An episulfide which has an alicyclic, aromatic or heterocyclic skeleton and has two or more moieties represented by the formula ##STR1## wherein X is S or O, and S is in an amount of 50% or more, on the average, of the total of S and O constituting a three-membered ring. A cured material obtained by polymerizing this episulfide compound is a desirable optical material for various uses, particularly as a lens material for spectacles.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a novel episulfide compound. More 
specifically, the present invention relates to a novel episulfide compound 
which can suitably be used as an optical material for plastic lenses, 
prisms, optical fibers, information recording substrates, filters and the 
like, above all, a material for plastic spectacle lenses. 
2. Description of the Related Art 
Plastic materials are lightweight, tough and easily dyeable, and for this 
reason, they have often been used as various optical materials, 
particularly spectacle lenses in recent years. As the performance of the 
optical materials, particularly the spectacle lenses, they are required to 
possess a low specific gravity, optical performances such as a high 
refractive index and a high Abbe's number, and physical performances such 
as a high heat resistance and a high strength. The high refractive index 
permits the lenses to be thin, the high Abbe's number decreases the 
chromatic aberration of the lenses, and the high heat resistance and the 
high strength can facilitate the secondary processing of the lenses and 
they are also important from the viewpoints of safety and the like. 
Typical plastic materials at an early stage of conventional techniques in 
this field are materials obtained by polymerizing compounds such as 
diethylene glycol bisallyl carbonate, a combination of this bisallyl 
carbonate and diallyl phthalate, and various kinds of methacrylates. These 
plastic materials have a refractive index of about 1.5 to 1.55, so that 
the obtained lenses are thick, and in consequence, the lightweight 
properties are lost. Therefore, the materials having the high refractive 
index have been desired, and various investigations have been conducted 
with the intention of obtaining a refractive index of 1.6 or more. There 
have already been suggested a polymer of a methacrylate compound 
containing a chlorine atom or a bromine atom, and a thermosetting optical 
material having a urethane structure obtained by the reaction of a hydroxy 
compound containing the bromine atom with an isocyanate (Japanese Patent 
Application Laid-open No. 164615/1983 and the like). However, when the 
compound containing the chlorine atom or the bromine atom is used, the 
specific gravity of the obtained lenses is large, and also in this case, 
the lightweight properties are eventually lost. Thus, thermosetting 
optical materials having thiourethane structures obtained by the reaction 
of polythiol compounds with polyisocyanate compounds have been suggested 
in Japanese Patent Publication No. 58489/1992 and Japanese Patent 
Application Laid-open No. 148340/1993. The various novel polythiol 
compounds which can be used as the materials of these thiourethanes have 
also been suggested. That is to say, Japanese Patent Application Laid-open 
No. 148340/1993 has suggested a branched polythiol compound having 4 
sulfur atoms in one molecule; Japanese Patent Application Laid-open No. 
270859/1990 has suggested a branched polythiol compound having 5 sulfur 
atoms in one molecule; and Japanese Patent Application Laid-open No. 
192250/1994 has suggested a polythiol compound having a dithiane ring 
structure in one molecule. Additionally, in Japanese Patent Laid-open No. 
81320/1991, there has been suggested a process for preparing a lens 
material by the use of a compound obtained by converting, into an 
episulfide group, a part or all of the epoxy groups of each of epoxy 
compounds such as known amine epoxy resins, phenolic epoxy resins, 
alcoholic epoxy resins, unsaturated compounds-containing epoxy resins, 
glycidyl ester epoxy resins, urethane epoxy resins and alicyclic epoxy 
resins. The thiourethane resin lenses which can be obtained by the 
polythiol compounds and the polyisocyanate compounds can possess a 
refractive index as high as about 1.66. However, episulfide resin lenses 
which can be obtained from episulfide compounds derived from known epoxy 
resins have a refractive index of at most about 1.6. Anyway, the problems 
of further thinning and reducing the weight of lenses can be solved to 
some extent by these conventional sulfur-containing compounds, but 
needless to say, a further higher refractive index is desirable. On the 
other hand, another important performance required for the optical 
material is that the chromatic aberration is low. The higher the Abbe's 
number is, the lower this chromatic aberration is, and therefore a 
material having the high Abbe's number is desired. That is to say, the 
simultaneous achievement of a high refractive index and a high Abbe's 
number is also desired. However, the Abbe's number usually tends to 
decline with an increase in the refractive index, and in plastic materials 
obtained by using conventional diethylene glycol bisallyl carbonate, known 
episulfide compounds and conventional compounds such as the polythiol 
compounds and the polyisocyanate compounds as raw materials, the Abbe's 
number is in the range of about 50 to 55 in the case of a refractive index 
of 1.5 to 1.55, and it is about 40 in the case of a refractive index of 
1.60 and it is at most about 32 in the case of a refractive index of 1.66. 
On the other hand, the improvement of the heat resistance has often been 
tried by the use of a polyfunctional compound and a crosslinking agent, 
but in general, for the expression of a high refractive index, the 
molecular weight of the material compound is increased, so that the 
crosslink density decreases. For the expression of a high Abbe's number, 
the alkyl group content is increased, so that the stiffness of molecules 
constituting the material compound deteriorates and a sufficient 
improvement effect has not been obtained yet. 
In the conventional optical materials obtained from the episulfide 
compounds and the combinations of the polythiol compounds and the 
isocyanate compounds, the increase in the refractive index is limited, and 
this increase in the refractive index leads to the deterioration of the 
Abbe's number. Therefore, there has been a problem that the sufficiently 
high refractive index and Abbe's number cannot be balanced with each 
other. Furthermore, the improvement of the above-mentioned optical 
properties, i.e., the refractive index and the Abbe's number leads to the 
deterioration of the heat resistance, and therefore there has been a 
problem that while the sufficiently high refractive index and Abbe's 
number are balanced with each other, the excellent heat resistance cannot 
be obtained. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a novel sulfur-containing 
compound which can become an optical material having a small thickness and 
a low chromatic aberration. 
Another object of the present invention is to provide a novel 
sulfur-containing compound which can become an optical material having a 
small thickness, a low chromatic aberration and a high heat resistance. 
Still another object of the present invention is to provide a novel optical 
material having such excellent optical properties as mentioned above. 
The present invention is directed to an episulfide compound having two or 
more moieties represented by the following formula (1) and having a cyclic 
skeleton 
##STR2## 
wherein X is S or O, and a numerical ratio of S is 50% or more, on the 
average, of the total of S and O constituting a three-membered ring. 
The episulfide compound having two or more moieties represented by the 
formula (1) and having the cyclic skeleton can typically roughly 
classified into 
(a) an episulfide compound in which the cyclic skeleton is an alicyclic 
skeleton, 
(b) an episulfide compound in which the cyclic skeleton is an aromatic 
skeleton, and 
(c) an episulfide compound in which the cyclic skeleton is a heterocyclic 
skeleton including a sulfur atom as a hetero-atom. 
Furthermore, each of these compounds may contain a linkage of a sulfide, an 
ether, a sulfone, a ketone, an ester or the like. 
Preferable and typical examples of the episulfide compound (a) having the 
alicyclic skeleton include 1,3- and 
1,4-bis(.beta.-epithiopropylthio)cyclohexane, 1,3- and 
1,4-bis(.beta.-epithiopropylthiomethyl)cyclohexane, 
bis4-(.beta.-epithiopropylthio)cyclohexyl!methane, 
2,2-bis4-(.beta.-epithiopropylthio)cyclohexyl!propane, 
bis4-(.beta.-epithiopropylthio)cyclohexyl!sulfide, 
2,5-bis(.beta.-epithiopropylthio)-1,4-dithiane, and 
2,5-bis(.beta.-epithiopropylthioethylthiomethyl)-1,4-dithiane. 
Preferable and typical examples of the episulfide compound (b) having the 
aromatic skeleton include 1,3- and 
1,4-bis(.beta.-epithiopropylthio)benzene, 1,3- and 
1,4-bis(.beta.-epithiopropylthiomethyl)benzene, 
bis4-(.beta.-epithiopropylthio)phenyl!methane, 
2,2-bis4-(.beta.-epithiopropylthio)phenyl!propane, 
bis4-(.beta.-epithiopropylthio)phenyl!sulfide, 
bis4-(.beta.-epithiopropylthio)phenyl!sulfone, and 
4,4-bis(.beta.-epithiopropylthio)biphenyl. 
Examples of the episulfide compound (c) having the heterocyclic skeleton 
including the sulfur atom as the hetero-atom include episulfide compounds 
having a structure represented by the formula (2) 
##STR3## 
wherein E.sub.ps is an epithiopropyl group represented by the following 
formula (3); Y is --(CH.sub.2 CH.sub.2 S); Z is a hydrogen atom, an alkyl 
group having 1 to 5 carbon atoms or --(CH.sub.2).sub.m SY.sub.n E.sub.ps ; 
U is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms; m is an 
integer of 1 to 5; and n is an integer of 0 to 4, 
##STR4## 
wherein X is S or O, and a numerical ratio of S is 50% or more, on the 
average, of the total of S and O constituting a three-membered ring. 
In the formula (2), n is an integer of 0 to 4, preferably 0 to 3, more 
preferably 0 to 2, most preferably 0. Moreover, m is an integer of 1 to 5, 
preferably 1 to 4, more preferably 1 to 3, most preferably 1. In the 
formula (3), X is S or O, and a numerical ratio of S is 50% or more, on 
the average, of the total of S and O constituting the three-membered ring, 
and it is preferably 80 to 100%, more preferably 90 to 100%, particularly 
preferably 95 to 100%, most preferably 100%. If n is more than 4, the heat 
resistance of an optical material obtained by polymerization/curing is too 
poor to be used as the optical material. Furthermore, even if n is 4 or 
less, the smaller it is, the more advantageous it is from the viewpoint of 
the heat resistance, but the larger it is, the more advantageous it is 
from the viewpoint of the flexibility of the material. When m is 4 or 5, 
the content of sulfur is low, so that a high refractive index cannot be 
attained and the heat resistance of the material deteriorates. A case 
where m is 1 is most advantageous from the viewpoints of the refractive 
index and the heat resistance. In the formula (3), if the numerical ratio 
of S in X is 80% or more, particularly 50% or less, on the average, of the 
total of S and O constituting the three-membered ring, the content of 
sulfur is low, so that a high refractive index cannot be attained, and the 
reactivity of the compound lowers, which requires the polymerization at a 
high temperature. In consequence, the material tends to be colored. The 
performance of the compound according to the present invention and the 
optical material obtained by its polymerization/curing depends upon the 
integers n and m as well as the ratio of S in X, as described above. 
However, in preferable embodiments and the like, the integers n and m are 
not independently decided within the above-mentioned ranges. Preferable 
examples include compounds in which n is in the range of 0 to 3 and m is 
in the range of 1 to 4. Above all, the compounds in which n is in the 
range of 0 to 2 and m is in the range of 1 to 3 are more preferable. Among 
others, the compounds in which n is 0 and m is 1 are most preferable. In 
addition, U is any of the hydrogen atom and the alkyl groups having 1 to 5 
carbon atoms, but in order to maintain the refractive index at a high 
level, the hydrogen atom is preferable. Z is any of the hydrogen atom, the 
alkyl groups having 1 to 5 carbon atoms and --(CH.sub.2).sub.m SY.sub.n 
E.sub.ps, but from the viewpoint of the high heat resistance, 
--(CH.sub.2).sub.m SY.sub.n E.sub.ps for increasing a crosslink density is 
desirable, but in consideration of balance between the heat resistance and 
the flexibility of the material, the hydrogen atom is more preferable. 
Of these compounds, some examples will actually be enumerated. That is to 
say, they include 2,5-bis(.beta.-epithiopropylthiomethyl)-1,4-dithiane, 
2,5-bis(.beta.-epithiopropylthioethylthiomethyl)-1,4-dithiane, 
2,5-bis(.beta.-epithiopropylthioethyl)-1,4-dithiane and 
2,3,5-tri(.beta.-epithiopropylthioethyl)-1,4-dithiane: 
##STR5## 
The optical material of the cured resin according to the present invention 
may be obtained by copolymerizing/curing any of one and mixtures of the 
materials (a), (b) and (c), so long as it is suitable for the objects of 
the present invention. 
The novel episulfide compound of the present invention represented by the 
formula (1) can be prepared by any of various methods, but for example, by 
a method which comprises reacting a compound of the formula (4) having two 
or more mercapto groups corresponding to the compound (a), (b) or (c) with 
an epihalohydrin typified by epichlorohydrin in the presence of an alkali 
to obtain a compound having an epoxy group represented by the formula (5), 
and then reacting the thus obtained epoxy compound with a thia-compound 
forming agent such as a thiocyanate, thiourea, triphenylphosphine sulfide 
or 3-methylbenzothiazole-2-thione, preferably the thiocyanate or thiourea: 
##STR6## 
wherein n is an integer of 2 or more; and R is a compound having a cyclic 
structure having 1 to 20 carbon atoms, and this compound may contain a 
linkage of a sulfide, an ether, a sulfone, an ester, a ketone or the like. 
In the preparation method of the epoxy compound represented by the formula 
(5), epichlorohydrin is preferable as the epihalohydrin compound. 
Furthermore, the epihalohydrin compound is stoichiometrically used in an 
amount of moles corresponding to the number of the mercapto groups of the 
mercaptan compound represented by the formula (4), but if the purity, the 
reaction rate, the economy and the like of the product are regarded as 
important, the amount of the epihalohydrin compound may be less than or 
more than the above-mentioned moles. For the reaction, the epihalohydrin 
compound can be used preferably in the range of from its stoichiometric 
amount to 5 times as much as the stoichiometric amount in terms of mol, 
more preferably in the range of from the stoichiometric amount to 2.5 
times as much as the stoichiometric amount in terms of mol. The reaction 
may be carried out under non-solvent or in a solvent, but when the solvent 
is used, it is preferable to use the solvent which can dissolve any of the 
epihalohydrin, the mercaptan compound of the formula (4) and a metallic 
salt of the mercaptan compound. Typical examples of the solvent include 
water, alcohols, ethers, aromatic hydrocarbons, halogenated hydrocarbons 
and mixtures thereof. The reaction can easily proceed in the presence of 
the stoichiometric amount or more of a base. Examples of the base include 
pyridine, tertiary amines such as triethylamine and diazabicycloundecene, 
and hydroxides of alkali metals and alkaline earth metals. Above all, the 
hydroxides of the alkali metals and the alkaline earth metals are 
preferable, and sodium hydroxide, potassium hydroxide and the like are 
more preferable. A reaction temperature is usually in the range of 0 to 
100.degree. C., preferably 0 to 60.degree. C. A reaction time is a time 
taken to complete the reaction under the selected requirements of the 
above-mentioned various conditions, but the proper reaction time is 
usually 10 hours or less. 
In the preparation method of the novel episulfide compound of the present 
invention from the epoxy compound represented by the formula (5), the 
thiocyanate can be used as the thia-compound forming agent, but in this 
case, examples of the preferable thiocyanate include salts of alkali 
metals and alkaline earth metals, and potassium thiocyanate and sodium 
thiocyanate are more preferable. Furthermore, the thiocyanate or thiourea 
which is the thia-compound forming agent can be stoichiometrically used in 
an amount of moles corresponding to the number of the epoxy groups of the 
epoxy compound represented by the formula (2), but if the purity, the 
reaction rate, the economy and the like of the product are regarded as 
important, the amount of the thiocyanate or thiourea may be less than or 
more than the above-mentioned moles. For the reaction, the thiocyanate or 
thiourea can be used preferably in the range of from its stoichiometric 
amount to 5 times as much as the stoichiometric amount in terms of mol, 
more preferably in the range of from the stoichiometric amount to 2.5 
times as much as the stoichiometric amount in terms of mol. The reaction 
may be carried out under non-solvent conditions or in a solvent, but when 
the solvent is used, it is preferable to use the solvent which can 
dissolve any of the thiocyanate, thiourea and the epoxy compound of the 
formula (5). Typical examples of the solvent include water, alcohols such 
as methanol and ethanol; ethers such as diethyl ether, tetrahydrofuran and 
dioxane; hydroxyethers such as methyl cellosolve, ethyl cellosolve and 
butyl cellosolve; aromatic hydrocarbons such as benzene, toluene and 
xylene; and halogenated hydrocarbons such as dichloroethane, chloroform 
and chlorobenzene. Some combinations of these solvents, for example, a 
combination of the alcohol and water, and a combination of the ether, 
hydroxyether, the halogenated hydrocarbon or the aromatic hydrocarbon and 
the alcohol are effective on occasion. In addition, it is an effective 
means for the enhancement of reaction results to add an acid, an acid 
anhydride or the like as a polymerization inhibitor to a reaction 
solution. Typical examples of the acid, the acid anhydride and the like 
include nitric acid, hydrochloric acid, sulfuric acid, fuming sulfuric 
acid, boric acid, arsenic acid, phosphoric acid, prussic acid, acetic 
acid, peracetic acid, thioacetic acid, oxalic acid, tartaric acid, 
propionic acid, butyric acid, succinic acid, maleic acid, benzoic acid, 
anhydrous nitric acid, anhydrous sulfuric acid, boron oxide, arsenic 
pentoxide, phosphorus pentoxide, chromic anhydride, acetic anhydride, 
propionic anhydride, butyric anhydride, succinic anhydride, maleic 
anhydride, benzoic anhydride, phthalic anhydride, silica gel, silica 
alumina and aluminum chloride, and they may be used singly or in a 
combination thereof. The amount of the acid, the acid anhydride or the 
like to be used is usually in the range of 0.001 to 10% by weight, 
preferably 0.01 to 1% by weight with respect to the total amount of the 
reaction solution. A reaction temperature is usually in the range of 0 to 
100.degree. C., preferably 20 to 70.degree. C. A reaction time is a time 
taken to complete the reaction under the selected requirements of the 
above-mentioned various conditions, but the proper reaction time is 
usually 20 hours or less. When the reaction product is washed with an 
aqueous acidic solution, the stability of the obtained compound can be 
improved. Typical examples of the acid which can be used for the aqueous 
acidic solution include nitric acid, hydrochloric acid, sulfuric acid, 
boric acid, arsenic acid, phosphoric acid, prussic acid, acetic acid, 
peracetic acid, thioacetic acid, oxalic acid, tartaric acid, succinic acid 
and maleic acid, and they may be used singly or in a mixture of two or 
more thereof. The aqueous solution of each of these acids can usually 
exert the effect when it is at a pH of 6 or less, but the more effective 
pH is in the range of 3 to 0. 
As a method other than described above, there is a method which comprises 
producing the epoxy compound of the formula (5) by oxidizing a 
corresponding unsaturated compound of the following formula (6) with an 
organic peracid, an alkyl hydroperoxide, hydrogen peroxide or the like, 
and then carrying out the above-mentioned manner to prepare the episulfide 
compound having two or more moieties represented by the formula (1) and 
having the cyclic skeleton: 
EQU R(--SCH.sub.2 CH.dbd.CH.sub.2).sub.n ( 6) 
wherein X is a chlorine atom or a bromine atom; and R and n are as defined 
in the case of the formula (4). 
As still another method, there is a useful method for preparing the 
episulfide compound from a halomercaptan compound represented by the 
formula (7) in accordance with a dehalogenation hydrogen reaction. It is 
known that the halomercaptan can easily be synthesized from the 
above-mentioned unsaturated compound and sulfur chloride or the like 
e.g., F. Lautenschlaerger et al., "J. Org. Chem.", 34, p. 396 (1969)!: 
EQU R(--SCH.sub.2 CHSHCH.sub.2 X).sub.n ( 7) 
wherein X is a chlorine atom or a bromine atom; and R and n are as defined 
in the case of the formula (4). 
The novel episulfide compound of the present invention can be heated and 
polymerized in the presence or absence of a curing catalyst to prepare a 
cured resin which is advantageous for an optical material and the like. A 
preferable method for the preparation of the cured resin is a process in 
which the curing catalyst is used, and examples of the usable curing 
catalyst include amines, phosfines, mineral acids, Lewis acids, organic 
acids, silicates and tetrafluoroboric acid. Typical examples of the curing 
catalyst include 
(1) amine compounds typified by primary amines such as ethylamine, 
n-propylamine, sec-propylamine, n-butylamine, sec-butylamine, 
iso-butylamine, tert-butylamine, pentylamine, hexylamine, heptylamine, 
octylamine, decylamine, laurylamine, myristylamine, 
1,2-dimethylhexylamine, 3-pentylamine, 2-ethylhexylamine, allylamine, 
aminoethanol, 1-aminopropanol, 2-aminopropanol, aminobutanol, 
aminopentanol, aminohexanol, 3-ethoxypropylamine, 3-propoxypropylamine, 
3-isopropoxypropylamine, 3-butoxypropylamine, 3-isobutoxypropylamine, 
3-(2-ethylhexyloxy)propylamine, aminocyclopentane, aminocyclohexane, 
aminonorbornene, aminomethylcyclohexane, amonobenzene, benzylamine, 
phenethylamine, .alpha.-phenylethylamine, naphthylamine and furfurylamine; 
primary polyamines such as ethylenediamine, 1,2-diaminopropane, 
1,3-diaminopropane, 1,2-diaminobutane, 1,3-diaminobutane, 
1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 
1,7-diaminoheptane, 1,8-diaminooctane, dimethylaminopropylamine, 
diethylaminopropylamine, bis-(3-aminopropyl)ether, 
1,2-bis-(3-aminopropoxy)ethane, 
1,3-bis-(3-aminopropoxy)-2,2'-dimethylpropane, amonoethylethanolamine, 
1,2-bisaminocyclohexane, 1,3-bisaminocyclohexane, 1,4-bisaminocyclohexane, 
1,3-bisaminomethylcyclohexane, 1,4-bisaminomethylcyclohexane, 
1,3-bisaminoethylcyclohexane, 1,4-bisaminoethylcyclohexane, 
1,3-bisaminopropylcyclohexane, 1,4-bisaminopropylcyclohexane, hydrogenated 
4,4'-diamonodiphenylmethane, 2-aminopiperidine, 4-aminopiperidine, 
2-aminomethylpiperidine, 4-aminomethylpiperidine, 2-aminoethylpiperidine, 
4-aminoethylpiperidine, N-aminoethylpiperidine, N-aminopropylpiperidine, 
N-aminoethylmorpholine, N-aminopropylmorpholine, isophoronediamine, 
methanediamine, 1,4-bisaminopropylpiperazine, o-phenylenediamine, 
m-phenylenediamine, p-phenylenediamine, 2,4-tolylenediamine, 
2,6-tolylenediamine, 2,4-toluenediamine, m-aminobenzylamine, 
4-chloro-o-phenylenediamine, tetrachloro-p-xylylenediamine, 
4-methoxy-6-methyl-m-phenylenediamine, m-xylylenediamine, 
p-xylylenediamine, 1,5-naphthalenediamine, 2,6-naphthalenediamine, 
benzidine, 4,4'-bis(o-toluidine), dianisidine, 
4,4'-diaminodiphenylmethane, 2,2-(4,4'-diaminodiphenyl)propane, 
4,4'-diamino diphenyl ether, 4,4'-thiodianiline, 
4,4'-diaminodiphenylsulfone, 4,4'-diaminoditolylsulfone, 
methylenebis(o-chloroaniline), 
3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro5.5!undecane, 
diethylenetriamine, iminobispropylamine, methyliminobispropylamine, 
bis(hexamethylene)triamine, triethylenetetramine, tetraethylenepentamine, 
pentaethylenehexamine, N-aminoethylpiperazine, N-aminopropylpiperazine, 
1,4-bis(aminoethylpiperazine), 1,4-bis(aminopropylpiperazine), 
2,6-diaminopyridine and bis(3,4-diaminophenyl)sulfone; secondary amines 
such as diethylamine, dipropylamine, di-n-butylamine, di-sec-butylamine, 
diisobutylamine, di-n-pentylamine, di-3-pentylamine, dihexylamine, 
octylamine, di(2-ethylhexyl)amine, methylhexylamine, diallylamine, 
pyrrolidine, piperidine, 2-picoline, 3-picoline, 4-picoline, 
2,4-lupetidine, 2,6-lupetidine, 3,5-lupetidine, diphenylamine, 
N-methylaniline, N-ethylaniline, dibenzylamine, methylbenzylamine, 
dinaphthylamine, pyrrole, indoline, indole and morpholine; secondary 
polyamines such as N,N'-dimethylethylenediamine, 
N,N'-dimethyl-1,2-diaminopropane, N,N'-dimethyl-1,3-diaminopropane, 
N,N'-dimethyl-1,2-diaminobutane, N,N'-dimethyl-1,3-diaminobutane, 
N,N'-dimethyl-1,4-diaminobutane, N,N'-dimethyl-1,5-diaminopentane, 
N,N'-dimethyl-1,6-diaminohexane, N,N'-dimethyl-1,7-diaminoheptane, 
N,N'-diethylethylenediamine, N,N'-diethyl-1,2-diaminopropane, 
N,N'-diethyl-1,3-diaminopropane, N,N'-diethyl-1,2-diaminobutane, 
N,N'-diethyl-1,3-diaminobutane, N,N'-diethyl-1,4-diaminobutane, 
N,N'-diethyl-1,6-diaminohexane, piperazine, 2-methylpiperazine, 
2,5-dimethylpiperazine, 2,6-dimethylpiperazine, homopiperazine, 
1,1-di-(4-piperidyl)methane, 1,2-di-(4-piperidyl)ethane, 
1,3-di-(4-piperidyl)propane, 1,4-di-(4-piperidyl)butane and 
tetramethylguanidine; tertiary amines such as trimethylamine, 
triethylamine, tri-n-propylamine, tri-iso-propylamine, 
tri-1,2-dimethylpropylamine, tri-3-methoxypropylamine, tri-n-butylamine, 
tri-iso-butylamine, tri-sec-butylamine, tripentylamine, tri-3-pentylamine, 
tri-n-hexylamine, tri-n-octylamine, tri-2-ethylhexylamine, 
tridodecylamine, trilaurylamine, tricyclohexylamine, 
dicyclohexylethylamine, monocyclohexyldiethylamine, 
N,N-dimethylhexylamine, N-methyldihexylamine, N,N-dimethylcyclohexylamine, 
N-methyldicyclohexylamine, triethanolamine, N,N-diethylethanolamine, 
N-ethyldiethanolamine, tribenzylamine, N,N-dimethylbenzylamine, 
diethylbenzylamine, triphenylamine, N,N-dimethylamino-p-cresol, 
N,N-dimethylaminomethylphenol, 2-(N,N-dimethylaminomethyl)phenol, 
N,N-dimethylaniline, N,N-diethylaniline, pyridine, quinoline, 
N-methylmorpholine, N-methylpiperidine and 
2-(2-dimethylaminoethoxy)-4-methyl-1,3,2-dioxabornane; tertiary polyamines 
such as tetramethylethylenediamine, pyrazine, N,N'-dimethylpiperazine, 
N,N'-bis((2-hydroxy)propyl)piperazine, hexamethylenetetramine, 
N,N,N',N'-tetramethyl-1,3-butaneamine, 2-dimethylamino-2-hydroxypropane, 
diethylaminoethanol, N,N,N-tris(3-dimethylaminopropyl)amine, 
2,4,6-tris(N,N-dimethylaminomethyl)phenol and heptamethylisobiguanide; 
various imidazoles such as imidazole, N-methylimidazole, 
2-methylimidazole, 4-methylimidazole, N-ethylimidazole, 2-ethylimidazole, 
4-ethylimidazole, N-butylimidazole, 2-butylimidazole, N-undecylimidazole, 
2-undecylimidazole, N-phenylimidazole, 2-phenylimidazole, 
N-benzylimidazole, 2-benzylimidazole, 1-benzyl-2-methylimidazole, 
N-(2'-cyanoethyl)-2-methylimidazole, N-(2-cyanoethyl)-2-undecylimidazole, 
N-(2'-cyanoethyl)-2-phenylimidazole, 
3,3-bis-(2-ethyl-4-methylimidazolyl)methane, adducts of alkylimidazoles 
with isocyanuric acid, and condensates of alkylimidazoles and 
formaldehyde; amidines such as 1,8-diazabicyclo5.4.0!undecene-7, 
1,5-diazabicyclo4.3.0!nonene-5 and 
6-dibutylamino-1,8-diazabicyclo5.4.0!undecene-7, 
(2) quaternary ammonium salts of the amines in the above-mentioned 
paragraph (1) and halogens, mineral acids, Lewis acids, organic acids, 
silicic acid, boron tetrafluoride and the like, 
(3) complexes of the amines in the above-mentioned paragraph (1), borane 
and boron trifluoride, 
(4) phosphines such as trimethylphosphine, triethylphosphine, 
tri-iso-propylphosphine, tri-n-butylphosphine, tri-n-hexylphosphine, 
tri-n-octylphosphine, tricyclohexylphosphine, triphenylphosphine, 
tribenzylphosphine, tris(2-methylphenyl)phosphine, 
tris(3-methylphenyl)phosphine, tris(4-methylphenyl)phosphine, 
tris(diethylamino)phosphine, tris(4-methylphenyl)phosphine, 
dimethylphenylphosphine, diethylphenylphosphine, 
dicyclohexylphenylphosphine, ethyldiphenylphosphine, 
diphenylcyclohexylphosphine and chlorodiphenylphosphine, 
(5) mineral acids such as hydrochloric acid, sulfuric acid, nitric acid, 
phosphoric acid and carbonic acid, and half esters thereof, 
(6) Lewis acids typified by boron trifluoride and esterates of boron 
trifluoride, and 
(7) organic acids typified by carboxylic acids and half esters thereof. 
Among these compounds, preferable examples which scarcely color the cured 
product include primary monoamines, secondary monoamines, tertiary 
monoamines, tertiary polyamines, imidazoles, amidines, quaternary ammonium 
salts and phosphines, and more preferable examples include secondary 
monoamines, tertiary monoamines, tertiary polyamines, imidazoles, 
amidines, quaternary ammonium salts and phosphines which have at most one 
group capable of reacting with an episulfide group. They may be used 
singly or in a mixture of two or more thereof. The above-mentioned curing 
catalyst can be used in an amount of 0.0001 mol to 1.0 mol per mol of a 
diepisulfide compound. 
Furthermore, the novel episulfide compound of the present invention can be 
polymerized/cured with a compound having two or more functional groups 
capable of reacting with the episulfide group, a compound having one or 
more of these functional groups and one or more other homopolymerizable 
functional groups, or a compound having one functional group which can 
react with the episulfide group and which is further homopolymerizable, 
thereby preparing an optical material. Examples of the compound having two 
or more functional groups capable of reacting with the episulfide group 
include epoxy compounds, known episulfide compounds, polyvalent carboxylic 
acids, polyvalent carboxylic anhydrides, mercaptocarboxylic acids, 
polymercaptans, mercaptoalcohols, mercaptophenols, polyphenols, amines and 
amides. On the other hand, examples-of the compound having one or more 
functional groups capable of reacting with the episulfide group and having 
one or more other homopolymerizable functional groups include epoxy 
compounds having unsaturated groups such as a vinyl group, amromatic vinyl 
groups, a methacrylic group, an acrylic group and an allyl group, 
episulfide compounds, carboxylic acids, carboxylic anhydrides, 
mercaptocarboxylic acids, mercaptans, phenols, amines and amides. 
Typical examples of the compound having two or more functional groups 
capable of reacting with the episulfide group are as follows. 
Typical examples of the epoxy compounds include phenolic epoxy compounds 
obtained by the condensation of polyvalent phenol compounds such as 
hydroquinone, catechol, resorcin, bisphenol A, bisphenol F, bisphenol 
sulfones, bisphenol ethers, bisphenol sulfides, halogenated bisphenol A 
and novolak resins with the epihalohydrin; alcoholic epoxy compounds 
obtained by the condensation of polyvalent alcohol compounds such as 
ethylene glycol, diethylene glycol, triethylene glycol, polyethylene 
glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 
1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 
glycerin, trimethylolpropane trimethacrylate, pentaerythritol, 1,3- and 
1,4-cyclohexanediol, 1,3- and 1,4-cyclohexanedimethanol, hydrogenated 
bisphenol A, bisphenol A.ethylene oxide adduct and bisphenol A.propylene 
oxide adduct with the epihalohydrin; glycidyl ester-containing epoxy 
compounds obtained by the condensation of polyvalent carboxylic acid 
compounds such as adipic acid, sebacic acid, dodecadicarboxylic acid, 
dimer acids, phthalic acid, isophthalic acid, terephthalic acid, 
tetrahydrophthalic acid, methyltetrahydrophthalic acid, hexahydrophthalic 
acid, HET acid, nadic acid, maleic acid, succinic acid, fumaric acid, 
trimellitic acid, benzenetetracarboxylic acid, benzophenonetracarboxylic 
acid, naphthalenedicarboxylic acid and diphenyldicarboxylic acid with the 
epihalohydrin; amine-containing epoxy compounds obtained by the 
condensation of primary diamines such as ethylenediamine, 
1,2-diaminopropane, 1,3-diaminopropane, 1,2-diaminobutane, 
1,3-diaminobutane, 1,4-diaminobutane, 1,5-diaminopentane, 
1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 
bis(3-aminopropyl)ether, 1,2-bis(3-aminopropoxy)ethane, 
1,3-bis(3-aminopropoxy)-2,2'-dimethylpropane, 1,2-, 1,3- and 
1,4-bisaminocyclohexane, 1,3- and 1,4-bisaminomethylcyclohexane, 1,3- and 
1,4-bisaminoethylcyclohexane, 1,3- and 1,4-bisaminopropylcyclohexane, 
hydrogenated 4,4'-diaminodiphenylmethane, isophoronediamine, 
1,4-bisaminopropylpiperadine, m- and p-phenylenediamine, 2,4- and 
2,6-tolylenediamine, m- and p-xylenediamine, 1,5- and 
2,6-naphthalenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl 
ether and 2,2-bis(4,4'-diaminodiphenyl)propane, and secondary diamines 
such as N,N'-dimethylethylenediamine, N,N'-dimethyl-1,2-diaminopropane, 
N,N'-dimethyl-1,3-diaminopropane, N,N'-dimethyl-1,2-diaminobutane, 
N,N'-dimethyl-1,3-diaminobutane, N,N'-dimethyl-1,4-diaminobutane, 
N,N'-dimethyl-1,5-diaminopentane, N,N'-dimethyl-1,6-diaminohexane, 
N,N'-dimethyl-1,7-diaminoheptane, N,N'-diethylethylenediamine, 
N,N'-diethyl-1,2-diaminopropane, N,N'-diethyl-1,3-diaminopropane, 
N,N'-diethyl-1,2-diaminobutane, N,N'-diethyl-1,3-diaminobutane, 
N,N'-diethyl-1,4-diaminobutane, N,N'-diethyl-1,6-diaminohexane, 
piperazine, 2-methylpiperazine, 2,5- and 2,6-dimethylpiperazine, 
homopiperazine, 1,1-di(4-piperidyl)methane, 1,2-di(4-piperidyl)ethane, 
1,3-di(4-piperidyl)propane and 1,4-di(4-piperidyl)butane with the 
epihalohydrin; epoxy compounds obtained by the epoxidation of alicyclic 
epoxy compounds such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane 
carboxylate, vinylcyclohexane dioxide, 
2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexanemetadioxane and 
bis(3,4-epoxycyclohexyl) adipate; and unsaturated compounds such as 
cyclopentadiene epoxide, epoxidized soybean oil, epoxidized polybutadiene 
and vinylcyclohexene epoxide; and urethane-containing epoxy compounds 
obtained by the reaction of the above-mentioned polyvalent alcohols and 
phenolic compounds with diisocyanates and glycidol. 
A typical example of the known episulfide compounds is an episulfide 
compound obtained by episulfiding a part or all of the epoxy groups of the 
above-mentioned epoxy compound. 
Typical examples of the polyvalent carboxylic acids, the polyvalent 
carboxylic anhydrides, the polyphenols, the amines and the like include 
compounds previously enumerated as the materials which are the partners of 
the reaction with the epihalohydrin described in the paragraphs regarding 
the epoxy compounds. 
Typical examples of the polymercaptans include straight-chain dimercaptan 
compounds such as 1,2-dimercaptoethane, 1,3-dimercaptopropane, 
1,4-dimercaptobutane, 1,6-dimercaptohexane, bis(2-mercaptoethyl)sulfide, 
1,2-bis(2-mercaptoethylthio)!ethane; branched aliphatic polymercaptan 
compounds such as 2-mercaptomethyl-1,3-dimercaptopropane, 
2-mercaptomethyl-1,4-dimercaptobutane, 
2-(2-mercaptoethylthio)-1,3-dimercaptopropane, 
1,2-bis(2-mercaptoethylthio)!-3-mercaptopropane, 
1,1,1-tris(mercaptomethyl)propane and tetrakismercaptomethylmethane; 
ester-containing aliphatic polymercaptan compounds such as ethylene glycol 
dithioglycolate, ethylene glycol dithiopropionate, 1,4-butanediol 
dithioglycolate, 1,4-butanedioldithiopropionate, 
trimethylolpropanetris(.beta.-thioglycolate), 
trimethylolpropanetris(.beta.-thioglycolate), 
pentaerythritoltetrakis(.beta.-thioglycolate) and 
pentaerythritoltetrakis(.beta.-thiopropionate); and alicyclic dimercaptan 
compounds such as 1,4-dimercaptocyclohexane, 1,3-dimercaptocyclohexane, 
1,4-dimercaptomethylcyclohexane, 1,3-dimercaptomethylcyclohexane, 
2,5-dimercaptomethyl-1,4-dithiane, 2,5-dimercaptoethyl-1,4-dithiane, 
2,5-dimercaptomethyl-1-thiane and 2,5-dimercaptoethyl-1-thiane. 
Typical examples of the mercaptoalcohols include 2-mercaptoethanol, 
3-mercapto-1-propanol, 1-mercapto-2-propanol, 4-mercapto-1-butanol, 
3-mercapto-2-butanol, 3-mercapto-1,2-propanediol, 
2-mercapto-1,3-propanediol, 1,3-dimercapto-2-propanol, 
2,3-dimercapto-1-propanol, 1-mercaptomethyl-1,1-dimethylolpropane, 
1,1-bis(mercaptomethyl)-1-methylolpropane, 
mercaptomethyltris(hydroxymethyl)methane, 
bis(mercaptomethyl)bis(hydroxymethyl)methane, 
tris(mercaptomethyl)hydroxymethylmethane and 
2-(2-mercaptoethylthio)ethanol. 
Typical examples of the mercaptophenols include 4-mercaptophenol and 
2-mercaptohydroquinone-4-hydroxy-4'-mercaptobiphenyl. 
Typical examples of the mercaptocarboxylic acids include thioglycolic acid, 
2-thiopropionic acid, 3-thiopropionic acid, thiolactic acid, 
mercaptosuccinic acid, thiomalic acid, N-(2-mercaptopropionyl)glycine, 
2-mercaptobenzoic acid, 2-mercaptonicotinic acid and 3,3-dithioisobutyric 
acide. 
Furthermore, typical examples of the compound having one or more functional 
groups capable of reacting with the episulfide group and having one or 
more other homopolymerizable functional groups will be enumerated 
hereinafter. Examples of the epoxy compound having an unsaturated group 
include vinylphenyl glycidyl ether, vinylbenzyl glycidyl ether, glycidyl 
methacrylate, glycidyl acrylate and allyl glycidyl ether. Examples of the 
episulfide compound having the unsaturated group include compounds 
obtained by episulfiding the epoxy groups of the above-mentioned epoxy 
compound having the unsaturated group, for example, vinylphenyl 
thioglycidyl ether, vinylbenzyl thioglycidyl ether, thioglycidyl 
methacryate, thiogrlycidyl acrylate and allyl thioglycidyl ether. 
Examples of the carboxylic acid compound having the unsaturated group 
include .alpha.,.beta.-unsaturated carboxylic acids such as acrylic acid, 
methacrylic acid, maleic acid, maleic anhydride and fumaric acid. 
Moreover, examples of the amides having the unsaturated group include 
amides of the above-mentioned .alpha.,.beta.-unsaturated carboxylic acids. 
Furthermore, typical examples of the preferable compound having one 
functional group which can react with the episulfide group and which is 
further homopolymerizable include compounds having one epoxy group or one 
episulfide group. More typical examples thereof include monoepoxy 
compounds such as ethylene oxide and propylene oxide, glycidyl esters of 
monocarboxylic acids such as acetic acid, propionic acid and benzoic acid, 
glycidyl ethers such as methyl glycidyl ether, ethyl glycidyl ether, 
propyl glycidyl ether and butyl glycidyl ether, monoepisulfide compounds 
such as ethylene sulfide and propylene sulfide, thioglycidyl esters having 
structures derived from the above-mentioned monocarboxylic acid and 
thioglycidol (1,2-epithio-3-hydroxypropane), and thioglycidyl ethers such 
as methyl thioglycidyl ether (1,2-epithiopropyloxymethane), ethyl 
thioglycidyl ether, propyl thioglycidyl ether and butyl thioglycidyl 
ether. Above all, the compound having one episulfide group is more 
preferable. 
The novel episulfide compound of the present invention can be 
polymerized/cured in the presence of a curing polymerization catalyst with 
the compound having two or more functional groups capable of reacting with 
the episulfide group of the novel episulfide compound of the present 
invention, the compound having one or more of these functional groups and 
one or more other homopolymerizable functional groups, or the compound 
having one functional group which can react with the episulfide group and 
which is further homopolymerizable, thereby preparing a cured resin. As 
the curing catalyst, there can be used the above-mentioned amines, 
phosphines and acids. Typical examples thereof include those which have 
been enumerated above. 
Furthermore, in using the compound having the unsaturated group, it is 
preferable to utilize a radical polymerization initiator as a 
polymerization promotor. The radical polymerization initiator may be any 
substance, so long as it can produce a radical by heating or irradiation 
with ultraviolet rays or electron beams. Examples of the radical 
polymerization initiator include known thermal polymerization catalysts, 
for example, peroxides such as cumyl peroxyneodecanoate, diisopropyl 
peroxydicarbonate, diallyl peroxydicarbonate, di-n-propyl 
peroxydicarbonate, dimyristyl peroxydicarbonate, cumyl peroxyneohexanoate, 
tert-hexyl peroxyneodecanoate, tert-butyl peroxyneodecanoate, tert-hexyl 
peroxyneohexanoate, tert-butyl peroxyneohexanoate, 2,4-dichlorobenzoyl 
peroxide, benzoyl peroxide, dicumyl peroxide and di-tert-butyl peroxide; 
hydroperoxides such as cumene hydroperoxide and tert-butyl hydroperoxide; 
azo-based compounds such as 
2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 
2,2'-azobis(2-cyclopropylpropionitrile), 
2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 
2,2'-azobis(2-methylbutyronitrile), 
1,1'-azobis(cyclohexane-1-carbonitrile), 
1-(1-cyano-1-methylethyl)azo!formamide, 
2-phenylazo-4-toxi-2,4-dimethyl-valeronitrile-2,2'-azobis(2-methylpropane) 
and 2,2'-azobis(2,4,4-trimethylpentane), and known photopolymerization 
catalysts such as benzophenone, benzoinbenzoin methyl ether. Above all, 
preferable are the peroxides, the hydroperoxides and the azo compounds, 
and more preferable are the peroxides and the azo compounds, and most 
preferable are azo-based compounds such as 
2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 
2,2'-azobis(2-cyclopropylpropionitrile), 
2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 
2,2-azobis(2-methylbutyronitrile), 
1,1'-azobis(cyclohexane-1-carbonitrile), 1-(1-cyano-1-methylethyl)azo!for 
mamide, 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 
2,2'-azobis(2-methylpropane) and 2,2'-azobis(2,4,4-trimethylpentane). They 
can all be used singly or in the form of a mixture thereof. 
The amount of the radical polymerization initiator depends upon the 
components of the composition and the curing method, and so it cannot be 
decided in a wholesale way. Nevertheless, it is usually in the range of 
0.01 to 5.0% by weight, preferably 0.1 to 2.0% by weight based on the 
total weight of the composition. 
Furthermore, in polymerizing/curing the novel episulfide compound of the 
present invention to obtain the cured resin, it is, needless to say, 
possible to add additives such as a known antioxidant, ultraviolet light 
absorber and the like for the purpose of further improving the 
practicality of the obtained material. Moreover, a known external and/or 
internal mold release agent can be used or added, thereby improving the 
release properties of the obtained cured material from a mold. Examples of 
the internal mold release agent referred to herein include 
fluorine-containing nonionic surface active agents, silicon-containing 
nonionic surface active agents, alkyl quaternary ammonium salts, 
phosphoric acid esters, acidic phosphoric acid esters, oxyalkylene type 
acidic phosphoric acid esters, alkali metal salts of the acidic phosphoric 
acid esters, alkali metal salts of the oxyalkylene type acidic phosphoric 
acid esters, metal salts of higher fatty acids, esters of the higher fatty 
acids, paraffins, waxes, higher aliphatic amides, higher aliphatic 
alcohols, polysiloxanes and aliphatic amine ethylene oxide adducts. 
When the novel episulfide compound of the present invention is 
polymerized/cured to obtain the cured resin, there can be used the 
episulfide compound which is the raw material, and if necessary, the 
above-mentioned curing catalyst, glycidyl methacrylate or thioglycidyl 
methacrylate (in which the epoxy group of glycidyl methacrylate is 
episulfided) capable of reacting with the episulfide group having an 
unsaturated group and the like, but in this case, after additives such as 
a radical polymerization initiator, a radically polmerizable monomer, a 
mold release agent, an antioxidant and an ultraviolet light absorber are 
mixed, the polymerization/curing can be carried out by the following 
procedure to obtain an optical material such as a lens. That is to say, 
the mixture of the raw material is poured into a glass mold or a metal 
mold, and a polymerization/curing reaction is then advanced by heating. 
Afterward, the cured product is released from the mold to prepare the 
desired product. A curing time is usually in the range of 0.1 to 100 
hours, preferably 1 to 48 hours, and a curing temperature is usually in 
the range of -10 to 160.degree. C., preferably -10 to 140.degree. C. 
Moreover, after the completion of the curing, the material may be 
subjected to an aneal treatment at a temperature of 50 to 150.degree. C. 
for a period of 10 minutes to 5 hours, which is preferable to remove the 
strain of the optical material of the present invention. If necessary, a 
surface treatment for the impartment of hard coat, anti-reflection 
properties, anti-fogging properties or the like can further be carried 
out. 
The preparation method of the optical material which is the cured resin 
regarding the present invention will be described in more detail. As 
described above, the main raw material is mixed with the secondary 
materials, and the resulting mixture is poured into a mold and then cured 
to prepare the optical material. In this case, the diepisulfide compound 
which is the main raw material may be mixed under stirring at one time 
with all of the suitably usable compound, i.e., the compound having two or 
more functional groups capable of reacting with the episulfide group, the 
compound having one or more of these functional groups and one or more 
other homopolymerizable functional groups, or the compound having one 
functional group which can react with the episulfide group and which is 
further homopolymerizable, and if necessary, a curing catalyst, a radical 
polymerization initiator, a mold release agent, a stabilizer and the like 
in one container, or the respective materials may stepwise be added and 
mixed, or several components are separately mixed and some resulting 
mixtures may be mixed again in one container. For the sake of the mixing, 
a temperature to be set, a time required for the mixing and the like 
should basically be such conditions as to sufficiently mix the components, 
but an excessive temperature and time cause some problems. For example, 
inconvenient reactions may occur among the materials and the additives, 
and the rise of viscosity may take place, which makes the casting 
operation difficult. The mixing temperature is in the range of about -10 
to 100.degree. C., preferably -10 to 50.degree. C., more preferably -5 to 
30.degree. C. The mixing time is in the range of 1 minute to 5 hours, 
preferably 5 minutes to 2 hours, more preferably 5 minutes to 30 minutes, 
most preferably 5 minutes to 15 minutes or so. Before or after the mixing 
of the respective materials and additives, a degassing operation may be 
carried out under reduced pressure, and this operation is preferable to 
prevent the formation of air bubbles during the subsequent cast 
polymerization/curing. At this time, the reduced pressure is in the range 
of about 0.1 to 700 mmHg, preferably about 10 to 300 mmHg. Furthermore, at 
the time of the pouring of the mixture, a microfilter or the like can be 
used to remove impurities and the like therefrom by filtration, which is 
preferable to further enhance the quality of the optical material 
according to the present invention. 
According to the novel episulfide compound of the present invention, an 
optical resin material having a sufficiently high refractive index and a 
good balance between the refractive index and an Abbe's number can be 
obtained which have scarcely been attained so long as a compound based on 
a conventional technique is used as a raw material. That is to say, the 
novel episulfide compound of the present invention permits the reduction 
of the weight of the optical resin material, the reduction of its wall 
thickness and the remarkable decrease in its chromatic aberration. 
Furthermore, the optical material obtained by polymerizing/curing the novel 
episulfide compound of the present invention can be used in various use 
applications, and it is particularly preferable as a lens material for 
spectacles. 
Next, the present invention will be described in detail with reference to 
examples, but the scope of the present invention should not be limited to 
these examples. Incidentally, the physical properties of obtained polymers 
were measured by the following procedures. 
Refractive index and Abbe's number: They were measured at 25.degree. C. by 
the use of an Abbe's refractometer. 
Specific gravity: It was measured at 25.degree. C. by the use of an 
electron gravimeter, and then calibrated in a usual manner. 
Heat resistance: A product having a Vicat softening point of 120.degree. C. 
or more was represented by .largecircle., a product having a softening 
point of less than 120.degree. C. and 80.degree. C. or more was 
represented by .DELTA., and a product having a softening point of less 
than 80.degree. C. was represented by X. 
Strength: In accordance with a three-point bending test using an autograph, 
a product having a strain of 0.1 or more was represented by .largecircle., 
a product having a strain of less than 0.1 and 5 or more was represented 
by .DELTA., and a product having a strain of less than 0.05 was 
represented by X.

EXAMPLE 1 
A solution of 170.3 g of 1,4-bis(mercaptomethyl)-benzene and 185.1 g of 
epichlorohydrin was cooled to 10.degree. C., and 40 ml of methanol and an 
aqueous solution obtained by dissolving 0.4 g of an aqueous sodium 
hydroxide solution in 4 ml of water were added to the cooled solution, 
followed by stirring at this temperature for 1 hour. Afterward, an aqueous 
solution obtained by dissolving 80.0 g of sodium hydroxide in 80 ml of 
water was added thereto, while a solution temperature was maintained at 
about 0 to 10.degree. C., followed by stirring for 3 hours at this 
temperature. Next, 200 ml of water was added to the reaction mixture, and 
extraction was carried out with 300 ml of toluene. The resulting toluene 
layer was dried over sodium sulfate, and the used solvent was distilled 
off to obtain 275.8 g (97% of a theoretical amount) of 
1,4-bis(glycidylthiomethyl)benzene in the state of a colorless transparent 
liquid. 
Next, in a flask equipped with a stirrer, a thermometer and a nitrogen 
introducing tube were placed 142.2 g of 
1,4-bis(glycidylthiomethyl)benzene, 304.2 g of thiourea, 11.3 g of acetic 
anhydride and 1 l of toluene as well as 1 l of methanol as solvents, and 
reaction was then carried out at 30.degree. C. for 9 hours. After the 
reaction, the reaction solution was extracted with toluene, and the 
resulting extract was washed with a 1% aqueous sulfuric acid solution and 
then water. Afterward, the excessive solvents were distilled off to obtain 
141.5 g of a product. From the results of elemental analysis, mass 
spectrometry, NMR analysis and IR analysis, it was apparent that the thus 
obtained product was 1,4-bis(.beta.-epithiopropylthiomethyl)benzene 
(yield=90%). 
______________________________________ 
Elemental analysis: 
Found Calcd. 
______________________________________ 
C 53.30% 53.46% 
H 5.91% 5.77% 
S 40.50% 40.78% 
______________________________________ 
Mass spectrum (EI): M.sup.+ 314 (theoretical molecular weight=314) 
Infrared absorption spectrum: 620 cm.sup.-1 (stretching vibration of an 
episulfide ring) 
.sup.1 H-NMR: 7.2 ppm (t, 1H) 7.0 ppm (m, 3H) 3.6 ppm (m, 2H) 3.1 ppm (m, 
2H) 3.0 ppm (m, 2H) 2.7 ppm (m, 2H) 2.6 ppm (m, 2H) 2.2 ppm (m, 2H) 
Furthermore, 0.5 part by weight of N,N-diethylethanolamine was blended with 
100 parts by weight of the compound obtained above, and the blend was then 
poured into a mold comprising 2 glass plates having an adjusted thickness 
of 2 mm. Afterward, the blend was polymerized/cured at 80.degree. C. for 5 
hours to obtain an optical material. The refractive index, the Abbe's 
number and the specific gravity of the obtained optical material were 
measured, and the results are shown in Table 1. 
EXAMPLE 2 
The same procedure as in Example 1 was repeated except that 
1,4-bis(mercaptomethyl)benzene was replaced with 
1,4-bis(mercaptomethyl)cyclohexane, thereby obtaining 
1,4-bis(.beta.-epithiopropylthiomethyl)cyclohexane in a total yield of 
80%. 
______________________________________ 
Elemental analysis: 
Found Calcd. 
______________________________________ 
C 52.34% 52.45% 
H 7.66% 7.55% 
S 39.90% 40.01% 
______________________________________ 
Mass spectrum (EI): M.sup.+ 320 (theoretical molecular weight=320) 
Infrared absorption spectrum: 620 cm.sup.-1 (stretching vibration of an 
episulfide ring) 
.sup.1 H-NMR:3.2-2.9 ppm (m, 10H) 2.7 ppm (m, 2H) 2.6 ppm (m, 2H) 2.2 ppm 
(m, 2H) 3.0 ppm (m, 2H) 1.9-0.9 ppm (m, 8H) 2.6 ppm (m, 2H) 2.2 ppm (m, 
2H) 
EXAMPLE 3 
(in the general formula (2), Z.dbd.H, U.dbd.H, m=1 and n=0) 
The same procedure as in Example 1 was repeated except that 
1,4-bis(mercaptomethyl)benzene was replaced with 
2,5-bis(mercaptomethyl)-1,4-dithiane, thereby obtaining 
2,5-bis(.beta.-epithiopropylthiomethyl)-1,4-dithiane in a total yield of 
82%. 
______________________________________ 
Elemental analysis: 
Found Calcd. 
______________________________________ 
C 40.33% 40.41% 
H 5.77% 5.65% 
S 53.79% 53.94% 
______________________________________ 
Mass spectrum (EI): M.sup.+ 356 (theoretical molecular weight=356) 
Infrared absorption spectrum: 620 cm.sup.-1 (stretching vibration of an 
episulfide ring) 
.sup.1 H-NMR: 3.2-2.9 ppm (m, 14H) 2.7 ppm (m, 2H) 2.6 ppm (m, 2H) 2.2 ppm 
(m, 2H) 
After polymerization/curing, the refractive index, the Abbe's number and 
the specific gravity of an obtained optical material were measured, and 
the results are shown in Table 1. 
EXAMPLE 4 
(in the general formula (2), Z.dbd.H, U.dbd.H, m=2 and n=0) 
The same procedure as in Example 1 was repeated except that 
1,4-bis(mercaptomethyl)benzene was replaced with 
2,5-bis(mercaptoethyl)-1,4-dithiane, thereby obtaining 
2,5-bis(.beta.-epithiopropylthiomethyl)-1,4-dithiane in a total yield of 
85%. 
______________________________________ 
Elemental analysis: 
Found Calcd. 
______________________________________ 
C 43.55% 43.71% 
H 6.39% 6.29% 
S 49.81% 50.01% 
______________________________________ 
Mass spectrum (EI): M.sup.+ 384 (theoretical molecular weight=384) 
Infrared absorption spectrum: 620 cm.sup.-1 (stretching vibration of an 
episulfide ring) 
.sup.1 H-NMR: 3.2-2.9 ppm (m, 14H) 2.7 ppm (m, 2H) 2.6 ppm (m, 2H) 2.2 ppm 
(m, 2H) 2.0 ppm (m, 4H) 
After polymerization/curing, the refractive index, the Abbe's number and 
the specific gravity of the resulting optical material were measured, and 
the results are shown in Table 1. 
EXAMPLE 5 
(in the general formula (2), Z.dbd.H, U.dbd.H, m=1 and n=1) 
The same procedure as in Example 1 was repeated except that 
1,4-bis(mercaptomethyl)benzene was replaced with 
2,5-bis(mercaptoethylthiomethyl)-1,4-dithiane, thereby obtaining 
2,5-bis(.beta.-epithiopropylthioethylthiomethyl)-1,4-dithiane in a total 
yield of 87%. 
______________________________________ 
Elemental analysis: 
Found Calcd. 
______________________________________ 
C 40.19% 40.29% 
H 6.05% 5.92% 
S 43.70% 53.79% 
______________________________________ 
Mass spectrum (EI): M.sup.+ 476 (theoretical molecular weight=476) 
Infrared absorption spectrum: 620 cm.sup.-1 (stretching vibration of an 
episulfide ring) 
.sup.1 H-NMR: 3.2-2.8 ppm (m, 22H) 2.7 ppm (m, 2H) 2.6 ppm (m, 2H) 2.2 ppm 
(m, 2H) 
After polymerization/curing, the refractive index, the Abbe's number and 
the specific gravity of the resulting optical material were measured, and 
the results are shown in Table 1. 
EXAMPLE 6 
(in the general formula (2), Z.dbd.CH.sub.2 SE.sub.PS, U.dbd.H, m=1 and 
n=0) 
The same procedure as in Example 1 was repeated except that 
1,4-bis(mercaptomethyl)-benzene was replaced with 
2,3,5,6-tetrakis(mercaptomethyl)-1,4-dithiane, thereby obtaining 
2,3,5,6-tetrakis(.beta.-epithiopropylthiomethyl)-1,4-dithiane in a total 
yield of 82%. 
______________________________________ 
Elemental analysis: 
Found Calcd. 
______________________________________ 
C 40.39% 40.50% 
H 5.55% 5.44% 
S 53.99% 54.06% 
______________________________________ 
Mass spectrum (EI): M.sup.+ 592 (theoretical molecular weight=592) 
Infrared absorption spectrum: 620 cm.sup.-1 (stretching vibration of an 
episulfide ring) 
.sup.1 H-NMR: 3.3-2.9 ppm (m, 20H) 2.7 ppm (m, 4H) 2.6 ppm (m, 4H) 2.2 ppm 
(m, 4H) 
After polymerization/curing, the refractive index, the Abbe's number and 
the specific gravity of the resulting optical material were measured, and 
the results are shown in Table 1. 
Comparative Example 1 
In Example 1, the same procedure as in Example 1 was repeated except that 
1,4-bis(mercaptomethyl)-benzene was replaced with 
2,5-bis(hydroxymethyl)-1,4-dioxane, thereby obtaining 
2,5-bis(.beta.-epithiopropyloxymethyl)-1,4-dioxane in a total yield of 
52%. After polymerization/curing, the refractive index, the Abbe's number 
and the specific gravity of the resulting optical material were measured, 
and the results are shown in Table 1. 
Comparative Example 2 
In Example 1, the same procedure as in Example 1 was repeated except that 
1,4-bis(mercaptomethyl)-benzene was replaced with 
2,5-bis(hydroxyethyloxymethyl)-1,4-dioxane, thereby obtaining 
2,5-bis(.beta.-epithiopropyloxyethyloxymethyl)-1,4-dioxane in a total 
yield of 55%. After polymerization/curing, the refractive index, the 
Abbe's number and the specific gravity of the resulting optical material 
were measured, and the results are shown in Table 1. 
Comparative Example 3 
In Example 1, the same procedure as in Example 1 was repeated except that 
162.3 g of 1,4-bis(glycidylthiomethyl)benzene was replaced with 50 g of 
thiourea. With regard to the resulting product, it was apparent from NMR 
spectra that the formula (2) had Z.dbd.H, U.dbd.H, m=1 and n=0, and a 
numerical ratio of S in X of the formula (1) was 30%, on the average, of 
the total of S and O constituting a three-membered ring. After 
polymerization/curing, the refractive index, the Abbe's number and the 
specific gravity of the resulting optical material were measured, and the 
results are shown in Table 1. 
Comparative Example 4 
A mixture of 48 parts by weight of 
1,8-dimercapto-4-mercaptomethyl-3,6-dithiaoctane and 52 parts by weight of 
metaxylylene diisocyanate was blended with dibutyltin chloride as a curing 
catalyst in an amount of 0.1 part by weight with respect to 100 parts by 
weight of the mixture, and after the formation of a uniform solution, 
degassing was sufficiently carried out under a reduced pressure of 10 
mmHg. Next, the solution was poured into a mold, and then 
polymerized/cured at 80.degree. C. for 20 hours in an oven. The refractive 
index, the Abbe's number and the specific gravity of the resulting optical 
material were measured, and the results are shown in Table 1. 
TABLE 1 
__________________________________________________________________________ 
Refractive 
Abbe's 
Episulfide Index 
Number 
Heat 
Compound N.sub.D 
.nu..sub.D 
Resistance 
Strength 
__________________________________________________________________________ 
Example 1 
1,4-bis(.beta.-epithio- 
1.67 34 .largecircle. 
.largecircle. 
propylthiomethyl)- 
benzene 
Example 2 
1,4-bis(.beta.-epithio- 
1.66 40 .largecircle. 
.largecircle. 
propylthioethyl)- 
cyclohexane 
Example 3 
2,5-bis(.beta.-epithio- 
1.70 36 .largecircle. 
.largecircle. 
propylthiomethyl)- 
1,4-dithiane 
Example 4 
2,5-bis(.beta.-epithio- 
1.69 37 .largecircle. 
.largecircle. 
propylthioethyl)- 
1,4-dithiane 
Example 5 
2,5-bis(.beta.-epithio- 
1.70 36 .largecircle. 
.largecircle. 
propylthioethyl- 
thiomethyl)-1,4- 
dithiane 
Example 6 
2,3,5,6-tetrakis- 
1.70 36 .largecircle. 
.largecircle. 
(.beta.-epithiopropyl- 
thiomethyl)-1,4- 
dithiane 
Comp. Ex. 1 
2,5-bis(.beta.-epithio- 
1.57 45 X X 
propyloxymethyl)- 
1,4-dioxane 
Comp. Ex. 2 
2,5-bis(.beta.-epithio- 
1.56 46 X X 
propyloxyethyl- 
oxymethyl)-1,4- 
dioxane 
Comp. Ex. 3 
Formula (2) had Z = H, 
1.63 42 .DELTA. 
.DELTA. 
U = H, m = 1 and n = 0, and 
number of S in X of 
Formula (3) was 
30% of total of S and 
0 on the average. 
Comp. Ex. 4 
1,8-dimercapto-4- 
1.66 32 X .largecircle. 
mercaptomethyl-3,6- 
dithiaoctane/ 
metaxylylene 
diisocyanate = 48/52 
__________________________________________________________________________