Compositions for optical materials

Abstract

Through the present invention, it is possible to provide a composition for an optical material containing (a) an episulfide compound, (b) a polymerization catalyst, and (c) an ester compound having a halogen at the α position. The (c) ester compound having a halogen at the α position is preferably at least one compound selected from the group consisting of dimethyl chloromalonate, diethyl chloromalonate, dimethyl bromomalonate, and diethyl bromomalonate.

Description

[Technical Field]

[0001] The present invention relates to a composition for optical materials, and more particularly to a composition for optical materials suitable for optical materials such as plastic lenses, prisms, optical fibers, information recording substrates, and filters, particularly suitable for plastic lenses. [Background technology]

[0002] Plastic materials are lightweight, highly tough, and easily dyeable, and thus have been widely used in recent years for various optical materials, particularly spectacle lenses. The physical properties required for optical materials, and spectacle lenses in particular, include low specific gravity, high transparency and low yellowness, high heat resistance, and high strength, and the optical properties required are high refractive index and high Abbe number. A high refractive index enables lenses to be made thinner, and a high Abbe number reduces chromatic aberration in lenses. However, as the refractive index increases, the Abbe number decreases, and therefore, studies are being conducted to simultaneously improve both. The most representative method among these studies is the method using an episulfide compound, as described in Patent Document 1. Furthermore, in order to improve oxidation resistance, Patent Document 2 proposes a composition in which a thiol compound is added to an episulfide compound. Studies aimed at achieving even higher refractive indices have also been conducted, and compositions comprising sulfur, episulfide, and thiol as disclosed in Patent Documents 3 and 4, and compositions comprising a compound having a cyclic skeleton and an episulfide as disclosed in Patent Document 5 have been proposed.

[0003] As described above, episulfide compounds are highly reactive and can be polymerized either alone or with many other compounds, making it possible to prepare compositions suitable for a variety of uses. However, these episulfide compounds or compositions containing them may increase in viscosity during preparation, making them difficult to work with. To address this issue, Patent Document 6 proposes a method of adding a halide of an element of Groups 13 to 16 of the long periodic table. However, even with these methods, there are cases where the coloring of the resin, the color change of the resin after heating, or the color change of the resin after light irradiation deteriorates, making it difficult to maintain a good balance among these physical properties. Therefore, there has been a demand for a method that can suppress an increase in viscosity during compounding and maintain a good balance among the coloring of the resin after curing, the color change of the resin after heating, and the color change of the resin after light irradiation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-110979 [Patent Document 2] Japanese Patent Application Publication No. 10-298287 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-2783 [Patent Document 4] Japanese Patent Application Laid-Open No. 2004-137481 [Patent Document 5] Japanese Patent Application Laid-Open No. 2010-242093 [Patent Document 6] Japanese Patent Application Laid-Open No. 2002-332350 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a composition for optical materials or the like which can suppress an increase in viscosity during formulation and can maintain a good balance between the coloration of the resin after curing, the color change of the resin after heating, and the color change of the resin after irradiation with light. [Means for solving the problem]

[0006] In view of the above circumstances, the present inventors have conducted extensive research and have solved the above problems by a composition for optical materials containing (a) an episulfide compound, (b) a polymerization catalyst, and (c) an ester compound having a halogen atom at the α-position, thereby completing the present invention. That is, the present invention is as follows. 1. A composition for optical materials comprising (a) an episulfide compound, (b) a polymerization catalyst, and (c) an ester compound having a halogen at the α-position. 2. The composition for optical materials according to the above item 1, wherein the (a) episulfide compound is a compound represented by the following formula (1): [ka] (where m is an integer from 0 to 4, and n is an integer from 0 to 2.) 3. The composition for optical materials according to 1 or 2 above, further comprising a polythiol compound. 4. The composition for optical materials according to any one of the above 1 to 3, further comprising sulfur and / or a compound represented by the following formula (9): [ka] (In the formula, X represents S, Se, or Te; a to f = 0 to 3, 8 ≥ (a + c + e) ≥ 1, 8 ≥ (b + d + f) ≥ 2, and (b + d + f) ≥ (a + c + e).) 5. The composition for optical materials according to any one of the above 1 to 4, wherein the (c) ester compound having a halogen at the α-position is a compound represented by the following formula (10): [ka] (wherein X represents a halogen. R 1 and R 2 each independently represents a hydrocarbon having 1 to 10 carbon atoms. 6. The composition for optical materials according to the above item 5, wherein the compound represented by formula (10) is one or more compounds selected from the group consisting of dimethyl chloromalonate, diethyl chloromalonate, dimethyl bromomalonate, and diethyl bromomalonate. 7. An optical material obtained by polymerizing the composition for optical materials according to any one of 1 to 6 above. [Effects of the Invention]

[0007] The present invention has made it possible to provide a composition for optical materials and the like that can suppress an increase in viscosity during blending, which was difficult to achieve with conventional techniques, and that can maintain a good balance among coloration of the resin after curing, color change after heating the resin, and color change after irradiation of the resin with light. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, the present invention will be described in detail by way of examples and working examples, but the present invention is not limited to the illustrated examples and working examples, and can be modified in any manner as long as it does not significantly deviate from the content of the present invention. The episulfide compound (a) used in the present invention encompasses all episulfide compounds, but specific examples are listed below, divided into compounds having a chain aliphatic skeleton, an aliphatic cyclic skeleton, and an aromatic skeleton. Examples of compounds having a chain aliphatic skeleton include compounds represented by the following formulas (1) to (4). [ka] In formula (1), m represents an integer of 0 to 4, and n represents an integer of 0 to 2. Preferably, n represents 0. [ka] [ka] [ka]

[0009] Examples of the compound having an aliphatic cyclic skeleton include compounds represented by the following formula (5) or (6). [ka] In formula (5), p and q each independently represent an integer of 0 to 4. Preferably, p represents 1 and q represents 2. [ka] In formula (6), p and q each independently represent an integer of 0 to 4. Preferably, p represents 1 and q represents 2. Examples of compounds having an aromatic skeleton include compounds represented by the following formula (7) or (8). [ka] In formula (7), p represents an integer of 0 to 4, and q represents an integer of 1 to 3. Preferably, p represents 1, and q represents 2. [ka] In formula (8), p and q each independently represent an integer of 0 or 1. Preferably, p represents 1 and q represents 1. Although specific examples have been shown above, the (a) compound of the present invention is not limited to these, and these (a) compounds may be used alone or in combination of two or more.

[0010] Among these, preferred compounds are those having a chain aliphatic skeleton and represented by the above formulas (1) and (2), specifically bis(β-epithiopropyl) sulfide, bis(β-epithiopropyl) disulfide, bis(β-epithiopropyl) trisulfide, bis(β-epithiopropylthio)methane, 1,2-bis(β-epithiopropylthio)ethane, 1,3-bis(β-epithiopropylthio)propane, 1,4-bis(β-epithiopropylthio)butane, bis(β-epithiopropylthioethyl) sulfide, and the compound of formula (2). Particularly preferred compounds are bis(β-epithiopropyl) sulfide (n=0 in the above formula (1)), bis(β-epithiopropyl) disulfide (m=0, n=1 in the above formula (1)), and the compound of formula (2), and the most preferred compound is bis(β-epithiopropyl) sulfide (n=0 in the above formula (1)).

[0011] The polymerization catalyst (b) used in the present invention for polymerizing and curing the composition includes amines, onium salts, and phosphine compounds. Specific examples include amines, quaternary ammonium salts, quaternary phosphonium salts, tertiary sulfonium salts, secondary iodonium salts, and phosphine compounds. Among these, quaternary ammonium salts, quaternary phosphonium salts, and phosphine compounds, which have good compatibility with the composition, are more preferred, and quaternary phosphonium salts are even more preferred. Specific examples of more preferred compounds include quaternary ammonium salts such as tetra-n-butylammonium bromide, tetraphenylammonium bromide, triethylbenzylammonium chloride, cetyldimethylbenzylammonium chloride, and 1-n-dodecylpyridinium chloride; quaternary phosphonium salts such as tetra-n-butylphosphonium bromide and tetraphenylphosphonium bromide; and phosphine compounds such as triphenylphosphine. Among these, more preferred compounds are triethylbenzylammonium chloride and tetra-n-butylphosphonium bromide, and the most preferred compound is triethylbenzylammonium chloride. The polymerization catalyst may be used alone or in combination of two or more kinds. (b) The amount of polymerization catalyst added cannot be determined in general because it varies depending on the components of the composition, the mixing ratio, and the polymerization and curing method. However, it is usually 0.001% by mass to 5% by mass, preferably 0.01% by mass to 1% by mass, and most preferably 0.01% by mass to 0.5% by mass, based on the total amount of the composition for optical materials. If the amount of polymerization catalyst added is more than 5% by mass, the refractive index and heat resistance of the cured product may decrease and the product may become discolored. If the amount is less than 0.001% by mass, the product may not cure sufficiently, resulting in insufficient heat resistance.

[0012] The (c) ester compound having a halogen at the α-position used in the present invention includes all ester compounds having a halogen at the α-position, but is preferably a compound represented by the following formula (10). [ka] In formula (10), X represents a halogen, preferably Cl, Br, or I. 1 and R 2 each independently represents a hydrocarbon having 1 to 10 carbon atoms, preferably a hydrocarbon having 1 to 4 carbon atoms, more preferably methyl, ethyl, or propyl. Specifically, it is a halogenated malonate, more preferably a diester compound having a halogen at the α-position, specifically dimethyl chloromalonate, diethyl chloromalonate, dimethyl bromomalonate, and diethyl bromomalonate, of which dimethyl chloromalonate and diethyl chloromalonate are particularly preferred. The amount of (c) compound added is usually 0.0001 to 5.0 mass%, preferably 0.0005 to 3.0 mass%, and more preferably 0.001 to 2.0 mass%, based on the total amount of the composition for optical materials. If the amount of (c) compound added is more than 5.0 mass%, the composition may not cure sufficiently, resulting in a decrease in the refractive index and heat resistance of the cured product. If the amount is less than 0.0001 mass%, the viscosity may increase during preparation.

[0013] A polythiol compound may be added to the composition for optical materials of the present invention. The polythiol compound includes all polythiol compounds, specifically, methanedithiol, 1,2-dimercaptoethane, 2,2-dimercaptopropane, 1,3-dimercaptopropane, 1,2,3-trimercaptopropane, 1,4-dimercaptobutane, 1,6-dimercaptohexane, bis(2-mercaptoethyl)sulfide, 1,2-bis(2-mercaptoethylthio)ethane, 1,5-dimercapto-3-oxapentane, 1,8-dimercapto-3,6-dioxaoctane, 2,2-dimethylpropane- 1,3-Dithiol, 3,4-dimethoxybutane-1,2-dithiol, 2-mercaptomethyl-1,3-dimercaptopropane, 2-mercaptomethyl-1,4-dimercaptopropane, 2-(2-mercaptoethylthio)-1,3-dimercaptopropane, 1,2-bis(2-mercaptoethylthio)-3-mercaptopropane, 1,1,1-tris(mercaptomethyl)propane, tetrakis(mercaptomethyl)methane, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane mercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 1,1,3,3-tetrakis(mercaptomethylthio)propane, ethylene glycol bis(2-mercaptoacetate), ethylene glycol bis(3-mercaptopropionate), 1,4-butanediol bis(2-mercaptoacetate), 1,4-butanediol bis(3-mercaptopropionate), trimethylolpropane tris(2-mercaptomethylthio)propane pentaerythritol tetrakis(2-mercaptoacetate), trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol tetrakis(3-mercaptopropionate), 1,1-dimercaptocyclohexane, 1,2-dimercaptocyclohexane, 1,3-dimercaptocyclohexane, 1,4-dimercaptocyclohexane, 1,3-bis(mercaptomethyl)cyclohexane, 1,4-bis(mercaptomethyl)cyclohexane, 2,5-bis(mercaptomethyl)-1,Examples of such mercaptomethylphenyl compounds include 4-dithiane, 2,5-bis(mercaptoethyl)-1,4-dithiane, 1,2-bis(mercaptomethyl)benzene, 1,3-bis(mercaptomethyl)benzene, 1,4-bis(mercaptomethyl)benzene, bis(4-mercaptophenyl)sulfide, bis(4-mercaptophenyl)ether, 2,2-bis(4-mercaptophenyl)propane, bis(4-mercaptomethylphenyl)sulfide, bis(4-mercaptomethylphenyl)ether, and 2,2-bis(4-mercaptomethylphenyl)propane. Although specific examples have been given above, the present invention is not limited to these, and these compounds may be used alone or in combination of two or more.

[0014] Among the above, specific examples of preferred compounds include bis(2-mercaptoethyl)sulfide, pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol tetrakis(3-mercaptopropionate), 2,5-bis(mercaptomethyl)-1,4-dithiane, 1,2-bis(2-mercaptoethylthio)-3-mercaptopropane, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 1,1,3,3-tetrakis(mercaptomethylthio)propane, 1,3-bis(mercaptomethyl)benzene, and 1,4-bis(mercaptomethyl)benzene. More preferred examples of the compound include bis(2-mercaptoethyl) sulfide and 1,3-bis(mercaptomethyl)benzene, and the most preferred compound is bis(2-mercaptoethyl) sulfide. The amount of the polythiol compound added is preferably 1 to 50 mass %, more preferably 2 to 30 mass %, and even more preferably 3 to 20 mass %, based on the total amount of the composition for optical materials.

[0015] Sulfur or a compound represented by formula (9) may be added to the composition for optical materials of the present invention. [ka] In formula (9), X represents S, Se, or Te, and preferably represents S. Each of a to f independently represents an integer of 0 to 3, and satisfies 8≧(a+c+e)≧1, 8≧(b+d+f)≧2, and (b+d+f)≧(a+c+e).

[0016] The compound represented by formula (9) includes all compounds, but specifically includes dithiirane, 1,2-dithietane, 1,3-dithietane, trithietane, 1,2-dithiolane, 1,3-dithiolane, 1,2,3-trithiolane, 1,2,4-trithiolane, tetrathiolane, 1,2-dithiane, 1,3-dithiane, 1,4-dithiane, 1,2,3-trithiane, 1,2,4-trithiane, 1,3,5-trithiane, 1,2,3,4-tetrathiane, 1,2,4,5-tetrathiane, thrathiane, bis(1,2,3,5,6-pentathiepano)methane, tris(1,2,3,5,6-pentathiepano)methane, 1,2-dithiepane, 1,3-dithiepane, 1,4-dithiepane, 1,2,3-trithiepane, 1,2,4-trithiepane, 1,2,5-trithiepane, 1,3,5-trithiepane, 1,2,3,4-tetrathiepane, 1,2,3,5-tetrathiepane, 1,2,4,5-tetrathiepane, 1,2,4,6-tetrathiepane, 1,2,3 ,4,5-Pentathiepane, 1,2,3,4,6-Pentathiepane, 1,2,3,5,6-Pentathiepane, Hexathiepane, Diselecyclobutane, Triselecyclobutane, Diselecyclopentane, Triselecyclopentane, Tetraselecyclopentane, Diselecyclohexane, Triselecyclohexane, Tetraselecyclohexane, Pentaselecyclohexane, Diselecycloheptane, Triselecycloheptane, Tetraselecycloheptane, Pentaselecyclohexane butane, hexatellurocycloheptane, ditellurocyclobutane, tritellurocyclobutane, ditellurocyclopentane, tritellurocyclopentane, tetratellurocyclopentane, ditellurocyclohexane, tritellurocyclohexane, tetratellurocyclohexane, pentatellurocyclohexane, ditellurocycloheptane, tritellurocycloheptane, tetratellurocycloheptane, pentatellurocycloheptane, and hexatellurocycloheptane. Specific examples of preferred compounds include 1,2-dithietane, trithietane, 1,2-dithiolane, 1,2,3-trithiolane, 1,2,4-trithiolane, tetrathiolane, 1,2-dithiane, 1,2,3-trithiane, 1,2,4-trithiane, 1,3,5-trithiane, 1,2,3,4-tetrathiane, 1,2,4,5-tetrathiane, pentathiane, 1,2,3-trithiepane, and 1,2,4-trithiane. epane, 1,2,5-trithiepane, 1,2,3,4-tetrathiepane, 1,2,3,5-tetrathiepane, 1,2,4,5-tetrathiepane, 1,2,4,6-tetrathiepane, 1,2,3,4,5-pentathiepane, 1,2,3,4,6-pentathiepane, 1,2,3,5,6-pentathiepane, and hexathiepane, particularly preferably 1,2,3,5,6-pentathiepane.

[0017] When sulfur or a compound represented by formula (9) is used, it is preferable to preliminarily react it with compound (a) in advance. The conditions for this preliminarily polymerization reaction are preferably -10 to 120°C for 0.1 to 240 hours, more preferably 0 to 100°C for 0.1 to 120 hours, and particularly preferably 20 to 80°C for 0.1 to 60 hours. It is effective to use a catalyst to promote the preliminary reaction, and preferred examples thereof include 2-mercapto-1-methylimidazole, triphenylphosphine, 3,5-dimethylpyrazole, N-cyclohexyl-2-benzothiazolylsulfinamide, dipentamethylenethiuram tetrasulfide, tetrabutylthiuram disulfide, tetraethylthiuram disulfide, 1,2,3-triphenylguanidine, 1,3-diphenylguanidine, 1,1,3,3-tetramethyleneguanidine, aminoguanidine urea, trimethylthiourea, tetraethylthiourea, dimethylethylthiourea, zinc dibutyldithiocarbamate, zinc dibenzyldithiocarbamate, zinc diethyldithiocarbamate, zinc dimethyldithiocarbamate, and pipecolium pipecolyldithiocarbamate. Furthermore, it is preferable that 10% or more (based on 100% before the reaction) of sulfur or the compound represented by formula (9) is consumed by this preliminary polymerization reaction, and more preferably 20% or more. The preliminary reaction may be carried out in any atmosphere, such as air, an inert gas such as nitrogen, or a sealed environment under normal pressure or increased or reduced pressure. Liquid chromatography or a refractometer can also be used to monitor the progress of the preliminary reaction.

[0018] The amount of sulfur or the compound represented by formula (9) added is usually 0.01 to 40 mass %, preferably 0.1 to 30 mass %, and more preferably 0.5 to 25 mass %, based on the total amount of the composition for optical materials.

[0019] In the present invention, it is preferable to degas the composition for optical materials beforehand. The degassing treatment is carried out under reduced pressure before, during, or after mixing of the compound capable of reacting with some or all of the compositional components, the polymerization catalyst, and the additives. Preferably, the degassing treatment is carried out under reduced pressure during or after mixing. The treatment conditions are a reduced pressure of 0.001 to 50 torr, for 1 minute to 24 hours, at 0°C to 100°C. The degree of vacuum is preferably 0.005 to 25 torr, more preferably 0.01 to 10 torr, and may be varied within these ranges. The degassing time is preferably 5 minutes to 18 hours, more preferably 10 minutes to 12 hours. The temperature during degassing is preferably 5°C to 80°C, more preferably 10°C to 60°C, and may be varied within these ranges. During the degassing treatment, it is preferable to renew the interface of the composition for optical materials by stirring, gas injection, ultrasonic vibration, or the like, in order to enhance the degassing effect. The components removed by degassing treatment are mainly dissolved gases such as hydrogen sulfide and low-boiling-point substances such as low-molecular-weight thiols, but the types of components to be removed are not particularly limited as long as the effects of the present invention are achieved. Furthermore, it is preferable to purify these compositions for optical materials and / or each raw material before mixing by filtering impurities and the like using a filter having a pore size of about 0.05 to 10 μm, in order to further improve the quality of the optical material of the present invention.

[0020] Furthermore, when the composition for optical materials of the present invention is polymerized and cured to obtain an optical material, it is of course possible to add known additives such as antioxidants, ultraviolet absorbers, and bluing agents to further improve the practicality of the obtained material. A preferred example of the antioxidant is a phenol derivative. Among them, preferred compounds are polyhydric phenols and halogen-substituted phenols, more preferred compounds are catechol, pyrogallol, and alkyl-substituted catechols, and most preferred compounds are catechol and pyrogallol. A preferred example of the ultraviolet inhibitor is a benzotriazole-based compound. Among these, specific preferred compounds are 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole, 5-chloro-2-(3,5-di-tert-butyl-2-hydroxyphenyl)-2H-benzotriazole, 2-(3-tert-butyl-2-hydroxy-5-methylphenyl)-5-chloro-2H-benzotriazole, 2-(3,5-di-tert-pentyl-2-hydroxyphenyl)-2H-benzotriazole, 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-2H-benzotriazole, 2-(2-hydroxy-4-octyloxyphenyl)-2H-benzotriazole, and 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole. Preferred examples of the bluing agent include anthraquinone compounds.

[0021] Furthermore, if the composition for optical materials of the present invention is prone to peeling from the mold during polymerization, it is possible to control and improve the adhesion between the resulting cured product and the mold by using or adding a known external and / or internal adhesion improver. Examples of adhesion improvers include known silane coupling agents and titanate compounds, which may be used alone or in combination of two or more. The amount added is typically 0.0001 to 5 mass% based on the total amount of the composition for optical materials. Conversely, if the composition for optical materials of the present invention is difficult to peel from the mold after polymerization, it is possible to use or add a known external and / or internal mold release agent to improve the mold releasability of the resulting cured product. Examples of the release agent include fluorine-based nonionic surfactants, silicon-based nonionic surfactants, phosphate esters, acidic phosphate esters, oxyalkylene-type acidic phosphate esters, alkali metal salts of acidic phosphate esters, alkali metal salts of oxyalkylene-type acidic phosphate esters, alkali metal salts of higher fatty acids, higher fatty acid esters, paraffin, wax, higher aliphatic amides, higher aliphatic alcohols, polysiloxanes, and aliphatic amine ethylene oxide adducts, which may be used alone or in combination of two or more. The amount added is usually 0.0001 to 5% by mass based on the optical material composition.

[0022] The method for producing an optical material by polymerizing and curing the composition for optical materials of the present invention is described in more detail below. The aforementioned components and additives such as antioxidant, UV absorber, polymerization catalyst, radical polymerization initiator, adhesion improver, and mold release agent may all be mixed simultaneously in the same container under stirring, or the raw materials may be added and mixed in stages, or several components may be mixed separately and then remixed in the same container. The raw materials and auxiliary raw materials may be mixed in any order. The set temperature, time required for mixing, and other conditions may basically be such that the components are thoroughly mixed.

[0023] The composition for optical materials that has undergone the above-described reaction and treatment is poured into a glass or metal mold, and the polymerization and curing reaction is carried out by heating or irradiation with active energy rays such as ultraviolet rays, and then the composition is removed from the mold. In this manner, an optical material is produced. The composition for optical materials is preferably polymerized and cured by heating to produce an optical material. In this case, the curing time is 0.1 to 200 hours, usually 1 to 100 hours, and the curing temperature is -10 to 160°C, usually -10 to 140°C. Polymerization can be carried out by holding at a predetermined polymerization temperature for a predetermined time, increasing the temperature by 0.1 to 100°C per hour, decreasing the temperature by 0.1 to 100°C per hour, or a combination thereof. Furthermore, in the method for producing an optical material of the present invention, after polymerization, annealing the cured product at a temperature of 50 to 150°C for approximately 10 minutes to 5 hours is a preferred treatment to remove distortion in the optical material. Furthermore, surface treatments such as dyeing, hard coating, impact-resistant coating, anti-reflection, and anti-fogging properties can be performed as needed.

[0024] The composition for optical materials of the present invention preferably has a viscosity of less than 450 cp, more preferably less than 350 cp, when the components are stirred uniformly and then kept at 20° C. for 3 hours and measured with a vibration viscometer. Furthermore, when the composition for optical materials of the present invention is polymerized and cured, and then subjected to a 48-hour weather resistance test to measure the change in color tone, ΔY.I. is preferably less than 3.5, and more preferably less than 2.5. [Example]

[0025] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these. Evaluations were carried out by the following methods.

[0026] To the compounds shown in Tables 3 and 4 below ((a) compound, sulfur, and polythiol compound), 0.03 mass% of triethylbenzylammonium chloride as a polymerization catalyst (b) based on the total amount of the composition for optical materials, and 0.3 mass% of a stabilizer shown in Tables 3 and 4 based on the total amount of the composition for optical materials were added, and after uniform stirring, the mixture was kept at 20°C for 3 hours, and the viscosity was measured using a vibration viscometer (VM-10A manufactured by Sekonic Corporation). Specifically, approximately 30 mL of the solution was placed in a 100 mL plastic container, and the container was placed in an oven at 20°C, and the viscosity was measured. The results based on the evaluation criteria shown in Table 1 below are shown in Tables 3 and 4.

[0027] [Table 1]

[0028] To the compounds shown in Tables 3 and 4 below ((a) compound, sulfur, and polythiol compound), 0.03 mass % of triethylbenzylammonium chloride (b) as a polymerization catalyst and 0.3 mass % of a stabilizer shown in Tables 3 and 4 were added, based on the total amount of the composition for optical materials, and the composition was polymerized and cured. A weathering test was conducted for 48 hours using a weatherometer (Atlas Weatherometer Ci4000) at a black panel temperature of 60°C and humidity of 50%, and the change in color tone (yellowing index (ΔY.I.)) before and after the weathering test was measured using a Konica Minolta CM-5 spectrophotometer. Specifically, the YI of a sample (t=5 mm) was measured in advance at 25°C, and the above-mentioned weathering test was then performed on this sample. After leaving the sample in a room at 25°C for 30 minutes or more, the YI was measured again. The difference in YI before and after the weathering test was defined as ΔY.I. The results based on the evaluation criteria shown in Table 2 below are shown in Tables 3 and 4.

[0029] [Table 2]

[0030] [Table 3] Compound abbreviation BES: Bis(β-epithiopropyl) sulfide S: sulfur BMES: Bis(2-mercaptoethyl) sulfide

[0031] [Table 4] Compound abbreviation BES: Bis(β-epithiopropyl) sulfide S: sulfur BMES: Bis(2-mercaptoethyl) sulfide

Claims

1. A composition for optical materials comprising (a) an episulfide compound, (b) a polymerization catalyst, and (c) an ester compound having a halogen atom at the α-position, The composition for optical materials, wherein the (c) ester compound having a halogen at the α-position is a compound represented by the following formula (10): 【Chemical 1】 (In the formula, X represents a halogen. R 1 and R 2 each independently represent a hydrocarbon having 1 to 10 carbon atoms.)

2. 2. The composition for optical materials according to claim 1, wherein the episulfide compound (a) is a compound represented by the following formula (1): 【Chemistry 2】 (where m is an integer from 0 to 4, and n is an integer from 0 to 2.)

3. The composition for optical materials according to claim 1 or 2, further comprising a polythiol compound.

4. The composition for optical materials according to any one of claims 1 to 3, further comprising sulfur and / or a compound represented by the following formula (9): 【Chemistry 3】 (In the formula, X represents S, Se, or Te; a to f = 0 to 3, 8 ≧ (a + c + e) ≧ 1, 8 ≧ (b + d + f) ≧ 2, and (b + d + f) ≧ (a + c + e).)

5. The composition for optical materials according to any one of claims 1 to 4, wherein the compound represented by formula (10) is one or more compounds selected from the group consisting of dimethyl chloromalonate, diethyl chloromalonate, dimethyl bromomalonate, and diethyl bromomalonate.

6. An optical material obtained by polymerizing the composition for optical materials according to any one of claims 1 to 5.

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