Curable composition

Abstract

To provide a novel curable composition applicable to an optical material or a diffraction optical element.SOLUTION: There is provided a curable composition which comprises metal oxide nanoparticles (A), a polyfunctional thiol compound (B) having three or more thiol groups in one molecule and a polyfunctional allyl compound (C) having three or more allyl groups in one molecule, wherein the content of the metal oxide nanoparticles (A) is 20 to 55 mass%, the content of the polyfunctional thiol compound (B) is 15 to 30 mass% based on the total amount of the composition and the content of the polyfunctional allyl compound (C) is 10 to 35 mass% based on the total amount of the composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a curable composition, a cured product obtained by curing the curable composition, an optical material or a diffractive optical element including the cured product, and a method for producing the optical material or the diffractive optical element. [Background technology]

[0002] Inorganic glass has excellent physical properties such as excellent light transmission and is used as an optical component in a wide range of fields. However, it has disadvantages such as being heavy and easily broken, and having poor processability and productivity. Therefore, transparent optical resins have been actively developed as alternative materials to inorganic glass.

[0003] Examples of such transparent optical resins include epoxy resins, unsaturated polyester resins, silicone resins, etc. There is a demand for general-purpose transparent resin materials that have good transparency in the visible light wavelength range and, compared to inorganic glass materials, have excellent characteristics such as moldability, mass productivity, flexibility, toughness, and impact resistance.

[0004] By imparting a high refractive index to such transparent resin materials, it is expected that they will be used in a variety of applications, including materials for highly refractive optical components such as thin, lightweight optical lenses (eyeglass lenses, Fresnel lenses, pickup lenses in information recording devices such as CDs and DVDs, lenses for photographic devices such as digital cameras), optical prisms, optical waveguides, optical fibers, thin film moldings, optical adhesives, sealing materials for optical semiconductors, diffraction gratings, light guide plates, liquid crystal substrates, light reflectors, and anti-reflection materials.

[0005] Sulfur-containing monomers or polycyclic aromatic acrylates are useful for increasing the refractive index of transparent resin materials. Examples of sulfur-containing monomers include resins obtained by polymerizing thiol compounds and allyl compounds to form bonds via a thiol-ene reaction, and resins (n ​​= approximately 1.7) obtained by polymerizing and curing episulfide or epithiosulfide compounds (see, for example, Patent Document 1). Resins obtained by forming bonds via a thiol-ene reaction have low glass transition temperatures, limiting their use to coating materials and adhesives. Furthermore, commercially available episulfide compounds have a viscosity of 100 cps or less, which causes dripping when adjusting the liquid volume during cast molding, making precise metering difficult.

[0006] A solution other than changing the monomer of the curable resin material is to incorporate metal oxide fine particles into the resin (for example, Patent Documents 2 and 3). This method tends to cause aggregation of the metal oxide fine particles, resulting in high haze, and its applications are limited to thin films. Dispersants that modify the surface of metal oxide fine particles are known to improve compatibility with resins. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-102933 [Patent Document 2] International Publication No. 2011 / 162293 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-155551 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of this background, there has been a demand for a novel curable composition that can be applied to optical materials or diffractive optical elements. [Means for solving the problem]

[0009] The present inventors have discovered that by using a curable composition containing specific amounts of metal oxide nanoparticles (A), a polyfunctional thiol compound (B) having three or more thiol groups in one molecule, and a polyfunctional allyl compound (C) having three or more allyl groups in one molecule, a cured product having high transparency, refractive index, and / or glass transition temperature can be obtained, and that the curable composition has a viscosity suitable for molding, thereby completing the present invention. That is, the present invention includes the following aspects. [1] The present invention comprises metal oxide nanoparticles (A), a polyfunctional thiol compound (B) having three or more thiol groups in one molecule, and a polyfunctional allyl compound (C) having three or more allyl groups in one molecule, The content of the metal oxide nanoparticles (A) is 20 to 55 mass% based on the total amount of the composition, the content of the polyfunctional thiol compound (B) is 15 to 40 mass% based on the total amount of the composition; A curable composition, wherein the content of the polyfunctional allyl compound (C) is 5 to 40 mass % based on the total amount of the composition. [2] The curable composition according to [1], further comprising a polyfunctional (meth)acrylate (D) having two or more (meth)acrylate groups in one molecule. [3] The curable composition according to [2], wherein the content of the polyfunctional (meth)acrylate (D) is 1 to 30 mass % based on the total amount of the composition. [4] The curable composition according to [2] or [3], wherein the polyfunctional (meth)acrylate (D) includes a polyfunctional (meth)acrylate (d1) represented by the following formula (5): [ka] (In formula (4), X's each independently represent a hydrogen atom, an acrylate group, or a methacrylate group (provided that at least two of the X's in the molecule are acrylate groups or methacrylate groups), and p represents an integer of 0 to 2.) [5] The curable composition according to any one of [2] to [4], wherein the molar ratio (Vi / SH) of the thiol group (SH) in the polyfunctional thiol compound (B) to the terminal vinyl group (Vi) in the polyfunctional allyl compound (C) and the polyfunctional (meth)acrylate (D) is 1.0 or more. [6] The curable composition according to any one of [1] to [5], wherein the polyfunctional thiol compound (B) comprises one or more compounds selected from the group consisting of a polyfunctional thiol compound (b1) represented by the following formula (1) and a polyfunctional thiol compound (b2) represented by the following formula (2): [ka] (In formula (1), X represents a sulfide group or a disulfide group.) [ka] (In formula (2), X and Z each independently represent a hydrogen atom, a mercapto group, or a methylthiol group (provided that at least one of X and Z in the molecule is a mercapto group or a methylthiol group), and p represents an integer of 2 to 4.) [7] The curable composition according to any one of [1] to [6], wherein the polyfunctional allyl compound (C) comprises one or more compounds selected from the group consisting of polyfunctional allyl compounds (c1) represented by the following formula (3) and polyfunctional allyl compounds (c2) represented by the following formula (4): [ka] (In formula (3), X1 to X3 represent an allyl group, and l, m, and n each independently represent an integer of 0 to 10.) [ka] (In formula (4), X1 to X3 represent an allyl group, and l, m, and n each independently represent an integer of 0 to 10.) [8] The curable composition according to any one of [1] to [7], further comprising a polymerization initiator (E). [9] The curable composition according to any one of [1] to [8], which has a viscosity at 23°C of 500 to 15,000 mPa·s.

[10] A cured product obtained by curing the curable composition according to any one of [1] to [9].

[11] The cured product according to

[10] , which has a refractive index of 1.635 or more at a wavelength of 589 nm.

[12] The cured product according to

[10] or

[11] , which has a glass transition temperature (Tg) of 90°C or higher.

[13] An optical material comprising the cured product according to any one of

[10] to

[12] .

[14] A diffractive optical element comprising the cured product according to any one of

[10] to

[12] . [15 A method for producing an optical material or a diffractive optical element, comprising curing the curable composition according to any one of [1] to [9]. [Effects of the Invention]

[0010] According to the present invention, a curable composition can be obtained that can produce a cured product having high transparency, refractive index, and / or glass transition temperature. Also, according to the present invention, a curable composition having a viscosity suitable for molding can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below. Note that the following is an example for explaining the present invention, and the present invention is not limited to the embodiment.

[0012] [Curable composition] The curable composition of the present invention (hereinafter also referred to as "the composition of the present invention") comprises metal oxide nanoparticles (A) (hereinafter also referred to as "component A"), a polyfunctional thiol compound (B) having three or more thiol groups in one molecule (hereinafter also referred to as "component B"), and a polyfunctional allyl compound (C) having three or more allyl groups in one molecule (hereinafter also referred to as "component C"), wherein the content of the metal oxide nanoparticles (A) is 20 to 55 mass% based on the total amount of the composition, the content of the polyfunctional thiol compound (B) is 15 to 40 mass% based on the total amount of the composition, and the content of the polyfunctional allyl compound (C) is 5 to 40 mass% based on the total amount of the composition. By containing these components in specific numerical ranges, the composition of the present invention can provide a composition having a viscosity suitable for molding while improving physical properties such as transparency, refractive index, and / or glass transition temperature of the cured product in a well-balanced manner at a high level.

[0013] The composition according to one embodiment of the present invention may further contain a polyfunctional (meth)acrylate (D) having two or more (meth)acrylate groups in one molecule (hereinafter also referred to as "component D"). Furthermore, the composition according to one embodiment of the present invention may contain components other than Components A to D, as long as the effects of the present invention can be exhibited. Each component constituting the composition of one embodiment of the present invention will be described below.

[0014] [Component A: Metal oxide nanoparticles] The composition of the present invention contains metal oxide nanoparticles (A). The metal oxide nanoparticles (A) may contain, for example, one or more metal atoms selected from the group consisting of zirconium, zinc, iron, copper, titanium, tin, indium, cerium, tantalum, niobium, tungsten, europium, and hafnium.

[0015] Examples of metal oxides constituting the metal oxide nanoparticles (A) include simple oxides such as titanium oxide (titania), aluminum oxide (alumina), zirconium oxide (zirconia), magnesium oxide (magnesia), and silicon oxide (silica); and complex oxides such as potassium titanate, barium titanate, strontium titanate, calcium titanate, magnesium titanate, lead titanate, aluminum titanate, lithium titanate, lead zirconate titanate (PZT), and indium tin oxide (ITO). Among these, from the viewpoint of improving the refractive index, light transmittance, and stability, one or more selected from the group consisting of titanium oxide (titania), aluminum oxide (alumina), zirconium oxide (zirconia), magnesium oxide (magnesia), and silicon oxide (silica) are preferred. These metal oxides may be used alone or in combination of two or more.

[0016] In one embodiment of the present invention, the metal oxide nanoparticles (A) have a median diameter (D50), which is the particle diameter that shows the 50% integrated value of the integrated distribution curve, of 20 nm or less, preferably 15 nm or less. By having such a particle diameter, high translucency can be imparted to the cured product obtained by curing the composition of one embodiment of the present invention. Furthermore, the metal oxide nanoparticles (A) preferably have a particle size D90, which is the 90% cumulative particle size in the particle size distribution, of 30 nm or less, more preferably 25 nm or less, which can further enhance the light transmittance of the cured product. The D50 and D90 of the metal oxide nanoparticles (A) can be measured based on the volume-based particle size distribution of equivalent sphere diameters using dynamic light scattering.

[0017] The metal oxide nanoparticles (A) may be crystalline or amorphous. They may be isotropic particles, anisotropic particles, or fibrous. Furthermore, the metal oxide nanoparticles (A) may be in the form of a powder or a sol.

[0018] In the composition of the present invention, the content of the metal oxide nanoparticles (A) is 20 to 55 mass% based on the total amount of the composition. The content of the metal oxide nanoparticles (A) is more preferably 25 to 52 mass%, even more preferably 30 to 52 mass%, and particularly preferably 35 to 52 mass%. By keeping the content of the metal oxide nanoparticles (A) within the above range, the transparency, refractive index, and / or glass transition temperature of the cured product can be improved in a balanced manner.

[0019] The method for producing the metal oxide nanoparticles (A) used in the present invention is not particularly limited, and those prepared by known methods can be used. For example, two typical production methods can be mentioned: a top-down method in which coarse particles are mechanically crushed and refined; and a bottom-up method in which several unit particles are generated and then agglomerated into clusters to form particles. These production methods can be either wet or dry, but the dry method has a large pulverization limit particle size and is significantly affected by light scattering, so the wet method is more preferred for optical applications. The medium used in these production methods can be aqueous or non-aqueous, or it can be gas phase.

[0020] The bottom-up method can be classified into physical and chemical methods, and either method may be used. A typical example of a physical method is a gas evaporation method in which bulk metal is evaporated in an inert gas and cooled and condensed by collision with the gas to produce nanoparticles. Typical examples of chemical methods include a liquid-phase reduction method (a method in which metal ions are reduced in a liquid phase in the presence of a protective agent, and the resulting zero-valent metal is stabilized at nanosize), a thermal decomposition method of a metal complex, and the like. More specific examples of liquid-phase reduction methods include chemical reduction, electrochemical reduction, photoreduction, and a combination of chemical reduction and photoirradiation.

[0021] When producing metal oxide nanoparticles (A) using the various methods described above, a protective agent can be used to extract the metal oxide nanoparticles (A) from the medium used in the production process. Examples of protective agents include surface modifiers that modify the surface of the metal oxide nanoparticles (A) and surface protective agents that protect the surface of the metal oxide nanoparticles (A). By coating the surface with or impregnating the protective agent, the metal oxide nanoparticles (A) can be stably extracted from the medium. Commonly used surface modifiers, such as coupling agents such as silane coupling agents, carboxylic acid derivatives, phosphate ester derivatives, and modified silicones, can be used without limitation as the surface treatment agent.

[0022] [Component B: Multifunctional thiol compound] The composition of the present invention contains a polyfunctional thiol compound (B) having three or more thiol groups in one molecule. In one embodiment of the present invention, component B is preferably a tri- to hexa-functional polyfunctional thiol compound (B), more preferably a tri- to penta-functional polyfunctional thiol compound (B), and even more preferably a tri- to tetra-functional polyfunctional thiol compound (B). In one embodiment of the present invention, the polyfunctional thiol compound (B) may be one or more selected from the group consisting of a trifunctional polyfunctional thiol compound (B1) and a tetrafunctional polyfunctional thiol compound (B2).

[0023] The polyfunctional thiol compound (B) used in one embodiment of the present invention may contain one or more compounds selected from the group consisting of a polyfunctional thiol compound (b1) represented by the following formula (1) and a polyfunctional thiol compound (b2) represented by the following formula (2): [ka] (In formula (1), X represents a sulfide group or a disulfide group.) [ka] (In formula (2), X and Z each independently represent a hydrogen atom, a mercapto group, or a methylthiol group (provided that at least one of X and Z in the molecule is a mercapto group or a methylthiol group), and p represents an integer of 2 to 4.)

[0024] In the above formula (2), X and Z are preferably a hydrogen atom or a methylthiol group, and p is preferably 2 to 3, and more preferably 2.

[0025] Specific examples of the polyfunctional thiol compound (B) used in one embodiment of the present invention include 1,2-bis[(2-mercaptoethyl)thio]-3-mercaptopropane, 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane. These may be used alone or in combination of two or more.

[0026] In one embodiment of the present invention, the polyfunctional thiol compound (B) may be an oligomer synthesized using the polyfunctional thiol compound (B). The use of an oligomer can increase the viscosity of the composition to a range suitable for molding. Known methods can be used for oligomerization. Examples include a method of oxidizing a portion of the thiol groups to form a disulfide bond (JP 2012-233113 A), a method of reacting a portion of the thiol groups with an ene compound, and a method of forming a thiourethane bond between a portion of the thiol groups and an isocyanate compound (WO 2012 / 147709 A). Examples of the ene compound with which a portion of the thiol groups are reacted include the compounds of Component C and / or Component D described below.

[0027] Examples of the isocyanate compound include aliphatic / alicyclic bifunctional isocyanates such as isophorone diisocyanate, hexamethylene diisocyanate, bis(isocyanatomethyl)cyclohexane, norbornene diisocyanate, and hydrogenated diphenylmethane diisocyanate, and aromatic bifunctional isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate. From the viewpoint of transparency of the cured product, etc., non-aromatic isocyanate compounds are preferred.

[0028] In the composition of the present invention, the content of the polyfunctional thiol compound (B) is 15 to 40 mass% based on the total amount of the composition. The content of the polyfunctional thiol compound (B) is more preferably 18 to 35 mass%, and even more preferably 20 to 30 mass%. By setting the content of the polyfunctional thiol compound (B) within the above range, the transparency, refractive index, and / or glass transition temperature of the cured product can be improved in a balanced manner.

[0029] The composition of one embodiment of the present invention may or may not contain a thiol compound other than the polyfunctional thiol compound (B). In one embodiment, from the viewpoint of improving the glass transition temperature, it is preferable that the composition does not contain a thiol compound other than the polyfunctional thiol compound (B). Examples of thiol compounds other than the polyfunctional thiol compound (B) include bifunctional thiol compounds having two thiol groups in one molecule and monofunctional thiol compounds having one thiol group in one molecule.

[0030] In the composition of one embodiment of the present invention, the content of thiol compounds other than the polyfunctional thiol compound (B) may be less than 3.0 mass%, less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, or less than 0.01 mass%, based on the total amount of the composition.

[0031] [Component C: Polyfunctional allyl compound] The composition of the present invention contains a polyfunctional allyl compound (C) having three or more allyl groups in one molecule. In one embodiment of the present invention, component C is preferably a tri- or tetrafunctional polyfunctional allyl compound (C), more preferably a trifunctional polyfunctional allyl compound (C). In one embodiment of the present invention, the polyfunctional allyl compound (C) may be one or more compounds selected from the group consisting of trifunctional polyfunctional thiol compounds (C1) and tetrafunctional polyfunctional allyl compounds (C2).

[0032] The polyfunctional allyl compound (C) used in one embodiment of the present invention may contain one or more compounds selected from the group consisting of polyfunctional allyl compounds (c1) represented by the following formula (3) and polyfunctional allyl compounds (c2) represented by the following formula (4): [ka] (In formula (3), X1 to X3 represent an allyl group, and l, m, and n each independently represent an integer of 0 to 10.) [ka] (In formula (4), X1 to X3 represent an allyl group, and l, m, and n each independently represent an integer of 0 to 10.)

[0033] In the above formula (3), l, m, and n are preferably 0 to 8, more preferably 0 to 4, and even more preferably 0 to 2.

[0034] In the above formula (4), l, m, and n are preferably 0 to 8, more preferably 0 to 4, and even more preferably 0 to 2.

[0035] Specific examples of the polyfunctional allyl compound (C) used in one embodiment of the present invention include triallyl isocyanurate and triallyl cyanurate. These may be used alone or in combination of two or more.

[0036] In the composition of the present invention, the content of the polyfunctional allyl compound (C) is 5 to 40 mass% based on the total amount of the composition. The content of the polyfunctional allyl compound (C) is more preferably 8 to 35 mass%, and even more preferably 10 to 30 mass%. By keeping the content of the polyfunctional allyl compound (C) within the above range, the transparency, refractive index, and / or glass transition temperature of the cured product can be improved in a balanced manner.

[0037] The composition of one embodiment of the present invention may or may not contain an allyl compound other than the polyfunctional allyl compound (C). In one embodiment, from the viewpoint of improving the glass transition temperature, it is preferable that the composition does not contain any allyl compound other than the polyfunctional allyl compound (C). Examples of allyl compounds other than the polyfunctional allyl compound (C) include bifunctional allyl compounds having two allyl groups in one molecule and monofunctional allyl compounds having one allyl group in one molecule.

[0038] In the composition of one embodiment of the present invention, the content of allyl compounds other than the polyfunctional allyl compound (C) may be less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, or less than 0.01 mass%, based on the total amount of the composition.

[0039] [Component D: Multifunctional (meth)acrylate] The composition of one embodiment of the present invention may further contain a polyfunctional (meth)acrylate (D) having two or more (meth)acrylate groups in one molecule. In one embodiment of the present invention, the polyfunctional (meth)acrylate (D) has two or more (meth)acrylate groups in one molecule and does not have an alicyclic structure.

[0040] In one embodiment of the present invention, Component D is preferably a di- to hexa-functional polyfunctional (meth)acrylate (D), more preferably a di- to penta-functional polyfunctional (meth)acrylate (D), and even more preferably a di- to tetra-functional polyfunctional (meth)acrylate (D). In one embodiment of the present invention, the polyfunctional (meth)acrylate (D) may be one or more selected from the group consisting of a difunctional polyfunctional (meth)acrylate (D1), a trifunctional polyfunctional (meth)acrylate (D2), and a tetrafunctional polyfunctional (meth)acrylate (D3). In this specification, "(meth)acrylate" means acrylate and / or methacrylate. Similarly, "(meth)acrylic" means acrylic and / or methacrylic.

[0041] The polyfunctional (meth)acrylate (D) used in one embodiment of the present invention may contain a polyfunctional (meth)acrylate (d1) represented by the following formula (5). [ka] (In formula (5), X's each independently represent a hydrogen atom, an acrylate group, or a methacrylate group (provided that at least two of the X's in the molecule are acrylate groups or methacrylate groups), and p represents an integer of 0 to 2.)

[0042] In the above formula (5), X is preferably a hydrogen atom or a methacrylate group, and p is preferably 0 to 1, and more preferably 1.

[0043] Specific examples of the polyfunctional (meth)acrylate (D) used in one embodiment of the present invention include (meth)acrylic compounds such as oligoethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and 2,2′-thiodiethanethiol di(meth)acrylate. These may be used alone or in combination of two or more.

[0044] In the composition of one embodiment of the present invention, the content of the polyfunctional (meth)acrylate (D) is 1 to 30 mass% based on the total amount of the composition. The content of the polyfunctional (meth)acrylate (D) is more preferably 5 to 25 mass%, and even more preferably 10 to 20 mass%. By keeping the content of the polyfunctional (meth)acrylate (D) within the above range, it is possible to improve the transparency, refractive index, and / or glass transition temperature of the cured product in a well-balanced manner.

[0045] The composition of one embodiment of the present invention may or may not contain a (meth)acrylic compound other than the polyfunctional (meth)acrylate (D). In one embodiment, from the viewpoint of improving the glass transition temperature, it is preferable that the composition does not contain a (meth)acrylic compound other than the polyfunctional (meth)acrylate (D). Examples of the (meth)acrylic compound other than the polyfunctional (meth)acrylate (D) include a monofunctional (meth)acrylic compound having one (meth)acrylic group in one molecule.

[0046] In the composition of one embodiment of the present invention, the content of the (meth)acrylic compound other than the polyfunctional (meth)acrylate (D) may be less than 1.0 mass%, less than 0.5 mass%, less than 0.1 mass%, or less than 0.01 mass%, based on the total amount of the composition.

[0047] In order to obtain a curable composition having a viscosity suitable for molding, the composition of one embodiment of the present invention preferably does not contain an alicyclic (meth)acrylate having an alicyclic structure. Examples of the alicyclic (meth)acrylate include cyclopropyl (meth)acrylate, cyclobutyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, cyclooctyl (meth)acrylate, bornyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate, as well as dimethylol-tricyclodecane diacrylate (DCP-A) and dimethylol-tricyclodecane dimethacrylate (DCP).

[0048] In the composition of one embodiment of the present invention, the content of the alicyclic (meth)acrylate may be less than 1.0 mass %, less than 0.5 mass %, less than 0.1 mass %, or less than 0.01 mass %, based on the total amount of the composition.

[0049] [Component E: Polymerization initiator] The composition of one embodiment of the present invention may further contain a polymerization initiator (E). Examples of polymerization initiators that can be used in one embodiment of the present invention include thermal polymerization initiators that generate polymerization-initiating radicals upon heating and photopolymerization initiators that generate polymerization-initiating radicals upon irradiation with ultraviolet light. These polymerization initiators may be used alone or in combination of two or more of the following:

[0050] Examples of the photopolymerization initiator include acetophenone-based, benzoin-based, α-aminoketone-based, acylphosphine oxide-based, benzophenone-based, xanthone-based, α-oxobenzeneacetic acid-based, and anthraquinone-based initiators. Examples of acetophenones include diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy)-phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexylphenyl ketone, and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1. Examples of the benzoin-based solvents include benzoin, α-methylbenzoin, α-phenylbenzoin, α-allylbenzoin, α-benzoylbenzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and benzyl dimethyl ketal. Examples of α-amino ketones include 2-methyl-1-(4-methylthiophenyl)-2-(4-morpholinyl)-1-propanone, 2-benzyl-2-(dimethylamino)-1-(4-(4-morpholinyl)phenyl)-1-butanone, and 2-(dimethylamino)-2-(4-methylphenyl)methyl-1-(4-(4-morpholinyl)phenyl)-1-butanone. Examples of the acylphosphine oxide include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide. Examples of the benzophenone-based compounds include benzophenone, 4-methylbenzophenone, 4-phenylbenzophenone, 4,4'-bis(diethylamino)benzophenone, benzoylbenzoic acid, and methyl benzoylbenzoate. Examples of xanthone compounds include xanthone, thioxanthone, diethylthioxanthone, and isopropylthioxanthone. Examples of the α-oxobenzeneacetic acid type include methyl α-oxobenzeneacetate, diethylene glycol di(α-oxobenzeneacetic acid) ester, and diethylene glycol mono(α-oxobenzeneacetic acid). Examples of the anthraquinone-based compounds include anthraquinone, 2-methylanthraquinone, and 2-ethylanthraquinone.

[0051] Examples of the thermal polymerization initiator include diisopropyl peroxydicarbonate, benzoyl peroxide, t-butyl peroxyisobutyrate, t-hexylperoxyisopropyl monocarbonate, t-hexylperoxy 2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy 2-ethylhexanoate, t-butyl peroxypivalate, t-hexyl peroxypivalate, t-butyl peroxyneodecanoate, and t-hexyl Examples of suitable peroxides include peroxyneodecanoate, 1,1,3,3-tetramethylbutylperoxyneodecanoate, 1,1-bis(t-hexylperoxy)cyclohexane, benzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, and lauroyl peroxide; and azo compounds such as azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), and dimethyl 2,2'-azobis(2-methylpropionate).

[0052] In the composition of one embodiment of the present invention, the content of the polymerization initiator (E) is preferably 0.1 to 5 mass %, more preferably 0.5 to 3 mass %, and even more preferably 1 to 2 mass %, based on the total amount of the composition.

[0053] [Other ingredients] The composition of the present invention may optionally contain components other than the above-mentioned components A to E. Examples of optional components include polymerization inhibitors, antioxidants, light stabilizers (HALS), ultraviolet absorbers, silane coupling agents, release agents, pigments, and dyes. The content of each of these optional components can be adjusted as appropriate within a range that does not impair the effects of the present invention, but is typically 0.001 to 10 mass%, preferably 0.005 to 8 mass%, and more preferably 0.01 to 5 mass%, for each component independently, based on the total amount of the composition.

[0054] [Production method and viscosity of curable composition] The composition of the present invention can be obtained by uniformly mixing the above-mentioned components. After mixing, the composition may be subjected to filtration, degassing, etc., as necessary. In the composition of one embodiment of the present invention, the molar ratio (Vi / SH) of the thiol group (SH) in the polyfunctional thiol compound (B) to the terminal vinyl group (Vi) in the polyfunctional allyl compound (C) and the polyfunctional (meth)acrylate (D) is, from the viewpoint of obtaining a curable composition having a viscosity suitable for molding while improving the transparency, refractive index, and / or glass transition temperature of the cured product in a well-balanced manner, preferably 0.1 or more, 0.2 or more, 0.4 or more, 0.6 or more, 0.8 or more, or 1.0 or more, and is preferably 3.0 or less, 2.5 or less, 2.0 or less, or less than 2.0.

[0055] The viscosity at 23°C of the curable composition obtained in one embodiment of the present invention is preferably 500 to 15,000 mPa·s, more preferably 750 to 12,500 mPa·s, even more preferably 1,000 to 10,000 mPa·s, and particularly preferably 1,100 to 6,000 mPa·s. In this specification, viscosity refers to a value measured at 23°C using an electromagnetic spinning system (EMS) viscometer or a general E-type viscometer. When the viscosity of the curable composition is in the above range, moldability can be improved.

[0056] In the composition of one embodiment of the present invention, the content of sulfur components, calculated as sulfur atoms, based on the total amount of the composition, is preferably 30.0 mass% or less, more preferably 25.0 mass% or less, even more preferably 20.0 mass% or less, particularly preferably 18.0 mass% or less, and is preferably 6.0 mass% or more, more preferably 8.0 mass% or more, even more preferably 10.0 mass% or more, particularly preferably 12.0 mass% or more. The sulfur component refers to the content of all sulfur components contained in the curable composition, including not only sulfur atoms derived from the polyfunctional thiol compound (B) but also sulfur atoms contained in other compounds containing sulfur atoms when such compounds are used as additives.

[0057] [Method for curing curable composition and cured product] The present invention provides a cured product obtained by curing the curable composition of one embodiment of the present invention. The method for curing the composition of the present invention is not particularly limited, and the composition can be cured by heat or active energy rays such as ultraviolet rays.

[0058] The cured product obtained by curing the composition of one embodiment of the present invention has a refractive index (d-line refractive index (nd)) at a wavelength of 589 nm of preferably 1.635 or more, more preferably 1.638 or more, and even more preferably 1.640 or more. The Abbe number (vd) of the cured product is preferably 38 or more, more preferably 39 or more, and even more preferably 40 or more. The glass transition temperature (Tg) of the cured product is preferably 90°C or higher, and more preferably 91°C or higher. The haze of the cured product is preferably 1.3 or less, more preferably 1.1 or less, and even more preferably 1.0 or less. A cured product having these physical property values ​​in the above ranges can be said to be suitable for use in optical materials and diffractive optical elements.

[0059] [Optical materials and diffractive optical elements] The present invention provides an optical material or a diffractive optical element comprising the cured product described above. Furthermore, the present invention also provides a method for producing an optical material or a diffractive optical element, the method comprising curing a composition according to one embodiment of the present invention. The method for producing an optical material or a diffractive optical element is not particularly limited, and may include a step of curing the composition of the present invention in any step of producing the optical material or the diffractive optical element.

[0060] Examples of optical materials include lenses such as eyeglass lenses, imaging lenses for (digital) cameras, light beam condensing lenses, and light diffusing lenses; LED sealing materials, optical adhesives, optical transmission bonding materials; prisms, filters, diffraction gratings, watch glasses, and transparent glasses and cover glasses for display devices.

[0061] The diffractive optical element may be a two-layer composite diffractive optical element that combines a high refractive index, low dispersion resin and a low refractive index, high dispersion resin, or a single-layer diffractive optical element. A two-layer composite diffractive optical element can be produced by laminating a layer of high refractive index, low dispersion resin and a layer of low refractive index, high dispersion resin. For example, a two-layer composite diffractive optical element can be produced by transferring a diffractive structure onto one surface of a refractive lens using one material, and then filling and curing the gap between this diffractive structure and another refractive lens with the other curable material. In a close-contact two-layer composite diffractive optical element according to one embodiment of the present invention, the refractive index difference between the high-refractive index, low-dispersion resin obtained by curing a high-refractive index, low-dispersion resin composition (i.e., the curable composition according to one embodiment of the present invention) and the low-refractive index, high-dispersion resin (not particularly limited, but examples include those described in Japanese Patent No. 6943238) at the e-line is in the range of 0.02 to 0.1, the refractive index difference at the F-line is 0.80 to 0.98 times (preferably 0.88 to 0.98 times) the refractive index difference at the e-line, and the refractive index difference at the C-line is 1.02 to 1.26 times (preferably 1.02 to 1.12 times) the refractive index difference at the e-line. These ranges ensure good characteristics of the close-contact two-layer composite diffractive optical element. If the refractive index difference at the e-line between the resins is less than 0.02, the diffraction grating height increases, which may adversely affect the characteristics of the close-contact two-layer composite diffractive optical element, such as making it easier for obliquely incident light to escape as zero-order light. Furthermore, if it exceeds 0.1, the diffraction grating height will be too low, which may cause productivity problems due to the small tolerances during manufacturing. Furthermore, if the difference in refractive index between the F line and the C line is not within the above range, the proportion of diffracted light of unnecessary orders will increase, which may adversely affect the characteristics of the close-contact two-layer composite diffractive optical element, such as causing a lot of flare. [Example]

[0062] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples.

[0063] <Preparation of high refractive index, low dispersion resin composition> [material] The curable compositions (compositions for high refractive index, low dispersion resins) of the examples and comparative examples were produced using the following materials.

[0064] (Component A: ZrO2) Nano zirconium oxide methyl ethyl ketone dispersion (solid content 70%) (product name "Zircostar-ZP-153", manufactured by Nippon Shokubai Co., Ltd.)

[0065] (Component B: GST) 1,2-bis[(2-mercaptoethyl)thio]-3-mercaptopropane represented by the following formula [ka]

[0066] (Component B: FFSH) Polythiols containing 4,8-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, 4,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane, and 5,7-dimercaptomethyl-1,11-dimercapto-3,6,9-trithiaundecane as the main components, which are represented by the following formulas: [ka]

[0067] GST and FFSH were each synthesized according to the method described in International Publication No. 2007 / 129450.

[0068] (Component C: TAIC) Triallyl isocyanurate represented by the following formula (trade name "TAICROS", manufactured by Evonik Japan Co., Ltd.) [ka]

[0069] (Component D:A-TMMT) Pentaerythritol tetraacrylate represented by the following formula (trade name "NK Ester A-TMMT", manufactured by Shin-Nakamura Chemical Co., Ltd.) [ka]

[0070] (Component D':DCP-A) Dimethylol-tricyclodecane diacrylate (trade name "Light Acrylate DCP-A", Kyoeisha Chemical Co., Ltd.) represented by the following formula: [ka]

[0071] (Component E: TPO) 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (trade name "Omnirad TPO H", manufactured by IGM Resins BV)

[0072] [Evaluation method] (1) Viscosity (mPa s) Measurement was performed at 23°C using an EMS viscometer (product name "EMS-1000S", manufactured by Kyoto Electronics Manufacturing Co., Ltd.). (2) Refractive index, Abbe number The d-line refractive index (nd) and Abbe number (νd) were measured using a refractometer (trade name "KPR-3000", manufactured by Shimadzu Corporation). The measurement temperature was 25°C. (3) Glass transition temperature (Tg) The peak temperature of tan δ obtained using a viscoelasticity measuring device (trade name "DMA7100", manufactured by Hitachi High-Tech Science Corporation) under conditions of a temperature rise of 2°C per minute and 10 Hz was taken as the glass transition temperature. (4) Hayes Measurement was carried out at a thickness of 0.25 mm using a spectrophotometer (product name "CM-5", manufactured by Konica Minolta, Inc.).

[0073] [Preparation of Curable Composition (High Refractive Index, Low Dispersion Resin Composition)] Example 1 65.6% by mass of Zircosta-ZP-153 (46% by mass in terms of solids), 23% by mass of GST, 18% by mass of A-TMMT, 14% by mass of TAIC, and 2% by mass of TPO were mixed and stirred in a brown recovery flask. The solvent was removed from the mixture using a rotary evaporator, and the mixture was further vacuum-dried for 3 hours while heating at 40°C using a vacuum pump to obtain a curable composition.

[0074] (Examples 2 to 5, Comparative Examples 1 to 3) Components A to D were blended in the compositions shown in Table 1 and mixed in the same manner as in Example 1 to obtain a curable composition.

[0075] [Preparation of cured product and evaluation of physical properties] The curable compositions of Examples 1 to 5 and Comparative Examples 1 to 3 were sandwiched between two opposing glass plates with a spacer having a thickness of 0.25 mm between them, and irradiated with 50 mW / cm of UV-LED light using UV-LED light irradiation device 405 (product name "UV Irradiation Device 405 nm LED", manufactured by CCS Inc., peak wavelength 405 nm). 2 The composition was cured by irradiating it with light for 10 minutes, and the glass plate was removed to obtain a cured product. The physical properties of the cured product were evaluated using the evaluation methods described above. The results are shown in Table 2.

[0076] [Table 1] [Table 2]

[0077] <Preparation of low refractive index, high dispersion resin composition> A low refractive index, high dispersion resin composition was produced using the following materials.

[0078] m-Phenoxybenzyl acrylate represented by the following formula (product name "Light Acrylate POB-A", manufactured by Kyoeisha Chemical Co., Ltd.) [ka]

[0079] A mixture of fluorene-based bifunctional acrylate and m-phenoxybenzyl acrylate (product name "Oguzol EA-F5710", manufactured by Osaka Gas Chemicals Co., Ltd.)

[0080] 70% by mass of Ogusol EA-F5710, 30% by mass of light acrylate POB-A, and 2% by mass of TPO were mixed uniformly to prepare a low refractive index, high dispersion resin composition.

[0081] <Creation of a close-contact two-layer composite diffractive optical element> The low-refractive-index, high-dispersion resin composition was poured into a nickel mold with a diffractive structure on one side and optical glass (N-BK7: SCHOTT) on the other side via a 100-μm-thick spacer, and cured by irradiating with light from an LED lamp with a wavelength of 365 nm and an illuminance of 50 mW / cm for 1 minute. The nickel mold was removed, yielding a glass-resin bonded two-layer composite diffractive optical element with the diffractive structure transferred to the low-refractive-index, high-dispersion resin. The surface of this glass-resin contact two-layer composite diffractive optical element bearing the diffractive structure was placed facing a glass mold via a 100 μm-thick spacer. The high-refractive-index, low-dispersion resin composition was poured into the glass mold and cured by irradiating it with light from an LED lamp with a wavelength of 365 nm and an illuminance of 30 mW / cm² for 1 minute. The photocurability of the high-refractive-index, low-dispersion resin composition and the diffraction characteristics of the resulting contact two-layer composite diffractive optical element were excellent. The results are shown in Table 3. The "composition ratio" in Table 3 indicates the composition of the low-refractive-index, high-dispersion resin composition, and the example number in Table 3 indicates the example number of the high-refractive-index, low-dispersion resin composition used. The diffraction characteristics were evaluated as follows:

[0082] [Diffraction characteristics] The diffraction characteristics of the close-contact two-layer composite diffractive optical element were evaluated by the minimum diffraction efficiency within the wavelength range of 430 nm to 680 nm when the diffraction grating height was set based on the refractive index difference of the resin used to minimize the amount of diffracted light of unwanted orders. A value of 90% or higher was rated as good, and a value of less than 90% was rated as poor.

[0083] [Table 3]

[0084] The results in Table 2 show that the cured product prepared using the curable composition of the present invention has high transparency, refractive index, and / or glass transition temperature, and that the composition before curing has a viscosity suitable for molding. Also, the results in Table 3 show that the close-contact two-layer composite diffractive optical element prepared using the curable composition of the present invention has good diffraction properties.

Claims

1. The present invention comprises metal oxide nanoparticles (A), a polyfunctional thiol compound (B) having three or more thiol groups in one molecule, and a polyfunctional allyl compound (C) having three or more allyl groups in one molecule, The content of the metal oxide nanoparticles (A) is 20 to 55 mass% based on the total amount of the composition, The content of the polyfunctional thiol compound (B) is 15 to 40 mass% based on the total amount of the composition, A curable composition, wherein the content of the polyfunctional allyl compound (C) is 5 to 40 mass % based on the total amount of the composition.

2. The curable composition according to claim 1 , further comprising a polyfunctional (meth)acrylate (D) having two or more (meth)acrylate groups in one molecule.

3. The curable composition according to claim 2, wherein the content of the polyfunctional (meth)acrylate (D) is 1 to 30 mass% based on the total amount of the composition.

4. The curable composition according to claim 2 or 3, wherein the polyfunctional (meth)acrylate (D) comprises a polyfunctional (meth)acrylate (d1) represented by the following formula (5): 【Chemistry 1】 In formula (4), X's each independently represent a hydrogen atom, an acrylate group, or a methacrylate group (provided that at least two of the X's in the molecule are acrylate groups or methacrylate groups), and p represents an integer of 0 to 2.

5. The curable composition according to any one of claims 2 to 4, wherein the molar ratio (Vi / SH) of the thiol group (SH) in the polyfunctional thiol compound (B) to the terminal vinyl group (Vi) in the polyfunctional allyl compound (C) and the polyfunctional (meth)acrylate (D) is 1.0 or more.

6. The curable composition according to any one of claims 1 to 5, wherein the polyfunctional thiol compound (B) comprises one or more compounds selected from the group consisting of a polyfunctional thiol compound (b1) represented by the following formula (1) and a polyfunctional thiol compound (b2) represented by the following formula (2): 【Chemistry 2】 (In formula (1), X represents a sulfide group or a disulfide group.) 【Transformation 3】 In formula (2), X and Z each independently represent a hydrogen atom, a mercapto group, or a methylthiol group (provided that at least one of X and Z in the molecule is a mercapto group or a methylthiol group), and p represents an integer of 2 to 4.

7. The curable composition according to any one of claims 1 to 6, wherein the polyfunctional allyl compound (C) comprises one or more compounds selected from the group consisting of a polyfunctional allyl compound (c1) represented by the following formula (3) and a polyfunctional allyl compound (c2) represented by the following formula (4): 【Chemistry 4】 (In formula (3), X １ ~X ３ represents an allyl group, and l, m, and n each independently represent an integer of 0 to 10. 【Transformation 5】 (In formula (4), X １ ~X ３ represents an allyl group, and l, m, and n each independently represent an integer of 0 to 10.

8. The curable composition according to any one of claims 1 to 7, further comprising a polymerization initiator (E).

9. The curable composition according to any one of claims 1 to 8, having a viscosity at 23°C of 500 to 15,000 mPa·s.

10. A cured product obtained by curing the curable composition according to any one of claims 1 to 9.

11. The cured product according to claim 10, having a refractive index of 1.635 or more at a wavelength of 589 nm.

12. The cured product according to claim 10 or 11, having a glass transition temperature (Tg) of 90°C or higher.

13. An optical material comprising the cured product according to any one of claims 10 to 12.

14. A diffractive optical element comprising the cured product according to any one of claims 10 to 12.

15. A method for producing an optical material or a diffractive optical element, comprising curing the curable composition according to any one of claims 1 to 9.

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