JPS59125725A - Photopolymerizable resin composition - Google Patents

Abstract

PURPOSE:To improve the adhesive strength of a photopolymerizable resin composition to a metallic surface by adding a very small amount of a specified compound to the composition which is used to form a photoresist for a printed wiring board. CONSTITUTION:This photopolymerizable resin composition consists of a thermoplastic polymer for a binder, a cross-linkable monomer having an ethylenic unsatd. group in the molecule, a photopolymn. initiator, and a compound represented by the formula (where R is H or 1-4C alkyl). The compound is a very effective component for improving the adhesive strength of a photoresist to a metallic plate, and the especially preferred compound is rhodanine, 3-methylrhodanine, 3-ethylrhodanine or 3-propylrhodanine. The amount of the compound contained in the composition depends on the components of the photoresist, the ratio among the components and the hardness of the photoresist after photosetting, and the preferred amount is 0.001-1wt% so as to produce a significant adhesive effect. More than the upper limit of the compound reduces the sensitivity, and less than the lower limit of the compound is liable to cause throwing during solder plating.

Description

[Detailed description of the invention] The present invention has improved adhesion to metal surfaces.

In particular, the present invention relates to a photopolymerizable resin composition used for forming photoresists for printed wiring boards.

The production of printed wiring boards using photoresists generally consists of the following steps. (11 Layer the photoresist on a substrate such as a glass/epoxy copper clad laminate. (2) Irradiate actinic rays through the pattern mask film to form an image. (3) Uncure the photoresist with an appropriate developer. A portion is selectively removed by bath solution to expose the copper surface and form a resist pattern. (4) After electrolytic copper plating is performed on the exposed copper surface, electroplating is performed.

(5) Peel off the cured resist with a suitable solvent to expose the copper surface. (6) Using the solder plating layer as a resist, the exposed copper surface is etched with a suitable solvent to obtain a printed wiring board in which the /X solder-coated portion becomes the wiring section.

In these manufacturing processes, a particularly important performance requirement for the photoresist is that the photoresist is not attacked by a liquid such as a plating solution, and that the base material coated with the photoresist can be sufficiently protected. In particular, peeling of the hardened resist that occurs during high-slow solder plating causes the plating solution to seep between the hardened resist and the copper surface, causing solder to be plated on areas other than the two circuits, resulting in short circuits between conductors and expansion of the conductor width. , problems such as irregularities in the shape of the peripheral portion of the conductor occurred.

These problems are due to the lack of adhesion between the cured resist and the copper surface, and research and development into adhesion promoters has been conducted, including benzotriazole as described in U.S. Pat. No. 3,622,334. It has been proposed to add a heterocyclic nitrogen-containing compound such as be/zimidazole to a photopolymerizable resin composition.

However, in order to manufacture printed wiring boards using wiring with narrow line width due to recent advances in high density and high precision, it is necessary to increase the amount of the above-mentioned heterocyclic nitrogen-containing compound to obtain a high precision pattern. However, this is causing new problems. i.e. benzotriazole.

Increasing the amount of benzimidazole has conventionally caused discoloration of dyes that are essential for confirming the pattern shape of photoresists and reduced the sensitivity of photoresists. On the other hand, if the amount of photopolymerization initiator added is increased to improve sensitivity, the cross section of the resolved pattern becomes an inverted trapezoid, resulting in a decrease in resolution. Also, increase the amount of additives with small molecular weight! ] This is undesirable because it promotes dissolution of the cured resist layer in many steps and reduces the resistance of the resist film.

As a result of intensive studies to overcome the conventional problems described above, the inventors of the present invention have found that by adding an extremely small amount of a specific compound to a photopolymerizable resin composition, the adhesion to metal surfaces can be improved. They found that it could be improved and completed the present invention.

In other words, there are two main points of the present invention.

(at thermoplastic polymer for binder (bl crosslinkable monomer having at least one ethylenically unsaturated group in the molecule) (J photoinitiator and (dl) following general formula (wherein R is H or A photopolymerizable resin composition comprising a compound represented by (which is an alkyl group having 1 to 4 carbon atoms).

The photopolymerizable resin composition of the present invention is characterized by the general formula [
Because it contains the compound shown in I], it has excellent adhesion between the photoresist and the copper plate, and does not cause any phenomena such as peeling of the resist or plating 9, making it suitable for manufacturing printed wiring boards with fine patterns. It is that you are.

As the thermoplastic polymer for the binder constituting the composition of the present invention, any suitable thermoplastic polymer can be used as long as it is soluble or swells in the developer used. As a specific example,
1,1.1) In the case of a photoresist using lichloroecune as a developer, polymethyl methacrylate or a copolymer containing methyl methacrylate as a main component is used. Specific examples of monomers used for copolymerization with methyl methacrylate include (c) methyl (meth)acrylate (meaning methyl acrylate or methyl methacrylate, hereinafter the same);
(meth)ethyl acrylate, n-propyl (meth)acrylate, inglovir (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate,
(meth)acrylic acid t-butyl, (meth)acrylic acid 2
- (Meth)acrylic acid esters such as ethylhexyl, lauryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and (meth)acrylic 22-hy)-0xypropyl.

Examples include styrene.

On the other hand, in the case of a photoresist using a dilute alkaline solution such as sodium carbonate as a developer, the above-mentioned (meth)acrylic ester or styrene is used with atarylic acid, methacrylic acid, or itaconic acid.

Examples include copolymers with carboxylic acids such as fumaric acid and maleinoic acid.

The molecular weight and composition of the copolymer of the thermoplastic resin for the binder of the present invention cannot be determined unconditionally depending on the purpose of use, but the molecular weight range is 20,
000 to 200,000 is good.

Examples of the crosslinkable monomer having at least one ethylenically unsaturated group in the molecule constituting the composition of the present invention include polyethylene glycol diacrylate-1, pentaerythritol diacrylate, and pentaerythritol triacrylate.

Examples include polyester acrylates such as pentaerythritol tetraacrylate and trimethylolpropane triacrylate, epoxy acrylates, and urethane acrylates.
It should be used in the composition in an amount of 25 to 50% by weight. If the amount of the crosslinkable monomer used is less than 25 parts by weight, the strength of the cured film will not be sufficient, and if it exceeds 50 parts by weight, the 7-otonist will become too soft and cause cold flow.

The photopolymerization initiator constituting the composition of the present invention is known, for example, benzophenone, Schichler's ketone, 4.4'-
Binu(diethylamino)benzofe/7. Examples include t-7-thylanthraquinone, 2-dithylanthraquinone, thioxanthones, benzoin alkyl ethers, and benzyl ketals, and these can be used alone or in combination of two or more. The amount of photopolymerization initiator used in the composition is determined from the viewpoint of cost, pattern finish, resolution, etc.
．． 5-5 FILit%.

In addition, among the compounds represented by general 2m used in the present invention, rhodanine is an extremely effective component for improving the adhesion of 27 otoresist to metal plates, and a particularly preferred compound is rhodanine.

3-MeF-Rurotanine, 3-Ethylrhodanine.

3-propyl rhodanine is mentioned. The amount of these compounds added to the composition cannot be determined unconditionally depending on the composition components and composition ratio of the photoresist, and the hardness of the photoresist after photocuring, but the amount to obtain an effective adhesion effect depends on the composition. 0.001 to 1 weight ratio in the product, preferably 0.01
It is in the range of ~0.5 weight factor. If there is too much, the sensitivity will decrease.

If it is too small, it will cause the plating to peel off when it is damaged.

The composition of the present invention can be used in the absence of a diluent, but it can be used in a solvent 9 that dissolves the base resin and that does not have a very high boiling point.
For example, methyl ethyl ketone.

Preferable results may be obtained by using methylene chloride, a mixture of methylene chloride/methyl alcohol, or isopropyl alcohol in combination.

The amount of the solvent to be used is 200% or less, preferably 100 to 20ON, based on the composition.

The composition of the present invention may contain a plasticizer, a thermal polymerization inhibitor, a filler, etc., if necessary.

The photopolymerizable resin composition of the present invention having the above-described component composition is used by laminating it on a metal surface 2 such as copper, nickel, chromium, preferably copper. It is used either by applying it as a liquid resist to a metal surface, and then covering it with a protective film after drying, or by laminating it onto a metal surface as a dry film photoresist. The thickness of the photoresist layer varies depending on the application, but the thickness after drying is about 5 to 100 μm.

As a protective film when used as a liquid resist, an inert polyolefin film such as polyethylene or polypropylene is preferably used. Dry film photoresists are made by coating a photopolymerizable resin composition on a polyester support film, and after drying, laminating a polyolefin protective film.

Actinic rays are irradiated through a negative film (evojimask putter/film) called artwork on the arrow.The active rays are carbon arc lamps.

A device that effectively emits ultraviolet rays, such as an ultra-high-pressure mercury lamp, a high-pressure mercury lamp, or a xenon lamp, is used.

The exposure amount is -300mJ/cr/L, although it cannot be determined generally.
2 or less, preferably 50 to 200 rrlJ/crtt
It is 2.

After exposure to actinic light, the unexposed portions are washed and removed using a suitable developer to obtain a resist pattern of the cured portions.

Developer solutions need to be safe and stable. But especially N
The important point is the operability of development, that is, the difference in dissolution rate between the cured and uncured parts of the photoresist is extremely large, and it is important to select a solvent as the developer that allows the dissolution rate of the uncured part to be appropriately fast. . General solvent-developed type: photoresist.

1.1.1)! J dichlorothane, an alkali-developable photoresist, and a dilute solution of sodium carbonate are preferably used.

There are various developing methods such as a dip method, a paddle method, and a spray method, but the high-pressure spray method is most suitable for improving resolution.

Electrical steel plating performed after development uses copper sulfate plating or birophosphate steel plating, and high-slow solder plating is often used for solder plating.

The photopolymerizable resin composition of the present invention has extremely excellent resist performance for wiring processing of metal laminate boards, particularly for wiring processing of copper-clad laminates used in printed wiring boards, and therefore has a high level of resistivity. It is suitable for wiring processing that requires precision and high density.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
Parts in the examples represent parts by weight.

Examples 1-6. Comparative Example 1 100 parts of a photosensitive resin composition polymethyl methacrylate (
Molecular weight (MN) = 60,000) Pentaerythritol triacrylate 50〃Benzopheno/
1 Shichler's Ketoy
O,2〃Hydroquinone
0,05 Macalite green
0,1〃Methyl ethyl ketone
150〃3-ethylrhodanine
Varying amounts were applied with a doctor knife and dried to diffuse the methyl ethyl ketone to a photoresist thickness of 50 μm. A 25 μm thick polyethylene film was laminated on top of this as a protective film, and the artwork was adhered onto this and exposed to light using an ultra-high pressure mercury lamp. The artwork used line and space patterns of 50 μm, 60 μm, 80 μm, and 1QQ μm. The ultra-high pressure mercury lamp used for exposure was USH-102D manufactured by Ushio Inc. and irradiated with 80 mJ/crrt2. What is the exposure intensity at this time?

Manufactured by Ushio Inc., UV intensity meter UI T-100
Attach the receiver UVD-365P to the
/(, L2 was set constant.

After exposure, leave it for 20 minutes and peel off the protective film.
1,1.1) Developed in a DuPont C" processor made by DuPont containing dichloroethane. The temperature was kept at 18-20°C. 2 Passing speed was 200 cyns per minute, and the spray pressure was 1.4 kP/min. Adjusted to Cm2.

The developed product was then immersed in a neutral detergent aqueous solution at room temperature for about 1 minute, and after degreasing, it was spray washed with water in an overflow tank for about 1 minute, and then immersed in an ammonium persulfate aqueous solution with a concentration of about 2ON for 1 minute. . Subsequently, spray washing was performed again for about 1 minute, and then immersed in a sulfuric acid aqueous solution bath of about 15% for 1 minute, and spray washing was performed again for 1 minute.

Next, a birophosphate copper plating tank (PH=8.2-8.4.
2.7A/dm2 for 45 minutes at a temperature of 50±2℃)
The plating was done with

Immediately after plating, it was washed with water, immersed in a 15% boric acid aqueous solution, and then the composition was as follows: Tin 15 jP (amount per 11 solder plating solution) Lead 10 F () Free surface hydrofluoric acid 400 y () Free boric acid 21. 6y () Peptone 5.2J'() at room temperature in a high-slow solder plating bath with 1.
Solder plating was performed at 5 A/dm2. After plating, it was washed with water and dried. In order to observe the development of the plating product, a sample was cut out and the cross section of the resist was observed using an optical microscope. The results are shown in Table 1.

Examples 7-8 Additive 770 Plating was performed in the same manner as in Example 1 except that 3-ethylrhodanine was replaced with rhodanine or 3-methylrhodanine, repeating <9 times, and its performance was evaluated.

The results obtained are shown in Table 1.

Comparative Examples 2 to 8 Plating was performed by repeating the same method as in Example 1, except that the additive 3-ethylrhodanine was changed to benzotriazole, and the usage amount and exposure amount were as shown in Table 1. was evaluated. The results obtained are shown in Table 1.

Procedural amendment (voluntary) Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office, dated February 2, 1948, special request for small case indication! ;g-AHk No. 2, Kabutori's name Photo-combining shiso composition 3, relationship with the amended case Patent applicant: Mitsubishi Rayon, 2-103-19 Kyobashi, Chuo-ku, Tokyo (603) President Osamu Kanazawa, 34, Agent, Mitsubishi Rayon Co., Ltd., 2-3-19 Kyobashi, Chuo-ku, Tokyo (6949), Toshio Yoshizawa, 5, Toshio Yoshizawa, Selector, Date of Amendment Order (1) Details ``(Meta)'' written in the bookcase from the -th line to the S line of the page.
Methyl acrylate (...su, (meth)ethyl acrylate, ヲ[acrylic? fl methyl, (meth)ethyl acrylate (4 groups of ethyl acrylate or methacrylic branched ethyl, hereinafter the same),] Correct your sleeves.

(1) Schichler's Ketone J on page S, line N of the Specification Box is corrected to "Michael's Ketone."

(3) 1 Michler's Ketone J K f+k T
h.

(Da) "Malachite Green" described on page 1, line 73 of Meijii Buttocks is [Malachite Green-IVC corrected.

(S) Correct the entire text of Table 1 on page 1A of the Meiji 11 Public Policy as shown in the attached sheet.

S: Grudge of a knotty shoe girl

Claims (1)

[Claims] 1. (a) Thermoplastic polymer for binder (b)
A crosslinkable monomer (c) having at least one ethylenically unsaturated group in the molecule, a photopolymerization initiator, and (dl) the following general formula] (wherein R is H or 1 to 4 carbon atoms A photopolymerizable resin composition comprising a metal compound having an alkyl group.