JPH06128794A - Electrodeposition coating method - Google Patents

Abstract

PURPOSE:To form a photoresist layer by electrodeposition coating with good coating workability and high efficiency by filtering a part of the soln. in the electrodeposition coating bath contg. a photopolymerizable unsaturated-bond component with an ultrafilter using a PVA-resin permeable membrane. CONSTITUTION:An electrodeposition tank 1 is filled with the electrodeposition coating bath consisting essentially of a polymer having 20-300 acid value, a compd. having a photopolymerizable unsaturated bond or a polymer having 20-300 acid value and a photopolymerizable unsaturated bond, a photopolymerization initiator, a basic compd. and water. A conductive substrate is dipped in the bath, and the coated substrate is cleaned in washing tanks 2a to 2c to form a photoresist layer on the substrate. In this process, a part of the bath is introduced into an ultrafilter 5 by a pump through an overflow tank 4 and filtered by a PVA-resin permeable membrane. The permeated liq. is used for cleaning the substrate in the tanks 2a and 2b, and the liq. concentrate is recycled to the bath along with the waste cleaning liq.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeposition coating method for forming a photoresist layer on the surface of a conductive substrate with good coating workability.

[0002]

2. Description of the Related Art When manufacturing a printed circuit board,
First, a photoresist layer is formed on a conductive substrate such as a copper clad laminate, and then actinic rays are imagewise irradiated to develop and remove the unexposed portion to form a resist pattern. As a method for forming the photoresist layer, there are many methods such as an electrodeposition coating method, which has good followability to irregularities on the substrate surface and can form a photoresist layer having a uniform film thickness with good adhesion in a short time. Because of its advantages, it has been widely adopted. Further, in the electrodeposition coating method, at least a part of the electrodeposition coating bath is usually subjected to an ultrafiltration treatment continuously or intermittently for maintenance and adjustment of the bath composition.

[0003]

By the way, a conventional electrodeposition coating bath which is applied to an object to be coated such as an automobile has a high molecular weight component (eg resin) and a low molecular weight component (eg water, neutralization). Agent) as the main component, and there are few components having an intermediate molecular weight between them. Therefore, when the electrodeposition coating bath is subjected to ultrafiltration, the concentrate and the permeate are clogged with the permeable membrane as frequently as left. It was able to be separated without causing it.

However, the photosensitive electrodeposition coating bath used for forming the photoresist layer contains a relatively large amount of components having an intermediate molecular weight such as a compound having a photopolymerizable unsaturated bond and a photopolymerization initiator. However, there is a problem that clogging occurs frequently and the workability of coating is very poor. Further, in order to collect the bath liquid adhering to the substrate on which the photoresist layer is formed on the bath except for the purpose of forming the photoresist layer, the above-mentioned permeated liquid is usually used to wash the surface of the substrate on which the bath is exposed, but clogging occurs. When this occurs, the absolute amount of the permeated liquid tends to be insufficient. Therefore, when pure water is replenished as the cleaning liquid, there is a problem that it becomes difficult to control the bath composition when the cleaning waste liquid is returned to the electrodeposition coating bath. On the other hand, if only a small amount of permeated liquid is used as the cleaning liquid without replenishing pure water, the heating residue of the cleaning liquid rises in the multi-stage cleaning system, and the substrate cannot be cleaned sufficiently, especially the cleaning of the through hole part There was a problem that became.

[0005]

The inventors of the present invention have made extensive studies to solve the above-mentioned problems while taking advantage of the advantages of the electrodeposition coating method. As a result, there is little clogging and good coating workability. Further, the present invention has been accomplished by finding an electrodeposition coating method which can sufficiently wash a substrate having through holes, has a small amount of carry-out of a bath liquid, and has a high paint efficiency.

That is, according to the present invention, (i) (a ') acid value is 2
A polymer having 0 to 300 and a compound having a photopolymerizable unsaturated bond, or (a ″) a polymer having a photopolymerizable unsaturated bond with an acid value of 20 to 300, (ii) a photopolymerization initiator, (iii)
Electrodeposition in which a conductive substrate is immersed in an electrodeposition coating bath containing (i) a basic compound for neutralizing the polymer and (iv) water as a main component to form a photoresist layer on the surface of the substrate. In the coating method, at least a part of the liquid in the electrodeposition coating bath is introduced into an ultrafiltration device using a permeable membrane made of a polyvinyl alcohol resin, and separated into a permeated liquid and a concentrated liquid, The present invention relates to an electrodeposition coating method, characterized in that the bath-based substrate on which the photoresist layer is formed is washed, and the cleaning waste liquid thus produced and the concentrated solution are refluxed to the electrodeposition coating bath.

The present invention will be described in detail below. The electrodeposition coating bath used in the present invention has (i) (a ') acid value of 20 to
A binder consisting of 300 polymer and a compound having a photopolymerizable unsaturated bond or (a ″) a binder consisting of a polymer having a photopolymerizable unsaturated bond with an acid value of 20 to 300, (i
i) a photopolymerization initiator, (iii) a basic compound for neutralizing the polymer constituting the binder, and (iv) water as a main component, and further, if necessary, an organic solvent, a colorant, a filler, a plasticizer. And various additives such as a film stabilizer, a film stabilizer, a thermal polymerization inhibitor, an adhesion promoter, and a surfactant.

The component (a ') is composed of a polymer having an acid value of 20 to 300 and a compound having a photopolymerizable unsaturated bond. As the polymer having an acid value of 20 to 300, acrylic acid and / or methacrylic acid are used as constituent monomers and, for example, methyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl. One or more general polymerizable monomers such as acrylate, n-hexyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-decyl methacrylate, cyclohexyl methacrylate, 2-hydroxyethyl acrylate, cyclohexyl methacrylate, acrylonitrile, styrene and vinyl chloride. Weight average molecular weight obtained by copolymerization is about 5,000 to 150,000
The copolymer of is preferable.

However, the polymer is not limited to the above-mentioned polymer, and if it is a polymer satisfying the mechanical strength and the electric insulation required for the resist film, the resin for electrodeposition coating which has been conventionally used is particularly preferable. It can be used without limitation. If the acid value of the polymer is less than 20, precipitation or the like is likely to occur and the stability of the electrodeposition coating bath is deteriorated, whereas if it exceeds 300, the appearance of the obtained electrodeposition coating film, that is, the photoresist layer is deteriorated. It is not preferable.

The compound having a photopolymerizable unsaturated bond is a water-insoluble monomer having two or more photopolymerizable unsaturated bonds in the molecule, for example, polyethylene glycol excluding one or more condensed ethylene glycol. Compounds obtained by adding α, β-unsaturated carboxylic acid to a polyhydric alcohol, for example, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane Compounds obtained by adding α, β-unsaturated carboxylic acid to a glycidyl group-containing compound, such as tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, for example, trimethylolpropane Triglyceride Ether triacrylate, bisphenol A diglycidyl ether di (meth) acrylate, substances having polycarboxylic acids such as phthalic anhydride or the like and a hydroxyl group and ethylenically unsaturated group, for example β-
An ester compound such as hydroxyethyl (meth) acrylate can be used, and a urethane diacrylate compound having a urethane skeleton can also be used. In any case, it is water-insoluble and can be cured by light irradiation. Good.

The ratio of the polymer and the compound constituting the component (a ') is (the former: the latter 50:85:50:
15) (weight basis) is suitable. Incidentally, when the amount of the polymer is less than the above range, the mechanical strength of the resist tends to decrease, and when the amount of the polymer is too large, the ratio of the compound relatively decreases and the sensitivity to light is decreased, and similarly the mechanical strength of the resist is decreased. Tends to decrease.

The polymer as the component (a ″) has an acid value of 20 to 300 and a photopolymerizable unsaturated bond which is photocured by irradiation with actinic rays, and has a mechanical strength required as a resist film. The resin for photocurable coatings that has been conventionally used can be used without particular limitation as long as it is a polymer satisfying the requirements such as glycidyl acrylate and glycidyl methacrylate. A polymer having an acid value of 20 to 300 to which a glycidyl group-containing unsaturated compound such as aryl glycidyl ether is added; an acrylic resin having an acid value of 20 to 300 and having a hydroxyl group, an excess amount of polyisocyanate and a hydroxyl group-containing unsaturated compound A polymer having an acid value of 20 to 300 obtained by reacting a reaction product having a free isocyanate group with; an epoxy resin and an unsaturated carbo Polymer having an acid value of 20 to 300 obtained by reacting an addition reaction product with an acid with a polybasic acid anhydride; a polymerizable monomer having a hydroxyl group in the addition reaction product between a conjugated diene (co) polymer and an unsaturated dicarboxylic acid anhydride Acid value of reacted 2
Typical examples are polymers of 0 to 300.

The polymer as the component (a ″) has a degree of unsaturation of 0.2 to 4.0 mol / kg and a number average molecular weight of 1,00.
Those of about 0 to 50,000 are suitable. Further, as the binder, the polymer as the component (a ″) may be used alone,
The polymer as the component (a ') and / or the compound having a photopolymerizable unsaturated bond may be used in combination.

Examples of the photopolymerization initiator include benzophenone, N, N'-tetramethyl-4,4'-diaminobenzophenone, 4-methoxy-4'-dimethylaminobenzophenone, 2-ethylanthraquinone and phenanthrenequinone. Aromatic ketones, benzoin methyl ether, benzoin ethyl ether, benzoin phenyl ether and other benzoin ethers, methylbenzoin, ethylbenzoin and other benzoins, 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- ( o-chlorophenyl) -4,5-di (m-methoxyphenyl) imidazole dimer, 2,4-di (p
-Methoxyphenyl) -5-phenylimidazole dimer and the like.

Examples of the basic compound include organic compounds such as triethylamine, monoethanolamine, diethanolamine, diisopropylamine, dimethylaminoethanol and morpholine, and inorganic compounds such as sodium hydroxide and potassium hydroxide.

The mixing ratio of each component of the electrodeposition coating bath is (i)
The component (ii) is about 0.1 to 15 with respect to 100 parts by weight of the component.
Parts by weight are suitable. Further, the component (iii) is 0. 1% with respect to 1 equivalent of the carboxyl group in the polymer which is the component (i).
A suitable amount is 3 to 1.0 equivalent.

The electrodeposition coating bath has a solid content of about 5 to 20% by weight and a pH of about 6.0 to 9.0.
It is also desirable from the viewpoint of electrodeposition paintability. When an organic solvent is added, it is preferably within 20% by weight in the bath.

Next, the electrodeposition coating method of the present invention will be described. FIG. 1 is a system diagram showing a typical electrodeposition coating apparatus used in the electrodeposition coating method of the present invention, and a typical procedure for performing the electrodeposition coating of the present invention will be described in accordance therewith. General feeder for conductive substrates such as copper clad laminates (not shown)
First, immerse in the electrodeposition coating bath 1 while transporting by
Electrodeposition coating is performed under the conditions described below to form a photoresist layer on the surface of the conductive substrate. Next, the substrate is bathed, and the excess coating material adhering to the substrate surface is washed and removed by the washing liquid sprayed from the water washing pipes 3a, 3b, 3c in a spray or shower shape, and the washing drainage thus produced is washed with water. It is supposed to be housed in the tanks 2a, 2b, 2c.

During electrodeposition coating, at least a part of the electrodeposition coating bath is continuously or intermittently taken out from the overflow tank 4 adjacent to the electrodeposition coating bath 1 and introduced into an ultrafiltration device 5 described later. The permeated liquid and the concentrated liquid are separated, the permeated liquid is used as the cleaning liquid, and the concentrated liquid is refluxed in the electrodeposition coating bath 1.

FIG. 1 shows an example of a three-stage type washing machine tank. In this case, the permeated liquid introduced into the washing tank 2b is used as the second-stage washing liquid, and the washing liquid is jetted from the washing pipe 3b. ,
The washing drainage is stored in the washing tank 2b. As the first-stage cleaning liquid, a liquid composed of the permeated liquid and the cleaning waste liquid in the cleaning tank 2b overflows from the cleaning tank 2b to the cleaning tank 2a, and is ejected from the cleaning pipe 3a. It is stored in the washing tank 2a.

The cleaning effluent stored in the water washing tank 2a is refluxed into the overflow tank 4 while adjusting the amount of the separately supplied replenishing paint so that the amount of the electrodeposition coating bath in the electrodeposition coating bath becomes substantially constant. It is desirable to use pure water as the third-stage (final stage) cleaning liquid, which is ejected from the water washing pipe 3c, and the cleaning waste liquid is absorbed in the water washing tank 2c. The ultrafiltration device used in the present invention is preferably a tubular type or spiral type device using a polyvinyl alcohol-based resin as the permeable membrane supported by the porous layer.

The polyvinyl alcohol resin is polyvinyl alcohol or an ethylene-polyvinyl alcohol copolymer containing 40 mol% or less of ethylene,
The copolymer further includes (meth) acrylic acid and (meth)
It may be a copolymer containing 10 mol% or less of a vinyl compound such as an acrylate ester, acrylonitrile, styrene or the like, or a diene compound such as butadiene, isoprene or chloroprene. The polyvinyl alcohol resin having a molecular weight of about 20,000 to 300,000 is preferably used.

Such a polyvinyl alcohol-based resin permeable membrane has hydrophilicity and is further excellent in durability, chemical stability, etc., and is superior to conventional ultrafiltration devices using other resin permeable membranes. Clogging is unlikely to occur, and therefore electrodeposition coating can be performed continuously for a long time, improving the coating workability. An example of such an ultrafiltration device is Nitto Denko's N
There are commercial products such as TU-2020 and NTU-2120.

Next, a method of manufacturing a resist pattern using the electrodeposition coating method of the present invention will be described. An electroconductive substrate as an anode, for example, a copper clad laminate is immersed in the above-mentioned electrodeposition coating bath, and a metal plate as a cathode is similarly immersed to perform electrodeposition coating. The electrodeposition coating is 10 to 10 in the case of the constant current method.
DC current of 400mA / dcm ² or 50 to 50 for constant voltage method
It is preferable to apply a DC voltage of 400 V for about 10 seconds to 5 minutes each, and to control the temperature of the electrodeposition coating bath at 15 to 30 ° C. The film thickness of the photoresist layer obtained by electrodeposition is preferably controlled to be in the range of 5 to 50 μm.

After the electrodeposition coating, the electroconductive substrate is pulled out from the electrodeposition coating bath, washed with water in the order of the first, second and third stages, drained and dried with hot air or the like. At this time, if the drying temperature is high, the photoresist layer is thermally cured and a part of the photoresist remains undeveloped in the developing step after exposure. Then, the photoresist layer is imagewise irradiated with an actinic ray to photo-cure the exposed portion of the photoresist layer and remove the unexposed portion by development to obtain a photo-cured resist pattern. As the light source of the actinic ray, one that emits a ray having a wavelength of 300 to 450 nm, for example, mercury vapor arc, carbon arc, xenon arc or the like is preferably used.

[0026]

EXAMPLES The present invention will now be described in more detail by way of examples. Preparation of electrodeposition coating bath A 1130 g of dioxane was added to a flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas introduction tube, and heated to a temperature of 90 ° C. while blowing nitrogen gas while stirring. . When the temperature became constant at 90 ° C., a solution prepared by mixing 169 g of methacrylic acid, 688 g of methyl methacrylate, 83 g of ethyl acrylate, 60 g of n-butyl acrylate and 10 g of azobisisobutyronitrile was dropped into the flask over 2.5 hours. , Then 3 hours 9
The mixture was kept warm with stirring at 0 ° C. After 3 hours, a solution prepared by dissolving 3 g of azobisdimethylvaleronitrile in 100 g of dioxane was added dropwise into the flask over 10 minutes, and then the temperature was again maintained at 90 ° C. for 4 hours with stirring.

The polymer thus obtained had a weight average molecular weight of 39,000, an acid value of 111 and a solid content of the polymer solution of 45.7% by weight. The glass transition point of this polymer was 85 ° C. Next, this polymer solution 6
To 50 g, 150 g of EO (ethylene oxide) modified bisphenol A dimethacrylate (manufactured by Shin Nakamura Chemical Co., Ltd., high product name NK ester BPE-200), 30 benzophenone
g and 1 g of N, N'-tetraethyl-4,4'-diaminobenzophenone were added and dissolved. To this solution, 20 g of triethylamine as a basic organic compound was added and dissolved to neutralize the polymer in the solution. Next, while stirring this solution, 4,200 g of ion-exchanged water was gradually added dropwise to obtain an electrodeposition coating bath A. The pH of this electrodeposition coating bath was 7.7 at 25 ° C.

Preparation of Electrodeposition Coating Bath B To the flask was added 175 g of phenol novolac type epoxy resin (trade name: Epicoat 152; epoxy equivalent 175, manufactured by Shell Co.) and 50 g of dioxane, and 100
The temperature was raised to ° C. There, 70 g of acrylic acid, 0.1 g of p-quinone and benzyltriethylammonium chloride.
The liquid obtained by mixing 3 g was added dropwise over 1 hour, and the mixture was further stirred at the same temperature for 10 hours to reduce the acid value of the reaction system to 1 or less.
Cooled to 0 ° C. Then tetrahydrophthalic anhydride 12
0 g and 170 g of dioxane were added, the temperature was raised again to 100 ° C. over about 2 hours, and the temperature was maintained while stirring for 12 hours.

The polymer thus obtained had a number average molecular weight of about 1500 and an acid value of 100. The solid content of the polymer solution was 63% by weight. Then, to 400 g of this polymer solution, 27 g of benzophenone, 1 g of N, N'-tetraethyl-4,4'-diaminobenzophenone and 180 g of dioxane were added and dissolved. To this solution, 35 g of triethylamine as a basic organic compound was added and dissolved to neutralize the polymer in the solution. Next, 2500 g of ion-exchanged water was gradually added dropwise to this solution with stirring to obtain an electrodeposition coating bath B. PH of this electrodeposition coating bath
Was 7.6 at 25 ° C.

Example 1 Using the electrodeposition coating apparatus shown in FIG. 1, the electrodeposition coating bath A in the electrodeposition coating bath was continuously taken out, and a tubular type using a permeable membrane made of polyvinyl alcohol resin was used. Ultrafiltration device (NTU2020 P18B, Nitto Denko Corporation)
Made, module size φ109 × 1319 mm, total membrane area 0.76 m ² , tube number 18) under the following conditions, permeate and concentrate are refluxed in the electrodeposition coating bath,
As a result of measuring the time when the initial amount of permeated liquid was reduced by half, it was as shown in Table 1.

Filtration conditions Flow rate: 13 l / min Ultrafiltration device inlet pressure: 2.5 ± 0.2 (kg / cm ² ) Electrodeposition coating bath temperature: 25 ± 1 (° C.)

Comparative Examples 1 and 2 In the same manner as in Example 1, except that a fluororesin permeable membrane and an acrylic resin permeable membrane were used in place of the polyvinyl alcohol resin permeable membrane, the time when the amount of permeated liquid was reduced by half was measured in the same manner. did.

Example 2 In Example 1, instead of the electrodeposition coating bath A, the electrodeposition coating bath B was used.
, And instead of the tubular type ultrafiltration device, a spiral type ultrafiltration device (NTU2120 F2E,
Nitto Denko product, module size φ62.5 × 1016mm,
The time when the amount of permeated liquid was halved was measured in the same manner except that the total membrane area of 1.2 m ² ) was used.

Comparative Examples 3 to 4 In the same manner as in Example 2, except that a fluororesin permeable membrane and an acrylic resin permeable membrane were used in place of the polyvinyl alcohol resin permeable membrane, the time when the amount of permeated liquid was halved was measured in the same manner. did.

[0035]

[Table 1]

As is clear from Table 1, in Examples 1 and 2 using the permeable membrane made of a polyvinyl alcohol-based resin, the time required for the permeated liquid amount to be reduced by half was compared with the conventional permeable membrane made of a fluororesin or an acrylic resin. Longer than Examples 1-4,
It was found that clogging was less likely to occur.

[0037]

According to the electrodeposition coating method of the present invention, the occurrence of clogging and the like can be reduced, the electrodeposition coating can be continuously performed for a long period of time, and the photoresist layer can be formed on the surface of the conductive substrate with good coating workability. In addition, the conductive substrate having the through holes can be sufficiently washed, and the electrodeposition coating can be performed with a small amount of carry-out of the bath liquid and a high paint efficiency.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of an electrodeposition coating apparatus used in an electrodeposition coating method of the present invention.

[Explanation of symbols]

 1 Electrodeposition coating bath 2a, 2b, 2c Washing tank 3a, 3b, 3c Washing pipe 4 Overflow tank 5 Ultrafiltration device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location G03F 7/038 // H05K 3/06 F 6921-4E (72) Inventor Hitoshi Amanokura Hitachi, Ibaraki Prefecture 4-13-1, Higashi-cho, Ichi, Ibaraki Research Laboratory, Hitachi Chemical Co., Ltd. (72) Inventor Shigeo Tachiki 4-3-1-1, Higashi-cho, Hitachi City, Ibaraki Hitachi, Ltd. (72) Inventor, Kato Takuro 4-13-1, Higashimachi, Hitachi City, Ibaraki Prefecture Yamazaki Plant, Hitachi Chemical Co., Ltd. (72) Inventor Katsushige Tsukada 4-13-1, Higashimachi, Hitachi City, Ibaraki Hitachi Chemical Co., Ltd. Yamazaki Plant (72 ) Inventor Yuji Yamazaki 1382-12 Shimoishikami, Otawara-shi, Tochigi Dainippon Paint Co., Ltd. Nasu factory (72) Inventor Shoji Yamada 1382-12 Shimoishi, Otawara-shi, Tochigi Prefecture Japan Paint Co., Ltd.Nasu Plant (72) Inventor Toshihiko Shiotani 1382-12 Shimoishigami, Otawara City, Tochigi Prefecture Dainippon Paint Co., Ltd.Nasu Plant (72) Inventor Yoshihisa Nagashima 1382-12 Shimoishigami, Otawara City, Tochigi Prefecture Japan Paint Co., Ltd. Nasu factory

Claims (1)

[Claims] 1. (i) (a ') a polymer having an acid value of 20 to 300 and a compound having a photopolymerizable unsaturated bond, or (a ") a polymer having an acid value of 20 to 300 and having a photopolymerizable unsaturated bond, (Ii) a photopolymerization initiator, (iii) the above (i)
A basic compound for neutralizing the polymer of (4) and (iv) an electrocoating bath containing water as a main component, wherein the conductive substrate is immersed to form a photoresist layer on the surface of the substrate. At least a part of the liquid in the electrodeposition coating bath is introduced into an ultrafiltration device using a permeable membrane made of polyvinyl alcohol-based resin, separated into a permeated liquid and a concentrated liquid, and the permeated liquid is discharged. A method for electrodeposition coating, comprising: cleaning the bathed substrate having the photoresist layer formed thereon, and refluxing the cleaning waste liquid thus produced and the concentrated solution to an electrodeposition coating bath.