Curable resin compositions, dry films, cured products, and printed circuit boards

Abstract

To provide a curable resin composition that, when applied to a dry film, maintains the resolution of the resin layer, prevents crack defects when thermal load is applied to the substrate, and also possesses good coatability without unevenness during coating. [Solution] The curable resin composition of the present invention is an alkali-developable curable resin composition containing (A) an alkali-soluble resin, (B) a photopolymerization initiator, (C) a thermosetting component, (D) an inorganic filler, and (E) a stress relaxant, wherein the maximum peak of the particle size distribution of the curable resin composition is located at 0.1 μm or more and 2.0 μm or less, and there is only one maximum peak, and the (D) inorganic filler contains two or more compounds, each having a maximum peak of a different particle size distribution, and at least one of the two or more (D) inorganic fillers has an (D-1) average particle diameter D50 of 0.3 μm or more and 1.15 μm or less.

Description

Technical Field

[0001] The present invention relates to a curable resin composition, a dry film, a cured product, and a printed wiring board.

Background Art

[0002] In recent years, due to the rapid progress of semiconductor components, electronic devices tend to be miniaturized, lightweight, high-performance, and multifunctional. Along with this, the miniaturization of patterns on printed wiring boards, the high-density mounting of components, and the increase in the number of pins are progressing. Therefore, a curable resin composition for forming a solder resist on a printed wiring board is required to have high resolution (particularly small-diameter aperture property). On the other hand, in the manufacturing process and use of printed wiring boards, since they are loaded by use at high temperatures, thermal stress is generated due to the difference in the coefficient of thermal expansion (CTE) from the base material. In order to cope with such temperature environment changes, the solder resist on the printed wiring board is also required to have resistance to thermal stress (crack resistance) and the like.

[0003] As a method for imparting high reliability, for example, it is generally performed to improve the thermal physical properties by filling an inorganic filler in the composition. Among these inorganic fillers, spherical silica in particular can be easily provided with a surface treatment, has a low coefficient of thermal expansion (CTE), and is widely used for improving the properties of solder resists due to physical properties such as crack resistance, cost, and ease of handling (Patent Documents 1 and 2).

[0004] However, when an inorganic filler such as spherical silica is filled in a curable resin composition, there are problems such as deterioration of the aperture shape due to halation caused by light scattering and occurrence of unevenness and defects during coating due to a decrease in dispersibility, resulting in deterioration of coating properties. Furthermore, in a system containing a plurality of inorganic fillers, the present inventors have found that the tendency is remarkable, the dispersibility decreases due to variations in the particle size distribution, and the coating properties deteriorate. In recent years, in order to improve the physical properties of the resin insulation layer, there has been a tendency to fill inorganic fillers having different particle diameters, so it has become important to achieve both resolution and coating properties.

Prior Art Documents

[0005] [Patent Document 1] International Publication No. 2013 / 161756 [Patent Document 2] Japanese Patent Publication No. 2012-83467 [Overview of the project] [Problems that the invention aims to solve]

[0006] Therefore, the object of the present invention is to provide a curable resin composition that, when applied to a dry film, maintains the resolution of the resin layer, prevents crack defects when a thermal load is applied to the substrate, and also possesses good coatability that prevents unevenness during coating. Furthermore, the object is to provide a dry film having a resin layer obtained from the curable resin composition, a cured product of the resin layer of the curable resin composition or the dry film, and a printed circuit board having the cured product. [Means for solving the problem]

[0007] As a result of diligent research, the inventors have discovered that a curable resin composition containing an inorganic filler having a specific particle size distribution can solve the aforementioned problems, and have completed the present invention. That is, the present invention is as follows.

[0008] [1] An alkali-developable curable resin composition comprising (A) an alkali-soluble resin, (B) a photopolymerization initiator, (C) a thermosetting component, (D) an inorganic filler, and (E) a stress relaxant, The particle size distribution of the curable resin composition has a maximum peak between 0.1 μm and 2.0 μm, and there is only one maximum peak. A curable resin composition characterized in that the (D) inorganic filler contains two or more compounds, each having a maximum peak in a different particle size distribution, and at least one of the two or more (D) inorganic fillers has an (D-1) average particle size D50 of 0.3 μm or more and 1.15 μm or less. [2] The curable resin composition according to [1], wherein the total content of the inorganic filler (D) is 25.0% by mass or more and 75.0% by mass or less on a solid content basis with respect to the total amount of the curable resin composition. [3] The curable resin composition according to [1] or [2], wherein the content of the inorganic filler having an average particle size D50 of 0.3 μm or more and 1.15 μm or less is 15.0% by mass or more and 70.0% by mass or less on a solid content basis with respect to the total amount of the curable resin composition. [4] The curable resin composition according to any one of [1] to [3], wherein the content of the inorganic filler having an average particle size D50 of 0.3 μm or more and 1.15 μm or less is 25.0% by mass or more and 90.0% by mass or less in terms of solid content relative to the total amount of the inorganic filler (D). [5] The curable resin composition according to any one of [1] to [4], wherein the D50 of the inorganic filler having an average particle diameter D50 of 0.3 μm or more and 1.15 μm or less is 0.3 μm or more and 0.9 μm or less. [6] (D-2) A curable resin composition according to any one of [1] to [5], further comprising an inorganic filler having an average particle size D50 of 0.1 μm or more and less than 0.3 μm. [7] The curable resin composition according to [6], wherein the content of the inorganic filler having an average particle size D50 of 0.1 μm or more and less than 0.3 μm is 5.0% by mass or more and 60.0% by mass or less on a solid content basis with respect to the total amount of the curable resin composition. [8] The curable resin composition according to [6] or [7], wherein the amount of inorganic filler having an average particle size D50 of 0.1 μm or more and less than 0.3 μm is 10.0% by mass or more and 75.0% by mass or less on a solid content basis, relative to the total amount of inorganic filler (D). [9] The curable resin composition according to any one of [1] to [8], wherein the (D) inorganic filler comprises at least one silica and barium compound.

[10] The curable resin composition according to any one of [1] to [9], wherein the content of (A) alkali-soluble resin is 15.0% by mass or more and 60.0% by mass or less on a solid content basis with respect to the total amount of the curable resin composition.

[11] The curable resin composition according to any one of [1] to

[10] , wherein the content of the (C) thermosetting component is 5.0% by mass or more and 30.0% by mass or less on a solid content basis with respect to the total amount of the curable resin composition.

[12] The curable resin composition according to any one of [1] to

[11] , wherein the content of the stress-relaxing agent (E) is 1.0% by mass or more and 10.0% by mass or less on a solid content basis with respect to the total amount of the curable resin composition.

[13] A dry film characterized by having a resin layer obtained from any of the curable resin compositions described in [1] to

[12] .

[14] A cured product characterized by being obtained by curing a curable resin composition described in any of [1] to

[12] . A cured product characterized by being obtained by curing the resin layer of the dry film described in

[15]

[13] .

[16]

[14] A printed circuit board comprising the cured material described above.

[17] A printed circuit board having the cured material described in

[15] . [Effects of the Invention]

[0009] The present invention provides a curable resin composition that, when applied to a dry film, achieves both thermal cyclic resistance (TST resistance) and coating properties, and can form a cured product with excellent resolution; a dry film having a resin layer made of the curable resin composition; a cured product of the curable resin composition or the resin layer of the dry film; and a printed circuit board equipped with the cured product. [Modes for carrying out the invention]

[0010] [Curable resin composition] The curable resin composition of the present invention is an alkali-developable curable resin composition containing (A) an alkali-soluble resin, (B) a photopolymerization initiator, (C) a thermosetting component, (D) an inorganic filler, and (E) a stress relaxant, The particle size distribution of the curable resin composition has a maximum peak between 0.1 μm and 2.0 μm, and there is only one maximum peak. The curable resin composition is characterized in that the (D) inorganic filler contains two or more compounds, each having a maximum peak in a different particle size distribution, and at least one of the two or more (D) inorganic fillers has an (D-1) average particle diameter D50 of 0.3 μm or more and 1.15 μm or less. The following describes each component constituting the curable resin composition of the present invention.

[0011] [Particle size distribution of curable resin composition] The curable resin composition of the present invention is characterized in that the maximum peak of the particle size distribution (frequency distribution based on volume) of the curable resin composition is located at 0.1 μm or more and 2.0 μm or less, and there is only one maximum peak. Conventionally, when two or more inorganic fillers, each having different peak maxima, were used, conventional curable resin compositions had two or more peaks in their particle size distribution. On the other hand, in the present invention, by reducing the number of peaks in the particle size distribution of the curable resin composition to one, it is possible to provide a curable resin composition that maintains resolution while preventing crack defects when thermal load is applied to the substrate and possesses good coatability without unevenness during coating. This is not entirely clear, but it can be inferred as follows: If there are two or more peaks in the particle size distribution of the curable resin composition as described above, the dispersion of two or more inorganic fillers is insufficient, and the dispersion state deteriorates due to interactions between fillers composed of different compounds and aggregation of each filler. On the other hand, if there is only one peak in the particle size distribution of the curable resin composition, the dispersion of two or more fillers is sufficient, and even if the filler consists of two or more inorganic fillers with different peak maxima, it is thought that the above-mentioned properties are exhibited because it exists like a group of one type of filler. However, these are merely in the realm of speculation and are not necessarily always the case.

[0012] In this specification, the particle size distribution of the resin composition is the particle size distribution when the powder such as extender pigment contained in the composition is assumed to be a group of powders and the average particle diameter has been determined. The average particle diameter is the value of D50 measured by the laser diffraction method, and as the measuring device for the average particle diameter (D50) by the laser diffraction method, Microtrac MT3300EXII manufactured by Microtrac Bell Co., Ltd. is used. The curable resin composition of the present invention has a maximum peak in the particle size distribution measured using the laser diffraction method located within the range of 0.1 μm or more and 2.0 μm or less, preferably within the range of 0.2 μm or more and 0.9 μm or less, and more preferably within the range of 0.3 μm or more and 0.7 μm or less. If the peak of the curable resin composition is within the above numerical range, a curable resin composition having good coating properties can be provided, which maintains resolution, does not cause crack defects when a heat load occurs on the substrate, and does not cause unevenness during coating.

[0013] In the present invention, the particle size distribution of the curable resin composition is measured using a Microtrac under the following conditions. First, prepare the following equipment and supplies. · Particle size distribution meter: Microtrac MT3300EX manufactured by Nikkiso Co., Ltd. · Circulation device: ASVR manufactured by Nikkiso Co., Ltd. Next, enter the measurement conditions using the following steps: Launch the software included with Microtrac ("Particle Size Distribution Measurement"), proceed from the SET UP screen, and set the time from the measurement condition settings options. Set the Setzero time to 30 sec., the measurement to 30 sec., and the number of measurements to 2. Next, enter the analysis conditions. In the analysis information, set the particle refractive index to 1.46 (fixed value: average value of the refractive index of all inorganic substances), and in the particle characteristics, set the permeability to permeable and the shape to non-spherical. Also, in the solvent information, select PMA and set the solvent refractive index to 1.40. Next, enter the scale settings. In the particle size range, set the minimum particle size to 0.021 μm and the maximum particle size to 2000 μm. Next, enter the sampling system. Set the number of ASVR washes to 4, the flow rate to 50%, the ultrasonic output to 40 W, and the ultrasonic time to 300 sec. After entering all the measurement conditions, press Save in the measurement condition settings to close. Next, measure the sample. Click on "Particle Size Distribution Measurement" in the software included with the Microtrac to open the sample loading screen. Using the dropper, drop a few drops of the prepared sample into the sample inlet of the main unit. When the red indicator bar appears on the sample loading screen, drop more of the prepared sample into the sample inlet until it moves from red to green. Once it moves within the green range, press the measurement button to start the measurement. The sample measurement should be completed within 5 minutes. Check the number of peaks in the particle size distribution measured by the above procedure. In this invention, in a particle size distribution graph, having one peak means having one local maximum, and having two or more peaks means having two or more local maximums.

[0014] In the present invention, the number and position of peaks in the particle size distribution of the curable composition can be adjusted, for example, by changing the dispersion and mixing method of the curable composition, or by changing the particle size and type of each component such as the filler in the curable composition, as well as their content. Preferably, the adjustment can be made by changing the particle size and type of each component such as the filler, as well as their content.

[0015] ((A) Alkali-soluble resin) The curable resin composition of the present invention comprises an alkali-soluble resin. The alkali-soluble resin is not particularly limited, and for example, a carboxyl group-containing resin may be used. As the carboxyl group-containing resin, various conventionally known resins having carboxyl groups in their molecules can be used. By including a carboxyl group-containing resin in the curable resin composition, alkali developability can be imparted to the curable resin composition. In particular, carboxyl group-containing photosensitive resins having an ethylenically unsaturated double bond in their molecules are preferred in terms of photocurability and developability. The ethylenically unsaturated double bond is preferably derived from acrylic acid, methacrylic acid, or their derivatives. When using only carboxyl group-containing resins that do not have an ethylenically unsaturated double bond, it is necessary to use a compound having multiple ethylenically unsaturated groups in its molecule, i.e., a photopolymerizable monomer, as described later, in order to make the composition photocurable. Specific examples of carboxyl group-containing resins include the following compounds (which may be either oligomers or polymers):

[0016] (1) A carboxyl group-containing resin obtained by copolymerization of an unsaturated carboxylic acid such as (meth)acrylic acid with an unsaturated group-containing compound such as styrene, α-methylstyrene, lower alkyl (meth)acrylate, or isobutylene.

[0017] (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 with carboxyl 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 hydroxyl groups and alcoholic hydroxyl groups.

[0018] (3) A partially acid anhydride modified product of a reaction between 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, or biphenol type epoxy resin, and a monocarboxylic acid compound having an ethylenically unsaturated double bond such as (meth)acrylic acid, as well as a carboxyl group-containing photosensitive urethane resin obtained by polyaddition reactions of carboxyl group-containing dialcohol compounds and diol compounds.

[0019] (4) A carboxyl group-containing photosensitive urethane resin obtained 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 of (2) or (3) above, and then (meth)acrylicating the terminal (meth)acrylic.

[0020] (5) A carboxyl group-containing photosensitive urethane resin in which a compound having one isocyanate group and one or more (meth)acryloyl groups in the molecule is added to the resin of (2) or (3) above during synthesis and then (meth)acrylicated at the terminal.

[0021] (6) A carboxyl group-containing photosensitive resin obtained by reacting a bifunctional or polyfunctional (solid) epoxy resin with (meth)acrylic acid and adding a dibasic acid anhydride to the hydroxyl groups present in the side chain.

[0022] (7) A carboxyl group-containing photosensitive resin obtained by reacting a polyfunctional epoxy resin, in which the hydroxyl groups of a bifunctional (solid) epoxy resin are further epoxidized with epichlorohydrin, with (meth)acrylic acid, and then adding a dibasic acid anhydride to the resulting hydroxyl groups.

[0023] (8) A carboxyl group-containing polyester resin obtained by reacting a bifunctional oxetane resin with dicarboxylic acids such as adipic acid, phthalic acid, and hexahydrophthalic acid, and adding dibasic acid anhydrides such as phthalic anhydride, tetrahydrophthalic anhydride, and hexahydrophthalic anhydride to the resulting primary hydroxyl groups.

[0024] (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 group of the resulting reaction product with a polybasic acid anhydride such as maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, or adipic acid.

[0025] (10) A carboxyl group-containing photosensitive resin obtained by reacting a reaction product obtained by reacting a compound having multiple 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.

[0026] (11) A carboxyl group-containing photosensitive resin obtained by reacting a reaction product 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 with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0027] (12) A carboxyl group-containing photosensitive resin obtained by adding a compound having one epoxy group and one or more (meth)acryloyl groups in one molecule to the resins of (1) to (11) above. In this specification, (meth)acrylate is a general term referring to acrylates, methacrylates, and mixtures thereof, and the same applies to other similar expressions.

[0028] The acid value of the carboxyl group-containing resin is preferably in the range of 30 to 150 mg KOH / g, and more preferably in the range of 50 to 120 mg KOH / g. If the acid value of the carboxyl group-containing resin is less than 30 mg KOH / g, alkaline development becomes difficult. On the other hand, if it exceeds 150 mg KOH / g, the dissolution of the exposed areas by the developer progresses, causing the exposed and unexposed areas to dissolve and peel off indiscriminately, making it difficult to draw a normal resist pattern, which is undesirable.

[0029] These carboxyl group-containing resins are not limited to those listed above and may be used individually or in combination of multiple types.

[0030] The alkali-soluble resin content in the curable resin composition is preferably 15.0% by mass or more and 60.0% by mass or less, based on solid content. A content of 15.0% by mass or more improves the strength of the coating film. A content of 60.0% by mass or less results in appropriate viscosity and improved processability. More preferably, the content is 20.0% by mass or more and 50.0% by mass or less.

[0031] ((B) Photopolymerization initiator) Photopolymerization initiators are used to react photosensitive carboxyl group-containing resins or photopolymerizable monomers upon exposure. Any known photopolymerization initiator can be used. A single photopolymerization initiator may be used, or two or more may be used in combination.

[0032] Examples of photopolymerization initiators include bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzoyl)phenylphosphine oxide, and bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phenylphosphine oxide. Sphingoxides, bisacylphosphine oxides such as bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphine methyl ester, 2-methylbenzoyldiphenylphosphine oxide, pivaloylphenylphosphine Monoacylphosphine oxides such as sopropyl esters and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate, 1-hydroxycyclohexylphenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-hydroxy Hydroxyacetophenones such as cy-2-methyl-1-phenylpropan-1-one; Benzoins such as benzoin, benzyl, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, and benzoin n-butyl ether; Benzoin alkyl ethers; Benzophenones such as benzophenone, p-methylbenzophenone, Michlar's ketone, methylbenzophenone, 4,4'-dichlorobenzophenone, and 4,4'-bisdiethylaminobenzophenone;Acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl)-1-[4-(4-morpholinyl)phenyl]-1-butanone-1 Acetophenones such as thioxanthone, N,N-dimethylaminoacetophenone; thioxanthones such as thioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropylthioxanthone; anthraquinone, chloroanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, 2-amylanthraquinone, Anthraquinones such as 2-aminoanthraquinone; ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal; benzoic acid esters such as ethyl-4-dimethylaminobenzoate, 2-(dimethylamino)ethyl benzoate, and p-dimethylbenzoate ethyl ester; 1,2-octanedione, 1-[4-(phenylthio)phenyl]-,2-(O-benzoyloxime)], ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-,1-(O-acetyl Examples include oxime esters such as bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)phenyl)titanium, bis(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1-pyr-1-yl)ethyl)phenyl]titanium, phenyl disulfide 2-nitrofluorene, butyroin, anisoin ethyl ether, azobisisobutyronitrile, tetramethylthiuram disulfide, etc.

[0033] Commercially available α-aminoacetophenone-based photopolymerization initiators include Omnirad 907, 369, 369E, and 379 from IGM Resins. Commercially available acylphosphine oxide-based photopolymerization initiators include Omnirad 819 from IGM Resins. Commercially available oxime ester-based photopolymerization initiators include Irgacure OXE01 and OXE02 from BASF Japan Ltd., N-1919 from ADEKA Corporation, ADEKA Arclus NCI-831 and NCI-831E, and TR-PBG-304 from Changzhou Strong Electronic New Materials Co., Ltd.

[0034] Other examples include carbazole oxime ester compounds described in Japanese Patent Publication No. 2004-359639, Japanese Patent Publication No. 2005-097141, Japanese Patent Publication No. 2005-220097, Japanese Patent Publication No. 2006-160634, Japanese Patent Publication No. 2008-094770, Japanese Patent Publication No. 2008-509967, Japanese Patent Publication No. 2009-040762, and Japanese Patent Publication No. 2011-80036.

[0035] The content of the photopolymerization initiator is preferably 0.1 to 10.0% by mass, and more preferably 1.0 to 7.0% by mass, based on the solid content of the total curable resin composition. When the photopolymerization initiator content is 0.1% by mass or more, the photocurability of the curable resin composition is good, and the properties of the cured product, such as chemical resistance, are also good. On the other hand, when the content is 10.0% by mass or less, light absorption on the surface of the cured product is good, and the deep curing properties do not tend to decrease.

[0036] In combination with the above-mentioned photopolymerization initiator, a photoinitiator, sensitizer, or catalyst may be used. Examples of photoinitiators, sensitizers, or catalysts include benzoin compounds, anthraquinone compounds, thioxanthone compounds, ketal compounds, benzophenone compounds, tertiary amine compounds, and xanthone compounds. In particular, it is preferable to use thioxanthone compounds such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, and 4-isopropylthioxanthone. The inclusion of a thioxanthone compound can improve deep curing properties. These compounds can sometimes be used as photopolymerization initiators, but it is preferable to use them in combination with a photopolymerization initiator. Furthermore, one type of photoinitiator, sensitizer, or catalyst may be used alone, or two or more types may be used in combination.

[0037] These photopolymerization initiators, photoinitiation aids, sensitizers, and catalysts absorb specific wavelengths, which can sometimes lead to reduced sensitivity and cause them to function as UV absorbers. However, they are not used solely for the purpose of improving the sensitivity of curable resin compositions. By absorbing light of specific wavelengths as needed, the photoreactivity of the surface can be increased, changing the line shape and apertures of the resist pattern to vertical, tapered, or reverse tapered shapes, while also improving the accuracy of line width and aperture diameter.

[0038] ((C) Thermosetting component) The curable resin composition of the present invention contains a thermosetting component. Various conventionally known compounds and resins with thermosetting properties can be used as the thermosetting component. The inclusion of a thermosetting component in the curable resin composition is expected to improve its heat resistance. Examples of thermosetting components used in the present invention include isocyanate compounds, blocked isocyanate compounds, amino resins, maleimide compounds, benzoxazine resins, carbodiimide resins, cyclocarbonate compounds, epoxy resins, oxetane compounds, and episulfide resins. The thermosetting component may be used alone or in combination of two or more. Among these, epoxy resins are preferred thermosetting components.

[0039] Examples of epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, hydrogenated bisphenol A type epoxy resin, bisphenol S type epoxy resin, novolac type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin, glycidylamine type epoxy resin, alicyclic epoxy resin, trihydroxyphenylmethane type epoxy resin, bixylenol type or biphenol type epoxy resin, tetraphenyloleethane type epoxy resin, heterocyclic epoxy resin, diglycidyl phthalate resin, tetraglycidyl xylenoylethane resin, glycidyl methacrylate copolymer epoxy resin, cyclohexylmaleimide and glycidyl methacrylate copolymer epoxy resin, and CTBN-modified epoxy resin. These can be used individually or in combination of two or more types depending on the required properties.

[0040] Examples of commercially available epoxy resins include jER(registered trademark) 828, 806, 807, YX8000, YX8034, 834, and YX4000 from Mitsubishi Chemical Corporation; YD-128, YDF-170, ZX-1059, and ST-3000 from Nippon Steel Chemical & Material Corporation; EPICLON(registered trademark) 830, 835, 840, 850, N-730A, N-695, N-860, and N-870 from DIC Corporation; and RE-306 from Nippon Kayaku Co., Ltd. These epoxy compounds may be used individually or in combination of two or more.

[0041] Examples of polyfunctional oxetane compounds include 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, and (3-ethyl-3-oxetanyl)methyl acrylate. Examples include polyfunctional oxetanes such as relates, (3-methyl-3-oxetanyl)methyl methacrylate, (3-ethyl-3-oxetanyl)methyl methacrylate, and their oligomers or copolymers, as well as ethers of oxetane alcohols with resins having hydroxyl groups such as novolac resins, poly(p-hydroxystyrene), cardo-type bisphenols, calixarenes, calixresorcinarenes, or silsesquioxane. Other examples include copolymers of unsaturated monomers having an oxetane ring with alkyl (meth)acrylates.

[0042] The content of the thermosetting component is preferably 5.0% by mass or more and 30.0% by mass or less in terms of solid content relative to the total amount of the curable resin composition. When the content of the thermosetting component is within the above numerical range, a cured product with better developability and superior flexibility, adhesion, and heat resistance can be obtained.

[0043] (Filler) ((D) Inorganic fillers) The curable resin composition of the present invention contains (D) an inorganic filler. The (D) inorganic filler contains two or more compounds, each having a maximum peak in a different particle size distribution, and at least one of the two or more (D) inorganic fillers has a (D-1) average particle diameter D50 of 0.3 μm or more and 1.15 μm or less. The curable resin composition of the present invention may contain only one inorganic filler (hereinafter referred to as "(D-1) inorganic filler") having a (D-1) average particle diameter D50 of 0.3 μm or more and 1.15 μm or less, or it may contain two or more (D-1) inorganic fillers with different average particle diameters D50.

[0044] Furthermore, the curable resin composition of the present invention may further contain an inorganic filler (hereinafter referred to as "(D-2) inorganic filler") having an average particle size D50 of 0.1 μm or more and less than 0.3 μm. The curable resin composition of the present invention may contain only one type of (D-2) inorganic filler, or it may contain two or more types of (D-2) inorganic fillers with different average particle sizes D50.

[0045] (D) The inorganic filler content is preferably 25.0% by mass or more and 75.0% by mass or less, and more preferably 30.0% by mass or more and 50.0% by mass or less, based on the solid content of the entire curable resin composition of the present invention. (D) When the inorganic filler content is within the above numerical range, good resolution and crack resistance can be achieved at the same time.

[0046] (Average particle size of inorganic fillers) The average particle size D50 of the (D-1) inorganic filler used in the present invention is 0.3 μm or more and 1.15 μm or less, preferably 0.3 μm or more and 0.9 μm or less, and more preferably 0.3 μm or more and 0.6 μm or less. (D-1) The content of the inorganic filler is preferably 15.0% by mass or more and 70.0% by mass or less in terms of solid content relative to the total amount of the curable resin composition. Furthermore, the content of (D-1) inorganic filler is preferably 25.0% by mass or more and 90.0% by mass or less in terms of solid content relative to the total amount of (D) inorganic filler. (D-1) When the content of inorganic fillers is within the above numerical range, the particle size distribution of the curable resin composition becomes favorable.

[0047] The average particle size D50 of the (D-2) inorganic filler used in the present invention is preferably 0.1 μm or more and less than 0.3 μm, and more preferably 0.2 μm or more and less than 0.3 μm. (D-2) The inorganic filler content is preferably 5.0% by mass or more and 60.0% by mass or less in terms of solid content relative to the total amount of the curable resin composition. Furthermore, the content of (D-2) inorganic filler is preferably 10.0% by mass or more and 75.0% by mass or less in terms of solid content relative to the total amount of (D) inorganic filler. (D-2) When the content of inorganic fillers is within the above numerical range, the particle size distribution of the curable resin composition becomes favorable.

[0048] In this specification, the average particle size of the inorganic filler refers to the average particle size before it is incorporated into the curable resin composition, and is the D50 value measured by laser diffraction. The Microtrac MT3300EXII manufactured by Microtrac-Bell Corporation is used as the device for measuring the average particle size (D50) by laser diffraction.

[0049] (Types of inorganic fillers) The inorganic filler (D) preferably comprises at least one of silica and barium compounds.

[0050] The silica mentioned above is not particularly limited as long as it is a compound used as an inorganic filler, and examples include amorphous silica, non-crystalline silica, crystalline silica, fused silica, spherical silica, etc. Silica may be used alone or in combination of two or more types. Spherical silica is preferably used as the silica. Examples of commercially available spherical silica include SO-C2, SO-C4, SO-C6 manufactured by Admatex Co., Ltd., and QSG-170 manufactured by Shin-Etsu Chemical Co., Ltd.

[0051] The barium compound is not particularly limited as long as it is a compound used as an inorganic filler, and examples include barium sulfate, barium titanate, barium oxide, and barium hydroxide. The barium compound may be used alone or in combination of two or more. Barium sulfate is preferably used as the barium compound. Examples of commercially available barium sulfate include B-30 and B-33 manufactured by Sakai Chemical Industry Co., Ltd.

[0052] (Surface-treated inorganic filler) The inorganic filler (D) preferably comprises at least one silica and barium compound, and more preferably the silica and barium compound are surface-treated silica and surface-treated barium compound.

[0053] The surface treatment method is not particularly limited, and any known and conventional method may be used, but it is preferable to treat the surface of the inorganic filler with a surface treatment agent having a curable reactive group, for example, a coupling agent having a curable reactive group as an organic group. As coupling agents, silane-based, titanate-based, aluminate-based, and zircoaluminate-based coupling agents can be used. Among these, silane-based coupling agents are preferred. Examples of such silane-based coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, N-(2-aminomethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-anilinopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane, which can be used alone or in combination. It is preferable that these silane-based coupling agents are pre-immobilized on the surface of the filler by adsorption or reaction. Here, the amount of coupling agent treated per 100 parts by mass of silica is preferably 0.5 to 10 parts by mass.

[0054] Any type of silica can be used to constitute the surface-treated silica, including amorphous silica, non-crystalline silica, crystalline silica, fused silica, and spherical silica. One type of silica may be used alone, or two or more types may be used in combination. Spherical silica is preferably used as the silica. Examples of commercially available spherical silica include SO-C2 and SO-E2 from Admatex Co., Ltd., and SFP-20M from Denka Co., Ltd. The particle size of the surface-treated silica is not particularly limited and can be set as appropriate, but for example, it can be 0.1 to 2.00 μm. Preferably, it is 0.1 to 1.0 μm, and more preferably 0.3 to 0.9 μm. By setting the average particle size of the surface-treated silica within this range, good resolution can be obtained.

[0055] Regarding surface-treated barium compounds, the term "barium compound" encompasses a wide range of compounds, including elemental barium and various compounds containing barium. In other words, surface-treated barium compounds include compounds formed by surface-treating elemental barium, and compounds formed by surface-treating barium compounds. Any barium compound can be used as the barium compound constituting the surface-treated barium compound, such as barium sulfate, barium titanate, barium oxide, or barium hydroxide. Barium sulfate is preferably used as the barium compound. The surface-treated barium compound may be used alone or in combination of two or more types. The particle size of the surface-treated barium compound is not particularly limited and can be set as appropriate, but is preferably 0.1 to 1.00 μm, more preferably 0.1 to 0.5 μm. By setting the average particle size of the surface-treated barium compound within this range, good resolution can be obtained.

[0056] The total content of surface-treated barium compound and surface-treated silica in the curable resin composition is preferably 25.0 to 75.0% by mass, more preferably 25.0 to 50.0% by mass, and even more preferably 30.0 to 45.0% by mass, based on the total mass of solids in the curable resin composition. By setting the total content of surface-treated barium compound and surface-treated silica, and their mass ratio based on solids, within this range, good resolution and crack resistance can be achieved simultaneously. Furthermore, the content of the surface-treated barium compound in the curable resin composition is not particularly limited as long as it satisfies the range of the sum of the solid-based content of the surface-treated barium compound and surface-treated silica, and the mass ratio of their solid-based content, but for example, it is 7.0 to 28.0% by mass on a solid-based basis with respect to the total mass of solid content of the curable resin composition.

[0057] The curable resin composition may further contain other fillers in addition to the surface-treated barium compound and surface-treated silica described above. Other fillers may include known inorganic or organic fillers, such as hydrotalcite, talc, and metal oxides such as titanium oxide and aluminum hydroxide to obtain a white appearance and flame retardancy.

[0058] ((E) Stress relaxant) The curable resin composition of the present invention contains a stress-relieving agent. By including a component that acts as a stress-relieving agent having impact resistance, such as a flexible polymer, the aggregation and orientation of the curable resin composition are suppressed, and in particular, developing residue at small diameter openings is reduced. For example, it is preferable to include at least one selected from rubber particles and non-particulate elastomers.

[0059] [rubber particles] Specifically, rubber particles can include silicone rubber particles, acrylic rubber particles, crosslinked acrylonitrile butadiene, crosslinked styrene butadiene rubber particles, and core-shell type rubber particles, from the viewpoint of crack resistance, adhesion, and electrical insulation of the cured product, but core-shell type rubber particles are particularly preferred.

[0060] <Core-shell type rubber particles> Core-shell type rubber particles refer to a multilayer rubber material composed of core layers with different compositions and one or more shell layers covering them. As described later, core-shell type rubber particles achieve good dispersibility while achieving a low modulus of elasticity through the blending of rubber components by composing the core layers with a material that has excellent flexibility and the shell layers with a material that has excellent affinity for other components.

[0061] The core layer is constructed from materials with excellent flexibility. Examples include silicone elastomers, butadiene elastomers, styrene elastomers, acrylic elastomers, polyolefin elastomers, and silicone / acrylic composite elastomers, but it is preferable that the core layer is composed of (meth)acrylate polymers.

[0062] Specifically, the (meth)acrylate polymers that make up the core layer are: • Ethyl acrylate and methyl methacrylate polymer, • Methyl acrylate and methyl methacrylate polymers, • Polymer of 2-ethylhexyl acrylate and methyl methacrylate, • Polymers of butyl acrylate, butyl methacrylate, and methyl methacrylate, • Polymers of 2-ethylhexyl acrylate, methyl acrylate, and methyl methacrylate, • Butyl methacrylate, methyl acrylate, and methyl methacrylate polymers, • Polymers of butyl acrylate, ethyl acrylate, and methyl methacrylate, • Butyl acrylate and methyl methacrylate polymer, • Butyl methacrylate and 2-ethylhexyl acrylate polymer, • Isobutyl acrylate and methyl methacrylate polymer, • Polymers of ethyl acrylate, methyl acrylate, and methyl methacrylate, • Butyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate polymer, • Polymers of butyl methacrylate, ethyl acrylate, and methyl methacrylate, • Butyl acrylate and isobutyl methacrylate polymer, • Polymers of butyl acrylate, ethyl methacrylate, and methyl acrylate, • Polymers of butyl acrylate, methyl acrylate, and methyl methacrylate, • Ethyl acrylate and ethyl methacrylate polymers, • Isobutyl acrylate and octadecyl methacrylate polymer, • Polymers of butyl acrylate, isobutyl methacrylate, and methyl methacrylate, • Polymers of butyl acrylate, methyl acrylate, and octadecyl methacrylate, • Polymers of ethyl acrylate, ethyl methacrylate, and methyl acrylate, • Polymers of butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, and methyl methacrylate. • Polymers of ethyl acrylate, isooctyl acrylate, and methyl methacrylate, • Butyl acrylate and dodecyl methacrylate polymer, • Butyl acrylate, butyl methacrylate, and 2-ethylhexyl acrylate polymers, • Polymer of 2-ethylhexyl acrylate, methyl methacrylate, and octadecyl methacrylate, • Polymers of butyl acrylate, methyl methacrylate, and octadecyl methacrylate, • Dodecyl methacrylate, 2-ethylhexyl acrylate, and tridecyl methacrylate polymer, • Polymers of 2-ethylhexyl acrylate, methyl methacrylate, pentadecyl methacrylate, and tetradecyl methacrylate, • Butyl acrylate, butyl methacrylate, tert-butyl methacrylate, and methyl methacrylate polymers, Examples include polymers of dodecyl methacrylate, ethyl acrylate, methyl methacrylate, and tridecyl methacrylate. The core layer is preferably composed of at least one of the above-mentioned (meth)acrylate polymers.

[0063] On the other hand, the shell layer is made of a material that has excellent affinity for other components. For example, if the curable resin composition contains epoxy resin, it is preferable to use core-shell type rubber particles having a shell layer made of a material with excellent affinity for epoxy resin.

[0064] The core layer is preferably composed of a rubbery polymer with a glass transition temperature of -30°C or lower, while the shell layer is preferably composed of a glassy polymer with a glass transition temperature of 70°C or higher. Such core-shell type rubber particles can be produced by a multi-stage seed emulsion polymerization method consisting of at least two consecutive steps. Alternatively, the seed latex prepared in the first stage can be partially aggregated by solvent coagulation or the like, and then graft polymerization can be performed on top of it to form the shell.

[0065] In the first stage of polymerization, a (meth)acrylate monomer having 2 to 8 C1 of the alkyl group, preferably with a crosslinkable monomer, is polymerized to prepare a rubbery seed polymer with a glass transition temperature of -30°C or lower.

[0066] As crosslinkable monomers, those having two or more double bonds with substantially equal reactivity can be used, such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, butylene glycol diacrylate, butylene glycol dimethacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, hexanediol diacrylate, hexanediol methacrylate, oligoethylene diacrylate, oligoethylene dimethacrylate, and aromatic divinyl monomers such as divinylbenzene, triallyl trimellitic acid, and triallyl isocyanurate. These crosslinkable monomers may be used individually or in combination of two or more, and the amount used is usually selected in the range of 0.01 to 5.0% by mass, preferably 0.1 to 2.0% by mass, based on the total weight of the monomers.

[0067] Furthermore, along with the (meth)acrylate monomer and the crosslinkable monomer, other copolymerizable monomers can be used as desired. Examples of these optional copolymerizable monomers include aromatic vinyl compounds such as styrene, vinyltoluene, and α-methylstyrene; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; and vinylidene cyanide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxybutyl acrylate, 2-hydroxyethyl fumarate, hydroxybutyl vinyl ether, monobutyl maleate, glycidyl methacrylate, and butoxyethyl methacrylate. These may be used individually or in combination of two or more, and the amount used is usually selected within a range of 50.0% by mass or less based on the total weight of the monomers.

[0068] Next, the (meth)acrylate polymer particles obtained in this way are used as the core, and a second stage of emulsion polymerization is performed to form a shell by graft copolymerization using a (meth)acrylate monomer with an alkyl group having 1 to 4 carbon atoms and a crosslinkable monomer. Examples of (meth)acrylate monomers with an alkyl group having 1 to 4 carbon atoms used in this step include ethyl acrylate, n-butyl acrylate, methyl methacrylate, and butyl methacrylate. These may be used individually or in combination of two or more, but methyl methacrylate is particularly preferred among them.

[0069] Furthermore, one or more of the crosslinkable monomers exemplified in the description of the (meth)acrylate polymers forming the core can be selected and used. The amount of this crosslinkable monomer used is usually selected in the range of 0.01 to 10.0% by mass, preferably 0.1 to 5.0% by mass, based on the total weight of the monomers. Furthermore, along with the (meth)acrylate monomer and the crosslinkable monomer, other copolymerizable monomers may be used as desired. These optional copolymerizable monomers can be selected from one or more of those exemplified in the description of the (meth)acrylate polymer forming the core. The amount used is typically selected within a range of 50.0% by mass or less, based on the total weight of the monomers.

[0070] Core-shell type rubber particles obtained by such multi-stage emulsion polymerization can usually be obtained by direct spray drying, resulting in core-shell type rubber particles with excellent dispersibility into resin components such as epoxy resins. These core-shell type rubber particles can be obtained by a multi-stage seed emulsion polymerization method with at least two stages as described above, but in some cases they may be produced by partially agglomerating the seed latex created in the first stage and then performing graft polymerization on top of it. Furthermore, after emulsion polymerization, the latex particles can be coagulated and separated by a salt-breaking method or a freezing method, and the prepared wet cake can be dried in a fluidized bed or similar to obtain aggregated particles.

[0071] In the core-shell type rubber particles obtained in this manner, it is preferable that the content of the constituent material in the core layer is in the range of 20.0 to 80.0% by mass, and the content of the constituent material in the shell layer is in the range of 80.0 to 20.0% by mass.

[0072] Furthermore, the weight-average particle diameter of the core of the core-shell type powder polymer is preferably in the range of 0.1 to 2.0 μm. The core particles may undergo polymerization of the shell component immediately following the polymerization of the core component, or the core particles may be aggregated by solvent coagulation or salting-out coagulation before polymerization for coating with the shell component. There are many known methods for secondary aggregation, and any of them can be used. If the particle diameter of the core particles is less than 0.1 μm, the surface area is larger for the same weight, resulting in poor dispersibility, and the mechanical strength and storage stability of the composition containing the core-shell type powder polymer are significantly reduced. Also, if the particle diameter of the core particles exceeds 2.0 μm, the shear strength and peel strength tend to decrease. In addition, the average thickness of the shell of the core-shell type powder polymer is preferably 50 Å or more. If it is less than 50 Å, the coating of the shell component is insufficient, which causes a decrease in storage stability.

[0073] Core-shell type rubber particles may have curable reactive groups on their surface, which may be thermosetting or photocurable reactive groups. Furthermore, core-shell type rubber particles may have two or more types of curable reactive groups.

[0074] Examples of thermosetting reactive groups include hydroxyl groups, carboxyl groups, isocyanate groups, imino groups, epoxy groups, oxetanyl groups, mercapto groups, methoxymethyl groups, methoxyethyl groups, ethoxymethyl groups, ethoxyethyl groups, and oxazoline groups. Epoxy groups are more preferred. Examples of photocurable reactive groups include vinyl groups, styryl groups, methacrylic groups, and ethylenically unsaturated groups such as acrylic groups.

[0075] The method for introducing curable reactive groups on the surface of rubber particles is not particularly limited, and can be introduced using known and conventional methods. For example, when forming a shell layer around a core layer, a material having curable reactive groups different from the functional groups that polymerize with the core layer can be introduced as a constituent material of the shell layer by polymerizing it with the core layer.

[0076] The rubber particles are preferably of an average particle size of 1 nm to 2 μm, as this does not hinder crosslinking. More preferably, the particle size is 0.05 to 1 μm.

[0077] (Non-particle elastomer) The curable resin composition of the present invention may contain non-particulate elastomers instead of, or in combination with, the above-mentioned rubber particles. As non-particle elastomers, known elastomers such as thermoplastic elastomers can be used. Examples of non-particle elastomers include polyester elastomers, polyurethane elastomers, polyester urethane elastomers, polyamide elastomers, polyesteramide elastomers, acrylic elastomers, and olefin elastomers. Resins obtained by modifying some or all of the epoxy groups of epoxy resins having various skeletons with carboxylic acid-modified butadiene-acrylonitrile rubber at both ends can also be used. Furthermore, epoxy-containing polybutadiene elastomers, acrylic-containing polybutadiene elastomers, hydroxyl-containing polybutadiene elastomers, hydroxyl-containing isoprene elastomers, block copolymers, and the like can also be used. For example, product names include R-45HT, Poly bd HTP-9 (both manufactured by Idemitsu Kosan Co., Ltd.), Epolid PB3600 (manufactured by Daicel Corporation), Denarex R-45EPT (manufactured by Nagase ChemteX Corporation), Toughselenium (manufactured by Sumitomo Chemical Co., Ltd.), Ricon 130, Ricon 131, Ricon 134, Ricon 142, Ricon 150, Ricon 152, Ricon 153, Ricon 154, Ricon 156, Ricon 157, Ricon 100, Ricon 181, Ricon 184, Ricon 130MA8, Ricon 130MA13, Ricon 130MA20, Ricon 131MA5, Ricon 131MA10, Ricon Examples include 131MA17, Ricon 131MA20, Ricon 184MA6, and Ricon 156MA17 (all manufactured by Clay Valley). These non-particle elastomers can be used individually or in combination of two or more types.

[0078] (Polyester polyol) As the non-particle elastomer according to the present invention, for example, a polyester polyol obtained by polycondensation of a polycarboxylic acid and a polyhydric alcohol can be used. The polyester polyol contained in the resin composition of the present invention may be one type or multiple types.

[0079] (Polyhydric carboxylic acid) Examples of polycarboxylic acids include polybasic acids. Specifically, these include malonic acid, succinic acid, succinic anhydride, glutaric acid, adipic acid, azelaic acid, sebacic acid, phthalic acid, phthalic anhydride, hexahydrophthalic anhydride, tetrahydrophthalic anhydride, isophthalic acid, terephthalic acid, nadic anhydride, maleic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, trimellitic acid, trimellitic anhydride, pyromellitic acid, and pyromellitic anhydride, among others. Among these, aliphatic polycarboxylic acids such as succinic acid, adipic acid, and sebacic acid are preferred.

[0080] (Polyhydric alcohol) Examples of polyhydric alcohols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,2-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, cyclohexanediol, bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, glycerin, trimethylolpropane, trimethylolethane, and pentaerythritol, among which 1,2-propylene glycol, 1,4-butylene glycol, and 1,6-hexanediol are preferred.

[0081] In particular, as the polyester polyol used as the elastomer according to the present invention, an aliphatic polyester polyol, which is a polycondensate of an aliphatic polycarboxylic acid and an aliphatic polyol, is preferred because it yields a fiber-reinforced composite material with high mechanical properties. In particular, an aliphatic polyester polyol using succinic acid, adipic acid, or sebacic acid as the aliphatic polycarboxylic acid and 1,2-propylene glycol, 1,4-butylene glycol, or 1,6-hexanediol as the aliphatic polyol is more preferred because it yields a fiber-reinforced composite material with high 90° bending strength.

[0082] The weight-average molecular weight of the polyester polyol is preferably 40,000 or less, more preferably 20,000 or less, and even more preferably 10,000 or less, from the viewpoint of developability. For example, product names include Polylight OD-X-2068 and OD-X-3100 (both polyester polyols manufactured by DIC Corporation).

[0083] The stress relaxation agent may be used alone or in combination of two or more types. The stress-relaxing agent content is preferably 0.1% to 10.0% by mass, more preferably 1.0% to 5.0% by mass, and even more preferably 1.5% to 4.0% by mass, based on the solid content of the total curable resin composition. When the stress-relaxing agent content is within the above numerical range, it is possible to provide a curable resin composition that maintains resolution, does not develop crack defects when thermal load is applied to the substrate, and possesses good coatability without unevenness during coating. This is presumed to be because the stress-relaxing agent suppresses aggregation and orientation of the curable resin composition, but this is merely a presumption and is not necessarily the case.

[0084] (Photopolymerizable monomer) The curable resin composition of the present invention may contain a photopolymerizable monomer. In the present invention, a photopolymerizable monomer is a photopolymerizable monomer having one or more ethylenically unsaturated double bonds in one molecule. By including a photopolymerizable monomer, the crosslinking density during photopolymerization of the curable resin composition is increased, and the heat resistance of the curable resin composition and the chemical resistance of the cured product can be improved. Examples of such photopolymerizable monomers include conventionally known polyester (meth)acrylates, polyether (meth)acrylates, urethane (meth)acrylates, carbonate (meth)acrylates, epoxy (meth)acrylates, etc. Specifically, alkyl acrylates such as 2-ethylhexyl acrylate and cyclohexyl acrylate; hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; mono- or diacrylates of alkylene oxide derivatives such as ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol; acrylamides such as N,N-dimethylacrylamide, N-methylolacrylamide, and N,N-dimethylaminopropylacrylamide; aminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate and N,N-dimethylaminopropyl acrylate; and polyacrylates such as hexanediol, trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, and trishydroxyethyl isocyanurate. Polyvalent acrylates derived from hydrogenic alcohols or their alkylene oxide adducts or ε-caprolactone adducts; polyvalent acrylates such as phenoxyacrylate, bisphenol A diacrylate, phenols, or their alkylene oxide adducts; acrylates derived from glycidyl ethers such as glycerin diglycidyl ether, trimethylolpropane triglycidyl ether, and triglycidyl isocyanurate; and, not limited to the above, acrylates obtained by directly acrylateting polyols such as polyether polyols, polycarbonate diols, hydroxyl-terminated polybutadienes, and polyester polyols, or by urethane acrylates via diisocyanates, as well as melamine acrylate and at least one of each methacrylate corresponding to the acrylates, can be appropriately selected and used. Such photopolymerizable monomers can also be used as reactive diluents. Photopolymerizable monomers can be used individually or in combination of two or more.

[0085] If photopolymerizable monomers are present, the content is preferably 10.0% by mass or less on a solids basis relative to the total amount of the curable resin composition. When the content of photopolymerizable monomers is within the above numerical range, the developability and resolution of the curable resin composition tend to improve more easily.

[0086] (Hardening agent) Examples of curing agents 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 sebacate dihydrazide; and phosphorus compounds such as triphenylphosphine. Furthermore, commercially available examples include 2MZ-A, 2MZ-OK, 2PHZ, 2P4BHZ, and 2P4MHZ (all trade names for imidazole compounds) manufactured by Shikoku Chemicals, Inc., and U-CAT 3513N (trade name for a dimethylamine compound), DBU, DBN, and U-CAT SA 102 (all bicyclic amidine compounds and their salts) manufactured by Sunapro Co., Ltd. In particular, it is not limited to these, and any curing agent for epoxy resins or oxetane compounds, or any agent that promotes the reaction between at least one of an epoxy group and an oxetanyl group and a carboxyl group will suffice, and it may be used alone or in combination of two or more.

[0087] Furthermore, 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 can also be used, and preferably these compounds that also function as adhesion imparters are used in combination with the curing agent. The curing agent may be used alone or in combination of two or more types.

[0088] The curing agent content is preferably 0.1 to 8.0% by mass, and more preferably 0.3 to 5.0% by mass, based on the solid content of the total curable resin composition.

[0089] (Coloring agent) The curable resin composition of the present invention may contain a coloring agent. The coloring agent is not particularly limited, and known coloring agents such as red, blue, green, and yellow can be used. It may be a pigment, dye, or colorant, but from the viewpoint of reducing environmental impact and minimizing effects on the human body, a halogen-free coloring agent is preferred.

[0090] Red colorants include monoazo, disazo, azolake, benzimidazolon, perylene, diketopyrrolopyrrole, condensed azo, anthraquinone, and quinacridone, and specifically those that are assigned a color index (CI; issued by The Society of Dyers and Colorists) number, as follows:

[0091] Examples of monoazo-based red colorants include Pigment Red 1, 2, 3, 4, 5, 6, 8, 9, 12, 14, 15, 16, 17, 21, 22, 23, 31, 32, 112, 114, 146, 147, 151, 170, 184, 187, 188, 193, 210, 245, 253, 258, 266, 267, 268, and 269. Examples of disazo-based red colorants include Pigment Red 37, 38, and 41. Examples of monoazolake-based red colorants include Pigment Red 48:1, 48:2, 48:3, 48:4, 49:1, 49:2, 50:1, 52:1, 52:2, 53:1, 53:2, 57:1, 58:4, 63:1, 63:2, 64:1, and 68. Examples of benzimidazolone-based red colorants include Pigment Red 171, 175, 176, 185, and 208. Examples of perylene-based red colorants include Solvent Red 135, 179, Pigment Red 123, 149, 166, 178, 179, 190, 194, and 224. Examples of diketopyrrolopyrrole-based red colorants include Pigment Red 254, 255, 264, 270, and 272. Examples of condensed azo-based red colorants include Pigment Red 220, 144, 166, 214, 220, 221, and 242. Examples of anthraquinone-based red colorants include Pigment Red 168, 177, 216, Solvent Red 52, 149, 150, and 207. Examples of quinacridone-based red colorants include Pigment Red 122, 202, 206, 207, and 209.

[0092] Blue colorants include phthalocyanine-based and anthraquinone-based compounds, while pigment-based compounds include those classified as pigments, such as Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, and 60. Dyes such as Solvent Blue 35, 63, 67, 68, 70, 83, 87, 94, 97, 122, and 136 can be used. In addition to the above, metal-substituted or unsubstituted phthalocyanine compounds can also be used.

[0093] Examples of yellow colorants include monoazo, disazo, condensed azo, benzimidazolon, isoindolinone, and anthraquinone. For example, anthraquinone yellow colorants include Solvent Yellow 163, Pigment Yellow 24, 108, 193, 147, 199, and 202. Isoindolinone yellow colorants include Pigment Yellow 110, 109, 139, 179, and 185. Condensed azo yellow colorants include Pigment Yellow 93, 94, 95, 128, 155, 166, and 180. Benzimidazolon yellow colorants include Pigment Yellow 120, 151, 154, 156, 175, and 181. Examples of monoazo-based yellow colorants include Pigment Yellow 1, 2, 3, 4, 5, 6, 9, 10, 12, 61, 62, 62:1, 65, 73, 74, 75, 97, 100, 104, 105, 111, 116, 167, 168, 169, 182, 183, etc. Examples of disazo-based yellow colorants include Pigment Yellow 12, 13, 14, 16, 17, 55, 63, 81, 83, 87, 126, 127, 152, 170, 172, 174, 176, 188, 198, etc.

[0094] Other colorants such as purple, orange, brown, black, and white may be added. Specifically, examples include Pigment Black 1, 6, 7, 8, 9, 10, 11, 12, 13, 18, 20, 25, 26, 28, 29, 30, 31, 32, Pigment Violet 19, 23, 29, 32, 36, 38, 42, Solvent Violet 13, 36, CIPigment Orange 1, 5, 13, 14, 16, 17, 24, 34, 36, 38, 40, 43, 46, 49, 51, 61, 63, 64, 71, 73, Pigment Brown 23, 25, carbon black, titanium dioxide, etc.

[0095] The colorant content in the curable resin composition is not particularly limited, but it can be 0.1% to 2.0% by mass, preferably 0.3% to 1.5% by mass, on a solid content basis, relative to the entire curable resin composition.

[0096] [Organic solvents] The curable resin composition of the present invention may contain organic solvents for purposes such as preparing the composition or adjusting its viscosity when applying it to a substrate or film. As organic solvents, known and commonly used organic solvents can be used, such as ketones like methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons like toluene, xylene, and tetramethylbenzene; glycol ethers like cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, diethylene glycol monomethyl ether acetate, and tripropylene glycol monomethyl ether; esters like ethyl acetate, butyl acetate, butyl lactate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and propylene carbonate; aliphatic hydrocarbons like octane and decane; and petroleum-based solvents such as petroleum ether, petroleum naphtha, and solvent naphtha. These organic solvents can be used individually or in combination of two or more.

[0097] The content of the organic solvent is not particularly limited and can be appropriately set according to the desired viscosity to facilitate the preparation of the curable resin composition.

[0098] [Other additives] The curable resin composition of the present invention may optionally further contain components such as cyanate compounds, mercapto compounds, urethane catalysts, thixonating agents, adhesion promoters, block copolymers, chain transfer agents, polymerization inhibitors, copper damage inhibitors, antioxidants, rust inhibitors, thickeners such as organic bentonite and montmorillonite, defoaming agents and leveling agents such as silicone-based, fluorine-based, and polymer-based agents, silane coupling agents such as imidazole-based, thiazole-based, and triazole-based agents, and flame retardants such as phosphinates, phosphate ester derivatives, and phosphazene compounds. These components may be those known in the field of electronic materials.

[0099] [Method for producing a curable resin composition] The curable resin composition of the present invention can be prepared by weighing and blending each component, followed by pre-mixing with a stirrer. Subsequently, the components are dispersed in a kneader and kneaded.

[0100] Examples of the above-mentioned kneaders include bead mills, ball mills, sand mills, three-roll mills, and two-roll mills. Among these, a bead mill is preferable for improving dispersibility. The dispersion conditions, such as the type and particle size of the beads in the bead mill, can be appropriately set according to the desired viscosity.

[0101] [Application] The curable resin composition of the present invention is useful for forming pattern layers as permanent coatings on printed circuit boards, and is also useful for forming solder resists, coverlays, interlayer insulating layers, redistribution layers, and the like. Furthermore, since the curable resin composition of the present invention can form cured products with excellent film strength even in thin films, it can be suitably used for forming pattern layers in printed circuit boards where thinness is required, such as package substrates (printed circuit boards used in semiconductor packages). Furthermore, the curable resin composition of the present invention can be used not only for applications that form a patterned layer, but also for applications that do not form a patterned layer, such as molding applications (sealing applications).

[0102] [Dry film] The curable resin composition of the present invention can also be in the form of a dry film comprising a first film and a resin layer consisting of a dried coating film of the curable resin composition formed on the first film. In the present invention, the first film refers to a film that is at least adhered to the resin layer when it is laminated onto a substrate such as a substrate by heating or the like so that the resin layer side of the dry film formed on the curable resin layer is in contact with the substrate. The first film may be peeled off from the resin layer in a process after lamination. In particular, in the present invention, it is preferable to peel it off from the resin layer in a process after exposure. When forming a dry film, the curable resin composition of the present invention is diluted with the above organic solvent to adjust to an appropriate viscosity, and applied to the first film to a uniform thickness using a comma coater, blade coater, lip coater, rod coater, squeeze coater, reverse coater, transfer roll coater, gravure coater, spray coater, etc., and usually dried at a temperature of 50 to 130°C for 1 to 30 minutes to obtain a film. There are no particular restrictions on the coating film thickness, but generally, the film thickness after drying is appropriately selected within the range of 1 to 150 μm, preferably 5 to 60 μm.

[0103] The first film can be any known film without particular limitations, and for example, films made of thermoplastic resins such as polyester films (polyethylene terephthalate, polyethylene naphthalate, etc.), polyimide films, polyamide-imide films, polypropylene films, and polystyrene films can be suitably used. Among these, polyester films are preferred from the viewpoint of heat resistance, mechanical strength, and ease of handling. Laminates of these films can also be used as the first film.

[0104] Furthermore, from the viewpoint of improving mechanical strength, the thermoplastic resin film described above is preferably a film stretched in one or two axes.

[0105] The thickness of the first film is not particularly limited, but can be, for example, 10 μm to 150 μm.

[0106] After forming a resin layer consisting of a dried coating of the curable resin composition of the present invention on the first film, it is preferable to further laminate a peelable second film onto the surface of the resin layer for purposes such as preventing dust from adhering to the surface of the resin layer. In the present invention, the second film refers to a film that is peeled off from the resin layer before lamination when integrally forming by lamination by heating or the like on a substrate such as a substrate so that the resin layer side of the dry film is in contact with it. Examples of peelable second films include polyethylene film, polytetrafluoroethylene film, polypropylene film, surface-treated paper, etc., and it is sufficient that the adhesive force between the resin layer and the second film is less than the adhesive force between the resin layer and the first film when the second film is peeled off.

[0107] The thickness of the second film is not particularly limited, but can be, for example, 10 μm to 150 μm.

[0108] [Cured product] The cured product of the present invention is obtained by curing the curable resin composition of the present invention described above, or the resin layer of the dry film of the present invention described above. Manufacturing conditions such as curing conditions will be described later in [Method for Manufacturing Printed Wiring Boards]. The cured product of the present invention can be suitably used in printed wiring boards, electronic components, and the like.

[0109] [Printed wiring board] The printed circuit board of the present invention comprises a circuit board and a cured product obtained from a resin layer of the curable resin composition or dry film of the present invention.

[0110] The above-mentioned substrates include printed circuit boards and flexible printed circuit boards with circuits pre-formed using copper, etc., as well as copper-clad laminates for high-frequency circuits using materials such as paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth / nonwoven fabric epoxy, glass cloth / paper epoxy, synthetic fiber epoxy, fluororesin / polyethylene / polyphenylene ether, polyphenylene oxide / cyanate, etc., and can be described as copper-clad laminates of all grades (FR-4, etc.), as well as metal substrates, polyimide films, polyethylene terephthalate films, polyethylene naphthalate (PEN) films, glass substrates, ceramic substrates, wafers, etc.

[0111] [Manufacturing method for printed circuit boards] As a method for manufacturing printed circuit boards according to the present invention, for example, the curable resin composition of the present invention is adjusted to a viscosity suitable for the coating method using the above-mentioned organic solvent, and then coated onto a substrate by methods such as dip coating, flow coating, roll coating, bar coating, screen printing, or curtain coating. After that, the organic solvent contained in the composition is evaporated and dried (pre-dried) at a temperature of 60 to 100°C for 15 to 90 minutes to form a tack-free resin layer. There are no particular restrictions on the coating film thickness, but generally, the film thickness after drying is appropriately selected in the range of 1 to 150 μm, preferably 5 to 60 μm. In the case of a dry film, the resin layer is bonded to the substrate using a laminator or the like so that the resin layer is in contact with the substrate, thereby forming a resin layer on the substrate.

[0112] The dry film is preferably laminated onto the substrate under pressure and heat using a vacuum laminator or the like. By using such a vacuum laminator, even if the circuit-formed substrate has irregularities on its surface, the dry film adheres closely to the circuit board, preventing the inclusion of air bubbles and improving the ability to fill in depressions on the substrate surface. The pressure is preferably around 0.1 to 2.0 MPa, and the heating is preferably around 40 to 120°C.

[0113] The volatilization drying performed after applying the curable resin composition of the present invention onto a substrate can be carried out using a hot air circulation drying oven, an IR oven, a hot plate, a convection oven, etc. (a method in which hot air in the dryer is brought into countercurrent contact using a heat source equipped with a steam-heated air heating method, and a method in which hot air is blown onto the support from a nozzle). Examples of such equipment include the DF610 manufactured by Yamato Scientific Co., Ltd. as a hot air circulation drying oven.

[0114] After forming a resin layer on the substrate, it is selectively exposed with active energy rays through a photomask with a predetermined pattern, and the unexposed areas are developed with a dilute alkaline aqueous solution (for example, a 0.3-3.0% by mass sodium carbonate aqueous solution) to form the pattern of the cured product. In the case of a dry film, after exposure, the first film is peeled off from the dry film and developed to form a patterned cured product on the substrate. However, within the limits that do not impair the properties, the first film may be peeled off from the dry film before exposure, and the exposed resin layer may be exposed and developed.

[0115] The exposure machine used for the above-mentioned active energy ray irradiation can be any device equipped with a high-pressure mercury lamp, ultra-high-pressure mercury lamp, metal halide lamp, mercury short-arc lamp, etc., that irradiates ultraviolet light in the range of 350 to 450 nm. Furthermore, a direct writing device (for example, a laser direct imaging device that directly draws images with a laser using CAD data from a computer) can also be used. The lamp light source or laser light source of the direct writing device can have a maximum wavelength in the range of 350 to 450 nm. The exposure amount for image formation varies depending on the film thickness, etc., but is generally 10 to 1,000 mJ / cm². 2 Preferably 20-800 mJ / cm² 2 It can be within the range of

[0116] The above-mentioned development method can be the dipping method, shower method, spray method, brush method, etc., and alkaline aqueous solutions such as potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, and amines can be used as the developing solution.

[0117] Furthermore, the cured material may be irradiated with active energy rays and then heat-cured (for example, at a temperature of 100-220°C for 30-90 minutes), or irradiated with active energy rays after heat curing (for example, 1,000-2,000 mJ / cm²). 2 Alternatively, by performing final finishing curing (main curing) solely through heat curing, a cured product with excellent properties such as adhesion and hardness is formed. Examples of equipment include the QRM-2082 manufactured by Oak Manufacturing Co., Ltd., which is a UV conveyor using a high-pressure mercury lamp. [Examples]

[0118] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following, "parts" and "%" all refer to mass on a solid content basis unless otherwise specified.

[0119] (Example of synthesis: alkali-soluble resin) In a flask equipped with a condenser and stirrer, 456 parts bisphenol A, 228 parts water, and 649 parts 37% formalin were charged. The temperature was maintained below 40°C, and 228 parts of 25% sodium hydroxide aqueous solution were added. After the addition was complete, the mixture was reacted at 50°C for 10 hours. After the reaction was complete, the mixture was cooled to 40°C and neutralized to pH 4 with 37.5% phosphoric acid aqueous solution while maintaining the temperature below 40°C. The mixture was then allowed to stand, and the aqueous layer was separated. After separation, 300 parts methyl isobutyl ketone was added and dissolved uniformly. The mixture was then washed three times with 500 parts distilled water, and water, solvent, etc., were removed under reduced pressure at a temperature below 50°C. The obtained polymethylol compound was dissolved in 550 parts methanol to obtain 1230 parts methanol solution of the polymethylol compound. A portion of the obtained methanol solution of the polymethylol compound was dried in a vacuum dryer at room temperature, and the solid content was 55.2%. 500 parts methanol solution of the obtained polymethylol compound and 440 parts 2,6-xylenol were charged and uniformly dissolved at 50°C. After uniform dissolution, methanol was removed under reduced pressure at a temperature below 50°C. Then 8 parts oxalic acid was added and the mixture was reacted at 100°C for 10 hours. After the reaction was complete, the distillate was removed under reduced pressure at 180°C and 50 mmHg to obtain 550 parts novolac resin A. Furthermore, 130 parts of the above novolac resin A, 2.6 parts 50% sodium hydroxide aqueous solution, and 100 parts toluene / methyl isobutyl ketone (mass ratio = 2 / 1) were charged into an autoclave equipped with a thermometer, a nitrogen introduction device / alkylene oxide introduction device, and a stirring device. The system was purged with nitrogen while stirring, and then heated to 150°C and 8 kg / cm³. 2 Then, 45 parts of ethylene oxide were gradually introduced and the reaction was carried out. The reaction was carried out at a gauge pressure of 0.0 kg / cm². 2The reaction was continued for approximately 4 hours until the reaction reached a certain point, after which it was cooled to room temperature. 3.3 parts of 36% hydrochloric acid aqueous solution were added to this reaction solution and mixed to neutralize the sodium hydroxide. The neutralization reaction product was diluted with toluene, washed three times with water, and desolvented using an evaporator to obtain an ethylene oxide adduct of novolac resin A with a hydroxyl value of 175 g / eq. This adduct contained an average of 1 mole of ethylene oxide per equivalent of phenolic hydroxyl groups. 175 parts of the ethylene oxide adduct of novolac resin A obtained in this way, 50 parts of acrylic acid, 3.0 parts of p-toluenesulfonic acid, 0.1 parts of hydroquinone monomethyl ether, and 130 parts of toluene were charged into a reactor equipped with a stirrer, thermometer, and air blowing tube. The mixture was stirred while blowing air into it, the temperature was raised to 115°C, and the reaction was continued for another 4 hours while distilling off the water produced by the reaction as an azeotropic mixture with toluene, after which it was cooled to room temperature. The resulting reaction solution was washed with a 5% NaCl aqueous solution, and toluene was removed by vacuum distillation. Diethylene glycol monoethyl ether acetate was then added to obtain an acrylate resin solution with a solid content of 68%. Next, 312 parts of the obtained acrylate resin solution, 0.1 part of hydroquinone monomethyl ether, and 0.3 parts of triphenylphosphine were charged into a four-necked flask equipped with a stirrer and reflux condenser. This mixture was heated to 110°C, 45 parts of tetrahydrophthalic anhydride were added, and the mixture was reacted for 4 hours. After cooling, an alkali-soluble resin solution with a solid content of 70% and a solid content acid value of 65 mg KOH / g was obtained.

[0120] [Method for preparing a curable resin composition] For each example and comparative example of a curable resin composition, the various components listed in Table 1 were blended in the proportions (parts by mass) shown in the table. After pre-mixing with a stirrer, the mixture was kneaded in a bead mill to prepare the curable resin composition. The amounts of each component in Table 1 are listed in terms of solid content by mass.

[0121] [Table 1]

[0122] The amounts in Table 1 are shown in parts by mass (based on solid content). The details of each component in Table 1 are as follows: *1: Alkali-soluble resin synthesized in the synthesis example. *2: Omnirad819 (photopolymerization initiator, manufactured by IGM Resins) *3:EPPN-201 (thermosetting component, manufactured by Nippon Kayaku Co., Ltd.) *4: SO-C2 (D50: 0.5 μm) (Spherical silica, manufactured by Admatex Co., Ltd.) *5: SO-C4 (D50: 1.05 μm) (Spherical silica, manufactured by Admatex Co., Ltd.) *6: B-30 (D50: 0.25 μm) (Barium sulfate, manufactured by Sakai Chemical Industry Co., Ltd.) *7: QSG-170 (D50: 0.17 μm) (Spherical silica, manufactured by Shin-Etsu Chemical Co., Ltd.) *8: SO-C6 (D50: 1.8~2.3μm) (Spherical silica, manufactured by Admatex Co., Ltd.) *9: Metabren C-223A (butadiene-based rubber, manufactured by Mitsubishi Chemical Corporation) *10: DPHA (Dipentaerythritol hexaacrylate, manufactured by Nippon Kayaku Co., Ltd.) *11: Melamine *12: Dicyandiamide *13: Phthalocyanine blue

[0123] [Particle size distribution of curable resin composition] The particle size distribution of the curable resin composition prepared by the above method was measured, and the position of the peak maxima in the particle size distribution was determined. The particle size distribution was measured using laser diffraction with a Microtrac MT3300EXII manufactured by Microtrac-Bell Corporation. The number of maximum peaks and their positions are shown in Table 2.

[0124] [Method for fabricating evaluation boards] As shown in the Examples and Comparative Examples, each curable resin composition was prepared and then applied to a PET film (25 μm thick) using an applicator so that the film thickness after drying was 20 μm and 25 μm, respectively. Dry films were then prepared by drying at 60-100°C. Each dry film prepared according to the procedure described above was chemically polished using MEC Etchbond CZ-8101 manufactured by MEC Corporation to form a copper circuit on a substrate. This substrate was then heat-laminated at 80°C for 1 minute at 80°C with a vacuum laminator CVP-300 manufactured by Nikko Materials Corporation at a temperature of 80°C, a vacuum pressure of 3 hPa, and a pressure of 0.4 MPa. Finally, it was flat-pressed at 70°C and a pressure of 0.5 MPa to obtain a substrate having layers (dry films) of each unexposed curable resin composition. Each of the obtained substrates was exposed to a standard exposure dose using a photomask with a φ50 μm diameter and an exposure apparatus equipped with a high-pressure mercury lamp (short arc lamp), and the PET film was peeled off from the dry film. Subsequently, the substrate was sprayed at 30°C and a spray pressure of 2 kg / cm². 2 Under these conditions, development was carried out for 60 seconds using a 1% by mass Na2CO3 aqueous solution to obtain each sample substrate having a cured product with a micropore pattern. Each obtained sample substrate was then subjected to an integrated exposure of 1000 mJ / cm using a UV conveyor furnace. 2 After irradiation with ultraviolet light, the cured material on each sample substrate was fully cured by heating at 150°C for 60 minutes.

[0125] [Resolution evaluation] After performing Pt sputtering on each sample substrate prepared according to the above procedure, the diameter of the bottom of the micropores on each sample substrate was measured using a scanning electron microscope (SEM), and the resolution was evaluated according to the evaluation criteria below. The results are shown in Table 2. [Evaluation Criteria] ◎: The diameter of the base is 25 μm or more and less than 50 μm. ○: The diameter of the base is 15 μm or more and less than 25 μm. ×: The diameter of the base is less than 15 μm.

[0126] [Evaluation of crack resistance (TST)] [Evaluation of crack resistance] Except for replacing the φ50 μm micro-pore pattern with a Si chip mounting pattern, a substrate with a cured material having a Si chip mounting pattern was obtained using the same procedure as for the evaluation substrate used in the resolution evaluation described above. Next, Au plating and solder bump formation were performed, and Si chips were mounted to obtain sample substrates for thermal shock testing (TST). Each obtained sample substrate was placed in a cold-heat cycling machine that performed temperature cycles between -65°C and 150°C in a liquid layer, and a TST was performed. During the TST, the surface of the cured material on each sample substrate was observed at 750 cycles and 1000 cycles, and crack resistance was evaluated according to the evaluation criteria below. The results are shown in Table 2. [Evaluation Criteria] ◎: No cracks were observed even after 1000 cycles. ○: No cracks were observed at 750 cycles, but cracks were observed at 1000 cycles. ×: Cracks are observed after 750 cycles.

[0127] [Evaluation of coating properties] The resin compositions prepared in the above examples and comparative examples were diluted appropriately by adding PMA to them so that the solid content was 50%, and stirred with a stirrer for 15 minutes to obtain a coating solution. The above coating solution was applied to a 25 μm thick PET film being transported using a coating machine, and then dried to produce a dry film with a thickness of 20 μm. The coating film on the surface of the dry film was visually observed, and the coating properties of the resin composition were evaluated based on the evaluation criteria below. [Evaluation Criteria] ○: Good coating properties were confirmed, free from streaks, unevenness, and air bubbles. ×: Streaks, unevenness, or air bubbles were observed.

[0128] [Table 2]

[0129] The results in Table 2 show that the curable resin compositions of each example all exhibited excellent long-term heat resistance, crack resistance, and resolution in thick films. Comparing Comparative Examples 1, 2, and 3 with Example 1, it was shown that Example 1, containing (D-1) inorganic filler, exhibited superior resolution, crack resistance, and coating properties compared to Comparative Examples 1, 2, and 3, which did not contain (D-1) inorganic filler. From this, it appears that Comparative Example 1 suffered from reduced resolution and poor coating properties due to the large average particle size of the inorganic filler and the variation in particle size distribution, while Comparative Examples 2 and 3 suffered from reduced crack resistance due to an increase in the resin-inorganic filler interface caused by the average particle size of the inorganic filler being too small. Similarly, a comparison of Comparative Example 4 with each of the Examples showed that each Example exhibited superior crack resistance and coating properties compared to Comparative Example 4, which did not contain a barium compound. This indicates that the curable resin composition of the present invention can exhibit excellent resolution, crack resistance, and coating properties by using a barium compound together with silica having a predetermined average particle size.

Claims

1. An alkali-developable curable resin composition comprising (A) an alkali-soluble resin, (B) a photopolymerization initiator, (C) a thermosetting component, (D) an inorganic filler, and (E) a stress relaxant, The particle size distribution of the curable resin composition has a maximum peak at 0.1 μm or more and 2.0 μm or less, and there is only one maximum peak. A curable resin composition characterized in that the (D) inorganic filler contains two or more compounds, each having a maximum peak in a different particle size distribution, and at least one of the two or more (D) inorganic fillers has an (D-1) average particle size D50 of 0.3 μm or more and 1.15 μm or less.

2. The curable resin composition according to claim 1, wherein the total content of the inorganic filler (D) is 25.0% by mass or more and 75.0% by mass or less on a solid content basis with respect to the total amount of the curable resin composition.

3. The curable resin composition according to claim 1, wherein the content of the inorganic filler having an average particle size D50 of 0.3 μm or more and 1.15 μm or less is 15.0% by mass or more and 70.0% by mass or less in terms of solid content relative to the total amount of the curable resin composition.

4. The curable resin composition according to claim 1, wherein the content of the inorganic filler having an average particle size D50 of 0.3 μm or more and 1.15 μm or less is 25.0% by mass or more and 90.0% by mass or less in terms of solid content relative to the total amount of the inorganic filler (D).

5. The curable resin composition according to claim 1, wherein the (D-1) average particle diameter D50 of the inorganic filler is 0.3 μm or more and 1.15 μm or less, and the D50 of the inorganic filler is 0.3 μm or more and 0.9 μm or less.

6. (D-2) The curable resin composition according to claim 1, further comprising an inorganic filler having an average particle size D50 of 0.1 μm or more and less than 0.3 μm.

7. The curable resin composition according to claim 6, wherein the content of the inorganic filler having an average particle size D50 of 0.1 μm or more and less than 0.3 μm is 5.0% by mass or more and 60.0% by mass or less in terms of solid content relative to the total amount of the curable resin composition.

8. The curable resin composition according to claim 6, wherein the content of the inorganic filler having an average particle size D50 of 0.1 μm or more and less than 0.3 μm is 10.0% by mass or more and 75.0% by mass or less in terms of solid content relative to the total amount of the inorganic filler (D).

9. The curable resin composition according to claim 1, wherein the (D) inorganic filler comprises at least one of silica and a barium compound.

10. The curable resin composition according to claim 1, wherein the content of (A) alkali-soluble resin is 15.0% by mass or more and 60.0% by mass or less on a solid content basis with respect to the total amount of the curable resin composition.

11. The curable resin composition according to claim 1, wherein the content of the thermosetting component (C) is 5.0% by mass or more and 30.0% by mass or less on a solid content basis with respect to the total amount of the curable resin composition.

12. The curable resin composition according to claim 1, wherein the content of the stress-relaxing agent (E) is 1.0% by mass or more and 10.0% by mass or less on a solid content basis with respect to the total amount of the curable resin composition.

13. A dry film characterized by having a resin layer obtained from a curable resin composition according to any one of claims 1 to 12.

14. A cured product characterized by being obtained by curing a curable resin composition according to any one of claims 1 to 12.

15. A cured product characterized by being obtained by curing the resin layer of the dry film described in claim 13.

16. A printed circuit board comprising the cured material described in claim 14.

17. A printed circuit board comprising the cured material described in claim 15.

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