JPH0745147B2 - Painting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an improvement in a painting method. More specifically, it is easy to make a painted synthetic resin molded product with excellent adhesion between the painted film and the base synthetic resin, as well as a painted synthetic resin molded product with a three-dimensional effect with fine irregularities on the surface. The present invention relates to a painting method that can be obtained from the above.

[Conventional technology]

A thermoplastic synthetic resin sheet or synthetic resin-impregnated paper on which characters, figures, patterns, paintings, etc. are printed or drawn is attached to the inner surface (shaped surface) of the mold by static electricity or vacuum suction, and then melted Material Thermoplastic synthetic resin is injected and integrally molded,
The so-called picture forming method is known.

Further, Japanese Patent Publication No. 50-19132 discloses a method of placing a three-dimensional picture film on a die surface in advance by vacuum forming not only the two-dimensional picture forming but also the three-dimensional picture forming.

[Problems to be solved by the invention]

Recently, synthetic resin molded products have been widely used, and there has been an increasing demand for high-value synthetic resin molded products with higher added value. Examples thereof include a wood grain pattern-shaped molded product having an uneven conduit pattern, and a painted molded product having an uneven hairline pattern. Conventionally, it is also difficult to make a film having such a fine concavo-convex pattern, and if industrial value is ignored, a method of making an acrylic resin film by a casting method or the like is conceivable as the film making method, In any case, there is a big limitation on the material of the film, and it cannot be called any film. In addition, even if a film with such a fine uneven pattern can be created, when using it as a painting film, the resin is injected into the mold and the painting temperature and resin pressure are used for painting. The minute irregularities on the corners of the film will drip down, reducing the realism and luxury.

Further, another problem of the painting with molding is the strength of adhesion between the painting film and the thermoplastic resin of the base material to be injection-molded.
Adhesion to the film due to insufficient adhesion at the contact surface between the film and the resin, even if the film with a temperature around room temperature attached to the inner surface of the mold is brought into close contact with the temperature and pressure of the thermoplastic resin for injection molding. It requires a lot of ingenuity, such as applying chemicals, etc., but even if it is industrially implemented, the reliability of its adhesive strength does not always reach a satisfactory level, and the occurrence of troubles in the market can be seen. Is.

[Means for solving problems]

The present inventors have improved the above-mentioned drawbacks of the conventional painting method,
The present invention was made by conducting intensive research to overcome the above problem and find out a molding method with which the adhesion strength between the painting film and the base resin is sufficiently large and a painting synthetic resin molded product having a fine uneven pattern can be easily manufactured. Came to.

That is, the present invention comprises mounting a paint film made of a thermoplastic resin on which characters, figures, patterns, paintings, etc. are printed or drawn on the inner surface of the mold, and the thermoplastic resin is injection-molded in the mold. In the picture forming method, a fine concavo-convex pattern for drawing is provided on the inner surface of the mold, and the mold temperature of the surface on which the picture film is attached is heated to a temperature not lower than the heat deformation temperature of the film. It is about.

According to the above method of the present invention, it is possible to easily obtain a painted synthetic resin molded article having excellent adhesion between the painted film and the base synthetic resin. Further, according to the method of the present invention, by providing a fine uneven pattern for painting on the inner surface of the mold,
It is possible to easily and surely obtain a painted synthetic resin molded article having a three-dimensional effect with a fine uneven pattern on the surface.
Therefore, the present invention relates to a method for forming a picture with a preferable embodiment in which a fine uneven pattern for drawing is provided on the inner surface of the mold.

Next, the present invention will be described in detail.

The paint film made of a thermoplastic synthetic resin used in the present invention is preferably of the same type or a close relative to the base synthetic resin forming the main body of the molded article in terms of the adhesiveness between the two. In the case of a combination that is made of different kinds of resins and cannot be bonded even by hot pressing, it is necessary to apply an appropriate adhesive.

The material of the painted film used in the present invention is not particularly limited, but is not limited to polyethylene, olefin resin such as polypropylene, polystyrene, styrene-acrylonitrile copolymer, ABS resin, styrene-styrene resin such as maleic anhydride copolymer. , Polyvinyl chloride, vinyl chloride resin such as vinyl chloride-vinyl acetate copolymer, polyester resin such as polyethylene terephthalate, polycarbonate resin, polyamide resin, polyphenylene ether resin, polyoxymethylene resin, polymethylmethacrylate resin So-called super engineering resins such as polyether imide resin, polyphenylene sulfide resin, and blends thereof are used. These may contain resin additives such as fillers and plasticizers.

The thickness of the present paint film is not particularly limited as long as it can be attached to or closely adhered to the injection molding die, and can be varied over a wide range. Usually 0.01 depending on the type of synthetic resin used.
A thickness of about 1 mm, preferably 0.02 to 0.3 mm is sufficient. Too thick film is uneconomical.

The decoration method for printing or drawing characters, figures, patterns, etc. on the present painting film is not essential to the present invention, and any ordinary method such as offset printing, gravure printing, screen printing or It can be performed by painting, vapor deposition of metal, plating, and drawing with paint.

In addition, the decorative surface of this decorative film is generally attached to the shaping surface of the mold, but when the decorative film is a transparent film, the transparent layer side opposite to the decorative surface is made of metal. When affixed to the shape-imparting surface of the mold and forming with a picture, the transparent resin layer is laminated on the decorative surface, resulting in a special decoration with depth and depth, a sense of luxury and a sense of weight. It is possible to obtain an effect.

To attach the paint film to the mold surface, ordinary static electricity or vacuum suction can be used. However, in the case of the vacuum suction method, since the vacuum hole traces are transferred to the molded product, it is better to install it in a place that does not impair its value in terms of the appearance of the molded product. Further, as disclosed in Japanese Patent Application Laid-Open No. 52-11255, etc., a paint film which has been thermoformed into a desired shape such as the shape of a molded product in advance may be mounted in the mold.

In order to give a fine pattern of the painted portion on the inner surface of the molding die in the present invention, a master (prototype) using an aluminum plate or a name tree with a fine pattern is used, and an electric casting method is used to obtain a fine pattern. It is also possible to create a mold steel material (nesting) such as beryllium copper or iron to which a pattern is transferred, or in the case of hairline processing or engraving of letters etc., it can be done by directly engraving or grinding on the mold steel material. it can.

The heating of the molding die in the present invention can be performed by flowing a heat medium through cooling water holes or the like provided in the conventional injection molding die. For example, it is possible to switch between steam and cooling water as necessary, and to flow them to control the temperature for heating. Further, it is possible to embed a cartridge heater or the like in the mold to heat while controlling the temperature, but to embed a coil, apply a high-frequency current to the coil, and impart a molded product shape, that is, a so-called mold block. The method of heating the cavity block or core block in the mold by high-frequency induction heating is an industrially useful method because of its excellent productivity and temperature controllability.

In the method of the present invention, at the time of picture formation, at least the mold surface in the vicinity of the picture film adhering portion is heated and placed, and the base resin is injection-molded to bond (adhesion) the picture film and the base resin.
At the same time, the fine pattern (fine irregularities) on the mold surface is transferred to the film surface to give a high-grade feeling such as a texture such as a three-dimensional effect. Therefore, in order to transfer the fine pattern on the die surface to the film surface by the resin temperature and the resin pressure of the base resin at the time of picture formation, there is a difference in the required die surface temperature depending on the material of the picture film. The transferability of the uneven surface depends on the required level of the transfer degree, but by heating the film to a temperature around the heat deformation temperature of the painted film or above, and picture-molding the molded film, the molded article aimed at by the present invention can be obtained. The degree of fine pattern that can be obtained by this method reaches a fine uneven pattern of a micrometer (μm) unit to a sub-μm unit.

The thermal deformation temperature referred to in the present invention means the temperature at which the paint film is deformed by the temperature rise and the injection pressure of the paint film due to heat transfer from the molten resin at the time of contact with the mold and injection of the resin for molding the main body. Method A (18.5 Kgf / cm) usually specified in JIS K 7207
² ) The deflection temperature under load is a guideline.

In addition, it is basically good to raise the temperature of the mold surface when attaching the painted film by heating the main body molding resin before it is melt-injected into the mold, but when the film significantly shrinks due to heat, etc. Is still in a molten state before it is filled with molten resin and cooled and solidified.In other words, the mold surface is heated when the resin pressure remains on the mold surface and the painted film surface. Is also good.

On the other hand, it goes without saying that this painting with molding is also a type of molding of thermoplastic resin, so after the base resin that forms the main body of the molded product is injected and filled into the painting die, the molding resin is cooled and solidified. However, since the molded product is obtained by releasing from the mold, it is necessary to cool the mold after injection filling. That is,
The mold, at least the mold block to which the painted film is attached, is preferably capable of rapid heating and rapid cooling as far as possible from the viewpoint of the productivity of the molded product with paint. From this viewpoint, the heating of the mold is performed by the above-mentioned heating method. Among them, the heating method utilizing the principle of high frequency induction heating is more advantageous because it is easy to increase the heating energy density and has good controllability.

As the base thermoplastic resin for the molded article body, any thermoplastic resin can be used as long as it can be injection-molded, and the same kind as the synthetic resin for the paint film is convenient. Examples of such thermoplastic resins include polyethylene, olefin resins such as polypropylene, polystyrene, styrene-acrylonitrile copolymers, ABS resins, styrene resins such as styrene-maleic anhydride copolymers, polyvinyl chloride,
Vinyl chloride resin such as vinyl chloride-vinyl acetate copolymer (EVA), polyester resin such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate resin, polyamide resin, polyphenylene ether resin, polyoxymethylene resin, polymethyl methacrylate Resins, polyetherimide resins, so-called super engineering resins such as polyphenylene sulfide resins, fibrin derivative resins such as cellulose acetate and blends thereof, and the like, and these include glass fiber, iron powder, talc, carbonic acid. Fillers such as calcium and usual resin additives such as plasticizers may be included.

Regarding the adhesion between the painted film and the base resin, cross-cut the film on the surface of the molded product into 100 square sections of 1 mm square and perform a cellotape peel test to evaluate the adhesion by the number of peeled squares. .

When the painting film and the base resin are the same type of resin, the adhesion is not bad even with the conventional painting method, but with the conventional painting method, if special measures such as applying adhesive to the adhesive interface are not used , The combination of paint film and base resin is polycarbonate and ABS resin, polyacetal and ABS resin, EVA
In the case of and ABS resin etc., 100/100 (100 squares peeled out of 100 squares) to 50/100 that does not adhere in the cellophane peeling test is about 50/100, but in the method of the present invention, excellent adhesion that does not peel off with 0/100 It was confirmed that

〔Example〕

 Next, examples will be shown.

Example 1 A stereo rectangular nameplate having a size of 3 cm × 20 cm and a wall thickness of 3 mm was molded. This nameplate was made by bonding an aluminum plate with a hairline to a rubber-reinforced polystyrene (abbreviated as HIPS) substrate with a boss for mounting the stereo body with a rubber adhesive. The one on the nameplate that is similar to or more luxurious than this conventional molded product,
It is intended to be prepared by picture-forming a film obtained by vapor-depositing aluminum on a polystyrene film.

The picture forming mold was prepared as follows. First, the mold nest that gives the hairline processed surface is made of an aluminum plate that has been carefully hairline processed as a master (prototype), and the beryllium copper is electrocasted.
It was made by casting it to a thickness of 3 mm and then lining it with iron to a thickness of 20 to 30 mm. Next, a coil for high frequency induction heating is arranged on the back side of the insert, a brass plate is arranged on the opposite side of the insert of the coil, and this is arranged on the mother die of the mold. Thus, when a high-frequency current is applied to the coil, the mold is produced so that the insert is selectively heated but the mother mold is not heated.

The film used for painting was a 30μ thick biaxially stretched GPPS (general polystyrene) with aluminum vapor deposited.

The aluminum deposition surface of the painted film was electrostatically adhered to the hairline processed surface of the mold. After that, a high-frequency current of 7 KHz and 10 KW was applied to the coil for 5 to 10 seconds so that the surface temperature of the contact surface of the photo film with the nest was 100 ° C. Next, HIPS for forming the substrate was melted and injected into the mold, and then cold water was poured into the mold to solidify and release the resin to obtain a desired molded product.

This molded product is a stereo nameplate that has a surface on which GPPS is directly transferred to the surface of the mold, which is finer than the mold surface, and has a fine irregularity pattern, surface hardness, etc. A high-quality molded product comparable to the nameplate attached with the processed plate was obtained.

The non-deposited surface of the biaxially stretched GPPS aluminum vapor-deposited film was brought into close contact with the mold hairline nesting portion, and otherwise the same as above. The molded product had a deep, subdued, astringent and metallic feel, and had an appearance not found in conventional plastic molded products.

Example 2 13 cm height x 10 cm width x 1.5 cm depth mini-component stereo speaker front frame, in the front frame a circular bass speaker with a diameter of 8 cm and a 2 cm height x 3 cm width treble speaker Has a shape that can be attached.

The entire surface of the molded product of the front frame of the speaker was subjected to picture-forming with a wood pattern with a conduit.

The method of making the mold was almost the same as that of Example 1, in which the fine concavities and convexities of the conduit in the wood grain were made by the electrocasting method of beryllium copper, and the lining was made with iron to make the cavity. A coil formed by winding a 6 mmφ copper tube into a substantially flat, rectangular, and spiral shape was arranged on the back of the cavity portion nest in the same manner as in Example 1. The mother die was also sealed with a copper plate so as not to be heated by high frequency induction.

A 0.1 mm thick vinyl chloride film printed with a wood pattern was used as the painting film. Using the above-mentioned cavity, or the aluminum mold of the same shape, the picture-added film is thermoformed into the same shape as the cavity shape and placed.
The thermoformed vinyl chloride film for painting was attached to the cavity portion of the mold attached to the injection molding material. Next, a high-frequency current of 300 KHz was passed through the coil so that the surface temperature of the die on the surface with the painted film was 130 ° C. Then, ABS resin (product name: Stylak ABS100) was used at resin temperature 2
It was injected at 40 ° C. Next, pour 50 ° C temperature controlled water into the mold, and
The S resin was cooled and solidified and released to obtain a desired molded product. The extra film in the speaker mounting hole was cut off with a knife.

This molded product was a molded product having a fine conduit pattern on the surface of the vinyl chloride printed with wood grain and having a high-class feeling that was indistinguishable from the front frame of a real wooden speaker. Also, an adhesion test was carried out using a cross-cut cellophane tape, and the peeling point was 0/100, no peeling was observed at all, and the adhesion was good.

Comparative Example 1 Using the same film and resin as in Example 2, ABS was used in the mold.
Before injection of resin, without performing high-frequency induction heating of the cavity / nesting, just by circulating temperature-controlled water at 50 ° C as in normal painting with high-frequency induction heating, and without heating by high-frequency induction heating, painting with molding was performed. However, the unevenness of the conduit pattern was not transferred to the surface of the film with a picture, and in the sense of high quality, it was lacking in real power. Also, in terms of adhesion strength, the portion where the injection pressure transmission at the end of the flow is poor is a little peeled off, so it was not always a satisfactory molded product.

〔The invention's effect〕

According to the method of the present invention, it is possible to easily obtain a molded article with a three-dimensional force, in which a fine uneven pattern is provided on the surface of the painted film. Also, the adhesion between the paint film and the base resin is very good. Furthermore, when transferring the pattern to the painted film, the painted film is press-molded at the mold temperature, resin temperature and resin pressure, so not only the fine irregularities on the mold surface can be transferred to the surface of the molded film with the painted film, but also with a gentle curved surface. If so, it is possible to form the painted film without the need to previously thermoform the painted film in a separate step. For example, when making a molded product with a moire effect, such as a concentric and radial minute marking pattern on the surface of a cosmetic compact case with a gentle convex surface, it seems that neither conventional painting nor hot stamping can be done. We believe that it is possible to easily obtain high-quality molded products with high added value, and their industrial value is incalculable.

Claims (2)

[Claims] 1. A painting method comprising mounting a painting film made of a thermoplastic resin, on which characters, figures, patterns, paintings, etc., are printed or drawn on the inner surface of the die, and injecting the thermoplastic resin into the die. In the molding method, a fine concavo-convex pattern for painting is provided on the inner surface of the die, and the die temperature of the painting film mounting surface is
A painting method comprising heating at a temperature not lower than the heat deformation temperature of the film. 2. The painting method according to claim 1, wherein the mold temperature is heated by high frequency induction heating.