WO2023100843A1

WO2023100843A1 - Curable resin composition, cured object, printed wiring board, and method for producing printed wiring board

Info

Publication number: WO2023100843A1
Application number: PCT/JP2022/043882
Authority: WO
Inventors: 義和大胡
Original assignee: 太陽インキ製造株式会社
Priority date: 2021-11-30
Filing date: 2022-11-29
Publication date: 2023-06-08

Abstract

[Problem] To provide a curable resin composition capable of forming solder resists which combine long-lasting low glossiness and resultant long-term freedom from solder adhesion with withstand voltage on a high level. [Solution] A curable resin composition comprising a curable resin, barium sulfate, and a heat-curing catalyst, the barium sulfate having an oil absorption of 40-70 mL/100 g.

Description

Curable resin composition, cured product, printed wiring board, and method for producing printed wiring board

The present invention relates to a curable resin composition, and more particularly to a curable resin composition that is suitable for forming solder resists. Furthermore, the present invention also relates to a printed wiring board using the curable resin composition and a method for producing the same.

The adhesion of solder to the solder resist, which occurs during the flow soldering process when manufacturing printed wiring boards, can cause defects such as solder bridging (solder shorts), resulting in printed wiring board defects. In recent years, as wiring patterns on printed wiring boards have become more and more precise, such solder bridges are particularly likely to occur, and are considered to be one of the factors that hinder the efficient manufacture of printed wiring boards. .

Conventionally, it is known that the adhesion of solder to the solder resist can be prevented by making the surface of the solder resist matte (low glossiness). Attempts have been made to incorporate a component called a delustering agent as a filler into the resin composition for forming. For example, Patent Literature 1 proposes forming a solder resist having a matte surface by using a resin composition containing fine particles of aluminum silicate having a matting effect as a filler. In addition, it is known to use ultrafine anhydrous silica, talc, fused silica having a large particle size, clay, aluminum hydroxide, and the like as matting agents.

By the way, with the recent increase in carbon neutral orientation, the electrification of social infrastructure and daily necessities has progressed, and the need for electrically driving large machines such as automobiles, for example, is increasing. Many of these social infrastructures and daily necessities are required to operate in harsh environments and to be energized with high voltage and large current. Solder resists forming wiring boards are required to meet such needs. For example, in Patent Document 2, a solder resist that has excellent heat resistance and moisture resistance, has a higher withstand voltage (insulation breakdown voltage) than conventional, and can be used stably for a long time even in a harsh environment is formed. An electrically insulating resin composition has been proposed.

JP-A-9-157574 JP 2005-314554 A

However, in solder resists, it has been difficult to achieve both the maintenance of low glossiness over time and the resulting solder adhesion resistance over time and the voltage resistance (dielectric breakdown voltage) at a high level. . Therefore, a solder resist that achieves both low glossiness over time and resistance to solder adhesion over time and voltage resistance at a high level, and a resin composition for forming such a solder resist. Providing it exists as a technical problem.

In addition, it is expected that printed wiring boards will be required to carry current at higher voltages and currents in the future. , and to provide a resin composition for forming such a solder resist also exist as technical problems.

Therefore, the present invention provides a solder resist that maintains low glossiness over time, which has been difficult to achieve in the past, and the resulting solder adhesion resistance over time, and voltage resistance at a high level. An object of the present invention is to provide a curable resin composition that can be formed, a cured product thereof, and a printed wiring board comprising the cured product. Another object of the present invention is to use the curable resin composition to provide a solder resist that achieves both low glossiness over time and solder adhesion resistance brought about by it and voltage resistance at a high level. It is an object of the present invention to provide a method for manufacturing a printed wiring board provided with.

As a result of intensive research, the present inventors found that by adjusting the oil absorption of barium sulfate to 40 to 70 mL / 100 g in a curable resin composition containing a curable resin, barium sulfate, and a thermosetting catalyst, the above-mentioned I got the knowledge that the problem can be solved. The present invention is based on such findings. That is, the gist of the present invention is as follows.

[1] A curable resin composition containing a curable resin, barium sulfate, and a thermosetting catalyst,
A curable resin composition, wherein the barium sulfate has an oil absorption of 40 to 70 mL/100 g.
[2] The curable resin composition according to [1], wherein the barium sulfate contains barium sulfate surface-treated with silica.
[3] The curable resin according to [1] or [2], wherein the curable resin contains one or more thermosetting resins selected from the group consisting of epoxy compounds, polyfunctional oxetane compounds and oxazoline compounds. Composition.
[4] The curable resin composition according to any one of [1] to [3], wherein the curable resin contains a carboxyl group-containing photosensitive resin having one or more ethylenically unsaturated groups in one molecule. thing.
[5] The curable resin composition according to [4], further comprising a photopolymerization initiator.
[6] The curable resin composition according to any one of [1] to [5], which is used for forming a solder resist.
[7] The curable resin composition according to [6], wherein the solder resist is a matte solder resist.
[8] A cured product of the curable resin composition according to any one of [1] to [7].
[9] A printed wiring board comprising the cured product of [8].
[10] A method for producing a printed wiring board comprising a solder resist, comprising the step of forming a solder resist by curing the curable resin composition according to any one of [1] to [7]. .

According to the present invention, a curable resin composition capable of forming a solder resist that maintains low glossiness over time and the resulting solder adhesion resistance over time and voltage resistance at a high level. product, a cured product thereof, and a printed wiring board comprising the cured product. Furthermore, using the curable resin composition, it is possible to provide a method for producing a printed wiring board having a solder resist that achieves both low gloss over time, solder adhesion resistance, and voltage resistance at a high level. can.

[Curable resin composition]
The curable resin composition of the present invention contains a curable resin, barium sulfate and a thermosetting catalyst as essential components. The curable resin composition of the present invention is suitable for forming a solder resist in the manufacture of a printed wiring board, particularly a solder resist in a printed wiring board requiring high voltage and large current, especially a matte solder resist. can be used for The curable resin composition of the present invention contains barium sulfate having an oil absorption of 40 to 70 mL / 100 g, so that the solder resist, which is a cured product of the curable resin composition, maintains low glossiness over time and it It is possible to provide the resistance to solder adhesion over time and the voltage resistance at a high level.

Conventionally, in solder resists, it has been difficult to maintain low glossiness over time, resulting in resistance to solder adhesion over time, and voltage resistance at a high level. The reasons for this are as follows. inferred to. That is, when the solder resist is to be matted (low glossiness), it is common to add a component called a delustering agent as a filler into the resin composition for forming the solder resist. When silica or the like, which is commonly used as a matting agent, is used, air bubbles adhere to those particles, air bubbles are present in the resin composition, and as a result in the solder resist formed by curing the resin composition. Air bubbles remain. Air bubbles adhering to silica or the like are difficult to separate and remove. For example, even if a large amount of antifoaming agent is added to the resin composition, a large amount of air bubbles remain in the resin composition. Similarly, when hydrophilic fillers such as aluminum hydroxide and aluminum silicate, which are commonly used as matting agents, are used, air bubbles adhere to the particles, resulting in a large amount of air bubbles remaining in the solder resist. . Since the presence of air bubbles in the solder resist greatly impairs the voltage resistance of the solder resist, when using conventional matting agents, the matting (low glossiness) in the solder resist and the resulting solder adhesion resistance It is considered that it was not possible to achieve both high-level and high voltage resistance.

On the other hand, in the curable resin composition of the present invention, by using barium sulfate having a specific oil absorption as the matting agent, adhesion of air bubbles to the barium sulfate as the matting agent is suppressed, and the curable resin composition is improved. Residual air bubbles in the solder resist formed by curing are suppressed. As a result, it is believed that the solder resist can maintain low glossiness over time, resulting in resistance to solder adhesion over time, and withstand voltage at a high level.

The curable resin composition of the present invention has a 60° glossiness of a cured product (cured coating film) having a thickness of 25 μm, which is formed immediately after preparation, is preferably 20 or less, more preferably 15 or less, It is more preferably 10 or less. In addition, the curable resin composition of the present invention, even after being stored at 30 ° C. for 6 months after preparation, a cured product that maintains a low glossiness comparable to that of the curable resin composition immediately after preparation. can be formed. That is, the curable resin composition of the present invention is stored at 30 ° C. for 6 months after preparation. Below, more preferably 15 or less, still more preferably 10 or less. The glossiness of the cured product of the curable resin composition was obtained by screen-printing the curable resin composition onto a copper plated FR-4 substrate with a thickness of 1.6 mm so that the film thickness after curing was 25 μm. and the cured product (cured coating film) of the curable resin composition formed by heating at 150 ° C for 30 minutes using a hot air circulation drying oven, BYK-Chemie gloss meter Micro Trigloss can be measured as the 60° specular reflectance measured using

In the curable resin composition of the present invention, a cured product (cured coating film) having a thickness of 50 μm has a withstand voltage value of preferably 5 kV (5 kV / 0.05 mm) or more, more preferably 5.5 kV (5.5 kV). /0.05 mm) or more, more preferably 6 kV (6 kV/0.05 mm) or more. The withstand voltage value of the curable resin composition was measured using a withstand voltage tester TOS5101 manufactured by Kikusui Electronics Co., Ltd. for a substrate having a cured product (cured coating film) with a thickness of 50 μm. can be measured as the voltage value when the dielectric breakdown of the cured product occurs when the voltage is increased at 0.5 kV/sec in AC mode.

Each component of the curable resin composition of the present invention will be described in detail below.
(Curable resin)
The curable resin composition of the present invention contains a curable resin. The curable resin is not particularly limited as long as it is cured by the action of heat, light, or the like. Specifically, a thermosetting resin, a photocurable resin, or the like can be used as the curable resin. The curable resin may be used singly or in combination of two or more. For example, a thermosetting resin or a photocurable resin may be used alone, or they may be used in combination.

A thermosetting resin can be blended into the curable resin composition of the present invention as a curable resin. By adding a thermosetting resin, it is expected that the heat resistance of the curable resin composition is improved. Thermosetting resins may be used singly or in combination of two or more. Any known thermosetting resin can be used. For example, known resins such as melamine resins, benzoguanamine resins, melamine derivatives, amino resins such as benzoguanamine derivatives, isocyanate compounds, blocked isocyanate compounds, cyclocarbonate compounds, epoxy compounds, oxetane compounds, oxazoline compounds, episulfide resins, bismaleimide, carbodiimide resins, etc. A thermosetting resin can be used. Each of these thermosetting resins may be monofunctional or polyfunctional. Among such thermosetting resins, thermosetting resins having a cyclic ether group or a cyclic thioether group in the molecule are preferably used. Examples of such thermosetting resins include epoxy compounds having an epoxy group in the molecule, oxetane compounds having an oxetanyl group in the molecule, oxazoline compounds having an oxazoline group in the molecule, and episulfide compounds having a thioether group in the molecule. Resin etc. are mentioned. The thermosetting resin preferably contains one or more selected from the group consisting of epoxy compounds, polyfunctional oxetane compounds and oxazoline compounds, particularly preferably epoxy compounds. By blending these compounds as a thermosetting resin in the curable resin composition, particularly excellent heat resistance, chemical resistance and adhesion can be imparted to the curable resin composition.

Epoxidized vegetable oil; bisphenol A type epoxy resin; hydroquinone type epoxy resin; bisphenol type epoxy resin; thioether type epoxy resin; brominated epoxy resin; Resin; bisphenol F type epoxy resin; hydrogenated bisphenol A type epoxy resin; glycidylamine type epoxy resin; hydantoin type epoxy resin; alicyclic epoxy resin; bisphenol A novolak epoxy resin; tetraphenylolethane epoxy resin; heterocyclic epoxy resin; diglycidyl phthalate resin; tetraglycidyl xylenoyl ethane resin; epoxy resin having a dicyclopentadiene skeleton; glycidyl methacrylate copolymer epoxy resin; copolymer epoxy resin of cyclohexylmaleimide and glycidyl methacrylate; epoxy-modified polybutadiene rubber derivative; It is not something that can be done. These epoxy resins may be used individually by 1 type, and may be used in combination of 2 or more type.

As the oxetane compound, a polyfunctional oxetane compound having two or more oxetanyl groups in one molecule is preferably used. 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, (3-ethyl-3- Oxetanyl)methyl acrylate, (3-methyl-3-oxetanyl)methyl methacrylate, (3-ethyl-3-oxetanyl)methyl methacrylate, and polyfunctional oxetanes such as their oligomers or copolymers, as well as oxetane alcohols and novolak resins , poly(p-hydroxystyrene), cardo-type bisphenols, calixarenes, calixresorcinarenes, and etherified products with resins having a hydroxyl group such as silsesquioxane. Other examples include copolymers of unsaturated monomers having an oxetane ring and alkyl (meth)acrylates.

Examples of oxazoline compounds include possible compounds having two or more oxazoline groups in one molecule. Examples of such oxazoline compounds include oxazoline group-containing polymers such as polymers of oxazoline group-containing monomers and copolymers of oxazoline group-containing monomers and other monomers. Examples of oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4,4-dimethyl-2-oxazoline, etc. is mentioned.

Examples of episulfide resins include compounds in which an oxygen atom constituting an epoxy group in any epoxy compound is substituted with a sulfur atom. Epoxy compounds include those mentioned above. As a method for substituting an oxygen atom constituting an epoxy group in an epoxy compound with a sulfur atom, a conventionally known method can be used.

Amino resins such as melamine derivatives and benzoguanamine derivatives include methylol melamine compounds, methylol benzoguanamine compounds, methylol glycoluril compounds and methylol urea compounds.

A polyisocyanate compound can be blended as the isocyanate compound. Polyisocyanate compounds include 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, naphthalene-1,5-diisocyanate, o-xylylene diisocyanate, m-xylylene diisocyanate and Aromatic polyisocyanates such as 2,4-tolylene dimer; Aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4-methylenebis(cyclohexyl isocyanate) and isophorone diisocyanate; bicyclo alicyclic polyisocyanates such as heptane triisocyanate; and adducts, biurets and isocyanurates of the above-mentioned isocyanate compounds.

As the blocked isocyanate compound, an addition reaction product of an isocyanate compound and an isocyanate blocking agent can be used. Examples of the isocyanate compound that can react with the isocyanate blocking agent include the aforementioned polyisocyanate compounds. Examples of isocyanate blocking agents include phenolic blocking agents; lactam blocking agents; active methylene blocking agents; alcohol blocking agents; oxime blocking agents; mercaptan blocking agents; Amine-based blocking agents; imidazole-based blocking agents; imine-based blocking agents, and the like.

The amount of the thermosetting resin compounded in the curable resin composition is not particularly limited as long as the effect of the present invention is exhibited, for example, 3 to 50 in terms of solid content with respect to the total mass of the curable resin composition. % by mass or the like.

The curable resin composition of the present invention can contain a photocurable resin as a curable resin. As the photocurable resin, a known and commonly used photocurable resin can be used. Among them, from the viewpoint of photocurability and development resistance, preferably a photocurable resin that can be cured by a radical addition polymerization reaction with an active energy ray, more preferably a photocurable resin having an ethylenically unsaturated group in the molecule. A flexible resin is used. The ethylenically unsaturated groups are preferably derived from acrylic acid, methacrylic acid, or derivatives thereof. The photocurable resin may be used singly or in combination of two or more. As the photocurable resin, a carboxyl group-containing photosensitive resin, which will be described later, is preferably used.

As the photocurable resin having an ethylenically unsaturated group in the molecule, commonly known photopolymerizable oligomers, photopolymerizable monomers, and the like are used. Examples of photopolymerizable oligomers include unsaturated polyester-based oligomers and (meth)acrylate-based oligomers. (Meth)acrylate oligomers include epoxy (meth)acrylates such as phenol novolac epoxy (meth)acrylate, cresol novolac epoxy (meth)acrylate, bisphenol type epoxy (meth)acrylate, urethane (meth)acrylate, epoxyurethane (meth)acrylate, ) acrylates, polyester (meth)acrylates, polyether (meth)acrylates, polybutadiene-modified (meth)acrylates, and the like.

On the other hand, as the photopolymerizable monomer, a monomer having an ethylenically unsaturated group is preferably used. Examples of such photopolymerizable monomers include commonly known polyester (meth)acrylates, polyether (meth)acrylates, urethane (meth)acrylates, carbonate (meth)acrylates, epoxy (meth)acrylates, and the like. Specifically, alkyl acrylates such as 2-ethylhexyl acrylate and cyclohexyl acrylate; hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate; alkylene glycols such as ethylene glycol, propylene glycol, diethylene glycol and dipropylene glycol. mono- or diacrylates of oxide derivatives; acrylamides such as N,N-dimethylacrylamide, N-methylolacrylamide, N,N-dimethylaminopropylacrylamide; N,N-dimethylaminoethyl acrylate, N,N-dimethylaminopropyl Aminoalkyl acrylates such as acrylates; Polyhydric alcohols such as hexanediol, trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol and trishydroxyethyl isocyanurate, or their alkylene oxide adducts or ε-caprolactone adducts, etc. polyvalent acrylates; phenols such as phenoxy acrylate and bisphenol A diacrylate or polyvalent acrylates such as alkylene oxide adducts thereof; glycidyls such as glycerin diglycidyl ether, trimethylolpropane triglycidyl ether, and triglycidyl isocyanurate Ether acrylates; not limited to the above, acrylates and melamine acrylates obtained by directly acrylated polyols such as polyether polyols, polycarbonate diols, hydroxyl-terminated polybutadiene, and polyester polyols, or urethane acrylated via diisocyanate, and the above acrylates can be appropriately selected from at least one of the methacrylates corresponding to and used. One type of the photopolymerizable monomer may be used alone, or two or more types may be used in combination. Photopolymerizable monomers can also be used as reactive diluents. The term "photopolymerizable monomer" refers to a compound that is a monomer among photocurable resins.

The amount of the photocurable resin in the curable resin composition is not particularly limited as long as the effect of the present invention is exhibited, for example, 10 to 50 in terms of solid content with respect to the total mass of the curable resin composition % by mass or the like.

The curable resin may preferably contain a carboxyl group-containing resin in order to impart alkaline developability to the curable resin composition. As the carboxyl group-containing resin, conventionally known various resins having a carboxyl group in the molecule can be used.
Specific examples of carboxyl group-containing resins include the following compounds (both oligomers and polymers).

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

(2) Diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates and aromatic diisocyanates; Polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A alkylene oxide adduct diols, carboxyl group-containing urethane resins obtained by polyaddition reaction of diol compounds such as compounds having phenolic hydroxyl groups and alcoholic hydroxyl groups.

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

(4) During the synthesis of the resin (2) or (3) above, a compound having one hydroxyl group and one or more (meth)acryloyl groups in the molecule such as hydroxyalkyl (meth)acrylate is added, and the terminal ( Meta) acrylated carboxyl group-containing photosensitive urethane resin.

(5) During the synthesis of the resin of (2) or (3), one isocyanate group and one or more (meth)acryloyl groups are added in the molecule, such as an equimolar reaction product of isophorone diisocyanate and pentaerythritol triacrylate. A carboxyl group-containing photosensitive urethane resin that is terminally (meth)acrylated by adding a compound having

(6) A carboxyl group-containing photosensitive resin obtained by reacting (meth)acrylic acid with a polyfunctional (solid) epoxy resin having two or more functionalities and adding a dibasic acid anhydride to the hydroxyl groups present in the side chains.

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

(8) A bifunctional oxetane resin is reacted with a dicarboxylic acid such as adipic acid, phthalic acid, and hexahydrophthalic acid, and the resulting primary hydroxyl group is treated with a dibasic such as phthalic anhydride, tetrahydrophthalic anhydride, and hexahydrophthalic anhydride. Carboxyl group-containing polyester resin to which acid anhydride is added.

(9) an epoxy compound having a plurality of epoxy groups in one molecule, a compound having at least one alcoholic hydroxyl group and one phenolic hydroxyl group in one molecule, such as p-hydroxyphenethyl alcohol; Maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, and adipine are reacted with an unsaturated group-containing monocarboxylic acid such as acrylic acid, and the alcoholic hydroxyl group of the resulting reaction product is treated with A carboxyl group-containing photosensitive resin obtained by reacting a polybasic acid anhydride such as an acid.

(10) A reaction 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 and reacting an unsaturated group-containing monocarboxylic acid. A carboxyl group-containing photosensitive resin obtained by reacting the product with a polybasic acid anhydride.

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

(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 (1) to (11).
In this specification, (meth)acrylate is a generic term for acrylate, methacrylate and mixtures thereof, and the same applies to other similar expressions.

In addition, as the photosensitive resin, a resin synthesized according to the procedure described in Examples described later can also be used.

The acid value of the carboxyl group-containing resin is suitably in the range of 30-150 mgKOH/g, more preferably in the range of 50-120 mgKOH/g. When the acid value of the carboxyl group-containing resin is 30 mgKOH/g or more, alkaline development can be performed appropriately. It is preferable because the exposed area and the unexposed area can be separated by dissolution and separation, and normal resist pattern drawing is facilitated.

Although the weight-average molecular weight of the carboxyl group-containing resin varies depending on the resin skeleton, it is generally preferably in the range of 2,000 to 150,000, more preferably in the range of 5,000 to 100,000. When the weight-average molecular weight is 2,000 or more, the moisture resistance of the coating film after exposure is good, film reduction does not occur during development, and excellent resolution can be easily obtained. On the other hand, when the weight average molecular weight is 150,000 or less, good developability is likely to be obtained, and good storage stability is likely to be obtained. Weight average molecular weight can be measured by gel permeation chromatography (GPC).

(barium sulfate)
The curable resin composition of the present invention contains barium sulfate with an oil absorption of 40 to 70 mL/100 g. When the curable resin composition contains barium sulfate having such a relatively high oil absorption, the solder resist, which is a cured product of the curable resin composition, maintains low glossiness over time and is thereby brought about. It is possible to provide a high level of resistance to solder adhesion over time and withstand voltage.

The oil absorption of barium sulfate is preferably 45-70 mL/100 g, more preferably 45-65 mL/100 g, and even more preferably 50-60 mL/100 g. The oil absorption of barium sulfate can be measured according to the method defined by Japanese Industrial Standards (JIS K5101-13-1).

As the barium sulfate, untreated barium sulfate may be used, or chemically and/or physically treated barium sulfate may be used. As such treated barium sulfate, for example, surface-treated barium sulfate can be used. Examples of substances for surface-treating barium sulfate include inorganic substances such as silica and alumina. Among them, it is particularly preferable to use barium sulfate surface-treated with silica by multiple treatments (also referred to as “multi-treatment processing”). The multi-treatment is a treatment in which a substance to be surface-treated (for example, silica, alumina, etc.) adheres to the surface of the barium sulfate to be surface-treated so that it exists very thickly. Examples of commercial products of barium sulfate surface-treated with silica include PFS-701 manufactured by Ishihara Sangyo Co., Ltd., and the like.

Barium sulfate, especially barium sulfate surface-treated with silica, has high matting performance compared to conventional matting agents, and by adding a small amount of barium sulfate surface-treated with silica to the curable resin composition, it is high. A matte effect can be obtained. Therefore, the inclusion of air bubbles in the curable resin composition, which is a problem when blending the matting agent, and the remaining air bubbles in the solder resist formed by curing the curable resin composition are suppressed, and as a result, , the decrease in voltage resistance of the solder resist can be suppressed. Furthermore, in general, when a matting agent is added to a resin composition, the viscosity of the resin composition increases. By using the treated barium sulfate, an increase in the viscosity of the curable resin composition can be suppressed, and as a result, deterioration in printability of the curable resin composition onto the substrate can be suppressed. Furthermore, barium sulfate, especially barium sulfate surface-treated with silica, has high acid resistance (acid resistance). Therefore, by blending barium sulfate as a matting agent in the curable resin composition, the curable resin composition has high acid resistance, and as a result, it is highly resistant to tin plating etc. performed under strong acidity. (Tin plating resistance).

In the curable resin composition, the amount of barium sulfate with an oil absorption of 40 to 70 mL/100 g is not particularly limited as long as the effect of the present invention is exhibited. , preferably 30 to 74% by mass, more preferably 40 to 70% by mass, and still more preferably 45 to 67% by mass in terms of solid content.

(Thermosetting catalyst)
The curable resin composition of the present invention contains a thermosetting catalyst. Examples of thermosetting catalysts include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, 1- Imidazole derivatives such as (2-cyanoethyl)-2-ethyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole; dicyandiamide, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzyl Amine compounds such as amines, 4-methoxy-N,N-dimethylbenzylamine and 4-methyl-N,N-dimethylbenzylamine; hydrazine compounds such as adipic acid dihydrazide and sebacic acid dihydrazide; phosphorus compounds such as triphenylphosphine; etc. In addition, commercially available products include, for example, 2MZ-A, 2MZ-OK, 2PHZ, 2PHZ-PW, 2P4BHZ, and 2P4MHZ manufactured by Shikoku Kasei Co., Ltd. (all are trade names of imidazole compounds), manufactured by San-Apro Co., Ltd. U-CAT 3513N (trade name of dimethylamine compounds), DBU, DBN, U-CAT SA 102 (both of which are bicyclic amidine compounds and salts thereof). In particular, it is not limited to these, and it may be a thermosetting catalyst for an epoxy resin or an oxetane compound, or any one that promotes the reaction between at least one of an epoxy group and an oxetanyl group and a carboxyl group. A mixture of seeds or more may be used. Also, 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 derivatives such as S-triazine/isocyanuric acid adducts and 2,4-diamino-6-methacryloyloxyethyl-S-triazine/isocyanuric acid adducts can also be used, and these adhesion-imparting agents are preferred. A compound that also functions is used in conjunction with a thermosetting catalyst. One of the thermosetting catalysts may be used alone, or two or more thereof may be used in combination.

The content of the thermosetting catalyst is preferably 2 to 30 parts by mass, more preferably 5 to 25 parts by mass, based on 100 parts by mass of the thermosetting resin.

(Photoinitiator)
When the curable resin composition of the present invention contains a photosensitive resin, the curable resin composition preferably contains a photopolymerization initiator. Any known photopolymerization initiator can be used. A photoinitiator may be used individually by 1 type, and may be used in combination of 2 or more type.

Specific 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 , bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2, bisacylphosphine oxides such as 4,6-trimethylbenzoyl)-phenylphosphine oxide; 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,4,6-trimethyl monoacylphosphine oxides such as benzoylphenylphosphinate methyl ester, 2-methylbenzoyldiphenylphosphine oxide, pivaloylphenylphosphinate isopropyl ester, 2,4,6-trimethylbenzoyldiphenylphosphine oxide; phenyl ( 2,4,6-trimethylbenzoyl)ethylphosphinate, 1-hydroxy-cyclohexylphenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1- one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-hydroxy-2-methyl-1 - hydroxyacetophenones such as phenylpropan-1-one; benzoins such as benzoin, benzyl, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, benzoin n-butyl ether; benzoin alkyl ethers; benzophenone , p-methylbenzophenone, Michler's ketone, methylbenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone and other benzophenones; 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-dimethyl Amino-1-(4-morpholinophenyl)-butanone-1,2-(dimethylamino)-2-[(4-methylphenyl)methyl)-1-[4-(4-morpholinyl)phenyl]-1- Acetophenones such as butanone and N,N-dimethylaminoacetophenone; thioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropyl Thioxanthones such as thioxanthone; anthraquinones such as anthraquinone, chloroanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, 2-amylanthraquinone, and 2-aminoanthraquinone; acetophenone dimethyl ketal , ketals such as benzyl dimethyl ketal; ethyl-4-dimethylaminobenzoate, 2-(dimethylamino) ethyl benzoate, benzoic acid esters such as p-dimethylbenzoic acid ethyl ester; 1,2-octanedione, 1-[ 4-(phenylthio)phenyl]-,2-(O-benzoyloxime), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-,1-(O -acetyloxime); bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium, bis (Cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1-pyr-1-yl)ethyl)phenyl]titanium; 2-dimethylamino-2-(4-methyl) -benzyl)-1-(4-morpholinophenyl)-butan-1-one and other alkylphenones; phenyl disulfide 2-nitrofluorene, butyroin, anisoin ethyl ether, azobisisobutyronitrile, tetramethylthiuram disulfide etc. can be mentioned.

A photoinitiation aid or a sensitizer may be used in combination with the photopolymerization initiator described above. Examples of photoinitiation aids or sensitizers include benzoin compounds, anthraquinone compounds, thioxanthone compounds, ketal compounds, benzophenone compounds, tertiary amine compounds, and xanthone compounds. Thioxanthone compounds such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, and 4-isopropylthioxanthone are particularly preferred. Inclusion of a thioxanthone compound can improve deep-part curability. These compounds can be used as a photopolymerization initiator in some cases, but are preferably used in combination with the photopolymerization initiator. The photoinitiation aids or sensitizers may be used singly or in combination of two or more.

In addition, since these photopolymerization initiators, photoinitiator aids, and sensitizers absorb specific wavelengths, the sensitivity may be lowered in some cases, and they may function as ultraviolet absorbers. However, these are not used only for the purpose of improving the sensitivity of the curable resin composition. It absorbs light of a specific wavelength as needed to increase the photoreactivity of the surface, change the line shape and opening of the resist to vertical, tapered, and reverse tapered shapes, and improve the accuracy of the line width and opening diameter. can be improved.

(filler)
The curable resin composition of the present invention may contain a filler other than barium sulfate as described above, if necessary, in order to increase the physical strength of the coating film, etc., as long as the effects of the present invention are not impaired. good. As such fillers, known inorganic or organic fillers can be used, and various types of silica (for example, finely divided silica, spherical silica, etc.), hydrotalcite and talc are particularly preferably used. Furthermore, metal oxides and metal hydroxides such as aluminum hydroxide can be used as extender fillers in order to obtain a white appearance and flame retardancy.

(Organic solvent)
The curable resin composition of the present invention can be blended with an organic solvent for the purpose of preparing the curable resin composition and adjusting the viscosity when applied to a substrate or film. Examples of organic solvents include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene and tetramethylbenzene; 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, tripropylene glycol monomethyl ether; ethyl acetate, butyl acetate, butyl lactate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbi Esters such as tall acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, and propylene carbonate; aliphatic hydrocarbons such as octane and decane; petroleum solvents such as petroleum ether, petroleum naphtha, and solvent naphtha; Conventional organic solvents can be used. These organic solvents may be used individually by 1 type, and may be used in combination of 2 or more type.

Volatilization drying of organic solvents is carried out by using a hot air circulating drying furnace, IR furnace, hot plate, convection oven, etc. (equipped with a heat source that heats the air using steam), and a method in which the hot air in the dryer is brought into contact with the counter current and supported by a nozzle. method of spraying on the body) can be used.

(other ingredients)
The curable resin composition of the present invention may optionally further contain a coloring agent, an elastomer, a mercapto compound, a urethanization catalyst, a thixotropic agent, an adhesion promoter, a block copolymer, a chain transfer agent, a polymerization inhibitor, copper damage inhibitor, antioxidant, rust inhibitor, organic bentonite, thickener such as montmorillonite, at least one of silicone-based, fluorine-based, polymer-based defoaming agent and leveling agent, imidazole-based, Components such as a thiazole-based or triazole-based silane coupling agent, a phosphinate, a phosphoric acid ester derivative, a phosphorus compound such as a phosphazene compound, and other flame retardants can be blended. As these, those known in the field of electronic materials can be used.

The curable resin composition of the present invention may be used as a dry film or as a liquid. Moreover, when it is used as a liquid, it may be one-liquid or two-liquid or more.

[Cured product]
The cured product of the present invention is obtained by curing the curable resin composition of the present invention described above, and maintains low glossiness over time and the resulting solder adhesion resistance over time and resistance to It is compatible with voltage characteristics at a high level. The cured product of the present invention is, for example, a solder resist having a thickness of 1 to 150 μm, especially a matte solder resist.

[Printed wiring board]
The printed wiring board of the present invention has a cured product obtained from the curable resin composition of the present invention described above. In the method for producing a printed wiring board of the present invention, for example, the curable resin composition of the present invention is adjusted to a viscosity suitable for the coating method using an organic solvent, and is coated on the substrate by a dip coating method, a flow After applying by a method such as coating method, roll coating method, bar coating method, screen printing method, curtain coating method, etc., the organic solvent contained in the composition is volatilized and dried (temporary drying) at a temperature of 60 to 100 ° C. to form a tack-free resin layer.

Examples of the substrate include printed wiring boards and flexible printed wiring boards on which circuits are formed in advance using copper or the like, paper phenol, paper epoxy, glass cloth epoxy, glass polyimide, glass cloth/non-woven cloth epoxy, glass cloth/paper epoxy. , Synthetic fiber epoxy, fluororesin, polyethylene, polyphenylene ether, polyphenylene oxide, cyanate, and other materials such as copper-clad laminates for high-frequency circuits, all grades (FR-4, etc.) of copper-clad laminates. Plates, metal substrates, polyimide films, polyethylene terephthalate films, polyethylene naphthalate (PEN) films, glass substrates, ceramic substrates, wafer plates and the like can also be used.

Volatilization drying performed after applying the curable resin composition of the present invention can be performed using a hot air circulation drying oven, an IR oven, a hot plate, a convection oven, etc. A method of bringing hot air into countercurrent contact and a method of blowing hot air onto the support from a nozzle) can be used.

After forming a resin layer on the substrate, it is selectively exposed to active energy rays through a photomask having a predetermined pattern, and the unexposed area is treated with a dilute alkaline aqueous solution (eg, 0.3 to 3% by mass aqueous solution of sodium carbonate). to form a pattern of the cured product. Furthermore, after irradiating the cured product with active energy rays, heat curing (e.g., 100 to 220 ° C), or after heat curing, irradiating the active energy rays, or final final curing (main curing) only by heat curing. Forms a cured coating film with excellent properties such as toughness and hardness.

The exposure machine used for the active energy ray irradiation may be any device equipped with a high-pressure mercury lamp, ultra-high pressure mercury lamp, metal halide lamp, mercury short arc lamp, etc., and irradiating ultraviolet rays in the range of 350 to 450 nm. In addition, a direct writing device (eg, a laser direct imaging device that draws an image with a laser directly from CAD data from a computer) can also be used. The lamp light source or laser light source of the direct drawing machine may have a maximum wavelength in the range of 350 to 450 nm. The amount of exposure for image formation varies depending on the film thickness and the like, but can generally be in the range of 10-1000 mJ/cm ² , preferably in the range of 20-800 mJ/cm ² .

As a developing method, a dipping method, a shower method, a spray method, a brush method, or the like can be used. , amines, etc. can be used.

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 examples, "parts" and "%" are based on mass unless otherwise specified.

[Preparation of photocurable resin solution]
A solution of a photocurable resin (an aromatic ring-containing carboxyl group-containing resin) used in this example was prepared according to the following procedure.
1070 g of ortho-cresol novolac type epoxy resin (EPICLON N-695, manufactured by DIC Corporation), 360 g (5.0 mol) of acrylic acid, and 1.5 g of hydroquinone were added to 600 g of diethylene glycol monoethyl ether acetate and heated at 100°C. A solution was obtained by stirring until the mixture became uniform. Next, 4.3 g of triphenylphosphine was added to the obtained solution, and after the reaction was carried out by heating at 110°C for 2 hours, the temperature was raised to 120°C and the reaction was further carried out for 12 hours to obtain a reaction solution. rice field. 415 g of an aromatic hydrocarbon (Solvesso 150, manufactured by Ando Parachemie Co., Ltd.) and 456.0 g (3.0 mol) of tetrahydrophthalic anhydride were added to the obtained reaction solution, and the reaction was carried out at 110° C. for 4 hours. After cooling, a photosensitive carboxyl group-containing resin solution having a solid content acid value of 89 mgKOH/g and a solid content of 65% by mass and having an aromatic ring was obtained.

[Preparation of curable resin composition]
Each component shown in Table 1 below was mixed in the amount shown in the same table, pre-stirred using a stirrer, and then kneaded using a three-roll mill to obtain Examples 1-6 and Comparative Examples 1-6. Each curable resin composition was prepared. The details of each component in Table 1 are as follows.
Thermosetting resin: phenol novolac epoxy resin (N-770, manufactured by DIC Corporation)
Photocurable resin (photosensitive resin): carboxyl group-containing resin solution having an aromatic ring prepared by the method described above, compounding amount is the value in terms of solid content Photocurable resin (photopolymerizable monomer): dipentaerythritol hexa Acrylate (manufactured by Nippon Kayaku Co., Ltd.)
Blue colorant: organic colorant phthalocyanine blue
Yellow coloring agent: Organic coloring agent Chromophthalo Yellow Antifoaming agent: Polydimethylsiloxane (KS-66, manufactured by Shin-Etsu Chemical Co., Ltd.)
Photoinitiator 1: Bis (η5-2,4-cyclopentadien-1-yl) - bis (2,6-difluoro-3- (1H-pyrrol-1-yl) phenyl) titanium (Irgacure 784, BASF Japan Co., Ltd.)
Photoinitiator 2: 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholinophenyl)-butan-1-one (Omnirad 379EG, manufactured by IGM Resins)
Thermosetting catalyst 1: 2-phenyl-4,5-dihydroxymethylimidazole (2PHZ-PW, manufactured by Shikoku Kasei Co., Ltd.)
Thermosetting catalyst 2: melamine aluminum silicate delustering agent: calcined kaolin (Satinton 5HB, manufactured by BASF Japan Ltd.)
Aluminum hydroxide matting agent: aluminum hydroxide (Higilite H-42, manufactured by Showa Denko K.K.)
Filler anti-settling agent: organic bentonite (BENTONE (registered trademark) 38, manufactured by Elementis Specialties)
Fine silica matting agent: Fine silica (ACEMATT (registered trademark) 82, manufactured by EVONIK)
Silica-alumina surface-treated barium sulfate (BARIACE (registered trademark) B-30, manufactured by Sakai Chemical Industry Co., Ltd.) (oil absorption: 18 mL/100 g)
Silica surface-treated barium sulfate (highly weather-resistant matte material PFS701, manufactured by Ishihara Sangyo Co., Ltd.) (oil absorption: 56 mL/100 g)
Organic solvent 1: diethylene glycol monoethyl ether acetate (carbitol acetate)
Organic solvent 2: petroleum solvent (SOLVESSO150, manufactured by Ando Parachemie Co., Ltd.)

[Evaluation of printability]
Each curable resin composition of Examples and Comparative Examples was printed on an IPC standard, pattern B substrate with a Tetoron 100-mesh screen using a printing machine (manufactured by Seria Corporation). The appearance of the coating film (cured coating film) after curing each curable resin composition was visually observed, and the printability of the curable resin composition was evaluated according to the following criteria. Table 1 shows the evaluation results.
○: Good printability (good leveling property)
△: Has acceptable printability (mesh pattern is observed)
×: Possesses unacceptable printability (there are pinholes and the base is visible through)

Furthermore, the curable resin compositions of Examples and Comparative Examples were stored at 30°C for 6 months after preparation, and then subjected to the same test to evaluate printability over time according to the same criteria. Table 1 shows the evaluation results.

[Preparation of substrates for evaluation (Examples 1 and 2 and Comparative Examples 1 and 2)]
Each curable resin composition of Examples 1 and 2 and Comparative Examples 1 and 2 was applied to a 1.6 mm thick FR-4 copper plated substrate by screen printing so that the film thickness after curing was 25 μm. It was applied and heated at 150° C. for 30 minutes using a hot air circulating drying oven to prepare a substrate for evaluation having a cured product (cured coating film) of each curable resin composition.

[Preparation of substrates for evaluation (Examples 3 to 6 and Comparative Examples 3 to 6)]
Each curable resin composition of Examples 3 to 6 and Comparative Examples 3 to 6 was applied to a 1.6 mm thick FR-4 copper plated substrate by screen printing so that the film thickness after drying was 25 μm. It was applied, dried at 80° C. for 30 minutes using a hot air circulating drying oven, and allowed to cool to room temperature. This substrate was exposed at 500 mJ/cm ² using an exposure device equipped with a high-pressure mercury lamp (short arc lamp), and developed by spraying a 1% by mass sodium carbonate aqueous solution at 30° C. at a spray pressure of 0.2 MPa for 90 seconds. rice field. Then, after irradiating with ultraviolet rays under the condition of an integrated exposure amount of 1000 mJ / cm ² using a UV conveyor furnace, it is heated at 160 ° C. for 60 minutes using a hot air circulation drying furnace, and the cured product of each curable resin composition (cured A substrate for evaluation having a coating film) was prepared.

[Glossiness evaluation]
The glossiness of the cured product of each curable resin composition of Examples and Comparative Examples formed on each evaluation substrate was measured using a gloss meter Micro Trigloss manufactured by BYK-Chemie 60 ° specular reflection measured as a percentage. In addition, the evaluation of the glossiness is performed for each of the five evaluation substrates, and the second decimal place of the average value of the glossiness of the five evaluation substrates is rounded off to the first decimal place. expressed. Based on the numerical values obtained, glossiness was evaluated according to the following criteria. Table 1 shows the glossiness values and evaluation results.
A: The glossiness is less than 10 and has an extremely low glossiness.
○: The glossiness is 10 or more and less than 20, and has a sufficiently low glossiness.
x: Glossiness is 20 or more and does not have low glossiness.

Furthermore, each curable resin composition of Examples and Comparative Examples was stored at 30 ° C. for 6 months after preparation, and then subjected to the same test for each evaluation substrate prepared, and the glossiness over time was measured according to the same criteria. evaluated. Table 1 shows the values of the glossiness over time and the evaluation results.

[Evaluation of solder adhesion resistance]
Using a flow soldering device on each evaluation board, without applying flux, in the atmosphere, the solder is flowed at a solder temperature of 260 ° C., a double wave, and a conveyor speed of 1.4 m / min, and then on each evaluation board. The adhesion state of solder on the surface of the cured product of the curable resin composition was visually observed, and solder adhesion resistance was evaluated according to the following criteria. Table 1 shows the evaluation results. In this evaluation, a copper circuit pattern board was used instead of the copper solid board in the production of the evaluation board, and the entire surface coating by screen printing in Examples 1 and 2 and Comparative Examples 1 and 2 was pattern printed. Instead, evaluation substrates prepared in the same manner as in Examples 3 to 6 and Comparative Examples 3 to 6 were used, except that pattern exposure was used.
◯: No adhesion of solder was observed on the surface of the cured product, and the resistance to solder adhesion was good.
x: Spike-like and web-like solder adhesion was observed, and the solder adhesion resistance was poor.

Furthermore, each curable resin composition of Examples and Comparative Examples was stored at 30 ° C. for 6 months after preparation, and then subjected to the same test for each evaluation board prepared. Evaluated according to criteria. Table 1 shows the evaluation results.

[Evaluation of withstand voltage]
For each evaluation substrate, using a withstand voltage tester TOS5101 manufactured by Kikusui Electronics Co., Ltd., the pressure is increased at 0.5 kV / sec in AC mode with an electrode with a diameter of 10 mm, and the curable resin composition on each evaluation substrate A voltage value (dielectric breakdown voltage) was measured when the cured product of the product broke down. In addition, the evaluation of the withstand voltage property was performed for each of three evaluation boards, and the average value of the dielectric breakdown voltage of the three evaluation boards was rounded to the first decimal place. expressed as a numerical value. Based on the obtained values, evaluation was made according to the following criteria. Table 1 shows the values of dielectric breakdown voltage and evaluation results of withstand voltage. Each value of the dielectric breakdown voltage (kV / 0.05 mm) in Table 1 is the value of the dielectric breakdown voltage of each evaluation substrate having a cured coating film with a thickness of 25 μm (0.025 mm) to 0.05 mm. It is converted.
◯: Dielectric breakdown voltage is 5 kV/0.05 mm or more, and extremely high voltage resistance.
x: The dielectric breakdown voltage is less than 5 kV/0.05 mm, and the withstand voltage is insufficient.

[Evaluation of acid resistance]
Each substrate for evaluation was tin-plated using a commercially available electroless tin-plating bath under conditions of 1±0.2 μm of tin. After visually observing the cured product of the curable resin composition on each substrate for evaluation after plating, the presence or absence of peeling of the cured product was confirmed by tape peeling, and the acid resistance was evaluated according to the following criteria. Table 1 shows the evaluation results. In this evaluation, a copper circuit pattern board was used instead of the copper solid board in the production of the evaluation board, and the entire surface coating by screen printing in Examples 1 and 2 and Comparative Examples 1 and 2 was pattern printed. Instead, evaluation substrates prepared in the same manner as in Examples 3 to 6 and Comparative Examples 3 to 6 were used, except that pattern exposure was used.
◯: Neither peeling nor whitening of the cured product was observed, and the acid resistance was sufficiently high.
x: Peeling and whitening of the cured product are observed, and the acid resistance is insufficient.

From the evaluation results shown in Table 1, when the curable resin composition of each example was used, the maintenance of low glossiness over time and the resulting solder adhesion resistance over time, voltage resistance, and It can be seen that it is possible to form a solder resist that satisfies both at a high level. Furthermore, it can be seen that when the curable resin composition of each example is used, a solder resist having high acid resistance can be formed. That is, according to a curable resin composition containing a curable resin, barium sulfate, and a thermosetting catalyst, and having an oil absorption of 40 to 70 mL/100 g of barium sulfate, a low glossiness is maintained over time and thereby brought about. It was shown that a solder resist that has both resistance to solder adhesion over time and voltage resistance at a high level and that has high acid resistance can be formed. On the other hand, when the curable resin composition of each comparative example was used, it was shown that the maintenance of the low glossiness over time and the resulting solder adhesion resistance over time and the voltage resistance are not compatible. was done.

Claims

A curable resin composition comprising a curable resin, barium sulfate, and a thermosetting catalyst,
A curable resin composition, wherein the barium sulfate has an oil absorption of 40 to 70 mL/100 g.
The curable resin composition according to claim 1, wherein the barium sulfate includes barium sulfate surface-treated with silica.
The curable resin composition according to claim 1, wherein the curable resin contains one or more thermosetting resins selected from the group consisting of epoxy compounds, polyfunctional oxetane compounds and oxazoline compounds.
The curable resin composition according to claim 1, wherein the curable resin contains a carboxyl group-containing photosensitive resin having one or more ethylenically unsaturated groups in one molecule.
The curable resin composition according to claim 4, further comprising a photopolymerization initiator.
The curable resin composition according to claim 1, which is used for forming a solder resist.
The curable resin composition according to claim 6, wherein the solder resist is a matte solder resist.
A cured product of the curable resin composition according to claim 1.
A printed wiring board comprising the cured product according to claim 8.
A method for manufacturing a printed wiring board comprising a solder resist, comprising the step of forming the solder resist by curing the curable resin composition according to claim 1.