consisting of a hydrogen atom, a methyl group, a halogen, a mercaptomethyl group, and an isocyanate methyl group; and n is 1 or 2.

The present disclosure relates to a xanthene derivative compound with a high refractive index and a manufacturing method therefor. More specifically, provided herein is a compound that has a xanthene-based complex cardo structure and a high refractive index and can be used as a monomer in optical resins requiring a refractive index of 1.7 or higher, and a (co)polymer and an optical lens manufactured therefrom. Given, the xanthene-based complex cardo structure of the compound maximally suppresses the fluidity of the molecular chains and can find applications in the production of resins with high glass transition temperature and excellent thermal stability.

A process for producing an episulfide compound for an optical material of the present invention includes a step of chlorinating glycerin to obtain dichloropropanol; a step of epoxidizing the dichloropropanol to obtain epichlorohydrin; a step of reacting the epichlorohydrin with a sulfating agent to obtain a bis(chlorohydrin) (di)sulfide compound thought a thiol compound; a step of epoxidizing the bis(chlorohydrin) (di)sulfide compound under basic conditions to obtain an epoxy compound; and a step of reacting the epoxy compound with a sulfating agent to obtain an episulfide compound represented by following General Formula (1): ##STR00001## wherein, in the formula, n represents 0 or 1.

Provided are: a method for producing a cured product, including a curable composition preparing step of preparing a curable composition by mixing a polythiol compound with a polyiso(thio)cyanate compound having a water content of 300 ppm or less on a mass basis, and a curing step of curing the curable composition to obtain a cured product; a cured product obtained by curing a curable composition containing a polythiol compound and a polyiso(thio)cyanate compound having a water content of 300 ppm or less on a mass basis; and an eyeglass lens substrate including the cured product.

According to the present invention, a polythiol compound having a total nitrogen content of 50 to 600 ppm inclusive can be provided. According to the present invention, a method for producing the polythiol compound can also be provided, said method being characterized by comprising the steps of: reacting a polyalcohol with thiourea to prepare a thiuronium salt; and adding at least one base selected from the group consisting of hydrazine (hydrate), ammonia and an amine and an inorganic base (that is different from hydrazine (hydrate) or ammonia) to the thiuronium salt in the presence of an organic solvent to hydrolyze the thiuronium salt.

According to the present invention, it is possible to provide an optical material composition that contains an episulfide compound represented by formula (1) and an episulfide compound represented by formula (2). According to this optical material composition, it is possible to suppress a reduction in the yield rate caused by molding defects, and possible to obtain an optical material having excellent dyeability. ##STR00001##
(In formula (1), m and p are each an integer between 0 and 4, and n and q are each an integer between 0 and 2.) ##STR00002##
(In formula (2), m is an integer between 0 and 4 and n is an integer between 0 and 2).

According to the present invention, a composition for an optical material can be provided, which is characterized by containing an episulfide compound having a value of turbidity in acetone of 3.0 ppm or less. According to a preferred embodiment of the present invention, a composition for an optical material can be provided, which comprises: (a) a compound (an episulfide compound) which has a structure represented by formula (1) and has a value of turbidity in acetone of 3.0 ppm or less; (b) a polyisocyanate compound; and (c) a polythiol compound. ##STR00001##
(In the formula, m represents an integer of 0 to 4; and n represents an integer of 0 or 1.)

The present disclosure relates to a diffraction light guide plate that has excellent thickness uniformity and flatness, and at the same time, has low haze, and excellent mechanical properties such as pencil hardness and strength, and a method for manufacturing the diffraction light guide plate.

According to the present invention, a composition for an optical material can be provided, which is characterized by containing an episulfide compound having a value of turbidity in acetone of 3.0 ppm or less. According to a preferred embodiment of the present invention, a composition for an optical material can be provided, which comprises: (a) a compound (an episulfide compound) which has a structure represented by formula (1) and has a value of turbidity in acetone of 3.0 ppm or less; (b) a polyisocyanate compound; and (c) a polythiol compound.

##STR00001##

(In the formula, m represents an integer of 0 to 4; and n represents an integer of 0 or 1.)

A polymerizable composition for an optical material of the present invention includes polyisocyanate (a) including aliphatic polyisocyanate (a1) and a modified aliphatic polyisocyanate (a2), an episulfide (b), and a polythiol (c).