Photosensitive thermosetting resin composition, dry film, cured product, and electronic component

Abstract

Provided is a photosensitive thermosetting resin composition from which it is possible to form a solder resist film that has high reflectance and excellent heat resistance and surface curability even with a low exposure amount. The photosensitive thermosetting resin composition contains a carboxy group-containing resin, a photoinitiator, a white pigment, and a thermosetting resin. The photoinitiator contains an oxime ester-based photoinitiator and a titanocene-based photoinitiator. The thermosetting resin contains an epoxy resin. A cured product obtained through thermosetting the photosensitive thermosetting resin composition has a b* value in the L*a*b* color system of 2.0 or less, and has a reflectance of 85% or more at a wavelength of 450 nm.

Description

Technical Field

[0001] The present invention relates to a photosensitive thermosetting resin composition, a dry film, a cured product, and an electronic component.

Background Art

[0002] A light-emitting device in which a light-emitting diode (hereinafter sometimes abbreviated as LED) is mounted on a printed wiring board is known. In order to efficiently use the light of the LED mounted on the printed wiring board, a white solder resist film having a high reflectance may be formed on the printed wiring board (see, for example, International Publication No. 2008 / 050768, Japanese Patent Application Laid-Open No. 2008-134621, Japanese Patent Application Laid-Open No. 2011-017010, International Publication No. 2012 / 141124). Further, Japanese Patent Application Laid-Open No. 2013-210443 proposes a photocurable thermosetting resin composition containing a photopolymerization initiator not containing a phosphorus atom in the molecular structure.

Summary of the Invention

Problems to be Solved by the Invention

[0003] An aspect of the present invention aims to provide a photosensitive thermosetting resin composition capable of forming a solder resist film excellent in surface curability and heat resistance and having a high reflectance even at a low exposure amount.

Means for Solving the Problems

[0004] The present invention includes the following aspects [1] A photosensitive thermosetting resin composition containing a carboxy group-containing resin, a photopolymerization initiator, a white pigment, and a thermosetting resin, The photopolymerization initiator includes an oxime ester-based photopolymerization initiator and a titanocene-based photopolymerization initiator, The thermosetting resin includes an epoxy resin, The cured product after thermosetting of the photosensitive thermosetting resin composition is L * a * b * b in the L*a*b* color system *A photosensitive thermosetting resin composition having a value of 2.0 or less and a reflectance of 85% or more at a wavelength of 450 nm.

[0005] [2] The photosensitive thermosetting resin composition according to [1], wherein the mass-based content ratio of the oxime ester-based photoinitiator to the titanocene-based photoinitiator is in the range of 1:10 to 10:1.

[0006] [3] A dry film having a resin layer obtained by applying and drying the photosensitive thermosetting resin composition according to [1] or [2] on a first film.

[0007] [4] A cured product obtained by curing the photosensitive thermosetting resin composition according to [1] or [2].

[0008] [5] An electronic component including the cured product according to [4]. [Effects of the Invention]

[0009] According to one aspect of the present invention, it is possible to provide a photosensitive thermosetting resin composition that is excellent in surface curability and heat resistance even at a low exposure amount and can form a solder resist film having a high reflectance. [Modes for Carrying Out the Invention]

[0010] In this specification, the term "step" includes not only an independent step but also a step in which, even if it cannot be clearly distinguished from other steps, the intended purpose of the step is achieved. Also, the content of each component in the composition means the total amount of the plurality of substances corresponding to each component in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. Further, the solid content means a substance after removing volatile components (e.g., organic solvents). Furthermore, the upper and lower limits of the numerical range described in this specification can be arbitrarily selected and combined with the numerical values exemplified as the numerical range. Hereinafter, embodiments of the present invention will be described in detail. However, the embodiments shown below are examples of a photosensitive thermosetting resin composition, a dry film, a cured product, and an electronic component for embodying the technical idea of the present invention, and the present invention is not limited to the photosensitive thermosetting resin composition, the dry film, the cured product, and the electronic component shown below.

[0011] Photosensitive thermosetting resin composition The photosensitive thermosetting resin composition is composed of a carboxyl group-containing resin, a photopolymerization initiator, a white pigment, and a thermosetting resin. The photopolymerization initiator includes at least an oxime ester-based photopolymerization initiator and a titanocene-based photopolymerization initiator. The thermosetting resin includes at least an epoxy resin. The cured product after thermosetting of the photosensitive thermosetting resin composition has an L * a * b * b value in the color system * of 2.0 or less and a reflectance at a wavelength of 450 nm of 85% or more.

[0012] By including a combination of photopolymerization initiators with a specific structure as the photopolymerization initiator, the photosensitive thermosetting resin composition can form a cured product with excellent surface curability, heat resistance, and high reflectance even at a low exposure amount. Also, discoloration due to heat, light, etc. in the cured product can be suppressed. Furthermore, a latent image can be formed with high sensitivity and excellent resolution. This can be considered to be due to, for example, the synergistic effect of an oxime ester-based photopolymerization initiator and a titanocene-based photopolymerization initiator. Note that the low exposure amount in the present invention specifically refers to 600 mJ / cm 2The following is stated.

[0013] Carboxy group-containing resin The carboxy group-containing resin may be any resin having a carboxy group in the molecule, and may or may not have a photosensitive functional group in the molecule. By including a carboxy group-containing resin in the photosensitive thermosetting resin composition, alkali developability can be imparted to the photocured product of the photosensitive thermosetting resin composition obtained by irradiating with active energy rays. It is preferable from the viewpoints of photocurability, developability resistance, etc. that the carboxy group-containing resin has an ethylenically unsaturated double bond as a photosensitive functional group in the molecule. The ethylenically unsaturated double bond in the molecule may be derived from acrylic acid, methacrylic acid, or their derivatives. The photosensitive thermosetting resin composition may contain a carboxy group-containing resin alone or in combination of two or more. In the case where the photosensitive thermosetting resin composition contains only a carboxy group-containing resin having no ethylenically unsaturated double bond as the carboxy group-containing resin, the photosensitive thermosetting resin composition can be made photocurable by using in combination a compound having a plurality of ethylenically unsaturated groups in the molecule, that is, a photopolymerizable monomer, as described later. Specific examples of the carboxy group-containing resin can include the following compounds (either oligomers or polymers). In the following, (meth)acrylate is a general term for acrylate, methacrylate, and their mixtures, and the same applies to other similar expressions.

[0014] (1) A carboxy group-containing resin obtained by copolymerization of an unsaturated carboxylic acid such as (meth)acrylic acid and an unsaturated group-containing compound such as styrene, α-methylstyrene, lower alkyl (meth)acrylate, isobutylene.

[0015] (2) A carboxyl group-containing urethane resin obtained by polyaddition reaction of diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates, carboxyl group-containing dialcohol compounds such as dimethylolpropionic acid and dimethylolbutanoic acid, polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A-based alkylene oxide adduct diols, and diol compounds such as compounds having phenolic hydroxyl groups and alcoholic hydroxyl groups.

[0016] (3) A carboxyl group-containing photosensitive urethane resin obtained by polyaddition reaction of a partial acid anhydride-modified product of a reaction product of a diisocyanate and a bifunctional epoxy resin such as bisphenol A-type epoxy resin, hydrogenated bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, bisphenol S-type epoxy resin, bixylenol-type epoxy resin, and biphenol-type epoxy resin and a monocarboxylic acid compound having an ethylenically unsaturated double bond such as (meth)acrylic acid, a carboxyl group-containing dialcohol compound, and a diol compound.

[0017] (4) A carboxyl group-containing photosensitive urethane resin having terminal (meth)acrylation by adding a compound having one hydroxyl group and one or more (meth)acryloyl groups in the molecule such as hydroxyalkyl (meth)acrylate during the synthesis of the resin described in (2) or (3) above.

[0018] (5) A carboxyl group-containing photosensitive urethane resin having terminal (meth)acrylation by adding a compound having one isocyanate group and one or more (meth)acryloyl groups in the molecule such as an equimolar reaction product of isophorone diisocyanate and pentaerythritol triacrylate during the synthesis of the resin described in (2) or (3) above.

[0019] (6) A carboxyl group-containing photosensitive resin obtained by reacting a bifunctional or higher polyfunctional (solid) epoxy resin with (meth)acrylic acid and adding a dibasic acid anhydride to the hydroxyl groups present in the side chain.

[0020] (7) A carboxyl group-containing photosensitive resin obtained by reacting (meth)acrylic acid with a polyfunctional epoxy resin obtained by further epoxidizing the hydroxyl groups of a bifunctional (solid) epoxy resin with epichlorohydrin and adding a dibasic acid anhydride to the resulting hydroxyl groups.

[0021] (8) A carboxyl group-containing polyester resin obtained by reacting a dicarboxylic acid such as adipic acid, phthalic acid, or hexahydrophthalic acid with a bifunctional oxetane resin and adding a dibasic acid anhydride such as phthalic anhydride, tetrahydrophthalic anhydride, or hexahydrophthalic anhydride to the resulting primary hydroxyl groups.

[0022] (9) A carboxyl group-containing photosensitive resin obtained by reacting an epoxy compound having a plurality of epoxy groups in one molecule with a compound having at least one alcoholic hydroxyl group and one phenolic hydroxyl group in one molecule such as p-hydroxyphenethyl alcohol and an unsaturated group-containing monocarboxylic acid such as (meth)acrylic acid, and reacting a polybasic acid anhydride such as maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, or adipic acid with respect to the alcoholic hydroxyl groups of the obtained reaction product.

[0023] (10) A carboxyl group-containing photosensitive resin obtained by reacting a compound having a plurality of phenolic hydroxyl groups in one molecule with an alkylene oxide such as ethylene oxide or propylene oxide, reacting the obtained reaction product with an unsaturated group-containing monocarboxylic acid, and reacting the obtained reaction product with a polybasic acid anhydride.

[0024] (11) A carboxyl group-containing photosensitive resin obtained by reacting a compound having a plurality of phenolic hydroxyl groups in one molecule with a cyclic carbonate compound such as ethylene carbonate or propylene carbonate, reacting the obtained reaction product with an unsaturated group-containing monocarboxylic acid, and reacting the obtained reaction product with a polybasic acid anhydride.

[0025] (12) A carboxyl group-containing photosensitive resin obtained by further adding a compound having one epoxy group and one or more (meth)acryloyl groups in one molecule to the resins of (1) to (11) described above.

[0026] Among these, the carboxyl group-containing resin, from the viewpoints of warp suppression in the cured product, heat resistance, reflectance, etc., is a carboxyl group-containing urethane resin obtained by polyaddition reaction of diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, aromatic diisocyanates, etc., carboxyl group-containing dialcohol compounds such as dimethylolpropionic acid, dimethylolbutanoic acid, etc., and diol compounds such as polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A-based alkylene oxide adduct diols, compounds having phenolic hydroxy groups and alcoholic hydroxy groups, etc. During the synthesis of the urethane resin, a compound having one hydroxyl group and one or more (meth)acryloyl groups in one molecule such as hydroxyalkyl (meth)acrylate is added, and it preferably contains at least one kind of carboxyl group-containing photosensitive urethane resin having terminal (meth)acrylation. More preferably, the carboxyl group-containing resin is a carboxyl group-containing urethane resin obtained by polyaddition reaction of aliphatic diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, etc., carboxyl group-containing dialcohol compounds, and diol compounds such as polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, etc. During the synthesis of the urethane resin, hydroxyalkyl (meth)acrylate is added, and it may contain at least one kind of carboxyl group-containing photosensitive urethane resin having terminal (meth)acrylation.

[0027] Further, from the viewpoints of the heat resistance and reflectance of the cured product, the carboxyl group-containing resin preferably contains at least one carboxyl group-containing photosensitive resin obtained by reacting a reaction product obtained by reacting a compound having a plurality of phenolic hydroxyl groups in one molecule with an alkylene oxide such as ethylene oxide or propylene oxide with an unsaturated group-containing monocarboxylic acid and then reacting the resulting reaction product with a polybasic acid anhydride.

[0028] The acid value of the carboxyl group-containing resin may be, for example, 10 mgKOH / g or more and 150 mgKOH / g or less, preferably 30 mgKOH / g or more and 120 mgKOH / g or less. When the acid value of the carboxyl group-containing resin is 10 mgKOH / g or more, the alkali developability of the photosensitive resin composition is improved. Further, when the acid value is 150 mgKOH / g or less, it is easy to draw a good resist pattern. The acid value of the carboxyl group-containing resin is a value measured in accordance with JIS K0070:1992.

[0029] The weight average molecular weight of the carboxyl group-containing resin may vary depending on the resin skeleton, and generally may be 2,000 or more and 150,000 or less, preferably 5,000 or more and 100,000 or less. When the weight average molecular weight is 2,000 or more, the tack-free performance, resolution, etc. can be improved. Further, when the weight average molecular weight is 150,000 or less, the developability, storage stability, etc. of the photosensitive resin composition can be improved. Here, the weight average molecular weight is a value in terms of polystyrene measured by gel permeation chromatography.

[0030] The content of the carboxyl group-containing resin in the photosensitive thermosetting resin composition may be, for example, 5% by mass or more and 40% by mass or less, preferably 10% by mass or more and 35% by mass or less in terms of solid content. When the content of the carboxyl group-containing resin is 5% by mass or more, the coating film strength can be improved. Further, when the content of the carboxyl group-containing resin is 40% by mass or less, the viscosity of the photosensitive resin composition becomes appropriate and the processability is improved.

[0031] Photosensitive compound The photosensitive thermosetting resin composition may further contain at least one photosensitive compound having no carboxy group. Examples of the photosensitive compound include compounds having an ethylenically unsaturated bond. The photosensitive compound may be a compound having a plurality of ethylenically unsaturated bonds.

[0032] Examples of the compound having an ethylenically unsaturated bond include the following compounds. Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate; acrylamides such as N,N-dimethyl (meth) acrylamide, N-methylol (meth) acrylamide, and N,N-dimethylaminopropyl (meth) acrylamide; aminoalkyl (meth) acrylates such as N,N-dimethylaminoethyl (meth) acrylate and N,N-dimethylaminopropyl (meth) acrylate; di (meth) acrylates derived from alkylene glycols such as ethylene glycol, polyethylene glycol, propylene glycol, and polypropylene glycol; polyhydric (meth) acrylates derived from polyhydric alcohols such as hexanediol, trimethylolpropane, pentaerythritol, dipentaerythritol, and tris-hydroxyethyl isocyanurate, or their ethylene oxide adducts, propylene oxide adducts, or ε-caprolactone adducts; aromatic group-containing polyhydric (meth) acrylates derived from bisphenol A, bisphenol F, and their ethylene oxide adducts or propylene oxide adducts of these phenols; polyhydric (meth) acrylates derived from glycidyl ethers such as glycerin diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, and triglycidyl isocyanurate; etc. Further, not limited to the above, (meth) acrylates obtained by directly (meth) acrylation of polyols such as polyether polyol, polycarbonate diol, hydroxyl-terminated polybutadiene, and polyester polyol, or urethane (meth) acrylation via a diisocyanate compound, and melamine (meth) acrylate, etc. are included.

[0033] Furthermore, examples include epoxy (meth)acrylate resins obtained by reacting polyfunctional epoxy resins such as cresol novolak type epoxy resins with (meth)acrylic acid, and epoxy urethane (meth)acrylate compounds obtained by reacting hydroxyacrylates such as pentaerythritol tri(meth)acrylate with half urethane compounds of diisocyanates such as isophorone diisocyanate to the hydroxyl groups of the epoxy (meth)acrylate resins. Such epoxy (meth)acrylate resins can improve photocurability without reducing the touch dryness.

[0034] The photosensitive compound may contain at least aromatic group-containing polyvalent (meth)acrylates derived from bisphenol A, bisphenol F, and ethylene oxide adducts or propylene oxide adducts of these phenols. The photosensitive resin may contain one type of the photosensitive compound alone, or may contain a combination of two or more types.

[0035] When the photosensitive thermosetting resin composition contains a photosensitive compound, the content of the photosensitive compound may be, for example, 5 parts by mass or more and 100 parts by mass or less, preferably 10 parts by mass or more and 80 parts by mass or less, based on 100 parts by mass of the carboxy group-containing resin in terms of solid content. When the content is 5 parts by mass or more, the photocurability is improved, and the pattern formability by alkali development after active energy ray irradiation tends to be further improved. When it is 100 parts by mass or less, sufficient solubility in an alkaline aqueous solution after active energy ray irradiation is obtained, and the strength of the formed coating film tends to be further improved.

[0036] Photopolymerization initiator The photosensitive thermosetting resin composition contains at least an oxime ester-based photopolymerization initiator and a titanocene-based photopolymerization initiator as the photopolymerization initiator.

[0037] Oxime ester-based photopolymerization initiator The oxime ester-based photoinitiator may be any photoinitiator having an O-acyl oxime structure in the molecule, and may be, for example, a photoinitiator containing a partial structure represented by the following formula (I).

[0038]

Chemical formula

[0039] In the formula, R 1 represents a hydrogen atom, a phenyl group which may have a substituent, an alkyl group having 1 to 20 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 8 carbon atoms, an alkanoyl group having 2 to 20 carbon atoms, or a benzoyl group which may have a substituent. R 2 represents a phenyl group which may have a substituent, an alkyl group having 1 to 20 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 8 carbon atoms, an alkanoyl group having 2 to 20 carbon atoms, or a benzoyl group which may have a substituent. R 1 Or substituents in the phenyl group represented by R 2 may include an alkyl group having 1 to 6 carbon atoms, a phenyl group, a halogen atom, etc. The number of substituents in the phenyl group may be 1 to 5. R 1 Or the alkyl group represented by R 2 may be linear or branched and may be substituted with one or more hydroxyl groups. Further, at least one of the methylene groups constituting the alkyl group may be substituted with an oxygen atom or a carbonyl group. R 1 Or substituents in the benzoyl group represented by R 2 may include an alkyl group having 1 to 6 carbon atoms, a phenyl group, etc. The number of substituents in the benzoyl group may be 1 to 5.

[0040] Examples of the compound in which the partial structure represented by the formula (I) can be substituted include diaryl sulfane, 9H-carbazole, thioxanthen-9-one, fluorene, and derivatives thereof. The partial structure represented by the formula (I) may be substituted and bonded to the hydrogen atom of these compounds, or may be bonded via a carbonyl group.

[0041] Specific examples of the oxime ester-based photoinitiator containing the partial structure represented by the formula (I) include compounds represented by the following formulas (I-1), (I-2), (I-3), etc.

[0042]

Chemical formula

[0043] In the formula (I-1), R 11 has the same meaning as R 1 in the formula (I), and R 12 has the same meaning as R 2 in the formula (I). R 13 represents a hydrogen atom, a hydroxy group, a carboxy group, a hydroxyalkoxy group, a hydroxyalkoxycarbonyl group, etc. The number of carbon atoms in the hydroxyalkoxy group in R 13 may be from 1 to 20. n represents 0 or 1.

[0044]

Chemical formula

[0045] In the formula (I-2), R 21 has the same meaning as R 1 in the formula (I), and R 22 and R 24 each independently represent a phenyl group which may have a substituent, an alkyl group having 1 to 20 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 8 carbon atoms, an alkanoyl group having 2 to 20 carbon atoms, or a benzoyl group which may have a substituent. R 24Examples of the substituent in the phenyl group represented by include an alkyl group having 1 to 18 carbon atoms, an organic group having an acetal bond, etc. The organic group having an acetal bond may be, for example, a (2,2-dimethyl-1,3-dioxolan-4-yl)methoxy group. R 23 represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms including substituents, a phenyl group, a benzyl group, a benzoyl group, an alkanoyl group having 2 to 12 carbon atoms, an alkoxycarbonyl group having 2 to 12 carbon atoms, or a phenoxycarbonyl group. R 23 When the alkyl group constituting the alkoxycarbonyl group represented by has 2 or more carbon atoms, it may be substituted with at least one hydroxyl group, and at least one of the methylene groups constituting the alkyl group may be substituted with an oxygen atom.

[0046]

Chemical formula

[0047] In formula (I-3), R 31 is synonymous with R 1 in formula (I), and R 32 is synonymous with R 2 in formula (I). R 33 represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms including substituents, etc.

[0048] As an oxime ester-based photoinitiator containing a structural moiety represented by formula (I), specifically, 1-[4-(phenylsulfanyl)phenyl]-1,2-octanedione 2-(O-benzoyloxime), 1-{4-[4-(2-hydroxyethoxy)phenylsulfanyl]phenyl}propane-1,2-dione 2-(O-acetoxyoxime), 2-(acetyloxyiminomethyl)thioxanthen-9-one, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]ethanone 1-(O-acetoxyoxime), 1-[9-ethyl-6-(2-methyl-4-tetrahydrofuranylmethoxybenzoyl)-9H-carbazole-3-yl]ethanone 1-(O-acetoxyoxime), 1-[9-ethyl-6-{2-methyl-4-(2,2-dimethyl-1,3-dioxolan-2-yl)methoxybenzoyl}-9H-carbazole-3-yl]ethanone 1-(O-acetoxyoxime), 1-[4-[3-[4-[[2-(acetyloxy)ethyl]sulfonyl]-2-methylbenzoyl]-6-[1-[(acetyloxy)imino]ethyl]-9H-carbazole]-9-yl]phenyloctanone 1-(O-acetoxyoxime), etc. can be mentioned. These oxime ester-based photoinitiators may be used alone or in combination of two or more.

[0049] As commercially available products of oxime ester-based photoinitiators, Adeka Arcurus NCI-700, Adeka Arcurus NCI-730, Adeka Arcurus NCI-831, Adeka Arcurus NCI-930; 1-4-[[4-(2-hydroxyethoxy)phenyl]thio]phenyl]-1,2-propanedione 2-(O-acetoxyoxime) (the above are manufactured by ADEKA CORPORATION), DFI-020, DFI-091 (the above are manufactured by Daito Kemicx Co., Ltd.), CGI-325, Irgacure OXE01, Irgacure OXE02; 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]ethanone 1-(O-acetoxyoxime), Irgacure OXE03, Irgacure OXE04 (the above are manufactured by BASF Japan Ltd.), etc. can also be used.

[0050] In the photosensitive thermosetting resin composition, the content of the oxime ester-based photopolymerization initiator may be, for example, 0.01 part by mass or more and 10 parts by mass or less, preferably 0.02 part by mass or more and 8 parts by mass or less, and more preferably 0.05 part by mass or more and 5 parts by mass or less, based on 100 parts by mass of the carboxyl group-containing resin in terms of solid content. When the content of the oxime ester-based photopolymerization initiator is 0.01 part by mass or more, sufficient photocuring can be achieved. Also, when it is 10 parts by mass or less, there is a tendency for a good balance between surface curing and bottom curing. In one aspect, the content of the oxime ester-based photopolymerization initiator may be 3 parts by mass or less, 2 parts by mass or less, or 1 part by mass or less.

[0051] Titanocene-based photopolymerization initiator Examples of the titanocene-based photopolymerization initiator include compounds represented by the following formula (II).

[0052]

Chemical formula

[0053] In the formula, R 9 and R 10 each independently represent a halogen atom, an aryl group, a halogenated aryl group, or a heterocyclic ring-containing halogenated aryl group.

[0054] Examples of the titanocene-based photoinitiator represented by the formula (II) include di(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1H-pyrrol-1-yl)ethyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-(3-(1H-pyrrol-1-yl)propyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-((1H-pyrrol-1-yl)methyl)phenyl]titanium, bis(methylcyclopentadienyl)-bis[2,6-difluoro-3-((1H-pyrrol-1-yl)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-((2,5-dimethyl-1H-pyrrol-1-yl)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-((2-isopropyl-5-methyl-1H-pyrrol-1,6-yl)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-((2-(2-methoxyethyl)-5-methyl-1H-pyrrol-1-yl)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-((3-trimethylsilyl-2,5-dimethyl-1H-pyrrol-1-yl)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-((2,5-dimethyl-3-(bis(2-methoxyethyl)aminomethyl)-1H-pyrrol-1-yl)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-((2,5-bis(morpholinomethyl)-1H-pyrrol-1-yl)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-((2,5-dimethyl-3-(1,3-dioxolan-2-yl)-1H-pyrrol-1-yl)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-4-((2,5-dimethyl-1H-pyrrol-1-yl)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-methyl-4-(2-(1H-pyrrol-1-yl)ethyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-((2,3,4,5 - Tetramethyl - 1H - pyrrol - 1 - yl)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,3,5,6 - tetrafluoro - 4-(3-(1H - pyrrol - 1 - yl)propyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-(2-(1H - pyrrol - 1 - yl)propyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-(1 - methyl - 2-(1H - pyrrol - 1 - yl)ethyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-(3-(2 - isoindol - 2 - yl)propyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-(2-(4,5,6,7 - tetrahydro - isoindol - 2 - yl)ethyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-(6-(9 - carbazol - 9 - yl)hexyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-(3-(2,3,4,5,6,7,8,9 - octahydro - 1 - carbazol - 9 - yl)propyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-(3-(4,5,6,7 - tetrahydro - 2 - methyl - 1 - indol - 1 - yl)propyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-((acetylamino)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-(2-(propionylamino)ethyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-(3-(acetylamino)propyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-(4-(bivaloylamino)butyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-(2-(2,2 - dimethylpentanoylamino)ethyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-(3-(benzoylamino)propyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6 - difluoro - 3-((2,(2-Dimethylpentanoylamino)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(2,2-dimethyl-3-chloropropanoylamino)ethyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-((2,2-dimethyl-3-ethoxypropanoylamino)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(lauroy lamino)ethyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(N-allylmethylsulfonylamino)ethyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-(3-(N-isobutylphenylsulfonylamino)propyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-((methylsulfonylamino)methyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-(3-(ethylsulfonylamino)propyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(butylsulfonylamino)ethyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-(4-(trisulfonylamino)propyl)phenyl]titanium, bis(η, 5 -2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium and the like can be mentioned. These metallocene-based photoinitiators may be used alone or in combination of two or more.

[0055] Commercially available products of metallocene-based photoinitiators include JMT-784 (manufactured by Yueyang Jinmaotai Technology Co., Ltd.; di(η 5 -2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium) and the like.

[0056] In the photosensitive thermosetting resin composition, the content of the titanocene-based photopolymerization initiator may be, for example, 0.01 part by mass or more and 10 parts by mass or less, preferably 0.02 part by mass or more and 8 parts by mass or less, more preferably 0.05 part by mass or more and 5 parts by mass or less, based on 100 parts by mass of the carboxyl group-containing resin in terms of solid content. When the content of the titanocene-based photopolymerization initiator is 0.01 part by mass or more, sufficient photocuring can be achieved. Also, when it is 10 parts by mass or less, uneven curing tends to be suppressed. In one aspect, the content of the titanocene-based photopolymerization initiator may be 2 parts by mass or less, 1 part by mass or less, or 0.5 part by mass or less.

[0057] The content ratio of the oxime ester-based photopolymerization initiator and the titanocene-based photopolymerization initiator in the photopolymerization initiator may be, for example, from 1:10 to 10:1, preferably from 1:8 to 8:1, more preferably from 1:5 to 5:1, and still more preferably from 1:2 to 2:1, on a mass basis of the oxime ester-based photopolymerization initiator:titanocene-based photopolymerization initiator. Within the above range, the balance between surface curability and deep curability is good, and a good pattern can be formed.

[0058] In the photosensitive thermosetting resin composition, the total content of the titanocene-based photopolymerization initiator and the oxime ester-based photopolymerization initiator may be, for example, 0.01 part by mass or more and 10 parts by mass or less, preferably 0.1 part by mass or more and 2 parts by mass or less, more preferably 0.2 part by mass or more and 1 part by mass or less, based on 100 parts by mass of the carboxyl group-containing resin in terms of solid content. When the total content of the titanocene-based photopolymerization initiator and the oxime ester-based photopolymerization initiator is 0.01 part by mass or more, sufficient photocuring can be achieved. Also, when it is 10 parts by mass or less, uneven curing tends to be suppressed.

[0059] In addition to oxime ester-based photoinitiators and titanocene-based photoinitiators, the photoinitiator may further contain other photoinitiators other than oxime ester-based and titanocene-based photoinitiators. Examples of other photoinitiators include benzophenone-based photoinitiators, acetophenone-based photoinitiators, aminoacetophenone-based photoinitiators, benzoin ether-based photoinitiators, benzyl ketal-based photoinitiators, oxime ether-based photoinitiators, alkylphenone-based photoinitiators, acylphosphine oxide-based photoinitiators, and the like.

[0060] When the photoinitiator contains other photoinitiators, in one aspect, the content thereof may be, for example, 80% by mass or more and 99% by mass or less, preferably 90% by mass or less and 97% by mass or less, in terms of solid content based on the total mass of the photoinitiator. In another aspect, it may be, for example, 10% by mass or less, preferably 1% by mass or less, more preferably 0.1% by mass or less.

[0061] White pigment The photosensitive thermosetting resin composition contains at least one kind of white pigment. By containing the white pigment, the cured product can be whitened. Examples of the white pigment include zinc oxide, potassium titanate, zirconium oxide, antimony oxide, lead white, zinc sulfide, lead titanate, etc. From the viewpoints of reflectance and discoloration suppression effect, it is preferable that the white pigment contains at least titanium oxide. As the titanium oxide, those produced by the sulfuric acid method, the chlorine method, etc., rutile type titanium oxide, anatase type titanium oxide, or titanium oxide surface-treated with a hydrous metal oxide or an organic compound can be used. Among these titanium oxides, from the viewpoint of photocatalytic activity, rutile type titanium oxide is preferable. By using rutile type titanium oxide, a more stable cured product (for example, a solder resist film) can be obtained. Specific examples of the rutile type titanium oxide include TR-600, TR-700, TR-750, TR-840 (all manufactured by Fuji Titanium Industry Co., Ltd.), R-550, R-580, R-630, R-820, CR-50, CR-60, CR-90 (all manufactured by Ishihara Sangyo Co., Ltd.), KR-270, KR-310, KR-380 (all manufactured by Titanium Industry Co., Ltd.), etc. Among these rutile type titanium oxides, it is particularly preferable to use titanium oxide whose surface is treated with hydrous alumina or aluminum hydroxide from the viewpoints of dispersibility, storage stability, and flame retardancy in the composition. The white pigment may be used alone or in combination of two or more kinds.

[0062] The volume average particle size of the white pigment may be, for example, 10 nm or more and 5 μm or less, preferably 100 nm or more and 1 μm or less. The volume average particle size of the white pigment is measured, for example, as the particle size corresponding to 50% of the volume cumulative from the small diameter side in the volume-based cumulative particle size distribution measured using a laser diffraction particle size distribution measuring device.

[0063] The whiteness of the white pigment may be, for example, 80 or more, preferably 85 or more. The whiteness is measured, for example, using a spectroscopic color whiteness meter (PF10, etc. manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with the "Method for Measuring ISO Whiteness (Diffuse Blue Light Reflectance)" of JIS P8148:2018.

[0064] In the photosensitive thermosetting resin composition, the content of the white pigment may be, for example, 200 parts by mass or more and 1000 parts by mass or less, preferably 250 parts by mass or more and 800 parts by mass or less, based on 100 parts by mass of the carboxyl group-containing resin in terms of solid content. When the content of the white pigment is 200 parts by mass or more, sufficient reflectance can be achieved in the cured product. Also, when it is 1000 parts by mass or less, an increase in the viscosity of the composition can be suppressed, the coating and moldability are good, and the brittleness of the cured product tends to be suppressed.

[0065] Thermosetting resin The photosensitive thermosetting resin composition contains at least one kind of thermosetting resin. As the thermosetting resin, known and commonly used ones such as isocyanate compounds, blocked isocyanate compounds, amino resins, maleimide compounds, benzoxazine resins, carbodiimide resins, cyclocarbonate compounds, epoxy resins, polyfunctional oxetane compounds, and episulfide resins can be used. Among these, the thermosetting resin preferably has at least one kind (hereinafter abbreviated as cyclic (thio)ether group) of a plurality of cyclic ether groups and cyclic thioether groups in one molecule. There are many commercially available types of thermosetting components having these cyclic (thio)ether groups, and various properties can be imparted depending on their structures.

[0066] The thermosetting resin having a plurality of cyclic (thio)ether groups in the molecule is a compound having a plurality of groups of at least one kind of 3-, 4- or 5-membered cyclic ether group or cyclic thioether group in the molecule. For example, a compound having a plurality of epoxy groups in the molecule, that is, a polyfunctional epoxy compound, a compound having a plurality of oxetanyl groups in the molecule, that is, a polyfunctional oxetane compound, a compound having a plurality of thioether groups in the molecule, that is, an episulfide compound, etc. can be mentioned.

[0067] Specific examples of the polyfunctional epoxy compound include, for example, bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, brominated bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, novolac type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, N-glycidyl type epoxy resin, novolac type epoxy resin of bisphenol A, bixylenol type epoxy resin, biphenol type epoxy resin, chelate type epoxy resin, glyoxal type epoxy resin, amino group-containing epoxy resin, rubber-modified epoxy resin, dicyclopentadiene phenolic type epoxy resin, diglycidyl phthalate resin, heterocyclic epoxy resin, tetraglycidyl xylyloyl ethane resin, silicone-modified epoxy resin, ε-caprolactone-modified epoxy resin, and the like. Further, as the polyfunctional epoxy resin, those in which halogen atoms such as chlorine and bromine, atoms such as phosphorus are introduced into the structure may be used. Thereby, for example, flame retardancy can be imparted. The polyfunctional epoxy resin may be used alone or in combination of two or more kinds.

[0068] Examples of the polyfunctional oxetane compound include polyfunctional oxetanes such as bis[(3-methyl-3-oxetanylmethoxy)methyl]ether, bis[(3-ethyl-3-oxetanylmethoxy)methyl]ether, 1,4-bis[(3-methyl-3-oxetanylmethoxy)methyl]benzene, 1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene, (3-methyl-3-oxetanyl)methyl acrylate, (3-ethyl-3-oxetanyl)methyl acrylate, (3-methyl-3-oxetanyl)methyl methacrylate, (3-ethyl-3-oxetanyl)methyl methacrylate, oligomers or copolymers thereof; and etherified products of oxetane alcohol with resins having hydroxyl groups such as novolak resins, poly(p-hydroxystyrene), calixarenes, calixresorcinarenes, or silsesquioxanes. Other examples include copolymers of unsaturated monomers having an oxetane ring and alkyl (meth)acrylate.

[0069] Examples of the episulfide resin include YL7000 (bisphenol A type episulfide resin) manufactured by Mitsubishi Chemical Corporation. In addition, episulfide resins obtained by replacing the oxygen atom of the epoxy group of novolak type epoxy resins with a sulfur atom using a similar synthesis method can also be used.

[0070] In the photosensitive thermosetting resin composition, the content of the thermosetting resin may be, for example, 10 parts by mass or more and 100 parts by mass or less, preferably 20 parts by mass or more and 80 parts by mass or less, based on 100 parts by mass of the carboxyl group-containing resin in terms of solid content. If the content of the thermosetting resin is within the above range, good solder heat resistance can be obtained in the cured product of the photosensitive resin composition, and various properties, particularly electrical insulation, tend to be good when used as an insulating protective film for printed wiring boards.

[0071] The photosensitive thermosetting resin composition may contain a thermosetting catalyst in addition to the thermosetting resin. Examples of the thermosetting catalyst include imidazole derivatives such as imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole; amine compounds such as dicyandiamide, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzylamine, 4-methoxy-N,N-dimethylbenzylamine, 4-methyl-N,N-dimethylbenzylamine; hydrazine compounds such as adipic acid dihydrazide, sebacic acid dihydrazide; phosphorus compounds such as triphenylphosphine, etc. Also, commercially available ones include, for example, 2MZ-A, 2MA-OK, 2PHZ-PW, 2P4BHZ-PW (all of the above are products of Shikoku Kasei Kogyo Co., Ltd.; all are trade names of imidazole-based compounds), DBU, DBN, U-CAT SA102, U-CAT5002 (all of the above are products of San-Apro Ltd.; all are bicyclic amidine compounds and their salts), etc. In particular, it is not limited to these, and any one that can promote the reaction of at least one of an epoxy group and an oxetanyl group with a carboxy group, such as a thermosetting catalyst for an epoxy resin or an oxetane compound, may be used. Also, S-triazine derivatives such as guanamine, acetoguanamine, benzoguanamine, melamine, 2,4-diamino-6-methacryloyloxyethyl-S-triazine, 2-vinyl-2,4-diamino-S-triazine, 2-vinyl-4,6-diamino-S-triazine·isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-S-triazine·isocyanuric acid adduct can also be used. The thermosetting catalyst alone may be used singly or in combination of two or more kinds.

[0072] When the photosensitive thermosetting resin composition contains a thermosetting catalyst, it may be, for example, 0.1 part by mass or more and 20 parts by mass or less, preferably 0.5 part by mass or more and 15 parts by mass or less, based on 100 parts by mass of the thermosetting resin in terms of solid content.

[0073] The photosensitive thermosetting resin composition may further contain at least one filler selected from the group consisting of inorganic fillers and organic fillers, if necessary, for the purpose of improving properties such as adhesion, hardness, and heat resistance. Examples of inorganic fillers include barium sulfate, calcium carbonate, silicon oxide, amorphous silica, talc, clay, hydrotalcite, mica powder, etc. Examples of organic fillers include silicon powder, nylon powder, fluorine powder, etc. Among the above fillers, silica is particularly excellent in terms of low hygroscopicity and low volume expansion. Silica may be in a molten or crystalline state, or a mixture thereof, but silica surface-treated with a coupling agent, etc. is particularly preferred because it can improve electrical insulation. The average particle size of the filler is desirably 25 μm or less, more preferably 10 μm or less, and even more preferably 3 μm or less. When the photosensitive thermosetting resin composition contains a filler, the filler content may be, for example, 150 parts by mass or less, preferably 50 parts by mass or less, based on 100 parts by mass of the carboxyl group-containing resin in terms of solid content. When the filler content is within the above ratio, the cured film has good folding resistance.

[0074] The photosensitive thermosetting resin composition may be added with other additives other than the above components. Examples of additives include thickeners such as organic bentonite and montmorillonite, at least one of defoaming agents and leveling agents such as silicone-based, fluorine-based, and polymer-based, and fiber reinforcing materials such as glass fiber, carbon fiber, and boron nitride fiber. Furthermore, if necessary, adhesion promoters, thermal polymerization inhibitors, peroxide decomposers, ultraviolet absorbers, silane coupling agents such as thiazole-based and triazole-based, dispersants, defoaming agents, plasticizers, foaming agents, flame retardants, antistatic agents, antioxidants, antibacterial and antifungal agents, etc. can be added.

[0075] The photosensitive thermosetting resin composition may further contain at least one of a radical scavenger and a peroxide decomposer, if necessary. Thereby, the reduction in function in the cured product can be suppressed. The radical scavenger and the peroxide decomposer may be so-called antioxidants.

[0076] Examples of radical scavengers include phenolic compounds such as hydroquinone, 4-t-butylcatechol, 2-t-butylhydroquinone, hydroquinone monomethyl ether, 2,6-di-t-butyl-p-cresol, 2,2-methylenebis(4-methyl-6-t-butylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 1,3,5-tris(3’,5’-di-t-butyl-4-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione; quinone compounds such as metakuinone and benzoquinone; and amine compounds such as bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate and phenothiazine.

[0077] The radical scavenger may be a commercially available product, such as AdekaStab (registered trademark) AO-30, AdekaStab AO-330, AdekaStab AO-20, AdekaStab LA-77, AdekaStab LA-57, AdekaStab LA-67, AdekaStab LA-68, AdekaStab LA-87 (all manufactured by ADEKA CORPORATION), Irganox (registered trademark) 1010, Irganox 1035, Irganox 1076, Irganox 1135, Tinuvin (registered trademark) 111FDL, Tinuvin 123, Tinuvin144, Tinuvin 152, Tinuvin 292, Tinuvin 5100 (all manufactured by BASF Japan Ltd.), and the like.

[0078] The ultraviolet absorber may be a commercially available product, such as Tinuvin PS, Tinuvin 99-2, Tinuvin 109, Tinuvin 384-2, Tinuvin 900, Tinuvin 928, Tinuvin 1130, Tinuvin 400, Tinuvin 405, Tinuvin 460, Tinuvin 479 (all manufactured by BASF Japan Ltd.), and the like.

[0079] The photosensitive thermosetting resin composition may further contain an organic solvent. By containing an organic solvent, each component can be easily dissolved or dispersed. Also, the viscosity can be easily adjusted to a viscosity suitable for application methods such as coating. Examples of the organic solvent include aromatic solvents such as toluene, xylene, ethylbenzene, and nitrobenzene; aliphatic hydrocarbon solvents such as cyclohexane; ether solvents such as diethylene glycol dimethyl ether and ethylene glycol diethyl ether; ester solvents such as carbitol acetate, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, dipropylene glycol methyl ether acetate, methyl methoxypropionate, ethyl methoxypropionate, methyl ethoxypropionate, ethyl ethoxypropionate, ethyl acetate, n-butyl acetate, isoamyl acetate, ethyl lactate, and γ-butyrolactone; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, and isophorone; amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; sulfoxide solvents such as dimethyl sulfoxide; and halogenated hydrocarbon solvents such as chloroform and methylene chloride. The organic solvent may be used alone or in combination of two or more. Also, the content of the organic solvent may be appropriately set according to the desired viscosity and the like.

[0080] The photosensitive thermosetting resin composition is obtained by dissolving or dispersing the above-described components using a mixer such as a disper, kneader, three-roll mill, bead mill, or the like.

[0081] In one aspect, the photosensitive thermosetting resin composition contains a photosensitive resin, a photopolymerization initiator, a white pigment, and an epoxy resin. The photosensitive resin contains a carboxyl group-containing resin. The photopolymerization initiator contains an oxime ester-based photopolymerization initiator and a titanocene-based photopolymerization initiator. The mass ratio of the content of the white pigment to the content of the photosensitive resin is 1.2 or more and 5 or less, and the mass ratio of the total content of the oxime ester-based photopolymerization initiator and the titanocene-based photopolymerization initiator to the content of the white pigment may be 0.0004 or more and 0.002 or less. By having the content of the white pigment within the above range and the photopolymerization initiator within the above range, excellent whiteness and high reflectance at a wavelength of 450 nm can be achieved.

[0082] Cured product The cured product of the photosensitive thermosetting resin composition can exhibit high whiteness and excellent reflectance at a wavelength of 450 nm. The cured product of the photosensitive thermosetting resin composition can be obtained, for example, under the following curing conditions.

[0083] Curing conditions After applying the photosensitive thermosetting resin composition onto a substrate so that the film thickness after heat curing becomes 55 μm, it is dried at 80°C for 30 minutes. It is exposed using a high-pressure mercury lamp at 400 mJ / cm 2 and development (30°C, 0.2 MPa, 1 mass% Na2CO3 aqueous solution) is carried out for 60 seconds. Thereafter, a cured product can be obtained by heat curing under the conditions of 150°C for 60 minutes.

[0084] The cured product of the photosensitive thermosetting resin composition after heat curing has an L * a * b * value of b in the L * a * value of b is preferably 2.0 or less, more preferably 1.8 or less, and even more preferably 1.5 or less. The L * a * b * value of b in the L * a value is measured by a spectrophotometer (manufactured by Konica Minolta Inc., model number: CM-5) for a cured product with a thickness of 55 μm produced under the above production conditions. The b value in the cured product* When the value is within the above range, yellowing due to heating tends to be suppressed.

[0085] Further, the cured product has a reflectance of 85% or more at a wavelength of 450 nm. The reflectance at a wavelength of 450 nm may preferably be 88% or more. The reflectance at a wavelength of 450 nm is measured by a measuring diameter of 8 mm in the SCI method of a spectrocolorimeter (manufactured by Konica Minolta, Inc., model number: CM-5) for a cured product having a thickness of 55 μm produced under the above-described curing conditions. When the reflectance of the cured product is within the above range, the light extraction efficiency in the display tends to be improved, and the reflected light can be effectively utilized.

[0086] The cured product formed from the photosensitive thermosetting resin composition exhibits excellent heat resistance and can maintain whiteness and reflectance. Specifically, for example, ΔEab after performing heat treatment (reflow process) once at a setting of a maximum temperature of 260 °C for 10 seconds * may be, for example, 2.0 or less, and preferably 1.0 or less. Here, ΔEab * is a value obtained by the following formula (1) using ΔL * , a * and b * before heat treatment and L * , a * and b * after heat treatment, and is an index indicating the degree of discoloration. * Δa * and Δb * : ΔEab * = ((ΔL * ) 2 + (Δa * ) 2 + (Δb * ) 2 ) (1 / 2) ···(1)

[0087] Further, the reduction width of the reflectance at a wavelength of 450 nm may be, for example, 5% or less, preferably 2% or less. Here, the reduction width of the reflectance is calculated by subtracting the reflectance (%) measured in the cured product after the heat treatment from the reflectance (%) measured in the cured product before the heat treatment.

[0088] The photosensitive thermosetting resin composition can be applied to a printed circuit board by an application method selected from commonly used application methods to form a resin composition layer. Further, it can be used in various forms and applications such as dry film or prepreg. Although various solvents can be used depending on the usage method, application, etc., in some cases, not only a good solvent but also a poor solvent may be used.

[0089] The photosensitive thermosetting resin composition is adjusted to a viscosity suitable for the application method with the above organic solvent, applied onto a substrate, and the organic solvent contained in the composition is volatilized and dried (pre-dried) at a temperature of about 60°C to 100°C, whereby a tack-free resin composition layer can be formed. Examples of the application method include a dip coating method, a flow coating method, a roll coating method, a bar coater method, a screen printing method, a curtain coating method, a spray coating method, etc. Further, the resin composition layer may be formed by applying the above photosensitive thermosetting resin composition onto a carrier film, drying it, winding it up as a film, and laminating it onto a substrate. Thereafter, by a contact (or non-contact) method, it is selectively exposed with active energy rays through a photomask having a pattern or directly pattern-exposed with a laser direct exposure machine, and the unexposed portion is developed with a dilute aqueous alkali solution (for example, an aqueous sodium carbonate solution of 0.3 mass% to 3 mass%) to form a resist pattern (pattern image). The exposure conditions are as follows. Further, for example, by heating at a temperature of about 140°C to 180°C for thermosetting, the carboxy group of the carboxy group-containing resin (or further phenolic hydroxy group) reacts with the cyclic (thio) ether group of the thermosetting resin, and in addition to properties such as adhesion to the substrate, fold resistance, low warpage, electroless gold plating resistance, solder heat resistance, electrical insulation, etc., flexibility and high reflectivity are achieved in a well-balanced manner at a high level, and a white cured film is formed in which a decrease in reflectivity and a decrease in whiteness over time are suppressed.

[0090] As the substrate, printed wiring boards, flexible printed wiring boards, paper-phenolic resins, paper-epoxy resins, glass cloth-epoxy resins, glass-polyimide, glass cloth / non-woven fabric-epoxy resins, glass cloth / paper-epoxy resins, composite materials such as synthetic fiber-epoxy resins, fluororesins, polyethylene, PPO, cyanate esters, etc. (all grades such as FR-4), polyimide films, PET films, glass substrates, ceramic substrates, wafer plates, etc. can be used. Circuits may be formed on the above-described substrates, and configurations such as transistors may be formed and mounted.

[0091] The evaporation drying carried out after applying the photosensitive resin composition can be performed using a hot air circulation drying furnace, an IR furnace, a hot plate, a convection oven, etc. (a method of making the hot air in the dryer in countercurrent contact using a device equipped with a heat source of an air heating method by steam and a method of spraying onto the support from a nozzle).

[0092] After applying the photosensitive resin composition onto a substrate and performing evaporation drying, exposure (irradiation with active energy rays) is performed on the obtained resin composition layer. The resin composition layer cures in the exposed portion (the portion irradiated with the active energy rays).

[0093] Examples of the exposure machine used for the above active energy ray irradiation include a direct drawing device (for example, a laser direct imaging device that directly draws an image with a laser based on CAD data from a computer), an exposure machine equipped with a metal halide lamp, an exposure machine equipped with a (super) high-pressure mercury lamp, an exposure machine equipped with a mercury short arc lamp, or a direct drawing device using an ultraviolet lamp such as a (super) high-pressure mercury lamp. The active energy ray may be laser light having a maximum wavelength in the range of 350 nm to 450 nm. The active energy ray can be irradiated using, for example, a gas laser, a solid laser, etc. Also, the exposure amount may be appropriately selected according to the film thickness, etc., and generally is 5 mJ / cm 2 to 800 mJ / cm 2 and preferably in the range of 5 mJ / cm 2 to 500 mJ / cm 2 Any device can be used as long as it is a device that oscillates laser light having a maximum wavelength in the range of 350 nm to 450 nm, for example, those manufactured by Orbotech Japan Co., Ltd. can be used as the above direct drawing device.

[0094] Examples of the development method include a dipping method, a shower method, a spray method, a brush method, etc. As the developer, an alkaline aqueous solution such as potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, amines, etc. can be used.

[0095] In addition to the method of directly applying the photosensitive thermosetting resin composition in a liquid state to a substrate, it can also be used in the form of a dry film having a resin composition layer formed by applying and drying the photosensitive thermosetting resin composition on a film such as polyethylene terephthalate in advance. An example of using the photosensitive resin composition as a dry film is shown below.

[0096] Dry film The dry film has a resin composition layer obtained by applying and drying the above-described photosensitive thermosetting resin composition on a film. The dry film may have a structure in which a first film, a resin composition layer, and an optional peelable second film are laminated in this order. The resin composition layer is, for example, a layer obtained by applying and drying the photosensitive thermosetting resin composition on the first film or the second film. A dry film can be obtained by laminating the second film thereon after forming the resin composition layer on the first film, or laminating the laminate obtained by forming the resin composition layer on the second film on the first film.

[0097] As the first film, a thermoplastic film such as a polyester film having a thickness of 2 μm to 150 μm is used. The resin composition layer is formed by uniformly applying the photosensitive thermosetting resin composition on the first film or the second film with a thickness of 10 μm to 150 μm using a blade coater, a lip coater, a comma coater, a film coater, etc., and drying. As the second film, a polyethylene film, a polypropylene film, etc. can be used, but those having an adhesive force with the resin composition layer smaller than that of the first film are preferred.

[0098] To form a protective film (permanent protective film) on a substrate using a dry film, the second film is peeled off, the resin composition layer and the substrate with circuits formed thereon are overlapped, and they are bonded together using a laminator or the like to form a resin composition layer on the substrate with circuits formed thereon. If the formed resin composition layer is exposed, developed, and heat-cured in the same manner as described above, a cured coating film can be formed. The first film may be peeled off either before or after exposure.

[0099] Electronic component The electronic component includes a cured product of the photosensitive thermosetting resin composition described above. Examples of the electronic component include a printed wiring board, a light source module, etc. The printed wiring board includes a substrate having a pattern conductor and a cured product of the photosensitive thermosetting resin composition disposed on the substrate. The cured product disposed on the substrate may be pattern-formed into a desired shape. The light source module includes a printed wiring board and a semiconductor light-emitting element disposed on the printed wiring board and connected to the pattern conductor. In the light source module, the semiconductor light-emitting element may be coated with a cured resin layer. The cured resin layer coating the semiconductor light-emitting element may contain, for example, a silicone resin.

[0100] In another aspect, the present invention also includes the use of the photosensitive thermosetting resin composition in the manufacture of a dry film or an electronic component, and the photosensitive thermosetting resin composition used in the manufacture of a dry film or an electronic component.

Examples

[0101] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples.

[0102] The following were prepared as materials for preparing the photosensitive thermosetting resin composition. Carboxy group-containing resin (Synthesis Example 1) Varnish A-1 Into a reaction vessel equipped with a stirring device, a thermometer, and a condenser, 2400 g (3 mol) of a polycarbonate diol (TJ5650J, manufactured by Asahi Kasei Corporation, number average molecular weight 800) derived from 1,5-pentanediol and 1,6-hexanediol, 603 g (4.5 mol) of dimethylolpropionic acid, and 238 g (2.6 mol) of 2-hydroxyethyl acrylate as a monohydroxy compound were charged. Next, 1887 g (8.5 mol) of isophorone diisocyanate as a polyisocyanate was charged, and the mixture was heated to 60 °C with stirring and then stopped. When the temperature in the reaction vessel began to decrease, it was heated again and stirring was continued at 80 °C. The reaction was terminated after confirming that the absorption spectrum of the isocyanate group (2280 cm -1 ) disappeared in the infrared absorption spectrum. Carbitol acetate was added so that the solid content became 50% by mass to obtain varnish A-1. The solid had an acid value of 50 mg KOH / g and a weight average molecular weight Mw of about 17,000.

[0103] (Synthesis Example 2) Varnish A-2 220 g of a cresol novolak type epoxy resin (EPICLON N-695, manufactured by DIC Corporation, epoxy equivalent: 220 g / eq.) was placed in a four-necked flask equipped with a stirrer and a reflux condenser, 214 g of carbitol acetate was added, and the mixture was heated and dissolved. Next, 0.1 g of hydroquinone as a polymerization inhibitor and 2.0 g of dimethylbenzylamine as a reaction catalyst were added. This mixture was heated from 95 °C to 105 °C, 72 g of acrylic acid was gradually added dropwise, and the reaction was carried out for 16 hours. The reaction product was cooled from 80 °C to 90 °C, 106 g of tetrahydrophthalic anhydride was added, and the reaction was carried out for 8 hours. After cooling, it was taken out. The thus-obtained varnish A-2 of the carboxyl group-containing resin had a solid content of 65%, an acid value of the solid of 100 mg KOH / g, and a weight average molecular weight Mw of about 3,500.

[0104] Photosensitive compound BPE-900: Manufactured by Shin-Nakamura Chemical Co., Ltd.; ethoxylated bisphenol A dimethacrylate

[0105] Photoinitiator Oxime ester type ADEKA ARKLES NCI-930: Manufactured by ADEKA CORPORATION; 1-4-[[4-(2-hydroxyethoxy)phenyl]thio]phenyl]-1,2-propanedione 2-(O-acetyloxime) ADEKA ARKLES NCI-730: Manufactured by ADEKA CORPORATION; Irgacure OXE04: Manufactured by BASF JAPAN LTD.; Irgacure OXE02: Manufactured by BASF JAPAN LTD.; 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone 1-(O-acetyloxime)

[0106] Titanocene type JMT-784: Manufactured by Yueyang Jinmaotai Technology Co., Ltd.; Bis(η 5 -2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium)

[0107] Alkylphenone type Omnirad 184: Manufactured by IGM JAPAN CO., LTD.; 1-hydroxycyclohexyl phenyl ketone

[0108] α-Aminoacetophenone type Omnirad 379: Manufactured by IGM JAPAN CO., LTD.; 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one Omnirad 907: Manufactured by IGM JAPAN CO., LTD.; 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one

[0109] White pigment CR-90: Manufactured by Ishihara Sangyo Kaisha, Ltd.; Rutile type titanium oxide

[0110] Thermosetting resin jER834: Manufactured by Mitsubishi Chemical Corporation; Bisphenol A type epoxy resin, epoxy equivalent 250 g / eq

[0111] Thermosetting catalyst DICY7: manufactured by Mitsubishi Chemical Corporation; dicyandiamide Wetting dispersant Disperbyk-111: manufactured by BYK Japan K.K. Defoaming agent KS-66: manufactured by Shin-Etsu Chemical Co., Ltd.; silicone oil compound type defoaming agent

[0112] Preparation of photosensitive resin composition Using each of the obtained varnishes A-1 and A-2, various components shown in Table 1 were blended at the indicated ratios (parts by mass), preliminarily mixed with a stirrer, and then kneaded with a three-roll mill to prepare the photosensitive thermosetting resin compositions of Examples 1 to 13 and Comparative Examples 1 to 5. The values in the table are parts by mass unless otherwise specified. Note that "-" in Tables 1 and 2 indicates that it was not added or not evaluated (due to inability to evaluate).

[0113] The following evaluations were performed on the photosensitive thermosetting resin compositions of Examples 1 to 13 and Comparative Examples 1 to 5 thus obtained. These results are also shown in Tables 1 and 2.

[0114] Preparation of evaluation substrate The photosensitive thermosetting resin compositions of Examples 1 to 13 and Comparative Examples 1 to 5 were screen-printed twice on a copper-plated substrate so that the total film thickness after heat curing was 55 μm to form a coating film. Specifically, the entire surface was coated by screen printing on the copper-plated substrate and dried in a hot air circulation drying oven at 80 °C for 10 minutes to form the first layer. The entire surface was further coated by screen printing on the first layer and dried in a hot air circulation drying oven at 80 °C for 20 minutes to form the second layer. The formed coating film was exposed at the optimum exposure amount using an exposure apparatus equipped with a high-pressure mercury lamp (Mms60: manufactured by Okou Seisakusho Co., Ltd.), and development (30 °C, 0.2 MPa, 1% by mass aqueous Na2CO3 solution) was performed for 60 seconds. Thereafter, heat curing was performed at 150 °C for 60 minutes in a hot air circulation drying oven to form a resin layer, and a substrate for evaluation was produced. The optimum exposure amount was determined by exposing the dried coating film using an exposure apparatus equipped with a high-pressure mercury lamp (Mms60: manufactured by Okou Seisakusho Co., Ltd.) through a Stouffer 41-step tablet, and developing for 60 seconds with a 1% by mass aqueous Na2CO3 solution at a spray pressure of 0.2 MPa and a liquid temperature of 30 °C. The exposure amount was set such that the pattern of the remaining step tablet was from 15 steps to 20 steps.

[0115] Evaluation of surface curability Except that the exposure amount was changed from the "optimum exposure amount" to "400 mJ / cm 2 ", a substrate for evaluation was produced according to the production of the substrate for evaluation until after development and before heat curing, and the surface of such a substrate was visually observed. The evaluation criteria for surface curability were as follows. a: The surface was smooth and in good condition. b: Roughness was observed on a part of the surface. c: Roughness was observed on the entire surface.

[0116] Evaluation of reflectance The reflectance at 450 nm of the resin layer formed on each substrate for evaluation obtained in the production of the above evaluation substrate and b * were measured by the SCI method of a spectrocolorimeter (manufactured by Konica Minolta, Inc., model number: CM-5) with a measurement diameter of 8 mm. The measurement results are shown in the rows of "reflectance" and b * in Table 1.

[0117] Also, for the above evaluation substrate, using a reflow device (NIS-20-82C manufactured by Aitech Tectron Co., Ltd.), the reflow process was performed once with a maximum temperature of 260°C for 10 seconds. Thereafter, the reflectance and b * were measured in the same manner as above. The measurement results are shown in Table 1 as the reflectance after the heat resistance test and b * after the heat resistance test.

[0118] ΔEab * evaluation ΔEab * is an index indicating the degree of discoloration, which is a value obtained by the following formula (1) using L * , a * , b * before reflow and L * , a * , b * after reflow. It was measured with a spectrophotometer (manufactured by Konica Minolta, Inc., model number: CM-5). The calculation results are shown in the row of ΔEab * in Table 1. ΔEab * = ((ΔL * ) 2 + (Δa * ) 2 + (Δb * ) 2 ) (1 / 2) ···(1)

[0119] Evaluation of solder heat resistance Rosin-based flux was applied to each of the above-obtained evaluation substrates and immersed in a solder bath set at 260°C in advance for 10 seconds. Then, after washing the flux with denatured alcohol, the swelling and peeling of the resin layer were visually evaluated. The evaluation criteria for heat resistance were as follows. a: There was no swelling or peeling in the resin layer after immersion for 10 seconds. b: There was no swelling or peeling in the resin layer after immersion for 5 seconds. c: There was clearly swelling and peeling in the resin layer after immersion for 5 seconds.

[0120] Evaluation of deep hardening (undercut) The photosensitive thermosetting resin compositions of Examples 1 to 13 and Comparative Examples 1 to 5 were screen-printed twice on a copper-plated substrate so that the total film thickness after heat curing was 55 μm to form a coating film. Specifically, the entire surface was coated by screen printing on the copper-plated substrate and dried in a hot air circulation drying oven at 80°C for 10 minutes to form the first layer. The entire surface was further coated by screen printing on the first layer and dried in a hot air circulation drying oven at 80°C for 20 minutes to form the second layer. The formed coating film was pattern-exposed at 400 mJ / cm 2 using an exposure apparatus equipped with a high-pressure mercury lamp (Mms60: manufactured by Okou Seisakusho Co., Ltd.), and developed (at 30°C, 0.2 MPa, 1 mass% aqueous Na2CO3 solution) for 60 seconds. The cross-section of the opening part of the obtained pattern was observed, and the lengths of the upper part (air side) and the lower part (substrate side) were measured. The undercut was calculated by the following formula to evaluate the deep part curability. Undercut = (Length of the upper part - Length of the lower part) / 2

[0121] [Table 1]

[0122] [Table 2]

[0123] As described above, according to the present invention, it can be seen that a photosensitive resin composition with less discoloration after the heating process and capable of maintaining a high reflectance can be provided. In particular, Examples 2 and 4, in which the blending amounts of the oxime ester-based photoinitiator and the titanocene-based photoinitiator are small and the blending amount of the white pigment is larger than that in Example 3, have high reflectance, while the b * value, surface curability, and solder heat resistance are all excellent. This can be considered to be because, for example, due to the synergistic effect of the oxime ester-based photoinitiator and the titanocene-based initiator, the desired characteristics can be exhibited even with a small amount of initiator.

[0124] For Comparative Example 1, a coating film could be formed, but since no firmly formed pattern remained that allowed evaluation of undercut after development, deep part curability could not be evaluated. In Comparative Example 2, since a coating film could not be formed, all evaluation items could not be evaluated. In Comparative Examples 4 and 5, since a resin layer could not be formed at the exposure amounts at which surface curability and deep part curability were evaluated, evaluation was not possible.

[0125] The disclosure of Japanese Patent Application No. 2023-055267 (filing date: March 30, 2023) is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described in this specification are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Claims

1. A photosensitive thermosetting resin composition comprising a carboxyl group-containing resin, a photopolymerization initiator, a white pigment, and a thermosetting resin, The carboxyl group-containing resin has an ethylenically unsaturated double bond in the molecule, The photopolymerization initiator includes an oxime ester-based photopolymerization initiator and a titanocene-based photopolymerization initiator, The oxime ester photopolymerization initiator has a structure in which a partial structure represented by the following formula (I) is substituted with a compound selected from the group consisting of diarylsulfane, 9H-carbazole, thioxanthen-9-one, fluorene, and derivatives thereof: 【Chemistry 1】 (In the formula, R １ represents a hydrogen atom, a phenyl group which may have a substituent, an alkyl group having 1 to 20 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 8 carbon atoms, an alkanoyl group having 2 to 20 carbon atoms, or a benzoyl group which may have a substituent. ２ represents a phenyl group which may have a substituent, an alkyl group having 1 to 20 carbon atoms which may have a substituent, a cycloalkyl group having 5 to 8 carbon atoms, an alkanoyl group having 2 to 20 carbon atoms, or a benzoyl group which may have a substituent. The titanocene-based photopolymerization initiator is a compound represented by the following formula (II): 【Chemistry 2】 (In the formula, R ９ and R １０ each independently represents a halogen atom, an aryl group, a halogenated aryl group, or a heterocycle-containing halogenated aryl group. The white pigment includes titanium oxide, the thermosetting resin includes an epoxy resin, a total content of the oxime ester photopolymerization initiator and the titanocene photopolymerization initiator is, in terms of solid content, 0.01 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the carboxy group-containing resin; The photosensitive thermosetting resin composition was heated at 400 mJ / cm using a high-pressure mercury lamp. ２ The resulting cured product had a film thickness of 55 μm and was then exposed to light at 150° C. for 60 minutes. ＊ a ＊ b ＊ b in color system ＊ The photosensitive thermosetting resin composition has a reflectance of 85% or more at a wavelength of 450 nm.

2. 2. The photosensitive thermosetting resin composition according to claim 1, wherein the content of the white pigment is 200 parts by mass or more and 1000 parts by mass or less based on 100 parts by mass of the carboxyl group-containing resin, calculated as a solid content.

3. 2. The photosensitive thermosetting resin composition according to claim 1, wherein the photopolymerization initiator contains an oxime ester-based photopolymerization initiator and a titanocene-based photopolymerization initiator in a mass ratio ranging from 1:10 to 10:

1.

4. A dry film having a resin layer obtained by applying the photosensitive thermosetting resin composition according to claim 1 to a first film and drying the applied resin layer.

5. A cured product obtained by curing the photosensitive thermosetting resin composition according to claim 1 .

6. An electronic part comprising the cured product according to claim 5 .

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