JPS60141769A - Ultraviolet-curable coating composition for shielding electromagnetic waves - Google Patents

Abstract

PURPOSE:The titled composition that is mainly composed of an epoxy resin, an ultra-violet-sensitive Lewis acid salt and a ferrite powder, thus being used for electronic appliances, because it forms coating films with high adhesion to substrates and high heat resistance. CONSTITUTION:The objective composition is obtained by adding 50-600pts.wt. of (C) ferrite powder, preferably of 0.1-10mu particle sizes, containing metal oxides such as Fe2O3, to 100pts.wt., in total, of (A) an epoxy resin and (B) a Lewis acid salt such as p-methoxybenzenediazonium hexafluorophosphate.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention provides an electromagnetic shielding coating that is easily cured by ultraviolet rays, has electromagnetic shielding properties, and has excellent adhesion to coated objects, heat resistance, and flexibility. The present invention relates to an ultraviolet curable electromagnetic shielding coating composition capable of forming a film.

[Background of the invention]

In recent years, electromagnetic interference in electronic devices has become a problem, and electromagnetic shielding technology is being considered as a countermeasure. Methods of electromagnetic shielding include thermal spraying, plating, vapor deposition of metal, and application of electromagnetic shielding paint. Among them, the method of applying electromagnetic shielding paint involves processing the tube and the processing cost is low. The most well-known electromagnetic shielding paint is a paint in which ferrite powder is added to a resin base that hardens through the chemical reaction of a hardening agent. However, paints based on resins that harden through a chemical reaction with a hardening agent require a long time to cure, and heat-curable paints pose a risk of damaging electronic equipment. There were restrictions on the scope of use. The present inventors have investigated electromagnetic shielding paints that can be cured by electron beams or ultraviolet rays instead of paints that are curable through chemical reactions of curing agents. Electron beam or ultraviolet curable paints can be rapidly cured by irradiation with electron beams or ultraviolet rays, making it possible to completely streamline the manufacturing process. Further, since there is no need for heating, there is no damage to the object to be coated. By the way, if we compare the case of curing with electron beam and the case of curing with ultraviolet rays, even if the paint is cured with electron beam, it does not impair the effect of speeding up curing and streamlining the manufacturing process, but
Electron beam irradiation equipment is relatively expensive, and requires maintenance and maintenance.
Management is also complicated compared to ultraviolet irradiation equipment. Furthermore, the range of use is limited if the object to be coated may be damaged by the electron beam. In view of this situation, the present inventors have developed a material that is particularly easily cured by ultraviolet rays, has electromagnetic shielding properties, and has excellent adhesion to the coated object, heat resistance,
We conducted research on a method for obtaining an electromagnetic shielding coating composition that can form a complete electromagnetic shielding coating with excellent flexibility.

However, in the case of electromagnetic shielding coating compositions, it is predicted that it will be impossible to cause the coating film to harden rapidly even when irradiated with ultraviolet rays, since ferrite powder that blocks light is added to the composition. Ta.

The present inventors have conducted intensive research on a method of curing an electromagnetic shielding coating composition by irradiating it with ultraviolet rays. As a result, we have developed an electromagnetic wave shield consisting of a paint base made from a resin base consisting mainly of UV-functional Lewis acid salts and epoxy resins among many UV-responsive resin systems, and a composition in which ferrite powder is completely added to this resin base. Although it was predicted that the addition of ferrite powder to the paint composition would block the incidence of ultraviolet rays inside the paint film by irradiating the paint film with ultraviolet rays. figure,
We have discovered an unexpected phenomenon in which the paint film can mysteriously harden to the inside.

[Summary of the invention]

The present invention was made based on the above findings, and
The gist thereof is an ultraviolet curable electromagnetic shielding coating composition characterized by containing an epoxy resin, an ultraviolet functional Lewis acid salt, and a ferrite powder as main components.

[Detailed description of the invention]

The resin serving as the paint base used in the present invention is mainly composed of an epoxy resin and an ultraviolet-functional Lewis acid salt. Here, the ultraviolet-functional Lewis acid salt refers to one that generates a Lewis acid that causes cationic polymerization of an epoxy resin upon irradiation with ultraviolet light. The epoxy resin and Lewis acid salt may be mixed at the time of preparing the paint, or may be mixed immediately before printing. Examples of Lewis acids are PF6 and BP.
Examples of the salts include Lewis acid diazonium salts (e.g. P-methoxybenzenediazonium hexafluorophosphate), Lewis acid iodonium salts (e.g. diphenyliodonium hexafluorophosphate), Lewis acid sulfonium salts (e.g. triphenylsulfonium hexafluorophosphate), etc.

In addition, commonly used photosensitizers such as carbonyl-based and nitrogen-containing types are added to the paint base to enhance UV functionality.

The ferrite powder used in the present invention is Fe20B and Mn
It contains metal oxides such as O, ZnO, MgO, and BaO. Although the particle size and shape of the ferrite powder are not particularly limited, those having a relatively small particle size of about 0.1 to 10 μm are suitable for forming a good coating film.

In the present invention, 50 to 600 parts by weight of ferrite powder is added to 100 parts by weight of the total amount of the epoxy resin and Lewis acid salt serving as the paint base. If the amount added is less than 50 parts by weight, it will not be possible to form a coating film with sufficient electromagnetic shielding properties=5= Also, if the amount added exceeds 600 parts by weight, the coating workability will decrease and The finished state of the film tends to be rather poor, and especially when flexibility is required for the coating film, there is a problem that the flexibility is impaired and the coating film will break if it is completely bent.

Particularly preferably, the amount added is 70 to 500 parts by weight, and an electromagnetic shield coating film having sufficient properties can be formed without causing the above-mentioned problems.

In the present invention, it is also possible to add viscosity control materials such as silicone compounds, fatty acid esters, amine compounds, surfactants, and coloring agents in order to adjust the coating form. A composition can be prepared by adding ferrite powder to a resin that serves as a paint base by uniformly and thoroughly kneading it using a conventional method for preparing a paint, such as roll mixing.

Methods for applying the coating composition according to the present invention include application using a brush or roller, screen printing, and the like.

61 After the coating composition based on the present invention is applied to the object to be coated,
It is cured by irradiating it with ultraviolet light. The ultraviolet irradiation conditions are preferably about 10 to 60 seconds using an ultraviolet lamp of about 50 to 200 W//771. In the coating material based on the present invention ν, after the coating film is cured by ultraviolet irradiation, the coating film is cured at a temperature of 80 to 200°C for 1 to 200°C as long as the object to be coated is not damaged in order to allow the curing to proceed sufficiently.
Heat treatment can be performed for about 60 minutes.

Example 1 Azoka Ultra Set AD? 200 100iii parts Curing catalyst PP33 g parts by weight Mn-Zn ferrite powder 100 parts by weight were kneaded using a three-roll roll to prepare a coating material. Apply this paint to a thickness of 50μ
The electromagnetic shield coating was screen printed on a 20-μm thick polyimide film and cured by irradiating it with ultraviolet light for 30 seconds using two lkW ultraviolet lamps. After curing, the membrane was immersed in methyl ethyl ketone for 5 minutes.

I rubbed the paint film strongly after taking it out, but there was no abnormality in the paint film.
It was confirmed that curing progressed well to the inside of the coating film.

Example 2 In Example 1, after curing the coating film with ultraviolet rays,
It was heat-treated at C for 30 minutes. The coating film hardness was improved compared to the case of Example 1, and a tough coating film was obtained.

Comparative Example 1 In Example 1, the composition of the paint was changed to 1 part by weight of Aloex oligomer, 20 parts by weight of lipoxy resin, 100 parts by weight of Mn-Z n-based ferrite powder, and 5 parts by weight of photosensitizer (benzyl dimethyl ketal). However, an electromagnetic shield coating film was created under the same conditions as in Example 1 except for the following conditions. Although the surface of the coating film was well cured, when the coating film was rubbed after being immersed in methyl ethyl ketone, it was found that the coating was displaced from the base film, indicating that the coating had not been sufficiently cured to the inside.

As described above, the coating composition based on the present invention cures easily and quickly with ultraviolet rays, has electromagnetic shielding properties, and has excellent adhesion to the material to be coated, heat resistance, and flexibility. Since it can form a film, it can be widely used for electromagnetic shielding coatings on electronic devices.

9- Continued from page 1 0 Inventor: Oki Ito - Osaka City Nishiyodo Jl Office Inventor Noriko Tsuriba Osaka City Nishisho 1 Office 0 Inventor Atsuko Yamamoto Osaka City Nishiyodo Jl Office 1 Ward Chifune 2-14-16 Nato Research Co., Ltd. 2-14-16 Senfune, Ward 1 Nato Research Co., Ltd. 2-14-16 Senfune, Ward 1 Nato Research Co., Ltd. Cr%0

Claims (1)

[Claims] An ultraviolet curable electromagnetic shielding coating composition comprising as main components an epoxy resin, an ultraviolet-functional Lewis acid salt, and a ferrite powder.