JPS6080843A - Photopolymerizable resin composition - Google Patents

Abstract

PURPOSE:To obtain a dry film forming resist by using a thermoplastic polymer for a binder prepd. by soln. polymn. in isopropanol, a solvent for improving the solubility of the polymer, a monomer having two ethylenic unsatd. groups, and a photopolymn. initiator. CONSTITUTION:A dry film forming resist is composed of a thermoplastic polymer soln. for a binder prepd. by soln. polymn. in isopropanol (IPA) or an IPA- base mixed solvent, a solvent for further improving the solubility of the polymer, a monomer having at least two ethylenic unsatd. groups in the molecule as a cross-linking agent, and a photopolymn. initiator which can be optically activated with active light. IPA dissolves the polymer and the monomer contained in large quantities, increases the polymn. temp., enables the formation of a polymer at a high rate of polymn. in a short time, and evaporates at a high speed, so a dry film can be formed at a low temp. in a short time without carrying out heat curing. The dry film forming resist has superior shelf stability, work efficiency and processability, gives a pattern with high resolution, and requires only an alkaline aqueous soln. in a stripping stage. It is not expensive and is used in printed wiring or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a photopolymerizable resin composition used particularly for forming an alkali-developable dry film resist for printed wiring boards.

(b) Prior art The thermoplastic polymer for the binder (hereinafter referred to as "binder resin") used in alkaline-developable dry film resists is insoluble or swellable in dilute alkaline aqueous solutions and is not soluble in water. must not. Conventionally, vinyl addition polymers containing carboxylic acid groups have been used as such thermoplastic polymers. However, when a resist formed from a polymer into which the minimum necessary amount of carboxylic acid groups has been introduced to be able to develop and resolve a fine pattern, the cured resist swells when it is immersed in a stripping solution consisting of an alkaline aqueous solution alone in the stripping process after exposure. However, it is peeled off while retaining the pattern form without becoming small pieces. For this reason, there were problems such as the peeled material getting wrapped around the conveyor roll in the peeling machine, and the hardened resist hitting the lower part of the overhanging plating peeling off, resulting in poor G resistance. In order to solve these problems, it has become necessary to introduce a large number of carbonic acid groups into the binder resin and peel it off while crushing the cured resist film when immersed in a stripping solution.

On the other hand, as a method for manufacturing an alkali-developable dry film resist, the following two methods have conventionally been adopted. The first method is to prepare a dry binder resin using various methods, and use this to dissolve a crosslinking monomer, a photoinitiator, and other additives in a solvent to prepare a coating solution. This is a method in which a dry film is obtained by coating the film on a support and then drying it to scatter the solvent. The second method is to prepare a coating solution by mixing and dissolving a crosslinkable R-mer, a photopolymerization initiator, and other additives in a polymer solution obtained by polymerizing a binder resin using a solution polymerization method. This method involves applying it to the body and then drying it to scatter the solvent to form a dry film.

The polymerization reaction used to produce the binder resin used in alkaline-developable dry film resists is mainly a radical reaction, and there are four known polymerization methods: bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. ing. In order to produce the binder resin having a high carboxylic acid group content, it is difficult to employ suspension polymerization or emulsion polymerization because the carboxylic acid group-containing vinyl monomer is water-soluble.

In addition, when the solution polymerization method is used to directly obtain the binder resin in a dry state in the first manufacturing method, reprecipitation and drying operations are required after polymerization, and it is necessary to use a solvent twice in the dry film manufacturing process. There is. On the other hand, when polymerization is carried out by bulk polymerization, a dry polymer can be obtained directly, but not only does it have to be crushed to facilitate dissolution when polymerizing the coating solution, but it is also difficult to control the polymerization. Industrially, the cost will be high. In any case, the first manufacturing method has the problem of high manufacturing costs.

In the second production method, the polymerization solvent is one that not only dissolves the monomer and the resulting polymer well, but also dissolves other components other than the binder resin, and after applying the coating liquid, the dry film resist is formed. It is necessary to use a solvent that can be dried at a low temperature that does not cause thermal curing and that can be easily dried in a short time. Although the co-solvent of methylene chloride and methyl alcohol as shown in JP-A-50-147,323 has excellent solubility of vinyl addition polymers with a high content of carboxylic acid groups and is extremely easy to dry, The boiling point is extremely low,
Since the polymerization temperature becomes low and a sufficient polymerization rate cannot be obtained, it is substantially impossible to polymerize, and only extremely low molecular weight polymers can be obtained, so that it cannot be used as a polymerization solvent for this purpose. On the other hand, when methyl cellosolve as shown in JP-A No. 52-94.388 is used as a polymerization solvent, it is industrially useful because it is a high boiling point solvent and it is possible to widen the temperature range of polymerization. Although it is advantageous, the drying load is large during drying after coating the coating liquid, resulting in a decrease in the productivity of the dry film resist.

(c) Purpose of the Invention The purpose of the present invention is to overcome the problems of the prior art as described above, and to use a polymerization solvent that can industrially advantageously carry out polymerization for preparing a binder resin with a high carboxylic acid content. , and by using a coating liquid solvent with a small drying load, and as a result,
In particular, it is an object of the present invention to provide a photopolymerizable resin composition that allows the production of an alkali-developable dry film resist in an industrially convenient manner.

(d) Structure of the Invention The photopolymerizable resin composition according to the present invention includes a thermoplastic polymer solution for a binder obtained by solution polymerization in an isopropyl alcohol solvent or a mixed solvent containing the same as a main component, and a thermoplastic polymer for the binder. It is characterized by consisting of a solvent for improving the solubility of the polymer, a monomer having at least two ethylenically unsaturated groups in the molecule as a crosslinking agent, and a photopolymerization initiator that can be photoactivated by actinic light. do.

(E) Embodiment Isopropyl alcohol, which is the main component of the polymerization solvent used in the present invention, not only dissolves the binder resin with a high carboxylic acid group content and its monomer, but also raises the polymerization temperature sufficiently. Therefore, a binder resin with a high polymerization rate required for the binder resin can be produced in a short time.

Also, isopropyl alcohol has a fast evaporation rate, so
It is extremely suitable for producing dry films because it can be dried in a short time at a low temperature that does not cause dry films to harden.

The polymerization solvent added to isopropyl alcohol can be used in an amount of 20% by weight or less based on the weight of the mixed solvent. As such a co-solvent, a solvent that can dissolve the monomer and the produced polymer and has a boiling point of 75° C. or lower can be used. Suitable cosolvents will vary depending on the type of thermoplastic binder polymer. For example, methylene chloride and methyl ethyl ketone are effective as polymerization solvent additives for methyl methacrylate/methacrylic acid copolymer.

The solution polymerization of the present invention includes a thermal polymerization method and a photopolymerization method.

Although any radiation polymerization method may be used, the thermal polymerization method is suitable for polymerizing a large amount of monomer in terms of equipment.

Typical examples of monomers to be solution polymerized to form thermoplastic polymers for binders used in alkali-developable dry film resists include acrylic esters, metal acrylic esters, styrene, etc., and carboxylic acids. Mixtures may be mentioned. Examples of acrylic esters or methacrylic esters include methyl (meth)acrylate, ethyl (meth)acrylate, 1ln-butyl (meth)acrylate, 1so-butyl (meth)acrylate, and tert (meth)acrylate. ,
Butyl, propyl (meth)acrylate.

Neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate.

(meth)octyl acrylate, (meth)acrylic acid 2-
Ethylhexyl, lauryl (meth)acrylate, tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (
Examples include 2-hydroxypropyl meth)acrylate. These may be used alone or in combination of two or more.

Examples of carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid. To develop dry film resist with alkaline aqueous solution,
The copolymerization ratio of carboxylic acid is 15 to 5 in the case of methacrylic acid.
It is desirable to use it in the range of 0% by weight. Addition amount is 15
Using less than % by weight of binder resin not only significantly increases development time but also reduces resolution. If a binder resin of 50% by weight or more is used, the development time becomes extremely short, it becomes difficult to control the development to obtain a high-resolution pattern, and the water resistance of the cured part also decreases. However, in order to cause crushing and peeling in the peeling process, it is necessary to adjust the carboxylic acid copolymerization ratio to 20 to 50% by weight of methacrylic acid.

If the amount is less than 20% by weight, the cured resist will not be crushed and peeled off, and peeled off pieces will become large, causing the above-mentioned problems. on the other hand,
If it exceeds 50% by weight, the development speed will be too fast and the exposed areas will also melt, resulting in a decrease in resolution. Acid value 1 for other carboxylic acids
When used in the range of 00 to 330, a binder resin for dry film resists that can be crushed and peeled can be obtained.

Examples of the polymerization initiator used in the polymerization of the binder resin include peroxides such as acetyl peroxide, benzoyl peroxide, and lauroyl peroxide; azobisisobutyronitrile;
Examples include azo compounds such as azobis-2,4-dimethylvaleronitrile and azobiscyclohexanecarbonyl. Furthermore, in order to appropriately adjust the degree of polymerization of the polymer, a polymerization regulator such as aldehyde or mercaptan may be added.

The weight average molecular weight of the copolymer used as the above binder resin is in the range of 40,000 to 200,000. If the molecular weight is less than 40,000, when stored as a dry film resist by winding it into a roll, so-called cold flow development occurs in which the resist composition oozes out from between the support films over time.

If it exceeds 200,000, unexposed areas will not be dissolved and development will not be possible, or the development time will be extremely long, resulting in a decrease in resolution and failure to cause crushing and peeling during peeling.

The binder resin solution prepared as described above tends to undergo phase separation at low temperatures. For this reason, it is necessary to transport the binder resin solution in a can and heat it again to dissolve it when taking it out from the can for preparing a coating solution. In order to omit this operation, a solvent for improving solubility is newly added to the binder resin solution.

This solvent is preferably one that has the ability to function as a cosolvent with the polymerization solvent and dissolve the binder resin well, and has a low boiling point. As such a solvent, for example, methyl ethyl ketone, methylene chloride, etc. can be effectively used. The amount of solvent added to improve solubility is based on the weight of the polymerization solvent.
．． The content is preferably 5 to 500% by weight.

Examples of the ethylenically unsaturated monomer used as a crosslinking agent include polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, l
, 4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanethiol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol di(meth)acrylate, penta In addition to polyester (meth)acrylates such as erythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, epoxy(meth)acrylate,
Examples include urethane (meth)acrylate. These may be used alone or in combination of two or more.

The blending ratio of binder resin/crosslinking agent can be in the range of 2/3 to 9. If the blending ratio is less than 2/3, the coating solution may not be uniformly coated, migration may occur in the resist layer after drying, or a cold flow phenomenon may occur. On the other hand, if it exceeds 9, the exposed areas of the resist will be rapidly dissolved by the developer, making development impossible.

Examples of the photopolymerization initiator to be added to the coating solution include benzoin, benzoin alkyl ethers, hensifhenone, Michler's ketone, 4,4'-bis(diethylamino)benzophenone, acetophenones, benzyl ketals, anthraquinones, thioxanthone, etc. Can be mentioned. These may be used alone or in combination. The amount of photopolymerization initiator is 0.00% of the dry film resist solid content.
A preferable range is 1 to 2% by weight.

After obtaining a binder resin solution by solution polymerization using the mixed solvent mainly composed of isopropyl alcohol, a solvent for improving the solubility of the binder resin is added to prepare the binder resin solution, and a crosslinking agent and A photopolymerization initiator is mixed to form a coating solution. Note that the coating liquid may contain components such as an adhesion promoter, a thermal polymerization inhibitor, a dye, a plasticizer, and a filler.

For mixing and stirring during the preparation of the coating liquid, a propeller type one-reversal type mixer or a kneader type mixer is mainly used.

The coating liquid prepared as described above is applied onto a support, and then the solvent is scattered. To apply the coating solution to the support,
Plaid coater, rod coater.

Knife coater, roll doctor coater, comma coater,
Reverse roll coater, transfer roll coater, gravure coater, kiss roll coater.

This can be done by using a curtain coater or the like. These selections are determined by coating weight, coating liquid viscosity, coating speed, etc. A plastic film such as polyester is mainly used as the support. Since a flammable solvent is used, the dryer should be equipped with an air-heating heat source using steam for safety reasons, such as a method in which the hot air inside the dryer is brought into countercurrent contact, or a method in which the hot air is blown onto the support from a nozzle. is used. The shape of the dryer can be selected from arch type or flat ring type depending on the purpose.

If necessary, the dry film of the dryer may be laminated with a protective film such as polyethylene or polypropylene.

(f) The dry film resist produced as described above has the following effects:
As an etching resist or a blating resist, it has excellent storage stability, workability, and process passability, and can provide high-resolution patterns. However, the noteworthy point is that the stripping step can be carried out using an alkaline aqueous solution alone. For this reason, it has been possible to completely eliminate the increase in printed circuit board production costs that would otherwise have been caused by adding a solvent such as butyl calpitol to an alkaline aqueous solution in order to break up the peeled pieces. In addition, in producing the above dry film resist, a binder resin solution is prepared by adding a solvent to improve the solubility of the binder resin to a solution polymerized with a solvent containing isopropyl alcohol as a main component, and a crosslinking agent is added to the binder resin solution. The method of obtaining a dry film resist by mixing a photopolymerization initiator and other additives, preparing a coating solution, coating it on a support, and drying it can sufficiently reduce production costs compared to conventional methods.

(g) Examples The present invention will be specifically described below with reference to Examples.

Comparative Example 1 A 1000 ml four-bottle flask was equipped with a stirrer, a condenser, a thermometer, and a nitrogen inlet. 200 g of isopropyl alcohol, 14 methyl methacrylate under nitrogen atmosphere
0g, ethyl acrylate 20g1 methacrylic acid 40g
Add and stir while raising the temperature of the water bath to 80°C. Next, 1.0 g of azobisisobutyronitrile dissolved in 10 g of isopropyl alcohol is added and polymerized for 4 hours. Next, add 1.0 g of azobisisobutyronitrile to 1
After the fifth addition, the internal temperature was raised to the boiling point of isopropyl alcohol and polymerization was continued for 2 hours.

After the polymerization is completed, 100 g of isopropyl alcohol is added and the polymerized product is taken out. The binder resin solution thus prepared had a Gardner viscosity of +26 and a degree of polymerization of 99.
It was 5% or more. 50ml of this binder resin solution
Approximately 5 g of the mixture was placed in a 1-size beaker, cooled in ice water at 0°C and a refrigerator at 7°C, and the state of phase separation was visually observed. The results are shown in Table 1.

Examples 1 to 4 After solution polymerization in the same manner as in Comparative Example 1, a mixed solvent of isopropyl alcohol and methylene chloride was added in place of isopropyl alcohol, and the ratio of isopropyl alcohol to methylene chloride in the solvent in the final binder resin solution was adjusted. was adjusted to four levels: 9515.90/10°, 85/15, and 80/20.

This was subjected to the same test as in Comparative Example 1. Table 1 shows the results.
Shown below.

Examples 5 to 8 Solution polymerization was carried out in the same manner as in Comparative Example 1, except that a polymerization solvent consisting of 95% by weight of isopropyl alcohol and 5% by weight of methyl ethyl ketone was used. A mixed solvent of isopropyl alcohol/methyl ethyl ketone was added to the obtained polymer solution so that the ratio of isopropyl alcohol to methylene chloride in the polymer solution was 97/3, 90/10, 85/15, and 80/20. It was adjusted.

Table 1 shows the results of a test similar to Comparative Example 1.

Examples 9 to 13 Using the binder resin solution prepared in Example 2, a coating liquid having the following composition was prepared.

Binder resin solution 228 parts by weight Trimethylolpropane triacrylate 50 parts by weight Tetraethylene glycol diacrylate 20 parts by weight Benzophenone 1.0 parts by weight Michler's ketone 0.2 parts by weight Tolyltriazole 0.4 parts by weight Methylene blue 0.75 parts by weight Mixed coating The liquid was stirred using a propeller type mixer and coated onto a polyester film having a thickness of 25 μm and a width of 360 mm using a blade coater to a coating width of 340 mm. Then,
Hot air was sent in countercurrent through a flat dryer with a width of 400 mm, a height of 100 mm, and a length of 8 m to give a dry coating thickness of 50 μm. At this time, the conveyance speed was 5 m/min, the wind speed was 3 m/sec, and the temperature inside the dryer was 80°C, 90°C, 100°C.
℃, 110℃, and 120'C.

A polyethylene protective film with a thickness of 35 μm was then laminated onto the dried coating, and then wound up into a roll. The obtained dry film resist is
The coated film surface was thermally laminated to the copper-clad laminate while peeling off the protective film, and after the temperature of the copper-clad laminate returned to room temperature, a photo tool was closely attached to the polyester film surface and exposed to light using an ultra-high pressure mercury lamp. Photo tools are 50μm and 60μm
.

A line and width pattern with widths of 80 μm and 100 μm was used. In addition, ultra-high pressure mercury lamps are manufactured by Ushio Inc. (US) 1
-1020 is used. Irradiation was performed at 100 mJ/ca. The exposure intensity at this time is Ushio Inc. UV intensity meter 1117-100.
Attach a photodetector UVD-365P to the
/crA. After exposure, the support film was peeled off after being left for 20 minutes, and developed with a 2% aqueous sodium carbonate solution. Development was carried out at a liquid temperature of 30 DEG C., a spray pressure of 1.4 kg/-, and a distance of 10 cm between the spray and the substrate. Next, it was immersed in a neutral detergent aqueous solution at room temperature for about 1 minute, and after degreasing, it was spray washed with water in an overflow tank for about 1 minute, and then immersed in an about 20% ammonium persulfate aqueous solution for 1 minute. After spray washing again for about 1 minute,
It was immersed in a 5% aqueous sulfuric acid solution for 1 minute, and then sprayed and washed with water again for 1 minute. Next, put it in a copper sulfate plating tank and heat it for 75 minutes.
2.3 A/dn per minute? The plating was done with The stirring temperature at this time was 22°C. Rinse with water immediately after plating,
Immersed in 15% borofluoric acid aqueous solution, then 1.8A for 18 minutes
/drrr, high-slow solder plating was performed at 22°C.

The composition of the solder plating solution is as follows.

Tin 15 g/6 Lead 10 g/A Free acid hydrofluoric acid 400 g/j! Free boric acid 21.6g/j! Peptone 5.2 g/12 After the plating was completed, it was washed with water and then dried.

Table 2 shows the amount of residual solvent, developability, and plating resistance in the dry film. If dried at high temperatures, heat curing will occur and development will become impossible, and if there is a large amount of residual solvent, plating may peel off during plating or cold flow development may occur.

Examples 14 to 18 Using the binder resin solution prepared in Example 6, dry film resists were made in the same manner as in Examples 9 to 13, and the same evaluations were performed. The results are shown in Table 2.

Comparative Examples 2 to 6 In place of isopropyl alcohol in Comparative Example 1, methyl cellosolve was used as a polymerization solvent for polymerization to prepare a binder resin solution. Dry film resists were made in the same manner as in Examples 9 to 13, and evaluated in the same manner. The results are shown in Table 2.

Below are blank spaces Examples 19 to 23 Dry film resists were obtained by changing the binder resin composition ratio of Example 11 as shown below and keeping other polymerization conditions, solvent addition ratio, coating liquid formulation, coating method, and drying method the same. Ta.

After this dry film was optimally developed using the same developing method as in Example 11, it was peeled off using a 5% aqueous sodium hydroxide solution. For stripping, adjust the stripping solution to 55℃ and spray pressure 1.
．． Assuming 0 kg/aa, the distance between the spray and the substrate is 10a.
It was conducted as m.

Table 3 shows the weight average molecular weight of the binder resin and the results of visual observation of peeled pieces.

Procedural amendment (voluntary) April 18, 1980 Kazuo Wakasugi, Commissioner of the Japan Patent Office 1, Indication of the case 1987 Patent Application No. 187699 2, Name of the invention Photopolymerizable resin composition 3, Person making the amendment Case Relationship with Patent applicant name (603) Mitsubishi Rayon Co., Ltd. 4, agent address 5-8-10 Toranomon-chome, Minato-ku, Tokyo 105
Target of amendment 6, contents of amendment (1) Lines 1 to 2 of page 2 of the specification, “insoluble in… soluble in water” should be amended to “soluble or swellable in water and insoluble in water” .

(2) Page 7, line 1 of the specification “The point is below 75°C” is changed to “The point is below 80°C”
℃ or less”.

(3) On page 7 of the specification, line 4, “methacrylic acid” should be amended as follows: “Mendarenone solvent”.

(5) Each S corresponding to Example 5 in the same page and table is corrected as follows.

(6) The numerical value in the methyl methacrylate column corresponding to Example 23 in the table on page 24 of the specification is corrected to "35".

(7) P corresponding to Example 23 in Table 3 on page 25 of the specification (
MMA/MA/MAA) Composition ratio column It'35/10
Corrected to 155J.

that's all

Claims (1)

[Claims] A solution of a thermoplastic polymer for a binder obtained by solution polymerization in an isopropyl alcohol solvent or a mixed solvent containing this as a main component, a solvent for improving the solubility of the thermoplastic polymer for a binder, and a crosslinking agent in the molecule. A photopolymerizable resin composition comprising a monomer having at least two ethylenically unsaturated groups, and a photopolymerization initiator that can be photoactivated by actinic radiation.