JP2022054425A - Photosensitive resin composition, cured product, and electronic circuit board - Google Patents

Abstract

To provide a photosensitive resin composition which has good heat resistance and flexibility and is easily removed by an alkali developer.SOLUTION: The photosensitive resin composition contains (A) a carboxyl group-containing photosensitive resin, (B) a photopolymerization initiator, (C) an epoxy compound, and (D) a reactive diluent. The epoxy compound (C) contains an epoxy compound having a tetraphenyl structure and having three epoxy groups in the molecule and (C-2) a crystalline epoxy compound. The reactive diluent (D) contains (D-1) a caprolactone-modified (meth)acrylate.SELECTED DRAWING: None

Description

The present invention relates to photosensitive resin compositions, cured products and electronic circuit boards.

An electronic circuit pattern provided on an electronic circuit board such as a printed wiring board may be covered with an insulating layer formed by using a photosensitive resin composition.

Since the insulating layer also plays a role of protecting the electronic circuit pattern from the external environment, characteristics such as heat resistance are required.

Further, for example, an insulating layer on an electronic circuit mounting board using a flexible printed wiring board may be required to have flexibility in addition to heat resistance.

WO2020 / 066601 Japanese Patent No. 5885269 Japanese Unexamined Patent Publication No. 2019-56867

The curable resin composition disclosed in Patent Document 1 and the negative photosensitive resin composition disclosed in Patent Document 2 can improve their heat resistance by blending a polyfunctional epoxy resin. be.
The photosensitive resin composition disclosed in Patent Document 3 can improve its flexibility by blending caprolactone-modified (meth) acrylate.

An object of the present invention is to provide a photosensitive resin composition having good heat resistance and flexibility and easy to remove with an alkaline developer.

The photosensitive resin composition according to the present invention contains (A) a carboxyl group-containing photosensitive resin, (B) a photopolymerization initiator, (C) an epoxy compound, and (D) a reactive diluent. The (C) epoxy compound (C-1) contains an epoxy compound having a structure represented by the following general formula (1) and (C-2) a crystalline epoxy compound, and the (D) reactive diluent is (D). D-1) Contains caprolactone-modified (meth) acrylate.

Further, the photosensitive resin composition according to the present invention preferably further contains (E) an inorganic ion exchanger.

Further, the (E) inorganic ion exchanger is a cation exchanger and preferably contains Zr.

Further, the (C-2) crystalline epoxy compound is preferably a biphenyl type.

The cured product of the present invention is a cured product of the above-mentioned photosensitive resin composition. Further, the electronic circuit board of the present invention has the cured product.

According to the present invention, it is possible to provide a photosensitive resin composition having good heat resistance and flexibility and easy to remove with an alkaline developer.

An embodiment of the photosensitive resin composition of the present invention will be described in detail below. It goes without saying that the present invention is not limited to these embodiments.

The photosensitive resin composition of the present embodiment contains (A) a carboxyl group-containing photosensitive resin, (B) a photopolymerization initiator, (C) an epoxy compound, and (D) a reactive diluent.

(A) Carboxyl group-containing photosensitive resin (A) As the carboxyl group-containing photosensitive resin, any resin having one or more photosensitive unsaturated double bonds and a carboxyl group is preferably used. obtain.
As the (A) carboxyl group-containing photosensitive resin, (A-1) a polybasic acid-modified radically polymerizable unsaturated monocarboxylic oxide epoxy resin (for example, a polybasic acid-modified epoxy (meth) acrylate) is preferably used. .. Such a polybasic acid-modified radically polymerizable unsaturated monocarboxylic oxide epoxy resin is produced, for example, by the following method.
That is, a radically polymerizable unsaturated monocarboxylic acid (for example, acrylic acid or methacrylic acid (hereinafter, these are collectively referred to as (meth) acrylic acid) or the like) is reacted with at least a part of the epoxy group of the polyfunctional epoxy resin. To prepare a radically polymerizable unsaturated monocarboxylic oxide epoxy resin (for example, epoxy (meth) acrylate, etc.), and further polybasic acid or more to the hydroxyl group generated in the radically polymerizable unsaturated monocarboxylic oxide epoxy resin by this reaction. It is obtained by reacting a radical acid anhydride.

As the polyfunctional epoxy resin, any epoxy resin having two or more epoxy groups in one molecule can be preferably used.
The epoxy equivalent of the polyfunctional epoxy resin is not particularly limited, but is preferably 3,000 g / eq or less, more preferably 1,000 g / eq or less, and particularly preferably 100 g / eq or more and 500 g / eq or less. be.
Examples of the polyfunctional epoxy resin include biphenyl type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, rubber-modified epoxy resin (for example, silicone-modified epoxy resin, etc.), ε-caprolactone-modified epoxy resin, and bisphenol A type. , Bisphenol F type, Bisphenol AD type and other phenol novolac type epoxy resins, cresol novolak type epoxy resins (eg о-cresol novolac type epoxy resins, etc.), cyclic aliphatic polyfunctional epoxy resins, glycidyl ester type polyfunctional epoxy resins, glycidyl Amin-type polyfunctional epoxy resin, heterocyclic polyfunctional epoxy resin, bisphenol-modified novolak type epoxy resin, polyfunctional modified novolak type epoxy resin, condensate type epoxy resin of phenols and aromatic aldehyde having phenolic hydroxyl group, etc. Can be mentioned. Further, those in which halogen atoms such as Br and Cl are introduced into these polyfunctional epoxy resins can also be used.
Further, these polyfunctional epoxy resins may be used alone or in admixture of a plurality of types.

As the radically polymerizable unsaturated monocarboxylic acid, for example, (meth) acrylic acid, crotonic acid, cinnamic acid and the like can be used. Among these, (meth) acrylic acid is preferably used.
Further, a known method can be used as the reaction method between the polyfunctional epoxy resin and the radically polymerizable unsaturated monocarboxylic acid. For example, the polyfunctional epoxy resin and the radically polymerizable unsaturated monocarboxylic acid are suitable. The reaction can be carried out by heating in a diluent.

As the polybasic acid or polybasic acid anhydride, either a saturated structure or an unsaturated structure can be used.
Examples of the polybasic acid include succinic acid, maleic acid, adipic acid, citric acid, phthalic acid, tetrahydrophthalic acid, 3-methyltetrahydrophthalic acid, 4-methyltetrahydrophthalic acid, 3-ethyltetrahydrophthalic acid, 4-. Ethyltetrahydrophthalic acid, hexahydrophthalic acid, 3-methylhexahydrophthalic acid, 4-methylhexahydrophthalic acid, 3-ethylhexahydrophthalic acid, 4-ethylhexahydrophthalic acid, methyltetrahydrophthalic acid, methylhexahydro Examples thereof include phthalic acid, endomethylenetetrahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, trimellitic acid, pyromellitic acid and diglycolic acid. Further, examples of the polybasic acid anhydride include these anhydrides.
The polybasic acid or polybasic acid anhydride is released into the radically polymerizable unsaturated monocarboxylic oxide epoxy resin by reacting the hydroxyl group generated in the radically polymerizable unsaturated monocarboxylic oxide epoxy resin with the hydroxyl group. It introduces a carboxyl group.
The polybasic acid or polybasic acid anhydride may be used alone or in combination of two or more.

In the present embodiment, if necessary, the carboxyl group of the (A-1) polybasic acid-modified radically polymerizable unsaturated monocarboxylic oxide epoxy resin has one or more radically polymerizable unsaturated groups and an epoxy group. By reacting the glycidyl compound, a radically polymerizable unsaturated group may be further introduced into the glycidyl compound to obtain a carboxyl group-containing photosensitive resin having further improved photosensitivity.

In the resin obtained by further introducing a radically polymerizable unsaturated group into the (A-1) polybasic acid-modified radically polymerizable unsaturated monocarboxylic oxide epoxy resin, the radically polymerizable unsaturated group of the glycidyl compound is the above (A-). 1) Polybasic acid-modified radically polymerizable unsaturated monocarboxylic oxide Epoxy resin By binding to the side chain of the skeleton, the photopolymerization reactivity can be improved, thereby imparting excellent photosensitive characteristics.
Examples of the glycidyl compound having one or more radically polymerizable unsaturated groups and an epoxy group include glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, pentaerythritol triacrylate monoglycidyl ether and the like. In addition, a plurality of glycidyl groups contained in the glycidyl compound having one or more radically polymerizable unsaturated groups and epoxy groups may be present in one molecule.
Further, these glycidyl compounds may be used alone or in admixture of a plurality of types.

Further, as the (A) carboxyl group-containing photosensitive resin, for example, the following can be used in addition to the (A-1) polybasic acid-modified radically polymerizable unsaturated monocarboxylic oxide epoxy resin.
That is, a) an epoxy resin of an epoxy resin having two or more epoxy groups in one molecule, b) a fatty acid having 10 or more carbon atoms per carboxyl group, and c) an ethylenically unsaturated group-containing carboxylic acid. To prepare a modified epoxy resin containing a long-chain fatty acid-modified ethylenically unsaturated group. Then, by adding d) polybasic acid anhydride to the hydroxyl group (mainly secondary) generated at this time, a free carboxyl group is introduced into the long-chain fatty acid-modified ethylenically unsaturated group-containing modified epoxy resin. (Hereinafter referred to as (A-2) photosensitive resin).

a) Epoxy resin having two or more epoxy groups in one molecule As the epoxy resin having two or more epoxy groups in one molecule, an epoxy resin having two or more epoxy groups in one molecule. If so, it can be preferably used.
The epoxy equivalent of the epoxy resin having two or more epoxy groups in one molecule is not particularly limited, but is preferably 3,000 g / eq or less, more preferably 1,000 g / eq or less, and particularly preferably 1,000 g / eq or less. It is 100 g / eq or more and 500 g / eq or less. By setting the epoxy equivalent in this range, the long-chain fatty acid of the produced long-chain fatty acid-modified ethylenically unsaturated group-containing modified epoxy resin and the photosensitivity due to the decrease in the introduction ratio of the ethylenically unsaturated group-containing carboxylic acid can be obtained. It is possible to prevent a decrease in flexibility.

Examples of the epoxy resin having two or more epoxy groups in one molecule include biphenyl aralkyl type epoxy resin, phenyl aralkyl type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, and rubber modification. Epoxy resin (for example, silicone-modified epoxy resin), ε-caprolactone-modified epoxy resin, bisphenol A type, bisphenol F type, bisphenol AD type and other phenol novolac type epoxy resin, cresol novolak type epoxy resin (for example, о-cresol novolac type epoxy) Resin, etc.), Cyclic aliphatic polyfunctional epoxy resin, glycidyl ester type polyfunctional epoxy resin, glycidylamine type polyfunctional epoxy resin, heterocyclic polyfunctional epoxy resin, bisphenol modified novolak type epoxy resin, polyfunctional modified novolak type epoxy resin , Condensed type epoxy resin of phenols and aromatic aldehyde having phenolic hydroxyl group, epoxy resin containing fluorene skeleton, epoxy resin having adamantan skeleton introduced and the like. Further, those having a halogen atom such as Br or Cl introduced into these epoxy resins can also be used.
Further, these epoxy resins may be used alone or in admixture of a plurality of types.

Of these epoxy resins, biphenyl aralkyl type epoxy resins and dicyclopentadiene type epoxy resins are preferable because they have excellent adhesion, flexibility and gold plating properties, and also have good developability, acid resistance and heat resistance. Used.

b) Fatty acid having 10 or more carbon atoms per carboxyl group The fatty acid having 10 or more carbon atoms per carboxyl group is an epoxy of an epoxy resin having two or more epoxy groups in one molecule. By reacting with the group, the long-chain hydrocarbon structure derived from the fatty acid is introduced into the epoxy resin. This makes it possible to improve the flexibility (flexibility), water resistance, and electrical insulation of the cured product of the photosensitive resin composition of the present embodiment.
As the fatty acid having 10 or more carbon atoms per carboxyl group, a saturated structure or an unsaturated structure can be used, and a linear type or a branched type can be used. Can be done.

Examples of the fatty acid having 10 or more carbon atoms per carboxyl group include a monobasic acid having 10 or more carbon atoms and a dibasic acid having 20 or more carbon atoms. From the viewpoint of the balance between flexibility and dryness to the touch, the monobasic acid having 10 or more carbon atoms and the dibasic acid having 20 or more carbon atoms are linear or have 2 side chains having 2 or less carbon atoms. Branched ones having the following are preferably used.

Further, it is preferable to use one or more dibasic acids as the fatty acid having 10 or more carbon atoms per carboxyl group. Such fatty acids can introduce a long-chain fatty acid structure into an epoxy resin having two or more epoxy groups in the one molecule. Further, in this case, different epoxy groups of the epoxy resin are bonded to each other via the fatty acid. As a result, the relatively rigid skeleton of the epoxy resin becomes a structure crosslinked by a covalent bond in the highly flexible long-chain hydrocarbon skeleton derived from the long-chain fatty acid. Such a structure can impart flexibility and heat resistance to the cured product of the photosensitive resin composition of the present embodiment.

As the dibasic acid having 20 or more carbon atoms, for example, a branched dibasic acid having two or less side chains having 2 or less carbon atoms is preferably used.

Further, if a larger amount of the above-mentioned long-chain hydrocarbon skeleton derived from the long-chain fatty acid and having high flexibility and insulation is introduced into the epoxy resin having two or more epoxy groups in the one molecule, the photosensitivity of the present embodiment is obtained. The flexibility and insulation of the cured product of the resin composition can be further improved.
When a dibasic acid having 20 or more carbon atoms per carboxyl group and a monobasic acid having 10 or more carbon atoms per carboxyl group are used in combination, the component derived from the above-mentioned long-chain fatty acid is used. It is possible to appropriately control the molecular weight of the reaction product of these fatty acids, the epoxy resin having two or more epoxy groups in the one molecule, and the ethylenically unsaturated group-containing carboxylic acid while improving the composition ratio. Therefore, it is possible to improve the dryness of the coating film after drying of the photosensitive resin composition of the present embodiment in a well-balanced manner, the solubility in a weak alkaline developing solution (developability), and its sensitivity. Further, in this case, the insulating property and the heat resistance of the cured product of the photosensitive resin composition of the present embodiment can be improved in a well-balanced manner.

Further, as the monobasic acid having 10 or more carbon atoms, for example, a linear saturated monobasic acid having 18 or more carbon atoms per carboxyl group is preferably used. When such a monobasic acid is used, the molecular weight of the above-mentioned reaction product can be controlled more appropriately, and the above-mentioned various properties can be improved in a more balanced manner.

The upper limit of the number of carbon atoms per carboxyl group of the fatty acid having 10 or more carbon atoms per carboxyl group is preferably 24, and 22 is particularly preferable. By setting the carbon number in this range, good developability can be maintained.

As the fatty acid having 10 or more carbon atoms per carboxyl group, for example, those listed below can be used.

Monobasic acid: capric acid (decanoic acid: C10), undecic acid (C11), lauric acid (dodecanoic acid: C12), tridecic acid (C13), myristic acid (tetradecanoic acid: C14), pentadecic acid (C15), palmitin Acid (hexadecanoic acid: C16), margaric acid (heptadecanoic acid: C17), stearic acid (C18), isostearic acid (C18), tubercross stearic acid (C19), arachidic acid (C20), behenic acid (C22), trichosyl Acid (C23), tetracosanoic acid (C24), hexacosanoic acid (C26), octacosanoic acid (C28), triacanthanoic acid (C30) and the like.

Dibasic acid: Eikosan diic acid (C20), ethyl octadecane diic acid (C20), Eikosadien diic acid (C20), vinyl octadecaen diic acid (C20), dimethyleikosadien diic acid (C22), dimethyleikosanni C36 dimer acid by dimerization reaction of unsaturated fatty acids such as acid (C22), diphenylhexadecanedioic acid (C28), oleic acid (C18), and water formed by hydrogenating the olefinic double bond of the C36 dimer acid. Addition C36 dimer acid, etc.

Further, the fatty acid having 10 or more carbon atoms per carboxyl group may be used alone or in combination of two or more.

As a reaction method between the epoxy resin having two or more epoxy groups in one molecule and the fatty acid having 10 or more carbon atoms per carboxyl group, a known method can be used, for example, 2 in the one molecule. An epoxy resin having one or more epoxy groups and a fatty acid having 10 or more carbon atoms per carboxyl group can be reacted by heating in an appropriate diluent.

The lower limit of the ratio (charged ratio) of the fatty acid having 10 or more carbon atoms per carboxyl group in the (A-2) photosensitive resin is preferably 10% by mass, particularly preferably 15% by mass. By setting the lower limit value in this range, the flexibility and insulating property of the cured product of the photosensitive resin composition of the present embodiment can be further improved. The upper limit thereof is preferably 50% by mass, particularly preferably 40% by mass. By setting the upper limit value in this range, the amount of the ethylenically unsaturated group-containing carboxylic acid introduced can be appropriately maintained, and excellent photosensitivity can be maintained.

c) Ethylene unsaturated group-containing carboxylic acid The ethylenically unsaturated group-containing carboxylic acid reacts with the epoxy group of an epoxy resin having two or more epoxy groups in one molecule, and the epoxy resin is subjected to light. Introduce a photocurable group that can be polymerized by the free radicals generated by the polymerization initiator.
As the ethylenically unsaturated group-containing carboxylic acid, any epoxy resin having two or more epoxy groups in one molecule can be preferably used as long as it imparts photocurability.
Examples of such an ethylenically unsaturated group-containing carboxylic acid include radically polymerizable unsaturated monocarboxylic acid. Examples of the radically polymerizable unsaturated monocarboxylic acid include acryloyl groups such as (meth) acrylic acid, β-acryloxypropionic acid, ω-carboxy-polycaprolactone- (meth) acrylic acid, crotonic acid, and cinnamon acid. Examples thereof include carboxylic acids capable of introducing a methacryloyl group into an epoxy resin. Of these, (meth) acrylic acid is preferably used, and acrylic acid is particularly preferably used.
The ethylenically unsaturated group-containing carboxylic acid may be used alone or in combination of two or more.

The lower limit of the ratio (charged ratio) of the ethylenically unsaturated group-containing carboxylic acid in the (A-2) photosensitive resin is preferably 2.0% by mass, particularly preferably 3.0% by mass. By setting the lower limit value in this range, the excellent photosensitivity of the cured product of the photosensitive resin composition of the present embodiment can be maintained. The upper limit is preferably 10.0% by mass, particularly preferably 8.0% by mass. By setting the upper limit value in this range, excellent flexibility and insulating property can be obtained by appropriately maintaining the introduction amount of the fatty acid having 10 or more carbon atoms per carboxyl group.

The reaction method between the epoxy resin having two or more epoxy groups in one molecule and the ethylenically unsaturated group-containing carboxylic acid is not particularly limited, and for example, an epoxy having two or more epoxy groups in the one molecule. The resin and the ethylenically unsaturated group-containing carboxylic acid can be reacted by heating in an appropriate diluent.

d) Polybasic acid anhydride The polybasic acid anhydride is produced by a reaction between an epoxy resin having two or more epoxy groups in one molecule and a fatty acid having 10 or more carbon atoms per carboxyl group. A long-chain fatty acid produced by reacting with the generated hydroxyl group and / or the hydroxyl group generated by the reaction between the epoxy resin having two or more epoxy groups in the one molecule and the ethylenically unsaturated group-containing carboxylic acid. A free carboxyl group is introduced into the modified epoxy resin containing a modified ethylenically unsaturated group.
As the polybasic acid anhydride, either a saturated structure or an unsaturated structure can be used.
Examples of such polybasic acid anhydrides include succinic acid, maleic acid, adipic acid, citric acid, phthalic acid, tetrahydrophthalic acid, 3-methyltetrahydrophthalic acid, 4-methyltetrahydrophthalic acid, and 3-ethyltetrahydrophthalic acid. Acid, 4-ethyltetrahydrophthalic acid, hexahydrophthalic acid, 3-methylhexahydrophthalic acid, 4-methylhexahydrophthalic acid, 3-ethylhexahydrophthalic acid, 4-ethylhexahydrophthalic acid, methyltetrahydrophthalic acid , Methylhexahydrophthalic acid, endomethylenetetrahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, trimellitic acid, pyromellitic acid and polybasic acid anhydrides such as diglycolic acid.
The polybasic acid anhydride may be used alone, or a plurality of types may be mixed and used in order to appropriately adjust the developability.

The lower limit of the ratio (charge ratio) of the polybasic acid anhydride in the (A-2) photosensitive resin is preferably 5.0% by mass, particularly preferably 8.0% by mass. By setting the lower limit value in this range, the developability of the photosensitive resin composition of the present embodiment can be improved. The upper limit is preferably 20.0% by mass, and particularly preferably 25.0% by mass. By setting the upper limit value in this range, excellent insulating properties can be obtained.

Further, as the (A) carboxyl group-containing photosensitive resin, for example, (A-3) acid-modified urethanized epoxy (meth) acrylate resin can be used.
The (A-3) acid-modified urethanized epoxy (meth) acrylate resin is produced, for example, by the following method.
That is, as described above, an epoxy (meth) acrylate is produced by reacting at least a part of the epoxy group of the polyfunctional epoxy resin with a radically polymerizable unsaturated monocarboxylic acid, and the hydroxyl group generated at this time is used as described above. It is obtained by reacting a polybasic acid or an anhydride thereof with a compound having two or more isocyanate groups in one molecule.

Examples of the compound having two or more isocyanate groups in one molecule include hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methylene diisocyanate (MDI), methylenebiscyclohexylisocyanate, and trimethylhexamethyldiisocyanate. Examples thereof include hexane diisocyanate, hexamethylamine diisocyanate, toluene diisocyanate, 1,2-diphenylethane diisocyanate, 1,3-diphenylpropane diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethyl diisocyanate and the like.
Further, these compounds may be used alone or in admixture of a plurality of types.

In the present embodiment, if necessary, a glycidyl compound having one or more radically polymerizable unsaturated groups and an epoxy group in the carboxyl group of the (A-3) acid-modified urethaneized epoxy (meth) acrylate resin. A radically polymerizable unsaturated group may be further introduced into the reaction to obtain a (A-3) acid-modified epoxide (meth) acrylate resin having improved photosensitivity.

The lower limit of the acid value of the (A) carboxyl group-containing photosensitive resin is preferably 30 mgKOH / g, and particularly preferably 40 mgKOH / g. By setting the lower limit value in this range, the alkali developability can be improved. The upper limit of the acid value is preferably 200 mgKOH / g from the viewpoint of preventing dissolution of the exposed portion by the alkaline developer, and the point of preventing deterioration of the moisture resistance and electrical characteristics of the cured product of the photosensitive resin composition of the present embodiment. From 150 mgKOH / g is particularly preferable.

The lower limit of the mass average molecular weight of the (A) carboxyl group-containing photosensitive resin is preferably 3,000, particularly preferably 5,000. By setting the lower limit value in this range, the toughness and the dryness to the touch of the cured product of the photosensitive resin composition of the present embodiment can be improved. The upper limit is preferably 200,000, and particularly preferably 50,000. By setting the upper limit value in this range, smooth alkaline developability can be imparted to the photosensitive resin composition of the present embodiment.

Examples of commercially available (A) carboxyl group-containing photosensitive resins include ZAR-2000, ZFR-1122, ZFR-1124, FLX-2089, ZCR-1601H, and ZCR-1569H (above, Nippon Kayaku). Cyclomer P (ACA) Z-250 (manufactured by Daicel Chemical Industry Co., Ltd.), Lipoxy SP-4621 (manufactured by Showa Denko KK), and the like.
Further, these (A) carboxyl group-containing photosensitive resins may be used alone or in admixture of a plurality of types.

(B) Photopolymerization Initiator The (B) photopolymerization initiator can be used without particular limitation as long as it can be generally used.
Examples of the (B) photopolymerization initiator include an oxime-based initiator (1,2-octanedione, 1- [4- (phenylthio) -2- (O-benzoyloxime)], and etanone 1- [9 ethyl-]. 6- (2-Methylbenzoyl) -9H-carbazole-3-yl] -1- (0-acetyloxime), 2- (acetyloxyiminomethyl) thioxanthen-9-one, etc.), benzoin, benzoinmethyl ether, Benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy- 2-Methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenylketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propane-1-one, 4- (2-) Hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butyl Anthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethylketal, acetophenonedimethylketal, P-dimethylaminobenzoic acid Ethyl ester, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, phenylbis (2,4,6-trimethylbenzoyl) phosphinoxide, ethyl-4- (dimethylamino) benzoate, 2-n-butoxyethyl-4- ( Examples include dimethylamino) benzoate, methyl-4- (dimethylamino) benzoate, isoamyl-4- (dimethylamino) benzoate, 2- (dimethylamino) ethylbenzoate, 2-ethylhexyl-4- (dimethylamino) benzoate and the like. Be done.
These (B) photopolymerization initiators may be used alone or in admixture of a plurality of types.

When the photosensitive resin composition of the present embodiment is irradiated with active energy rays such as ultraviolet light having a wavelength of 300 nm to 400 nm, the (B) photopolymerization initiator is the light of the (A) carboxyl group-containing photosensitive resin. Promotes curing.
The blending amount of the (B) photopolymerization initiator is preferably 1 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the (A) carboxyl group-containing photosensitive resin (solid content), and is 2 parts by mass or more and 30 parts by mass. More preferably, it is more preferably 2 parts by mass or more and 20 parts by mass or less.

(C) Epoxy compound The mechanical strength of the (C) epoxy compound can be improved by increasing the crosslink density of the cured product of the photosensitive resin composition of the present embodiment.
Examples of the (C) epoxy compound include epoxy resins.
Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, and novolak type epoxy resin (for example, biphenyl novolak type epoxy resin, phenol novolak type epoxy resin, o-cresol novolak type epoxy resin, p-tert-butylphenol. Novolak type, etc.), bisphenol F type epoxy resin (obtained by reacting bisphenol F with epichlorohydrin), bisphenol S type epoxy resin (obtained by reacting bisphenol F with epichlorohydrin), cyclohexene oxide group, tricyclodecane oxide group , Alicyclic epoxy resin having a cyclopentene oxide group, triglycidyl isocyanurate having a triazine ring such as tris (2,3-epoxypropyl) isocyanurate, triglycidyltris (2-hydroxyethyl) isocyanurate, dicyclopentadiene. Examples thereof include a type epoxy resin and an adamantan type epoxy resin.
These (C) epoxy compounds may be used alone or in admixture of a plurality of types.

The blending amount of the (C) epoxy compound is preferably 15 parts by mass or more and 90 parts by mass or less, and 25 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the (A) carboxyl group-containing photosensitive resin (solid content). Is more preferable, and 35 parts by mass or more and 55 parts by mass or less is particularly preferable.

Further, in the photosensitive resin composition of the present embodiment, as the (C) epoxy compound, (C-1) an epoxy compound having a structure represented by the following general formula (1) and (C-2) crystalline epoxy It preferably contains a compound.
Further, in this case, the blending ratio of the (C-1) epoxy compound and the (C-2) crystalline epoxy compound is 100 mass by mass of the (C-1) epoxy compound from the viewpoint of surely improving the developability and heat resistance. The (C-2) crystalline epoxy compound is preferably 40 parts by mass or more and 140 parts by mass or less, more preferably 60 parts by mass or more and 130 parts by mass or less, and particularly preferably 80 parts by mass or more and 120 parts by mass or less. ..

The (C-1) epoxy compound is a trifunctional glycidyl ether type epoxy compound having an aromatic ring in its composition. Since the (C-1) epoxy compound has a property of being difficult to thermally decompose at a low temperature, it is possible to impart high heat resistance to the photosensitive resin composition of the present embodiment. Further, since the (C-1) epoxy compound can impart flexibility to the cured product of the photosensitive resin composition of the present embodiment, the cured product can have both heat resistance and flexibility.
Examples of commercially available such (C-1) epoxy compounds include TECHMORE VG3101L (manufactured by Printech Co., Ltd.).

The blending amount of the (C-1) epoxy compound is preferably 5 parts by mass or more and 40 parts by mass or less, preferably 10 parts by mass or more and 35 parts by mass with respect to 100 parts by mass of the (A) carboxyl group-containing photosensitive resin (solid content). More than 15 parts by mass, and particularly preferably 15 parts by mass or more and 30 parts by mass or less.

Examples of the (C-2) crystalline epoxy compound include biphenyl aralkyl type, biphenyl type, bisphenol type, stilbene type, triglycidyl isocyanurate type, hydroquinone type and thiol type crystalline epoxy resins. In the present specification, the "crystalline epoxy compound" means an epoxy compound which is solid below the melting point and has many portions (crystal portions) in which the polymer chains are regularly arranged (highly crystalline). ..

The (C-1) epoxy compound is solid at room temperature (for example, 25 ° C.) and becomes liquid above the melting point. Here, the (C-1) epoxy compound tends to be sticky even after being liquefied by heating and then becoming solid. Therefore, there is a risk that the solubility of the photosensitive resin composition in the weak alkaline developer after drying may be reduced.
On the other hand, the (C-2) crystalline epoxy compound has high crystallinity in the solid state as described above. The photosensitive resin composition of the present embodiment has the flexibility of the cured product of the photosensitive resin composition by using the (C-1) epoxy compound and the (C-2) crystalline epoxy compound in combination. It is possible to suppress the above-mentioned decrease in solubility in a weak alkaline developer without inhibiting the above-mentioned.

As the (C-2) crystalline epoxy compound, a biphenyl type crystalline epoxy resin is preferably used. Since the biphenyl-type crystalline epoxy resin has good heat resistance and flexibility, the heat resistance, flexibility, and solubility in a weak alkaline developer of the photosensitive resin composition of the present embodiment are more balanced. Can be made to.

The epoxy equivalent of the (C-2) crystalline epoxy compound is not particularly limited, but is preferably 90 g / eq or more and 300 g / eq or less, more preferably 100 g / eq or more and 250 g / eq or less, and particularly preferably 150 g. It is more than / eq and 200 g / eq or less. By setting the epoxy equivalent in this range, the flexibility, solubility in a weak alkaline developer, and heat resistance of the photosensitive resin composition of the present embodiment can be further improved.
The melting point of the (C-2) crystalline epoxy compound is preferably 80 ° C. or higher and 200 ° C. or lower, more preferably 90 ° C. or higher and 150 ° C. or lower, and particularly preferably 100 ° C. or higher and 120 ° C. or lower. By setting the melting point in this range, the heat resistance of the photosensitive resin composition of the present embodiment can be further improved.
The mass average molecular weight of the (C-2) crystalline epoxy compound is preferably 200 or more and 1,000 or less, more preferably 250 or more and 600 or less, and particularly preferably 300 or more and 450 or less. By setting the mass average molecular weight in this range, the solubility of the photosensitive resin composition of the present embodiment in a weak alkaline developer can be further improved.

The blending amount of the (C-2) crystalline epoxy compound is preferably 5 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the (A) carboxyl group-containing photosensitive resin (solid content), and is preferably 10 parts by mass or more. 35 parts by mass or less is more preferable, and 15 parts by mass or more and 25 parts by mass or less are particularly preferable. By setting the blending amount within this range, it is possible to further suppress the decrease in solubility in the above-mentioned weak alkaline developer without impairing the flexibility of the cured product of the photosensitive resin composition of the present embodiment. can.

Examples of commercially available (C-2) crystalline epoxy compounds include jER YX-4000, jER YX-4000H, and jER YX-4000HK (above, biphenyl type crystalline epoxy manufactured by Mitsubishi Chemical Corporation). Resin), TEPIC-HP (Triglycidyl isocyanurate type crystalline epoxy resin manufactured by Nissan Chemical Co., Ltd.), YDC-1312 (Hydroquinone type bifunctional crystalline epoxy resin, manufactured by Nittetsu Chemical & Materials Co., Ltd.), YSLV- Examples thereof include 120TE (thiol-type functional crystalline epoxy resin, manufactured by Nittetsu Chemical & Materials Co., Ltd.).

(D) Reactive Diluent The photosensitive resin composition of the present embodiment preferably contains (D-1) caprolactone-modified (meth) acrylate as the (D) reactive diluent. The (D-1) caprolactone-modified (meth) acrylate has excellent flexibility and heat resistance. Therefore, the cured product of the photosensitive resin composition of the present embodiment can have both heat resistance and flexibility, and can exhibit good heat resistance even when soldered at 350 ° C. or higher, for example.

The (D-1) caprolactone-modified (meth) acrylate can be preferably used as long as it is a caprolactone-modified form of the (meth) acrylate compound, and examples thereof include caprolactone-modified polyfunctional (meth) acrylate.
Examples of the caprolactone-modified polyfunctional (meth) acrylate include the following.
5 or more functional: caprolactone-modified dipentaerythritol hexa (meth) acrylate, caprolactone-modified dipentaerythritol penta (meth) acrylate, etc. 4-functional: caprolactone-modified pentaerythritol tetra (meth) acrylate, caprolactone-modified ditrimethylolpropane tetra (meth) acrylate, Caprolactone-modified dipentaerythritol tetra (meth) acrylate, etc. 2 or trifunctional: caprolactone-modified pentaerythritol tri (meth) acrylate, caprolactone-modified trimethylolpropane tri (meth) acrylate, caprolactone-modified dipentaerythritol tri (meth) acrylate, caprolactone-modified Dicyclopentenyldi (meth) acrylates and the like These caprolactone-modified polyfunctional (meth) acrylates may be used alone or in admixture.
Examples of commercially available (D-1) caprolactone-modified (meth) acrylates include DPCA-60 and DPCA-120 (all manufactured by Nippon Kayaku Co., Ltd.).

As the (D-1) caprolactone-modified (meth) acrylate, those having five or more functionalities are preferably used. Particularly preferably, it is a hexafunctional one, and among them, caprolactone-modified dipentaerythritol hexa (meth) acrylate is particularly preferably used. By using such caprolactone-modified (meth) acrylate, the solder heat resistance of the cured product of the photosensitive resin composition of the present embodiment can be further improved.

The average number of repeating units of caprolactone in the (D-1) caprolactone-modified (meth) acrylate is particularly preferably 2 or more and 3 or less. By setting the average number of repeating units as such, the flexibility of the photosensitive resin composition of the present embodiment can be further improved.

The blending amount of the (D-1) caprolactone-modified (meth) acrylate is not particularly limited, but the lower limit thereof is 10 parts by mass with respect to 100 parts by mass (solid content) of the (A) carboxyl group-containing photosensitive resin. Is preferable, 20 parts by mass is more preferable, and 25 parts by mass is particularly preferable. By setting the lower limit value in this range, the flexibility of the photosensitive resin composition of the present embodiment can be further improved. The upper limit thereof is preferably 100 parts by mass, particularly preferably 50 parts by mass with respect to 100 parts by mass (solid content) of the (A) carboxyl group-containing photosensitive resin. By setting the upper limit value in this range, a tack-free coating film by pre-drying can be more reliably formed in the photosensitive resin composition of the present embodiment.

The photosensitive resin composition of the present embodiment is referred to as a reactive diluent other than the (D-1) caprolactone-modified (meth) acrylate as the (D) reactive diluent (hereinafter, referred to as “other reactive diluent”). .) Can be used together. However, the other reactive diluent is preferably a (meth) acrylate compound having no urethane bond.

Examples of the other reactive diluent include 2-hydroxyethyl methacrylate, phenoxyethyl methacrylate, diethylene glucol monomethacrylate, 2-hydroxy-3-phenoxypropyl acrylic rate, and 1,4-butanediol di (meth) acrylate. , 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, neopentyl glycol adipate di (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate , Dicyclopentanyldi (meth) acrylate, ethylene oxide-modified di (meth) acrylate, allylated cyclohexyl di (meth) acrylate, trimethyl propanetri (meth) acrylate, ditrimethylol propanetetra (meth) acrylate, dipenta Elythritol tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide-modified trimethylol propantri (meth) acrylate, propionic acid-modified dipentaerythritol penta (meth) acrylate, dipenta Examples thereof include erythritol hexa (meth) acrylate.
In addition, these other reactive diluents may be used alone or in combination of two or more.

The lower limit of the blending amount of the (D) reactive diluent is preferably 10 parts by mass, more preferably 20 parts by mass, and 25 parts by mass with respect to 100 parts by mass (solid content) of the (A) carboxyl group-containing photosensitive resin. Part is particularly preferable. The upper limit thereof is preferably 100 parts by mass, particularly preferably 50 parts by mass, with respect to 100 parts by mass (solid content) of the (A) carboxyl group-containing photosensitive resin.

Here, the material and properties of the printed wiring board differ depending on the application of the device or component into which the electronic circuit board manufactured using the printed wiring board is incorporated. For example, a rigid printed wiring board with high hardness and a flexible printed circuit board with high flexibility. Examples include wiring boards.
Of these, the flexible printed wiring board is often used as a member to be bent or folded due to its nature, and therefore, a high flexibility is required for the insulating layer formed on the flexible printed wiring board. The insulating layer is also required to have heat resistance that can withstand heating when electronic components are mounted on a flexible printed wiring board, that is, during soldering.

Further, for example, as a method of connecting the rigid printed wiring board and the flexible printed wiring board, a method of connecting via a connector component, a method of connecting using an anisotropic conductive adhesive, or a method of connecting by thermocompression bonding using solder is used. There is a way to do it.
Here, in the case of the method of connecting by thermocompression bonding using solder, it is necessary to perform thermocompression bonding with heat equal to or higher than the melting temperature of the solder (for example, 300 ° C.) by using a hot bar or the like. The insulating layer formed on the plate is required to have a performance that can withstand this thermocompression bonding.

The photosensitive resin composition of the present embodiment has the above-mentioned (C-1) epoxy compound having the structure represented by the above-mentioned general formula (1), (C-2) crystalline epoxy compound and the above-mentioned (D-1) caprolactone. When used in combination with a modified (meth) acrylate, good heat resistance and flexibility can be imparted to the cured product, and these effects can be balanced in a well-balanced manner, so that heating and pressurization are simultaneously applied. It also has good resistance in some cases. Therefore, for example, even when the cured product of the photosensitive resin composition of the present embodiment is heated and pressed at the same time, cracks generated in the cured product and peeling (from the substrate on which the cured product is formed) are suppressed. can do. Further, the photosensitive resin composition of the present embodiment can achieve both heat resistance and flexibility without impairing the insulating property and the like.
As described above, the photosensitive resin composition of the present embodiment is particularly preferably used for a printed wiring board used in an application in which heating and pressurization are simultaneously applied, and among them, a flexible printed wiring board. Can be done.

(E) Inorganic ion exchanger The photosensitive resin composition of the present embodiment may be further blended with (E) an inorganic ion exchanger. As the (E) inorganic ion exchanger, either a cation exchange type or an anion exchange type can be used, but the cation exchange type is preferable.
The inorganic ion exchanger (E) can prevent the occurrence of an ion migration phenomenon in the cured product by capturing and fixing ionic impurities and metal ions contained in the photosensitive resin composition of the present embodiment. Thereby, the insulation reliability of the cured product of the photosensitive resin composition of the present embodiment can be improved.
Further, when the surface of the insulating layer formed on the flexible printed wiring board is subjected to surface treatment such as gold plating, the (E) inorganic ion exchanger is oriented in the cross section of the mask opening. As a result of capturing sodium ions and the like in the gold plating treatment liquid that cause erosion of the interface between the insulating layer and the conductor in the gold plating treatment, it is considered that the heat-resistant pressure-bonding property of the insulating layer after the gold plating treatment is particularly improved.
As the (E) inorganic ion exchanger, for example, one containing at least one of Sb, Bi, Zr, Ti, Sn, Mg and Al is preferable, and one containing Zr is particularly preferable. Examples of commercially available (E) inorganic ion exchangers include IXE-100, IXE-500, IXE-600, and IXE-800 (all manufactured by Toagosei Corporation).

The blending amount of the (E) inorganic ion exchanger is preferably 1 part by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the (A) carboxyl group-containing photosensitive resin (solid content), and 2 parts by mass or more and 10 parts by mass. It is more preferably 4 parts by mass or more, and particularly preferably 4 parts by mass or more and 8 parts by mass or less.

Other Ingredients For example, a colorant, a non-reactive diluent, an antifoaming agent, a flame retardant, an additive and the like can be further added to the photosensitive resin composition of the present embodiment.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. The present invention is not limited to these examples.

<Preparation of synthetic resin A>
In a 500 mL separable flask equipped with a stirrer and a reflux condenser, 86.45 g of ethyldiglycolacetate (hereinafter referred to as "EDGAC") and 8-ethyloctadecanedic acid (hereinafter referred to as "EDGAC") under a nitrogen / air (2: 1) atmosphere. Product name: SB-20, manufactured by Okamura Oil Co., Ltd.) 26.54 g (6.3 parts by mass), 45.35 g of behenic acid (10.7 parts by mass), 9.71 g of steaic acid (2.3 parts by mass) , Acrylic acid 14.36 g (3.4 parts by mass), triphenylphosphine 0.65 g (0.1 part by mass), methoxyhydroquinone 0.43 g (0.1 part by mass), and nitrogen / air in the reaction vessel. While blowing 0.3 mL / sec of (2: 1), the mixture was heated and stirred at 110 ° C. until it was dissolved.
Separately, 80 of 137.65 g (32.6 parts by mass) of biphenyl aralkyl type epoxy resin (product name: NC-3000, manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent 265 to 285 g / eq) is added to 59.8 g of EDGAC solvent. The mixture was heated to ℃ to uniformly dissolve, put into the flask, heated and stirred at 115 ℃ for 15 to 17 hours, and reacted until the acid value of the reaction solution became 6 mgKOH / g or less. To this reaction product, add 42.23 g (9.9 parts by mass) of hydrogenated trimellitic anhydride (product name: HTMAn, manufactured by Mitsubishi Gas Chemical Company, Inc.) and stir at 100 ° C. for 2 to 3 hours under an air atmosphere. bottom. After that, it was confirmed by FT-IR (infrared spectrophotometer) that the acid anhydride disappeared.
As a result, a synthetic resin A (carboxy group-containing resin having a biphenyl aralkyl structure) having a solid content (resin content) of 65% by mass and an acid value of 85 mgKOH / g shown in Table 1 was obtained.

<Preparation of photosensitive resin composition>
In the compositions and formulations shown in Tables 1 and 2, each component was mixed and dispersed at room temperature using three rolls to obtain each photosensitive resin composition according to Examples 1 to 9 and Comparative Examples 1 to 5. .. In Tables 1 and 2, the unit of the numerical value relating to the one representing the composition is a mass part unless otherwise specified.

* 1 Acid-modified biphenyl type epoxy acrylate resin (65% by mass), ethyldiglycol acetate (35% by mass), manufactured by Nippon Kayaku Co., Ltd. * 2 Acid-modified bisphenol F type epoxy acrylate resin (65% by mass), ethyldi Glycolacetate (35% by mass), manufactured by Nippon Kayaku Co., Ltd. * 3 (9-ethyl-6-nitro-9H-carbazole-3-yl) (4-((1-methoxypropane-2-yl) oxy) -2-Methylphenyl) Metanon O-Acetyloxysm, manufactured by ADEKA Co., Ltd. * 4 2-Benzyl-2- (dimethylamino) -1- (4-morpholinophenyl) -1-butanone, IGM Resins B.I. V. * 5 High heat resistant trifunctional epoxy resin, manufactured by Printec Co., Ltd. * 6 Bisphenol A type epoxy resin, manufactured by DIC Co., Ltd. * 7 Cresol novolac type epoxy resin, manufactured by DIC Co., Ltd. * 8 Biphenyl type crystalline epoxy Resin, manufactured by Mitsubishi Chemical Co., Ltd. * 9 Trifunctional crystalline epoxy resin with triazine skeleton, manufactured by Nissan Chemical Co., Ltd. * 10 Hydroquinone type bifunctional crystalline epoxy resin, manufactured by Nittetsu Chemical & Materials Co., Ltd. * 11 Thiol Type functional crystalline epoxy resin, manufactured by Nittetsu Chemical & Materials Co., Ltd. * 12 Caprolactone-modified acrylate (average number of repeating units of caprolactone is 1), manufactured by Nippon Kayaku Co., Ltd. * 13 Caprolactone-modified acrylate (average repeating unit of caprolactone) Number is 2), manufactured by Nippon Kayaku Co., Ltd. * 14 Urethane acrylate, manufactured by Dycel Ornex Co., Ltd. * 15 Phtalocyanin compound, manufactured by Toyo Color Co., Ltd. * 16 Carbon black, manufactured by Mitsubishi Chemical Co., Ltd. * 17 Powdered urethane Resin, manufactured by Dainichi Seika Kogyo Co., Ltd. * 18 Aluminum hydroxide, manufactured by Nippon Light Metal Co., Ltd. * 19 Organic phosphate, manufactured by Clariant Japan Co., Ltd. * 20 Ethyl diglycol acetate, manufactured by Sanyo Kasei Co., Ltd. * 21 Silicone polymer, manufactured by Shin-Etsu Chemical Industry Co., Ltd. * 22 Cyan ion exchanger (Zr-based), manufactured by Toa Synthetic Co., Ltd. * 23 Dicyandiamide, manufactured by Mitsubishi Chemical Co., Ltd.

<Preparation of test pieces for evaluation>
Flexible printed wiring board with a conductor (copper foil) thickness of 18 μm, line width of 100 μm, and space width of 100 μm on a polyimide film (product name: Kapton 100H, manufactured by Toray DuPont Co., Ltd.) with a thickness of 25 μm. I prepared. Then, after surface-treating the flexible printed wiring board with a 3% by mass sulfuric acid aqueous solution, the photosensitive resin composition according to each Example and Comparative Example is applied by a screen printing method so that the DRY film thickness on the conductor becomes 20 μm. Then, these were pre-dried in a BOX furnace at 70 ° C. for 20 minutes.
A negative film having a pattern having a translucent pattern other than the land of the circuit pattern is adhered to each photosensitive resin composition (dried coating film) after pre-drying, and an exposure apparatus (product name: HMW-680GW, Co., Ltd.) (Manufactured by ORC Manufacturing Co., Ltd.) was used to irradiate 400 mJ / cm ² ultraviolet rays (wavelength 300 to 400 nm). Each flexible printed wiring board after irradiation with ultraviolet rays was developed using a 1% by mass sodium carbonate aqueous solution at 30 ° C. at a spray pressure of 0.1 MPa for 60 seconds. After development, each flexible printed wiring board was post-cured in a BOX furnace at 150 ° C. for 60 minutes to prepare each evaluation test piece having a cured product of each photosensitive resin composition.

1. 1. Alkaline developability test Each dry coating film was prepared on each flexible printed wiring board in the same process as the above-mentioned production step of each evaluation test piece until pre-drying. Next, each dry coating film was developed using a 1% by mass sodium carbonate aqueous solution at 30 ° C. and a spray pressure of 0.2 MPa. Then, the time (breakpoint) required from the start of development to the time when it was visually confirmed that each dry coating film on each flexible printed wiring board was removed was measured and evaluated based on the following criteria. The results are shown in Table 3.
◯: Breakpoint less than 30 seconds Δ: Breakpoint 30 seconds or more and less than 60 seconds ×: Breakpoint 60 seconds or more

2. 2. Foldability test Each of the evaluation test pieces was bent 180 ° by folding with a 1 kg load and held for 5 seconds (hereinafter referred to as "bending step"), which was performed a plurality of times. Whether or not cracks were generated in the cured product was visually observed and observed with a × 200 optical microscope. Then, the number of bending steps until cracks were generated in each of the cured products (the steps in which cracks were generated were not included) were measured and evaluated based on the following criteria. The results are shown in Table 3.
◎: 5 times or more 〇: 2 times or more and 4 times or less △: 1 time ×: 0 times

3. 3. Heat-resistant crimping test For each evaluation test piece, each test substrate provided with a pad having a mask opening diameter of 0.8 mm on the surface on which the cured product was formed was prepared. Then, after electroless gold plating treatment (nickel 3 to 5 μmt, gold 0.05 μmt) was applied to each test substrate, 0.01 mg of flux was applied to each opening portion. After that, the stage temperature of the thermocompression bonding machine (pulse heat unit: manufactured by Nippon Avionics Co., Ltd.) was set to 170 to 180 ° C., a glass plate (thickness: 3 mm) was installed on the stage, and the cured product of each test substrate was prepared. The formed surface was brought into contact with the glass plate, and this was pressure-bonded at a pressure of 0.5 MPa at 315 to 325 ° C. for 6 to 10 seconds. After crimping, the flux residue on each evaluation test substrate was removed, and its appearance was observed with an optical microscope. Then, these steps were regarded as one step, and the number of steps until cracks or peeling occurred in the cured product on each evaluation test substrate was evaluated based on the following criteria. The results are shown in Table 3.
◎: 30 times or more 〇: 20 times or more and 29 times or less △: 10 times or more and 19 times or less ×: 0 times or more and 9 times or less

As shown above, the photosensitive resin composition of the examples includes the epoxy compound having the structure represented by the general formula (1) in (C-1), the crystalline epoxy compound in (C-2), and the (D) above. -1) By using in combination with caprolactone-modified (meth) acrylate, good heat resistance and flexibility can be imparted to the cured product, and these effects can be compatible in a well-balanced manner. Therefore, for example, even when the cured product of the photosensitive resin composition according to the examples is heated and pressed at the same time, cracks generated in the cured product and its peeling can be suppressed.
Further, since the photosensitive resin composition of the example uses the (C-1) epoxy compound and the (C-2) crystalline epoxy compound in combination, the heat resistance and flexibility of the cured product are not impaired. Good developability can be exhibited.

Claims (6)

It contains (A) a carboxyl group-containing photosensitive resin, (B) a photopolymerization initiator, (C) an epoxy compound, and (D) a reactive diluent.
The (C) epoxy compound (C-1) contains an epoxy compound having a structure represented by the following general formula (1) and (C-2) a crystalline epoxy compound, and the (D) reactive diluent is (D-1) A photosensitive resin composition containing caprolactone-modified (meth) acrylate.

The photosensitive resin composition according to claim 1, further comprising (E) an inorganic ion exchanger. The photosensitive resin composition according to claim 2, wherein the (E) inorganic ion exchanger is a cation exchanger and contains Zr. The photosensitive resin composition according to any one of claims 1 to 3, wherein the (C-2) crystalline epoxy compound is a biphenyl type. The cured product of the photosensitive resin composition according to any one of claims 1 to 4. An electronic circuit board having the cured product according to claim 5.