Optical material composition and optical material using same

Abstract

This uniform-system optical material composition can be provided easily without performing a preliminary polymerization reaction, and can provide an optical material having excellent heat resistance.　The optical material composition comprises (a) an episulfide compound, (b) sulfur, and (c) a cyclic compound represented by formula (1). The mass ratio (b / c) of (b) the sulfur with respect to (c) the cyclic compound is 8 or less. The content of (c) the cyclic compound is less than 10 parts by mass with respect to a total of 100 parts by mass of (a) the episulfide compound, (b) the sulfur, and (c) the cyclic compound. (In formula (1), each X independently represents S, Se, or Te, and a to f each independently represent 0-3, provided that 8≥(a+c+e)≥1, 8≥(b+d+f)≥2, and (b+d+f)≥(a+c+e) are satisfied.)

Description

Composition for optical material and optical material using the same

[0001] The present invention relates to a composition for optical materials and an optical material using the same.

[0002] Plastic materials are widely used in optical materials, especially eyeglass lenses, because they are lightweight, highly tough, and easy to dye. Optical materials are required to have physical properties such as low specific gravity, high transparency, high heat resistance, and high strength, as well as optical properties such as high refractive index and high Abbe number.

[0003] Conventionally, methods of using polyepisulfide compounds as optical materials having excellent physical properties and optical characteristics have been investigated. For example, Patent Document 1 describes an invention relating to a composition for optical materials containing an episulfide compound and a cyclic compound containing sulfur and a predetermined atom (sulfur, selenium, or tellurium).

[0004] Patent Document 1 describes that an optical material having a high refractive index of 1.7 or more can be obtained by using a polyepisulfide compound. Furthermore, Patent Document 1 describes that the optical material obtained from the composition for optical materials described above has excellent heat resistance and mold releasability.

[0005] International Publication No. 2016 / 204080

[0006] However, for example, the optical material obtained from the composition for optical materials described in Patent Document 1 has room for improvement in heat resistance. Furthermore, since sulfur and cyclic compounds are solid at low temperatures (e.g., 40°C or below), simply mixing raw materials at low temperatures results in a heterogeneous composition for optical materials containing solid components, which can result in insufficient performance of the resulting optical material. Therefore, in the past, in order to produce a homogeneous composition for optical materials, a preliminary polymerization reaction (e.g., a polymerization reaction of sulfur and an episulfide compound) using the solid components as raw materials has been carried out in the production process of the composition for optical materials to increase the solubility of the solid components. However, the preliminary polymerization reaction requires certain considerations, such as the need to monitor the progress of the curing reaction (polymerization reaction) in-line, making the production process complicated.

[0007] Therefore, the present invention can obtain an optical material having excellent heat resistance, and can easily provide a homogeneous composition for optical materials without carrying out a preliminary polymerization reaction.

[0008] That is, the present invention provides, for example, the following: [1] (a) an episulfide compound, (b) sulfur, and (c) a compound represented by the following formula (1): (in the above formula (1), X each independently represents S, Se, or Te, and a to f each independently represent 0 to 3, with the proviso that 8 ≧ (a + c + e) ​​≧ 1, 8 ≧ (b + d + f) ≧ 2, and (b + d + f) ≧ (a + c + e) ​​are satisfied), wherein the mass ratio (b / c) of the (b) sulfur to the (c) cyclic compound is 8 or less, and the content of the (c) cyclic compound is less than 10 parts by mass per 100 parts by mass of the total of the (a) episulfide compound, (b) sulfur, and (c) cyclic compound. [2] The composition for optical materials according to the above item [1], wherein the total content of the (b) sulfur and the (c) cyclic compound is 9 to 30 parts by mass per 100 parts by mass of the total of the (a) episulfide compound, (b) sulfur, and (c) cyclic compound. [3] The composition for optical materials according to the above [1] or [2], further comprising (d) a thiol compound. [4] An optical material comprising a cured product of the composition for optical materials according to any one of the above [1] to [3].

[0009] According to the present invention, an optical material having excellent heat resistance can be obtained, and a homogeneous composition for optical materials can be easily obtained without carrying out a preliminary polymerization reaction.

[0010] The present invention will be described in detail below with reference to embodiments and examples, but the present invention is not limited to the embodiments and examples shown below, and can be modified and implemented as desired within the scope of the present invention.

[0011] 1. Composition for Optical Materials The composition for optical materials according to the present invention contains (a) an episulfide compound, (b) sulfur, and (c) a cyclic compound represented by the following formula (1). In this case, the mass ratio (b / c) of the (b) sulfur to the (c) cyclic compound is 8 or less. In addition, the content of the (c) cyclic compound is less than 10 parts by mass relative to a total of 100 parts by mass of the (a) episulfide compound, (b) sulfur, and (c) cyclic compound.

[0012] The composition for optical materials according to the present invention allows a homogeneous composition for optical materials to be easily obtained without a preliminary polymerization reaction by controlling the contents of (b) sulfur and (c) cyclic compound, and the obtained optical material has excellent heat resistance. Since the composition for optical materials is produced without a preliminary polymerization reaction, it does not contain, or contains little to no prepolymerization products of (a) episulfide compound and (b) sulfur, for example. Furthermore, in this specification, the term "homogeneous" refers to a state in which a curing reaction (polymerization reaction) using the composition for optical materials occurs in a single phase, and preferably refers to a homogeneous solution state that does not contain solid components. When the evaluation of "presence or absence of solid components" in the examples is evaluated as "○," the composition for optical materials is "homogeneous."

[0013] [(a) Episulfide Compound] The episulfide compound is not particularly limited, and examples thereof include episulfide compounds having a chain aliphatic skeleton, episulfide compounds having a cyclic aliphatic skeleton, and episulfide compounds having an aromatic skeleton.

[0014] Examples of the episulfide compound having a chain aliphatic skeleton include compounds represented by the following formulas (2) to (5).

[0015] In this case, in the above formula (2), m represents an integer of 0 to 4, preferably 0 to 2, and more preferably 0 or 1. In one embodiment, m is 0. In another embodiment, m is 1.

[0016] Furthermore, n represents an integer of 0 to 2, preferably 0 to 2, and more preferably 0 or 1. In one embodiment, n is 0. In another embodiment, n is 1.

[0017] Specific examples of the episulfide compound having a chain aliphatic skeleton represented by formula (2) include 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, and bis(β-epithiopropylthioethyl)sulfide.

[0018] Examples of the episulfide compound having a cyclic aliphatic skeleton include compounds represented by the following formulas (6) and (7).

[0019] In the above formulas (6) and (7), p represents an integer of 0 to 4, preferably 0 to 2, and more preferably 0 or 1. In one embodiment, p is 0. In another embodiment, p is 1.

[0020] Furthermore, q represents an integer of 1 to 4, preferably 1 to 3, and more preferably 2 or 3. In one embodiment, q is 2. In another embodiment, q is 3.

[0021] Examples of the episulfide compound having a cyclic aliphatic skeleton represented by formula (6) include 1,3-bis(β-epithiopropylthio)cyclohexane, 1,4-bis(β-epithiopropylthio)cyclohexane, 1,3-bis(β-epithiopropylthiomethyl)cyclohexane, and 1,4-bis(β-epithiopropylthiomethyl)cyclohexane.

[0022] Examples of the episulfide compound having a cyclic aliphatic skeleton represented by formula (7) include 2,5-bis(β-epithiopropylthio)-1,4-dithiane, 2,5-bis(β-epithiopropylthioethylthiomethyl)-1,4-dithiane, and the like.

[0023] Examples of the episulfide compound having an aromatic skeleton include compounds represented by the following formulas (8) and (9).

[0024] In the above formulas (8) and (9), each r independently represents an integer of 0 to 4, preferably 0 to 2, and more preferably 0 or 1. In one embodiment, r is 0. In another embodiment, r is 1.

[0025] Each s independently represents an integer of 1 to 3, and is preferably 2 or 3. In one embodiment, s is 2. In another embodiment, s is 3.

[0026] Furthermore, each t independently represents an integer of 0 or 1. In one embodiment, s is 0. In another embodiment, s is 1.

[0027] Examples of the episulfide compound having an aromatic skeleton represented by formula (8) include 1,3-bis(β-epithiopropylthio)benzene, 1,4-bis(β-epithiopropylthio)benzene, 1,3-bis(β-epithiopropylthiomethyl)benzene, and 1,4-bis(β-epithiopropylthiomethyl)benzene.

[0028] Examples of the episulfide compound having an aromatic skeleton represented by formula (9) include 9,9-bis(4-(β-epithiopropyloxy)phenyl-1-yl)fluorene (wherein both t's are 0), 9,9-bis(4-(2-(β-epithiopropyloxy)ethoxy)phenyl-1-yl)fluorene (wherein both t's are 1), and the like.

[0029] Of the above-mentioned episulfide compounds, the episulfide compound preferably contains an episulfide compound having a chain aliphatic skeleton, more preferably contains at least one of a compound represented by formula (2) and a compound represented by formula (3), further preferably contains at least one selected from the group consisting of bis(β-epithiopropyl) sulfide, bis(β-epithiopropyl) disulfide, and a compound represented by formula (3), particularly preferably contains at least one of bis(β-epithiopropyl) sulfide and bis(β-epithiopropyl) disulfide, and most preferably contains bis(β-epithiopropyl) sulfide. The above-mentioned episulfide compounds may be used alone or in combination of two or more.

[0030] The content of the episulfide compound is preferably 30 to 95 mass %, more preferably 50 to 95 mass %, further preferably 70 to 90 mass %, and particularly preferably 75 to 90 mass %, relative to the total mass of the optical material composition.

[0031] In one embodiment, the content of the episulfide compound is preferably 30 to 95 parts by mass, more preferably 50 to 95 parts by mass, still more preferably 70 to 90 parts by mass, and particularly preferably 75 to 90 parts by mass, relative to 100 parts by mass in total of (a) the episulfide compound, (b) sulfur, and (c) the cyclic compound.

[0032] In addition, in one embodiment, when the optical material composition further contains a (d) thiol compound described below, the content of the episulfide compound is preferably 30 to 95 parts by mass, more preferably 50 to 95 parts by mass, still more preferably 70 to 90 parts by mass, and particularly preferably 75 to 90 parts by mass, relative to 100 parts by mass in total of the (a) episulfide compound, (b) sulfur, (c) cyclic compound, and (d) thiol compound.

[0033] [(b) Sulfur] Sulfur has a function of improving the refractive index of optical materials.

[0034] Sulfur refers to an elemental sulfur having a unit structure of S8 sulfur, and is readily available commercially.

[0035] The form of sulfur is not particularly limited and may be any form. Specific forms include finely divided sulfur, colloidal sulfur, precipitated sulfur, crystalline sulfur, and sublimed sulfur. Among these, finely divided sulfur is preferred from the viewpoint of dissolution rate and the like.

[0036] The particle size (diameter) of sulfur is preferably smaller than 10 mesh (opening 1.70 mm), more preferably smaller than 30 mesh (opening 500 μm), and even more preferably smaller than 60 mesh (opening 250 μm). A particle size of sulfur smaller than 10 mesh is preferred because sulfur is easily dissolved.

[0037] The purity of sulfur is not particularly limited, but is preferably 98% or more, more preferably 99.0% or more, even more preferably 99.5% or more, and particularly preferably 99.9% or more. A sulfur purity of 98% or more is preferred because the color tone of the resulting optical material is further improved.

[0038] The sulfur content is preferably 1 to 30% by mass, more preferably 3 to 20% by mass, even more preferably 8.2 to 15% by mass, and particularly preferably 9 to 15% by mass, based on the total mass of the optical material composition. A sulfur content within the above range is preferred because it provides an excellent balance between the refractive index improvement effect and solubility.

[0039] In one embodiment, the content of sulfur is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass, still more preferably 8.2 to 15 parts by mass, and particularly preferably 9 to 15 parts by mass, relative to 100 parts by mass in total of (a) the episulfide compound, (b) sulfur, and (c) the cyclic compound.

[0040] In addition, in one embodiment, when the optical material composition further contains a (d) thiol compound described below, the content of sulfur is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass, further preferably 8.2 to 15 parts by mass, and particularly preferably 9 to 15 parts by mass, relative to 100 parts by mass in total of the (a) episulfide compound, (b) sulfur, (c) cyclic compound, and (d) thiol compound.

[0041] [(c) Cyclic Compound] The cyclic compound has the function of dissolving solids such as sulfur contained in the optical material composition and the function of improving the refractive index of the optical material. By including a cyclic compound, a homogeneous solution-state optical material composition can be obtained even at low temperatures (e.g., 40°C or below) without conducting a preliminary polymerization reaction using solid components as raw materials (e.g., a polymerization reaction of sulfur and an episulfide compound). Furthermore, since a preliminary polymerization reaction is not required, problems associated with the prepolymer obtained by the preliminary polymerization reaction do not arise. For example, although the prepolymer has higher solubility than the solid components (e.g., sulfur, cyclic compound, etc.) used as raw materials, it has sometimes been found that its solubility in some solvents, such as tetrahydrofuran, is insufficient. In such cases, when attempting to clean the pipes or the like using a solvent such as tetrahydrofuran, precipitates derived from the prepolymer may form, and the precipitates may adhere to the pipes or the like. That is, when producing an optical material composition containing the prepolymer, cleaning the pipes or the like requires the use of a mixed solvent, such as a mixture of tetrahydrofuran and N-methylpyrrolidone, which does not have high cleanability. In contrast, the optical material composition according to the present invention does not contain or contains almost no prepolymerized product, and therefore can be used to clean pipes, etc. with a solvent such as tetrahydrofuran, etc. In other words, the optical material composition according to the present invention can have high cleanability.

[0042] The cyclic compound is represented by the following formula (1).

[0043] In the above formula (1), X each independently represents S, Se, or Te, and is preferably S or Se, more preferably S, from the viewpoints of easy availability and high safety.

[0044] In formula (1), when there are two or more X's, the two or more X's may be the same or different from one another, but it is preferable that the two or more X's are the same. In one embodiment, it is preferable that all of X's are S. In another embodiment, it is preferable that all of X's are Se. Furthermore, in another embodiment, it is preferable that all of X's are Te.

[0045] a to f are each independently 0 to 3, provided that 8 ≧ (a + c + e) ​​≧ 1, 8 ≧ (b + d + f) ≧ 2, and (b + d + f) ≧ (a + c + e). From the viewpoint of further improving the refractive index of the optical material, a to f preferably satisfy 8 ≧ (a + c + e) ​​≧ 1 and 7 ≧ (b + d + f) ≧ 2, more preferably satisfy 5 ≧ (a + c + e) ​​≧ 1 and 7 ≧ (b + d + f) ≧ 2, and even more preferably satisfy 5 ≧ (a + c + e) ​​≧ 1, 7 ≧ (b + d + f) ≧ 2, and (b + d + f) ≧ (a + c + e).

[0046] In one embodiment, it is preferable to satisfy (b+d+f)≧(a+c+e).

[0047] In one embodiment, from the viewpoint of further improving the refractive index of the optical material, the total mass of S, Se, and Te in the cyclic compound is preferably 50 mass% or more with respect to the total mass of the cyclic compound.

[0048] Specific examples of the cyclic compound include, but are not limited to, 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, 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 Epane, 1,2,3,5,6-pentathiepane, hexathiepane, diselecyclobutane, triselecyclobutane, diselecyclopentane, triselecyclopentane, tetraselecyclopentane, diselecyclohexane, triselecyclohexane, tetraselecyclohexane, pentaselecyclohexane, diselecycloheptane, triselecycloheptane, tetraselecycloheptane, pentaselecycloheptane, hexaselecycloheptane, ditellurocyclobutane, tritellurocyclo Examples of cyclohexyl cyclohexyl include ditellurocyclopentane, ditellurocyclopentane, tritellurocyclopentane, tetratellurocyclopentane, ditellurocyclohexane, tritellurocyclohexane, tetratellurocyclohexane, pentatellurocyclohexane, ditellurocycloheptane, tritellurocycloheptane, tetratellurocycloheptane, pentatellurocycloheptane, hexatellurocycloheptane, and derivatives having these cyclic skeleton structures (compounds in which hydrogen atoms are replaced with various substituents).In this case, the substituent that can be substituted for the hydrogen atom of the cyclic compound is not particularly limited, and examples thereof include alkyl groups having 1 to 10 carbon atoms (methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, etc.), alkoxy groups having 1 to 10 carbon atoms (methoxy group, ethoxy group, propyloxy group, isopropyloxy group, tert-butoxy group, etc.), halogen atoms (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), etc. The cyclic compound may have only one type of these substituents or may have two or more types in combination.

[0049] Among the above, from the viewpoints of ease of availability and synthesis, and further improving the refractive index of optical materials, cyclic compounds are 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, 1,2,4-trithiepane, 1,2,5-trithiepane, 1,2,3,4-tetrathiane, and the like. Preferably, the cyclic compound contains at least one selected from the group consisting of lathiepane, 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, and derivatives thereof having a cyclic skeleton structure (in which various substituents are attached in place of hydrogen atoms), and more preferably contains at least one of 1,2,4,5-tetrathiane and 1,2,3,5,6-pentathiepane. The cyclic compounds may be used alone or in combination of two or more.

[0050] The method for obtaining the cyclic compound is not particularly limited, and a commercially available product may be used, or the cyclic compound may be extracted from natural products such as crude oil, animals, and plants, or may be synthesized by a known method. Examples of methods for synthesizing the cyclic compound include N. Takeda et al., Bull. Chem. Soc. Jpn., 68, 2757 (1995), F. Feher et al., Angew. Chem. Int. Ed., 7, 301 (1968), and G. W. Kutney et al., Can. J. Chem, 58, 1233 (1980).

[0051] The content of the cyclic compound is less than 10% by mass relative to the total mass of the optical material composition, and from the viewpoint of dissolving solid components and making it easier to obtain a homogeneous solution, the content is preferably 1.1 to 9.5% by mass, more preferably 1.8 to 9% by mass, even more preferably 1.8 to 7% by mass, and particularly preferably 3 to 7% by mass.

[0052] In one embodiment, the content of the cyclic compound is less than 10 parts by mass relative to 100 parts by mass of the total of (a) the episulfide compound, (b) sulfur, and (c) the cyclic compound, and from the viewpoint of making it easier to dissolve solid components and obtain a homogeneous solution, the content is preferably 1.1 to 9.5 parts by mass, more preferably 1.8 to 9 parts by mass, even more preferably 1.8 to 7 parts by mass, and particularly preferably 3 to 7 parts by mass. Note that when the content of the cyclic compound is less than 10 parts by mass, a decrease in heat resistance due to the cyclic compound can be suppressed.

[0053] In one embodiment, when the optical materials composition further contains a (d) thiol compound described below, the content of the cyclic compound is less than 10 parts by mass relative to 100 parts by mass in total of the (a) episulfide compound, (b) sulfur, (c) cyclic compound, and (d) thiol compound, and from the viewpoint of making it easier to dissolve solid components and obtain a homogeneous solution, the content is preferably 1.1 to 9.5 parts by mass, more preferably 1.8 to 9 parts by mass, even more preferably 1.8 to 7 parts by mass, and particularly preferably 3 to 7 parts by mass.

[0054] The mass ratio (b / c) of (b) sulfur to (c) cyclic compound is 8 or less, preferably 0.5 to 8, more preferably 0.5 to 7, and from the viewpoint of further increasing the refractive index, is further preferably 1.2 to 8, particularly preferably 1.2 to 7. When the mass ratio (b / c) is 8 or less, the (b) sulfur can be suitably dissolved in the optical material composition due to the action of the (c) cyclic compound, which is preferable.

[0055] The total content of (b) sulfur and (c) cyclic compound is preferably 9 to 30 mass %, more preferably 9 to 20 mass %, even more preferably 10 to 20 mass %, and particularly preferably 12 to 18 mass %, relative to the total mass of the optical material composition.

[0056] The total content of (b) sulfur and the (c) cyclic compound is preferably 9 to 30 parts by mass, more preferably 9 to 20 parts by mass, even more preferably 10 to 20 parts by mass, and particularly preferably 12 to 18 parts by mass, relative to 100 parts by mass of the total of (a) episulfide compound, (b) sulfur, and (c) cyclic compound. Note that when the total content is within the above range, (b) sulfur dissolves in the optical material composition to easily obtain a homogeneous solution, and the heat resistance of the obtained optical material is increased, and the refractive index of the optical material can also be increased, which is preferable.

[0057] In addition, in one embodiment, when the optical material composition further contains a (d) thiol compound described below, the total content of (b) sulfur and the (c) cyclic compound is preferably 9 to 30 parts by mass, more preferably 9 to 20 parts by mass, still more preferably 10 to 20 parts by mass, and particularly preferably 12 to 18 parts by mass, relative to 100 parts by mass in total of the (a) episulfide compound, (b) sulfur, (c) cyclic compound, and (d) thiol compound.

[0058] [(d) Thiol Compound] In one embodiment, the composition for optical materials preferably further contains a thiol compound. The thiol compound has a function of improving the color tone of the optical material, etc. In this specification, the term "thiol compound" refers to a compound having one or more thiol groups (-SH) in the molecule. The thiol compound may further have an episulfide group. In addition, when a compound having an episulfide group further has a thiol group, it corresponds to "(d) thiol compound", and when it does not have a thiol group, it corresponds to "(a) episulfide compound".

[0059] The thiol compound is not particularly limited, but examples thereof include methanedithiol, (sulfanylmethyldisulfanyl)methanethiol, bis(2-mercaptoethyl)sulfide, 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-di Examples thereof include mercapto-3,6,9-trithiaundecane, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 1,1,3,3-tetrakis(mercaptomethylthio)propane, 1,2,6,7-tetramercapto-4-thiaheptane, tetramercaptopentaerythritol, 1,3-bis(mercaptomethyl)benzene, 1,4-bis(mercaptomethyl)benzene, and thiiranemethanethiol. Of these, from the viewpoint of easy availability and the like, the thiol compound preferably includes at least one selected from the group consisting of methanedithiol, (sulfanylmethyldisulfanyl)methanethiol, bis(2-mercaptoethyl)sulfide, 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, 1,2,6,7-tetramercapto-4-thiaheptane, tetramercaptopentaerythritol, 1,3-bis(mercaptomethyl)benzene, and thiiranemethanethiol. The above-mentioned thiol compounds may be used alone or in combination of two or more kinds.

[0060] The content of the thiol compound is preferably 0.1 to 15 mass %, more preferably 0.5 to 12 mass %, relative to the total mass of the optical material composition. From the viewpoint of preventing roughening of the surface of the optical component, the content is further preferably 1 to 10 mass %, and particularly preferably 2 to 5 mass %.

[0061] In one embodiment, the content of the thiol compound is preferably 0.1 to 15 parts by mass and more preferably 0.5 to 12 parts by mass, relative to 100 parts by mass in total of (a) the episulfide compound, (b) sulfur, and (c) the cyclic compound. From the viewpoint of preventing roughening of the surface of the optical member, for example, the content is still more preferably 1 to 10 parts by mass and particularly preferably 2 to 5 parts by mass.

[0062] In one embodiment, the content of the thiol compound is preferably 0.1 to 15 parts by mass and more preferably 0.5 to 12 parts by mass, relative to 100 parts by mass in total of (a) the episulfide compound, (b) sulfur, (c) the cyclic compound, and (d) the thiol compound. From the viewpoint of preventing roughening of the surface of the optical member, the content is further preferably 1 to 10 parts by mass and particularly preferably 2 to 5 parts by mass.

[0063] [Polymerizable Compound] In one embodiment, the composition for optical materials may further contain a polymerizable compound. The polymerizable compound has a function of adjusting the physical properties of the optical material, etc. In this specification, the term "polymerizable compound" refers to a compound having a polymerizable functional group other than (a) episulfide compounds, (b) sulfur, (c) cyclic compounds, and (d) thiol compounds.

[0064] The polymerizable compound is not particularly limited, but examples thereof include vinyl compounds, methacrylic compounds, acrylic compounds, allyl compounds, etc. These compounds may be used alone or in combination of two or more.

[0065] The amount of the polymerizable compound added can be adjusted appropriately depending on the desired physical properties of the optical material.

[0066] [Polymerization Catalyst] In one embodiment, the composition for optical materials may further contain a polymerization catalyst. By containing the polymerization catalyst, the composition for optical materials can be suitably polymerized to produce an optical material.

[0067] The polymerization catalyst is not particularly limited, but examples thereof include amines, phosphines, onium salts (quaternary ammonium salts, quaternary phosphonium salts, tertiary sulfonium salts, secondary iodonium salts, etc.), and phosphine compounds.

[0068] Examples of the quaternary ammonium salt include tetra-n-butylammonium bromide, tetraphenylammonium bromide, triethylbenzylammonium chloride, cetyldimethylbenzylammonium chloride, and 1-n-dodecylpyridinium chloride.

[0069] Examples of the quaternary phosphonium salt include tetra-n-butylphosphonium bromide and tetraphenylphosphonium bromide.

[0070] Examples of the phosphine compound include triphenylphosphine.

[0071] The polymerization catalyst preferably contains at least one selected from the group consisting of quaternary ammonium salts, quaternary phosphonium salts, and phosphine compounds, more preferably contains a quaternary ammonium salt, and further preferably contains at least one of triethylbenzylammonium chloride and tetra-n-butylphosphonium bromide. The polymerization catalysts may be used alone or in combination of two or more.

[0072] The amount of polymerization catalyst added varies depending on the components, mixing ratio, curing method, etc. of the composition for optical materials, but is preferably 0.0001 to 10.0 mass % relative to the total mass of the composition for optical materials, and from the viewpoints of improving the refractive index and heat resistance of the optical material and preventing coloration, etc., it is more preferably 0.0005 to 5.0 mass %, and even more preferably 0.01 to 3 mass %.

[0073] [Polymerization modifier] In one embodiment, the composition for optical materials may further contain a polymerization modifier.

[0074] The polymerization modifier is not particularly limited, but examples thereof include halides of Groups 13 to 16 of the long-term periodic table, and ketone compounds having a halogen at the α-position.

[0075] Halides of Groups 13 to 16 of the long-term periodic table include halides of silicon, germanium, tin, and antimony, and more preferably chlorides of germanium, tin, and antimony having an alkyl group. Specific examples of halides of Groups 13 to 16 of the long-term periodic table include dibutyltin dichloride, butyltin trichloride, dioctyltin dichloride, octyltin trichloride, dibutyldichlorogermanium, butyltrichlorogermanium, diphenyldichlorogermanium, phenyltrichlorogermanium, and triphenylantimony dichloride.

[0076] Examples of the ketone compound having a halogen at the α-position include dimethyl chloromalonate and diethyl chloromalonate.

[0077] The above polymerization regulators may be used alone or in combination of two or more kinds.

[0078] The content of the polymerization modifier is preferably 0.0005 to 5 mass %, more preferably 0.0001 to 3 mass parts, based on the total mass of the composition for optical materials.

[0079] [Additives] In one embodiment, the composition for optical materials may further contain additives.

[0080] Examples of the additives include antioxidants, ultraviolet absorbers, bluing agents, adhesion improvers, and mold release agents.

[0081] The antioxidant is not particularly limited, but may be a phenol derivative. Examples of the phenol derivative include polyhydric phenols such as catechol, pyrogallol, and alkyl-substituted catechol, and halogen-substituted phenols. Of these, the antioxidant is preferably catechol or pyrogallol.

[0082] The ultraviolet protection agent is not particularly limited, but includes benzotriazole-based compounds, such as 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, 2-(2-hydroxy-4-butyloxyphenyl)-2H-benzotriazole, and 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole.

[0083] The bluing agent is not particularly limited, but may include anthraquinone compounds.

[0084] The adhesion improver is not particularly limited, and examples thereof include a silane coupling agent, a titanate compound, etc. The adhesion improver has a function of improving the adhesion between a mold and a cured product when the composition for optical materials is placed in a mold and cured, and the cured product is prone to peeling from the mold.

[0085] The release agent is not particularly limited, and examples thereof 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, aliphatic amine ethylene oxide adducts, etc. When a composition for optical materials is placed in a mold and cured, and the cured product is difficult to peel from the mold, the release agent has a function of controlling the adhesion between the mold and the cured product, thereby making it easier to peel the cured product from the mold (improving mold releasability), etc.

[0086] The above-mentioned additives may be used alone or in combination of two or more kinds.

[0087] The content of the additives is not particularly limited, but is preferably 0.0001 to 5% by mass, based on the total mass of the composition for optical materials.

[0088] 2. Method for Producing Composition for Optical Materials The composition for optical materials is not particularly limited and can be produced by a known method. For example, the composition for optical materials can be produced by mixing (a) an episulfide compound, (b) sulfur, and (c) a cyclic compound, and, as necessary, (d) a thiol compound, a polymerization catalyst, a polymerization modifier, additives, etc.

[0089] The mixing temperature is not particularly limited, but is preferably 40°C or lower, and more preferably 10 to 40°C. When the mixing temperature is 40°C or lower, (b) sulfur and (c) cyclic compound are solid in nature, and therefore, in conventional compositions for optical materials, solids may remain even when mixed at that mixing temperature. However, according to the present invention, (b) sulfur and (c) cyclic compound are suitably dissolved in the composition for optical materials, and therefore, even when the mixing temperature is 40°C or lower, a composition for optical materials in a homogeneous solution state, preferably a homogeneous solution state containing no solid components, can be easily produced without performing a preliminary polymerization reaction.

[0090] It is preferable that the raw materials before mixing and / or the produced composition for optical materials are purified by filtering impurities, etc. In this case, the pore size of the filter is preferably 0.05 to 10 μm.

[0091] 3. Optical Material According to one aspect of the present invention, there is provided an optical material, which includes a cured product of the composition for optical materials described above.

[0092] The composition for optical materials is in a homogeneous solution state, preferably a homogeneous solution state containing no solid components, and the curing reaction can proceed uniformly within the system, so that the optical material has excellent heat resistance. Furthermore, since the composition for optical materials contains (a) an episulfide compound, (b) sulfur, etc., the optical material has an excellent refractive index.

[0093] In one embodiment, the refractive index of the optical material is preferably 1.700 or more, more preferably 1.720 or more, even more preferably 1.730 or more, and particularly preferably 1.733 or more. The refractive index of the optical material is measured by the method described in the examples.

[0094] 4. Method for Producing Optical Material According to one aspect of the present invention, there is provided a method for producing an optical material. The method for producing an optical material includes a curing step of curing the composition for optical material described above. The method may further include a degassing step before the curing step.

[0095] [Degassing Step] The degassing step is a step of degassing the composition for optical materials described above. By performing the degassing step, the quality of the obtained optical material can be improved.

[0096] The degassing treatment can be carried out by placing the composition for optical materials in an atmosphere under reduced pressure.

[0097] The degree of reduced pressure in the degassing treatment is preferably 0.001 to 100 torr, more preferably 0.001 to 100 torr, further preferably 0.005 to 50 torr, and particularly preferably 0.01 to 50 torr.

[0098] The temperature for the degassing treatment is preferably 0°C to 40°C, more preferably 5°C to 40°C, and even more preferably 10°C to 40°C.

[0099] The degassing treatment time is preferably 1 minute to 24 hours, more preferably 5 minutes to 18 hours, and even more preferably 10 minutes to 12 hours.

[0100] In one embodiment, the reduced pressure treatment is preferably carried out at a reduced pressure of 0.001 to 100 torr for 1 minute to 24 hours at 0°C to 40°C, more preferably at a reduced pressure of 0.005 to 50 torr for 5 minutes to 18 hours at 5°C to 40°C, and even more preferably at a reduced pressure of 0.01 to 50 torr for 10 minutes to 12 hours at 10°C to 40°C.

[0101] [Curing Step] The curing step is a step of curing the composition for optical materials described above.

[0102] The curing step is usually carried out by injecting the composition for optical materials into a mold made of glass, metal, or the like, and curing the composition for optical materials (causing a curing reaction of the components in the composition for optical materials) by heating or irradiating it with active energy rays such as ultraviolet rays. After curing, the cured product is removed from the mold, whereby the optical material can be produced.

[0103] The curing temperature is preferably from -10 to 160°C, and more preferably from -10 to 140°C.

[0104] The curing time is preferably 0.1 to 200 hours, and more preferably 1 to 100 hours. When the curing step includes a temperature increasing step and a temperature decreasing step, the curing time includes the time for the temperature increasing step and the temperature decreasing step.

[0105] The curing step may include a temperature increase step, a curing temperature holding step, and a temperature decrease step. In this case, the temperature increase rate in the temperature increase step is preferably 0.1 to 100°C / hour. Furthermore, the temperature decrease rate in the temperature decrease step is preferably 0.1 to 100°C / hour. In one embodiment, the curing step includes a step of increasing the temperature to a first curing temperature, a step of holding the temperature at the first curing temperature, a step of increasing the temperature to a second curing temperature, a step of holding the temperature at the second curing temperature, and a step of decreasing the temperature. In another embodiment, the polymerization step includes a step of increasing the temperature to the first curing temperature, a step of holding the temperature at the first curing temperature, a step of increasing the temperature to a second curing temperature, a step of holding the temperature at the second curing temperature, and a step of decreasing the temperature.

[0106] After curing, the resulting optical material is preferably annealed. By performing the annealing treatment, distortion of the optical material can be prevented or suppressed. The annealing temperature is preferably 50 to 150°C. The annealing time is preferably 10 minutes to 5 hours.

[0107] The obtained optical material may be subjected to surface treatment such as dyeing, hard coating, impact-resistant coating, anti-reflection coating, anti-fogging coating, etc., as required.

[0108] <Uses of Optical Materials> The optical materials described above are useful for various applications, including optical components, mechanical component materials, electrical and electronic component materials, automotive component materials, civil engineering and construction materials, molding materials, as well as paint and adhesive materials. Among these, the optical materials are suitable for optical applications such as eyeglass lenses, (digital) camera imaging lenses, light beam focusing lenses, light diffusing lenses, and other lenses; LED encapsulants, optical adhesives, optical transmission bonding materials, optical fibers, prisms, filters, diffraction gratings, watch glasses, and transparent glass and cover glass for display devices; and display device applications such as substrates for display elements such as LCDs, organic ELs, and PDPs, substrates for color filters, touch panel substrates, information recording substrates, display backlights, light guide plates, display protective films, anti-reflection films, anti-fogging films, and other coating agents (coating films). The optical materials are particularly preferably used for applications such as optical lenses, prisms, optical fibers, information recording substrates, and filters, and more preferably for optical lenses. That is, in one embodiment, an optical lens comprising the optical material described above is provided.

[0109] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0110] Example 1 (a) 81.6 parts by mass of bis(β-epithiopropyl) sulfide, which is an episulfide compound, (b) 12.8 parts by mass of sulfur, and (c) 1.6 parts by mass of 1,2,3,5,6-pentathiepane, which is a cyclic compound, were stirred at 40°C under a reduced pressure of 30 torr until the solid was dissolved.

[0111] To the resulting mixture, 4 parts by mass of bis(2-mercaptoethyl)sulfide (d) (also referred to as "d-1 compound"), which is a thiol compound, 0.05 parts by mass of triethylbenzylammonium chloride, which is a polymerization catalyst, and 0.15 parts by mass of dibutyltin dichloride, which is a polymerization modifier, were further added, and the mixture was stirred at 40°C under a reduced pressure of 30 torr and filtered through a 1 μm PTFE filter to produce an optical material composition. The total amount of (a) to (d) added was 100 parts by mass.

[0112] [Examples 2 to 8 and Comparative Examples 1 to 3] Optical material compositions were produced in the same manner as in Example 1, except that the compositions and mixing temperatures of the optical material compositions were changed to those shown in Table 1. The d-2 compound was 1,2-bis(2-mercaptoethylthio)-3-mercaptopropane.

[0113] The structural formulae of the compounds used in the examples and comparative examples are as follows:

[0114] [Evaluation] The optical material compositions produced in Examples 1 to 8 and Comparative Examples 1 to 3 were subjected to various evaluations.

[0115] (1) Evaluation of Optical Material Compositions The optical material compositions were evaluated for the presence or absence of solid components and for their cleanability.

[0116] [Presence or Absence of Solid Components] The optical material composition heated to 40°C was visually inspected for the presence or absence of solid components, and evaluated according to the following criteria. When no solid components remain in the optical material composition, it can be said to be a homogeneous system. The results are shown in Table 2 below. ○: No solid components remain ×: Solid components remain

[0117]

[0043] 350 g of an optical material composition was added to a 500 mL glass flask and stirred for 10 minutes. The glass flask was then tilted so that the opening was facing vertically downward, and the optical material composition was discharged from the glass flask. In this state, the inside of the glass flask was washed with 100 mL of tetrahydrofuran.

[0118] After cleaning, the glass flask was visually inspected for any deposits on its exterior surface, and evaluated according to the following criteria. However, if any solid components remained in the optical material composition, it was marked as "-" since it was not possible to evaluate it. If there is no deposit on the exterior surface of the glass flask after cleaning, the optical material composition is easy to clean and has excellent handleability. The results are shown in Table 2 below. ○: No deposits on the exterior surface of the glass flask ×: Deposits on the exterior surface of the glass flask

[0119] (2) Evaluation of Optical Materials Optical materials were produced from the optical material compositions, and the heat resistance and refractive index of the optical materials were evaluated.

[0120] [Production of Optical Material] 10 g of the optical material composition was poured into a lens mold, heated at 30°C for 10 hours, then heated to 60°C over 3 hours, heated at 60°C for 7 hours, further heated to 100°C over 4 hours, and heated at 100°C for 3 hours to polymerize and harden, thereby producing an optical material.

[0121] [Heat Resistance] An optical material was cut out to prepare a measurement sample (length: 2.5 mm, width: 5 mm, thickness: 3 mm). Using the measurement sample, the softening point (Tg) was measured using a thermomechanical analyzer (TMA) TMA7100 (manufactured by Hitachi High-Tech Science Corporation) and evaluated according to the following criteria. However, if a solid component remained in the optical material composition, it was marked as "-" since it was not possible to evaluate. In the TMA, a 10 g load was applied to a 0.5 mmφ pin, and the temperature was raised from 25°C at a rate of 5°C / min. If the heat resistance is high, it can be said that the optical material has excellent physical properties. The results obtained are shown in Table 2 below. ○: Softening point is 60°C or higher ×: Softening point is less than 60°C

[0122] [Refractive Index] The refractive index at e-line at 25°C was measured using a digital precision refractometer KPR-3000 (Shimadzu Corporation). A high refractive index indicates that the optical material has excellent optical properties. However, if solid components remain in the optical material composition, the evaluation is impossible and the result is indicated as "-". The results are shown in Table 2 below.

[0123]

[0124] The results in Table 2 show that in Examples 1 to 8, homogeneous compositions for optical materials can be easily produced without a preliminary polymerization reaction. It was also found that the optical materials obtained from the compositions for optical materials of Examples 1 to 8 had excellent heat resistance. Furthermore, it was found that the compositions for optical materials of Examples 1 to 8 had excellent cleanability, and the obtained optical materials had a high refractive index.

Claims

1. (a) an episulfide compound, (b) sulfur, and (c) a compound represented by the following formula (1): (in the above formula (1), X each independently represents S, Se, or Te, and a to f each independently represents 0 to 3, with the proviso that 8≧(a+c+e)≧1, 8≧(b+d+f)≧2, and (b+d+f)≧(a+c+e) are satisfied), wherein a mass ratio (b / c) of the (b) sulfur to the (c) cyclic compound is 8 or less, and a content of the (c) cyclic compound is less than 10 parts by mass per 100 parts by mass of the total of the (a) episulfide compound, (b) sulfur, and (c) cyclic compound.

2. The composition for optical materials according to claim 1, wherein a total content of the (b) sulfur and the (c) cyclic compound is 9 to 30 parts by mass per 100 parts by mass of the total of the (a) episulfide compound, (b) sulfur, and (c) cyclic compound.

3. The composition for optical materials according to claim 1, further comprising (d) a thiol compound.

4. An optical material comprising a cured product of the composition for optical materials according to any one of claims 1 to 3.