JPH04239070A - Thermosetting ink composition for printed circuit board - Google Patents

Abstract

PURPOSE:To provide the title compsn. which can be easily washed off with an aq. alkali soln. CONSTITUTION:The title compsn. which can be washed off with an aq. alkali soln. comprises a mixture of a varnish comprising an org. solvent soln. of a copolymer consisting of 10-50mol% (meth)acrylic acid, 30-80mol% radical- polymerizable monomer having a styrene backbone, and 0-40mol% radical- polymerizable monomer copolymerizable with those monomers and having a wt.-average mol.wt. of 1000-20,000 and an acid value of 100-300 and/or a copolymer consisting of 20-50mol% maleic anhydride, 30-80mol% radical- polymerizable monomer having a styrene backbone, and 0-40mol% radical- polymerizable monomer copolymerizable with those monomers, half-esterified with an aliph. or araliph. alcohol, and having a wt.-average mol.wt. of 1000-20,000 and an acid value of 100-300 with an epoxy compd. having at least two epoxy groups.

Description

Description: [0001] The present invention relates to a thermosetting ink composition for printed wiring boards that can be washed with an alkaline aqueous solution and has excellent heat resistance, electrical properties, etc. [0002] Conventionally, solder resists for thermosetting solder masks for screen printing used for printed wiring boards, marking inks for printing component names, etc. are made of hydrophobic epoxy resin. (See, for example, Japanese Patent Publication No. 51-14044). When this type of ink is used, chlorinated hydrocarbons such as 1,1,1-trichloroethane and flammable organic solvents are used to clean the plate after screen printing. Furthermore, in screen printing, situations often occur during printing in which the printing substrate needs to be repaired due to bleeding, rubbing, etc., and the above-mentioned solvents are also used in such cases. [Problems to be Solved by the Invention] However, the above-mentioned chlorinated hydrocarbons and flammable organic solvents have problems such as toxicity to the human body, air pollution, and environmental destruction, as well as the risk of fire. Due to these problems, restrictions have been gradually placed on its use in recent years. Therefore, when cleaning the plate or modifying the printed circuit board after screen printing, it is required to use an alkaline aqueous solution that poses no risk of fire and is not toxic to the human body. have been developed to withstand this. However, the reality is that a fully satisfactory thermosetting ink composition for screen printing that can be easily cleaned with an alkaline aqueous solution has not yet appeared. Therefore, an object of the present invention is to provide a thermosetting ink composition for printed wiring boards that can be easily cleaned with an alkaline aqueous solution. [Means for Solving the Problems] In order to solve the above problems, the present inventors conducted studies and found that a specific copolymer having a styrene skeleton and containing carboxylic acid The present inventors have discovered that a thermosetting ink composition composed of an epoxy compound and an epoxy compound is soluble in a dilute alkaline aqueous solution and has excellent electrical properties and moisture absorption properties, leading to the completion of the present invention. That is, the thermosetting ink composition for printed wiring boards of the present invention can be washed with an alkaline aqueous solution, and (1) (a) acrylic acid or methacrylic acid 10
~50 mol%, 30~80 mol% of a radically polymerizable monomer having a styrene skeleton, and ~40 mol% of a radically polymerizable monomer copolymerizable with these, with a weight average molecular weight of 1000~20000 and an acid value of 100. ~30
and/or (b) 20 to 50 mol% of maleic anhydride, 30 to 80 mol% of a radically polymerizable monomer having a styrene skeleton, and a radically polymerizable monomer copolymerizable with these O. ~40 mol%, half-esterified with alcohol having an aliphatic or aromatic ring, weight average molecular weight 1000-2000
0 and an acid value of 100 to 300 dissolved in an organic solvent; and (2) an epoxy compound having at least two epoxy groups. The present invention will be explained in detail below. In the present invention, the copolymer (a) contains acrylic acid or methacrylic acid in a range of 10 to 50 mol%. If the content is less than 10 mol%, sufficient solubility in an alkaline aqueous solution will not be obtained, and if it is more than 50 mol%, the electrical properties will deteriorate, so the above range is appropriate. It is. [0007] Maleic anhydride in the copolymer (b) is contained in a range of 20 to 50 mol%. If the content is less than 20 mol%, sufficient solubility in alkaline aqueous solutions will not be obtained, and if the content is less than 20 mol%,
If the amount is more than that, the electrical properties will deteriorate, so the above range is appropriate. The carboxyl group of the maleic anhydride unit in the copolymer is half-esterified with an alcohol having an aliphatic or aromatic ring having 1 to 12 carbon atoms. Examples of the aliphatic or aromatic aliphatic alcohol having 1 to 12 carbon atoms include methanol, ethanol, propanol, benzyl alcohol, and the like. In the above copolymers (a) and (b), examples of the radically polymerizable monomer having a styrene skeleton include styrene, α-methylstyrene, and vinyltoluene. These radically polymerizable monomers having a styrene skeleton are contained in a range of 30 to 80 mol%. If the content is less than 30%, the electrical properties and hardness will decrease, and if the content is more than 80 mol%,
The above range is appropriate since heat resistance and alkali solubility will decrease. [0009] Furthermore, as radically polymerizable monomers,
Examples include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, benzyl acrylate, benzyl methacrylate, acrylonitrile, methacrylonitrile, methyl vinyl ether, ethyl vinyl ether, isobutylene, vinyl acetate, and vinylpyrrolidone. These radically polymerizable monomers are contained in a content of 40 mol% or less. Content is 40
If the amount is more than mol%, the heat resistance and electrical properties will deteriorate, which is not preferable. The above copolymers (a) and (b) in the present invention must have a weight average molecular weight in the range of 1,000 to 20,000, particularly preferably in the range of 2,000 to 10,000. Weight average molecular weight is 1000
If it is lower than , when it is made into ink, there will be problems such as a decrease in solubility due to interaction that incorporates and dissolves alkali-insoluble components (for example, hydrophobic epoxy resin components), and a decrease in the properties of the cured product. Also, 20000
If it is higher than this, it is difficult to form into an ink, and the solubility in an alkaline aqueous solution decreases. [0011] Furthermore, the above copolymers (a) and (b) must have an acid value in the range of 100 to 300,
Particularly preferred are those in the range of 150 to 250. acid value is 1
If it is lower than 00, the solubility in a dilute alkali aqueous solution, for example, a 1% by weight sodium carbonate aqueous solution, will decrease, and if it is higher than 300, it will remain in the cured product when it is cured under normal curing conditions for printed wiring boards. An increase in carboxylic acid results in a decrease in electrical properties. One or both of the above copolymers (a) and (b) are dissolved in a suitable organic solvent to prepare a varnish. The concentration of the varnish is usually adjusted to a range of 40 to 75% by weight. Organic solvents used for making varnishes include:
Examples include diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and the like. Examples of the epoxy compound having at least two epoxy groups added to the varnish include bisphenol A type epoxy resins such as Epicoat 8281 and 1001 manufactured by Yuka Shell Co., Ltd., and Denacol EX- manufactured by Nagase Kasei Co., Ltd. Bisphenol S type epoxy resin such as 251, phenol novolac type epoxy resin such as DEN-438 manufactured by Dow Chemical Company, cresol novolac type epoxy resin such as Epiclon N-695 manufactured by Dainippon Ink Company, manufactured by Nagase Kasei Co., Ltd. Denacol EX-5
Polyglycidyl ethers such as No. 21, alicyclic epoxy resins such as Celoxide 2021 manufactured by Daicel Chemical Co., Ltd., tetraglycidyldiaminodiphenylmethane, triglycidyl isocyanurate, phthalic acid diglycidyl ester, bisphenol diglycidyl ether, and the like. Among these, preferred are powdered resins that are difficult to dissolve in the above organic solvents, such as Denacol EX.
-251, triglycidyl isocyanurate, bisphenol diglycidyl ether, and the like. The mixing ratio of the above copolymers (a) and (b) and the epoxy compound having at least two epoxy groups can be set as appropriate. However, from the viewpoint of the properties of the cured coating film, it is preferable to mix the epoxy group in a range of 1 to 1.5 moles per 1 mole of carboxyl group. The thermosetting ink composition of the present invention may contain coloring pigments (for example, titanium oxide, phthalocyanine, etc.), extender pigments (for example, barium sulfate, talc,
silica, etc.), curing catalyst (e.g., dicyandiamide, etc.)
, a water-soluble resin (e.g., water-soluble melamine resin, etc.), a flow regulator (e.g., organic bentonite, acrylic oligomer, finely divided silica, etc.), an antifoaming agent (e.g., silicone, acrylic oligomer, etc.), etc. may be included. It is possible. [0016] The thermosetting ink composition of the present invention having the above-mentioned structure can be prepared using a dilute aqueous alkaline solution (pH 11 or higher,
For example, 1% by weight aqueous sodium carbonate solution, 1% by weight potassium carbonate aqueous solution, etc.).
It can be cured by heating at 0 to 160°C. [Examples] The present invention will be explained below with reference to Examples. Example 1 Joncryl 68 (manufactured by Johnson Polymer Co., acid value = 195, weight average molecular weight = 10,000) 50 obtained by copolymerizing acrylic acid and styrene at a ratio of 1:2 as a carboxylic acid-containing copolymer 1 part was dissolved in 50 parts of dipropylene glycol monomethyl ether
68 varnish and 50 parts of Epikot 1001, a bisphenol A type epoxy resin (manufactured by Yuka Shell Co., Ltd., epoxy equivalent = 475) as an epoxy resin component, dissolved in 50 parts of diethylene glycol monoethyl ether acetate.10 parts, and triglycidyl isocyanurate (epoxy equivalent = 10
5) Coloring pigments, extender pigments, curing catalysts, flow regulators, antifoaming agents, etc. are added to the 20 parts composition as shown below, and the mixture is kneaded in a three-roll mill. J-68 varnish
100 copies
Epicote 1001 varnish
10 copies
triglycidyl isocyanurate
20 parts titanium oxide

50 parts talc

30 parts Cydiandiamide
0.5 part fine powder silica
6 parts Silicone antifoaming agent
1 part Example 2 Carboxylic acid copolymer: SMA-2 obtained by copolymerizing maleic anhydride and styrene in a ratio of 1:2.
000 (manufactured by Arco Chemical Co., Ltd.) acid value = 350, weight average molecular weight = 1700) was dissolved in 100 parts of diethylene glycol monoethyl ether acetate,
Add 0.1 part of triethylamine as a half-esterification catalyst, further add 12 parts of methanol, and heat from room temperature to 7
40 parts of SMA-2000 half ester varnish obtained by esterification reaction at 0°C, 50 parts of J-68 varnish used in Example 1, and a cresol novolac type epoxy resin Epicron as an epoxy resin component. A composition consisting of 12 parts of Epiclon N-695 varnish, which is obtained by dissolving 10 parts of N-695 (manufactured by Dainippon Ink Co., Ltd., epoxy equivalent = 235) in 30 parts of diethylene glycol monoethyl ether acetate, and 14 parts of triglycidyl isocyanurate. As shown below, a coloring pigment, an extender pigment, a curing catalyst, a flow regulator, and an antifoaming agent are added, and the mixture is kneaded in a three-roll mill. SMA-2000 Half Ester Varnish 40 parts J-6
8 varnish
50 parts Epicron N-695 varnish
12 parts triglycidyl isocyanurate 14 parts phthalocyanine green
Part 3
barium sulfate
50 copies
talc
1
0 parts dicyandiamide
0.2 parts organic bentonite
Part 2 Silicone antifoaming agent
0.5 part [0
Example 3 As a carboxylic acid copolymer, SMA-1440 (manufactured by Arco Chemical Co., Ltd., acid value = 175) was obtained by reacting alcohol with a 1:1 copolymer of maleic anhydride and styrene.
, weight average molecular weight = 2500) dissolved in 50 parts of diethylene glycol monoethyl ether acetate to a composition consisting of 100 parts of SMA-1440 varnish and 22 parts of triglycidyl isocyanurate as an epoxy resin component as follows. Coloring pigments, extender pigments, water-soluble resins, flow regulators, and antifoaming agents are added to the mixture, and the mixture is kneaded using a three-roll mill. SMA-1440 varnish
100 copies
triglycidyl isocyanurate
Part 22 Phthalocyanine green
3 parts barium sulfate

30 parts talc

40 parts hexamethoxymethylolamine
4 parts fine powder silica

Part 3 Silicone antifoaming agent

Comparative Example 1 As a conventional solder resist, epoxy resin Epicoat 828 (manufactured by Yuka Shell Co., Ltd., epoxy equivalent = 190) was used.
The following is a composition for curing with imidazole 2MZ-AZ (manufactured by Shikoku Kasei Co., Ltd.). Epicote 828
100 copies
Imidazole 2MZ-AZ
Part 8
Dicyandiamide
Part 1
phthalocyanine green
3 parts barium sulfate
80 parts talc
20 copies
fine powder silica
5th part
diethylene glycol mono

ethyl ether acetate
Comparative Example 2 Joncryl 611, a copolymer containing acrylic acid and styrene, was used as a carboxylic acid copolymer with a low acid value (manufactured by Johnson Polymer Co., acid value = 53, molecular weight = 6000)
100 parts of J-611 varnish dissolved in 50 parts of diethylene glycol monoethyl ether acetate
and 6 parts of triglycidyl isocyanurate as an epoxy resin component, a coloring pigment, an extender pigment, a curing catalyst, a flow regulator, and an antifoaming agent were added as shown below, and the mixture was processed using a three-roll mill. Knead. J-611 varnish
100 copies
Triglycidyl isocyanurate
Part 6 Phthalocyanine Green
Part 3
barium sulfate
50 copies
talc
1
0 parts dicyandiamide
0.2 parts fine powder silica

4 parts Silicone antifoaming agent

1 part Comparative Example 3 Acrylic acid and methyl methacrylate 1:2 (acid value = 20
6), 100 parts of acrylic acid-MMA varnish prepared by dissolving 50 parts of the synthesized acrylic acid copolymer in 50 parts of diethylene glycol monoethyl ether acetate so as to have a molecular weight of about 10,000, and as an epoxy resin component, Cresol novolac type epoxy resin Epiclon N-695 (manufactured by Dainippon Ink Co., Ltd., epoxy equivalent = 2
35) 10 parts of Epiclon N-6 dissolved in 30 parts of diethylene glycol monoethyl ether acetate
To a composition consisting of 10 parts of 95 varnish and 25 parts of triglycidyl isocyanurate, a coloring pigment, an extender pigment, a curing catalyst, a flow regulator, and an antifoaming agent are added as shown below, and the mixture is kneaded in a three-roll mill. . Acrylic acid-MMA varnish
100 copies
Epicron N-695 varnish
10 parts triglycidyl isocyanurate
Part 25 Phthalocyanine green

3 parts barium sulfate

50 parts dicyandiamide

0.5 part organic bentonite

Part 3 Silicone antifoaming agent

1 part Comparative Example 4 The acid value obtained by copolymerizing acrylic acid and styrene at a ratio of 1:2 was
200, and 40 parts of a resin with a molecular weight of about 30,000 were mixed with 60 parts of diethylene glycol monoethyl ether acetate.
To a composition consisting of 100 parts of varnish dissolved in 100 parts and 18 parts of triglycidyl isocyanurate as an epoxy resin component, an extender pigment and an antifoaming agent were added as follows,
Knead using a three-roll mill. Acrylic acid-styrene varnish
100 copies
(Molecular weight = approx. 30000)
triglycidyl isocyanurate
18 parts barium sulfate

50 parts talc

10 parts silicone antifoaming agent
Part 1 0024 [Performance evaluation 1
] The compositions of the above Examples and Comparative Examples were pattern printed on circuit-formed pudding and wiring boards by screen printing,
Examples 1 to 3 and Comparative Examples 2 to 4 were cured at 150°C for 40 minutes. In the case of Comparative Example 1, the temperature was 30 at 140°C.
Cured for minutes. The above substrate was evaluated by the following method. The results are shown in Table 1. (1) A board coated with solder heat-resistant rosin-based flux is coated with two
After being immersed in a solder bath set at 60° C. for 30 seconds and cleaning the flux with trichloroethane, the resist layer was inspected for abnormalities such as swelling and peeling by a peel test using cellophane tape and visual inspection. (2) Pencil hardness According to JIS K5400, the pencil hardness when the resist surface was scratched was examined using a pencil hardness tester with a load of 1 kg applied. (3) Alkali resistance After immersing the substrate in a 10% by weight aqueous sodium hydroxide solution at room temperature for 30 minutes, washing with water and removing moisture, inspect for abnormalities such as peeling of the resist layer by a peel test with sellotape and visual inspection. Ta. (4) Acid resistance The substrate was immersed in a 10% by volume aqueous hydrochloric acid solution at room temperature for 30 minutes, and after washing with water and removing moisture, the resist layer was inspected for abnormalities such as peeling by peel test with sellotape and visual inspection. . (5) Insulation resistance The above composition was printed and cured on a JIS Z-3197 comb-shaped substrate, and the substrate was left in a constant temperature and humidity chamber at a temperature of 40°C and a humidity of 95% RH for 240 hours. D.C.
An applied voltage of 500 V was applied and the insulation resistance value was measured. [Performance Evaluation 2] After screen printing the compositions of the above Examples and Comparative Examples, the plate was coated with 1 wt%
The ink was washed with an aqueous sodium carbonate solution to examine its washability. The results are shown in Table 1. [Table 1] [Effects of the Invention] Since the thermosetting ink composition for printed wiring boards of the present invention has the above-mentioned structure, it does not pollute the environment and does not cause harm to the human body. It also dissolves easily in dilute alkaline aqueous solutions without causing any dangers such as fire. therefore,
Screen printing plates and the like can be cleaned, and the ink composition can be removed with an alkaline aqueous solution after inspecting the printed circuit board, so the printed circuit board can be easily corrected. Further, it can be cured by heating, and the cured film formed by heating curing exhibits excellent properties in terms of soldering heat resistance, hardness, alkali resistance, insulation resistance, etc. Therefore, it is extremely useful as a thermosetting ink for printed wiring boards.

Claims (1)

[Claims] (1) (a) 10 to 50 mol% of acrylic acid or methacrylic acid, 30 to 80 mol% of a radically polymerizable monomer having a styrene skeleton, and a radically polymerizable monomer O copolymerizable with these. ~40 mol%, weight average molecular weight 1000~20000, acid value 1
00 to 300, and/or (b) 20 to 50 mol% of maleic anhydride and 30 to 80 mol% of a radically polymerizable monomer having a styrene skeleton, and a radical polymerizable copolymerizable with these. Consisting of monomer O ~ 40 mol%, half-esterified with aliphatic or araliphatic alcohol, weight average molecular weight 1000 ~ 2
0,000 and an acid value of 100 to 300 dissolved in an organic solvent; and (2) an epoxy compound having at least two epoxy groups, and is washable with an alkaline aqueous solution. Thermosetting ink composition for printed wiring boards.