JP7709846B2 - Divinylbenzylfluorene compound and its manufacturing method, curable resin composition obtained therefrom, cured product of curable resin, optical article, and imaging device - Google Patents

Description

The present invention relates to a divinylbenzylfluorene compound that is excellent in processability and has a high refractive index and a method for producing the same, as well as a curable resin composition obtained from the compound, a cured resin product obtained by curing the compound, and an optical article and an imaging device that include the same.

In recent years, resin materials have been widely used for optical components such as optical overcoats, hard coats, anti-reflection films, eyeglass lenses, optical fibers, optical waveguides, holograms, and optical elements of various cameras because of their excellent processability and productivity. In addition, there is a demand for resin materials with a high refractive index in view of the trend toward smaller and thinner optical components or the adjustment of anti-reflection properties.
In particular, in recent years, there has been a growing demand for miniaturization, high resistance, and high brightness in liquid crystal display elements used in displays for liquid crystal televisions, notebook computers, portable game consoles, mobile phones, etc., and to achieve this, it is essential to increase the refractive index of prism sheets. In order to manufacture molding materials such as prism sheets, optical materials with high refractive index and low viscosity are required. However, conventional resin materials have the problem that when the refractive index is increased, the viscosity increases and even crystallization occurs.
Optical glass or optical transparent resin is used as a material for optical elements used in the optical systems of various cameras such as cameras, film-integrated cameras, and video cameras. Optical glass is excellent in heat resistance, transparency, dimensional stability, chemical resistance, etc., and many types of materials with various refractive indices and Abbe numbers exist, but it has problems such as high material costs, poor moldability, and low productivity. In particular, processing it into aspherical lenses used for aberration correction requires extremely advanced technology and high costs, which is a major obstacle to practical use.
In contrast to the above optical glass, optical lenses made of optical transparent resins have the advantages of being excellent in moldability, allowing for mass production, and being easy to manufacture aspherical lenses, and are currently used as camera lenses. Examples of optical transparent resins with high refractive index include polycarbonate, polyester, and episulfide compounds.

In recent years, compounds having a fluorene skeleton have been proposed as optical materials with a high refractive index in order to provide materials with a high refractive index. For example, bifunctional compounds in which an acryloyl group is bonded to a fluorene skeleton via an alkyleneoxy group (Patent Document 1, Patent Document 2, Patent Document 3), and compounds obtained by reacting a diglycidyl ether containing a fluorene skeleton with acrylic acid or methacrylic acid (Patent Document 4) are known, and these have attracted attention as having high heat resistance and a high refractive index. However, the bulky and rigid fluorene derivatives described above are generally solid or high-viscosity liquids of several tens of Pa·s or more at room temperature, so when used as a molding material such as a prism sheet, it is necessary to dilute them with a large amount of reactive diluents to obtain an appropriate viscosity, which results in a problem of a low refractive index of the resulting cured product.

Meanwhile, Patent Document 5 discloses a curable polyvinylbenzyl compound obtained by reacting a fluorene compound with a vinylbenzyl halide in the presence of an alkali. However, the vinylbenzyl units used in the divinylbenzylfluorene disclosed in this patent publication have a 50/50 weight % m-/p-isomer ratio mixture, which results in high crystallinity and low solubility in reactive diluents. Therefore, when attempting to use this compound in optical components that require transparency, there is a problem in that haze occurs and only molded products with low transparency are obtained.

Japanese Patent Application Publication No. 04-325508 JP 2007-84815 A WO2005/033061 Japanese Patent Application Publication No. 03-106918 WO2002/083610

The object of the present invention is therefore to provide a novel divinylbenzylfluorene compound with improved properties such as transparency and solubility, a method for producing this compound, and a curable resin composition, a cured cured product, an optical article, and an imaging device obtained from the compound.

Compounds that have multiple vinyl groups in the molecule tend to undergo intermolecular crosslinking reactions by polymerization. By utilizing this property, it is possible to add such compounds to a polymerization system and copolymerize them to form crosslinked bodies, thereby making the polymer insoluble or imparting functionality to it.
For example, divinylbenzene is an example of a compound having multiple vinyl groups in the molecule, and can be used as an ion exchange resin by adding a small amount of this to a styrene polymerization system to copolymerize it and then introducing a functional group such as a sulfonic acid group. In addition, it can be used as a crosslinking agent for styrene-based resins such as synthetic rubber, ABS resin, MBS resin, and unsaturated polyester resin, and as a modifier for polyethylene. As another example, by copolymerizing it with a transparent resin system such as (meth)acrylate, it may be possible to impart functionality such as strength and heat resistance to optical materials such as optical waveguides and optical lenses.

Specifically, the divinylbenzylfluorene compound disclosed in Patent Document 5 is known, but the m-/p-isomer ratio of the vinylbenzyl units used is a 50/50 weight % mixture, resulting in a high melting point of 145°C, and no divinylbenzylfluorene compound with a melting point of 130°C or less has been reported.

In this situation, the inventors conducted extensive research to achieve the above-mentioned object, and as a result, synthesized a divinylbenzylfluorene compound having an m-/p-isomer ratio of the vinylbenzyl unit of 0.6 to 1.0, and discovered that the compound had a melting point of 130°C or less and improved solubility in reactive diluents. Furthermore, the inventors unexpectedly discovered that a molded and cured product of the divinylbenzylfluorene compound having an m-/p-isomer ratio of the vinylbenzyl unit within a specific range had sufficiently improved optical properties such as total light transmittance and haze, and had a high refractive index, thereby completing the present invention.

That is, the present invention provides a divinylbenzylfluorene compound represented by the following general formula (1):

(In the formula, R ¹ independently represents one substituent selected from a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group, a thioalkoxy group, an aryl group having 6 to 30 carbon atoms, and a heteroaryl group having 3 to 30 carbon atoms, and x independently represents an integer of 0 to 4.)
The divinylbenzylfluorene compound is characterized in that, when measured using a differential scanning calorimeter at a heating rate of 10° C./min, it has a melting point of 130° C. or less or has no melting point at all.
The divinylbenzylfluorene compound of the present invention preferably has a ratio of p-isomer/(m-isomer+p-isomer) of vinylbenzyl groups of 0.6 to 1.0.

The present invention provides a method for producing a divinylbenzylfluorene compound, which comprises reacting one or more fluorene compounds represented by the following general formula (2) with a vinylbenzyl halide having a p-isomer/(m-isomer+p-isomer) ratio of 0.6 to 1.0 in the presence of an alkali:

(In the formula, R ¹ and x have the same meanings as those in general formula (1)).
In the method for producing a divinylbenzylfluorene compound of the present invention, it is preferable that the vinylbenzyl halide is at least one selected from the group consisting of m-vinylbenzyl chloride and p-vinylbenzyl chloride, and the ratio of p-vinylbenzyl chloride/(p-vinylbenzyl chloride+m-vinylbenzyl chloride) is 0.6 to 1.0.

The present invention relates to a curable resin composition comprising the above divinylbenzylfluorene compound and a monomer, oligomer and/or polymer copolymerizable with the divinylbenzylfluorene compound.
Furthermore, the present invention relates to a cured resin product obtained by curing the above-mentioned curable resin composition, an optical article including the cured curable resin product, and an imaging device incorporating the optical article.

The divinylbenzylfluorene compound of the present invention has improved solubility, and its molded and cured products have improved optical properties such as transmittance, haze, and refractive index, making it useful as an optical material or various modifiers.

The divinylbenzylfluorene compound, the curable resin composition, and the components contained therein of the present invention are described in detail below.

The divinylbenzylfluorene compound of the present invention is a divinylbenzylfluorene compound represented by the above general formula (1) having two polymerizable unsaturated bonds, and is characterized in that when measured using a differential scanning calorimeter at a heating rate of 10°C/min, it has a melting point of 130°C or less or has no melting point.

The divinylbenzylfluorene compound of the present invention must have a melting point of 130°C or less or no melting point, but a melting point of 125°C or less is more preferable, and a melting point of 120°C or less is most preferable. If the melting point of the divinylbenzylfluorene compound exceeds 130°C, the crystallinity will increase and the melting point will overlap with the thermal polymerization initiation temperature of the vinyl group, resulting in poor processability and reduced transparency of the molded, cured product.

In the above general formula (1), R ¹ independently represents one substituent selected from a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group, a thioalkoxy group, an aryl group having 6 to 30 carbon atoms, and a heteroaryl group having 3 to 30 carbon atoms, and is preferably an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 30 carbon atoms, or a heteroaryl group having 3 to 30 carbon atoms. More preferably, it is an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a heteroaryl group having 6 to 12 carbon atoms, and even more preferably an alkyl group having 1 to 3 carbon atoms.
x is the number of substitutions and independently represents an integer of 0 to 4, preferably an integer of 0 to 2, and more preferably 0.

In the divinylbenzylfluorene compound, the ratio of p-isomer/(m-isomer+p-isomer) of the vinylbenzyl group is preferably 0.6 to 1.0, more preferably 0.8 or more, and even more preferably 0.9 or more. Ideally, the ratio is 1.0, but in practice, the upper limit is 0.995, more preferably 0.99, and even more preferably 0.98.
From the viewpoint of thermal stability, it is preferable that the o-isomer is not contained, and even if it is contained, the amount of the o-isomer is less than 5 mol % based on all vinylbenzyl groups. In other words, the total amount of the p-isomer and m-isomer is 95 mol % or more, more preferably 99 mol % or more, of all vinylbenzyl groups.

Here, the structure of the p-isomer of the divinylbenzylfluorene compound is exemplified by the following general formula (3).

The structure of the m-isomer of the divinylbenzylfluorene compound is exemplified by the following general formula (3).

The fluorene compound used in the synthesis of the divinylbenzylfluorene compound of the present invention includes unsubstituted fluorene, or a fluorene compound in which the aromatic ring portion is substituted with an alkyl group, an alkoxy group, a thioalkoxy group, an aryl group, or a heteroaryl group, as shown in the above general formula (2). These may be used alone or in combination of two or more compounds. Of these, the fluorene compound that is most suitable for industrial implementation because of its ease of availability is unsubstituted fluorene.

Next, examples of vinylbenzyl halides used in the synthesis of the divinylbenzyl fluorene compound of the present invention include m-vinylbenzyl chloride, p-vinylbenzyl chloride, m-vinylbenzyl bromide, p-vinylbenzyl bromide, etc., and these may be used alone or in combination of two or more compounds. Of the above, m-vinylbenzyl chloride and p-vinylbenzyl chloride are easily available and are most preferred for industrial implementation.

Furthermore, when vinylbenzyl halide is used to synthesize the divinylbenzylfluorene compound of the present invention, a novel divinylbenzylfluorene compound with improved properties such as transparency, solubility, and processability can be obtained by setting the ratio of p-isomer/(m-isomer+p-isomer) to 0.6 to 1.0.

For vinylbenzyl halide as a raw material, the lower limit of the ratio of p-isomer/(m-isomer+p-isomer) is preferably 0.7, more preferably 0.8, and even more preferably 0.9. On the other hand, from the viewpoint of the price or ease of production of vinylbenzyl halide, the upper limit is preferably 0.995, more preferably 0.99, and even more preferably 0.98. If the ratio of p-isomer/(m-isomer+p-isomer) is less than 0.6, the crystallinity and melting point of the resulting divinylbenzylfluorene compound will increase, its solubility in reactive diluents will deteriorate, and the temperature will overlap with the thermal polymerization initiation temperature of the vinyl group, resulting in a decrease in the transparency of the molded and cured product.

The divinylbenzylfluorene compound of the present invention can be synthesized by reacting one or more of the fluorenes or fluorene compounds represented by the general formula (2) with vinylbenzyl halide in the presence of an alkali. If necessary, a dihalomethyl compound having 2 to 20 carbon atoms may be added.
This reaction can be carried out according to the conditions of known vinylbenzylation reactions. The vinylbenzylation reaction can be carried out, for example, by the method described in L. J. Mathias et al., J. Polym. Sci., Part B;, 2869 (1998), J. Polym. Sci., Part A;, 587 (1997), or C. J. Kelly et al., J. Chem. Res. (S), 446 (1997).

Reaction solvents include aprotic polar solvents such as dimethylformamide, dimethylsulfoxide, dimethylacetamide, N-methylpyrrolidone, dioxane, acetonitrile, tetrahydrofuran, ethylene glycol dimethyl ether, 1,3-dimethoxypropane, 1,2-dimethoxypropane, tetramethylene sulfone, hexamethylphosphoamide, methyl ethyl ketone, methyl isobutyl ketone, acetone, and cyclohexanone, as well as aromatic solvents such as benzene, toluene, and xylene, and mixtures thereof. From these, a solvent type that will make the reaction system uniform can be selected according to the raw material type and reaction conditions.

The alkali used in this reaction includes alkoxides, hydrides, and hydroxides of alkali metals or alkaline earth metals, such as sodium methoxide, sodium ethoxide, sodium hydride, sodium borohydride, potassium hydride, and potassium hydroxide. The type of alkali can be selected depending on whether the reaction system is non-aqueous or aqueous. The proportion of alkali used is preferably about 1.1 to 3.0 equivalents per equivalent of hydrogen at the 9th position of the raw material fluorene compound. If the amount is less than 1 equivalent, the reaction rate will be significantly slowed, the reaction will not proceed completely, and raw materials will remain, which will have an undesirable effect on the cured physical properties. Furthermore, if more than 3 equivalents are used, a large amount of removal solvent such as washing water will be used to remove the remaining alkali, which is not economical.

A phase transfer catalyst can be used in the reaction. Examples of the phase transfer catalyst include various onium salts, for example, quaternary ammonium compounds such as tetra-n-butylammonium bromide, tetra-n-butylammonium hydrogen sulfate, benzyltrimethylammonium chloride, and tricaprylmethylammonium chloride, quaternary phosphonium compounds such as tetra-n-butylphosphonium bromide, benzyltriphenylphosphonium chloride, tetraphenylphosphonium chloride, and tetraphenylphosphonium bromide, tertiary sulfonium compounds such as benzyltetramethylenesulfonium bromide, and mixtures thereof.
The amount of these phase transfer catalysts used cannot be generally defined because the catalytic effect varies depending on the catalyst type or reaction temperature, but generally, about 0.01 to 0.2 equivalents are used per equivalent of hydrogen at the 9-position of the raw fluorene compound.

The reaction temperature and reaction time vary depending on the type of raw material compounds used and the reaction conditions, so cannot be generally specified, but a temperature of 30 to 100°C and a time of 0.5 to 20 hours will suffice. At reaction temperatures above 100°C, undesirable reactions such as thermal polymerization often occur at the same time, while at temperatures below 30°C, although the reaction will proceed, it is not economical because it takes a long time.

In the present invention, since an unsaturated halide having high thermal polymerizability such as vinylbenzyl halide is used, a thermal polymerization inhibitor may be added to the reaction system as necessary. Examples of such inhibitors include t-butylcatechol, 2,4-di-t-butylphenol, 2-t-butylphenol, 2-t-butyl-4-nitrophenol, 2,4-dinitrophenol, hydroquinone, methylhydroquinone, hydroquinone monomethyl ether, t-butylhydroquinone, resorcinol, pyrogallol, phenothiazine, and copper salts. Furthermore, the use of an appropriate amount of air is also effective in inhibiting polymerization.
The amount of these thermal polymerization inhibitors to be used cannot be generally defined because the effect differs depending on the type of thermal polymerization inhibitor, but is approximately several ppm to 2000 ppm based on the curable vinylbenzyl compound.

The divinylbenzylfluorene compound of the present invention can be blended with a copolymerizable monomer, oligomer and/or polymer to form a curable resin composition with improved moldability, within the scope of not impairing the effects of the present invention. Specific examples include vinyl ester resins, unsaturated polyester resins, diallyl phthalate resins, maleimide resins, polyphenol polycyanate resins, and other oligomers or polymers having polymerizable unsaturated groups, monomers and prepolymers such as triallyl isocyanurate and triallyl cyanurate, styrene, vinyl toluene, divinyl benzene, vinyl benzyl ether compounds, monofunctional or polyfunctional (meth)acrylic acid derivative compounds, etc.

When a copolymerizable monomer, oligomer and/or polymer is used, the amount used cannot be generally determined because it depends on the type, compatibility with the divinylbenzylfluorene compound of the present invention, and the use of the cured product. For example, the amount is 10 to 300 parts by weight, preferably 20 to 200 parts by weight, and more preferably 50 to 150 parts by weight, per 100 parts by weight of the divinylbenzylfluorene compound of the present invention. If the amount exceeds 300 parts by weight, separation or leaching from the divinylbenzyl compound of the present invention is likely to occur.

The divinylbenzyl compound and the curable resin composition of the present invention can be cured by using known methods such as heat, light, and electron beams. It is also useful to use a curing agent to lower the curing temperature and accelerate the curing reaction. The cured product can be suitably used for optical components in the optical and electronic equipment fields, such as optical lenses.

When a curing agent is used, examples of the curing agent include benzoyl peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, t-butylcumyl peroxide, methyl ethyl ketone peroxide, dicumyl peroxide, and t-butyl perbenzoate, which can be used depending on the application.
The amount used varies depending on the type and concentration of the unsaturated group in the divinylbenzyl compound or the curable resin composition of the present invention, the type of the curing agent used, the half-life temperature, the required stability, and the like, but is generally 0.1 to 10 parts by weight per 100 parts by weight of the divinylbenzyl fluorene compound or the curable resin composition of the present invention.

In the case of photocuring, a photopolymerization initiator is preferably used. Since the divinylbenzylfluorene compound of the present invention has a vinyl group (ethylenically unsaturated group) which is radically polymerizable as a polymerizable compound, a photoradical polymerization initiator can be used.
Examples of the photopolymerization initiator include benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, and benzoin isobutyl ether; acetophenones such as acetophenone, 2,2-diethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 2-hydroxy-2-methyl-phenylpropan-1-one, diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one; 2-ethylanthraquinone, 2-tertiary butyric acid anthraquinone, and the like. anthraquinones such as 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, etc.; ketals such as acetophenone dimethyl ketal, benzyl dimethyl ketal, etc.; benzophenones such as benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 4,4'-bismethylaminobenzophenone, etc.; phosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc.

These can be used alone or as a mixture of two or more kinds, and can also be used in combination with accelerators such as tertiary amines such as triethanolamine and methyldiethanolamine, and benzoic acid derivatives such as N,N-dimethylaminobenzoic acid ethyl ester and N,N-dimethylaminobenzoic acid isoamyl ester.

Examples of commercially available photopolymerization initiators include Irgacure 184, 369, 651, 500, 819, 907, 784, 2959, CGI-1700, -1750, -1850, CG24-61, Darocur 116, 1173 (all manufactured by Chiba Specialty Chemicals Co., Ltd.), Lucirin TPO, LR8893, LR8970 (all manufactured by BASF), and Ubecryl P36 (manufactured by UCB).
The amount of the compound used is, for example, 0.1 to 10 parts by weight based on 100 parts by weight of the divinylbenzylfluorene compound or the curable resin composition of the present invention.

In addition, known curing accelerators such as manganese naphthenate, lead naphthenate, zinc naphthenate, cobalt naphthenate, zinc octylate, dimethylaniline, and phenylmorpholine can also be used.

The curing temperature varies depending on the type of polymerizable unsaturated group, the type and amount of curing agent used, etc. and cannot be generally specified, but is 20 to 250° C., preferably 50 to 250° C. If the curing temperature is less than 20° C., curing may be insufficient.
To adjust the curing conditions, a known curing retarder such as hydroquinone, benzoquinone, or copper salts may be added.

In addition, antioxidants, release agents, photosensitizers, organic solvents, silane coupling agents, leveling agents, defoamers, antistatic agents, as well as ultraviolet absorbers, light stabilizers, various inorganic and organic fillers, antifungal agents, antibacterial agents, etc. may be added to the curable resin composition of the present invention as necessary to impart the desired functionality.

The curable resin composition of the present invention can be obtained by mixing the components in any order. The curable resin composition of the present invention is stable over time.

The curable resin composition of the present invention can be cured by irradiating it with active energy rays such as ultraviolet rays. Specific examples of light sources used when irradiating it with active energy rays for curing include xenon lamps, carbon arcs, germicidal lamps, fluorescent lamps for ultraviolet rays, high-pressure mercury lamps for copying, medium-pressure mercury lamps, high-pressure mercury lamps, extra-high-pressure mercury lamps, electrodeless lamps, metal halide lamps, and electron beams from scanning and curtain-type electron beam accelerating paths. When the curable resin composition of the present invention is cured by irradiating it with ultraviolet rays, the amount of ultraviolet rays required for curing may be about 300 to 20,000 mJ/cm ^2. In order to sufficiently cure the resin composition, it is desirable to irradiate it with active energy rays such as ultraviolet rays in an inert gas atmosphere such as nitrogen gas.

The curable resin composition of the present invention can be used for cast products such as plastic lenses. A method for producing a plastic lens using the resin composition of the present invention includes preparing a mold using a gasket made of polyvinyl chloride, ethylene-vinyl acetate copolymer, or the like, and two glass molds of the desired shape, injecting the resin composition of the present invention into the mold, curing the resin composition by irradiating it with active energy rays such as ultraviolet rays, and peeling the cured product from the mold.

As a method for applying the curable resin composition of the present invention as a resin composition for a prism lens sheet to a film-like substrate, various methods known in the industry can be used. Specific methods include, for example, applying the resin composition to a mold having a prism lens shape on the surface, providing a layer of the resin composition, pressing a colorless and transparent film-like substrate (e.g., polyvinyl chloride, polystyrene, polycarbonate, poly(meth)acrylate, polyester, polyethylene terephthalate, etc.) onto the resin composition layer while preventing air bubbles from being trapped, and then irradiating ultraviolet light from the film-like substrate side in this state using a high-pressure mercury lamp to cure the layer of the resin composition, and then peeling off the film-like substrate on which the prism lens-shaped resin layer has been formed from the mold.

The refractive index of the cured product of the resin composition for optical materials of the present invention obtained by irradiating it with active energy rays such as ultraviolet rays is preferably 1.59 or more at 25°C, more preferably 1.60 or more at 25°C, and particularly preferably 1.62 or more at 25°C. In particular, when producing a prism lens sheet using the curable resin composition for optical materials of the present invention, if the refractive index of the cured product is less than 1.59 at 25°C, a problem may arise in that sufficient front brightness cannot be ensured.

The Abbe number of the cured product of the present invention is preferably 40.0 or less, and more preferably 30.0 or less. If the Abbe number of the cured product exceeds 40.0, it is not preferable because the chromatic aberration is large and color bleeding occurs when the imaging element is thinned.

The water absorption rate of the cured product of the present invention is preferably 1.0 wt% or less, more preferably 0.5 wt% or less. It is particularly preferably 0.35 wt% or less, and most preferably 0.2 wt% or less. If the water absorption rate of the cured product exceeds 1.0 wt%, the refractive index of the material changes as the product absorbs water, which tends to increase chromatic aberration and cause color bleeding.

The cured resin obtained by molding and curing the curable resin composition of the present invention can be suitably used as an optical article. Among optical articles, it is particularly useful as optical lenses such as prism lens sheets, Fresnel lenses, lenticular lenses, eyeglass lenses, and aspherical lenses. Such optical lenses are suitably incorporated into imaging devices. The curable resin composition or cured resin of the present invention can also be used for optical articles for optoelectronics such as optical disks, optical fibers, and optical waveguides, multilayer substrates, prepregs, metal foils with resins, printing inks, paints, clear coat agents, gloss varnishes, and the like.

An image pickup device incorporating an optical article, which is one embodiment of the present invention, will be exemplified below.
The optical article of the present invention can be suitably used in various devices equipped with a lens module for an imaging device, such as a camera, a computer, a word processor, a printer, a copy machine, a fax machine, a telephone, a mobile device (a mobile phone, a smartphone, a game device, a personal digital assistant (PDA) such as a tablet), an automotive device, an architectural device, an astronomical device, etc. In particular, it is useful as a lens module for an imaging device such as a small-sized lens for an imaging device (or a high-precision lens), for example, a small camera (for example, a camera for a mobile phone (a camera for a so-called camera-equipped mobile phone), an in-vehicle camera module, etc.).
Small, thin imaging devices are mounted on portable electronic terminals such as mobile phones, smartphones, game devices, tablets, etc. Such imaging devices include a lens module having a light receiving element and a lens for forming a subject image on the light receiving element.
The lens module can be used in the imaging device disclosed in, for example, JP-A-2010-266664, JP-A-2003-046825, JP-A-2006-313185, JP-A-2003-032525, WO2011/074531, and the like.
The optical lens of the present invention can be suitably used as a lens or a lens portion of the imaging device exemplified above.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Note that all parts in each example are by weight unless otherwise specified, and each physical property was evaluated by the method shown below.

1) Molecular weight and molecular weight distribution Measurement of molecular weight and molecular weight distribution was performed using GPC (HLC-8220GPC, manufactured by Tosoh Corporation) with analytical columns of two TSKgel MultiporeH _XL -M and one TSKgel G1000H _XL , manufactured by Tosoh Corporation, and one TSKguardcolumn MP(XL), using tetrahydrofuran (THF) as a solvent, a flow rate of 1.0 ml/min, a column temperature of 38° C., and a calibration curve based on monodisperse polystyrene.

2) Structure of divinylbenzylfluorene compound The structure was determined by ¹³ C-NMR and ¹ H-NMR analysis using a JNM-LA600 nuclear magnetic resonance spectrometer manufactured by JEOL. Chloroform- _d1 was used as the solvent, and the resonance line of tetramethylsilane was used as the internal standard. The mass of the divinylbenzylfluorene compound was measured by FD-MS analysis using a Hitachi M-80B mass spectrometer.

3) Measurement of glass transition temperature (Tg), melting point (Tm), and softening temperature The divinylbenzylfluorene compound was uniformly applied to a glass substrate so that the thickness after drying was 20 μm, and then heated to 90° C. for 30 minutes using a hot plate to dry. The resin film on the obtained glass substrate was set together with the glass substrate in a TMA (thermomechanical analyzer) measuring device, and heated to 220° C. at a heating rate of 10° C./min under a nitrogen stream, and further heated at 220° C. for 20 minutes to remove the remaining solvent. After the glass substrate was allowed to cool to room temperature, an analytical probe was brought into contact with the sample in the TMA measuring device, and the measurement was performed by scanning from 30° C. to 360° C. at a heating rate of 10° C./min under a nitrogen stream, and the softening temperature was obtained by the tangential method. If the probe did not penetrate the resin film due to the heat resistance of the sample and did not show a probe penetration amount smaller than the film thickness, the maximum temperature at which the probe did not penetrate was displayed as an index of the softening temperature.
The melting point of the divinylbenzylfluorene compound was measured by scanning from −20° C. to 320° C. at a temperature increase rate of 10° C./min under a nitrogen stream using a DSC (differential scanning calorimeter).

4) Measurement of weight loss at 300°C, heat discoloration resistance, and solder heat resistance test The weight loss at 300°C and heat discoloration resistance of the divinylbenzylfluorene compound were measured by setting the sample in a TGA (thermobalance) measuring device and scanning it from 30°C to 320°C at a heating rate of 10°C/min under a nitrogen gas flow to determine the weight loss at 300°C. The discoloration of the sample after the measurement was visually confirmed and the heat discoloration resistance was evaluated by classifying the sample into A: no heat discoloration, B: pale yellow, C: brown, and D: black.
Furthermore, in the solder heat resistance test of the divinylbenzylfluorene compound, a hardened test piece sheet of 2.0 mm thickness and 10 mm square was immersed in a lead-free solder bath at 280°C for 30 seconds, and then the test piece was removed and visually inspected for changes in the shape of the test piece after immersion. The solder heat resistance was evaluated by classifying the results as follows: A: no change, B: warping, C: deformation/blistering.

5) Measurement of Solvent Resistance The solvent resistance of the divinylbenzylfluorene compound was measured by immersing a sample plate cured by vacuum press molding in toluene at room temperature for 10 minutes, and visually checking the change in the sample after immersion. The solvent resistance was evaluated by classifying the result as follows: A: no change, B: swelling, C: deformation/blistering.

6) Measurement of Haze and Total Light Transmittance Flat test specimens having a thickness of 2 mm or 200 μm were prepared, and the haze (turbidity) and total light transmittance were measured using a spectrophotometer (SZ-Σ90, manufactured by Nippon Denshoku Industries Co., Ltd.).

7) Refractive index and Abbe number A test piece of 4 cm x 0.8 cm was prepared, and the refractive index and Abbe number were measured using a multi-wavelength Abbe refractometer (manufactured by Atago Co., Ltd., "Multi-wavelength Abbe refractometer DR-M2"). A methylene iodide solution with a higher refractive index than the sample was used as the intermediate liquid, and the refractive index and Abbe number were measured using an interference filter with a D line of 589 nm.

8) Spectral transmittance Using a parallel plate having a thickness of 1.0 mm as a test piece, the spectral transmittance at a wavelength of 400 nm was measured using a spectrophotometer (Konica Minolta, Inc., "CM-3600d") The measurement was performed before a heat resistance test in which post-curing was performed at 190°C for 60 minutes, and after a heat resistance test in an air oven at 260°C for 8 minutes.

9) Water absorption rate A flat plate-shaped sample with a thickness of 1 mm, width of 30 mm, and length of 30 mm was prepared, dried under vacuum at 100°C for 2 hours, cooled to room temperature, and then left to stand in a desiccator until a constant weight was reached. The sample mass at a constant weight was taken as the initial value (m0). Next, the sample was left in a thermohygrostat at 85°C and a relative humidity of 85% for 500 hours, after which the mass (md) was measured, and the water absorption rate was measured from the initial value and the change in mass after immersion using the following formula.
(md-m0) x 100/m0 = water absorption rate (%)

Example 1 Synthesis of divinylbenzylfluorene compound (A-1) 203.54g of fluorene (purity: 98%, 1.20mol), 800g of toluene, 18.09g of tetra-n-butylammonium bromide (purity: 98%, 0.055mol), 2.78g of hydroquinone (purity: 99%, 0.025mol), and further, an aqueous solution of NaOH in which 174.42g of NaOH (purity: 97%, 4.23mol) was dissolved in 320ml of water was charged, and the temperature was raised to 60°C while stirring to make a uniform solution. 449.83g of vinylbenzyl chloride CMS-14 (m-/p-isomer: 5/95% by weight mixture) manufactured by AGC Seimi Chemical Co., Ltd. (purity: 95%, 2.8mol) was added dropwise to this solution over 20 minutes, and then reacted at 60-61°C for 8 hours. To the resulting green reaction product, 200 ml of toluene was added, the solution was neutralized with 2N hydrochloric acid, and then washed three times with distilled water. The toluene was removed under reduced pressure, and the resulting pale yellow viscous solid was recrystallized from fresh methanol to obtain 349.44 g (yield 72.8%) of a white solid having a melting point of 119° C. as determined by DSC. This is designated as Compound A-1.
The structure of compound A-1 was confirmed by ¹ H-NMR spectrum, ¹³ C-NMR spectrum, IR spectrum, and FD-MS measurement. From the FD-MS measurement result, Mw was 400, and from these measurement results, it was confirmed that the product was divinylbenzylfluorene (in general formula 1, R ¹ is a hydrogen atom), and from the NMR spectrum, the vinylbenzyl unit was a 5/95% mixture of m-/p-isomers. When compound A-1 was dissolved in toluene at room temperature at a concentration of 10 wt %, a transparent solution was obtained, and it was confirmed that the compound had good solubility.

Compound A-1 was placed in a mold via a 2.0 mm spacer, and cured in a vacuum at 200° C. for 1 hour using a vacuum press molding machine.
The resulting cured sheet was cut out and subjected to measurement of optical properties, tensile properties and thermal analysis. The results were: total light transmittance: 91.3%, haze: 0.30, refractive index: 1.652, Abbe number: 23.6, linear expansion coefficient: 83 ppm/°C, water absorption: 0.15%, solvent resistance: A, and solder heat resistance: A.
Furthermore, the results of the TMA measurement showed that the softening temperature was 300° C. or higher. The results of the TGA measurement showed that the weight loss at 300° C. was 0.3 wt %, and the heat discoloration resistance was A.

Comparative Example 1 Synthesis of Divinylbenzylfluorene Compound (B-1) 203.54g of fluorene (purity: 98%, 1.20mol), 800g of toluene, 18.09g of tetra-n-butylammonium bromide (purity: 98%, 0.055mol), 2.78g of hydroquinone (purity: 99%, 0.025mol), and further, 174.42g of NaOH (purity: 97%, 4.23mol) was dissolved in 320ml of water to prepare an aqueous NaOH solution, which was heated to 60°C while stirring to obtain a uniform solution. 445.14g of vinylbenzyl chloride VBC (m-/p-isomer: 57/43% by weight mixture) manufactured by Dow Chemical Company (purity: 96%, 2.8mol) was added dropwise to this solution over 20 minutes, and then reacted at 60-61°C for 8 hours. 200 ml of toluene was added to the obtained green reaction product, the solution was neutralized with 2N hydrochloric acid, and then washed three times with distilled water. After removing the toluene under reduced pressure, the obtained pale yellow viscous solid was recrystallized from fresh toluene to obtain 324.48 g (yield 67.6%) of a white solid having a melting point of 144° C. as measured by DSC. This is designated as Compound B-1.
The structure of compound B-1 was confirmed by ¹ H-NMR spectrum, ¹³ C-NMR spectrum, IR spectrum, and FD-MS measurement. From the FD-MS measurement result, Mw was 400, and from these measurement results, the product was divinylbenzylfluorene (in general formula 1, R ¹ is a hydrogen atom), and the vinylbenzyl unit was a mixture of m-/p-isomers: 57/43%. When compound B-1 was dissolved in toluene at room temperature at a concentration of 10 wt%, a cloudy solution was obtained, and it was confirmed that the solubility was insufficient.

Compound B-1 was placed in a mold via a 2.0 mm spacer, and cured in a vacuum at 200° C. for 1 hour using a vacuum press molding machine.
The resulting cured sheet was cut out, and the optical properties and tensile properties were measured, and a thermal analysis was performed.
The results were: total light transmittance: 89.6%, haze: 3.64, refractive index: 1.648, Abbe number: 23.9, linear expansion coefficient: 87 ppm/° C., water absorption: 0.16%, solvent resistance: A, and solder heat resistance: A.
Furthermore, the results of the TMA measurement showed that the softening temperature was 300° C. or higher. The results of the TGA measurement showed that the weight loss at 300° C. was 0.4 wt %, and the heat discoloration resistance was A.

Comparative Example 2 Synthesis of divinylbenzylfluorene compound (C-1) 203.54g of fluorene (purity: 98%, 1.20mol), 800g of toluene, 18.09g of tetra-n-butylammonium bromide (purity: 98%, 0.055mol), 2.78g of hydroquinone (purity: 99%, 0.025mol), and further, 174.42g of NaOH (purity: 97%, 4.23mol) was dissolved in 320ml of water, and the mixture was heated to 60°C while stirring to obtain a uniform solution. 449.83g of vinylbenzyl chloride CMS-P (m-/p-isomer: 50/50% by weight mixture) (purity 95%, 2.8mol) manufactured by Seimi Chemical Co., Ltd. was added dropwise to this solution over 20 minutes, and then reacted at 60-61°C for 8 hours. To the resulting green reaction product, 200 ml of toluene was added, the solution was neutralized with 2N hydrochloric acid, and then washed three times with distilled water. The toluene was removed under reduced pressure, and the resulting pale yellow viscous solid was recrystallized from fresh toluene to obtain 313.92 g (yield 65.4%) of a white solid having a melting point of 145° C. as determined by DSC. This is designated as Compound C-1.
The structure of compound C-1 was confirmed by ¹ H-NMR spectrum, ¹³ C-NMR spectrum, IR spectrum, and FD-MS measurement. From the FD-MS measurement result, Mw was 400, and from these measurement results, the product was divinylbenzylfluorene (in general formula 1, R ¹ is a hydrogen atom), and the vinylbenzyl unit was a 50/50% mixture of m-/p-isomers. When compound C-1 was dissolved in toluene at room temperature at a concentration of 10 wt %, a cloudy solution was obtained, and it was confirmed that the solubility was insufficient.

Compound C-1 was placed in a mold via a 2.0 mm spacer, and cured in a vacuum at 200° C. for 1 hour using a vacuum press molding machine.
The resulting cured sheet was cut out and subjected to measurement of optical properties, tensile properties and thermal analysis. The results were: total light transmittance: 89.4%, haze: 4.14, refractive index: 1.649, Abbe number: 23.9, linear expansion coefficient: 88 ppm/°C, water absorption: 0.18%, solvent resistance: A, solder heat resistance: A.
Furthermore, the results of the TMA measurement showed that the softening temperature was 300° C. or higher. The results of the TGA measurement showed that the weight loss at 300° C. was 0.42 wt %, and the heat discoloration resistance was A.

Example 2 and Comparative Examples 3 to 4
Using the compounds A-1, B-1, and C-1 obtained in Example 1 and Comparative Examples 1 and 2, each component was mixed in the ratio shown in Table 1 to obtain a curable resin composition. Next, this curable resin composition was cured by various test methods and performance evaluation was performed. The performance evaluation results are also shown in Table 1.

Copolymerizable monomers:
NK Ester A-LEN-10; 2-(o-phenylphenoxy)ethyl acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
Hardener:
Perbutyl P: α,α'-bis(t-butylperoxy)diisopropylbenzene (manufactured by NOF Corporation)
Photoinitiator:
Irgacure 184: 1-hydroxy-cyclohexyl-phenyl-ketone (manufactured by Ciba Specialty Chemicals)
Stabilizers:
Adeka STAB AO-60: Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (ADEKA Corporation)

The divinylbenzylfluorene compound and the curable resin composition of the present invention, as well as the resin cured product obtained by molding and curing the curable resin composition, are excellent as optical materials. They are particularly useful as materials for optical plastic lenses such as prism lens sheets, Fresnel lenses, lenticular lenses, eyeglass lenses, and aspherical lenses, and such lenses are advantageously used in imaging devices. In addition, the curable resin composition or the resin cured product of the present invention can also be used in optoelectronic applications such as optical disks, optical fibers, and optical waveguides, as well as multilayer substrates, prepregs, resin-attached metal foils, printing inks, paints, clear coat agents, gloss varnishes, and the like.
The modified vinyl aromatic copolymer of the present invention is also useful as a dielectric material, insulating material, heat-resistant material, structural material, adhesive, sealant, paint, coating agent, sealing material, printing ink, paint, clear coat agent, gloss varnish, dispersant, etc. in the fields of the electric/electronic industry, the space/aircraft industry, the building/construction industry, etc. It can also be used as a modifier for modifying the properties such as heat resistance, dielectric properties, adhesiveness/adhesion, and optical properties of a thermoplastic resin or a curable resin composition.

Claims (7)

A divinylbenzylfluorene compound represented by the following general formula (1), in which the ratio of p-isomer/(m-isomer+p-isomer) of the vinylbenzyl group is 0.6 to 0.98,
(In the formula, R ¹ independently represents a substituent of an alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 30 carbon atoms, and x independently represents an integer of 0 to 2.)
A divinylbenzylfluorene compound having a melting point of 130° C. or less or no melting point when measured at a heating rate of 10° C./min using a differential scanning calorimeter. The method for producing a divinylbenzylfluorene compound according to claim 1, characterized in that one or more fluorene compounds represented by the following general formula (2) are reacted with a vinylbenzyl halide having a p-isomer/(m-isomer+p-isomer) ratio of 0.6 to 0.98 in the presence of an alkali:
(In the formula, R ¹ and x have the same meanings as in general formula (1).) A curable resin composition comprising the divinylbenzylfluorene compound according to claim 1 and a monomer, oligomer and/or polymer copolymerizable with the divinylbenzylfluorene compound. A cured resin product obtained by curing the curable resin composition according to claim 3 . An optical article comprising the cured product of the curable resin according to claim 4 . The optical article according to claim 5 , which is an optical lens. An imaging device incorporating the optical article according to claim 5 .