JPH049124B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a method of decorating a synthetic resin injection molded product using a transfer foil.

《Prior art》 Methods for decorating injection molded products with transfer foil include:
Conventionally, a sheet-shaped transfer foil is interposed between the dividing surfaces of a split mold for injection molding, and when a molten resin is injected into the cavity of the split mold to obtain a molded product, the transfer foil is attached to the molded product. A method for transferring is known. To explain this more specifically, in the conventionally known method, a decorative layer 4 is placed on a base layer 2 made of polyethylene terephthalate or the like through a release layer 3.
A split mold consisting of a cavity mold 6 in which a cavity 7 corresponding to a molded product is formed and a core mold 8, using a sheet-like transfer foil 1 (see Fig. 1) formed by laminating a, 4b and an adhesive layer 5. The mold is clamped with the transfer foil 1 interposed between the divided surfaces of the mold, and the molten thermoplastic resin 9 is injected into the cavity 7 (see Fig. 2).
As a result, the adhesive layer 5 of the transfer foil 1 is welded to the resin 9, and when the split mold is opened after the resin 9 has solidified, the release layer 3 is peeled off from the base layer 2 and the decorative layers 4a and 4b are transferred to the molded product. It's becoming like that.

<<Problems to be solved by the invention>> However, the release layer 3 and the decorative layers 4a, 4b
When peeled off together with the adhesive layer 5 from the sheet-like transfer foil 1 at the edge of the molded product, the release layer 3 and the decorative layers 4a, 4b are not necessarily cut in a straight line along the edge of the molded product. First, it has been pointed out that many burrs are produced, resulting in a poor finish, and that complicated secondary processing is required to remove the burrs.

<<Object of the Invention>> The present invention was made in view of the above-mentioned circumstances, and its purpose is to provide a method for decorating an injection molded product by which transfer foil can be transferred to the molded product with almost no burrs. It's about doing.

<Means for Achieving the Object> In order to achieve this object, the present invention provides decoration for injection molded products using a sheet-like transfer foil formed by sequentially laminating a decorative layer and an adhesive layer on a base layer via a release layer. The method comprises: between one split mold in which a cavity corresponding to the injection molded product is formed and the other split mold in which a recess having a depth of 200 to 300 μm is formed opposite to the cavity. Injecting heated molten resin having a welding property with the adhesive layer into the cavity with the transfer foil interposed, and bending the transfer foil along the recessed part by the injection pressure and heat. Cracks are generated in the release layer, decorative layer, and adhesive layer of the transfer foil except for the base layer near the edge of the transfer foil, and the molten resin and the adhesive layer of the transfer foil are bonded, and the molten resin is solidified. After the injection molded product is formed, the split mold is divided, and when the injection molded product is taken out from the split mold, the release layer, decorative layer, and adhesive layer of the transfer foil are cut by a crack. It is characterized by peeling off from the base layer.

<<Examples>> Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The transfer foil used to decorate the molded product in the present invention is similar to that used in the conventional method described above, and is applied to the decorative layers 4a, 4b and the adhesive layer on the base layer 2 made of polyethylene terephthalate or the like through the release layer 3. It has a sheet-like structure in which layers 5 are laminated in order, and the decorative layers 4a and 4b are printed on the release layer 3 with ink colored in different colors, and the adhesive layer 5 is formed by printing on the release layer 3 with ink colored in different colors. It is made of resin that has weldability.

As shown in FIG. 3, the split mold 10 consists of an upper cavity mold 11 and a lower core mold 12. A runner 14 is formed which is open inward and whose other end is connected to an injection molding machine (not shown). Also, core type 1
A recess 15 having a shape that matches the cavity 13 is formed on the upper surface of 2, and this recess 15 has a diameter of about 20 to
It is formed to have a depth of 300μ.

Then, the two-piece mold 1 configured in this way
0 dividing plane, that is, cavity mold 11 and core mold 12
Split mold 1 with transfer foil 1 interposed on the joint surface with
0 is clamped and the molten thermoplastic resin 16 is injected into the cavity 13 from the runner 14.
The resin 16 is filled into the cavity 13, and the loosely stretched transfer foil 1 is pressed into the recess 15 of the core mold 12 by its heat and injection pressure. At this time, since the resin 16 has a weldability to the adhesive layer 5, it is adhered to the adhesive layer 5. This state is shown in FIG. 4, where the transfer foil 1 is gradually pressed from the lower surface of the center to the bottom surface of the recess 15, and when the filling of the resin 16 is finally completed, the transfer foil 1 is The foil 1 is bent along the bottom and inner surfaces of the recess 15 except for the lower corner of the recess 15 (see FIG. 5).

The transfer foil 1 is bent into a curved cross-section without coming into contact with the lower end corner of the recess 15. This is transfer foil 1
This is due to its own rigidity, and also due to the repulsive force generated when the air existing in the recess 15 is compressed during the filling process with the resin 16, and this compressed air concentrates near the lower corner of the recess 15. It's for that reason. Since the air in the recess 15 is concentrated near the lower corner of the recess 15 in this way, the air does not remain scattered on the bottom surface of the recess 15 during the filling process with the resin 16, so that the decorative surface of the molded product can be smoothed. Not only can the molded product have a smooth finish, but the corners of the molded product are curved, giving it a smooth feel.

Note that at the upper end corner of the recess 15, that is, at the edge of the recess 15, the repulsive force of the compressed air does not occur and the rigidity of the transfer foil 1 acts in the opposite direction. is bent at right angles along this edge.

As described above, since the transfer foil 1 is bent into a curved shape without contacting the lower end corner of the recess 15, the transfer foil 1 includes the release layer 3 excluding the base layer 2 having relatively high bending strength, the decorative layer 4a, 4b and the adhesive layer 5 create a crack 17 at its right angle bend. In this case, since the depth of the recess 15 is approximately 200 to 300 μm, although a crack is formed at the bent portion of the transfer foil 1, the transfer foil 1 is not cut.

Therefore, when the split mold 10 is opened and the molded product is taken out after the resin 16 is cooled and solidified, the peeling layer 3 of the transfer foil 1, the decorative layers 4a and 4b, and the adhesive layer 5 are cut by the cracks 17 and The peeling layer 3 and the decorative layers 4a and 4b are peeled off from the base layer 2, and the adhesive layer 5
The image is transferred to the molded product through the . Since the end of the adhesive layer 5 is welded to the resin 16, it is cut along the end surface of the molded product, as shown in FIG. After the molding of the molded product and the decoration with the transfer foil 1 are completed in this way, the sheet-like transfer foil 1 is pulled off by a certain amount, for example, toward the right in the figure, and the split mold 10 is again clamped and the same procedure as above is performed. By going through the steps, a desired molded product is formed one after another.

In the molded article 20 molded and decorated by the above method, the peeling layer 3 and the decorative layers 4a, 4b are cut along the cracks 17 and transferred, as shown in FIG. Almost finished product 20
It is provided along the end face of the steel sheet, and an extremely good finish can be obtained with almost no burrs. Therefore, secondary processing for removing burrs, which has been required in the past, is unnecessary or requires only a very small amount of work, and efficiency is greatly improved. In addition, this molded product 20 has a smooth decorative surface and has good molding quality, and the lower corner has a curved shape, so a smooth feel can be obtained. Furthermore, in the present invention, a transfer foil 1 similar to that conventionally used is used.
Moreover, since the cavity mold 11 of the split mold does not require any changes, the molding cost does not increase, but rather the cost can be reduced due to the simplification of the work.

<<Effects of the Invention>> As described above, in the method for decorating injection molded products using the transfer foil according to the present invention, the decorative layer is transferred with almost no burrs, and therefore the finishing work is extremely simplified and efficiently carried out. When the transfer foil is bent, the air in the recesses concentrates at the corners and does not remain in the center, so the decorative surface can be finished smoothly, and the corners can be curved. It has excellent effects such as being able to provide a smooth feel.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of a transfer foil used in the present invention, FIG. 2 is a cross-sectional view illustrating a conventional method of decorating an injection molded product using the transfer foil, and FIG.
The figure is a cross-sectional view showing an example of a mold used in the present invention, Figures 4 and 5 are enlarged cross-sectional views for explaining the method according to the present invention, and Figure 6 is an injection mold according to an embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view of the main part of the molded product. DESCRIPTION OF SYMBOLS 1... Sheet-like transfer foil, 2... Base layer, 3... Peeling layer, 4a, 4b... Decorative layer, 5... Adhesive layer, 1
0...Split mold, 11...Cavity mold, 12...Core mold, 13...Cavity, 15...Concavity, 16
...Resin, 17...Crack, 20...Molded product.

Claims (1)

[Scope of Claims] 1. A method for decorating an injection molded product using a sheet-like transfer foil formed by sequentially laminating a decorative layer and an adhesive layer on a base layer via a release layer, which corresponds to the injection molded product described above. One split mold in which a cavity is formed, and one part facing the cavity.
The transfer foil is interposed between the mold and the other split mold in which a recessed portion having a depth of 200 to 300 μm is formed, and heated molten resin having weldability with the adhesive layer is injected into the cavity; The injection pressure and heat bend the transfer foil along the recess, causing cracks in the release layer, decorative layer, and adhesive layer of the transfer foil excluding the base layer near the edge of the recess. ,
After the molten resin and the adhesive layer of the transfer foil are bonded together and the molten resin is solidified to form an injection molded product,
When the split mold is divided and the injection molded product is taken out from the split mold, the release layer, decorative layer, and adhesive layer of the transfer foil are cut from the crack and peeled from the base layer of the transfer foil. A method of decorating injection molded products using transfer foil.