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
1999-02-23
2002-08-13
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
C522S099000, C522S103000
Reexamination Certificate
active
06432612
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ultraviolet-curable and thermo-setting type photo solder resist ink which can be developed by a diluted alkali aqueous solution, and particularly the photo solder resist ink which is preferably used to manufacture a printed wiring board having a fine, high-density conductive pattern.
2. Disclosure of the Prior Art
Recently, to manufacture various kinds of printed wiring boards having fine, high-density conductive patterns, excellent resolution and dimensional accuracy have been required for a solder resist formation step. For this purpose, methods using liquid-type photo solder resist inks have been adopted in place of a conventional screen printing method. For example, as disclosed in Japanese Patent Early Publications [KOKAI] No. 61-243869, No.2-173747, No. 7-72624, and No. 9-235348, these photo solder resist inks use an ultraviolet-curable type resin composition which is obtained by adding an unsaturated group or a carboxyl group to a novolac-type epoxy resin or an acrylic copolymer.
In general, the photo solder resist ink using the above-mentioned ultraviolet-curable type resin composition is applied on a printed wiring board, and then required portions thereof are cured by ultraviolet radiation to remove needless portions by developing. A diluted alkali aqueous solution is usually used as a developer. In this case, it is required to use the developer having a pH value of 11 or more. When the pH value of the developer decreases to about 10, a dried ink film after a selective exposing is difficult to be developed. That is, when the alkalinity of the developer lowers, there is a problem that a predrying condition width, in which the developing property can be maintained, i.e., a developing width, becomes narrow. The developing width is also known as a predrying control width or a predrying acceptable range. In addition, there is a resist ink including melamine to prevent a discoloration of copper. However, since melamine acts as an enhancer of a reaction between a carboxyl group of a novolac-type ultraviolet curable resin or an acrylic ultraviolet curable resin and an epoxy group of an epoxy compound, there is a problem that a viscosity of the resist ink increases, so that a storage stability of the resist ink deteriorates.
SUMMARY OF THE INVENTION
In view of the above-mentioned defects, an object of the present invention is to provide an ultraviolet-curable type photo solder resist ink having excellent storage stability, which exhibits a good developing property even when a developer having a pH value of about 10 is used, and is capable of providing electrical corrosion resistance, electric performance, chemical resistance, plating resistance, heat resistance to solder, adhesion, and pencil hardness of resist. That is, the photo solder resist ink of the present invention comprises the following components (A) to (E). The component (A) is an ultraviolet-curable resin having at least two ethylenically unsaturated groups and a carboxyl group per one molecule thereof. The component (B) is an epoxy compound having at least two epoxy groups per one molecule thereof. The component (C) is at least one selected from a compound having at least one carboxyl group and a polycarboxylic acid anhydride. The component (D) is a photopolymerization initiator. The component (E) is a diluent including an organic solvent.
In a preferred embodiment of the present invention, the component (A) is an ultraviolet-curable resin obtained by a reaction of a copolymer, which is obtained by a polymerization between a first ethylenically-unsaturated monomer having an epoxy group and a second ethylenically-unsaturated monomer different from the first ethylenically-unsaturated monomer, with a third ethylenically-unsaturated monomer having a carboxyl group and one of saturated and unsaturated polybasic acid anhydrides. In particular, it is preferred that the first ethylenically-unsaturated monomer includes glycidyl (meth) acrylate.
It is also preferred that the component (C) includes dicarboxylic acid, or dicarboxylic acid anhydride. In this case, there is an advantage that an influence of pH value of the developer to the developing property of the photo solder resist ink is very small. In particular, it is preferred that a content of dicarboxylic acid or dicarboxylic acid anhydride is within a range of 0.01 to 3.0 wt % with respect to a total amount of the components (A) to (E) except for the organic solvent included in the diluent.
These and still other objects and advantages will become apparent from the following detail descriptions of the preferred embodiments and examples of the invention.
DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENTS
First, a component (A) of an ultraviolet-curable type photo solder resist ink of the present invention is explained in detail. The component (A) is an ultraviolet-curable resin having at least two ethylenically unsaturated groups and a carboxyl group per one molecule thereof. The carboxyl group is used to provide a dissolution, dispersion or swelling property against a diluted alkali aqueous solution to the ultraviolet-curable resin (A) before an exposing step. After the exposing step, the dissolution, dispersion or swelling property against the diluted alkali aqueous solution of the ultraviolet-curable resin (A) lower, so that the photo solder resist ink can be developed by the diluted alkali aqueous solution to obtain a desired image. From this viewpoint, it is preferred that an acid value originated from the carboxyl group of the ultraviolet-curable resin (A) is within a range of 25 to 250 mgKOH/g. On the other hand, at least two ethylenically unsaturated groups are required to the ultraviolet curable resin (A) due to the following reason. That is, as described above, the ultraviolet-curable resin (A) must have the dissolution, dispersion or swelling property against the diluted alkali aqueous solution before the exposing step, so that the desired image can be formed by a selective exposure. For this purpose, an increase of molecular weight and a bridge formation by a photopolymerization are utilized in the ultraviolet-curable resin (A). Therefore, the ultraviolet-curable resin (A) must have at least two ethylenically unsaturated groups with photopolymerization capability. For example, as the ultraviolet-curable resin (A), it is possible to use an ultraviolet-curable resin, in which two or more groups having an ethylenically-unsaturated bonding are introduced to molecular terminal(s) or side chain(s) of a back bone polymer.
For example, as the ultraviolet-curable resin (A), it is possible to use one of ultraviolet-curable resins (A1) to (A4) explained below or a combination thereof. The ultraviolet-curable resin (A1) is obtained by a reaction of a compound, which is obtained by a polymerization of an ethylenically-unsaturated monomer (a) having an epoxy group and the other ethylenically-unsaturated monomer (b), with an ethylenically-unsaturated monomer (d) having a carboxyl group and a saturated or unsaturated polybasic acid anhydride (e). The ultraviolet-curable resin (A2) is obtained by reacting an epoxy compound (c) having at least two epoxy groups per one molecule thereof with the ethylenically-unsaturated monomer (d) having a carboxyl group and the saturated or unsaturated polybasic anhydride (e). The ultraviolet-curable resin (A3) is obtained by a reaction of an acid anhydride copolymer (f) with an alcohol (g) having an ethylenically unsaturated group. The ultraviolet-curable resin (A4) is obtained by a reaction of a compound, which is obtained by a polymerization of the ethylenically unsaturated monomer (d) having the carboxyl group and the ethylenically unsaturated monomer (b) having a polymerization capability with the monomer (d), with the ethylenically-unsaturated monomer (a) having the epoxy group.
As the ethylenically-unsaturated monomer (a), for example, it is possible to use an epoxy cyclohexyl derivative of an acrylic acid or methacrylic acid such as g
Hamada Nobuhito
Hashimoto Soichi
Yoshioka Koichi
Goo Chemical Co., Ltd.
Hamilton Cynthia
Rader & Fishman & Grauer, PLLC
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