JPH083634B2 - Method for electrodeposition coating of electrodeposition coating composition for printed wiring photoresist - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrodeposition coating method for an electrodeposition coating composition for printed wiring photoresist, and more particularly, to a method for applying an electrodeposition coating to a copper clad laminate to obtain an adhesive property. The present invention relates to a method for electrodeposition coating of an electrodeposition coating composition for a printed wiring photoresist, which is capable of forming a smooth coating film that is not exposed to ultraviolet rays through a negative or positive film.

[Prior Art] Conventionally, in order to create a printed wiring board, generally, a copper foil-clad laminate is copper-plated, and a photosensitive film is laminated on the copper-plated laminate. After development, unnecessary copper foil other than the circuit pattern is subjected to etching treatment, and then the photosensitive film is removed to form a printed circuit on the laminated plate which is an insulator.

The thickness of the photosensitive film used in the above method is generally around 50 μm, so the circuit pattern formed by exposure and development is not sharp. Laminate the photosensitive film evenly on the copper foil surface. Is difficult, and the photosensitive film is expensive, but it is almost wasted in the developing process. Therefore, it is a reality that a technical means to replace the photosensitive film is desired. is there.

[Problems to be Solved by the Invention] In order to solve the above-mentioned problems due to the use of a photosensitive film in producing a printed wiring board, the present invention uses a photocurable resin by electrodeposition coating instead of the photosensitive film. The purpose was to use a coating film, and for this purpose, that is, to form a uniform and developable coating film on the surface of the copper clad laminate, which is also excellent in UV curability. It is intended to provide an electrodeposition coating method for an electrodeposition coating composition for a printed wiring photoresist, which can be used.

[Means for Solving Problems] The present inventor has conducted diligent research to obtain an electrodeposition coating method of an electrodeposition coating composition that meets the above-mentioned object, and as a result, has obtained an aqueous solution or water of a specific unsaturated acrylic resin. In order to complete the present invention, it was found that the photocurable coating film obtained by electrodeposition coating an electrodeposition coating composition comprising a combination of a dispersion liquid, a photopolymerization initiator and a hydrophilic solvent exhibits satisfactory performance for the above-mentioned applications. I arrived.

Thus, according to the present invention, (A) an acid value of 20 to 300 obtained by adding a glycidyl group-containing unsaturated compound to a high acid value acrylic resin, and an unsaturation degree of 0.2 to 4.0 mol /
kg, number average molecular weight 1,000 to 100,000 and glass transition temperature 0
A photocurable unsaturated resin aqueous solution or water dispersion obtained by neutralizing a carboxyl group contained in the resin skeleton of a water-soluble or water-dispersible photocurable unsaturated resin at a temperature of ℃ or higher with an alkali, (B) non- The copper clad substrate for printed wiring is immersed as an anode in an electrodeposition coating bath consisting of a water-soluble photopolymerization initiator and a water-soluble or water-dispersible composition containing (C) a hydrophilic solvent,
There is provided an electrodeposition coating method of an electrodeposition coating composition for a printed wiring photoresist, which is characterized in that the electrodeposition coating is performed by applying electricity.

The water-soluble or water-dispersible photocurable unsaturated resin (hereinafter, simply referred to as “photocurable resin”) in the present invention is a high acid value acrylic resin to which a glycidyl group-containing unsaturated compound is added.

A high acid value acrylic resin contains α, β-ethylenically unsaturated acids such as acrylic acid and methacrylic acid as essential components, to which esters of (meth) acrylic acid [eg methyl (meth) acrylate, ethyl (meth)) Acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hydroxyethyl (meth) acrylate, etc.], styrene,
It is a generally known one obtained by copolymerizing an unsaturated monomer such as (meth) acrylonitrile or acrylamide. Here, the amount of the α, β-ethylenically unsaturated acid used is such that the acid value of the acrylic resin is in the range of 40 to 650, preferably 60 to 500. Further, the number average molecular weight and the glass transition temperature (Tg) of the acrylic resin are appropriately adjusted so that the photocurable resin obtained by adding the glycidyl group-containing unsaturated compound to the acrylic resin has the above-mentioned number average molecular weight and Tg. Adjusted.

Further, the glycidyl group-containing unsaturated compound is specifically glycidyl acrylate, glycidyl methacrylate, aryl glycidyl ether, etc., and the amount added to the high acid value acrylic resin is the unsaturated of the resulting photocurable resin. The degree is 0.2 to 4.0 mol / kg, preferably 0.7 to 0.3 mol / kg.

The addition reaction of the high acid value acrylic resin and the glycidyl group-containing unsaturated compound is generally known reaction conditions, for example, using a catalyst such as tetraethylammonium bromide.
It can be easily carried out by reacting at 80 to 120 ° C. for 1 to 5 hours.

The photocurable resin thus obtained has an acid value of 20 to 300, preferably 30 to 100, and a number average molecular weight in addition to the above-mentioned degree of unsaturation.
It is necessary to have 1,000 to 100,000, preferably 3,000 to 50,000 and Tg 0 ° C or higher, preferably 20 to 70 ° C.

If the acid value of the photocurable resin is less than 20, it cannot be made water-soluble or water-dispersible and the composition will not be an electrodeposition coating composition.If the acid value exceeds 300, the electrodeposition coating will be applied to the substrate. It becomes difficult, and a large amount of electric power is required to increase the coating amount.

When the number average molecular weight of the photocurable resin is 1,000 or less,
The coating film applied during electrodeposition coating is easily destroyed, and a uniform coating film cannot be obtained. On the other hand, when it is 100,000 or more, the smoothness of the electrodeposition coating film is poor and the coating surface becomes uneven, resulting in poor resolution of image lines.

If the Tg of the photocurable resin is less than 0 ° C, the electrodeposition coating film becomes tacky, and dust and dirt easily stick to the coating film, making it difficult to handle. Conversely, if the Tg exceeds 100 ° C, it forms. The resulting electrodeposition coating becomes hard and cracks.

Further, if the degree of unsaturation of the photocurable resin is less than 0.2 mol / kg, the photosensitivity is poor and the coating film must be irradiated with light for a long time to cure. On the other hand, if it exceeds 4.0 mol / kg, the thermal stability of the photocurable resin is poor, and there is a drawback that gelation occurs during resin synthesis and storage.

The electrodeposition coating composition used for the electrodeposition coating of the present invention is a photocurable resin capable of anion electrodeposition in addition to the above-mentioned photocurable resin (for example, hydroxyl group-containing high acid value acrylic resin with diisocyanate and hydroxyethyl (meth)). Resin reacted with an equimolar adduct of acrylate), polymerizable unsaturated group-containing resin (for example, polyester acrylate resin containing ethylenically unsaturated group, polyurethane resin, epoxy resin, acrylic resin, etc.), vinyl monomer Body (for example, (meth) acrylic acid ester), oligomer (for example, diethylene glycol di (meth) acrylate, etc.) in an amount of 100 parts by weight or less, preferably 50 parts by weight or less, relative to 100 parts by weight of the photocurable resin. It is also possible to mix them in the range to adjust the coating performance appropriately.

Water dispersion or water solubilization of the photocurable resin in the present invention is carried out by neutralizing the carboxyl group contained in the resin skeleton with an alkali (neutralizing agent). Examples of the neutralizing agent include alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, alkylamines such as triethylamine, diethylamine, monoethylamine, diisopropylamine, trimethylamine and diisobutylamine, and alkylalkanolamines such as dimethylaminoethanol. Alicyclic amines such as cyclohexylamine, alkali metal hydroxides such as caustic soda and causticaline, and ammonia, which can be used alone or as a mixture. The amount of the neutralizing agent used is preferably in the range of 0.4 to 1.0 equivalent with respect to 1 mol of the carboxy group contained in the resin skeleton, and
If it is less than 4 equivalents, the water dispersibility will be lowered, making electrodeposition coating difficult, and if it is more than 1.0 equivalent, storage stability will be poor, such being undesirable.

A hydrophilic solvent (for example, isopropanol, n-butanol, t-butanol, methoxyethanol, ethoxyethanol, butoxyethanol, diethylene glycol, methyl ether, dioxane, tetrahydrofuran, etc.) for water-solubilizing or water-dispersing to further improve the fluidity of the resin component. ) Can be added. The amount of the hydrophilic solvent used is preferably 300 parts by weight or less based on 100 parts by weight of the resin component.

Hydrophobic solvents (for example, petroleum-based solvents such as toluene and xylene, ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as ethyl acetate and butyl acetate, 2-ethylhexyl alcohol) in order to increase the coating amount on the object to be coated. Alcohols, etc.) can also be added. The amount of hydrophobic solvent used is 200 per 100 parts by weight of the resin component.
A range of less than or equal to parts by weight is desirable.

As the water-insoluble photopolymerization initiator in the present invention, benzoin, benzoin methyl ether, benzoin ethyl ether, benzyl, diphenyl disulfide, tetramethyl thiuram monosulfide, eosin, thionine,
Diacetyl, Michler's ketone, anthraquinone, chloranthraquinone, methylanthraquinone, α-hydroxyisobutylphenone, p-isopropylαhydroxyisobutylphenone, α · α′dichloro-4-phenoxyacetophenone, 1-hydroxy1-cyclohexylacetophenone, 2.2 dimethoxy-2. -Phenylacetophenone, methylbenzoyl formate, 2-methyl-1- [4- (methylthio) phenyl] -2.morpholinopropene, thioxanthone, benzophenone and the like can be applied, and the amount of these used is 100 (resin component)
The range of 0.1 to 10 parts by weight is preferable with respect to parts by weight, and if less than 0.1 parts by weight, the curability is lowered, which is not preferable,
If it exceeds 10 parts by weight, the mechanical strength of the cured film deteriorates. A water-soluble photopolymerization initiator is not preferable because it makes it difficult to electrodeposit in a state of being uniformly mixed with the photocurable resin. If necessary, dyes and pigments can be added.

The electrodeposition coating performed on the printed wiring board using the electrodeposition coating composition of the present invention is performed as follows.

The pH of the electrodeposition coating bath whose main component is a neutralized photocurable resin
6.5 to 9, bath concentration (solid content concentration) 3 to 25% by weight, preferably 5 to 15% by weight, bath temperature 15 to 40 ° C, preferably 15 to 30 ° C
The insulating substrate coated with copper foil is immersed as an anode in the electrodeposition coating bath thus controlled, and a direct current of 40 to 400 V is applied. in this case,
It is suitable that the energization time is 30 seconds to 5 minutes, and the film thickness obtained is a dry film thickness of 5 to 100 μm, preferably 20 to 60 μm.

After the electrodeposition coating, the object to be coated is lifted from the electrodeposition bath and washed with water, and then the water contained in the electrodeposition coating film is removed by hot air or the like.

Then, a pattern mask is formed on the uncured photocurable electrodeposition coating film formed on the substrate and exposed with an actinic ray, and the unexposed portion other than the portion to be a conductor circuit is removed by a developing process.

The actinic ray used for exposing the photocurable electrodeposition coating film formed by the electrodeposition coating of the present invention is preferably a ray having a wavelength of 3000 to 4500Å, although it depends on the absorption amount of the photopolymerization initiator.
As these light sources, sunlight, mercury lamp, xenon lamp,
There is an arc lamp. Curing of the coating film by irradiation with actinic rays is carried out within a few minutes, usually in the range of 1 second to 20 minutes.

The developing treatment is carried out by spraying weak alkaline water on the surface of the coating film to wash away the uncured portion of the coating film. As the weak alkaline water, water such as caustic soda, sodium carbonate, caustic potash, and ammonia water which can neutralize the free carboxylic acid contained in the coating film to give water solubility can be used.

Then, the copper foil portion (non-circuit portion) exposed on the substrate by the developing treatment is removed by a usual etching treatment using ferric chloride or the like. After that, the photo-cured coating film on the circuit pattern is also dissolved and removed by a strong alkali such as caustic soda to form a printed circuit on the substrate.

[Function] According to the electrodeposition coating method using the electrodeposition coating composition of the present invention, anion electrodeposition coating can be easily carried out on a copper foil, and the deposited coating film is heated and dried to form a uniform photosensitive film. When this photosensitive film is exposed through a negative film or a positive film, the unexposed area can be developed with a weak alkali and the exposed area can be dissolved and removed with a strong alkali, so that it can be replaced with a conventional photosensitive film.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples.

Photocurable resin synthesis example 1 40 parts by weight of methyl methacrylate, butyl acrylate
A mixed solution consisting of 40 parts by weight, 20 parts by weight of acrylic acid and 2 parts by weight of azobisisobutyronitrile was kept in a nitrogen gas atmosphere at 110 ° C. for 90 hours in 90 parts by weight of propylene glycol monomethyl ether (hydrophilic solvent) for 3 hours. Was added dropwise. After the dropping, the mixture was aged for 1 hour, a mixed solution of 1 part by weight of azobisdimethylvaleronitrile and 10 parts by weight of propylene glycol monomethyl ether was added dropwise over 1 hour, and the mixture was aged for 5 hours to obtain a high acid value acrylic resin (acid. 155) solution was obtained. Next, 24 parts by weight of glycidyl methacrylate, 0.12 parts by weight of hydroquinone and 0.6 parts by weight of tetraethylammonium bromide were added to this solution, and the mixture was reacted at 110 ° C. for 5 hours while blowing air to obtain a photocurable resin (acid value about 50, unsaturated). Degree 1.35 mol / kg, Tg
A solution having a point of 20 ° C. and a number average molecular weight of about 20,000) was obtained.

Synthesis Example 2 of photocurable resin 60 parts by weight of styrene, 10 parts by weight of methyl acrylate, 30 parts by weight of acrylic acid and azobisisobutyronitrile 3
120 parts by weight of a mixed solution in a nitrogen gas atmosphere.
It was added dropwise to 90 parts by weight of cellosolve kept at 0 ° C over 3 hours. After dropping, the mixture was aged for 1 hour, and a mixed solution containing 1 part by weight of azobisdimethylvaleronitrile and 10 parts by weight of cellosolve was added dropwise over 1 hour, and then aged for 5 hours, and a high acid value acrylic resin (acid value 233) was added. A solution was obtained. Next, 35 parts by weight of glycidyl methacrylate, 0.13 parts by weight of hydroquinone and 0.6 parts by weight of tetraethylammonium bromide were added to this solution and reacted at 110 ° C. for 5 hours while blowing air to obtain a photocurable resin (acid value about 70, unsaturated degree). A 1.83 mol / kg, Tg point of 45 ° C., number average molecular weight of about 15,000) solution was obtained.

Photocurable resin synthesis example 3 40 parts by weight of methyl methacrylate, butyl acrylate
Dioxane (hydrophilic solvent) 100 in which a mixed system consisting of 25 parts by weight, 15 parts by weight of 2-hydroxyethyl methacrylate, 20 parts by weight of acrylic acid and 2 parts by weight of azobisisobutyronitrile was kept at 105 ° C. under a nitrogen gas atmosphere. The solution was added dropwise to 2 parts by weight over 2 hours and aged at the same temperature for 1 hour to obtain a high acid value acrylic resin (acid value 155) solution.
Next, 20 parts by weight of an equimolar adduct of 2-hydroxyethyl methacrylate and tolylene diisocyanate was added to 200 parts by weight of this solution, and the mixture was reacted in a nitrogen gas atmosphere at a temperature of 80 ° C. for 5 hours to give a light usable in the present invention. Curable resin (acid value about 120, degree of unsaturation 0.56 mol / kg, number average molecular weight about 2
0,000) solution was obtained.

Example 1 After 6.7 parts by weight of triethylamine was added to 227 parts by weight of the photocurable resin solution of Synthesis Example 1 to sufficiently neutralize, 6 parts by weight of a photopolymerization initiator α-hydroxyisobutylphenone was added, and the solid content was Deionized water was added to 10% by weight to prepare an electrodeposition coating bath (pH 7.0). Using this electrodeposition coating bath, copper clad laminate for printed wiring (50 x 1000 x 1.5 mm)
Was used as an anode and a direct current of 120 V was applied for 3 minutes at a bath temperature of 25 ° C. for electrodeposition coating. Wash the coating with water and dry at 70 ° C for 10 minutes.
A 25 μm-thick, non-sticky, smooth photosensitive film was obtained. Then, the negative film was brought into close contact with this coated plate by a vacuum device, and 150 mJ / cm ^{2 was} irradiated on both sides using a 3 KW ultra-high pressure mercury lamp. Next, the unexposed area is washed out with a 1% sodium carbonate solution for development, washed with water and the copper foil is etched away with ferric chloride to remove it, and then the cured coating film in the exposed area is removed with 5% sodium hydroxide solution. The result was a printed circuit board with a clean and sharp pattern.

Example 2 To 240 parts of the photocurable resin solution of Synthesis Example 2, 8.5 parts by weight of triethylamine was added to be sufficiently neutralized. Next, after adding 40 parts by weight of isobutyl alcohol and 7 parts by weight of a photopolymerization initiator benzoin ethyl ether, deionized water was added so that the solid content was 10% by weight, and an electrodeposition coating bath (pH 7.
3) A treatment with this electrodeposition bath was carried out in the same manner as in Example 1 to obtain a printed circuit board having a clean and sharp pattern.

Example 3 To 240 parts by weight of the photocurable resin solution of Synthesis Example 2, 4 parts by weight of pentaerythritol triacrylate was added, and 40 parts by weight of isobutyl alcohol and 8.5 parts by weight of triethylamine were added to sufficiently neutralize. Next, after adding 40 parts by weight of isobutyl alcohol and 7 parts by weight of a photopolymerization initiator benzoin ethyl ether, deionized water was added so that the solid content would be 10% by weight to prepare an electrodeposition coating bath (pH 7.3). did.
By treating with this electrodeposition bath in the same manner as in Example 1, a printed circuit board having a clean and sharp pattern was obtained.

Example 4 After mixing 100 parts by weight of the photocurable resin solution of Synthesis Example 1 with 10 parts by weight of the photocurable resin of Synthesis Example 3, triethylamine was added.
It was fully neutralized by adding 3.3 parts by weight. Then, 16 parts by weight of isobutyl alcohol and 5.5 parts by weight of α-hydroxyisobutylphenone were added, and then deionized water was added so that the solid content was 10% by weight to prepare an electrodeposition coating bath (pH 7.4). A treatment with this electrodeposition bath was carried out in the same manner as in Example 1 to obtain a printed circuit board having a clean and sharp pattern.

Comparative Example 1 To 220 parts of the photocurable resin solution of Synthesis Example 3 was added 13 parts by weight of triethylamine for sufficient neutralization, and then 40 parts by weight of isobutyl alcohol and 6 parts by weight of benzoin ethyl ether were added to obtain a solid content of 10 parts. Deionized water was added so as to make the weight% to prepare an electrodeposition coating bath (pH 7.7). The same treatment as in Example 1 was carried out using this electrodeposition bath, but the obtained electrodeposition coating film was inferior in smoothness and the state of the raised pattern was inferior, and was not suitable as a printed circuit board. .

Claims (1)

[Claims] 1. An acid value of 20 to 300 obtained by adding an unsaturated compound containing a glycidyl group to a high acid value acrylic resin (A), the degree of unsaturation.
0.2 to 4.0 mol / kg, number average molecular weight of 1,000 to 100,000, and glass transition temperature of 0 ° C or higher, the carboxyl group contained in the resin skeleton of a water-soluble or water-dispersible photocurable unsaturated resin is neutralized with an alkali. In an electrodeposition coating bath comprising a water-soluble or water-dispersible composition containing the resulting photocurable unsaturated resin aqueous solution or water dispersion, (B) a water-insoluble photopolymerization initiator, and (C) a hydrophilic solvent. Immerse a copper clad board for printed wiring as an anode in
An electrodeposition coating method for an electrodeposition coating composition for a printed wiring photoresist, which is characterized in that the electrodeposition coating is performed by applying electricity.