Curable resin composition for solder resist, cured product, and printed wiring board

Abstract

To provide a curable resin composition for a solder resist that avoids nozzle clogging occurring at a nozzle portion of an apparatus during printing and stabilizes printing quality in inkjet printing.SOLUTION: A curable resin composition for a solder resist contains a compound represented by a specific formula, a (meth)acrylic monomer, a thermosetting component, and a photopolymerization initiator. The thermosetting component may contain a blocked isocyanate. The (meth)acrylic monomer may contain a (meth)acrylic monomer having a hydroxyl group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a curable resin composition for a solder resist, particularly a curable resin composition for a solder resist suitable for inkjet printing, and also to a cured product thereof and a printed wiring board. [Background technology]

[0002] When manufacturing printed wiring boards, methods such as screen printing have long been known as methods for coating a board with a solder resist. Because the screen printing method for forming a coating requires many processing steps, such as development, and is cumbersome, in recent years, a method of directly applying a curable resin composition to desired locations using an inkjet method has been adopted. The inkjet method does not require the preparation of a screen mesh or photomask, and can reduce the number of steps compared to methods such as screen printing, offering significant advantages in terms of cost reduction and takt time reduction (see Patent Document 1, etc.).

[0003] Taking advantage of the advantages of the inkjet method described above, a curable resin composition that can be printed by the inkjet method has been disclosed, for example, as a curable resin composition containing a specific radical polymerizable monomer, a compound having a (meth)acryloyl group, a photopolymerization initiator, and a thermosetting component (see Patent Document 2, etc.). Furthermore, a piezoelectric element is used in the inkjet printing. In order to stably discharge the solder resist composition from the piezoelectric element, it is necessary to ensure the fluidity of the solder resist composition within the pores. For this reason, the solder resist composition is heated within the device.

[0004] Although the fluidity of the solder resist composition is increased by the aforementioned heating, the components contained in the composition may volatilize due to heating. As a result, it has been pointed out that the solder resist composition may accumulate in the nozzle of the inkjet ejection device, causing nozzle clogging. In the inkjet method, the nozzle diameter is very small, and nozzle clogging is therefore considered to be a problem as it directly leads to a decrease in print quality. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2013 / 146706 [Patent Document 2] International Publication No. 2022 / 114133 Summary of the Invention [Problem to be solved by the invention]

[0006] However, with regard to the curable resin composition described in Patent Document 2, deposition on the nozzles of a discharge device for inkjet use has not been fully considered, and there is room for further consideration.

[0007] The present invention has been made in consideration of the above points, and provides a curable resin composition for a solder resist that suppresses nozzle clogging of a discharge device and stabilizes printing quality, and also provides a cured product of the curable resin composition and a printed wiring board having the cured product. [Means for solving the problem]

[0008] As a result of extensive investigations to achieve the above object, the inventors have found that a curable resin composition for a solder resist, which is capable of suppressing nozzle clogging of a discharge device and stabilizing printing quality, can be obtained by containing a compound represented by the following formula (i), a (meth)acrylic monomer, a thermosetting component, and a photopolymerization initiator, and have thus completed the present invention.

[0009] That is, the curable resin composition for a solder resist of the embodiment is characterized by containing a compound represented by the following formula (i), a (meth)acrylic monomer, a thermosetting component, and a photopolymerization initiator.

[0010] [ka]

[0011] In the curable resin composition for a solder resist of the embodiment, the thermosetting component may contain a blocked isocyanate. In the curable resin composition for a solder resist of the embodiment, the (meth)acrylic monomer may contain a (meth)acrylic monomer having a hydroxyl group.

[0012] In the curable resin composition for a solder resist of the embodiment, the viscosity of the curable resin composition for a solder resist at 50° C. may be 50 mPa·s or less.

[0013] The curable resin composition for a solder resist according to the embodiment may be for inkjet printing.

[0014] The cured product of the embodiment is a cured product obtained by curing the curable resin composition for a solder resist.

[0015] A printed wiring board according to an embodiment is characterized in that it is a printed wiring board including the cured product. [Effects of the Invention]

[0016] The curable resin composition for a solder resist of the present invention contains a compound represented by formula (i), a (meth)acrylic monomer, a thermosetting component, and a photopolymerization initiator, and therefore the curable resin composition for a solder resist can avoid nozzle clogging that occurs in the nozzle of a discharge device during printing, thereby stabilizing printing quality. In another aspect of the present invention, a cured product obtained by curing the curable resin composition for a solder resist and a printed wiring board comprising the cured product can have a good finish. DETAILED DESCRIPTION OF THE INVENTION

[0017] A curable resin composition for a solder resist according to an embodiment contains a compound represented by the following formula (i), a (meth)acrylic monomer, a thermosetting component, and a photopolymerization initiator. When preparing the curable resin composition for a solder resist, the components are weighed out in a predetermined blending ratio and stirred and mixed by a known preparation method. Each component constituting the curable resin composition for a solder resist according to the present invention will be described below.

[0018] [Compound represented by formula (i)] The compound represented by the following formula (i) acts as a radical polymerization monomer. This compound is also sometimes referred to as cyclohexyl α-allyloxymethylacrylate, etc. Based on the verification of the examples described below, the compound of formula (i) has good printing properties as a curable resin composition for a solder resist and is effective in preventing nozzle clogging in a discharge device. The reason for this is not entirely clear, but is presumed to be as follows: The compound of formula (i) has low viscosity, high solubility, and excellent dilution properties. However, it is believed that the presence of a cyclohexyl group, which has a large molecular weight and a bulky structure compared to methyl α-allyloxymethylacrylate, etc., increases intermolecular forces and raises the boiling point. As a result, when the curable resin composition for a solder resist is heated in a discharge device, volatilization is suppressed, making it possible to prevent deposition of the curable resin composition for a solder resist in the nozzles of the discharge device.

[0019] [ka]

[0020] The radical reaction in the compound represented by formula (i) is represented by the following reaction formula: (In the formula, "X·" represents an initiating radical or propagating radical, and "C·" represents the flow of electrons.) In the reaction between "X·" and the compound represented by formula (i), a polymerization reaction proceeds with cyclization within the compound represented by formula (i). This allows for the formation of a main chain skeleton with repeating units of a five-membered ring ether structure with methylene groups on both sides. Note that not all of the compound represented by formula (i) undergoes cyclization during polymerization; polymerization in a mixture of cyclized and non-cyclized states is also permitted.

[0021] [ka]

[0022] [ka]

[0023] The five-membered ring ether structure, with methylene groups on both sides, has excellent adhesion to a variety of substrates, and is flexible and conformable while possessing a high glass transition temperature and hardness. It also has high resistance to thermal decomposition, allowing it to adhere to many types of substrates, not just plastics, and is highly durable.

[0024] The amount of the compound represented by formula (i) is, in terms of solid content, preferably 1 part by mass or more and 99 parts by mass or less, more preferably 5 parts by mass or more and 95 parts by mass or less, and even more preferably 30 parts by mass or more and 95 parts by mass or less, relative to 100 parts by mass in total of the compound represented by formula (i) and the (meth)acrylic monomer described below. When the amount of the compound of formula (i) is within the above range, the viscosity of the curable resin composition for a solder resist becomes more suitable for inkjet coating.

[0025] [(Meth)acrylic monomer] The (meth)acrylic monomer is a monomer having an ethylenically unsaturated double bond, and for example, a monofunctional (meth)acrylate or a polyfunctional (meth)acrylate can be used. The (meth)acrylic monomer excludes the compound represented by the formula (i). The polyfunctional (meth)acrylate can be a bifunctional (meth)acrylate or a trifunctional or higher functional (meth)acrylate. In this specification, the term "(meth)acrylic monomer" collectively refers to acrylates, methacrylates, and mixtures thereof, and the same applies to other similar expressions. The (meth)acrylic monomer may be used alone or in combination of two or more types.

[0026] Examples of the monofunctional (meth)acrylate that can be used include (meth)acrylates, acryloylmorpholine, etc. Specific examples of the (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and glycidyl methacrylate. Specific examples of the acrylic morpholine include 4-acrylic morpholine.

[0027] Examples of the bifunctional (meth)acrylate include (meth)acrylates of diols, di(meth)acrylates of diols, di(meth)acrylates of glycols, and di(meth)acrylates having a cyclic structure. Specific examples of the (meth)acrylates of diols include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, and 1,10-decanediol di(meth)acrylate. Specific examples of the (meth)acrylates of diols include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate. di(meth)acrylates of glycols such as ethylene oxide, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, di(meth)acrylates of diols obtained by adding at least one of ethylene oxide and propylene oxide to neopentyl glycol, caprolactone-modified hydroxypivalic acid neopentyl glycol di(meth)acrylate, diacrylates having a cyclic structure such as bisphenol A EO adduct di(meth)acrylate, bisphenol A PO adduct di(meth)acrylate, tricyclodecane dimethanol diacrylate, hydrogenated dicyclopentadienyl diacrylate, and cyclohexyl diacrylate.

[0028] Examples of the tri- or higher functional (meth)acrylate include trimethylolpropane tri(meth)acrylate, trimethylolmethane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, epichlorohydrin-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, ethylene oxide-modified phosphate tri(meth)acrylate, propylene oxide-modified phosphate tri(meth)acrylate, epichlorohydrin-modified glycerol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and polyfunctional (meth)acrylates such as silsesquioxane-modified versions of these.

[0029] Among the above-mentioned (meth)acrylic monomers, it is preferable to contain a (meth)acrylic monomer having a hydroxyl group, which can promote curing of the curable resin composition for a solder resist.

[0030] The (meth)acrylic monomer having a hydroxyl group is not particularly limited, and examples thereof include hydroxyl group-containing alkyl (meth)acrylates. Specific examples of hydroxyl group-containing alkyl (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-acryloyloxypropyl (meth)acrylate, 2-hydroxy-3-phenoxyethyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol monohydroxypenta(meth)acrylate.

[0031] [Thermosetting component] Any known thermosetting component can be used as the thermosetting component. When the curable resin composition for a solder resist contains a thermosetting component, the heat resistance of the cured product is improved. Examples of known thermosetting components that can be used include amino resins such as melamine resins, benzoguanamine resins, melamine derivatives, and benzoguanamine derivatives, isocyanate compounds, blocked isocyanate compounds, cyclocarbonate compounds, epoxy compounds, oxetane compounds, episulfide resins, bismaleimides, and carbodiimide resins. Among the above-mentioned thermosetting components, epoxy compounds and blocked isocyanate compounds are preferred, and blocked isocyanate compounds are more preferred. The thermosetting components can be used alone or in combination of two or more.

[0032] Examples of epoxy compounds include bisphenol A type epoxy resins, bisphenol F type epoxy resins, hydrogenated bisphenol A type epoxy resins, brominated bisphenol A type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol A novolac type epoxy resins, biphenyl type epoxy resins, naphthalene type epoxy resins, dicyclopentadiene type epoxy resins, and triphenylmethane type epoxy resins.

[0033] Other examples include epoxy acrylate resins obtained by reacting acrylic acid with a polyfunctional epoxy resin such as a cresol novolac epoxy resin, and epoxy urethane acrylate compounds obtained by reacting a half urethane compound of a hydroxy acrylate such as pentaerythritol triacrylate and a diisocyanate such as isophorone diisocyanate with the hydroxyl group of the epoxy acrylate resin.

[0034] Examples of commercially available epoxy resins include jER 828, 806, 807, YX8000, YX8034, and 834 manufactured by Mitsubishi Chemical Corporation; YD-128, YDF-170, ZX-1059, and ST-3000 manufactured by Nippon Steel Chemical & Material Co., Ltd.; EPICLON 830, 835, 840, 850, N-730A, and N-695 manufactured by DIC Corporation; and RE-306 manufactured by Nippon Kayaku Co., Ltd.

[0035] 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 of suitable oxetane compounds include polyfunctional oxetanes such as acrylate, (3-methyl-3-oxetanyl)methyl methacrylate, (3-ethyl-3-oxetanyl)methyl methacrylate, and oligomers or copolymers thereof, as well as ethers of oxetane alcohols with novolak resins, poly(p-hydroxystyrene), cardo-type bisphenols, calixarenes, calixresorcinarenes, or hydroxyl group-containing resins such as silsesquioxane. Other examples include copolymers of unsaturated monomers having an oxetane ring and alkyl (meth)acrylates.

[0036] Examples of compounds having multiple cyclic thioether groups in the molecule include bisphenol A episulfide resins. Similar synthesis methods can also be used to produce episulfide resins in which the oxygen atoms of the epoxy groups in novolac epoxy resins are replaced with sulfur atoms. Furthermore, examples of amino resins, such as melamine derivatives and benzoguanamine derivatives, include methylolmelamine compounds, methylolbenzoguanamine compounds, methylolglycoluril compounds, and methylolurea compounds.

[0037] As the isocyanate compound or blocked isocyanate compound, a compound having multiple isocyanate groups or blocked isocyanate groups in one molecule can be used. Examples of such compounds having multiple isocyanate groups or blocked isocyanate groups in one molecule include polyisocyanate compounds and blocked isocyanate compounds. A blocked isocyanate group is a group in which an isocyanate group is protected and temporarily inactivated by reaction with a blocking agent; when heated to a predetermined temperature, the blocking agent dissociates to generate an isocyanate group. Addition of the polyisocyanate compound or blocked isocyanate compound improves curability and the toughness of the resulting cured product. As the polyisocyanate compound, an aromatic polyisocyanate, an aliphatic polyisocyanate, or an alicyclic polyisocyanate can be used.

[0038] Specific examples of aromatic isocyanates include 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, naphthalene-1,5-diisocyanate, o-xylylene diisocyanate, m-xylylene diisocyanate, and 2,4-tolylene dimer.

[0039] Specific examples of aliphatic polyisocyanates include tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4-methylenebis(cyclohexyl isocyanate), and isophorone diisocyanate.

[0040] Specific examples of the alicyclic polyisocyanate include alicyclic polyisocyanates such as bicycloheptane triisocyanate; and adducts, biuret compounds and isocyanurates of the isocyanate compounds mentioned above.

[0041] The blocked isocyanate compound may be an addition reaction product of an isocyanate compound and an isocyanate blocking agent. Examples of the isocyanate compound that can react with the isocyanate blocking agent include the polyisocyanate compounds described above.

[0042] Examples of isocyanate blocking agents that can be used include phenol-based blocking agents, lactam-based blocking agents, active methylene-based blocking agents, alcohol-based blocking agents, oxime-based blocking agents, mercaptan-based blocking agents, acid amide-based blocking agents, imide-based blocking agents, amine-based blocking agents, imidazole-based blocking agents, and imine-based blocking agents.

[0043] The amount of the thermosetting component is not particularly limited, but is preferably 1 part by mass or more and 50 parts by mass or less, and more preferably 5 parts by mass or more and 30 parts by mass or less, relative to 100 parts by mass of the total of the compound represented by formula (i) and the (meth)acrylic monomer in the curable resin composition for a solder resist, calculated as solid content. By being within this range, the viscosity of the curable resin composition for a solder resist is easily made more suitable for inkjet coating, and ultraviolet curing is less likely to be inhibited.

[0044] [Photopolymerization initiator] Any photopolymerization initiator can be used as long as it is a compound that generates radicals and initiates a radical polymerization reaction when exposed to light, a laser, an electron beam, etc. The photopolymerization initiator may be used alone or in combination of two or more types.

[0045] As the photopolymerization initiator, benzoins, benzoin alkyl ethers, acetophenones, aminoacetophenones, anthraquinones, thioxanthones, ketals, thiol compounds, organic halogen compounds, benzophenones, oxime esters, titanocene compounds, and the like can be used.

[0046] Specific examples of benzoins and benzoin alkyl ethers include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, and benzoin n-butyl ether. Specific examples of acetophenones include acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, and the like. Specific examples of aminoacetophenones include 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, and N,N-dimethylaminoacetophenone. Specific examples of anthraquinones include anthraquinone, 1-chloroanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, and 1-chloroanthraquinone.

[0047] Specific examples of thioxanthones include 2-ethylthioxanthone, 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, and 2,4-diisopropylthioxanthone. Specific examples of ketals include acetophenone dimethyl ketal and benzyl dimethyl ketal. Specific examples of the thiol compound include 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, and 2-mercaptobenzothiazole. Specific examples of the organic halogen compound include 2,2,2-tribromoethanol and tribromomethylphenyl sulfone. Specific examples of benzophenones include benzophenone, 4,4'-bisdiethylaminobenzophenone, and the like. Specific examples of oxime esters include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime), etc. Specific examples of titanocene compounds include bis(2,4-cyclopentadienyl)bis[2,6-difluoro-3-(1-pyrryl)phenyl]titanium, etc. However, the component added as a photopolymerization initiator is not limited to these, and any component that absorbs light in the ultraviolet or visible light region and initiates radical polymerization of an ethylenically unsaturated group such as a (meth)acryloyl group may be used.

[0048] In addition to the above, a photoinitiator assistant can be used. As the photoinitiator assistant, a tertiary amine or the like can be used. Specific examples of the tertiary amine include N,N-dimethylaminobenzoic acid ethyl ester, N,N-dimethylaminobenzoic acid isoamyl ester, pentyl-4-dimethylaminobenzoate, triethylamine, triethanolamine, etc.

[0049] The amount of the photopolymerization initiator is a necessary and sufficient amount to promote the reaction between the compound represented by the above formula (i) and the (meth)acrylic monomer. The relative amount of the photopolymerization initiator per 100 parts by mass of the curable resin composition for a solder resist is 3 to 10 parts by mass. The amount of the photopolymerization initiator can be adjusted depending on the composition of the photopolymerization initiator, the type of (meth)acrylic monomer, reaction conditions, etc.

[0050] [Coloring agent] A colorant may be added to the curable resin composition for a solder resist of the present invention for the purpose of coloring. Known colorants such as red, blue, green, and yellow can be used as the colorant, and any of pigments, dyes, and coloring matters can be used. From the viewpoints of reducing the environmental load and minimizing the impact on the human body, it is preferable that the colorant does not contain halogen.

[0051] Red colorants include monoazos, disazos, azo lakes, benzimidazolone, perylene, diketopyrrolopyrrole, condensed azos, anthraquinones, and quinacridones, and specific examples thereof include colorants assigned the following Color Index (CI; published by The Society of Dyers and Colourists) numbers.

[0052] Examples of monoazo 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 red colorants include Pigment Red 37, 38, and 41. Examples of monoazo lake-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. Condensed azo red colorants include Pigment Red 220, 144, 166, 214, 220, 221, and 242. Anthraquinone red colorants include Pigment Red 168, 177, and 216, Solvent Red 149, 150, 52, and 207. Quinacridone red colorants include Pigment Red 122, 202, 206, 207, and 209.

[0053] Blue colorants include phthalocyanine-based and anthraquinone-based compounds, and examples of pigment-based compounds include compounds classified as pigments, such as Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, and 60. Examples of dye-based compounds that can be used include Solvent Blue 35, 63, 68, 70, 83, 87, 94, 97, 122, 136, 67, and 70. In addition to the above, metal-substituted or unsubstituted phthalocyanine compounds can also be used.

[0054] Yellow colorants include monoazo, disazo, condensed azo, benzimidazolone, isoindolinone, and anthraquinone. Examples of anthraquinone yellow colorants include Solvent Yellow 163, Pigment Yellow 24, 108, 193, 147, 199, and 202. Examples of isoindolinone yellow colorants include Pigment Yellow 110, 109, 139, 179, and 185. Examples of condensed azo yellow colorants include Pigment Yellow 93, 94, 95, 128, 155, 166, and 180. Examples of benzimidazolone yellow colorants include Pigment Yellow 120, 151, 154, 156, 175, and 181. Furthermore, examples of monoazo 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, and 183. Examples of disazo yellow colorants include Pigment Yellow 12, 13, 14, 16, 17, 55, 63, 81, 83, 87, 126, 127, 152, 170, 172, 174, 176, 188, and 198.

[0055] Other colorants such as purple, orange, brown, black, and white may be added as needed. Specific examples include Pigment Black 1, 6, 7, 8, 9, 10, 11, 12, 13, 18, 20, 25, 26, 28, 29, 30, 31, and 32, Pigment Violet 19, 23, 29, 32, 36, 38, and 42, Solvent Violet 13 and 36, CI Pigment Orange 1, 5, 13, 14, 16, 17, 24, 34, 36, 38, 40, 43, 46, 49, 51, 61, 63, 64, 71, and 73, Pigment Brown 23 and 25, carbon black, and titanium oxide.

[0056] The amount of colorant blended is not particularly limited, and is an amount necessary and sufficient for coloring the curable resin composition for a solder resist. The relative amount of colorant per 100 parts by mass of the curable resin composition for a solder resist is 0.2 to 2 parts by mass, preferably 0.3 to 1 part by mass. The amount of colorant blended can be adjusted depending on the color intensity of the colorant itself, its dispersibility in the (meth)acrylic monomer, etc.

[0057] [Other added ingredients] The curable resin composition for a solder resist of the embodiment may contain, as necessary, components such as organic solvents, cyanate compounds, elastomers, mercapto compounds, urethanization catalysts, thixotropic agents, adhesion promoters, block copolymers, chain transfer agents, polymerization inhibitors, antioxidants, surface tension modifiers, rust inhibitors, thickeners such as finely divided silica, organic bentonite, and montmorillonite, antifoaming agents and / or leveling agents such as silicone-based, fluorine-based, and polymer-based, silane coupling agents such as imidazole-based, thiazole-based, and triazole-based, flame retardants such as phosphinates, phosphate ester derivatives, and phosphorus compounds such as phosphazene compounds, etc. These may be compounds known in the field of electronic materials.

[0058] [Physical properties (viscosity)] The curable resin composition for solder resist according to the embodiment preferably has a viscosity that takes into account the flowability in a discharge device for inkjet printing, the flight properties of ink particles, and the adhesion to a printed wiring board after application. The viscosity of the curable resin composition for solder resist (inkjet solder resist) at 50°C is preferably 50 mPa·s or less, and more preferably 20 mPa·s or less. The viscosity of the curable resin composition for solder resist is measured in accordance with JIS Z 8803:2011, Section 10, "Method of measuring viscosity using a cone-plate rotational viscometer." Detailed conditions are described in the examples below.

[0059] [Application] The curable resin composition for a solder resist according to the embodiment is useful as a material for forming an insulating layer of a printed wiring board. The insulating layer of a printed wiring board can be formed either on the board itself or on a substrate. It is particularly useful as a solder resist formed on a substrate, and is preferably used as an inkjet solder resist. Furthermore, since the curable resin composition for a solder resist of the present invention has heat resistance, it is also useful as a marking ink or the like that requires heat resistance.

[0060] [Cured product] The cured product of the curable resin composition for a solder resist of the embodiment is a curable resin composition for a solder resist, which is applied to a layer of the curable resin composition for a solder resist immediately after inkjet printing using an inkjet printer at a dose of 50 to 100 mJ / cm 2 . 2 ~1000mJ / cm 2 The curable resin composition for a solder resist can be obtained by photo-curing the layer of the curable resin composition for a solder resist by irradiating it with active energy rays such as ultraviolet rays, electron beams, and actinic rays, preferably ultraviolet rays.

[0061] Inkjet printers use a light source such as a high-pressure mercury lamp, metal halide lamp, or UV LED attached to the side of the print head, and scan the print head or substrate by moving it. In this case, printing and UV irradiation are performed almost simultaneously.

[0062] The cured product after irradiation with active energy rays is thermally cured using known heating means, for example, a heating furnace such as a hot air furnace, an electric furnace, an infrared induction heating furnace, etc. The heating conditions are preferably 130°C to 170°C for 5 to 90 minutes.

[0063] [Printed wiring board] The printed wiring board is a substrate comprising a cured product formed by applying a curable resin composition for a solder resist according to an embodiment and curing the composition on the substrate. Examples of substrate base materials include printed wiring boards and flexible printed wiring boards with circuits pre-formed using copper or the like, as well as copper-clad laminates for high-frequency circuits made of 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 the like. Examples of copper-clad laminates include all grades (e.g., FR-4), metal substrates, polyimide films, polyethylene terephthalate films, polyethylene naphthalate (PEN) films, glass substrates, ceramic substrates, and wafer plates. [Example]

[0064] In the following description of examples and comparative examples, the present invention is not limited to the embodiments of the examples and comparative examples. In the following, "parts" and "%" are all based on mass unless otherwise specified.

[0065] [Raw materials used] The raw materials and abbreviations used in the examples and comparative examples are as follows. (Compound represented by formula (i)) AOMA-CH: 2-(allyloxymethyl) cyclohexyl acrylate ((Meth)acrylic monomer) A-BPE-4: Ethoxylated bisphenol A diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) DPGDA: Dipropylene glycol diacrylate (manufactured by Daicel Allnex Co., Ltd.) 1,9-NDA: 1,9-nonanediol diacrylate (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) AOMA: 2-(allyloxymethyl)methyl acrylate (manufactured by Nippon Shokubai Co., Ltd.) 4HBA: 4-hydroxybutyl acrylate (Mitsubishi Chemical Corporation)

[0066] (Thermosetting component) SBL-100: Blocked isocyanate (manufactured by Asahi Kasei Corporation) jER828: Bisphenol A epoxy resin (manufactured by Mitsubishi Chemical Corporation) (Photopolymerization initiator) Omnirad® 379: 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one (IGM Resins BV) Omnirad® 819: bis(2,6-dimethoxybenzoyl) 2,4,4-trimethylpentylphosphine oxide (manufactured by IGM Resins B.V.) (Thermosetting catalyst) DICY7: Dicyandiamide (Mitsubishi Chemical Corporation)

[0067] (coloring agent) Phthalocyanine blue: FASTOGEN (registered trademark) BLUE (DIC Corporation) Cromophtal Yellow: Cromophtal Yellow GR (BASF Japan Ltd.) (rust prevention material) Melamine (Melamine: Nissan Chemical Co., Ltd.) (surface tension adjuster) BYK-307: Silicone additive (manufactured by BYK Japan Co., Ltd.)

[0068] [Preparation of curable resin composition for solder resist] The components were charged into a dissolver and stirred based on the composition and blending amounts (parts by mass) shown in Tables 1 and 2. The mixture was then dispersed using a bead mill for 2 hours to prepare curable resin compositions for solder resist of Examples 1 to 4 and Comparative Examples 1 and 2. A conical type K-8 bead mill (manufactured by Buehler Co., Ltd.) was used, and kneading was carried out under conditions of a rotation speed of 1200 rpm, a discharge rate of 20%, a bead particle size of 0.65 mm, and a filling rate of 88%.

[0069] [Viscosity Measurement of Curable Resin Composition for Solder Resist] The viscosity (mPa s) of the curable resin compositions for solder resist of Examples 1 to 4 and Comparative Examples 1 and 2 was measured in accordance with JIS Z 8803:2011, Section 10, "Method for measuring viscosity using a cone-plate rotational viscometer," using a cone rotor of 1°34' x R24 and a cone-plate viscometer (TVE-33H, manufactured by Toki Sangyo Co., Ltd.) at 50°C, 100 rpm, and 30 seconds.

[0070] [Evaluation of printing quality of curable resin composition for solder resist] The printing quality of the curable resin composition for a solder resist was evaluated by checking for any smearing in the coating film after printing caused by nozzle clogging as described below. First, for each of the curable resin compositions for solder resist in Examples 1 to 4 and Comparative Examples 1 and 2, an inkjet printing device (Microcraft Co., Ltd., CPS6151) was used to eject the curable resin composition for solder resist from the nozzle of an inkjet head (Konica Minolta, Inc., KM1024i) heated to 50 to 60°C, and the composition was exposed to light at an exposure dose of 800 mJ / cm using a UV-LED of 395 nm. 2The ink was cured at 200°C and ten evaluation substrates were printed onto a 140 mm x 85 mm, 1.6 mm thick FR-4 substrate (having 100 through-holes with a ring width of 100 μm (10 × 10 through-holes arranged at 2 mm intervals) (Shengyi Technology Co., Ltd., Autolad1) so that the coating film thickness was 40 μm. The ejection properties were evaluated by visually observing the coating films on the first, fifth, and tenth evaluation substrates, and the presence or absence of smearing due to nozzle clogging was confirmed on each evaluation substrate. ◯: No scratches were observed on the coating film of the evaluation substrate. ×: Scratches were observed on the coating film of the evaluation substrate.

[0071] [Evaluation of long-term reliability (cracking) of curable resin compositions for solder resist] The long-term stability of the curable resin composition for a solder resist was evaluated based on the presence or absence of cracks. First, for each of the curable resin compositions for solder resist in Examples 1 to 4 and Comparative Examples 1 and 2, an inkjet printing device (Microcraft Co., Ltd., CPS6151) was used to eject the curable resin composition for solder resist from the nozzle of an inkjet head (Konica Minolta, Inc., KM1024i) heated to 50 to 60°C, and the composition was exposed to light at an exposure dose of 800 mJ / cm using a UV-LED of 395 nm. 2 The paste was cured at 4000 K and printed onto an FR-4 substrate measuring 140 mm x 85 mm and 1.6 mm thick (with 100 through-holes with a ring width of 100 μm (10 × 10 through-holes arranged at 2 mm intervals) (Shengyi Technology Co., Ltd., Autolad1) to a coating thickness of 40 μm. After printing, each substrate was thermally cured at 150°C for 60 minutes in a hot air circulation drying oven, and then a reflow device (NIS-20-82, manufactured by Atec Techtron Co., Ltd.) was used to heat the substrate to 260°C at a rate of 60°C / min and hold the temperature at 260°C for 1 minute, for a total of 6 cycles of air reflow treatment. After the reflow treatment, 100 through-holes in each board were observed at a magnification of 100x using an optical microscope (Keyence Corporation, Digital Microscope VH-ZST), and the number of through-holes with cracks nearby was counted and the crack occurrence rate was calculated using the following formula. The calculated crack occurrence rate was evaluated according to the following criteria, and the evaluation results are shown in the table.

[0072]

number

[0073] The compositions and evaluations of the curable resin compositions for solder resists of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Tables 1 and 2.

[0074] [Table 1]

[0075] [Table 2]

[0076] [Consideration] From the results of each example and comparative example, all examples using cyclohexyl α-allyloxymethylacrylate, a compound represented by formula (i), showed good evaluations of print quality and cracking. In other words, it was found that incorporating cyclohexyl α-allyloxymethylacrylate, a compound represented by formula (i), is effective in suppressing nozzle clogging during inkjet printing. Furthermore, the occurrence of cracking when a curable resin composition for solder resist was prepared using cyclohexyl α-allyloxymethylacrylate was also suppressed, ensuring the reliability of printed wiring boards. Furthermore, the type of (meth)acrylic monomer used in the examples and comparative examples had little effect; rather, the presence or absence of the compound represented by formula (i) influenced the properties.

[0077] The main difference between Example 1 and Example 2 is the difference in the thermosetting component. Example 1 uses a blocked isocyanate, while Example 2 uses an epoxy resin. The difference between the two is the difference in the viscosity and crack evaluation. As in Example 1, it was found that the use of a blocked isocyanate reduces the viscosity and improves the crack evaluation.

[0078] The difference between Example 3 and Example 4 is the blending ratio of cyclohexyl α-allyloxymethylacrylate, the compound represented by formula (i). The same as in Example 3, the viscosity was reduced without any performance problems. Furthermore, the same as in Example 4, the viscosity did not increase dramatically and good performance was achieved.

[0079] Comparative Examples 1 and 2 are examples of curable resin compositions for solder resist that do not contain cyclohexyl α-allyloxymethylacrylate, a compound represented by formula (i). The viscosity was reduced by selecting the (meth)acrylic monomer. However, nozzle clogging occurred, which affected print quality. Therefore, in consideration of print quality (prevention of nozzle clogging), it is essential to contain cyclohexyl α-allyloxymethylacrylate, a compound represented by formula (i).

[0080] The results for the curable resin compositions for solder resists in each example show that the viscosity of the curable resin compositions for solder resists at 50°C is 50 mPa s or less, preferably 20 mPa s or less, and more preferably 15 mPa s or less. Therefore, by lowering the viscosity, it is possible to ensure the fluidity when heated while also preventing nozzle clogging during inkjet printing.

Claims

1. A compound represented by the following formula (i): a (meth)acrylic monomer; a thermosetting component; a photopolymerization initiator; 1. A curable resin composition for a solder resist, comprising: 【Chemistry 1】

2. 2. The curable resin composition for a solder resist according to claim 1, wherein the thermosetting component contains a blocked isocyanate.

3. 2. The curable resin composition for a solder resist according to claim 1, wherein the (meth)acrylic monomer comprises a (meth)acrylic monomer having a hydroxyl group.

4. 2. A curable resin composition for a solder resist according to claim 1, wherein the viscosity of said curable resin composition for a solder resist at 50° C. is 50 mPa·s or less.

5. 2. The curable resin composition for a solder resist according to claim 1, wherein the curable resin composition for a solder resist is for inkjet printing.

6. A cured product obtained by curing the curable resin composition for a solder resist according to any one of claims 1 to 5.

7. A printed wiring board comprising the cured product according to claim 6.

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