JP7806557B2 - Curable composition, cured product - Google Patents

Description

The present invention relates to a curable composition and a cured product of the curable composition.

Surface mounting technology is advancing rapidly, and with the widespread use of small, lightweight, and high-performance electronic devices, particularly mobile phones and laptops, electronic components are also rapidly becoming smaller. Cameras are one example of this trend, and camera lenses are also required to be smaller. These lenses are required to have a high refractive index, a low Abbe number, high transparency, high heat resistance, and low adhesion of foreign matter. For example, camera modules for mobile phones typically use multiple lenses with different refractive indices, and fluorene-based polyester resins are primarily used as materials for high-refractive-index lenses. However, because fluorene-based polyester resins are thermoplastic resins, they have the disadvantage of being easily melted by heat during solder reflow (poor heat resistance and reflow resistance).

A known method for improving reflow resistance is to introduce a crosslinked structure into a resin material using a (meth)acrylate having a fluorene structure. This method has a high refractive index and excellent transparency, and is therefore considered useful for various plastic lenses (Patent Documents 1 to 3).

JP 2008-94987 A JP 2011-126991 A JP 2012-82387 A

However, the methods of Patent Documents 1 to 3 have insufficient reflow resistance, so vaporized components from the lens can become foreign matter and contaminate the lens itself and its surrounding components. In applications where camera lenses are becoming smaller and greater visibility than ever before is required, materials that cause the adhesion of such foreign matter cannot be said to be suitable for use.

The present invention has been made to overcome the above-mentioned problems, and has an object to provide a curable composition that has a high refractive index, high transparency, and reflow resistance, and that, when cured, causes little adhesion of foreign matter to the cured product itself and surrounding components, and a cured product thereof.

The present invention has the following aspects.
[1] A curable composition comprising a (meth)acrylate having a fluorene structure and a polymerization initiator, the temperature at which a mass loss of 10% occurs when the composition is heated from 30°C at a heating rate of 10°C/min in an air atmosphere in simultaneous thermogravimetry and differential thermal analysis is 180°C or higher.
[2] The curable composition according to [1], wherein the (meth)acrylate having a fluorene structure is a compound represented by the following formula (1):
In formula (1), R ¹ , R ² , R ³ , and R ⁴ each independently represent a hydrogen atom or a methyl group;
m represents an integer of 0 to 5; n represents an integer of 0 to 5;
[3] The curable composition according to [1] or [2], containing a (meth)acrylate having a biphenyl or phenoxyphenyl structure.
[4] The curable composition according to any one of [1] to [3], containing a trifunctional or higher polyfunctional (meth)acrylate.
[5] The curable composition according to any one of [1] to [4], which contains an antioxidant.
[6] A cured product of the curable composition according to any one of [1] to [5].
[7] A lens made of the cured product according to [6].

According to the present invention, it is possible to provide a curable composition that has reflow resistance and that, when cured, forms a cured product that has little adhesion of foreign matter to the cured product itself and surrounding components, and a cured product that has reflow resistance and has little adhesion of foreign matter to the cured product itself and surrounding components.

Hereinafter, embodiments of the present invention will be described in detail.
In the present invention, "(meth)acrylate" is a general term for acrylate or methacrylate.
The numerical range indicated by "to" means that the numerical values before and after it are included as the lower and upper limits.

<Curable composition>
The curable composition of the present invention contains a (meth)acrylate having a fluorene structure and a polymerization initiator, the temperature at which the mass loss when heated from 30°C at a heating rate of 10°C/min in an air atmosphere is 180°C or higher, as measured by simultaneous thermogravimetry and differential thermal analysis.

(Meth)acrylate having a fluorene structure is a material for increasing the refractive index,
The compound has a (meth)acrylate moiety to impart reflow resistance and is cured by a radical reaction. Conventionally known (meth)acrylates having a fluorene structure can be used. Among these, the compound of the following formula (1) is preferred because it increases the refractive index and glass transition temperature of the cured product.

In formula (1), R ¹ , R ² , R ³ , and R ⁴ each independently represent a hydrogen atom or a methyl group;
m represents an integer of 0 to 5, and n represents an integer of 0 to 5. Among these, ^R1 and ^R4 are preferably hydrogen atoms, as this increases the refractive index and reactivity of the cured product. From the viewpoint of moldability, m and n are each preferably 1 or 2, and more preferably 1. In addition, from the viewpoint of moldability, it is more preferable that ^R2 and ^R3 are also hydrogen atoms.

In addition, it is also a preferred embodiment that the curable composition contains a (meth)acrylate having a biphenyl or phenoxyphenyl structure, from the viewpoint of increasing the refractive index and improving the solubility and moldability of the (meth)acrylate having a fluorene structure in the curable composition.

As the (meth)acrylate having a biphenyl or phenoxyphenyl structure, a conventionally known compound can be used. Examples of the (meth)acrylate having a biphenyl structure include ortho-phenylphenoxyethyl (meth)acrylate, meta-phenylphenoxyethyl (meth)acrylate, para-phenylphenoxyethyl (meth)acrylate, ortho-phenylphenoxypropyl (meth)acrylate, meta-phenylphenoxypropyl (meth)acrylate, and para-phenylphenoxypropyl (meth)acrylate.
meth)acrylate, ortho-phenylphenoxybutyl (meth)acrylate, meth-
Phenylphenoxyalkyl (meth)acrylates such as phenylphenoxybutyl (meth)acrylate and para-phenylphenoxybutyl (meth)acrylate; phenylphenoxyalkoxyalkyl (meth)acrylates such as ortho-phenylphenoxyethoxyethyl (meth)acrylate, meta-phenylphenoxyethoxyethyl (meth)acrylate and para-phenylphenoxyethoxyethyl (meth)acrylate; ortho-biphenylmethyl (meth)acrylate and meta-biphenylmethyl (meth)acrylate;
Biphenyl alkyl (meth)acrylates such as para-biphenylmethyl (meth)acrylate, ortho-biphenylethyl (meth)acrylate, meta-biphenylethyl (meth)acrylate, para-biphenylethyl (meth)acrylate, ortho-biphenylpropyl (meth)acrylate, meta-biphenylpropyl (meth)acrylate, para-biphenylpropyl (meth)acrylate, ortho-biphenylbutyl (meth)acrylate, meta-biphenylbutyl (meth)acrylate, and para-biphenylbutyl (meth)acrylate
Examples of suitable isomers include acrylates. Among these, phenylphenoxy alkyl (meth)acrylates, phenylphenoxy alkoxy alkyl (meth)acrylates, and biphenyl alkyl (meth)acrylates are preferred from the viewpoint of high refractive index, and in consideration of solubility and moldability, phenylphenoxy alkyl (meth)acrylates and phenylphenoxy alkoxy alkyl (meth)acrylates are more preferred, and phenylphenoxy ethyl (meth)acrylate is even more preferred. Among positional isomers, the ortho position is preferred. Furthermore, in consideration of reactivity, acrylates are preferred over methacrylates. These compounds may be used alone or in combination of two or more.

Examples of the (meth)acrylate having a phenoxyphenyl structure include ortho-phenoxyphenylmethyl (meth)acrylate and meta-phenoxyphenylmethyl (meth)acrylate.
Acrylate, para-phenoxyphenylmethyl (meth)acrylate, ortho-phenoxyphenylethyl (meth)acrylate, meta-phenoxyphenylethyl (meth)acrylate, para-phenoxyphenylethyl (meth)acrylate, ortho-phenoxyphenylpropyl (meth)acrylate, meta-phenoxyphenylpropyl (meth)
Acrylate, para-phenoxyphenylpropyl (meth)acrylate, ortho-phenoxyphenylbutyl (meth)acrylate, meta-phenoxyphenylbutyl (meth)
Acrylate, para-phenoxyphenyl butyl (meth)acrylate, ortho-phenoxyphenyl pentyl (meth)acrylate, meta-phenoxyphenyl pentyl (meth)acrylate, para-phenoxyphenyl pentyl (meth)acrylate, ortho-phenoxyphenyl hexyl (meth)acrylate, meta-phenoxyphenyl hexyl (
phenoxyphenyl alkyl (meth)acrylates such as para-phenoxyphenylhexyl (meth)acrylate, ortho-phenoxyphenyloxymethyl (meth)acrylate, meta-phenoxyphenyloxymethyl (meth)acrylate, para-phenoxyphenyloxymethyl (meth)acrylate, ortho-phenoxyphenyloxyethyl (meth)acrylate, meta-phenoxyphenyloxyethyl (meth)acrylate, para-phenoxyphenyloxyethyl (meth)acrylate, ortho-phenoxyphenyloxypropyl (meth)acrylate, meta-phenoxyphenyl Phenoxyphenyloxyalkyl (meth)acrylates such as ortho-phenoxyphenyloxypropyl (meth)acrylate, para-phenoxyphenyloxypropyl (meth)acrylate, ortho-phenoxyphenyloxybutyl (meth)acrylate, meta-phenoxyphenyloxybutyl (meth)acrylate, and para-phenoxyphenyloxybutyl (meth)acrylate; ortho-phenoxyphenylmethoxyethyl (meth)acrylate, meta-phenoxyphenylmethoxyethyl (meth)acrylate, para-phenoxyphenylmethoxyethyl (meth)acrylate, and ortho-phenoxyphenylethoxyethyl (meth)acrylate;
Acrylate, meta-phenoxyphenylethoxyethyl (meth)acrylate, para-
Examples include phenoxyphenyl alkoxyalkyl (meth)acrylates such as phenoxyphenyl ethoxyethyl (meth)acrylate. Among these, phenoxyphenyl alkyl (meth)acrylates are preferred from the viewpoint of solubility and moldability, and phenoxyphenyl methyl (meth)acrylate and phenoxyphenyl ethyl (meth)acrylate are particularly preferred from the viewpoint of a high refractive index, with phenoxyphenyl methyl (meth)acrylate being even more preferred. Among positional isomers, the meta position is preferred. Furthermore, in consideration of reactivity, acrylates are preferred over methacrylates. These compounds may be used alone or in combination of two or more. In consideration of moldability and yellowing at high temperatures, (meth)acrylates having a phenoxyphenyl structure are more preferred.

The curable composition may also contain other active energy ray-curable compounds than those mentioned above. For example, aromatic ring-containing (meth)acrylates such as benzyl (meth)acrylate, phenyl (meth)acrylate, and phenoxyalkyl (meth)acrylate are preferred because of their high refractive index. By including these compounds, it is possible to achieve a viscosity suitable for moldability. Furthermore, benzyl methacrylate and phenyl methacrylate are more preferred in terms of the glass transition temperature of the cured product.

Furthermore, from the viewpoint of moldability, a mixture of one or more monofunctional (meth)acrylates, difunctional (meth)acrylates, and trifunctional or higher polyfunctional (meth)acrylates excluding (meth)acrylates having a fluorene structure, a biphenyl structure, or a phenoxyphenyl structure;
Commercially available curable resin materials, or materials containing other components added thereto, can be used as long as the object of this embodiment is not impaired. In consideration of the strength of the cured product, and in order to make the cured product less likely to deform even at high temperatures, a high glass transition point is desirable, and to achieve this, it is preferable to contain a trifunctional or higher polyfunctional (meth)acrylate.

Monofunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate,
Acrylate, butyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, morpholyl (meth)
acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (
(meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycidyl (meth)
Acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, tricyclodecane (meth)acrylate, polyethylene glycol mono(meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, isobornyl (meth)acrylate, allyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, adamantyl (meth)acrylate,
(Meth)acrylic acid and the like.

The difunctional polyfunctional (meth)acrylate is not particularly limited, but examples thereof include 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate,
acrylate, alkanediol di(meth)acrylates such as 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and tricyclodecanedimethylol di(meth)acrylate; bisphenol-modified di(meth)acrylates such as bisphenol A ethylene oxide-modified di(meth)acrylate and bisphenol F ethylene oxide-modified di(meth)acrylate; polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, urethane di(meth)acrylate, and epoxy di(meth)acrylate.

The trifunctional or higher polyfunctional (meth)acrylate is not particularly limited, but may be:
For example, ethylene oxides such as dipentaerythritol hexa(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethylene oxide-modified dipentaerythritol hexa(meth)acrylate, ethylene oxide-modified pentaerythritol tetra(meth)acrylate, and ethylene oxide-modified pentaerythritol tri(meth)acrylate Modified (meth)acrylates, isocyanuric acid-modified tri(meth)acrylates such as ethylene oxide-modified isocyanurate and ε-caprolactone-modified tris(acryloxyethyl)isocyanurate, urethane (meth)acrylates such as pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer,
Among these, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol tetra(meth)acrylate, and pentaerythritol tri(meth)acrylate are more preferred from the viewpoints of increasing the glass transition temperature of the cured product, and of curability, strength, and reflow resistance.

Furthermore, active energy ray-curable compounds other than (meth)acrylates can also be used in the curable composition. Examples include vinyl compounds such as styrene, vinyl halide, and vinyl acetate, and diene compounds such as vinylidene halide, 1,3-butadiene, isoprene, and chloroprene. Furthermore, to prevent discoloration during high-temperature processes, it is preferable that the composition does not contain sulfur or nitrogen elements, especially sulfur. In addition, from the perspective of uniformity of the components when formed into a cured product, it is preferable that the composition does not contain siloxane compounds or inorganic components. If the components are not uniform, visibility will be reduced and the product will become brittle.

Furthermore, the curable composition was measured by simultaneous thermogravimetry and differential thermal analysis in an air atmosphere at a temperature rise rate of 10
The polymerization initiator contains a temperature of 180°C or higher at which the mass loss when heated from 30°C at a rate of °C/min is 10%. When a polymerization initiator within the above range is used, the unreacted remaining compound is less likely to volatilize and become foreign matter during high-temperature processes such as reflow treatment, resulting in a cured product with good visibility. Furthermore, the polymerization initiator is more preferably a photopolymerization initiator (a compound having an active group that generates radicals when irradiated with active energy rays).

As a polymerization initiator having a temperature of 180°C or higher at which the mass loss is 10% when heated from 30°C at a temperature increase rate of 10°C/min in an air atmosphere in simultaneous thermogravimetry and differential thermal analysis, a conventionally known polymerization initiator can be used. For example, 2-hydroxy-1-{4-[
4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide. Among these, from the viewpoint of foreign matter, the molecular weight of the radical generated is 95
It is more preferable that the polymerization initiator is not more than 70, and even more preferable that the polymerization initiator is not more than 70. In terms of chemical structure, taking into consideration reactivity, an intramolecular cleavage type polymerization initiator is preferred, and among these, an α-hydroxyketone type polymerization initiator is particularly preferred. Furthermore, from the viewpoint of preventing yellowing, a polymerization initiator that does not contain a nitrogen element or a sulfur element, particularly a sulfur element, is preferred. These polymerization initiators may be used alone or in combination of two or more types.

The polymerization initiator has a temperature of 180°C or higher when the mass loss is 10%, preferably 200°C or higher, more preferably 220°C or higher, and even more preferably 240°C or higher.
° C. or higher, most preferably 260 ° C. or higher. There is no particular upper limit, but 450 ° C. or higher is preferred.
By setting the content within the above range, generation of foreign matter can be suppressed and a cured product with good visibility can be obtained.

Furthermore, it is also a preferred embodiment that the curable composition contains an antioxidant to prevent yellowing during high-temperature processes such as reflow.

Examples of antioxidants include 2,6-di-t-butylphenol, 2,6-di-t-
Butyl-p-cresol, n-octadecyl-3-(3',5'-di-t-butyl-4'
-hydroxyphenyl)propionate, tetrakis-[methylene-3-(3',5'-
phenolic antioxidants such as triphenyl phosphite, tris(isodecyl phosphite), tris(tridecyl phosphite), tris(2,4-
phosphorus-based antioxidants such as di-t-butylphenyl) phosphite;
Thiodipropionate, ditridecyl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate,
Examples of antioxidants include sulfur-based antioxidants such as pentaerythritol tetrakis(β-laurylthiopropionate). Among these, phenol-based antioxidants and sulfur-based antioxidants are preferred from the viewpoint of solubility in the curable composition, and phenol-based antioxidants are more preferred from the viewpoint of preventing yellowing of the cured product. Among these, antioxidants having a molecular weight of 540
Preferably, the tetrakis-[methylene-3-
(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane is the most preferred. These antioxidants may be used alone or in combination of two or more.

The curable composition may contain components other than the above-mentioned compounds as long as the effects of the present invention are not impaired. Examples of other components include curing aids, various resins, rubbers,
Examples of additives include particles, antistatic agents, plasticizers, ultraviolet absorbers, infrared absorbers, light stabilizers, leveling agents, antifoaming agents, thixotropic agents, polymerization inhibitors, release agents, fillers, fluorescent materials, pigments, and dyes.

The proportion of the (meth)acrylate having a fluorene structure relative to the total mass of all structural units constituting the curable composition is preferably in the range of 15 to 95 mass%, more preferably 25 to 85 mass%, and even more preferably 40 to 75 mass%. By setting it in this range, the refractive index can be increased.

The proportion of the (meth)acrylate having a biphenyl or phenoxyphenyl structure relative to the total mass of all structural units constituting the curable composition is preferably 80 mass% or less, more preferably 50 mass% or less, and even more preferably 40 mass% or less.
The content is preferably 5% by mass or more, and more preferably 8% by mass or more. By setting the content within this range, the refractive index can be increased and compatibility with (meth)acrylates having a fluorene structure can also be improved.

The content of trifunctional or higher polyfunctional (meth)acrylate (having a fluorene structure, a biphenyl structure, or a phenoxyphenyl structure) relative to the total mass of all structural units constituting the curable composition is
The proportion of (meth)acrylates) is preferably 50% by mass or less, more preferably 40% by mass or less.
The range is preferably 5% by mass or less, more preferably 35% by mass or less.
By setting the content in this range, it is possible to increase the glass transition temperature, improve moldability, and increase the strength of the cured product while maintaining the refractive index.

The mass loss when heated from 30°C at a heating rate of 10°C/min in an air atmosphere in simultaneous thermogravimetry and differential thermal analysis is 10% of the total mass of all constituent units constituting the curable composition.
The proportion of the polymerization initiator that gives rise to a temperature of 180°C or higher when the reaction temperature reaches the temperature of 180°C or higher is preferably in the range of 0.1 to 10% by mass, more preferably 0.2 to 8% by mass, and even more preferably 0.3 to 5% by mass. By setting the proportion in this range, the curability of the polymerizable composition is improved, and a cured product having high strength and transparency and little foreign matter can be obtained.

The proportion of the antioxidant relative to the total mass of all structural units constituting the curable composition is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less. The lower limit is preferably 0.01% by mass or more, more preferably 0.1% by mass or more. By setting the proportion within this range, the effect of preventing yellowing during high-temperature processes such as reflow is enhanced.

<Cured product>
The cured product is obtained by curing the above-mentioned curable composition. The cured product can be obtained by the following method:
For example, a method of forming a curable composition into a predetermined shape and curing the cured composition to obtain a cured product having the predetermined shape can be mentioned. Examples of methods for obtaining a cured product having a predetermined shape in this way include a coating method in which the curable composition is applied to a film substrate or the like, a potting molding method, a casting molding method, a printing molding method, a liquid resin injection molding method (LIM method), and a transfer molding method. In addition, as a method for curing the curable composition, any of photopolymerization, thermal polymerization, and redox polymerization can be used depending on the type of polymerization initiator contained in the curable composition.

When the curable composition is cured by photopolymerization to obtain a cured product, the wavelength of the light irradiated onto the curable composition is not particularly limited, but it is preferable to irradiate the curable composition with ultraviolet light having a wavelength of 200 to 400 nm.
Specific examples of ultraviolet light sources include ultra-high pressure mercury lamps, high pressure mercury lamps, metal halide lamps, high power metal halide lamps, and UV-LED lamps.
For example, when ultraviolet light is used, the cumulative light amount of irradiation is 100 mJ/cm ² or more and 10,000 m
It is preferable to irradiate so that the dose is 500 mJ/cm2 or ^less , and 500 mJ/cm2 or more to 8000 mJ/ ^cm2 or less.
It is more preferable that the illuminance is 5 mW/ ^cm2 or more and 1000 mW/ ^cm2 or less.
/cm ² or less is preferable, 10 mW/cm ² or more and 500 mW/cm ² or less is more preferable, and 20 mW/cm ² or more and 300 mW/cm ² or less is even more preferable.

After photopolymerizing the curable composition, it is preferable to further perform after-cure. This can reduce the amount of unreacted (meth)acryloyl groups remaining in the cured product, and further increase the strength of the cured product. The after-cure conditions are 70 to 120°C.
Preferably, the heating time is 160°C for 0.1 to 24 hours, and more preferably, the heating time is 80 to 130°C for 0.2 to 10 hours.

When the curable composition is cured by thermal polymerization to obtain a cured product, the curing conditions are not particularly limited.
The curing temperature is preferably 40 to 200°C, more preferably 60 to 150°C, since this makes it easier to obtain a cured product with reduced coloration.
The curing time (heating time) when a curable composition is injected into a preheated mold and molded, such as in the LIM method or transfer molding method, varies depending on the curing temperature. For example, when the curing temperature is 100°C, the curing time is preferably 1 to 180 seconds, more preferably 1 to 120 seconds, and 1 to 180 seconds is more preferable.
On the other hand, when the curable composition is poured into a mold at room temperature and then heated, as in the case of a casting molding method, the curing time varies depending on the curing temperature, but for example, when the curing temperature is 70°C, the curing time is preferably 5 minutes to 5 hours, and more preferably 10 minutes to 3 hours.
After the curable composition is thermally polymerized, it is preferable to further perform after-curing. The after-curing conditions are preferably 50 to 150°C for 0.1 to 10 hours, and more preferably 70 to 1
More preferably, the temperature is 30°C for 0.2 to 5 hours.

When a curable composition is cured by redox polymerization to obtain a cured product, the use of a redox polymerization initiator allows curing at room temperature of 5° C. to 40° C. The curing temperature is preferably 15 to 40° C., since this can reduce the amount of unreacted (meth)acryloyl groups remaining in the obtained cured product and further increase the strength of the cured product.
A preferred method for curing involves dissolving a reducing agent in the curable composition in advance and then adding a peroxide to the curable composition, since the curable composition is less likely to gel and can be handled stably.

The refractive index of the cured product is preferably 1.590 or more, more preferably 1.595 or more, measured at 25°C with sodium D line (589 nm).
It is more preferable that the molecular weight is 1.596 or more. There is no particular upper limit, but it is preferably 1.
By setting the value in the above range, various designs become possible and the range of applications becomes wider.

The glass transition point of the cured product is determined by measuring the dynamic viscoelasticity and loss tangent of the cured product with a dynamic viscoelasticity measuring device, and is the temperature at which the loss tangent (tan δ) reaches a maximum value. The temperature is preferably 100°C or higher, more preferably 110°C or higher, even more preferably 120°C or higher, and particularly preferably 130°C or higher. There is no particular upper limit, but it is preferably 250°C or lower. By setting the temperature within the above range, the shape of the cured product becomes stable and less likely to deform even at high temperatures, improving the reliability of the material and broadening the range of applicable applications.

<Lens>
The lens is made of a cured product obtained by curing the above-described curable composition. This lens can be used, for example, in electronic devices such as mobile phones, laptops, tablets, and digital cameras, as well as cameras installed in automobiles, etc. The lens may be a molded product made solely of the cured product of the present invention, or it may be a hybrid lens made of a transparent substrate such as flat glass or a glass wafer and the above-described cured product molded on this transparent substrate.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention.
The measurement and evaluation methods used in the present invention are as follows.

(1) In simultaneous thermogravimetry and differential thermal analysis, the temperature rise rate is 10°C/min in an air atmosphere to 30°C.
The temperature at which the mass loss when heated from 100°C is 10%. The polymerization initiator was measured using a thermal analyzer (Rigaku Thermo Plus EVO TG).
8120), the heating rate was 10°C/min, the starting temperature was 30°C, and the set temperature was 330°C.
The measurement was carried out under the condition of an air atmosphere of 50 mL/min. The temperature at which the mass of the polymerization initiator decreased by 10% was used.

(2) Refractive Index The curable composition was cured to prepare a cured product having a thickness of 1 mm. The refractive index of the cured product (sodium D line (589 nm), 25°C) was measured using a multi-wavelength Abbe refractometer (manufactured by Atago Co., Ltd., "DR
The measurement was performed using a methyl iodide solution (manufactured by Atago Co., Ltd.).

(3) Glass transition point The curable composition was cured to prepare a cured product having a thickness of 1 mm. The dynamic viscoelasticity and loss tangent of the cured product were measured, and the temperature at which the loss tangent (tan δ) reached its maximum value was taken as the glass transition point of the cured product. For the measurement, a dynamic viscoelasticity measuring device (manufactured by TA Instruments Japan, Inc., "RSA-II") was used, and the measurement conditions were tensile mode and a measurement frequency of 10 Hz.

(4) Evaluation of foreign matter The curable composition was cured to prepare a 1 mm thick cured product (lens). Both sides of the cured product were covered with silicone rubber sheets (300 mm x 30 mm silicone rubber sheets manufactured by AS ONE Corporation).
The lens was sandwiched between two pieces of glass (0.0 mm x 1 mm thick) and both sides were fixed with glass plates. That is, the structure was glass plate/silicone rubber sheet/cured product/silicone rubber sheet/glass plate. This structure was subjected to a heating test at 240°C for 10 minutes, and foreign matter adhering to the cured product (lens) and the glass plate was visually inspected. If no foreign matter was observed, it was rated A (good condition), and if foreign matter was observed, it was rated B.
It was evaluated as follows.

(Production of Curable Composition)
The materials shown in Table 1 were mixed in the mass ratios shown in Table 1. The materials in Table 1 are as follows.
(Meth)acrylate having a fluorene structure: A
A compound represented by the above formula (1), wherein R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms, and m and n are 1.
(Meth)acrylate having a biphenyl structure: B-1
Ortho-phenylphenoxyethyl acrylate (meth)acrylate having a phenoxyphenyl structure: B-2
Meta-phenoxyphenyl methyl acrylate, trifunctional or higher polyfunctional (meth)acrylate:
Trimethylolpropane trimethacrylate (C-1)
Dipentaerythritol hexaacrylate (C-2)
Benzyl methacrylate: D
Photopolymerization initiator: E
2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one (temperature at which the mass loss is 10% when heated from 30°C at a heating rate of 10°C/min in an air atmosphere in simultaneous thermogravimetry and differential thermal analysis: 260°C)
Photopolymerization initiator: F
1-Hydroxycyclohexyl phenyl ketone (temperature at which mass loss is 10% when heated from 30°C at a heating rate of 10°C/min in an air atmosphere in simultaneous thermogravimetry and differential thermal analysis: 160°C)
・Antioxidant: G
Tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane

[Example 1]
A curable composition having the composition shown in Table 1 was poured into a mold consisting of a silicone rubber sheet and a glass plate, 1 mm thick and 30 mm in inner diameter, and then sealed by laminating a glass plate on top. The glass surface was then irradiated with ultraviolet light from a high-pressure mercury lamp at an illuminance of 60 mW and an integrated light dose of 2000 mJ/ ^cm² , producing a cured product (lens) 30 mm in diameter and 1 mm thick. The cured product was then peeled off from the glass plate and heat-treated at 160°C for 1 hour.
The obtained cured product was measured or evaluated by the above-mentioned methods for the items shown in Table 2. As shown in Table 2, the results were good, with high refractive index and glass transition point, and no generation of foreign matter.

[Examples 2 to 5]
A cured product was obtained by producing the product in the same manner as in Example 1, except that the formulation of the curable composition was changed as shown in Table 1. The properties of the obtained cured product are shown in Table 2 below.

[Comparative Examples 1 and 2]
A cured product was obtained by the same production method as in Example 1, except that the formulation of the curable composition in Example 1 was changed as shown in Table 1. The properties of the obtained cured product are shown in Table 2 below, and foreign matter was found to be generated.

Claims (5)

The composition contains a (meth)acrylate having a fluorene structure, a (meth)acrylate having a phenoxyphenyl structure, a trifunctional or higher polyfunctional (meth)acrylate (excluding (meth)acrylates having a fluorene structure, a biphenyl structure, or a phenoxyphenyl structure), and an intramolecular cleavage type polymerization initiator that, in simultaneous thermogravimetry and differential thermal analysis, has a temperature of 180°C or higher at which a mass loss of 10% occurs when heated from 30°C at a heating rate of 10°C/min in an air atmosphere ,
The (meth)acrylate having a fluorene structure is a compound represented by the following formula (1):
A curable composition, wherein the proportion of the (meth)acrylate having a fluorene structure is 25 to 85 mass %, the proportion of the (meth)acrylate having a phenoxyphenyl structure is 5 to 80 mass %, and the proportion of the trifunctional or higher polyfunctional (meth)acrylate is 5 to 50 mass %, relative to the total mass of all structural units constituting the curable composition.
In formula (1), R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or a methyl group, m represents an integer of 0 to 5, and n represents an integer of 0 to 5. The curable composition according to claim 1 , which contains a (meth)acrylate having a biphenyl structure. The curable composition according to claim 1 or 2 , which contains an antioxidant. A cured product of the curable composition according to any one of claims 1 to 3 . A lens comprising the cured product according to claim 4 .