JPH0662729B2 - Photocurable resin composition for resist / ink of flexible printed wiring board - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a photocurable resin composition, and more particularly to a resin composition suitable for a photocurable resist ink for flexible printed wiring boards.

The object of the present invention is to cure by actinic rays such as ultraviolet rays, and has excellent adhesion, heat resistance, cold resistance, and electrical characteristics,
Another object of the present invention is to provide a photocurable resist / ink composition for a flexible printed wiring board which is excellent in flexibility.

In recent years, the development of photocurable resins, which are so-called solventless resins, has been actively promoted in response to social demands such as resource saving, pollution-free and safety. However, none of the cured products satisfy various properties such as flexibility, adhesion, and electrical properties in a well-balanced manner. Generally speaking, those having excellent flexibility tend to be inferior in any performance such as electrical characteristics and heat resistance, and conversely those having these latter various characteristics tend to be inferior in flexibility,
At present, no one has been found that satisfies these various performances at the same time.

Typical performance required for photocurable resist inks for flexible printed wiring boards is: (1) Since the substrate film is flexible, the resist ink itself to be coated must have the same flexibility. To be done. Further, since there is a step of contacting with high heat such as soldering, flexibility should not be deteriorated even after contact with this high heat. Conventional alkyd / melamine-based and epoxy-based resist inks lack this flexibility.

(2) Strong adhesion to the substrate film and copper foil is required.

(3) Soldering heat resistance and solvent resistance are required. The heat resistance during soldering is relatively excellent in the above-mentioned heat-curable resist ink, but the flexibility is insufficient as described above.

(4) Excellent electrical performance is required.

Some proposals have been made so far as resist inks for flexible printed wiring boards having such performances. For example, a photopolymerizable composition containing an aryloxoalkyl acrylate as a main component, and an unsaturated monomer having a polymerizable unsaturated bond such as ethylene glycol diacrylate and methylenebisacrylamide, and a photopolymerization initiator. However, although the cured product obtained from this composition has relatively good electrical properties and solvent resistance, it has a serious drawback of being extremely poor in flexibility and has a high heat resistance. And the adhesiveness is not enough.

In addition, JP-B-50-4395 and JP-B-53-10636 disclose that a polymerizable unsaturated bond such as sulfomethylene acrylate or ethylene acrylate phosphate having a polymerizable unsaturated bond is added to a polymerizable unsaturated bond. Although a composition containing a polyfunctional unsaturated monomer having two or more epoxy groups or an epoxy compound has been proposed, a cured product having relatively good flexibility can be obtained, but the heat resistance is remarkable. It has a defect.

The inventors of the present invention have conducted extensive studies to solve such defects of conventional resists and inks for flexible printed wiring boards. As a result, the photopolymerizable epoxy acrylate resin and the photopolymerizable epoxy resin having a carboxyl group in the molecule have been developed. The inventors have found that the defect of the conventional resist / ink for flexible printed wiring board described above can be solved by combining the compounds, and have reached the present invention. That is, the present invention is a photopolymerizable epoxy acrylate resin (A) having two or more terminal acrylate groups or terminal acrylate groups in the molecule.
And a photopolymerizable compound (B) having one or more carboxyl groups in the molecule, or the compound (B) and another photopolymerizable compound
A photocurable resin composition comprising a mixture with (C) and a photoinitiator.

The composition of the present invention not only has excellent flexibility and heat resistance, which have hitherto not been obtained, but also has various properties such as good electric insulation properties, adhesiveness, and water resistance. Also,
The photocurable resin composition also has another great advantage that it is excellent in storage stability.

A photopolymerizable epoxy acrylate resin (A) containing two or more terminal methacrylate groups or terminal methacrylate groups (collectively referred to as acryloyloxy groups and / or methacryloyloxy groups; hereinafter the same) in the molecule of the present invention.
Has a structure in which at least two acryloyloxy groups and / or methacryloyloxy groups and hydroxyl groups are present in the molecule. Examples thereof include a reaction product of polyepoxide and acrylic acid or / and methacrylic acid or a reaction product of glycidyl acrylate and / or glycidyl methacrylate and a polybasic acid or a mixture of polybasic acid anhydride and water.

Examples of the polyepoxide include polyhydric alcohols such as bisphenol A, bisphenol F, halogenated bisphenol A, ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol,
1,6-hexanediol, trimethylolpropane, polyglycidyl ethers such as pentaerythritol, polyvalent carboxylic acids such as dimer acid, phthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, succinic acid, maleic acid, trimellitic acid, There are polyglycidyl esters such as pyromellitic acid.

As a method of reacting polyepoxide with acrylic acid or methacrylic acid, for example, there is a method of reacting at 60 to 150 ° C. with a tertiary amine or quaternary ammonium salt as a catalyst.

Examples of the polybasic acid or its acid anhydride include phthalic acid, tetrahydrofuran acid, hexahydrophthalic acid, succinic acid, maleic acid, trimellitic acid, pyromellitic acid and its acid anhydride.

As a method for reacting glycidyl acrylate or glycidyl methacrylate with a polybasic acid or a mixture of polybasic acid anhydride and water, for example, a tertiary amine or a quaternary ammonium salt is reacted at 60 to 150 ° C. as a catalyst. There is a way.

The photopolymerizable epoxy acrylate resin used in the present invention may be a urethane-modified epoxy acrylate resin obtained by reacting a hydroxyl group present in the molecule of the epoxy acrylate resin with a polyisocyanate compound.

Photopolymerizable compound (B) having one or more carboxyl groups in the molecule, which is an essential component of the photocurable resin composition of the present invention
Examples thereof include (i) unsaturated carboxylic acid compounds such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid and fumaric acid, and (ii) compounds represented by the following general formula (I).

(In the formula, R ₁ represents hydrogen or a methyl group, and R ₂ and R _2
3 represents an aliphatic, aromatic or alicyclic residue, A represents an ester bond, and m and n each represent a positive integer of 1 to 3. ) In the general formula (I), R ₂ has 2 to 10 carbon atoms 2
To a tetravalent hydrocarbon group or a hydroxyl group-containing hydrocarbon group, R ₃ is a divalent to tetravalent aliphatic polybasic acid residue having 2 to 10 carbon atoms, and 6 to 15 carbon atoms. A divalent to tetravalent aromatic polybasic acid residue or 6 to 6 carbon atoms
It is preferably a divalent to tetravalent alicyclic polybasic acid residue of 10.

The compounds represented by the general formula (I) include the following compounds.

Examples of the compound in which m = 1 and n = 1 include succinic acid mono (meth) acryloyloxyethyl ester (acryloyloxyethyl ester and methacryloyloxy ester are shown. The same applies hereinafter), phthalic acid mono (meth) acryloyloxy. Ethyl ester, maleic acid mono (meth) acryloyloxyethyl ester,
Tetrahydrophthalic acid mono (meth) acryloyloxyethyl ester, hexahydrophthalic acid mono (meth) acryloyloxyethyl ester, endo-bicyclo (2,2,1) -5-heptene-2,3-dicarboxylic acid mono (meth ) Acryloyloxyethyl ester, tetrahydrophthalic acid mono-2- (meth) acryloyloxy-1- (phenoxymethyl) ethyl ester, phthalic acid mono-2-hydroxy-3- (meth) acryloyloxypropyl ester, succinic acid mono -2-hydroxy-
3-methacryloyloxypropyl ester and the like.

Examples of the compound having m = 1 and n = 2 include trimellitic acid mono-2- (meth) acryloyloxyethyl ester. Examples of the compound having m = 1 and n = 3 include pyromellitic acid mono-2- (meth) acryloyloxyethyl ester.

Examples of compounds having m = 2 and n = 1 include phthalic acid mono [2,3-bis (meth) acryloyloxyisopropyl] ester and methyltetrahydrophthalic acid mono- [2,
3-bis (meth) acryloyloxyisopropyl],
Examples include tetrahydrophthalic acid mono- [2,3-bis (meth) acryloyloxyisopropyl] ester and succinic acid mono- [2,3-bis (meth) acryloyloxyisopropyl] ester. Examples of compounds having m = 2 and n = 2 include trimellitic acid mono- [4,5-bis (meth) acryloyloxyneopentyl] ester and trimellitic acid mono- [3,4-bis (meth) acryloyloxyisobutyl]. There are esters, etc.

Examples of the compound having m = 3 and n = 2 include trimellitic acid mono- [3,4,5-tris (meth) acryloyloxyneopentyl] ester.

Examples of the compound having m = 3 and n = 3 include mono- [3,4,5-tris- (meth) acryloyloxypentyl] pyromellitic acid ester.

Of the above-mentioned compounds, the photopolymerizable compound (B) is preferably the compound (ii). These photopolymerizable compounds (B) having a carboxyl group in the molecule are used alone or in combination of two or more, or in combination with one or more kinds of other photopolymerizable compounds (C) described below. used.

The amount of the photopolymerizable compound (B) having one or more carboxyl groups in the molecule in the photopolymerizable compound (B + C) used in the present invention is 10 to 100% by weight.

The other photopolymerizable compound (C) used in the present invention is a photopolymerizable compound having one or more photopolymerizable double bonds in the molecule, excluding the photopolymerizable compound (B). .

Examples of the photopolymerizable compound having one photopolymerizable double bond in the molecule include (i) styrene and α
-Styrene compounds such as methylstyrene and chlorostyrene, (ii) methyl (meth) acrylate, ethyl (meth) acrylate, n- and i-propyl (meth) acrylate, n-, sec- and t-butyl (meth ) Acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, alkyl (meth) acrylates such as stearyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, butoxyethyl (meth) Alkoxyalkyl (meth) acrylates such as acrylate, Allyloxyalkyl (meth) acrylates such as phenoxyethyl (meth) acrylate, Hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate , Halogen-substituted alkyl (meth) acrylates, or polyoxyalkylene glycol mono (meth) acrylates such as polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, etc. heterocycles such as tetrahydrofurfuryl (meth) acrylate Containing (meth) acrylates, (iii) mono (meth) acrylates of alkylene oxide adducts of bisphenol A such as ethylene oxide and propylene oxide adducts of bisphenol A, hydrogen such as ethylene oxide and propylene oxide adducts of hydrogenated bisphenol A (I) diisocyanate compound and two or more alcoholic hydroxyl group-containing compounds, which are alkylene oxide adducts of modified bisphenol A Urethane-modified mono (meth) acrylates having one (meth) acryloyloxy group in the molecule obtained by further reacting the terminal isocyanate group-containing compound obtained by the reaction with an alcoholic hydroxyl group-containing (meth) acrylate , (V) Epoxy mono (meth) acrylates obtained by reacting a compound having one or more epoxy groups in the molecule with acrylic acid or methacrylic acid, and (vi)
Examples include oligoester mono (meth) acrylates obtained by reacting acrylic acid or methacrylic acid and a polyvalent carboxylic acid as a carboxylic acid component with a divalent or higher polyvalent alcohol as an alcohol component.

Examples of the photopolymerizable compound having two photopolymerizable double bonds in the molecule include (i) ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, and 1,4-butanediol. Alkylene glycol di (meth) acrylates such as di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate ) Polyoxyalkylene glycol di (meth) acrylates such as acrylate, dipropylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, halogen-substituted alkylene glycol Distearate (meth) acrylates substituted alkylene glycol di (meth) acrylates such as, (ii) di (meth) acrylates of alkylene oxide adducts of bisphenol A such as ethylene oxide and propylene oxide adducts of bisphenol A,
Di (meth) acrylates of hydrogenated bisphenol A alkylene oxide adducts such as ethylene oxide and propylene oxide adducts of bisphenol A,
(iii) Two in the molecule obtained by further reacting a terminal isocyanate group-containing compound obtained by previously reacting a diisocyanate compound with two or more alcoholic hydroxyl group-containing compounds with an alcoholic hydroxyl group-containing (meth) acrylate Of urethane-modified di (meth) acrylates having a (meth) acryloyloxy group, (iv) acrylic acid or methacrylic acid as a carboxylic acid component and a polyvalent carboxylic acid, and a divalent or higher polyhydric alcohol as an alcohol component There are oligoester di (meth) acrylates obtained as a result.

Examples of the photopolymerizable compound having three or more photopolymerizable double bonds in the molecule include (i) trimethylolpropane tri (meth) acrylate, trimethylolethanetri (meth) acrylate, pentaerythritol tetra ( Poly (meth) acrylates of trivalent or higher valent aliphatic polyhydric alcohol such as (meth) acrylate, poly (meth) acrylates of trivalent or higher valent halogen-substituted aliphatic polyhydric alcohol, (ii) diisocyanate compound and 3 or more Having at least 3 (meth) acryloyloxy groups in the molecule obtained by further reacting the terminal isocyanate group-containing compound obtained by previously reacting the alcoholic hydroxyl group-containing compound of (1) with the alcoholic hydroxyl group-containing (meth) acrylate Examples include urethane-modified poly (meth) acrylates.

Epoxy acrylate resin used in the present invention (A) and a photopolymerizable compound having a carboxyl group in the molecule (B) or
The compounding ratio of the mixture of (B) and the other photopolymerizable compound (C) is (A) / (B + C): 10/90 <(A) / (B + C) <
90/10 (weight ratio). Epoxy acrylate resin
When (A) is 10% by weight or less, sufficient performance in soldering heat resistance, solvent resistance and electrical characteristics cannot be obtained among the various performances required for resist ink for flexible printed wiring boards, and, Epoxy acrylate resin (A) is 90
If the content is more than 10% by weight, the adhesion to the copper foil is reduced and sufficient soldering heat resistance cannot be obtained.

The photoinitiator used in the present invention is a compound that accelerates the photopolymerization reaction of a photopolymerizable compound, and examples thereof include ketals such as benzyl dimethyl ketal, benzoin methyl ether, benzoin ethyl ether, and benzoin-i-propyl ether. Benzoins such as benzoin and α-methylbenzoin, anthraquinones such as 9,10-anthraquinone, 1-chloroanthraquinone, 2-chloroanthraquinone and 2-ethylanthraquinone, benzophenone, P-chlorobenzophenone and P-dimethylaminobenzophenone Benzophenones, 2-hydroxy-2-methylpropiophenone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropiophenone and other propiophenones, dibenzosuperone and other sperones, Phenyl disulfide, tetramethylthiuram disulfide, sulfur-containing compounds such as thioxanthone, methylene blue, eosin, etc. dyes such as fluorescein and the like, these photoinitiators are used in combination alone or two or more.

In the present invention, the compounding amount of this photoinitiator is 0.0 with respect to the total amount of the epoxy compound (A) and the photopolymerizable compound (B + C).
It is 5 to 20% by weight, preferably 0.5 to 10% by weight.

The photocurable resin composition of the present invention may contain various other components, if necessary, in addition to the above essential components. For example, various inorganic fillers, thixotropic agents, leveling agents, defoamers, plasticizers, coloring agents and the like. The photocurable resin composition of the present invention can be manufactured according to a conventional method, for example, by using a triple roll or the like to give a composition having good storage stability.

The photocurable resin composition of the present invention is cured by, for example, printing, coating, or the like, followed by irradiation with an actinic ray such as an ultraviolet ray or an electron beam. As a light source used for ultraviolet ray irradiation, sun rays, chemical lamps, low-pressure mercury lamps, high-pressure mercury lamps, metal high-ride lamps, xenon lamps and the like are used.

The cured product obtained from the composition of the present invention not only has excellent flexibility and heat resistance, which cannot be obtained by the conventional heat-curable resin composition and photocurable resin composition. It has various properties such as good electric insulation, adhesiveness and water resistance.

The photocurable resin composition of the present invention can be used as a permanent protective film for a flexible printed wiring board such as a solder resist, an overcoat, an undercoat, and an insulating coat by taking advantage of the above advantages.

Examples will be given below to describe the present invention more specifically, but of course the present invention is not limited to these examples.

In the examples, parts and% mean parts by weight and% by weight, respectively.

Performance evaluations in Examples and Comparative Examples were according to the following methods.

<Adhesiveness> The cured film was subjected to cross-cut cellophane tape peeling test (JIS K-5400).

<Flexibility> The presence or absence of cracks was determined by a 180 ° outer folding and inner folding test.

<Solder Heat Resistance> The appearance change and the adhesiveness after dipping in a solder bath at 260 ± 5 ° C. for 10 seconds or 1 minute were evaluated.

<Chemical resistance> The appearance change and the adhesiveness after immersion in 15% sodium persulfate or isopropanol were evaluated.

<Electrical properties> Comb-shaped electrode (JIS Z-319
Insulation resistance (500V
-1 minute application) was measured.

Synthesis Example 1 Diglycidyl ether of bisphenol A and Epicoat 828 were placed in a reaction vessel equipped with a thermometer and a stirrer reflux condenser.
("Okaka Shell Epoxy") 380 parts, acrylic acid 152
Parts and hydroquinone (0.05 parts), trimethylbenzylammonium chloride (1.19 parts) was added as a catalyst, esterification was performed at 120 ° C, and the reaction was continued until the reaction rate reached 95% or more by acid value measurement.
Got (I).

Synthesis Example 2 The same reaction vessel as in Synthesis Example 1 was charged with 470 parts of bisphenol F type epoxy resin (synthesized from bisphenol F and epichlorohydrin: average molecular weight 470), 152 parts of acrylic acid and 0.05 part of hydroquinone, and 1.19 parts of trimethylbenzylammonium chloride as a catalyst. Was added, esterification was performed at 120 ° C., and the reaction was allowed to proceed until the reaction rate reached 95% or more by acid value measurement, to obtain an acrylate compound (II).

Synthetic Examples 3 and 4 Using the same method as in Synthetic Example 1, diglycidyl ester of dimer acid, Epikote 871 (“Yukaka Shell Epoxy”) and polyglycidyl ether of polyhydric alcohol, Araldite CT508 (“Ciba Geigy”). ) And acrylic acid to react with each other to form an acrylate compound (I
II) and an acrylate compound (IV) were obtained.

Example 1 100 parts of acrylate compound (I) obtained in Synthesis Example 1, 50 parts of monoacryloyloxyethyl succinate, 5 parts of benzyl dimethyl ketal, 1 part of finely powdered silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.), pigment As a photocurable resin composition (a), 0.8 parts of phthalocyanine green and 0.5 parts of a silicon-based defoaming agent are well kneaded using a three-roll mill.
And

Flexible printed wiring board (Kapton 25μm / copper foil 35μm, line width 500
The above photo-curable resin composition (a) is applied to a thickness of 60 μm and a space of 500 μm by a normal screen printing method, and then irradiated with an 80 W / cm water-cooled ultra-high pressure mercury lamp at a distance of 15 cm for 20 seconds to cure. It was

The performance of the obtained cured film on the flexible printed wiring board was measured and the following results were obtained.

<Adhesiveness> No peeling phenomenon was observed.

<Flexibility> No cracks were found at all.

<Solder heat resistance> No abnormalities such as blistering or peeling were observed.

<Chemical resistance> No abnormalities were observed as shown in Table 1.

<Electrical Insulation> A photocurable resin composition (a) is applied (60 μm) by a screen printing method on a comb-shaped electrode (JIS Z-3197) which is previously formed by an etching method, and cured under the irradiation conditions to give a test piece. And Insulation resistance values (500 V-1 minute application) after various tests using this test piece showed good results as shown in Table 2.

Comparative Example 1 A photocurable resin composition was prepared and carried out in the same manner as in Example 1 except that the succinic acid monoacryloyloxyethyl ester of Example 1 was replaced with 1,6 hexanediol diacrylate containing no carboxyl group. A cured film was obtained in the same manner as in Example 1.

Various tests were conducted on this cured film in the same manner as in Example 1. As a result, no remarkable difference in flexibility and electric insulation from Example 1 was observed, but the adhesiveness to the copper foil was poor. Therefore, peeling occurred in the chemical resistance test. Further, in the solder heat resistance test, swelling, peeling, and abnormalities in the solder mist were observed at 260 ° C for 10 seconds.

Examples 2 to 5 4 having the blending composition shown in Table 3 in the same manner as in Example 1
A variety of photocurable resin compositions (b, c, d, e) were prepared. In each composition, as in Example 1, 3 parts of benzyl dimethyl ketal as a photoinitiator and 1 part of finely powdered silica (described above) were used.
Parts, 0.5 parts of phthalocyanine green and 0.3 parts of a silicon-based antifoaming agent were added.

A cured film was obtained in the same manner as in Example 1 using each of the photocurable resin compositions of Examples 2 to 5 above.

Various tests were performed on each cured film in the same manner as in Example 1. As shown in Table 4, good results were obtained with respect to adhesion, flexibility, solder heat resistance, chemical resistance, and electrical insulation. It was

Examples 6 to 9 and Comparative Examples 2 to 3 In the same manner as in Example 1, the compounding composition shown in Table 5 was used 6
A variety of photocurable resin compositions (f, g, h, i, j, k) were prepared.
In each composition, as in Example 1, 3 parts of benzyl dimethyl ketal as a photoinitiator and 1 part of finely powdered silica (supra) were used.
Parts, 0.5 parts of phthalocyanine green and 0.3 parts of a silicon-based antifoaming agent were added.

A cured film was obtained in the same manner as in Example 1 using the photocurable resin compositions of Examples 6 to 9 and Comparative Examples 2 to 3.

Various tests were carried out on each cured film in the same manner as in Example 1, and in Examples 6 to 9, regarding the adhesiveness, flexibility, solder heat resistance, chemical resistance and electrical insulation,
It showed good results. However, in Comparative Example 2, sufficient performance in soldering heat resistance, solvent resistance and electrical characteristics was not obtained, and in Comparative Example 3, sufficient adhesion to the copper foil was not obtained.

Claims (1)

[Claims] 1. A photopolymerizable epoxy acrylate resin (A) having two or more terminal acrylate groups or terminal methacrylate groups in the molecule and a photopolymerizable compound (B) having one or more carboxyl groups in the molecule. Or the compound (B)
Of other photopolymerizable compound (C) (weight ratio) (A) /
A photocurable resin composition for a resist / ink of a flexible printed wiring board, which comprises a mixture of (B + C) in the range of 10/90 <(A) / (B + C) <90/10 and a photoinitiator. object.