JPH0689285B2 - Curable resin composition for solder-resist ink - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel and useful curable resin composition for a solder resist ink, and more specifically, it is derived from a phenol novolac and a cresol novolac type epoxy resin. A resin solution obtained by dissolving both epoxy vinyl ester resins in an organic solvent and / or a specific photopolymerizable polyfunctional vinyl monomer, a photopolymerization initiator, and an amine curing agent as essential components, The present invention relates to a resin composition having excellent heat resistance and electric insulation used for a printed wiring circuit board, and its object is to use a liquid photoresist instead of a conventional dry film developing type solder resist. Is applied to the entire surface of the printed wiring circuit board and exposed to active energy rays through a photomask. In an attempt to provide a photoimageable solder resist ink curable resin composition that produce the developed resist pattern to Chi.

[Problems to be Solved by Prior Art and Invention]

Such solder resist ink is used for the purpose of soldering parts to the printed wiring circuit board, to prevent the adhesion of solder to places other than the target part, and to protect the circuit on the printed wiring circuit board. It is an ink that is used and is required to have various properties such as heat resistance, electrical insulation, adhesion, chemical resistance, and screen printability.

Initially, melamine-based heat-curable solder resist ink was used, but thereafter epoxy-based heat-curable solder resist ink with excellent heat resistance, hardness, adhesion and chemical resistance will be developed. In particular, it is the mainstream in the printed wiring circuit boards for industrial equipment such as computers that place importance on high reliability. On the other hand, the solder resist ink used in consumer printed wiring circuit boards requires workability and productivity, so ultraviolet curable solder resist ink in the form of acrylate of epoxy resin or urethane resin is It has become the mainstream, replacing the heat-curable solder resist ink of the system.

However, as is well known, such a UV-curable solder resist is a system in which a radical reaction is caused by irradiation of UV rays to cure, and when the coating film is thick, internal curability is poor, and especially in a printed wiring board for industrial equipment. ,
The thickness of the conductor is as thick as 70 μm or more due to copper plating / solder plating, and it is inevitable that the solder resist coated on this will have a coating film thickness of 50 μm or more. I will end up. For this reason, the curing reaction has not been completely completed in a portion that has not been exposed to ultraviolet rays (a lower portion of the edge of the circuit), and thus defective electrical insulation (including electrolytic corrosion) is likely to occur.

Therefore, in order to prevent these, the coating film is
Make the screen mesh fine and thin the emulsion film.
It was necessary to make the coating film less than or equal to .mu.m, and the result was limited to the use of only the consumer-use 35 .mu.m copper foil circuit.

By the way, with the recent miniaturization of electronic devices, high functionality, resource saving, cost reduction, etc., there is a growing demand for improving the accuracy of the circuit pattern density even in the industrial printed wiring circuit boards. From 2 pins between 3 to 5 pins are required.
With the current screen printing method using epoxy-based or UV-curable solder resist ink, satisfactory results have not been obtained because of limitations in printing accuracy and poor dimensional accuracy due to screen elongation. Further, the UV-curable solder resist used in this screen printing method contains a monofunctional to trifunctional monomer such as 2-hydroxyethyl acrylate, ethylene glycol diacrylate or trimethyl roll propane triacrylate, or various acrylate oligomers. However, when these substances are used for a printed wiring board having two or more pins between them, these substances appear as a serious defect such as no soldering when these substances are screen-printed.

Then, in order to prevent such a situation, the coating film thickness is made thin to improve the resolution. However, in this case, the solder resist is not uniformly coated between the circuits, the electric insulation is deteriorated, and eventually the original function as the solder resist is rendered ineffective.

Recently, a photographic method using a dry film has been developed in order to improve the resolution. However, although such a method can improve the resolution, the penetration of the dry film between circuits is poor. However, there were problems such as “blister” in the coating film and poor adhesion.

Therefore, for the purpose of improving the poor penetrability between the circuits of this dry film, the development of a photo-developing liquid solder resist ink is also underway, and U.S. Pat.No. 4,390,615 describes polyepoxy side and ethylene. Disclosed is a photopolymerizable composition comprising a vinyl ester resin obtained by reacting a polyunsaturated carboxylic acid in approximately equivalent amounts, an inert inorganic filler, a photopolymerization initiator and a volatile organic solvent. However, this photopolymerizable composition also improves the ability to penetrate into the circuit of the printed wiring circuit board, but since there are almost no epoxy groups in the molecule, phenol novolac is used to improve heat resistance. -Type epoxy resin or cresol novolac type epoxy resin and vinyl ester resin obtained by reacting unsaturated carboxylic acid are used, the adhesion to the substrate and the electrical insulation are poor, and the adhesion to the substrate When a bisphenol type epoxy vinyl ester resin is used in order to raise the temperature, heat resistance and solvent resistance are poor, and satisfactory ones have not been obtained at present.

Further, when using the photopolymerizable composition disclosed in the above-mentioned U.S. Pat.No. 4,390,615, in order to improve the adhesion to the substrate, polyepoxide and ethylenically unsaturated carboxylic acid in approximately equivalent amounts. It is extremely easy to come up with a photopolymerizable resin composition comprising a vinyl ester resin obtained by reaction, a photopolymerizable initiator, a volatile organic solvent, an epoxy resin, and a curing agent for the epoxy resin. However, when such a resin composition is used as a solder resist ink, it is exposed to an active energy ray through a photomask and then developed to form a resist pattern. In this case, the epoxy resin in the resist ink is used. Is not crosslinked by actinic energy rays and remains unreacted in the exposed coating film. To please allowed to remove the unexposed portion with a solvent such as Ren, the epoxy resin present in the exposed coating also results eluted simultaneously, satisfactory coating film can not be obtained. Therefore, even if the resist pattern formed here is not sharp, the adhesion between the coating film and the substrate and the heat resistance are remarkably lowered, and the photographic development type solder aimed at by the present invention is obtained. No resist ink is obtained.

Further, in JP-A-58-62636, an epoxy resin and a compound containing a chalcone group, for example, 4,4'-dihydroxydistyryl ketone, bis- (p-hydroxy-benzyrivinyl) phenylene, and further p-hydroxy are disclosed. A composition for a solder resist ink, which comprises a photosensitive epoxy resin obtained by reaction with phenyl-p-hydroxystyryl ketone, a curing agent, an organic solvent, and a filler, is disclosed.

However, even with such a composition, due to whitening of the coating film at the time of coating or generation of small “blisters” in the coating film at the time of heat curing after exposure to actinic energy rays, the electrical insulation property is also deteriorated. There is a problem such as a decrease in power consumption and a short circuit of the circuit which causes soldering failure.

[Means for solving problems]

However, as a result of intensive studies conducted by the present inventors in view of the various problems in the prior art as described above, a specific epoxy vinyl ester which can be cured by photopolymerization and which can be cured by heating with an amine. By using a resin as an essential base resin component and also using a photopolymerizable initiator and an amine-based curing agent in combination, a solder resist ink with excellent heat resistance, adhesion, chemical resistance and electrical insulation properties can be obtained. The inventors have found that and completed the present invention.

That is, the present invention, as an essential component, an epoxy vinyl ester obtained by reacting 1.0 chemical equivalent of a phenol novolac type epoxy resin with 0.40 to 0.80 chemical equivalent of an unsaturated monobasic acid (however, excluding 0.80 chemical equivalent) Resin (A
-A) and cresol novolac type epoxy resin
Epoxy vinyl ester resin (A obtained by reacting 1.0 chemical equivalent with 0.40 to 0.70 chemical equivalent of unsaturated monobasic acid)
-B) is at least one selected from the group consisting of trifunctional or higher polyoxyalkylene glycol poly (meth) acrylate, poly (meth) acrylate of polyoxyalkyl isocyanurate, and poly (meth) acrylate of acetal compound. Epoxy vinyl ester resin solution (A) obtained by dissolving in photopolymerizable polyfunctional vinyl monomer (A-c) and / or organic solvent (A-d), photopolymerizable initiator (B), and amine-based The present invention provides a curable resin composition for a solder resist ink, which comprises a curing agent (C).

Here, the above-mentioned phenol novolac type epoxy resin refers to a resin obtained by reacting a phenol novolac resin obtained from phenol and formaldehyde with epichlorohydrin or methyl epichlorohydrin.

On the other hand, the cresol novolac type epoxy resin refers to a resin obtained by reacting a cresol novolac resin obtained from cresol and formaldehyde with epichlorohydrin or methylepichlorohydrin.

Typical examples of the unsaturated monobasic acids to be reacted with these epoxy resins include acrylic acid, methacrylic acid, crotonic acid, monomethylmalate, monopropylmalate, monobutylmalate, sorbic acid or monocarboxylic acid. (2-ethylhexyl) malate and the like. Needless to say, these unsaturated monobasic acids may be used alone or in combination of two or more kinds.

The epoxy vinyl ester resin as the component (Aa) is a phenol novolac type epoxy resin as described above and an unsaturated monobasic acid in the presence of an esterification catalyst at 60 to 140 ° C., preferably 80 to 140 ° C. It is obtained by reacting at a temperature of about 120 ° C., and in that case, the ratio of the phenol novolac type epoxy resin to the unsaturated monobasic acid is such that the unsaturated novolac type epoxy resin is equivalent to 1.0 chemical equivalent of the phenol novolac type epoxy resin. A ratio of 0.40 to 0.80 chemical equivalent (excluding 0.80 chemical equivalent) of the basic acid, preferably 0.35 to 0.75 chemical equivalent is suitable.

The epoxy vinyl ester resin (A-
It should be understood that a) is a compound containing a vinyl group and an epoxy group in one molecule obtained by adding an unsaturated monobasic acid to a part of the epoxy group in a phenol novolac type epoxy resin.

Here, as the esterification catalyst, tertiary amines such as triethylamine, N, N-dimethylbenzylamine, N, N-dimethylaniline or diazabicyclooctane; or diethylamine hydrochloride, dimethylamine acetate or dimethylamine nitrate, etc. Examples of such compounds include, but it goes without saying that known and commonly used catalysts can be used as they are.

Furthermore, the above-mentioned epoxy vinyl ester resin (A-
When preparing a), it is recommended to use a polymerization inhibitor for the purpose of preventing gelation and adjusting the storage stability or curability of the produced resin. Typical examples of such a polymerization inhibitor are hydroquinones such as hydroquinone, pt-butylcatechol or mono-t-butylhydroquinone; phenols such as hydroquinone monomethyl ether or di-t-butyl-p-cresol; p-benzoquinone. , Quinones such as naphthoquinone or p-toluquinone; or copper salts such as copper naphthenate.

Further, the epoxy vinyl ester resin as the component (Ab) is completely the same as the above-described method for preparing the epoxy vinyl ester resin (A-a) from the cresol novolac type epoxy resin and the unsaturated monobasic acid as described above. It is obtained in the same manner. However, as the use ratio of these cresol novolac type epoxy resin and unsaturated monobasic acid, 0.40 ~ 0.70 chemical equivalent of unsaturated monobasic acid to 1.0 chemical equivalent of cresol novolac type epoxy resin, preferably 0.45 ~ A ratio of 0.65 chemical equivalent is appropriate.

As the vinyl ester resin (Ab), substantially, an epoxy group and a vinyl group in one molecule in a form in which unsaturated monobasic acid is added to a part of the epoxy group in the cresol novolac type epoxy resin. It is desirable that the resin coexists with.

The so-called phenol novolac type epoxy vinyl ester resin (Aa) and cresol novolac type epoxy vinyl ester resin (Ab) thus obtained.
Is dissolved in a specific photopolymerizable polyfunctional vinyl monomer (A-c) and / or an organic solvent (A-d) as described below to obtain a stable resin solution.

First, typical examples of the photopolymerizable polyfunctional vinyl monomer (A-c) include dipentaerythritol tri-,
Tetra-, penta-, hexa (meth) acrylate, tri-, tetra-, penta-, hexa (meth) acrylate of caprolactone adduct of dipentaerythritol, tri (meth) acrylate or trimethylol of propylene oxide adduct of glycerin Tri (meth) acrylate of propylene oxide adduct of propane, or dipentaerythritol and lower fatty acid (C ₁
~ C ₄ ) and (meth) acrylic acid,
Moreover, tri- or higher functional polyoxyalkylene glycol poly (meth) acrylate represented by tri- or penta-functional monomers; bis [(meth) acryloyloxyethyl] hydroxyethyl isocyanurate or tris [(meth) acryloyloxyethyl] Poly (meth) acrylate of polyoxyalkyl isocyanurate represented by isocyanurate; or 2- (2-
Poly (meth) acrylate, which is an acetal compound represented by hydroxy-1,1-dimethylethyl) -5-hydroxymethyl-5-ethyl-1,3-dioxane diacrylate, has a high photo-curability and heat resistance. It is preferable from the viewpoint. However, such as ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, glycerin tri (meth) acrylate, trimethylolethane tri (meth) acrylate or trimethylol pentane tri (meth) acrylate, an ether bond is included in the molecule. The use of photopolymerizable vinyl monomers (acrylic monomers) that do not contain is excluded.

Of course, the monomer (A-c) may be used alone or in combination of two or more kinds.

The amount of the monomer (A-c) used is not particularly limited, but from the viewpoint of workability, the epoxy vinyl ester resins (A-a) and (A-b) described above are used.
5 to 60% by weight based on the total solid content of, and preferably
A range of 10 to 40% by weight is suitable.

Next, typical examples of the above-mentioned organic solvent (Ad) are aromatic hydrocarbons such as toluene and xylene; alcohols such as methanol and isopropanol; ethers such as 1,4-dioxane and tetrahydrofuran: methyl ethyl ketone. , Methyl isobutyl ketone, etc .; glycol derivatives such as cellosolve, butyl cellosolve; alicyclic hydrocarbons such as cyclohexanone and cyclohexanol; or petroleum-based solvents such as petroleum ether and petroleum naphtha. Of course, a combination of two or more species may be used.

The concentration of the organic solvent (A-d) is not particularly limited, but from the viewpoint of workability, it is 5 to 60% by weight,
It is preferably in the range of 10 to 40% by weight.

Typical examples of the photopolymerization initiator (B) described above include p-t-butyltrichloroacetone, 2,2-diethoxyacetophenone, benzophenone, 4,4-bismethylaminobenzophenone, benzyl, benzoin and benzoin. Methyl ether, benzoin isobutyl ether,
Carbonyl compounds such as benzyl methyl ketal, methyl-o-benzoyl benzoate, α-hydroxyisobutylphenone; sulfur compounds such as tetramethyl thiuram monosulfide, thioxanthone, 2-chlorothioxanthone; or azo compounds such as azobisisovaleronitrile. However, it goes without saying that these may be used alone or in combination of two or more kinds.

And as the usage-amount of the said photopolymerization initiator (B),
The epoxy vinyl ester resins (A-a) and (A
It is preferably in the range of 0.5 to 20% by weight based on the total solid content of -b).

Further, typical amine curing agents (C) are aliphatic polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, diethylaminopropylamine and xylylenediamine; metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone. Aromatic polyamines such as:
Alicyclic polyamines such as menthanediamine, isophoronediamine, bis (4-amino-3-methylcyclohexyl) methane: dicyandiamide; 2-methylimidazole, imidazoles such as 2-ethyl-4-methylimidazole; benzyldimethylamine, There are tertiary amines such as tridimethylaminomethylphenol and dimethylaminomethylphenol; or amine complex compounds such as BF ₃ · monoethylamine.

Among these, in order to obtain a resist ink having a long pot life from the aspect of workability, a curing agent that is slow in reactivity at room temperature and rapidly reacts when heated, for example, aromatic polyamines, The use of imidazoles, tertiary amines or dicyandiamide is preferred.

Furthermore, if necessary, the resin composition of the present invention may contain fillers such as silica, talc and clay; thixotropic agents such as Aerosil: silicon-based or fluorine-based leveling agents or defoaming agents; or coloring agents. Various additives as described above can be added for the purpose of further improving various performances of the solder resist ink.

The solder resist ink using the curable resin composition for a solder resist ink of the present invention thus obtained is applied to the entire surface of a printed wiring circuit board by a screen printing method, a roll coater method, a curtain coater method or the like.

Next, when a solvent is contained, preliminary drying is carried out to remove the solvent so that the ink surface is tack-free.

A photomask is brought into close contact with the tack-free ink surface and irradiated with active energy rays to insolubilize the ink by radical polymerization. If the ink surface does not become tack-free, it is also possible to hold the photomask on a transparent support and irradiate parallel lines of active energy rays without adhering to the ink surface.

Next, the portion not exposed to the active energy ray is dissolved and removed with a developing solution such as trichloroethylene, perchlorethylene or methylene chloride.

After that, a method of forming a resist pattern by reacting an epoxy group by heat curing is adopted.

Next, the present invention will be described more specifically by reference examples, examples and comparative examples. In the following, all parts and% are based on weight unless otherwise specified.

Reference Example 1 A three-necked flask equipped with a thermometer, a stirrer and a condenser was charged with "Epiclon N-740" [phenol novolac type epoxy resin manufactured by Dainippon Ink and Chemicals, Inc .; epoxy equivalent = 180]. Charge 1,800 parts (corresponding to 10 epoxy groups), 504 parts of acrylic acid (corresponding to 7 carboxyl groups), 1.15 parts of hydroquinone and 9.2 parts of triethylamine, raise the temperature to 110 ° C and continue the reaction for 6 hours. Thus, an epoxy vinyl ester resin (Aa-1) having an acid value of 3.0 and an epoxy equivalent of 770 was obtained.

Reference Examples 2 to 4 As shown in the same table as in Reference Example 1, except that “Epiclone N-740”, acrylic acid, hydroquinone and triethylamine were used in the proportions shown in Table 1. An epoxy vinyl ester resin having various acid values and epoxy equivalents was obtained.

Reference Examples 5 and 6 "Epiclone N-660" (cresol novolac type epoxy resin manufactured by the same company; epoxy equivalent = 220), acrylic acid, hydroquinone and triethylamine
An epoxy vinyl ester resin having the property values shown in the same table was obtained in the same manner as in Reference Example 1 except that the ratio was changed to that shown in the table.

Reference Examples 7 and 8 "Epiclone 850" (produced by the same company, bisphenol A type epoxy resin; epoxy equivalent = 185) or "Epiclone 1050"(above; epoxy equivalent = 470), acrylic acid, hydroquinone and triethylamine, Third
An epoxy vinyl ester resin having the property values shown in the same table was obtained in the same manner as in Reference Example 1 except that the ratio was changed to that shown in the table.

Examples 1 to 5 and Comparative Examples 1 to 4 The epoxy vinyl ester resin or epoxy resin obtained in Reference Examples 1 to 8, a photopolymerizable polyfunctional vinyl monomer and / or an organic solvent, and a photopolymerizable initiator, An amine curing agent and a solder resist ink were prepared in accordance with the compounding ratios shown in Table 4, and were separately applied to a copper through-hole printed wiring board by screen printing at a film thickness of 30 to 40 mμ.

Then, after drying each coating film for 5 minutes at 130 ℃ if necessary, apply a photomask separately, and use a 5kW ultra-high pressure mercury lamp to emit UV light with a wavelength of around 350nm and an illuminance of 2mw / cm ^2. Irradiation was carried out for 60 seconds, and then an unirradiated part of the coating film was removed with an organic solvent such as trichlorethylene.

Then, each of the specimens obtained by individually performing heat curing at 130 ° C. for 30 minutes using a hot air dryer was compared with various types of performance.

The results are summarized in the same table.

The evaluation of various performances shown in the table was carried out as follows.

(Solvent resistance) Using a 5 kW ultra-high pressure mercury lamp, the wavelength is around 350 nm, and the illuminance is 20 mw / cm ² irradiate each sample for 60 seconds, then after removing the unirradiated portion with trichlorethylene, The state of the coating film in the irradiated portion was judged.

The criteria for judgment at that time are as follows.

◯: Appearance of coating film, no abnormalities ×: Melting or swelling [Soldering resistance] Judgment of coating film state after immersing each specimen in molten solder of tin 60% at 260 ° C for 2 minutes did.

The criteria for judgment at that time are as follows.

○ …… No appearance of coating film, no abnormalities × …… Blistering, melting and / or peeling [Cohesion of goggles] 100 coats of 1 × 1mm gobangs on each test film peeled off with cellophane tape After that, the adhesiveness was determined by the number of residual stitches (JIS D-020
2).

[Surface Insulation Resistance] The test sample coated on the test pattern substrate of IPC-840B-25 of the mil standard is left for 240 hours in an atmosphere of 30 ° C and 95% RH, and the surface insulation resistance of each coating is measured according to JIS Z It measured according to -3197.

Also from the results shown in Table 4, the coating film obtained using the curable resin composition for a solder resist ink of the present invention,
It can be clearly seen that it has excellent heat resistance, adhesion, solvent resistance and electrical insulation.

Claims (2)

[Claims] 1. An epoxy vinyl ester resin obtained by reacting Aa) 1.0 chemical equivalent of a phenol novolac type epoxy resin with 0.40 to 0.80 chemical equivalent of an unsaturated monobasic acid (excluding 0.80 chemical equivalent), And b) an epoxy vinyl ester resin obtained by reacting 1.0 chemical equivalent of a cresol novolac type epoxy resin with 0.4 to 0.70 chemical equivalent of an unsaturated monobasic acid, and c) a trifunctional or higher functional polyoxyalkylene glycol poly ( Dissolved in one or more photopolymerizable polyfunctional vinyl monomers selected from the group consisting of (meth) acrylate, poly (meth) acrylate of pooxyalkyl isocyanate, and poly (meth) acrylate of acetal compound and / or d) an organic solvent. The resulting epoxy vinyl ester resin solution, B. photopolymerization initiator, C. amine-based hardener Comprising a material as essential components, a solder resist ink curable resin composition. 2. Obtained by reacting 1.0 a chemical equivalent of a) a phenol novolac type epoxy resin and 0.40 to 0.80 chemical equivalent of an unsaturated monobasic acid (excluding 0.80 chemical equivalent) as essential components. And an epoxy vinyl ester resin obtained by reacting b) 1.0 chemical equivalent of a cresol novolac type epoxy resin with 0.40 to 0.70 chemical equivalent of an unsaturated monobasic acid, and c) a trifunctional or higher functional resin. One or more photopolymerizable polyfunctional vinyl monomers selected from the group consisting of polyoxyalkylene glycol poly (meth) acrylate, poly (meth) acrylate of polyoxyalkyl isocyanurate, and poly (meth) acrylate of acetal compound and / Or d) an epoxy vinyl ester resin solution (A And 100 parts by weight of the solid content of,
0.1 to 20 parts by weight of the photopolymerizable initiator (B) and 0.4 to 1.0 equivalent of the epoxy group remaining in the resin solution (A)
To 1.5 equivalents (however, when the amine-based curing agent (C) described below is a tertiary amine or an imidazole, it is 0.1 to 100 parts by weight of the solid content of the resin solution (A). Amine curing agent (C) in a proportion of 30 parts by weight
Claim 1 characterized in that it comprises
Composition.