JPS61188117A - In-mold printing - Google Patents

Abstract

PURPOSE:To enable to realize the in-mold printing of a deeply drawn-shaped product by a method wherein a process to slacken a transfer film in the cavity of a female mold in advance with no substantial elongation of the film. CONSTITUTION:Firstly, a cavity 11 is evacuated through a suction hole 12 provided in a female mold 1 in the order of vacuum, which causes no elongation of a transfer film 4. Secondary, the pressing force of a clamper 3 to the transfer film 4 is reduced so as to realize the slacken state of the transfer film in the cavity 11 of the female mold 1 with no substantial elongation of the film. Thirdly, the transfer film 4 is pressed and fixed again by the clamper 3. Fourthly, the film 4 is heated so as to evacuate the cavity 11 of the female mold 1 under the state that the transfer film is brought in softened state in order to turn the film into the same shape as the face constituting the cavity 11 of the female mold 1. Finally, the female mold 1 and a male mold 2 are clamped together in order for molten plastic 6 to pour through a gate 21 into the cavity, resulting in printing simultaneously with molding plastic.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is a method for forming plastic products, especially plastic products having a deep drawing shape, by injection molding and simultaneously printing pictures, letters, etc. on the surface of the product. Regarding printing methods.

[Conventional technology]

In recent years, in-mold printing technology, which uses a transfer film to print on the surface of a molded product at the same time as injection molding, has become a method that can meet needs such as adding multiple colors to the appearance of products, and can also shorten the process. This is a technology that is widely used in household products, home appliances, etc. However, most of the in-mold printing molding methods that are currently in practical use are applied to products with flat shapes. This is because when trying to apply in-mold printing technology to deep-drawn products, the film set on the mold mating surface of the mold is stretched significantly when the mold is closed, molded, and printed. This is because defects such as cracks and distortion may occur in the parts.

[Problem that the invention seeks to solve]

The present invention has been made in view of the above problems.
The purpose is to eliminate restrictions on the shape of products to which in-mold printing technology can be applied, and to provide an in-mold printing method that does not cause defects such as cracks and distortion in the printed part even for products with deep drawing shapes. be.

[Means for solving problems]

The in-mold printing method of the present invention consists of a male mold and a female mold that are clamped, and injects resin into a cavity equipped with a transfer film to print on the surface of the molded product at the same time as molding. In the printing method, before the resin is injected, the transfer film is held and fixed on the female mold cavity in a slidable state and a substantially uniform force is applied to the surface of the film to substantially deform the film. It is characterized by having a step of slackening in the direction of the cavity of the female mold without stretching the mold.

〔Example〕

FIGS. 1 to 4 are longitudinal sectional views of a luminescent mold showing the process of forming and printing a deep-drawn product by the in-mold printing method of the present invention. Detailed explanation of.

First, as shown in FIG. 1, a transfer film 4 is set on the mold matching surface of a female mold 1 for injection molding, and the film 4 is fixed by being pressed with a clamper 3. At this time, the transfer film 4 is such that its base film is in the cavity 11.
Attach the thermal transfer printing layer so that it faces the male mold 2. Next, reduce the pressure of the air in the cavity 11 through the suction hole 12 provided in the female mold 1 to the extent that the transfer film 4 does not stretch. do.

Next, the pressing force of the clamper 3 against the transfer film 4 is weakened. Since the pressure inside the cavity 11 is reduced,
By this operation, the transfer film 4 is allowed to slacken into the cavity li of the female mold 1 without being substantially stretched, as shown in FIG. That is, width L, depth H'
The film is drawn in the deep-drawn cavity of
(S<28) By making the film slack, the elongation rate of the film is reduced from 2H/L of conventional □ to 2H/t, +s.

So that the transfer film 4 is sagged in the cavity 11 of the female mold l in advance without using any means such as vacuum suction.
Setting the film 4 on the mold mating surface of the female mold 1 takes time and effort, and it is extremely easy to cause many wrinkles on the film 4. However, when the transfer film 4 is In the above-described method used by the present invention to create slack in the cavity 11 of the mold I, a uniform vacuum suction force is applied to the surface of the transfer male film 4 set in advance on the female mold l, so that the film 4 is Even if it sag, it is extremely unlikely to wrinkle, and it is easy to operate and requires no effort.

Next, the clamper 3 presses and fixes the transfer film 4 again, and the heater 5 heats the transfer film 4 within a range that does not impair its characteristics. The pressure inside the cavity 11 of the female mold 1 is reduced. By this operation, as shown in FIG. 3, the transfer film 4' is stretched and processed into the same shape as the surface constituting the female cavity 11.

The transfer film 4 processed in this way is as follows.

Since the film 4 is placed in the cavity 11 of the female mold 1 with a slack □ in advance, the elongation of the film 4 is smaller than the elongation of the transfer film when the transfer film □ without being slack is processed as it is by heating and vacuum forming. Therefore, after the product is completed, appearance defects such as cracks and distortions are unlikely to occur in the printed area.Moreover, the transfer film 4, which has been left sagging inside the female die cavity 11 as described above, has almost no wrinkles. Since it is not heated, it adheres neatly to the cavity forming surface of the female mold 1 by heating and reducing pressure. As a result, it is possible to mark the molded product neatly.

Next, as shown in FIG. 4, the female mold 1 and the male mold 2 are closed, and molten plastic 6 is injected into the cavity through the gate 21, thereby performing printing at the same time as molding the plastic.

In addition to the method using reduced pressure described above, it is also possible to make the transfer film slack in the female mold without elongating it by a method as shown in FIG.

That is, the transfer film 4 is placed on the female mold 1 by the clamper 3.
5. Then, when force is applied to the surface, the pressing force of the clamper 3 is reduced to such an extent that the film 4 can slide.
After that, move the pressing body 7 in the direction of arrow 8 to remove the film 4.
The film 4 can also be slackened by pressing it against the surface of the film. The pressing body 7 used has a surface shape that does not cause wrinkles in the film when it is pressed against the transfer film 4. Further, in order to avoid damaging the transfer film 4, the surface of the compressed body 7 is preferably a flexible and i-type body.

Even in the above method, the surface of the transfer film can be pressed with uniform pressure, so the film can be easily sagged into the cavity of the female mold without causing wrinkles.

〔Effect of the invention〕

As explained above, the in-mold printing method of the present invention, which employs the step of letting the film slack in the cavity of the female die in advance without substantially stretching the transfer film, allows the transfer film to be removed during molding and printing. It has become possible to reduce the elongation rate when elongating. Furthermore, it has become possible to neatly adhere the transfer film to the cavity-constituting surface of the female mold without causing wrinkles.

As a result, it has become possible to perform in-mold printing without causing defects such as cracks or distortion in the printed area, even for products with deep drawn shapes.

[Brief explanation of drawings]

Figures 1 to 4 are longitudinal cross-sectional views of a mold to show one implementation step of the in-mold printing method of the present invention, and Figure 5 shows a method of slackening the transfer film into the female mold using a pressing body. FIG. ■ = Female mold ll: Cavity 12 = Suction hole 2: Male mold 21: Gate 3: Clan/riichi 4: Transfer film 5: Heater 6: Molten plastic 7: Pressing body 8: Arrow indicating the direction in which the compression body is pressed Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (4)

[Claims] (1) In an in-mold printing method in which resin is injected into a cavity consisting of a clamped male mold and a female mold and equipped with a transfer film to print on the surface of the molded product at the same time as molding. Before injection of the resin, the transfer film is slidably held and fixed over the female mold cavity while applying a substantially uniform force to the surface of the film without substantially stretching the film. An in-mold printing method comprising the step of causing slack in the direction of a cavity of a female mold. (2) After pressing and fixing the transfer film on the mold matching surface of the female mold, the pressure inside the cavity of the female mold is reduced, and then the pressing force on the mold matching surface to the film is weakened to remove the film. The in-mold printing method according to claim 1, wherein a substantially uniform vacuum pressure is applied to the surface to cause the film to sag. (3) The in-mold printing method according to claim 1, wherein a pressing body is pressed against the transfer film in the direction of the female mold to apply a substantially uniform force to the surface of the film to cause the film to slacken. (4) The in-mold printing method according to claim 1, wherein after the transfer film is slackened toward the cavity of the female mold, the film is heated and the pressure inside the cavity is reduced.