JPH071824B2 - Method for producing molded article having printed circuit and transfer sheet used in the production - Google Patents

Description

Detailed Description of the Invention

 Purpose of the invention

[Industrial applications]

The present invention relates to a method for producing a molded article having a printed circuit having a three-dimensional shape and high heat resistance and high reliability on the surface, and also includes a transfer sheet used for the production.

[Prior art]

There are cases where it is desired to form an electric or electronic circuit (hereinafter simply referred to as “circuit”) on the surface of a synthetic resin molded product. As a method of forming a circuit, a so-called printed circuit board manufacturing method has been widely practiced in which etching is performed by leaving a necessary portion of a copper foil attached to a board. This is a wet process and has the problem of taking time,
It is difficult to apply to bulky molded products. In place of etching, there is a method of forming a circuit by printing a conductive paste by a method such as screen printing, which is used for manufacturing a membrane switch or the like. Although this technique can be applied to a molded product, it can be printed only on a flat surface and is difficult to implement depending on the shape. Furthermore, there is the troublesomeness of requiring a drying step after printing. If a circuit is used to transfer the circuit to a molded product using a transfer sheet that has been printed on the base material film in advance, it can be applied to three-dimensional shapes such as boxes, and it can be used for curved surfaces. Is not impossible. However, this method consists of two steps, the molding of the molded product and the transfer of the circuit, and especially when trying to transfer to a curved surface, in addition to the molding die, a transfer die is used. is necessary. The present inventor has invented a method for producing a molded article having a printed circuit for solving the above problems and has already proposed it (Japanese Patent Application No. 60-140791). The invention is to place a transfer sheet on which a circuit is printed with a conductive ink on a substrate film in an injection molding die, and inject a molten synthetic resin into the die to obtain a molded product and at the same time to obtain a molded product on the surface. It is characterized by forming a circuit. As a result, a desired circuit can be formed on the surface of a three-dimensionally shaped synthetic resin molded product regardless of whether it is a flat surface or a curved surface, and it is carried out with simple equipment and processes. A method was provided. It is desirable to use solder when connecting circuit elements, electronic components, or other printed circuits to this printed circuit. The one in which a circuit is formed by directly printing a curable conductive ink on a mere flat injection molded product can withstand the use of solder, but it is difficult to apply this technique to a curved injection molded product. Even with the technique using a transfer sheet, the one obtained by printing a circuit with a curable conductive ink and curing it is still limited in the production of a molded article having a curved surface. Further, it is required that the printed circuit is completely bonded and integrated with the molded product to maintain high reliability of the circuit itself. Solving these problems was the next task.

[Problems to be Solved by the Invention]

The object of the present invention is to improve the heat resistance of a desired three-dimensional shape on the surface of a three-dimensionally shaped synthetic resin molded product, regardless of whether it is formed by the intersection of flat surfaces or a curved surface. An object of the present invention is to provide a method capable of forming a circuit having high reliability and reliability and performing the circuit with simple equipment and steps. The provision of the transfer sheet used for carrying out the above-mentioned manufacturing method is also included in the object of the present invention. Structure of the invention

[Means for solving problems]

As shown in FIG. 1, the method for producing a molded article having a printed circuit according to the present invention prints a circuit on the releasable surface of a releasable sheet 11 with a conductive ink containing a curable synthetic resin as a main component of a binder. Then, the transfer sheet 1 having the uncured printed circuit 12 is preformed as shown in FIG. 2, and the obtained transfer sheet preform is injection-molded with a die 21 as shown in FIG.
And 22 to perform injection molding of a molten synthetic resin to obtain a molded article 3 having a printed circuit on the surface, and to cure the conductive ink of the printed circuit to cure the printed circuit having a three-dimensional shape on the surface. 12B is formed to obtain a product as illustrated in FIG. As shown in FIG. 1, the transfer sheet 1 of the present invention is formed by printing a circuit on the releasable surface of the releasable sheet 11 with a conductive ink containing a curable synthetic resin as a main component of a binder. It is used to manufacture a molded product having a printed circuit 12A. The basic constitution of the transfer sheet is that the printed circuit is on the peelable surface of the peelable sheet, but if necessary, a peeling layer and a protective layer may be provided between the peelable sheet and the circuit, and then the printed circuit may be bonded. An agent layer is provided. The material of the peelable sheet is polyvinyl chloride, polyamide,
Polyvinylidene chloride, polypropylene, polyurethane,
A single or laminated film of a plastic film such as polycarbonate, polystyrene, polysulfone, polyarylate, and polyethersulfone having relatively high heat resistance and good moldability is preferable. Polyester can be used as long as it has a small aperture. As the peelable sheet, the one whose surface is peelable is
Alternatively, a non-peeling sheet provided with a peeling layer is used. The material of the release layer is preferably a thermoplastic resin such as polyvinyl chloride, acrylic, polyamide, nitrocellulose, polyurethane, polyvinyl acetate, or a thermosetting resin such as melamine, phenol or polyurethane. To form the release layer, a roll coating method, a gravure printing method, a silk screen printing method or any other method may be used. The release layer includes a type that remains on the release sheet side after transfer and a type that moves to the printed circuit side, and is selected according to the application of the molded product. If it is transferred to the printed circuit side, it can also serve as a protective layer of the circuit. If necessary, do not print the release layer on the parts where the terminals and parts are mounted. To form an uncured printed circuit, print a conductive ink containing a curable synthetic resin as the main component of the binder on the peelable sheet or peeling layer by a method such as screen printing, gravure printing or offset printing. By. The printed resistor and the protective layer may be formed simultaneously with the formation of the printed circuit. The conductive ink is prepared by kneading powder of metal such as Au, Pb, Ag, Ni, Cu or powder of C with a binder. The binder is mainly composed of curable synthetic resin,
Thermosetting resin such as epoxy resin, phenol resin, unsaturated polyester resin, ultraviolet curing resin such as acrylic resin, acrylic modified resin, polyester resin, ethylene vinyl acetate copolymer, unsaturated polyester resin, acrylic resin Appropriate ones are selected and used from resins, acrylic modified resins, electron beam curable resins such as copolymers of ethylene and acrylic acid or its esters. The term "uncured" here means that the curing is not completed. When the thermosetting resin is used as the main component of the binder, the formation of the cured printed circuit, that is, the curing of the conductive ink of the printed circuit, is performed simultaneously with the injection molding by utilizing the heat given by the molten resin during the injection molding. If the curing is not sufficient with only the heat at the time of injection molding, it may be reheated after that. Needless to say, when an ultraviolet curable resin or an electron beam curable resin is used, it should be cured by irradiating it with ultraviolet rays or an electron beam after injection molding. The peeling of the peelable sheet may be performed after the curing of the conductive ink is completed or before the curing is completed. When it is desired to ensure the adhesion between the printed circuit and the molded product, an adhesive layer may be provided on the printed circuit. This increases the degree of freedom in combining the conductive ink and the molding resin. As the material for the molded product, any thermosetting resin that can be injection-molded and a thermoplastic resin having good heat resistance, such as polysulfone, polyether sulfone, polyphenyl sulfone, fluororesin, polyphenylene sulfide, polyamide imide, polyether imide, etc. You can use the one selected from. The pre-molding of the transfer sheet is carried out by a molding method selected from vacuum molding, pressure molding, vacuum pressure molding and matched die molding. If an injection mold is used as a vacuum and / or compressed air mold, the equipment is simplified. Placing a preformed body of a transfer sheet in an injection molding die and performing injection molding is known as so-called "painting molding", and the present invention may be carried out according to the technique.

[Action]

According to the manufacturing method using the transfer sheet of the present invention, molding of a synthetic resin molded product and printing of a circuit can be performed in one step, and a three-dimensional circuit can be formed on any surface of a molded product of any three-dimensional shape. A product with is obtained. Since the printed circuit of the obtained product is formed of a conductive ink containing a hardened synthetic resin as a main component of a binder, it has good heat resistance and can be conveniently connected by soldering. In addition, the curing of the conductive ink in the printed circuit occurs at the same time as or after injection molding, and since the curing is not completed until injection molding, the printed circuit has excellent ductility, and it can be used during preforming and injection molding. It does not crack and impair conductivity. Therefore, a highly reliable printed circuit can be formed. There is also a method in which the transfer sheet is placed in an injection molding die without being preformed and a three-dimensional shape is produced by the heat and pressure of the injection resin, but there are the following limitations. * Since the transfer sheet is stretched without giving sufficient heat, it is difficult to maintain the conductivity and stability of the printed circuit. * Because uniform heat cannot be applied, pattern reproducibility is low and it is not suitable for producing complicated shapes. Therefore, preforming of the transfer sheet is indispensable for forming a printed circuit having high performance as an electric circuit and high reliability on the surface of a molded product having a complicated three-dimensional shape.

Example 1 On a 100 μm thick polycarbonate film having a release layer formed by coating a nitrocellulose-based resin, Ag
The conductive ink obtained by kneading the powder of 1. with a binder containing a thermosetting epoxy resin as a main component was silk-screen printed. A transfer sheet having a hardened printed circuit was prepared by drying at a temperature of 80 ° C. for 3 minutes. This transfer sheet was heated on a hot platen at a temperature of 170 ° C. and preformed by vacuum pressure forming. The preform was placed in an injection molding die at a temperature of 120 ° C., and the glass fiber reinforced polyetherimide was injection molded at a resin temperature of 400 ° C. This was taken out of the mold, and after peeling off the peelable sheet, it was heated at a temperature of 120 ° C. for 20 minutes to obtain a molded article having a three-dimensional cured printed circuit on the surface. On the surface of the molded product, the three-dimensional circuit was firmly formed at a predetermined position. This circuit had good solderability.

Example 2 The same procedure as in Example 1 was performed except that a binder containing an ultraviolet-curable acrylic modified resin as a main component was used as the conductive ink and the heating after the peeling of the peelable sheet was replaced with the irradiation of ultraviolet rays. However, the circuit of the obtained molded product had good performance as in the case of Example 1.

[Example 3] The same as Example 1 except that a binder containing an electron beam-curable acrylic modified resin as a main component was used as the conductive ink and the heating after peeling the peelable sheet was replaced with electron beam irradiation. As a result, the circuit of the obtained molded product had good performance as in the case of Example 1. Effects of the Invention According to the manufacturing method using the transfer sheet of the present invention, it is possible to manufacture a molded article having a printed circuit with high heat resistance and high reliability.
The process can be simplified and easy to automate. There is no restriction on the shape of the molded product or on the surface on which the printed circuit is provided. When a printed circuit is formed in a three-dimensional shape including a curved surface, a pressing die for transfer is not necessary, and the product cost is low. Moreover, this method itself is a dry process, and the wet process is only performed in the manufacturing process of the transfer sheet, and it is easy to maintain a good working environment.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the basic structure of a transfer sheet used for producing the molded article of the present invention. 2 and 3 are cross-sectional views for explaining the manufacturing process of the present invention. FIG. 2 shows the transfer sheet preformed, and FIG. 3 shows the transfer sheet preformed body by injection molding. The parts placed in the mold are shown. FIG. 4 is a cross-sectional view of a molded product having a printed circuit manufactured by the method of FIGS. 2 and 3. 1 ... Transfer sheet 11 ... Peeling sheet 12A ... Uncured printed circuit 12B ... Cured printed circuit 21,22 ... Injection mold 3 ... Molded product with printed circuit

Claims (5)

[Claims] 1. A circuit is printed on the releasable surface of a releasable sheet with a conductive ink containing a curable synthetic resin as a main component of a binder, and a transfer sheet having this uncured printed circuit is preformed and obtained. The transfer sheet preform is placed in the injection mold and injection molding of the molten synthetic resin is performed to obtain a molded product with a printed circuit on the surface. A method for producing a molded article having a printed circuit, comprising forming a cured printed circuit having a three-dimensional shape on the substrate. 2. The method according to claim 1, wherein the conductive ink of the printed circuit is cured simultaneously with injection molding. 3. The method according to claim 1, wherein the conductive ink of the printed circuit is cured after injection molding. 4. The method according to claim 1, wherein the transfer sheet is preformed by a forming method selected from vacuum forming, pressure forming, vacuum pressure forming and matched die forming. 5. A molded article having a printed circuit having an uncured printed circuit, which is obtained by printing a circuit on a peelable surface of a peelable sheet with a conductive ink containing a curable synthetic resin as a main component of a binder. Transfer sheet used in the manufacture of.