Sclerotic resin composition, cured product, diffractive optical element, multilayer diffractive optical element, and oxide nanoparticles

Abstract

To provide a cured product that is suitable as a material of a low refractive index layer in a multilayer type diffraction optical element, which can obtain desired chromatic aberration reduction action from a near infrared wavelength region to a short wave infrared wavelength when being used in the multilayer type diffraction optical element, and can exhibit high transmittance in the wavelength region, a curable resin composition which is suitable for obtaining the cured product, a diffraction optical element containing the cured product, and a multilayer type diffraction optical element.SOLUTION: There are provided a curable resin composition containing oxide nanoparticles containing indium and cerium, a mono- or more-functional (meth)acrylate compound, and a dispersion agent; a cured product using the same, a diffraction optical element and a multilayer type diffraction optical element; and oxide nanoparticles used in the composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a curable resin composition. The present invention also relates to a cured product, a diffractive optical element, and a multilayer diffractive optical element obtained by using the above curable resin composition. The present invention also relates to oxide nanoparticles used in the above curable resin composition.

Background Art

[0002] By using a diffractive optical element, a lens can be obtained in which the focal length becomes shorter as the wavelength becomes longer, and chromatic aberration appears in the opposite direction to that of a conventional refractive lens. Different from a refractive lens that requires a plurality of lenses for chromatic aberration correction, since chromatic aberration can be corrected by changing the period of the diffraction structure of the lens, it is possible to design a more compact and high-performance lens unit by using a diffractive optical element.

[0003] In a multilayer diffractive optical element having a configuration in which diffractive optical elements formed of two different materials are in contact with each other at their grating planes, one diffractive optical element is formed of a material having a relatively high refractive index and a high Abbe number, and the other diffractive optical element is formed of a material having a relatively low refractive index and a low Abbe number, thereby suppressing the occurrence of flare in the lens and sufficiently utilizing the chromatic aberration reducing effect. At this time, if the optical characteristics are such that the refractive index difference between the two diffractive optical elements is larger at a longer wavelength, the chromatic aberration reducing effect can be obtained in a wide wavelength range.

[0004] In recent years, in order to obtain a chromatic aberration reducing effect in a wide wavelength range as described above, it has been proposed to add ITO (indium tin oxide) particles to a low Abbe number diffractive optical element in a multilayer diffractive optical element. For example, Patent Document 1 discloses a curable resin composition for producing a diffractive optical element, which is characterized in that ITO particles are dispersed in a resin containing a photopolymerization initiator, a dispersant, and two or more acrylic groups, methacrylic groups, vinyl groups, or a mixture of these unsaturated ethylene groups. In addition, Patent Document 2 describes a resin composition containing ITO particles and a near-ultraviolet light-absorbing organic compound. According to Patent Document 2, by curing this resin composition, the refractive index of the obtained cured product in the near-infrared wavelength region can be lowered, and the refractive index in the near-ultraviolet wavelength region can be increased to adjust the wavelength dependence of the refractive index of the cured product. Therefore, even if the blending amount of ITO particles is suppressed to realize the desired wavelength dependence of the refractive index, and the transmittance in the near-infrared wavelength region of the cured product is increased, it is said that a desired low refractive index and low Abbe number can be realized.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Conventionally, a general camera has been assumed as an application target of a lens using a diffractive optical element. Therefore, as described in Patent Document 1 or 2, when used in a multilayer diffractive optical element (also referred to as a stacked diffractive optical element), in the visible light wavelength region visible to humans, or in the near-infrared wavelength region of about 1.0 μm from visible light, a chromatic aberration reduction effect can be obtained, and research has been conducted to obtain a diffractive optical element having a low Abbe number (large wavelength dependence of refractive index) showing high transmittance in this wavelength range. On the other hand, in various inspections such as electronic substrate inspection and solar cell inspection, a short-wave infrared imaging technique using light in the short-wave infrared wavelength region of about 1.0 to 1.7 μm is used. Therefore, for the applied lens as well, a diffractive optical element having a desired wavelength dependence of refractive index, which can obtain a chromatic aberration reduction effect in a wide wavelength range from near-infrared to short-wave infrared wavelength regions when used in a multilayer diffractive optical element, and showing high transmittance in this wide wavelength range is required. The inventors have repeatedly studied a technique for applying a diffractive optical element that can adjust the wavelength dependence of the refractive index by adding ITO particles and obtain an effect of reducing chromatic aberration when used in a low refractive index layer in a multilayer diffractive optical element to an optical system that uses light in the near-infrared to short-wavelength infrared wavelength range. As a result, it has been found that it is difficult to achieve a high transmittance over the entire wavelength range from near-infrared to short-wavelength infrared with the ITO particles described in Patent Document 1 or 2. Therefore, there is a need for a new technique that can achieve the desired wavelength dependence of the refractive index and high transmittance in the near-infrared to short-wavelength infrared wavelength range.

[0007] The present invention provides a cured product suitable as a material for a low refractive index layer in a multilayer diffractive optical element, which can obtain a desired chromatic aberration reducing effect over the near-infrared to short-wavelength infrared wavelength range when used in a multilayer diffractive optical element, and can exhibit a high transmittance in this wavelength range, and a curable resin composition suitable for obtaining this cured product. Another object of the present invention is to provide a diffractive optical element and a multilayer diffractive optical element containing this cured product.

Means for Solving the Problems

[0008] The above problems have been solved by the following means. 〔1〕 A curable resin composition containing oxide nanoparticles containing indium and cerium, a (meth)acrylate compound having one or more functional groups, and a dispersant. 〔2〕 The curable resin composition according to 〔1〕, wherein the oxide nanoparticles contain at least one element selected from zirconium, hafnium, and tin. 〔3〕 The curable resin composition according to 〔2〕, wherein the oxide nanoparticles contain tin. 〔4〕 The curable resin composition according to any one of 〔1〕 to 〔3〕, wherein the cerium concentration of the oxide nanoparticles is 0.5 to 3.0 at%. 〔5〕 The curable resin composition according to [2] or [3], wherein the total concentration of zirconium, hafnium and tin in the oxide nanoparticles is 0.1 to 2.0 at%. [6] The curable resin composition according to any one of [1] to [5], wherein the content of the oxide nanoparticles in the curable resin composition is 10 to 60% by mass. [7] The curable resin composition according to any one of [1] to [6], wherein the average particle diameter of the oxide nanoparticles is 16 to 30 nm. [8] The curable resin composition according to [7], wherein the average particle diameter of the oxide nanoparticles is 20 to 30 nm. [9] The curable resin composition according to any one of [1] to [8], which contains a photo radical polymerization initiator.

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

[11] ) The cured product according to

[10] , wherein the refractive index at a wavelength of 852 nm is 1.500 to 1.650.

[12] The cured product according to

[10] or

[11] , wherein the refractive index at a wavelength of 1530 nm is 1.300 to 1.550.

[13] A diffractive optical element including a surface having a diffractive grating shape formed of the cured product according to any one of

[10] to

[12] .

[14] Including a first diffractive optical element and a second diffractive optical element, wherein the first diffractive optical element is the diffractive optical element according to

[13] , A multilayer diffractive optical element, wherein the surface having a diffractive grating shape in the first diffractive optical element faces the surface having a diffractive grating shape in the second diffractive optical element.

[15] The multilayer diffractive optical element according to

[14] , wherein the refractive index of the second diffractive optical element at a wavelength of 852 nm is 1.550 to 1.700, and this refractive index is larger than the refractive index of the first diffractive optical element at a wavelength of 852 nm.

[16] The multilayer diffractive optical element according to

[14] or

[15] , wherein the surface having the diffraction grating shape in the first diffractive optical element is in contact with the surface having the diffraction grating shape in the second diffractive optical element.

[17] The multilayer diffractive optical element according to any one of

[14] to

[16] , including a transparent substrate, wherein the first diffractive optical element, the second diffractive optical element, and the transparent substrate are arranged in this order.

[18] Oxide nanoparticles containing indium and cerium and at least one element selected from tin, zirconium, and hafnium, and having an average particle diameter of 16 to 30 nm.

[19] A lens additive for adjusting the wavelength dependence of the refractive index, comprising the oxide nanoparticles according to

[18] .

[0009] In the present invention, the display of compounds and substituents is used in the meaning including their salts and ions in addition to the compounds and substituents themselves. For example, a carboxy group or the like may have a dissociated hydrogen atom to form an ionic structure or may have a salt structure. That is, in the present invention, the "carboxy group" is used in the meaning including a carboxylate ion or its salt. The same applies to other acidic groups. The monovalent or polyvalent cations constituting the salt structure are not particularly limited, and examples include inorganic cations and organic cations. Specifically, Na + , Li + and K + and other cations of alkali metals, Mg 2+ , Ca 2+ and Ba 2+ and other cations of alkaline earth metals, and organic ammonium cations such as trialkylammonium cations and tetraalkylammonium cations. In the case of a salt structure, the type of the salt may be one kind, or two or more kinds may be mixed, a salt form group and a free acid structure group may be mixed in the compound, or a compound having a salt structure and a compound having a free acid structure may be mixed. In the present invention, when there are a plurality of substituents, linking groups, structural units, etc. (hereinafter referred to as substituents, etc.) represented by specific symbols or formulas, or when a plurality of substituents, etc. are defined simultaneously, unless otherwise specified, each of the substituents, etc. may be the same as or different from each other (regardless of the presence or absence of the expression "each independently", each of the substituents, etc. may be the same as or different from each other). This also applies to the definition of the number of substituents, etc. Further, when a plurality of substituents, etc. are close to each other (especially when adjacent), unless otherwise specified, they may be linked to each other to form a ring. Further, unless otherwise specified, a ring, for example, an alicyclic ring, an aromatic ring, or a heterocyclic ring may be further condensed to form a fused ring. In the present invention, unless otherwise specified, for a double bond, when both an E-form and a Z-form exist in the molecule, either one or a mixture thereof may be used. Further, in the present invention, unless otherwise specified, when a compound has one or more asymmetric carbons, the stereochemistry of such asymmetric carbons may each independently take either the (R)-form or the (S)-form. As a result, the compound may be a mixture of stereoisomers such as optical isomers or diastereoisomers, or may be a racemate. Also, in the present invention, the representation of the compound includes those in which a part of the structure is changed within a range not impairing the effects of the present invention. Further, for a compound in which substitution or non-substitution is not specified, it means that it may have any substituent within a range not impairing the effects of the present invention. Regarding substituents for which substitution or non-substitution is not specified in the present invention (the same applies to linking groups and rings), it means that within a range that does not impair the desired effect, the group may have any substituent, and there is no particular limitation on the number of substituents that may be present. For example, in the case of an "alkyl group", it means including both unsubstituted alkyl groups and substituted alkyl groups. Similarly, for example, in the case of an "aryl group", it means including both unsubstituted aryl groups and substituted aryl groups. In the present invention, when defining the number of carbon atoms of a certain group, unless otherwise specified in the present invention or in this specification, the number of carbon atoms means the total number of carbon atoms of the entire group. That is, when this group is in a form having further substituents, it means the total number of carbon atoms including these substituents.

[0010] In the present invention, the numerical range represented by "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value. In the present invention, each component may be used alone or two or more of them may be mixed and used. In the description of the content of each component in the curable resin composition of the present invention, when the curable resin composition contains a solvent, the content of each component is based on the component composition obtained by removing the solvent from the curable resin composition. For example, when the curable resin composition is composed of 20 parts by mass of a solvent, 40 parts by mass of component A, and 40 parts by mass of component B, for a total of 100 parts by mass, the content of this component A in the composition is based on 80 parts by mass after removing the solvent, so it is 50% by mass.

[0011] In the present invention, "(meth)acrylate" represents either acrylate or methacrylate, or both, and "(meth)acryloyl" represents either acryloyl or methacryloyl, or both. The monomers in the present invention are distinguished from oligomers and polymers and refer to compounds having a weight average molecular weight of 1000 or less.

[0012] In the present invention, the term "aliphatic hydrocarbon group" means a group obtained by removing any one hydrogen atom from a straight-chain or branched alkane, straight-chain or branched alkene, or straight-chain or branched alkyne. In the present invention, the aliphatic hydrocarbon group is preferably an alkyl group obtained by removing any one hydrogen atom from a straight-chain or branched alkane. Examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, 1-methylbutyl group, 3-methylbutyl group, hexyl group, 1-methylpentyl group, 4-methylpentyl group, heptyl group, 1-methylhexyl group, 5-methylhexyl group, 2-ethylhexyl group, octyl group, 1-methylheptyl group, nonyl group, 1-methyloctyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group and the like. In the present invention, the unsubstituted aliphatic hydrocarbon group is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 12 carbon atoms.

[0013] In the present invention, the term "alkyl group" means a straight-chain or branched alkyl group. Examples of the alkyl group include the above examples. The same applies to the alkyl group in a group containing an alkyl group (alkoxy group, alkoxycarbonyl group, acyl group, etc.). In the present invention, examples of the straight-chain alkylene group include groups obtained by removing one hydrogen atom bonded to the terminal carbon atom from the straight-chain alkyl groups among the above alkyl groups.

[0014] In the present invention, the alicyclic hydrocarbon ring means a saturated hydrocarbon ring (cycloalkane). Examples of the alicyclic hydrocarbon ring include cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane and the like. In the present invention, the unsaturated hydrocarbon ring means a hydrocarbon ring having a carbon-carbon unsaturated double bond and not being an aromatic ring. Examples of the unsaturated hydrocarbon ring include indene, indane, and fluorene.

[0015] In the present invention, when referring to an alicyclic hydrocarbon group, it means a cycloalkyl group obtained by removing any one hydrogen atom from cycloalkane. Examples of the alicyclic hydrocarbon group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, etc., and a cycloalkyl group having 3 to 12 carbon atoms is preferred. In the present invention, the cycloalkylene group represents a divalent group obtained by removing any two hydrogen atoms from cycloalkane. An example of the cycloalkylene group is a cyclohexylene group.

[0016] In the present invention, when referring to an aromatic ring, it means either one or both of an aromatic hydrocarbon ring and an aromatic heterocyclic ring.

[0017] In the present invention, the aromatic hydrocarbon ring means an aromatic ring formed only by carbon atoms. The aromatic hydrocarbon ring may be a monocyclic ring or a condensed ring. Examples of the aromatic hydrocarbon ring include benzene, biphenyl, biphenylene, naphthalene, anthracene, phenanthrene, etc. In the present invention, when the aromatic hydrocarbon ring is bonded to another ring, the aromatic hydrocarbon ring may be substituted on the other ring as a monovalent or divalent aromatic hydrocarbon group. Also, in the present invention, the unsubstituted aromatic hydrocarbon ring is preferably an aromatic hydrocarbon ring having 6 to 14 carbon atoms.

[0018] In the present invention, when referring to a monovalent group as an aromatic hydrocarbon group (also referred to as an aryl group), it means a monovalent group obtained by removing any one hydrogen atom from an aromatic hydrocarbon ring. Examples of the monovalent aromatic hydrocarbon group include a phenyl group, a biphenyl group, a 1-naphthyl group, a 2-naphthyl group, a 1-anthracenyl group, a 2-anthracenyl group, a 3-anthracenyl group, a 4-anthracenyl group, a 9-anthracenyl group, a 1-phenanthryl group, a 2-phenanthryl group, a 3-phenanthryl group, a 4-phenanthryl group, a 9-phenanthryl group, and the like. Among these, a phenyl group, a 1-naphthyl group, and a 2-naphthyl group are preferred.

[0019] In the present invention, when referring to a divalent aromatic hydrocarbon group, it means a divalent group obtained by removing any two hydrogen atoms from an aromatic hydrocarbon ring. Examples of the divalent aromatic hydrocarbon group include divalent groups obtained by removing any one hydrogen atom from the above-mentioned monovalent aromatic hydrocarbon groups. Among these, a phenylene group is preferred, and a 1,4-phenylene group is more preferred.

[0020] In the present invention, an aromatic heterocyclic ring means an aromatic ring formed by at least one heteroatom and atoms selected from carbon atoms and heteroatoms. Examples of the heteroatom include an oxygen atom, a nitrogen atom, and a sulfur atom. The aromatic heterocyclic ring may be a monocyclic ring or a condensed ring, and the number of atoms constituting the ring is preferably 5 to 20, more preferably 5 to 14. The number of heteroatoms in the atoms constituting the ring is not particularly limited, but is preferably 1 to 3, more preferably 1 to 2. Examples of the aromatic heterocyclic ring include a furan ring, a thiophene ring, a pyrrole ring, imidazole, isothiazole, isoxazole, pyridine, pyrazine, quinoline, benzofuran, benzothiazole, benzoxazole, and examples of the nitrogen-containing condensed aromatic rings described below. In the present invention, when the aromatic heterocyclic ring is bonded to another ring, the aromatic heterocyclic ring may be substituted on the other ring as a monovalent or divalent aromatic heterocyclic group.

[0021] In the present specification, when referring to a monovalent group as an aromatic heterocyclic group (also referred to as a heteroaryl group), it means a monovalent group obtained by removing any one hydrogen atom from an aromatic heterocycle. Examples of the monovalent aromatic heterocyclic group include a furyl group, a thienyl group (preferably a 2-thienyl group), a pyrrolyl group, an imidazolyl group, an isothiazolyl group, an isoxazolyl group, a pyridyl group, a pyrazinyl group, a quinolyl group, a benzofuranyl group (preferably a 2-benzofuranyl group), a benzothiazolyl group (preferably a 2-benzothiazolyl group), a benzoxazolyl group (preferably a 2-benzoxazolyl group), and the like. Among these, a furyl group, a thienyl group, a benzofuranyl group, a benzothiazolyl group, and a benzoxazolyl group are preferred, and a 2-furyl group and a 2-thienyl group are more preferred.

[0022] In the present invention, when referring to a divalent aromatic heterocyclic group, it means a divalent group obtained by removing any two hydrogen atoms from an aromatic heterocycle. Examples of the divalent aromatic heterocyclic group include divalent groups obtained by removing any one hydrogen atom from the above-mentioned monovalent aromatic heterocyclic groups. In the present invention, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

Effects of the Invention

[0023] The curable resin composition of the present invention is a curable resin composition containing oxide nanoparticles containing indium and cerium. By subjecting this composition to a curing reaction, when used in a multilayer diffractive optical element, it exhibits a desired wavelength dependence of refractive index (hereinafter, also simply referred to as "wavelength dependence of refractive index") that contributes to reducing chromatic aberration over the near-infrared to short-wave infrared wavelength range, and a cured product having a high transmittance over the entire wavelength range can be obtained. In addition, the cured product of the present invention can be suitably used as a material for a diffractive optical element and a multilayer diffractive optical element that exhibit a desired wavelength dependence of refractive index that contributes to reducing chromatic aberration over the near-infrared to short-wave infrared wavelength range and a high transmittance over the entire wavelength range when used in a multilayer diffractive optical element.

Modes for Carrying Out the Invention

[0024] <<Curable resin composition>> The curable resin composition of the present invention contains at least oxide nanoparticles containing indium and cerium, a mono- or higher functional (meth)acrylate compound, and a dispersant. The curable resin composition of the present invention means a composition that has curability and is capable of giving a cured product (resin) by a curing reaction. The curable resin composition of the present invention may contain other components in addition to the above components. Each component will be described below.

[0025] <Oxide nanoparticles containing indium and cerium> The curable resin composition of the present invention contains oxide nanoparticles containing indium and cerium (hereinafter, also referred to as "ICO particles (A)"). In the present invention, "oxide nanoparticles containing indium and cerium" means nanoparticles composed of oxides of elements containing indium and cerium. By using ICO particles (A) instead of indium tin oxide particles (ITO particles) contained in the curable resin composition, a cured product can be obtained in which the decrease in transmittance in the short wave infrared wavelength range (SWIR) that occurs when ITO particles are added is suppressed, as described in Patent Document 1. This is because, by making the compound constituting the nanoparticles an oxide containing indium and cerium, it is possible to adjust the absorption to be sharper while maintaining the wavelength showing the maximum absorption compared to when ITO particles are used, so that the absorption in the tail of the absorption of ICO particles (A) in the SWIR is reduced compared to ITO particles, and the transmittance in the SWIR is increased.

[0026] The oxide of an element containing indium and cerium constituting the ICO particles (A) may be an oxide of an organic compound or an oxide of an inorganic compound as long as it contains indium and cerium, and is preferably a metal oxide. In addition to indium and cerium, the ICO particles (A) preferably contain at least one element selected from zirconium, hafnium, and tin, and more preferably contain tin, from the viewpoint of making the absorption of the ICO particles (A) sharper and realizing a better wavelength dependence of the refractive index.

[0027] (Concentration of constituent elements) In the present invention, the concentration of element α in the ICO particles (A) (element α represents any arbitrary element) means the ratio (at%) of element α in the metal elements constituting the ICO particles (A). The cerium concentration of the ICO particles (A) can be, for example, 0.1 to 3.5 at%, preferably 0.5 to 3.0 at%, and more preferably 0.5 to 2.0 at% from the viewpoint of making the wavelength dependence of the refractive index better. When the ICO particles (A) contain zirconium, the zirconium concentration of the ICO particles (A) can be, for example, 3.0 at% or less, preferably 2.0 at% or less, and more preferably 1.0 at% or less. When the ICO particles (A) contain hafnium, the hafnium concentration of the ICO particles (A) can be, for example, 3.0 at% or less, preferably 2.0 at% or less, and more preferably 1.0 at% or less. When the ICO particles (A) contain tin, the tin concentration of the ICO particles (A) can be, for example, 3.0 at% or less, preferably 2.0 at% or less, and more preferably 1.5 at% or less. The total concentration of zirconium, hafnium, and tin in the ICO particles (A) (the ratio of the total amount of zirconium, hafnium, and tin in the metal elements constituting the ICO particles (A)) can be, for example, 0.1 to 3.0 at%, preferably 0.1 to 2.0 at%, and more preferably 0.2 to 2.0 at% from the viewpoint of further improving the transmittance. In the present invention, the ICO particles (A) are oxides obtained by doping indium oxide with cerium and further optionally an element. The indium concentration of the ICO particles (A) can be, for example, 90.0 to 99.5 at%, preferably 92.0 to 99.0 at%, and more preferably 94.0 to 99.0 at%.

[0028] The concentration of element α of the above ICO particles (A) can be adjusted by the concentration of element α in each precursor solution used for the preparation of the ICO particles (A).

[0029] (Average particle diameter) The average particle diameter of the ICO particles (A) can be, for example, 5 to 50 nm. From the viewpoint of further improving the transmittance, 16 to 30 nm is preferable, and 20 to 30 nm is more preferable. By setting it below the above upper limit value, it is possible to prevent the deterioration of the transmittance due to Rayleigh scattering. Also, at 5 nm or more, it is possible to manufacture the ICO particles (A) without technical difficulties. In particular, by setting the average particle diameter to 16 nm or more (more preferably 20 nm or more), the solidification of the composition is less likely to occur when preparing the curable resin composition of the present invention, the filling rate of the ICO particles (A) in the composition can be easily increased, and the wavelength dependence of the refractive index can be made better.

[0030] Among the ICO particles (A) used in the present invention, oxide nanoparticles containing indium, cerium, and at least one element selected from tin, zirconium, and hafnium and having an average particle diameter of 16 to 30 nm are preferable from the viewpoint of making the wavelength dependence of the refractive index better and further improving the transmittance. The ICO particles (A) used in the present invention can be used as an additive for lenses for adjusting the wavelength dependence of the refractive index.

[0031] Hereinafter, the methods for measuring and calculating the concentration of element α and the average particle diameter of the ICO particles (A) will be summarized. Details such as the measurement conditions are as described in the examples below.

[0032] (ICP-MS analysis) The concentration of element α in the ICO particles (A) can be measured by ICP-MS (Inductively Coupled Plasma Mass Spectrometry).

[0033] (TEM analysis) The average particle diameter of the ICO particles (A) can be determined by averaging the equivalent circle diameters of the primary particles measured by a transmission electron microscope (Transmission Electron Microscopy: TEM). That is, for one particle in the electron micrograph taken by TEM, the area S of the particle is measured, and the diameter of the perfect circle corresponding to this area S (equivalent circle diameter = 2(S / π) 0.5 ) is obtained. The average particle diameter in the present invention is the arithmetic mean of the equivalent circle diameters obtained for 500 randomly extracted particles.

[0034] Also, regarding the concentration or average particle diameter of element α in the ICO particles (A) in the cured product, for the particles obtained by dissolving the cured product using an alkaline solution or the like, as described above, they can be measured and calculated by ICP-MS or TEM.

[0035] (Preparation of ICO particles (A), preparation of the composition) The curable resin composition of the present invention is preferably prepared by mixing ICO particles (A) in a dispersed state in a solvent with a dispersant and a (meth)acrylate compound described below. After mixing, the solvent used for dispersing the ICO particles (A) may or may not be removed from the curable resin composition by distillation or the like, but it is preferably removed.

[0036] The ICO particles (A) can have their dispersibility in a solvent increased by making them surface-modified ICO particles (A). The surface modification of the ICO particles (A) is preferably carried out, for example, using a monocarboxylic acid having 6 to 20 carbon atoms as a surface-modifying compound. The surface modification of the ICO particles (A) with the monocarboxylic acid can be carried out by a conventional method, and it is preferable that a carboxy group derived from the monocarboxylic acid forms an ester bond with an oxygen atom on the surface of the ICO particles (A), or that the carboxy group coordinates to an In or Ti atom. Examples of the monocarboxylic acid having 6 to 20 carbon atoms include oleic acid (18 carbon atoms), stearic acid (18 carbon atoms), palmitic acid (16 carbon atoms), myristic acid (14 carbon atoms), or decanoic acid (10 carbon atoms), with oleic acid (18 carbon atoms) being preferred.

[0037] In the curable resin composition, the site derived from the surface-modifying compound in the above-described surface-modified ICO particles (A) (for example, a group derived from a monocarboxylic acid having 6 to 20 carbon atoms) may be directly bonded to the ICO particles (A), may be partially replaced by a group derived from a dispersant described later, or may all be replaced by a group derived from the dispersant described later. In the curable resin composition of the present invention, it is preferable that both a site derived from the surface-modifying compound (for example, a group derived from a monocarboxylic acid having 6 to 20 carbon atoms) and a group derived from a dispersant described later are bonded to the surface of the ICO particles (A).

[0038] As the above solvent, it is preferable that the component of the polar term (δp) of the solubility parameter (SP value) is 0 to 6 MPa 1 / 2 of the solvent. The component of the polar term (δp) of the SP value is a value calculated by the Hansen solubility parameter. The Hansen solubility parameter is composed of the intermolecular dispersion force energy (δd), the intermolecular polar energy (δp), and the intermolecular hydrogen bonding energy (δh). In the present invention, the Hansen solubility parameter is assumed to be calculated using HSPiP (version 4.1.07) software. Specifically, the solvent is preferably toluene (1.4), xylene (1.0) or hexane (0), more preferably toluene. The values in parentheses are the δp values, with the unit being MPa. (1 / 2) It is.

[0039] The method for producing the ICO particles (A) is not particularly limited. For example, it can be produced according to the procedures described in ACS Nano 2016, 10, 6942 - 6951 and Nano Lett. 2016, 16, 3390 - 3398. By the procedures in the same literature, a dispersion of the ICO particles (A) can be obtained, and for the surface modification, it can also be carried out with reference to the description in the same literature. Specifically, a mixed solution (hereinafter referred to as "mixed solution α") of a monocarboxylic acid having 6 to 20 carbon atoms, an indium salt (such as indium acetate), and a cerium salt (such as cerium acetylacetonate) is heated and mixed to prepare a precursor solution (hereinafter referred to as "precursor solution β"). This precursor solution β is dropped into an alcohol (a long-chain alcohol such as oleyl alcohol) heated to a high temperature. After the reaction is completed, the heating is stopped and it is cooled to room temperature. Thereafter, by performing centrifugation or adding a poor solvent (a lower alcohol such as ethanol) with low solubility of the polymer to precipitate the particles, removing the supernatant, and redispersing in a solvent such as the above-mentioned toluene, a dispersion of the surface-modified ICO particles (A) can be obtained. In addition, other compounds may be added to the above-mentioned mixed solution α according to the constituent elements of the target ICO particles (A). For example, a tin salt (such as tin acetate), a zirconium salt (such as zirconium acetylacetonate), and a hafnium salt (such as hafnium acetylacetonate) can be added. Also, the compounding concentration of each compound in the above-mentioned mixed solution α may be adjusted according to the content ratio of the constituent elements of the target ICO particles (A). For elements such as cerium, zirconium, and hafnium whose element concentration in the obtained ICO particles (A) becomes low with respect to the compounding concentration of each element in the above-mentioned mixed solution α, consideration should be given to this point for compounding. In the step of heating and mixing the above-mentioned mixed solution α to obtain the above-mentioned precursor solution β, the temperature and time for heating and mixing are not particularly limited as long as a precursor in which a monocarboxylic acid having 6 to 20 carbon atoms is coordinated to indium, cerium, etc. (such as indium oleate, cerium oleate, etc.) can be obtained. In the step of dropping the above-mentioned mixed solution α into alcohol heated to a high temperature, the heating temperature of the alcohol and the dropping rate of the above-mentioned mixed solution α are not particularly limited as long as the target ICO particles (A) can be obtained.

[0040] The content ratio of the ICO particles (A) in the curable resin composition of the present invention is preferably 10 to 70% by mass, more preferably 10 to 60% by mass, and even more preferably 20 to 50% by mass.

[0041] <Dispersant> The curable resin composition of the present invention contains a dispersant for dispersing the ICO particles (A) in the composition. As the above-mentioned dispersant, a cationic surfactant, an anionic surfactant, or an amphoteric surfactant can be used. By using these dispersants, the ICO particles (A) can be dispersed in the composition.

[0042] The cationic surfactant preferably has an amine salt type group or a quaternary ammonium salt type group. As the anionic surfactant, as an acidic group, it preferably has any one or any salt of a carboxy group, a phosphono group (-PO(OH)2), a phosphonooxy group (phosphoric acid group, -OPO(OH)2), a hydrohydroxyphosphoryl group (-PH(O)(OH)), a sulfino group (-SO(OH)), a sulfo group (-SO2(OH)), and a sulfanyl group (-SH). The above-mentioned acidic group is more preferably any one or any salt of a carboxy group, a phosphono group, and a phosphonooxy group, and even more preferably a carboxy group or a salt thereof. Examples of such anionic surfactants include carboxylic acid type such as (meth)acrylic acid compounds and hydroxystearic acid compounds, phosphoric acid type such as phosphoric acid compounds, sulfonic acid type such as amidosulfonic acid compounds, polycarboxylic acid type such as poly(meth)acrylic acid, or anionic surfactants of polyphosphoric acid type. Examples of amphoteric surfactants include amino acid type or betaine type amphoteric surfactants. The ionic groups such as acidic groups in the above dispersant exhibit an adsorption action by at least one of ionic bond, covalent bond, hydrogen bond or coordination bond with respect to the surface of the ICO particles (A), thereby functioning as a dispersant. Among these, anionic surfactants are preferred as the above dispersant.

[0043] Specific examples of the above dispersant include DISPERBYK-106, 108, 110, 111, 118, 140, 142, 145, 161, 162, 163, 164, 167, 168, 180, 2013, 2055, 2155 in the DISPERBYK series (trade name, manufactured by BYK Japan), and Hosmer M, Hosmer PE, Hosmer MH, Hosmer PP, etc. in the Hosmer series (trade name, manufactured by Uni-Chemical).

[0044] (Acidic polymer) In addition, as the above dispersant, acidic polymers having the above acidic groups as adsorption groups that adsorb to the ICO particles (A) (hereinafter also referred to as acidic polymers) are also preferably mentioned. The acidic group of the acidic polymer is preferably a carboxy group or a salt thereof. The acidic polymer containing a carboxy group has higher compatibility with the (meth)acrylate compound described below than, for example, a phosphoric acid-based dispersant having a phosphono group or a phosphonoxy group. Therefore, when curing the curable resin composition to which the acidic polymer having a carboxy group is added, phase separation or whitening hardly occurs. Further, when forming the diffraction grating shape, the adhesiveness between the resin and the mold is good, and the curing shrinkage is small, so that roughness of the peeling surface hardly occurs. Furthermore, an increase in viscosity hardly occurs as compared with, for example, an amine-based dispersant having an amine salt type group or a quaternary ammonium salt type group.

[0045] The acidic polymer preferably contains a (meth)acrylate polymer skeleton composed of (meth)acrylate structural units. By including the (meth)acrylate polymer skeleton, the compatibility between the acidic polymer and the (meth)acrylate compound in the curable resin composition can be further improved. Further, the refractive index control of the cured product obtained by curing the curable resin composition becomes easy. Examples of the (meth)acrylate structural unit include structural units derived from the (meth)acrylate monomers described in paragraph 0042 of JP-A-2012-107191, and structural units represented by the following general formula (P) are preferable.

[0046] [Chemical formula]

[0047] In the above formula, R P1 represents a hydrogen atom or a methyl group, and R P2 represents a monovalent substituent. * represents a bonding portion for incorporation into the polymer main chain. R P2 is preferably an alkyl group or an alicyclic hydrocarbon group, and an alkyl group is preferable. The number of carbon atoms of this alkyl group is preferably 1 to 20, more preferably 1 to 12, still more preferably 1 to 8, particularly preferably 1 to 4, and most preferably 1. R P1The methyl group and R that can be adopted P2 From the viewpoint of preventing an increase in the viscosity of the curable resin composition, it is preferable that the alkyl group and the alicyclic hydrocarbon group that can be adopted do not contain the acidic group as a substituent.

[0048] The above (meth)acrylate polymer skeleton may be linear or branched. Among them, it is preferably linear.

[0049] The number of (meth)acrylate structural units constituting one (meth)acrylate polymer skeleton is preferably 5 to 50, more preferably 8 to 40, and still more preferably 10 to 30.

[0050] The number of (meth)acrylate polymer skeletons contained in one molecule of the above acidic polymer may be 1 or 2 or more. For example, 1 to 6 is preferable, and 1 to 4 is more preferable.

[0051] The above acidic polymer preferably has a site containing an acidic group on at least one terminal side of the above (meth)acrylate polymer skeleton. "Having a site containing an acidic group on at least one terminal side of the (meth)acrylate polymer skeleton" means having a site containing an acidic group directly or via a linking group with respect to at least one terminal of the (meth)acrylate polymer skeleton. By having a site containing an acidic group on the terminal side in the (meth)acrylate polymer skeleton, an increase in the viscosity of the curable resin composition due to the acidic polymer can be prevented. More preferably, the above acidic polymer has a site containing the above acidic group at the terminal of the polymer chain, and more preferably, the acidic polymer has a site containing an acidic group only on one terminal side of the above (meth)acrylate polymer skeleton. When the acidic polymer contains two or more (meth)acrylate polymer skeletons in one molecule, it is preferable that all the (meth)acrylate polymer skeletons have a site containing an acidic group on at least one terminal side of at least one of the (meth)acrylate polymer skeletons. More preferably, all the (meth)acrylate polymer skeletons have a site containing an acidic group only on one terminal side of any one of the (meth)acrylate polymer skeletons.

[0052] More preferably, the acidic polymer contains an acidic group only in the (meth)acrylate polymer skeleton. Even more preferably, the (meth)acrylate polymer skeleton is linear and has a site containing an acidic group only at one end thereof. Thereby, an increase in the viscosity of the curable resin composition can be prevented.

[0053] Preferably, the acidic polymer has a structural part represented by the following general formula (PA) as the structural part containing the acidic group.

[0054]

Chemical formula

[0055] In the above formula, A P represents an acidic group, LL represents a single bond or a (x + 1)-valent linking group, x is an integer from 1 to 10. * indicates the bonding position with the remaining part of the acidic polymer.

[0056] A P The acidic group that can be adopted as A has the same meaning as the acidic group described for the above acidic polymer, and the preferred forms are also the same. Examples of the (x + 1)-valent linking group that can be adopted as LL include a (x + 1)-valent saturated fatty acid hydrocarbon group (a group obtained by removing x + 1 hydrogen atoms from an alkane) and a (x + 1)-valent alicyclic hydrocarbon group (a group obtained by removing x + 1 hydrogen atoms from an alicyclic hydrocarbon). Further, examples include a (x + 1)-valent group composed of a combination of these groups and a bond selected from -O-, -(C=O)-O- and -(C=O)-NH-. The number of carbon atoms of the x + 1-valent saturated fatty acid hydrocarbon group that can be taken as LL is preferably from 1 to 10, more preferably from 1 to 7, and even more preferably from 1 to 5. LL is preferably a group composed of an x + 1-valent saturated fatty acid hydrocarbon group or a combination of an x + 1-valent saturated fatty acid hydrocarbon group and -O-. x is preferably an integer from 2 to 8, more preferably an integer from 2 to 4, and even more preferably an integer of 2.

[0057] The structure represented by the above general formula (PA) is preferably the structure represented by the following general formula (PA1), and from the viewpoint of improving the adsorptivity to the ICO particles (A) by having a carboxy group in the adjacent site, it is more preferably the structure represented by the following formula (PA2).

[0058] [Chemical formula]

[0059] LL and x in the above formula have the same meanings as LL and x in the above general formula (PA). * indicates the bonding position with the remaining part of the acidic polymer.

[0060] The number of structures represented by the above formula (PA), (PA1) or (PA2) contained in the acidic polymer is preferably from 1 to 4.

[0061] The acid value of the acidic polymer is preferably 2.0 mgKOH / g or more and less than 100 mgKOH / g, and more preferably 2.0 mgKOH / g or more and less than 70 mgKOH / g. The acid value means the number of mg of potassium hydroxide required to neutralize the acidic components present in 1 g of the acidic polymer. By adjusting the molecular weight of the acidic polymer and the number of acidic groups such as carboxyl groups so that the acid value of the acidic polymer falls within the above-preferred range, it is possible to achieve both an appropriate viscosity and particle dispersion performance as a curable resin composition. When the acid value of the acidic polymer is 2.0 mgKOH / g or more, the acidic polymer can be sufficiently adsorbed and dispersed on the ICO particles (A). Further, when the acid value of the acidic polymer is less than 100 mgKOH / g, the number of adsorbing groups and the molecular size can be adjusted, and the viscosity of the curable resin composition can be adjusted to an appropriate range.

[0062] Preferred examples of the acidic polymer include acidic polymers having a structure represented by the following general formula (1). (R 1 -S-L 2 ) n -L 1 -(L 3 -A-R 2 ) m (1) In the above formula, R 1 is synonymous with -LL-(A P ) x in the above general formula (PA), and A represents a (meth)acrylate polymer skeleton represented by the above general formula (P). R 2 represents a hydrogen atom or a substituent containing no acidic group, L 1 represents a single bond or a (m + n)-valent linking group, and L 2 and L 3 represent a single bond or a divalent linking group. m is an integer in the range of 1 to 8, and n is an integer in the range of 1 to 9. However, m + n satisfies 2 to 6.

[0063] R 1 is preferably an alkyl group substituted with a carboxyl group, more preferably an alkyl group having 1 to 10 carbon atoms substituted with 2 to 4 carboxyl groups, still more preferably an alkyl group having 1 to 7 carbon atoms substituted with 2 to 3 carboxyl groups, and particularly preferably an alkyl group having 1 to 5 carbon atoms substituted with 2 carboxyl groups. Among them, the structure represented by the above formula (PA2) is preferred. R2 is preferably a hydrogen atom. L 1 Examples of the (m + n)-valent linking group that can be adopted as L include a group formed by removing any (m + n) hydrogen atoms in a linear or branched alkane, and the following groups.

[0064] [Chemical formula]

[0065] L 2 and L 3 Examples of the divalent linking group that can be adopted as L include an alkylene group having 1 to 10 carbon atoms, and a group in which any one or two or more non-adjacent -CH2- groups in an alkylene group having 1 to 10 carbon atoms are replaced by -O-, -S-, -C(=O)-, -OC(=O)-, -C(=O)O-, -OC(=O)O-, -NHC(=O)-, -C(=O)NH-, -OC(=O)NH-, -NHC(=O)O-, -SC(=O)- or -C(=O)S-.

[0066] The weight average molecular weight of the acidic polymer is preferably from 1000 to 20000, more preferably from 1000 to 15000, and even more preferably from 1000 to 7000. By setting it to 1000 or more, the incorporation of bubbles generated during the curing of the curable resin composition can be suppressed. Further, by setting it to be equal to or less than the above preferable upper limit value, the fluidity hardly decreases even when the amount necessary for the dispersion of the ICO particles (A) is added to the curable resin composition, and when forming the diffraction grating shape, air hardly enters the step of the mold and gaps hardly occur.

[0067] Specific examples of the acidic polymer include compounds having the following structures. In the following structural formulas, one end of the (meth)acrylate polymer skeleton (R in the general formula (1)) is a hydrogen atom. m and n have the same meanings as m and n in the general formula (1) above. 2 is a hydrogen atom. m and n are synonymous with m and n in the above general formula (1).

[0068] [Chemical formula]

[0069] The above polymer dispersant can be produced by a conventional method. For example, it can be produced by reacting a (meth)acrylate monomer with a compound capable of terminating the polymerization reaction of this monomer and having an acidic group. Examples of such a compound include mercaptosuccinic acid, mercaptosuccinic acid, or mercaptomalonic acid, and mercaptosuccinic acid is preferred. Further, polyol mercaptoalkylate or the like can be added and reacted to form a structure having a plurality of (meth)acrylate polymer skeletons in one molecule. For the polymer dispersant having a phosphonooxy group at one end, the method described in JP-A-6-20261 can be referred to.

[0070] In the curable resin composition, the content of the acidic polymer with respect to 100 parts by mass of the content of the ICO particles (A) is preferably 5 to 50 parts by mass, more preferably 5 to 30 parts by mass, still more preferably 5 to 25 parts by mass, and particularly preferably 5 to 20 parts by mass. By setting the content ratio within the above preferred range, it is possible to stably disperse the ICO particles (A) in the curable resin composition and suppress the incorporation of bubbles generated during curing.

[0071] <(meth)acrylate compound> The curable resin composition of the present invention contains a (meth)acrylate compound having one or more functional groups. The (meth)acrylate compound having one or more functional groups means a compound having one or more (meth)acryloyl groups as functional groups, and in the present invention, it is also simply referred to as "(meth)acrylate compound". The curable resin composition of the present invention can disperse the ICO particles (A) in a medium containing a (meth)acrylate compound by a dispersant, and from the curable resin composition of the present invention, a cured product in which the ICO particles (A) are dispersed in a resin containing the (meth)acrylate compound as a constituent component can be obtained. The (meth)acrylate compound only needs to have one or more functional groups, and there is no particular limitation on the number of functional groups. For example, it can be 8 functional groups or less. Specific examples of the monofunctional or difunctional (meth)acrylate compound include, for example, monomer 1 (phenoxyethyl acrylate), monomer 2 (benzyl acrylate), monomer 3 (tricyclodecane dimethanol diacrylate), and monomer 4 (dicyclopentanyl acrylate). Further, M-1 (1,6-hexanediol diacrylate), M-2 (1,6-hexanediol dimethacrylate), M-3 (benzyl acrylate), M-4 (isobornyl methacrylate), M-5 (dicyclopentanyl methacrylate), M-6 (dodecyl methacrylate), M-7 (2-ethylhexyl methacrylate), M-8 (2-hydroxyethyl acrylate), M-9 (hydroxypropyl acrylate), and M-10 (4-hydroxybutyl acrylate) can be mentioned.

[0072]

Chem.

[0073]

Chem.

[0074] There is no particular limitation on the method for obtaining the (meth)acrylate compound, and it may be obtained commercially or synthesized by a conventional method. When commercially available, for example, Biscote #192 PEA (the above monomer 1) (manufactured by Osaka Organic Chemical Industry Co., Ltd.), Biscote #160 BZA (the above monomer 2) (manufactured by Osaka Organic Chemical Industry Co., Ltd.), Light Ester Bz (the above monomer 2) (manufactured by Kyoeisha Chemical Co., Ltd.), A-DCP (the above monomer 3) (manufactured by Shin-Nakamura Chemical Co., Ltd.), FA-513AS (the above monomer 4) (manufactured by Hitachi Chemical Co., Ltd.), A-HD-N (the above M-1) (manufactured by Shin-Nakamura Chemical Co., Ltd.), HD-N (the above M-2) (manufactured by Shin-Nakamura Chemical Co., Ltd.), FA-BZA (the above M-3) (manufactured by Hitachi Chemical Co., Ltd.), Light Ester IB-X (the above M-4) (manufactured by Kyoeisha Chemical Co., Ltd.), FA-513M (the above M-5) (manufactured by Hitachi Chemical Co., Ltd.), Light Ester L (the above M-6) (manufactured by Kyoeisha Chemical Co., Ltd.), 2EHA (the above M-7) (manufactured by Toagosei Co., Ltd.), HEA (the above M-8) (manufactured by Osaka Organic Chemical Industry Co., Ltd.), Light Ester HOP-A(N) (the above M-9) (manufactured by Kyoeisha Chemical Co., Ltd.), 4-HBA (the above M-10) (manufactured by Osaka Organic Chemical Industry Co., Ltd.) can be preferably used.

[0075] When it is necessary to increase the surface hardness or abrasion resistance of the cured product, the curable resin composition preferably contains a polyfunctional (meth)acrylate compound having three or more (meth)acryloyl groups in the molecule. By containing a polyfunctional (meth)acrylate compound having three or more (meth)acryloyl groups in the molecule, the crosslinking density of the cured product can be effectively improved, so that the surface hardness and abrasion resistance can be increased while maintaining a high partial dispersion ratio. The upper limit of the number of (meth)acryloyl groups of the polyfunctional (meth)acrylate compound having three or more (meth)acryloyl groups in the molecule is not particularly limited, but it is preferably 8 or less, and more preferably 6. When commercially available, for example, A-TMPT (monomer 5), A-TMMT (monomer 6), AD-TMP (monomer 7), A-DPH (monomer 8) (manufactured by Shin-Nakamura Chemical Co., Ltd.) can be preferably used.

[0076]

Chemical formula

[0077] In addition to the above, examples include (meth)acrylate monomers described in paragraphs 0037 to 0046 of JP-A-2012-107191. The molecular weight of the (meth)acrylate compound is preferably from 100 to 500.

[0078] The content of the (meth)acrylate compound in the curable resin composition of the present invention is preferably from 1 to 60% by mass, more preferably from 2 to 50% by mass, and even more preferably from 3 to 50% by mass. By adjusting the amount of the (meth)acrylate compound in the curable resin composition, the function of relaxing the stress during thermal change of the cured product can be adjusted.

[0079] In particular, when it is necessary to increase the surface hardness and abrasion resistance of the cured product, the curable resin composition preferably contains a polyfunctional (meth)acrylate compound having three or more (meth)acryloyl groups in the molecule, based on the total mass of the curable resin composition (excluding the solvent when the solvent is included, the solid content mass), preferably from 5 to 50% by mass, more preferably from 10 to 45% by mass, and even more preferably from 25 to 40% by mass.

[0080] <Other Components> The curable resin composition of the present invention may further contain other components in addition to the ICO particles (A), the dispersant, and the (meth)acrylate compound. Specific examples of the other components include, for example, the following polymerization initiators. Further, it may contain the polymers described in paragraphs

[0099] to

[0108] of WO 2020 / 171197.

[0081] [Polymerization Initiator] The curable resin composition of the present invention preferably contains at least one selected from thermal radical polymerization initiators and photo radical polymerization initiators as the polymerization initiator.

[0082] (Thermal Radical Polymerization Initiator) The curable resin composition of the present invention preferably contains a thermal radical polymerization initiator. By thermally polymerizing the curable resin composition by the action of this thermal radical polymerization initiator, a cured product having high heat resistance can be molded.

[0083] As the thermal radical polymerization initiator, a compound usually used as a thermal radical polymerization initiator can be appropriately used according to the conditions of the thermal polymerization (thermal curing) process described later. For example, organic peroxides and the like can be mentioned, and specifically, the following compounds can be used. For example, 1,1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(4,4-di-(t-butylperoxy)cyclohexyl)propane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, dicumyl peroxide, di-t-butyl peroxide, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, cumene hydroperoxide, t-butyl hydroperoxide, t-butylperoxy-2-ethylhexyl, 2,3-dimethyl-2,3-diphenylbutane and the like can be mentioned.

[0084] When containing a thermal radical polymerization initiator, the content of the thermal radical polymerization initiator in the curable resin composition of the present invention is preferably 0.01 to 10% by mass, more preferably 0.05 to 5.0% by mass, and even more preferably 0.05 to 2.0% by mass.

[0085] (Photo radical polymerization initiator) The curable resin composition of the present invention preferably contains a photo radical polymerization initiator. As the photo radical polymerization initiator, a compound usually used as a photo radical polymerization initiator can be appropriately used according to the conditions of the photo polymerization (photo curing) process described later, and specifically, the following compounds can be used. For example, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,6-dimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,6-dichlorobenzoyl)-2,4,4-trimethylpentylphosphine oxide, 1-phenyl-2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 1,2-diphenylethanedione, methylphenylglyoxylate, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc. can be mentioned.

[0086] Among them, in the present invention, as the photoinitiator for free radical polymerization, 1-hydroxycyclohexyl phenyl ketone (for example, Irgacure 184 (trade name) manufactured by BASF), bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (for example, Irgacure 819 (trade name) manufactured by BASF), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (for example, Irgacure TPO (trade name) manufactured by BASF), 2,2-dimethoxy-1,2-diphenylethane-1-one (for example, Irgacure 651 (trade name) manufactured by BASF), 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one can be preferably used.

[0087] When containing a photoinitiator for free radical polymerization, the content of the photoinitiator for free radical polymerization in the curable resin composition of the present invention is preferably 0.01 to 5.0% by mass, more preferably 0.05 to 1.0% by mass, and still more preferably 0.05 to 0.5% by mass. In addition, it is also preferable that the curable resin composition contains both a photoinitiator for free radical polymerization and a thermal initiator for free radical polymerization. In this case, the total content of the photoinitiator for free radical polymerization and the thermal initiator for free radical polymerization in the above curable resin composition is preferably 0.01 to 5% by mass, more preferably 0.05 to 1.0% by mass, and still more preferably 0.05 to 0.5% by mass.

[0088] (Other additives, etc.) Within the range where the effects of the present invention are achieved, the curable resin composition of the present invention may contain additives such as polymers or monomers, dispersants, plasticizers, heat stabilizers, and mold release agents other than the above-described components.

[0089] <Other properties of the curable resin composition, etc.> The viscosity of the curable resin composition of the present invention is preferably 5000 mPa·s or less, more preferably 3000 mPa·s or less, still more preferably 2500 mPa·s or less, and particularly preferably 2000 mPa·s or less. By setting the viscosity of the curable resin composition within the above range, the handleability during the formation of the cured product can be improved, and a high-quality cured product can be formed. In addition, the viscosity of the curable resin composition is preferably 50 mPa·s or more, more preferably 100 mPa·s or more, still more preferably 200 mPa·s or more, and particularly preferably 500 mPa·s or more.

[0090] <Use of the curable resin composition> The use of the curable resin composition of the present invention is not particularly limited, but it is preferably used as a material for producing a diffractive optical element. In particular, among the low-refractive-index layer and the high-refractive-index layer in a multilayer diffractive optical element, it is used as a material for producing a low-refractive-index layer (a diffractive optical element having a low refractive index and a large wavelength dispersion of the refractive index), and can provide excellent diffraction efficiency.

[0091] <<Cured product>> The cured product of the present invention is formed from the curable resin composition of the present invention. The cured product is obtained by polymerizing a polymerizable compound such as a (meth)acrylate compound. Note that the cured product of the present invention may contain unreacted monomers. The cured product obtained by curing the curable resin composition of the present invention is transparent over the near-infrared to short-wave infrared wavelength region (approximately 800 to 1600 nm), and the refractive index at a wavelength of 852 nm and the refractive index at a wavelength of 1530 nm are both low as described below. For example, when the above cured product is formed as a sheet with a thickness of 6 μm, a transmittance value of 90% or more can be obtained at a wavelength of 852 nm, and a transmittance value of 40% or more can be obtained at a wavelength of 1650 nm, preferably 50% or more, more preferably 60% or more. Here, the transmittance means a value measured using a spectrophotometer (for example, the spectrophotometer "V-670" manufactured by JASCO Corporation).

[0092] The refractive index of the cured product obtained by curing the curable resin composition of the present invention at a wavelength of 852 nm is preferably 1.500 to 1.650, more preferably 1.500 to 1.600. The refractive index of the cured product obtained by curing the curable resin composition of the present invention at a wavelength of 1530 nm is preferably 1.300 to 1.550, more preferably 1.350 to 1.550, and even more preferably 1.400 to 1.510. The value obtained by subtracting the refractive index at a wavelength of 1530 nm from the refractive index at a wavelength of 852 nm of the cured product obtained by curing the curable resin composition of the present invention is preferably 0.010 to 0.100, more preferably 0.030 to 0.100. In the present invention, the refractive index means a value measured using ellipsometry, and can be measured, for example, with reference to the method described in the examples below. Note that the refractive index in the present invention is a value obtained by rounding off the fourth decimal place of the measured refractive index.

[0093] The birefringence Δn of the cured product of the curable resin composition of the present invention at a wavelength of 587 nm (also referred to as birefringence Δn(587 nm) in the present invention) is preferably 0.00 ≦ Δn ≦ 0.01. The birefringence Δn(587 nm) is more preferably 0.001 or less, and even more preferably less than 0.001. The lower limit value of the birefringence Δn(587 nm) may be 0.00001 or 0.0001.

[0094] The birefringence Δn(587 nm) of the cured product can be determined by the following method. A film-like sample is prepared, and using a birefringence evaluation apparatus (for example, trade name: WPA-100, manufactured by Photonic Lattice Co., Ltd.), the birefringence within a circle with a diameter of 10 mm including the center of the sample is measured, and the average value of the birefringence at a wavelength of 587 nm is obtained to obtain the birefringence Δn(587 nm).

[0095] <Method for manufacturing a cured product> The cured product of the present invention can be produced by photocuring the curable resin composition of the present invention by light irradiation or thermocuring by heating. When photocuring, it is preferable to contain the above-mentioned photo radical polymerization initiator in the curable resin composition, and when thermocuring, it is preferable to contain the above-mentioned thermal radical polymerization initiator. Regarding the conditions for photocuring, the description of light irradiation in the diffractive optical element described below can be preferably applied. In thermocuring, the heating temperature can be, for example, 150°C or higher, preferably 160 - 270°C, more preferably 165 - 250°C, and even more preferably 170 - 230°C. When heating, pressure can be applied together with heating. The pressure when applying pressure is preferably 0.098 MPa - 9.8 MPa, more preferably 0.294 MPa - 4.9 MPa, and even more preferably 0.294 MPa - 2.94 MPa. The thermocuring time is preferably 30 - 1000 seconds, more preferably 30 - 500 seconds, and even more preferably 60 - 300 seconds. The atmosphere during thermocuring (thermal polymerization) is preferably air or an atmosphere replaced with an inert gas, and more preferably an atmosphere replaced with nitrogen until the oxygen concentration becomes 1% or less.

[0096] <<Diffractive Optical Element>> The diffractive optical element of the present invention is a diffractive optical element including a surface having a diffractive grating shape formed of the cured product of the present invention, and is formed by curing the curable resin composition of the present invention. The diffractive optical element of the present invention preferably has a maximum thickness of 2 μm - 100 μm. The maximum thickness is more preferably 2 μm - 50 μm, and even more preferably 2 μm - 30 μm. Also, the step (grating thickness) of the diffractive grating shape (periodic structure) of the diffractive optical element is preferably 1 μm - 100 μm, and more preferably 1 μm - 50 μm. Furthermore, the pitch of the diffractive grating shape of the diffractive optical element may be between 0.1 mm and 10 mm, and it is preferably changed within the same diffractive optical element according to the required optical aberration.

[0097] The diffractive optical element can be manufactured, for example, by the following procedure. The curable resin composition is sandwiched between the surface of a mold having a surface processed into a diffraction grating shape and a transparent substrate. After this, the curable resin composition may be pressurized and stretched to a desired range. In the sandwiched state, light is irradiated from the transparent substrate side to cure the curable resin composition. Then, the cured product is released from the mold. After release, light may be irradiated from the opposite side to the transparent substrate side.

[0098] Examples of the transparent substrate include flat glass and flat transparent resin (such as (meth)acrylic resin, polycarbonate resin, and polyethylene terephthalate). The transparent substrate used in the above production may be included in the diffractive optical element as it is, or may be peeled off.

[0099] The surface of the mold that has been machined into the diffraction grating shape is preferably treated with chromium nitride, which provides good mold releasability and increases the efficiency of manufacturing diffractive optical elements. An example of the chromium nitride treatment is a method for forming a chromium nitride film on the surface of a mold. Methods for forming a chromium nitride film on the surface of a mold include, for example, CVD (Chemical Vapor Deposition) and PVD (Physical Vapor Deposition). The CVD method is a method for forming a chromium nitride film on the surface of a substrate by reacting a raw material gas containing chromium with a raw material gas containing nitrogen at high temperature. The PVD method is a method for forming a chromium nitride film on the surface of a substrate by utilizing an arc discharge (arc type vacuum deposition method). This arc type vacuum deposition method is a method in which a cathode (evaporation source) made of, for example, chromium is placed in a vacuum vessel, an arc discharge is caused between the cathode and the wall surface of the vacuum vessel via a trigger, the cathode is evaporated, and at the same time, the metal is ionized by the arc plasma, a negative voltage is applied to the substrate, and a reactive gas (for example, nitrogen gas) is introduced into the vacuum vessel at a pressure of about several tens of mTorr (1.33 Pa), whereby the ionized metal and the reactive gas react with each other on the surface of the substrate to form a compound film.

[0100] The light used for light irradiation for curing the curable resin composition is preferably ultraviolet light or visible light, and more preferably ultraviolet light. For example, a metal halide lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a germicidal lamp, a xenon lamp, an LED (Light Emitting Diode) light source lamp, etc. are preferably used. The illuminance of the ultraviolet light used for light irradiation for curing the curable resin composition is preferably 1 to 100 mW / cm 2 and more preferably 1 to 75 mW / cm 2 and even more preferably 5 to 50 mW / cm 2 The ultraviolet light with different illuminances may be irradiated multiple times. The exposure amount of the ultraviolet light is preferably 0.4 to 10 J / cm 2 and more preferably 0.5 to 5 J / cm 2 and even more preferably 1 to 3 J / cm 2 The atmosphere during light irradiation is preferably air or an inert gas-substituted atmosphere, and more preferably an atmosphere in which air is replaced with nitrogen until the oxygen concentration becomes 1% or less.

[0101] <<Multilayer Diffractive Optical Element>> The multilayer diffractive optical element of the present invention includes a first diffractive optical element and a second diffractive optical element, the first diffractive optical element being a diffractive optical element formed of the cured product of the present invention, and the surface having the diffraction grating shape in the first diffractive optical element and the surface having the diffraction grating shape in the second diffractive optical element being opposed to each other. The surfaces having the diffraction grating shapes of each other are preferably in contact. It is preferable to use the diffractive optical element formed by curing the curable resin composition of the present invention as the first diffractive optical element, and further stack a second diffractive optical element formed of a different material so that the surfaces of the grating shapes face each other to form a multilayer diffractive optical element. At this time, the surfaces of the grating shapes of each other are preferably in contact. By forming the second diffractive optical element with a material having a higher refractive index and a smaller wavelength dispersion of the refractive index than the first diffractive optical element, the generation of flare and the like can be suppressed, and the chromatic aberration reduction effect of the multilayer diffractive optical element can be fully utilized.

[0102] The refractive index of the second diffractive optical element at a wavelength of 852 nm (hereinafter also abbreviated as "n852") is preferably 1.550 to 1.700, more preferably 1.560 to 1.650. Further, the refractive index of the second diffractive optical element at a wavelength of 852 nm is greater than the refractive index of the first diffractive optical element that is used simultaneously in the multilayer diffractive optical element, that is, it satisfies the refractive index of the second diffractive optical element at a wavelength of 852 nm > the refractive index of the first diffractive optical element at a wavelength of 852 nm. The refractive index of the second diffractive optical element at a wavelength of 1530 nm (hereinafter also abbreviated as "n1530") is preferably 1.550 to 1.700, more preferably 1.560 to 1.650. Further, the refractive index of the second diffractive optical element at a wavelength of 1530 nm is greater than the refractive index of the first diffractive optical element that is used simultaneously in the multilayer diffractive optical element, that is, it satisfies the refractive index of the second diffractive optical element at a wavelength of 1530 nm > the refractive index of the first diffractive optical element at a wavelength of 1530 nm. The value obtained by subtracting the refractive index at a wavelength of 1530 nm from the refractive index at a wavelength of 852 nm of the second diffractive optical element (hereinafter also abbreviated as "n852 - n1530") is preferably 0.010 or less, more preferably 0.005 or less. Further, n852 - n1530 of the second diffractive optical element is smaller than n852 - n1530 of the first diffractive optical element that is used simultaneously in the multilayer diffractive optical element, that is, it satisfies [n852 - n1530 of the second diffractive optical element] < [n852 - n1530 of the first diffractive optical element].

[0103] The material for forming the second diffractive optical element is not particularly limited as long as a cured product having a high refractive index and a small wavelength dispersion of the refractive index can be obtained. For example, a curable resin composition containing a (meth)acrylate monomer having a sulfur atom, a halogen atom, or an aromatic ring structure, or a curable resin composition containing zirconium oxide and a (meth)acrylate monomer can be used.

[0104] The multilayer diffractive optical element can be manufactured, for example, by the following procedure. A material for forming a second diffractive optical element is sandwiched between the diffractive grating-shaped surface (the surface obtained after the above-mentioned mold release) of the diffractive optical element formed by curing the curable resin composition of the present invention and the transparent substrate. Thereafter, the material may be pressurized and stretched to a desired extent. While being sandwiched, light is irradiated from the transparent substrate side to cure the above-mentioned material. Thereafter, the cured product is released from the mold. That is, as the multilayer diffractive optical element of the present invention, it is preferable that the first diffractive optical element, the second diffractive optical element, and the transparent substrate are arranged in this order.

[0105] Examples of the transparent substrate include the same ones as those used in the production of the diffractive optical element (the first diffractive optical element). The transparent substrate used in the above production may be included in the multilayer diffractive optical element as it is, or may be peeled off.

[0106] It is preferable that the diffractive efficiency of the multilayer diffractive optical element is high. For example, the diffractive efficiency of the first-order light at a wavelength of 852 nm of the multilayer diffractive optical element is preferably 85% or more, more preferably 95% or more. Also, the diffractive efficiency of the first-order light at a wavelength of 1530 nm of the multilayer diffractive optical element is preferably 85% or more, more preferably 90% or more, and even more preferably 95% or more. Since the diffractive efficiency of the first-order light of the multilayer diffractive optical element shows a high diffractive efficiency at the wavelengths of 852 nm and 1530 nm as described above, unnecessary diffracted light can be sufficiently suppressed, and a high-performance lens excellent in chromatic aberration reduction effect can be realized.

[0107] The maximum thickness of the multilayer diffractive optical element is preferably 50 μm to 20 mm. The maximum thickness is more preferably 50 μm to 10 mm, and particularly preferably 50 μm to 3 mm.

[0108] <Lens> The diffractive optical element and the multilayer diffractive optical element of the present invention can each be used as a lens. A film or a member can be provided on the surface or around the lens according to the usage environment or application of the lens. For example, a protective film, an antireflection film, a hard coat film, etc. can be formed on the surface of the lens. Also, it can be made into a composite lens laminated on a glass lens or a plastic lens. Further, the periphery of the lens can be fitted and fixed into a base material holding frame or the like. However, these films or frames are members added to the lens and are distinguished from the lens itself as referred to in this specification.

[0109] The lens is preferably used as an imaging lens for a mobile phone or a digital camera, a shooting lens for a television, a video camera, etc., and further an in-vehicle lens.

Example

[0110] The present invention will be described in more detail based on the following examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below. In the present invention, "room temperature" means 25°C.

[0111] [Synthesis Example] Oxide nanoparticles and a dispersant were synthesized as follows.

[0112] [1. Synthesis of Oxide Nanoparticles] (1) Synthesis of In-Ce-Sn-O nanoparticles (ITCO-01) First, 420 ml of oleic acid (manufactured by FUJIFILM Wako Pure Chemical Corporation), 57.508 g of indium acetate (manufactured by Alfa Aesar), 4.777 g of cerium acetylacetonate (manufactured by SigmaAldrich), and 0.745 g of tin(IV) acetate (manufactured by Alfa Aesar) were charged into a flask, and heated at 160 °C for 2 hours under an environment of nitrogen flow to obtain a yellow transparent precursor solution A with a cerium concentration of 5.2 at% and a tin concentration of 1 at%. The prepared precursor solution A was filled to about 100 ml in a gastight syringe. Subsequently, 52 ml of oleyl alcohol (manufactured by FUJIFILM Wako Pure Chemical Corporation) was added to another flask and heated at 290 °C under nitrogen flow. The precursor solution A filled in the above gastight syringe was dropped into the heated solvent at a rate of 1.4 ml / min for 88 ml using a syringe pump. After the dropping of the precursor solution A was completed, the heating was stopped and cooled to room temperature. The obtained reaction solution was centrifuged to remove the supernatant, redispersed with toluene, and then a series of operations of adding ethanol, centrifuging, removing the supernatant, and redispersing with toluene were repeated 3 times to obtain 68 ml of a toluene dispersion of In-Ce-Sn-O nanoparticles (ITCO-01) coordinated with oleic acid. The average particle size of the above ITCO particles by TEM analysis was 21 nm. Also, when the molar ratio of the constituent elements (metal elements) was measured by ICP-MS analysis, it was In:Ce:Sn = 97.6:1.0:1.4.

[0113] (2) Synthesis of ITO nanoparticles (ITO-01) 420 ml of oleic acid, 60.451 g of indium acetate, and 1.043 g of tin(IV) acetate were charged into a flask, and heated at 160 °C for 2 hours under an environment of nitrogen flow to obtain a yellow transparent precursor solution B with a tin concentration of 1.4 at%. The prepared precursor solution B was filled to about 100 ml in a gastight syringe. In the synthesis of the above (ITCO-01), 68 ml of a toluene dispersion of In-Sn-O (ITO-01) coordinated with oleic acid was obtained in the same manner except that the precursor solution B was used instead of the precursor solution A. The average particle size of the above ITO particles by TEM analysis was 21 nm. Also, when the molar ratio of the constituent elements (metal elements) was measured by ICP-MS analysis, In:Sn = 98.6:1.4.

[0114] (3) Synthesis of In-Ce-O nanoparticles (ICO-01) First, 420 ml of oleic acid (manufactured by Fujifilm Wako Pure Chemical Corporation), 58.121 g of indium acetate (manufactured by Alfa Aesar), and 4.777 g of cerium acetylacetonate (manufactured by SigmaAldrich) were introduced into a flask, and heated at 160 °C for 2 hours in an environment of nitrogen flow to obtain a yellow transparent precursor solution C with a cerium concentration of 5.2 at%. The prepared precursor solution C was filled to about 100 ml in a gastight syringe. In the synthesis of the above (ITCO-01), in the same manner except that precursor solution C was used instead of precursor solution A, 68 ml of a toluene dispersion of oleic acid-coordinated In-Ce-O (ICO-01) was obtained. The average particle size of the above ICO particles by TEM analysis was 21 nm. Also, when the molar ratio of the constituent elements (metal elements) was measured by ICP-MS analysis, In:Ce = 98.8:1.2.

[0115] (4) Synthesis of In-Ce-Sn-O nanoparticles (ITCO-02) First, 420 ml of oleic acid (manufactured by Fujifilm Wako Pure Chemical Corporation), 53.339 g of indium acetate (manufactured by Alfa Aesar), 11.023 g of cerium acetylacetonate (manufactured by SigmaAldrich), and 0.745 g of tin(IV) acetate (manufactured by Alfa Aesar) were introduced into a flask, and heated at 160 °C for 2 hours in an environment of nitrogen flow to obtain a yellow transparent precursor solution D with a cerium concentration of 12 at% and a tin concentration of 1 at%. The prepared precursor solution D was filled to about 100 ml in a gastight syringe. In the synthesis of the above (ITCO-01), in the same manner except that precursor solution D was used instead of precursor solution A, 68 ml of a toluene dispersion of oleic acid-coordinated In-Ce-Sn-O nanoparticles (ITCO-02) was obtained. The average particle size of the above ITCO particles by TEM analysis was 21 nm. Also, when the molar ratio of the constituent elements (metal elements) was measured by ICP-MS analysis, it was In:Ce:Sn = 95.3:3.4:1.3.

[0116] (5) Synthesis of In-Ce-Sn-O nanoparticles (ITCO-03) First, 420 ml of oleic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 58.183 g of indium acetate (manufactured by Alfa Aesar), 2.388 g of cerium acetylacetonate (manufactured by SigmaAldrich), and 1.863 g of tin(IV) acetate (manufactured by Alfa Aesar) were introduced into a flask, and heated at 160 °C for 2 hours in an environment under a nitrogen flow to obtain a yellow transparent precursor solution E with a cerium concentration of 2.6 at% and a tin concentration of 2.5 at%. The prepared precursor solution E was filled to about 100 ml in a gastight syringe. In the synthesis of the above (ITCO-01), 68 ml of a toluene dispersion of In-Ce-Sn-O nanoparticles (ITCO-03) with oleic acid coordination was obtained in the same manner except that precursor solution E was used instead of precursor solution A. The average particle size of the above ITCO particles by TEM analysis was 21 nm. Also, when the molar ratio of the constituent elements (metal elements) was measured by ICP-MS analysis, it was In:Ce:Sn = 96.9:0.7:2.4.

[0117] (6) Synthesis of In-Ce-Zr-O nanoparticles (IZCO-01) First, 420 ml of oleic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 56.895 g of indium acetate (manufactured by Alfa Aesar), 4.777 g of cerium acetylacetonate (manufactured by SigmaAldrich), and 2.048 g of zirconium acetylacetonate (manufactured by Sigma Aldrich) were introduced into a flask, and heated at 160 °C for 2 hours in an environment under a nitrogen flow to obtain a yellow transparent precursor solution F with a cerium concentration of 5.2 at% and a zirconium concentration of 2 at%. The prepared precursor solution F was filled to about 100 ml in a gastight syringe. In the synthesis of the above (ITCO-01), 68 ml of a toluene dispersion of oleic acid-coordinated In-Ce-Zr-O nanoparticles (IZCO-01) was obtained in the same manner except that precursor solution F was used instead of precursor solution A. The average particle size of the above IZCO particles by TEM analysis was 21 nm. Also, when the molar ratio of the constituent elements (metal elements) was measured by ICP-MS analysis, it was In:Ce:Zr = 98.6:1.1:0.3.

[0118] (7) Synthesis of In-Ce-Hf-O nanoparticles (IHCO-01) First, 420 ml of oleic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 55.669 g of indium acetate (manufactured by Alfa Aesar), 4.777 g of cerium acetylacetonate (manufactured by SigmaAldrich), and 4.829 g of hafnium acetylacetonate (manufactured by Alfa Aesar) were charged into a flask, and heated at 160 °C for 2 hours under an environment of nitrogen flow to obtain a yellow transparent precursor solution G with a cerium concentration of 5.2 at% and a hafnium concentration of 4 at%. The prepared precursor solution G was filled to about 100 ml in a gastight syringe. In the synthesis of the above (ITCO-01), 68 ml of a toluene dispersion of oleic acid-coordinated In-Ce-Hf-O nanoparticles (IHCO-01) was obtained in the same manner except that precursor solution G was used instead of precursor solution A. The average particle size of the above IHCO particles by TEM analysis was 21 nm. Also, when the molar ratio of the constituent elements (metal elements) was measured by ICP-MS analysis, it was In:Ce:Hf = 98.3:1.2:0.5.

[0119] (8) Synthesis of In-Ce-Sn-O nanoparticles (ITCO-04) In the synthesis of the above (ITCO-01), 20 ml of a toluene dispersion of oleic acid-coordinated In-Ce-Sn-O nanoparticles (ITCO-04) was obtained in the same manner except that the dropping amount of precursor solution A was changed from 88 ml to 9.5 ml. The average particle size of the above ITCO particles by TEM analysis was 14 nm. Also, when the molar ratio of the constituent elements (metal elements) was measured by ICP-MS analysis, it was In:Ce:Sn = 97.6:1.0:1.4.

[0120] (9) Synthesis of In-Ce-Sn-O nanoparticles (ITCO-05) In the synthesis of the above (ITCO-01), except that the dropping amount of the precursor solution A was changed from 88 ml to 134 ml and the amount of oleyl alcohol was changed from 52 ml to 79 ml, and a step of holding at 290 °C for 30 minutes after the dropping of the precursor solution A was provided, 100 ml of a toluene dispersion of oleic acid-coordinated In-Ce-Sn-O nanoparticles (ITCO-05) was obtained in the same manner. The average particle size of the above ITCO particles by TEM analysis was 31 nm. Also, when the molar ratio of the constituent elements (metal elements) was measured by ICP-MS analysis, it was In:Ce:Sn = 97.6:1.0:1.4.

[0121] The solid content concentration of the dispersion of each oxide nanoparticle prepared above was 6% by mass, and the ratio of the surface modification component (oleic acid) in this solid content was 6% by mass. (Solid content concentration evaluation method) 10 ml of the dispersion of each oxide nanoparticle obtained was collected, heated at 200 °C for 30 minutes in a glass petri dish on a hot plate, and the solid content concentration was calculated from the mass of the residue after heating and the mass of the dispersion before heating.

[0122] The details of the TEM analysis and ICP-MS analysis of each oxide nanoparticle prepared above are as follows. [Measurement A: TEM analysis] The average particle size of each oxide nanoparticle was calculated based on the measurement method of the average particle size of the aforementioned ICO particles (A) using JFM-ARM300F2 GRAND (trade name, manufactured by JEOL Ltd.) as TEM. [Measurement B: ICP-MS analysis] Using an Agilent 8900 triple quadrupole (trade name, manufactured by Agilent Technologies) as ICP-MS, the concentrations of tin, cerium, tin, zirconium, and hafnium in the particles were measured.

[0123] [2. Synthesis of Dispersant] (Synthesis of Dispersant (A-1)) 24.0 g of methyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Corporation) and 1.80 g of mercaptosuccinic acid (manufactured by Fujifilm Wako Pure Chemical Corporation) were dissolved in 28 mL of methyl ethyl ketone and heated to 70 °C under a nitrogen stream. To this solution, a solution prepared by dissolving 0.24 g of a polymerization initiator (V-65, manufactured by Fujifilm Wako Pure Chemical Corporation) in 12 mL of methyl ethyl ketone was added dropwise over 30 minutes. After completion of the dropwise addition, the reaction was further carried out at 70 °C for 4.5 hours. After cooling, the reaction solution was added dropwise to a mixed solution of 200 mL of cooled water and 600 mL of methanol, and the precipitated powder was collected by filtration and dried to obtain 15 g of the following dispersant (A-1). This polymer dispersant (A-1) is substantially composed of a polymer having a carboxy group at one end. The weight average molecular weight of the obtained polymer was 5900 in terms of standard polystyrene by the GPC (Gel Permeation Chromatography) method, and the dispersity (Mw / Mn) was 1.70. Also, when the acid value was determined by measuring the number of mg of potassium hydroxide required to neutralize the free fatty acid present in 1 g of the obtained polymer, it was 24 mgKOH / g.

[0124] [Chemical Formula]

[0125] [Examples] The toluene dispersion of the oxide nanoparticles prepared above was diluted with toluene in advance so that the solid content concentration was 5% by mass, and each curable resin composition was prepared as follows. [1. Preparation of Curable Resin Compositions 1-1 to 1-9] To 48.8 g of the toluene dispersion of (ITCO-01) (solid content: 5%, 2.44 g as ITCO particles), 0.535 g of a dispersant (A-1) and 2.02 g of 1,6-hexanediol dimethacrylate (HDDMA, manufactured by Tokyo Chemical Industry Co., Ltd.) were added and dissolved. While heating in a water bath at about 70 °C, toluene was distilled off under reduced pressure by suction. To the mixture obtained after distillation, 0.01 g of IRGACURE 819 (trade name, manufactured by BASF, a photo radical polymerization initiator) was added and dissolved to prepare a curable resin composition 1-1. In the preparation of the above curable resin composition 1-1, curable resin compositions 1-2 to 1-9 were prepared in the same manner except that the type of oxide nanoparticles was changed so as to have the constitution described in the following table.

[0126] 〔2. Preparation of curable resin composition 2〕 To 82.1 g of a zirconium oxide dispersion (trade name: SZR-K, manufactured by Sakai Chemical Industry Co., Ltd.), 22.3 g of FA-512AS (trade name, dicyclopentenyl oxyethyl acrylate, manufactured by Hitachi Chemical Co., Ltd.) was added and stirred until homogeneous. While heating in a water bath at about 70 °C, methanol and MEK (methyl ethyl ketone) were distilled off under reduced pressure by suction. To the mixture obtained after distillation, 0.20 g of IRGACURE 651 (trade name, a photo radical polymerization initiator, manufactured by BASF) was added and dissolved to prepare a curable resin composition 2.

[0127] 〔3. Preparation of cured products of curable resin compositions 1-1 to 1-9〕 The curable resin composition 1-1 was sandwiched between hydrophobically treated glass plates, and using a UV irradiation device (trade name: EXECURE 3000, manufactured by HOYA CANDEO OPTRONICS), with an integrated light amount of 1.0 J / cm 2 and an illuminance of 30 mW / cm 2 under the conditions of UV (ultraviolet) irradiation, and then again with an integrated light amount of 1.0 J / cm 2 and an illuminance of 5 mW / cm 2 under the conditions of UV irradiation, a cured product was prepared. The film thickness of the cured product obtained as described above was 6 μm. In the production of the cured product of the curable resin composition 1-1, the cured products of the curable resin compositions 1-2 to 1-9 were produced in the same manner except that the curable resin compositions 1-2 to 1-9 were used instead of the curable resin composition 1-1.

[0128] 〔4. Production of the cured product of the curable resin composition 2〕 The curable resin composition 2 was sandwiched between hydrophobically treated glass plates, and using a UV irradiation device (trade name: EXECURE3000, manufactured by HOYA CANDEO OPTRONICS), with an integrated light quantity of 2.0 J / cm 2 , an illuminance of 5 mW / cm 2 , UV irradiation was carried out under these conditions to produce a cured product. The film thickness of the cured product obtained as described above was 6 μm.

[0129] 〔Evaluation 1: Transmittance measurement〕 Regarding the cured products of the respective curable resin compositions produced under the above conditions, using a spectrophotometer (trade name: V-670, manufactured by JASCO Corporation), the transmittance in the wavelength range of 400 to 1800 nm was measured, and the transmittance %T 852 at 852 nm and the transmittance %T 1650 at 1650 nm were used to evaluate the transmittance of the cured product according to the following evaluation criteria. In the following evaluation criteria, evaluation A is the best, followed by B, C, D, and E in order of excellence, and F is the worst. The results are shown in Table 1. - Evaluation criteria - A: %T 852 is 90% or more, and %T 1650 is 60% or more B: %T 852 is 90% or more, and %T 1650 is 50% or more and less than 60% C: %T 852 is 90% or more, and %T 1650 is 40% or more and less than 50% D: %T 852 is 90% or more, and %T 1650 is 30% or more and less than 40% E: %T 852 is 90% or more, and %T 1650 is less than 30% F: %T 852is less than 90% (%T 1650 regardless of the value)

[0130] 〔Evaluation 2: Evaluation of refractive index〕 The refractive indices n852 at a wavelength of 852 nm and n1530 at a wavelength of 1530 nm of the cured products of the above curable resin compositions 1-1 to 1-9 and the cured product of the above curable resin composition 2 were measured using spectroscopic ellipsometry. The evaluation was performed by measuring the ellipsometry data and transmittance data of the cured product and performing simultaneous fitting. The detailed conditions of ellipsometry are as follows. Incident angle: 50, 60, 70° Measurement wavelength: 210 to 1690 nm Optical model: Harmonic oscillator model considering the absorption and Kramers-Kronig relationship The cured product of the curable resin composition 2 had n852 = 1.608 and n1530 = 1.605. The n852 and n1530 of the cured products of the curable resin compositions 1-1 to 1-9 are summarized in Table 1. All of the n852 of the cured products of the curable resin compositions 1-1 to 1-9 were smaller than the n852 of the cured product of the curable resin composition 2, and all of the n1530 of the cured products of the curable resin compositions 1-1 to 1-9 were smaller than the n1530 of the cured product of the curable resin composition 2. Also, all of n852 - n1530 in the cured products of the curable resin compositions 1-1 to 1-9 were larger than n852 - n1530 = 0.003 in the cured product of the curable resin composition 2.

[0131] 〔Evaluation 3: Evaluation of chromatic aberration reduction effect of multilayer diffractive optical element〕 Using the cured products of the resin compositions of the combinations described in Table 2 below, in the diffractive optical element shown in Fig. 2 of JP-A-2008-241734, as the first diffraction grating, any of the cured products of the above curable resin compositions 1-1 to 1-11 was used, and as the second diffraction grating, the cured product of the above curable resin composition 2 was used. The chromatic aberration reduction effect of the multilayer diffractive optical element was evaluated when the common grating thickness of the first and second diffraction gratings was 12 μm. The chromatic aberration reduction effect of the multilayer diffractive optical element was evaluated by calculating the diffraction efficiencies of the first-order light at wavelengths of 852 nm and 1530 nm using the refractive index and grating thickness values measured in Evaluation 2 above, and using the equations 23 and 24 of Japanese Patent Application Laid-Open No. 2008-241734, and evaluating according to the following evaluation criteria. The larger the diffraction efficiency, the more the occurrence of flare in the lens can be suppressed, and the more the chromatic aberration can be reduced. In the following evaluation criteria, Evaluation A is the best, followed by B + , B - , C + and C - in this order, and D is the worst. The results are shown in Table 1. - Evaluation Criteria - A: The diffraction efficiency at a wavelength of 852 nm was 95% or more, and the diffraction efficiency at a wavelength of 1530 nm was 95% or more. B + : The diffraction efficiency at a wavelength of 852 nm was 95% or more, and the diffraction efficiency at a wavelength of 1530 nm was 90% or more and less than 95%. B - : The diffraction efficiency at a wavelength of 852 nm was 95% or more, and the diffraction efficiency at a wavelength of 1530 nm was 85% or more and less than 90%. C + : The diffraction efficiency at a wavelength of 852 nm was 85% or more and less than 95%, and the diffraction efficiency at a wavelength of 1530 nm was 95% or more. C - : The diffraction efficiency at a wavelength of 852 nm was 85% or more and less than 95%, and the diffraction efficiency at a wavelength of 1530 nm was 85% or more and less than 95%. D: At least one of the diffraction efficiency at a wavelength of 852 nm and the diffraction efficiency at a wavelength of 1530 nm was less than 85%.

[0132]

Table 1

[0133] Each component in the table is as follows. (Oxide Nanoparticles) Each oxide nanoparticle prepared above (Dispersant) A-1: Dispersant (A-1) prepared above ((Meth)acrylate compound) HDDMA: 1,6 - Hexanediol dimethacrylate (Photoinitiator) IRGACURE 819 (also denoted as Irgacure 819): Trade name, manufactured by BASF

[0134]

Chemical formula

[0135] The unit of the compounding amount is mass% (also referred to as wt%). The compounding amount of the oxide nanoparticles is described in terms of the solid content. The units of both the cerium concentration (Ce concentration) and the total concentration of zirconium, tin, and hafnium (Zr + Sn + Hf concentration) are at%. The unit of the average particle diameter of the oxide nanoparticles is nm. In the column of constituent elements, the metal elements qualitatively analyzed by ICP - MS are described.

[0136] From the results in Table 1, the following can be understood. The cured product obtained from Comparative Curing Resin Composition 1 - 2 containing indium tin oxide (ITO) nanoparticles has a transmittance at 1650 nm as low as less than 40%, and it was not possible to achieve a high transmittance while maintaining the desired wavelength dependence of the refractive index over the near - infrared to short - wave infrared wavelength region. On the other hand, the cured product obtained from any of the curable resin compositions 1-1 and 1-3 to 1-9 of the present invention containing oxide nanoparticles containing indium and cerium, a (meth)acrylate compound having one or more functional groups, and a dispersant exhibits a desired wavelength dependence of the refractive index over the near-infrared to short-wave infrared regions, and when used in a multilayer diffractive optical element, a desired chromatic aberration reducing effect can be obtained over the near-infrared to short-wave infrared wavelength regions. Moreover, a high transmittance can be achieved while maintaining the desired wavelength dependence of the refractive index over the near-infrared to short-wave infrared regions, and it was superior in transmittance in the short-wave infrared wavelength region compared to the case where ITO nanoparticles were used.

Claims

1. A curable resin composition comprising oxide nanoparticles containing indium and cerium, a (meth)acrylate compound having one or more functional groups, and a dispersant.

2. The curable resin composition according to claim 1, wherein the oxide nanoparticles contain at least one element selected from zirconium, hafnium, and tin.

3. The curable resin composition according to claim 2, wherein the oxide nanoparticles contain tin.

4. The curable resin composition according to any one of claims 1 to 3, wherein the cerium concentration of the oxide nanoparticles is 0.5 to 3.0 at%.

5. The curable resin composition according to claim 2 or 3, wherein the total concentration of zirconium, hafnium, and tin in the oxide nanoparticles is 0.1 to 2.0 at%.

6. The curable resin composition according to any one of claims 1 to 5, wherein the content of the oxide nanoparticles in the curable resin composition is 10 to 60% by mass.

7. The curable resin composition according to any one of claims 1 to 6, wherein the average particle diameter of the oxide nanoparticles is 16 to 30 nm.

8. The curable resin composition according to claim 7, wherein the average particle diameter of the oxide nanoparticles is 20 to 30 nm.

9. The curable resin composition according to any one of claims 1 to 8, containing a photo radical polymerization initiator.

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

11. The cured product according to claim 10, having a refractive index of 1.500 to 1.650 at a wavelength of 852 nm.

12. The cured product according to claim 10 or 11, having a refractive index of 1.300 to 1.550 at a wavelength of 1530 nm.

13. A diffractive optical element including a surface having a diffractive grating shape formed of the cured product according to any one of claims 10 to 12.

14. Including a first diffractive optical element and a second diffractive optical element, wherein the first diffractive optical element is the diffractive optical element according to claim 13, and a surface having a diffractive grating shape in the first diffractive optical element and a surface having a diffractive grating shape in the second diffractive optical element face each other, a multilayer diffractive optical element.

15. The multilayer diffractive optical element according to claim 14, wherein the refractive index of the second diffractive optical element at a wavelength of 852 nm is 1.550 to 1.700, and the refractive index is greater than the refractive index of the first diffractive optical element at a wavelength of 852 nm.

16. The multilayer diffractive optical element according to claim 14 or 15, wherein the surface having the diffraction grating shape in the first diffractive optical element is in contact with the surface having the diffraction grating shape in the second diffractive optical element.

17. The multilayer diffractive optical element according to any one of claims 14 to 16, comprising a transparent substrate, wherein the first diffractive optical element, the second diffractive optical element, and the transparent substrate are arranged in this order.

18. Oxide nanoparticles containing indium and cerium and at least one element selected from tin, zirconium, and hafnium, having an average particle diameter of 16 to 30 nm.

19. An additive for a lens for adjusting the wavelength dependence of the refractive index, comprising the oxide nanoparticles according to claim 18.

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