JPH03156993A - Manufacture of circuit-patterned molding - Google Patents

Abstract

PURPOSE:To enable the use of adhesive which can secure a sufficient adhesion and show a high heat-resistance by preheating a transfer sheet before its supply into a die. CONSTITUTION:A heater 1 is set above a die 2 to allow a transfer sheet to pass through. The portion of a transfer sheet which is located in the heater 1 is designed for a next molding: this portion there undergoes the preheating of a circuit pattern (b). Next, molten resin 4 is ejected into the closed die 2 and undergoes the transfer molding of the preheated circuit pattern (a). After a molding 5 is peeled off from the base film 6 and the mold release layer 7, the transfer sheet moves in an arrow direction by operation of a take-up roller 3 with the result that the circuit pattern (b) and a circuit pattern (c) move into the die 2 and the heater 1, respectively. Since a transfer sheet is preheated in the heater 1 before feeding into the die 2, adhesive 9 softens and melts to become sticky. This method enables the use of adhesive which can secure a sufficient adhesion and show a high heat-resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present application relates to a method for manufacturing a thermoplastic resin injection molded article, and particularly to a method for manufacturing an injection molded article with a circuit.

<Prior Art> A method of manufacturing a printed wiring board by injection molding using a thermoplastic resin as a base material is conventionally known. Methods for forming circuits on these printed wiring boards include (a) electroless plating method (b) method using conductive paint (c) circuit formation using thermal transfer method (d) in-mold in-mold method using thermal transfer foil Circuit formation by JP-A-57
-7193), etc. have been attempted. However, each of these methods has its own problems; for example, with the electroless plating method, it is difficult to create a circuit with a film thickness of 18 to 35 mp;
Furthermore, the process is complicated, such as requiring various cleaning steps, and imaging technology for three-dimensional shapes has not been established. In the case of the method using conductive paint, the reliability of the formed circuit is
For example, there are problems with uniformity of resistance, circuit breakage when subjected to heating cycles, etc., and problems such as insufficient printing and difficulty in printing into three-dimensional shapes.

Circuit formation using the thermal transfer method generally uses a filler-containing conductor such as conductive paint as the transfer circuit material.
Similarly, there are problems with circuit reliability and transfer to three-dimensional shapes. Furthermore, since the above method is a method of forming a circuit after molding the molded body, the number of steps increases accordingly, resulting in high costs. On the other hand, the in-mold in-mold method using thermal transfer foil, which is a method of forming a circuit on the surface of a molded object at the same time as the molding in injection molding, is a method that forms a circuit at the same time as the molding, compared to the above-mentioned methods. Therefore, it is possible to obtain a molded body with a circuit based on the molding cycle of injection molding, so the process for forming a circuit on the base material can be omitted, and when the target is a mass-produced molded body, it is possible to obtain a molded body with a circuit. is a highly tailored manufacturing method. However, this method is also not suitable for actual production because circuit materials made of conductive paint tend to damage the circuit or cause poor adhesion. In addition, in the case of copper foil circuits, the circuit formation process can be easily carried out using a normal etching method, and the circuit reliability is sufficient, but there is a problem that the adhesive strength between the molded body and the copper foil circuit is weak. there were.

The applicant has proposed a method of preheating the mold temperature in order to improve the adhesion between the circuit conductor and the base resin. (Unexamined Japanese Patent Publication No. 1-108779) <Problems to be Solved by the Invention> However, it has been found that this method is severely limited by the base material and has the following problems. Namely, a) If the temperature inside the mold is too high, the molded product may warp, twist,
On the other hand, if the temperature is too low, the fluidity of the resin will deteriorate and molding defects will occur, causing defects such as flaking. Therefore, the mold temperature must be adjusted strictly within the molding conditions suitable for the base material, which is complicated.

b) If an adhesive with a high melting temperature is used on a base resin with a low molding temperature, sufficient adhesive strength will not be obtained.

The purpose of the present invention is to preheat the transfer sheet before feeding it into the mold to ensure sufficient adhesive strength and to enable the use of a highly heat-resistant adhesive. That is.

1 to 3 show embodiments of the method for manufacturing a molded article having a circuit according to the present invention. FIG. 1 shows the mold opened state before injection molding, FIG. 2 shows the mold closed state during injection molding, and FIG. 3 shows the mold opened state after injection molding is completed. Further, FIG. 4 shows an embodiment of the transfer sheet according to the present invention.

First, in the mold open state shown in FIG. 1, the temperature of the mold 2 is adjusted to meet the molding conditions as in the conventional method. As a preheating section for the transfer sheet, a heater 1 is installed above the mold so that the transfer sheet passes through it. The transfer sheet placed inside this heater is only for the next molding, and the circuit pattern b is sufficiently preheated here.

Next, as shown in FIG. 2, molten resin 4 is injected into the closed mold, and the preheated circuit pattern a is transfer-molded. FIG. 3 shows the state after completion of molding, where the molded product 5 is peeled off from the base film 6 and the mold release layer 7. Then, the transfer sheet is transferred to the film winding roller 3.
When activated, it moves in the direction of the arrow.

Along with this, the circuit pattern b moves into the mold, and the circuit pattern C moves into the heater section 1. Then, the process returns to the process shown in FIG. 1 again.

As a result, the adhesive 9 in the transfer sheet shown in FIG. 4 is always fed into the mold in a preheated state. By providing the heater part 1, the following characteristics can be obtained compared to the conventional preheating using only a mold.

a) Strong adhesion can be obtained even with adhesives having a high melting temperature.

b) The conductor portion can be preheated at any temperature without being limited to resin molding conditions.

The range of this heating temperature is preferably set to +10° C. to 70° C., which is the melting temperature of the adhesive used. The melting temperature of the adhesive is determined by placing an appropriate amount (about 1 to several grams) of the adhesive on a preheated hot plate, and checking whether it has melted using a Teflon rod while gradually raising the temperature. Note that the melting temperature refers to the temperature at which the material has a slight viscosity and becomes stringy.

Further, as a method for preheating the material before entering the mold, the following methods may be mentioned, but the method is of course not limited to these methods as long as the material can be heated to the target temperature.

1) Hot air method Attach a hot air circulation type heater to the top of the mold and heat the transfer sheet with hot air.

2) Heating Roller: Heat the transfer sheet by bringing the transfer sheet into close contact with the one-sided heating roller.

3) Radiant heat method Heating is performed using radiant heat from an infrared heater or a far-infrared heater.

Effect〉 Before the transfer sheet is sent into the mold, the conductor part is sufficiently preheated in the heater, so that the adhesive on the conductor part softens during molding and becomes molten and sticky, so that it adheres to the base material. Increases adhesion with.

<Example> The present invention will be explained below with reference to Examples.

First, ABS resin (Denka ABSGR
-2000) is used. The transfer sheet shown in FIG. 4 was prepared and molded under the conditions shown in each example, with an adhesive coating amount of 30 g/m 2 and a mold temperature of 60°C. As the adhesive, those listed in Table 1 were used.

Example 1 Injection molding was carried out using Adhesive A and setting the temperature of a part of the heater to 100°C. The results are shown in Table 2.

Example 2 Adhesive A was used, and the temperature of a part of the heater was set at 150° C., and injection molding was performed. The results are shown in Table 2.

Example 3 Adhesive B was used, and the temperature of a part of the heater was set at 200° C., and injection molding was performed. The results are shown in Table 2.

As a comparative example, a molding example will be shown in which adhesives A and B used in Examples were not preheated with a heater. The results are shown in Table 2.

Table 1 Table 2 3...Film winding roller, 4...Resin, 5...
... Molded product, 6... Base film, 7... Mold release, meter/copper foil, 9... Adhesive, a... Conductor part, b... Conductor part, C... Conductor Department.

Adhesive crab conforms to JIS C-6481.

<Effects of the Invention> Thus, according to the manufacturing method of the present invention, it is possible to manufacture a three-dimensional molded body with a circuit that has improved adhesion.

[Brief explanation of the drawing]

This figure schematically shows the process from when the transfer material is preheated by a portion of the heater until it is molded in a temperature-controlled mold. 1, 2, and 3 show the process until the molded product is completed, and FIG. 4 shows a part of the cross-sectional structure of the transfer sheet according to the present invention. The numbers in the drawings indicate parts, instruments, materials, etc. with the following names. 1... Heater part, 2... Mold,

Claims (1)

[Claims] (1) After preheating a transfer sheet with a metal foil circuit pattern coated with adhesive on a base sheet, insert it into an injection mold, and after closing the mold, injection mold the heated and melted thermoplastic resin. A method for producing a molded article with a circuit, characterized in that a circuit pattern is transferred onto the surface of the molded article at the same time as molding.