JPH07202369A - Flexible wiring member - Google Patents

Abstract

PURPOSE:To provide a flexible wiring member where the conductivity (electrical resistance) of the contacting part of the connection between each terminal and a connector does not change with time. CONSTITUTION:In a flexible wiring member where a silver conductive circuit covered with carbon conductor is formed, a silver conductive circuit 4 of each terminal 2 to be connected to at least connectors is covered with carbon and silver and the conductor containing carbon and silver contains silver and carbon in the ratio of 1:1 in weight ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible wiring member having improved conductive properties.

[0002]

2. Description of the Related Art A flexible wiring member (abbreviated as FPWB) is a wiring member in which an electric circuit is formed on an electrically insulating substrate, and an insulating substrate having a flexible electric circuit,
For example, since it is formed on a film such as PET (polyethylene terephthalate) or polyimide, it is flexible and has high functionality (heat resistance, dimensional accuracy, etc.), and thin and high-density wiring is also possible, and it is lightweight and space efficient. It is used in various fields as an excellent member such as high price. This FPWB
The electric circuit forming method is generally a method of directly printing a desired circuit pattern on the film substrate using a conductive ink (or a conductive paste) by a printing technique such as screen printing. The conductive ink used here is, for example, silver, gold, platinum, lead, copper, nickel,
Aluminum or a mixture thereof is used as a conductive substance, and this is mixed with a thermosetting resin precursor (an uncured polymer having a plasticity, an oligomer, etc.) as a main component and other monomers, a solvent, a catalyst, etc. The viscosity is adjusted to an appropriate value. Among these conductive inks, an ink containing silver as a conductive substance is often used because of its small resistance value and relatively low price. Therefore, in terms of application, there is a great demand for FPWB using a silver conductive circuit.

The above-mentioned FPWB using the silver conductive circuit also has an unavoidable drawback. That is, it is a problem that the conductive characteristics are changed due to easy oxidation and migration (internal migration of silver). In order to solve this problem, in general, a measure of coating the entire surface of the formed silver conductive circuit with a carbon conductor, for example, an ink in which carbon is mixed to give conductivity, is overprinted by a printing method, and the like. Has been taken.

[0004]

In practical use of FPWB, first insert the terminal portion of the electric circuit into the connector,
Although the metal of the contact portion of the connector is pressed and connected by a spring or the like to function, it has been found that the following problems have newly arisen due to the check of strict quality and performance with the recent expansion of applications. For example, a resistive touch panel LCD
When used in combination with a (liquid crystal display) to visualize the input from the touch panel on the LCD, the input image is said to have changed or misaligned. This phenomenon appears more clearly with the change of time, but since it is progressing gradually, it is difficult to judge unless it is checked carefully. Such a phenomenon is particularly observed in the conventional FPWB in which the entire circuit containing silver as a main component is coated with a carbon conductor. It can be said that As a result of various investigations by the present inventors regarding this cause, FPWB and LC generated from the touch panel
There is a secular change in the electrical conductivity (electrical resistance value) between the pressure contact connection portion between each terminal portion of the FPWB and the connector, which is also from D, that is, the carbon conductive layer covering the silver conductive circuit of the FPWB and the contact portion in the connector. It turned out to be seen. Therefore, in order to solve the problem caused by this cause, as a result of diligent studies from multiple angles, the inventors finally found a solution to the problem and reached the present invention.

[0005]

The flexible wiring member of the present invention is a flexible wiring member forming a silver conductive circuit coated with a carbon conductor, and at least the silver conductive circuit of the terminal portion connected to the connector is carbon. It is characterized by being coated with a conductor containing silver.

Furthermore, the conductor containing carbon and silver is characterized in that it is a conductor containing silver in an amount of 1 or more silver with respect to 1 carbon by weight.

The carbon conductor is a conductive carbon black generally used as a conductive agent for a conductive carbon ink (or paste), and examples thereof include Ketchin black and acetylene black. Electrical resistance of the carbon itself (volume resistivity) of ¹⁰ 0 - 10
^Although it is in the range of about ^-1 Ωcm, in the case of actually forming a circuit, it is mixed with other components such as a resin and printed as an ink or a paste. Is also large, but is normal. Here, the other component is generally a resin that is cured by heat, for example, an epoxy-based or ester-based precursor, and if necessary, an organic solvent, a catalyst and the like are added as complementary components. In addition, those that are made into ink or paste by mixing these other components,
Since many conductive carbon inks (or pastes) are marketed by many related manufacturers, they may be used.

The silver conductor forming the silver conductive circuit is silver generally used as a conductive agent for conductive silver ink or paste, and its own electric resistance (volume resistance) is about 10.
^It shows about ⁻⁵ to 10 ⁻⁶ Ωcm. However, in the case of actually forming a circuit, since it is printed as an ink (paste) by mixing a thermosetting resin precursor, an organic solvent, a catalyst, and the like as in the case of the carbon conductor, the actual condition The electrical resistance of the circuit is generally greater than said resistance. This ink (paste) is marketed by many related manufacturers as well as the conductive carbon ink, and thus it may be used. It is also permissible to slightly mix other metal powders having an electric resistance similar to that of silver.

The connector is generally used for FPWB and is not a special connector. The connection between the connector and the FPWB is such that when the terminal portion is inserted into the connector, the connection terminal is pressed into contact with the connection terminal provided inside the connector by the force of a spring or the like and is electrically connected. Since they are in strong contact with each other under pressure, they do not come off easily. still,
Since there are various numbers and intervals of electric circuits provided in the FPWB, various types of connectors are selected to suit them.

Regarding the printing method for forming the above circuit,
There is no particular limitation, and for example, there are three-dimensional printing, intaglio printing, lithographic printing (direct or indirect), etc., but the printed film of the conductive ink (or paste) is thick, and a conductive circuit with low electrical resistance can be obtained. Therefore, screen printing is often used.

The specific method for conducting conductive circuit printing by screen printing is also a method that is usually used and is not particularly limited. For example, a photoresist having a mesh of about several hundreds mesh is coated with photoresist, exposed through a plate-making film on which a desired body pattern is formed, and then dried to make a plate. To make. This is mounted on a screen printing machine, a thermosetting conductive silver ink (or paste) is placed on the plate, and printing is performed on the surface of the flexible film-like substrate. After printing, heat for curing and fixing. The heating temperature varies depending on the type of ink (or paste) used, but is generally about 100 to 150 ° C. and about several tens of minutes.

When the printed circuit of the silver conductor is completed,
Next, it is necessary to cover at least the connection terminal of the silver conductive circuit, which is in pressure contact with the connector, with a conductor containing silver and carbon. The coating method is not particularly limited, and the printing method is used, but the screen printing method is particularly effective. The coating may be applied only to the connection terminal portion, and the silver conductive circuit portion which is not in pressure contact may be coated with the conventional carbon conductor or the conductor containing silver and carbon of the present invention. . It is also permissible to coat the entire silver conductive circuit of the FPWB with a carbon conductor in the conventional manner, and further coat at least the pressure contact portion with the connector with the conductor containing silver and carbon of the present invention. .

The conductor containing carbon and silver is a conductor obtained by mixing carbon of the above-mentioned carbon conductor and silver of the silver conductor. And when actually coating, each ink (or paste) of the conductive carbon or silver
In the same manner as described above, for example, based on a precursor of thermosetting resin such as epoxy type or ester type, a predetermined amount of silver and carbon is mixed with this as an ink (or paste). The conductor is used as the conductor.

It is desirable to determine the mixing ratio of carbon and silver in consideration of the correlation with the effect of the present invention and the influence of the oxidation of silver itself on the electrical resistance. Considering comprehensively, the mixing ratio of both is approximately 1 or more in terms of weight ratio of carbon to 1 of silver, preferably 1.5 to 19 of silver to carbon 1 and more preferably 1 to 1 of carbon. As for silver, about 2 to 9 can be exemplified.

The thickness of the coating of the conductor containing carbon and silver is preferably in the range of about 5 to 40 μm, but is not limited thereto.

The thickness of the silver conductive circuit formed on the FPWB is generally 10 to 20 μm.
It is about before and after. Further, the coating thickness of the conventional conductive carbon is about 10 to 20 .mu.m.

[0017]

Although it is not clear what kind of mechanism the effect of the present invention is based on, the conventional FPWB has a terminal portion press-contacted to the connector whose electric resistance is influenced by the pressing force. It is considered that this pressing is not substantially influenced by the coating with the conductor containing silver and carbon.

The present invention will be described in more detail below by way of examples together with comparative examples, but this does not limit the present invention.

[0019]

【Example】

Embodiment 1 A terminal portion 2 used in an analog type touch panel 1 adopting an FPWB according to the present invention will be described with reference to the drawings. The FPWB used for the terminal portion 2 on which the silver conductive circuit 4 is formed is created by the screen printing method according to the following procedure. First, 250-mesh Tetoron gauze was adhered to an aluminum mold, and a PVA (polyvinyl alcohol) -based photosensitive resin was applied and dried to prepare a raw plate for plate making. On the other hand, the silver conductive circuit 4 has four 1 mm (± 0) wide lines arranged at 2.54 mm (± 0) pitch in parallel.
I made a set layout. Create a masking film,
This is vacuum-adhered to the photosensitive surface of the raw plate, exposed to ultraviolet rays, washed with water and developed with hot air to prepare a plate for screen printing,
This was mounted on a screen printing machine.

Next, a 125 μ thick polyester (PE
T) was suction-fixed to the printing table with the suction cup of the screen printing machine. Polyester silver conductive paste "Dowtie 303" (trade name, manufactured by Fujikura Kasei Co., Ltd.) was used as the silver conductor of the silver conductive circuit 4, and isophorone was added as an organic solvent to this to have a viscosity of 120 to 140 poises. It was made into an ink, and this was placed on the plate and screen-printed. After printing, hot air heating was performed at 120 ° C. for 20 minutes. P
Four silver conductive circuits 4 were formed on the ET according to the pattern on the plate. The thickness of the circuit was 10 to 11 μ. Two of these are created and are referred to as FPWB-1 and FPWB-2.

Next, the silver conductive circuit 4 of FPWB-1 is coated with a conductor containing silver and carbon according to the present invention by a screen printing method. As a conductor containing silver and carbon, a polyester-based silver conductive paste “Dowtie FA-
303 g of 80 g and polyester-based carbon conductive paste "Dowtai FC-404" (manufactured by Fujikura Kasei Co., Ltd., product name) of 20 g are mixed, and finally isophorone is added as an organic solvent to dilute it, and the viscosity is 120 to 140. We prepared an ink adjusted to a poise.
It contains 2 g and 6 g of carbon. (This corresponds to 8.7 silver to 1 carbon by weight.) Hereinafter, this mixed ink is referred to as M ink.

A screen printing plate used for coating was prepared in the same manner as described above and mounted on a screen printing machine. However, the plate-making film has a conductive circuit line width of 1.1 mm.
It is made wide and this is patterned as one set.

Next, the FPWB-1 was placed on a printing table with a suction cup of the screen printing machine, fixed by suction so as to match the circuit line for coating the plate, and printing for coating was performed with the M ink. After printing, hot air heating was performed at 120 ° C. for 20 minutes. The entire silver conductive circuit 4 was completely covered with the M ink, and the coating thickness was 15μ. Hereinafter, this is referred to as a coated FPWB-1 and is used as the terminal portion 2.

Finally, the following test was conducted in order to confirm whether or not the electric resistance value of the coated FPWB-1 changed.

First, an analog type touch panel 1 is prepared. Size 125μ (t) × 200mm (X) × 1
Two 50 mm (Y) PET films 5 are prepared, and an ITO (indium tin oxide) thin film is sputtered on one surface of each of them to form conductive films 7, 7 having a thickness of 0.025 or more.
Is formed, and one of them is appropriately fine (about 100 in diameter).
A circular insulating spacer 8 having a size of μ and a height of 500 was formed by a printing method. Next, these two conductive films 5,
As shown in the plan views of FIG. 3 and FIG.
A silver ink circuit (Dowtie FA-303) having a thickness of 10 μm and a thickness of 10 μm was screen-printed to form silver conductive circuits 6, 6 ... And the terminals 9 and 10 of the circuit
It is adapted to be connected to the coated FPWB-1, that is, the terminal portion 2 by thermocompression bonding.

In the touch panel 1, the conductive films 7 and 7 are formed, and the PET films 5 and 5 on which the silver conductive circuits 6 and 6 are formed are combined with the conductive films 7 and 7 facing each other through the insulating spacer 6. In this case, the PET films 5 and 5 were assembled by applying an adhesive around the PET films 5 and 5 with a thickness of 20 μm and a width of 4 mm, and laminating them together. Silver conductive circuits 6, 6 ends 6, 1
The terminal portion 2 is connected to 0 by thermocompression bonding, and a commercially available connector 11 (product type 68147-004, manufactured by DuPont) is inserted and connected to the other end.

A commercially available connector 11 on the touch panel 1
With HIOKI 3224 type m connected
ΩH: Changes with time of the electric resistance values in the X-axis direction and the Y-axis direction were measured by a tester. The results are shown in Table 1.

[0028]

[Table 1]

Comparative Example Using the other FPWB-2 prepared in Example 1, the carbon conductive paste "Dotai FC" was added thereto.
-404 "was used. The coating method and procedure were exactly the same as in Example 1. The silver conductive circuit of FPWB-2 was completely covered with the carbon conductive ink, and its thickness was 15 μm Coated FPWB-
2 was replaced with the coated FPWB-1 of Example 1, and a touch panel 1a (not shown) was assembled in the same manner, and the connector 11a (not shown) of the commercially available product was inserted and connected to the touch panel 1a. The change was measured. The measurement results are also shown in Table 1.

As is clear from Table 1, the FPWB of the present invention is compared with the conventional carbon conductor-coated FPWB-2.
It can be understood that in -1, there is substantially no change with time in the electric resistance value.

Example 2 The analog touch panel 1 obtained in Example 1 and the comparative example,
Each of 1a and 1a was connected to a liquid crystal display (not shown).
Next, when a circle mark was input on these touch panels with a pen, as for Example 1, an image was projected on the display at the same position as the touch panel, and no change with time was observed. However, in the comparative example, it was confirmed that the image was imaged at a position displaced by 1 to 2 mm from the input position on the touch panel, and the displacement amount gradually increased with the lapse of time.

[0032]

EFFECTS OF THE INVENTION The flexible wiring member of the present invention does not deteriorate the electric characteristics (resistance) brought about at the connecting portion with the connector with the passage of time, and can always maintain constant conductivity even when used for a long time. Therefore, various devices incorporated as parts for connecting the member to various connectors are evaluated as products without deterioration in quality performance due to aging.

[Brief description of drawings]

FIG. 1 is a plan view of a touch panel using a flexible wiring member according to the present invention for a terminal portion.

FIG. 2 is a cross-sectional view of an essential part of the embodiment according to the present invention.

FIG. 3 is a plan view of one conductive film of the example.

FIG. 4 is a plan view of the other conductive film of the example.

[Explanation of symbols]

 1. Touch panel 2. Terminal part 4. Silver conductive circuit 5. Conductive film 6. Silver conductive circuit 7. Conductive film 8. Insulating spacer 9. Edge 10. Edge 11. connector

Claims (2)

[Claims] 1. In a flexible wiring member having a silver conductive circuit formed by coating with a carbon conductor, at least a silver conductive circuit of a terminal portion connected to a connector is coated with a conductor containing carbon and silver. Flexible wiring member characterized by 2. The flexible wiring member according to claim 1, wherein the conductor containing carbon and silver is a conductor containing 1 to carbon in a weight ratio of 1 or more silver.