JP7463732B2 - Infrared light cut filter, filter for solid-state image sensor, solid-state image sensor, and method for manufacturing filter for solid-state image sensor - Google Patents

Description

The present invention relates to an infrared light cut filter, a filter for a solid-state imaging device, a solid-state imaging device, and a method for manufacturing a filter for a solid-state imaging device.

Solid-state imaging devices such as CMOS image sensors and CCD image sensors have photoelectric conversion elements that convert the intensity of light into an electrical signal. One example of a solid-state imaging device is capable of detecting light corresponding to multiple colors. The solid-state imaging device has a color filter for each color and a photoelectric conversion element for each color, and detects light for each color using the photoelectric conversion element for each color (see, for example, Patent Document 1). Another example of a solid-state imaging device has an organic photoelectric conversion element and an inorganic photoelectric conversion element, and detects light of each color using each photoelectric conversion element without using a color filter (see, for example, Patent Document 2).

The solid-state imaging element is provided with an infrared light cut filter on the photoelectric conversion element. The infrared light absorbing pigment in the infrared light cut filter absorbs infrared light, thereby cutting off infrared light that can be detected by each photoelectric conversion element to the photoelectric conversion element. This improves the detection accuracy of visible light in each photoelectric conversion element. The infrared light cut filter contains, for example, a cyanine pigment that is an infrared light absorbing pigment (see, for example, Patent Document 3).

JP 2003-060176 A JP 2018-060910 A JP 2007-219114 A

However, in the manufacture of an infrared cut filter using a coloring composition containing a cyanine dye, the infrared cut filter manufactured through multiple steps may have deteriorated spectral characteristics in the visible light region and in the infrared light region of the cyanine dye contained in the coloring composition. Therefore, it is required to suppress the deterioration of the spectral characteristics in both the visible light region and the infrared light region in the infrared cut filter.

The present invention aims to provide an infrared light cut filter that can suppress deterioration of the spectral characteristics of the infrared light cut filter in the visible light region and the infrared light region, a filter for a solid-state imaging device, a solid-state imaging device, and a method for manufacturing a filter for a solid-state imaging device.

The infrared cut filter for solving the above problem includes polymethine, a cyanine dye containing tris(pentafluoroethyl)trifluorophosphate and a cation having two nitrogen-containing heterocycles, one at each end of the polymethine, an acrylic polymer, and an organic peroxide containing an aromatic ring. When the acrylic polymer is taken as 100 parts by weight, the filter contains less than 0.35 parts by weight of the organic peroxide.

A method for manufacturing a filter for a solid-state imaging device to solve the above problem includes forming an infrared cut filter including polymethine, a cyanine dye including tris(pentafluoroethyl)trifluorophosphate, and an acrylic polymer, the cyanine dye including polymethine and a cation having two nitrogen-containing heterocycles, one at each end of the polymethine, and tris(pentafluoroethyl)trifluorophosphate, and the acrylic polymer, and patterning the infrared cut filter by dry etching. Forming the infrared cut filter includes forming the acrylic polymer by radical polymerization using a thermal polymerization initiator that is at least one of an azo compound and an organic peroxide containing an aromatic ring. When the acrylic polymer after polymerization is 100 parts by weight, the organic peroxide is less than 0.35 parts by weight.

A solid-state imaging device that solves the above problem includes a photoelectric conversion element and the above-mentioned filter for the solid-state imaging device.

According to each of the above configurations, the content of the aromatic ring-containing organic peroxide is less than 0.35 parts by weight, which suppresses deterioration of the spectral characteristics of the infrared cut filter in both the visible light region and the infrared light region.

In the infrared cut filter, the acrylic polymer may contain a first repeating unit derived from phenyl methacrylate. According to the above configuration, the phenyl group of the first repeating unit is located between the cyanine dye and another cyanine dye located in the vicinity of the cyanine dye, so that a distance sufficient to suppress association of the cyanine dyes can be formed between the cyanine dyes. This suppresses deterioration of the spectral characteristics at wavelengths expected to be absorbed by the cyanine dye.

In the infrared cut filter, the acrylic polymer may include the first repeating unit, a second repeating unit derived from a monomer containing a phenol group, and a third repeating unit derived from glycidyl methacrylate.

According to the above configuration, a crosslinked structure is formed by crosslinking the phenol group of the second repeating unit with the epoxy group of the third repeating unit. This prevents the absorbance of the infrared cut filter from decreasing due to heating.

A filter for solid-state imaging devices that solves the above problem includes the infrared cut filter and a barrier layer that covers the infrared cut filter and suppresses the transmission of an oxidation source that oxidizes the infrared cut filter. With the above configuration, the barrier layer prevents the oxidation source from reaching the infrared cut filter, so that the infrared cut filter is less likely to be oxidized by the oxidation source.

The present invention makes it possible to suppress deterioration of the spectral characteristics of the infrared cut filter in both the visible light region and the infrared light region.

FIG. 1 is an exploded perspective view showing a structure of a solid-state imaging element according to an embodiment.

With reference to FIG. 1, an embodiment of an infrared light cut filter, a filter for a solid-state imaging device, a solid-state imaging device, and a manufacturing method for a filter for a solid-state imaging device will be described. Below, a manufacturing method, manufacturing example, and working example of a solid-state imaging device and a filter for a solid-state imaging device will be described in order. Note that in this embodiment, infrared light is light having a wavelength in the range of 0.7 μm or more and 1 mm or less, and near-infrared light is infrared light having a wavelength in the range of 700 nm or more and 1100 nm or less. Also, in this embodiment, visible light is light having a wavelength in the range of 400 nm or more and 600 nm or less.

[Solid-state imaging element]
The solid-state imaging device will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the individual layers of a portion of the solid-state imaging device in a separated manner.

As shown in FIG. 1, the solid-state imaging device 10 includes a filter 10F for solid-state imaging devices and a plurality of photoelectric conversion elements 11.
The photoelectric conversion elements 11 include a red photoelectric conversion element 11R, a green photoelectric conversion element 11G, a blue photoelectric conversion element 11B, and an infrared photoelectric conversion element 11P. The photoelectric conversion elements 11R, 11G, and 11B for each color measure the intensity of visible light having a specific wavelength associated with the photoelectric conversion element 11R, 11G, and 11B. Each infrared photoelectric conversion element 11P measures the intensity of infrared light.

The solid-state imaging element 10 includes a plurality of red photoelectric conversion elements 11R, a plurality of green photoelectric conversion elements 11G, a plurality of blue photoelectric conversion elements 11B, and a plurality of infrared photoelectric conversion elements 11P. Note that, for convenience of illustration, FIG. 1 shows the repeating unit of the photoelectric conversion elements 11 in the solid-state imaging element 10.

The solid-state imaging element filter 10F includes multiple visible light filters, an infrared light pass filter 12P, an infrared light cut filter 13, multiple visible light microlenses, and an infrared light microlens 15P.

The visible light color filter is composed of a red filter 12R, a green filter 12G, and a blue filter 12B. The red filter 12R is located on the light incident side of the red photoelectric conversion element 11R. The green filter 12G is located on the light incident side of the green photoelectric conversion element 11G. The blue filter 12B is located on the light incident side of the blue photoelectric conversion element 11B.

The infrared light pass filter 12P is located on the light incident side of the infrared light photoelectric conversion element 11P. The infrared light pass filter 12P blocks visible light that can be detected by the infrared light photoelectric conversion element 11P from being transmitted to the infrared light photoelectric conversion element 11P. This improves the detection accuracy of infrared light by the infrared light photoelectric conversion element 11P. The infrared light that can be detected by the infrared light photoelectric conversion element 11P is, for example, near-infrared light.

The infrared light cut filter 13 is located on the light incident side of the color filters 12R, 12G, and 12B. The infrared light cut filter 13 has a through hole 13H. When viewed from a viewpoint opposite the plane on which the infrared light cut filter 13 extends, the infrared light pass filter 12P is located within the area defined by the through hole 13H. On the other hand, when viewed from a viewpoint opposite the plane on which the infrared light cut filter 13 extends, the infrared light cut filter 13 is located above the red filter 12R, the green filter 12G, and the blue filter 12B.

The infrared light cut filter 13 contains a cyanine dye, which is an infrared light absorbing dye. The cyanine dye has a maximum value in the infrared light absorptance at any wavelength included in the near-infrared light. Therefore, the infrared light cut filter 13 can reliably absorb the near-infrared light that passes through the infrared light cut filter 13. As a result, the near-infrared light that can be detected by the photoelectric conversion element 11 for each color is sufficiently cut by the infrared light cut filter 13. The infrared light cut filter 13 can have a thickness of, for example, 300 nm or more and 3 μm or less.

The barrier layer 14 suppresses the transmission of the oxidation source of the infrared cut filter 13 toward the infrared cut filter 13. The oxidation source is oxygen, water, or the like. The oxygen permeability of the barrier layer 14 is preferably, for example, 5.0 cc/m ² /day/atom or less. The oxygen permeability is a value in accordance with JIS K7126:2006. Since the oxygen permeability is set to 5.0 cc/m ² /day/atom or less, the barrier layer 14 suppresses the oxidation source from reaching the infrared cut filter 13, and the infrared cut filter 13 is less likely to be oxidized by the oxidation source. Therefore, the light resistance of the infrared cut filter 13 can be improved.

The material forming the barrier layer 14 is an inorganic compound. The material forming the barrier layer 14 is preferably a silicon compound. The material forming the barrier layer 14 may be, for example, at least one selected from the group consisting of silicon nitride, silicon oxide, and silicon oxynitride.

The microlenses are composed of a red microlens 15R, a green microlens 15G, a blue microlens 15B, and an infrared microlens 15P. The red microlens 15R is located on the light incident side of the red filter 12R. The green microlens 15G is located on the light incident side of the green filter 12G. The blue microlens 15B is located on the light incident side of the blue filter 12B. The infrared microlens 15P is located on the light incident side of the infrared light pass filter 12P.

Each microlens 15R, 15G, 15B, and 15P has an incident surface 15S, which is the outer surface. Each microlens 15R, 15G, 15B, and 15P has a refractive index difference between itself and the outside air to focus the light that enters the incident surface 15S toward each photoelectric conversion element 11R, 11G, 11B, and 11P. Each microlens 15R, 15G, 15B, and 15P contains a transparent resin.

[Infrared cut filter]
The infrared cut filter 13 will be described in more detail below.
The infrared cut filter 13 includes a cyanine dye, an acrylic polymer, and an organic peroxide having an aromatic ring. The cyanine dye includes a cation and an anion. The cation includes a polymethine and two nitrogen-containing heterocycles, one at each end of the polymethine. The anion is tris(pentafluoroethyl)trifluorophosphate (FAP).

The cyanine dye may have a structure shown in formula (1) below.

In the above formula (1), X is a methine or polymethine. The hydrogen atoms bonded to the carbon atoms contained in the methine may be substituted with halogen atoms or organic groups. The polymethine may have a cyclic structure containing the carbons forming the polymethine. The cyclic structure may contain three consecutive carbons among the carbons forming the polymethine. When the polymethine has a cyclic structure, the number of carbons in the polymethine may be 5 or more. Each nitrogen atom is contained in a five- or six-membered heterocycle. The heterocycle may be condensed.

The cyanine dye may also have a structure shown in formula (2) below.

In the above formula (2), n is an integer of 1 or more. n indicates the number of repeating units contained in the polymethine chain. R4 and R5 are hydrogen atoms or organic groups. R6 and R7 are hydrogen atoms or organic groups. R6 and R7 are preferably linear alkyl groups or branched alkyl groups having 1 or more carbon atoms. Each nitrogen atom is contained in a five-membered or six-membered heterocycle. The heterocycle may be condensed.

In addition, in formula (1), when the polymethine contains a cyclic structure, the cyclic structure may be, for example, a cyclic structure having at least one unsaturated bond such as an ethylenic double bond, and the unsaturated bond may undergo electron resonance as part of the polymethine chain. Such a cyclic structure may be, for example, a cyclopentene ring, a cyclopentadiene ring, a cyclohexene ring, a cyclohexadiene ring, a cycloheptene ring, a cyclooctene ring, a cyclooctadiene ring, or a benzene ring. Any of these cyclic structures may have a substituent.

In addition, in formula (2), a compound where n is 1 is a cyanine, a compound where n is 2 is a carbocyanine, and a compound where n is 3 is a dicarbocyanine. In formula (2), a compound where n is 4 is a tricarbocyanine.

The organic groups of R4 and R5 may be, for example, alkyl groups, aryl groups, aralkyl groups, and alkenyl groups. The alkyl groups may be, for example, methyl groups, ethyl groups, propyl groups, isopropyl groups, n-butyl groups, sec-butyl groups, isobutyl groups, tert-butyl groups, isopentyl groups, neopentyl groups, hexyl groups, cyclohexyl groups, octyl groups, nonyl groups, and decyl groups. The aryl groups may be, for example, phenyl groups, tolyl groups, xylyl groups, and naphthyl groups. The aralkyl groups may be, for example, benzyl groups, phenylethyl groups, and phenylpropyl groups. The alkenyl groups may be, for example, vinyl groups, allyl groups, propenyl groups, isopropenyl groups, butenyl groups, hexenyl groups, cyclohexenyl groups, and octenyl groups.

At least a portion of the hydrogen atoms in each organic group may be substituted with a halogen atom or a cyano group. The halogen atom may be fluorine, bromine, or chlorine. The organic group after substitution may be, for example, a chloromethyl group, a chloropropyl group, a bromoethyl group, a trifluoropropyl group, or a cyanoethyl group.

R6 or R7 may be, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a neopentyl group, a hexyl group, a cyclohexyl group, an octyl group, a nonyl group, or a decyl group.

Heterocycles containing each nitrogen atom may be, for example, pyrrole, imidazole, thiazole, pyridine, and the like.
The cation contained in such a cyanine dye may have a structure represented by, for example, the following formula (3) or (4).

The cation contained in the cyanine dye may have a structure shown in, for example, formula (5) to formula (44) below. That is, each nitrogen atom contained in the cyanine dye may be included in a cyclic structure shown below.

The cyanine dye has a maximum infrared light absorptance at any wavelength between 700 nm and 1100 nm. Therefore, the infrared light cut filter 13 can reliably absorb the near-infrared light that passes through the infrared light cut filter 13. As a result, the near-infrared light that can be detected by the photoelectric conversion element 11 for each color is sufficiently cut by the infrared light cut filter 13.

The absorbance Aλ at the wavelength λ is calculated by the following formula (1).
Aλ=-log ₁₀ (%T/100) ... Formula (1)
The transmittance T is represented by the ratio (TL/IL) of the intensity of transmitted light (TL) to the intensity of incident light (IL) when infrared light passes through the infrared cut filter 13 containing a cyanine dye. In the infrared cut filter 13, the intensity of transmitted light when the intensity of incident light is set to 1 is the transmittance T, and the value obtained by multiplying the transmittance T by 100 is the transmittance percentage %T.

Tris(pentafluoroethyl)trifluorophosphate ([(C ₂ F ₅ ) ₃ PF ₃ ] ⁻ ) has the structure shown by the following formula (45):

During the manufacturing process of the solid-state imaging device 10, the infrared light cut filter 13 is heated to about 200°C. When the above-mentioned cyanine dye is heated to about 200°C, the structure of the cyanine dye changes, and as a result, the absorbance of the cyanine dye to infrared light may decrease.

In this regard, since FAP has a molecular weight and molecular structure that allows it to be located in the vicinity of the polymethine chain in the cyanine dye, the polymethine chain in the cyanine dye is prevented from being cut by heating the cyanine dye. Therefore, the decrease in the infrared light absorbance of the cyanine dye caused by heating the cyanine dye is prevented, and as a result, the decrease in the infrared light absorbance of the infrared light cut filter 13 is prevented.

As described above, the infrared light cut filter 13 contains an acrylic polymer. The acrylic polymer is a polymer compound formed by polymerizing a monomer containing acrylic acid or methacrylic acid. The monomer containing acrylic acid is an acrylate, and the monomer containing methacrylic acid is a methacrylate. The acrylic polymer may be formed from a single monomer, or may be a copolymer formed from two or more types of monomers.

The acrylic polymer preferably contains repeating units derived from a monomer containing at least one of an aromatic ring, a phenol group, and a cyclic ether group. It is more preferable that the acrylic polymer is a copolymer containing repeating units derived from a monomer containing an aromatic ring, a repeating unit derived from a monomer containing a phenol group, and a repeating unit derived from a monomer containing a cyclic ether group.

Examples of monomers containing an aromatic ring include benzyl (meth)acrylate, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxy polyethylene glycol (meth)acrylate, nonylphenoxy polyethylene glycol (meth)acrylate, phenoxy polypropylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hydrogen phthalate, ethoxylated ortho-phenylphenol ( (meth)acrylate, o-phenylphenoxyethyl (meth)acrylate, 3-phenoxybenzyl (meth)acrylate, 4-hydroxyphenyl (meth)acrylate, 2-naphthol (meth)acrylate, 4-biphenyl (meth)acrylate, 9-anthrylmethyl (meth)acrylate, 2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl (meth)acrylate, phenol ethylene oxide (EO) modified acrylate, nonylphenol EO modified acrylate, phthalic acid 2-(meth)acryloyloxyethyl, and hexahydrophthalic acid 2-(meth)acryloyloxyethyl.

The monomer containing a phenol group may be, for example, 4-hydroxyphenyl (meth)acrylate, 3-(tert-butyl)-4-hydroxyphenyl (meth)acrylate, and 4-(tert-butyl)-2-hydroxyphenyl (meth)acrylate. The monomer containing a phenol group does not have to be an acrylic monomer. The monomer other than the acrylic monomer may be, for example, 4-hydroxyphenyl maleimide and 3-hydroxyphenyl maleimide.

Examples of monomers containing a cyclic ether group include glycidyl (meth)acrylate, 2-methylglycidyl (meth)acrylate, 2-ethylglycidyl (meth)acrylate, 2-oxiranylethyl (meth)acrylate, 2-glycidyloxyethyl (meth)acrylate, 3-glycidyloxypropyl (meth)acrylate, glycidyloxyphenyl (meth)acrylate, oxetanyl (meth)acrylate, 3-methyl-3-oxetanyl (meth)acrylate, 3-ethyl-3-oxetanyl (meth)acrylate, (3-methyl-3-oxetanyl)methyl (meth)acrylate, (3-ethyl-3-oxetanyl)methyl (meth)acrylate, 2-(3-methyl-3-oxetanyl)ethyl (meth)acrylate, 2-(3-ethyl-3-oxetanyl)ethyl (meth)acrylate, 2-[(3-methyl-3-oxetanyl)methyloxy]ethyl (meth)acrylate, 2-[(3-ethyl-3-oxetanyl)methyloxy]ethyl (meth)acrylate, 3-[(3-methyl-3-oxetanyl)methyloxy]propyl (meth)acrylate, 3-[(3-ethyl-3-oxetanyl)methyloxy]propyl (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate may be used.

The acrylic polymer preferably contains a first repeating unit derived from phenyl methacrylate represented by the following formula (46):

The acrylic polymer forming the infrared cut filter 13 contains a first repeating unit derived from phenyl methacrylate, so that the phenyl group of the first repeating unit is located between the cyanine dye and other cyanine dyes located in the vicinity of the cyanine dye. This makes it possible to form a distance between the cyanine dyes that is sufficient to suppress association of the cyanine dyes. This suppresses deterioration of the spectral characteristics at wavelengths that are expected to be absorbed by the cyanine dyes.

The acrylic polymer preferably contains a second repeating unit derived from 4-hydroxyphenyl methacrylate represented by the following formula (47):

In addition, the acrylic polymer preferably contains a third repeating unit derived from glycidyl methacrylate represented by the following formula (48):

A crosslinked structure is formed by crosslinking the phenol group of the second repeating unit with the epoxy group of the third repeating unit. This prevents the absorbance of the infrared cut filter 13 from decreasing due to heating.

The acrylic polymer may be an acrylic copolymer consisting of a first repeating unit, a second repeating unit, and a third repeating unit, or may contain a unit structure derived from a monomer other than the monomer for forming the first repeating unit to the third repeating unit.

The acrylic polymer may contain repeating units derived from a monomer containing an alicyclic structure. Examples of the monomer containing an alicyclic structure include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, 4-t-cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, adamantyl (meth)acrylate, norbornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, and tetracyclododecyl (meth)acrylate.

The acrylic polymer may contain repeating units derived from monomers other than the above-mentioned acrylic monomers.
The monomers other than the above-mentioned acrylic monomers may be, for example, styrene-based monomers, (meth)acrylic monomers, vinyl ester-based monomers, vinyl ether-based monomers, halogen-containing vinyl-based monomers, and diene-based monomers. The styrene-based monomers may be, for example, styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, p-methoxystyrene, p-hydroxystyrene, p-acetoxystyrene, vinyltoluene, ethylstyrene, phenylstyrene, and benzylstyrene. The (meth)acrylic monomers may be, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl methacrylate. The vinyl ester-based monomers may be, for example, vinyl acetate. The vinyl ether-based monomers may be, for example, vinyl methyl ether. The halogen-containing vinyl-based monomers may be, for example, vinyl chloride. The diene-based monomers may be, for example, butadiene, isobutylene, and the like. The acrylic polymer may be a polymer containing only one type of monomer other than the above-mentioned acrylic monomers, or may be a copolymer containing two or more types.

In addition, a monomer for adjusting the polarity of the acrylic polymer may be polymerized in the acrylic polymer. The monomer for adjusting the polarity adds an acid group or a hydroxyl group to the acrylic polymer. Such a monomer may be, for example, acrylic acid, methacrylic acid, maleic anhydride, maleic acid half ester, 2-hydroxyethyl acrylate, and 4-hydroxyphenyl (meth)acrylate.

In addition, when the acrylic polymer is a copolymer in which two or more kinds of acrylic monomers are polymerized, the acrylic polymer may have any of the following structures: random copolymer, alternating copolymer, block copolymer, and graft copolymer. If the acrylic polymer has a random copolymer structure, the manufacturing process and preparation with the cyanine dye are easy. Therefore, random copolymers are more preferable than other copolymers.

The polymerization solvent may be, for example, an ester solvent, an alcohol ether solvent, a ketone solvent, an aromatic solvent, an amide solvent, and an alcohol solvent. The ester solvent may be, for example, methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, t-butyl acetate, methyl lactate, and ethyl lactate. The alcohol ether solvent may be, for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, 3-methoxy-1-butanol, and 3-methoxy-3-methyl-1-butanol. The ketone solvent may be, for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. The aromatic solvent may be, for example, benzene, toluene, and xylene. The amide solvent may be, for example, formamide and dimethylformamide. The alcohol-based solvent may be, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, s-butanol, t-butanol, diacetone alcohol, and 2-methyl-2-butanol. Among these, ketone-based solvents and ester-based solvents are preferred because they can be used in the manufacture of filters for solid-state imaging devices. The above-mentioned polymerization solvents may be used alone or in combination of two or more.

In radical polymerization, the amount of polymerization solvent used is not particularly limited, but when the total amount of acrylic monomers is set to 100 parts by weight, the amount of polymerization solvent used is preferably 1 part by weight or more and 1,000 parts by weight or less, and more preferably 10 parts by weight or more and 500 parts by weight or less.

In this embodiment, the polymerization initiator is a thermal polymerization initiator that generates radicals, which are active species, by heating, i.e., a thermal radical polymerization initiator. The polymerization initiator is at least one of an organic peroxide and an azo compound. The organic peroxide is a derivative of hydrogen peroxide (H ₂ O ₂ ). The azo compound contains an azo group (-N=N-) that generates carbon radicals. When producing an acrylic polymer, multiple types of thermal polymerization initiators may be used in combination. By combining multiple types of thermal polymerization initiators, it is possible to control the polymerization rate.

In the organic peroxide, the hydrogen atom of hydrogen peroxide is replaced by an organic atomic group. The organic peroxide may include, for example, at least one selected from the group consisting of hydroperoxides, dialkyl peroxides, diacyl peroxides, and peroxy esters. The organic peroxide having an aromatic ring may be, for example, benzoyl peroxide (BPO), t-butyl peroxybenzoate, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, t-butylcumyl peroxide, di-(3-methylbenzoyl)peroxide, benzoyl(3-methylbenzoyl)peroxide, cumyl peroxyneodecanoate, t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, and 2,3-dimethyl-2,3-diphenylbutane.

Organic peroxides that do not contain an aromatic ring may be, for example, dilauroyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, t-hexylperoxy-ethylhexanoate, and t-butylperoxy-2-ethylhexanoate.

Examples of azo compounds include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclopentadiene). 1,1'-azobis(1-cyclohexanecarbonitrile), 2,2'-azobis(N-butyl-2-methylpropionamide), dimethyl 1,1'-azobis(1-cyclohexanecarboxylate), 1,1'-azobis(1-acetoxy-phenylethane), azobisamidinopropane salt, azobiscyanovaleric acid (salt), and 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide].

Among the above-mentioned thermal polymerization initiators, BPO and AIBN are preferable because they can be used at reaction temperatures of 100°C or less and are therefore easily applicable to polymerization using organic solvents. Furthermore, BPO does not contain nitrogen atoms, so it is even more preferable in that it is less likely to interact with cyanine dyes that contain nitrogen atoms and less likely to affect the absorption characteristics of the cyanine dyes.

The infrared cut filter 13 contains less than 0.35 parts by weight of an organic peroxide having an aromatic ring when the acrylic polymer is taken as 100 parts by weight, so that the deterioration of the spectral characteristics of the infrared cut filter in the visible light region and the infrared light region is suppressed. The organic peroxide having an aromatic ring remaining in the infrared cut filter 13 decomposes when the infrared cut filter 13 is exposed to heat when the infrared cut filter 13 is mounted or used, and generates a decomposition product containing an aromatic ring. The decomposition product itself has absorption at a specific wavelength in the visible light region or the infrared light region, or the decomposition product contains a π-conjugated benzene ring that affects the absorption characteristics of a cyanine dye that is also a π-conjugated system. As a result, the absorption rate of the infrared cut filter 13 for wavelengths in the visible light region increases or the absorption rate for wavelengths in the infrared light region decreases compared to the spectral characteristics of the coloring composition for forming the infrared cut filter 13. Such deterioration of the spectral characteristics deteriorates the spectral characteristics expected of the infrared cut filter 13.

In this regard, as described above, when the acrylic polymer is 100 parts by weight in the infrared cut filter 13, by containing less than 0.35 parts by weight of an organic peroxide having an aromatic ring, deterioration of the spectral characteristics of the infrared cut filter 13 is suppressed in both the visible light region and the infrared light region.

The amount of organic peroxide having an aromatic ring contained in the infrared light cut filter 13 can be adjusted, for example, by the amount of organic peroxide used when synthesizing the acrylic polymer. In addition, by purifying or heating the acrylic polymer after synthesis, the amount of organic peroxide contained in the infrared light cut filter 13 can be reduced compared to the case where purification or heating is not performed.

The amount of polymerization initiator used is preferably 0.0001 parts by weight or more and 20 parts by weight or less, more preferably 0.001 parts by weight or more and 15 parts by weight or less, and even more preferably 0.005 parts by weight or more and 10 parts by weight or less, when the total amount of acrylic monomers is set to 100 parts by weight. The polymerization initiator may be added to the acrylic monomers and polymerization solvent before the start of polymerization, or may be added dropwise to the polymerization reaction system. Adding the polymerization initiator dropwise to the acrylic monomers and polymerization solvent in the polymerization reaction system is preferable in that heat generation due to polymerization can be suppressed.

The reaction temperature for radical polymerization is appropriately selected depending on the type of polymerization initiator and polymerization solvent. From the viewpoints of ease of production and reaction controllability, the reaction temperature is preferably 60°C or higher and 110°C or lower.

The glass transition temperature of the acrylic polymer is preferably 75°C or higher, and more preferably 100°C or higher. If the glass transition temperature is 75°C or higher, it is possible to increase the reliability of suppressing a decrease in the absorbance of infrared light when the infrared cut filter 13 is heated.

The molecular weight of the acrylic polymer is preferably 30,000 or more and 150,000 or less, and more preferably 50,000 or more and 150,000 or less. By having the molecular weight of the acrylic polymer fall within this range, it is possible to increase the reliability of suppressing a decrease in the absorbance of infrared light when the infrared light cut filter 13 is heated.

Acrylic polymers having a molecular weight of more than 150,000 are difficult to form into a coating liquid together with a cyanine dye due to the increase in viscosity during polymerization. Therefore, when the molecular weight of the acrylic polymer exceeds 150,000, it is not easy to form the infrared light cut filter 13. On the other hand, when the molecular weight of the acrylic polymer is 150,000 or less, it is possible to form a coating liquid containing the acrylic polymer and the cyanine dye, so that it is easier to form the infrared light cut filter 13. The average molecular weight of the acrylic polymer is the weight average molecular weight. The weight average molecular weight of the acrylic polymer can be measured, for example, by gel permeation chromatography. For example, in a radical polymerization reaction, the molecular weight of the acrylic polymer can be controlled by changing the concentration of the acrylic monomer and the polymerization initiator in the solution.

The percentage (MM/MS x 100) of the weight of the acrylic monomer (MM) to the sum (MS) of the weight of the acrylic polymer and the weight of the acrylic monomer that constitutes the acrylic polymer is preferably 20% or less. Compared to when the amount of residual monomer is more than 20%, the infrared light absorbance of the cyanine dye is less likely to decrease when the infrared light cut filter 13 is heated.

The percentage (MM/MS x 100) of the weight of the acrylic monomer (MM) to the sum (MS) of the weight of the acrylic polymer and the weight of the acrylic monomer that constitutes the acrylic polymer is more preferably 10% or less, and even more preferably 3% or less. The weight of the acrylic polymer and the weight of the acrylic monomer can be quantified based on the analysis results of the acrylic polymer. The method for analyzing the acrylic polymer may be, for example, gas chromatography mass spectrometry (GC-MS), nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), etc.

The method of changing the weight ratio of the acrylic monomer to the sum of the weight of the acrylic polymer and the weight of the acrylic monomer may be, for example, a method of changing the polymerization time, a method of changing the polymerization temperature, etc. Furthermore, the method of changing the weight ratio of the acrylic monomer to the sum of the weight of the acrylic polymer and the weight of the acrylic monomer may be, for example, a method of changing the concentration of the acrylic monomer and the polymerization initiator at the start of the polymerization reaction. The method of changing the weight ratio of the acrylic monomer to the sum of the weight of the acrylic polymer and the weight of the acrylic monomer may be, for example, a method of changing the purification conditions after the polymerization reaction. Of these, the method of changing the polymerization time is preferred because it provides high control accuracy in changing the weight ratio of the acrylic monomer.

[Method of manufacturing a filter for a solid-state imaging device]
The manufacturing method of the filter 10F for solid-state imaging devices includes forming an infrared cut filter 13 and patterning the infrared cut filter 13 by dry etching. By forming the infrared cut filter 13, an infrared cut filter 13 containing a cyanine dye and an acrylic polymer is formed. The manufacturing method of the filter 10F for solid-state imaging devices will be described in more detail below. The filter 10F for solid-state imaging devices is formed on a semiconductor substrate including a photoelectric conversion element 11 by the method described below.

The color filters 12R, 12G, 12B, and the infrared light pass filter 12P are formed by forming a coating film containing a colored photosensitive resin and patterning the coating film using a photolithography method. For example, the coating film containing a red photosensitive resin is formed by applying a coating liquid containing a red photosensitive resin and drying the coating film. The red filter 12R is formed by exposing the coating film containing a red photosensitive resin to an area corresponding to the red filter 12R and developing it. The green filter 12G, the blue filter 12B, and the infrared light pass filter 12P are also formed by the same method as the red filter 12R.

The pigments contained in the coloring compositions of the red filter 12R, the green filter 12G, and the blue filter 12B may be organic or inorganic pigments, either alone or in combination. The pigment is preferably a pigment with high color development and high heat resistance, particularly a pigment with high resistance to thermal decomposition, and is preferably an organic pigment. The organic pigment may be, for example, a phthalocyanine pigment, an azo pigment, an anthraquinone pigment, a quinacridone pigment, a dioxazine pigment, an anthanthrone pigment, an indanthrone pigment, a perylene pigment, a thioindigo pigment, an isoindoline pigment, a quinophthalone pigment, or a diketopyrrolopyrrole pigment.

The coloring component contained in the infrared light pass filter 12P may be a black pigment or a black dye. The black pigment may be a single pigment having a black color, or a mixture having a black color from two or more pigments. The black dye may be, for example, an azo dye, an anthraquinone dye, an azine dye, a quinoline dye, a perinone dye, a perylene dye, or a methine dye. The photosensitive coloring composition of each color further contains a binder resin, a photopolymerization initiator, a polymerizable monomer, an organic solvent, and a leveling agent.

When forming the infrared cut filter 13, a coating liquid containing the above-mentioned cyanine dye, acrylic polymer, and organic solvent is applied onto the color filters 12R, 12G, and 12B and the infrared pass filter 12P, and the coating is dried. Next, the dried coating is hardened by heating. In this way, the infrared cut filter 13 is formed.

As described above, at least one of an azo compound, which is a thermal radical polymerization initiator, and an organic peroxide is used in the synthesis of an acrylic polymer. In the synthesis of an acrylic polymer, it is preferable to polymerize so that the organic peroxide is less than 0.35 parts by weight when the acrylic polymer is 100 parts by weight. Note that the organic peroxide may be 0.35 parts by weight or more when synthesizing the acrylic polymer. Even in this case, it is possible to reduce the organic peroxide to less than 0.35 parts by weight by purifying or heating the acrylic polymer, as described above.

When forming the through hole 13H of the infrared cut filter 13, first, a photoresist layer is formed on the infrared cut filter 13. This photoresist layer is patterned to form a resist pattern. Next, the infrared cut filter 13 is etched by dry etching using this resist pattern as an etching mask. Then, the resist pattern remaining on the infrared cut filter 13 after etching is removed with a stripping solution to form the through hole 13H. This allows the infrared cut filter to be patterned.

The stripping liquid may be a liquid capable of dissolving the resist pattern. The stripping liquid may be, for example, N-methylpyrrolidone or dimethyl sulfoxide. The method for contacting the infrared cut filter 13 with the stripping liquid may be any method, such as a dipping method, a spraying method, or a spinning method. In addition, the infrared cut filter 13 contains an acrylic polymer having a crosslinked structure between the phenol group of the second repeating unit and the epoxy group of the third repeating unit, so that the infrared cut filter 13 can satisfy resistance to the stripping liquid and heat resistance.

The barrier layer 14 is formed by a vapor-phase deposition method such as a sputtering method, a CVD method, or an ion plating method, or a liquid-phase deposition method such as a coating method. The barrier layer 14 made of silicon oxide is formed, for example, by sputtering a target made of silicon oxide onto a substrate on which an infrared cut filter 13 is formed. The barrier layer 14 made of silicon oxide is formed, for example, by CVD using silane and oxygen onto a substrate on which an infrared cut filter 13 is formed. The barrier layer 14 made of silicon oxide is formed, for example, by applying a coating solution containing polysilazane, modifying it, and drying the coating. The layer structure of the barrier layer 14 may be a single layer structure made of a single compound, a laminated structure of layers made of a single compound, or a laminated structure of layers made of different compounds.

Each of the microlenses 15R, 15G, 15B, and 15P is formed by forming a coating film containing a transparent resin, patterning the coating film using a photolithography method, and reflowing the coating film by heat treatment. Examples of the transparent resin include acrylic resin, polyamide resin, polyimide resin, polyurethane resin, polyester resin, polyether resin, polyolefin resin, polycarbonate resin, polystyrene resin, and norbornene resin.

[Production Example]
As shown in Table 1 below, acrylic polymers of Production Examples 1 to 18 were obtained using the acrylic monomers, polymerization solvents, and polymerization initiators of each Production Example. The results of measuring the extrapolated glass transition onset temperatures of the acrylic polymers obtained in Production Examples 1 to 18 were as shown in Table 1. In the acrylic copolymers described below, the weight ratio of the repeating units derived from the monomers in the acrylic copolymer is equal to the weight ratio of the monomers at the time of producing the acrylic copolymer.

[Production Example 1]
80 parts by weight of propylene glycol monomethyl ether acetate (PGMAc) was prepared as a polymerization solvent. 20 parts by weight of dicyclopentanyl methacrylate (DCPMA) ( _C14H20O2 ) was prepared as an acrylic monomer. Furthermore, _0.22 parts by weight of _benzoyl peroxide (BPO) was prepared as a polymerization initiator. These were placed in a reaction vessel equipped with a stirrer and a reflux tube, and stirred and refluxed for 8 hours while heating to 80°C while introducing nitrogen gas into the reaction vessel. As a result, a polymer solution containing a polymer formed from repeating units derived from dicyclopentanyl methacrylate was obtained.

Then, the resulting polymer solution was poured into methanol, the resulting precipitate was filtered off, and the resulting residue was vacuum dried to obtain an acrylic polymer powder. This acrylic polymer powder was heated in a vacuum dryer at 150°C to 160°C for 2 hours.

The extrapolated glass transition onset temperature of the dried acrylic polymer powder was calculated using a method in accordance with JIS K7121-1987, and was found to be 175°C.

[Production Example 2]
A polymer solution containing a polymer formed from repeating units derived from dicyclopentanyl methacrylate was obtained in the same manner as in Production Example 1, except that the amount of benzoyl peroxide was changed to 0.11 parts by weight and heating was not performed after polymerization. The extrapolated glass transition onset temperature of the acrylic polymer was found to be 175° C.

[Production Example 3]
A polymer solution containing an acrylic polymer formed from repeating units derived from dicyclopentanyl methacrylate was obtained in the same manner as in Production Example 1, except that the amount of benzoyl peroxide was changed to 0.15 parts by weight and heating was not performed after polymerization. The extrapolated glass transition onset temperature of the acrylic polymer was found to be 175° C.

[Production Example 4]
A polymer solution containing a polymer containing repeating units derived from dicyclopentanyl methacrylate was obtained in the same manner as in Production Example 1, except that heating after polymerization was not performed in Production Example 1. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 175° C.

[Production Example 5]
A polymer solution containing a polymer formed from repeating units derived from dicyclopentanyl methacrylate was obtained in the same manner as in Production Example 1, except that the amount of benzoyl peroxide was changed to 0.44 parts by weight and heating was not performed after polymerization. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 175° C.

[Production Example 6]
A polymer _formed from repeating units derived from phenyl methacrylate was obtained in the same _manner as in Preparation Example 1, except that 20 parts by weight of phenyl methacrylate (PhMA) ( _C10H10O2 ) was prepared as an acrylic monomer and 0.30 parts by weight of BPO was prepared as a polymerization initiator. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 113°C.

[Production Example 7]
A polymer solution containing a polymer formed from repeating units derived from phenyl methacrylate was obtained in the same manner as in Production Example 6, except that the amount of benzoyl peroxide was changed to 0.15 parts by weight and heating was not performed after polymerization. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 113° C.

[Production Example 8]
A polymer solution containing a polymer formed from repeating units derived from phenyl methacrylate was obtained in the same manner as in Production Example 6, except that the amount of benzoyl peroxide was changed to 0.30 parts by weight and heating was not performed after polymerization. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 113° C.

[Production Example 9]
A polymer solution containing a polymer formed from repeating units derived from phenyl methacrylate was obtained in the same manner as in Production Example 6, except that the amount of BPO was changed to 0.45 parts by weight and heating was not performed after polymerization. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 113° C.

[Production Example 10]
A polymer solution containing a polymer formed from repeating units derived from phenyl methacrylate was obtained in the same manner as in Production Example 6, except that the amount of BPO was changed to 0.60 parts by weight and heating was not performed after polymerization. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 113° C.

[Production Example 11]
A polymer formed from repeating units derived from methyl methacrylate was obtained in the same _manner as in Preparation Example 1, except that 20 parts by weight of methyl methacrylate ( _MMA ) ( _C5H8O2 ) was prepared as an acrylic monomer and 0.48 parts by weight of BPO was prepared as a polymerization initiator. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 105°C.

[Production Example 12]
A polymer solution containing a polymer formed from repeating units derived from methyl methacrylate was obtained in the same manner as in Production Example 11, except that the amount of BPO was changed to 0.24 parts by weight and heating was not performed after polymerization. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 105° C.

[Production Example 13]
A polymer solution containing a polymer formed from repeating units derived from methyl methacrylate was obtained in the same manner as in Production Example 11, except that heating after polymerization was not performed. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 105° C.

[Production Example 14]
A polymer solution containing a polymer formed from repeating units derived from methyl methacrylate was obtained in the same manner as in Production Example 11, except that the amount of BPO was changed to 0.72 parts by weight and heating was not performed after polymerization. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 105° C.

[Production Example 15]
A polymer solution containing a polymer formed from repeating units derived from methyl methacrylate was obtained in the same manner as in Production Example 14, except that the polymerization initiator was changed to 0.33 parts by weight of azobisisobutyronitrile (AIBN) and the temperature during stirring and reflux was changed to 70° C. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 105° C.

[Production Example 16]
14 parts by weight of phenyl methacrylate and 6 parts by weight of 4 _- hydroxyphenyl methacrylate ( _HPMA ) ( _C10H10O3 ) were prepared as acrylic monomers, and 0.29 parts by weight of BPO was prepared as a polymerization initiator. A copolymer formed of repeating units derived from phenyl methacrylate and repeating units derived from 4-hydroxyphenyl methacrylate was obtained by the same method as in Preparation Example 1. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 118°C.

[Production Example 17]
14 parts by weight of phenyl methacrylate, 3 parts by weight of 4-hydroxyphenyl methacrylate, and 3 parts by weight of glycidyl _methacrylate ( _GMA ) ( _C7H10O3 ) were prepared as acrylic monomers, and 0.30 parts by weight of BPO was prepared as a polymerization initiator. A polymer solution containing a copolymer formed from a first repeat unit derived from phenyl methacrylate, a second repeat unit derived from 4-hydroxyphenyl methacrylate, and a third repeat unit derived from glycidyl methacrylate was obtained in the same manner as in Preparation Example 1, except that heating was not performed after polymerization. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 101°C.

[Production Example 18]
14 parts by weight of phenyl methacrylate, 4 parts by weight of 4-hydroxyphenyl methacrylate, and 2 parts by weight of glycidyl methacrylate were prepared as acrylic monomers, and 0.30 parts by weight of BPO was prepared as a polymerization initiator. In addition, a polymer solution containing a copolymer formed from a first repeating unit derived from phenyl methacrylate, a second repeating unit derived from 4-hydroxyphenyl methacrylate, and a third repeating unit derived from glycidyl methacrylate was obtained by the same method as in Preparation Example 1, except that heating was not performed after polymerization. The extrapolated glass transition onset temperature of the produced acrylic polymer was found to be 107°C.

[Test Example]
The acrylic polymers obtained in each of Production Examples 1 to 18 were used to form the infrared cut filters of Test Examples 1 to 18.

In this case, in Test Examples 1, 6, 11, and 16, propylene glycol monomethyl ether acetate was added to the acrylic polymer powder after the heat treatment to prepare an acrylic polymer solution with a solids concentration of 17%. On the other hand, in Test Examples 2 to 5, 7 to 10, 2 to 15, 17, and 18, propylene glycol monomethyl ether acetate was added to the polymer solution to prepare an acrylic polymer solution with a solids concentration of 17%.

Next, a coating solution containing 0.3 g of cyanine dye, 12.0 g of acrylic polymer solution, and 10 g of PGMAc was prepared. In this case, the dye represented by the above formula (3) was used as the cyanine dye. The coating solution was applied onto a transparent substrate to form a coating film, and the coating film was dried. The coating film was then cured by heating at 230°C to obtain an infrared light cut filter having a thickness of 1 μm.

[Evaluation method]
[Residual amount of organic peroxide]
A nuclear magnetic resonance apparatus (400 MHz) (AVANCE NEO 400, manufactured by Bruker) was used to analyze an infrared cut filter to obtain a ¹ H NMR spectrum. The remaining amount (parts by weight) of the organic peroxide was calculated using the peak area of the organic peroxide contained in the ¹ H NMR spectrum according to the following formula.

[(Peak area A) x (Molecular weight A) / (Peak area B) x (Molecular weight B))] x 100
When the acrylic polymer is composed of a single acrylic monomer, the amount of the remaining organic peroxide can be calculated using the above formula. In the above formula, the peak area A is the peak area of the organic peroxide, and the molecular weight A is the molecular weight of the organic peroxide. The peak area B is the peak area of the acrylic polymer, and the molecular weight B is the molecular weight of the monomer that constitutes the acrylic polymer.

When the acrylic polymer is an acrylic copolymer composed of multiple monomers, it is calculated using the following formula (2). In the following formula (2), Mi is the molecular weight of monomer i, and Si is the area of the polymer peak derived from monomer i. In addition, peak area A is the peak area of the organic peroxide, and molecular weight A is the molecular weight of the organic peroxide.

[Spectral characteristics]
Using a spectrophotometer (U-4100, manufactured by Hitachi High-Technologies Corporation), the transmittance of the infrared cut filter was measured for light having each wavelength from 350 nm to 1200 nm. From the transmittance measurement results, the absorbance was calculated using the above-mentioned formula (1). As a result, the absorbance spectrum was obtained for each infrared cut filter.

[Average absorbance in the visible light region]
The average absorbance at each wavelength from 400 nm to 600 nm was calculated. The average absorbance of 0.140 or less was evaluated as "◯", and the average absorbance of more than 0.140 was evaluated as "×".

[Absorbance at 950 nm]
The absorbance spectrum of the cyanine dye represented by the above formula (3) has a peak at 950 nm. Therefore, the absorbance at 950 nm of each infrared cut filter was evaluated. When the absorbance at 950 nm was greater than 0.80, it was evaluated as "◎", when it was 0.70 or more and 0.80 or less, it was evaluated as "◯", and when it was less than 0.70, it was evaluated as "×". Note that an infrared cut filter having an absorbance at 950 nm of 0.7 or more has an infrared light absorption ability suitable for application to a solid-state imaging device.

[comprehensive evaluation]
A comprehensive evaluation was performed based on the evaluation results of the average absorbance in the visible light region and the absorbance at 950 nm. In this case, when the average absorbance was evaluated as "good" and the absorbance at 950 nm was evaluated as "good", when both the average absorbance and the absorbance at 950 nm were evaluated as "good", it was evaluated as "good". On the other hand, when the average absorbance was evaluated as "bad", it was evaluated as "bad".

[Evaluation results]
In the infrared cut filters of Test Examples 1 to 18, the residual amount of organic peroxide and the spectral characteristics were as shown in Table 2 below.

As shown in Table 2, in Test Examples 1 to 4, 6 to 9, 11 to 13, and 15 to 18, the remaining amount of organic peroxide was found to be less than 0.35 parts by weight. In contrast, in Test Examples 5, 10, and 14, the remaining amount of organic peroxide was found to be 0.35 parts by weight or more.

In addition, in Test Examples 1 to 4, 6 to 9, 11 to 13, and 15 to 18, the average absorbance in the visible light region was found to be 0.140 or less. In contrast, in Test Examples 5, 10, and 14, the average absorbance in the visible light region was found to exceed 0.140.

In this way, it was found that by having the remaining amount of organic peroxide be less than 0.35 parts by weight, it is possible to keep the average absorbance in the visible light region low enough that it does not affect the detection sensitivity of the photoelectric conversion element associated with the color filter located below the infrared light cut filter.

In addition, while the absorbance at 950 nm in Test Example 14 was less than 0.70, the absorbance at 950 nm in the other Test Examples was 0.70 or more. More specifically, in Test Examples 1 to 5, 11 to 13, and 15, the absorbance at 950 nm was 0.70 or more and 0.80 or less. On the other hand, in Test Examples 6 to 10, and 16 to 18, the absorbance at 950 nm was greater than 0.80.

In addition, a comparison of the absorbance at 950 nm in Test Examples 5, 10, and 14 shows that even when the amount of remaining organic peroxide is large, it is most preferable for the acrylic polymer to contain phenyl methacrylate, and next most preferable for the acrylic polymer to contain dicyclopentanyl methacrylate, in order to suppress a decrease in absorbance in the infrared light region. On the other hand, when the acrylic polymer is formed only from methyl methacrylate, it was found that when the amount of remaining organic peroxide exceeds 0.35 parts by weight, not only does the absorbance in the visible light region increase, but the absorbance at 950 nm decreases.

As described above, according to one embodiment of the infrared light cut filter, the filter for a solid-state imaging device, the solid-state imaging device, and the method for manufacturing the filter for a solid-state imaging device, the following effects can be obtained.

(1) By having the organic peroxide content be less than 0.35 parts by weight, deterioration of the spectral characteristics of the infrared cut filter 13 is suppressed in both the visible light region and the infrared light region.

(2) By positioning the phenyl group of the first repeating unit between the cyanine dye and other cyanine dyes located in the vicinity of the cyanine dye, it is possible to form a distance between the cyanine dyes that is sufficient to suppress association of the cyanine dyes. This suppresses deterioration of the spectral characteristics at wavelengths that are expected to be absorbed by the cyanine dyes.

(3) A crosslinked structure is formed by crosslinking the phenol group of the second repeating unit with the epoxy group of the third repeating unit. This prevents the absorbance of the infrared cut filter 13 from decreasing due to heating.

(4) The barrier layer 14 prevents the oxidation source from reaching the infrared cut filter 13, making the infrared cut filter 13 less susceptible to oxidation by the oxidation source.

[Example of change]
The above-described embodiment can be modified as follows.
[Acrylic polymer]
The acrylic polymer may contain a unit structure other than the first repeating unit, the second repeating unit, and the third repeating unit. Even in this case, it is possible to obtain the effect equivalent to the above-mentioned (1) as long as the organic peroxide contained in the infrared cut filter 13 is less than 0.35 parts by weight per 100 parts by weight of the acrylic polymer.

The acrylic polymer does not have to contain at least one of the first repeating unit, the second repeating unit, and the third repeating unit. Even in this case, if the organic peroxide contained in the infrared cut filter 13 is less than 0.35 parts by weight per 100 parts by weight of the acrylic polymer, it is possible to obtain an effect equivalent to that of (1) described above.

[Barrier layer]
The barrier layer 14 may be located not only between the infrared light cut filter 13 and each microlens, but also on the outer surface of each microlens. In this case, the outer surface of the barrier layer 14 functions as an incident surface through which light is incident on the solid-state imaging element 10. In short, the barrier layer 14 may be located on the light incident side of the infrared light cut filter 13. According to this configuration, the barrier layer 14 is located on the optical surface of each microlens.

The solid-state imaging element 10 can be modified to a configuration in which the barrier layer 14 is omitted and the oxygen permeability of the laminated structure located on the side of the incident surface 15S with respect to the infrared light cut filter 13 is 5.0 cc/ ^m2 /day/atom or less. For example, the laminated structure may be another functional layer such as a planarizing layer or an adhesion layer, and the oxygen permeability thereof together with each microlens may be 5.0 cc/ ^m2 /day/atom or less.

Even if the barrier layer 14 is omitted, if the organic peroxide contained in the infrared cut filter 13 is less than 0.35 parts by weight per 100 parts by weight of the acrylic polymer, it is possible to obtain an effect similar to that of (1) described above.

[Anchor layer]
The solid-state imaging element 10 may be modified to a configuration including an anchor layer between the barrier layer 14 and the layer below the barrier layer 14, which increases the adhesion between the barrier layer 14 and the layer below the barrier layer 14. The solid-state imaging element 10 may also be modified to a configuration including an anchor layer between the barrier layer 14 and the layer above the barrier layer 14, which increases the adhesion between the barrier layer 14 and the layer above the barrier layer 14.

The material forming the anchor layer is, for example, a polyfunctional acrylic resin or a silane coupling agent. The thickness of the anchor layer is, for example, 50 nm or more and 1 μm or less. If it is 50 nm or more, it is easy to obtain adhesion between the layers, and if it is 1 μm or less, it is easy to suppress light absorption in the anchor layer.

[Color filter]
The color filter can be changed to a three-color filter consisting of a cyan filter, a yellow filter, and a magenta filter. The color filter may also be changed to a four-color filter consisting of a cyan filter, a yellow filter, a magenta filter, and a black filter. The color filter may also be changed to a four-color filter consisting of a transparent filter, a yellow filter, a red filter, and a black filter.

[others]
The microlens may also function as an infrared light cut filter. In this case, the microlens, which has the function of taking in light toward the photoelectric conversion element, also has the function of cutting infrared light, so that the layer structure of the filter for solid-state imaging elements can be simplified.

- The materials forming the infrared light pass filter 12P and the infrared light cut filter 13 may contain additives to provide other functions, such as light stabilizers, antioxidants, heat stabilizers, and antistatic agents.

- The solid-state imaging element 10 may be provided with a bandpass filter on the light incident side of the multiple microlenses. The bandpass filter is a filter that transmits only light having a specific wavelength in visible light and near-infrared light, and has a similar function to the infrared light cut filter 13. In other words, the bandpass filter can cut out unnecessary infrared light that can be detected by the photoelectric conversion elements for each color 11R, 11G, and 11B. This can improve the detection accuracy of visible light by the photoelectric conversion elements for each color 11R, 11G, and 11B, and the detection accuracy of near-infrared light having a wavelength in the 850 nm or 940 nm band that is the detection target of the infrared light photoelectric conversion element 11P.

REFERENCE SIGNS LIST 10...solid-state imaging element 10F...filter for solid-state imaging element 11...photoelectric conversion element 11R...red photoelectric conversion element 11G...green photoelectric conversion element 11B...blue photoelectric conversion element 11P...infrared light photoelectric conversion element 12R...red filter 12G...green filter 12B...blue filter 12P...infrared light pass filter 13...infrared light cut filter 13H...through hole 14...barrier layer 15R...red microlens 15G...green microlens 15B...blue microlens 15P...infrared light microlens 15S...incident surface

Claims (7)

a cyanine dye comprising polymethine, a cation having two nitrogen-containing heterocycles, one at each end of the polymethine, and tris(pentafluoroethyl)trifluorophosphate;
An acrylic polymer;
and an organic peroxide containing an aromatic ring,
containing less than 0.35 parts by weight of said organic peroxide per 100 parts by weight of said acrylic polymer,
The cation is represented by any one of the following formulas (3) to (11) and (13) to (44):
Infrared cut filter. a cyanine dye comprising polymethine, a cation having two nitrogen-containing heterocycles, one at each end of the polymethine, and tris(pentafluoroethyl)trifluorophosphate;
An acrylic polymer;
and an organic peroxide containing an aromatic ring,
The organic peroxide is contained in an amount of 0.002 parts by weight or less per 100 parts by weight of the acrylic polymer.
Infrared cut filter. a cyanine dye comprising polymethine, a cation having two nitrogen-containing heterocycles, one at each end of the polymethine, and tris(pentafluoroethyl)trifluorophosphate;
An acrylic polymer;
and an organic peroxide containing an aromatic ring,
containing less than 0.35 parts by weight of said organic peroxide per 100 parts by weight of said acrylic polymer,
The cation is represented by the following formula (3):
The organic peroxide is benzoyl peroxide.
Infrared cut filter. The acrylic polymer comprises a first repeating unit derived from phenyl methacrylate, a second repeating unit derived from a monomer containing a phenol group, and a third repeating unit derived from glycidyl methacrylate.
The infrared light cut filter according to claim 1 . The infrared light cut filter according to any one of claims 1 to 4 ,
a barrier layer covering the infrared cut filter and suppressing transmission of an oxidation source that oxidizes the infrared cut filter. A photoelectric conversion element;
A solid-state imaging device comprising the filter for solid-state imaging devices according to claim 5 . forming an infrared light cut filter comprising polymethine, a cyanine dye comprising tris(pentafluoroethyl)trifluorophosphate, and a cation having two nitrogen-containing heterocycles, each of which is located at each end of the polymethine, and an acrylic polymer;
patterning the infrared light cut filter by dry etching;
The formation of the infrared light cut filter includes:
forming the acrylic polymer by radical polymerization using a thermal polymerization initiator which is at least one of an azo compound and an aromatic ring-containing organic peroxide;
the organic peroxide is less than 0.35 parts by weight per 100 parts by weight of the acrylic polymer after polymerization;
The cation is represented by any one of the following formulas (3) to (11) and (13) to (44):
A method for manufacturing a filter for a solid-state imaging device.