Photosensitive resin composition for microlenses

Abstract

The object of the present invention is to provide a novel photosensitive resin composition for microlenses. The solution is the following photosensitive resin composition for microlenses, which contains the following component (A), the following component (B) and the following component (C), and contains at least 0.5% by mass of the component (B) with respect to 100% by mass of the component (A). (A): A copolymer having a structural unit represented by the following formula (1), a structural unit represented by the following formula (2) and a structural unit represented by the following formula (3), with a weight average molecular weight of 5000 to 25000 (B): A photoacid generator (C): A solvent [In formula (1) to formula (3), R 1 , R 2 and R 3 each independently represent a hydrogen atom or a methyl group, X 1 and X 2 each independently represent an alkylene group having 2 to 4 carbon atoms, Z 1 represents an acid dissociable group, and Z 2 represents a blocked isocyanate group.]

Description

Technical Field

[0001] The present invention relates to a photosensitive resin composition for forming microlenses, which contains a specific alkali-soluble polymer, a photoacid generator, and a solvent. In particular, it relates to a photosensitive resin composition for microlenses produced by the reflow method. Background Art

[0002] As solid-state imaging elements, CCD / CMOS image sensors are known. In recent years, as a new image sensor, a distance image sensor using the TOF (Time of Flight) method used in three-dimensional (3D) cameras has been developed. The so-called TOF method is a method of measuring the distance to a measurement object by detecting the flight time of light emitted from a light source until it is reflected by the measurement object and received by a sensor. An image sensor adopting this TOF method can obtain a high-precision three-dimensional distance image by detecting distance information for each pixel.

[0003] Conventionally, in CCD / CMOS image sensors, microlenses have been provided to improve the light collection efficiency. As one of the methods for manufacturing the above microlenses, the reflow method is known (for example, refer to Patent Document 1). That is, a photosensitive resin composition is coated on a substrate, and after a pattern having a rectangular cross-sectional shape is formed by photolithography, the rectangular pattern is melted by heat treatment to make it flow, and a lens shape is produced by surface tension.

[0004] On the other hand, a photosensitive resin composition containing a polymer, a photoacid generator, a solvent, and titanium black is known (refer to Patent Document 2). The polymer in the photosensitive resin composition described in Patent Document 2 satisfies at least one of a polymer having a first structural unit in which a group having an acid group is protected by an acid-decomposable group and a second structural unit having a crosslinkable group, and a polymer having the first structural unit and a polymer having the second structural unit. However, Patent Document 2 does not describe or suggest that the above photosensitive resin composition is for forming microlenses, particularly for forming microlenses by the reflow method.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-337956

[0008] Patent Document 2: International Publication No. 2015 / 125870 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] By mounting microlenses on the above-described distance image sensor in the TOF method, electronic display devices such as organic EL displays, an improvement in the light condensing efficiency of the sensor and an improvement in the brightness of the display are expected.

[0011] The photosensitive resin composition for forming microlenses is required to be able to form a pattern of a desired shape by photolithography. Further, in order to form a pattern of a desired shape, generation of residues is required to be suppressed after development using an alkaline developer. Further, in order to fabricate microlenses by a reflow method, the above pattern needs to be able to reflow. In addition, when a coating film such as a planarizing film is formed on the fabricated microlenses by a coating method, the film-forming composition used usually contains a solvent, and thus the fabricated microlenses are required to have solvent resistance.

[0012] Means for Solving the Problems

[0013] The present invention solves all of the above problems. That is, the present invention is a photosensitive resin composition for microlenses, which contains the following component (A), the following component (B), and the following component (C), and contains at least 0.5% by mass of the component (B) with respect to 100% by mass of the component (A).

[0014] Component (A): A copolymer having a structural unit represented by the following formula (1), a structural unit represented by the following formula (2), and a structural unit represented by the following formula (3), and having a weight average molecular weight of 5000 to 25000

[0015] Component (B): A photoacid generator

[0016] Component (C): A solvent

[0017]

[0018] [In formulas (1) to (3), R 1 , R 2 and R 3 each independently represent a hydrogen atom or a methyl group, X 1 and X 2 each independently represent an alkylene group having 2 to 4 carbon atoms, Z 1 represents an acid dissociable group, and Z 2 represents a blocked isocyanate group.]

[0019] The above acid dissociable group is, for example, a group represented by the following formula (a).

[0020]

[0021] (In the formula, * represents a bonding bond with an oxygen atom, R 4 represents a methyl group, R 5represents an alkyl group having 1 to 6 carbon atoms, which may have a branched structure when the number of carbon atoms in the alkyl group is 3 to 6, R 5 may also be connected to R 4 to form a cyclic ether structure.)

[0022] The above-mentioned blocked isocyanate group is, for example, a group represented by the following formula (b) or the following formula (c).

[0023]

[0024] [In formula (b) and formula (c), * represents a bonding bond with the alkylene group represented by the above X 2 , R 6 and R 7 each independently represent a hydrogen atom, a methyl group or an ethyl group, R 8 represents a methyl group, and a represents an integer of 0 to 3.]

[0025] The above-mentioned copolymer may further have at least one of a structural unit represented by the following formula (4a) and a structural unit represented by the following formula (4b).

[0026]

[0027] [In formula (4a) and formula (4b), R 9 represents a hydrogen atom or a methyl group, R 10 represents an alkyl group having 1 to 6 carbon atoms, which may have a branched structure or a ring structure when the number of carbon atoms in the alkyl group is 3 to 6, R 11 represents a cyclohexyl group or a phenyl group.]

[0028] The above-mentioned photoacid generator is, for example, a diphenyl[4-(phenylthio)phenyl]sulfonium salt compound, or N-(trifluoromethanesulfonyloxy)-1,8-naphthalenedicarboximide or a derivative thereof.

[0029] Another aspect of the present invention is a method for manufacturing the following microlens, which has the following steps: a step of coating the above-mentioned microlens with a photosensitive resin composition on a substrate and pre-baking the photosensitive resin composition to form a resin film; an exposure step of exposing the above-mentioned resin film through a mask; a baking step of baking the resin film after the above-mentioned exposure step; a developing step of developing the resin film after the above-mentioned baking step with an alkaline developer; a reflux step of causing the pattern obtained after the above-mentioned developing step to reflux; and a step of curing the pattern after the above-mentioned reflux step to form a lens pattern.

[0030] The above-mentioned reflux step is a step of heating the pattern obtained after the above-mentioned development, for example, at a temperature of 120°C to 200°C.

[0031] Effects of the Invention

[0032] The photosensitive resin composition for microlenses of the present invention can form a pattern with a rectangular cross-sectional shape by photolithography, and no residue is generated in the exposed part where no pattern is formed after development, nor at the bottom of the formed pattern. Further, the above-mentioned pattern can be reflowed, and the photosensitive resin composition for microlenses of the present invention can be used to fabricate microlenses with a solvent-resistant thick film (maximum height 10 μm to 20 μm). Detailed Description of Embodiments

[0033] The present invention relates to a photosensitive resin composition for microlenses, which contains component (A), component (B), and component (C), and contains at least 0.5% by mass of the component (B) relative to 100% by mass of the component (A). The photosensitive resin composition for microlenses of the present invention is a positive-type photosensitive resin composition. Hereinafter, the detailed content of each component of the present invention will be described. The solid content obtained by removing the solvent from the photosensitive resin composition for microlenses of the present invention is usually 1% by mass to 50% by mass. In this specification, the components of the photosensitive resin composition for microlenses of the present invention other than the solvent are defined as the solid content.

[0034] <Component (A)>

[0035] Component (A) in the photosensitive resin composition for microlenses of the present invention is a copolymer having a structural unit represented by the above formula (1), a structural unit represented by the above formula (2), and a structural unit represented by the above formula (3), with a weight-average molecular weight of 5000 to 25000. This copolymer is not limited to a terpolymer obtained from three monomers, and can be a copolymer obtained from four monomers or a copolymer obtained from five monomers. The weight-average molecular weight of the above copolymer is a value obtained by gel permeation chromatography (GPC) using polystyrene as a standard sample.

[0036] The structural unit represented by the above formula (1) is represented by the following formula (1a), for example. The structural unit represented by the formula (1) is not limited to the structural unit represented by the following formula (1a) as long as it is a structural unit having an acid-dissociable group. Here, the acid-dissociable group is a group that dissociates by an acid to become a base-soluble group. In the present invention, the above acid is an acid generated from the photoacid generator of component (B) by exposure, and the base-soluble group is a carboxyl group.

[0037]

[0038] (In the formula, R 1 represents a hydrogen atom or a methyl group, R 4 represents a methyl group, R 5 represents an alkyl group having 1 to 6 carbon atoms, and may have a branched structure when the number of carbon atoms in the alkyl group is 3 to 6, R5 It can also be connected to R 4 to form a cyclic ether structure.)

[0039] Specific examples of the monomer that forms the structural unit represented by the above formula (1) include 1-methoxyethyl (meth)acrylate, 1-ethoxyethyl (meth)acrylate, 1-propoxyethyl (meth)acrylate, 1-isopropoxyethyl (meth)acrylate, 1-n-butoxyethyl (meth)acrylate, 1-tert-butoxyethyl (meth)acrylate, 1-n-hexyloxyethyl (meth)acrylate, 1-cyclohexyloxyethyl (meth)acrylate, and tetrahydro-2H-pyran-2-yl (meth)acrylate. These monomers can be used alone, or two or more of them can be used in combination. In the present specification, (meth)acrylate refers to methacrylate and acrylate.

[0040] The structural unit represented by the above formula (2) is a structural unit having a hydroxyl group as a crosslinkable group. Specific examples of the monomer that forms the structural unit represented by the formula (2) include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. These monomers can be used alone, or two or more of them can be used in combination.

[0041] The structural unit represented by the above formula (3) is represented by, for example, the following formula (3b) or the following formula (3c). The structural unit represented by the formula (3) is not limited to the structural unit represented by the following formula (3b) or the following formula (3c) as long as it is a structural unit having a blocked isocyanate group. Here, the blocked isocyanate group is a group obtained by blocking an isocyanate group (-NCO) with a protecting group capable of thermal dissociation, that is, a group obtained by reacting a blocking agent with an isocyanate group.

[0042]

[0043] [In the formulas (3b) and (3c), R 3 represents a hydrogen atom or a methyl group, X 2 represents an alkylene group having 2 to 4 carbon atoms, R 6 and R 7 each independently represent a hydrogen atom, a methyl group or an ethyl group, R 8 represents a methyl group, and a represents an integer of 0 to 3.]

[0044] Specific examples of the monomer that forms the structural unit represented by the above formula (3) include compounds obtained by adding a blocking agent such as methyl ethyl ketoxime, ε-caprolactam, 3,5-dimethylpyrazole, and diethyl malonate to an isocyanate-containing (meth)acrylate such as 2-isocyanatoethyl methacrylate and 2-isocyanatoethyl acrylate. These monomers can be used alone, or two or more of them can be used in combination.

[0045] The copolymer of the above component (A) may further have at least one of the structural units represented by the above formula (4a) and the structural units represented by the above formula (4b). Specific examples of the monomer that forms the structural unit represented by the formula (4a) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, cyclopentyl (meth)acrylate, n-hexyl (meth)acrylate, and cyclohexyl (meth)acrylate. Specific examples of the monomer that forms the structural unit represented by the above formula (4b) include N-cyclohexylmaleimide and N-phenylmaleimide. These monomers may be used alone or in combination of two or more.

[0046] In the copolymer of the above component (A), based on 100 mol% of the sum of the structural units represented by the above formula (1), the structural units represented by the above formula (2), the structural units represented by the above formula (3), the structural units represented by the above formula (4a), and the structural units represented by the above formula (4b), the content of the structural units represented by the above formula (1) is, for example, 12 mol% to 30 mol%, preferably 17 mol% to 25 mol%, the content of the structural units represented by the above formula (2) is, for example, 5 mol% to 40 mol%, preferably 10 mol% to 30 mol%, the content of the structural units represented by the above formula (3) is, for example, 5 mol% to 40 mol%, preferably 10 mol% to 30 mol%, the content of the structural units represented by the above formula (4a) is, for example, 0 mol% to 60 mol%, and the content of the structural units represented by the above formula (4b) is, for example, 0 mol% to 60 mol%.

[0047] When the content ratio of the structural unit represented by the above formula (1) is less than the lower limit value, when forming a pattern by photolithography, the solubility of the exposed part in the developer is insufficient, and a pattern with a desired shape may not be obtained. When the content ratio of the structural unit represented by the above formula (1) is greater than the upper limit value, the solvent resistance of the produced microlens may not be obtained. When the content ratios of the structural unit represented by the above formula (2) and the structural unit represented by the above formula (3) are less than the lower limit value, the solvent resistance of the produced microlens may not be obtained. When the content ratios of the structural unit represented by the above formula (2) and the structural unit represented by the above formula (3) are more than the upper limit value, when forming a pattern by photolithography, the solubility of the exposed part in the developer is insufficient, and a pattern with a desired shape may not be obtained. The copolymer of the above component (A) has the structural unit represented by the above formula (2) and the structural unit represented by the above formula (3), so that a crosslinking reaction proceeds by baking. Therefore, the content ratios of the structural unit represented by the above formula (2) and the structural unit represented by the above formula (3) are preferably equimolar. The structural unit represented by the above formula (4a) and the structural unit represented by the above formula (4b) can adjust the glass transition temperature (Tg) of the copolymer by their content ratios, so that the reflow property of the pattern can be easily controlled.

[0048] The method for obtaining the copolymer of the above component (A) is not particularly limited. Generally, it is obtained by polymerizing at least one of the monomer forming the structural unit represented by the above formula (1), the monomer forming the structural unit represented by the above formula (2), the monomer forming the structural unit represented by the above formula (3), and optionally the monomer forming the structural unit represented by the above formula (4a) and the monomer forming the structural unit represented by the above formula (4b) in a solvent in the presence of a polymerization initiator, usually at a temperature of 50 °C to 120 °C. The copolymer obtained by such an operation is usually in a solution state dissolved in a solvent and can be used in the photosensitive resin composition for microlenses of the present invention without separation in this state.

[0049] <Component (B)>

[0050] Component (B) in the photosensitive resin composition for microlenses of the present invention is a photoacid generator. This photoacid generator is not particularly limited as long as it is a compound that generates an acid upon exposure. Specific examples of such compounds include salt compounds, sulfimide compounds, and disulfonyldiazomethane compounds.

[0051] As the above Specific examples of the salt compound include diphenyliodonium hexafluorophosphate, diphenyliodonium trifluoromethanesulfonate, diphenyliodonium nonafluoro-n-butanesulfonate, diphenyliodonium Perfluoro-n-octanesulfonate, diphenyliodonium Camphorsulfonate, bis(4-tert-butylphenyl)iodonium Camphorsulfonate, bis(4-tert-butylphenyl)iodonium Iodonium salts such as trifluoromethanesulfonate Salt compounds, and triphenylsulfonium hexafluorophosphate, triphenylsulfonium tris(pentafluoroethyl)trifluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, triphenylsulfonium nonafluoro-n-butanesulfonate, triphenylsulfonium camphorsulfonate, triphenylsulfonium trifluoromethanesulfonate, diphenyl[4-(phenylthio)phenyl]sulfonium hexafluorophosphate, diphenyl[4-(phenylthio)phenyl]sulfonium tris(pentafluoroethyl)trifluorophosphate, diphenyl[4-(phenylthio)phenyl]sulfonium hexafluoroantimonate, diphenyl[4-(phenylthio)phenyl]sulfonium tetrakis(pentafluorophenyl)borate and other sulfonium salt compounds. Among these salt compounds, sulfonium salt compounds are preferred, and as compounds that generate acids upon exposure to i-ray (365 nm), diphenyl[4-(phenylthio)phenyl]sulfonium salt compounds are more preferred.

[0052] As specific examples of the above-mentioned sulfonimide compounds, N-(trifluoromethanesulfonyloxy)succinimide, N-(nonafluoro-n-butanesulfonyloxy)succinimide, N-(camphorsulfonyloxy)succinimide, N-(trifluoromethanesulfonyloxy)-1,8-naphthalimide, N-(trifluoromethanesulfonyloxy)-2-alkyl-1,8-naphthalimide, N-(trifluoromethanesulfonyloxy)-3-alkyl-1,8-naphthalimide, and N-(trifluoromethanesulfonyloxy)-4-alkyl-1,8-naphthalimide can be cited. Among these sulfonimide compounds, N-(trifluoromethanesulfonyloxy)-1,8-naphthalimide and its derivatives are preferred.

[0053] As specific examples of the above-mentioned disulfonyldiazomethane compounds, bis(trifluoromethylsulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane, bis(phenylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane, bis(2,4-dimethylbenzenesulfonyl)diazomethane, and methylsulfonyl-p-toluenesulfonyldiazomethane can be cited.

[0054] As specific examples of the above photoacid generators, Adeka Arcles (registered trademark) SP-056, Adeka Arcles SP-066, Adeka Arcles SP-140, Adeka Arcles SP-141, Adeka Arcles SP-082, Adeka Arcles SP-601, Adeka Arcles SP-606, Adeka Arcles SP-701, Adeka Arcles SP-150, Adeka Arcles SP-170, Adeka Arcles SP-171 (the above are manufactured by ADEKA CORPORATION), CPI (registered trademark)-110P, CPI-110B, CPI-310B, CPI-210S, CPI-100P, CPI-101A, CPI-200K (the above are manufactured by SAN-APRO LTD.), DPI-105, DPI-106, DPI-109, DPI-201, BI-105, MPI-105, MPI-106, MPI-109, BBI-102, BBI-103, BBI-105, BBI-106, BBI-109, BBI-110, BBI-200, BBI-201, BBI-300, BBI-301, TPS-102, TPS-103, TPS-105, TPS-106, TPS-109, TPS-200, TPS-300, TPS-1000, HDS-109, MDS-103, MDS-105, MDS-205, MDS-209, BDS-109, MNPS-109, DTS-102, DTS-103, DTS-105, DTS-200, NDS-103, NDS-105, NDS-155, NDS-165, SI-105, NDI-105, NDI-109, NAI-105, NAI-109 (the above are manufactured by Midori Chemical Co., Ltd.) can be mentioned. These photoacid generators can be used alone, one kind at a time, or two or more kinds can be used in combination.

[0055] The photoacid generator of the above component (B) contains at least 0.5% by mass relative to 100% by mass of the above component (A). If the content of the photoacid generator is less than 0.5% by mass, the acid dissociable group of the above component (A) will not dissociate and the base-soluble group will not appear. Therefore, when forming a pattern by photolithography, the solubility of the exposed portion in the developer is insufficient, and a pattern with a desired shape may not be obtained. The upper limit of the content of the above photoacid generator varies depending on the strength of the acid generated by exposure. For example, the stronger the acid generated from the photoacid generator by exposure, the smaller the upper limit of the content of the photoacid generator can be made. When the above Adeka Arculex (registered trademark) SP-606 is used as the photoacid generator, the upper limit of its content is, for example, 5% by mass relative to 100% by mass of the above component (A). If the content of the photoacid generator is excessive, when forming a pattern by photolithography, the photoacid generator is likely to remain as a residue in the exposed portion after development.

[0056] <(C) Component>

[0057] The (C) component in the photosensitive resin composition for microlenses of the present invention is a solvent. As long as it is a solvent that dissolves the above component (A), the above component (B), and other components described later, there is no particular limitation. Specific examples of the solvent include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol propyl ether acetate, propylene glycol monobutyl ether, propylene glycol monobutyl ether acetate, toluene, xylene, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl glycolate, methyl 2-hydroxy-3-methylbutyrate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate, methyl pyruvate, ethyl acetate, butyl acetate, ethyl lactate, butyl lactate, 2-heptanone, γ-butyrolactone. These solvents can be used alone, or two or more of them can be used in combination.

[0058] <Surfactant>

[0059] For the purpose of improving the coatability on a substrate, the photosensitive resin composition for microlenses of the present invention may contain a surfactant. Specific examples of the surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether; polyoxyethylene alkyl aryl ethers such as polyoxyethylene octyl phenyl ether and polyoxyethylene nonyl phenyl ether; polyoxyethylene / polyoxypropylene block copolymers; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, sorbitan trioleate, and sorbitan tristearate; polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan trioleate, and polyoxyethylene sorbitan tristearate; and other nonionic surfactants; EFTOP (registered trademark) EF301, EF303, EF352 (manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.); Megafac (registered trademark) F-171, F-173, R-30, R-40, R-40-LM (manufactured by DIC Corporation); Fluorad FC430, FC431 (manufactured by 3M Japan Ltd.); Asahi Guard (registered trademark) AG710; Surflon (registered trademark) S-382, SC101, SC102, SC103, SC104, SC105, SC106 (manufactured by AGC Inc.); and fluorosurfactants such as the FTX-206D, FTX-212D, FTX-218, FTX-220D, FTX-230D, FTX-240D, FTX-212P, FTX-220P, FTX-228P, FTX-240G series (manufactured by Neos Co., Ltd.); and the silicone oxygen polymer KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0060] The above surfactants may be used singly or in combination of two or more. When the photosensitive resin composition for microlenses of the present invention contains the surfactant, its content is 3% by mass or less, preferably 1% by mass or less, and more preferably 0.5% by mass or less based on the content in the solid components of the composition.

[0061] <Other Additives>

[0062] The photosensitive resin composition for microlenses of the present invention may contain, as other additives, a curing aid, an ultraviolet absorber, a sensitizer, a plasticizer, an antioxidant, an adhesion aid, or a dissolution promoter such as a polyphenol or a polycarboxylic acid, as needed, provided that the effects of the present invention are not impaired. It should be noted that since the copolymer of the component (A) of the photosensitive resin composition for microlenses of the present invention is self-crosslinkable, a crosslinking agent is not required.

[0063] <Method for preparing photosensitive composition for microlenses>

[0064] The method for preparing the photosensitive resin composition for microlenses of the present invention is not particularly limited. For example, a method of mixing a solution of the copolymer of the component (A) and the photoacid generator of the component (B) in a solvent of the component (C) in a specified ratio to form a uniform solution can be cited. Further, a method of optionally further adding the surfactant and the other additives and mixing them at an appropriate stage of the preparation method can be cited.

[0065] <Fabrication of microlenses>

[0066] By applying the photosensitive resin composition for microlenses of the present invention on a substrate [for example, a semiconductor substrate such as silicon coated with a silicon oxide film, a silicon nitride film, or a silicon oxynitride film, a semiconductor substrate such as silicon coated with an organic film such as a color filter or a planarization film, a compound semiconductor substrate such as gallium nitride (GaN), gallium arsenide (GaAs), gallium phosphide (GaP), or indium phosphide (InP), a silicon nitride substrate, a quartz substrate, a glass substrate (including non-alkali glass, low-alkali glass, and crystalline glass), a glass substrate formed with an ITO film], through an appropriate coating method such as a spinner or a coater, and then performing pre-baking using a heating device such as a hot plate, a resin film is formed. As the pre-baking conditions, they are appropriately selected from a baking temperature of 80°C to 150°C and a baking time of 0.3 minutes to 60 minutes, and preferably a baking temperature of 80°C to 120°C and a baking time of 0.5 minutes to 5 minutes.

[0067] The film thickness of the resin film formed from the photosensitive resin composition for microlenses of the present invention is 0.005 μm to 30 μm, preferably 0.01 μm to 20 μm.

[0068] Next, the obtained resin film is exposed through a mask (intermediate mask) for forming a pattern of a desired shape. The exposure can use near-ultraviolet rays or visible light such as g-rays, i-rays, or a KrF excimer laser. Further, the exposed resin film is baked (Post Exposure Bake). As the baking conditions after exposure, they are appropriately selected from a baking temperature of 80°C to 120°C and a baking time of 0.3 minutes to 60 minutes.

[0069] Then, the above resin film is developed using an alkaline developer. As a result, a pattern with a desired shape is formed on the above substrate. Examples of such an alkaline developer include aqueous solutions of alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, aqueous solutions of quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and choline, and alkaline aqueous solutions such as aqueous solutions of amines like ethanolamine, propylamine, and ethylenediamine. Further, a surfactant can also be added to these developers.

[0070] As the conditions for the above development, they are appropriately selected from a development temperature of 5°C to 50°C and a development time of 10 seconds to 300 seconds. The above resin film can be easily developed at room temperature using an aqueous solution of tetramethylammonium hydroxide. After development, for example, ultrapure water is used as the rinsing liquid and rinsing is appropriately performed.

[0071] Further, the above-formed pattern is refluxed by a first post-baking. As the conditions for the above first post-baking, they are appropriately selected from a baking temperature of 120°C to 200°C and a baking time of 0.3 minutes to 60 minutes. Then, near-ultraviolet light or visible light such as g-rays, i-rays, and KrF excimer lasers can be used to perform overall exposure on the refluxed pattern. Further, after the overall exposure, the above pattern can be subjected to post-exposure baking again. As the conditions for this post-exposure baking, for example, they are appropriately selected from a baking temperature of 120°C to 200°C and a baking time of 0.3 minutes to 60 minutes. Finally, the above refluxed pattern is cured by a second post-baking to form a lens pattern. As the conditions for the above second post-baking, they are appropriately selected from a baking temperature of 150°C to 250°C and a baking time of 0.3 minutes to 60 minutes.

[0072] Examples

[0073] Hereinafter, synthesis examples and examples are given to explain the present invention in more detail, but the present invention is not limited to the following examples.

[0074] [Measurement of weight-average molecular weight]

[0075] Apparatus: GPC system manufactured by JASCO Corporation

[0076] Columns: Shodex [registered trademark] GPC KF-804L and GPC KF-803L

[0077] Column oven: 40°C

[0078] Flow rate: 1 ml / minute

[0079] Eluent: Tetrahydrofuran

[0080] Standard sample: Polystyrene

[0081] [Synthesis Example 1]

[0082] After dissolving 7.0 g of 1-butoxyethyl methacrylate, 4.9 g of 2-hydroxyethyl methacrylate, 9.1 g of 2-[0-(1'-methylpropylideneamino)carboxylamino]ethyl methacrylate [Karex MOI-BM (registered trademark) manufactured by Showa Denko K.K.], 7.5 g of methyl methacrylate, and 1.4 g of 2,2'-azobisisobutyronitrile in 89.8 g of propylene glycol monomethyl ether, the solution was added dropwise to a flask containing 79.8 g of propylene glycol monomethyl ether maintained at 70°C over 3 hours. After completion of the dropwise addition, the reaction was allowed to proceed for 18 hours. After cooling the reaction solution, it was poured into a large amount of hexane solution to reprecipitate the polymer, followed by heating and drying to obtain a copolymer having structural units represented by the following formula (1-1), structural units represented by the following formula (2-1), structural units represented by the following formula (3-1), and structural units represented by the following formula (4a-1). The weight-average molecular weight Mw of the obtained copolymer was 16,000 (in terms of polystyrene).

[0083]

[0084] [Synthesis Example 2]

[0085] After dissolving 9.0 g of 1-butoxyethyl methacrylate, 3.1 g of 2-hydroxyethyl methacrylate, 5.9 g of 2-[0-(1'-methylpropylideneamino)carboxylamino]ethyl methacrylate [Karex MOI-BM (registered trademark) manufactured by Showa Denko K.K.], 12.1 g of methyl methacrylate, 4.2 g of N-phenylmaleimide, and 1.7 g of 2,2'-azobisisobutyronitrile in 36.0 g of propylene glycol monomethyl ether, the solution was added dropwise to a flask containing 18.0 g of propylene glycol monomethyl ether maintained at 70°C over 3 hours. After completion of the dropwise addition, the reaction was allowed to proceed for 18 hours to obtain a solution (solid content concentration: 40% by mass) of a copolymer having structural units represented by the following formula (1-1), structural units represented by the following formula (2-1), structural units represented by the following formula (3-1), structural units represented by the following formula (4a-1), and structural units represented by the following formula (4b-1). The weight-average molecular weight Mw of the obtained copolymer was 22,000 (in terms of polystyrene).

[0086]

[0087] [Synthesis Example 3]

[0088] 8.5 g of 1-butoxyethyl methacrylate, 3.0 g of 2-hydroxyethyl methacrylate, 5.5 g of 2-[0-(1'-methylpropylamino)carboxylamino]ethyl methacrylate [KARENZ MOI-BM (registered trademark), manufactured by Showa Denko K.K.], 9.1 g of methyl methacrylate, 7.9 g of N-phenylmaleimide, and 1.7 g of 2,2'-azobisisobutyronitrile were dissolved in 35.7 g of propylene glycol monomethyl ether, and the solution was added dropwise to a flask maintained at 70 °C and containing 17.9 g of propylene glycol monomethyl ether over 3 hours. After completion of the dropwise addition, the reaction was carried out for 18 hours to obtain a solution (solid content concentration: 40% by mass) of a copolymer having structural units represented by the above formula (1-1), structural units represented by the above formula (2-1), structural units represented by the above formula (3-1), structural units represented by the above formula (4a-1), and structural units represented by the above formula (4b-1). The weight-average molecular weight Mw of the obtained copolymer was 19,000 (in terms of polystyrene).

[0089] [Synthesis Example 4]

[0090] 9.5 g of 1-butoxyethyl methacrylate, 20.4 g of methyl methacrylate, and 1.5 g of 2,2'-azobisisobutyronitrile were dissolved in 31.4 g of propylene glycol monomethyl ether, and the solution was added dropwise to a flask maintained at 70 °C and containing 26.9 g of propylene glycol monomethyl ether over 3 hours. After completion of the dropwise addition, the reaction was carried out for 18 hours to obtain a solution (solid content concentration: 35% by mass) of a copolymer having structural units represented by the following formula (1-1) and structural units represented by the following formula (4a-1). The weight-average molecular weight Mw of the obtained copolymer was 16,000 (in terms of polystyrene).

[0091]

[0092] [Synthesis Example 5]

[0093] 5.1 g of 1-butoxyethyl methacrylate, 24.7 g of methyl methacrylate, and 1.5 g of 2,2'-azobisisobutyronitrile were dissolved in 31.3 g of propylene glycol monomethyl ether, and the solution was added dropwise to a flask maintained at 70 °C and containing 26.8 g of propylene glycol monomethyl ether over 3 hours. After completion of the dropwise addition, the reaction was carried out for 18 hours to obtain a solution (solid content concentration: 35% by mass) of a copolymer having structural units represented by the above formula (1-1) and structural units represented by the above formula (4a-1). The weight-average molecular weight Mw of the obtained copolymer was 20,000 (in terms of polystyrene).

[0094] [Synthesis Example 6]

[0095] 8.4 g of 1-butoxyethyl methacrylate, 5.9 g of 2-hydroxyethyl methacrylate, 10.9 g of 2-[0-(1'-methylpropylamino)carboxylamino]ethyl methacrylate [Kalen's MOI-BM (registered trademark), manufactured by Showa Denko K.K.], 9.0 g of methyl methacrylate, and 1.7 g of 2,2'-azobisisobutyronitrile were dissolved in 35.9 g of propylene glycol monomethyl ether. Then, this solution was added dropwise over 3 hours to a flask containing 18.0 g of propylene glycol monomethyl ether maintained at 70°C. After the addition was completed, the reaction was carried out for 18 hours to obtain a solution (solid content concentration: 40% by mass) of a copolymer having the structural unit represented by the above formula (1-1), the structural unit represented by the above formula (2-1), the structural unit represented by the above formula (3-1), and the structural unit represented by the above formula (4a-1). The weight-average molecular weight Mw of the obtained copolymer was 28,000 (in terms of polystyrene).

[0096] [Example 1]

[0097] 16.6 g of the copolymer obtained in Synthesis Example 1 as component (A), 0.83 g of SP-606 (manufactured by ADEKA Corporation) as the photoacid generator as component (B), and 0.0052 g of DFX-18 (manufactured by NEO Chemicals Co., Ltd.) as the surfactant were dissolved in 29.1 g of propylene glycol monomethyl ether and 3.2 g of propylene glycol monomethyl ether acetate as component (C) to prepare a solution. Then, this solution was filtered using a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses. The photoacid generator used in this Example and Examples 2 to 4, 8, and 9 described below is a derivative of N-(trifluoromethanesulfonyloxy)-1,8-naphthalenedicarboximide.

[0098] [Example 2]

[0099] 18.6 g of the copolymer obtained in Synthesis Example 1 as component (A), 0.37 g of SP-606 (manufactured by ADEKA Corporation) as the photoacid generator as component (B), and 0.0057 g of DFX-18 (manufactured by NEO Chemicals Co., Ltd.) as the surfactant were dissolved in 27.9 g of propylene glycol monomethyl ether and 3.1 g of propylene glycol monomethyl ether acetate as component (C) to prepare a solution. Then, this solution was filtered using a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses.

[0100] [Example 3]

[0101] 18.8 g of the copolymer obtained in Synthesis Example 1 as component (A), 0.19 g of SP-606 (manufactured by ADEKA Corporation) as the photoacid generator as component (B), and 0.0057 g of DFX-18 (manufactured by Neos Corporation) as the surfactant were dissolved in 27.9 g of propylene glycol monomethyl ether and 3.1 g of propylene glycol monomethyl ether acetate as component (C) to prepare a solution. Then, this solution was filtered through a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses.

[0102] [Example 4]

[0103] 18.9 g of the copolymer obtained in Synthesis Example 1 as component (A), 0.095 g of SP-606 (manufactured by ADEKA Corporation) as the photoacid generator as component (B), and 0.0057 g of DFX-18 (manufactured by Neos Corporation) as the surfactant were dissolved in 27.9 g of propylene glycol monomethyl ether and 3.1 g of propylene glycol monomethyl ether acetate as component (C) to prepare a solution. Then, this solution was filtered through a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses.

[0104] [Example 5]

[0105] 18.1 g of the copolymer obtained in Synthesis Example 1 as component (A), 0.91 g of CPI-110B (manufactured by San-Apro Ltd.) as the photoacid generator as component (B), and 0.0057 g of DFX-18 (manufactured by Neos Corporation) as the surfactant were dissolved in 27.9 g of propylene glycol monomethyl ether and 3.1 g of propylene glycol monomethyl ether acetate as component (C) to prepare a solution. Then, this solution was filtered through a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses. The photoacid generator used in this example is a diphenyl[4-(phenylthio)phenyl]sulfonium salt compound.

[0106] [Example 6]

[0107] 18.1 g of the copolymer obtained in Synthesis Example 1 as component (A), 0.91 g of CPI-110P (manufactured by San-Apro Ltd.) as the photoacid generator as component (B), and 0.0057 g of DFX-18 (manufactured by Neos Corporation) as the surfactant were dissolved in 27.9 g of propylene glycol monomethyl ether and 3.1 g of propylene glycol monomethyl ether acetate as component (C) to prepare a solution. Then, this solution was filtered through a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses. The photoacid generator used in this example is a diphenyl[4-(phenylthio)phenyl]sulfonium salt compound.

[0108] [Example 7]

[0109] 18.1 g of the copolymer obtained in Synthesis Example 1 as component (A), 0.91 g of CPI-210S (manufactured by San-Apro Ltd.) as the photoacid generator as component (B), and 0.0057 g of DFX-18 (manufactured by Neos Co., Ltd.) as the surfactant were dissolved in 27.9 g of propylene glycol monomethyl ether and 3.1 g of propylene glycol monomethyl ether acetate as component (C) to prepare a solution. Then, this solution was filtered through a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses. The photoacid generator used in this example is equivalent to a diphenyl[4-(phenylthio)phenyl]sulfonium salt compound.

[0110] [Example 8]

[0111] 44.0 g of the solution of the copolymer obtained in Synthesis Example 2 as component (A) (solid content concentration: 40% by mass), 0.88 g of SP-606 (manufactured by ADEKA Corporation) as the photoacid generator as component (B), and 0.0055 g of DFX-18 (manufactured by Neos Co., Ltd.) as the surfactant were dissolved in 1.9 g of propylene glycol monomethyl ether and 3.1 g of propylene glycol monomethyl ether acetate as component (C) to prepare a solution. Then, this solution was filtered through a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses.

[0112] [Example 9]

[0113] 44.0 g of the solution of the copolymer obtained in Synthesis Example 3 as component (A) (solid content concentration: 40% by mass), 0.88 g of SP-606 (manufactured by ADEKA Corporation) as the photoacid generator as component (B), and 0.0055 g of DFX-18 (manufactured by Neos Co., Ltd.) as the surfactant were dissolved in 1.9 g of propylene glycol monomethyl ether and 3.1 g of propylene glycol monomethyl ether acetate as component (C) to prepare a solution. Then, this solution was filtered through a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses.

[0114] [Comparative Example 1]

[0115] 43.5 g of the copolymer solution obtained in Synthesis Example 4 (solid content concentration: 35% by mass), 0.76 g of SP-606 (manufactured by ADEKA Corporation) as the photoacid generator as the (B) component, and 0.0048 g of DFX-18 (manufactured by Neos Co., Ltd.) as the surfactant were dissolved in 2.3 g of propylene glycol monomethyl ether and 3.4 g of propylene glycol monomethyl ether acetate as the (C) component to prepare a solution. Then, this solution was filtered using a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses. The copolymer used in this comparative example does not correspond to the (A) component of the photosensitive resin composition for microlenses of the present invention.

[0116] [Comparative Example 2]

[0117] 43.5 g of the copolymer solution obtained in Synthesis Example 5 (solid content concentration: 35% by mass), 0.76 g of SP-606 (manufactured by ADEKA Corporation) as the photoacid generator as the (B) component, and 0.0048 g of DFX-18 (manufactured by Neos Co., Ltd.) as the surfactant were dissolved in 2.3 g of propylene glycol monomethyl ether and 3.4 g of propylene glycol monomethyl ether acetate as the (C) component to prepare a solution. Then, this solution was filtered using a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses. The copolymer used in this comparative example does not correspond to the (A) component of the photosensitive resin composition for microlenses of the present invention.

[0118] [Comparative Example 3]

[0119] 43.5 g of the copolymer solution obtained in Synthesis Example 6 (solid content concentration: 35% by mass), 0.76 g of SP-606 (manufactured by ADEKA Corporation) as the photoacid generator as the (B) component, and 0.0048 g of DFX-18 (manufactured by Neos Co., Ltd.) as the surfactant were dissolved in 2.3 g of propylene glycol monomethyl ether and 3.4 g of propylene glycol monomethyl ether acetate as the (C) component to prepare a solution. Then, this solution was filtered using a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses. The copolymer used in this comparative example does not correspond to the (A) component of the photosensitive resin composition for microlenses of the present invention.

[0120] [Comparative Example 4]

[0121] 19.0 g of copolymer 1 obtained as component (A) in Synthesis Example 1, 0.019 g of SP-606 (manufactured by ADEKA Corporation) as a photoacid generator as component (B), and 0.0057 g of DFX-18 (manufactured by Neos Co., Ltd.) as a surfactant were dissolved in 27.9 g of propylene glycol monomethyl ether and 3.1 g of propylene glycol monomethyl ether acetate as component (C) to prepare a solution. Then, this solution was filtered using a polyethylene microfilter with a pore size of 1 μm to prepare a photosensitive resin composition for microlenses. The content of component (B) in the photosensitive resin composition for microlenses of this Comparative Example was less than 0.5% by mass relative to 100% by mass of component (A).

[0122] [Pattern rectangularity evaluation]

[0123] The photosensitive resin compositions for microlenses prepared in Examples 1 to 9 and Comparative Examples 1 to 4 were respectively coated on a silicon wafer using a spin coater, placed on a hot plate, and pre-baked at 100 °C for 90 seconds to form a resin film with a thickness of 10 μm. The above pre-baking was carried out in the air. Then, using an i-ray stepper NSR-2205i12D (NA = 0.63) (manufactured by Nikon Corporation), the above resin film was exposed through a binary mask, and then placed on a hot plate and heated (Post Exposure Bake) at 100 °C for 90 seconds. Then, the above resin film was developed with a 2.38% by mass aqueous solution of tetramethylammonium hydroxide (TMAH) for 50 seconds, rinsed with ultrapure water for 20 seconds, and dried. As a result, a pattern was formed on the above silicon wafer. The cross-sectional shape of the obtained pattern was observed using a scanning electron microscope S-4800 (manufactured by Hitachi High-Technologies Corporation). When the cross-sectional shape of the above pattern was not rectangular, it was set as "×", and when the cross-sectional shape of the above pattern was a 10 μm × 10 μm rectangle, it was set as "○", and the rectangularity of the pattern was evaluated. The results are shown in Table 1.

[0124] [Evaluation of residue after development]

[0125] By observing the exposed portion around the pattern formed on the above silicon wafer, the residue after development was evaluated. When a large amount of residue was observed in the exposed portion where the above pattern was not formed, it was set as "×", when no residue was observed in the exposed portion where the pattern was not formed but residue was observed at the bottom of the pattern, it was set as "△", and when no residue was observed in the exposed portion where the pattern was not formed and at the bottom of the pattern, it was set as "○", and the residue after development was evaluated. The evaluation results are shown in Table 1.

[0126] [Pattern reflow evaluation]

[0127] A silicon wafer with a rectangular pattern formed from the photosensitive resin composition for microlenses prepared in Examples 1 to 9, Comparative Example 1, and Comparative Example 3 was placed on a hotplate and baked at 140 °C for 5 minutes. After the above post-baking, the cross-sectional shape of the resulting pattern was observed using a scanning electron microscope S-4800 (manufactured by Hitachi High-Technologies Corporation). When the cross-sectional shape of the pattern remained completely unchanged, it was designated as "×", and when the cross-sectional shape of the pattern changed to a semicircle, it was designated as "○", and the reflow property of the pattern was evaluated. The evaluation results are shown in Table 1.

[0128] [Solvent Resistance Evaluation]

[0129] The photosensitive resin compositions for microlenses prepared in Examples 1 to 9, Comparative Example 1, and Comparative Example 3 were respectively coated on a silicon wafer using a spin coater and pre-baked on a hotplate at 100 °C for 90 seconds to form a resin film with a film thickness of 10 μm. Then, after baking on a hotplate at 100 °C for 90 seconds, post-baking was continued at 140 °C for 5 minutes and further at 220 °C for 5 minutes to form a cured film on the above silicon wafer. The above pre-baking and post-baking were both carried out in the atmosphere. For these cured films, a test of immersing them in propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ethyl lactate, and an aqueous solution of tetramethylammonium hydroxide (TMAH) with a concentration of 2.38% by mass at a temperature of 23 °C for 5 minutes was conducted. The film thickness change of the above cured film was measured before and after immersion. When the film thickness increase or decrease was 5% or more relative to the film thickness of the cured film before immersion in any one of the solvents used in the immersion test, it was designated as "×", and when the film thickness increase or decrease was less than 5% in all solvents, it was designated as "○", and the solvent resistance was evaluated. The evaluation results are shown in Table 1.

[0130] [Table 1]

[0131] Table 1

[0132] Pattern rectangularity Residue after development Pattern reflowability Solvent resistance Example 1 ○ △ ○ ○ Example 2 ○ △ ○ ○ Example 3 ○ △ ○ ○ Example 4 ○ △ ○ O Example 5 ○ △ ○ ○ Example 6 ○ ○ ○ ○ Example 7 ○ ○ ○ ○ Example 8 ○ △ ○ ○ Example 9 ○ △ ○ ○ Comparative Example 1 ○ ○ ○ × Comparative Example 2 × × - - Comparative Example 3 ○ △ × ○ Comparative Example 4 × × - -

[0133] As shown in Table 1, the resin films formed from the photosensitive resin compositions for microlenses prepared in Examples 1 to 9 obtained excellent results in terms of pattern rectangularity, the degree of residue after development, and pattern reflow property, and the cured films formed from the resin films showed excellent solvent resistance.

[0134] On the other hand, the resin films formed from the photosensitive resin compositions for microlenses prepared in Comparative Examples 2 to 4 did not give good results in any of the aspects of pattern rectangularity, degree of residue after development, and pattern reflowability. The cured film formed from the photosensitive resin composition for microlenses of Comparative Example 1 was confirmed to have low solvent resistance, indicating the advantages of the present invention.

Claims

1. A photosensitive resin composition for a microlens, which contains the following component (A), the following component (B) and the following component (C), and contains at least 0.5% by mass of the component (B) relative to 100% by mass of the component (A). (A) Component: A copolymer having a structural unit represented by the following formula (1), a structural unit represented by the following formula (2) and a structural unit represented by the following formula (3), with a weight-average molecular weight of 5000 to 25000, and the copolymer further has at least one of a structural unit represented by the following formula (4a) and a structural unit represented by the following formula (4b). In Formula (4a) and Formula (4b), R 9 represents a hydrogen atom or a methyl group, R 10 represents an alkyl group having 1 to 6 carbon atoms, and when the number of carbon atoms of the alkyl group is 3 to 6, it may have a branched structure or a cyclic structure, R 11 represents a cyclohexyl group or a phenyl group, In the copolymer, based on the sum of 100 mol% of the structural unit represented by the formula (1), the structural unit represented by the formula (2), the structural unit represented by the formula (3), the structural unit represented by the formula (4a) and the structural unit represented by the formula (4b), the content of the structural unit represented by the formula (1) is 12 mol% to 30 mol%, the content of the structural unit represented by the formula (2) is 5 mol% to 40 mol%, the content of the structural unit represented by the formula (3) is 5 mol% to 40 mol%, the content of the structural unit represented by the formula (4a) is 0 mol% to 60 mol%, and the content of the structural unit represented by the formula (4b) is 0 mol% to 60 mol%, wherein, Except for the case where the content rate of the structural unit represented by the formula (4a) and the content rate of the structural unit represented by the formula (4b) are both 0 mol%. (B) Component: A photoacid generator. (C) Component: A solvent. In Formulas (1) to (3), R 1 , R 2 and R 3 each independently represent a hydrogen atom or a methyl group, X 1 and X 2 each independently represent an alkylene group having 2 to 4 carbon atoms, Z 1 represents an acid dissociable group, and Z 2 represents a blocked isocyanate group.

2. The photosensitive resin composition for a microlens according to claim 1, wherein the acid dissociable group is a group represented by the following formula (a). In the formula, * represents a bonding bond with an oxygen atom, and R 4 represents a methyl group, and R 5 represents an alkyl group having 1 to 6 carbon atoms, and may have a branched structure when the number of carbon atoms in the alkyl group is 3 to 6. R 5 may also be connected to R 4 to form a cyclic ether structure.

3. The photosensitive resin composition for a microlens according to claim 1 or 2, wherein the blocked isocyanate group is a group represented by the following formula (b) or the following formula (c). In formula (b) and formula (c), * represents a bonding bond with the alkylene group shown by the said X 2 , R 6 and R 7 each independently represent a hydrogen atom, a methyl group or an ethyl group, R 8 represents a methyl group, and a represents an integer of 0 to 3.

4. The photosensitive resin composition for a microlens according to claim 1 or 2, wherein the photoacid generator is a diphenyl [4-(phenylthio)phenyl] sulfonium salt compound.

5. The photosensitive resin composition for a microlens according to claim 1 or 2, wherein the photoacid generator is N-(trifluoromethanesulfonyloxy)-1,8-naphthalenedicarboximide or a derivative thereof.

6. The photosensitive resin composition for a microlens according to claim 1 or 2, wherein the copolymer has the structural unit represented by the formula (4a) and the structural unit represented by the formula (4b).

7. A method for manufacturing a microlens, which has the following steps: A step of coating the photosensitive resin composition for a microlens according to any one of claims 1 to 6 on a substrate and pre-baking the photosensitive resin composition to form a resin film. An exposure step of exposing the resin film through a mask. A baking step of baking the resin film after the exposure step. A developing step of developing the resin film after the baking step using an alkaline developer. A reflow step of reflowing the pattern obtained after the developing step. And A step of curing the pattern after the reflow step to form a lens pattern.

8. The method for manufacturing a microlens according to claim 7, wherein the reflow step is a step of heating the pattern obtained after the developing step at a temperature of 120°C to 200°C.

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