JPS63288093A - Circuit transferring foil for injection molding and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a transferring foil capable of forming conductive circuits which can be soldered by means of a general purpose solder, by printing a circuit pattern easy to peel off on a supporting film a conductive coating paint. CONSTITUTION:A circuit transferring foil comprises a supporting film 1 on which a circuit pattern 2 is provided by printing a conductive coating paint according to circuit configurations as desired, while the conductive coating paint shows easiness in peeling off just after it is thermally pressed against the supporting film 1. A thermoplastic resin and polyisocyanate are mixed at a weight ratio 10:90-80:20, and a curing agent for curing the polyisocyanate is added to the mixture at a ratio 10:26.5-10:1.9, so that a conductive paint containing 300-1000 parts by weight of conductive particles per 100 parts by weight of resin is produced. After the curing agent is added thereto, the circuit pattern is printed on the supporting film with this conductive coating paint within a serviceable time period allowed for the coating paint.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a circuit transfer foil for injection molding and a method for manufacturing the same, and more particularly, a circuit transfer foil capable of transferring a conductive circuit having heat resistance that is suitable for general-purpose soldering. and its manufacturing method.

[Technical background of the invention]

Conventionally, as a method for transferring electric circuits such as wiring boards, conductive illumination made of thermoplastic resin is used on a support film.
A method of forming a circuit by forming a film over the entire surface, laminating it on the object to be transferred, and using a heating plate that can heat and press only the circuit portion (transferred portion) to transfer only the circuit portion to the object to be transferred ( JP-A-55-141789) is known.

According to such a circuit transfer method, (1) a heating plate that can be heated and pressurized is required for only a predetermined portion, and the person performing the circuit transfer needs to purchase said heating plate; will be discarded, resulting in wasted materials and high costs. ■Since the circuit pattern is transferred by heating and pressing only a predetermined portion using the heating plate, the conductive aF
There were drawbacks such as the need for the film to have a good cut, and (1) general-purpose solder could not be used because the resin used as the base material could not withstand the melting point of general-purpose solder.

In order to eliminate these drawbacks, a circuit pattern is printed using a semi-cured conductive paint made by adding metal particles to thermosetting epoxy, and a transfer foil is used to transfer this circuit pattern to the object to be transferred. has been developed (Japanese Unexamined Patent Publication No. 1986-5)
No. 2089).

For transfer foils using such thermosetting resin,
It has the advantage that even if a large amount of conductive particles is added, there is no possibility that the circuit pattern will become brittle, and that it has good heat resistance and can be used as a general-purpose solder.

However, it is necessary to heat the resin when curing it, but this heating has a major disadvantage in that the metal particles are oxidized and the conductivity is reduced. Furthermore, the thermosetting resin has the disadvantage that metal particles are difficult to mix uniformly and tend to be unevenly distributed, resulting in variations in conductivity within the formed circuit.

Furthermore, the thermosetting resin remains in a semi-cured state even after transfer, and is completely cured in a post-processing heating process to be bonded to the object to be transferred, so the object to be transferred requires heat resistance. In addition, there is a drawback in that the material to be transferred must have a group reactive with the thermosetting resin.

In addition, as mentioned above, the circuit pattern on the transfer foil is in a semi-cured state, so there is also the disadvantage that strict control of the storage conditions of the transfer foil manufacturing conditions and the temperature and time of the post-transfer heat treatment is required. .

[Summary of the invention]

The present invention has been made in view of the above points, and basically uses a thermoplastic resin as a circuit pattern resin, and can be transferred to many types of transfer objects with good peel strength, and is also suitable for the production of transfer foils. To provide a circuit transfer foil for injection molding and a method for manufacturing the same, capable of preventing deterioration of metal particles without requiring high heat, and capable of manufacturing a conductive circuit that has excellent heat resistance and can be soldered for general use.

Therefore, the circuit transfer foil for injection molding according to the present invention is prepared by disposing a thermoplastic resin and a polyurethane resin mixed in a weight ratio of 10:90 to 80:20 on a support film. Add 300-100 conductive particles to the
With the conductive paint containing 0 parts by weight, it is easy to apply immediately after heating and pressurizing the support film. It is characterized by printing a circuit pattern showing +I separation property.

Further, the method for manufacturing a circuit transfer foil for injection molding according to the present invention includes a thermoplastic resin and a polyisocyanate in a weight ratio of 1 to 1.
In the step of mixing at a ratio of 0:90 to 80:20, a curing agent for curing polyisocyanate is added to the mixture at a weight ratio of 10:26.5 to 10:1.9, based on 100 parts by weight of the resin content. 300 to 1 conductive particles
000 parts by weight, and after adding the curing agent, printing a circuit pattern on a support film with the conductive paint during the pot life of the paint. It is something.

In the present invention, since a mixed resin of thermoplastic resin and polyurethane, which is a room-temperature curing resin, is used, it can be easily transferred to various objects, and has good heat resistance and conductivity. It has the advantage of being able to manufacture circuits.

Further, according to the circuit transfer foil for injection molding according to the present invention, since the curing agent for curing the polyisocyanate is added immediately before the printing process, the circuit pattern can be printed well, and the thermoplastic resin and room temperature curing Since a synthetic resin is used, there is no need to heat the metal particles to high temperatures, and there is no need for long-term exposure to temperatures of 40° C. or higher, which promotes oxidation of metal particles.

[Detailed description of the invention]

As shown in FIG. 1, the circuit transfer foil according to the present invention is produced by printing a conductive paint on a support film 1 in a desired circuit shape, which is easily peelable immediately after heating and pressing the support film 1. It has a structure that forms 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 possible to effectively use a synthetic resin film that is peelable from the circuit pattern 2, has heat resistance and smoothness, and is not attacked by the solvent contained in the conductive paint. Specific examples of the support film 1 include plastic films such as polyester films, polyimide films, and polypropylene films, and aluminum foil.

The conductive paint for printing 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 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.

In the present invention, first, a mixed resin of a thermoplastic resin and a cold-setting resin is used as such a resin.

The thermoplastic resin that serves as the base material for such a conductive paint has adhesiveness or heat-meltability with the resin to be transferred, has adhesion to the support film 1 at room temperature, and is easily peelable immediately after heating and pressing. A resin component (solute) that can form a circuit pattern, such as acrylic, polyamide, epoxy, polyether, or polyester resin, or one or more of cyclized rubber, chlorinated rubber, and rosin, for example, MEK.
, NrBK, ketone solvents such as cyclohexanone, aromatic hydrocarbon solvents such as toluene and xylene, ether solvents, ester solvents, and DMF as others.
It can be a resin solution dissolved in one or more solvents such as N-methylpyrrolidone.

Further, examples of polyurethane resins that are mixed to impart heat resistance to such thermoplastic resins include tolylene diisocyanate (TDr), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), A polyisocyanate containing at least one type of incyanate such as xylene diisocyanate (MDI) is treated with an ester solvent such as ethyl acetate or butyl acetate, acetone, M
It can be a resin solution dissolved in one or more solvents such as a ketone solvent such as EK or a chlorine solvent such as methylene chloride.

As a curing agent for curing such a polyisocyanate, a curing agent conventionally added to form a polyurethane resin can be used. Examples of such curing agents include one or more polyols such as acrylic polyols, polyester polyols, and polyether polyols, copolymers having carboxyl groups such as vinyl chloride-vinyl acetate-maleic acid, and , 4''methylene-bis-(2-chloroaniline), hydroxypropylated ethylenediamine, and the like can be used.

The mixing ratio of the thermoplastic resin and polyurethane resin is 10:90 to 80,720 by weight. 80:
If the ratio of the thermoplastic resin is too high (20:0 or more), the transferability is good, but there is a risk that the heat resistance will be insufficient.On the other hand, if the ratio of the facilitative resin exceeds 10:90, the heat resistance will be good, but the transferability will be insufficient. There is a risk that the properties of the film may be impaired and problems may arise in peel strength after being transferred to a transfer target.

The conductive particles added to the resin solution described above are not fundamentally limited in the present invention. For example, gold, silver,
It can be metal particles such as platinum, copper, nickel, aluminum, tin, zinc, etc., or one or more types of composites and alloy powders whose surfaces are coated with the above metals, or conductive particles such as carbon black. .

Such conductive particles are used in an amount of 300 parts by weight per 100 parts by weight of resin.
Add ~1000 parts by weight. If it is less than 300 parts by weight, the density of the conductive particles of the circuit pattern 2 may be too low to exhibit good conductivity, while if it exceeds 1000 parts by weight, there is a risk that the adhesive strength will deteriorate.

The average particle size of the conductive particles is preferably 10 μm or less. If the thickness exceeds 10μ, there is a possibility that the circuit pattern 2 cannot be printed by printing means such as screen printing.

Next, a method for manufacturing a circuit transfer foil for injection molding according to the present invention will be explained.

First, as described above, a thermoplastic resin solution, a polyisocyanate solution, and a curing agent are mixed to produce a conductive paint containing conductive particles.

The polyisocyanate solution and the curing agent are mixed immediately before printing the circuit pattern, and after mixing, the circuit pattern is printed on the support film within the pot life. This is because if the polyisocyanate solution and curing agent are mixed and left for a long time in this way, the structure of the mixed solution will progress and the viscosity will increase, making it difficult to print.

In the present invention, it is preferable that the conductive particles are mixed with the curing agent. This is because such a curing agent generally has the effect of uniformly dispersing the conductive particles in an open container. In general, as the 011 value decreases, the reaction with polyisocyanate gradually becomes less active, but there is also the advantage that the properties as a thermoplastic resin tend to be better expressed.

Although the circuit pattern 2 is printed on the easily peelable 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 μm.

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

Naturally, it is preferable that the line width or the distance between lines of the circuit pattern 2 be small. In the circuit transfer foil used in the present invention, the above-mentioned line width or line distance is 1 tsta
In order to make it possible to form the following circuit, the viscosity of the conductive paint to be printed is set to 10 to 1000 voids, most preferably 10 to 1000 voids.
It is preferable to adjust to 400 voices. If the viscosity of the conductive paint is less than 10 voids, there is a risk that the wires will be distorted and the circuit will be short-circuited, whereas if it exceeds 1000 voids, it will be difficult to print the circuit pattern on the support film 1. be.

When the mixed resin polyisocyanate that constitutes the circuit pattern 2 of the circuit transfer foil manufactured in this way comes into contact with a curing agent such as a polyol and the organic solvent is evaporated, the curing progresses rapidly, resulting in good heat resistance. Thus, a circuit pattern 2 is formed.

When manufacturing a conductive circuit using the circuit transfer foil for injection molding according to the present invention, as shown in FIG. 1 is left in contact with the inner wall of the mold 3a, the mold 3a is covered with the mold 3b, and the molten resin 5 is injected from the resin injection port 4 to manufacture the transfer target 6 and at the same time form a circuit. It is intended to be transcribed.

At this time, the thermoplastic resin portion in the mixed resin becomes plastic, and the circuit pattern 2 is transferred to the transfer target 6 (see FIG. 3).

In the method of forming a circuit simultaneously with injection molding as described above, the pressure and temperature within the injection mold 3 are particularly important. That is, when the pressure inside the mold is small, the circuit of the circuit transfer foil is not transferred well, and the support film 1
There is a risk that the negative part will remain on the support film 1 when it is peeled off, and if the pressure inside the mold is large, there is a risk that the drawn circuit will collapse.

The pressure inside the mold is preferably 200 to 1000K.
g/-. The pressure inside the mold can be controlled by the viscosity of the molten resin injected into the mold and the injection pressure.

If the viscosity of the molten resin is too high, uneven pressure will be applied to the circuit transfer foil, and the areas with low pressure load will be on the support film l.
There is a risk that the injection pressure will remain, and the injection pressure will also increase, so there is a risk that the circuit will be damaged. 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. Taking this into consideration, the viscosity of the resin for manufacturing the transfer target 6 when injected into the injection mold 3 is preferably 10<3> to 10' poise. If the above-mentioned viscosity is less than 103 poise, the pressure load on the circuit transfer foil will be small, and there is a risk that good transfer will not be performed.On the other hand, if it exceeds 105 poise, the pressure load will become uneven, resulting in poor transfer. There is a risk of producing defective parts and defective parts.

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 lower.

In addition, the injection pressure of the above molten resin is 400 to 2300 kg.
/- is better. If the injection pressure of resin in the above viscosity range exceeds 2300 kg/cj, the pressure inside the mold will become too large and may damage the circuit.
This is because if it is lower than Kg/-, the circuit may not be transferred well.

The resin for forming such a transfer object 6 includes resins conventionally used as transfer objects, such as polysulfone, PPO, modified PPO, glass fiber-containing polycarbonate, polyetherimide, PPS, polyethersulfone, and glass. Thermosetting resins such as fiber-filled PBT, phenol, and epoxy can be used.

[Example 1] A conductive paint (with the following composition) was applied on a polyester film.
Viscosity 70 voids), line width 0.8 +uw, line distance %! A circuit pattern was printed with IO, 8 tags and a thickness of 25 μm.

Composition 1 Thermoplastic acrylic resin 50 parts by weight Aromatic solvent 120 parts by weight Polyisocyanate 12 parts by weight (Isocyanate content: 12.5%) Acrylic polyol 50 parts by weight (0)
Monovalence: 30) Silver-coated copper particles 600 parts by weight Dispersed 2 parts by weight This circuit transfer foil was placed in several parts by weight so that the support film was in contact with the injection mold for molding the transfer object, and then the polycarbonate resin containing glass fiber was placed. Injection conditions: injection temperature 220-240°C, injection pressure (gauge pressure) 800 Kg/-1, back pressure 5 Kg/cj, screw rotation speed 5 Or, p, m, ), the transfer target molded the body.

In this way, a line width of 0.8 nu+ and a distance between lines of 0.8 nv were formed on a glass fiber-filled polycarbonate resin molded product.
A good circuit was formed with high precision. The electrical conductivity of this circuit was less than 0.1 Ω/hole, and the cellophane tape peeling resistance test was 100/100.

Further, a copper wire lead wire was soldered to the circuit part and the peel strength was measured, and as a result, a value of 2 kg/3 mm2 or more was obtained.

In addition, as a comparative example, the peel strength of the circuit part when only thermoplastic resin is used as the base resin is 1 kr/3
It was ts2.

〔Effect of the invention〕

As explained above, according to the circuit transfer foil according to the present invention, a mixed resin of thermoplastic resin and polyurethane resin is used as the base material of the circuit pattern formed by printing means such as screen printing and gravure printing. This has the advantage that it becomes a circuit transfer foil for injection molding that can form a conductive circuit with good heat resistance without impairing transferability.

Further, according to the method for manufacturing a circuit transfer foil according to the present invention, it is possible to print a circuit pattern well using the conductive paint, and by adding conductive particles to the curing agent, the conductive particles can be printed. It has the advantage of being able to be uniformly dispersed.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a specific example of a circuit transfer foil used in the present invention, Fig. 2 is a schematic view of a circuit being transferred and molded onto an object at the same time, and Fig. 3 is a cross-section of the transferred circuit. It is a diagram. l...Support film, 2...Circuit pattern, 3
...Injection mold.

Claims (3)

[Claims] (1) On the support film, conductive paint is prepared by adding 300 to 100 parts by weight of conductive particles to 100 parts by weight of a resin that is a mixture of thermoplastic resin and polyurethane resin at a weight ratio of 10:90 to 80:20. A circuit transfer foil for injection molding, characterized in that a circuit pattern is printed that exhibits easy peelability immediately after heating and pressurizing the support film. (2) A step of mixing a thermoplastic resin and a polyisocyanate at a weight ratio of 10:18 to 10:0.4, and adding a curing agent for curing the polyisocyanate to the mixture at a weight ratio of 1
0:26.5 to 10:1.9 to form a conductive paint containing 300 to 1000 parts by weight of conductive particles per 100 parts by weight of resin, after adding the curing agent. A method for manufacturing a circuit transfer foil for injection molding, comprising the step of printing a circuit pattern on a support film with the conductive paint within a short time. (3) Circuit transfer for injection molding according to claim 2, characterized in that conductive particles are added to the curing agent in an amount of 300 to 1000 parts by weight based on 100 parts by weight of the resin. Method of manufacturing foil.