WO2025052998A1 - Curable composition, cured product, and optical member - Google Patents

Abstract

Provided is a curable composition containing: particles A that include at least one selected from TiO₂ particles and ZrO₂ particles; a resin; a polymerizable compound; a photopolymerization initiator; and a polyfunctional thiol compound. Also provided are a cured product and an optical member, each using the above-described curable composition.

Description

CURABLE COMPOSITION, CURED PRODUCT, AND OPTICAL MEMBER

The present invention relates to a curable composition containing at least one selected from _TiO2 particles and _ZrO2 particles. The present invention also relates to a cured product and an optical component using the curable composition.

　In the past, attempts have been made to colorize images using color filters in solid-state imaging devices such as charge-coupled device (CCD) image sensors. In addition, optical components such as microlenses made of a hardened material with a high refractive index have been placed on the light path of the color filter to increase the sensitivity of the pixels in each color filter.

Optical components such as microlenses have been manufactured using curable compositions containing high refractive index particles such as _TiO2 particles or _ZrO2 particles.

Patent Document 1 discloses an invention related to a photosensitive resin composition containing particles such as _TiO2 particles or _ZrO2 particles, a dispersant, an alkali-soluble resin, a polymerizable compound, a photopolymerization initiator, and a solvent.

JP 2019-203932 A

In general, optical components such as microlenses are used by laminating them on other components or by laminating other layers on their surfaces. For example, microlenses are sometimes used with inorganic films formed on their surfaces.

The present inventors have conducted extensive studies on a cured product formed using a curable composition containing _TiO2 particles or _ZrO2 particles, and have found that when a composite having the cured product and another layer in contact with the cured product is left in a humid environment for a long period of time, wrinkles tend to form on the surface of the cured product in contact with the other layer.

Furthermore, when the inventors investigated the photosensitive resin composition disclosed in Patent Document 1, they found that even in the cured product obtained using this photosensitive resin composition, wrinkles tend to form on the surface in contact with other layers when the product is left in a humid environment for a long period of time.

Therefore, an object of the present invention is to provide a curable composition that can form a cured product in which the occurrence of wrinkles is suppressed even when the composition is left in a humid environment for a long period of time. Another object of the present invention is to provide a cured product and an optical component.

The inventors have found through their research that the above object can be achieved by using the curable composition described below, and have completed the present invention. Therefore, the present invention provides the following.

<1> Particles A including at least one selected from TiO2 _particles and _ZrO2 particles;
Resin and
A polymerizable compound,
A photopolymerization initiator;
A curable composition comprising: a polyfunctional thiol compound.
<2> The curable composition according to <1>, wherein the polyfunctional thiol compound is a compound having 2 to 4 secondary thiol groups in one molecule.
<3> The curable composition according to <1> or <2>, wherein the particle A contains _TiO2 particles.
<4> The curable composition according to any one of <1> to <3>, wherein the particles A are transparent or white particles.
<5> The curable composition according to any one of <1> to <4>, wherein the content of the particles A in the total solid content of the curable composition is 50 to 80 mass %.
<6> The curable composition according to any one of <1> to <5>, wherein the content of the polyfunctional thiol compound in the total solid content of the curable composition is 0.1 to 5 mass%.
<7> The curable composition according to any one of <1> to <6>, further comprising 10 to 45 parts by mass of the photopolymerization initiator relative to 100 parts by mass of the polymerizable compound.
<8> The curable composition according to any one of <1> to <7>, further comprising 100 to 2,000 parts by mass of the photopolymerization initiator relative to 100 parts by mass of the polyfunctional thiol compound.
<9> The curable composition according to any one of <1> to <8>, wherein the photopolymerization initiator contains an oxime compound.
<10> The curable composition according to any one of <1> to <9>, wherein the photopolymerization initiator contains an oxime compound having two or more oxime groups in one molecule.
<11> The curable composition according to any one of <1> to <10>, wherein the resin includes a resin having a graft chain and an acid group.
<12> The curable composition according to any one of <1> to <11>, further comprising a compound having a cyclic ether group.
<13> The curable composition according to any one of <1> to <12>, in which, when the curable composition is used to form a film having a thickness of 0.4 to 1.0 μm by heating at 220° C. for 5 minutes, the film has a minimum transmittance of 75% or more in a wavelength range of 400 to 700 nm.
<14> A cured product obtained by using the curable composition according to any one of <1> to <13>.
<15> An optical member obtained by using the curable composition according to any one of <1> to <13>.
<16> The optical member according to <15>, which is a microlens.

The present invention provides a curable composition that can form a cured product that is less susceptible to wrinkles even when left in a humid environment for a long period of time. The present invention also provides a cured product and an optical component.

The present invention will be described in detail below.
In this specification, the use of "to" means that the numerical values before and after it are included as the lower limit and upper limit.
In the description of groups (atomic groups) in this specification, when there is no indication of whether they are substituted or unsubstituted, the term encompasses both unsubstituted groups (atomic groups) and substituted groups (atomic groups). For example, the term "alkyl group" encompasses not only alkyl groups that have no substituents (unsubstituted alkyl groups) but also alkyl groups that have substituents (substituted alkyl groups).
In this specification, unless otherwise specified, the term "exposure" includes not only exposure using light but also drawing using particle beams such as electron beams and ion beams. Examples of light used for exposure include the bright line spectrum of a mercury lamp, far ultraviolet light represented by an excimer laser, extreme ultraviolet light (EUV light), X-rays, active rays or radiation such as electron beams.
In this specification, "(meth)acrylate" refers to both or either of acrylate and methacrylate, "(meth)acrylic" refers to both or either of acrylic and methacrylic, and "(meth)acryloyl" refers to both or either of acryloyl and methacryloyl.
In this specification, in the structural formulae, Me represents a methyl group, Et represents an ethyl group, Bu represents a butyl group, and Ph represents a phenyl group.
In this specification, the weight average molecular weight and number average molecular weight are values calculated as polystyrene standards measured by GPC (gel permeation chromatography).
In this specification, the total solids content refers to the total mass of all components of the composition excluding the solvent.
In this specification, the term "process" refers not only to an independent process, but also to a process that cannot be clearly distinguished from other processes, as long as the process achieves its intended effect.

<Curable Composition>
The curable composition of the present invention comprises
Particles A containing at least one selected from _TiO2 particles and _ZrO2 particles;
Resin and
A polymerizable compound,
A photopolymerization initiator;
and a polyfunctional thiol compound.

Since _TiO2 particles and ZrO2 _particles have a high refractive index, when a curable composition containing such particles is exposed to light and cured, the exposure light may be scattered by the particles during exposure, or the exposure light may not reach the bottom of the film sufficiently, and the polymerization reaction of the polymerizable compound tends to be insufficient. It is presumed that the curable composition of the present invention, which contains a multifunctional thiol compound, can sufficiently promote the polymerization reaction of the polymerizable compound by exposure, even though it contains _TiO2 particles or _ZrO2 particles. Therefore, the curable composition of the present invention can form a cured product in which the occurrence of wrinkles is suppressed even if it is placed in a humid environment for a long period of time. More specifically, it can form a cured product in which the occurrence of wrinkles is suppressed on the surface of the adjacent other layer side even if it is placed in a humid environment for a long period of time.

When the curable composition of the present invention is heated at 220°C for 5 minutes to form a film having a thickness of 0.4 to 1.0 μm, the minimum transmittance of the film in the wavelength range of 400 to 700 nm is preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, and especially preferably 90%. The average transmittance of the film in the wavelength range of 400 to 700 nm is preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, and especially preferably 90%.

The solids concentration of the curable composition of the present invention is preferably 5 to 30% by mass. The lower limit is preferably 7.5% by mass or more, and more preferably 10% by mass or more. The upper limit is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

The components used in the curable composition of the present invention are described below.

<<Particle A>>
The curable composition of the present invention contains particles A which contain at least one kind selected from _TiO2 particles and _ZrO2 particles.

The average primary particle size of the _TiO2 particles and _ZrO2 particles is preferably 10 to 200 nm. The upper limit is preferably 150 nm or less, more preferably 100 nm or less. The lower limit is preferably 15 nm or more.

In this specification, the average primary particle diameter of the particles is a value measured by the following method. That is, the primary particle diameter of the particles can be obtained by observing the particles with a transmission electron microscope (TEM) and observing the parts where the particles are not aggregated (primary particles). The particle size distribution of the primary particles can be obtained by taking a transmission electron micrograph of the primary particles with a transmission electron microscope, and then measuring the particle size distribution using the photograph with an image processing device. In this specification, the average primary particle diameter of the particles is defined as the arithmetic mean diameter on a number basis calculated from the particle size distribution of the primary particles. In this specification, an electron microscope (H-7000) manufactured by Hitachi, Ltd. is used as the transmission electron microscope, and Luzex AP manufactured by Nireco Corporation is used as the image processing device.

The _TiO2 particles and the ZrO2 _particles are preferably white or transparent particles. Also, the particles A are preferably white or transparent particles.

It is preferred that particles A comprise _TiO2 particles.
Particle A preferably contains at least one selected from _TiO2 particles and ZrO2 _particles in an amount of 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit can be 100% by mass.
In particular, the particles A preferably contain 70% by mass or more of TiO2 _particles , more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit can be 100% by mass.

The content of particles A in the total solid content of the curable composition is preferably 50 to 80 mass%. The upper limit is preferably 75 mass% or less, and more preferably 70 mass% or less. The lower limit is preferably 55 mass% or more, and more preferably 60 mass% or more.

The curable composition of the present invention may contain only one type of particle A, or may contain two or more types. When two or more types of particle A are contained, it is preferable that the total amount thereof is within the above range.

<<Resin>>
The curable composition of the present invention contains a resin. The resin is blended, for example, for dispersing particles in the curable composition or for use as a binder. Note that a resin used mainly for dispersing particles in the curable composition is also called a dispersant. However, such uses of the resin are merely examples, and the resin can also be used for purposes other than such uses.

Examples of resins include (meth)acrylic resins, epoxy resins, (meth)acrylamide resins, ene-thiol resins, polycarbonate resins, polyether resins, polyarylate resins, polysulfone resins, polyethersulfone resins, polyphenylene resins, polyarylene ether phosphine oxide resins, polyimide resins, polyamideimide resins, polyolefin resins, cyclic olefin resins, polyester resins, styrene resins, and siloxane resins. Further, examples of the resin include the resin described in paragraphs 0091 to 0099 of WO 2022/065215, the blocked polyisocyanate resin described in JP 2016-222891 A, the resin described in JP 2020-122052 A, the resin described in JP 2020-111656 A, the resin described in JP 2020-139021 A, the resin described in JP 2017-138503 A containing a structural unit having a ring structure in the main chain and a structural unit having a biphenyl group in the side chain, and the resin described in paragraphs 0199 to 0199 of JP 2020-186373 A. Resins described in JP-A-0233, alkali-soluble resins described in JP-A-2020-186325, resins represented by formula 1 described in Korean Patent Publication No. 10-2020-0078339, copolymers containing epoxy groups and acid groups described in WO 2022/030445, resins described in JP-A-2018-135514, copolymers described in JP-A-2020-041046, resins described in JP-A-2023-033156, resins described in JP-A-2023-030386, and resins described in JP-A-2023-027753 can also be used.

The weight average molecular weight (Mw) of the resin is preferably 3,000 to 2,000,000. The upper limit is preferably 1,000,000 or less, and more preferably 500,000 or less. The lower limit is preferably 4,000 or more, and more preferably 5,000 or more.

As the resin, it is preferable to use a resin having an acid group. Examples of the acid group include a carboxy group, a phosphate group, a sulfo group, and a phenolic hydroxy group.

The acid value of the resin having acid groups is preferably 30 to 500 mgKOH/g. The lower limit is more preferably 40 mgKOH/g or more, and particularly preferably 50 mgKOH/g or more. The upper limit is more preferably 400 mgKOH/g or less, even more preferably 300 mgKOH/g or less, and particularly preferably 200 mgKOH/g or less. The weight average molecular weight (Mw) of the resin having acid groups is preferably 5,000 to 100,000, and more preferably 5,000 to 50,000. The number average molecular weight (Mn) of the resin having acid groups is preferably 1,000 to 20,000.

The resin having an acid group preferably contains a repeating unit having an acid group on the side chain, and more preferably contains 5 to 70 mol% of the repeating units having an acid group on the side chain out of all the repeating units of the resin. The upper limit of the content of repeating units having an acid group on the side chain is preferably 50 mol% or less, and more preferably 30 mol% or less. The lower limit of the content of repeating units having an acid group on the side chain is preferably 10 mol% or more, and more preferably 20 mol% or more.

For the resin having an acid group, the description in paragraphs 0558 to 0571 of JP 2012-208494 A (corresponding paragraphs 0685 to 0700 of the specification of US Patent Application Publication No. 2012/0235099) and the description in paragraphs 0076 to 0099 of JP 2012-198408 A can be referred to, and the contents of these are incorporated herein. In addition, a commercially available product can also be used as the resin having an acid group. In addition, there is no particular restriction on the method of introducing an acid group into the resin, but an example of the method is the method described in Japanese Patent No. 6349629 A. Furthermore, as a method of introducing an acid group into a resin, a method of reacting an acid anhydride with a hydroxyl group generated by a ring-opening reaction of an epoxy group to introduce an acid group can also be used.

As the resin, a resin having a basic group can also be used. The resin having a basic group is preferably a resin containing a repeating unit having a basic group in the side chain, more preferably a copolymer having a repeating unit having a basic group in the side chain and a repeating unit not having a basic group, and even more preferably a block copolymer having a repeating unit having a basic group in the side chain and a repeating unit not having a basic group. The resin having a basic group can also be used as a dispersant. The amine value of the resin having a basic group is preferably 5 to 300 mgKOH/g. The lower limit is preferably 10 mgKOH/g or more, more preferably 20 mgKOH/g or more. The upper limit is preferably 200 mgKOH/g or less, more preferably 100 mgKOH/g or less.

Commercially available resins with basic groups include DISPERBYK-161, 162, 163, 164, 166, 167, 168, 174, 182, 183, 184, 185, 2000, 2001, 2050, 2150, 2163, 2164, BYK-LPN6919 (all manufactured by BYK-Chemie), Solsperse 11200, 13240, 13650, 13940, 24 000, 26000, 28000, 32000, 32500, 32550, 32600, 33000, 34750, 35100, 35200, 37500, 38500, 39000, 53095, 56000, 7100 (all manufactured by Lubrizol Japan), Efka PX 4300, 4330, 4046, 4060, 4080 (all manufactured by BASF), and the like. In addition, the resin having a basic group may be a block copolymer (B) described in paragraphs 0063 to 0112 of JP 2014-219665 A, a block copolymer A1 described in paragraphs 0046 to 0076 of JP 2018-156021 A, or a vinyl resin having a basic group described in paragraphs 0150 to 0153 of JP 2019-184763 A, the contents of which are incorporated herein by reference.

It is also preferable to use a resin having an acid group and a resin having a basic group. According to this embodiment, the storage stability of the curable composition can be further improved. When a resin having an acid group and a resin having a basic group are used in combination, the content of the resin having a basic group is preferably 20 to 500 parts by mass, more preferably 30 to 300 parts by mass, and even more preferably 50 to 200 parts by mass per 100 parts by mass of the resin having an acid group.

As the resin, it is also preferable to use a resin having an aromatic carboxy group. In a resin having an aromatic carboxy group, the aromatic carboxy group may be included in the main chain of a repeating unit, or may be included in a side chain of the repeating unit. It is preferable that the aromatic carboxy group is included in the main chain of a repeating unit. In this specification, an aromatic carboxy group refers to a group having a structure in which one or more carboxy groups are bonded to an aromatic ring. In an aromatic carboxy group, the number of carboxy groups bonded to an aromatic ring is preferably 1 to 4, and more preferably 1 to 2. Examples of resins having an aromatic carboxy group include the resins described in paragraphs 0082 to 0107 of WO 2021/166858.

As the resin, it is also preferable to use a resin having a crosslinkable group. Examples of the crosslinkable group include a (meth)acryloyl group, an epoxy group, and an oxetanyl group. When a resin having a crosslinkable group is used, the content of the resin having a crosslinkable group in the resin contained in the curable composition is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more.

As the resin, it is preferable to use a resin having an acid group and a graft chain (hereinafter, also referred to as an acidic graft resin). The acidic graft resin may be used as a binder or a dispersant. In this specification, the graft chain means a polymer chain that branches out from the main chain of the repeating unit. The graft chain preferably has 40 to 10,000 atoms excluding hydrogen atoms, more preferably 50 to 2,000 atoms excluding hydrogen atoms, and even more preferably 60 to 500 atoms excluding hydrogen atoms.

The graft chain preferably contains repeating units of at least one structure selected from a polyether structure, a polyester structure, a poly(meth)acrylic structure, a polystyrene structure, a polyurethane structure, a polyurea structure, and a polyamide structure, more preferably contains repeating units of at least one structure selected from a polyether structure, a polyester structure, a poly(meth)acrylic structure, and a polystyrene structure, even more preferably contains repeating units of a polyether structure or a polyester structure, and particularly preferably contains repeating units of a polyester structure.

Examples of the repeating unit of the polyester structure include a repeating unit of the structure represented by formula (G-1), formula (G-4) or formula (G-5). Examples of the repeating unit of the polyether structure include a repeating unit of the structure represented by formula (G-2). Examples of the repeating unit of the poly(meth)acrylic structure include a repeating unit of the structure represented by formula (G-3). Examples of the repeating unit of the polystyrene structure include a repeating unit of the structure represented by formula (G-6).

In the above formula, R ^G1 and R ^G2 each independently represent an alkylene group. The alkylene group represented by R ^G1 and R ^G2 is not particularly limited, but is preferably a linear or branched alkylene group having 1 to 20 carbon atoms, more preferably a linear or branched alkylene group having 2 to 16 carbon atoms, and even more preferably a linear or branched alkylene group having 3 to 12 carbon atoms.

In the above formula, R ^G3 represents a hydrogen atom or a methyl group, Q ^G1 represents --O-- or --NH--, L ^G1 represents a single bond or a divalent linking group, and R ^G4 represents a hydrogen atom or a substituent.
Examples of the divalent linking group represented by L ^G1 include an alkylene group (preferably an alkylene group having 1 to 12 carbon atoms), an alkyleneoxy group (preferably an alkyleneoxy group having 1 to 12 carbon atoms), an oxyalkylenecarbonyl group (preferably an oxyalkylenecarbonyl group having 1 to 12 carbon atoms), an arylene group (preferably an arylene group having 6 to 20 carbon atoms), -NH-, -SO-, -SO ₂ -, -CO-, -O-, -COO-, OCO-, -S-, and groups formed by combining two or more of these.
Examples of the substituent represented by R ^G4 include a hydroxy group, a carboxy group, an alkyl group, an aryl group, a heteroaryl group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an alkylthioether group, an arylthioether group, a heteroarylthioether group, an ethylenically unsaturated bond-containing group, an epoxy group, an oxetanyl group, and a blocked isocyanate group.

R ^G5 represents a hydrogen atom or a methyl group, and R ^G6 represents an aryl group. The number of carbon atoms of the aryl group represented by R ^G6 is preferably 6 to 30, more preferably 6 to 20, and still more preferably 6 to 12. The aryl group represented by ^{R G6} may have a substituent. Examples of the substituent include a hydroxy group, a carboxy group, an alkyl group, an aryl group, a heteroaryl group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an alkylthioether group, an arylthioether group, a heteroarylthioether group, an ethylenically unsaturated bond-containing group, an epoxy group, an oxetanyl group, and a blocked isocyanate group.

The terminal structure of the graft chain is not particularly limited. It may be a hydrogen atom or a substituent. Examples of the substituent include an alkyl group, an aryl group, a heteroaryl group, an alkoxy group, an aryloxy group, a heteroaryloxy group, an alkylthioether group, an arylthioether group, and a heteroarylthioether group. From the viewpoint of particle dispersibility, etc., it is preferable that the group has a steric repulsion effect, and it is preferable that the group is an alkyl group or an alkoxy group having 5 to 24 carbon atoms. The alkyl group and the alkoxy group may be linear, branched, or cyclic, and is preferably linear or branched.

The graft chain is preferably a structure represented by the following formula (G-1a), (G-2a), (G-3a), (G-4a), (G-5a) or (G-6a), and more preferably a structure represented by formula (G-1a), (G-4a) or (G-5a).

In the above formula, R ^G1 and R ^G2 each represent an alkylene group, R ^G3 represents a hydrogen atom or a methyl group, Q ^G1 represents -O- or -NH-, L ^G1 represents a single bond or a divalent linking group, R ^G4 represents a hydrogen atom or a substituent, R ^G5 represents a hydrogen atom or a methyl group, R ^G6 represents an aryl group, W ¹⁰⁰ represents a hydrogen atom or a substituent, and n1 to n6 each independently represent an integer of 2 or more. R ^G1 to R ^G6 , Q ^G1 , and L ^G1 are synonymous with R ^G1 to R ^G6 , Q ^G1 , and L ^G1 described in formulas (G-1) to (G-6), and the preferred ranges are also the same.

In formulae (G-1a) to (G-6a), W ¹⁰⁰ is preferably a substituent. Examples of the substituent include the above-mentioned substituents.

In formulas (G-1a) to (G-6a), n1 to n6 are each preferably an integer from 2 to 100, more preferably an integer from 2 to 80, and even more preferably an integer from 8 to 60.

In formula (G-1a), when n1 is 2 or more, R ^G1 in each repeating unit may be the same or different. When R ^G1 contains two or more different repeating units, the arrangement of each repeating unit is not particularly limited and may be random, alternating, or block. The same applies to formulas (G-2a) to (G-6a). In addition, it is also preferable that the graft chain has a structure represented by formula (G-1a), formula (G-4a), or formula (G-5a) and contains two or more different repeating units in R ^G1 .

The acidic graft resin is preferably a resin having a repeating unit having a graft chain. An example of the repeating unit having a graft chain is a repeating unit represented by formula (e3).

In the formula, A ^e30 represents a trivalent linking group, L ^e30 represents a single bond or a divalent linking group, and W ^e30 represents a graft chain.

Examples of the trivalent linking group represented by A ^e30 include a poly(meth)acrylic linking group, a polyalkyleneimine linking group, a polyester linking group, a polyurethane linking group, a polyurea linking group, a polyamide linking group, a polyether linking group, and a polystyrene linking group. A poly(meth)acrylic linking group or a polyalkyleneimine linking group is preferable, and a poly(meth)acrylic linking group is more preferable.

Examples of the divalent linking group represented by L ^e30 include an alkylene group (preferably an alkylene group having 1 to 10 carbon atoms), an arylene group (preferably an arylene group having 6 to 20 carbon atoms), -NH-, -SO-, -SO ₂ -, -CO-, -O-, -COO-, OCO-, -CONR ^x3 -, -S-, and a group formed by combining two or more of these groups. R ^x3 represents a hydrogen atom, an alkyl group, or an aryl group. The alkylene group and the arylene group may have a substituent.

The graft chain represented by W ^e30 includes the above-mentioned graft chain.

The weight average molecular weight of the repeating unit having a graft chain is preferably 1000 or more, more preferably 1000 to 10000, and even more preferably 1000 to 7500. In this specification, the weight average molecular weight of the repeating unit having a graft chain is a value calculated from the weight average molecular weight of the raw material monomer used in the polymerization of the repeating unit. For example, a repeating unit having a graft chain can be formed by polymerizing a macromonomer. Here, a macromonomer means a polymeric compound in which a polymerizable group is introduced at the polymer end. When a repeating unit having a graft chain is formed using a macromonomer, the weight average molecular weight of the macromonomer corresponds to the repeating unit having a graft chain.

The acid groups contained in the acidic graft resin include a carboxy group, a sulfo group, and a phosphate group, with the carboxy group being preferred.

The acidic graft resin is preferably a resin containing a repeating unit having a graft chain and a repeating unit having an acid group. In addition, the acidic graft resin preferably contains 1 mol% or more of repeating units having a graft chain, more preferably 2 mol% or more, and even more preferably 3 mol% or more of repeating units having a graft chain, among all repeating units of the acidic graft resin. The upper limit can be 90 mol%, 80 mol% or less, 70 mol% or less, 60 mol% or less, or 50 mol% or less. In addition, the acidic graft resin preferably contains 1 mol% or more of repeating units having an acid group, more preferably 2 mol% or more, and even more preferably 3 mol% or more of repeating units having an acid group, among all repeating units of the acidic graft resin. The upper limit can be 90 mol%, 80 mol% or less, 70 mol% or less, 60 mol% or less, or 50 mol% or less.

The acidic graft resin may further contain other repeating units in addition to those mentioned above. Examples of the other repeating units include repeating units having a polymerizable group. Examples of the polymerizable group include an ethylenically unsaturated bond-containing group and a cyclic ether group.

The acid value of the acidic graft resin is preferably 20 to 150 mgKOH/g. The upper limit is preferably 130 mgKOH/g or less, and more preferably 110 mgKOH/g or less. The lower limit is preferably 30 mgKOH/g or more, and more preferably 40 mgKOH/g or more.

The weight average molecular weight of the acidic graft resin is preferably 5,000 to 100,000, more preferably 10,000 to 50,000, and even more preferably 10,000 to 30,000. The number average molecular weight (Mn) of the acidic graft resin is preferably 2,500 to 50,000, more preferably 5,000 to 30,000, and even more preferably 5,000 to 15,000.

Specific examples of acidic graft resins include the resins described in paragraphs 0025 to 0094 of JP 2012-255128 A and the resins having the structures described in the examples described below.

The curable composition of the present invention preferably contains a resin as a dispersant. Examples of dispersants include acidic dispersants (acidic resins) and basic dispersants (basic resins). Here, the term "acidic dispersant (acidic resin)" refers to a resin in which the amount of acid groups is greater than the amount of basic groups. The acidic dispersant (acidic resin) is preferably a resin in which the amount of acid groups is 70 mol% or more when the total amount of the acid groups and the basic groups is 100 mol%. The acid group possessed by the acidic dispersant (acidic resin) is preferably a carboxy group. The acid value of the acidic dispersant (acidic resin) is preferably 10 to 105 mgKOH/g. The basic dispersant (basic resin) refers to a resin in which the amount of basic groups is greater than the amount of acid groups. The basic dispersant (basic resin) is preferably a resin in which the amount of basic groups is greater than the amount of acid groups when the total amount of the acid groups and the basic groups is 100 mol%. The basic group possessed by the basic dispersant is preferably an amino group.

The resin used as the dispersant is preferably a graft resin. For details of the graft resin, refer to paragraphs 0025 to 0094 of JP 2012-255128 A, the contents of which are incorporated herein by reference.

It is also preferable that the resin used as the dispersant is a resin having an aromatic carboxy group. Examples of resins having an aromatic carboxy group include those mentioned above.

The resin used as the dispersant is preferably a polyimine-based dispersant containing nitrogen atoms in at least one of the main chain and side chain. The polyimine-based dispersant is preferably a resin having a main chain with a partial structure having a functional group with a pKa of 14 or less, a side chain with 40 to 10,000 atoms, and having a basic nitrogen atom in at least one of the main chain and side chain. There are no particular restrictions on the basic nitrogen atom, so long as it is a nitrogen atom that exhibits basicity. For details of polyimine-based dispersants, please refer to the description in paragraphs 0102 to 0166 of JP 2012-255128 A, the contents of which are incorporated herein by reference.

The resin used as the dispersant is preferably one having a structure in which multiple polymer chains are bonded to a core portion. Examples of such resins include dendrimers (including star-shaped polymers). Specific examples of dendrimers include polymer compounds C-1 to C-31 described in paragraphs 0196 to 0209 of JP2013-043962A.

The resin used as the dispersant is also preferably a resin containing a repeating unit having an ethylenically unsaturated bond-containing group in the side chain. The content of the repeating unit having an ethylenically unsaturated bond-containing group in the side chain is preferably 10 mol % or more of the total repeating units of the resin, more preferably 10 to 80 mol %, and even more preferably 20 to 70 mol %.

As dispersants, resins described in JP 2018-087939 A, block copolymers (EB-1) to (EB-9) described in paragraphs 0219 to 0221 of Japanese Patent No. 6,432,077 A, polyethyleneimine having a polyester side chain described in WO 2016/104803 A, block copolymers described in WO 2019/125940 A, block polymers having an acrylamide structural unit described in JP 2020-066687 A, block polymers having an acrylamide structural unit described in JP 2020-066688 A, dispersants described in WO 2016/104803 A, and the like can also be used.

Dispersants are also available as commercially available products, and specific examples include the DISPERBYK series manufactured by BYK-Chemie, the SOLSPERSE series manufactured by Lubrizol Nippon, the Efka series manufactured by BASF, and the AJISPER series manufactured by Ajinomoto Fine-Techno Co., Ltd. In addition, the products described in paragraph 0129 of JP2012-137564A and the products described in paragraph 0235 of JP2017-194662A can also be used as dispersants.

The resin content in the total solid content of the curable composition is preferably 1 to 40% by mass. The upper limit is preferably 30% by mass or less, and more preferably 25% by mass or less. The lower limit is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more.
The content of the acidic graft resin in the total solid content of the curable composition is preferably 1 to 30% by mass. The upper limit is preferably 25% by mass or less, more preferably 20% by mass or less. The lower limit is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more.
The curable composition of the present invention may contain only one type of resin, or may contain two or more types of resins. When two or more types of resins are contained, the total amount thereof is preferably within the above range.

<<Polymerizable compound>>
The curable composition of the present invention contains a polymerizable compound. The polymerizable compound may be a compound having an ethylenically unsaturated bond-containing group. The ethylenically unsaturated bond-containing group may be a vinyl group, a (meth)allyl group, or a (meth)acryloyl group. The polymerizable compound used in the present invention is preferably a radical polymerizable compound.

The polymerizable compound may be in any chemical form, such as a monomer, prepolymer, or oligomer, but is preferably a monomer. The molecular weight of the polymerizable compound is preferably 100 to 2500. The upper limit is preferably 2000 or less, more preferably 1500 or less. The lower limit is preferably 150 or more, more preferably 250 or more.

The ethylenically unsaturated bond-containing group value (hereinafter referred to as the C=C value) of the polymerizable compound is preferably 2 to 14 mmol/g from the viewpoint of the storage stability of the curable composition. The lower limit is preferably 3 mmol/g or more, more preferably 4 mmol/g or more, and even more preferably 5 mmol/g or more. The upper limit is preferably 12 mmol/g or less, more preferably 10 mmol/g or less, and even more preferably 8 mmol/g or less. The C=C value of the polymerizable compound is a value calculated by dividing the number of ethylenically unsaturated bond-containing groups contained in one molecule of the polymerizable compound by the molecular weight of the polymerizable compound.

The polymerizable compound is preferably a compound containing 3 or more ethylenically unsaturated bond-containing groups, more preferably a compound containing 3 to 15 ethylenically unsaturated bond-containing groups, and even more preferably a compound containing 3 to 6 ethylenically unsaturated bond-containing groups. The polymerizable compound is preferably a 3-15 functional (meth)acrylate compound, and more preferably a 3-6 functional (meth)acrylate compound. Specific examples of the polymerizable compound include the compounds described in paragraphs 0075 to 0083 of WO 2022/065215 and the compounds described in Taiwan Patent Application Publication No. 201832008.

Preferred polymerizable compounds include dipentaerythritol tri(meth)acrylate (commercially available product is KAYARAD D-330; manufactured by Nippon Kayaku Co., Ltd.), dipentaerythritol tetra(meth)acrylate (commercially available product is KAYARAD D-320; manufactured by Nippon Kayaku Co., Ltd.), dipentaerythritol penta(meth)acrylate (commercially available product is KAYARAD D-310; manufactured by Nippon Kayaku Co., Ltd.), dipentaerythritol hexa(meth)acrylate (commercially available products are KAYARAD DPHA; manufactured by Nippon Kayaku Co., Ltd., and NK Ester A-DPH-12E; manufactured by Shin-Nakamura Chemical Co., Ltd.), and compounds in which the (meth)acryloyl groups are bonded via ethylene glycol and/or propylene glycol residues (e.g., SR454, SR499, commercially available from Sartomer Corporation). Examples of polymerizable compounds include diglycerol EO (ethylene oxide) modified (meth)acrylate (commercially available product is M-460; manufactured by Toagosei Co., Ltd.), pentaerythritol tetraacrylate (NK Ester A-TMMT, manufactured by Shin-Nakamura Chemical Co., Ltd.), 1,6-hexanediol diacrylate (KAYARAD HDDA, manufactured by Nippon Kayaku Co., Ltd.), RP-1040 (manufactured by Nippon Kayaku Co., Ltd.), Aronix TO-2349 (manufactured by Toagosei Co., Ltd.), and NK Oligo UA-7200 (manufactured by Shin-Nakamura Chemical Co., Ltd.). Co., Ltd.), DPHA-40H (Nippon Kayaku Co., Ltd.), UA-306H, UA-306T, UA-306I, AH-600, T-600, AI-600, LINC-202UA (Kyoeisha Chemical Co., Ltd.), 8UH-1006, 8UH-1012 (all manufactured by Taisei Fine Chemical Co., Ltd.), Light Acrylate POB-A0 (Kyoeisha Chemical Co., Ltd.), and polymerizable compounds having a dendrimer structure or hyperbranch structure as described in JP-A-2023-043479 can also be used.

As the polymerizable compound, a polymerizable compound having an ethylene oxide repeating chain can also be used. According to this embodiment, the effects of the present invention are more remarkable. As the polymerizable compound having an ethylene oxide repeating chain, a compound represented by formula (EO-1) can be mentioned.

R ^E1 in formula (EO-1) represents a hydrogen atom or a methyl group.

L ^E1 in formula (EO-1) represents an m-valent linking group. Examples of the m-valent linking group represented by L ^E1 include a hydrocarbon group, a heterocyclic group, -O-, -S-, -NR ^A1 -, -CO-, -COO-, -OCO-, -SO ₂ -, and a group obtained by combining two or more of these groups. R ^A1 represents a hydrogen atom, an alkyl group, or an aryl group, and is preferably a hydrogen atom. The hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be cyclic or non-cyclic. The non-cyclic aliphatic hydrocarbon group may be a straight-chain aliphatic hydrocarbon group or a branched aliphatic hydrocarbon group. The aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. The hydrocarbon group may have a substituent or may not have a substituent. The cyclic aliphatic hydrocarbon group and the aromatic hydrocarbon group may be a monocyclic ring or a condensed ring. The heterocyclic group may be a single ring or a condensed ring. The heterocyclic group is preferably a 5-membered or 6-membered ring. The heterocyclic group may be an aliphatic heterocyclic group or an aromatic heterocyclic group. The heteroatom constituting the heterocyclic group may be a nitrogen atom, an oxygen atom, a sulfur atom, etc.

In formula (EO-1), n represents an integer from 1 to 20, and m represents an integer from 2 to 10. n is preferably an integer from 1 to 15, and more preferably an integer from 1 to 10. m is preferably an integer from 2 to 8, and more preferably an integer from 2 to 6.

As the polymerizable compound, a polymerizable compound having a fluorene skeleton can also be used. The polymerizable compound having a fluorene skeleton is preferably a bifunctional polymerizable compound. As the polymerizable compound having a fluorene skeleton, a compound having a partial structure represented by the following formula (Fr) can be mentioned.

In the formula, * represents a bond, R ^f1 and R ^f2 each independently represent a substituent, and m and n each independently represent an integer of 0 to 5. When m is 2 or more, m R ^f1s may be the same or different from each other, and two R ^f1s among the m R ^f1s may be bonded to each other to form a ring. When n is 2 or more, n R ^f2s may be the same or different from each other, and two R ^f2s among the n R ^f2s may be bonded to each other to form a ring. Examples of the substituents represented by R ^f1 and R ^f2 include a halogen atom, a cyano group, a nitro group, an alkyl group, an aryl group, a heteroaryl group, -OR ^f11 , -COR ^f12 , -COOR ^f13 , -OCOR ^f14 , -NR ^f15 R ^f16 , -NHCOR ^f17 , -CONR ^f18 R ^f19 , -NHCONR ^f20 R ^f21 , -NHCOOR ^f22 , -SR ^f23 , -SO ₂ R ^f24 , -SO ₂ OR ^f25 , -NHSO ₂ R ^f26 , and -SO ₂ NR ^f27 R ^f28 . R ^f11 to R ^f28 each independently represent a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group.

Specific examples of the polymerizable compound having a fluorene skeleton include compounds having the following structure: Furthermore, commercially available products of the polymerizable compound having a fluorene skeleton include OGSOL EA-0200 and EA-0300 (manufactured by Osaka Gas Chemicals Co., Ltd., (meth)acrylate monomers having a fluorene skeleton).

The content of the polymerizable compound in the total solid content of the curable composition is preferably 1 to 25 mass%. The upper limit is preferably 20 mass% or less, and more preferably 15 mass% or less. The lower limit is preferably 3 mass% or more, and more preferably 5 mass% or more.

The curable composition preferably contains 5 to 100 parts by mass of the polymerizable compound per 100 parts by mass of the resin. The upper limit of the content of the polymerizable compound is preferably 80 parts by mass or less, and more preferably 70 parts by mass or less. The lower limit of the content of the polymerizable compound is preferably 10 parts by mass or more, and more preferably 20 parts by mass or more.

The curable composition of the present invention may contain only one type of polymerizable compound, or may contain two or more types. When two or more types of polymerizable compounds are contained, it is preferable that the total amount thereof is within the above range.

<<Photopolymerization initiator>>
The curable composition of the present invention contains a photopolymerization initiator. The photopolymerization initiator is not particularly limited and can be appropriately selected from known photopolymerization initiators. For example, a compound having photosensitivity to light rays in the ultraviolet range to the visible range is preferred. The photopolymerization initiator is preferably a photoradical polymerization initiator.

Photopolymerization initiators include halogenated hydrocarbon derivatives (e.g., compounds having a triazine skeleton, compounds having an oxadiazole skeleton, etc.), acylphosphine compounds, hexaarylbiimidazole compounds, oxime compounds, organic peroxides, thio compounds, ketone compounds, aromatic onium salts, α-hydroxyketone compounds, α-aminoketone compounds, etc. From the viewpoint of exposure sensitivity, the photopolymerization initiator is preferably a trihalomethyltriazine compound, a benzyl dimethyl ketal compound, an α-hydroxyketone compound, an α-aminoketone compound, an acylphosphine compound, a phosphine oxide compound, a metallocene compound, an oxime compound, a hexaarylbiimidazole compound, an onium compound, a benzothiazole compound, a benzophenone compound, an acetophenone compound, a cyclopentadiene-benzene-iron complex, a halomethyloxadiazole compound, or a 3-aryl substituted coumarin compound, more preferably a compound selected from an oxime compound, an α-hydroxyketone compound, an α-aminoketone compound, and an acylphosphine compound, and even more preferably an oxime compound. In addition, examples of the photopolymerization initiator include the compounds described in paragraphs 0065 to 0111 of JP 2014-130173 A, the compounds described in Japanese Patent No. 6301489 A, and the compounds described in MATERIAL STAGE 37 to 60p, vol. 19, No. 3, 2019, a photopolymerization initiator described in WO 2018/221177, a photopolymerization initiator described in WO 2018/110179, a photopolymerization initiator described in JP 2019-043864 A, a photopolymerization initiator described in JP 2019-044030 A, a peroxide-based initiator described in JP 2019-167313 A, an aminoacetophenone-based initiator having an oxazolidine group described in JP 2020-055992 A, Oxime-based photopolymerization initiators described in JP-A-0459, polymers described in JP-A-2020-172619, compounds represented by formula 1 described in WO 2020/152120, compounds described in JP-A-2021-181406, photopolymerization initiators described in JP-A-2022-013379, compounds represented by formula (1) described in JP-A-2022-015747, fluorine-containing fluorene oxime ester-based photoinitiators described in JP-T-2021-507058, Chinese Patent Application Publication No. 1107643 Initiators described in JP-A-2022-518535, initiators described in WO 2021/175855, compounds described in Taiwan Patent Application Publication No. 202200534, compounds described in JP-A-2022-078550, compounds described in Korean Patent Publication No. 10-2017-0087330, compounds described in WO 2022/075452, oxime ester compounds described in Chinese Patent Application Publication No. 110066225, Korean Patent Publication No. 10-2017-0087330, Examples of the photopolymerization initiator include the compound described in WO 2019/013112, the compound having a triarylamine or N-arylcarbazole skeleton described in paragraphs 0042 to 0062 of WO 2019/013112, the oxime ester-based photopolymerization initiator described in Japanese Patent Publication No. 7219378, the photopolymerization initiator described in Korean Patent Publication No. 10-2021-0146174, the photopolymerization initiator described in WO 2019/013112, and the photopolymerization initiator described in JP 2023-033731.

Specific examples of hexaarylbiimidazole compounds include 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4,5-diphenyl-1,1'-biimidazole.

Commercially available α-hydroxyketone compounds include Omnirad 184, Omnirad 1173, Omnirad 2959, Omnirad 127 (all manufactured by IGM Resins B.V.), Irgacure 184, Irgacure 1173, Irgacure 2959, Irgacure 127 (all manufactured by BASF), etc. Commercially available α-aminoketone compounds include Omnirad 907, Omnirad 369, Omnirad 369E, Omnirad 379EG (all manufactured by IGM Resins B.V.), Irgacure 907, Irgacure 369, Irgacure 369E, Irgacure 379EG (all manufactured by BASF), etc. Commercially available acylphosphine compounds include Omnirad 819, Omnirad TPO (all manufactured by IGM Resins B.V.), Irgacure 819, Irgacure TPO (all manufactured by BASF), etc.

Examples of oxime compounds include the compound described in paragraph 0142 of WO 2022/085485, the compound described in Japanese Patent No. 5,430,746, the compound described in Japanese Patent No. 5,647,738, the compound represented by general formula (1) and the compounds described in paragraphs 0022 to 0024 of JP 2021-173858 A, the compound represented by general formula (1) and the compounds described in paragraphs 0117 to 0120 of JP 2021-170089 A, and the like. Specific examples of the oxime compound include 3-benzoyloxyiminobutan-2-one, 3-acetoxyiminobutan-2-one, 3-propionyloxyiminobutan-2-one, 2-acetoxyiminopentan-3-one, 2-acetoxyimino-1-phenylpropan-1-one, 2-benzoyloxyimino-1-phenylpropan-1-one, 3-(4-toluenesulfonyloxy)iminobutan-2-one, 2-ethoxycarbonyloxyimino-1-phenylpropan-1-one, 1-[4-(phenylthio)phenyl]-3-cyclohexyl-propane-1,2-dione-2-(O-acetyloxime), and the like. Commercially available products include Irgacure OXE01, Irgacure OXE02, Irgacure OXE03, and Irgacure OXE04 (all manufactured by BASF), TR-PBG-301, TR-PBG-304, and TR-PBG-327 (manufactured by TRONLY), and Adeka Optomer N-1919 (manufactured by ADEKA Corporation, photopolymerization initiator 2 described in JP 2012-014052 A). In addition, it is also preferable to use a compound that is not colorable or a compound that is highly transparent and does not easily discolor as the oxime compound. Commercially available products include Adeka Arcles NCI-730, NCI-831, and NCI-930 (all manufactured by ADEKA Corporation).

As the photopolymerization initiator, an oxime compound having a fluorene ring, an oxime compound having a skeleton in which at least one benzene ring of a carbazole ring is replaced with a naphthalene ring, an oxime compound having a fluorine atom, an oxime compound having a nitro group, an oxime compound having a benzofuran skeleton, an oxime compound in which a substituent having a hydroxyl group is bonded to a carbazole skeleton, or a compound described in paragraphs 0143 to 0149 of WO 2022/085485 can be used.

As a photopolymerization initiator, a compound represented by formula (OX-1) can also be used.

In formula (OX-1), X ^1a represents a divalent linking group containing at least one ring selected from the group consisting of an aromatic ring and a heterocycle;
R ^1a represents a hydrogen atom or an acyl group;
^R2a represents an alkyl group or an aryl group;
R ^3a and R ^4a each independently represent a hydrogen atom or an alkyl group;
Alk ¹ and Alk ² each independently represent an alkyl group;
R ^3a and R ^4a may be bonded to form a ring;
Alk ¹ and Alk ² may be linked to form a ring;
n represents 0 or 1.

Examples of the divalent linking group represented by X ^1a in formula (OX-1) include a divalent aromatic ring group, a divalent heterocyclic group, a divalent group in which two or more aromatic rings are bonded via a single bond or a linking group, a divalent group in which two or more heterocycles are bonded via a single bond or a linking group, and a divalent group in which an aromatic ring and a heterocycle are bonded via a single bond or a linking group. Examples of the linking group that bonds the above-mentioned aromatic rings, heterocyclic groups, or aromatic rings and heterocycles include -CH ₂ -, -O-, -CO-, -S-, -NR ^x -, and groups combining these. R ^x represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group.

X ^1a in formula (OX-1) is preferably a group represented by any one of formulas (X-1) to (X-13), more preferably a group represented by formula (X-1), formula (X-2), formula (X-4), formula (X-6) or formula (X-8), and further preferably a group represented by formula (X-2) or formula (X-6).
In the formula, R ^X1 to R ^X9 each independently represent a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group.

The number of carbon atoms in the alkyl group represented by R ^X1 to R ^X9 is preferably 1 to 15, and more preferably 1 to 10. The alkyl group may be linear, branched, or cyclic. The alkyl group may have a substituent. Examples of the substituent include a halogen atom, an aryl group, and a heterocyclic group.

The number of carbon atoms in the alkenyl group represented by R ^X1 to R ^X9 is preferably 2 to 15, and more preferably 2 to 10. The alkenyl group may be linear, branched, or cyclic. The alkenyl group may have a substituent. Examples of the substituent include a halogen atom, an aryl group, and a heterocyclic group.

The number of carbon atoms in the alkynyl group represented by R ^X1 to R ^X9 is preferably 2 to 15, and more preferably 2 to 10. The alkynyl group may be linear, branched, or cyclic. The alkynyl group may have a substituent. Examples of the substituent include a halogen atom, an aryl group, and a heterocyclic group.

The number of carbon atoms in the aryl group represented by R ^X1 to R ^X9 is preferably 6 to 20, more preferably 6 to 12, still more preferably 6 to 10, and particularly preferably 6. The aryl group may have a substituent. Examples of the substituent include a halogen atom, an alkyl group, an alkenyl group, an alkynyl group, and a heterocyclic group.

The heterocyclic group represented by R ^X1 to R ^X9 is preferably a 5-membered or 6-membered ring. The heteroatoms contained in the heterocyclic group are preferably an oxygen atom, a nitrogen atom, or a sulfur atom. The number of heteroatoms contained in the heterocyclic group is preferably 1 to 3. The heterocyclic group may have a substituent. Examples of the substituent include a halogen atom, an alkyl group, an alkenyl group, an alkynyl group, and an aryl group.

In formula (OX-1), R ^1a represents a hydrogen atom or an acyl group, and is preferably an acyl group.
The acyl group represented by R ^1a is preferably a group represented by —C(O)—R ^101. R ¹⁰¹ represents an aryl group or a heterocyclic group, and is preferably an aryl group.

The number of carbon atoms of the aryl group represented by R ¹⁰¹ is preferably 6 to 20, and more preferably 6 to 12. The aryl group may have a substituent. Examples of the substituent include a halogen atom, an alkyl group, an alkenyl group, an alkynyl group, and a heterocyclic group. The aryl group represented by ^{R 101} is preferably a phenyl group, a methylphenyl group, or a naphthyl group, and more preferably a methylphenyl group or a naphthyl group.

The heterocyclic group represented by R ¹⁰¹ is preferably a 5-membered or 6-membered ring. The heteroatoms contained in the heterocyclic group are preferably an oxygen atom, a nitrogen atom, or a sulfur atom. The number of heteroatoms contained in the heterocyclic group is preferably 1 to 3. The heterocyclic group may have a substituent. Examples of the substituent include a halogen atom, an alkyl group, an alkenyl group, an alkynyl group, and an aryl group.

R ^2a in formula (OX-1) represents an alkyl group or an aryl group, and is preferably an alkyl group because the reactivity of the generated radical is high.
The number of carbon atoms of the alkyl group represented by R ^2a is preferably 1 to 15, more preferably 1 to 10, even more preferably 1 to 5, and even more preferably 1 to 3. The alkyl group may be linear, branched, or cyclic, but is preferably linear or branched, and more preferably linear. The alkyl group may have a substituent, but is preferably an unsubstituted alkyl group. The alkyl group represented by R ^2a is preferably an unsubstituted linear or branched alkyl group, and more preferably an unsubstituted linear alkyl group.
The number of carbon atoms in the aryl group represented by R ^2a is preferably 6 to 20, more preferably 6 to 12, still more preferably 6 to 10, and particularly preferably 6. The aryl group may have a substituent, but is preferably an unsubstituted aryl group.

In formula (OX-1), R ^3a and R ^4a each independently represent a hydrogen atom or an alkyl group, and preferably a hydrogen atom.
The number of carbon atoms in the alkyl group represented by R ^3a and R ^4a is preferably 1 to 15, more preferably 1 to 10, even more preferably 1 to 5, and even more preferably 1 to 3. The alkyl group may be linear, branched, or cyclic, but is preferably linear or branched, and more preferably linear. The alkyl group may have a substituent, but is preferably an unsubstituted alkyl group.
^R3a and ^R4a may be bonded to form a ring. The ring formed is preferably a 5- or 6-membered ring, and more preferably a 5- or 6-membered aliphatic hydrocarbon ring.

In formula (OX-1), Alk ¹ and Alk ² each independently represent an alkyl group. The number of carbon atoms in the alkyl group is preferably 1 to 15, more preferably 1 to 10, even more preferably 1 to 5, and even more preferably 1 to 3. The alkyl group may be linear, branched, or cyclic, but is preferably linear or branched, and more preferably linear. The alkyl group may have a substituent, but is preferably an unsubstituted alkyl group.
^Alk1 and ^Alk2 may be bonded to form a ring, and preferably form a ring. The ring formed is preferably a 5- or 6-membered ring, more preferably a 5- or 6-membered aliphatic hydrocarbon ring, and more preferably a cyclopentane ring or a cyclohexane ring.

In formula (OX-1), n represents 0 or 1, and is preferably 0.

Specific examples of the compound represented by formula (OX-1) include the compounds described in paragraphs 0092 to 0096 of JP2012-113104A and the compounds described in paragraph 0041 of JP2012-189997A.

As a photopolymerization initiator, a compound represented by formula (OX-2) can also be used.

In formula (OX-2), R ^1b and R ^2b each independently represent a substituent, R ^3b to R ^7b each independently represent a hydrogen atom or a substituent, Ar ^1b represents an aromatic ring group or a heterocyclic group which may have a substituent, and n represents 0 or 1.

Examples of the substituent represented by R ^1b and R ^2b include an alkyl group and an aryl group, and an alkyl group is preferable. The number of carbon atoms of the alkyl group is preferably 1 to 15, and more preferably 1 to 10. The alkyl group may be linear, branched, or cyclic. The alkyl group may have a substituent. Examples of the substituent include a halogen atom, an aryl group, an alkenyl group, an alkynyl group, and a heterocyclic group. The number of carbon atoms of the aryl group is preferably 6 to 20, more preferably 6 to 12, even more preferably 6 to 10, and particularly preferably 6. The aryl group may have a substituent. Examples of the substituent include a halogen atom, an alkyl group, an alkenyl group, an alkynyl group, and a heterocyclic group.

The substituents represented by R ^3b to R ^7b include a halogen atom, an alkyl group and an aryl group, the alkyl group and the aryl group being as described above.
R ^3b to R ^7b are preferably hydrogen atoms.

Ar ^1b represents an aromatic ring group or a heterocyclic group which may have a substituent, and Ar ^1b is preferably an aromatic ring group which may have a substituent. The aromatic ring group is preferably a benzene ring group or a naphthalene ring group, and more preferably a benzene ring group. Examples of the substituent include a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aryloxy group, an alkylthio group, an arylthio group, a nitro group, and an acyl group, and an acyl group is preferable. Examples of the acyl group include the acyl groups described above.

As a photopolymerization initiator, a compound represented by formula (OX-3) can also be used.

In formula (OX-3), Ar ^1c represents a (k+m+1)-valent aromatic ring group or a (k+m+1)-valent heterocyclic group;
Ar ^2c represents a (k+2)-valent aromatic ring group or a (k+2)-valent heterocyclic group;
R ^1c to R ^3c each independently represent a substituent;
L ^1c represents a single bond or CR ^11c R ^12c , and R ^11c and R ^12c each independently represent a hydrogen atom, an alkyl group, or an aryl group;
X ^1c represents -O- or -S-;
k represents 0 or 1; m represents an integer of 0 to 4; and n represents 0 or 1.

Examples of the substituent represented by R ^1c and R ^2c include an alkyl group and an aryl group, and an alkyl group is preferable. The number of carbon atoms of the alkyl group is preferably 1 to 15, and more preferably 1 to 10. The alkyl group may be linear, branched, or cyclic. The alkyl group may have a substituent. Examples of the substituent include a halogen atom, an aryl group, an alkenyl group, an alkynyl group, and a heterocyclic group. The number of carbon atoms of the aryl group is preferably 6 to 20, more preferably 6 to 12, even more preferably 6 to 10, and particularly preferably 6. The aryl group may have a substituent. Examples of the substituent include a halogen atom, an alkyl group, an alkenyl group, an alkynyl group, and a heterocyclic group.
R ^2c is preferably an alkyl group having a branched or cyclic structure.

Examples of the substituent represented by ^R3c include a halogen atom, an alkyl group, an alkoxy group, an aryl group, an aryloxy group, and an acyl group, and an acyl group is preferable. Examples of the acyl group include the acyl groups described above.

Ar ^1c represents a (k+m+1)-valent aromatic ring group or a (k+m+1)-valent heterocyclic group, and is preferably a (k+m+1)-valent aromatic ring group. The aromatic ring group is preferably a benzene ring group or a naphthalene ring group, and more preferably a benzene ring group.

^Ar2c represents a (k+2)-valent aromatic ring group or a (k+2)-valent heterocyclic group, and is preferably a (k+2)-valent aromatic ring group. The aromatic ring group is preferably a benzene ring group or a naphthalene ring group, and more preferably a benzene ring group.

k represents 0 or 1, and is preferably 0.

m represents an integer from 0 to 4, preferably 0 or 1, and more preferably 1.

As the photopolymerization initiator, it is also preferable to use an oxime compound having two or more oxime groups in one molecule. According to this embodiment, it is possible to form a cured product such as an optical component in which the occurrence of wrinkles on the surface adjacent to other layers is further suppressed in a humid environment.

The oxime compound having two or more oxime groups in one molecule is preferably a compound represented by formula (OX-10).
In formula (OX-10), ^X represents a divalent linking group.
R ¹¹ and R ¹² each independently represent an alkyl group, an aryl group, or a heteroaryl group;
R ¹³ and R ¹⁴ each independently represent an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a heteroaryl group, or a heteroaryloxy group;
m and n each independently represent 0 or 1.

The divalent linking group represented by X ¹¹ in formula (OX-10) is preferably a divalent linking group containing at least one ring selected from an aromatic ring and a heterocyclic ring.
Examples of the divalent linking group represented by ^X11 include a divalent aromatic ring group, a divalent heterocyclic group, a divalent group in which two or more aromatic rings are bonded via a single bond or a linking group, a divalent group in which two or more heterocycles are bonded via a single bond or a linking group, and a divalent group in which an aromatic ring and a heterocycle are bonded via a single bond or a linking group. Examples of the linking group include _-CH2- , -O-, -CO-, -S-, ^-NRx- , and groups combining these. ^Rx represents a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group.

Specific examples of the divalent linking group represented by ^X11 include groups represented by any of formulas (X-101) to (X-109). From the viewpoint of the remarkable effect of the present invention, a group represented by any of formulas (X-101) to (X-104) is preferable, and a group represented by formula (X-101) is more preferable.

In the formula, * represents a bond, and R ^Y1 to R ^Y4 each independently represent a halogen atom, an alkyl group, an aryl group, or a heterocyclic group.
R ^X1 to R ^X3 each independently represent a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group;
m1 and m2 each independently represent 0 to 4;
m3 and m4 each independently represent 0 to 3.

The halogen atom represented by R ^Y1 to R ^Y4 includes a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
The number of carbon atoms of the alkyl group represented by R ^Y1 to R ^Y4 and R ^X1 to R ^X3 is preferably 1 to 15, and more preferably 1 to 10. The alkyl group may be linear, branched, or cyclic. The alkyl group may have a substituent. Examples of the substituent include a halogen atom, an aryl group, and a heterocyclic group.
The number of carbon atoms in the aryl group represented by R ^Y1 to R ^Y4 and R ^X1 to R ^X3 is preferably 6 to 15, more preferably 6 to 12, still more preferably 6 to 10, and particularly preferably 6. The aryl group may have a substituent. Examples of the substituent include a halogen atom and an alkyl group.

The number of carbon atoms constituting the ring of the heterocyclic group represented by R ^Y1 to R ^Y4 and R ^X1 to R ^X3 is preferably 1 to 15, more preferably 1 to 10. The types of heteroatoms constituting the ring of the heterocyclic group include nitrogen atoms, oxygen atoms, and sulfur atoms. The number of heteroatoms constituting the ring of the heterocyclic group is preferably 1 to 3, more preferably 1 to 2. The heterocyclic group may be a monocyclic ring or a condensed ring. The heterocyclic group may have a substituent. Examples of the substituent include a halogen atom and an alkyl group.

In formula (OX-10), R ¹¹ and R ¹² each independently represent an alkyl group, an aryl group, or a heteroaryl group.

The number of carbon atoms of the alkyl group represented by R ¹¹ and R ¹² is preferably 1 to 15, more preferably 1 to 10, even more preferably 1 to 5, and even more preferably 1 to 3. The alkyl group may be linear, branched, or cyclic. The alkyl group may have a substituent, but is preferably unsubstituted. Examples of the substituent include a halogen atom, an aryl group, and a heterocyclic group. The alkyl group represented by R ¹¹ and R ¹² is particularly preferably a methyl group.
The number of carbon atoms in the aryl group represented by R ¹¹ and R ¹² is preferably 6 to 15, more preferably 6 to 12, still more preferably 6 to 10, and particularly preferably 6. The aryl group may have a substituent. Examples of the substituent include a halogen atom and an alkyl group.
The number of carbon atoms constituting the ring of the heteroaryl group represented by R ¹¹ and R ¹² is preferably 1 to 15, more preferably 1 to 10. The types of heteroatoms constituting the ring of the heteroaryl group include a nitrogen atom, an oxygen atom, and a sulfur atom. The number of heteroatoms constituting the ring of the heteroaryl group is preferably 1 to 3, more preferably 1 to 2. The heteroaryl group may be a single ring or a condensed ring. The heteroaryl group may have a substituent. Examples of the substituent include a halogen atom and an alkyl group.

In formula (OX-10), R ¹¹ and R ¹² each independently represent preferably an alkyl group or an aryl group, and more preferably an alkyl group.

R ¹³ and R ¹⁴ in formula (OX-10) each independently represent an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a heteroaryl group, or a heteroaryloxy group, preferably an alkyl group or an aryl group, more preferably an alkyl group.
The alkyl group, aryl group and heteroaryl group represented by R ¹³ and R ¹⁴ include those groups represented by R ¹¹ and R ¹² in formula (OX-10), and the preferred ranges are also the same.
The number of carbon atoms of the alkoxy group represented by R ¹³ and R ¹⁴ is preferably 1 to 15, and more preferably 1 to 10. The alkoxy group may be either linear or branched. The alkoxy group may have a substituent. Examples of the substituent include a halogen atom, an aryl group, and a heterocyclic group.
The number of carbon atoms in the aryloxy group represented by R ¹³ and R ¹⁴ is preferably 6 to 15, more preferably 6 to 12, still more preferably 6 to 10, and particularly preferably 6. The aryloxy group may have a substituent. Examples of the substituent include a halogen atom and an alkyl group.
The number of carbon atoms constituting the ring of the heteroaryl moiety in the heteroaryloxy group represented by R ¹³ and R ¹⁴ is preferably 1 to 15, more preferably 1 to 10. The types of heteroatoms constituting the ring of the heteroaryl moiety include nitrogen atoms, oxygen atoms, and sulfur atoms. The number of heteroatoms constituting the ring of the heteroaryl moiety is preferably 1 to 3, more preferably 1 to 2. The heteroaryl moiety may be a monocyclic ring or a condensed ring. The heteroaryloxy group may have a substituent. Examples of the substituent include a halogen atom and an alkyl group.

In formula (OX-10), m and n each independently represent 0 or 1, and are preferably 1.

Specific examples of oxime compounds include the compounds shown below and the compounds described in the Examples below.

The content of the photopolymerization initiator in the total solid content of the curable composition is preferably 0.1 to 10 mass%. The lower limit is preferably 0.5 mass% or more, and more preferably 1 mass% or more. The upper limit is preferably 8 mass% or less, and more preferably 5 mass% or less.

The curable composition of the present invention preferably contains 10 to 45 parts by mass of a photopolymerization initiator per 100 parts by mass of the polymerizable compound. The upper limit is preferably 40 parts by mass or less. The lower limit is preferably 11 parts by mass or more, and more preferably 12 parts by mass or more.

The curable composition of the present invention preferably contains 100 to 2000 parts by mass of a photopolymerization initiator per 100 parts by mass of a multifunctional thiol compound described below. The upper limit is preferably 1500 parts by mass or less, and more preferably 1000 parts by mass or less. The lower limit is preferably 150 parts by mass or more, and more preferably 200 parts by mass or more.

The curable composition of the present invention may contain only one type of photopolymerization initiator, or may contain two or more types. When two or more types are contained, it is preferable that the total amount thereof is within the above range.

<<Multifunctional thiol compounds>>
The curable compound of the present invention includes a polyfunctional thiol compound. The polyfunctional thiol compound is a compound having two or more thiol groups in one molecule.

The number of thiol groups in the polyfunctional thiol compound is preferably 2 to 10, more preferably 2 to 6, and even more preferably 2 to 4.

The thiol group of the polyfunctional thiol compound may be a primary thiol group, a secondary thiol group, or a tertiary thiol group. A secondary thiol group is preferable because it can improve the storage stability of the curable composition and can form a cured product such as an optical component in which the occurrence of wrinkles on the surface adjacent to other layers is more suppressed in a humid environment. Note that a primary thiol group means a thiol group in which the carbon atom to which the thiol group is bonded is a primary carbon atom, a secondary thiol group means a thiol group in which the carbon atom to which the thiol group is bonded is a secondary carbon atom, and a tertiary thiol group means a thiol group in which the carbon atom to which the thiol group is bonded is a tertiary carbon atom.

The secondary thiol group is preferably a group represented by formula (th-1).

In formula (th-1), * represents a bond, and R ^th1 represents an alkyl group.

The number of carbon atoms in the alkyl group represented by R ^th1 is preferably 1 to 10, more preferably 1 to 5, and further preferably 1 to 3. ^{R th1} is preferably a methyl group or an ethyl group, and more preferably a methyl group.

The molecular weight of the polyfunctional thiol compound is preferably 100 to 1000. The upper limit is preferably 800 or less, and more preferably 600 or less. The lower limit is preferably 150 or more, and more preferably 200 or more.

The polyfunctional thiol compound is preferably a compound represented by formula (T-1).

In formula (T-1), L ^T1 represents an n-valent group, R ^T1 and R ^T2 each independently represent a hydrogen atom or an alkyl group, and n represents an integer of 2 or more.

In formula (T-1), it is preferable that one of R ^T1 and R ^T2 is a hydrogen atom, and the other is an alkyl group.
The number of carbon atoms in the alkyl group represented by R ^T1 and R ^T2 is preferably 1 to 10, more preferably 1 to 5, and further preferably 1 to 3. The alkyl group represented by R ^T1 and R ^T2 is preferably a methyl group or an ethyl group, and more preferably a methyl group.

Examples of the n-valent group represented by L ^T1 in formula (T-1) include a hydrocarbon group, a heterocyclic group, -O-, -S-, -NR ^LT1 -, -CO-, -COO-, -OCO-, -SO ₂ -, or a group consisting of a combination thereof. R ^LT1 represents a hydrogen atom, an alkyl group, or an aryl group, and is preferably a hydrogen atom. The hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group. The aliphatic hydrocarbon group may be cyclic or noncyclic. The aliphatic hydrocarbon group may be a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. The hydrocarbon group may have a substituent or may not have a substituent. The cyclic aliphatic hydrocarbon group and the aromatic hydrocarbon group may be a monocyclic ring or a condensed ring. The heterocyclic group may be a monocyclic ring or a condensed ring. The heterocyclic group is preferably a 5-membered ring or a 6-membered ring. The heterocyclic group may be an aliphatic heterocyclic group or an aromatic heterocyclic group. Examples of the heteroatom constituting the heterocyclic group include a nitrogen atom, an oxygen atom, and a sulfur atom.

In formula (T-1), n represents an integer of 2 or more, preferably an integer of 2 to 10, more preferably an integer of 2 to 6, and even more preferably an integer of 2 to 4.

Specific examples of polyfunctional thiol compounds include the compounds described in the Examples below and the compounds described in paragraphs 0100 to 0103 of WO 2019/188652. Commercially available polyfunctional thiol compounds include PEMP (manufactured by SC Organic Chemical Co., Ltd.), Suncerar M (manufactured by Sanshin Chemical Industry Co., Ltd.), Karenz MT BD1, Karenz MT TPMB, Karenz MT PE1, Karenz MT NR1 (all manufactured by Resonac Co., Ltd.), etc.

The content of the polyfunctional thiol compound in the total solid content of the curable composition is preferably 0.1 to 5 mass%. The lower limit is preferably 0.3 mass% or more, and more preferably 0.5 mass% or more, because this allows for the formation of a cured product in which the occurrence of wrinkles is suppressed. The upper limit is preferably 3 mass% or less, and more preferably 2 mass% or less, from the viewpoint of the pattern shape.

The curable composition of the present invention may contain only one type of polyfunctional thiol compound, or may contain two or more types. When two or more types are contained, it is preferable that the total amount thereof is within the above range.

<<Solvent>>
The curable composition of the present invention preferably contains a solvent. Examples of the solvent include organic solvents. The type of solvent is not particularly limited as long as the solubility of each component and the coatability of the curable composition are satisfied. Examples of the organic solvent include ester-based solvents, ketone-based solvents, alcohol-based solvents, amide-based solvents, ether-based solvents, and hydrocarbon-based solvents. For details of these, reference can be made to paragraph number 0223 of International Publication No. 2015/166779, the contents of which are incorporated herein by reference. In addition, ester-based solvents substituted with a cyclic alkyl group and ketone-based solvents substituted with a cyclic alkyl group can also be preferably used. Specific examples of organic solvents include polyethylene glycol monomethyl ether, dichloromethane, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, ethyl cellosolve acetate, ethyl lactate, diethylene glycol dimethyl ether, butyl acetate, methyl 3-methoxypropionate, 2-heptanone, 2-pentanone, 3-pentanone, 4-heptanone, cyclohexanone, 2-methylcyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone, cycloheptanone, cyclooctanone, cyclohexyl acetate, cyclopentanone, ethyl carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether, propylene glycol Examples of the ethylene glycol monomethyl ether acetate include 3-methoxy-N,N-dimethylpropanamide, 3-butoxy-N,N-dimethylpropanamide, propylene glycol diacetate, 3-methoxybutanol, methyl ethyl ketone, gamma butyrolactone, sulfolane, anisole, 1,4-diacetoxybutane, diethylene glycol monoethyl ether acetate, butane-1,3-diyl diacetate, dipropylene glycol methyl ether acetate, diacetone alcohol (also known as diacetone alcohol and 4-hydroxy-4-methyl-2-pentanone), 2-methoxypropyl acetate, 2-methoxy-1-propanol, and isopropyl alcohol. However, there are cases where it is better to reduce the amount of aromatic hydrocarbons (benzene, toluene, xylene, ethylbenzene, etc.) used as organic solvents for environmental reasons, etc. (for example, the amount can be 50 ppm (parts per million) by mass or less, 10 ppm by mass or less, or 1 ppm by mass or less, relative to the total amount of organic solvents).

The metal content of the organic solvent is preferably low. The metal content of the organic solvent is preferably, for example, 10 parts per billion (ppb) by mass or less. If necessary, organic solvents at the ppt (parts per trillion) by mass level may be used, and such organic solvents are provided, for example, by Toyo Gosei Co., Ltd. (The Chemical Daily, November 13, 2015).

Methods for removing impurities such as metals from organic solvents include, for example, distillation (molecular distillation, thin-film distillation, etc.) and filtration using a filter. The filter used for filtration preferably has a pore size of 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less. The filter material is preferably polytetrafluoroethylene, polyethylene, or nylon.

The organic solvent may contain isomers (compounds with the same number of atoms but different structures). In addition, the organic solvent may contain only one type of isomer, or multiple types of isomers.

The peroxide content in the organic solvent is preferably 0.8 mmol/L or less, and more preferably substantially free of peroxide.

The content of the solvent in the curable composition is preferably 10 to 95% by mass, more preferably 20 to 90% by mass, and even more preferably 30 to 90% by mass.

From the viewpoint of environmental regulations, it is preferable that the curable composition of the present invention is substantially free of environmentally regulated substances. In the present invention, substantially free of environmentally regulated substances means that the content of environmentally regulated substances in the curable composition is 50 ppm by mass or less, preferably 30 ppm by mass or less, more preferably 10 ppm by mass or less, and particularly preferably 1 ppm by mass or less. Examples of environmentally regulated substances include benzene; alkylbenzenes such as toluene and xylene; and halogenated benzenes such as chlorobenzene. These substances are registered as environmentally regulated substances under the REACH (Registration Evaluation Authorization and Restriction of Chemicals) regulations, the PRTR (Pollutant Release and Transfer Register) Act, the VOC (Volatile Organic Compounds) regulations, etc., and their usage and handling methods are strictly regulated. These compounds may be used as solvents when producing each component used in the curable composition, and may be mixed into the curable composition as a residual solvent. From the viewpoint of human safety and environmental consideration, it is preferable to reduce these substances as much as possible. As a method for reducing the environmentally regulated substances, a method of reducing the environmentally regulated substances by heating or reducing the pressure in the system to a temperature above the boiling point of the environmentally regulated substances and distilling off the environmentally regulated substances from the system can be mentioned. In addition, when distilling off a small amount of environmentally regulated substances, it is useful to perform azeotropy with a solvent having a boiling point equivalent to that of the corresponding solvent in order to increase efficiency. In addition, when a radically polymerizable compound is contained, a polymerization inhibitor or the like may be added and then distilled off under reduced pressure in order to suppress the radical polymerization reaction from proceeding during distillation under reduced pressure and causing crosslinking between molecules. These distillation methods can be used at any stage, such as the stage of the raw materials, the stage of the product obtained by reacting the raw materials (for example, a resin solution or a polyfunctional monomer solution after polymerization), or the stage of the curable composition prepared by mixing these compounds.

<<Compound Having Cyclic Ether Group>>
The curable composition of the present invention may contain a compound having a cyclic ether group. Examples of the cyclic ether group include an epoxy group and an oxetanyl group. The epoxy group may be an alicyclic epoxy group. The alicyclic epoxy group means a monovalent functional group having a cyclic structure in which an epoxy ring and a saturated hydrocarbon ring are condensed. The compound having a cyclic ether group is preferably a compound having an epoxy group (hereinafter also referred to as an epoxy compound). Examples of the epoxy compound include compounds having one or more epoxy groups in one molecule, and compounds having two or more epoxy groups are preferred. The epoxy compound is preferably a compound having 1 to 100 epoxy groups in one molecule. The upper limit of the epoxy groups contained in the epoxy compound can be, for example, 10 or less, or 5 or less. The lower limit of the epoxy groups contained in the epoxy compound is preferably 2 or more. As the epoxy compound, the compounds described in paragraphs 0034 to 0036 of JP-A-2013-011869, paragraphs 0147 to 0156 of JP-A-2014-043556, and paragraphs 0085 to 0092 of JP-A-2014-089408, and the compounds described in JP-A-2017-179172 can also be used.

The compound having a cyclic ether group may be a low molecular weight compound (e.g., a molecular weight of less than 2000, or even less than 1000) or a high molecular weight compound (macromolecule) (e.g., a molecular weight of 1000 or more, or in the case of a polymer, a weight average molecular weight of 1000 or more). The weight average molecular weight of the compound having a cyclic ether group is preferably 200 to 100,000, more preferably 500 to 50,000. The upper limit of the weight average molecular weight is more preferably 10,000 or less, particularly preferably 5,000 or less, and even more preferably 3,000 or less.

Commercially available compounds having a cyclic ether group include, for example, EHPE3150 (manufactured by Daicel Corporation), EPICLON N-695 (manufactured by DIC Corporation), Marproof G-0150M, G-0105SA, G-0130SP, G-0250SP, G-1005S, G-1005SA, G-1010S, G-2050M, G-01100, and G-01758 (all manufactured by NOF Corporation, epoxy group-containing polymers).

The content of the compound having a cyclic ether group in the total solid content of the curable composition is preferably 0.1 to 20 mass%. The lower limit is, for example, more preferably 0.5 mass% or more, and even more preferably 1 mass% or more. The upper limit is, for example, more preferably 15 mass% or less, and even more preferably 10 mass% or less. Only one type of compound having a cyclic ether group may be used, or two or more types may be used. When two or more types are used, it is preferable that the total amount thereof is within the above range.

<<Ultraviolet absorbing agent>>
The curable composition of the present invention may contain an ultraviolet absorber. Examples of ultraviolet absorbers include conjugated diene compounds, aminodiene compounds, salicylate compounds, benzophenone compounds, benzotriazole compounds, acrylonitrile compounds, hydroxyphenyltriazine compounds, indole compounds, triazine compounds, and dibenzoyl compounds. Specific examples of such compounds include the compounds described in paragraph 0179 of International Publication No. 2022/085485, the reactive triazine ultraviolet absorbers described in JP-A-2021-178918, the ultraviolet absorbers described in JP-A-2022-007884, the compounds described in Korean Patent Publication No. 10-2022-0014454, and the compounds described in JP-A-2023-013321. The content of the ultraviolet absorber in the total solid content of the curable composition is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass. In the present invention, the ultraviolet absorbing agent may be used alone or in combination with two or more kinds. When two or more kinds are used, it is preferable that the total amount is in the above range.

<<Polymerization inhibitor>>
The curable composition of the present invention may contain a polymerization inhibitor. Examples of the polymerization inhibitor include hydroquinone, p-methoxyphenol, di-tert-butyl-p-cresol, pyrogallol, tert-butylcatechol, benzoquinone, 4,4'-thiobis(3-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), and N-nitrosophenylhydroxyamine salt (ammonium salt, cerous salt, etc.). Among these, p-methoxyphenol is preferred. The content of the polymerization inhibitor in the total solid content of the curable composition is preferably 0.0001 to 5% by mass. The polymerization inhibitor may be one type or two or more types. In the case of two or more types, the total amount is preferably within the above range.

<<Silane coupling agents>>
The curable composition of the present invention may contain a silane coupling agent. Examples of the silane coupling agent include silane compounds having a hydrolyzable group, and it is preferable that the silane coupling agent is a silane compound having a hydrolyzable group and other functional groups. The hydrolyzable group refers to a substituent that is directly bonded to a silicon atom and can generate a siloxane bond by at least one of a hydrolysis reaction and a condensation reaction. Examples of the hydrolyzable group include a halogen atom, an alkoxy group, and an acyloxy group, and an alkoxy group is preferable. That is, the silane coupling agent is preferably a compound having an alkoxysilyl group. In addition, examples of functional groups other than the hydrolyzable group include a vinyl group, a (meth)allyl group, a (meth)acryloyl group, a mercapto group, an epoxy group, an oxetanyl group, an amino group, a ureido group, a sulfide group, an isocyanate group, and a phenyl group, and an amino group, a (meth)acryloyl group, and an epoxy group are preferable. Specific examples of the silane coupling agent include the compounds described in paragraph 0177 of International Publication No. 2022/085485 and the compounds described in JP-A-2019-183020. The content of the silane coupling agent in the total solid content of the curable composition is preferably 0.01 to 15.0% by mass, more preferably 0.05 to 10.0% by mass. The silane coupling agent may be one type or two or more types. In the case of two or more types, it is preferable that the total amount is within the above range.

<<Surfactants>>
The curable composition of the present invention may contain a surfactant. As the surfactant, various surfactants such as fluorine-based surfactants, nonionic surfactants, cationic surfactants, anionic surfactants, and silicone-based surfactants may be used. The surfactant is preferably a silicone-based surfactant or a fluorine-based surfactant, and more preferably a silicone-based surfactant. For the surfactant, reference may be made to the surfactants described in paragraphs 0238 to 0245 of WO 2015/166779, the contents of which are incorporated herein by reference.

As fluorosurfactants, the compounds described in paragraphs 0167 to 0173 of WO 2022/085485 can be used.

Nonionic surfactants include the compounds described in paragraph 0174 of WO 2022/085485.

Silicone surfactants include DOWSIL SH8400, SH8400 FLUID, FZ-2122, 67 Additive, 74 Additive, M Additive, and SF 8419. OIL (all manufactured by Dow Toray Co., Ltd.), TSF-4300, TSF-4445, TSF-4460, TSF-4452 (all manufactured by Momentive Performance Materials, Inc.), KP-341, KF-6000, KF-6001, KF-6002, KF-6003 (all manufactured by Shin-Etsu Chemical Co., Ltd.), BYK-307, BYK-322, BYK-323, BYK-330, BYK-333, BYK-3760, BYK-UV3510 (all manufactured by BYK-Chemie), etc. As the silicone surfactant, a compound having the following structure can also be used.

The content of the surfactant in the total solid content of the curable composition is preferably 0.001% by mass to 5.0% by mass, and more preferably 0.005% by mass to 3.0% by mass. The surfactant may be one type or two or more types. When two or more types are used, it is preferable that the total amount is within the above range.

<<Antioxidants>>
The curable composition of the present invention may contain an antioxidant. Examples of the antioxidant include phenolic compounds, phosphite compounds, and thioether compounds. As the phenolic compound, any phenolic compound known as a phenolic antioxidant may be used. A preferred phenolic compound is a hindered phenolic compound. A compound having a substituent at the site (ortho position) adjacent to the phenolic hydroxy group is preferred. As the aforementioned substituent, a substituted or unsubstituted alkyl group having 1 to 22 carbon atoms is preferred. In addition, the antioxidant is also preferably a compound having a phenolic group and a phosphite ester group in the same molecule. In addition, a phosphorus-based antioxidant may also be suitably used as the antioxidant. Examples of phosphorus-based antioxidants include tris[2-[[2,4,8,10-tetrakis(1,1-dimethylethyl)dibenzo[d,f][1,3,2]dioxaphosphepin-6-yl]oxy]ethyl]amine, tris[2-[(4,6,9,11-tetra-tert-butyldibenzo[d,f][1,3,2]dioxaphosphepin-2-yl)oxy]ethyl]amine, and ethylbis(2,4-di-tert-butyl-6-methylphenyl)phosphite. Commercially available antioxidants include, for example, Adeka STAB AO-20, Adeka STAB AO-30, Adeka STAB AO-40, Adeka STAB AO-50, Adeka STAB AO-50F, Adeka STAB AO-60, Adeka STAB AO-60G, Adeka STAB AO-80, and Adeka STAB AO-330 (manufactured by ADEKA Corporation). In addition, the antioxidant may be a compound described in paragraphs 0023 to 0048 of Japanese Patent No. 6268967, a compound described in International Publication No. WO 2017/006600, a compound described in International Publication No. WO 2017/164024, or a compound described in Korean Patent Publication No. 10-2019-0059371. The content of the antioxidant in the total solid content of the curable composition is preferably 0.01 to 20 mass%, more preferably 0.3 to 15 mass%. Only one type of antioxidant may be used, or two or more types may be used. When two or more types are used, it is preferable that the total amount is in the above range.

<<Other ingredients>>
The curable composition of the present invention may contain, as necessary, a sensitizer, a plasticizer, and other auxiliaries (e.g., conductive particles, fillers, defoamers, flame retardants, leveling agents, peeling promoters, fragrances, surface tension regulators, chain transfer agents, etc.). By appropriately incorporating these components, properties such as film properties can be adjusted. As these components, the compounds described in paragraph 0182 of WO 2022/085485 can be used.

It is also preferable that the curable composition of the present invention is substantially free of terephthalic acid esters. Here, "substantially free" means that the content of terephthalic acid esters in the total amount of the curable composition is 1000 ppb by mass or less, more preferably 100 ppb by mass or less, and particularly preferably zero.

In view of environmental regulations, it is preferable that the curable composition of the present invention has a melamine content of 10,000 ppm by mass or less.

The curable composition of the present invention preferably has a free metal content of 100 ppm or less, more preferably 50 ppm or less. The free halogen content is preferably 100 ppm or less, more preferably 50 ppm or less. Methods for reducing free metals and halogens in the curable composition include washing with ion-exchanged water, filtration, ultrafiltration, and purification with ion-exchange resins.

From the viewpoint of environmental regulations, the use of perfluoroalkylsulfonic acid and its salts, and perfluoroalkylcarboxylic acid and its salts may be restricted. When the content of the above-mentioned compounds is reduced in the curable composition of the present invention, the content of perfluoroalkylsulfonic acid (particularly perfluoroalkylsulfonic acid having 6 to 8 carbon atoms in the perfluoroalkyl group) and its salts, and perfluoroalkylcarboxylic acid (particularly perfluoroalkylcarboxylic acid having 6 to 8 carbon atoms in the perfluoroalkyl group) and its salts is preferably in the range of 0.01 ppb to 1,000 ppb, more preferably in the range of 0.05 ppb to 500 ppb, and even more preferably in the range of 0.1 ppb to 300 ppb, based on the total solid content of the curable composition. The curable composition of the present invention may be substantially free of perfluoroalkylsulfonic acid and its salts, and perfluoroalkylcarboxylic acid and its salts. For example, by using a compound that can be a substitute for perfluoroalkylsulfonic acid and its salt, and a compound that can be a substitute for perfluoroalkyl carboxylic acid and its salt, a curable composition that is substantially free of perfluoroalkylsulfonic acid and its salt, and perfluoroalkyl carboxylic acid and its salt may be selected. Examples of compounds that can be a substitute for regulated compounds include compounds that are excluded from the scope of regulation due to the difference in the number of carbon atoms in the perfluoroalkyl group. However, the above content does not prevent the use of perfluoroalkylsulfonic acid and its salt, and perfluoroalkyl carboxylic acid and its salt. The curable composition of the present invention may contain perfluoroalkylsulfonic acid and its salt, and perfluoroalkyl carboxylic acid and its salt within the maximum allowable range.

The use of fluorine-containing compounds may be restricted from the perspective of environmental regulations. When the content of fluorine-containing compounds in the curable composition is reduced, the content of fluorine-containing compounds in the curable composition is preferably 5% by mass or less, more preferably 1% by mass or less, and even more preferably 0.1% by mass or less. The curable composition may be substantially free of fluorine-containing compounds.

The water content of the curable composition of the present invention is usually 3% by mass or less, preferably 0.01 to 1.5% by mass, and more preferably in the range of 0.1 to 1.0% by mass. The water content can be measured by the Karl Fischer method.

The curable composition of the present invention can be used by adjusting the viscosity for the purpose of adjusting the film surface state (flatness, etc.) and film thickness. The viscosity value can be selected appropriately as needed, but for example, a value of 0.3 mPa·s to 50 mPa·s at 25°C is preferable, and 0.5 mPa·s to 20 mPa·s is more preferable. The viscosity can be measured, for example, using a cone-plate type viscometer with the temperature adjusted to 25°C.

<<Storage container>>
The container for storing the curable composition is not particularly limited, and a known container can be used. In addition, the container described in paragraph 0187 of WO 2022/085485 can be used as the container.

<Method of preparing curable composition>
The curable composition of the present invention can be prepared by mixing the above-mentioned components. When preparing the curable composition, all the components may be simultaneously dissolved and/or dispersed in a solvent to prepare the curable composition, or, if necessary, each component may be appropriately prepared as two or more solutions or dispersions, which are mixed at the time of use (at the time of application) to prepare the curable composition.

In addition, when preparing the curable composition, it is preferable to include a process for dispersing particles. In the process for dispersing particles, mechanical forces used for dispersing particles include compression, squeezing, impact, shear, and cavitation. Specific examples of these processes include bead mills, sand mills, roll mills, ball mills, paint shakers, microfluidizers, high-speed impellers, sand grinders, flow jet mixers, high-pressure wet atomization, and ultrasonic dispersion. In addition, when grinding particles in a sand mill (bead mill), it is preferable to use beads with a small diameter and increase the bead packing rate to perform processing under conditions that increase the grinding efficiency. In addition, it is preferable to remove coarse particles by filtration, centrifugation, or the like after the grinding process. In addition, the process and dispersing machine for dispersing particles can be suitably used as described in "Dispersion Technology Encyclopedia, published by Information Technology Co., Ltd., July 15, 2005" or "Dispersion Technology and Industrial Application Practice Focusing on Suspension (Solid/Liquid Dispersion System) - Comprehensive Data Collection, published by Management Development Center Publishing Department, October 10, 1978", and JP2015-157893, paragraph number 0022. In the process for dispersing particles, the particles may be refined in a salt milling process. For the materials, equipment, processing conditions, etc. used in the salt milling process, the descriptions in, for example, JP2015-194521A and JP2012-046629A can be referred to. Examples of materials for beads used for dispersion include zirconia, agate, quartz, titania, tungsten carbide, silicon nitride, alumina, stainless steel, and glass. The beads may also be made of an inorganic compound with a Mohs hardness of 2 or more. The curable composition may contain 1 to 10,000 ppm of the beads.

When preparing the curable composition, it is preferable to filter the curable composition with a filter for the purpose of removing foreign matter and reducing defects. Examples of the types of filters and filtration methods used for filtration include the filters and filtration methods described in paragraphs 0196 to 0199 of WO 2022/085485.

<Cured Product>
The cured product of the present invention is obtained by using the above-mentioned curable composition of the present invention. The cured product of the present invention can be preferably used for optical members such as microlenses.

The minimum transmittance of the cured product of the present invention in the wavelength range of 400 to 700 nm is preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, and particularly preferably 90% or more.
The average transmittance of the cured product of the present invention in the wavelength range of 400 to 700 nm is preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, and particularly preferably 90% or more.
The refractive index of the cured product of the present invention with respect to light having a wavelength of 550 nm is preferably 1.5 to 2.2. The upper limit is preferably 2.1 or less, and more preferably 2.0 or less. The lower limit is preferably 1.7 or more, and more preferably 1.8 or more.

<Optical components>
The curable composition of the present invention can be used for optical members. Examples of the optical members include microlenses, waveguides, and anti-reflection films, and the microlenses are preferred. The optical members of the present invention are particularly preferably used as microlenses for solid-state imaging devices.

When the optical member of the present invention is used as a microlens, it is preferable to process the curable composition of the present invention into a lens shape before use. In other words, it is preferable that the microlens is obtained by processing the curable composition of the present invention into a lens shape.

For microlenses, the minimum transmittance in the wavelength range of 400 to 700 nm is preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, and especially preferably 90% or more. For microlenses, the average transmittance in the wavelength range of 400 to 700 nm is preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, and especially preferably 90% or more.

The refractive index of the microlens for light with a wavelength of 550 nm is preferably 1.5 to 2.2. The upper limit is preferably 2.1 or less, and more preferably 2.0 or less. The lower limit is preferably 1.7 or more, and more preferably 1.8 or more.

The lens shape of the microlens is not particularly limited, and can take a variety of shapes derived from optical system design. Examples include convex and concave shapes. In addition, the radius of curvature of the lens is not particularly limited, and is preferably set appropriately within a range that produces the desired effect.

The thickness of the microlens is preferably 0.3 to 1.5 μm. The upper limit is preferably 1.3 μm or less, and more preferably 1.0 μm or less. The lower limit is preferably 0.4 μm or more, and more preferably 0.5 μm or more. Here, the thickness of the microlens refers to the thickness of the thickest part of the microlens. For example, in the case of a double-convex lens, it refers to the distance from the apex of one convex surface to the apex of the other convex surface.

A protective layer may be provided on the surface of the macro lens. By providing a protective layer, various functions such as oxygen blocking, low reflection, hydrophilicity/hydrophobicity, and blocking of light of a specific wavelength (ultraviolet rays, infrared rays, etc.) can be imparted. The thickness of the protective layer is preferably 0.01 to 10 μm, and more preferably 0.1 to 5 μm. Methods for forming the protective layer include a method of forming the protective layer by applying a resin composition for forming the protective layer, a chemical vapor deposition method, and a method of attaching a molded resin with an adhesive. The components constituting the protective layer include (meth)acrylic resin, ene-thiol resin, polycarbonate resin, polyether resin, polyarylate resin, polysulfone resin, polyethersulfone resin, polyphenylene resin, polyarylene ether phosphine oxide resin, polyimide resin, polyamideimide resin, polyolefin resin, cyclic olefin resin, polyester resin, styrene resin, polyol resin, polyvinylidene chloride resin, melamine resin, urethane resin, aramid resin, polyamide resin, alkyd resin, epoxy resin, modified silicone resin, fluorine resin, polyacrylonitrile resin, cellulose resin, Si, C, W, Al ₂ O ₃ , Mo, SiO ₂ , and Si ₂ N ₄ , and may contain two or more of these components. For example, in the case of a protective layer intended for oxygen blocking, the protective layer preferably contains a polyol resin, SiO ₂ , and Si ₂ N _4. In addition, in the case of a protective layer intended for low reflection, the protective layer preferably contains a (meth)acrylic resin and a fluorine resin.

When forming a protective layer by applying a resin composition, known methods such as spin coating, casting, screen printing, and inkjet can be used as a method for applying the resin composition. Known organic solvents (e.g., propylene glycol 1-monomethyl ether 2-acetate, cyclopentanone, ethyl lactate, etc.) can be used as the organic solvent contained in the resin composition. When forming the protective layer by chemical vapor deposition, known chemical vapor deposition methods (thermal chemical vapor deposition, plasma chemical vapor deposition, photochemical vapor deposition) can be used as the chemical vapor deposition method.

The protective layer may contain additives such as organic or inorganic fine particles, absorbents for light of specific wavelengths (e.g., ultraviolet light, infrared light, etc.), refractive index adjusters, antioxidants, adhesion agents, and surfactants, as necessary. Examples of organic or inorganic fine particles include polymer fine particles (e.g., silicone resin fine particles, polystyrene fine particles, melamine resin fine particles), titanium oxide, zinc oxide, zirconium oxide, indium oxide, aluminum oxide, titanium nitride, titanium oxynitride, magnesium fluoride, hollow silica, silica, calcium carbonate, and barium sulfate. Known absorbents can be used as absorbents for light of specific wavelengths. The content of these additives can be adjusted as appropriate, but is preferably 0.1 to 70% by mass, and more preferably 1 to 60% by mass, based on the total mass of the protective layer.

The protective layer may be the one described in paragraphs 0073 to 0092 of JP2017-151176A.

<Method of manufacturing microlenses>
Next, a method for producing a microlens will be described. The method for producing a microlens preferably includes a step of forming a composition layer by applying the above-mentioned curable composition of the present invention onto a support, and a step of processing the curable composition layer into a lens shape. Each step will be described below.

(Step of forming composition layer)
In the step of forming a composition layer, the curable composition of the present invention is used to form a composition layer on a support. Examples of the support include a glass substrate and a silicon substrate, and a silicon substrate is preferable. In addition, a charge-coupled device (CCD), a complementary metal oxide semiconductor (CMOS), a transparent conductive film, an optical filter such as a color filter, etc. may be formed on the silicon substrate. In addition, a black matrix that isolates each pixel may be formed on the silicon substrate.

　The curable composition can be applied by any known method. Examples of the method include the drop casting method, slit coating method, spray method, roll coating method, spin coating method, casting method, slit and spin method, pre-wetting method (for example, the method described in JP 2009-145395 A), various printing methods such as ejection printing such as inkjet (for example, on-demand method, piezo method, thermal method) and nozzle jet, flexographic printing, screen printing, gravure printing, reverse offset printing, and metal mask printing method, transfer method using a mold, etc., and nanoimprint method. The application method using an inkjet printer is not particularly limited, and examples of the method include those described in "Expanding and Usable Inkjet Printing - Infinite Possibilities Seen in Patents -, published in February 2005 by Sumibe Techno Research" (particularly pages 115 to 133), and those described in JP-A-2003-262716, JP-A-2003-185831, JP-A-2003-261827, JP-A-2012-126830, and JP-A-2006-169325. In addition, the description of the application method of the curable composition can be found in WO 2017/030174 and WO 2017/018419, the contents of which are incorporated herein by reference.

The composition layer formed on the support may be dried (prebaked). When prebaking is performed, the prebaking temperature is preferably 100°C or less, more preferably 90°C or less, even more preferably 80°C or less, and particularly preferably 70°C or less. The lower limit can be, for example, 40°C or more. The prebaking time is preferably 10 to 3600 seconds. Prebaking can be performed using a hot plate, an oven, etc.

(Process to form lens shape)
The composition layer can be processed into a lens shape by a conventionally known processing method, such as a transfer method, an imprint method, or a heat drip method.

In the transfer method, a composition layer formed on a support is cured to form a cured layer, a resist layer is formed on the cured layer, the resist layer is patterned into a lens shape, and the cured layer is dry etched using the patterned resist layer as a mask to transfer the lens shape to the cured layer. Lenses can be manufactured by using the transfer method in the methods described in JP 2006-073605 A, JP 2006-190903 A, JP 2008-281414 A, JP 2014-029524 A, and the like, the contents of which are incorporated herein by reference.

In the imprint method, a mold having a pattern is pressed onto a composition layer formed on a support, the composition layer is sandwiched between the mold and the support, the composition layer is exposed to light in this sandwiched state and cured, and then the mold is peeled off from the support to produce the product.

In the thermal dripping method, a composition layer formed on a support is cured to form a cured layer, which is then heated to cause thermal dripping of the surface of the cured layer, allowing the cured layer to be processed into a lens shape.

The process of processing into a lens shape may include a process of exposing the composition layer to light. Exposure is used as a curing process for the composition layer. Exposure is preferably performed by irradiating the composition layer with radiation. Examples of radiation include g-line and i-line. Light with a wavelength of 300 nm or less (preferably light with a wavelength of 180 to 300 nm) can also be used. Examples of light with a wavelength of 300 nm or less include KrF line (wavelength 248 nm) and ArF line (wavelength 193 nm), with KrF line (wavelength 248 nm) being preferred. Long-wavelength light sources of 300 nm or more can also be used.

In addition, during exposure, light may be applied continuously or in pulses (pulse exposure). Pulse exposure is an exposure method in which light is applied and paused repeatedly in short cycles (e.g., milliseconds or less).

The irradiation amount (exposure amount) is, for example, preferably 0.03 to 2.5 J/cm ² , more preferably 0.05 to 1.0 J/cm ^2. The oxygen concentration during exposure can be appropriately selected, and in addition to being performed under air, exposure may be performed under a low-oxygen atmosphere with an oxygen concentration of 19 volume% or less (e.g., 15 volume%, 5 volume%, or substantially oxygen-free), or under a high-oxygen atmosphere with an oxygen concentration of more than 21 volume% (e.g., 22 volume%, 30 volume%, or 50 volume%). The exposure illuminance can be appropriately set, and can usually be selected from the range of 1000 W/m ² to 100,000 W/m ² (e.g., 5,000 W/m ² , 15,000 W/m ² , or 35,000 W/m ² ). The oxygen concentration and exposure illuminance may be appropriately combined. For example, the oxygen concentration can be 10% by volume and the illuminance can be 10,000 W/m ² , and the oxygen concentration can be 35% by volume and the illuminance can be 20,000 W/m ² .

<Solid-state imaging element>
The optical member of the present invention can be used for a solid-state imaging device. The configuration of the solid-state imaging device is not particularly limited as long as it includes the optical member of the present invention and functions as a solid-state imaging device. For example, the following configurations can be mentioned.

The optical element of the present invention has a structure in which a substrate is provided with a plurality of photodiodes constituting the light receiving area of a solid-state imaging element (such as a CCD (charge-coupled device) image sensor or a CMOS (complementary metal-oxide semiconductor) image sensor) and a transfer electrode made of polysilicon or the like, a light-shielding film is provided on the photodiodes and the transfer electrode with only the light receiving portion of the photodiode being opened, a device protective film made of silicon nitride or the like formed on the light-shielding film so as to cover the entire light-shielding film and the light receiving portion of the photodiode, and a color filter is provided on the device protective film. The optical element of the present invention can be provided on the device protective film below the color filter (the side closer to the substrate) or on the color filter. For example, when the optical element of the present invention is used as a microlens, a microlens can be provided on the color filter.

In the solid-state imaging element, the color filter may have a structure in which each colored pixel is embedded in a space partitioned by partitions, for example in a lattice pattern. In this case, it is preferable that the partitions have a lower refractive index than each colored pixel. Examples of imaging devices having such a structure include the devices described in JP 2012-227478 A, JP 2014-179577 A, and WO 2018/043654 A. In addition, as shown in JP 2019-211559 A, an ultraviolet absorbing layer may be provided in the structure of the solid-state imaging element to improve light resistance. Imaging devices equipped with solid-state imaging elements can be used for digital cameras, electronic devices with imaging functions (such as mobile phones), as well as in-vehicle cameras and surveillance cameras.

<Image display device>
The optical member of the present invention can be used in an image display device. Examples of image display devices include liquid crystal display devices and organic electroluminescence display devices. The definition of an image display device and details of each image display device are described, for example, in "Electronic Display Devices" (written by Akio Sasaki, published by Kogyo Chosakai Co., Ltd. in 1990) and "Display Devices" (written by Junsho Ibuki, published by Sangyo Tosho Co., Ltd. in 1989). Liquid crystal display devices are described, for example, in "Next Generation Liquid Crystal Display Technology" (edited by Tatsuo Uchida, published by Kogyo Chosakai Co., Ltd. in 1994). There is no particular limitation on the liquid crystal display device to which the present invention can be applied, and the present invention can be applied to various types of liquid crystal display devices described in the above-mentioned "Next Generation Liquid Crystal Display Technology."

The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

<Preparation of Dispersion>
(Formulation 1)
A mixture of 22.7 parts by mass of particles, 6.1 parts by mass of dispersant (solid content equivalent), and 71.1 parts by mass of solvent was mixed and dispersed for 3 hours using a bead mill (zirconia beads 0.1 mm diameter). Thereafter, a dispersion treatment was carried out using a high-pressure disperser NANO-3000-10 (manufactured by Japan BEE Co., Ltd.) equipped with a pressure reducing mechanism under conditions of a pressure of 2000 kg/ ^cm2 and a flow rate of 500 g/min. This dispersion treatment was repeated a total of 10 times to obtain a dispersion. The particles, dispersant, and solvent were made from the materials shown in the table below.

Details of the materials listed in the table above are as follows:

(particle)
P-1: _TiO2 particles (transparent or white particles, average primary particle size 20 nm)
P-2: _ZrO2 particles (transparent or white particles, average primary particle size 50 nm)

(Dispersant)
D-1: Resin having the following structure (the numbers attached to the main chain are molar ratios, and the numbers attached to the side chains are the numbers of repeating units. Weight average molecular weight: 24,000, acid value: 48.7 mgKOH/g)
D-2: Resin having the following structure (the numbers attached to the main chain are molar ratios, and the numbers attached to the side chains are the numbers of repeating units. Weight average molecular weight: 20,000, acid value: 70.1 mgKOH/g)
D-3: (The numbers attached to the main chain are molar ratios, and the numbers attached to the side chains are the numbers of repeating units. Weight average molecular weight: 23,000, acid value: 61.4 mgKOH/g)

(solvent)
S-1: Cyclohexanone

<Preparation of Curable Composition>
Each material was mixed in the ratio of formulations 1 to 13 shown below, and filtered through a nylon filter with a pore size of 0.45 μm (manufactured by Nippon Pall Co., Ltd.) to produce each curable composition. In the following table, the content of particles in the total solid content of the curable composition is shown in the column "Particle concentration (mass%)", and the content of thiol compound in the total solid content of the curable composition is shown in the column "Thiol compound concentration (mass%)".

Details of the materials indicated by the abbreviations in the table showing the formulation of the above curable composition are as follows:

(Dispersion)
Dispersions 1 to 4: Dispersions 1 to 4 described above

(Monomer (polymerizable compound))
M-1: A mixture of compounds having the following structure (a mixture of the compound on the left and the compound on the right in a molar ratio of 7:3)
M-2: A mixture of compounds having the following structure (a mixture of the compounds on the left and right in a molar ratio of 45:55)
M-3: Compound having the following structure
M-4: Compound having the following structure
M-5: Compound having the following structure

(Photopolymerization initiator)
I-1 to I-9, I'-1: Compounds having the following structures

(binder)
B-1: 40% by mass solution of a resin having the following structure (the numerical values attached to the main chain are molar ratios; weight average molecular weight 14,000, acid value 79.3 mgKOH/g) in propylene glycol monomethyl ether acetate (PGMEA)
B-2: 40% by mass PGMEA solution of a resin having the following structure (the numerical values added to the main chain are molar ratios; weight average molecular weight 11,000, acid value 31.8 mgKOH/g)
B-3: 40% by mass PGMEA solution of a resin having the following structure (the number attached to the main chain is the molar ratio, and the number attached to the side chain is the number of repeating units; weight average molecular weight 20,000, acid value 70.1 mgKOH/g)
B-4: 40% by mass PGMEA solution of a resin having the following structure (the number attached to the main chain is the molar ratio, and the number attached to the side chain is the number of repeating units; weight average molecular weight 23,000, acid value 61.4 mgKOH/g)

(Thiol Compounds)
SH-1: Compound having the following structure (a multifunctional thiol compound having two secondary thiol groups)
SH-2: Compound having the following structure (a multifunctional thiol compound having three secondary thiol groups)
SH-3: Compound having the following structure (a multifunctional thiol compound having three secondary thiol groups)
SH-4: Compound having the following structure (a multifunctional thiol compound having four secondary thiol groups)
SH-5: Compound having the following structure (a polyfunctional thiol compound having four primary thiol groups)
SH-6: Compound having the following structure (a polyfunctional thiol compound having two primary thiol groups)
SH-7: Compound having the following structure (a polyfunctional thiol compound having three primary thiol groups)
SH-8: Compound having the following structure (a polyfunctional thiol compound having three primary thiol groups)
SH-9: Compound having the following structure (a multifunctional thiol compound having six primary thiol groups)
SHC-1: Compound having the following structure (monofunctional thiol compound having one primary thiol group, comparative compound)

(Epoxy Compound)
E-1: Compound having the following structure

(Surfactant)
Su-1: Compound having the following structure (silicone surfactant)

(Polymerization inhibitor)
In-1: p-methoxyphenol

(solvent)
S-1: Cyclohexanone

<Reliability evaluation>
Each curable composition was applied onto a glass substrate by spin coating, then heat-treated (pre-baked) at 100°C for 120 seconds using a hot plate, then exposed to i-line at an exposure dose of 1000mJ/ ^cm2 , and then heated at 220°C for 5 minutes to produce a film with a thickness of 0.6μm. Next, a _SiO2 film with a thickness of 100nm was formed on the surface of the film formed on the glass substrate by chemical vapor deposition deposition to produce a test specimen. The transmittance of the produced test specimen in the wavelength range of 400 to 700nm was measured using a spectrometer (Otsuka Electronics Co., Ltd., MCPD-9800).
The test specimen was placed in a thermohygrostat (EHS-221M, manufactured by Yamato Scientific Co., Ltd.) and left to stand for 500 hours, 1000 hours, and 2000 hours in an atmosphere of a temperature of 85° C. and a relative humidity of 85%, for a reliability test. After the reliability test, the test specimen was measured for transmittance in the wavelength range of 400 to 700 nm using a spectrometer (MCPD-9800, manufactured by Otsuka Electronics Co., Ltd.).
The maximum change in transmittance (ΔT%) of the test specimen before and after the reliability test was determined, and the reliability was evaluated according to the following evaluation criteria. The maximum change in transmittance (ΔT%) means the change in the wavelength at which the change in transmittance of the test specimen before and after the reliability test is the largest in the wavelength range of 400 to 700 nm. The smaller the ΔT%, the more the transmittance fluctuation due to wrinkles can be suppressed, and the better the reliability.
-Evaluation criteria-
5: ΔT% was 10% or less. 4: ΔT% was more than 10% and less than 20%. 3: ΔT% was more than 20% and less than 30%. 2: ΔT% was more than 30% and less than 40%. 1: ΔT% was more than 40%.

<Evaluation of storage stability>
The viscosity (mPa·s) of each curable composition was measured using "RE-85L" manufactured by Toki Sangyo Co., Ltd. After the above measurement, each curable composition was left to stand at 45°C, shielded from light, for 3 days, and the viscosity (mPa·s) was measured again. The storage stability was evaluated according to the following evaluation criteria from the viscosity difference (ΔVis) before and after the above standing. It can be said that the smaller the viscosity difference (ΔVis) value, the better the storage stability of the curable composition. The above viscosity measurements were all performed in a laboratory where the temperature and humidity were controlled to 22±5°C and 60±20%, and the temperature of the curable composition was adjusted to 25°C.
-Evaluation criteria-
5: ΔVis was 0.2 mPa·s or less. 4: ΔVis was greater than 0.2 mPa·s and less than 0.4 mPa·s. 3: ΔVis was greater than 0.4 mPa·s and less than 0.6 mPa·s. 2: ΔVis was greater than 0.6 mPa·s and less than 1.0 mPa·s. 1: ΔVis was greater than 1.0 mPa·s.

<Evaluation of Pattern Shape>
On a silicon wafer with a diameter of 8 inches (20.32 cm), a composition for underlayer (CT-4000, manufactured by FUJIFILM Electronic Materials Co., Ltd.) was applied by spin coating so that the film thickness was 0.1 μm, and heated at 220 ° C. for 1 hour using a hot plate to form an underlayer. Each curable composition was applied by spin coating on the silicon wafer with the underlayer, and then heated at 100 ° C. for 2 minutes using a hot plate to form a composition layer. Next, using an i-line exposure machine, the composition layer was exposed at an exposure dose of 100 mJ / cm ² through a mask having a Bayer pattern of 0.8 μm square. Next, paddle development was performed at 23 ° C. for 60 seconds using a 0.3 mass % aqueous solution of tetramethylammonium hydroxide. Thereafter, rinsing with a spin shower and washing with pure water were performed, and further heating was performed at 230 ° C. for 5 minutes using a hot plate to form a pattern with a thickness of 0.6 μm and a line width of 10 μm square.
The silicon wafer on which the pattern was formed was observed by observing the top surface of the pattern using a scanning electron microscope (SEM) to evaluate the pattern shape. The closer the pattern area ratio shown below is to 1, the better the pattern shape is.
Pattern area ratio=(area of formed pattern/area of rectangle circumscribing formed pattern)
-Evaluation criteria-
5: The pattern area ratio is 0.950 or more and 1.000 or less. 4: The pattern area ratio is 0.900 or more and less than 0.950. 3: The pattern area ratio is 0.850 or more and less than 0.900. 2: The pattern area ratio is 0.800 or more and less than 0.850. 1: The pattern area ratio is less than 0.800.

<Transparency assessment>
The curable composition was applied onto a glass substrate by spin coating and heated at 220° C. for 5 minutes to prepare a film having a thickness of 0.6 μm. The transmittance of the obtained film in the wavelength range of 400 to 700 nm was measured using a spectrometer (MCPD-9800, manufactured by Otsuka Electronics Co., Ltd.). The higher the transmittance in the wavelength range of 400 to 700 nm, the better the transparency.
-Evaluation criteria-
5: The minimum transmittance in the wavelength range of 400 to 700 nm is 90% or more. 4: The minimum transmittance in the wavelength range of 400 to 700 nm is 75% or more and less than 90%. 3: The minimum transmittance in the wavelength range of 400 to 700 nm is 50% or more and less than 75%. 2: The minimum transmittance in the wavelength range of 400 to 700 nm is 30% or more and less than 50%. 1: The minimum transmittance in the wavelength range of 400 to 700 nm is less than 30%.

As shown in the table above, the examples had excellent reliability ratings, and even when placed in a humid environment for a long period of time, they were able to form a cured product in which the occurrence of wrinkles on the surface of the adjacent layer was suppressed.

The curable compositions of the examples can be suitably used for microlenses.

Claims (16)

Particles A containing at least one selected from _TiO2 particles and _ZrO2 particles;
Resin and
A polymerizable compound,
A photopolymerization initiator;
A curable composition comprising: a polyfunctional thiol compound. The curable composition according to claim 1, wherein the polyfunctional thiol compound is a compound having 2 to 4 secondary thiol groups in one molecule. 3. The curable composition according to claim 1, wherein the particles A comprise _TiO2 particles. The curable composition according to claim 1 or 2, wherein the particles A are transparent or white particles. The curable composition according to claim 1 or 2, wherein the content of particles A in the total solid content of the curable composition is 50 to 80 mass %. The curable composition according to claim 1 or 2, wherein the content of the polyfunctional thiol compound in the total solid content of the curable composition is 0.1 to 5 mass %. The curable composition according to claim 1 or 2, which contains 10 to 45 parts by mass of the photopolymerization initiator per 100 parts by mass of the polymerizable compound. The curable composition according to claim 1 or 2, comprising 100 to 2000 parts by mass of the photopolymerization initiator per 100 parts by mass of the multifunctional thiol compound. The curable composition according to claim 1 or 2, wherein the photopolymerization initiator includes an oxime compound. The curable composition according to claim 1 or 2, wherein the photopolymerization initiator includes an oxime compound having two or more oxime groups in one molecule. The curable composition according to claim 1 or 2, wherein the resin includes a resin having a graft chain and an acid group. The curable composition according to claim 1 or 2, further comprising a compound having a cyclic ether group. The curable composition according to claim 1 or 2, wherein when the curable composition is used to form a film having a thickness of 0.4 to 1.0 μm by heating at 220°C for 5 minutes, the minimum transmittance of the film in the wavelength range of 400 to 700 nm is 75% or more. A cured product obtained using the curable composition according to claim 1 or 2. An optical member obtained using the curable composition according to claim 1 or 2. The optical element according to claim 15, wherein the optical element is a microlens.