JP6508921B2 - Method for producing fluorene skeleton-containing epoxy resin, epoxy resin composition, and cured product - Google Patents

Description

  The present invention relates to a method for producing a fluorene skeleton-containing epoxy resin, an epoxy resin composition containing the fluorene skeleton-containing epoxy resin obtained by the production method and a curing agent for epoxy resin, and a cured product of the composition. . Since this cured product is excellent in heat resistance and light resistance, it is useful as an epoxy resin composition for an optical element related to an optical semiconductor such as a light emitting diode (LED).

  Epoxy resins are excellent in heat resistance, adhesiveness, water resistance, mechanical strength and electrical properties etc., so they are used in various fields such as adhesives, paints, materials for civil engineering and construction, insulation materials for electric and electronic parts, etc. It is used. As the normal temperature or heat curing epoxy resin, aromatic epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, phenol or cresol novolac epoxy resin are generally used.

  In recent years, most of light emitting devices such as LEDs, which are put to practical use in various display boards, light sources for image reading, traffic signals, large display units, etc., are manufactured by resin sealing. The resin for sealing used here generally contains the above-mentioned aromatic epoxy resin and an alicyclic acid anhydride as a curing agent.

  In addition, with the rapid progress of LEDs today, high power and short wavelength of LED elements are rapidly becoming a reality, and especially LEDs using nitride semiconductors emit light with short wavelength and high power. Is possible. However, when an LED element using a nitride semiconductor is sealed with the above-mentioned general-purpose aromatic epoxy resin, the aromatic ring absorbs light of a short wavelength, so that the sealed resin deteriorates over time, causing yellowing. Due to the change, a problem occurs that the light emission luminance is significantly reduced.

  Therefore, there is proposed an LED sealed using an alicyclic epoxy resin obtained by oxidizing a cyclic olefin represented by 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate ((4) Patent documents 1, 2). However, the cured resin sealed with this cycloaliphatic epoxy resin is very brittle, is susceptible to cracking due to thermal cycling, and has extremely poor moisture resistance, so it is used in applications where long-term reliability characteristics are required. It was unsuitable.

  On the other hand, there has been proposed an LED which is mainly composed of a hydrogenated bisphenol A epoxy resin, is blended with an alicyclic epoxy resin and a phosphorus-based antioxidant, and is sealed using a methyl hexahydrophthalic acid curing agent (patented) Literature 3). Although this epoxy cured product is excellent in colorless transparency, it has a drawback that it is easily yellowed due to a decrease in heat resistance, and there was a problem in the use for sealing an LED element that is required to have heat resistance characteristics. Further, Patent Document 4 describes a cured product in which transparency is obtained without lowering heat resistance by producing a cured product using a bisphenol fluorene type epoxy resin. However, even when using a bisphenol fluorene type epoxy resin, the light transmittance was insufficient.

  Furthermore, an epoxy resin composition obtained by reacting a bifunctional epoxy resin, a fluorene ring-containing phenol, and an acid anhydride has been proposed (Patent Document 5). Although the heat resistance of this cured product is improved, there is a problem that the moisture resistance is poor due to the relatively large number of ester bonds in the cured product, and it was unsuitable for applications requiring long-term reliability characteristics. . In addition, the manufacturing method of 9,9-bis (4-hydroxyphenyl) fluorene is known as a fluorene frame | skeleton containing phenol compound or its manufacturing method (patent document 6).

JP-A-9-213997 Japanese Patent Laid-Open No. 2000-196151 JP 2003-12896 A JP-A-7-247339 JP, 2012-177038, A JP-A 5-980

  The present invention provides a method for producing a fluorene skeleton-containing epoxy resin of good quality that can improve moisture resistance, have transparency, heat resistance, electrical properties, and can give a cured product excellent in heat yellowing resistance as well. It is an object of the present invention to provide an epoxy resin composition and an epoxy resin cured product which are useful as an encapsulant for LEDs emitting particularly short wavelength light.

  It finds that the polyfunctional phenol compound resulting from the fluorene skeleton in the raw material phenol compound is related to the heat resistance and the heat resistance yellowing resistance of the epoxy resin composition and the epoxy resin cured product, and the content thereof can be controlled to an appropriate range We have reached a good manufacturing method.

  That is, the present invention is obtained by reacting a phenol compound containing a fluorene skeleton-containing phenol compound represented by the following general formula (1) with a bifunctional epoxy resin, and has an epoxy equivalent of 700 to 1500 g / eq. A method for producing a fluorene skeleton-containing epoxy resin having a skeleton content of 15 to 70 mol%, wherein the fluorene skeleton-containing phenol compound contains 50% by mass or more of a compound (a) in which n in the general formula (1) is 0 And n is 1 or 2 as measured by high performance liquid chromatography and contains 0.01 to 1.0% by area of a compound (b), and the presence of a catalyst which promotes the addition reaction of phenolic hydroxyl group and epoxy group Containing a fluorene skeleton characterized by reacting a hydroxyl group of a phenol compound and an epoxy group of a bifunctional epoxy resin under A method for producing epoxy resin.

（式中、Ｒは、それぞれ独立に、水素原子または炭素数１〜８の炭化水素基であり、環状構造を含んでもよい。）

(Wherein each R independently represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and may contain a cyclic structure).

  Some fluorene skeleton-containing phenol compounds contain 90% by mass or more of 9,9-bis (4-hydroxyphenyl) fluorene. As a bifunctional epoxy resin, there is a bisphenol A type epoxy resin.

  In addition, a part of the bifunctional epoxy resin may be an epoxy resin having a fluorene skeleton, and the epoxy equivalent in this case is 230 to 500 g / eq, which is lower than the epoxy equivalent of the target fluorene skeleton-containing epoxy resin.

  The above-mentioned catalysts include phosphines or quaternary phosphonium salts.

  Moreover, this invention is a fluorene frame | skeleton containing epoxy resin manufactured by said manufacturing method. Furthermore, the present invention is an epoxy resin composition comprising an epoxy resin (A) and an epoxy resin curing agent (B) as essential components, wherein the fluorene skeleton-containing epoxy according to claim 6 as a component (A) It is an epoxy resin composition characterized by containing resin. An acid anhydride is mentioned as said (B) component.

  The present invention also relates to an epoxy resin composition for an optical element comprising the above epoxy resin composition, and a sealing agent for an optical element obtained by using the epoxy resin composition for an optical element, or a substrate for an optical element. is there.

  Furthermore, the present invention is a cured product obtained by curing the above epoxy resin composition. The cured product desirably has a thickness of 1 mm and a YI value of 20 or less after heat treatment under conditions of 180 ° C. and 100 hours.

  The fluorene skeleton-containing epoxy resin obtained by the production method of the present invention can be made to have a hue close to colorless, and the cured product of the epoxy resin composition using it can be heat resistant (heat resistant yellowing resistance) and moisture resistant. Because of its excellent properties, it can be used particularly advantageously as an epoxy resin composition for LED encapsulants.

It is an HPLC chart of BPFL used in the example. It is a graph which shows the relationship between the softening point of an epoxy resin, and the glass transition temperature of hardened | cured material.

  Hereinafter, embodiments of the present invention will be described in detail.

  The method for producing a fluorene skeleton-containing epoxy resin of the present invention is a method in which a phenolic compound and a bifunctional epoxy resin are reacted in the presence of a catalyst.

  The phenol compound used as a raw material includes the fluorene skeleton-containing phenol compound represented by the above general formula (1). The main component of the fluorene skeleton-containing phenol compound is a compound (a) in which n in the general formula (1) is 0, and includes a component in which n is 1 or more as a minor component. And the compound whose n is 1 or 2 is called compound (b). The compound (a) is typically 9,9-bis (4-hydroxyphenyl) fluorene (also referred to as BPFL or bisphenol fluorene).

  The amount of compound (b) present in the phenolic compound is in the range of 0.01 to 1.0 area% as measured by HPLC. The conditions for HPLC measurement follow the conditions described in the examples.

The fluorene skeleton-containing epoxy resin obtained by the production method of the present invention has an epoxy equivalent of 700 to 1500 g / eq and a fluorene skeleton content of 15 to 70 mol%. The content of the fluorene skeleton is determined by the content of the phenolic compound used as a raw material and the content of the fluorene skeleton contained in the bifunctional epoxy resin, and the resin skeleton (residue obtained by removing hydroxyl groups from the phenolic compound and glycidyl ether group from the epoxy resin It can be determined as a percentage of the number of moles of the bisphenol fluorene skeleton represented by the following general formula (3) with respect to the total number of moles of the remaining residue). That is, in the case of the phenol compound and epoxy resin whose resin skeleton is only a bisphenol fluorene skeleton, the fluorene skeleton content is 100 mol%. Also, for example, when the resin skeleton is 25 mol% of bisphenol fluorene skeleton and 75 mol% of other skeletons, the fluorene skeleton content of the compound is 25 mol%. The fluorene skeleton content of the fluorene skeleton-containing epoxy resin obtained by the production method of the present invention is determined by a weighted average of the fluorene skeleton content in the raw material. For example, the fluorene skeleton content of a fluorene skeleton-containing epoxy resin obtained from 600 g of an epoxy resin having a fluorene skeleton content of 10 mol% and an epoxy equivalent of 200 g / eq and 250 mol of the fluorene skeleton content 100 mol% and a phenol compound having a hydroxyl equivalent of 125 g / eq. Can be calculated by the following equation to be 46 mol%.
(10 × 600/200 + 100 × 250/125) / (600/200 + 250/125) = 46

  Hereinafter, the fluorene skeleton-containing phenol compound represented by the above general formula (1) is referred to as bisphenol fluorenes or BPFLs. Bisphenol fluorenes are used in the meaning including the said compound (a) and a compound (b). In addition, the phenol compound used as a raw material may also contain other phenol compounds other than BPFLs.

  In general formula (1), R is each independently a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and may contain a cyclic structure. Preferably, R is a methyl group, an ethyl group, a tert-butyl group, a cyclohexyl group, a phenyl group, an indanyl group or an α-methylbenzyl group, and more preferably a methyl group, a phenyl group or an α-methylbenzyl group It is. A methyl group and a phenyl group can be introduce | transduced by using cresol, xylenol, or phenyl phenol instead of a phenol, when manufacturing BPFL with the manufacturing method of patent document 6. Further, indanyl group and α-methylbenzyl group can be introduced by adding indene and styrene to BPFL, respectively.

  By containing bisphenol fluorenes in the phenol compound of the raw material, a fluorene skeleton can be introduced into the obtained epoxy resin. Moreover, in order to adjust the introduction amount of fluorene structure, you may use together phenol compounds other than bisphenol fluorenes in the quantity of 70 mass% or less with respect to the whole quantity of a phenol compound. As a phenol compound which can be used in combination, bisphenol A, bisphenol F, bisphenol S, 4,4'-biphenol, tetramethyl bisphenol A, dimethyl bisphenol A, tetramethyl bisphenol F, dimethyl bisphenol F, tetramethyl bisphenol S, dimethyl bisphenol S, Tetramethyl-4,4'-biphenol, dimethyl-4,4'-biphenol, 1- (4-hydroxyphenyl) -2- [4- (1,1-bis- (4-hydroxyphenyl) ethyl) phenyl] Propane, 2,2'-methylene-bis (4-methyl-6-tert-butylphenol), 4,4'-butylidene-bis (3-methyl-6-tert-butylphenol), trishydroxyphenylmethane, resorcinol, hydride It includes dihydric phenol compound quinone such, can be used alone or as a mixture of two or more of, but are not limited to.

（式中、（Ｅ）はエポキシ樹脂由来の骨格残基であり、（Ｐ）はフェノール化合物由来の骨格残基であり、ｎは繰り返し数を示す） The fluorene skeleton-containing epoxy resin obtained by the production method of the present invention is typically represented by the following general formula (2).

(Wherein (E) is a backbone residue derived from epoxy resin, (P) is a backbone residue derived from a phenol compound, and n is the number of repetitions)

（式中、Ｒは、上記一般式（１）のＲと同義である。） The fluorene skeleton-containing epoxy resin contains a bisphenol fluorene skeleton represented by the following general formula (3). The content range is 15 to 70 mol%, and the mol% of the total of (P) and (E) having a bisphenol fluorene skeleton is relative to the total of (P) and (E) of the general formula (2). It can be asked. It can also be determined from the type and amount of raw material used.

(Wherein R has the same meaning as R in the above general formula (1))

Bisphenol fluorenes which are generally commercially available include compounds (a) in which n is 0 in the general formula (1), but compounds in which n is 1 or more are not included (not detected by HPLC) . Therefore, the compound (b) in which n is 1 or 2 is not included.
However, in the general production method of bisphenol fluorenes, a small amount of a compound in which n is 1 or more in general formula (1) is by-produced. This is considered to be removed in the purification step. However, excessive purification is not preferable in consideration of environmental load.
In applications where bisphenol fluorenes are used to make epoxy resins, reducing the compound (b) below the detection limit not only results in excess quality but also reduces the crosslink density more than necessary.

  Therefore, the content of the compound (a) in the raw material bisphenol fluorenes needs to be 50% by mass or more, but the compound (b) is 0.01 to 1.0 area% as measured by HPLC. Preferably, it is 0.05-0.7 area%, More preferably, it is 0.07-0.5 area%. In the general formula (1), although a component in which n is 3 or more (a component having a phenol nucleus of 5 or more) may exist, the upper limit of n is 10 or less, and general bisphenol fluorenes In the method of preparation of the present invention, a component having n of 3 or more is not detected, so there is little need to consider it. In addition, even if it is detected, the trinuclear component and the tetranuclear component which are the compound (b) increase in the same tendency, so they are not suitable for the raw material of the present invention.

Moreover, the fluorene skeleton content can also be adjusted by introduce | transducing a fluorene skeleton into the target fluorene structure containing epoxy resin with the bifunctional epoxy resin used with a phenol compound as a raw material as needed. A bifunctional epoxy resin for introducing a fluorene skeleton into a fluorene skeleton-containing epoxy resin (also referred to as “bifunctional epoxy resin F” because it has a fluorene skeleton) is an epoxy resin represented by the following general formula (4) The epoxy resin is preferably an epoxy resin obtained by the reaction of bisphenol fluorenes and epihalohydrin and in which m is 0 in the general formula (4).
The epoxy equivalent of the bifunctional epoxy resin F is 230 to 500 g / eq, preferably 230 to 400 g / eq, and more preferably 230 to 350. The epoxy equivalent of the bifunctional epoxy resin F is preferably 100 g / eq or more lower, more preferably 400 g / eq or more lower than the epoxy equivalent of the target fluorene skeleton-containing epoxy resin.

  In the reaction for obtaining bifunctional epoxy resin F, that is, in the epoxidation reaction of bisphenol fluorenes and epihalohydrin, there may be a case where a phenol compound (b) is present in the raw material bisphenol fluorenes, but this may Since it is also consumed during the epoxidation reaction or removed as an impurity in the subsequent purification step, it can be said that the phenol compound (b) is hardly present in the bifunctional epoxy resin F obtained by this epoxidation reaction.

In General Formula (4), R ₂ has the same meaning as R in General Formula (1). R ₁ is a hydrogen atom or a methyl group. m represents an integer of 0 to 3, preferably 0. k represents the number of repetitions, and is 0 to 5 in average value (number average), preferably 0 to 3, and more preferably 0 to 1.

  Examples of the bifunctional epoxy resin (including bifunctional epoxy resin F) that can be used as a raw material in the production method of the present invention include the following. Bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethyl bisphenol A, tetramethyl bisphenol F, tetramethyl bisphenol S, dimethyl bisphenol A, dimethyl bisphenol F, dimethyl bisphenol S, terpene diphenol, thiodiphenol, bisphenol fluorene, Bisphenol type epoxy resin obtained from biscresol fluorene, dihydroxy diphenyl ether, etc. Biphenol type epoxy resin obtained from biphenol, tetramethyl biphenol, dimethyl biphenol etc. Benzene diol obtained from hydroquinone, methyl hydroquinone, dibutyl hydroquinone, resorcinol, methyl resorcinol etc. Epoxy resin, dihydroxy Naphthalene type epoxy resins obtained from Futaren like although not limited thereto. These epoxy resins may be used alone or in combination of two or more. From the viewpoint of generality, bisphenol A epoxy resins are preferred, and from the viewpoint of heat resistance, bisphenol fluorene epoxy resins or biscresol fluorene epoxy resins are preferred.

  The heat resistance and heat yellowing resistance of the fluorene skeleton-containing epoxy resin is improved by increasing the content of the bisphenol fluorene skeleton, but if it is too large, the softening point becomes high, the viscosity also tends to be thickened, and actual use becomes difficult. When the amount is too small, the moisture resistance and the yellowing resistance may be reduced. The content range of the bisphenol fluorene skeleton of the fluorene skeleton-containing epoxy resin is more preferably 20 to 60 mol%, and still more preferably 30 to 50 mol%.

  The content of the bisphenol fluorene skeleton is determined by the number of moles of the bisphenol fluorene skeleton-containing phenolic compound and the bisphenol fluorene skeleton-containing epoxy resin relative to the total number of moles of the raw material phenolic compound and the epoxy resin, and the fluorene skeleton content is adjusted at the time of production. be able to. The content of the bisphenol fluorene skeleton in the fluorene skeleton-containing epoxy resin obtained by the production method of the present invention can also be determined by analysis. First, after confirming the skeleton (corresponding to (E) and (P) of the above general formula (2) of structural units) by NMR, the analysis method described in JP-A-2001-194300 is followed, ie, fluorene skeleton The UV absorption spectrum of the contained epoxy resin is measured, and the content of the bisphenol fluorene skeleton is determined by the characteristic absorption (310 nm) by the π-π * transition of the fluorene ring. A calibration curve is prepared by BPFL, and the amount of BPFL contained in the fluorene skeleton-containing epoxy resin is determined and converted to the number of moles of the structural unit. As another method, an epoxy resin and a phenol compound having a skeleton of a constituent unit, an epoxy resin having an epoxy equivalent equivalent to that of the target epoxy resin is synthesized, and used as a standard substance. At this time, the calibration curve is obtained by changing the fluorene skeleton content into several types such as 0 mol%, 50 mol%, 100 mol%, and the like. Whichever calibration curve is used, the content of the bisphenol fluorene skeleton in the fluorene skeleton-containing epoxy resin can be accurately determined.

  When the fluorene skeleton-containing epoxy resin of the present invention is applied as a sealing material for an optical element such as a light emitting element or a light receiving element, the compound (b) is measured by HPLC in the raw material fluorene skeleton containing phenol compound. Sometimes when it exists more than 1.0 area%, the hue of the hardened | cured material using the obtained fluorene frame | skeleton containing epoxy resin will deteriorate, or yellowing resistance will fall. This is because while the hydroxyl groups at both ends of the compound (b) face outward, the internal hydroxyl group is a structure sandwiched between the fluorene rings, so the reactivity is low and the reaction with the epoxy group does not proceed, leaving the hydroxyl group as it is It is considered to be because it remains in the fluorene skeleton-containing epoxy resin. Therefore, it is preferable to use bisphenol fluorenes that do not contain any of these impurities as a raw material, but in order to obtain such bisphenol fluorenes, it is necessary to repeat the purification process such as recrystallization many times. Rates are also uneconomical. Moreover, since heat resistance (Tg) is also slightly inferior, there is a concern about use in applications with high heat resistance requirements, which is not preferable.

  The epoxy equivalent of the fluorene skeleton-containing epoxy resin obtained by the production method of the present invention is 700 to 1500 g / eq. If the epoxy equivalent is small, a good heat resistance yellowing effect may not be expected. Conversely, if the epoxy equivalent is large, the softening point of the resulting epoxy resin may be high, which may make molding or coating difficult. . Preferably, it is 750 to 1400 g / eq, more preferably 800 to 1200 g / eq, and still more preferably 900 to 1100 g / eq. Here, the epoxy equivalent is the number of grams of resin containing 1 gram equivalent of epoxy group (g / eq), and is measured according to the method defined in JIS K-7236.

  The catalyst which can be used by the manufacturing method of the fluorene frame | skeleton containing epoxy resin of this invention can use the well-known catalyst used by manufacture of an epoxy resin. As the catalyst which can be used, phosphines such as triphenylphosphine, tris (2,6-dimethoxyphenyl) phosphine and the like, tetrabutylphosphonium · benzotriazolate, tetra-n-butylphosphonium · hexafluorophosphate, tetra-n-butyl Quaternary phosphonium salts such as phosphonium o, o-diethyl phosphorodithioate, methyl tributyl phosphonium dimethyl phosphate, tetra-n-butyl phosphonium tetrafluoroborate, n-butyl triphenyl phosphonium bromide, ethyl triphenyl phosphonium iodide and the like Imidazoles such as 2-ethyl-4-methylimidazole and 2-phenylimidazole; quaternary ammonium such as tetramethylammonium chloride and tetraethylammonium bromide Um salts, triethylamine, tertiary amines such as benzyl dimethyl amine and the like, include known catalysts, but is not limited thereto. Of these catalysts, phosphines or quaternary phosphonium salts are preferred. The amount of these catalysts used is preferably in the range of 0.005 to 1 part by mass, and more preferably 0.01 to 0.5 part by mass, with respect to 100 parts by mass of the total amount of phenol compounds.

  A reaction solvent may be used in the production method of the present invention. The organic solvent which can be used is not particularly limited as long as it is non-reactive. Specifically, aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene and acetone, ketones such as methyl ethyl ketone, methyl butyl ketone, dipropyl ketone, cyclopentanone and cyclohexanone, dialkyl ethers, 2-ethoxyethyl ethyl ether And ethers such as tetrahydrofuran and dioxane. These reaction solvents may be used alone or in combination of two or more. Among these organic solvents, an organic solvent having a boiling point of 70 to 170 ° C. at normal pressure is preferable. An organic solvent having a boiling point of less than 70 ° C. at normal pressure is not preferable because the reaction proceeds slowly because the reaction temperature is low when the reaction is performed under reflux at normal pressure. If the boiling point exceeds 170 ° C., it takes a long time at high temperature to distill off the organic solvent, and the organic solvent may easily remain in the fluorene skeleton-containing epoxy resin. Moreover, 100 mass parts or less are preferable with respect to 100 mass parts of total amounts of a phenol compound and bifunctional epoxy resin as the usage-amount of these organic reaction solvents.

  The epoxy resin composition of the present invention comprises an epoxy resin (A) and an epoxy resin curing agent (B). And the fluorene skeleton containing epoxy resin (A1) manufactured by said manufacturing method is contained in (A) component. The epoxy resin (A) and the epoxy resin curing agent (B) are respectively referred to as (A) component and (B) component. The fluorene skeleton-containing epoxy resin (A1) produced by the production method of the present invention is referred to as component (A1).

  It is preferable that it is an epoxy resin which contains 80 mass% or more of (A1) components, and contains another epoxy resin by less than 20 mass% as (A) component. When the other epoxy resin is blended in a proportion of 20% by mass or more, the heat resistance and the heat yellowing resistance of the resulting cured product tend to be lowered. Moreover, it is preferable to mix | blend 0.1-200 mass parts of (B) component with respect to 100 mass parts of (A) component.

  Examples of the epoxy resin other than the fluorene skeleton-containing epoxy resin that can be used in the present invention include the following. Bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethyl bisphenol A, tetramethyl bisphenol F, tetramethyl bisphenol S, dimethyl bisphenol A, dimethyl bisphenol F, dimethyl bisphenol S, terpene diphenol, thiodiphenol, dihydroxydiphenyl ether, etc. Type epoxy resin obtained from the above, biphenol type epoxy resin obtained from biphenol, tetramethyl biphenol, dimethyl biphenol etc., hydroquinone, methyl hydroquinone, dibutyl hydroquinone, diresorcinol, benzenediol type epoxy resin obtained from methyl resorcinol etc, dihydroxynaphthalene etc. Naphthalene type epoxy resin obtained from Polyvalent epoxy resin obtained from various polyhydric phenols such as novolac resin, cresol novolac resin, novolac resin of bisphenol A, dicyclopentadiene phenol resin, terpene phenol resin, terpene phenol resin, phenol aralkyl resin, biphenyl aralkyl resin, naphthol novolac resin And amine type epoxy resins obtained from various amine compounds such as diaminodiphenylmethane, aminophenol and xylene diamine, and glycidyl ester type epoxy resins obtained from various carboxylic acids such as methyl hexahydroxyphthalic acid and dimer acid. In addition to this, epoxy resins obtained by direct hydrogenation of aromatic epoxy resins such as polyvalent aliphatic alcohol epoxy resins and hydrogenated bisphenol A type epoxy resins, 3,4-epoxycyclohexylmethyl-3 ', 4'-epoxycyclohexane carboxy Although the alicyclic epoxy resin etc. which are obtained by oxidizing double bonds, such as a rate, are mentioned, it is not limited to these. These epoxy resins may be used alone or in combination of two or more. Among these epoxy resins, it is more preferable to use a hydrogenated epoxy resin or an alicyclic epoxy resin in combination, because the light resistance is improved.

  The epoxy resin curing agent usable in the present invention is not particularly limited as long as it has a function of curing the epoxy resin, and (1) amine-based curing agent, (2) acid anhydride curing agent, (3) many Preferred curing agents such as phenol-based curing agents or (4) other curing agents can be preferably used, and examples thereof include the following.

  As an amine curing agent, bis (4-aminocyclohexyl) methane, bis (aminomethyl) cyclohexane, m-xylylenediamine, isophorone diamine, 3,9-bis (3-aminopropyl) -2,4,8, Aliphatic and alicyclic amines such as 10-tetraspiro [5,5] undecane, metaphenylene diamine, aromatic amines such as diaminodiphenylmethane, diaminodiphenyl sulfone, diaminoethylbenzene etc., benzyldimethylamine, 2,4,6- Tertiary amines such as tris (dimethylaminomethyl) phenol, 1,8-diazabicyclo- (5,4,0) -undecene-7, 1,5-azabicyclo- (4,3,0) -nonene-7 and the like And salts thereof.

  As an acid anhydride type curing agent, aromatic acid anhydrides such as phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyl anhydride Cycloaliphatic acid anhydrides such as hexahydrophthalic acid, methyl endomethylenetetrahydrophthalic anhydride, dodecenyl succinic anhydride, trialkyltetrahydrophthalic anhydride, etc., 3,3 ', 4,4'-diphenyl sulfone tetracarboxylic acid dianhydride And carboxylic acid dianhydrides such as 1,2,3,4-butanetetracarboxylic acid dianhydride.

  Examples of polyvalent phenol-based curing agents include hydroxybenzenes such as catechol, resorcin and hydroquinone, biphenols, binaphthols, bisphenols F, bisphenols A, bisphenols such as bisphenol S, phenols -Novolaks of divalent phenols such as lunovolaks, cresolyl novolaks, bisphenol A, etc., alkylphenol novolaks, aralkylphenol novolaks, triazine ring-containing phenol novolaks, biphenylaralkylphenols, trishydroxyphenylmethane Type novolaks, aralkyl naphthalene diols, dicyclopentadiene polyphenols and the like.

Other curing agents include amine trifluoride (BF ₃ ) complex compounds, aliphatic sulfonium salts, aromatic sulfonium salts, Bronsted acid salts such as iodonium salts and phosphonium salts, dicyandiamides, adipic acid dihydrazide and phthalic acid Organic acid hydrazides such as acid dihydrazide, resols, adipic acid, sebacic acid, terephthalic acid, trimellitic acid and polycarboxylic acids such as carboxyl group-containing polyester, etc. may be mentioned.

  These epoxy resin curing agents may be used alone or in combination of two or more.

In the epoxy resin composition of the present invention, the mixing ratio of the epoxy resin and the epoxy resin curing agent is 0.4 to 1.2 moles of active hydrogen group of the epoxy resin curing agent to 1 mole of epoxy group of the epoxy resin. The range is preferable, 0.5 to 1.1 mol is more preferable, and 0.7 to 1.0 mol is more preferable. For example, in the case of using a polyhydric phenol-based curing agent or an amine-based curing agent, an equimolar amount of active hydrogen group is blended with the epoxy group, and in the case of using an acid anhydride-based curing agent, 1 mole of epoxy group The acid anhydride group is blended in an amount of 0.5 to 1.2 moles, preferably 0.6 to 1.0 moles, per mole of the acid anhydride group. When the reaction proceeds in contact with imidazole compounds and the like, they may be blended at a predetermined mass ratio to the epoxy resin. The active hydrogen group in the present invention is a functional group having an active hydrogen reactive with an epoxy group, and specific examples thereof include an acid anhydride group, a carboxyl group, an amino group and a phenolic hydroxyl group. With respect to the active hydrogen group, it is calculated that 1 mole of carboxyl group or phenolic hydroxyl group is 1 mole, and that of amino group (NH ₂ ) is 2 moles.

  When the epoxy resin composition of the present invention is used for an optical element, the curing agent for epoxy resin is preferably an acid anhydride curing agent. The acid anhydride curing agent includes, for example, aromatic anhydrides such as phthalic anhydride, trimellitic anhydride and pyromellitic anhydride described above, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and hexahydrophthalic anhydride. And cycloaliphatic acid anhydrides such as methyl hexahydrophthalic anhydride, methyl endo ethylene tetrahydrophthalic anhydride, methyl endo ethylene hexahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride and the like. Among these, it is more preferable to use a hydrogenated cyclic aliphatic acid anhydride such as hexahydrophthalic anhydride or methylhexahydrophthalic anhydride because the light resistance of the epoxy resin composition of the present invention is improved. .

  A hardening accelerator can be used for the epoxy resin composition of this invention as needed. Specific examples of curing accelerators that can be used include imidazoles such as 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2- (dimethylaminomethyl) phenol, 1,8-diaza -Tertiary amines such as bicyclo (5,4,0) undecene-7, phosphines such as triphenylphosphine, tricyclohexylphosphine, triphenylphosphine triphenylborane, and metal compounds such as tin octylate . The curing accelerator may be used alone or in combination of two or more. 0.01-10 mass parts is preferable with respect to 100 mass parts of epoxy resins of (A) component, and, as for the usage ratio of a hardening accelerator, 0.02-5 mass parts is more preferable. By selectively using these curing accelerators, the curing temperature can be lowered and the curing time can be shortened.

  When using the epoxy resin composition of this invention for optical elements, it is preferable to mix | blend an antioxidant and to prevent the oxidative degradation at the time of a heating, and to set it as a hardened | cured material with few colorings. The antioxidants that can be used may be phenol type, sulfur type or phosphorus type antioxidants, each of which can be used alone, but used in combination of phenol type / sulfur type or phenol type / phosphorus type Is more preferred. An antioxidant is mix | blended 0.01-10 mass parts with respect to 100 mass parts of epoxy resin compositions.

  In the epoxy resin composition of the present invention, if necessary, (1) a UV absorber, (2) a curable resin other than an epoxy resin or a thermoplastic resin, (3) a filler or a filler, (4) a colorant Alternatively, various components such as a pigment, (5) a coupling agent, (6) a flame retardant, (7) other additives such as a thixotropic agent, and (8) an organic solvent can be added.

As the UV absorber, a UV absorber may be used to further improve the light resistance of the cured product. In the resin composition of the present invention, the amount of the ultraviolet absorber used is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the epoxy resin composition. . If the content is too low, the effect of blending the ultraviolet light absorber can not be obtained sufficiently. As UV absorbers, UV absorbers for general plastics can be used,
It may be used alone or in combination of two or more.

  A curable resin other than an epoxy resin and a thermoplastic resin are blended for the purpose of imparting flexibility and toughness to a cured product, and maintaining good processability at the time of coating a resin composition. In the epoxy resin composition of the present invention, the compounding amount in the case of using these curable resin and thermoplastic resin is blended within a range not to impair the transparency of the epoxy composition of the present invention, and 100 mass of the epoxy resin composition 5-30 mass parts is preferable with respect to a part, and 15-20 mass parts is more preferable. When the content is too small, the effect of blending these resins can not be obtained sufficiently, and when the content is too large, the viscosity of the composition tends to increase, and the moisture resistance of the cured product tends to decrease. It is in. The curable resin and the thermoplastic resin other than the epoxy resin may be used alone or in combination of two or more.

  The filler or the filler is blended for the purpose of preventing moisture permeation of the cured product, preventing peeling during film processing, and the like. The compounding amount in the case of using a filler or a filler is mix | blended in the range which does not impair the transparency of an epoxy composition, 5-80 mass parts is preferable with respect to 100 mass parts of epoxy resin compositions, and 15-60 mass. Part is more preferable, and 30 to 50 parts by mass is further preferable. If the content is too small, the effect of blending can not be obtained sufficiently, and if the content is too large, the viscosity of the composition tends to increase and the strength of the cured product tends to be reduced to become brittle. From the viewpoint of maintaining the low moisture permeability and high adhesion of the cured resin, the filler or filler is preferably talc or mica, more preferably talc. Other examples include fibrous fillers such as glass fibers, polyester fibers, pulp fibers, aramid fibers, synthetic fibers and ceramic fibers, and organic fillers such as fine particle rubber and thermoplastic elastomer. The fillers may be used alone or in combination of two or more.

  Examples of coloring agents or pigments include coloring pigments such as titanium dioxide, molybdenum red, bitumen, ultramarine blue, cadmium yellow, cadmium red or organic pigments, and extender pigments such as silica powder, quartz powder, talc, calcium carbonate or barium sulfate Can be mentioned.

  The coupling agent is blended for the purpose of improving the adhesion and improving the moisture permeation resistance of the cured product. 0.01-10 mass parts is preferable with respect to 100 mass parts of epoxy resin compositions, and, as for the compounding quantity in the case of using a coupling agent, 0.1-5 mass parts is more preferable, 0.5-5 mass Parts are more preferred. Outside this range, the effect of improving the adhesion and the like by the addition of the coupling agent can not be obtained. As a coupling agent, a silane coupling agent is preferable, and an epoxy type silane coupling agent is more preferable. It is possible to use one kind or two or more kinds in combination.

  As a flame retardant, an antimony trioxide, a brominated compound, or a phosphorus compound etc. are mentioned, for example.

  As other additives, if necessary, a thixotropic agent, a stress reducing agent, a lubricant, a flow control agent, and an anti-sagging agent can be blended.

  The organic solvent is blended for the purpose of viscosity adjustment and the like. The organic solvent is not particularly limited, but includes amides, ethers, ketones, alcohols, aromatic hydrocarbons, esters, and aprotic polar solvents. These solvents may be used alone or in combination of two or more.

  The epoxy resin composition of the present invention is suitable as a resin composition used for an optical element such as an LED, and is excellent as an optical element sealing agent or a raw material thereof. An optical element substrate can be obtained from the epoxy resin composition of the present invention. In addition, the epoxy resin composition of the present invention can be cured by heating and curing.

  The glass transition temperature (Tg) of the cured product of the present invention is preferably in the range of 100 ° C to 160 ° C. When the cured product has a low Tg, the cured product is likely to be colored due to the heat generation of the light source when used for an optical element. The higher the Tg, the better the heat resistance. However, in the epoxy resin composition of the present invention, the viscosity of the composition tends to be high, and there is a concern that the flowability at the time of molding may be insufficient to cause molding failure. In addition, a correlation is generally recognized between the Tg of the cured product and the softening point of the epoxy resin. FIG. 2 shows the correlation between the softening point of the fluorene skeleton-containing epoxy resin obtained by the production method of the present invention and the Tg of the cured product. Here, the horizontal axis indicates the softening point of the fluorene skeleton-containing epoxy resin, and the vertical axis indicates the Tg of the cured product. From FIG. 2, in order to make the Tg of the cured product in the range of 100 ° C. to 160 ° C., the softening point of the fluorene skeleton-containing epoxy resin needs to be 100 to 150 ° C., more preferably 110 to 140 ° C. . When the softening point is low, a curing agent giving a good composition lowers the Tg of the cured product, and when used for an optical element, the heat generation of the light source tends to cause coloring of the cured product. In addition, if the softening point is high, it can not be taken out from the reaction vessel at a high temperature unless the temperature is increased by 50 ° C. or more above the softening point at the time of epoxy resin synthesis. Become. In addition, even when a solvent is added at the time of synthesis to form a solution, the temperature needs to be higher than the softening point in order to obtain sufficient drying, and coloring of the fluorene skeleton-containing epoxy resin is likely to occur.

  The cured product of the present invention may have a YI value of 30 or less, preferably 20 or less after heat treatment under conditions of 180 ° C. for 100 hours as a flat plate with a thickness of 1 mm.

  The present invention will be specifically described based on examples and comparative examples, but the scope of the present invention is not limited to these examples. In the following synthesis examples, examples and comparative examples, "part" indicates a mass part, and "%" indicates a mass%. Furthermore, the following test methods were used in the present invention.

(1) Content of Phenolic Compound (b) (HPLC Measurement Conditions): Agilent 1100 series (manufactured by HewLett Packerd) equipped with Cadenza CD-C18 CD006 (manufactured by Intact Co., Ltd.) as a separation column was used. The column temperature was 40 ° C., the eluent was water and acetonitrile, and the flow rate was 1 mL / min. Moreover, the detection was performed by an absorbance detector, and quantification was performed in area% based on the absorption at a wavelength of 272 nm.
(2) Phenolic hydroxyl group equivalent: Tetrahydrofuran containing 4% of methanol was added to the sample and completely dissolved, then 10% tetrabutylammonium hydroxide was added, and the wavelength was between 400 nm and 250 nm using an ultraviolet-visible spectrophotometer. The absorbance of the compound was measured, and the phenolic hydroxyl group was determined as the number of grams of sample per equivalent of hydroxyl group.
(3) Epoxy equivalent: Measured according to JIS K-7236.
(4) Softening point: Measured by the ring and ball method according to JIS K-7234.
(5) Hue: Hazen unit color number was measured according to JIS K-0071-1. The sample used the resin varnish of 50% of the non volatile matter which melt | dissolved resin in tetrahydrofuran.

(6) Glass transition temperature (Tg): Measured at a temperature rising rate of 20 ° C. to 10 ° C./min using a differential scanning calorimeter (EXTER DSC 6200 manufactured by SII).
(7) Hardened product hue: A test piece with a thickness of 1 mm was used to measure the YI value using a colorimetric color difference meter (TC-1500 MC-88, manufactured by Tokyo Denshoku Co., Ltd.). The test pieces after storage for a predetermined time in an oven maintaining a constant temperature at a predetermined temperature were also measured, with the measurement value of the test piece before being subjected to heat history as a blank. The smaller the value, the better the hue. Moreover, the smaller the numerical value of the test piece after the heat history is applied, the better the heat yellowing resistance.
(8) Moisture resistance: The water absorption was measured according to JIS K-6911. A disk-shaped cured product having a thickness of 1 mm and a diameter of 50 mm was used as a test piece. The smaller the value is, the better the moisture resistance is.
(9) Moldability: The above-mentioned moisture resistance test piece was visually confirmed, and a case where there was no "chipping" or "cracking" was taken as ○, and the others were made as x.

Synthesis example 1
9,9-Bis (4-hydroxyphenyl) fluorene was synthesized according to the example of Patent Document 6 to obtain BPFL (1). The resulting BPFL (1) was purified by recrystallization. Specifically, methanol is added and warmed to dissolve, and then a solid is precipitated while cooling at room temperature with stirring or around the container with cold water as needed, and then the obtained solid is Filter and dry to obtain BPFL (2). The BPFL (2) was recrystallized again to obtain BPFL (3).

  The HPLC chart of BPFL (2) is shown in FIG. The peak derived from the trinuclear component is (A), and the peak derived from the tetranuclear component is (B). At this time, the trinuclear component and the tetranuclear component contain isomeric structures. The content of the compound (b) is the sum of the trinuclear component and the tetranuclear component, and the peak (A) area derived from the trinuclear component and the peak (B) area derived from the tetranuclear component The result is obtained by dividing the sum of the areas by the sum of the areas of all the peaks and expressing the area%. In addition, when 2 or more types of phenol compounds were used, content of the phenol compound (b) in each phenol compound was calculated | required, respectively, and it calculated | required by calculation by the weighted average.

  The content of the phenol compound (b) (total of trinuclear component and tetranuclear component) determined by HPLC is 2.3 area% for BPFL (1), 0.92 area% for BPFL (2), BPFL It was 0.18 area% in (3).

  Repeated recrystallization and analysis by HPLC in order to obtain higher purity BPFL, it takes 4 times in total for the content of phenol compound (a1) to be 0.01 area% or less. , It became BPFL (4) which performed five recrystallizations that became 0 area% (not detected).

Explanation of abbreviations used in Examples and Comparative Examples.
(Epoxy resin)
・ YD-128; diglycidyl ether of 2,2-bis (4-hydroxyphenyl) propane, epoxy equivalent 185 g / eq, viscosity 12800 mPs · s / 25 ° C., manufactured by Nippon Steel Sumikin Chemical Co., Ltd., Epototh YD-128
ESF-300; diglycidyl ether of 9,9-bis (4-hydroxyphenyl) -9H-fluorene, epoxy equivalent 250 g / eq, softening point 87 ° C., Nippon Steel Sumikin Chemical Co., Ltd. ZX-1658 GS; 1,4 -Diglycidyl ether of cyclohexanedimethanol, epoxy equivalent 134 g / eq, viscosity 37 mPs · s / 25 ° C, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., Epototh ZX-1658GS
· 2021 P; 3 ', 4'- epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, epoxy equivalent 133 g / eq, viscosity 240 mPa · s / 25 ° C, manufactured by Daicel Chemical Industries, Ltd., Celoxide 2021 P

(Phenolic compound)
-BPFL (1) to (4);-BPA described above; 2,2-bis (4-hydroxyphenyl) propane, equivalent weight of hydroxyl group = 114 g / eq, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.

(catalyst)
TPP-BB; n-butyltriphenylphosphonium bromide, manufactured by Hokuko Chemical Co., Ltd. TPP; triphenylphosphine, manufactured by Hokuko Chemical Co., Ltd.

(Hardening agent)
・ HH: Hexahydrophthalic anhydride, Shin Nippon Rika Co., Ltd., Rikasid HH
MH: 4-Methylhexahydrophthalic anhydride, Shin Nippon Rika Co., Ltd., RIKASHID MH

(Hardening accelerator)
・ PX-4ET; organic phosphonium salt compound, manufactured by Nippon Chemical Industrial Co., Ltd., Hishikorin PX-4ET

(Antioxidant)
HCA: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, manufactured by Sanko Co., Ltd.

Example 1
In a reaction apparatus equipped with a stirrer, thermometer, nitrogen blowing tube and cooling tube, 370 parts of YD-128 as bifunctional epoxy resin, 121 parts of BPFL (2) as phenol compound, and 121 parts of BPFL (3) are prepared. The temperature was raised to 130 ° C., 0.242 parts of TPP-BB as a catalyst was charged, and the temperature was further raised to 165 ° C., and stirring was performed for 4 hours to obtain an epoxy resin 1.

Examples 2 to 8
Epoxy resins 2 to 8 were obtained in the same manner as in Example 1 using the apparatus used in Example 1 and according to the formulations in Table 1. The epoxy resin obtained in Example 1 is referred to as epoxy resin 1, and so forth.

Comparative Examples 1 to 7
Epoxy resins 9 to 15 were obtained in the same manner as in Example 1 using the apparatus used in Example 1 and according to the composition in Table 2. The epoxy resin obtained in Comparative Example 1 is referred to as the epoxy resin 9, and hereinafter, Comparative Example No. + 8 is referred to as the epoxy resin No. In addition, in Comparative Example 3 and Comparative Example 5, since the viscosity became high at the end of the reaction and could not be taken out, the temperature was raised to 200 ° C. and taken out.

  The properties of the epoxy resins 1 to 8 obtained in Examples 1 to 8 are shown in Table 3, and the properties of the epoxy resins 9 to 15 obtained in Comparative Examples 1 to 7 are shown in Table 4. The content (area%) of the phenolic compound (b) in the raw material phenolic compound is calculated by weighted average of the content of the phenolic compound (b) of all the used phenolic compounds, and the BPFL skeleton content (mol%) The content was calculated from the total molar amount of the epoxy resin having a BPFL skeleton and the phenolic compound with respect to the total molar amount of the starting epoxy resin and the phenolic compound.

注）（−）は溶融粘度が高すぎて試験片の作成ができず測定不可を示す。

Note) (-) indicates that the melt viscosity is too high to make a test piece and measurement is impossible.

Example 9
After mixing 100 parts of the epoxy resin 1 obtained in Example 1 as an epoxy resin and 16.2 parts of RIKACIDH MH as a curing agent until uniform at a temperature of 100 ° C., PX-4ET as a curing accelerator The resulting mixture was stirred and dissolved to obtain an epoxy resin composition. The composition was degassed under vacuum and then poured into molds and cured in an oven at 120 ° C. for 3 hours and then at 150 ° C. for 10 hours to obtain test specimens.

Examples 10 to 17
Test pieces were prepared and evaluated in the same manner as in Example 9 using 100 parts of the epoxy resins 2 to 8 obtained in Examples 2 to 8 as epoxy resins and the curing agent shown in Table 5. .
Table 5 shows the types of epoxy resin and curing agent, and the amount of curing agent used. Table 6 shows the results of evaluating the Tg, the cured product color, the water resistance, and the moldability of the cured product.

Comparative Examples 8 to 15
Test pieces were prepared and evaluated in the same manner as in Example 9 using 100 parts of the resins 9 to 15 obtained in Comparative Examples 1 to 7 as epoxy resins and the curing agent shown in Table 7.
Table 7 shows the types of epoxy resin and curing agent and the amount of curing agent used. The evaluation results are shown in Table 8.

注）（−）は溶融粘度が高すぎて試験片の作成ができず測定不可を示す。

Note) (-) indicates that the melt viscosity is too high to make a test piece and measurement is impossible.

  As is clear from Table 6, all of the cured products of the epoxy resin composition using Examples 9 to 17, that is, 100% by mass of the fluorene skeleton-containing epoxy resin produced by the production method of the present invention as the epoxy resin component It has well-balanced characteristics of the hue, heat-resistant yellowing, hygroscopicity and moldability of the cured product required for optical element applications. On the other hand, as is clear from Table 8, the cured products of Comparative Examples 8 to 15 do not satisfy all the respective characteristics except Comparative Example 14. That is, most of the comparative examples are inferior in heat-resistant yellowing resistance (the hue at 180 ° C. × 100 hr is more than 20), and the comparative examples 10 and 12 have too high melt viscosity to make even test pieces impossible. Only Comparative Example 14 satisfies the physical properties, but this is an example in which the phenol compound (b) is removed by repeating the washing step five times, and it is based on a process which is difficult to use. In the examples, the required properties of the cured product are satisfied without the need for such excess quality (high purity).

Examples 18 to 20, Comparative Example 16
An epoxy resin, a curing agent, a curing accelerator, and an antioxidant are blended according to the recipe of Table 9 and mixed until they become uniform at a temperature of 100 ° C. Then, a curing accelerator is added, stirred, and dissolved The epoxy resin composition was obtained. The composition was degassed under reduced pressure, poured into a mold, and cured in an oven at 120 ° C. for 3 hours and then at 150 ° C. for 10 hours to obtain a cured product. The physical properties of this cured product are shown in Table 9.

  As is clear from Table 9, the cured product of the epoxy resin composition using the fluorene skeleton-containing epoxy resin produced by the production method of the present invention as the epoxy resin component has the hue and heat resistance of the cured product required for optical element applications It has yellowing, hygroscopicity and moldability characteristics in a well-balanced manner.

Claims (13)

Obtained by reacting a phenol compound containing a fluorene skeleton-containing phenol compound represented by the following general formula (1) with a bifunctional epoxy resin, having an epoxy equivalent of 700 to 1500 g / eq, and a fluorene skeleton content of 30 to A method for producing a fluorene skeleton-containing epoxy resin having 70 mol%, wherein the fluorene skeleton-containing phenolic compound contains 50% by mass or more of a compound (a) having n in the general formula (1), and n is 1 or 2 Of the compound (b), which is 0.01% to 1.0% by area as measured by high performance liquid chromatography, in the presence of a catalyst which promotes the addition reaction of the phenolic hydroxyl group and the epoxy group, A process for producing a fluorene skeleton-containing epoxy resin, which comprises reacting a hydroxyl group and an epoxy group of a bifunctional epoxy resin Law.

(Wherein each R independently represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and may contain a cyclic structure).   The method for producing a fluorene skeleton-containing epoxy resin according to claim 1, wherein the fluorene skeleton-containing phenol compound contains 90% by mass or more of 9,9-bis (4-hydroxyphenyl) fluorene.   The method for producing a fluorene skeleton-containing epoxy resin according to claim 1 or 2, wherein the bifunctional epoxy resin is a bisphenol A type epoxy resin.   The method for producing a fluorene skeleton-containing epoxy resin according to claim 1 or 2, wherein at least a part of the bifunctional epoxy resin has a fluorene skeleton and an epoxy equivalent is 230 to 500 g / eq.   The method for producing a fluorene skeleton-containing epoxy resin according to any one of claims 1 to 4, wherein the catalyst is a phosphine or a quaternary phosphonium salt.   The fluorene skeleton containing epoxy resin manufactured by the manufacturing method of any one of Claims 1-5.   An epoxy resin composition comprising the epoxy resin (A) and the epoxy resin curing agent (B) as essential components, which comprises the fluorene skeleton-containing epoxy resin according to claim 6 as the component (A). An epoxy resin composition characterized by the above.   The epoxy resin composition according to claim 7, wherein the component (B) is an acid anhydride.   The epoxy resin composition for optical elements which consists of an epoxy resin composition of Claim 7 or 8.   The sealing agent for optical elements obtained using the epoxy resin composition for optical elements of Claim 9.   The board | substrate for optical elements obtained using the epoxy resin composition for optical elements of Claim 9.   A cured product obtained by curing the epoxy resin composition according to claim 7 or 8.     The cured product according to claim 12, wherein the cured product has a thickness of 1 mm and a YI value of 20 or less after heat treatment under an environment of 180 ° C for 100 hours.

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