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

Abstract

To provide a photosensitive thermosetting resin composition capable of forming a solder resist film having excellent surface curability, excellent heat resistance, and high reflectance even at a low exposure dose.SOLUTION: The photosensitive thermosetting resin composition contains a carboxy group-containing resin, a photopolymerization initiator, a white pigment, and a thermosetting resin. The photopolymerization initiator contains an oxime ester-based photopolymerization initiator and a titanocene-based photopolymerization initiator, and the thermosetting resin contains an epoxy resin. A cured product of the photosensitive thermosetting resin composition has a b* value in the L*a*b* color system of 2.0 or less and a reflectance of 85% or more at a wavelength of 450 nm.SELECTED DRAWING: None

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 technology]

[0002] Light-emitting devices are known in which light-emitting diodes (hereinafter sometimes abbreviated as LEDs) are mounted on a printed wiring board. In order to efficiently utilize the light from the LEDs mounted on the printed wiring board, a highly reflective white solder resist film may be formed on the printed wiring board (see, for example, Patent Documents 1, 2, 3, and 4). Furthermore, Patent Document 5 proposes a photocurable thermosetting resin composition containing a photopolymerization initiator that does not contain a phosphorus atom in its molecular structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2008 / 050768 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-134621 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-017010 [Patent Document 4] International Publication No. 2012 / 141124 [Patent Document 5] Japanese Patent Application Laid-Open No. 2013-210443 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one aspect of the present invention is to provide a photosensitive thermosetting resin composition that is excellent in surface curability and heat resistance even at a low exposure dose and that can form a solder resist film with high reflectivity. [Means for solving the problem]

[0005] The present invention encompasses the following aspects: [1] A photosensitive thermosetting resin composition comprising a carboxyl 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 thermal curing of the photosensitive thermosetting resin composition is L * a * b * b in color space * A photosensitive thermosetting resin composition having a reflectance of 85% or more at a wavelength of 450 nm and a value of 2.0 or less.

[0006] [2] The photosensitive thermosetting resin composition according to [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.

[0007] [3] A dry film having a resin layer obtained by applying the photosensitive thermosetting resin composition according to [1] or [2] to a first film and drying the applied resin layer.

[0008] [4] A cured product obtained by curing the photosensitive thermosetting resin composition according to [1] or [2].

[0009] [5] An electronic component comprising the cured product according to [4]. [Effects of the Invention]

[0010] 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 dose and that can form a solder resist film with high reflectivity. DETAILED DESCRIPTION OF THE INVENTION

[0011] As used herein, the term "process" refers not only to an independent process, but also to processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. Furthermore, the content of each component in a composition refers to the total amount of the components present in the composition, unless otherwise specified, when multiple substances corresponding to each component are present in the composition. Furthermore, the solid content refers to the substance remaining after removing volatile components (e.g., organic solvents). Furthermore, the upper and lower limits of the numerical ranges described herein can be arbitrarily selected and combined from the numerical values ​​exemplified as numerical ranges. Below, embodiments of the present invention are described in detail. However, the embodiments described below exemplify photosensitive thermosetting resin compositions, dry films, cured products, and electronic components intended to embody the technical concepts of the present invention. The present invention is not limited to the photosensitive thermosetting resin compositions, dry films, cured products, and electronic components shown below.

[0012] Photosensitive thermosetting resin composition The photosensitive thermosetting resin composition comprises a carboxyl group-containing resin, a photopolymerization initiator, a white pigment, and a thermosetting resin. The photopolymerization initiator comprises at least an oxime ester-based photopolymerization initiator and a titanocene-based photopolymerization initiator. The thermosetting resin comprises at least an epoxy resin. The cured product of the photosensitive thermosetting resin composition after thermal curing is L * a * b * b in color space * The value is 2.0 or less, and the reflectance at a wavelength of 450 nm is 85% or more.

[0013] The photosensitive thermosetting resin composition contains a photopolymerization initiator having a specific structure in combination as a photopolymerization initiator, and thus can form a cured product with excellent surface curability and heat resistance and high reflectivity even at a low exposure dose. It can also suppress discoloration of the cured product due to heat, light, etc. Furthermore, it can form a latent image with high sensitivity and excellent resolution. This can be attributed to, for example, the synergistic effect of the oxime ester photopolymerization initiator and the titanocene photopolymerization initiator. The low exposure dose in the present invention is specifically 600 mJ / cm. 2This refers to the following:

[0014] 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 it with active energy rays. It is preferable that the carboxy group-containing resin have an ethylenically unsaturated double bond as a photosensitive functional group in the molecule in terms of photocurability, development resistance, etc. The ethylenically unsaturated double bond in the molecule may be derived from acrylic acid, methacrylic acid, or a derivative thereof. The photosensitive thermosetting resin composition may contain one carboxy group-containing resin alone, or two or more carboxy group-containing resins in combination. When the photosensitive thermosetting resin composition contains only a carboxy group-containing resin without an ethylenically unsaturated double bond as the carboxy group-containing resin, the photosensitive thermosetting resin composition can be made photocurable by using a compound having multiple ethylenically unsaturated groups in the molecule, i.e., a photopolymerizable monomer, as described below. Specific examples of carboxyl group-containing resins include the following compounds (which may be either oligomers or polymers): Note that, hereinafter, (meth)acrylate is a general term for acrylate, methacrylate, and mixtures thereof, and the same applies to other similar expressions.

[0015] (1) Carboxy group-containing resins obtained by copolymerizing unsaturated carboxylic acids such as (meth)acrylic acid with unsaturated group-containing compounds such as styrene, α-methylstyrene, lower alkyl (meth)acrylates, and isobutylene.

[0016] (2) Carboxy group-containing urethane resins obtained by polyaddition reaction of diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates with carboxy group-containing dialcohol compounds such as dimethylolpropionic acid and dimethylolbutanoic acid, and diol compounds such as polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A alkylene oxide adduct diols, and compounds having phenolic hydroxy groups and alcoholic hydroxy groups.

[0017] (3) Carboxy group-containing photosensitive urethane resins obtained by polyaddition reaction of diisocyanates with partially acid anhydride-modified products of reaction products of bifunctional epoxy resins such as bisphenol A epoxy resins, hydrogenated bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, bixylenol epoxy resins, and biphenol epoxy resins with monocarboxylic acid compounds having ethylenically unsaturated double bonds such as (meth)acrylic acid, carboxy group-containing dialcohol compounds, and diol compounds.

[0018] (4) A carboxyl group-containing photosensitive urethane resin that is (meth)acrylated at the terminal by adding a compound having one hydroxyl group and one or more (meth)acryloyl groups in the molecule, such as a hydroxyalkyl (meth)acrylate, during the synthesis of the resin (2) or (3) described above.

[0019] (5) A carboxyl group-containing photosensitive urethane resin that is (meth)acrylated at the terminal 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 (2) or (3) described above.

[0020] (6) A carboxyl group-containing photosensitive resin obtained by reacting a bifunctional or more polyfunctional (solid) epoxy resin with (meth)acrylic acid and adding a dibasic acid anhydride to the hydroxyl group present in the side chain.

[0021] (7) A carboxyl group-containing photosensitive resin in which the hydroxyl groups of a bifunctional (solid) epoxy resin are further epoxidized with epichlorohydrin to form a multifunctional epoxy resin, which is then reacted with (meth)acrylic acid, and a dibasic acid anhydride is added to the resulting hydroxyl groups.

[0022] (8) Carboxy group-containing polyester resins obtained by reacting a dicarboxylic acid such as adipic acid, phthalic acid, or hexahydrophthalic acid with a bifunctional oxetane resin, and then adding a dibasic acid anhydride such as phthalic anhydride, tetrahydrophthalic anhydride, or hexahydrophthalic anhydride to the resulting primary hydroxyl groups.

[0023] (9) A carboxyl group-containing photosensitive resin obtained by reacting an epoxy compound having multiple 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 then reacting the alcoholic hydroxyl groups of the resulting reaction product with a polybasic acid anhydride, such as maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, or adipic acid.

[0024] (10) A carboxyl group-containing photosensitive resin obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with an alkylene oxide such as ethylene oxide or propylene oxide, reacting the resulting reaction product with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0025] (11) A carboxyl group-containing photosensitive resin obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with a cyclic carbonate compound such as ethylene carbonate or propylene carbonate, reacting the resulting reaction product with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0026] (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 (1) to (11) above.

[0027] Among these, from the viewpoints of suppressing warpage in the cured product, heat resistance, reflectivity, and the like, the carboxyl group-containing resin preferably includes at least one carboxyl group-containing photosensitive urethane resin obtained by a polyaddition reaction between a diisocyanate such as an aliphatic diisocyanate, a branched aliphatic diisocyanate, an alicyclic diisocyanate, or an aromatic diisocyanate, a carboxyl group-containing dialcohol compound such as dimethylolpropionic acid or dimethylolbutanoic acid, and a diol compound such as a polycarbonate polyol, a polyether polyol, a polyester polyol, a polyolefin polyol, an acrylic polyol, a bisphenol A alkylene oxide adduct diol, or a compound having a phenolic hydroxy group and an alcoholic hydroxy group, and which is terminated (meth)acrylated by adding a compound having one hydroxyl group and one or more (meth)acryloyl groups in the molecule, such as a hydroxyalkyl (meth)acrylate, during the synthesis of the urethane resin. More preferably, the carboxy group-containing resin is a carboxy group-containing urethane resin obtained by a polyaddition reaction between an aliphatic diisocyanate such as an aliphatic diisocyanate, a branched aliphatic diisocyanate, or an alicyclic diisocyanate, a carboxy group-containing dialcohol compound, and a diol compound such as a polycarbonate polyol, a polyether polyol, a polyester polyol, a polyolefin polyol, or an acrylic polyol, and may contain at least one carboxy group-containing photosensitive urethane resin that has been terminally (meth)acrylated by adding a hydroxyalkyl (meth)acrylate during the synthesis of the urethane resin.

[0028] From the viewpoint of heat resistance and reflectance of the cured product, it is also preferable that the carboxyl group-containing resin includes at least one type of carboxyl group-containing photosensitive resin obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with an alkylene oxide such as ethylene oxide or propylene oxide, reacting the resulting reaction product with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0029] The acid value of the carboxyl group-containing resin may be, for example, 10 mgKOH / g or more and 150 mgKOH / g or less, and 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 alkaline developability of the photosensitive resin composition is improved. Furthermore, when the acid value is 150 mgKOH / g or less, it becomes easier 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.

[0030] The weight-average molecular weight of the carboxyl group-containing resin may vary depending on the resin skeleton, but may generally be 2,000 to 150,000, preferably 5,000 to 100,000. A weight-average molecular weight of 2,000 or more can improve tack-free performance, resolution, etc. A weight-average molecular weight of 150,000 or less can improve the developability, storage stability, etc. of the photosensitive resin composition. Here, the weight-average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography.

[0031] 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, calculated as solid content. A carboxyl group-containing resin content of 5% by mass or more can improve the coating strength. Furthermore, a carboxyl group-containing resin content of 40% by mass or less can provide an appropriate viscosity for the photosensitive resin composition, improving processability.

[0032] photosensitive compound The photosensitive thermosetting resin composition may further contain at least one photosensitive compound that does not have a carboxy group. Examples of the photosensitive compound include a compound having an ethylenically unsaturated bond. The photosensitive compound may also be a compound having multiple ethylenically unsaturated bonds.

[0033] Specific examples of compounds 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; hexanediol, trimethylolpropane, pentane, methylprop ... Examples of suitable (meth)acrylates include polyhydric (meth)acrylates derived from polyhydric alcohols such as 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 ethylene oxide adducts or propylene oxide adducts of bisphenol A, bisphenol F, and these phenols; and polyhydric (meth)acrylates derived from glycidyl ethers such as glycerin diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, and triglycidyl isocyanurate. Furthermore, examples of suitable (meth)acrylates include, but are not limited to, melamine (meth)acrylates obtained by directly (meth)acrylating polyols such as polyether polyols, polycarbonate diols, hydroxyl-terminated polybutadienes, and polyester polyols, or by urethane (meth)acrylating them via a diisocyanate compound.

[0034] Further examples include epoxy(meth)acrylate resins obtained by reacting (meth)acrylic acid with a multifunctional epoxy resin such as a cresol novolac epoxy resin, and epoxy urethane(meth)acrylate compounds obtained by reacting the hydroxyl groups of the epoxy(meth)acrylate resin with a half-urethane compound of a hydroxyacrylate such as pentaerythritol tri(meth)acrylate and a diisocyanate such as isophorone diisocyanate. Such epoxy(meth)acrylate resins can improve photocurability without reducing dryness to touch.

[0035] The photosensitive compound may contain at least an aromatic group-containing polyvalent (meth)acrylate derived from bisphenol A, bisphenol F, or an ethylene oxide or propylene oxide adduct of these phenols. The photosensitive resin may contain one type of photosensitive compound alone or two or more types in combination.

[0036] 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, relative to 100 parts by mass of the carboxyl group-containing resin, calculated as solid content. When the content is 5 parts by mass or more, the photocurability is improved, and the pattern formability by alkaline development after irradiation with active energy rays tends to be further improved. Furthermore, when the content is 100 parts by mass or less, sufficient solubility in an alkaline aqueous solution after irradiation with active energy rays tends to be obtained, and the strength of the formed coating film tends to be further improved.

[0037] Photopolymerization initiator The photosensitive thermosetting resin composition contains at least an oxime ester-based photopolymerization initiator and a titanocene-based photopolymerization initiator as photopolymerization initiators.

[0038] Oxime ester photoinitiator The oxime ester photopolymerization initiator may be any photopolymerization initiator having an O-acyloxime structure in the molecule, and may be, for example, a photopolymerization initiator containing a partial structure represented by the following formula (I).

[0039] [ka]

[0040] 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 an optionally substituted phenyl group, an optionally substituted alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 5 to 8 carbon atoms, an alkanoyl group having 2 to 20 carbon atoms, or an optionally substituted benzoyl group. 1 or R 2 Examples of the substituents in the phenyl group represented by the formula (I) include an alkyl group having 1 to 6 carbon atoms, a phenyl group, and a halogen atom. The number of substituents in the phenyl group may be 1 to 5. 1 or R 2 The alkyl group represented by R may be linear or branched and may be substituted with one or more hydroxyl groups. At least one of the methylene groups constituting the alkyl group may be substituted with an oxygen atom or a carbonyl group. 1 or R 2 Examples of the substituent in the benzoyl group represented by the formula (I) 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.

[0041] Examples of compounds that can be substituted with the partial structure represented by formula (I) include diarylsulfane, 9H-carbazole, thioxanthen-9-one, fluorene, and derivatives thereof. The partial structure represented by formula (I) may be bonded to these compounds by substituting a hydrogen atom therein, or may be bonded via a carbonyl group.

[0042] Specific examples of the oxime ester photopolymerization initiator containing the partial structure represented by formula (I) include compounds represented by the following formulae (I-1), (I-2), (I-3), etc.

[0043] [ka]

[0044] In formula (I-1), R 11 is R in formula (I) 1 is synonymous with R 12 is R in formula (I) 2 It is synonymous with R. 13 represents a hydrogen atom, a hydroxy group, a carboxy group, a hydroxyalkoxy group, a hydroxyalkoxycarbonyl group, etc. 13 The number of carbon atoms in the hydroxyalkoxy group in the formula (I) may be 1 to 20. n represents 0 or 1.

[0045] [ka]

[0046] In formula (I-2), R 21 is R in formula (I) 1 is synonymous with R 22 and R 24 R each independently 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. 24Examples of the substituent on the phenyl group represented by the formula (I) include an alkyl group having 1 to 18 carbon atoms and an organic group having an acetal bond. 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. 23 When the alkyl group constituting the alkoxycarbonyl group represented by the formula (I) has two or more carbon atoms, it may be substituted with at least one hydroxyl group, and at least one methylene group constituting the alkyl group may be substituted with an oxygen atom.

[0047] [ka]

[0048] In formula (I-3), R 31 is R in formula (I) 1 is synonymous with R 32 is R in formula (I) 2 It is synonymous with 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 the substituent, or the like.

[0049] Specific examples of the oxime ester photopolymerization initiator containing the structural moiety represented by formula (I) include 1-[4-(phenylsulfanyl)phenyl]-1,2-octanedione 2-(O-benzoyloxime), 1-{4-[4-(2-hydroxyethoxy)phenylsulfanyl]phenyl}propane-1,2-dione 2-(O-acetyloxime), 2-(acetyloxyiminomethyl)thioxanthen-9-one, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone 1-(O-acetyloxime), 1-[9-ethyl-6-(2-methyl- Examples of suitable oxime ester photopolymerization initiators include 4-tetrahydrofuranylmethoxybenzoyl)-9H-carbazol-3-yl]ethanone 1-(O-acetyloxime), 1-[9-ethyl-6-{2-methyl-4-(2,2-dimethyl-1,3-dioxolanyl)methoxybenzoyl}-9H-carbazol-3-yl]ethanone 1-(O-acetyloxime), and 1-[4-[3-[4-[[2-(acetyloxy)ethyl]sulfonyl]-2-methylbenzoyl]-6-[1-[(acetyloxy)imino]ethyl]-9H-carbazol]-9-yl]phenyloctanone 1-(O-acetyloxime). These oxime ester photopolymerization initiators may be used alone or in combination of two or more.

[0050] Commercially available oxime ester photopolymerization initiators include ADEKA ARCLES NCI-700, ADEKA ARCLES NCI-730, ADEKA ARCLES NCI-831, and ADEKA ARCLES NCI-930; 1-4-[[4-(2-hydroxyethoxy)phenyl]thio]phenyl]-1,2-propanedione 2-(O-acetyloxime) (manufactured by ADEKA Corporation), DFI-020, and DFI-091 (manufactured by Daito Chemische Co., Ltd.), CGI-325, Irgacure OXE01, and Irgacure OXE02; 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone 1-(O-acetyloxime), Irgacure OXE03, and Irgacure OXE04 (manufactured by BASF Japan Ltd.).

[0051] The content of the oxime ester photopolymerization initiator in the photosensitive thermosetting resin composition may be, for example, 0.01 to 10 parts by mass, preferably 0.02 to 8 parts by mass, and more preferably 0.05 to 5 parts by mass, based on 100 parts by mass of the carboxyl group-containing resin, calculated as solid content. When the content of the oxime ester photopolymerization initiator is 0.01 parts by mass or more, sufficient photocuring can be achieved. Furthermore, when the content is 10 parts by mass or less, a good balance between surface curing and bottom curing tends to be achieved. In one embodiment, the content of the oxime ester photopolymerization initiator may be 3 parts by mass or less, 2 parts by mass or less, or 1 part by mass or less.

[0052] Titanocene photoinitiators Examples of the titanocene photopolymerization initiator include compounds represented by the following formula (II).

[0053] [ka]

[0054] 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.

[0055] Examples of the titanocene photopolymerization initiator represented by 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, and 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-((2-(2-methoxyethyl)-5-methyl-1H-pyrrol-1-yl)methyl)phenyl]titanium Di(pentadienyl)-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-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) 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- 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 di(cyclopentadienyl)-bis[2,6-difluoro-3-(3-(acetylamino)propyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-(4-(pivaloylamino)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,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-(lauroylamino)ethyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(allylmethylsulfonylamino)ethyl)phenyl]titanium, di(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(N-allylmethylsulfonylamino)ethyl)phenyl]titanium, di(cyclopentadienyl) 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. These titanocene photopolymerization initiators may be used alone or in combination of two or more.

[0056] Commercially available titanocene photopolymerization initiators 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).

[0057] The content of the titanocene photopolymerization initiator in the photosensitive thermosetting resin composition may be, for example, 0.01 to 10 parts by mass, preferably 0.02 to 8 parts by mass, and more preferably 0.05 to 5 parts by mass, based on 100 parts by mass of the carboxyl group-containing resin, calculated as solid content. When the content of the titanocene photopolymerization initiator is 0.01 parts by mass or more, sufficient photocuring can be achieved. Furthermore, when the content is 10 parts by mass or less, uneven curing tends to be suppressed. In one embodiment, the content of the titanocene photopolymerization initiator may be 2 parts by mass or less, 1 part by mass or less, or 0.5 parts by mass or less.

[0058] The mass ratio of the oxime ester photopolymerization initiator to the titanocene photopolymerization initiator in the photopolymerization initiator may be, for example, 1:10 to 10:1 (oxime ester photopolymerization initiator:titanocene photopolymerization initiator), preferably 1:8 to 8:1, more preferably 1:5 to 5:1, and even more preferably 1:2 to 2:1. Within the above range, a good balance between surface curability and deep curability can be achieved, enabling the formation of a good pattern.

[0059] The total content of the titanocene photopolymerization initiator and the oxime ester photopolymerization initiator in the photosensitive thermosetting resin composition may be, for example, 0.01 to 10 parts by mass, preferably 0.1 to 2 parts by mass, and more preferably 0.2 to 1 part by mass, in terms of solid content, relative to 100 parts by mass of the carboxyl group-containing resin. When the total content of the titanocene photopolymerization initiator and the oxime ester photopolymerization initiator is 0.01 parts by mass or more, sufficient photocuring can be achieved. Furthermore, when the content is 10 parts by mass or less, uneven curing tends to be suppressed.

[0060] The photopolymerization initiator may further include, in addition to the oxime ester-based photopolymerization initiator and the titanocene-based photopolymerization initiator, a photopolymerization initiator other than the oxime ester-based and titanocene-based photopolymerization initiators. Examples of the other photopolymerization initiator include a benzophenone-based photopolymerization initiator, an acetophenone-based photopolymerization initiator, an aminoacetophenone-based photopolymerization initiator, a benzoin ether-based photopolymerization initiator, a benzyl ketyl-based photopolymerization initiator, an oxime ether-based photopolymerization initiator, an alkylphenone-based photopolymerization initiator, and an acylphosphine oxide-based photopolymerization initiator.

[0061] When the photopolymerization initiator contains another photopolymerization initiator, the content thereof may be, for example, 80% by mass or more and 99% by mass or less, and preferably 90% by mass or less and 97% by mass or less, in terms of solid content, relative to the total mass of the photopolymerization initiator in one embodiment. In another embodiment, the content may be, for example, 10% by mass or less, preferably 1% by mass or less, and more preferably 0.1% by mass or less.

[0062] White pigment The photosensitive thermosetting resin composition contains at least one white pigment. The inclusion of a white pigment can whiten the cured product. Examples of white pigments include zinc oxide, potassium titanate, zirconium oxide, antimony oxide, white lead, zinc sulfide, and lead titanate. From the viewpoints of reflectance and discoloration suppression, the white pigment preferably contains at least titanium oxide. Examples of titanium oxide that can be used include those produced by the sulfuric acid method, the chlorine method, rutile titanium oxide, anatase titanium oxide, and titanium oxide that has been surface-treated with a hydrous metal oxide or an organic compound. Among these titanium oxides, rutile titanium oxide is preferred from the viewpoint of photocatalytic activity. The use of rutile titanium oxide allows for the production of a more stable cured product (e.g., a solder resist film). Specific examples of rutile titanium dioxide include TR-600, TR-700, TR-750, and TR-840 (all manufactured by Fuji Titanium Industry Co., Ltd.), R-550, R-580, R-630, R-820, CR-50, CR-60, and CR-90 (all manufactured by Ishihara Sangyo Kaisha, Ltd.), and KR-270, KR-310, and KR-380 (all manufactured by Titanium Industry Co., Ltd.). Among these rutile titanium dioxides, titanium dioxide whose surface is treated with hydrous alumina or aluminum hydroxide is particularly preferred from the viewpoints of dispersibility in the composition, storage stability, and flame retardancy. The white pigment may be used alone or in combination of two or more.

[0063] The volume average particle size of the white pigment may be, for example, 10 nm to 5 μm, and preferably 100 nm to 1 μm, and is measured as the particle size corresponding to 50% of the cumulative volume from the smallest diameter side in a volume-based cumulative particle size distribution measured, for example, using a laser diffraction particle size distribution analyzer.

[0064] The whiteness of the white pigment may be, for example, not less than 80, and preferably not less than 85. The whiteness is measured, for example, using a spectrophotometer (such as PF10 manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS P8148:2018 "Method for measuring ISO whiteness (diffuse blue light reflectance)."

[0065] The content of the white pigment in the photosensitive thermosetting resin composition may be, for example, 200 to 1,000 parts by mass, preferably 250 to 800 parts by mass, relative to 100 parts by mass of the carboxyl group-containing resin, calculated as solid content. When the content of the white pigment is 200 parts by mass or more, the cured product can achieve sufficient reflectance. When the content is 1,000 parts by mass or less, the viscosity increase of the composition can be suppressed, and the coating and moldability are good, and the brittleness of the cured product tends to be suppressed.

[0066] thermosetting resin The photosensitive thermosetting resin composition contains at least one thermosetting resin. Examples of thermosetting resins that can be used include known and commonly used isocyanate compounds, blocked isocyanate compounds, amino resins, maleimide compounds, benzoxazine resins, carbodiimide resins, cyclocarbonate compounds, epoxy resins, polyfunctional oxetane compounds, and episulfide resins. Among these, the thermosetting resin preferably contains at least one of a plurality of cyclic ether groups and a cyclic thioether group (hereinafter referred to as cyclic (thio)ether groups) in one molecule. Many types of thermosetting components containing these cyclic (thio)ether groups are commercially available, and their structures can impart a variety of properties.

[0067] The thermosetting resin having multiple cyclic (thio)ether groups in the molecule is a compound having multiple groups of at least one type of 3-, 4-, or 5-membered ring cyclic ether group or cyclic thioether group in the molecule, and examples thereof include a compound having multiple epoxy groups in the molecule, i.e., a polyfunctional epoxy compound; a compound having multiple oxetanyl groups in the molecule, i.e., a polyfunctional oxetane compound; and a compound having multiple thioether groups in the molecule, i.e., an episulfide compound.

[0068] Specific examples of polyfunctional epoxy compounds include bisphenol A epoxy resins, hydrogenated bisphenol A epoxy resins, brominated bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, novolac epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, N-glycidyl epoxy resins, bisphenol A novolac epoxy resins, bixylenol epoxy resins, biphenol epoxy resins, chelate epoxy resins, glyoxal epoxy resins, amino group-containing epoxy resins, rubber-modified epoxy resins, dicyclopentadiene phenolic epoxy resins, diglycidyl phthalate resins, heterocyclic epoxy resins, tetraglycidyl xylenoylethane resins, silicone-modified epoxy resins, and ε-caprolactone-modified epoxy resins. Polyfunctional epoxy resins may also be used that incorporate halogen atoms such as chlorine and bromine, or atoms such as phosphorus, into their structures. This can impart flame retardancy, for example. The polyfunctional epoxy resins may be used alone or in combination of two or more.

[0069] 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, and oligomers or copolymers thereof, as well as ethers of oxetane alcohols with novolak resins, poly(p-hydroxystyrene), cardo-type bisphenols, calixarenes, calixresorcinarenes, silsesquioxane, and other resins having a hydroxyl group. Other examples include copolymers of unsaturated monomers having an oxetane ring and alkyl (meth)acrylates.

[0070] An example of the episulfide resin is YL7000 (bisphenol A episulfide resin) manufactured by Mitsubishi Chemical Corporation. Furthermore, using a similar synthesis method, an episulfide resin in which the oxygen atom of the epoxy group of a novolac epoxy resin is replaced with a sulfur atom can also be used.

[0071] The content of the thermosetting resin in the photosensitive thermosetting resin composition may be, for example, 10 to 100 parts by mass, and preferably 20 to 80 parts by mass, relative to 100 parts by mass of the carboxyl group-containing resin, calculated as solid content. When the content of the thermosetting resin is within the above range, the cured product of the photosensitive resin composition has good solder heat resistance, and when used as an insulating protective film for a printed wiring board, various properties, particularly electrical insulation, tend to be good.

[0072] 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, and 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole; amine compounds such as dicyandiamide, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzylamine, 4-methoxy-N,N-dimethylbenzylamine, and 4-methyl-N,N-dimethylbenzylamine; hydrazine compounds such as adipic acid dihydrazide and sebacic acid dihydrazide; and phosphorus compounds such as triphenylphosphine. Commercially available examples include 2MZ-A, 2MA-OK, 2PHZ-PW, and 2P4BHZ-PW (all manufactured by Shikoku Chemical Industry Co., Ltd.; all are trade names of imidazole-based compounds), DBU, DBN, U-CATSA102, and U-CAT5002 (all manufactured by San-Apro Co., Ltd.; all are bicyclic amidine compounds and salts thereof).These are not particularly limited, and any catalyst may be used as long as it is a heat curing catalyst for an epoxy resin or an oxetane compound, or promotes the reaction of at least one of an epoxy group and an oxetanyl group with a carboxy group. Also usable are 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, and 2,4-diamino-6-methacryloyloxyethyl-S-triazine·isocyanuric acid adduct. The single thermal curing catalyst may be used alone or in combination of two or more.

[0073] When the photosensitive thermosetting resin composition contains a thermosetting catalyst, the amount thereof may be, for example, 0.1 parts by mass or more and 20 parts by mass or less, and preferably 0.5 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the thermosetting resin, in terms of solid content.

[0074] The photosensitive thermosetting resin composition may further contain at least one filler selected from the group consisting of inorganic and organic fillers, as needed, to improve properties such as adhesion, hardness, and heat resistance. Examples of inorganic fillers include barium sulfate, calcium carbonate, silicon oxide, amorphous silica, talc, clay, hydrotalcite, and mica powder. Examples of organic fillers include silicon powder, nylon powder, and fluorine powder. Among the above fillers, silica is particularly excellent in terms of low moisture absorption and low volume expansion. Silica may be fused or crystalline, or a mixture thereof. However, silica surface-treated with a coupling agent or the like is particularly preferred, as it can improve electrical insulation. The average particle size of the filler is desirably 25 μm or less, more desirably 10 μm or less, and even more desirably 3 μm or less. When the photosensitive thermosetting resin composition contains a filler, the amount of the filler may be, for example, 150 parts by mass or less, and preferably 50 parts by mass or less, per 100 parts by mass of the carboxyl group-containing resin, calculated as solid content. When the filler amount is within this range, the cured film has good folding resistance.

[0075] The photosensitive thermosetting resin composition may contain additives other than the above components. Examples of such additives include thickeners such as organic bentonite and montmorillonite, at least one of silicone-based, fluorine-based, and polymer-based antifoaming agents and leveling agents, and fiber reinforcements such as glass fiber, carbon fiber, and boron nitride fiber. Furthermore, if necessary, adhesion promoters, thermal polymerization inhibitors, peroxide decomposers, UV absorbers, thiazole-based, triazole-based, and other silane coupling agents, dispersants, antifoaming agents, plasticizers, foaming agents, flame retardants, antistatic agents, antioxidants, antibacterial and antifungal agents, and the like may be added.

[0076] The photosensitive thermosetting resin composition may further contain at least one of a radical scavenger and a peroxide decomposer, as needed. This can suppress functional degradation in the cured product. The radical scavenger and the peroxide decomposer may be so-called antioxidants.

[0077] 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-methylene-bis(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, and 1,3,5-tris(3',5'-di-t-butyl-4-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione; quinone compounds such as methaquinone and benzoquinone; and amine compounds such as bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate and phenothiazine.

[0078] The radical scavenger may be a commercially available product, and examples thereof include ADK STAB (registered trademark) AO-30, ADK STAB AO-330, ADK STAB AO-20, ADK STAB LA-77, ADK STAB LA-57, ADK STAB LA-67, ADK STAB LA-68, and ADK STAB LA-87 (all manufactured by ADEKA CORPORATION), Irganox (registered trademark) 1010, Irganox 1035, Irganox 1076, Irganox 1135, Tinuvin (registered trademark) 111FDL, Tinuvin 123, Tinuvin 144, Tinuvin 152, Tinuvin 292, and Tinuvin 5100 (all manufactured by BASF Japan Ltd.).

[0079] The ultraviolet absorber may be a commercially available product, and examples thereof include Tinuvin PS, Tinuvin 99-2, Tinuvin 109, Tinuvin 384-2, Tinuvin 900, Tinuvin 928, Tinuvin 1130, Tinuvin 400, Tinuvin 405, Tinuvin 460, and Tinuvin 479 (all manufactured by BASF Japan Ltd.).

[0080] The photosensitive thermosetting resin composition may further contain an organic solvent. By containing the organic solvent, each component can be easily dissolved or dispersed. In addition, the viscosity can be easily adjusted to a value suitable for the application method, such as coating. Examples of organic solvents 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 ethylpropionate, 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. The content of the organic solvent may be appropriately determined depending on the desired viscosity, etc.

[0081] The photosensitive thermosetting resin composition can be obtained by dissolving or dispersing the above-mentioned components using a mixer such as a disper, kneader, three-roll mill, or bead mill.

[0082] In one embodiment, the photosensitive thermosetting resin composition includes a photosensitive resin, a photopolymerization initiator, a white pigment, and an epoxy resin. The photosensitive resin includes a carboxyl-containing resin, and the photopolymerization initiator includes an oxime ester photopolymerization initiator and a titanocene photopolymerization initiator. The weight ratio of the white pigment content to the photosensitive resin content may be 1.2 to 5, and the weight ratio of the total content of the oxime ester photopolymerization initiator and the titanocene photopolymerization initiator to the white pigment content may be 0.0004 to 0.002. By keeping the white pigment content within these ranges and the photopolymerization initiator content within these ranges, excellent whiteness and high reflectance at a wavelength of 450 nm can be achieved.

[0083] 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.

[0084] Curing conditions The photosensitive thermosetting resin composition is applied to a substrate so that the film thickness after thermal curing is 55 μm, and then dried at 80° C. for 30 minutes. 2 The film is exposed to light at 1000 K and developed (30°C, 0.2 MPa, 1 mass % Na2CO3 aqueous solution) for 60 seconds, and then thermally cured at 150°C for 60 minutes to obtain a cured product.

[0085] The cured product after thermal curing of the photosensitive thermosetting resin composition is L * a * b * b in color space * The value is 2.0 or less. * The value may be preferably 1.8 or less, more preferably 1.5 or less. * a * b * b in color space * The b value is measured for a cured product having a thickness of 55 μm produced under the above-mentioned production conditions using a spectrophotometer (manufactured by Konica Minolta, Inc., model number: CM-5).* When the value is within the above range, yellowing due to heating tends to be suppressed.

[0086] The cured product also 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 using a spectrophotometer (manufactured by Konica Minolta, Inc., model number: CM-5) in the SCI mode with a measuring diameter of 8 mm for a cured product having a thickness of 55 μm produced under the curing conditions described above. When the reflectance of the cured product is within the above range, the light extraction efficiency of the display improves, and reflected light tends to be more effectively utilized.

[0087] The cured product formed from the photosensitive thermosetting resin composition exhibits excellent heat resistance and can maintain whiteness and reflectance. Specifically, for example, after a single heat treatment (reflow process) at a maximum temperature of 260°C for 10 seconds, the ΔEab * may be, for example, 2.0 or less, and preferably 1.0 or less. * is the L before heat treatment * , a * and b * and L after heat treatment * , a * and b * The difference between ΔL * , Δa * and Δb * This is a value calculated using the following formula (1) and is an index showing the degree of discoloration. ΔEab * =((ΔL * ) 2 +(Δa * ) 2 +(Δb * ) 2 ) (1 / 2) ···(1)

[0088] The decrease in reflectance at a wavelength of 450 nm may be, for example, 5% or less, and preferably 2% or less, where the decrease in reflectance is calculated by subtracting the reflectance (%) measured on the cured product after the heat treatment from the reflectance (%) measured on the cured product before the heat treatment.

[0089] The photosensitive thermosetting resin composition can be applied to a printed circuit board by a method selected from commonly used application methods to form a resin composition layer. It can also be used in various forms and applications, such as dry films and prepregs. Various solvents can be used depending on the application method and application, and in some cases, not only good solvents but also poor solvents can be used.

[0090] The photosensitive thermosetting resin composition can be adjusted to a viscosity suitable for the application method using, for example, an organic solvent, applied to a substrate, and then subjected to volatilization (pre-drying) of the organic solvent contained in the composition at a temperature of approximately 60°C to 100°C to form a tack-free resin composition layer. Examples of application methods include dip coating, flow coating, roll coating, bar coating, screen printing, curtain coating, and spray coating. Alternatively, the photosensitive thermosetting resin composition can be applied to a carrier film, dried, and wound up as a film, which is then laminated onto the substrate to form a resin composition layer. Subsequently, the photosensitive thermosetting resin composition is selectively exposed to active energy rays through a patterned photomask using a contact (or non-contact) method, or directly exposed to a pattern using a laser direct exposure device. The unexposed areas are developed using a dilute alkaline aqueous solution (e.g., a 0.3% to 3% by weight sodium carbonate aqueous solution) to form a resist pattern (pattern image). The exposure conditions are as follows: Furthermore, by heating the resin to a temperature of, for example, about 140°C to 180°C for thermal curing, the carboxy groups (or further the phenolic hydroxy groups) of the carboxy group-containing resin react with the cyclic (thio)ether groups of the thermosetting resin, forming a white cured coating that not only exhibits properties such as adhesion to the substrate, folding resistance, low warpage, resistance to electroless gold plating, solder heat resistance, and electrical insulation, but also achieves a high level of flexibility and high reflectivity in a well-balanced manner, and that suppresses deterioration in reflectivity and whiteness over time.

[0091] Examples of substrates that can be used include printed wiring boards, flexible printed wiring boards, paper-phenolic resin, paper-epoxy resin, glass cloth-epoxy resin, glass-polyimide, glass cloth / nonwoven cloth-epoxy resin, glass cloth / paper-epoxy resin, synthetic fiber-epoxy resin, copper-clad laminates of all grades (e.g., FR-4) made from composites such as fluororesin, polyethylene, PPO, and cyanate ester, polyimide films, PET films, glass substrates, ceramic substrates, and wafer plates. Circuits may be formed on the above-mentioned substrates, and transistors and other components may be formed and mounted on them.

[0092] The volatilization drying carried out after the application of the photosensitive resin composition can be carried out using a hot air circulation drying oven, an IR oven, a hot plate, a convection oven, or the like (a method in which hot air in a dryer equipped with a heat source of an air heating method using steam is brought into countercurrent contact with the support, or a method in which hot air is blown onto the support from a nozzle).

[0093] A photosensitive resin composition is applied to a substrate, and after volatilization and drying, the resulting resin composition layer is exposed to light (irradiated with active energy rays). The exposed portions of the resin composition layer (portions irradiated with active energy rays) are cured.

[0094] Examples of exposure devices used for the above-mentioned active energy ray irradiation include direct imaging devices (for example, laser direct imaging devices that directly draw images with a laser based on CAD data from a computer), exposure devices equipped with a metal halide lamp, exposure devices equipped with a (super) high-pressure mercury lamp, exposure devices equipped with a mercury short arc lamp, and direct imaging devices that use an ultraviolet lamp such as a (super) high-pressure mercury lamp. The active energy ray may be laser light with 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-state laser, etc. The exposure dose may be selected appropriately depending on the film thickness, etc., and is generally 5 mJ / cm. 2 to 800mJ / cm 2 , preferably 5 mJ / cm 2 to 500mJ / cm 2 As the direct imaging device, for example, a device manufactured by Orbotech Japan Co., Ltd. may be used, and any device may be used as long as it emits laser light with a maximum wavelength of 350 nm to 450 nm.

[0095] Examples of the developing method include dipping, showering, spraying, brushing, etc. As the developer, an aqueous alkali solution such as potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, or amines can be used.

[0096] The photosensitive thermosetting resin composition can be used not only by directly applying it to a substrate in liquid form, but also in the form of a dry film having a resin composition layer formed by applying the photosensitive thermosetting resin composition to a film such as polyethylene terephthalate and drying it in advance. An example of using the photosensitive resin composition as a dry film is shown below.

[0097] Dry Film The dry film has a resin composition layer obtained by applying the above-mentioned photosensitive thermosetting resin composition to a film and drying it. 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 a photosensitive thermosetting resin composition to a first film or a second film and drying it. A dry film can be obtained by forming a resin composition layer on a first film and then laminating a second film thereon, or by forming a resin composition layer on a second film and laminating the resulting laminate on the first film.

[0098] The first film is a thermoplastic film such as a polyester film having a thickness of 2 μm to 150 μm. The resin composition layer is formed by uniformly applying a photosensitive thermosetting resin composition to the first film or the second film to a thickness of 10 μm to 150 μm using a blade coater, lip coater, comma coater, film coater, or the like, and then drying. The second film can be a polyethylene film, a polypropylene film, or the like, but preferably has a lower adhesive strength with the resin composition layer than the first film.

[0099] To prepare a protective film (permanent protective film) on a substrate using a dry film, the second film is peeled off, and the resin composition layer and the substrate on which a circuit is formed are superimposed and laminated using a laminator or the like to form a resin composition layer on the substrate on which a circuit is formed. The formed resin composition layer can be exposed, developed, and heat-cured in the same manner as above to form a cured coating film. The first film can be peeled off either before or after exposure.

[0100] Electronic Components The electronic component includes a cured product of the above-mentioned photosensitive thermosetting resin composition. Examples of the electronic component include a printed wiring board and a light source module. 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 patterned 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 include, for example, a silicone resin.

[0101] Other aspects of the present invention include the use of the photosensitive thermosetting resin composition in the production of a dry film or an electronic component, and the photosensitive thermosetting resin composition used in the production of a dry film or an electronic component. [Example]

[0102] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0103] The following materials were prepared as materials for preparing a photosensitive thermosetting resin composition. Carboxy group-containing resin (Synthesis Example 1) Varnish A-1 A reaction vessel equipped with a stirrer, thermometer, and condenser was charged with 2400 g (3 mol) of a polycarbonate diol derived from 1,5-pentanediol and 1,6-hexanediol (TJ5650J, number average molecular weight 800, manufactured by Asahi Kasei Corporation), 603 g (4.5 mol) of dimethylolpropionic acid, and 238 g (2.6 mol) of 2-hydroxyethyl acrylate as a monohydroxy compound. Next, 1887 g (8.5 mol) of isophorone diisocyanate as a polyisocyanate was charged, and the mixture was heated to 60 °C with stirring. The mixture was then stopped, and when the temperature in the reaction vessel began to decrease, the mixture was heated again and continued stirring at 80 °C. The absorption spectrum of the isocyanate group (2280 cm) was measured by infrared absorption spectroscopy. -1 The reaction was terminated after confirming that the saturation gas had disappeared. Carbitol acetate was added so that the solid content was 50% by mass, to obtain varnish A-1. The solid had an acid value of 50 mgKOH / g and a weight-average molecular weight Mw of approximately 17,000.

[0104] (Synthesis Example 2) Varnish A-2 220 g of cresol novolac epoxy resin (DIC Corporation, EPICLON N-695, epoxy equivalent: 220 g / eq.) was placed in a four-neck flask equipped with a stirrer and reflux condenser, and 214 g of carbitol acetate was added and heated to dissolve. Next, 0.1 g of hydroquinone as a polymerization inhibitor and 2.0 g of dimethylbenzylamine as a reaction catalyst were added. The mixture was heated to 95-105°C, and 72 g of acrylic acid was slowly added dropwise. The reaction mixture was allowed to react for 16 hours. The reaction product was cooled to 80-90°C, and 106 g of tetrahydrophthalic anhydride was added. The reaction mixture was allowed to react for 8 hours, cooled, and then discharged. The resulting carboxyl-containing resin varnish A-2 had a solids content of 65%, an acid value of 100 mgKOH / g, and a weight-average molecular weight (Mw) of approximately 3,500.

[0105] photosensitive compound BPE-900: Shin-Nakamura Chemical Co., Ltd.; ethoxylated bisphenol A dimethacrylate

[0106] Photopolymerization initiator Oxime esters ADEKA ARCLES NCI-930: ADEKA Corporation; 1-4-[[4-(2-hydroxyethoxy)phenyl]thio]phenyl]-1,2-propanedione 2-(O-acetyloxime) ADEKA Arcles NCI-730: manufactured by ADEKA Corporation; Irgacure OXE04: BASF Japan Ltd.; Irgacure OXE02: BASF Japan Ltd.; 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone 1-(O-acetyloxime)

[0107] Titanocene JMT-784: Manufactured by Yueyang Jin Maotai Technology Co., Ltd. 5 -2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium

[0108] Alkylphenone Omnirad 184: IGM Japan LLC; 1-hydroxycyclohexyl phenyl ketone

[0109] α-aminoacetophenone Omnirad 379: 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one (manufactured by IGM Japan LLC) Omnirad 907: 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (manufactured by IGM Japan LLC)

[0110] White pigment CR-90: Ishihara Sangyo Kaisha; rutile titanium dioxide

[0111] thermosetting resin jER834: Mitsubishi Chemical Corporation; bisphenol A epoxy resin, epoxy equivalent 250g / eq

[0112] thermosetting catalyst DICY7: Mitsubishi Chemical Corporation; dicyandiamide Wetting and dispersing agents Disperbyk-111: BYK Japan Co., Ltd. Antifoaming agents KS-66: Shin-Etsu Chemical Co., Ltd.; Silicone-based oil compound defoamer

[0113] Preparation of photosensitive resin composition Using each of the obtained varnishes A-1 and A-2, various components shown in Table 1 were blended in the indicated proportions (parts by mass), premixed in a mixer, and then kneaded in a three-roll mill to prepare the photosensitive thermosetting resin compositions of Examples 1 to 13 and Comparative Examples 1 to 5. Values ​​in the tables are parts by mass unless otherwise specified. In Tables 1 and 2, "-" indicates that the component was not added or was not evaluated (because evaluation was not possible).

[0114] The photosensitive thermosetting resin compositions thus obtained in Examples 1 to 13 and Comparative Examples 1 to 5 were evaluated as follows. The results are shown in Tables 1 and 2.

[0115] Fabrication of evaluation board The photosensitive thermosetting resin compositions of Examples 1 to 13 and Comparative Examples 1 to 5 were screen-printed twice onto a copper substrate to form a coating film with a total thickness of 55 μm after thermal curing. Specifically, the composition was screen-printed onto the entire copper substrate and dried for 10 minutes in a hot air circulation oven at 80°C to form a first layer. The first layer was then screen-printed onto the entire surface and dried for 20 minutes in a hot air circulation oven at 80°C to form a second layer. The formed coating film was exposed to an optimal exposure dose using an exposure device (Mms60: manufactured by Oak Manufacturing Co., Ltd.) equipped with a high-pressure mercury lamp, and developed (30°C, 0.2 MPa, 1 wt% NaCO aqueous solution) for 60 seconds. The composition was then thermally cured in a hot air circulation oven at 150°C for 60 minutes to form a resin layer, and an evaluation substrate was prepared. The optimum exposure dose was determined by exposing the dried coating film through a Stouffer 41-step step tablet using an exposure device (Mms60: manufactured by Oak Manufacturing Co., Ltd.) equipped with a high-pressure mercury lamp, and developing it for 60 seconds with a 1% by mass Na2CO3 aqueous solution at a spray pressure of 0.2 MPa and a liquid temperature of 30°C, resulting in a remaining step tablet pattern of 15 to 20 steps.

[0116] Surface hardening evaluation Change the exposure from "optimum exposure" to "400mJ / cm 2 The evaluation substrate was prepared in the same manner as above except that "the surface hardening property was not improved" and the surface of the substrate was visually observed. The evaluation criteria for surface hardening property were as follows: a: The surface was smooth and in good condition. b: Roughness was observed on some parts of the surface. c: Roughness was observed on the entire surface.

[0117] Reflectance evaluation The reflectance at 450 nm and b * The measurement results are shown in Table 1 under "Reflectance" and b * is shown in the row.

[0118] The evaluation substrate was subjected to a reflow process once using a reflow machine (NIS-20-82C manufactured by Atec Techtron Co., Ltd.) at a maximum temperature of 260°C for 10 seconds. After that, the reflectance and b * The measurement results were the reflectance after the heat resistance test and the b * The results are shown in Table 1.

[0119] ΔEab * Rating ΔEab * is the L before reflow * , a * , b * and L after reflow * , a * , b * The value calculated by the following formula (1) using the above formula is an index showing the degree of discoloration. Measurements were made using a spectrophotometer (Konica Minolta, Inc., model number: CM-5). The calculation results are shown in Table 1 as ΔEab * is shown in the row. ΔEab * =((ΔL * ) 2 +(Δa * ) 2 +(Δb * ) 2 ) (1 / 2) ···(1)

[0120] Evaluation of solder heat resistance A rosin-based flux was applied to each evaluation board obtained above, and the board was immersed in a solder bath pre-set to 260°C for 10 seconds. The flux was then washed off with denatured alcohol, and the resin layer was visually evaluated for swelling and peeling. The heat resistance evaluation criteria were as follows: a: After immersion for 10 seconds, the resin layer did not blister or peel. b: After immersion for 5 seconds, the resin layer did not blister or peel. c: After immersion for 5 seconds, the resin layer was clearly blistered and peeled off.

[0121] Deep curability (undercut) evaluation The photosensitive thermosetting resin compositions of Examples 1 to 13 and Comparative Examples 1 to 5 were screen-printed twice on a copper solid substrate to form a coating film with a total film thickness of 55 μm after thermal curing. Specifically, the coating was applied to the entire surface of the copper solid substrate by screen printing and dried for 10 minutes in a hot air circulation drying oven at 80°C to form a first layer, and then another coating was applied to the entire surface of the first layer by screen printing and dried for 20 minutes in a hot air circulation drying oven at 80°C to form a second layer. The formed coating film was exposed to 400 mJ / cm using an exposure device (Mms60: manufactured by Oak Manufacturing Co., Ltd.) equipped with a high-pressure mercury lamp. 2 The pattern was exposed to light at 1000 K and developed (30°C, 0.2 MPa, 1% by mass Na2CO3 aqueous solution) for 60 seconds. The cross section of the opening of the resulting pattern was observed, and the lengths of the top (air side) and bottom (substrate side) were measured. The undercut was calculated using the following formula to evaluate deep curing. Undercut = (Top length - Bottom length) / 2

[0122] [Table 1]

[0123] [Table 2]

[0124] As described above, it can be seen that the present invention can provide a photosensitive resin composition that is less likely to discolor after a heating process and can maintain a high reflectance. In particular, Examples 2 and 4, which contain a small amount of oxime ester photopolymerization initiator and titanocene photopolymerization initiator and a larger amount of white pigment than Example 3, have high reflectance, but b * This is thought to be due to the synergistic effect of the oxime ester photopolymerization initiator and the titanocene photopolymerization initiator, which allows the desired properties to be achieved even with a small amount of initiator.

[0125] In Comparative Example 1, a coating film was formed, but a pattern strong enough to evaluate undercutting was not left after development, so deep curing properties could not be evaluated. In Comparative Example 2, a coating film could not be formed, so all evaluation items could not be evaluated. In Comparative Examples 4 and 5, a resin layer could not be formed at the exposure dose used to evaluate surface curing properties and deep curing properties, so evaluation was not possible.

[0126] 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 herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was 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 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 of the photosensitive thermosetting resin composition after thermal curing is L ＊ a ＊ b ＊ b in the color system ＊ A photosensitive thermosetting resin composition having a reflectance of 85% or more at a wavelength of 450 nm and a value of 2.0 or less.

2. 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.

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

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

5. An electronic part comprising the cured product according to claim 4.

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