Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
2001-01-05
2003-08-05
Hamilton, Cynthia (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C522S084000, C522S085000, C522S086000, C522S078000
Reexamination Certificate
active
06602651
ABSTRACT:
TECHNICAL FIELD
The present invention relates to novel aqueous solder resist compositions.
BACKGROUND ART
In production of printed circuit boards, photographic methods have been widely employed to form patterns.
For use in the photographic methods, dilute alkali-developable or water-developable solder resists are preferable to organic solvent-developable solder resists, because they are less likely to cause problems such as harm to the human body, environmental pollution and fire. Accordingly, there have been proposed dilute alkali-developable solder resists prepared using, for example, carboxyl-containing resins.
For instance, Japanese Unexamined Patent Publication No. 1986-243869 discloses a photocurable, thermosetting resist ink composition comprising an active energy radiation-curable resin, a photoinitiator, a diluent and an epoxy compound, wherein the active energy radiation-curable resin is a resin obtained by reaction of a novolak epoxy compound with an unsaturated monocarboxylic acid followed by addition of a polybasic acid anhydride to hydroxyl groups produced. However, the composition is not dilutable with water, and therefore needs to be diluted a large amount of organic solvent when used for spray coating or curtain coating. Thus, the composition has drawbacks such as poor application workability, polluting properties, fire hazard and the like.
Japanese Unexamined Patent Publication No. 1994-324490 discloses a photocurable, thermosetting resist ink composition comprising an unsaturated group-containing polycarboxylic acid resin, a photoinitiator, a diluent and a curing component (epoxy compound, melamine derivative or the like), wherein the unsaturated group-containing polycarboxylic acid resin is a resin obtained by addition of a polybasic acid anhydride to hydroxyl groups of a reaction product of a polyepoxy compound, an unsaturated monocarboxylic acid and a polyhydroxyl-containing monocarboxylic acid compound. The disclosed composition has satisfactory performance characteristics as a solder resist. However, the composition is disadvantageous in that it is of two-pack type which requires admixing of the curing component at the time of use. Further, the composition has a short pot life of several hours to a day after admixing of the curing component, and possesses the above drawbacks involved in the dilution with a large amount of organic solvent.
On the other hand, Japanese Unexamined Patent Publication No. 1993-202330 discloses, as a water-dilutable solder resist composition, a photocurable, thermosetting, aqueous solder resist ink composition comprising a photosensitive resin having an ethylenically unsaturated group and a carboxyl group neutralized with an amine compound, a photopolymerizable monomer, a photoinitiator, an amino resin and a diluent.
This aqueous composition is disadvantageous in that, if the composition contains an epoxy compound, it undergoes crosslinking and curing owing to the epoxy resin when heated in the drying step. As a result, the composition produces undeveloped portions when exposed and developed, showing poor developability. The composition is therefore heat-cured only with an amino resin without an epoxy compound, so that it does not sufficiently crosslinked. Further, the heat-cured film contains residual carboxyl groups. Thus, the solder resist film formed from the composition is not capable of withstanding the gold plating process which involves exposure to a high-temperature alkaline aqueous solution.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a novel aqueous solder resist composition free from the above problems of the prior art.
Another object of the present invention is to provide a novel aqueous solder resist composition which is excellent in storage stability, dilutable with water, developable with water or a dilute aqueous alkali solution, free from decrease in developability, and capable of forming a resist film excellent in chemical resistance, heat resistance, electrolytic corrosion resistance and like properties.
Further objects and features of the present invention will be apparent from the following description.
The present invention provides an aqueous solder resist composition comprising (a) a water-soluble or water-dispersible, photopolymerizable resin containing at least one polymerizable unsaturated group and at least one carboxyl group, the carboxyl group being neutralized with an amine compound;
(b) a photoinitiator;
(c) an amino resin; and
(d) a low reactivity epoxy compound free of an epoxy group represented by the formula
wherein Y is oxygen or nitrogen.
The present inventors conducted extensive research to obtain an aqueous solder resist composition free from the drawbacks of the prior art. As a result, they found that the above composition comprising a photopolymerizable resin, a photoinitiator, an amino resin and the above-specified low reactivity epoxy compound, is excellent in storage stability, dilutable with water, unlikely to undergo curing in the drying process and therefore unliable to decrease in developability, and developable with water or a dilute aqueous alkali solution. The present inventors also found that when the composition is heated after development, a film can be formed in which the photopolymerizable resin, amino resin and epoxy resin are highly crosslinked with one another by the reaction, and that the crosslinked film is excellent in chemical resistance, heat resistance, electrolytic corrosion resistance and other properties.
The present invention has been accomplished based on these novel findings.
The present invention will be described below in further detail.
The aqueous solder resist composition of the invention is photocurable and thermosetting, dilutable with water, and developable with water or a dilute aqueous alkali solution. The composition is preferably usable for, for example, a printed circuit board.
The photopolymerizable resin (a) for use in the aqueous resist composition of the invention is, for example, a resin obtained by neutralizing, with an amine compound, a polymerizable unsaturated group- and carboxyl-containing resin selected from the following resins (1) to (6). As used herein, “polymerizable unsaturated group” means a group capable of causing radical polymerization reaction upon exposure to active energy radiation. Examples of such groups include acryloyl, methacryloyl, vinyl, styryl and vinyl ether.
(1) A polymerizable resin prepared by addition reaction of a compound containing polymerizable unsaturated group(s) and either glycidyl group(s) or alicyclic epoxy group(s) with a carboxyl-containing acrylic resin. The carboxyl-containing acrylic resin preferably has a high acid value. A suitable acid value of the acrylic resin is about 20 to 700 mg KOH/g, more preferably about 30 to 600 mg KOH/g.
Preferred examples of the polymerizable resin (1) include resins prepared by addition reaction of a carboxyl-containing acrylic resin prepared by copolymerizing styrene, a carboxyl-containing unsaturated monomer [e.g., acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and “Aronix M-5600” (tradename of acrylic acid dimer manufactured by Toa Gosei Chemical Co.)] and other copolymerizable unsaturated monomer(s), with glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, or like polymerizable unsaturated group- and glycidyl-containing compound.
(2) A polymerizable resin prepared by addition reaction of a polymerizable unsaturated group- and carboxyl-containing compound with a glycidyl-containing acrylic resin, followed by addition of a dibasic acid anhydride to produced hydroxyl group(s).
Preferred examples of the polymerizable resin (2) include resins prepared by addition reaction of an acrylic resin prepared by copolymerizing a glycidyl-containing unsaturated monomer [e.g., glycidyl (meth)acrylate] and other copolymerizable unsaturated monomer(s), with (meth)acrylic acid or like polymerizable unsaturated group- and carboxyl-containing compound, followed by half-esterifi
Akui Jun
Furusawa Satoru
Ogawa Tetsuo
Seko Kenji
Yoshikawa Yutaka
Armstrong Westerman & Hattori, LLP.
Hamilton Cynthia
Kansai Paint Co. Ltd.
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