Alkali developable photosensitive resin composition, dry film, cured product, and printed wiring board

Abstract

Provided is an alkali developable photosensitive resin composition which contains a carboxyl group-containing resin, an epoxy-based thermosetting component, a (meth)acrylic monomer, and a photopolymerization initiator, wherein: the equivalent ratio (carboxyl group equivalent / epoxy group equivalent) of the carboxyl group to the epoxy group is 5.0 to 8.0; and the epoxy-based thermosetting component contains a novolac-type epoxy resin and a bifunctional crystalline epoxy resin that has a softening point of 70°C to 120°C.

Description

Alkali-developable photosensitive resin composition, dry film, cured product, and printed wiring board

[0001] The present invention relates to an alkali-developable photosensitive resin composition, a dry film, a cured product, and a printed wiring board.

[0002] Printed wiring boards used in electronic devices have electronic circuit patterns printed on a substrate using copper wire, and various components are mounted on them. When components are mounted on a printed wiring board with exposed copper wire, there is a risk of the copper wire breaking due to external force, or short circuits due to solder adhering to areas other than the circuit pattern. Therefore, a solder resist layer is formed to protect the circuit pattern and prevent short circuits.

[0003] The solder resist layer is formed, for example, by an alkaline development method using a photosensitive resin composition. The alkaline development method is a method in which the photosensitive resin composition is applied to the entire surface of a substrate, dried to form a coating film, exposed to light to partially cure the dried coating film, and then developed with an alkaline solution to develop the uncured photosensitive resin composition, thereby forming a pattern.

[0004] In recent years, with the miniaturization and increasing density of electronic devices, there has been a demand for forming finer patterns in addition to conventional sizes. In addition to the above-mentioned method, pores can be formed by irradiating a solder resist layer with a laser, and patterns of various sizes can be formed (see, for example, Patent Document 1).

[0005] International Publication No. 2013 / 094606 Pamphlet

[0006] On the other hand, hole formation by laser irradiation is achieved by removing part of the solder resist film with laser light. During this removal process, a component of the solder resist film called "smear" is generated. If mounting is performed with the smear remaining on the surface of the solder resist layer, it may cause connection failure. For this reason, after forming holes with laser light, a "desmear" process is required to remove the smear. Desmearing generally involves swelling the solder resist with a concentrated alkaline solution, followed by decomposition and removal with a permanganate solution. However, desmearing the solder resist layer can sometimes cause the solder resist layer to peel off.

[0007] On the other hand, one way to make the solder resist layer resistant to desmearing is to increase the proportion of epoxy resin in the photosensitive resin composition. However, increasing the proportion of epoxy resin in the photosensitive resin composition may deteriorate the thermal stability, etc. Furthermore, the resolution, which is an index of the ease of pattern formation required for the photosensitive resin composition that forms the solder resist layer, may also deteriorate.

[0008] The present invention has been made in light of the above circumstances, and an object of the present invention is to provide an alkali-developable photosensitive resin composition, a dry film, a cured product, and a printed wiring board, which are capable of forming a cured product having good resolution, thermal stability, and desmear resistance.

[0009] As a result of extensive research, the inventors have found that two factors are necessary for an alkali-developable photosensitive resin composition capable of forming a cured product with excellent resolution, thermal stability, and desmear resistance. One is the equivalent ratio of carboxyl groups to epoxy groups (carboxyl group equivalent / epoxy equivalent), which is the ratio of the carboxyl group-containing resin to the epoxy thermosetting component. If this equivalent ratio is less than 5.0, the proportion of the epoxy thermosetting component will be small, resulting in insufficient desmear resistance. If this equivalent ratio is more than 8.0, the proportion of the epoxy thermosetting component will be large, resulting in poor thermal stability, and the proportion of the carboxyl group-containing resin that improves the resolution of the alkali-developable resin composition will be small, resulting in poor resolution. The other factor is the combined use of a novolac epoxy resin and a bifunctional crystalline epoxy resin as the epoxy thermosetting component. Because novolac epoxy resins have excellent desmear resistance and bifunctional crystalline epoxy resins have excellent thermal stability, combining these resins can improve resolution, thermal stability, and desmear resistance.

[0010] That is, the alkali-developable photosensitive resin composition according to the present invention contains a carboxyl group-containing resin, an epoxy-based thermosetting component, a (meth)acrylic monomer, and a photopolymerization initiator, and is characterized in that the equivalent ratio of carboxyl groups to epoxy groups (carboxyl group equivalent / epoxy equivalent) is 5.0 to 8.0, and the epoxy-based thermosetting component contains a novolac epoxy resin and a bifunctional crystalline epoxy resin having a softening point of 70°C to 120°C.

[0011] In an embodiment of the present invention, the weight ratio of the novolac epoxy resin to the difunctional crystalline epoxy resin (novolac epoxy resin / difunctional crystalline epoxy resin) is preferably 1.0 to 2.0.

[0012] A dry film according to another aspect of the present invention is characterized by having a resin layer obtained from the above-mentioned alkali-developable photosensitive resin composition.

[0013] A cured product according to another aspect of the present invention is characterized by being obtained by curing the above-mentioned alkali-developable photosensitive resin composition or the above-mentioned resin layer.

[0014] A printed wiring board according to another aspect of the present invention is characterized by having the above-mentioned cured product.

[0015] According to the present invention, it is possible to provide an alkali-developable photosensitive resin composition capable of forming a cured product having good resolution, thermal stability, and desmear resistance, a dry film, a cured product, and a printed wiring board.

[0016] The alkali-developable photosensitive resin composition, dry film, cured product, and printed wiring board according to this embodiment will be described below. In this specification, when a numerical range is expressed with "to", it means a range that includes the numerical values ​​(i.e., from ... to ...).

[0017] (Alkali-developable photosensitive resin composition) The alkali-developable photosensitive resin composition according to this embodiment (hereinafter also referred to as "photosensitive resin composition") contains a carboxyl group-containing resin, an epoxy-based thermosetting component, a (meth)acrylic monomer, and a photopolymerization initiator, and may further contain other components as necessary.

[0018] <Carboxyl Group-Containing Resin> The carboxyl group-containing resin is a resin having a carboxyl group in the molecule, and various conventionally known resins can be used. By including a carboxyl group-containing resin in a photosensitive resin composition, resolution can be imparted to the photosensitive resin composition. In particular, a carboxyl group-containing photosensitive resin having an ethylenically unsaturated double bond in the molecule is preferred in terms of photocurability and resolution. The ethylenically unsaturated double bond is preferably derived from acrylic acid, methacrylic acid, or a derivative thereof.

[0019] Specific examples of the carboxyl group-containing resin include the following compounds (which may be either oligomers or polymers): These may be used alone or in combination of two or more.

[0020] (1) Carboxyl group-containing resins obtained by copolymerizing an unsaturated carboxylic acid such as (meth)acrylic acid with an unsaturated group-containing compound such as styrene, α-methylstyrene, lower alkyl (meth)acrylate, or isobutylene.

[0021] (2) Carboxyl group-containing urethane resins obtained by the polyaddition reaction of diisocyanates such as aliphatic diisocyanates, branched aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates with carboxyl group-containing dialcohol compounds such as dimethylolpropionic acid and dimethylolbutanoic acid, and diol compounds such as polycarbonate polyols, polyether polyols, polyester polyols, polyolefin polyols, acrylic polyols, bisphenol A alkylene oxide adduct diols, and compounds having a phenolic hydroxyl group and an alcoholic hydroxyl group.

[0022] (3) Carboxylic acid group-containing photosensitive urethane resins obtained by polyaddition reaction of diisocyanates with partially acid anhydride-modified products of reaction products of bifunctional epoxy resins such as bisphenol A epoxy resins, hydrogenated bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, bixylenol epoxy resins, and biphenol epoxy resins with monocarboxylic acid compounds having ethylenically unsaturated double bonds such as (meth)acrylic acid, carboxyl group-containing dialcohol compounds, and diol compounds.

[0023] (4) A carboxyl group-containing photosensitive urethane resin having a terminal (meth)acrylate formed by adding a compound having one hydroxyl group and one or more (meth)acryloyl groups in the molecule, such as a hydroxyalkyl (meth)acrylate, during the synthesis of the resin (2) or (3).

[0024] (5) A carboxyl group-containing photosensitive urethane resin that has been (meth)acrylated at its terminal by adding a compound having one isocyanate group and one or more (meth)acryloyl groups in the molecule, such as an equimolar reaction product of isophorone diisocyanate and pentaerythritol triacrylate, during the synthesis of the resin (2) or (3).

[0025] (6) A carboxyl group-containing photosensitive resin obtained by reacting a difunctional or more polyfunctional (solid) epoxy resin with (meth)acrylic acid and adding a dibasic acid anhydride to the hydroxyl group present in the side chain.

[0026] (7) A carboxyl group-containing photosensitive resin obtained by reacting a polyfunctional epoxy resin in which the hydroxyl groups of a bifunctional (solid) epoxy resin are further epoxidized with epichlorohydrin with (meth)acrylic acid, and then adding a dibasic acid anhydride to the resulting hydroxyl groups.

[0027] (8) Carboxyl group-containing polyester resins obtained by reacting a dicarboxylic acid such as adipic acid, phthalic acid, or hexahydrophthalic acid with a bifunctional oxetane resin, and then adding a dibasic acid anhydride such as phthalic anhydride, tetrahydrophthalic anhydride, or hexahydrophthalic anhydride to the resulting primary hydroxyl groups.

[0028] (9) A carboxyl group-containing photosensitive resin obtained by reacting an epoxy compound having multiple epoxy groups in one molecule with a compound having at least one alcoholic hydroxyl group and one phenolic hydroxyl group in one molecule, such as p-hydroxyphenethyl alcohol, and an unsaturated group-containing monocarboxylic acid, such as (meth)acrylic acid, and then reacting the alcoholic hydroxyl groups of the resulting reaction product with a polybasic acid anhydride, such as maleic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, or adipic acid.

[0029] (10) A carboxyl group-containing photosensitive resin obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with an alkylene oxide such as ethylene oxide or propylene oxide, reacting the resulting reaction product with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0030] (11) A carboxyl group-containing photosensitive resin obtained by reacting a compound having multiple phenolic hydroxyl groups in one molecule with a cyclic carbonate compound such as ethylene carbonate or propylene carbonate, reacting the resulting reaction product with an unsaturated group-containing monocarboxylic acid, and then reacting the resulting reaction product with a polybasic acid anhydride.

[0031] (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 any of the resins (1) to (11).

[0032] In this specification, (meth)acrylate is a general term that refers to acrylate, methacrylate, and mixtures thereof, and the same applies to other similar expressions.

[0033] The acid value of the carboxyl group-containing photosensitive resin is preferably 40 mgKOH / g to 150 mgKOH / g, more preferably 50 mgKOH / g to 130 mgKOH / g. By adjusting the acid value of the carboxyl group-containing photosensitive resin to 40 mgKOH / g to 150 mgKOH / g, the resolution becomes good.

[0034] The weight-average molecular weight of the carboxyl group-containing photosensitive resin varies depending on the resin skeleton, but is generally preferably 2,000 to 150,000, and more preferably 2,000 to 100,000. By making the weight-average molecular weight 2,000 or more, tack-free performance and resolution can be improved. Furthermore, by making the weight-average molecular weight 150,000 or less, resolution and storage stability can be improved.

[0035] The carboxyl group equivalent of the carboxyl group-containing photosensitive resin is preferably 100 g / eq. to 1,000 g / eq., and more preferably 400 g / eq. to 800 g / eq. Here, "eq." is an abbreviation for "equivalent." By setting the carboxyl group equivalent to 100 g / eq. or more, the number of carboxyl groups becomes appropriate, thereby improving developability. Furthermore, by setting the carboxyl group equivalent to 1,000 g / eq. or less, the crosslinking density can be increased, thereby improving the strength of the cured product.

[0036] The content of the carboxyl group-containing photosensitive resin in the photosensitive resin composition is preferably 20% by mass to 60% by mass, more preferably 20% by mass to 50% by mass, calculated as solid content. By making the content of the carboxyl group-containing photosensitive resin 20% by mass or more, the strength of the cured product can be improved. Furthermore, by making the content of the carboxyl group-containing photosensitive resin 60% by mass or less, the viscosity of the photosensitive resin composition becomes appropriate, and printability is improved.

[0037] <Epoxy-based thermosetting component> The epoxy-based thermosetting component is a compound having an epoxy group in the molecule. When the photosensitive resin composition contains the epoxy-based thermosetting component, desmear resistance can be imparted to a cured product of the photosensitive resin composition.

[0038] The epoxy thermosetting component contains a novolac epoxy resin and a difunctional crystalline epoxy resin.

[0039] Examples of novolac epoxy resins include those obtained by reacting a novolac obtained by reacting a phenol such as phenol, cresol, halogenated phenol, alkylphenol, or bisphenol A with formaldehyde in the presence of an acidic catalyst, with an epihalohydrin such as epichlorohydrin or methylepichlorohydrin. These may be used alone or in combination of two or more.

[0040] The novolac type epoxy resin can be used in any of liquid, semi-solid and solid forms, with the solid form being preferred.

[0041] When the novolac type epoxy resin has a softening point, it is 60 to 140°C, preferably 60 to 130°C.

[0042] A bifunctional crystalline epoxy resin is a crystalline epoxy resin having two epoxy groups, such as a biphenyl structure, a sulfide structure, a phenylene structure, a naphthalene structure, or a bisphenol structure.

[0043] The softening point of the bifunctional crystalline epoxy resin is 70°C to 120°C, preferably 70°C to 110°C.

[0044] The weight ratio of the novolac epoxy resin to the difunctional crystalline epoxy resin (novolac epoxy resin / difunctional crystalline epoxy resin) is preferably 1.0 to 2.0, more preferably 1.4 to 1.8. When the weight ratio (novolac epoxy resin / difunctional crystalline epoxy resin) is 1.0 or more, the desmear resistance of the cured product of the photosensitive resin composition can be improved, and when the weight ratio is 2.0 or less, the thermal stability of the photosensitive resin composition can be improved.

[0045] The epoxy equivalent of the epoxy-based thermosetting component is preferably 100 g / eq. to 1,000 g / eq., and more preferably 150 g / eq. to 200 g / eq. Here, the epoxy equivalent is the mass of a resin containing one equivalent of epoxy groups, as defined in JIS K 7236:2001. Note that "eq." is an abbreviation for "equivalent."

[0046] The equivalent ratio of carboxyl groups to epoxy groups (carboxyl group equivalent (g / eq.) / epoxy equivalent (g / eq.)) is 5.0 to 8.0, and preferably 6.0 to 7.0. If this equivalent ratio is less than 5.0, the desmear resistance of the cured product of the photosensitive resin composition may deteriorate, and if it exceeds 8.0, the resolution may deteriorate. The epoxy equivalent and carboxyl group equivalent here refer to the epoxy groups and carboxyl groups of all compounds contained in the alkali-developable photosensitive resin composition.

[0047] <(Meth)acrylic Monomer> The (meth)acrylic monomer is a compound having a (meth)acryloyl group in the molecule, which is contained in order to promote photocuring of the carboxyl group-containing resin.

[0048] As the (meth)acrylic monomer, known and commonly used (meth)acrylic monomers can be used. For example, polyfunctional allyl compounds such as triallyl isocyanurate, diallyl phthalate, and diallyl isophthalate; alkylene polyol poly(meth)acrylate compounds such as ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; polyoxyalkylene compounds such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, ethoxylated trimethylolpropane triacrylate, and propoxylated trimethylolpropane tri(meth)acrylate. Examples of such poly(meth)acrylates include glycol poly(meth)acrylates; poly(meth)acrylates such as hydroxypivalic acid neopentyl glycol ester di(meth)acrylate; isocyanurate-type poly(meth)acrylates such as tris[(meth)acryloxyethyl]isocyanurate; acrylamides such as N,N-dimethylacrylamide, N-methylolacrylamide, and N,N-dimethylaminopropylacrylamide; aminoalkyl acrylates such as N,N-dimethylaminoethyl acrylate and N,N-dimethylaminopropyl acrylate; and polyhydric acrylates of glycidyl ethers such as glycerin diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, and triglycidyl isocyanurate. These may be used alone or in combination of two or more.

[0049] The content of the (meth)acrylic monomer is preferably 5 to 100 parts by mass, more preferably 5 to 70 parts by mass, relative to 100 parts by mass of the carboxyl group-containing resin, calculated as solid content. By setting the content of the (meth)acrylic monomer to 5 to 100 parts by mass relative to 100 parts by mass of the carboxyl group-containing resin, photocurability and resolution are improved.

[0050] <Photopolymerization initiator> The photopolymerization initiator is contained in order to cure the photosensitive resin composition. The photopolymerization initiator is not particularly limited as long as it is one that is used in ordinary photosensitive resin compositions, and can be appropriately selected depending on the purpose, and any known photopolymerization initiator can be used. One type of photopolymerization initiator may be used alone, or two or more types may be used in combination.

[0051] Examples of the photopolymerization initiator include bis-(2,6-dichlorobenzoyl)phenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis-(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis-(2,6-dimethoxybenzoyl)phenylphosphine oxide, and bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide. bisacylphosphine oxides such as bis-(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide and bis-(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylphosphinic acid methyl ester, 2-methylbenzoyldiphenylphosphine oxide, pivaloylphenylphosphinic acid isopropyl monoacylphosphine oxides such as phenyl(2,4,6-trimethylbenzoyl)phosphinate, ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate, 1-hydroxy-cyclohexyl phenyl ketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, 2-hydroxy- Hydroxyacetophenones such as 2-methyl-1-phenylpropan-1-one; benzoins such as benzoin, benzil, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, benzoin isopropyl ether, and benzoin n-butyl ether; benzoin alkyl ethers; benzophenones such as benzophenone, p-methylbenzophenone, Michler's ketone, methylbenzophenone, 4,4'-dichlorobenzophenone, and 4,4'-bisdiethylaminobenzophenone;Acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl)-1-[4-(4-morpholinyl)phenyl]-1-butanone acetophenones such as thioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropylthioxanthone; anthraquinone, chloroanthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone, 2-amylanthraquinone, Anthraquinones such as 2-aminoanthraquinone; ketals such as acetophenone dimethyl ketal and benzil dimethyl ketal; benzoic acid esters such as ethyl 4-dimethylaminobenzoate, 2-(dimethylamino)ethyl benzoate and 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-acetyl oxime esters such as bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl)titanium and titanocenes such as bis(cyclopentadienyl)-bis[2,6-difluoro-3-(2-(1-pyr-1-yl)ethyl)phenyl]titanium; phenyl disulfide 2-nitrofluorene, butyroin, anisoin ethyl ether, azobisisobutyronitrile, tetramethylthiuram disulfide, and the like.

[0052] The content of the photopolymerization initiator excluding the oxime ester-based photopolymerization initiator is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, based on the solid content, relative to 100 parts by mass of the carboxyl group-containing resin. By setting the content of the photopolymerization initiator excluding the oxime ester-based photopolymerization initiator to 0.01 parts by mass or more, the photocurability of the photosensitive resin composition is improved, the coating film is less likely to peel, and coating properties such as chemical resistance are also improved. Furthermore, by setting the content of the photopolymerization initiator excluding the oxime ester-based photopolymerization initiator to 30 parts by mass or less, light absorption at the surface of the solder resist coating film is improved, and deep curing properties are less likely to decrease. The content of the oxime ester-based photopolymerization initiator is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 3.9 parts by mass, based on 100 parts by mass of the carboxyl group-containing resin, based on the solid content. By setting the content of the oxime ester photopolymerization initiator to 0.01 parts by mass or more, the photocurability of the photosensitive resin composition is improved, and the film properties such as heat resistance, chemical resistance, etc. are also improved. Furthermore, by setting the content of the oxime ester photopolymerization initiator to 5 parts by mass or less, light absorption at the surface of the solder resist coating film is improved, and deep curing properties are less likely to decrease.

[0053] <Other Components> The other components are not particularly limited as long as they are those typically used in photosensitive resin compositions and can be appropriately selected depending on the purpose, and examples thereof include a curing catalyst, a colorant, a filler, etc. These may be used alone or in combination of two or more.

[0054] <<Curing Catalyst>> The curing catalyst is a compound that has the property of being cured by heat. Examples of the curing catalyst include imidazole derivatives such as imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 1-cyanoethyl-2-phenylimidazole, and 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole; dicyandiamide, benzyldimethylamine, 4-(dimethylamino)-N,N-dimethylbenzylamine, 4-methoxy-N,N-dimethylbenzylamine, and 4-methyl-N,N-dimethylbenzylamine. hydrazine compounds such as adipic acid dihydrazide and sebacic acid dihydrazide; phosphorus compounds such as triphenylphosphine; and S-triazine derivatives such as guanamine, acetoguanamine, benzoguanamine, melamine, 2,4-diamino-6-methacryloyloxyethyl-S-triazine, 2-vinyl-2,4-diamino-S-triazine, 2-vinyl-4,6-diamino-S-triazine·isocyanuric acid adduct, and 2,4-diamino-6-methacryloyloxyethyl-S-triazine·isocyanuric acid adduct.

[0055] <<Colorant>> The colorant is not particularly limited as long as it is one that is commonly used in photosensitive resin compositions and can be appropriately selected depending on the purpose. Conventional and well-known colorants such as black, red, blue, green, yellow, and white can be used, and any of pigments, dyes, and colorants can be used.

[0056] Examples of black colorants include carbon black, zirconium nitride, and Pigment Black 1, 6, 7, 8, 9, 10, 11, 12, 13, 18, 20, 25, 26, 28, 29, 30, 31, and 32. Red colorants include monoazo, disazo, azo-lake, benzimidazolone, perylene, diketopyrrolopyrrole, condensed azo, anthraquinone, and quinacridone. Blue colorants include phthalocyanine and anthraquinone, and pigment compounds can be used. In addition to these, metal-substituted or unsubstituted phthalocyanine compounds can also be used. Green colorants include phthalocyanine, anthraquinone, and perylene. In addition to these, metal-substituted or unsubstituted phthalocyanine compounds can also be used. Yellow colorants include monoazo, disazo, condensed azo, benzimidazolone, isoindolinone, and anthraquinone colorants. White colorants include rutile or anatase titanium oxide. In addition, purple, orange, brown, and other colorants may be added to adjust the color tone.

[0057] <<Filler>> As the filler, known inorganic or organic fillers can be used, but barium sulfate, spherical silica, and talc are particularly preferably used.

[0058] The photosensitive resin composition of the present invention may further contain, as necessary, components such as a photoinitiator aid, a cyanate compound, an elastomer, a mercapto compound, a urethanization catalyst, a thixotropy agent, an adhesion promoter, a block copolymer, a chain transfer agent, a polymerization inhibitor, a copper inhibitor, an antioxidant, a rust inhibitor, a thickener such as organic bentonite or montmorillonite, at least one of a silicone-based, fluorine-based, or polymer-based antifoaming agent and a leveling agent, an imidazole-based, thiazole-based, or triazole-based silane coupling agent, a phosphinate, a phosphate ester derivative, a phosphorus compound such as a phosphazene compound, or the like.

[0059] The content of other components is not particularly limited as long as it does not impair the effects of the present invention, and can be appropriately selected depending on the purpose.

[0060] <Method for Producing Photosensitive Resin Composition> The method for producing the photosensitive resin composition is not particularly limited, and the photosensitive resin composition can be produced by, for example, blending the above-described components in a predetermined ratio and then kneading or mixing them at room temperature using a kneading means such as a triple roll mill, a ball mill, a bead mill, or a sand mill, or a stirring means such as a super mixer or a planetary mixer. Furthermore, prior to the kneading or mixing, pre-kneading or pre-mixing may be performed as necessary.

[0061] (Dry Film) The dry film according to this embodiment includes a resin layer and, if necessary, further includes other components.

[0062] <Resin Layer> The resin layer is formed on the first film described below and is obtained from the photosensitive resin composition described above. Here, the resin layer refers to a layer formed by applying and drying the photosensitive resin composition, and is not laminated with other layers such as the first film described below or other members. The thickness of the resin layer is not particularly limited and can be appropriately selected depending on the purpose.

[0063] <Other Components> The other components are not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a first film and a second film.

[0064] <<First Film>> The first film has a role of supporting the resin layer of the dry film, and is coated with a photosensitive resin composition when forming a resin layer made of the photosensitive resin composition. In the present invention, the first film refers to a film that is adhered to at least the resin layer when the dry film is laminated by heating or the like so that the resin layer side of the dry film is in contact with a base material such as a substrate to form an integral mold. The first film may be peeled from the resin layer in a step after lamination. In particular, in this embodiment, it is preferable to peel it from the resin layer in a step after exposure.

[0065] The first film can be any known film without particular limitation, and examples of suitable films include polyester films such as polyethylene terephthalate and polyethylene naphthalate, and films made of thermoplastic resins such as polyimide films, polyamideimide films, polypropylene films, and polystyrene films. Among these, polyester films are preferred from the viewpoints of heat resistance, mechanical strength, ease of handling, etc. A laminate of these films can also be used as the first film.

[0066] Moreover, from the viewpoint of improving mechanical strength, the film made of a thermoplastic resin is preferably a film stretched in a uniaxial or biaxial direction.

[0067] When a thermoplastic resin film is used as the first film, a film having a specific surface configuration may be used by adding a filler to the resin when forming the film (kneading treatment), by matte coating (coating treatment), by subjecting the film surface to a blasting treatment such as sandblasting, or by hairline processing or chemical etching, etc.

[0068] The thickness of the first film is not particularly limited, but can be, for example, 10 μm to 150 μm.

[0069] <<Second Film>> The second film is a film that is laminated for the purpose of preventing dust from adhering to the surface of the resin layer, etc. Specifically, when the dry film is laminated by heating or the like so that the resin layer side of the dry film is in contact with a base material such as a substrate to form an integral mold, the second film is a film that is peeled off from the resin layer before lamination.

[0070] The second film may be, for example, a polyethylene film, a polytetrafluoroethylene film, a polypropylene film, or surface-treated paper. The adhesive strength of the second film to the resin layer may be smaller than the adhesive strength between the resin layer and the first film. Since the adhesive strength of the second film is smaller than that of the first film, the second film can be peeled off without moving the first film.

[0071] The thickness of the second film is not particularly limited, but can be, for example, 10 μm to 150 μm.

[0072] <Method for producing dry film> To produce a dry film, the photosensitive resin composition described above is diluted with the organic solvent to adjust the viscosity to an appropriate level, and then coated to a uniform thickness on a first film using a comma coater, blade coater, lip coater, rod coater, squeeze coater, reverse coater, transfer roll coater, gravure coater, spray coater, applicator, or the like, and typically dried for 1 minute to 30 minutes at a temperature of 50° C. to 130° C. There are no particular restrictions on the coating film thickness, but it is generally selected appropriately from the range of 1 μm to 150 μm, preferably 5 μm to 60 μm, in terms of film thickness after drying.

[0073] (Cured Product) The cured product according to the embodiment is obtained by curing the above-described photosensitive resin composition or the resin layer of the above-described dry film. The size and shape of the cured product are not particularly limited and can be appropriately selected depending on the purpose.

[0074] As a method for producing a cured product, for example, the photosensitive resin composition of the present invention is adjusted to a viscosity suitable for the coating method using an organic solvent, and coated on a substrate by a method such as dip coating, flow coating, roll coating, bar coating, screen printing, or curtain coating so that the thickness after drying is, for example, 10 μm to 100 μm, and then the organic solvent contained in the composition is evaporated and dried (pre-dried) for 15 to 90 minutes at a temperature of 60 to 100° C. to form a tack-free resin layer. In addition, in the case of a dry film, the resin layer is attached to the substrate using a laminator or the like so that the resin layer is in contact with the substrate, and then the first film is peeled off to form a resin layer on the substrate.

[0075] Examples of the substrate include printed wiring boards and flexible printed wiring boards on which circuits have been formed in advance using copper or the like, copper-clad laminates made of materials such as 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, and polyphenylene oxide / cyanate, metal substrates, polyimide films, polyethylene terephthalate films, polyethylene naphthalate (PEN) films, glass substrates, ceramic substrates, and wafer plates.

[0076] The dry film is preferably bonded to the substrate under pressure and heat using a vacuum laminator or the like. By using such a vacuum laminator, when a circuit-formed substrate is used, the dry film adheres tightly to the circuit board even if the circuit board surface is uneven, preventing the inclusion of air bubbles and improving the ability to fill recesses in the substrate surface. The pressure condition is preferably about 0.1 to 2.0 MPa, and the heating condition is preferably 40 to 120°C.

[0077] The volatilization drying carried out after coating the photosensitive resin composition of the present invention can be carried out using a hot air circulation drying oven, an IR oven, a hot plate, a convection oven, or the like (a method in which hot air in a dryer equipped with a heat source of an air heating type using steam is brought into countercurrent contact with the substrate, or a method in which hot air is blown onto the substrate from a nozzle).

[0078] After forming a resin layer on a substrate, the resin layer is selectively exposed to active energy rays through a photomask with a predetermined pattern, and the unexposed areas are developed with a dilute alkaline aqueous solution (e.g., a 0.3 to 3% by weight aqueous solution of sodium carbonate) to form a cured product pattern. In the case of a dry film, after exposure, the first film is peeled off from the dry film and development is carried out, thereby forming a patterned cured product on the substrate. It should be noted that, as long as the properties are not impaired, the first film may be peeled off from the dry film before exposure, and the exposed resin layer may be exposed and developed. Furthermore, a cured coating film with excellent properties such as adhesion and hardness can be formed by irradiating the cured product with active energy rays and then heat-curing (e.g., 100 to 220°C), or by irradiating active energy rays after heat-curing, or by heat-curing alone to perform final finish curing (main curing).

[0079] The exposure device used for the active energy ray irradiation may be any device equipped with a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a mercury short arc lamp, or the like, and capable of irradiating ultraviolet rays in the range of 350 to 450 nm. Furthermore, a direct imaging device (for example, a laser direct imaging device that draws an image directly with a laser based on CAD data from a computer) may also be used. The lamp or laser light source of the direct imaging device may have a maximum wavelength in the range of 350 to 450 nm. The exposure dose for image formation varies depending on factors such as the film thickness, but is generally 10 to 1,000 mJ / cm. ２ , preferably 20 to 800 mJ / cm ２ The range may be:

[0080] The developing method may be a dipping method, a shower method, a spray method, a brush method, or the like, and the developing solution may be an aqueous alkali solution such as potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, sodium phosphate, sodium silicate, ammonia, or an amine.

[0081] (Printed Wiring Board) A printed wiring board according to one embodiment of the present invention has the above-described cured product. There are no particular limitations on the size or type of the printed wiring board, and they can be appropriately selected depending on the purpose.

[0082] Next, tests conducted by the present inventors will be described, but the present invention is not limited to these.

[0083] Synthesis Example 1: Preparation of Carboxyl Group-Containing Resin (A-1) 220 parts (1 equivalent) of cresol novolac epoxy resin (ECON-104S, manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 220 g / eq.) was placed in a four-neck flask equipped with a stirrer and a reflux condenser, and 218 parts of carbitol acetate was added and dissolved by heating. Next, 0.46 parts of methylhydroquinone as a polymerization inhibitor and 1.38 parts of triphenylphosphine as a reaction catalyst were added. This mixture was heated to 95°C to 105°C, and 50.4 parts (0.7 equivalents) of acrylic acid and 41.5 parts (0.3 equivalents) of p-hydroxyphenethyl alcohol were slowly added dropwise, followed by a 16-hour reaction. This reaction product (hydroxyl group: 1.3 equivalents) was cooled to 80-90°C, and 91.2 parts (0.6 equivalents) of tetrahydrophthalic anhydride was added. The reaction was allowed to proceed for 8 hours, and after cooling, the mixture was removed. The carboxyl group-containing resin thus obtained had a nonvolatile content of 65%, an acid value of 83 mg KOH / g of the solid matter, a carboxyl group equivalent of 676 g / eq. of the solid matter, and a weight-average molecular weight of 12,000. Hereinafter, this resin solution will be abbreviated as A-1.

[0084] Synthesis Example 2: Preparation of Carboxyl Group-Containing Resin (A-2)> 119.4 g of a novolac cresol resin (Shonor CRG951, manufactured by Aica Kogyo Co., Ltd., OH equivalent: 119.4), 1.19 g of potassium hydroxide, and 119.4 g of toluene were charged into an autoclave equipped with a thermometer, a nitrogen introducing device / alkylene oxide introducing device, and a stirrer, and the system was purged with nitrogen while stirring, and heated to an elevated temperature. Next, 63.8 g of propylene oxide was gradually added dropwise, and the temperature was raised to 125°C to 132°C and 0 kg / cm. ２ ~4.8 kg / cm ２The mixture was reacted at 100°C for 16 hours. The mixture was then cooled to room temperature, and 1.56 g of 89% phosphoric acid was added to the reaction solution to neutralize the potassium hydroxide, yielding a propylene oxide reaction solution of novolac cresol resin with a nonvolatile content of 62.1% and a hydroxyl value of 182.2 g / eq. This solution had an average of 1.08 moles of propylene oxide added per equivalent of phenolic hydroxyl group. Next, 293.0 g of the resulting propylene oxide reaction solution of novolac cresol resin, 43.2 g of acrylic acid, 11.53 g of methanesulfonic acid, 0.18 g of methylhydroquinone, and 252.9 g of toluene were charged into a reactor equipped with a stirrer, thermometer, and air inlet tube. Air was blown in at a rate of 10 mL / min, and the mixture was reacted at 110°C for 12 hours while stirring. The water produced by the reaction was distilled as an azeotrope with toluene, and 12.6 g of water was distilled off. The mixture was then cooled to room temperature, and the resulting reaction solution was neutralized with 35.35 g of 15% aqueous sodium hydroxide solution and then washed with water. The toluene was then removed by distillation using an evaporator, while being replaced with 118.1 g of diethylene glycol monoethyl ether acetate, to obtain a novolac acrylate resin solution. Next, 332.5 g of the resulting novolac acrylate resin solution and 1.22 g of triphenylphosphine were charged into a reactor equipped with a stirrer, thermometer, and air inlet tube. Air was blown in at a rate of 10 mL / min, and while stirring, 60.8 g of tetrahydrophthalic anhydride was gradually added. The mixture was reacted at 95°C to 101°C for 6 hours, cooled, and then discharged. The carboxyl group-containing resin thus obtained had a nonvolatile content of 71%, an acid value of 88 mg KOH / g of solids, a carboxyl group equivalent of 638 g / eq. of solids, and a weight-average molecular weight of 2,000. Hereinafter, this resin solution will be abbreviated as A-2.

[0085] (Examples 1 to 7, Comparative Examples 1 to 3) <Preparation of Photosensitive Resin Compositions> Each material was blended in the proportions shown in Table 1, premixed in a mixer, and then kneaded in a triple roll mill to prepare a photosensitive resin composition. The values ​​in the table are the contents in a solution containing a solvent. The units in the table are parts by mass.

[0086]

[0087] Details of each component in Table 1 are as follows: <Carboxyl group-containing resin> A-1 (Synthesis Example 1) A-2 (Synthesis Example 2) The values ​​for the carboxyl group-containing resin in Table 1 are values ​​for the resin solution. <Epoxy-based thermosetting component> N-770 (phenol novolac epoxy resin, epoxy equivalent: 190 g / eq., softening point: 70°C, manufactured by DIC Corporation) YX4000H (bifunctional crystalline epoxy resin, epoxy equivalent: 192 g / eq., softening point: 105°C, manufactured by Mitsubishi Chemical Corporation) jER-828 (bifunctional liquid epoxy resin (bisphenol A epoxy resin), epoxy equivalent: 189 g / eq., manufactured by Mitsubishi Chemical Corporation) <(Meth)acrylic monomer> Dipentaerythritol hexaacrylate <Photopolymerization initiator> Omnirad 907 (2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, manufactured by IGM Resins B.V.)・DETX-S (2,4-diethylthioxanthone, manufactured by Nippon Kayaku Co., Ltd.) <Other ingredients> <<Curing catalyst>> ・DICY (dicyandiamide, manufactured by Mitsubishi Chemical Corporation) ・Melamine (manufactured by Nissan Chemical Industries, Ltd.) <<Pigment>> ・Phthalocyanine Blue (manufactured by Tokyo Chemical Industry Co., Ltd.) ・Chrome Phthal Yellow (manufactured by Tokyo Chemical Industry Co., Ltd.) <<Filler>> ・Admafine SO-E2 (spherical silica, manufactured by Admatechs Co., Ltd.)

[0088] The carboxyl group equivalent, epoxy equivalent, and softening point of the epoxy resin in Table 1 were measured or calculated as follows.

[0089] <Calculation Method of Carboxyl Group Equivalent> First, the oxidation of each photosensitive resin composition was measured. The oxidation was measured in accordance with "7. Potentiometric titration method (acid value)" of JIS K2501:2003. The carboxyl group equivalent was calculated from the measured acid value (mg KOH / g) according to the following formula: Carboxyl group equivalent (g / eq.) = 56.11 / acid value (mg KOH / g) × 1000

[0090] <Method for measuring epoxy equivalent> The first equivalent of each photosensitive resin composition was measured using tetraethylammonium bromide in accordance with JIS K7236:2001. Meanwhile, the second equivalent was measured in the same manner as in the measurement of the first equivalent, except that tetraethylammonium bromide was not used. The epoxy equivalent was calculated by subtracting the second equivalent from the first equivalent according to the following formula: Epoxy equivalent (g / eq.) = 1 / ((1 / first equivalent) - (1 / second equivalent)).

[0091] <Method for measuring softening point of epoxy-based thermosetting component> The softening point of the epoxy-based thermosetting component was measured in accordance with "4.1 Ring and ball method" of JIS K7234:1986.

[0092] <Thermal Stability> The obtained photosensitive resin composition was applied to the entire surface of a copper foil substrate by screen printing so that the film thickness after drying would be 20 μm, and the substrate was dried at 80° C. for 50 minutes and 70 minutes, respectively. After cooling to room temperature, the substrate was developed with a 1 mass % Na2CO3 aqueous solution at 30° C. at a spray pressure of 0.2 MPa for 60 seconds, and the presence or absence of undeveloped residue of the dried coating film was visually observed and evaluated based on the following evaluation criteria. -Evaluation Criteria- ◎: No undeveloped residue of composition in both 50-minute drying and 70-minute drying ○: No undeveloped residue of composition in 50-minute drying, but some residue in 70-minute drying △: Some undeveloped residue of composition in 50-minute drying, and clear undeveloped residue in 70-minute drying ×: Clear undeveloped residue of composition in both 50-minute drying and 70-minute drying

[0093] <Resolution> The obtained photosensitive resin composition was applied to the entire surface of a copper foil substrate by screen printing so that the film thickness after drying would be 20 μm, and then dried at 80° C. for 30 minutes. After cooling to room temperature, a Kodak Step Tablet No. 2 was placed on the dried coating film, and direct imaging exposure was performed using a direct imaging exposure device with an SRO (Solder Resist Opening) aperture size of 60 μm at an exposure amount that would result in 7 steps after exposure. Next, the coating film on the pattern-exposed substrate was exposed to 1% by mass of Na at 30° C. ２ CO ３The resulting film was developed using an aqueous solution for 60 seconds and then washed with water. Finally, the film was cured at 150°C for 60 minutes to prepare a test piece for evaluating resolution. The top and bottom diameters of the SRO of the test piece for evaluation were then observed using a scanning electron microscope (SEM) at 1,000x magnification, and evaluated based on the following evaluation criteria. -Evaluation criteria- ◎: The ratio of the bottom diameter to the top diameter was 1.00 or less and 0.85 or more. ○: The ratio of the bottom diameter to the top diameter was less than 0.85 and 0.70 or more. ×: The ratio of the bottom diameter to the top diameter was less than 0.70.

[0094] <Desmear Resistance> The evaluation test piece prepared in the above resolution evaluation was immersed in a swelling solution (a mixture of Swelling Dip Securigant P (manufactured by Atotech Japan) and 48% sodium hydroxide) at 60°C for 5 minutes. Next, it was immersed in a roughening solution (a mixture of Concentrate Compact CP (manufactured by Atotech Japan) and 48% sodium hydroxide) at 80°C for 20 minutes, and finally in a neutralizing solution (Reduction Securigant P500 (manufactured by Atotech Japan) and 96% sulfuric acid) at 40°C for 5 minutes to perform a desmear treatment. After the desmear treatment, the periphery of the SRO on the surface of the cured coating film was observed using a 1,000x scanning electron microscope (SEM) and evaluated based on the following evaluation criteria. - Evaluation criteria - ⊚: No damage was observed in the periphery of the SRO even after the desmear treatment. ◯: Slight damage was observed in the periphery of the SRO after the desmear treatment, but no peeling was observed. △: Partial peeling was observed in the periphery of the SRO after the desmear treatment. ×: Peeling was observed in the entire periphery of the SRO after the desmear treatment.

[0095]

[0096] In Examples 1 to 7, in which the equivalent ratio (carboxyl group equivalent / epoxy equivalent) was 5.0 to 8.0, the evaluation results for thermal stability, resolution, and desmear resistance were "◎", "◯", or "Δ". In contrast, in Comparative Example 1, in which the equivalent ratio (carboxyl group equivalent / epoxy equivalent) was 4.1, the evaluation result for desmear resistance was "×", and in Comparative Example 2, in which the equivalent ratio (carboxyl group equivalent / epoxy equivalent) was 8.9, the evaluation results for thermal stability and resolution were "×". In addition, in Comparative Example 3, which did not contain a bifunctional crystalline epoxy resin as an epoxy-based thermosetting component, the evaluation result for thermal stability was "×". That is, the compositions of Comparative Examples 1 to 3 were evaluated as "×" for any of the thermal stability, resolution, and desmear resistance. From the above, it can be said that the alkali-developable photosensitive resin compositions of Examples 1 to 7 are alkali-developable photosensitive resin compositions capable of forming cured products with excellent resolution, thermal stability, and desmear resistance.

[0097] Examples 1 to 4 and 7, which had an equivalent ratio (carboxyl group equivalent / epoxy equivalent) of 5.0 to 8.0 and an epoxy thermosetting component weight ratio (novolac epoxy resin / bifunctional crystalline epoxy resin) of 1.0 to 2.0, were evaluated as having desmear resistance of "◎" or "◯", whereas Example 6, which had an epoxy thermosetting component weight ratio (novolac epoxy resin / bifunctional crystalline epoxy resin) of 0.7, was evaluated as having desmear resistance of "△", and Example 5, which had an epoxy thermosetting component weight ratio (novolac epoxy resin / bifunctional crystalline epoxy resin) of 2.3, was evaluated as having thermal stability of "△". Therefore, it can be said that an alkali-developable photosensitive resin composition having an equivalent ratio (carboxyl group equivalent / epoxy equivalent) of 5.0 to 8.0 and an epoxy thermosetting component weight ratio (novolac epoxy resin / bifunctional crystalline epoxy resin) of 1.0 to 2.0 is an alkali-developable photosensitive resin composition capable of forming a cured product with even better resolution, thermal stability, and desmear resistance.

[0098] Although the embodiments for carrying out the present invention have been specifically described above, the present invention is not limited to these and can be modified in various ways without departing from the spirit of the present invention.

Claims

1. An alkali-developable photosensitive resin composition containing a carboxyl group-containing resin, an epoxy-based thermosetting component, a (meth)acrylic monomer, and a photopolymerization initiator, wherein the equivalent ratio of carboxyl groups to epoxy groups (carboxyl group equivalent / epoxy equivalent) is 5.0 to 8.0, and the epoxy-based thermosetting component contains a novolac epoxy resin and a bifunctional crystalline epoxy resin with a softening point of 70°C to 120°C.

2. The alkali-developable photosensitive resin composition according to claim 1, wherein the weight ratio of the novolac epoxy resin to the bifunctional crystalline epoxy resin (novolac epoxy resin / bifunctional crystalline epoxy resin) is 1.0 to 2.

0.

3. A dry film having a resin layer obtained from the alkali-developable photosensitive resin composition according to claim 1.

4. A cured product obtained by curing the alkali-developable photosensitive resin composition according to claim 1 or the resin layer of the dry film according to claim 3.

5. A printed wiring board comprising the cured product according to claim 4.

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