JPS62291991A - Circuit transcription foil for injection molding and method of forming circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a circuit transfer foil for injection molding and a circuit transfer method, and more particularly to a circuit transfer foil for injection molding that can transfer a circuit at the same time as molding an object to be transferred by injection molding. The present invention relates to a circuit forming method in which a circuit can be formed at the same time as a transfer target is formed using the circuit transfer foil.

[Technical background of the invention]

Conventionally, as a method for transferring electrical circuits such as wiring boards, a conductive thin film is formed over the entire surface of a support film, laminated onto the object to be transferred, and heat is applied to heat and press only the circuit portion (transfer portion). A method of forming a circuit by transferring only the circuit portion onto an object using a board (Japanese Unexamined Patent Application Publication No. 1983-1999)
No. 141789) is known.

According to such a circuit transfer method, (1) a heating plate that can heat and press only a predetermined portion is required, and the person performing the circuit transfer must purchase said heating plate; (2) the conductive thin film other than the transferred portion is Since the material will be discarded, the material will be wasted and the cost will be high. ■Because the circuit pattern is transferred by heating and pressurizing only the predetermined area using the heating plate, the conductive thin film has a good cut. There were disadvantages such as the need to be present.

This breakage of the conductive thin film tends to worsen as the thickness of the thin film increases, so it is not possible to make the conductive thin film thicker. If the amount of particles is increased, the adhesion of the conductive thin film will deteriorate and it will tend to become brittle, making it difficult to manufacture circuits with good conductivity and adhesive strength. It was happening.

In order to eliminate such drawbacks, the present inventor applied conductive paint onto a support film by screen printing, gravure printing,
We have developed a circuit transfer foil and a circuit transfer method that can transfer a circuit with good conductivity by printing a circuit pattern in advance using offset printing or pad printing and transferring this circuit pattern to a transfer target, and have filed a patent application. (Japanese Patent Application No. 117264/1984, etc.)

According to this method, it is possible to easily transfer a circuit that has better conductivity compared to an electric circuit that uses a conventional conductive coating film as a conductive part without requiring special equipment. There is an advantage to having one. However, in order to transfer a circuit to a previously formed transfer object, there is a drawback that two steps are required: a step of molding the transfer object and a circuit transfer step.

[Summary of the invention]

The present invention has been made in view of the above points, and it is possible to form a circuit at the same time as forming a transferred object without requiring special or expensive equipment or increasing costs due to wasted materials. The purpose of the present invention is to provide a circuit transfer foil and a circuit forming method that can be used.

Therefore, the circuit transfer foil for injection molding according to the present invention is a conductive paint that is basically made by adding 300 to 1,000 parts by weight of conductive particles to 100 parts by weight of resin on a support film, and then heating the support film with the conductive paint. It is characterized by having a printed circuit pattern that shows easy peelability immediately after pressurization.

Further, in the circuit forming method according to the present invention, 300 to 1000 parts of conductive particles are added to 100 parts by weight of resin on the support film.
The inner wall of a mold for injection molding a transfer target with a circuit transfer foil printed with a circuit pattern that is easily peelable immediately after heating and pressurizing the supporting film using a conductive paint that is basically made by adding parts by weight. Place the support film in contact with the
The method is characterized in that a molten resin is press-fitted into the mold to form a transfer object, and then the support film is peeled off, thereby molding the transfer object and simultaneously transferring the circuit.

The circuit transfer foil for injection molding according to the present invention has the advantage that a circuit can be formed on the transfer target at the same time as the transfer target is injection molded. In addition, in the circuit forming method according to the present invention, a circuit transfer foil is used in which a circuit pattern is formed on a support film using a conductive paint using a printing method such as screen printing or gravure printing, and a transfer target is formed by injection molding. This has the advantage that circuits can be transferred and formed at the same time as molding.

[Detailed description of the invention]

As shown in FIG. 1, the circuit transfer foil according to the present invention is produced by printing a desired circuit pattern on a support film L and a conductive paint that exhibits easy peelability immediately after heating and pressing. 2.

The support film 1 on which the circuit pattern 2 is formed by conductive paint is not fundamentally limited in the present invention, and has good adhesion to the circuit pattern 2 at room temperature and is easily bonded to the circuit pattern 2 immediately after heating and pressing. It is necessary that the substrate be peelable from the circuit pattern 2.

Furthermore, it is possible to effectively use a synthetic resin film that has heat resistance to the extent that it does not soften or deteriorate at the temperature during injection molding, is smooth, and is not immersed in the solvent contained in conductive paint. can. The support film 1
Specific examples include plastic films such as polyester film, polyimide film, and polypropylene film, and aluminum foil.

The conductive paint used to print the desired circuit pattern 2 on the support film 1 described above must be capable of printing a good and fine circuit pattern on the support film 1, and must also have basic performance as a transfer foil, such as It is necessary that various conditions such as good peeling from the support film 1 immediately after heating and pressurization are satisfied. In addition, in the present invention, since the circuit pattern 2 is transferred at the same time as the injection molding, the rigidity and circuit pattern on the support film 1 are made such that the pattern on the support film 1 does not collapse under the pressure and temperature conditions during injection molding. Adhesion strength between the support film 1 and the pattern 2 must be such that the pattern 2 does not flow, and furthermore, the support film 1 must be easily peelable immediately after injection molding.

In order to satisfy these conditions, the support film, the resin liquid (solvent and solute) that is the base material of the conductive paint,
Furthermore, it is important to select the type of conductive particles to be added to this resin liquid, and it is also necessary to consider the amount and particle size of the conductive particles. The resin that serves as the base material for such a conductive paint should be one that has adhesive properties with the support film 1 at room temperature, can form an easily peelable circuit pattern immediately after heating and pressurizing, and is softened by the temperature during injection molding. Alternatively, one or more resins that do not deteriorate (e.g., acrylic, polyamide, epoxy, polyether, polyester resins, etc.) or one or more of cyclized rubber, chlorinated rubber, rosin, etc., such as MEK, M
Ketone solvents such as IBK and cyclohexanone, aromatic hydrocarbon solvents such as toluene and xylene, alcohol solvents such as rPA and butanol, ether solvents, ester solvents, and other solvents such as MF and N-methylpyrrolidone. It can be a resin solution in which one or more of the following are dissolved.

The conductive particles added to the resin solution are not fundamentally limited in the present invention as long as they can be uniformly dispersed in the resin solution and impart good conductivity.

For example, gold, silver, platinum, copper, nickel, aluminum,
It can be one or more of metal particles such as tin and zinc, composites and alloy powders whose surfaces are coated with the above-mentioned metals, and carbon particles.

A circuit that maintains rigidity and peel strength such that the pattern on the support film 1 does not collapse or flow under the pressure and temperature conditions during injection molding, and that allows the support film 1 to be easily peeled off after injection molding. It has been found that forming Pattern 2 depends particularly on the amount of the conductive particles added and the particle size.

That is, if the amount of conductive particles contained in the conductive paint is too large, the rigidity of the circuit pattern 2 formed on the support film 1 will improve; If the amount of conductive particles is too small, sufficient conductivity for an electric circuit may not be ensured. At the same time, the adhesion strength to the support film 1 becomes too large, making it difficult to peel off the support film 1 after transferring the circuit. Furthermore, since the rigidity of the circuit pattern 2 formed on the support film I is reduced, there is a possibility that the mold surface may warp due to the pressure of the molten resin during injection molding.

Therefore, it becomes necessary to add controlled amounts of the above-mentioned conductive particles. In the present invention, the conductive particles are added in an amount of 300 to 1000 parts by weight per 100 parts by weight of the resin. If it is less than 300 parts by weight, the adhesion strength of the circuit pattern 2 to the support film becomes too large, making it difficult to separate from the support film, and the rigidity is insufficient.
There is a risk that the circuit pattern 2 will collapse during injection molding, and on the other hand,
If it exceeds 1,000 parts by weight, the adhesion to the support film 1 will be insufficient and the circuit pattern 2 may become too brittle.

The particle size of the conductive particles is an important factor in the circuit transfer foil for injection molding according to the present invention, in which the circuit pattern 2 is transferred simultaneously with the molding of the object to be transferred by injection molding as described above.

It has been found that a circuit with good conductivity can be transferred by mixing and adding conductive particles having a relatively large particle size and conductive particles having a smaller particle size than the conductive particles. The reason for this is not necessarily clear, but it is thought to be due to the following reasons. That is, due to the pressure of the molten resin during injection molding, the support film 1
The upper circuit pattern 2 is under pressure load, and the circuit pattern 2
The density per unit volume of the conductive particles contained within increases, but in this case, by combining two or more types of particles with particle sizes within a certain range according to the close-packing theory,
By lowering the porosity and adding injection pressure, the filling rate per unit volume increases. Therefore, it is thought that the number of contact points will also be increased (a circuit formed by transferring the circuit pattern 2 formed by the conductive paint of the same composition onto a pre-formed transfer object, rather than by injection molding). (This makes it possible to obtain a resistance value that is approximately A times as large as

Therefore, it is preferable to add conductive particles of at least two different particle sizes to the conductive paint according to the invention. In this case, the size of the particle size is determined by the relative size of two or more types of particles to determine the combination having the optimum particle size. The particle size of the large conductive particles is preferably 10 to 2 μm.

If it exceeds 10 μm, it becomes difficult to form the circuit board 2 on the support film 1 by printing means such as screen printing, while if it is less than 2 μm, the effect of mixing with relatively small-sized conductive particles becomes difficult. becomes smaller.

The particle diameter of the conductive particles having smaller dimensions than the above-mentioned large conductive particles is preferably 4 μm or less. This is because if it exceeds 4 μm, there is no point in dividing the particle size of the conductive particles into two or more types, and no improvement in conductivity can be expected.

Further, the weight mixing ratio of such large-sized conductive particles and small-sized conductive particles is preferably from 9515 to 515.
It is good to be. This is because if the mixing ratio deviates from this, there is a possibility that the meaning of mixing the two types will be lost.

Other additives such as antioxidants, dispersants, etc. can be optionally added to the conductive paint.

Although the circuit pattern 2 is printed on the support film 1 using such a conductive paint, this printing method is not limited in the present invention. For example, it can be effectively printed using known printing methods such as screen printing and gravure printing.

This conductive paint is preferably applied to the support film 1 by:
It is preferable to print to a thickness of 15 to 40 microns.

If the thickness of the conductive paint is less than 15 μm, good conductivity cannot be obtained, while if it exceeds 40 μm, printing a circuit pattern by screen printing or the like may become difficult.

Naturally, it is preferable that the line width of the circuit pattern 2 or the distance between the lines be tight. In the circuit transfer foil used in the present invention, in order to make it possible to form a circuit with the above-mentioned line width or line distance of 1 mm or less, the viscosity of the conductive paint to be printed is set to 10 to 1000 voids, most preferably 10 to 40 voids.
It is preferable to adjust to 0 poise. If the viscosity of the conductive paint is less than 10 poise, there is a risk that the wires will be distorted and the circuit will be shorted, whereas if it exceeds 1000 poise, it will be difficult to print the circuit pattern on the support film 1. be.

According to the circuit forming method of the present invention, the circuit transfer foil 3 described above is placed in one of the molds 4a of the injection mold 4 for producing the transferred object.
Then, the support film 1 is placed so as to be in contact with the inner wall of the mold 4a, the mold 4b is placed over the mold 4a, and the molten resin 6 is injected from the resin injection port 5 to cover the transfer target. This allows the circuit to be transferred at the same time as manufacturing. and,
By peeling off the support film 1 of the circuit transfer foil 3, it is possible to form a circuit buried in the transfer object at the same time as molding the transfer object.

In the method of forming a circuit simultaneously with injection molding as described above, the pressure and temperature within the injection mold 4 are especially important. That is, if the pressure inside the mold is small, the circuit pattern 2 of the circuit transfer foil 3 may not be transferred well, and a portion of the circuit pattern 2 may remain on the support film 1 when the support film 1 is peeled off. Furthermore, when the pressure inside the mold is high, there is a risk that the drawn circuit will not collapse.

Furthermore, if the temperature of the injected resin is too high, there is a risk that the conductive paint portion or support film portion may be damaged.

Among the above-mentioned injection conditions, the pressure within the mold is particularly important.

It has been found that a good pressure in the mold as described above is preferably 200-1000 Kg/cI11, taking into account the above. The pressure inside the mold is as follows: mold 4
It can be controlled by the viscosity of the molten resin injected into the molten resin and the injection pressure.

If the viscosity of the molten resin is too high, non-uniform pressure will be applied to the circuit transfer foil 3, which may cause parts with a small pressure load to remain on the support film 1, and the injection pressure will also increase.
There is also a risk of damaging the circuit.

If the viscosity is too low, the applied pressure will be relatively small, making it difficult to transfer the circuit on the circuit transfer foil 3.

Taking this into consideration, the viscosity of the resin used to manufacture the transfer object when injected into the injection mold 4 is preferably 103 to 105 voids. The above viscosity is 1
If it is less than 0.03 poise, the pressure load on the circuit transfer foil 3 will be small, and there is a risk that good transfer will not be performed.
If the pressure exceeds 0'' poise, the pressure load may become non-uniform and there is a possibility that some parts have good transfer and some parts have bad transfer.

The viscosity of the resin as described above changes depending on the temperature of the molten resin, but this temperature must not be such as to damage the conductive paint portion or the support film portion as described above. Therefore, it is desirable that the temperature at the time of injection of the resin having the above viscosity range is 400° C. or less.

In addition, the injection pressure of the above molten resin is 400 to 2300 kg.
/ci is better. If the injection pressure of resin in the above viscosity range exceeds 2300 Kg/IJl, the pressure inside the mold will become too large and there is a risk of damaging the circuit.
This is because if it is lower than 0.00 kg/cal, there is a possibility that the circuit transfer will not be performed well.

For example, AB is a resin that satisfies these conditions.
S, polyacecool, polysulfan, PP01 modified PPO, polycarbonate, polycarbonate, old SP
, PP, PMMA, etc. can be mentioned as examples.

Example A conductive paint (with the following composition) was applied on the polyester film.
A circuit pattern was printed with a line width of 0.8 mm, a line-to-line path Fa of 0.8 ms, and a thickness of 25 μm.

Composition 1 Thermoplastic polyester resin 100 parts by weight Aromatic solvent 120 parts by weight Silver-coated copper particles (particle size 8 μm) 480 parts by weight Silver-coated copper particles (particle size 2 μm) 320 parts by weight This circuit transfer foil was covered with the support film. A[lS resin (viscosity 4 x 1
Injection conditions: Injection temperature 220~2
40"c, injection pressure (gauge pressure') 800 Kg/c
d, back pressure 5Kg/ci, screw rotation speed 5Or, p,
m, ), the transfer target was molded.

Next, by peeling off the support film, lines with a line width of 0.8 mm and a distance between lines of 0.8 mm were formed on the AnS resin molded product.
A good circuit was formed with high precision. The electrical conductivity of this circuit was 0.3 Ω/port or less, and the adhesive strength was also good.

In the circuit obtained by transferring the circuit pattern at the same time as molding as in this example, the surface of the molded product and the surface of the circuit are on the same level (only the circuit part does not become convex), so care must be taken when handling. Another advantage is that it is possible to prevent the circuit from being disconnected.

Further, using the same circuit transfer foil, a circuit was formed by transferring onto a pre-formed ABS resin transfer target at 190° C. and 8 Kg/cJ. The surface resistance of the circuit at this time was 1.0 Ω/port, which was about 1/4 of the surface resistance of the circuit manufactured in the above example.

〔Effect of the invention〕

As explained above, according to the circuit transfer foil for injection molding and the circuit forming method of the present invention, a circuit transfer foil on which a circuit pattern of conductive paint is printed by a printing method such as screen printing or gravure printing is used. Because the circuit is formed by transferring to the transfer target at the same time as the transfer body is formed, there is no need for expensive or special equipment, and there is no waste of conductive material, resulting in even better conductivity. There is an advantage that a circuit having the following characteristics can be formed in one step.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a specific example of a circuit transfer foil used in the present invention, and FIG. 2 is a schematic diagram when a circuit is transferred and simultaneously formed onto an object to be transferred.

1...Support film, 2...Circuit pattern, 3...
-Circuit transfer foil, 4...injection mold.

Applicant's agent Tadashi Ame Miya Box 1 diagram Procedural amendment (dark) July 29, Akebono 1

Claims (4)

[Claims] (1) A circuit that is basically a conductive paint made by adding 300 to 1000 parts by weight of conductive particles to 100 parts by weight of resin on a support film, and exhibits easy peelability immediately after heating and pressurizing the support film. A circuit transfer foil for injection molding that is characterized by having a pattern printed on it. (2) The circuit transfer foil for injection molding according to claim 1, wherein the conductive particles are conductive particles having at least two different particle sizes. (3) A conductive paint that is basically made by adding 300 to 1,000 parts by weight of conductive particles to 100 parts by weight of resin on a support film, and exhibits easy peelability immediately after heating and pressurizing the support film. A circuit transfer foil with a circuit pattern printed thereon is placed on the inner wall of a mold for injection molding the object to be transferred so that the support film is in contact with the inner wall of the mold, and molten resin is press-fitted into the mold to mold the object to be transferred. and then peeling off the support film to form the transfer target and simultaneously transfer the circuit. (4) The circuit forming method according to claim 3, wherein the conductive particles are conductive particles of at least two different particle sizes.