JP2002313147A - Flat cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost flat cable excellent in electric characteristics, flexibility and durability, by doing away with etching treatment. SOLUTION: A conductive paste 26 kneaded with carbon nanotubes generated by using catalytic reduction of carbon dioxide, arc discharge method, laser evaporation method, CVD method, or pyrolysis with a binder-use polymer made of thermoplastic resin as a conductive filler under certain physical conditions, is printed on a base film 1 of polyimide, polyester or the like with a screen printer to form conductive ways (2a to 2d). Since physical and electric characteristics of the conductive ways are improved due to adhesiveness of this conductive filler, it becomes possible to form microscopic conductive ways.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat cable used for electronic equipment, and more particularly to a flat cable used for high-density electronic equipment such as a camera and a mobile phone.

[0002]

2. Description of the Related Art In recent years, small electronic devices such as mobile phones have been required to be mounted at higher densities as their functions become higher. For high-density mounting, not only miniaturization of electronic components and component parts, but also miniaturization of connection cables for connecting them have become one of the important issues that are indispensable.

Conventionally, as connection cables for these small electronic devices, flat cables in which conductive paths having a constant width are formed in parallel at regular intervals on a base film which is a film-like insulating base material are often used. . As a method of forming the conductive path, a copper-clad laminated film is prepared by using FIGS. 4 (a) to 4 (d).
A subtractive method of dissolving and removing unnecessary portions of copper metal by etching in accordance with the manufacturing process shown in FIG. In this subtractive method, FIG.
As shown in (a), a film in which a copper foil 31a is previously laminated is used as a base film 31, and an etching resist 32 is applied to a portion of the surface left as a conductive path (b)
Next, an etching solution is sprayed onto the surface of the copper foil 31a to dissolve the copper foil 31a other than the conductive path pattern (c), and the etching resist 32 is peeled and removed with a chemical to form a predetermined conductive path 33 ( d). Also, using a base film that is a film-like insulating base material, a conductive paste formed by kneading silver or carbon as a conductive filler with a binder polymer is printed on the base film to form predetermined conductive paths. Is also used.

[0004]

The conventional flat cable is formed by combining the above-mentioned materials. However, the flat cable in which the conductive path is formed by etching has a complicated manufacturing process and is difficult to use. Since waste liquid treatment such as neutralization of the used acidic or alkaline etching solution is required, there is a problem that a large number of man-hours and cost are required to manufacture a flat cable.

In a flat cable printed with a conventional silver-based conductive paste, the conductive paste is expensive, and silver is easily oxidized and migration occurs. There is a problem that the insulation property is easily deteriorated. In addition, the flat cable printed using carbon-based conductive paste,
There is a problem that the physical and electrical characteristics of the conductive path at the time of bending are greatly changed, the flexibility is poor, and the volume specific resistance is high, so that the conductive path is unsuitable for a fine conductive path used for a minute current. The present invention has been made in view of such circumstances, and does not require a complicated manufacturing process such as etching, and therefore does not require waste liquid treatment, is excellent in flexibility, and has a small electric current conductivity. It is an object of the present invention to provide a low-cost flat cable suitable for roads.

[0006]

In order to achieve the above-mentioned object, a flat cable according to the present invention comprises a film-shaped insulating substrate on one or both sides of which at least a conductive filler, which is a carbon nanotube, and a polymer for a binder. The conductive path is printed by a conductive paste produced by kneading the conductive paste. The flat cable of the present invention does not require an etching step, improves flexibility,
Electronic equipment can be expected to be smaller and lower in cost.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flat cable according to the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of a flat cable according to an embodiment of the present invention. This flat cable is made of a conductive film produced by mixing a conductive filler of carbon nanotubes and a polymer for binder at a constant weight ratio on the surface of a base film 1 made of polyester, polyimide or the like.
2d) is formed by printing, and portions other than the end portions 3 and 4 are insulated and coated with a resin material 5 as necessary.

The conductive paste is prepared by mixing a polymer for a binder as described below, a carbon nanotube, and a mixed solvent composed of toluene, xylene and methyl ethyl ketone at a constant weight ratio, and kneading them under the following conditions. Generated by

As the binder polymer, a thermoplastic resin such as an acrylic resin, a polyester resin, a polyurethane resin or a vinyl chloride resin can be used. In particular, polyvinyl alcohol and butyraldehyde are reacted with each other. Polyvinyl butyral produced (P
VB) is most preferable because it has excellent flexibility.

[0010] The carbon nanotubes shown in FIG.
It is produced by catalytic hydrogen reduction of carbon dioxide using a flow-type fixed-bed reactor as shown in (1). This flow-type fixed-bed reactor is a quartz-made cylindrical reaction tube 11 having an inner diameter of 8 cm and an inner volume of 300 mmL, an electric furnace 12 surrounding the tube, and discharging the reaction gas in the reaction tube 11. And a valve 13.

In the center of the reaction tube 11, Fe, Co, Ni
About 40 g of a catalyst 14 having a transition metal such as the above or a transition metal supported on SiO ₂ and glass wool 1 above and below it
After hydrogen gas was supplied at a flow rate of 2 L / min and reduced at 400 ° C. for 1 hour, a mixed gas consisting of H ₂ gas and CO ₂ gas at a volume ratio of 2: 1 was supplied at a flow rate of 7.5 L.
After reacting at 500 ° C. for 6 hours, the inside of the reaction tube 11 is replaced with nitrogen and cooled to room temperature, thereby mainly producing a diameter of 1 to 10 nm and a length of 10 to 100 n.
As a result, carbon nanotubes having a single or multiple cylindrical shape of about m are generated.

The carbon nanotube may be formed by a known method such as an arc discharge method, a laser evaporation method, a CDV method (chemical vapor deposition method), or a pyrolysis method. It can be used as a conductive filler for a conductive paste of a cable.

The binder polymer, the plasticizer, the antioxidant and the like are appropriately added so that the concentration of the carbon nanotubes obtained by the above method becomes 30 to 40% by weight, and the mixture is kneaded with a ball mill for 40 minutes. Since the conductive fillers, which are carbon nanotubes, have an extremely long and thin shape, they can be entangled with each other. A stable conductive paste is generated. A conductive path printed with this conductive paste can obtain a substantially constant volume resistivity even when its thickness and width are changed, so that a fine conductive path for a minute current can be formed, thereby forming a flat conductive path. The cable can be made smaller than before. In addition, the bonding force between the carbon nanotubes and the binder polymer is stronger than that of the conventional carbon-based conductive paste, and this flat cable has the characteristic that resistance changes and cracks hardly occur even when it is bent and used. I have.

In order to print the conductive paste on the base film, a screen 21 as shown in FIG. 3, a squeegee 22 disposed on the screen, and a squeegee vertical cylinder 23 for moving the squeegee 22 in the vertical direction are provided. And a screen printing machine provided with a squeegee front-rear cylinder 24 for moving the squeegee 22 in the front-rear direction indicated by an arrow.

The base film 20 is supplied in the form of a roll, and the length required for printing is sequentially fed to the lower portion of the screen 21 by rollers 25. With the base film 20 stopped at a predetermined position, the conductive paste 26 supplied on the screen 21 is
The conductive path is printed on the base film 20 while being moved back and forth while being held down by the squeegee 22 held by the printer. The slider 27 is driven by a squeegee front / rear cylinder 24,
The height of the squeegee 22 is adjusted by a squeegee vertical cylinder 23. After the conductive paths are printed on the base film 20, the base film 20 is sent to a drying process (not shown), and the conductive paste 26 is fixed to the base film 20. Alternatively, the base film 20 may be cut in advance to a required flat cable size and supplied one by one to print the conductive path. After the printing and drying processes, the number of conductive paths can be increased by printing conductive paths on the back surface.

The present invention eliminates the use of an etchant by using carbon nanotubes as the conductive filler of the conductive paste 26 printed on the flat cable,
Oxidation of the printed conductive path, characterized in that the change in physical and electrical properties at the time of bending was reduced, the mixing ratio of carbon nanotubes, binder polymer, mixed solvent is limited to this embodiment Not something.

[0017]

According to the flat cable of the present invention, since a conductive path in which carbon nanotubes are dispersed in a polymer is printed on a ribbon, the flat cable can be manufactured at a low cost without using an etching solution, and can be manufactured at a lower cost than a conventional conductive paste printing method. Flexibility and electrical characteristics are improved, and fine conductive paths can be formed.

[Brief description of the drawings]

FIG. 1 is a plan view of a flat cable according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a flow-type fixed bed reactor according to an example.

FIG. 3 is a configuration diagram of a screen printing machine used in the present embodiment.

FIG. 4 is a manufacturing process diagram of a conventional flat cable.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 31 ... Base film 2a-2d, 33 ... Conductive path 3, 4 ... End part 5 ... Resin material 11 ... Reaction tube 12 ... Electric furnace 13 ... Valve 14 ... Catalyst 15 ... Glass wool 21 ... Screen 22 ... Squeegee 23 ... Squeegee Up / down cylinder 24 ... Squeegee front / back cylinder 25 ... Roller 26 ... Conductive paste 27 ... Slider 31a ... Copper foil 32 ... Etching resist

Claims (1)

[Claims] 1. A conductive path is printed on one or both surfaces of a film-like insulating substrate by a conductive paste formed by kneading at least a conductive filler as a carbon nanotube and a polymer for a binder. A flat cable characterized by the following.