Electrodeposition coating composition

This invention relates to a positive-type photosensitive electrodeposition coating composition, and more specifically, to an anionic or cationic electrodeposition coating composition suitable for forming a printed wiring photoresist by coating an electrically conductive material-clad laminated plate by electrodeposition to form a smooth film whose portion exposed to actinic rays such as ultraviolet light through a positive photomask can be washed away with a developing solution.
In the prior art, a printed wiring board for use in an integrated circuit or the like is formed by plating a laminated plate obtained by cladding an insulator with an electrically conductive material such as a copper foil, laminating a photosensitive film, overlaying a photographic negative on it, exposing the photosensitive film through the negative, removing the unexposed portion, etching away the unnecessary electrically conductive material from the circuit pattern, and thereafter removing the photosensitive film on the circuit pattern. Since the photosensitive film is generally as thick as 50 micrometers, the circuit pattern formed by exposure and development is not sharp, and moreover, it is difficult to laminate the photosensitive film uniformly to the surface of the electrically conductive material. In particular, it is more difficult to protect the metal on through-hole portions with the photosensitive film.
A method is also known to form a circuit pattern for printed wiring which comprises applying an etching resist ink to a metal-clad laminated plate having a through-hole portion by screen printing, etching the laminated plate to remove metal from the non-printed portion, and removing the resist ink in the printed portion. According to this method, it is hard to form a pattern having a thickness of less than 200 micrometers with high reliability, the ink is difficult to coat on the through-hole portion, and the metal in the through-hole portion is frequently removed by the etching treatment. To avoid this, it is also the practice to embed an organic material in the through-hole portion so as to prevent the metal in the through-hole portion from being removed by the etching treatment, and finally remove the organic material. This method, however, has the defect that the cost of the circuit plate finally obtained is high and the circuit pattern has low sharpness.
As improvements over these prior methods, U.S. Pat. Nos. 4,632,900 and 4,673,458 disclose a method which comprises forming a positive-type photosensitive resin resist on a printed wiring board by electrodeposition, overlaying a photographic positive on it, exposing the board through the positive, and removing the exposed portion with an aqueous alkaline solution to form an image. Since according to this method, a coating can be formed easily on the through-hole portion by electrodeposition and the unexposed portion remains as a resist coating, a printed wiring board having excellent resolution can be obtained.
In the above-cited U.S. Pat. No. 4,632,900, polyoxymethylene polymer, o-nitrocarbinol ester, o-nitrophenyl acetal, and a quinonediazidesulfonyl ester of novolak resin are used as the resin in the resin composition for forming the photosensitive resin resist by electrodeposition. In U.S. Pat. No. 4,673,458, a resin obtained by esterifying a hydroxyl group contained in an unsaturated monomer with a sulfonic acid group contained in naphthoquinone diazidesulfonic acid, and copolymerizing the resulting unsaturated monomer with another unsaturated monomer is used as the above resin. However, the former method cannot produce a high-density fine pattern circuit board of sufficient reliability whichever resin may be used. Moreover, since the electrodeposition paint has insufficient stability, flocculation is liable to occur and tends to cause filter clogging or imperfections on the coated surface upon long-term running of the electrodeposition bath. In the latter method, a photosensitive naphthoquinone diazide group is introduced into the resin through a sulfonic acid ester group. Hence, when the electrodeposition is carried out over a long period of time (the turnover of the electrodeposition paint is long), the sulfonic acid ester group in the resin is easily hydrolyzed by a hydrolytic substance in the electrodeposition bath such as water, an acid, a base or an alcohol to degrade the resin frequently. As a result, the resin component flocculates in the electrodeposition bath or precipitates at the bottom of the bath. This causes filter clogging or greatly varies the electrodeposition characteristics such as application voltage. Alternatively, abnormal electrodeposition such as pinholing occurs, and the electrodeposition coating bath becomes difficult to control. Moreover, the coated film formed from the electrodeposition bath has poor smoothness and alkali developability, and it is impossible to obtain a printed wiring board having excellent resolution.
It is an object of this invention to solve the aforesaid problems in the preparation of printed wiring boards, and to provide an electrodeposition coating composition for forming a positive photoresist, which has excellent sensitiveness to actinic rays such as ultraviolet light, can form a developable uniform coated film on the surface or the through-hole portion of the circuit plate, and can give an electrodeposition coating bath having good stability over a long period of time.
According to this invention, there is provided a positive-type photosensitive electrodeposition coating composition comprising
(A) a photosensitive compound having a molecular weight of not more than 6,000 and containing at least one modified quinonediazidesulfonic acid unit represented by the following formula (I) ##STR3## wherein R.sub.1 represents ##STR4## R.sub.2 represents a hydrogen atom, an alkyl group, a cycloalkyl group or an alkyl ether group,
R.sub.3 represents an alkylene group, a cycloalkylene group or an alkylene ether group, and
A represents a carboxylic acid ester linkage, in a molecule and
(B) a water-soluble or water-dispersible resin having a salt-forming group.
The "alkyl group" for R.sub.2 in formula (I) may be linear or branched, and examples include alkyl groups having 1 to 15 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, neopentyl, n-hexyl, isohexyl, 1-methylpentyl, 2-methylpentyl, n-heptyl, 5-methylhexyl, n-octyl, n-nonyl, n-decyl, dodecyl, tridecyl and tetradecyl groups.
Examples of the "cycloalkyl group" include cycloalkyl groups having 3 to 8 carbon atoms, such as ##STR5##
Examples of the "alkylether group" include (lower alkyl)-0-(lower alkylene) groups such as ##STR6##
R.sub.2 is preferably a lower alkyl group having 1 to 6 carbon atoms, especially a methyl group.
The "alkylene group" for R.sub.3 may be linear or branched. Examples include alkylene groups having 1 to 8 carbon atoms, such as ##STR7##
Examples of the "cycloalkylene group" include cycloalkylene groups having 3 to 8 carbon atoms, such as cyclopropylene, cyclobutylene, cyclohexylene and ##STR8##
Examples of the "alkylene ether group" are (lower alkylene)-0-(lower alkylene) groups such as ##STR9##
R.sub.3 is preferably a linear alkylene group having 2 to 6 carbon atoms.
Moreover, the "carboxylic acid ester linkage" indicated at A includes a linkage represented by --COO--.
The positive-type photosensitive electrodeposition coating composition of this invention includes anionic or cationic compositions capable of forming a continuous film on an electrically conductive material by electrodeposition. When the continuous film is exposed, the exposed portion can be washed away with a developing solution.
The compound (A) containing the modified quinonediazidesulfonic acid units of general formula (I) used as a positive-type photosensitive component can be produced, for example, by the following methods.
First, a hydroxyl-containing quinonediazide compound represented by the following formula ##STR10## wherein R.sub.1, R.sub.2 and R.sub.3 are as defined above, is produced by addition-reaction between quinonediazidesulfonic acid and/or a quinonediazidesulfonyl halide (to be referred to as the "quinonediazide compound") represented by the following formula ##STR11## wherein X represents a hydrogen atom or a halogen atom such as Cl, F, Br and I, and a hydroxyl-containing amine compound of the following formula ##STR12## wherein R.sub.2 and R.sub.3 are as defined above.
Then, the resulting hydroxyl-containing quinonediazide compound of formula (V) is reacted with a polyacid chloride compound (e.g. an acrylic acid chloride copolymer), or the compound of formula (V) is reacted with an alpha,beta-unsaturated carboxylic acid chloride such as acrylic acid chloride or methacrylic acid chloride at a ratio of 1 mol of an acid chloride group per mol of a hydroxyl group, and the resulting monovinyl compound is copolymerized with an unsaturated group-containing compound or subjected to Michael addition reaction with an amino group-containing compound.
Of the quinonediazide compounds of formula (II) or (III), 1,2-benzoquinonediazidesulfonyl chloride and 1,2-naphthoquinonediazide-5-sulfonyl chloride are preferred. Examples of preferred hydroxyl-containing amine compounds of formula (IV) include ethanolamine, neopentanolamine, 2-hydroxy-2'-aminoethyl ether, 2-hydroxy-2'-(amine-propoxy)ethyl ether, N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-methylpropanol amine, N-ethylpropanolamine, and N-propylpropanolamine. Of these, N-methylethanolamine and N-methylpropanolamine are preferred.
The reaction of the quinonediazide compound of formula (II) or (III) with the hydroxyl-containing amine compound of formula (IV) may be carried out in the presence of an inert organic solvent capable of dissolving or dispersing a mixture of the compound of formula (II) or (III) and the compound of formula (IV) at a temperature of generally room temperature to about 80 .degree. C., preferably room temperature to about 60.degree. C., for a period of about 10 minutes to about 60 hours, preferably about 1 to 3 hours. The progress of the reaction can be monitored by measuring the amine value of the reaction mixture or by an infrared spectrum analysis.
Specific examples of the inert organic solvent that can be used in the above reaction include dioxanes such as dioxane and dioxolane; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; and aromatic hydrocarbons such as benzene, toluene and xylene. Of these, the dioxanes are preferred because they have an excellent ability to dissolve the quinonediazidesulfonyl halide and can be easily removed.
The ratio of the compound (II) or (III) and the compound of formula (IV) mixed is not particularly limited. Usually, it is suitable to mix them so that the mole ratio of the --SO.sub.2 X group to the >NH is about 1:1. In the above reaction, the --SO.sub.2 X group of the quinonediazide compound reacts with the >NH group of the hydroxyl-containing amine compound preferentially to the OH group. Hence, the main reaction product obtained by this reaction is the hydroxyl-containing quinonediazide compound represented by formula (V).
Preferred examples of the compound of formula (V) are given below.
In order to trap hydrogen chloride formed during the reaction, for example, sodium hydroxide, sodium carbonate and an amine of the same type as used in the addition reaction can be used as required.
Preferred examples of the compound of formula (V) are given below. ##STR13##
Examples of the acid chloride compound capable of reacting with the hydroxyl-containing diazide compound of formula (V) include acrylic acid chloride, methacrylic acid chloride, crotonic acid chloride and a copolymer thereof (polyacid chloride compound).
The reaction of the acid chloride compound with the hydroxyl-containing quinonediazide compound of formula (V) to obtain the photosensitive compound in accordance with this invention can be carried out by mixing the acid chloride compound with the hydroxyl-containing quinonediazide compound at a ratio of nearly 1 mol of a hydroxyl group per mol of an acid chloride in the presence of an inert organic solvent if required and maintaining the mixture at room temperature for about 1 to 2 hours. The state of the reaction can be monitored by measuring a peak ascribable to an acid chloride group in the vicinity of 1,780 cm.sup.-1 in an infrared spectrum analysis. The inert organic solvent that can be used here is a solvent selected from ketonic, aliphatic and ethereal organic solvents which do not cause reaction with the acid chloride compound.
The thus obtained unsaturated group-containing quinonediazide compound can be copolymerized with the other unsaturated group-containing monomer by radical polymerization, etc., or reacted with a polyfunctional amino compound by Michael addition reaction to obtain a final photosensitive compound. Moreover, the photosensitive compound can also be prepared by previously forming the polyacid chloride compound and then adding the hydroxyl-containing quinonediazide compound of formula (V).
The thus obtained photosensitive compound (A) is a compound having in a molecule, 1 or more, preferably on the average, 1.5 or more, and preferably at most 5 quinonediazidesulfonic acid units represented by formula (I). The molecular weight of the photosensitive compound (A) is 6,000 or less, preferably 500 to 5,000. When the molecular weight exceeds 6,000, the compatibility with the water-soluble or water-dispersible resin (B) tends to decrease, worsening the stability of the coating. Meanwhile, the water-soluble or water-dispersible resin (B) having the salt-forming group [to be referred to as a "resin (B)"], used in this invention, includes a resin having a group capable of forming a salt by e.g. neutralization.
Examples of the resin (B) include a carboxyl group-containing acrylic resin, an amino group-containing acrylic resin, an ammonium salt, a sulfonium salt-containing acrylic resin, a carboxyl group-containing polyester resin, an epoxy resin amine adduct and an onium chloride epoxy resin. The acrylic resin is especially preferable from the aspect of stability of the electrodeposition bath.
Meanwhile, the acrylic resin (B) having the salt-forming group, used in this invention, includes an acrylic resin having a group capable of forming a salt by neutralization. Examples of the salt-forming group when the composition of this invention is used as an anionic electrodeposition coating are anion-forming groups such as a carboxyl group, a sulfonyl group and a phosphoric acid group. Above all, the carboxyl group is preferable. On the other hand, examples of the salt-forming group when the composition of this invention is used as a cationic electrodeposition coating are cation-forming groups such as an amino group, an ammonium salt group, a sulfonium group and a phosphonium salt group.
The acrylic resin (B) can be produced by, for example, polymerizing an unsaturated monomer mixture containing as an essential component the polymerizable unsaturated monomer having the above salt-forming group by the usual radical copolymerization method, or polymerising an unsaturated monomer including an epoxy group-containing polymerizable unsaturated monomer in like manner, and then adding the epoxy group in the resin together with the amino compound or reacting the resulting substance with onium salt-forming compounds such as tertiary amino compounds and acids to form the onium salt.
Regarding the polymerizable unsaturated monomer used to produce the acrylic resin (B), examples of the anion-forming group-containing unsaturated monomer are (meth)acrylic acid, crotonic acid, itaconic acid, itaconic anhydride, maleic acid, maleic anhydride, fumaric acid and 2-hydroxyethyl acrylate acid phosphate. Examples of the cation-forming group-containing unsaturated monomer are aminoethyl (meth)acrylate, N-tert-butylaminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate and N,N-dimethylaminobutyl (meth)acrylate.
Examples of the epoxy group-containing unsaturated monomer are glycidyl (meth)acrylate, glycidyl (meth)acrylamide and allylglycidyl ether.
Examples of the other polymerizable unsaturated monomer which is optionally used are C.sub.1 -C.sub.26 alkyl or cycloalkyl esters of acrylic or methacrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate and stearyl (meth)acrylate; hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; acrylamides or methacrylamides such as (meth)acrylamide, N-methyl (meth)acrylamide, diacetoneacrylamide, N-methylol (meth)acrylamide and N-butoxymethylacrylamide; and vinyl monomers such as styrene, vinyl toluene, vinyl propionate, alpha-methylstyrene, vinyl acetate, (meth)acrylonitrile, vinyl propionate, vinyl pivalate and Veoba monomer (a product of Shell Chemical Co.).
The copolymerization of the above monomers is normally carried out by reacting a mixture of the above monomers in a suitable organic solvent in the presence of a radical-polymerizable initiator such as azobisisobutyronitrile or benzoyl peroxide at a temperature of about 30.degree. to 180.degree. C., preferably about 60.degree. to 120.degree. C., for a period of about 1 to 20 hours. Water-soluble organic solvents, especially alcohols and ethers, used in electrodeposition paints are suitable as the organic solvent. Examples include methanol, ethanol, n-propanol, isopropanol, butanol, ethylene glycol, butyl Cellosolve, ethyl Cellosolve, diethylene glycol, methylcarbitol, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether.
The amount of the salt-forming group in the resin (B) of this invention is generally 0.3 to 4.5 moles, preferably 0.5 to 1.6 moles/kg based on the total amount of the photosensitive compound (A) and the resin (B). If the amount of the salt-forming group is less than 0.3 mole/kg, it is difficult to make the resin water-soluble or water-dispersible, and an electrodeposition coating composition is difficult to prepare from the resin. If, on the other hand, it exceeds 4.5 moles/kg, it is difficult to coat the resulting electrodeposition paint on a substrate.
The resin (B) used in this invention generally may have a number average molecular weight of 3,000 to 100,000, preferably 5,000 to 30,000. If the number average molecular weight is lower than 3,000, a coated film prepared from the resin during electrodeposition tends to be broken and frequently, a uniform coated film cannot be obtained. If, on the other hand, it is higher than 100,000, the smoothness and levelness of the electrodeposited film are degraded and the coated surface tends to become uneven. Consequently, the resolution of line images tends to be reduced.
In accordance with another embodiment of this invention, the photosensitive compound (A) can be formed by the reaction of an aliphatic, alicyclic or aromatic polyfunctional amino compound having at least 2, preferably 3 to 4 primary and/or secondary amino groups with o-benzoquinonediazidesulfonic acid chloride or o-naphthoquinonediazidesulfonic acid chloride at a ratio of nearly the same equivalent as an equivalent of an amine.
The reaction can be performed by maintaining the quinonediazidesulfonic acid chloride and the polyfunctional amino compound in the presence of an inert organic solvent capable of dissolving or dispersing them at a reaction temperature of usually room temperature to about 50.degree. C., preferably room temperature to 40.degree. C. for about 10 minutes to about 20 hours, preferably about 1 to about 3 hours.
Examples of the inert solvent available in the above reaction include dioxanes such as dioxane and dioxolane; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; and aromatic hydrocarbons such as benzene, toluene and xylene. Of these, the dioxanes are preferable because they have excellent solubility in quinonediazide sulfonic acid halide and can easily be removed. Further, to trap hydrogen chloride formed during the reaction, alkaline compounds such as sodium hydroxide and sodium carbonate may be used.
Examples of the polyfunctional amino compound used in the above reaction include ethylenediamine, diethylenetriamine, triethylenetetramine, polyamideamine, phenylenediamine, xylylenediamine, isophoronediamine, a polyamine compound represented by formula R.sub.4 --NH--R.sub.5 --NH--R.sub.5 --NH.sub.2 wherein R.sub.4 is an alkyl group having 8 to 18 carbon atoms and R.sub.5 is an alkylene group having 2 to 6 carbon atoms, and mixtures thereof.
The thus obtained photosensitive compound (A) contains in a molecule, at least 1, preferably on the average 1.5 or more, and preferably at most 5 quinonediazidesulfonic acid units. The average molecular weight of the photosensitive compound is usually 6,000 or less, preferably 500 to 3,000. When the molecular weight exceeds 3,000, the compatibility with the water-soluble or water-dispersible resin (B) having the salt-forming group tends to decrease, worsening the stability of the coating.
In accordance with still another embodiment of this invention, the water-soluble or water-dispersible resin (B), having the salt-forming group, used in combination with the photosensitive compound (A), can be the aforesaid water-soluble or water-dispersible resin (B).
A mixing ratio of the photosensitive compound (A) to the resin (B) in the positive-type photosensitive electrodeposition coating composition in this invention is not strictly limited, but is generally adjusted such that the amount of the quinonediazidesulfonic acid unit contained in the photosensitive compound (A) is 5 to 60 parts by weight, preferably 10 to 50 parts by weight, per 100 parts by weight of the resin (B).
If the amount of the quinonediazidesulfonic acid unit less than 5 parts by weight, the amount of carboxyl given when the formed coating is exposed to light is generally too small, making hard the development with a weak alkali. Meanwhile, if it is larger than 60 parts by weight, the coating tends to be hard and brittle. Consequently, as adhesion to the substrate is decreased or cracks occur in the coating during development and etching, break of the obtained line images is liable to occur. Moreover, since permeability of actinic energy rays such as ultraviolet rays, etc. are decreased, the irradiation dose has to be disadvantageously as high as 1,000 mj/cm.sup.2 for pattern formation.
The electrodeposition coating composition in this is obtained such that when the resin (B) contains the anionic group, it is neutralized with an amine or alkali compound and when the resin (B) contains the cationic group, it is neutralized with an organic or inorganic acid, and then dispersed or dissolved in water. When the cationic group is a quaternary ammonium salt group, a quaternary phosphonium salt group or a sulfonium salt, it can also be dispersed or dissolved in water as such. Examples of the neutralizing agent used include alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, alkylamines such as triethylamine, diethylamine, monoethylamine, diisopropylamine, trimethylamine and diisobutylamine, alkylalkanolamines such as dimethylaminoethanol, alicyclic amines such as cyclohexylamine, alkali metal hydroxide such as sodium hydroxide and potassium hydroxide, ammonia; and also acids such as acetic acid, lactic acid, hydrochloric acid and phosphoric acid. They may be used either singly or as a mixture.
A hydrophilic solvent may be added to the electrodeposition coating composition in order to increase the flowability of the water-solubilized or water-dispersed electrodeposition paint further. Examples of the hydrophilic solvent are isopropanol, n-butanol, t-butanol, methoxyethanol, ethoxyethanol, butoxyethanol, diethylene glycol methyl ether, dioxane and tetrahydrofuran. Generally, the amount of the hydrophilic solvent used is desirably not more than 300 parts by weight per 100 parts by weight of the mixture of compound (A) and the resin (B).
To increase the amount of the coating composition coated on the substrate, a hydrophobic solvent may also be added to the composition. Examples of the hydrophobic solvent include petroleum solvents such as toluene and xylene, ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and butyl acetate, and hydrophobic alcohols such as 2-ethylhexyl alcohol). Usually, the amount of the hydrophobic solvent is desirably not more than 200 parts by weight per 100 parts by weight of the above mixture.
As required, other resins may be incorporated to adjust the properties of the electrodeposited film. It is also possible to add a dye or a pigment.
The positive-type photosensitive electrodeposition coating composition obtained in this invention has the following characteristics, for example.
(1) The photosensitive compound (A) having higher hydrophobic nature than the resin (B) is mixed with said resin (B), so that the compound (A) is easily incorporated into the resin particles to reduce the probability that quinonediazide easily decomposable by bases contacts the bases. This is safer than in the case of introducing the quinonediazide group into the resin, and the photosensitivity little changes in the long-term electrodeposition coating.
(2) The amount of the photosensitive group can easily be adjusted only by changing the mixing ratio of the resin (B) to the photosensitive compound (A). Consequently, the photosensitivity and the resolution of the resist film can easily be changed, and the resist composition be freely designed according to the high density of the circuit plate pattern and the production line speed.
Production of the printed wiring substrate using the positive-type electrodeposition coating composition in this invention is performed as follows.
In an electrodeposition coating bath (a solids content in the bath: 3 to 30% by weight) is dipped a printed wiring substrate (e.g. a copper-clad plate) as an anode in the anionic electrodeposition coating or as a cathode in the cationic electrodeposition coating. A DC current of 20 to 400 V is passed. The suitable passing time is 30 seconds to 5 minutes. The film thickness is 2 to 100 micrometers, preferably 3 to 20 micrometers as a dry film thickness.
After the electrodeposition coating, the coated product is withdrawn from the electrodeposition bath, and washed with water, followed by removing the moisture contained in the electrodeposited film with hot air, etc.
Subsequently, the surface of the thus formed photosensitive electrodeposited film is irradiated with actinic rays such as ultraviolet rays via a pattern mask (positive). As the ortho-quinonediazide compound in the exposed portion becomes a carboxylic acid via a ketene, it is removed by the developing treatment with a developer such as an alkali aqueous solution, making it possible to realize a high resolution.
The actinic light used for exposure in this invention preferably has a wavelength of 3000 to 4500 .ANG.. Sources of this light are, for example, solar light, a mercury lamp, a xenone lamp and an arc light. Irradiation of the actinic light is carried out usually in an irradiation dose of 50 to 800 mj/cm.sup.2, preferably 50 to 500 mj/cm.sup.2.
The developing treatment is carried out by spraying weakly alkaline water against the surface of the coated film to wash away the exposed portions of the coated film. The weakly alkaline water may be, for example, sodium hydroxide, potassium hydroxide, sodium metasilicate, sodium carbonate, organic amine or aqueous ammonia, which has pH of 8 to 12, and which neutralizes the free carboxylic acid in the coated film to make it water-soluble.
The metal portion (non-circuit portion) exposed on the substrate by the development is removed by an ordinary etching treatment using a ferric chloride, copper chloride solution or ammonium chloride/ammonia etching solution, for example. Then, the unexposed coated film on the circuit pattern is removed by dissolving with a Cellosolve-type solvent such as ethyl Cellosolve and ethyl Cellosolve acetate, an aromatic hydrocarbon solvent such as toluene and xylene, a ketone-type solvent such as methyl ethyl ketone and methyl isobutyl ketone, an acetate-type solvent such as ethyl acetate and butyl acetate, or a chlorine-type solvent such as trichloroethylene, or also with a sodium hydroxide, potassium hydroxide, sodium carbonate or sodium metasilicate aqueous solution of pH 8 or more in the case of using an anionic electrodeposition paint, or also with an organic acid such as acetic acid or lactic acid in the case of using a cationic electrodeposition paint.
The positive-type photosensitive electrodeposition boating composition can be easily coated on a electrically conductive materials such as copper foil by electrodeposition, and the electrodeposited film is dried to form a uniform photosensitive film. When light is irradiated onto the photosensitive film through a positive film, the exposed portion changes as described above and is developed with weakly alkaline water. The unexposed portion can also be removed by dissolving with the solvent, alkali solution (in the case of using the anionic paint) or the acid (in the case of using the cationic paint). Accordingly, this can supersede conventional photosensitive films.
The electrodeposition coating composition of this invention is particularly suitable for the production of a printed circuit board having through-holes. This composition obviates a soldering step unlike the case of using a photosensitive dry film, and shortens the process of producing the printed circuit board. With a photocurable negative-type electrodeposition paint, it is difficult to form a cured film on through-holes of small diameters. In contrast, since the unexposed portion remains as a resist film in the present invention, the composition of this invention is suitable for the production of printed circuit board having through-holes of a small diameter.
Using the composition in this invention, the printed wiring substrate having landless through-holes can easily be produced by exposure via a circuit pattern mask designed so as not to shade the light from the through-hole portion.
In the positive-type photosensitive electrodeposition coating composition of this invention, the photosensitive material with the quinonediazide group incorporated through the less hydrolyzable sulfonamide or (sulfonimide), a sulfonamide (imide) linkage or a carboxylic acid ester linkage is used. It is higher in hydrophobic nature than the resin (B) used in this invention. When the aqueous dispersion is therefore formed, the photosensitive material is incorporated into the dispersion particles and it is less likely to directly contact water, amines and acids that expedite hydrolysis. Consequently, it does not happen that agglomeration or precipitation in the bottom of the bath occurs in the electrodeposition coating bath over a long period of time and a coating voltage greatly changes. Thus, the stability of the electrodeposition coating bath is high, permitting the easy handling and controlling.

The following Examples illustrate this invention in more detail. Parts and percentages in Examples are all by weight.
Production of an Acrylic Resin Solution 1
______________________________________ parts______________________________________2-Methoxypropanol 450 In-Butyl acrylate 692Styrene 200Acrylic acid 108 IIt-Butylperoxy octoate 50 2-Methoxypropanol 50 IIIt-Butylperoxy octoate 10______________________________________
The solvent I was charged into a flask and heated to 110.degree. C. The mixture II was added dropwise at 110.degree. C. for 3 hours, and the temperature was kept at 100.degree. C. for 1 hour. Subsequently, the mixture III was added dropwise at 110.degree. C. for 1 hour and the temperature of 110.degree. C. was further kept for 2 hours to afford an acrylic resin solution 1 having a solids content of 67%, a number average molecular weight of 11,000 and an acid value of 84.
Production of Acrylic Resin Solutions 2 to 5
In the same manner as in Production Example 1, acrylic resin solutions 2 to 5 were produced according to the formulation shown in Table 1.
TABLE 1______________________________________Acrylic Resin Solution 2 3 4 5______________________________________Solvent IButyl Celloslve 450 4002-Methoxypropanol 300Methyl diglyme 450n-Butanol 100i-Propanol 150Mixed solution IIn-Butyl acrylate 643 222 629n-Butyl methacrylate 400 750Methyl methacrylate 200 1002-Hydroxyethyl 50 100methacrylateStyrene 200 200Glycidyl methacrylate 71t-Butylperoxy octoate 80Azobisisobutyro- 80nitrileBenzoyl peroxide 60 50Dimethylamino-ethyl methacrylate 157Acrylic acid 128 100Methacrylic acid 50Mixed solution IIIButyl Cellosolve 50 50Dimethyl diglyme 50i-Propanol 50t-Butylperoxy octoate 5Azobisisobutyro- 10nitrileBenzoyl peroxide 5 10Reaction temperature 100.degree. C. 100.degree. C. 120.degree. C. 100.degree. C.PropertiesSolids content 67% 67% 67% 67%Number average 8,500 12,000 7,000 14,000molecular weightAcid value -- 100 110 --Amine value 56 -- -- --______________________________________
Production of an Acrylic Resin Solution 6
A flask was charged with 1,550 parts of the acrylic resin solution 5 obtained in Production Example 5, and heated at 40.degree. C. While keeping the temperature at 40.degree. C., a mixed solution of 44.5 parts of dimethylaminoethanol and 30 parts of acetic acid was added dropwise over the course of 30 minutes, and the mixture was maintained at 60.degree. C. for 5 hours. There resulted an acrylic resin solution 6 having a solids content of 66% and a quaternary ammonium salt content of 0.46 mole/kg.
Production of an Acrylic Resin Solution 7
A flask was charged with 100 parts of the acrylic resin solution 4, and a solution of 18.7 parts of 1,2-naphthoquinonediazide-5-sulfonyl chloride in 360 parts of acetone was added thereto. While stirring the mixture at 30.degree. C. 10 parts of triethylamine was added dropwise over the course of 1 hour. After the resulting mixture was maintained at 30.degree. C. for 2 hours, the reaction product was added dropwise to 5,000 parts of deionized water which was being stirred, over the course of 1 hour. The aqueous layer was separated and dried at 40.degree. C. under reduced pressure. Thereafter, 40 parts of dimethyl diglyme was added and dissolved to obtain an acrylic resin solution 7 having a solids content of 67% and an acid value of 89.
Production of a Hydroxyl-containing Ortho-quinonediazide Compound 1
A four-necked flask was charged with 269 parts of ortho-naphthoquinonediazidesulfonyl chloride and 1345 parts of dioxane, and with stirring at room temperature, 150 parts of N-methylethanolamine was added dropwise over 1 hour. After the dropwise addition, the mixture was stirred further for about 3 hours. After determining that the absorption of the amino group near 3300 cm.sup.-1 in the IR spectrum of the reaction mixture disappeared, the reaction was terminated.
The resulting solution was put in deionized water, and the quaternary amine which trapped hydrochloric acid formed during the reaction was removed. The product was then extracted with isobutyl acetate, and the solvent was evaporated. The residue was dried in a dessicator under reduced pressure to give a hydroxyl-containing ortho-quinonediazide compound 1.
Production of a Hydroxyl-containing Ortho-qinonediazide Compound 2
A four-necked flask was charged with 269 parts of ortho-naphthoquinonediazidesulfonyl chloride and 1345 parts of dioxane, and with stirring at room temperature, 122 parts of monoethanolamine was added over the course of 1 hour. After the dropwise addition, the mixture was further stirred for about 3 hours, and then worked up as in the production of the quinonediazide compound 1. As a result, a hydroxyl-containing ortho-quinonediazide compound 2 was obtained.
Production of an Unsaturated Group-containing Ortho-quinonediazide Compound-1 (UQ-1 Compound)
A four-necked flask was charged with 307 parts of the hydroxyl-containing ortho-quinonediazide compound 1 and 500 parts of dimethyl diglyme, and the mixture was stirred at room temperature. After the hydroxyl-containing ortho-quinonediazide compound 1 was dissolved in dimethyl diglyme, 90.5 parts of acrylic acid chloride was added over the course of 1 hour, and the mixture was stirred at room temperature for 3 hours. Subsequently, after dimethyl diglyme was evaporated to a solids content of 60% at 60.degree. C. under reduced pressure, the reaction product was put in methanol, and the product was precipitated, filtered, and placed in a vacuum dryer for drying to obtain an unsaturated group-containing orthoquinonediazide compound-1.
Production of an Unsaturated Group-containing Ortho-quinonediazide Compound-2 (UQ-2 Compound)
A four-necked flask was charged with 307 parts of the hydroxyl-containing ortho-quinonediazide compound 1 and 500 parts of dimethyl diglyme, and the mixture was stirred at room temperature. After the hydroxyl-containing ortho-quinonediazide compound 1 was dissolved in dimethyl diglyme, 104.5 parts of methacrylic acid chloride was added over the course of 1 hour, and the resulting mixture was then stirred at room temperature for 3 hours. Then, after dimethyl diglyme was evaporated to a solids content of 60% at 60.degree. C. under reduced pressure, the reaction product was put in methanol, and the product was precipitated, filtered, and placed in a vacuum dryer for drying to obtain an unsatured group-containing ortho-quinonediazide compound-2.
Production of an Unsaturated Group-containing Ortho-quinonediazide Compound-3 (UQ-3 Compound)
A four-necked flask was charged with 293 parts of a hydroxyl-containing ortho-quinonediazide compound-2 and 500 parts of dimethyl diglyme, and the mixture was stirred at room temperature. After the hydroxyl-containing ortho-quinonediazide compound-2 was dissolved in dimethyl diglyme, 90.5 parts of acrylic acid chloride was added over the course of 1 hour, and the mixture was then stirred at room temperature for 3 hours. Subsequently, after dimethyl diglyme was evaporated to a solids content of 60% at 60.degree. C. under reduced pressure, the reaction product was put in methanol, and the product was precipitated, filtered, and placed in a vacuum dryer for drying to obtain an unsaturated group-containing ortho-quinonediazide compound-3.
Production of an Unsaturated Group-containing Ortho-quinonediazide Compound-4 (UQ-4 Compound)
A four-necked flask was charged with 293 parts of the hydroxyl-containing ortho-quinonediazide compound 2 and 500 parts of dimethyl diglyme, and the mixture was stirred at room temperature. After the hydroxyl-containing ortho-quinonediazide compound 2 was dissolved in dimethyl diglyme, 104.5 parts of methacrylic acid chloride was added over the course of 1 hour, and the mixture was then stirred at room temperature for 3 hours. Subsequently, dimethyl-diglyme was evaporated to a solids content of 60% at 60.degree. C. under reduced pressure, the reaction product was then put in methanol, and the product was precipitated, filtered and placed in a vacuum dryer for drying to obtain an unsaturated group-containing ortho-quinonediazide compound-4.
Production of a Photosensitive Compound-1
______________________________________ parts______________________________________2-Methoxypropanol 600 In-Butyl acrylate 4002-Hydroxyethyl acrylate 239Unsaturated group-containing 361ortho-quinonediazide compound-1Dimethyl diglyme 400 IIAzobismethoxydimethyl valero- 60nitriletert.-Dodecylmercaptane 10Azobismethoxydimethyl valero- 10nitrile III2-Methoxypropanol 20______________________________________
The solvent I was charged in a four-necked flask and heated at 60.degree. C. The mixture II was added dropwise at 60.degree. C. over the course of 3 hours and maintained at that temperature for 1 hour. Then, the mixture III was added dropwise at 60.degree. C. over the course of 1 hour and further maintained at 60.degree. C. for 2 hours to obtain a photosensitive compound having a solids content of 50% and a number average molecular weight of 3,000.
Production of Photosensitive Compounds-2 to -12
According to the formulation shown in Table 2, photosensive compounds-2 to -12 were prepared in the same way as the photosensitive compound-1.
TABLE 2__________________________________________________________________________Photosensitive compound -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 -12__________________________________________________________________________Solvent IButy cellosolve 600 600 600 600 600 600 600 600 600 600Methyl diglyme 600Mixed solution IIn-Butyl acrylate 400 323 400 400 323 400 400 323 400 400 323methyl acrylate 239 225 253 2392-Hydroxyethyl acryalte 239 225 225 253 253 239 239Acrylie acid 77 77 77 77UQ-1 compound (*1) 361 361UQ-2 compound (*1) 375 375 375UQ-3 compound (*1) 347 347 347UQ-4 compound (*1) 361 361 361V-70 (*2) 60 60 60 60 60 60 60 60 60 60 60tert-Dodecylmercaptan 10 10 10 10 10 10 10 10 10 10 10Butyl cellosolve 400 400 400 400 400 400 400Methyl diglyme 400 400 400 400Mixed solution IIIButyl cellosolve 20 20 20 20 20 20 20Methyl diglyme 20 20 20 20V-70 (*2) 10 10 10 10 10 10 10 10 10 10 10Reaction temperature 60.degree. C. 60.degree. C. 60.degree. C. 60.degree. C. 60.degree. C. 60.degree. C. 60.degree. C. 60.degree. C. 60.degree. C. 60.degree. C. 60.degree. C.PropertiesSolids content 50% 50% 50% 50% 50% 50% 50% 50% 50% 50% 50%Number average molecular weight 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000 3000Acid value 0 60 0 0 60 0 0 60 0 0 60__________________________________________________________________________ *1: UQ Unsaturated groupcontaining naphthoquinonediazide compound *2: V70 Azobismethoxydimethylvaleronitrile
Production of a Photosensitive Compound-13
A four-necked flask was charged with 313 parts of coconut oil-type triamine (R-82 of KAO)* and 313 parts of dimethyl diglyme and the mixture was stirred at room temperature, followed by adding 1,083 parts of the unsaturated group-containing ortho-quinonediazide compound-1 over the course of 1 hour. Subsequently, the reaction temperature was raised to 50.degree. C. and stirring was further conducted for 3 hours to obtain 74.2% of a photosensitive compound-13 containing ortho-quinonediazide units.
*containing as a principal component a mixture of C.sub.12 H.sub.25 --NH--CH.sub.2 --CH.sub.2 --CH.sub.2 --NH--CH.sub.2 --CH.sub.2 --CH.sub.2 --NH.sub.2 and C.sub.14 H.sub.29 --NH--CH.sub.2 --CH.sub.2 --CH.sub.2 --NH--CH.sub.2 --CH.sub.2 --CH.sub.2 --NH.sub.2
Production of a Photosensive Compound-14
A four-necked flask was charged with 313 parts of a coconut oil-type triamine (R-82 of KAO) and 313 parts of dimethyl diglyme, and the mixture was stirred at room temperature, followed by adding 1,125 parts of the unsaturated group-containing ortho-quinonediazide compound-2 over the course of 1 hour. Subsequently, the reaction temperature was raised to 50.degree. C. and stirring was further conducted for 3 hours to obtain a photosensitive compound-14 containing 74.2 % of ortho-quinonediazide units.
Production of a photosensitive compound-15
A four-necked flask was charged with 313 parts of a coconut oil-type triamine (R-82 of KAO) and 313 parts of dimethyl diglyme, and the mixture was stirred at room temperature, followed by adding 1,041 parts of the unsaturated group-containing ortho-quinonediazide compound 1 over the course of 1 hour. Then, the reaction temperature was raised to 50.degree. C. and stirring was further conducted for 3 hours to obtain a photosensitive compound-15 containing 74.2% of ortho-quinonediazide units.
Production of a Photosensitive Compound-16
A four-necked flask was charged with 313 parts of a coconut oil-type triamine (R-82 of KAO) and 313 parts of dimethyl diglyme, and the mixture was stirred at room temperature, followed by adding 1,093 parts of the unsaturated group-containing orthoquinonediazide compound 1. Subsequently, the reaction temperature was raised to 50.degree. C., and stirring was further conducted for 3 hours to obtain a photosensitive compound-16 containing 74.2% of ortho-quinonediazide units.
Production of a Photosensitive Compound-17
A four-necked flask was charged with 313 parts of dimethyl diglyme, 313 parts of a coconut oil-type triamine (R-82 of KAO) and 312 parts of sodium carbonate. With stirring at room temperature, a solution of 807 parts of naphthoquinonediazidesulfonic acid chloride in 4,035 parts of dioxane was added dropwise over the course of 1 hour. After the addition was over, stirring continued for about 3 hours. After confirming that absorption of the amino group in the vicinity of 3,300 cm.sup.-1 in the IR spectrum analysis disappeared, the reaction was finished.
Subsequently, this solution was charged in deionized water, followed by removing the quaternary amine that trapped hydrochloric acid formed during the reaction. After the product was extracted with isobutyl acetate, the solvent was evaporated, and the residue was put in a vacuum dryer for drying to obtain a photosensitive compound-17.
EXAMPLE 1
Hundred parts of the acrylic resin solution 1 obtained in Production Example 1 was mixed with 3.8 parts of triethylamine and 5 parts of butyl carbitol for neutralization. Subsequently, 16.7 parts of the photosensitive compound 1 was added and they were well mixed. While stirring the mixture by a high-speed mixer at a stirring rate of 1,000 to 2,000 rpm, 717 parts of deionized water was gradually added to obtain a stable dispersion. Said dispersion had the solids content of 8% and pH of 7.8.
EXAMPLES 2 TO 24 AND COMPARATIVE EXAMPLE 1
In the same way as in Example 1, dispersions were obtained in accordance with the formulation shown in Table 3.
TABLE 3__________________________________________________________________________ Example 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17__________________________________________________________________________Acrylic resin-1 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100Acrylic resin-2Acrylic resin-3Acrylic resin-4Acrylic resin-5Acrylic resin-6Acrylic resin-7Acetic acidTriethylamine 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13Photosensitive compound-1 33Photosensitive compound-2 33Photosensitive compound-3 33Photosensitive compound-4 33Photosensitive compound-5 33Photosensitive compound-6 33Photosensitive compound-7 33Photosensitive compound-8 33Photosensitive compound-9 33Photosensitive compound-10 33Photosensitive compound-11 33Photosensitive compound-12 33Photosensitive compound-13 33Photosensitive compound-14 33Photosensitive compound-15 33Photosensitive compound-16 33Photosensitive compound-17Photosensitive compound-18*Deionized water 1150 1150 1150 1150 1150 1150 1150 1150 1150 1150 1150 1150 1150 1150 1150 1150Bath solids content (%) 8% 8% 8% 8% 8% 8% 8% 8% 8% 8% 8% 8% 8% 8% 8% 8%pH 7.2 7.6 7.4 7.4 7.5 7.6 7.2 7.5 7.1 7.4 7.5 7.3 7.6 7.4 7.3 7.5__________________________________________________________________________ Comparative Example Example 18 19 20 21 22 23 24 1__________________________________________________________________________Acrylic resin-1 100 100Acrylic resin-2 100Acrylic resin-3 100Acrylic resin-4 100Acrylic resin-5Acrylic resin-6 100Acrylic resin-7 100Acetic acid 4.5 4.5Triethylamine 13 13 13 13 13 13Photosensitive compound-1 33 33 33 16.5 33Photosensitive compound-2Photosensitive compound-3Photosensitive compound-4Photosensitive compound-5Photosensitive compound-6Photosensitive compound-7Photosensitive compound-8Photosensitive compound-9Photosensitive compound-10Photosensitive compound-11Photosensitive compound-12Photosensitive compound-13Photosensitive compound-14Photosensitive compound-15Photosensitive compound-16Photosensitive compound-17 16Photosensitive compound-18* 15Deionized water 1150 1150 1150 1150 1150 1150 1150 1150Bath solids content (%) 8% 8% 8% 8% 8% 8% 8% 8%pH 7.2 7.6 7.4 7.4 7.5 7.6 7.2 7.5__________________________________________________________________________ *: tri1,2-Naphthoquinonediazide-5-sulfonylester of 2,3,4trihydroxybenzophenone (solids content 100%, quinonediazidesulfone units 75.2%)
A two-sided circuit plate for printed wiring board with a copper thickness of 35 microns obtained by subjecting an insulated plate having through-holes 0.4 mm in diameter to electroless copper plating and electrolytic copper plating was dipped in the aqueous dispersion of 25.degree. C. obtained in each of Examples 1 to 24 and Comparative Examples 1. Said plate was used as an anode in each of Examples 1-18, 20-22 and 24, and 2 and as a cathode in each of Examples 19 and 23, and was connected with the opposite pole dipped in the aqueous dispersion. After the electrodeposition was carried out under fixed electricity passage conditions shown in Table 4, the circuit plate was washed with water and dried at 80.degree. C. for 5 minutes. The electrodeposited films were all free from pinholes and had the uniform thickness. The insides of the through-holes were completely coated.
These aqueous dispersions were stored at 30.degree. C. for 6 months. As a result, the appearance remained unchanged in Examples 1 to 24, but in the dispersions in Comparative Example 1, the precipitation of the resin was observed.
Moreover, after the dispersions were stored at 30.degree. C. for 6 months, the above experiment was repeated. As a result, in Examples 1 to 24, the films were free from pinholes and had the uniform thickness, and the insides of the through-holes were completely coated. However, in Comparative Example 1, the abnormal resin precipitation was partially observed, the thickness was nonuniform and pinholes occurred around the through-holes.
TABLE 4__________________________________________________________________________ Film thickness Film after storage Electrodeposition coating conditions thickness (after 6 months)__________________________________________________________________________Example 1 Constant current 50 mA/dm.sup.-1 120 seconds 10 .mu.m 9 .mu.m 2 Constant current 50 mA/dm.sup.-1 120 9 9 3 Constant current 50 mA/dm.sup.-1 120 10 9 4 Constant current 50 mA/dm.sup.-1 180 15 15 5 Constant current 50 mA/dm.sup.-1 180 15 14 6 Constant current 50 mA/dm.sup.-1 180 14 15 7 Constant current 35 mA/dm.sup.-1 120 8 7 8 Constant current 35 mA/dm.sup.-1 120 8 9 9 Constant current 35 mA/dm.sup.-1 120 8 810 Constant current 35 mA/dm.sup.-1 180 11 1011 Constant current 35 mA/dm.sup.-1 180 12 1212 Constant current 35 mA/dm.sup.-1 180 12 1113 Constant voltage 600V 120 11 1014 Constant voltage 600V 120 10 1015 Constant voltage 600V 120 11 1016 Constant voltage 600V 100 8 817 Constant voltage 600V 100 8 718 Constant voltage 600V 100 8 719 Constant voltage 400V 120 8 820 Constant voltage 400V 120 8 721 Constant voltage 400V 120 8 822 Constant voltage 400V 100 7 823 Constant voltage 400V 100 7 724 Constant voltage 400V 100 7 7Comparative Constant current 50 mA/dm.sup.-1 120 seconds 12 .mu.m abnormalExample precipitation__________________________________________________________________________
A positive photomask was closely adhered to the resulting film and both surfaces were exposed. Subsequently, development was conducted with 2% sodium metasilicate and 2% sodium carbonate, followed by etching and removal of the resin film. The resulting circuit patterns were observed by an electron microscope and found to be complete circuit patterns having a circuit width (conductor width) of 30 micrometers. The unexposed through-hole portion remained completely without undergoing the copper etching to secure passage of both surfaces.
Moreover, the same experiment was repeated on the films obtained from the baths stored at 30.degree. C. for 6 months. Consequently, in Examples 1-24, the circuit patters were as good as those before storage. However, in Comparative Example 1, breakage of the circuit ascribable to the undissolved portion of the film in the exposed portion in the development, breakage of the circuit due to pinholes and lack of passage of through-holes frequently occured, and good circuit patterns could not be obtained.

Number	Name	Date
3046110	Schmidt	Jul 1962
3130049	Neugebauer	Apr 1964
3759711	Rauner et al.	Sep 1973
3902906	Iwama et al.	Sep 1975
4632900	Demmer et al.	Dec 1986
4898656	Hoshino et al.	Feb 1990
4975351	Akaki et al.	Dec 1990
5134054	Iwasawa et al.	Jul 1992
5162190	Zahn et al.	Nov 1992

	Number	Date	Country
Parent	126732	Sep 1993
Parent	718255	Jun 1991

Electrodeposition coating composition

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