Cyclic olefin copolymer and hydrogenated product thereof, and optical element

Abstract

The present invention provides a resin that can achieve all of high refractive index, high heat resistance and low birefringence. A hydrogenated product of a cyclic olefin copolymer according to the present invention is obtained by hydrogenating a cyclic olefin copolymer comprising structural units derived from 1-naphthyl norbornene and structural units derived from 2-naphthyl norbornene and having an average endo substance ratio of 1-naphthyl norbornene and 2-naphthyl norbornene of 50% by mole or more. The hydrogenated product of the cyclic olefin copolymer according to the present invention is suitably used for a material of optical elements such as optical lenses.

Description

[Technical Field]

[0001] The present invention relates to a cyclic olefin copolymer, a hydrogenated cyclic olefin copolymer, and an optical element. [Background technology]

[0002] In recent years, polymers obtained by polymerizing cyclic olefins have been attracting attention as materials for optical elements and medical containers.

[0003] For example, Patent Document 1 discloses a norbornene-based ring-opening (co)polymer that has excellent transparency and heat resistance, high solubility in organic solvents, and unique birefringence and wavelength dependence. Patent Document 2 discloses a cycloolefin copolymer that effectively exhibits reverse wavelength dispersion of birefringence, and a film made of the copolymer. Patent Document 3 discloses a cyclic olefin copolymer that has a high refractive index and can adjust the Abbe number to a low level, and a medical container that is less susceptible to discoloration by electron beam or gamma ray irradiation and has excellent transparency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-46615 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-46614 [Patent Document 3] International Publication No. 2019 / 107363 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to increase the degree of freedom in design for a wide range of applications, there is a demand for resins that have a high refractive index and heat resistance, and that also have small birefringence when made into optical elements such as optical lenses.

[0006] However, the above-mentioned conventional polymers have not been able to simultaneously achieve a high refractive index, high heat resistance, and low birefringence (for example, stress birefringence).

[0007] Therefore, an object of the present invention is to provide a resin that can simultaneously achieve a high refractive index, high heat resistance, and low birefringence. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to solve the above-mentioned problems, and have newly discovered that a hydrogenated cyclic olefin copolymer obtained by hydrogenating a cyclic olefin copolymer obtained by polymerizing a monomer composition containing a mixture of 1-naphthylnorbornene and 2-naphthylnorbornene having a predetermined average endo isomer ratio can simultaneously achieve a high refractive index, high heat resistance, and low birefringence, thereby completing the present invention.

[0009] That is, the present invention aims to advantageously solve the above-mentioned problems. The cyclic olefin copolymer of the present invention is characterized by containing structural units derived from 1-naphthylnorbornene and structural units derived from 2-naphthylnorbornene, and the average endo isomer ratio of the 1-naphthylnorbornene and the 2-naphthylnorbornene is 50 mol % or more. Hydrogenation of such a cyclic olefin copolymer can provide a resin (hydrogenated cyclic olefin copolymer) that can simultaneously achieve a high refractive index, high heat resistance, and low birefringence. Therefore, the cyclic olefin copolymer of the present invention is useful as a raw material for a resin that can simultaneously achieve a high refractive index, high heat resistance, and low birefringence. In the present invention, the "average endo isomer ratio of 1-naphthylnorbornene and 2-naphthylnorbornene" can be determined, for example, by the method described in the Examples.

[0010] In the cyclic olefin copolymer of the present invention, the total proportion of structural units derived from 1-naphthylnorbornene and structural units derived from 2-naphthylnorbornene is preferably 30 mol % to 70 mol % of all structural units. If the total proportion of structural units derived from 1-naphthylnorbornene and structural units derived from 2-naphthylnorbornene is within the above range, it becomes possible to obtain a resin that simultaneously exhibits a high refractive index, high heat resistance, and low birefringence at an even higher level. In the present invention, the "proportion of each structural unit" can be measured by nuclear magnetic resonance (NMR) analysis.

[0011] Furthermore, in the cyclic olefin copolymer of the present invention, the proportion of structural units derived from 1-naphthylnorbornene to the total of structural units derived from 1-naphthylnorbornene and structural units derived from 2-naphthylnorbornene is preferably 1 mol % or more and 30 mol % or less. If the proportion of structural units derived from 1-naphthylnorbornene is within the above range, it becomes possible to obtain a resin that simultaneously exhibits a high refractive index, high heat resistance, and low birefringence at an even higher level.

[0012] Furthermore, the cyclic olefin copolymer of the present invention preferably further contains structural units derived from a norbornene-based monomer other than 1-naphthylnorbornene and 2-naphthylnorbornene.

[0013] The cyclic olefin copolymer of the present invention is preferably a ring-opening polymer.

[0014] The present invention also aims to advantageously solve the above-mentioned problems, and provides a hydrogenated cyclic olefin copolymer obtained by hydrogenating any of the above-mentioned cyclic olefin copolymers. The hydrogenated cyclic olefin copolymer obtained by hydrogenating the above-mentioned cyclic olefin copolymer has a high refractive index and heat resistance and low birefringence, and is therefore useful as a material for optical elements such as optical lenses.

[0015] The hydrogenated cyclic olefin copolymer of the present invention preferably has a glass transition temperature of at least 135° C. If the glass transition temperature is at least 135° C., the heat resistance can be further improved. In the present invention, the "glass transition temperature" can be measured using differential scanning calorimetry in accordance with JIS K6911.

[0016] The present invention also provides an optical element containing any one of the hydrogenated cyclic olefin copolymers described above. The use of the hydrogenated cyclic olefin copolymers described above allows for the production of optical elements with high refractive index, high heat resistance, and low birefringence. [Effects of the Invention]

[0017] According to the present invention, it is possible to obtain a resin that can simultaneously achieve a high refractive index, high heat resistance, and low birefringence, as well as a copolymer that is useful as a raw material for the resin. Furthermore, according to the present invention, an optical element having a high refractive index, a high heat resistance, and a low birefringence can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail. The cyclic olefin copolymer of the present invention may be used as a material for various molded articles such as optical elements without any particular limitation, but is preferably used as a raw material for the hydrogenated cyclic olefin copolymer of the present invention. Furthermore, the hydrogenated cyclic olefin copolymer of the present invention is preferably used as a material for the optical elements of the present invention (e.g., optical lenses, etc.) without any particular limitation.

[0019] (cyclic olefin copolymer) The cyclic olefin copolymer of the present invention is obtained by polymerizing a monomer composition containing 1-naphthylnorbornene and 2-naphthylnorbornene, and optionally further containing at least one of a norbornene-based monomer other than 1-naphthylnorbornene and 2-naphthylnorbornene (hereinafter sometimes referred to as "other norbornene-based monomer") and a non-norbornene-based monomer. That is, the cyclic olefin copolymer of the present invention contains structural units derived from 1-naphthylnorbornene and structural units derived from 2-naphthylnorbornene, and may optionally further contain at least one of a structural unit derived from another norbornene-based monomer and a structural unit derived from a non-norbornene-based monomer. Furthermore, the cyclic olefin copolymer of the present invention requires that the average endo isomer ratio of the 1-naphthylnorbornene and 2-naphthylnorbornene used in the polymerization be 50 mol % or more.

[0020] <Structural unit derived from 1-naphthylnorbornene> In 1-naphthylnorbornene that can form a structural unit derived from 1-naphthylnorbornene, the bonding mode of the 1-naphthyl group to the norbornene ring can be stereoisomerically either an exo bond (a bond in the same direction as the methylene at the bridgehead position) or an endo bond (a bond in the opposite direction to the methylene at the bridgehead position). As the 1-naphthylnorbornene, exo-1-naphthylnorbornene, endo-1-naphthylnorbornene, or a mixture thereof can be used as long as the desired average endo isomer ratio can be satisfied. As the 1-naphthylnorbornene, bicyclo[2,2,1]hept-2-ene-5-(1-naphthyl) in which the 1-naphthyl group is bonded to the 5-position of norbornene (bicyclo[2,2,1]hept-2-ene) is preferred.

[0021] <Structural unit derived from 2-naphthylnorbornene> In addition, with regard to 2-naphthylnorbornene, which can form a structural unit derived from 2-naphthylnorbornene, the bonding mode of the 2-naphthyl group to the norbornene ring can be an exo bond or an endo bond. As the 2-naphthylnorbornene, exo-2-naphthylnorbornene, endo-2-naphthylnorbornene, or a mixture thereof can be used as long as the desired average endo isomer ratio can be satisfied. As the 2-naphthylnorbornene, bicyclo[2,2,1]hept-2-ene-5-(2-naphthyl) in which the 2-naphthyl group is bonded to the 5-position of norbornene (bicyclo[2,2,1]hept-2-ene) is preferred.

[0022] <Average endo body ratio> The average endo isomer ratio of 1-naphthylnorbornene used to form the structural units derived from 1-naphthylnorbornene and 2-naphthylnorbornene used to form the structural units derived from 2-naphthylnorbornene must be 50 mol% or more, preferably 60 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more. That is, in the cyclic olefin copolymer, the ratio of the total of the structural units derived from endo-1-naphthylnorbornene and endo-2-naphthylnorbornene to the total of the structural units derived from exo-1-naphthylnorbornene, the structural units derived from endo-1-naphthylnorbornene, the structural units derived from exo-2-naphthylnorbornene, and the structural units derived from endo-2-naphthylnorbornene must be 50 mol% or more, preferably 60 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more. When the average endo isomer ratio is within the above range, the hydrogenated cyclic olefin copolymer obtained by hydrogenating the cyclic olefin copolymer can simultaneously achieve a high refractive index, high heat resistance, and low birefringence at a high level. The upper limit of the average endo isomer ratio is not particularly limited.

[0023] In the cyclic olefin copolymer, the total proportion of structural units derived from 1-naphthylnorbornene and structural units derived from 2-naphthylnorbornene in all structural units is preferably 30 mol% or more, more preferably 35 mol% or more, and even more preferably 40 mol% or more, and preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less. When the total proportion of structural units derived from 1-naphthylnorbornene and structural units derived from 2-naphthylnorbornene is within the above range, the hydrogenated cyclic olefin copolymer obtained by hydrogenating the cyclic olefin copolymer can simultaneously achieve a high refractive index, high heat resistance, and low birefringence at an even higher level.

[0024] Furthermore, the proportion of structural units derived from 1-naphthylnorbornene to the total of structural units derived from 1-naphthylnorbornene and structural units derived from 2-naphthylnorbornene is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, and preferably 30 mol% or less, more preferably 25 mol% or less, and even more preferably 20 mol% or less. If the proportion of structural units derived from 1-naphthylnorbornene is within the above range, the hydrogenated cyclic olefin copolymer obtained by hydrogenating the cyclic olefin copolymer can simultaneously achieve a high refractive index, high heat resistance, and low birefringence at an even higher level.

[0025] <Structural units derived from other norbornene-based monomers> The other norbornene-based monomers that can form structural units derived from other norbornene-based monomers are not particularly limited, and examples thereof include norbornene-based monomers that do not have a naphthyl group, and norbornene-based monomers that have a naphthyl group other than 1-naphthylnorbornene and 2-naphthylnorbornene.

[0026] Specifically, the norbornene-based monomer having no naphthyl group is not particularly limited as long as it has a norbornene ring and does not have a naphthyl group, but examples thereof include: norbornenes that are unsubstituted or have an alkyl group, such as norbornene, 5-methylnorbornene, 5-ethylnorbornene, 5-butylnorbornene, 5-hexylnorbornene, 5-decylnorbornene, 5-cyclohexylnorbornene, and 5-cyclopentylnorbornene; norbornenes having an alkenyl group, such as 5-ethylidenenorbornene, 5-vinylnorbornene, 5-propenylnorbornene, 5-cyclohexenylnorbornene, and 5-cyclopentenylnorbornene; norbornenes with aromatic rings such as 5-phenylnorbornene; norbornenes having a polar group containing an oxygen atom, such as 5-methoxycarbonylnorbornene, 5-ethoxycarbonylnorbornene, 5-methyl-5-methoxycarbonylnorbornene, 5-methyl-5-ethoxycarbonylnorbornene, norbornenyl-2-methylpropionate, norbornenyl-2-methyloctanate, 5-hydroxymethylnorbornene, 5,6-di(hydroxymethyl)norbornene, 5,5-di(hydroxymethyl)norbornene, 5-hydroxy-i-propylnorbornene, 5,6-dicarboxynorbornene, and 5-methoxycarbonyl-6-carboxynorbornene; norbornenes having a polar group containing a nitrogen atom, such as 5-cyanonorbornene; Dicyclopentadiene, methyldicyclopentadiene, tricyclo[5.2.1.0 2,6 ] Polycyclic norbornenes having three or more rings and not containing an aromatic ring structure, such as dec-8-ene; Tetracyclo[9.2.1.0 2,10 .0 3,8 ]tetradeca-3,5,7,12-tetraene (also known as 1,4-methano-1,4,4a,9a-tetrahydro-9H-fluorene), tetracyclo[10.2.1.0 2,11 .0 4,9] Polycyclic norbornenes having three or more aromatic rings, such as pentadeca-4,6,8,13-tetraene (also known as 1,4-methano-1,4,4a,9,9a,10-hexahydroanthracene); Tetracyclododecene, 8-methyltetracyclododecene, 8-ethyltetracyclododecene, 8-cyclohexyltetracyclododecene, 8-cyclopentyltetracyclododecene, 8-methoxycarbonyl-8-methyltetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene and other unsubstituted or alkyl-substituted tetracyclododecenes; tetracyclododecenes having an exocyclic double bond, such as 8-methylidenetetracyclododecene, 8-ethylidenetetracyclododecene, 8-vinyltetracyclododecene, 8-propenyltetracyclododecene, 8-cyclohexenyltetracyclododecene, and 8-cyclopentenyltetracyclododecene; tetracyclododecenes having an aromatic ring such as 8-phenyltetracyclododecene; tetracyclododecenes having a substituent containing an oxygen atom, such as 8-methoxycarbonyltetracyclododecene, 8-methyl-8-methoxycarbonyltetracyclododecene, 8-hydroxymethyltetracyclododecene, 8-carboxytetracyclododecene, tetracyclododecene-8,9-dicarboxylic acid, and tetracyclododecene-8,9-dicarboxylic anhydride; tetracyclododecenes having a nitrogen atom-containing substituent, such as 8-cyanotetracyclododecene and tetracyclododecene-8,9-dicarboxylic acid imide; tetracyclododecenes having a substituent containing a halogen atom, such as 8-chlorotetracyclododecene; tetracyclododecenes having a silicon atom-containing substituent, such as 8-trimethoxysilyltetracyclododecene; hexacycloheptadecenes such as the Diels-Alder adducts of the above-mentioned tetracyclododecenes with cyclopentadiene; Examples include:

[0027] The norbornene monomer having a naphthyl group is not particularly limited as long as it is a compound having a norbornene ring and a naphthyl group. For example, 9-naphthyltetracyclo[6.2.1.1 3,6 .0 2,7 ]dodec-4-ene, 5-dinaphthylmethylsilylmethyl-2-norbornene, 5-trinaphthylsilylmethyl-2-norbornene, 5-(2-dinaphthylmethylsilylethyl)-2-norbornene, 5-(2-trinaphthylsilylethyl)-2-norbornene, and the like.

[0028] Among these, from the viewpoint of obtaining a hydrogenated cyclic olefin copolymer having a high refractive index, high heat resistance, and low birefringence all at the same time at a higher level, non-polar norbornene-based monomers are preferred as the other norbornene-based monomers, and examples thereof include unsubstituted norbornenes or norbornenes having an alkyl group (e.g., norbornene, 8-ethyltetracyclododecene), norbornenes having an alkenyl group (e.g., ethylidenetetracyclododecene (8-ethylidenetetracyclododecene)), dicyclopentadiene, and norbornene derivatives having an aromatic ring (e.g., tetracyclo[9.2.1.0] 2,10 .0 3,8 ]tetradeca-3,5,7,12-tetraene (also known as 1,4-methano-1,4,4a,9a-tetrahydro-9H-fluorene)), unsubstituted or alkyl-substituted tetracyclododecenes (e.g., tetracyclododecene, 8-methoxycarbonyl-8-methyltetracyclo[4.4.0.1 2,5 .1 7,10 ]-3-dodecene) is more preferred, and tetracyclododecene, tetracyclo[9.2.1.0 2,10 .0 3,8 ]Tetradeca-3,5,7,12-tetraene (also called 1,4-methano-1,4,4a,9a-tetrahydro-9H-fluorene) is more preferred.

[0029] The above-mentioned other norbornene-based monomers can be used alone or in combination of two or more kinds. The other norbornene-based monomers may also be a mixture of isomers.

[0030] In the cyclic olefin copolymer, the proportion of structural units derived from other norbornene-based monomers in all structural units is preferably 30 mol% or more, more preferably 35 mol% or more, and even more preferably 40 mol% or more, and is preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less.

[0031] <Structural units derived from non-norbornene monomers> The non-norbornene monomer capable of forming a structural unit derived from a non-norbornene monomer is not particularly limited as long as it is a copolymerizable compound that does not have a norbornene ring, and examples thereof include cycloolefins such as cyclobutene, cyclopentene, cyclohexene, 3,4-dimethylcyclopentene, 3-methylcyclohexene, 2-(2-methylbutyl)-1-cyclohexene, cyclooctene, and 3a,5,6,7a-tetrahydro-4,7-methano-1H-indene; non-conjugated dienes such as 1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, and 1,7-octadiene; etc. These non-norbornene monomers can be used alone or in combination of two or more.

[0032] In the cyclic olefin copolymer, the proportion of structural units derived from non-norbornene monomers in all structural units is preferably 30 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less. The proportion of structural units derived from non-norbornene monomers in all structural units may be 0 mol%.

[0033] <Structure of Cyclic Olefin Copolymer> The cyclic olefin copolymer of the present invention is a copolymer formed by polymerizing a monomer composition containing the above-mentioned 1-naphthylnorbornene and 2-naphthylnorbornene, and optionally further containing at least one of other norbornene-based monomers and non-norbornene-based monomers. Here, the polymerization may be either ring-opening polymerization or addition polymerization, and one cyclic olefin copolymer may contain both a ring-opening polymerized portion and an addition polymerized portion. Among these, ring-opening polymerization is preferred. That is, the cyclic olefin copolymer of the present invention is preferably a ring-opening polymer, specifically a ring-opening polymer polymerized by ring-opening of a norbornene ring.

[0034] <Method of producing cyclic olefin copolymer> The cyclic olefin copolymer of the present invention is not particularly limited, and can be obtained, for example, by carrying out a step (polymerization step) of polymerizing (ring-opening polymerization or addition polymerization) a monomer composition containing 1-naphthylnorbornene and 2-naphthylnorbornene, and optionally further containing at least one of other norbornene-based monomers and non-norbornene-based monomers, to obtain a copolymer, and then, optionally, carrying out a step (recovery step) of recovering the copolymer.

[0035] The proportion of each monomer in the monomer composition is adjusted to match the proportion of structural units derived from that monomer in the target cyclic olefin copolymer. The 1-naphthylnorbornene and 2-naphthylnorbornene used in the polymerization can be produced, for example, by a palladium coupling reaction (e.g., the reaction of norbornadiene with bromonaphthalene) or a Diels-Alder reaction (e.g., the reaction of cyclopentadiene with vinylnaphthalene). The 1-naphthylnorbornene and 2-naphthylnorbornene are not particularly limited, and 1-naphthylnorbornenes and 2-naphthylnorbornenes with different endo isomer content ratios can be mixed to achieve the desired average endo isomer ratio.

[0036] [Polymerization process] When preparing a cyclic olefin copolymer by ring-opening polymerization, a monomer composition can be subjected to ring-opening metathesis polymerization in the presence of a metathesis polymerization catalyst. Ring-opening metathesis polymerization may be carried out in a reaction system in which the monomer composition and the metathesis polymerization catalyst are mixed in a solvent (e.g., an organic solvent). To improve polymerization efficiency, the reaction system may further contain an activator, a chain transfer agent, or other auxiliary agents (e.g., a Lewis base). The following describes the reagents, such as the catalyst, used in ring-opening polymerization, and the reaction conditions.

[0037] As the metathesis polymerization catalyst, a transition metal imide complex represented by formula (1) can be used. M(NR a )X 4-p (OR b ) p L q (1) (In the formula, M is a metal atom selected from transition metal atoms of Group 6 of the periodic table; R a represents a phenyl group optionally having a substituent at at least one of the 3-, 4-, and 5-positions, or -CHR c where R c represents a hydrogen atom, an optionally substituted alkyl group, or an optionally substituted aryl group, R b represents an optionally substituted alkyl group or an optionally substituted aryl group, X is a halogen atom, an alkyl group, an aryl group, an aralkyl group, or an alkylsilyl group; L is a neutral electron donating ligand; p is 0 or 1; q is an integer from 0 to 2, When multiple X's are present, the multiple X's may be the same or different. When there are multiple L's, the multiple L's may be the same or different.

[0038] M in formula (1) is a transition metal atom of Group 6 of the periodic table and can be selected from chromium, molybdenum, and tungsten, of which molybdenum and tungsten are preferred, with tungsten being more preferred.

[0039] The transition metal imido complex of formula (1) has a metal imido bond (N=R a ) included. R a is a substituent on the nitrogen atom that constitutes the metal imido bond.

[0040] R in Equation (1) a represents a phenyl group optionally having a substituent at at least one of the 3-, 4-, and 5-positions, or -CHR c It is a group represented by the following formula:

[0041] R a The substituent of the phenyl group which may have a substituent at at least one of the 3-, 4- and 5-positions is Alkyl groups (for example, alkyl groups having 1 to 4 carbon atoms, such as methyl and ethyl groups); Halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, etc.); Alkoxy groups (for example, alkoxy groups having 1 to 4 carbon atoms, such as a methoxy group, an ethoxy group, or an isopropoxy group); and the like, and the substituents present at at least two of the 3-, 4- and 5-positions may be bonded to each other.

[0042] Examples of the phenyl group which may have a substituent at at least one of the 3-, 4- and 5-positions include: phenyl group; mono-substituted phenyl groups such as a 4-methylphenyl group, a 4-chlorophenyl group, a 3-methoxyphenyl group, a 4-cyclohexylphenyl group, and a 4-methoxyphenyl group; disubstituted phenyl groups such as a 3,5-dimethylphenyl group, a 3,5-dichlorophenyl group, a 3,4-dimethylphenyl group, and a 3,5-dimethoxyphenyl group; trisubstituted phenyl groups such as a 3,4,5-trimethylphenyl group and a 3,4,5-trichlorophenyl group; a 2-naphthyl group which may have a substituent, such as a 2-naphthyl group, a 3-methyl-2-naphthyl group, or a 4-methyl-2-naphthyl group; etc.

[0043] R a of -CH2R c R in the group represented by c The number of carbon atoms in the alkyl group, which may have a substituent, is not particularly limited and is usually 1 to 20, preferably 1 to 10, and more preferably 1 to 4. This alkyl group may be linear or branched. The substituent is not particularly limited and examples thereof include a phenyl group, a phenyl group which may have a substituent (e.g., a 4-methylphenyl group, etc.); an alkoxy group (e.g., an alkoxy group having 1 to 4 carbon atoms, such as a methoxy group or an ethoxy group); and the like.

[0044] R c Examples of the aryl group which may have a substituent include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, etc. The substituent is not particularly limited, and examples thereof include a phenyl group, a phenyl group which may have a substituent (for example, a 4-methylphenyl group, etc.), an alkoxy group (for example, an alkoxy group having 1 to 4 carbon atoms such as a methoxy group, an ethoxy group, etc.), etc.

[0045] R c As the alkyl group, an alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, a hexyl group, an octyl group, or a decyl group is preferred.

[0046] In formula (1), (4-p) is 4 or 3, and formula (1) has 4 or 3 Xs. Xs are halogen atoms, alkyl groups, aryl groups, aralkyl groups, or alkylsilyl groups. Xs may be the same or different. Regarding X, examples of the halogen atom include a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, and a neopentyl group. Examples of the aryl group include a phenyl group, a 4-methylphenyl group, a 2,6-dimethylphenyl group, a 1-naphthyl group, and a 2-naphthyl group. Examples of the aralkyl group include a benzyl group and a neophyl group. Examples of the alkylsilyl group include a trimethylsilyl group, a triethylsilyl group, and a t-butyldimethylsilyl group.

[0047] In formula (1), p is 0 or 1, and formula (1) is a metal alkoxide bond or a metal aryloxide bond (OR b ) may be included. b is a substituent on an oxygen atom that constitutes a metal alkoxide bond or a metal aryloxide bond.

[0048] R b is an alkyl group which may have a substituent or an aryl group which may have a substituent, and c The examples and preferred examples of the alkyl group which may have a substituent and the aryl group which may have a substituent are applicable.

[0049] In formula (1), q is an integer of 0 to 2, and formula (1) may have one or two electron-donating neutral ligands (L). L includes an electron donor compound containing an atom of Group 14 or 15 of the periodic table; Phosphines such as trimethylphosphine, triisopropylphosphine, tricyclohexylphosphine, and triphenylphosphine; ethers such as diethyl ether, dibutyl ether, 1,2-dimethoxyethane, tetrahydrofuran, and tetrahydropyran; amines such as trimethylamine, triethylamine, pyridine, and lutidine; Among these, ethers are preferred.

[0050] The transition metal imido complex of formula (1) may be a tungsten imido complex having a phenylimido group (wherein M is a tungsten atom and R a is a phenyl group), and tetrachlorotungsten phenylimide (tetrahydrofuran) and tetrachlorotungsten phenylimide (tetrahydropyran) are more preferred.

[0051] The transition metal imido complexes of formula (1) may be used alone or in combination of two or more kinds.

[0052] The transition metal imido complex of formula (1) can be synthesized by a method (e.g., the method described in JP-A-5-345817) in which an oxyhalide of a Group 6 transition metal and a phenyl isocyanate or a monosubstituted methyl isocyanate, which may have a substituent at at least one of the 3-, 4-, and 5-positions, are mixed together, if necessary, with an electron-donating neutral ligand (L), an alcohol, a metal alkoxide, or a metal aryloxide. The synthesized transition metal imido complex may be purified and isolated by crystallization or the like before use in a ring-opening polymerization reaction, or the resulting mixture may be used as a catalyst solution without purification.

[0053] The amount of the transition metal imide complex of formula (1) used can be 0.00005 mol % to 1 mol % relative to 100 mol % of the monomer, preferably 0.0001 mol % to 0.7 mol % and more preferably 0.0002 mol % to 0.5 mol %. Within the above range, difficulty in catalyst removal can be sufficiently avoided, and sufficient polymerization activity can be obtained.

[0054] The transition metal imido complex of formula (1) exhibits catalytic activity even when used alone, but can become a more highly active polymerization catalyst when combined with an activator.

[0055] Examples of the activator include compounds of Groups 1, 2, 12, 13, and 14 of the periodic table that have a hydrocarbon group (e.g., an alkyl group) with 1 to 20 carbon atoms. Among these, organolithium, organomagnesium, organozinc, organoaluminum, and organotin are preferably used, with organoaluminum and organotin being particularly preferred.

[0056] Examples of the organolithium include methyllithium, n-butyllithium, and phenyllithium. Examples of organic magnesium compounds include butylethyl magnesium, butyloctyl magnesium, dihexyl magnesium, ethyl magnesium chloride, n-butyl magnesium chloride, and allyl magnesium bromide. Examples of organic zinc compounds include dimethyl zinc, diethyl zinc, and diphenyl zinc. Examples of organoaluminum include trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylaluminum chloride, ethylaluminum sesquichloride, ethylaluminum dichloride, diethylaluminum ethoxide, diisobutylaluminum isobutoxide, ethylaluminum diethoxide, and isobutylaluminum diisobutoxide. Examples of organotin compounds include tetramethyltin, tetra(n-butyl)tin, and tetraphenyltin.

[0057] The activators may be used alone or in combination of two or more.

[0058] When an activator is used, the amount used can be 0.1 to 100 mol times, preferably 0.2 to 50 mol times, and more preferably 0.5 to 20 mol times, relative to the transition metal imido complex of formula (1). Within the above range, the use of the activator can sufficiently improve the polymerization activity, and side reactions can be sufficiently avoided.

[0059] In addition, a Lewis base can be added to control the polymerization rate and the molecular weight distribution of the resulting copolymer. Examples of Lewis bases include ethers such as diethyl ether and tetrahydrofuran; ketones such as acetone and cyclohexanone; nitriles such as acetonitrile and benzonitrile; amines such as triethylamine and N,N-diethylaniline; pyridines such as pyridine and lutidine; phosphines such as triphenylphosphine; amides such as dimethylformamide; sulfoxides such as dimethyl sulfoxide; phosphine oxides such as triphenylphosphine oxide; and esters such as ethyl acetate. Among these, ethers, pyridines, and nitriles are preferred. Lewis bases may be used alone or in combination of two or more.

[0060] When a Lewis base is used, the amount used can be 0.1 mol or more and 1,000 mol or less, preferably 0.2 mol or more and 500 mol or less, and more preferably 0.5 mol or more and 200 mol or less, relative to the amount of the transition metal imido complex of formula (1).

[0061] In the polymerization reaction, a chain transfer agent can be used. By using the chain transfer agent, the molecular weight of the resulting ring-opening polymer can be adjusted and the content of dimers and the like can be effectively reduced.

[0062] Examples of chain transfer agents include α-olefins, internal olefins, and aromatic vinyl compounds. Internal olefins are compounds that have a double bond inside the olefin chain rather than at the end. Aromatic vinyl compounds include compounds that have a substituent (e.g., an alkyl group) on the vinyl group.

[0063] Examples of α-olefins include alkenes having 2 to 20 carbon atoms and a double bond at the α-position, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. Examples of internal olefins include 2-butene and 3-hexene. Examples of aromatic vinyl compounds include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, and 4-t-butylstyrene. Among these, 1-hexene, styrene, and 1-decene are preferred, and 1-hexene and styrene are more preferred, from the viewpoints of reactivity and molecular weight controllability.

[0064] The chain transfer agents may be used alone or in combination of two or more.

[0065] When a chain transfer agent is used, the amount of the chain transfer agent can be 0.1 mol% or more and less than 15 mol% based on 100 mol% of the monomer. Within the above range, the effect of using the chain transfer agent can be fully obtained. From the viewpoint of reducing the content of dimers and the like, the amount of the chain transfer agent is preferably 0.3 mol% or more and less than 10 mol%, more preferably 0.5 mol% or more and 9 mol% or less, and even more preferably 1 mol% or more and 6 mol% or less.

[0066] The organic solvent is not particularly limited as long as it can dissolve or disperse the monomers and the target copolymer and is inert to the reaction. For example, Aliphatic hydrocarbons such as pentane, hexane, and heptane; Alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, ethylcyclohexane, diethylcyclohexane, decahydronaphthalene, bicycloheptane, tricyclodecane, hexahydroindene, and cyclooctane; aromatic hydrocarbons such as benzene, toluene, and xylene; Halogenated aliphatic hydrocarbons such as dichloromethane, chloroform, and 1,2-dichloroethane; Halogenated aromatic hydrocarbons such as chlorobenzene and dichlorobenzene; Nitrogen-containing hydrocarbon solvents such as nitromethane, nitrobenzene, and acetonitrile; Ethers such as diethyl ether and tetrahydrofuran, or mixed solvents thereof are included. Among these solvents, aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, and ethers are preferably used.

[0067] The organic solvents may be used alone or in combination of two or more kinds.

[0068] The organic solvent can be used in an amount such that the monomer concentration is 1% by mass or more and 50% by mass or less, and the monomer concentration is preferably 2% by mass or more and 45% by mass or less, and more preferably 3% by mass or less and 40% by mass or less. Within the above range, productivity is sufficient and handling is convenient.

[0069] The ring-opening polymerization reaction can be carried out by stirring the monomer, the transition metal imide complex of formula (1), and any optional activator and chain transfer agent in an organic solvent, and at least a portion of the norbornene-based monomer (1-naphthylnorbornene, 2-naphthylnorbornene, or other norbornene-based monomer) may be added continuously during the reaction.

[0070] The components other than the norbornene-based monomer to be continuously added may be charged into the reactor in advance and stirred. The reaction solution in the reactor can be continuously stirred during the continuous addition of the norbornene-based monomer to allow the polymerization reaction to proceed.

[0071] The norbornene-based monomer may be continuously added in its entirety or in part. From the viewpoint of reaction selectivity and reaction stability, it is preferable to continuously add only a portion of the norbornene-based monomer, with the remainder being pre-charged in the reactor. The amount of norbornene-based monomer pre-charged in the reactor can be 0.1% by mass or more and 70% by mass or less, preferably 0.5% by mass or more and 50% by mass or less, and more preferably 1% by mass or more and 35% by mass or less, assuming the total amount to be 100% by mass. Within the above range, it is easy to control the weight-average molecular weight of the resulting copolymer.

[0072] The continuous addition of the norbornene-based monomer can be carried out by continuously adding it dropwise as a liquid dissolved or dispersed in the organic solvent. The concentration of the norbornene-based monomer in the liquid can be 1% by mass or more and 50% by mass or less, preferably 2% by mass or more and 45% by mass or less, and more preferably 3% by mass or more and 40% by mass or less. This range ensures sufficient productivity and is convenient in terms of handling.

[0073] The time for continuous addition can be from 20 to 200 minutes, preferably from 40 to 180 minutes, more preferably from 60 to 160 minutes, from the viewpoint of controlling stereochemistry.

[0074] The polymerization temperature can be from 20° C. to 60° C. From the viewpoint of controlling stereochemistry, it is preferably from 25° C. to 55° C., more preferably from 30° C. to 50° C.

[0075] From the viewpoint of molecular weight control, the continuous addition of the norbornene-based monomer is preferably carried out so that the polymerization conversion rate of the norbornene-based monomer in the polymerization reaction system at the end of the continuous addition is 40% or more. The polymerization conversion rate is more preferably 60% or more. The polymerization conversion rate can be controlled by adjusting the addition conditions, such as the rate of addition of the norbornene-based monomer, and the polymerization reaction conditions, such as the polymerization temperature. When the conditions other than the rate of addition are the same, an increase in the rate tends to increase the polymerization conversion rate, and a decrease in the rate tends to decrease the polymerization conversion rate. A higher temperature tends to increase the polymerization conversion rate, and a lower temperature tends to decrease the polymerization conversion rate. The upper limit is not particularly limited, but is usually 99% or less.

[0076] After the continuous addition is completed, the reaction solution is continuously stirred to complete the polymerization reaction. The mixing and stirring time after the addition can be 15 minutes or more and 300 minutes or less. From the viewpoint of the polymerization conversion rate and productivity, the mixing and stirring time is preferably 20 minutes or more and 270 minutes or less, and more preferably 30 minutes or more and 240 minutes or less.

[0077] At least a portion of the transition metal imide complex may be added continuously. This is expected to improve reaction selectivity. The transition metal imide complex to be added continuously can be dissolved or dispersed in the organic solvent as a liquid and then continuously added dropwise. The concentration of the transition metal imide complex in the liquid can be 0.01% by mass or more and 20% by mass or less. From the viewpoint of solution stability of the complex, the concentration of the transition metal imide complex is preferably 0.1% by mass or more and 15% by mass or less, and more preferably 0.5% by mass or more and 10% by mass or less. The timing of the continuous addition may be the same as or different from the timing of the continuous addition of the norbornene-based monomer.

[0078] When a chain transfer agent is used, from the viewpoint of controlling stereochemistry and reducing the content of dimers and the like, the amount of the chain transfer agent continuously added can be set to 0.060 mol / min or more, preferably 0.080 mol / min or more, and can be set to 2.000 mol / min or less, preferably 1.000 mol / min or less.

[0079] When preparing the cyclic olefin copolymer by addition polymerization, the addition polymerization can be carried out in the presence of, for example, a Ziegler-Natta catalyst, a metallocene catalyst, a nickel catalyst, or a palladium catalyst. The addition polymerization may be carried out under reaction conditions obtained by appropriately modifying known reaction conditions.

[0080] [Recovery process] The copolymer obtained in the polymerization step can be recovered as a cyclic olefin copolymer. For example, the reaction solution can be mixed with a precipitant (e.g., a poor solvent such as isopropanol or methanol) to precipitate the cyclic olefin copolymer, and the cyclic olefin copolymer can be recovered as a precipitate. The recovered cyclic olefin copolymer may be dried (e.g., vacuum dried).

[0081] (Hydrogenated cyclic olefin copolymer) The hydrogenated cyclic olefin copolymer of the present invention is obtained by hydrogenating the above-mentioned cyclic olefin copolymer of the present invention, and the hydrogenated cyclic olefin copolymer obtained by hydrogenating the above-mentioned cyclic olefin copolymer of the present invention can simultaneously achieve a high refractive index, high heat resistance, and low birefringence.

[0082] <Hydrogenation> The cyclic olefin copolymer of the present invention may have a carbon-carbon unsaturated bond in the main chain. Furthermore, depending on the type of monomer used in the polymerization, the copolymer may have a carbon-carbon unsaturated bond in the main chain, a substituent bonded to the five-membered ring, or a condensed ring with the five-membered ring (hereinafter referred to as a side chain). By hydrogenating the cyclic olefin copolymer, at least a portion of these carbon-carbon unsaturated bonds is hydrogenated to form saturated bonds, thereby obtaining a hydrogenated product.

[0083] Known methods can be used for hydrogenation. For example, hydrogenation can be carried out by supplying hydrogen to a solution of a cyclic olefin copolymer in the presence of a hydrogenation catalyst and causing an addition reaction. The hydrogenation catalyst is preferably a catalyst that hydrogenates the carbon-carbon double bonds in the main chain but does not hydrogenate aromatic rings (e.g., the naphthalene ring of a naphthyl group). Examples of such hydrogenation catalysts include ruthenium catalysts (chlorohydridocarbonyltris(triphenylphosphine)ruthenium) and palladium catalysts. Hydrogenation can be carried out, for example, by supplying hydrogen at high pressure (e.g., 1 MPa or higher) and stirring at high temperature (e.g., 120°C or higher).

[0084] The resulting hydrogenated cyclic olefin copolymer can be recovered, for example, by the same method as described above for the cyclic olefin copolymer.

[0085] <Hydrogenation rate> The hydrogenated cyclic olefin copolymer of the present invention is more preferably sufficiently hydrogenated. The hydrogenation rate of the hydrogenated cyclic olefin copolymer of the present invention is preferably 90 mol% or more, more preferably 95 mol% or more, and even more preferably 99 mol% or more. If the hydrogenation rate is equal to or higher than the above lower limit, the heat resistance of the hydrogenated cyclic olefin copolymer can be further improved. Note that the hydrogenation rate is the hydrogenation rate of carbon-carbon unsaturated bonds in the main chain, and aromatic rings such as naphthalene rings are usually not hydrogenated.

[0086] <Physical properties of hydrogenated cyclic olefin copolymers> The hydrogenated cyclic olefin copolymer of the present invention preferably has the following physical properties.

[0087] [Glass transition temperature] From the viewpoint of heat resistance, the glass transition temperature of the hydrogenated cyclic olefin copolymer is preferably 135° C. or higher, and more preferably 140° C. or higher. The glass transition temperature of the hydrogenated cyclic olefin copolymer is not particularly limited and may be 250° C. or lower.

[0088] [Refractive Index] In addition, the refractive index (n d In order to ensure that the optical element exhibits its optical function, the refractive index (n d ) is preferably 1.640 or less, and more preferably 1.635 or less, in order for the optical element to function properly. The refractive index can change depending on the wavelength and temperature. In this specification, the refractive index refers to the refractive index (n d )

[0089] [Stress birefringence] Stress birefringence (C R ) can be determined by applying stress (F) to a measurement sample, then measuring the in-plane retardation (Re(b) [nm]) and thickness (T(b) [mm]) at the center of the measurement sample at a specific wavelength (e.g., 543 nm), and calculating the Δn value using the following formulas (X1) and (X2). δn=Re(b)×(1 / T(b))×10 -6 ···(X1) C R =δn / F (X2) The closer the δn value is to 0, the smaller the birefringence. A film with a slow axis in the stretching direction has a positive value, and a film with a slow axis perpendicular to the stretching direction has a negative value. The stress birefringence (C R ) is a 750×10 -12 Pa -1 Preferably, it is 400×10 or less. -12 Pa-1 More preferably, it is:

[0090] (Applications of hydrogenated cyclic olefin copolymers) The hydrogenated cyclic olefin copolymer of the present invention can be used as a composition. The composition contains the hydrogenated cyclic olefin copolymer of the present invention and optionally further contains additives such as weather stabilizers, heat stabilizers, antistatic agents, flame retardants, slip agents, antiblocking agents, antifogging agents, lubricants, dyes, pigments, natural oils, synthetic oils, waxes, and fillers, as well as solvents. The hydrogenated cyclic olefin copolymer of the present invention can be mixed with the additives and solvents using known mixing methods.

[0091] Specific examples of the additives that can be used herein include those exemplified in JP-A No. 2005-330465. Furthermore, known solvents such as the organic solvents described above can be used as the solvent.

[0092] The hydrogenated cyclic olefin copolymer of the present invention or a composition containing the hydrogenated cyclic olefin copolymer of the present invention can be advantageously used as a material for optical elements and the like.

[0093] Furthermore, the hydrogenated cyclic olefin copolymer of the present invention can be used as a molded article. The molded article is obtained by molding the hydrogenated cyclic olefin copolymer of the present invention or a composition containing the hydrogenated cyclic olefin copolymer of the present invention. The molded article obtained from the hydrogenated cyclic olefin copolymer of the present invention can be advantageously used as an optical element, etc.

[0094] Examples of methods that can be used to form the molded body include injection molding, extrusion blow molding, injection blow molding, two-stage blow molding, multi-layer blow molding, connection blow molding, stretch blow molding, rotational molding, vacuum molding, extrusion molding, calendar molding, solution casting, hot press molding, and inflation molding. [Example]

[0095] The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to these examples. In the following examples and comparative examples, various physical properties were measured according to the following methods. In the examples and comparative examples, naphthylnorbornenes synthesized in the following Synthesis Examples 1 to 4 were used.

[0096] <Endo / exo ratio of naphthylnorbornene> Using deuterated chloroform as a solvent, 1 The endo / exo ratio of naphthylnorbornene was determined by H-NMR measurement. Specifically, the endo / exo ratio (molar ratio) was calculated based on the intensity ratio of the signal at 5.79 ppm derived from the endo isomer and the signal at 6.20 ppm derived from the exo isomer. <Glass transition temperature> The glass transition temperature (Tg) was measured using a differential scanning calorimeter (manufactured by Nano Technology Co., Ltd., product name: DSC6220SII) at a temperature rise rate of 10°C / min in accordance with JIS K6911. The higher the glass transition temperature, the better the heat resistance. <Stress birefringence C R > The hydrogenated copolymer was molded into a sheet measuring 35 mm long, 10 mm wide, and 1 mm thick to obtain a sample sheet. Both ends of the sample sheet were secured with clips, and a 55 g weight was attached to one of the clips. The sample sheet was then stretched for 1 hour by hanging it from the clip that did not have the weight attached in an oven set at a temperature 15°C above the glass transition temperature (Tg) of the hydrogenated copolymer. The sample sheet was then slowly cooled to room temperature, and a measurement sample was obtained. The in-plane retardation (Re(b) [nm]) of the center of this measurement sample was measured at a wavelength of 543 nm using a birefringence meter (Photonic Lattice Co., Ltd., product name: WPA-100). The thickness (T(b) [mm]) of the center of the measurement sample was also measured. Using these measured values ​​Re(b) and T(b), the Δn value was calculated according to the following formula (X1). δn=Re(b)×(1 / T(b))×10 -6 (X1) Using the δn value and the stress (F) applied to the sample, the stress birefringence (C R ) was calculated. C R =δn / F [Pa -1 ] (X2) δn value is close to 0, C R The closer to 0 the value is, the smaller the birefringence is. Note that a film with a slow axis in the stretching direction exhibits a positive value, and a film with a slow axis perpendicular to the stretching direction exhibits a negative value. <Refractive index> The hydrogenated copolymer was formed into a sheet having a thickness of 5 mm and left in an atmosphere at a glass transition temperature (Tg) of -15°C for 20 hours to prepare a measurement sample. The refractive index (n) of the obtained measurement sample at 25°C was measured using a precision refractometer (Shimadzu Corporation, product name: KPR-200, light source = He lamp (wavelength: 587.6 nm) and H lamp (wavelength: 656.3 nm and 486.1 nm). d , n C and n F The table shows the refractive index (n d ) is shown.

[0097] <Synthesis Example 1: Production of exo-enriched 1-naphthylnorbornene> 458 g of 1-bromonaphthalene (Wako Pure Chemical Industries, Ltd.), 500 mL of dimethylformamide (Wako Pure Chemical Industries, Ltd.), 455 mL of norbornadiene (Tokyo Chemical Industry Co., Ltd.), 656 mL of piperidine (Wako Pure Chemical Industries, Ltd.), 220 mL of formic acid (99%, Wako Pure Chemical Industries, Ltd.), and 2.75 g of a palladium catalyst (palladium dichlorobistriphenylphosphine, Tokyo Chemical Industry Co., Ltd., product code: B1667) were charged into a reactor and stirred at 90°C for 6.5 hours. The resulting reaction solution was extracted with ethyl acetate / water, and the organic layer was dried over magnesium sulfate. This was filtered and evaporated. The residue was subjected to column chromatography (eluent: hexane) to remove the palladium residue. The resulting solution was evaporated, and the remaining liquid was distilled under reduced pressure (1.2 mmHg / 135-152°C). As a result, 269 g of 1-naphthylnorbornene (1-NPNB: bicyclo[2,2,1]hept-2-ene-5-(1-naphthyl)) was obtained as a colorless, transparent liquid. The endo / exo ratio was measured and found to be 0 / 100.

[0098] <Synthesis Example 2: Production of exo-enriched 2-naphthylnorbornene> 458 g of 2-bromonaphthalene (Wako Pure Chemical Industries, Ltd.), 500 mL of dimethylformamide (Wako Pure Chemical Industries, Ltd.), 455 mL of norbornadiene (Tokyo Chemical Industry Co., Ltd.), 656 mL of piperidine (Wako Pure Chemical Industries, Ltd.), 220 mL of formic acid (99%, Wako Pure Chemical Industries, Ltd.), and 2.75 g of palladium catalyst (palladium dichlorobistriphenylphosphine, Tokyo Chemical Industry Co., Ltd., product code: B1667) were charged into a reactor and stirred at 90°C for 6.5 hours. The resulting reaction solution was extracted with ethyl acetate / water, and the organic layer was dried over magnesium sulfate. This was filtered and evaporated. The residue was subjected to column chromatography (eluent: hexane) to remove palladium residues. The resulting solution was evaporated, and the remaining liquid was distilled under reduced pressure (1.2 mmHg / 135-152°C). As a result, 269 g of 2-naphthylnorbornene (2-NPNB: bicyclo[2,2,1]hept-2-ene-5-(2-naphthyl)) was obtained as a colorless, transparent liquid. The endo / exo ratio was measured and found to be 0 / 100.

[0099] <Synthesis Example 3: Production of endo-enriched 1-naphthylnorbornene> 264 g of dicyclopentadiene (Tokyo Chemical Industry Co., Ltd.), 1234 g of 1-vinylnaphthalene (Tokyo Chemical Industry Co., Ltd.), and 15 g of N-nitrosophenylhydroxylamine aluminum salt (Wako Pure Chemical Industries, Ltd.) were charged into a reactor and stirred at 180 °C for 1 hour. The resulting crude product was distilled under reduced pressure (1.2 mmHg / 135-152 °C). As a result, 42 g of 1-naphthylnorbornene (1-NPNB: bicyclo[2,2,1]hept-2-ene-5-(1-naphthyl)) was obtained as a colorless, transparent liquid. The endo / exo ratio was measured and found to be 85 / 15.

[0100] <Synthesis Example 4: Production of endo-enriched 2-naphthylnorbornene> 264 g of dicyclopentadiene (Tokyo Chemical Industry Co., Ltd.), 1234 g of 2-vinylnaphthalene (Aldrich Chemical Co., Ltd.), and 15 g of N-nitrosophenylhydroxylamine aluminum salt (Wako Pure Chemical Industries, Ltd.) were charged into a reactor and stirred at 180 °C for 1 hour. The resulting crude product was distilled under reduced pressure (1.2 mmHg / 135-152 °C). As a result, 58 g of 2-naphthylnorbornene (2-NPNB: bicyclo[2,2,1]hept-2-ene-5-(2-naphthyl)) was obtained as a colorless, transparent liquid. The endo / exo ratio was measured and found to be 86 / 14.

[0101] Example 1 <Preparation of Cyclic Olefin Copolymer> The exo-rich 1-naphthylnorbornene (Synthesis Example 1), exo-rich 2-naphthylnorbornene (Synthesis Example 2), endo-rich 1-naphthylnorbornene (Synthesis Example 3), and endo-rich 2-naphthylnorbornene (Synthesis Example 4) prepared in Synthesis Examples 1 to 4 were mixed in a molar ratio of Synthesis Example 1 / Synthesis Example 2 / Synthesis Example 3 / Synthesis Example 4 = 0.3 / 3.1 / 10.7 / 85.9 to obtain a naphthylnorbornene (NPNB) mixture. The endo / exo ratio of this mixture was measured and found to be 83 / 17. Next, 96 g of dehydrated toluene, 2 mol% 1-hexene, 1.2 mol% diethylaluminum ethoxide (EtAl(OEt)), and 1 mol% of a mixture of naphthylnorbornene (NPNB) and tetracyclododecene (TCD) (mol ratio = 70:30) were mixed in a nitrogen-purged glass reactor at room temperature. Then, while maintaining the temperature at 50 °C, a 2.0 wt% toluene solution of tetrachlorotungsten phenylimide (tetrahydrofuran) was added to the reactor to a final concentration of 0.4 mol%. Subsequently, a mixture of naphthylnorbornene (NPNB) and tetracyclododecene (TCD) (mol ratio = 70:30, total 0.03 mol) was added continuously over 2 hours to initiate ring-opening polymerization. Subsequently, 48 mol% isopropyl alcohol was added to the polymerization solution to inactivate the polymerization catalyst and terminate the polymerization reaction. The conversion of the monomers to polymer was 100%. In the following description, "mol %" indicates a percentage value based on the number of moles of the mixed monomers. <Preparation of Hydrogenated Cyclic Olefin Copolymer> Next, 155 g of cyclohexane was added to 95 g of the reaction solution containing the obtained ring-opened polymer (cyclic olefin copolymer), and 0.05 mass% of chlorohydridocarbonyltris(triphenylphosphine)ruthenium was further added as a hydrogenation catalyst. The mixture was pressurized to 4.5 MPa with hydrogen and heated to 160°C with stirring, and then reacted for 8 hours to obtain a reaction solution containing a hydrogenated cyclic olefin copolymer. The resulting solution was poured into a large amount of isopropanol to precipitate the hydrogenated cyclic olefin copolymer. The precipitated hydrogenated cyclic olefin copolymer was collected by filtration and then dried in a vacuum dryer (200°C, 1 Torr) for 10 hours to obtain 5 g of hydrogenated cyclic olefin copolymer. The glass transition temperature (Tg) and stress birefringence (C R ) and refractive index (n d ) was measured by the method described above. The results are shown in Table 1.

[0102] Example 2 When preparing the cyclic olefin copolymer, a mixture of naphthylnorbornene (NPNB) was used in a ratio of Synthesis Example 1 / Synthesis Example 2 / Synthesis Example 3 / Synthesis Example 4 = 1.0 / 3.3 / 28.0 / 67.7 (molar ratio), and a mixture of naphthylnorbornene and tetracyclododecene (TCD) was used in a ratio of 30:70 (molar ratio). Except for this, a cyclic olefin copolymer and a hydrogenated cyclic olefin copolymer were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0103] Example 3 When preparing cyclic olefin copolymer, naphthylnorbornene (NPNB) mixture was used as synthesis example 1 / synthesis example 2 / synthesis example 3 / synthesis example 4 = 0 / 1.0 / 11.0 / 88.0 (molar ratio), and as mixed monomer, naphthylnorbornene mixture and 1,4-methano-1,4,4a,9a-tetrahydro-9H-fluorene (MTF) were used as mixed monomer to be 50:50 (molar ratio), except that in the same manner as in Example 1, cyclic olefin copolymer and cyclic olefin copolymer hydrogenation were prepared and evaluated. The results are shown in Table 1.

[0104] Example 4 When preparing the cyclic olefin copolymer, a mixture of naphthylnorbornene (NPNB) was used in a ratio of Synthesis Example 1 / Synthesis Example 2 / Synthesis Example 3 / Synthesis Example 4 = 4.7 / 34.8 / 7.3 / 53.2 (molar ratio), and a mixed monomer in which the mixture ratio of naphthylnorbornene mixture and tetracyclododecene (TCD) was changed to 30:70 (molar ratio) was used. Except for this, a cyclic olefin copolymer and a hydrogenated cyclic olefin copolymer were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0105] (Comparative Example 1) In preparing the cyclic olefin copolymer, exo-isomer-rich 2-naphthylnorbornene (Synthesis Example 2) was used instead of the naphthylnorbornene mixture, and a mixed monomer mixture in which the exo-isomer-rich 2-naphthylnorbornene (Synthesis Example 2) and tetracyclododecene (TCD) were mixed in a ratio of 56:44 (molar ratio) was used. A cyclic olefin copolymer and a hydrogenated cyclic olefin copolymer were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0106] (Comparative Example 2) When preparing the cyclic olefin copolymer, a mixture of naphthylnorbornene (NPNB) was used in a molar ratio of Synthesis Example 1 / Synthesis Example 2 / Synthesis Example 3 / Synthesis Example 4 = 4.7 / 0 / 95.3 / 0, and a mixed monomer mixture of naphthylnorbornene and tetracyclododecene (TCD) was used in a molar ratio of 30:70. Except for this, a cyclic olefin copolymer and a hydrogenated cyclic olefin copolymer were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0107] (Comparative Example 3) A cyclic olefin copolymer and a hydrogenated cyclic olefin copolymer were prepared and evaluated in the same manner as in Example 1, except that a naphthylnorbornene (NPNB) mixture was used in the preparation of the cyclic olefin copolymer, with the molar ratio of Synthesis Example 1 / Synthesis Example 2 / Synthesis Example 3 / Synthesis Example 4 being 3.9 / 40.2 / 5.1 / 50.8. The results are shown in Table 1.

[0108] [Table 1]

[0109] It can be seen from Table 1 that the hydrogenated cyclic olefin copolymers of Examples 1 to 4 can simultaneously achieve a high refractive index, high heat resistance, and low birefringence. It can also be seen from Table 1 that the hydrogenated cyclic olefin copolymers of Comparative Examples 1 and 3 have low heat resistance, and the hydrogenated cyclic olefin copolymer of Comparative Example 2 exhibits poor birefringence. [Industrial Applicability]

[0110] According to the present invention, it is possible to obtain a resin that can simultaneously achieve a high refractive index, high heat resistance, and low birefringence, as well as a copolymer that is useful as a raw material for the resin. Furthermore, according to the present invention, an optical element having a high refractive index, a high heat resistance, and a low birefringence can be obtained.

Claims

1. Contains a structural unit derived from 1-naphthylnorbornene and a structural unit derived from 2-naphthylnorbornene, The cyclic olefin copolymer has an average endo-isomer ratio of the 1-naphthylnorbornene and the 2-naphthylnorbornene of 50 mol % or more.

2. 2. The cyclic olefin copolymer according to claim 1, wherein the total proportion of structural units derived from 1-naphthylnorbornene and structural units derived from 2-naphthylnorbornene in all structural units is 30 mol % or more and 70 mol % or less.

3. 3. The cyclic olefin copolymer according to claim 1, wherein the proportion of structural units derived from 1-naphthylnorbornene to the total of structural units derived from 1-naphthylnorbornene and structural units derived from 2-naphthylnorbornene is 1 mol % or more and 30 mol % or less.

4. 4. The cyclic olefin copolymer according to claim 1, further comprising a structural unit derived from a norbornene-based monomer other than 1-naphthylnorbornene and 2-naphthylnorbornene.

5. The cyclic olefin copolymer according to any one of claims 1 to 4, which is a ring-opening polymer.

6. A hydrogenated cyclic olefin copolymer obtained by hydrogenating the cyclic olefin copolymer according to any one of claims 1 to 5.

7. The hydrogenated cyclic olefin copolymer according to claim 6, which has a glass transition temperature of 135°C or higher.

8. An optical element comprising the hydrogenated cyclic olefin copolymer according to claim 6 or 7.

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