JP2007087663A - Flat cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive flat cable excelling in flame resistance and heat resistance by directly fusion-bonding a pair of single-layer polyether imide films to each other without interlaying an adhesive layer. <P>SOLUTION: This flat cable is composed by arranging a plurality of core materials in parallel with one another and by sandwiching them between a pair of films. In the flat cable, the films contain polyether imide as a main constituent and are fusion-bonded to each other at a temperature higher than the glass transition point of the films. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flat cable covering insulating member widely used in electronic devices, home appliances, automobiles and the like.

First, a conventional flat cable will be described with reference to FIG.
FIG. 4 is a cross-sectional view of an example of a conventional flat cable. In FIG. 4, 1 is a core material, 2 'is a base material layer such as a polyethylene terephthalate (PET) film, and 7 is an adhesive layer.
A conventional flat cable is manufactured by passing a laminated film sandwiching a core material 1 such as a conductor, an electric wire, or an optical fiber through a pair of heat rolls and thermally bonding the adhesive layers facing each other. The laminate film is generally composed of a base material layer 2 ′ that does not melt at the temperature of the hot roll and an adhesive layer 7 that is fused by the heat of the hot roll. This general laminate film requires a manufacturing process such as applying the adhesive layer 7 to the base film 2 ', drying and curing it to such an extent as not causing problems such as blocking, and winding the film into a roll. Therefore, it becomes high price. Furthermore, it is inevitable to use a solvent such as toluene in the process of applying the adhesive layer. The solvent is removed as much as possible in the drying process, but the remaining solvent may volatilize when the product is used, and there is a risk of inducing so-called VOC (volatile organic compound) problems such as odor complaints and health hazards.
In general, since the base material layer 2 'is a resin film, it is difficult to transfer heat. Therefore, it takes time for the heat from the heat roll to pass through the base material layer 2 ′ and reach the adhesive layer 7. Therefore, the adhesive used for the adhesive layer 7 is required to have the ability to be fused at as low a temperature as possible. As a result, no matter how much a heat-resistant material is used for the base material layer, the heat resistance of the adhesive layer is low, so that the heat resistance as a flat cable tends to be low.
When the heat resistance of the adhesive layer is required, a cross-linking technique for the adhesive layer is used. As a method for crosslinking, it has been common to add a crosslinking agent such as peroxide to the adhesive layer to chemically crosslink the adhesive layer. In that case, if the adhesive layer is cross-linked before fusing, sufficient adhesive strength will not be exhibited, so the laminate film before cross-linking needs to be transported and stored in a refrigerated state. It was very expensive. Moreover, since the crosslinking reaction proceeds little by little no matter how refrigerated it is stored, the usable period of the product is shortened, and usually only about one month can be stocked. As a result, laminate films had to be manufactured for each usage as every month, and it was difficult to improve production efficiency by mass production.
As the base layer of the laminate film, a polyethylene terephthalate (PET) film is generally used from the balance of cost, mechanical and thermal performance. On the other hand, as the adhesive layer, a polyester-based adhesive is generally used from the viewpoint of good compatibility with the PET film, adhesive performance, and price balance. However, since both PET film and polyester adhesives are very flammable materials, in order to obtain sufficient flame retardant performance as a flat cable, a combination of a flame retardant with a high flame retardant effect and antimony trioxide is added. As a result, it has the disadvantage of containing a large amount of environmentally hazardous substances. Moreover, the glass transition point of PET film is as low as around 70 ° C., and the glass transition point is straddled during use depending on the use environment and current value. When a PET film that has become soft at 70 ° C. or higher is cooled as it is to a normal temperature or a low temperature, a so-called heat setting phenomenon occurs in which the shape at the time of high temperature is wrinkled. In particular, in a flat cable used in a place where an operation such as bending and stretching is required, if a heat set phenomenon occurs, the operation stability is greatly impaired.

Moreover, as a flat cable which does not have an adhesive layer, for example, there is an extruded flat cable listed in Patent Document 1. In order to produce an extruded flat cable, it is necessary to prepare an extrusion mold for each specification such as the conductor size and the number of cores. Flat cables are often required for various specifications, and it is necessary to produce a wide variety of products in small quantities, but in order to meet all requirements with extruded flat cables, a large number of extrusion molds are not prepared. It had the disadvantage that it was difficult to recover the capital investment.
JP 2002-358837 A

  An object of the present invention is to provide a flat cable that can be manufactured without using a conventional adhesive layer, is inexpensive, and has excellent flame resistance and heat resistance, in order to solve the above problems.

As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by directly fusing a pair of single layer polyetherimide films without the presence of an adhesive layer. . The present invention has been made based on this finding.
That is, the present invention
(1) A flat cable in which a plurality of core members are arranged in parallel and sandwiched and integrated by a pair of films, wherein the film is mainly composed of polyetherimide, and the film is separated from its glass transition point. A flat cable characterized by being heat-sealed at a high temperature,
(2) The flat cable as set forth in (1), wherein the film is fused at a temperature 5 ° C. or more higher than its glass transition point.
(3) The flat cable according to (1) or (2), wherein the core material is made of a metal conductor, and (4) the thickness of the film is 1/3 or more and 1 or less of the thickness of the metal conductor. The flat cable according to item (3) is provided.

  The flat cable of the present invention can be manufactured without using a conventional adhesive layer, and is inexpensive and excellent in flame retardancy and heat resistance.

Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of each drawing, the same elements are denoted by the same reference numerals.
First, the preferable flat cable of this invention is demonstrated based on FIG.
FIG. 1 is a sectional view showing one preferred embodiment (two core members) of the flat cable of the present invention. In the figure, 1 is a core material, 2 is a polyetherimide film, and a dotted line 2 a is a fused portion of the polyetherimide film 2.
As shown in FIG. 1, the present invention is a flat cable having a configuration in which a plurality of core materials 1 such as conductors, electric wires or optical fibers are arranged in parallel and the core material 1 is sandwiched between a pair of polyetherimide films 2. And it is a flat cable formed by heat fusion without using an adhesive layer.

In the present invention, a material obtained by processing a polyetherimide (hereinafter referred to as PEI) excellent in flame retardancy and heat resistance into a film (hereinafter referred to as PEI film) is used. The PEI film of the present invention contains PEI as a main component, but from the viewpoint of chemical resistance to machine oils and alkalis, a siloxane block copolymer of 50% by mass or less may be copolymerized in the polymer. Examples of the PEI film obtained by copolymerizing such a siloxane block copolymer include films made of SILTEM, STM1500 (trade name, manufactured by Nippon GE Plastics Co., Ltd.) and the like.
Although there is no restriction | limiting in particular in the thickness of the said PEI film, 12-100 micrometers is preferable. Moreover, when the metal conductor mentioned later is used as a core material, it is preferable that the thickness of a PEI film is 1/3 or more and 1 or less of the thickness of a metal conductor. By setting the thickness of the PEI film within the above range, it is possible to obtain a flat cable having excellent flexibility.
As will be described later, the flat cable of the present invention can be produced by sandwiching a plurality of core materials with PEI films, heat laminating them, and fusing the films together. The fusing temperature is preferably 5 ° C. or more higher than 215 to 250 ° C., which is the glass transition point of PEI, and more preferably 5 to 50 ° C. higher. For example, it is preferable to fuse at 230 to 260 ° C. The fusion is preferably performed by a hot roll described later. The fusing temperature corresponds to the surface temperature of the hot roll, and the fusing time is controlled by the rotation speed of the hot roll.

The PEI film is often subjected to a roughening process called “texture processing” in order to prevent a so-called blocking defect in which the films stick to each other and are not peeled off when the roll is wound.
When manufacturing the flat cable of the present invention by heat laminating and fusing such embossed PEI films, if the embossed surfaces are bonded together, the embossed projections are It is preferable that the fusion strength can be increased by digging in and exhibiting the anchor effect. On the other hand, if the textured surface is applied in a direction that is exposed to the outside, the unevenness caused by the textured surface becomes the starting point of the crack, which may undesirably deteriorate the bending resistance of the flat cable.

The core material may be of any material and may have an arbitrary cross-sectional shape, for example, an arbitrary conductor such as a round cross-section conductor, an arbitrary electric wire such as a covered electric wire, or an arbitrary light A fiber etc. are mentioned. The number of cores is not particularly limited but is preferably 2-30. The thickness and diameter of the core material are not particularly limited but are preferably 25 to 250 μm. The width of the core material is not particularly limited, but is preferably 0.5 to 15 mm. The spacing between the core members is not particularly limited as long as insulation is maintained, but 0.5 to 5 mm is preferable.
In this specification, the “width” direction of the cable or the core material represents a direction in which the core materials are arranged in a plane orthogonal to the length direction of the cable or the core material, and the “thickness” direction represents the cable or the core. This represents a direction orthogonal to the width direction in a plane orthogonal to the length direction of the material.

  The width of the flat cable is not particularly limited, but is preferably 2 to 100 mm, and the width corresponds to the width of the PEI film.

Next, an example of the flat cable manufacturing method of the present invention will be described with reference to FIG.
FIG. 2 is an explanatory view of a heat laminating apparatus for producing the flat cable of the present invention. In the figure, 1 is a core material, 2 is a PEI film, 3 is a heat roll, 4 is a PEI film wound in a roll shape (hereinafter referred to as a PEI film bobbin), and the PEI film 2 is supplied from the PEI film bobbin 4. The
A plurality of core members 1 separated from each other by a predetermined distance in the width direction of the flat cable to be formed are guided to a pair of heat rolls 3 as shown in FIG. Is sandwiched between the PEI films 2 supplied from the vertical direction of the core material 1 (arrows h and i, respectively), and the PEI films 2 facing each other with the core material 1 interposed therebetween are heat-sealed and integrated. Thus, the flat cable of the present invention can be manufactured.
At this time, the line speed to be advanced in the length direction indicated by the arrow j in the drawing, that is, the production speed is not particularly limited, but is preferably 0.4 to 10 m / min, and more preferably 1 to 5 m / min. This production speed is controlled by the rotation speed of the heat roll 3. Further, the surface pressure between which the core material 1 and the PEI film 2 are sandwiched by the pair of heat rolls 3 is not particularly limited.
The hot roll 3 may have an arbitrary diameter such as 6 inches, and may be covered with an arbitrary material such as fluororubber.
Another aspect of the flat cable manufacturing method of the present invention will be described with reference to FIG.
FIG. 3 is a sectional view showing another embodiment of the flat cable of the present invention. In the figure, 5 indicates a gap between the core material and 6 indicates both end portions in the width direction of the flat cable.
The flat cable of the present invention can also be manufactured by any ultrasonic heat fusion using an ultrasonic horn or the like instead of the above-described heat laminating process. That is, as shown in FIG. 3, a flat cable is manufactured by fusing the core portion of the PEI film and the gap portion 5 and both end portions 6 of the core material continuously by applying an ultrasonic horn in the cable length direction. can do.

EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited by these.
First, various test methods shown in Tables 1 and 2 below will be described.
[Flexibility]
It is the number of times until the core material in the flat cable breaks at a normal temperature (25 ° C.) until it is bent to a bending radius of 7 mm or straightened, and the larger the number, the better. In the case of a flat cable having a flat conductor as a core material, the number of bends is compared with the example using a conductor having the same thickness among the flat cables using the conventional PET film with an adhesive layer described in Comparative Examples 1 to 3. A case where the performance dropped extremely was regarded as unacceptable.
[Peel strength]
The peel strength between the films was determined by measuring the adhesive strength using a T-type peel test (peel rate 50 mm / min).
The peel strength between the film and the core was measured by a 180 ° peel test (peel rate 50 mm / min).
[Flame retardance]
About flame retardancy, the VW-1 vertical combustion test prescribed | regulated by UL1581 was done. The case where it was not completely burned even if flame contact for 15 seconds was repeated until no ignition occurred was regarded as acceptable.
[Heat set rate]
A flat cable was inserted so as to be in close contact with the inner surface of a brass pipe having an inner diameter of 14 mm (radius 7 mm), heated as it was at 85 ° C. for 24 hours, sufficiently cooled, taken out, and left for another 24 hours. The outer radius of curvature R ′ of the flat cable is measured, and the value obtained by dividing the radius of the inner radius by 7 is defined as the heat set rate. This heat set rate ranges from 0 to 1, and the larger the value, the easier the curl is attached. In particular, a flat cable used in a part that operates like a rotating connector has a higher operation stability as the curl is less likely to be attached. Therefore, the smaller the heat set rate, the better.
[Flexibility after heating]
The obtained flat cable was heated at 130 ° C. or 140 ° C. for 10,000 hours, the cooled flat cable was wound around a mandrel having a diameter of 3 mm, and the flexibility after heating was evaluated.
[Rotary connector durability test]
It was incorporated into a rotary connector disclosed in Japanese Patent Laid-Open No. 05-234651 or a rotary connector disclosed in Japanese Utility Model Laid-Open No. 62-168581, heat-treated at 90 ° C. for 168 hours, and gradually cooled in a stationary state. Thereafter, the endurance test was conducted by rotating 400000 cycles with 2 rotations left and right at a speed of 5 rotations per second.

Reference example 1
A PEI film (made by GE Plastics Co., Ltd., trade name Ultem 1000B, glass transition point of about 215 ° C.) molded into a 50 μm-thick film under the conditions of a production rate of 2 m / min and a hot roll 4 surface temperature of 230 ° C. When the film was passed through a 6-inch diameter fluororubber-coated hot roll machine, the films exhibited fusion strength that would cause material destruction.
Reference example 2
The above film was replaced with a heat-resistant product (trade name Ultem XH6050B, glass transition point about 250 ° C., manufactured by GE Plastics Inc., Japan) processed to a 25 μm thick film, and the surface temperature of the hot roll 4 was 255 ° C. In contrast, the films showed a high fusion strength of 3 N / cm.
Example 1
When a plurality of rectangular conductors with a thickness of 100 μm and a width of 1.5 mm are arranged in the width direction between a pair of 50 μm thick films used in Reference Example 1 and heat laminated at 230 ° C. under the same conditions, halogen or the like A flat cable having such a high flame retardant performance as to pass the UL 1581 VW-1 combustion test was able to be formed without containing any environmentally hazardous substances. In addition, as apparent from Table 1 below, the film remains sufficiently flexible even when this flat cable is heated at 130 ° C. or 140 ° C. for 10,000 hours, and even if it is wound around a mandrel having a diameter of 3 mm, There were no failures.

Examples 2-3
In Example 2, even if the surface temperature of the heat roll 4 was changed to 250 ° C., a high fusion strength was exhibited, and a flat cable having high flame retardancy was able to be formed.
In Example 3, as in Reference Example 2, even if the film is replaced with a heat-resistant product (glass transition point of about 250 ° C.), a high fusion strength is exhibited and a flat cable having high flame retardancy is formed. I was able to do it.

Examples 4-11
In Examples 4 to 11, when the PEI film thickness was changed in the range of 25 to 125 μm and the conductor thickness was changed in the range of 25 to 150 μm as apparent from Table 1 below, a flat cable could be formed in any case. It was possible and the bending resistance was sufficient.
As can be seen from Table 1 below, Examples 4 and 11 (0.25 and 0.167, respectively) with a small film thickness / conductor thickness ratio, and Examples 6 and 8 with large ratios (respectively, respectively) 1.25 and 2) have relatively low flex resistance. On the other hand, it can be seen that Examples 1-3, 5, 7, 9, and 10 in which the ratio of film thickness / conductor thickness is in the range of 1/3 or more and 1 or less are particularly excellent in bending resistance.

Examples 12-14
Moreover, in Examples 12-14, even if the core material was replaced with a covered electric wire, a round cross-section conductor, or an optical fiber, a flat cable could be formed without any problem.

Example 15
For the pair of films and conductors used in Example 1, ultrasonic fusion was performed instead of thermal lamination. When the conductor and the gap portion between the conductors and the film on both ends were fused by applying an ultrasonic horn continuously in the length direction, a flat cable having high bending resistance and flame retardancy could be formed.
Moreover, when the heat set rate was measured for the flat cables of Examples 1 to 11 and 15, as apparent from Table 1 below, there was no problem in practical use at a value of 0.5 or less.
In addition, the flat cables of Examples 1 to 3, 7 and 8 were incorporated into a rotary connector disclosed in Japanese Utility Model Laid-Open No. 62-168581 or Japanese Patent Application Laid-Open No. 05-234651, and subjected to heat treatment at 90 ° C. for 168 hours to be stationary. No problem was caused at all even when subjected to a durability test (4,000 cycles with two rotations left and right at a speed of 5 rotations per second).

Comparative Examples 1-3
A laminate film in which a bromine-based flame retardant and an antimony trioxide-added adhesive were applied to a PET film was constructed, and thermal lamination was performed with a 25-150 μm thick conductor sandwiched between them. Although we were able to manufacture a flat cable with high flexibility, the heat resistance is slightly low and the flexibility is not lost even if heated at 120 ° C for 10,000 hours, but the diameter is 3mm for 10,000 hours at 130 ° C. When wound around the mandrel, the coating cracked and lost its electrical insulation performance. In addition, there are problems such as high price, containing a large amount of environmentally hazardous substances, and solvent remaining in the adhesive volatilizes during use and induces VOC problems.
Moreover, when the heat set rate was measured about the flat cable of these Comparative Examples 1-3, all became a value of 0.8 or more. When the flat cable of Comparative Example 3 incorporated in the rotary connector disclosed in Japanese Patent Laid-Open No. 05-234651 was heated at 90 ° C. for 168 hours and gradually cooled as it was, a large reaction force was felt during rotation. This is probably due to the heat set phenomenon that occurred in the flat cable. When this rotating connector was subjected to an endurance test (400,000 cycles, with two rotations left and right at a speed of 5 rotations per second), the internal flat cable was disconnected. When this rotary connector was disassembled, the flat cable inside showed a large heat set phenomenon, and as a result, the rotation stability was impaired, and the flat cable was entangled to the extent that it was disconnected. confirmed.

Comparative Examples 4-6
Instead of the pair of PEI films used in Reference Example 1, a 50 μm thick biaxially stretched PET film was used. The surface temperature of the hot roll was changed to 90 ° C. (Comparative Example 4) or 250 ° C. (Comparative Example 5), which was higher than the glass transition point of the PET film, but the film was only peeled off at a lower temperature. Since the film was not fused and the film was shrunk from around 200 ° C., a flat cable could not be formed. Moreover, in Comparative Example 6, when a flat cable in which a conductor was sandwiched between PET films using an ultrasonic welding technique in the same manner as in Example 15 was prepared and the flame retardancy was evaluated, it was completely burned and rejected in the UL1581VW-1 combustion test. Met.
Comparative Example 7
Instead of the PEI film of Reference Example 1, a PPS (polyphenylene sulfide) film having a thickness of 50 μm and extremely high flame retardancy was used. Even if the surface temperature of the hot roll was raised to 270 ° C., which was close to the melting point of PPS, sufficient fusion strength could not be obtained, and it could be easily peeled off by hand.

  The configurations of Reference Examples 1 and 2, Examples 1 to 15, and Comparative Examples 1 to 7, and the test results thereof are shown in the following table. In the table, “material breakage” indicates that the material was firmly fused and the material was broken in the peel strength test. "-" Indicates not used or not tested.

FIG. 1 is a cross-sectional view showing one preferred embodiment of the flat cable of the present invention. FIG. 2 is an explanatory diagram of the heat laminating process for manufacturing the flat cable of the present invention. FIG. 3 is a cross-sectional view showing another embodiment of the flat cable of the present invention. FIG. 4 is a cross-sectional view of an example of a conventional flat cable.

Explanation of symbols

1 Core material 2 Polyetherimide film

Claims (4)

  A flat cable in which a plurality of core materials are arranged in parallel and sandwiched and integrated by a pair of films, wherein the film is mainly composed of polyetherimide, and the film is heated at a temperature higher than its glass transition point. A flat cable characterized by being fused.   The flat cable according to claim 1, wherein the film is fused at a temperature higher than the glass transition point by 5 ° C. or more.   The flat cable according to claim 1, wherein the core material is made of a metal conductor.   The flat cable according to claim 3, wherein a thickness of the film is 1/3 or more and 1 or less of a thickness of the metal conductor.

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