Optical material manufacturing method

Abstract

A method for producing an optical material which comprises a step in which a first starting material is mixed with a second starting material to obtain a polymerizable composition for the optical material, the polymerizable composition having a standard deviation determined under condition 1 of 60 or less and having a viscosity of 30-1,000 mPa·s when examined with a Brookfield viscometer under the conditions of 25°C and 60 rpm, and a step in which the polymerizable composition for the optical material is used to produce the optical material. Condition 1: The mixture of the first starting material and the second starting material is put into a quartz cell having an optical path length of 8 mm, an area of 360 mm2, and a thickness of 12 mm; an image is taken using a glass-stria inspection device under the conditions of a shutter speed of 1 / 5000 (sec), a gamma correction of 100, a sharpness of 500, and a contrast and brightness of 0; the image is analyzed using an image analysis software (ImageJ); and a standard deviation is calculated on the assumption that the distribution is a normal distribution in which the ordinate is the number of pixel dots and the abscissa is luminance.

Description

[Technical Field]

[0001] The present disclosure relates to a method for producing an optical material. [Background technology]

[0002] As a method for producing a resin used in an optical material for a plastic lens, for example, a cast polymerization method in which a polymerizable composition containing a monomer is poured into a mold and heated to harden can be mentioned. In the cast polymerization method, a polymerizable composition is prepared and degassed, then the polymerizable composition is injected into a mold (die), and after heat curing (polymerization reaction), the product is removed from the mold (demolding) and annealed to obtain an optical material (for example, a lens, a semi-finished blank, etc.).

[0003] For example, Patent Document 1 describes a process for preparing a molded optical article, comprising the steps of: a) introducing each of two separate reactive components A and B from separate supply containers into a mixing chamber having a volume of 200 mL to 2000 mL; b) mixing the components together in the mixing chamber for 50 to 200 seconds to form a reaction mixture; c) injecting the reaction mixture into a mold at a temperature of up to 130°C; d) holding the reaction mixture in the mold at a temperature and for a time sufficient to harden the reaction mixture and form a molded optical article; and e) removing the article from the mold.

[0004] Patent document 1: Patent No. 5735663 Summary of the Invention [Problem to be solved by the invention]

[0005] A polymerizable composition for an optical material may be prepared by mixing two or more different monomers for an optical material and a polymerization catalyst in one supply vessel. For example, a polymerizable composition for optical materials may be produced by mixing a first raw material containing a portion of two or more different monomers for optical materials, a second raw material containing the remainder of the two or more different monomers for optical materials, and a polymerization catalyst. The present inventors have found that when a polymerizable composition for an optical material is produced by such a method, the following problems arise. That is, when the first raw material and the second raw material are mixed to prepare the polymerizable composition for an optical material, the raw materials may not be mixed well, resulting in unevenness in the polymerizable composition for an optical material. In addition, striae may occur in the optical component obtained by casting the polymerizable composition for an optical material into a mold and curing the composition (in the present disclosure, such striae are also referred to as "casting striae"). The unevenness in the polymerizable composition for an optical material, which is the cause of cast striae, is likely to occur when, for example, either one of the first raw material or the second raw material has a high viscosity, or when both of the first raw material and the second raw material have a high viscosity.

[0006] General striae tend to be caused by convection in a polymerizable composition for an optical material due to non-uniform heating temperature when the polymerizable composition for an optical material is polymerized. This commonly known striae is the wrinkle-like striae that form in the optical material. In contrast, the cast striae discovered by the present inventors tend to be caused mainly by the fact that when a plurality of raw material compositions are mixed together, they are not mixed well and unevenness occurs. Examples of the cast striae include U-shaped striae formed across the optical material, and striae formed in a substantially straight line from the casting port of the optical material. The U-shaped striae are often large, distinct, and dark in color, and therefore tend to impair the quality of optical materials. Therefore, it is necessary to suppress the U-shaped striae. Patent Document 1 does not consider suppressing cast striae.

[0007] An object of one embodiment of the present disclosure is to provide a method for producing an optical material that can suppress casting striae in the resulting optical material. [Means for solving the problem]

[0008] Specific means for solving the problems include the following aspects. <1> A method for producing an optical material, comprising: a first step of mixing a first raw material and a second raw material to obtain a polymerizable composition for an optical material, the polymerizable composition containing two or more different monomers for an optical material and a polymerization catalyst, wherein the polymerizable composition for an optical material has a standard deviation of 60 or less as measured under the following condition 1 and a viscosity of 30 mPa·s to 1000 mPa·s as measured with a Brookfield viscometer at 25°C and 60 rpm; and a second step of producing an optical material using the polymerizable composition for an optical material. [Condition 1] The standard deviation is determined by measuring the mixture of the first and second raw materials with an optical path length of 8 mm and an area of ​​360 mm. 2 The sample is placed in a 12 mm thick quartz cell, and the image is measured using a glass striae inspection device under the following conditions: shutter 1 / 5000 (sec), gamma correction 100, sharpness 500, contrast and brightness 0. The image is analyzed using image analysis software (ImageJ), and calculations are made assuming a normal distribution with the vertical axis representing the number of pixel dots and the horizontal axis representing brightness. <2> The standard deviation is 20 or more <1> 1. A method for producing the optical material according to claim 1. <3> The first raw material includes a prepolymer obtained by mixing a part of the two or more different monomers for optical materials with at least a part of the polymerization catalyst and polymerizing at least a part of the part of the two or more different monomers for optical materials. <1> or <2> 1. A method for producing the optical material according to claim 1. <4> The second step is a step of producing an optical material by casting the polymerizable composition for an optical material into a mold and curing it. <1> ~ <3> 10. A method for producing an optical material according to any one of the above. <5> The two or more different monomers for optical materials include an isocyanate compound (A) containing two or more isocyanate groups, and an active hydrogen compound (B) containing at least one selected from the group consisting of a polythiol compound having two or more mercapto groups, a hydroxythiol compound having one or more mercapto groups and one or more hydroxyl groups, a polyol compound having two or more hydroxyl groups, and an amine compound. <1> ~ <4> 10. A method for producing an optical material according to any one of the above. <6> The polymerization catalyst includes at least one selected from the group consisting of a basic catalyst having a pKa value of 4 to 8 and an organometallic catalyst. <1> ~ <5> 10. A method for producing an optical material according to any one of the above. <7> The polymerization catalyst comprises at least one selected from the group consisting of amine-based catalysts and organotin-based catalysts. <1> ~ <6> 10. A method for producing an optical material according to any one of the above. <8> The polymerization catalyst contains at least one selected from the group consisting of 3,5-lutidine, 2,4,6-collidine, triethylenediamine, N,N-dimethylethanolamine, triethylamine, N-ethylmorpholine, dibutyltin dichloride, dimethyltin dichloride, dibutyltin dilaurate, and dibutyltin diacetate. <1> ~ <7> 10. A method for producing an optical material according to any one of the above. <9> The absolute value V of the difference between the viscosity Va of the first raw material measured with a Brookfield viscometer at 25°C and 60 rpm and the viscosity Vb of the second raw material measured with a Brookfield viscometer at 25°C and 60 rpm is 10 mPa·s or more. <1> ~ <8> 10. A method for producing an optical material according to any one of the above. [Effects of the Invention]

[0009] According to one embodiment of the present disclosure, it is possible to provide a method for producing an optical material that can suppress casting striae in the resulting optical material. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 2 is a schematic diagram for explaining shearing and stirring of a raw material mixture. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. In the present disclosure, when a plurality of substances corresponding to each component are present in the composition, the amount of each component in the composition means the total amount of the plurality of substances present in the composition, unless otherwise specified. In the numerical ranges described in stages in this disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples. In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved.

[0012] <Method for manufacturing optical materials> The method for producing an optical material according to the present disclosure includes a first step of mixing a first raw material and a second raw material to obtain a polymerizable composition for an optical material, the polymerizable composition containing two or more different monomers for an optical material and a polymerization catalyst, wherein the standard deviation measured under the following condition 1 is 60 or less and the viscosity measured with a Brookfield viscometer at 25°C and 60 rpm is 30 mPa·s to 1000 mPa·s; and a second step of producing an optical material using the polymerizable composition for an optical material. [Condition 1] The standard deviation is the mixture of the first and second raw materials with an optical path length of 8 mm and an area of ​​360 mm 2 The sample is placed in a 12 mm thick quartz cell, and the image is measured using a glass striae inspection device under the following conditions: shutter 1 / 5000 (sec), gamma correction 100, sharpness 500, contrast and brightness 0. The image is analyzed using image analysis software (ImageJ), and calculations are made assuming a normal distribution with the vertical axis representing the number of pixel dots and the horizontal axis representing brightness.

[0013] The method for producing an optical material according to the present disclosure includes the first step, and thus can suppress the occurrence of casting striae in the resulting optical material. The present inventors have found that, in a polymerizable composition for an optical material obtained by mixing a first raw material and a second raw material, unevenness in the polymerizable composition for an optical material can be suppressed by setting the standard deviation to not more than 60. Therefore, by producing an optical material using the polymerizable composition for an optical material according to the present disclosure, casting striae in the obtained optical material can be suppressed.

[0014] The method for producing an optical material according to the present disclosure is a method for producing an optical material using a polymerizable composition for an optical material that contains two or more different types of monomers for an optical material and a polymerization catalyst.

[0015] <Polymerizable composition for optical materials> The polymerizable composition for an optical material contains two or more different monomers for an optical material and a polymerization catalyst.

[0016] (Monomer for optical materials) Examples of the monomer for optical materials include an isocyanate compound containing two or more isocyanate groups, a polythiol compound having two or more mercapto groups, a hydroxythiol compound having one or more mercapto groups and one or more hydroxyl groups, a polyol compound having two or more hydroxyl groups, and an amine compound.

[0017] The two or more different monomers for optical materials preferably include an isocyanate compound (A) containing two or more isocyanate groups, and an active hydrogen compound (B) containing at least one selected from the group consisting of a polythiol compound having two or more mercapto groups, a hydroxythiol compound having one or more mercapto groups and one or more hydroxyl groups, a polyol compound having two or more hydroxyl groups, and an amine compound.

[0018] [Isocyanate compound (A) containing two or more isocyanate groups] Examples of the isocyanate compound (A) containing two or more isocyanate groups include aliphatic isocyanate compounds, alicyclic isocyanate compounds, aromatic isocyanate compounds, and heterocyclic isocyanate compounds, and these compounds may be used alone or in combination. These isocyanate compounds containing two or more isocyanate groups may include dimers, trimers, and prepolymers. Examples of these isocyanate compounds containing two or more isocyanate groups include the compounds exemplified in WO 2011 / 055540. In the present disclosure, an alicyclic isocyanate compound refers to an isocyanate compound that includes an alicyclic structure and may include a heterocyclic structure. An aromatic isocyanate compound refers to an isocyanate compound that includes an aromatic structure and may include an alicyclic structure and a heterocyclic structure. A heterocyclic isocyanate compound refers to an isocyanate compound that includes a heterocyclic structure and does not include an alicyclic structure or an aromatic structure.

[0019] The isocyanate compound (A) containing two or more isocyanate groups preferably contains at least one selected from an aliphatic isocyanate compound, an alicyclic isocyanate compound, an aromatic isocyanate compound, and a heterocyclic isocyanate compound, and more preferably contains at least one of an alicyclic isocyanate compound and an aromatic isocyanate compound.

[0020] In the present disclosure, from the viewpoints of suppressing striae in the optical material and shortening the production time of the optical material, the isocyanate compound (A) containing two or more isocyanate groups preferably includes at least one selected from 2,5-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane, 2,6-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane, m-xylylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, dicyclohexylmethane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, isophorone diisocyanate, 1,6-hexamethylene diisocyanate, 1,5-pentamethylene diisocyanate, and isocyanurate of 1,5-pentamethylene diisocyanate, It is more preferable that the methyl methyl ether compound contains at least one selected from 2,5-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane, 2,6-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane, m-xylylene diisocyanate, dicyclohexylmethane diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane, and it is even more preferable that the methyl methyl ether compound contains at least one selected from m-xylylene diisocyanate, 2,5-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane, and 2,6-bis(isocyanatomethyl)bicyclo-[2.2.1]-heptane.

[0021] [Active hydrogen compound (B)] Examples of the active hydrogen compound (B) include polythiol compounds having two or more mercapto groups, hydroxythiol compounds having one or more mercapto groups and one or more hydroxyl groups, polyol compounds having two or more hydroxyl groups, and amine compounds. As the active hydrogen compound (B), oligomers of the above active hydrogen compounds and halogen-substituted products (for example, chlorine-substituted products, bromine-substituted products, etc.) of the above active hydrogen compounds may be used. The active hydrogen compound (B) may be used alone or in combination of two or more.

[0022] (Polythiol compounds having two or more mercapto groups) The polythiol compound is a compound having two or more mercapto groups, and examples thereof include the compounds exemplified in WO 2016 / 125736. In the present disclosure, from the viewpoint of suppressing striae in an optical material and shortening the production time of the optical material, the polythiol compound is 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, pentaerythritol, methyl ... It is preferable that the mercaptomethylthio-based copolymer contains at least one selected from the group consisting of thritol tetrakis(3-mercaptopropionate), bis(mercaptoethyl) sulfide, pentaerythritol tetrakis(2-mercaptoacetate), 2,5-bis(mercaptomethyl)-1,4-dithiane, 1,1,3,3-tetrakis(mercaptomethylthio)propane, 4,6-bis(mercaptomethylthio)-1,3-dithiane, and 2-(2,2-bis(mercaptomethylthio)ethyl)-1,3-dithietane, more preferably, the mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane is at least one selected from 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptoacetate), and 2,5-bis(mercaptomethyl)-1,4-dithiane; It is more preferable that the solvent contains at least one selected from 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and pentaerythritol tetrakis(3-mercaptopropionate).

[0023] (Hydroxythiol compounds having one or more mercapto groups and one or more hydroxyl groups) Examples of thiol compounds having a hydroxy group include 2-mercaptoethanol, 3-mercapto-1,2-propanediol, glycerin bis(mercaptoacetate), 4-mercaptophenol, 2,3-dimercapto-1-propanol, pentaerythritol tris(3-mercaptopropionate), and pentaerythritol tris(thioglycolate), but are not limited to these exemplary compounds.

[0024] (Polyol compounds having two or more hydroxyl groups) The polyol compound may be one or more aliphatic or alicyclic alcohols. Specific examples include linear or branched aliphatic alcohols, alicyclic alcohols, and alcohols obtained by adding at least one selected from the group consisting of ethylene oxide, propylene oxide, and ε-caprolactone to these alcohols. More specific examples include the compounds exemplified in WO 2016 / 125736.

[0025] The polyol compound is preferably at least one selected from ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,2-cyclopentanediol, 1,3-cyclopentanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol.

[0026] (amine compounds) Examples of the amine compound include ethylenediamine, 1,2- or 1,3-diaminopropane, 1,2-, 1,3-, or 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,10-diaminodecane, 1,2-, 1,3-, or 1,4-diaminocyclohexane, o-, m-, or p-diaminobenzene, 3,4- or 4,4'-diaminobenzophenone, 3,4- or 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3' or primary polyamine compounds such as 4,4'-diaminodiphenylsulfone, 2,7-diaminofluorene, 1,5-, 1,8-, or 2,3-diaminonaphthalene, 2,3-, 2,6-, or 3,4-diaminopyridine, 2,4- or 2,6-diaminotoluene, m- or p-xylylenediamine, isophoronediamine, diaminomethylbicycloheptane, 1,3- or 1,4-diaminomethylcyclohexane, 2- or 4-aminopiperidine, 2- or 4-aminomethylpiperidine, 2- or 4-aminoethylpiperidine, N-aminoethylmorpholine, and N-aminopropylmorpholine; monofunctional secondary amine compounds such as diethylamine, dipropylamine, di-n-butylamine, di-sec-butylamine, diisobutylamine, di-n-pentylamine, di-3-pentylamine, dihexylamine, dioctylamine, di(2-ethylhexyl)amine, methylhexylamine, diallylamine, N-methylallylamine, piperidine, pyrrolidine, diphenylamine, N-methylamine, N-ethylamine, dibenzylamine, N-methylbenzylamine, N-ethylbenzylamine, dicyclohexylamine, N-methylaniline, N-ethylaniline, dinaphthylamine, 1-methylpiperazine, and morpholine; 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-diamino secondary polyamine compounds such as nobutane, N,N'-diethyl-1,3-diaminobutane, N,N'-diethyl-1,4-diaminobutane, N,N'-diethyl-1,5-diaminopentane, N,N'-diethyl-1,6-diaminohexane, N,N'-diethyl-1,7-diaminoheptane, 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; and the like.

[0027] Among the above, the active hydrogen compound (B) preferably contains a polythiol compound having two or more mercapto groups. The content of the polythiol compound having two or more mercapto groups is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, based on the total mass of the active hydrogen compound (B).

[0028] Furthermore, in the active hydrogen compound (B) of the present disclosure, the total content of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane and pentaerythritol tetrakis(3-mercaptopropionate) is preferably 60 mass% or more, more preferably 70 mass% or more, and even more preferably 80 mass% or more, based on the total mass of the active hydrogen compound (B).

[0029] In the polymerizable composition for optical materials, the molar ratio (NCO groups / (OH groups+SH groups)) of the sum of hydroxyl groups (OH groups) and mercapto groups (SH groups) in the active hydrogen compound to the isocyanate groups (NCO groups) in the isocyanate compound (A) containing two or more isocyanate groups is preferably 0.8 to 1.2, more preferably 0.85 to 1.15, and even more preferably 0.9 to 1.1.

[0030] In the method for producing an optical material according to the present disclosure, the first raw material preferably contains at least one compound selected from the group consisting of polyisocyanate compounds, epoxy compounds, and epithio compounds.

[0031] Furthermore, it is preferable that the second raw material contains at least one active hydrogen compound selected from the group consisting of a polythiol compound having two or more mercapto groups, a hydroxythiol compound containing one or more mercapto groups and one or more hydroxyl groups, a polyol compound containing two or more hydroxyl groups, and an amine compound.

[0032] <Polymerization catalyst> The polymerization catalyst is not particularly limited, but for example, a basic catalyst, an organometallic catalyst, zinc carbamate, ammonium salt, sulfonic acid, etc. can be used. The polymerization catalysts may be used alone or in appropriate combination of two or more.

[0033] (basic catalyst) Examples of the basic catalyst include amine-based catalysts and imidazole-based catalysts. Specific examples include tertiary amine catalysts such as triethylenediamine, N,N-dimethylethanolamine, triethylamine, and N-ethylmorpholine, 2-methylpyrazine, pyridine, α-picoline, β-picoline, γ-picoline, 2,6-lutidine, 3,5-lutidine, 2,4,6-collidine, 3-chloropyridine, N,N-diethylaniline, N,N-dimethylaniline, hexamethylenetetramine, quinoline, isoquinoline, N,N-dimethyl-p-toluidine, N,N-dimethylpiperazine, quinaldine, 4-methylmorpholine, triallylamine, trioctylamine, 1,2-dimethylimidazole, and 1-benzyl-2-methylimidazole.

[0034] Among the above, the amine catalyst is preferred as the basic catalyst. Examples of the amine catalyst include tertiary amine catalysts such as 3,5-lutidine, 2,4,6-collidine, triethylenediamine, N,N-dimethylethanolamine, triethylamine, and N-ethylmorpholine.

[0035] The amine catalyst preferably contains at least one selected from 3,5-lutidine, 2,4,6-collidine, triethylenediamine, N,N-dimethylethanolamine, triethylamine, and N-ethylmorpholine.

[0036] The basic catalyst preferably contains a compound represented by the following general formula (2) and / or a compound represented by the following general formula (3).

[0037] [ka]

[0038] In general formula (2), R1 represents a linear alkyl group having 1 to 20 carbon atoms, a branched alkyl group having 3 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or a halogen atom, and multiple R1s may be the same or different. Q represents a carbon atom or a nitrogen atom. m represents an integer of 0 to 5.

[0039] [ka]

[0040] In the general formula (3), R2, R3, and R4 each independently represent a linear alkyl group having 1 to 20 carbon atoms, a branched alkyl group having 3 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, or an allyl group.

[0041] The basic catalyst preferably has a pKa value of 1-9, more preferably 3-8, and even more preferably 4-8.

[0042] The pKa value (acid dissociation index) can be measured, for example, by (a) the method described in The Journal of Physical Chemistry, vol. 68, number 6, page 1560 (1964), (b) a method using an automatic potentiometric titrator (AT-610 (trade name) or the like) manufactured by Kyoto Electronics Manufacturing Co., Ltd., or the like. In addition, (c) the acid dissociation index described in the Chemistry Handbook compiled by the Chemical Society of Japan (revised 3rd edition, June 25, 1984, published by Maruzen Co., Ltd.) can also be used.

[0043] (organometallic catalyst) Examples of organometallic catalysts include organotin catalysts; organic acid salts of iron, nickel, zinc, and the like; acetylacetonate complexes; catalyst compositions comprising a metal carboxylic acid compound and a quaternary ammonium salt compound; catalyst compositions comprising a bicyclic tertiary amine compound and a quaternary ammonium salt compound; and metal catalysts in which an alkoxy group, a carboxy group, or the like is coordinated to titanium or aluminum. Of the above organometallic catalysts, organotin catalysts are preferred. Examples of organotin catalysts include dibutyltin dichloride (DBC), dimethyltin dichloride (DMC), dibutyltin dilaurate (DBTDL), and dibutyltin diacetate.

[0044] The organotin catalyst preferably contains at least one selected from dibutyltin dichloride, dimethyltin dichloride, dibutyltin dilaurate, and dibutyltin diacetate.

[0045] The polymerization catalyst preferably contains at least one selected from the group consisting of basic catalysts having a pKa value of 4 to 8 and organometallic catalysts.

[0046] The polymerization catalyst preferably contains at least one selected from the group consisting of amine-based catalysts and organotin-based catalysts.

[0047] The polymerization catalyst preferably contains at least one selected from the group consisting of 3,5-lutidine, 2,4,6-collidine, triethylenediamine, N,N-dimethylethanolamine, triethylamine, N-ethylmorpholine, dibutyltin dichloride, dimethyltin dichloride, dibutyltin dilaurate, and dibutyltin diacetate.

[0048] The polymerizable composition for an optical material preferably contains a total of 100 parts by mass of two or more different monomers for an optical material, and 0.010 to 2.0 parts by mass of a polymerization catalyst. That is, in the method for producing an optical material according to the present disclosure, it is preferable to use 0.010 to 2.0 parts by mass of a polymerization catalyst relative to a total of 100 parts by mass of two or more different monomers for an optical material. The amount of the polymerization catalyst used in the present disclosure is large compared to conventional methods for producing optical materials. This allows the reaction heat of the polymerizable composition for optical materials to be generated in a short time when the monomer for optical materials in the polymerizable composition for optical materials is polymerized in the curing step. By utilizing this reaction heat for further polymerization, the polymerization reaction can be favorably promoted, and a high-quality optical material with suppressed striae can be obtained in a shorter time than before.

[0049] By using 0.010 parts by mass or more of a polymerization catalyst per 100 parts by mass of two or more different monomers for optical materials, the polymerization reaction can be promoted well, allowing high-quality optical materials with suppressed striae to be obtained in a short time. In addition, by promoting the polymerization reaction well, the releasability of the cured material when it is removed from the mold can be improved. From the above viewpoints, the polymerization catalyst is preferably used in an amount of 0.015 parts by mass or more, more preferably 0.038 parts by mass or more, even more preferably 0.10 parts by mass or more, and particularly preferably 0.17 parts by mass or more, per 100 parts by mass of two or more different monomers for optical materials.

[0050] The range of the content of the polymerization catalyst described above may be changed as appropriate depending on the types of the monomer for an optical material and the polymerization catalyst. For example, when the monomers for optical materials include 2,5(6)-bis(isocyanatomethyl)-bicyclo-[2.2.1]-heptane, pentaerythritol tetrakis(3-mercaptopropionate), and 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, and the polymerization catalyst includes 3,5-lutidine, the polymerization catalyst is preferably used in an amount of 0.10 parts by mass or more, and more preferably 0.17 parts by mass or more, per 100 parts by mass of the two or more different monomers for optical materials.

[0051] For example, when the monomers for optical materials include m-xylylene diisocyanate, 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and the polymerization catalyst includes 3,5-lutidine, the polymerization catalyst is preferably used in an amount of 0.015 parts by mass or more, and more preferably 0.020 parts by mass or more, per 100 parts by mass of the two or more different monomers for optical materials.

[0052] For example, when the monomer for an optical material contains m-xylylene diisocyanate and 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane and the polymerization catalyst contains 3,5-lutidine, the polymerization catalyst is preferably used in an amount of 0.010 parts by mass or more, and more preferably 0.015 parts by mass or more, per 100 parts by mass of two or more different monomers for an optical material.

[0053] For example, when the monomer for an optical material contains dicyclohexylmethane diisocyanate and a mixture of 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and the polymerization catalyst contains 3,5-lutidine, the polymerization catalyst is preferably used in an amount of 1.0 part by mass or more, and more preferably 1.5 parts by mass or more, per 100 parts by mass of the two or more different monomers for an optical material.

[0054] For example, when the monomers for optical materials include 1,3-bis(isocyanatemethyl)cyclohexane, pentaerythritol tetrakis(2-mercaptoacetate), and 2,5-bis(mercaptomethyl)-1,4-dithiane, and the polymerization catalyst includes 3,5-lutidine, the polymerization catalyst is preferably used in an amount of 0.03 parts by mass or more, and more preferably 0.07 parts by mass or more, per 100 parts by mass of two or more different monomers for optical materials.

[0055] By using 2.0 parts by mass or less of a polymerization catalyst per 100 parts by mass of two or more different monomers for an optical material, it is possible to improve the handling properties, for example, when the polymerizable composition for an optical material is cast into a mold. From the above viewpoint, it is preferable to use 1.5 parts by mass or less of the polymerization catalyst per 100 parts by mass of two or more different monomers for optical materials. Furthermore, depending on the types of the monomer for an optical material and the polymerization catalyst, the polymerization catalyst may be used in an amount of 1.0 part by mass or less, 0.3 part by mass or less, or 0.15 part by mass or less per 100 parts by mass of two or more different monomers for an optical material.

[0056] The amount of the polymerization catalyst can be appropriately set depending on the type of polymerization catalyst, the type and amount of monomers used (isocyanate compounds containing two or more isocyanate groups, active hydrogen compounds, other components, etc.), and the shape of the desired molded product.

[0057] The polymerization catalyst preferably satisfies the following condition 1. [Condition 1] -Ea / R is between -7100 and -2900. (Ea is the activation energy calculated by Arrhenius plot from the reaction rate constants of two or more different monomers for optical materials at two or more different temperatures, and R is the gas constant (8.314 J / mol / K).)

[0058] When the polymerization catalyst satisfies condition 1, the variation in the polymerization rate can be suppressed during the polymerization and curing process of the polymerizable composition for an optical material, and as a result, the occurrence of optical distortion and striae can be suppressed, and an optical material with excellent appearance can be obtained.

[0059] The value of Ea is calculated by the following method. a property acquisition step of acquiring a property value 1a derived from a functional group of the monomer for an optical material before heating and a property value 1b derived from a remaining functional group after heating for a predetermined time when a composition 1 containing a monomer for an optical material and a predetermined amount of a polymerization catalyst is heated and maintained at a plurality of temperatures; a residual functional group ratio calculation step of calculating a residual functional group ratio 1 at a plurality of temperatures from the physical property value 1a and the physical property value 1b; a reaction rate constant calculation step of calculating a reaction rate constant 1 at a plurality of temperatures based on a reaction rate equation from the residual functional group ratio 1; A fitting step of calculating the activation energy Ea1 and the frequency factor A1 by an Arrhenius plot from the reaction rate constant 1 at multiple temperatures; The value of Ea is calculated by performing the above. Using the calculated Ea, it is determined whether the polymerization catalyst satisfies condition 1. Specific embodiments of the method for calculating the value of Ea and the method for determining whether the polymerization catalyst satisfies condition 1 are the same as those described in WO 2020 / 256057.

[0060] <First step> The first step is a step of mixing a first raw material and a second raw material to obtain a polymerizable composition for optical materials containing two or more different monomers for optical materials and a polymerization catalyst, wherein the polymerizable composition for optical materials has a standard deviation of 60 or less as measured under the following condition 1 and a viscosity of 30 mPa s to 1000 mPa s as measured with a Brookfield viscometer at 25°C and 60 rpm: [Condition 1] The standard deviation is the mixture of the first and second raw materials with an optical path length of 8 mm and an area of ​​360 mm 2 The sample is placed in a 12 mm thick quartz cell, and the image is measured using a glass striae inspection device under the following conditions: shutter 1 / 5000 (sec), gamma correction 100, sharpness 500, contrast and brightness 0. The image is analyzed using image analysis software (ImageJ), and calculations are made assuming a normal distribution with the vertical axis representing the number of pixel dots and the horizontal axis representing brightness.

[0061] The first step makes it possible to obtain a polymerizable composition for optical materials that contains two or more different monomers for optical materials and a polymerization catalyst, and that has a viscosity of 30 mPa·s to 1000 mPa·s measured at 25°C and 60 rpm with a Brookfield viscometer and a standard deviation of 60 or less. By producing an optical material using this polymerizable composition for optical materials, it is possible to suppress casting striae in the resulting optical material.

[0062] (viscosity) The polymerizable composition for optical materials has a viscosity (in the present disclosure, also simply referred to as "viscosity") of 30 mPa·s to 1000 mPa·s, measured using a Brookfield viscometer at 25°C and 60 rpm. In the step of casting the polymerizable composition for an optical material into a mold, the polymerizable composition for an optical material preferably has a viscosity of 30 mPa·s to 1000 mPa·s as measured with a Brookfield viscometer at 25° C. and 60 rpm. By adjusting the viscosity of the polymerizable composition for an optical material to fall within the above range and casting the polymerizable composition for an optical material, the viscosity of the polymerizable composition for an optical material can be kept within an appropriate range, and striae can be suppressed in the resulting optical material.

[0063] From the above viewpoints, the viscosity of the polymerizable composition for an optical material is preferably 40 mPa·s or more, more preferably 70 mPa·s or more, even more preferably 80 mPa·s or more, particularly preferably 100 mPa·s or more, and even more preferably 120 mPa·s or more. The viscosity of the polymerizable composition for an optical material is preferably 700 mPa·s or less, and more preferably 400 mPa·s or less, from the viewpoint of maintaining good handleability when molding the optical material into a desired shape.

[0064] In this disclosure, when measuring viscosity with a Brookfield viscometer, the rotor number is 2.

[0065] The method for adjusting the viscosity of the polymerizable composition for an optical material is not particularly limited. For example, the viscosity of the polymerizable composition for an optical material may be adjusted by adding a high-viscosity compound, heating, stirring, or the like.

[0066] The viscosity Va of the first raw material measured using a Brookfield viscometer at 25°C and 60 rpm (revolutions per minute), The absolute value V of the difference between the viscosity Vb of the second raw material measured at 25°C and 60 rpm using a Brookfield viscometer (also referred to as the viscosity difference V) may be 10 mPa·s or more. When the viscosity difference V is large, unevenness is likely to occur in the polymerizable composition for an optical material. However, in the present disclosure, even when V is 10 mPa s or more, for example, casting striae in the optical material can be effectively suppressed. From the above viewpoint, the viscosity difference V may be 20 mPa·s or more, or 100 mPa·s or more.

[0067] Furthermore, from the viewpoint of suppressing the occurrence of casting striae in the resulting optical material, the viscosity difference V is preferably 1500 mPa·s or less, more preferably 1000 mPa·s or less, even more preferably 500 mPa·s or less, and particularly preferably 300 mPa·s or less.

[0068] The viscosity difference V may be, for example, 10 mPa·s or more and 1500 mPa·s or less.

[0069] Va is the viscosity of the first ingredient before mixing, and Vb is the viscosity of the second ingredient before mixing.

[0070] The viscosity Va of the first raw material measured with a Brookfield viscometer at 25°C and 60 rpm is preferably in the range of 10 mPa·s to 2000 mPa·s, more preferably in the range of 50 mPa·s to 1500 mPa·s, and even more preferably in the range of 100 mPa·s to 1000 mPa·s.

[0071] The polymerizable composition for an optical material contains two or more different monomers for an optical material and a polymerization catalyst. The polymerizable composition for an optical material is obtained by mixing the first raw material and the second raw material. Therefore, the first raw material and the second raw material as a whole contain two or more different types of monomers for optical materials and a polymerization catalyst. The first raw material and the second raw material may each be a single compound or a composition containing multiple compounds. Furthermore, when the first raw material and the second raw material are compositions, it is preferable that the first raw material and the second raw material are not compositions having the same composition. For example, the first raw material and the second raw material may each contain different types of monomers for optical materials, and at least one of the first raw material and the second raw material may contain a polymerization catalyst.

[0072] There are no particular limitations on the first raw material and the second raw material as long as they contain two or more different types of monomers for optical materials and a polymerization catalyst as a whole. The first raw material and the second raw material may be ready-made products, or may be prepared by mixing a monomer for an optical material with a polymerization catalyst. The method of mixing is not particularly limited, and any known method can be used.

[0073] The temperature at which the above components are mixed is not particularly limited, but is preferably 30° C. or lower, and more preferably room temperature (25° C.) or lower. From the viewpoint of the pot life of the polymerizable composition for an optical material to be prepared, it may be preferable to set the temperature lower than 25° C. However, when the solubility of an additive such as an internal mold release agent with each of the above components is poor, the temperature of each of the above components may be raised in advance to dissolve the additive in each of the above components.

[0074] When mixing the above components, it is preferable to carry out the mixing in a dry inert gas in order to prevent the incorporation of moisture into the polymerizable composition for an optical material.

[0075] A polymerization catalyst may be mixed in advance with a portion of two or more different monomers for optical materials, and then the remaining two or more different monomers for optical materials may be mixed in a single batch or in multiple batches. Specific embodiments for obtaining the first and second raw materials include, for example, the following embodiments.

[0076] First, a mixture is prepared by adding a portion of the optical material monomer and an additive (such as an internal mold release agent). This mixture is stirred at 25°C for 1 hour to completely dissolve each component, after which the remaining portion of the optical material monomer is added and stirred to form a homogeneous solution. This solution is then degassed to obtain the first raw material. The remainder of the monomer for optical materials and the catalyst are then stirred at 25° C. for 30 minutes to completely dissolve them into a homogeneous solution, which is then degassed to obtain a second raw material.

[0077] The first raw material preferably contains a prepolymer obtained by mixing a portion of two or more different monomers for optical materials with at least a portion of a polymerization catalyst and polymerizing at least a portion of the portions of the two or more different monomers for optical materials. When the first raw material contains a prepolymer, the viscosity of the first raw material increases, making it difficult for the first raw material to mix with the second raw material, which means that unevenness is more likely to occur in the polymerizable composition for optical materials, making the problem of the present disclosure more apparent. However, even when a polymerizable composition for an optical material obtained by mixing a first raw material containing a prepolymer with a second raw material is used, the production method for an optical material according to the present disclosure can suppress casting striae in the obtained optical material.

[0078] <Filtration process> The method for producing an optical material according to the present disclosure may further include a filtration step of filtering the mixture of the first raw material and the second raw material, or the polymerizable composition for an optical material. The filtration step can be carried out using a filter. As the filter, for example, a capsule filter can be used. The filtration accuracy of the filter is preferably 1.0 μm to 4.5 μm. When the method for producing an optical material according to the present disclosure includes a filtering step and a stirring step described below, the filtering step is preferably provided at least either before or after the stirring step.

[0079] (standard deviation) The polymerizable composition for an optical material has a standard deviation of 60 or less when measured under the following condition 1. [Condition 1] The standard deviation is the mixture of the first and second raw materials with an optical path length of 8 mm and an area of ​​360 mm 2The sample is placed in a 12 mm thick quartz cell, and the image is measured using a glass striae inspection device under the following conditions: shutter 1 / 5000 (sec), gamma correction 100, sharpness 500, contrast and brightness 0. The image is analyzed using image analysis software (ImageJ), and calculations are made assuming a normal distribution with the vertical axis representing the number of pixel dots and the horizontal axis representing brightness.

[0080] When the standard deviation is 60 or less, unevenness in the polymerizable composition for an optical material can be suppressed, and casting striae in the resulting optical material can be suppressed. From the above viewpoint, the standard deviation is preferably 50 or less, and more preferably 40 or less.

[0081] From the viewpoint of the handleability of the polymerizable composition for an optical material, the standard deviation is preferably 5 or more, more preferably 10 or more, and even more preferably 20 or more. It is also preferable that the standard deviation is 5 or more and 60 or less.

[0082] The standard deviation is measured according to condition 1 above. An example of a glass striae inspection device is FG100-RT-L3 (manufactured by Kato Koken Co., Ltd., effective observation diameter: 100 mm, length when opened: 300 mm).

[0083] The dimensions of the quartz cell are preferably, for example, 12 mm wide, 49 mm high, and 12 mm thick, and the dimensions of the part through which the liquid passes are preferably, for example, 8 mm wide, 45 mm high, and 8 mm thick.

[0084] The standard deviation is calculated by taking 30 images per second, measuring the standard deviation for each image, and averaging the standard deviation over 15 seconds.

[0085] The method for producing an optical material according to the present disclosure preferably includes at least one of the following shearing step and stirring step, which makes it easier to keep the standard deviation within the above range. The method for producing an optical material according to the present disclosure preferably includes, for example, in the first step, both the shearing step and the stirring step described below.

[0086] <Shearing process> The shearing step is a step of applying a shear force to a mixture of the first raw material and the second raw material (also simply referred to as a raw material mixture).

[0087] In this disclosure, the force applied in a direction crossing the flow direction is also referred to as shear force. In this disclosure, applying a force primarily in a direction crossing the flow direction is also referred to as "shearing."

[0088] The term "fluidizing" refers to causing the raw material mixture to flow by, for example, transferring the raw material mixture from a tank to a power mixer, transferring the raw material mixture from a power mixer to a stirring tank, or the like.

[0089] During shearing, the flow rate of the raw material mixture is preferably 3 g / s or more, more preferably 6 g / s or more, and even more preferably 9 g / s or more, from the viewpoint of increasing productivity while suppressing an increase in viscosity of the polymerizable composition for an optical material. During shearing, the flow rate of the raw material mixture is preferably 30 g / s or less, more preferably 25 g / s or less, and even more preferably 20 g / s or less, from the viewpoint of suppressing unevenness in the polymerizable composition for an optical material and suppressing casting striae in the optical material.

[0090] There are no particular limitations on the method for applying force to the raw material mixture in a direction intersecting the flow direction, and examples of such methods include a method using a power mixer (i.e., an electrically driven rotating device).

[0091] The rotation speed in the shearing step is preferably 200 rpm or more, more preferably 400 rpm or more, and even more preferably 500 rpm or more. The rotation speed in the shearing step is preferably 3000 rpm or less, more preferably 2500 rpm or less, and even more preferably 2000 rpm or less.

[0092] <Mixing process> The stirring step is a step of applying a stirring force to the mixture of the first raw material and the second raw material. In the present disclosure, a force applied in a direction substantially parallel to and opposite to the flow direction is also referred to as a stirring force.

[0093] When applying a force in a direction substantially parallel to the flow direction, the preferred range of the flow velocity of the raw material mixture is the same as the preferred range of the flow velocity of the raw material mixture in the above-mentioned <shearing step>.

[0094] There are no particular limitations on the method for applying a force to the raw material mixture in a direction substantially parallel to and opposite to the flow direction, and examples of such a method include a method using a stirring vessel containing a stirring bar.

[0095] The rotation speed in the stirring step is preferably 50 rpm or more, more preferably 100 rpm or more, and even more preferably 200 rpm or more. The rotation speed in the stirring step is preferably 800 rpm or less, more preferably 600 rpm or less, and even more preferably 400 rpm or less.

[0096] The method for producing an optical material according to the present disclosure includes a shearing step and a stirring step, thereby enabling continuous production of a uniform polymerizable composition for an optical material, and thereby enabling better suppression of casting striae in the resulting optical material.

[0097] From the viewpoint of suppressing the occurrence of casting striae in the resulting optical material, the method for producing an optical material according to the present disclosure also preferably includes a shearing step and a stirring step in this order.

[0098] <Second process> The second step is a step of producing an optical material using the polymerizable composition for an optical material. This makes it possible to obtain an optical material in which cast striae are suppressed. The second step may be a step of producing an optical material by casting the polymerizable composition for an optical material into a mold and curing it.

[0099] (casting) Casting may be carried out by a multi-screw method or by a mixing method just before casting. The casting method may be manual casting or automatic casting by machine. The automatic casting method may be pressurized feeding with nitrogen, or liquid feeding using a pump (diaphragm pump, gear pump, etc.).

[0100] It is preferable to apply pressure (for example, back pressure) to the polymerizable composition for an optical material using nitrogen or the like to cast the polymerizable composition for an optical material into a mold. This makes it possible to more preferably cast the polymerizable composition for an optical material into the mold by a multi-screw method.

[0101] (hardening) Curing can be carried out by polymerizing two or more different types of monomers for optical materials in the polymerizable composition for optical materials in the mold. The polymerizable composition for an optical material can be polymerized to produce an optical material.

[0102] The polymerization method is not particularly limited, and may be a method in which a polymerization reaction is caused by heating using a known method. For example, a method may be used in which the polymerizable composition is poured into a molding mold (casting die) held by a gasket or tape, and the temperature is gradually increased while heating to promote the polymerization reaction. In this case, depending on the physical properties required for the resulting optical material, it is preferable to perform a degassing treatment under reduced pressure or a filtration treatment under pressure or reduced pressure, as necessary.

[0103] The polymerization method may be a method in which the polymerization reaction is carried out without heating. That is, the polymerizable composition for an optical material may be left to stand, whereby the polymerizable composition for an optical material may be cured by polymerization.

[0104] The environment in which the curing is carried out is not particularly limited, and the mold can be heated from the outside of the mold to cause curing. However, from the viewpoint of achieving polymerization in a short period of time while improving optical quality such as striae, it is preferable to cure the polymerizable composition for an optical material by leaving the polymerizable composition for an optical material to stand in a closed space. By leaving the polymerizable composition for an optical material at rest in a closed space, it is possible to prevent the heat generated by the self-heating of the polymerizable composition for an optical material from being released to the outside, which makes it possible to retain the heat generated by the self-heating within the closed space, thereby promoting the polymerization reaction more efficiently and enabling the production of an optical material in a shorter time. An example of a closed space is an insulated environment. The term "insulating environment" refers to an environment in which heat is retained inside and heat conduction between the inside and the outside is suppressed. The term "environment in which heat conduction between the inside and the outside is suppressed" refers to an environment in which, when a polymerizable composition for an optical material is left standing in a closed space, the heat conductivity between the inside and the outside of the closed space is such that the polymerizable composition for an optical material can be cured.

[0105] The insulating environment can be created, for example, using insulating materials. That is, by leaving the polymerizable composition for an optical material in a heat-insulating container made of a heat-insulating material, heat can be retained inside the heat-insulating container, and heat conduction between the inside and outside can be suppressed.

[0106] The thermal conductivity of the heat insulating material is preferably 0.50 W / m·K or less, more preferably 0.10 W / m·K or less, and even more preferably 0.05 W / m·K or less.

[0107] The density of the insulating material is 10 kg / m 3 It is preferable that the saturation is 15 kg / m or more.3 More preferably, it is 20 kg / m or more. 3 More preferably, it is equal to or greater than this.

[0108] In the "insulation" or "insulation environment" of the present disclosure, it is preferable to perform heating to make the adiabatic reactor a constant temperature state (constant temperature reactor) within a range that does not interfere with the polymerization reaction of the polymerizable composition for an optical material due to reaction heat or does not excessively promote the polymerization reaction of the polymerizable composition for an optical material due to external heating. This allows the environmental temperature inside the reaction tank (constant temperature reaction tank) in which the mold is placed to be kept warm or at a constant temperature depending on the temperature rise caused by the self-heating of the monomer for optical material, thereby more effectively promoting the polymerization reaction.

[0109] As the adiabatic environment, for example, an adiabatic reactor or a constant temperature reactor as described above can be used. For example, when a mold into which a monomer has been injected is placed in a vacuum container that is an adiabatic reactor, adiabatic polymerization in an adiabatic environment using an adiabatic reactor (constant temperature reactor) can be carried out by the following procedure. The inner surface of the vacuum vessel is covered with a material having heat insulating and heat retaining properties such as urethane foam or cork, and the mold into which the monomer has been injected is wrapped with a material such as a cloth as needed.Then, the mold into which the monomer has been injected is left to stand inside the vacuum vessel.

[0110] The curing step may be a step of curing the polymerizable composition for an optical material by leaving the polymerizable composition for an optical material to stand without external heating. As described above, in the present disclosure, it is not always necessary to heat the polymerizable composition for an optical material. External heating may require the use of equipment, which can be economically burdensome, but methods that do not require external heating can simplify the production of optical materials and reduce the economic burden.

[0111] The curing step is preferably a step of curing the polymerizable composition for an optical material by leaving the polymerizable composition for an optical material to stand for 2 to 10 hours. In the curing step, it is more preferable to leave the polymerizable composition for an optical material standing for 8 hours or less. In addition, from the viewpoint of carrying out a polymerization reaction to obtain a well-cured optical material, the polymerizable composition for an optical material is preferably left to stand for 2 hours or more, more preferably 3 hours or more.

[0112] In the curing step, if necessary, a microwave irradiation step of irradiating the polymerizable composition for an optical material with microwaves for a predetermined period of time may be provided.

[0113] One embodiment of the curing step includes the following steps a and b. Step a: The polymerizable composition for optical materials is poured (cast) into a casting mold (into a cavity of a mold). Step b: The mold into which the polymerizable composition for optical materials has been poured is left standing in a closed space for a predetermined period of time to allow adiabatic polymerization.

[0114] (Step a) First, the polymerizable composition is poured into a molding mold (casting die) held by a gasket, tape, etc. At this time, depending on the physical properties required for the resulting optical material, it is preferable to carry out a degassing treatment under reduced pressure or a filtration treatment under pressure, reduced pressure, etc., as necessary.

[0115] (Step b) The polymerization conditions are not limited, but are preferably adjusted appropriately depending on the composition of the polymerizable composition for optical materials, the type and amount of catalyst used, the shape of the mold, and the like. The mold into which the polymerizable composition for an optical material has been poured may be left to stand in an insulating environment for 2 to 4 hours to allow polymerization to occur.

[0116] In step b, if necessary, a heating step may be added after the adiabatic polymerization process in which the mold into which the polymerizable composition for an optical material has been injected is left standing in an adiabatic environment for a certain period of time. In step b, if necessary, in parallel with the step of leaving the mold into which the polymerizable composition for an optical material has been injected in an adiabatic environment (adiabatic polymerization), the mold into which the polymerizable composition for an optical material has been injected may be heated continuously or intermittently at a temperature not exceeding the self-heat generated by the polymerizable composition for an optical material in the adiabatic polymerization process, or the inside of the adiabatic reaction vessel may be heated to maintain the environmental temperature inside the adiabatic reaction vessel.

[0117] <Annealing process> The method for producing an optical material according to the present disclosure may optionally include an annealing step of annealing the cured polymerizable composition for an optical material. The temperature at which the annealing treatment is carried out is usually 50 to 150°C, preferably 90 to 140°C, and more preferably 100 to 130°C.

[0118] <Applications of optical materials> The optical material produced by the method for producing an optical material according to the present disclosure can be used for plastic lenses, prisms, optical fibers, information recording substrates, filters, light-emitting diodes, and the like. Among the above, the optical material can be suitably used for plastic lenses, and more suitably used for plastic lenses for spectacles. [Example]

[0119] Hereinafter, one embodiment of the present disclosure will be specifically described using examples, but the present disclosure is not limited to these examples. The viscosity measurement method in the examples is the same as the method described above. The method for measuring the standard deviation in the examples is the same as that described above. The molded articles obtained in each of the Examples and Comparative Examples were evaluated as follows.

[0120] (cast striae) The molded product was projected with an ultra-high pressure mercury lamp (light source model OPM-252HEG: manufactured by Ushio Inc.), and the transmitted image was visually observed and evaluated according to the following criteria. A: No striae were observed. Specifically, no striae having a length of 1.0 mm or more were visually observed in the molded product. B: Striae were observed and the product was unacceptable. Specifically, striae with a length of 1.0 mm or more were visually observed on the molded product.

[0121] [Examples 1 to 2, and Comparative Examples 1 to 3] (Preparation of Composition) A mixed solution was prepared by adding 1.5 parts by weight of Tinuvin 329 (UV absorber) and 50.7 parts by weight of m-xylylene diisocyanate (monomer for optical materials). This mixed solution was stirred at 25°C for 1 hour to achieve complete dissolution. Next, 9.9 parts by weight of a mixture of 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane was added to the mixed solution, which was stirred at 25°C for 5 minutes to obtain a homogeneous solution. Furthermore, 0.03 parts by weight of 3,5-lutidine (polymerization catalyst) was added to the resulting homogeneous solution, which was stirred at 40°C for 1 hour to polymerize the monomer for optical materials while adjusting the viscosity, resulting in a mixture containing a prepolymer. The mixture containing the prepolymer was then degassed at 400 Pa and 25°C for 1 hour, and 0.085 parts by mass of JP-506H (manufactured by Johoku Chemical Industry Co., Ltd.), an acidic phosphate ester, was added and mixed for 5 minutes at 20°C to obtain a first raw material. The viscosity Va of the first raw material is shown in Table 1. A second raw material was obtained by charging 39.4 parts by mass of a mixture of 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and degassing the mixture at 400 Pa and 20° C. for 1 hour. The viscosity Vb of the second raw material is shown in Table 1.

[0122] (Shearing and Stirring the Composition) The first raw material was placed in the first tank, and the second raw material was placed in the second tank. Each composition was delivered to a power mixer using a gear pump, and the delivered first and second raw materials were then mixed by applying shear force using the power mixer to obtain a raw material mixture. As shown in FIG. 1, the mixed raw material mixture was sent to a power mixer 1. FIG. 1 is a schematic diagram for explaining shearing and stirring of the raw material mixture. Using the power mixer 1, shear force was applied to the raw material mixture. Next, the mixture was filtered through Capsule Filter 2 (manufactured by F-Tech Co., Ltd.). A first measurement point 51 for the standard deviation was provided after the power mixer 1 and before the capsule filter 2 .

[0123] The raw material mixture after passing through the capsule filter 2 was transferred to a buffer tank 4 (stirring tank) having a water bath 3, and stirred in the buffer tank 4, applying a force to the raw material mixture in a direction approximately parallel to the direction of flow and opposite to the direction of stirring. At that time, back pressure was applied from the liquid surface side of the stirring vessel using nitrogen. A second measurement point 52 for the standard deviation was provided after the capsule filter 2 and before the buffer tank 4 .

[0124] Thereafter, while adjusting the flow rate with a pinch valve 5, the raw material mixture was stirred with a static mixer (32) 6 (number of elements: 32) or a static mixer (48) 7 (number of elements: 48). A third measurement point 53 for the standard deviation was provided after the buffer tank 4 and before the static mixer (32) 6 and the static mixer (48) 7. A fourth measurement point 54 for the standard deviation was provided after the static mixer (32) 6. A fifth measurement point 55 for the standard deviation was provided after the static mixer (48) 7. Table 1 shows the measurement points for standard deviation in each example and comparative example.

[0125] When measuring the standard deviation at each of the above measurement points, a flow cell 8 was installed at each measurement point, and the raw material mixture at the measurement point was used as a polymerizable composition for an optical material and flowed through the flow cell 8 to measure the standard deviation.

[0126] In each example and comparative example, the raw material mixture collected at each measurement point was used as a polymerizable composition for optical materials and cast into a mold for producing a lens having a diameter of 78 mm, 4 curves, and a center thickness of 10 mm. That is, the polymerizable composition for an optical material used in each of the Examples and Comparative Examples is a raw material mixture at each measurement point, and the mixed state of the polymerizable composition for an optical material used in each of the Examples and Comparative Examples is the same as the mixed state of the raw material mixture at each measurement point.

[0127] (Curing of the composition) The polymerization reaction was carried out in the following manner. After casting, the mold was placed in an insulated container at 25°C and left to stand for 2 hours to allow adiabatic polymerization. After that, the cast was removed from the container and further heated to 120°C for 1 hour to allow polymerization.

[0128] After the polymerization reaction, the mold was allowed to cool naturally, and the hardened molded body was released from the mold and further subjected to annealing treatment at 120° C. for 2 hours to obtain a molded body (lens).

[0129] [Examples 3 to 4, and Comparative Examples 4 to 6] A molded body (lens) was obtained in the same manner as in Example 1, except that the first raw material and the second raw material were changed to the following first raw material and second raw material.

[0130] (Preparation of Composition) A mixed solution was prepared by adding 1.5 parts by weight of Tinuvin 329 (UV absorber) and 50.7 parts by weight of m-xylylene diisocyanate (monomer for optical materials). This mixture was stirred at 25°C for 1 hour to completely dissolve the components. Then, 7.4 parts by weight of a mixture of 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane was added to the mixed solution and stirred at 25°C for 5 minutes to obtain a homogeneous solution. Furthermore, 0.03 parts by weight of 3,5-lutidine (polymerization catalyst) was added to the resulting homogeneous solution and stirred at 40°C for 1 hour to polymerize the monomer for optical materials while adjusting the viscosity, resulting in a mixture containing a prepolymer. The mixture containing the prepolymer was then degassed at 400 Pa and 25°C for 1 hour, and 0.085 parts by mass of JP-506H (manufactured by Johoku Chemical Industry Co., Ltd.), an acidic phosphate ester, was added and mixed for 5 minutes at 20°C to obtain a first raw material. The viscosity Va of the first raw material is shown in Table 1. A second raw material was obtained by charging 41.9 parts by mass of a mixture of 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and degassing the mixture at 400 Pa and 20° C. for 1 hour. The viscosity Vb of the second raw material is shown in Table 1.

[0131] Comparative Example 7 In Comparative Example 7, the first raw material and the second raw material were not prepared, and the following composition was used as the polymerizable composition for an optical material.

[0132] (Preparation of Composition) A mixed solution was prepared by adding 0.008 parts by weight of dimethyltin(II) dichloride (also known as DMC), 0.1 parts by weight of an internal release agent for MR manufactured by Mitsui Chemicals, Inc., 0.6 parts by weight each of the ultraviolet absorbers Tinuvin 329 and Seesorb 709, and 50.7 parts by weight of m-xylylene diisocyanate. This mixed solution was stirred at 25°C for 1 hour to achieve complete dissolution. Subsequently, 49.3 parts by weight of a mixture of 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane was added to this mixture, and the mixture was stirred at 25°C for 30 minutes to obtain a homogeneous solution. This solution was degassed at 400 Pa and 25° C. for 1 hour to obtain a polymerizable composition for optical materials.

[0133] The obtained polymerizable composition for optical materials was filtered through a capsule filter (manufactured by F-Tech Co., Ltd.) A measurement point for standard deviation was provided after the capsule filter. After filtration, the polymerizable composition for optical materials was cast into a mold for producing a lens having a diameter of 78 mm, 4 curves, and a center thickness of 10 mm.

[0134] (Curing of the composition) The polymerization reaction was carried out in the following manner. After casting, the mold was heated in an oven from 20°C to 120°C over time, and thermal polymerization was carried out over 30 hours.

[0135] After the polymerization reaction, the mold was allowed to cool naturally, and the hardened molded body was released from the mold and further subjected to annealing treatment at 120° C. for 2 hours to obtain a molded body (lens).

[0136] [Table 1]

[0137] In Table 1, "-" means that the corresponding operation was not performed or the corresponding value does not exist.

[0138] As shown in Table 1, in the examples using the method for producing an optical material including: a first step of obtaining a polymerizable composition for an optical material, which contains two or more different monomers for an optical material and a polymerization catalyst by mixing a first raw material and a second raw material, and a second step of producing an optical material using the polymerizable composition for an optical material, the polymerizable composition having a standard deviation of 60 or less as measured under the above-mentioned condition 1 and a viscosity of 30 mPa·s to 1000 mPa·s as measured with a Brookfield viscometer at 25°C and 60 rpm, the method gave excellent evaluations of casting striae, and was able to suppress casting striae in the obtained optical material. On the other hand, Comparative Examples 1 to 6, in which the standard deviation was more than 60, were poorly evaluated for cast striae, and cast striae could not be suppressed in the obtained optical materials. Furthermore, Comparative Example 7, in which the first raw material and the second raw material were not mixed and the polymerizable composition for optical materials was used as a single raw material composition, showed excellent results in the evaluation of cast striae. This is thought to be because the polymerizable composition for optical materials was produced without mixing multiple raw material compositions, and thus no unevenness occurred in the polymerizable composition for optical materials.

[0139] [Example 5 and Comparative Example 8] A molded body (lens) was obtained in the same manner as in Example 1, except that the first raw material and the second raw material were changed to the following first raw material and second raw material. Table 2 shows various physical property values, catalyst type, catalyst concentration, measurement location of standard deviation, standard deviation, and evaluation.

[0140] (Preparation of Composition) A mixture was prepared by adding 0.1 parts by weight of Mitsui Chemicals' internal release agent for MR (internal release agent), 1.5 parts by weight of Tinuvin 329 (ultraviolet absorber), and 50.6 parts by weight of 2,5(6)-bis(isocyanatomethyl)-bicyclo-[2.2.1]-heptane (monomer for optical materials). The mixture was stirred at 25°C for 1 hour to achieve complete dissolution. Subsequently, 3.3 parts by weight of pentaerythritol tetrakis(3-mercaptopropionate) (monomer for optical materials) and 3.6 parts by weight of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane (monomer for optical materials) were added to the mixture, and the mixture was stirred at 25°C for 5 minutes to obtain a homogeneous solution. The resulting homogeneous solution was then charged with 0.2 parts by mass of 3,5-lutidine (a polymerization catalyst) and stirred at 40°C for 3 hours to polymerize the monomer for optical materials while adjusting the viscosity, yielding a mixture containing a prepolymer. The mixture containing the prepolymer was then degassed at 400 Pa and 25°C for 1 hour to obtain a first raw material. The viscosity Va of the first raw material is shown in Table 2.

[0141] 20.6 parts by mass of pentaerythritol tetrakis(3-mercaptopropionate) [monomer for optical materials] and 21.9 parts by mass of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane [monomer for optical materials] were added and stirred at 25°C for 15 minutes to obtain a homogeneous solution. This mixture was degassed at 400 Pa and 25°C for 1 hour to obtain a second raw material. The viscosity Vb of the second raw material is shown in Table 2.

[0142] [Table 2]

[0143] In Table 2, "-" means that the corresponding operation was not performed or the corresponding value does not exist.

[0144] As shown in Table 2, in the examples using the method for producing an optical material including: a first step of obtaining a polymerizable composition for an optical material, which contains two or more different monomers for an optical material and a polymerization catalyst by mixing a first raw material and a second raw material, and a second step of producing an optical material using the polymerizable composition for an optical material, the polymerizable composition having a standard deviation of 60 or less as measured under the above-mentioned condition 1 and a viscosity of 30 mPa·s to 1000 mPa·s as measured with a Brookfield viscometer at 25°C and 60 rpm, the method gave excellent evaluations of casting striae, and was able to suppress casting striae in the obtained optical material. On the other hand, Comparative Example 8, in which the standard deviation was more than 60, was poorly evaluated for cast striae, and cast striae could not be suppressed in the obtained optical material.

[0145] [Examples 6 and 7] A molded body (lens) was obtained in the same manner as in Example 1, except that the first raw material and the second raw material were changed to the following first raw material and second raw material. Table 3 shows various physical property values, catalyst type, catalyst concentration, measurement location of standard deviation, standard deviation, and evaluation.

[0146] (Preparation of Composition) A mixture was prepared by adding 1.5 parts by weight of Tinuvin 329 (UV absorber) and 48.9 parts by weight of m-xylylene diisocyanate (monomer for optical materials). This mixture was stirred at 25°C for 1 hour to completely dissolve the components. Then, 10.1 parts by weight of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane (monomer for optical materials) was added to the mixture and stirred at 25°C for 5 minutes to obtain a homogeneous solution. 0.025 parts by weight of 3,5-lutidine (polymerization catalyst) was then added to the resulting homogeneous solution and stirred at 40°C for 1 hour to polymerize the monomer for optical materials while adjusting the viscosity, resulting in a mixture containing a prepolymer. The mixture containing the prepolymer was then degassed at 400 Pa and 25°C for 1 hour, after which 0.1 parts by weight of JP-506H (mold release agent) was added and stirred for 10 minutes to obtain the first raw material. The viscosity Va of the first raw material is shown in Table 3. A mixture was prepared by adding 37.9 parts by weight of 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane and 3.1 parts by weight of m-xylylene diisocyanate (monomer for optical materials). This mixture was stirred at 25°C for 5 minutes to obtain a homogeneous solution. 0.005 parts by weight of 3,5-lutidine (polymerization catalyst) was then added to the resulting homogeneous solution and stirred at 40°C for 1 hour to polymerize the monomer for optical materials while adjusting the viscosity, yielding a mixture containing a prepolymer. This mixture was then degassed at 400 Pa and 25°C for 1 hour to obtain the second raw material. The viscosity Vb of the second raw material is shown in Table 3.

[0147] [Table 3]

[0148] In Table 3, "-" means that the corresponding operation was not performed or the corresponding value does not exist.

[0149] As shown in Table 3, in the examples using the method for producing an optical material including: a first step of obtaining a polymerizable composition for an optical material, which contains two or more different monomers for an optical material and a polymerization catalyst by mixing a first raw material and a second raw material, and a second step of producing an optical material using the polymerizable composition for an optical material, the polymerizable composition having a standard deviation of 60 or less as measured under the above-mentioned condition 1 and a viscosity of 30 mPa·s to 1000 mPa·s as measured with a Brookfield viscometer at 25°C and 60 rpm, the method gave excellent evaluations of casting striae, and was able to suppress casting striae in the obtained optical material.

[0150] The disclosure of Japanese Patent Application No. 2022-011070, filed on January 27, 2022, is incorporated herein by reference in its entirety. All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. a first step of mixing a first raw material and a second raw material to obtain a raw material mixture containing two or more different monomers for optical materials and a polymerization catalyst, measuring a standard deviation of the obtained raw material mixture according to the following condition 1, and obtaining a raw material mixture having a standard deviation of 60 or less and a viscosity of 30 mPa s to 1000 mPa s measured with a Brookfield viscometer at 25°C and 60 rpm as a polymerizable composition for optical materials; a second step of producing an optical material using the polymerizable composition for an optical material; A method for producing an optical material comprising the steps of: [Condition 1] The standard deviation is determined by measuring the mixture of the first and second raw materials with an optical path length of 8 mm and an area of ​​360 mm. ２ The image was measured using a glass striae inspection device under the conditions of a shutter speed of 1 / 5000 (sec), gamma correction of 100, sharpness of 500, and contrast and brightness of 0. The image was analyzed using image analysis software (ImageJ), and calculations were performed assuming a normal distribution with the vertical axis representing the number of pixel dots and the horizontal axis representing brightness.

2. The method for producing an optical material according to claim 1, wherein the standard deviation is 20 or more.

3. 3. The method for producing an optical material according to claim 1, wherein the first raw material comprises a prepolymer obtained by mixing a portion of the two or more different monomers for optical materials with at least a portion of the polymerization catalyst and polymerizing at least a portion of the portion of the two or more different monomers for optical materials.

4. 3. The method for producing an optical material according to claim 1, wherein the second step is a step of producing an optical material by casting the polymerizable composition for an optical material into a mold and curing it.

5. The two or more different monomers for optical materials include an isocyanate compound (A) containing two or more isocyanate groups, a polythiol compound having two or more mercapto groups, a hydroxythiol compound having one or more mercapto groups and one or more hydroxyl groups, and two or more and an active hydrogen compound (B) containing at least one selected from the group consisting of a polyol compound having a hydroxyl group and an amine compound.

6. 3. The method for producing an optical material according to claim 1, wherein the polymerization catalyst comprises at least one selected from the group consisting of a basic catalyst having a pKa value of 4 to 8 and an organometallic catalyst.

7. 3. The method for producing an optical material according to claim 1, wherein the polymerization catalyst comprises at least one selected from the group consisting of an amine-based catalyst and an organotin-based catalyst.

8. 3. The method for producing an optical material according to claim 1, wherein the polymerization catalyst comprises at least one selected from the group consisting of 3,5-lutidine, 2,4,6-collidine, triethylenediamine, N,N-dimethylethanolamine, triethylamine, N-ethylmorpholine, dibutyltin dichloride, dimethyltin dichloride, dibutyltin dilaurate, and dibutyltin diacetate.

9. 3. The method for producing an optical material according to claim 1, wherein an absolute value V of a difference between a viscosity Va of the first raw material measured with a Brookfield viscometer at 25° C. and 60 rpm and a viscosity Vb of the second raw material measured with a Brookfield viscometer at 25° C. and 60 rpm is 10 mPa s or more.

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