JPH04276437A - Manufacture of copper foil radiation beam curable coating - Google Patents

Abstract

PURPOSE:To enable a copper foil which has heat resistance is the press opera tion and radiation beam curable coating for protection soluble in warm water or warm water in short time, to be provided by a method in which, after the copper foil is coated with a radiation beam-curable coating which contains acryl copolymer as a main component, the coating is irradiated with the radia tion beam. CONSTITUTION:Copper foil is coated with a radiation beam-curable coating containing the acryl copolymer as a main component which has unsaturated double bond in the molecule and weight-average molecular weight in the range of 1000-5000 and contains the acrylamide monomer of 5-50wt.% shown by the general formula as a component monomer of constituting the copolymer, and then radiation beam is irradiated to said coating. Acrylamide monomer polymerized by a radical generator such as e.g.alpha,alpha'-azobisisbutyronitrile, benzoyl peroxide which reacts only with the double bond of the monomer molecule together with heavy metal.

Description

[Detailed description of the invention]

0001

FIELD OF INDUSTRIAL APPLICATION This invention relates to a method for manufacturing copper foil used in the copper-clad laminate of the present invention.

0002

2. Description of the Related Art When a plurality of laminates are simultaneously manufactured in the same press platen, the process is generally performed as follows.

In the case of copper-clad laminates, the materials to be molded include copper foil, prepreg (a base material made of organic or inorganic fibers in the form of cloth or paper, impregnated with thermosetting resin, dried, (semi-hardened). These laminated materials are alternately stacked with smooth and uniformly thick metal plates (mirror plates) to form the required number of sheets. Metal plates (mirrors) are placed on the top and bottom, and cushioning material is placed on the outside. This is placed in a hot platen of a press that can heat and pressurized to harden the prepreg resin. The copper-clad laminate is then separated from the metal plate to complete the process.

[0004] A multilayer printed wiring board is made of an inner layer board having conductor circuits on one or both sides, a prepreg, copper foil if necessary, and a single-sided copper-clad laminate for the outer layer. Manufactured under pressure.

[0005] In such a manufacturing method, wrinkles, folds, foreign matter, and dents are unavoidable during the production of copper-clad laminates or multilayer printed wiring boards (hereinafter referred to as laminates). As a countermeasure to this problem, in order to provide a copper foil that can reduce the occurrence of wrinkles, folds, foreign objects, and dents,
BACKGROUND ART A so-called film-attached copper foil, which has a peelable heat-resistant film bonded to one side, as described in Japanese Patent No. 360, is known.

[0006]

[Problems to be Solved by the Invention] This film-coated copper foil can prevent wrinkles, folds, foreign objects, and dents from occurring during the pressing process, but the following problems occur regarding the peeling of the heat-resistant film on the copper foil. There was a problem. That is, with the recent advancement in electronics, film peeling robots are used, but as the film becomes thinner to 20 μm or less, peeling failures occur. Further, it is possible to dissolve the film in an acid, alkali, water, organic solvent, etc., but no film has been found that dissolves in a short time of 5 minutes or less and satisfies the heat resistance during the pressing process.

[0007]Also, as described in Japanese Patent Application No. 2-101270, a radiation-curable paint coated copper foil has been proposed in which a coating film soluble in an alkaline solution is provided on the surface of the copper foil. Copper foil coated with radiation-curable paint, which is soluble in alkaline solutions, requires an alkaline solution, which has inherent problems such as difficulty in handling and maintenance of the alkaline solution.

[0008] The present invention provides a method for manufacturing a copper foil coated with a radiation-curable coating for protection, which has heat resistance during the pressing process and dissolves in water or warm water in a short time.

[0009]

[Means for Solving the Problems] The present invention has an unsaturated double bond in the molecule and a weight average molecular weight of 1,000 to 50.
,000 and contains 5 to 50% by weight of an acrylamide monomer represented by the general formula as a component monomer of the copolymer. The present invention provides a method for producing a radiation-curable coated copper foil, which is characterized in that the copper foil is coated with radiation and then irradiated with radiation. The specific radiation-curable coating material of the present invention has heat resistance during pressing and can be dissolved or removed in a short time with water or hot water.

The present invention will be explained in detail below. The acrylic copolymer used in the present invention is prepared using a conventional synthesis method, such as α,α′-azobisisobutyronitrile, benzoyl peroxide, etc. Polymerization is carried out using an initiator (polymerization catalyst) such as a radical generator such as a radical generator or a catalyst system that acts in contact with heavy metals.
It is desirable to do so without the use of organic solvents or diluents such as benzene. At this time, if the polymerization conditions are appropriately controlled by using a regulator such as lauryl mercaptan or carbon tetrachloride, or by adjusting the high concentration of a radical generator, polymerization time, or polymerization temperature, a relatively low weight average viscosity can be achieved in a solvent-free state. Acrylic copolymers having a molecular weight in the range of 1,000 to 50,000 can be obtained.

The acrylamide monomer which is an essential component of this acrylic copolymer may be acrylic or methacrylic. In addition, from the point of view of solubility or removability in water or hot water, it is desirable to copolymerize a large amount of acrylamide monomer, but it is also desirable to copolymerize a large amount of acrylamide monomer, but it also increases the heat resistance or the adhesion with copper foil due to the increase in the glass transition point of the entire system. It is used within the range of 5 to 50% by weight.

[0012] In addition, monomers other than acrylamide constituting this acrylic copolymer include methyl (meth)
Acrylate, ethyl (meth)acrylate, butyl (
Acrylic or methacrylic alkyl ester monomers such as meth)acrylate, vinyl monomers such as styrene and vinyl acetate, and side chain functionality such as (meth)acrylic acid, 2-hydroxyethyl (meth)acrylate, and glycidyl (meth)acrylate. Examples include group-containing vinyl monomers. Their usage ratio is determined by the glass transition point of the entire system so that the adhesion to the copper foil is not impaired.

[0013] Examples of the group having an unsaturated double bond to be introduced into the molecule include vinyl group, vinyloxy group, vinyl carbonyloxy group, acryloyl group, methacryloyl group, etc., and particularly good results can be obtained. Acryloyl and methacryloyl groups have excellent reactivity.

The radiation-curable coating material according to the present invention may optionally contain a diluent, a crosslinking monomer, a plasticizer, a tackifier,
Additives such as antioxidants and fillers may be added.

[0015] The copper foil may be either an electrolytic foil or a rolled foil. Since the resulting radiation-curable paint has a low viscosity, it is applied to copper foil using a conventional coating method and then irradiated with radiation. The coating thickness of the coating material is usually about 0.1 to 50 .mu.m, but is preferably about 1 to 15 .mu.m from the viewpoint of heat resistance, solubility or removability in water or warm water, and cost.

Although the radiation-curable paint is a solvent-free paint whose main component is an acrylic copolymer of relatively low molecular weight, a small amount of solvent may be used from the viewpoint of coating workability.

Radiation as used in the present invention refers to active energy rays, including ionizing radiation such as α rays, β rays, γ rays, neutron beams, and accelerated electron beams, as well as ultraviolet rays. The dose of ionizing radiation can usually be used in the range of 0.5 to 50 Mrad, but 1
~20 Mrad is desirable. Further, in the case of ultraviolet rays, the wavelength range is about 180 to 460 nm, and a high-pressure mercury lamp or the like is suitable as the source.

[0018] Furthermore, when performing irradiation, care must be taken regarding the irradiation atmosphere. In other words, since the generated radicals are inhibited from polymerization by oxygen in the air, it may be necessary to use an inert gas such as nitrogen to maintain an appropriate oxygen concentration.

The copper foil coated with protective paint thus obtained is used in the production of laminates as described above, and has excellent heat resistance during pressing, and after use, is easily dissolved or dissolved in water or hot water. Can be removed.

[0020]

[Function] Although the effects of the radiation-curable paint used in the present invention regarding heat resistance and dissolution/removability in water or hot water are not clear, the following is presumed. That is, the basic reaction is radical polymerization of unsaturated double bonds in the acrylic copolymer that proceeds with radiation. This reaction proceeds at high speed, resulting in dense crosslinking and maintaining heat resistance. It is thought that when immersed in water or hot water, the hydroxyl groups of water molecules approach the amide groups, allowing the water molecules to easily penetrate into the interface between the paint and the copper foil, resulting in the paint being dissolved or removed.

[0021]

[Examples] The present invention will be explained below based on Examples, but the present invention is not limited thereto.

Examples 1 and 2 60 parts by weight of methyl methacrylate, 25 parts by weight of acrylamide, 15 parts by weight of acrylic acid, and α, α' were placed in a four-necked flask equipped with a stirrer, thermometer, dropping funnel, and nitrogen gas blowing device. - Add a mixture consisting of 4 parts by weight of azobisisobutyronitrile, and while stirring in a nitrogen stream,
℃. By continuing the reaction for another 6 hours at the same temperature, the viscosity was approximately 104 centipoise (E-type viscometer, 30°C).
), a prepolymer having a weight average molecular weight Mw of about 8,000 (polystyrene equivalent value measured by GPC method) was obtained. Then, the temperature was raised to 100°C, and 5 parts by weight of glycidyl methacrylate and 0.5 parts of triethylbenzylammonium chloride were added.
parts by weight and 0.1 parts by weight of a thermal polymerization inhibitor are added dropwise through a dropping funnel over 30 minutes, and the reaction is continued for about 20 hours at the same temperature to form an unsaturated double bond in the side chain. An acrylic copolymer with This acrylic copolymer was used as a radiation-curable paint on the surface of an 18 μm electrolytic copper foil to a thickness of 3 μm (Example 1) and 15 μm (Example 1).
Example 2) was coated using a knife coater method. Thereafter, each sample was irradiated with a dose of 10 Mrad at an oxygen concentration of 40 ppm using a low-energy electron beam irradiation device (manufactured by Energy Science Co., Ltd., trade name Electro Curtain Model CB-175/15/10L) with an accelerating voltage of 175 KV. Table 1 summarizes the properties of the copper foil coated with radiation-curable paint produced as described above.

Example 3 In the same manner as in Example 1, a prepolymer was synthesized using 45 parts by weight of styrene, 40 parts by weight of acrylamide, and 15 parts by weight of acrylic acid, and 5 parts by weight of glycidyl methacrylate was further added to produce an acrylic copolymer. A radiation-curable paint was created by combining these two methods. Then, the coating was applied and irradiated with electron beams in the same manner as in Example 1 to create a copper foil coated with radiation-curable paint. The characteristics are shown in Table 1.

Comparative Example 1 In the same manner as in Example 1, an acrylamide-free acrylic copolymer was synthesized from 85 parts by weight of methyl methacrylate and 15 parts by weight of acrylic acid. Using this radiation-curable paint, a radiation-curable paint-coated copper foil was prepared in the same manner as in Example 1, and its properties are shown in Table 1.

Comparative Example 2 In the same manner as in Example 1, an acrylic copolymer containing no acrylamide was synthesized from 85 parts by weight of butyl acrylate and 15 parts by weight of acrylic acid. Using this radiation-curable paint, a radiation-curable paint-coated copper foil was prepared in the same manner as in Example 1, and its properties are shown in Table 1.

[Table 1]

* Observation of the surface condition of the radiation-curable paint. ( ) is pencil hardness. ** Copper foil with radiation curing paint coated with glass epoxy 2
Layered with 5 sheets of 00μm prepreg, 170℃, 90kg
/cm2 for 90 minutes to produce a single-sided copper foil-clad laminate. The surface condition of the radiation-curable coating for protecting copper foil at that time was compared with the initial condition. *** The single-sided copper-clad laminate with the radiation-curable paint was immersed in water and hot water at 80°C, and the dissolution time of the paint was measured and the surface condition of the copper foil after dissolution was examined.

[0027]

[Effects of the Invention] As described above, the present invention has excellent heat resistance,
By using copper foil coated with a radiation-curable paint that produces a coating film that is soluble in water or hot water, it is possible to reduce the occurrence of wrinkles, smudges, foreign objects, and dents during handling during the production of laminates. At the same time, the paint film can be easily removed by simply passing it through a water or hot water treatment tank for a short time, making it possible to improve the finish of pin holes when used in multilayer printed wiring boards.

Claims (3)

[Claims] Claim 1: having an unsaturated double bond in the molecule and having a weight average molecular weight in the range of 1,000 to 50,000;
After coating a copper foil with a radiation-curable paint mainly composed of an acrylic copolymer containing 5 to 50% by weight of an acrylamide monomer represented by the general formula as a constituent monomer of the copolymer, radiation is applied. A method for producing copper foil with a radiation-curable paint, which comprises irradiating the copper foil. 2. The method for producing a radiation-curable paint-coated copper foil according to claim 1, wherein the unsaturated double bond is an acryloyl group or a methacryloyl group. [Claim 3] Claim 1 or 2, wherein the radiation is an electron beam.
The method for producing the radiation-curable paint-coated copper foil.