JP3292324B2 - Flat cable - Google Patents

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 wiring electrical and electronic equipment, and more particularly to a flat cable having excellent bending characteristics.

[0002]

2. Description of the Related Art In recent years, in order to reduce the wiring work and to prevent erroneous wiring in response to the complexity of wiring in various devices, internal wiring of video equipment, audio equipment, OA equipment, computer equipment and the like has been developed. A multi-core flat cable is used as an electric wire. In general, a flat cable is manufactured by sandwiching a plurality of conductors in parallel between two insulating base materials, heat-sealing the insulating base materials together, and integrating them. As the insulating base material, a two-layer structure having a biaxially stretched polyethylene terephthalate (PET) film layer having excellent mechanical properties and electric properties and an adhesive layer for fusing the film layer has been widely used. As the base polymer of the adhesive layer, polyethylene (PE), polyvinyl chloride (PVC) copolymerized polyester and the like are widely used.

[0003] By the way, flat cables are sometimes used for movable parts, and there are cases where bending resistance is required. The flex resistance of the flat cable is better when the insulating base material and the conductor are in close contact with each other, so the conventional flex-resistant product uses a copolyester for the adhesive layer, which is 25 μm thick. 40 ~ 50μ on PET film
m coatings were common. For example, 3
The bending characteristics of the flat cable using a flat conductor having a thickness of 5 μm are the bending resistance test method (bending radius = 4.8 mm) of JIS C5016, and the number of bending times is generally of the order of 10 ⁶ .

[0004]

However, in recent years, the demand for bending resistance has become strict, and there have been cases where conventional products cannot cope. That is, there has been a need to provide a flat cable that can guarantee the number of times of bending on the order of 10 ⁷ with a bending radius of 4.8 mm.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is characterized in that it is disposed in parallel between two insulating substrates each comprising an insulating film layer and an adhesive layer. The thickness of the insulating film layer (Ti) and the thickness of the adhesive layer (Ta) in the flat cable integrated by sandwiching the plurality of conductors are defined by the following equation. Ta> 15 μm Ta + Ti ≦ 80 μm 1.2 ≦ Ti / Ta ≦ 2.0 In particular, in the cable, the insulating film is made of polyethylene terephthalate, and the resin composition of the adhesive layer has a tensile modulus at 20 ° C. of 20 kg / mm. It is preferably at least ² .

Here, as the insulating film layer, various engineering plastic films can be used. For example, polyimide (PI), polyphenylene sulfide (PPS), polyethylene naphthalate (PEN), polyethylene terephthalate (PET) and the like can be used. Can be mentioned. PPS, PEN, and PET are preferably biaxially stretched for the purpose of improving strength.

[0007] The resin composition of the adhesive layer preferably has an adhesive property to a conductor as much as possible. For example, a resin composition based on a thermosetting adhesive such as an epoxy resin or a hot melt adhesive such as a copolymerized polyester, a silane-modified polyolefin, or a maleic anhydride-grafted polyolefin is conceivable. When a polyolefin resin is used as the base resin of the adhesive layer, it is preferable to improve heat resistance and mechanical properties by irradiating ionizing radiation.

[0008] The coating of the adhesive layer on the insulating film is performed by a method using a roll coater or a T-die extrusion method. An anchor coat agent (AC agent) may be used to further increase the adhesive strength between the insulating film and the adhesive layer.

[0009]

According to the present invention, as a result of studying a method for improving the bending characteristics of a flat cable, it has been found that the effect of changing the thickness composition ratio between the insulating film layer and the adhesive layer is very large. That is, most of the conventional high-flexion type flat cables have an insulating film (PET) thickness of 25 μm and an adhesive layer thickness of 40 to 50 μm. They found that bending was possible. This can be explained that the strength of the insulating base material was increased by increasing the proportion of the insulating film layer, and as a result, the bending characteristics were also improved.

However, if the ratio of “thickness of the insulating film layer / thickness of the adhesive layer = (Ti / Ta)” exceeds 2.0, the insulating base material becomes hard, so that when a flat cable is used, the flexibility is poor. turn into. Conversely, if the composition ratio is less than 1.2, the bending resistance becomes insufficient. On the other hand, if the thickness of the insulating base material exceeds 80 μm, the distortion when bending is increased, and the bending characteristics are deteriorated. Further, when the thickness of the adhesive layer is less than 15 μm, the conductor may not be embedded in the adhesive layer. Then, if biaxially stretched PET is used as the insulating film, an inexpensive flat cable can be manufactured. Further, if the resin composition of the adhesive layer has a tensile modulus of 20 kg / mm ² or more, Since the deformation of the adhesive during bending can be minimized, a flat cable having extremely excellent bending resistance can be obtained.

[0011]

The present invention will be described below with reference to examples and comparative examples. A sample for evaluation was produced as follows.
First, as an example and a comparative example, each adhesive was extrusion-coated to a predetermined thickness on an insulating film shown in Tables 1 and 2 by a T-die extruder to obtain each insulating base material. Next, 10 pieces of 35 μm thick × 0.8 mm width tin-plated flat soft copper conductors are sandwiched in parallel between the two obtained insulating base materials at a pitch of 1.5 mm, and passed through a heat roller. Was integrated into a laminate to obtain a sample. FIG. 1 shows a cross-sectional view of the obtained sample. In the figure, 1 is an insulating film, 2 is an adhesive, and 3 is a conductor.

The bending characteristics of the sample are determined according to JIS C
5016. This involves bending a predetermined radius between the slide bar of the tester and the sample fixing frame to mount the sample, reciprocating the slide bar with a predetermined stroke, and energizing the conductor pattern of the sample. And the number of bends until the current stops for 10 ^-6 seconds or more. The evaluation criteria are as follows. ○: 10,000,000 times or more △: 1,000,000 times or more, 10,000,000 times or less ×: Less than 1,000,000 times Regarding the burial property of the conductor, when looking at the cross section of the flat cable, if there is no cavity beside the conductor, ○, that It was X.

[0013]

[Table 1]

[0014]

[Table 2]

Example 1 is a biaxially stretched PPS having a thickness of 50 μm.
Insulating film layer made of film and tensile modulus of elasticity 15k
A flat cable using an insulating substrate consisting of an adhesive layer having a thickness of 25 μm and a thickness of 25 g / mm ² showed good bending characteristics and good burying characteristics. In Example 2, the PPS film of Example 1 was replaced with a PI film, and good results were obtained. Example 3 uses 38 as an insulating film.
The flat cable was made of biaxially stretched PET having a thickness of mm and having an adhesive layer having a tensile modulus of elasticity of 30 kg / mm ² and a thickness of 30 μm. Both the bending characteristics and the filling characteristics were good. Further, in Examples 4 and 5, the ratio of the thickness of the PET film to the thickness of the adhesive layer was set to 1.9 or 2.0 from the flat cable of Example 3, which also had good bending characteristics and filling. The characteristics were shown.

On the other hand, in Comparative Example 1, 25 μm thick PPS
Although it is a flat cable using a 0 μm thick adhesive,
Although the flexibility was good, the conductor was not completely embedded because the adhesive layer was too thin. Comparative Example 2 was a combination of a PPS having a thickness of 50 μm and an adhesive having a thickness of 40 μm. However, since the thickness of the insulating base material layer was too large, the bending characteristics were not sufficient. Comparative Examples 3 and 4 use PET as the insulating film and 30 kg / mm ^{2 as} the adhesive layer, but the Ti / Ta is less than 1.2 and the bending properties are not sufficient.

[0017]

As described above, the flat cable of the present invention has better bending resistance than the conventional cable by limiting the thickness of the insulating film layer and the thickness of the adhesive layer. Therefore, when severe bending resistance is required, it is an extremely effective wiring material.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a flat cable according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating film 2 Adhesive 3 Conductor

Claims (2)

(57) [Claims] 1. A flat cable in which a plurality of parallelly arranged conductors are sandwiched between two insulating bases each including an insulating film layer and an adhesive layer, and the thickness of the insulating film layer ( A flat cable characterized in that Ti) and the thickness (Ta) of the adhesive layer have the following relationship. Ta> 15 μm Ta + Ti ≦ 80 μm 1.2 ≦ Ti / Ta ≦ 2.0 2. The flat cable according to claim 1, wherein the insulating film layer is made of polyethylene terephthalate, and the resin composition of the adhesive layer has a tensile modulus at 20 ° C. of 20 kg / mm ² or more.