JPS60240418A - Preparation of plastic container with conductive film - Google Patents

Abstract

PURPOSE:To impart conductive coating and decorative paint film by an easy operation to a plastic container by in-mold decorating through a method wherein the inside of a cavity mold is decorated with decorative paint and the surface of a core mold is decorated with conductive paint containing conductive powder. CONSTITUTION:The film 5 of decorative paint is generally from about 30mum- 1mm. in thickness and applied separately to the inside of a cavity mold 1. The thickness of paint film 7 provided by applying conductive paint is generally between about 50mum and about 1mm. and applied separately on to the core mold 2. In the injection molding process D, molds 1, 2 are closed, melted thermoplastic plastics is injected from the charging hole 3 to mold the container 8, and the film 5 of decorative paint with which the inside of the cavity mold 1 is coated separatably and the film 7 of conductive paint adhered separately to the surface of the core mold 2 are respectively transferred to and united in one body with the external surface and the internal surface of the container 8.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for manufacturing a plastic casing having a conductive film, and is used in the fields of electrical and electronic equipment industries for electromagnetic wave shielding effect or charging. The present invention relates to a method of manufacturing a plastic casing having a preventive effect.

[Background of the invention]

Plastic casings are widely used as casings for electrical and electronic equipment. However, plastics are generally transparent to radio waves, and electromagnetic waves emitted from electrical and electronic devices can have a negative impact on other electrical and electronic devices.
There is a risk of causing noise, malfunction, etc. Therefore, there is an increasing demand for a casing that can shield electromagnetic waves so that interference radio waves generated inside the device do not leak to the outside and interference radio waves from the outside do not reach the inside.

Furthermore, since plastic is an electrical insulator, it is easily charged with static electricity, which can cause various malfunctions in electrical and electronic devices inside the plastic casing, and there is a desire to improve this problem. [Prior Art] As a method for imparting electromagnetic wave shielding effects and static electricity prevention effects to plastic casings used for electrical and electronic equipment casings, the following methods have been proposed in the past.

■ A method of forming a conductive film or layer by applying conductive paint to the inner surface of the molded plastic case, thermal spraying of metal such as zinc, ° or metal vapor deposition, or plating.

■ A method in which the housing is injection molded from a resin composition mixed with carbon black, metal powder, etc. and conductive filler, and the conductive filler is dispersed in the resin to make the entire body conductive.

■ A method of laminating carbon fiber mats, wire mesh, or thin metal plates with plastic sheets and forming the casing using press molding, etc.

Among these methods, method (1) of forming a conductive film or layer has the disadvantage that the adhesion of the coating film may be insufficient and the sprayed zinc tends to peel off.

In addition, the conductive compound method (■) has so far been
In order to obtain a certain degree of conductivity, K is expensive because it is necessary to mix a large amount of conductive filler. Another drawback is that the molding machine and mold are subject to severe wear due to the use of filler.

Furthermore, with the press molding method (2), the molding efficiency is poor and the shape of the resulting casing is also limited.

On the other hand, Tokugan Shoj Ku, 20/lIdaO issue, Tokugan Sho! T-Kukuku/ and Japanese Patent Application Shoj Day Aztryt propose an in-mold molding method in which a plastic casing having a conductive film on its surface is molded in a mold. This method involves molding a plastic casing in a mold and
The film of conductive paint that has been applied to the surface of the mold in advance is transferred to the surface of the plastic casing and is tightly integrated. Since it is integrated, there is no fear of peeling, and the effect of imparting electrical conductivity is particularly excellent. In particular, this method
When forming a conductive coating on the inner surface of the casing, all you need to do is spray the conductive paint onto the convex mold that forms the inner surface of the casing, so you can coat the casing that has already been molded. Compared to the case where conductive paint is post-coated on the inner surface of the surface by spraying, it has the advantage that the operation is simple and a uniform coating film can be obtained.

[Problem that the invention seeks to solve]

However, even when a conductive film is formed on the inner surface of the housing by in-mold molding, when the plastic housing is actually used, the outer surface is often decoratively coated depending on the purpose.

In this case, even if a plastic casing is obtained by the in-mold molding method, there is no need to perform a subsequent painting process and post-painting, and the advantage of process simplification by the in-mold molding method is diminished.

[Structure of the invention]

The present invention relates to an in-mold molding method in which a cosmetic coating is transferred and integrated onto the outer surface of a casing, and a conductive coating is integrated into the inner surface of the casing. A method for manufacturing a plastic casing that does not necessarily require a post-painting process, the gist of which is to apply a cosmetic paint to the inner surface of the mold that forms the outer surface of the casing, among the molds for the plastic casing. After applying a conductive paint containing conductive powder to the surface of the mold that forms the inner surface of the housing, the mold is closed and the mold is filled with thermoplastic plastic. A conductive method characterized in that: 1) a coating film of cosmetic paint is applied to the outer surface of the housing, and a coating film of conductive paint is integrally transferred to the inner surface of the housing; The present invention relates to a method of manufacturing a plastic casing having a coating.

[Manufacturing process of plastic casing]

The manufacturing method of the present invention will be explained step by step with reference to the drawings.

FIG. 1 is a process diagram consisting of a schematic cross-sectional view for explaining the steps of the method for manufacturing a plastic casing of the present invention. In Figure 1, A is the pre-painting process, B is the cosmetic paint coating process, C is the conductive paint coating process, D is the injection molding process,
E is a demolding process. Steps B and C can here be carried out in parallel.

The mold consists of a cavity mold that forms the outer surface and a core mold that forms the inner surface, and the cavity mold is provided with a filling hole 3 for injecting a melted thermoplastic. There is.

In the pre-coating process, a masking material such as a magnetic sheet may be provided in advance in the cavity mold/and/or core mold as required.

In the cosmetic paint coating step B, various coating methods can be employed depending on the type of cosmetic paint. Although FIG. 1 shows an example of spray painting using a spray paint using a solvent-based paint, it is of course possible to apply paint using a spray paint. In addition, solvent-free paints are also suitably used as cosmetic paints, and in that case, a paint tank containing solvent-free paint is placed under the cavity mold l, and the solvent-free paint is removed by pressurized gas. An example is a method in which a solvent-free paint is made to float and adhered to the inner surface of the cavity mold l to form a coating film.

Cosmetic paint film! is usually about 30 microns or li
millimeter degree, and is removably coated on the inner surface of the cavity mold. Further, in order to form a coating film of a cosmetic paint, the cavity mold/mold may be heated depending on the type of paint.

As cosmetic paints, both thermoplastic paints and thermosetting paints can be used, and both solvent-based paints and solvent-free paints can be used, such as acrylic paints,
Examples include urethane paints and polyester paints.

In the conductive paint coating step C, the conductive paint is applied to the bottom of the core mold. The method for applying the conductive paint is various methods depending on the type of conductive paint. In Figure 1,
Although an example has been shown in which a solvent-based conductive paint is sprayed using the spray coating 6, it is of course possible to perform bald coating. In addition, when using a solvent-free conductive paint, the method of floating and adhering the paint using pressurized gas as described above and other fluidized dipping methods can be used.

Both thermoplastic paints and thermosetting paints can be used as the conductive paint, but in the case of thermoplastic paints in particular, the conductive paint is plasticized during the injection molding of the thermoplastic plastic, which will be described later. This is a particularly good building because the two are tightly integrated. Examples of binder resins for conductive paint include acrylic, urethane, and polyvinyl chloride, and conductive powders include powders of nickel, copper, surface-treated steel, silver, silver-coated copper, etc. spherical, resinous,
Powders with various aspect ratios, such as those shaped like grape bunches, can be used, but powders with an aspect ratio of about 10 microns to about θ0 microns are usually exemplified.

The thickness of the coating film formed by applying the conductive paint is usually about 30 microns to about 1 millimeter, and in order to form the coating film, the core mold is heated as necessary. Things are also done. As a result, a film of conductive paint is releasably applied onto the core mold a.

It is desirable that the above steps B and C are performed in parallel.

In the injection molding process, the mold is closed, and a molten thermoplastic is injected and filled from the filling hole 3 to form the casing T, which is removably adhered to the inner surface of the cavity mold. The coating film 3 of the cosmetic paint was transferred to the outer surface of the casing S, and the coating film of the conductive paint that was removably adhered to the surface of the core mold 1 was transferred to the inner surface of the casing. The clothes are integrated. Further, it is preferable that injection filling of the resin is performed using a side gate device as illustrated in FIG. Furthermore, if a thermoplastic paint is used as a cosmetic paint and/or a conductive paint, the thermoplastic paint will soften or become plasticized due to the heat of the filled thermoplastic plastic material, so the relationship between the paint film and the housing will be reduced. Close integration makes it even stronger.

Examples of thermoplastic plastics used in injection molding include polyolefins such as polypropylene, AaS resins, and the like.

The thickness of the coating film that is closely integrated with the outer or inner surface of the housing by injection molding is determined by
Alternatively, it is desirable that the coating film be thinner than the thickness of the coating film formed on the core mold. In particular, it is desirable that the thickness of the conductive paint film formed on the inner surface of the casing be compressed to about 0 to about goqb of the original film thickness. The close integration between the membrane and the housing t becomes particularly strong.

In the demolding process, the mold is opened and a cosmetic coating is applied to the outer surface!
Then, a plastic casing l having a conductive coating film tightly integrated on its inner surface is taken out.

An example of a plastic casing obtained by the present invention is shown in cross-sectional view in FIG.

[Effects of the present invention]

According to the present invention, a conductive coating 4 is applied to a plastic casing by an in-mold molding method, and a cosmetic coating is applied! The film can be applied by a simple operation. In addition, the resulting plastic casing and these coatings or paints are tightly and tightly integrated, so they do not peel off, have excellent electromagnetic wave shielding and antistatic effects, and are resistant to cosmetic paint on the outer surface. The coating film is also excellent in smoothness and has a rust-preventing effect, so a housing with high commercial value can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a process diagram consisting of a schematic cross-sectional view for explaining the steps of a method for manufacturing a plastic casing. FIG. 1 is a sectional view showing an example of a plastic housing. No. Jfg is a sectional view showing an example of a tid gate. A... River Pre-coating process B... Song Cosmetic paint coating process C... Song Conductive paint coating process D... River... Injection molding process R... Mold removal process l ...Cavity mold J ...Core mold J ...Filling hole, 6... Spray gun! ... River Cosmetic paint film ... Song Conductive paint film t ... Song Plastic casing ... Side gate applicant Tokai Kogyo Co., Ltd. Mitsui Petrochemical Industries Co., Ltd. Agent Kazu Yamaguchi, Figure F, Figure 2, Figure 2, 1, 3 (!0 Procedural amendment it' (spontaneous), 1925 (Showa 2), Director General of the Patent Office, Kazuo Wakasugi, Incident Display, Showa! 9, S/6 Patent application (co) 3 Title of invention Method for manufacturing a plastic casing with a conductive coating 3 Relationship to the case of the person making the amendment Patent applicant 1 Naganeyama, Kyowa-cho, Obu-shi, Aichi Prefecture Postal code: Dakutei Tokai Kogyo Co., Ltd. Representative Masaru Ki Kutsu 3-3 Kasumigaseki, Chiyoda-ku, Tokyo Postal code 100 Mitsui Petrochemical Industries Co., Ltd. Representative Nakano Seisei Yoshitsugi agent 〒io. Date of amendment order Voluntary amendment Due to the amendment Increase in the number of inventions Detailed explanation of the invention in the specification subject to amendment Details of the amendment (1) Add the following sentence between line l1 and line 7.2 on page J of the specification Note 2 [Example] The injection molding machine used was KS-, y30m (mold clamping pressure J j Oton) manufactured by Yorozaikokansha, and the mold was a molded product size that adopted a side normal gate. 2oox horizontal θ
Main molding was carried out using a box-shaped piece of θ×depth 100×J-work. First, as a cosmetic paint, PP coat I6.200 manufactured by Tanabe Kagaku ■ was sprayed onto the cavity mold using a spray gun, and the solvent was evaporated with hot air at about 60°C. 'tfC, part by weight of copper powder SO having an average particle size of 30 μm in the core mold. A conductive paint containing 20 parts by weight of an acrylic resin as a binder and 50 parts by weight of a solvent containing toluene as a main component was sprayed and dried in the same manner as described above. Resin (polypropylene resin, polypropylene resin,
J-Kuda 0 (manufactured by Mitsui Petrochemical Industries, Ltd.) was injected to obtain a molded product. The obtained molded product had an excellent appearance and exhibited various good magnetic shielding properties as shown in the table below. In addition, when the surface resistance of the cosmetic paint on the surface of the molded product was measured using a tester, it was found to be 10'Ω.
The resistance value was as follows. Table 7

Claims (1)

[Claims] After applying a conductive paint containing conductive powder to the surface of the mold forming the inner surface of the housing, the mold is closed and the inside of the mold is coated. A casing is formed by filling thermoplastic plastic into the casing, and a coating film of cosmetic paint is applied to the outer surface of the casing, and a coating film of conductive paint is applied to the inner surface of the casing, respectively. A method of manufacturing a plastic casing having a conductive film, characterized in that: (2) The manufacturing method according to claim (1), wherein the cosmetic paint and/or the conductive paint is a solvent-free paint. (3) The manufacturing method according to claim (1) or (2), wherein the cosmetic paint and/or the conductive paint is a thermosetting paint.