JP2002050233A - Tflat cable and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize easy peeling of an insulating film to a linear conductor and to prevent position deviation in the insulating film. SOLUTION: A notched part 16 or the like is formed on a side part of a linear conductor 15 so as to prevent position deviation in insulating films 11 and 13 of the linear conductor 15. Both insulating films 11 and 13 are adhered at the notch part 16 by a thermal laminating method, ultrasound method or the like, whereby the connection part functions as a stopper preventing position deviation of the linear conductor 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat cable in which a plurality of linear conductors arranged in parallel at a predetermined interval are sandwiched between two insulating films, and a method of manufacturing the flat cable.

[0002]

2. Description of the Related Art For the purpose of saving space and weight, flat cables in which a rectangular linear conductor is sandwiched between insulating films have been used in various fields. FIG. 16 is a diagram showing a method for manufacturing a conventional flat cable, and FIG. 17 is a sectional view showing a conventional flat cable. In general, as shown in FIG. 16, a flat cable is formed by sandwiching a plurality of linear conductors 5 arranged in parallel with an interval between two insulating films 1 and 3. Insulating film 1,
3 is a base material 1a, 3 made of resin such as PET as shown in FIG.
a is used in which the thermoplastic adhesive layers 1b and 3b are applied in advance to one surface of the insulating film 1a.
Is sandwiched. Then, as shown in FIG. 16, in a state where the linear conductor 5 is sandwiched between the insulating films 1 and 3, the insulating films 1 and 3 are passed between the thermocompression bonding rollers 7 to melt the adhesive layers 1b and 3b. The insulating films 1 and 3 are bonded together.

Here, as the thermoplastic adhesive layers 1b and 3b, for example, a polyester elastomer is used.
For example, a material that is in a molten state when heated at 170 degrees Celsius or higher is used. That is, the thermoplastic adhesive layer 1
b and 3b have such a property that the tackiness increases in a heated state, but the tackiness disappears at room temperature.

In this case, the portions of the two insulating films 1 and 3 where the thermoplastic adhesive layers 1b and 3b are directly bonded to each other have the same molecular structure. Once the layers 1b and 3b are firmly adhered to each other at the time of heating, even if the temperature subsequently changes to room temperature, the adhesive strength is kept strong.

[0005] However, even if the thermoplastic adhesive layers 1b and 3b once become tacky in a heated state, the linear conductors 5 having completely different molecular structures will not be cured when the temperature drops to room temperature. Conductor 5 and thermoplastic adhesive layers 1b, 3
The adhesive strength with b is greatly reduced, and it is close to a state where almost no bonding is performed.

As described above, when the adhesive strength of the thermoplastic adhesive layers 1b and 3b to the linear conductor 5 is extremely low, the linear conductor 5 has a rectangular linear shape. Thus, there is a possibility that the linear conductor 5 is displaced in its longitudinal direction. This means that the quality of the flat cable as a product may be reduced.

In order to avoid this, in the conventional flat cable, the thermoplastic adhesive layers 1b, 3b of the insulating films 1, 3 attached to both sides of the linear conductor 5 having a thickness of about 100 μm are provided. The thickness of the thermoplastic adhesive layers 1b and 3b is set to be large to about 60 μm to secure a large amount of melting, so that the upper surfaces 5a and 5
In addition, the thermoplastic adhesive layers 1b and 3b are wrapped around not only the side surfaces 5c but also the side surfaces 5c, whereby the periphery of the linear conductor 5 is filled with the thermoplastic adhesive layers 1b and 3b, and the thermoplastic adhesive layers 1b and 3b Efforts have been made to prevent the longitudinal displacement of the linear conductor 5 due to the interfacial frictional force with the linear conductor 5.

However, when the thickness of the thermoplastic adhesive layers 1b and 3b is increased, the displacement of the linear conductor 5 in the longitudinal direction can be prevented, but both insulating films are formed in the region adjacent to the linear conductor 5. When the insulating films 1 and 3 are peeled off at the end portions for external connection, a part of the thermoplastic adhesive layers 1b and 3b remain as residues because the first and third materials are strongly adhered to each other. Depending on the shape of the residue, the residue may be caught on the linear conductor 5 and may not be easily removed.

Therefore, in the conventional manufacturing method, as shown in FIG. 16, windows 1c and 3c are provided in the insulating films 1 and 3 at positions corresponding to each other intermittently in the longitudinal direction.
By cutting the flat cable at portions c and 3c, the end of the linear conductor 5 can be reliably exposed without substantially peeling.

[0010]

However, FIG.
In the conventional manufacturing method shown in FIG. 1, it is necessary to provide windows 1c and 3c for exposing the end of the linear conductor 5,
There is a problem that a complicated process for forming c and 3c is required. In particular, since cutting can be performed only at the portions where the windows 1c and 3c are formed, the degree of freedom in the variation of the length of the flat cable can be limited. If the windows 1c and 3c are formed in the middle portion of the flat cable without being used for cutting, the linear conductor 5 remains exposed in the windows 1c and 3c. Therefore, there is a problem that a protective sheet for closing the windows 1c and 3c of the flat cable must be attached in a later step.

The purpose of peeling the insulating films 1 and 3 from the linear conductor 5 is not only to expose the end of the linear conductor 5 but also to remove the metallic linear conductor when disposing of the flat cable. 5 and the insulating films 1 and 3 made of resin are separated from the linear conductor 5 to separate the insulating films 1 and 3 from the resin.
3 needs to be removed. However, in the conventional flat cable shown in FIG. 16, as described above, the residue of the thermoplastic adhesive layers 1b and 3b may be left on the side portions of the linear conductor 5 or the like, and as a result, the linear conductor The problem that the residual ratio of impurities of No. 5 is increased occurs, which is not preferable.

[0012] Therefore, an object of the present invention is to make it possible to easily peel off the insulating film from the linear conductor without providing a window in both insulating films, and to extend the longitudinal direction of the linear conductor. It is an object of the present invention to provide a flat cable and a method for manufacturing the flat cable, which can surely prevent the displacement of the flat cable.

[0013]

Means for Solving the Problems In order to solve the above problems,
The invention according to claim 1 is provided between two insulating films.
A flat cable sandwiching a plurality of linear conductors arranged in parallel at regular intervals, wherein the linear conductors are formed with a plurality of displacement prevention portions intermittently along a longitudinal direction, At least the insulating films are heat-bonded to each other through a thermoplastic adhesive layer having a thickness of 1 to 3 μm so as to include a region corresponding to the position shift preventing portion.

According to a second aspect of the present invention, there is provided a flat cable in which a plurality of linear conductors arranged in parallel at a predetermined interval are sandwiched between two insulating films. A plurality of misalignment preventing portions are formed intermittently along the longitudinal direction, and the insulating films are ultrasonically welded to each other so as to include a region corresponding to the misalignment preventing portion.

According to a third aspect of the present invention, there is provided the flat cable according to the first or second aspect, wherein the misalignment preventing portion is a notch formed on a side portion of the linear conductor. There is something.

According to a fourth aspect of the present invention, there is provided the flat cable according to the first or second aspect, wherein the displacement preventing portion is a hole formed in a part of the linear conductor. It is.

According to a fifth aspect of the present invention, there is provided the flat cable according to the first or second aspect, wherein the misalignment preventing portion is an unevenness formed on a surface of the linear conductor. is there.

According to a sixth aspect of the present invention, there is provided the flat cable manufacturing method according to the first aspect, wherein a thermoplastic adhesive layer having a thickness of 1 to 3 μm is previously formed on at least one side of each of the insulating films. Then, in a state in which a plurality of linear conductors are sandwiched between the two insulating films, when the two insulating films are heated and bonded to each other, the thermoplastic adhesive layer is thermally fused into the misalignment preventing portion. It is to be filled.

According to a seventh aspect of the present invention, there is provided the flat cable manufacturing method according to the second aspect, wherein a plurality of linear conductors are arranged so as to be sandwiched between the insulating films. When the two insulating films are ultrasonically welded to each other, the insulating film is thermally melted by an ultrasonic wave to fill the inside of the displacement preventing portion.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 is a sectional plan view showing a flat cable according to a first embodiment of the present invention, FIG. 2 is a sectional side view thereof, and FIG. Is a perspective sectional view thereof, FIG. 4 is a perspective view showing a linear conductor,
FIG. 5 is a diagram showing a method of manufacturing a flat cable.

In the flat cable according to this embodiment, as shown in FIG. 5, a plurality of substantially rectangular wire conductors 15 arranged in parallel with a constant interval between two insulating films 11 and 13 are provided. In particular, as shown in FIGS. 1 to 4, cutouts 16 functioning as position shift preventing portions are provided at regular intervals along the longitudinal direction on the side of the linear conductor 15 as shown in FIGS. 1 to 4. It was formed.

The insulating films 11 and 13 are a substrate made of a resin such as PET, and have a thickness of 1 μm to 3 μm made of a thermoplastic resin of the same system as the substrate on the inner surface of the substrate.
m of a thin adhesive layer is applied. As the adhesive layer, a thermoplastic adhesive such as a polyester-based elastomer is used, for example, and has a property of melting only at 170 ° C. or higher (that is, having a tackiness).

In the thermal laminating method, the insulating films 11 and 13 are used as upper and lower film rolls 17 and 13.
It is pulled out from the device 19 and supplied to a thermocompression unit (here, a pair of upper and lower thermocompression rollers) 21. As the thermocompression bonding roller 21, an elastic rubber roller or the like is used.
Thereby, even if the portion where the linear conductor 15 is not disposed is thinner than the portion where the linear conductor 15 is disposed, it is possible to sufficiently press and crimp the thin portion. Note that the lower insulating film 13 is
And supplied to the thermocompression bonding roller 21.

Each linear conductor 15 has trapezoidal cutouts 16 at predetermined intervals along the longitudinal direction on the side of a rectangular material having a thickness of about 100 μm, as shown in FIG. The formed one is used. Each linear conductor 15
In the heat laminating method, is drawn from a conductor roll (not shown), guided by a guide roller 25, and supplied to a thermocompression bonding roller 21. The cutouts 16 of the respective linear conductors 15 are arranged so as to be aligned in the width direction of the flat cable. At this time, the respective linear conductors 15 are arranged in parallel at a predetermined interval, and are sandwiched between the two insulating films 11 and 13 supplied between the two thermocompression rollers 21 so as to be used for thermocompression bonding. It is supplied between the rollers 21.

The hatched portion 24 in FIG. 1 is formed by a pair of insulating films 11 and 1 on the side of the linear conductor 15.
3 shows an area where three pieces are bonded by an adhesive layer.
Since the notch 16 is formed on the side of the linear conductor 15 as described above, the region where the insulating films 11 and 13 are adhered to each other by the adhesive layer is the linear conductor 15.
Of the linear conductor 15 at the notch portion 16 of FIG.

As described above, in the thermal lamination method,
The insulating films 11 and 13 sandwiching the linear conductor 15 are
When the roller 21 is passed between the two thermocompression bonding rollers 21, the two rollers 21
And heat-compression bonding.
The adhesive layers 1 and 13 are heated and melted, and after being melted, the two insulating films 11 and 13 are separated by the cured adhesive layer into a gap portion between the plurality of linear conductors 15, that is, both ends of the linear conductor 15 and It is bonded in a region other than the linear conductor 15 such as the cutout portion 16.

As a result, the bonding portion between the insulating films 11 and 13 is firmly bonded, but the thermoplastic bonding layer 1
Since the thickness of the adhesive layer is extremely thin, such as 1 μm to 3 μm, as compared with the conventional example in which the thicknesses of b and 3b are 60 μm, the amount of fusion of the adhesive layer at the time of heat melting is reduced. Is very small compared to
1 and 13 can be adhered to each other with an appropriate adhesive strength that facilitates peeling when peeling. In particular, since the amount of fusion of the adhesive layer at the time of heat melting is extremely smaller than that of the conventional example, the amount of the adhesive layer flowing to the side of the linear conductor 15 at the time of heat fusion is reduced. For this reason, the adhesive force between the adhesive layers of the insulating films 11 and 13 becomes extremely weak as compared with the conventional example, and the peeling can be easily performed.

Furthermore, in the peeling step, even if the adhesive layer is left as a residue and adheres to the surface or the side of the linear conductor 15, the thickness of the adhesive layer is extremely thin as compared with the conventional example. In addition, the amount of residue is significantly reduced as compared with the conventional example. Therefore, for example, in the material separation process at the time of disposal, the impurity remaining rate of the linear conductor 15 can be reduced as compared with the conventional example. In this way, since the skinning process can be easily performed, the labor for forming the windows 1c and 3c as in the conventional example shown in FIG. 16 can be omitted, and
Since the manufacturing process is simplified, manufacturing efficiency can be improved.

As described above, in order to reduce the adhesive strength between the insulating films 11 and 13 and reduce the amount of thermal fusion of the adhesive layer to reduce the wraparound of the linear conductor 15 to the side surface, the longitudinal direction of the linear conductor 15 may be reduced. However, as described above, since the two insulating films 11 and 13 are adhered to each other by the adhesive layer at the notch 16 of the linear conductor 15, the two insulating films at the notch 16 Film 11,
13 is the insulating film 1 of the linear conductor 15
It serves as a stopper for the positional deviation in the longitudinal direction with respect to 1 and 13. Therefore, even if the adhesive strength of the two insulating films 11 and 13 to the linear conductor 15 sandwiched between the two insulating films 11 and 13 is weak, it is easy to prevent the linear conductor 15 from being displaced in the longitudinal direction. Can be.

When the flat cable is terminated, the linear conductor 15 is cut at the portion where the notch 16 is formed, so that the portion of the linear conductor 15 where the notch 16 is formed is cut. (That is, a narrow portion) can be used as an external connection terminal.

FIG. 6 is a view showing a flat cable according to a second embodiment of the present invention, and FIG.
Is an enlarged view of the same. In FIGS. 6 and 7, elements having the same functions as in the first embodiment are denoted by the same reference numerals.

As shown in FIGS. 6 and 7, the flat cable according to the first embodiment is different from the first embodiment in that notches 16 (position shift preventing portions) are formed at regular intervals on the side of the linear conductor 15. However, the difference is that a flat cable is manufactured by an ultrasonic method instead of the heat laminating method.

In the ultrasonic method, the insulating film 11,
For example, a PET film is used as the substrate 13. No adhesive layer was applied to this substrate.

A plurality of cutouts 16 are formed between the insulating films 11 and 13 by forming cutouts 16 at regular intervals in the same linear conductor 15 as in the first embodiment, that is, a rectangular metal wire. The linear conductors 15 are arranged in parallel, sandwiched and mixed, and the base material itself is melted and bonded by frictional heat generated by ultrasonic waves.
The cutouts 16 of the linear conductor 15 are arranged so as to be aligned in the width direction of the flat cable.

The positions where the frictional heat is applied by the ultrasonic waves are, as shown in FIGS. 6 and 7, conductor parallel lines 31 set parallel to the linear conductors 15 along the sides of the respective linear conductors 15;
There is a width direction line 32 set in the width direction of the flat cable so as to cross the cutout portion 16 of the entire linear conductor 15. By applying frictional heat by ultrasonic waves at the width direction line 32 and welding the base materials of the insulating films 11 and 13 to each other, the two insulating films 11 and 13 are linearly formed from the side line of the linear conductor 15. The welding is performed at the notch 16 drawn inside the conductor 15.

In such a configuration, both insulating films 1
Although the insulating films 11 and 13 are welded to each other in the cutout 16 of the linear conductor 15 even though the linear conductors 15 and 13 are not bonded at all, the linear conductor 15 is Even if it is attempted to shift the position, the portion where the two insulating films 11 and 13 are welded in the notch 16 serves as a stopper, so that the position shift of the linear conductor 15 in the longitudinal direction can be easily prevented.

Further, the linear conductor 15 and the insulating film 11,
Since no bonding with the cable 13 is performed, it is possible to provide a flat cable that can be easily peeled.

When the flat cable is terminated, the stripping process can be easily performed by cutting the linear conductor 15 at the portion where the cutout portion 16 is formed.

The shape of the notch 16 is not limited to a trapezoid, but may be another shape such as a semicircle.

Third Embodiment FIG. 8 is a sectional plan view showing a flat cable according to a third embodiment of the present invention, FIG. 9 is a plan view showing a linear conductor 15, and FIG. FIG. 8 to 10.
In the description, elements having the same functions as those in the first and second embodiments are denoted by the same reference numerals.

In the flat cables according to the first and second embodiments, the notch 16 is formed on the side of the linear conductor 15, whereas the flat cable according to this embodiment In the cable, the cutout portion 16 (position shift preventing portion) is formed at, for example, the center of the linear conductor 15 in the width direction. The notch 16 is formed in the linear conductor 15.
Are formed in the thickness direction of the insulating film 1.
By fixing the first and the first 13 to each other, the displacement of the linear conductor 15 in the longitudinal direction is prevented.

FIG. 8 shows that the insulating films 11 and 13 each have a thickness of 1 μm to 1 μm on one surface of the base material as in the first embodiment.
Use a 3μm thin thermoplastic adhesive layer applied,
This figure shows a state in which the linear conductor 15 is sandwiched and adhered by the heat lamination method. The hatched portion 24 in FIG. 8 is a pair of insulating films 11 and 1 on the side of the linear conductor 15.
3 shows an area where three pieces are bonded by an adhesive layer.

Alternatively, as in the second embodiment, the insulating films 11 and 13 may be formed of only a base material, and the base materials may be welded to each other by an ultrasonic method.

The shape of the notch 16 is not limited to a circular hole, but may be a hole having another shape such as a rectangular hole.

Fourth Embodiment FIG. 11 is a view showing a flat cable according to a fourth embodiment of the present invention. In FIG. 11, the same reference numerals are given to elements having the same functions as those in the first to third embodiments.

The flat cable according to this embodiment is different from the first to third embodiments in that the notch 16 described in the first to third embodiments is replaced with an uneven surface 35 on the surface of the linear conductor 15.
(Position shift prevention part).

As described above, by forming the irregularities 35, the linear conductors 15 are sandwiched between the insulating films 11 and 13 made of only a base material such as PET, and the insulating films 11 and 13 are formed by the ultrasonic method. At the time of melting, it is possible to use the irregularities 35 of the linear conductor 15 as a mold and form the joining surfaces of the insulating films 11 and 13 to the linear conductor 15 in a shape that matches the irregularities 35.

The shape of the unevenness 35 may be any shape such as a wedge shape as shown in FIG. 12 or a substantially hemispherical shape as shown in FIG. In addition, as shown in FIG. 14, the unevenness 35 may be formed uniformly over the front surface of the linear conductor 15, or as shown in FIG. 15, an island 36 in which a plurality of unevennesses 35 are formed at regular intervals. May be formed intermittently at a plurality of locations.

This embodiment is the same as the first to third embodiments in that the linear conductors 15 are arranged in parallel. Similarly to the second embodiment, the two insulating films 11 and 13 other than the linear conductor 15 are bonded to each other by the ultrasonic method.

According to this method, the insulating films 11 and
13 and the linear conductor 15 do not have an adhesive force, but the surfaces of the insulating films 11 and 13 are
5, the insulating films 11 and 13 and the unevenness 35 of the linear conductor 15 are fitted to each other, so that the displacement of the linear conductor 15 in the insulating films 11 and 13 can be reduced. Can be prevented.

In this embodiment, the ultrasonic method has been described as an example. However, the insulating films 11 and 13 each having a thin thermoplastic adhesive layer formed on one surface of a substrate are used.
Needless to say, the same advantage can be obtained even if the linear conductor 15 is sandwiched by the thermal lamination method.

[0052]

According to the first and second aspects of the present invention, the insulating film is peeled off from the linear conductor at the end for external connection, or the insulating film is formed into a linear form in the sorting operation at the time of disposal. At the same time it is easy to peel off from the conductor,
The displacement of the linear conductor in the insulating film can be prevented by the displacement preventing portion such as the cutout portion (claim 3), the hole (claim 4) or the unevenness (claim 5).

According to the first and sixth aspects of the present invention, the insulating film has a thickness of 1 to 3 μm with respect to the substrate.
When a thin thermoplastic adhesive layer having a thickness of m is applied, the amount of melting of the thermoplastic adhesive layer can be limited, and peeling can be easily performed. Also in this case, the position shift preventing portion can sufficiently prevent the position shift of the linear conductor. Alternatively, according to the invention described in claim 2 and claim 7,
The same applies to the case where the insulating film is melted by the ultrasonic method.

[Brief description of the drawings]

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

FIG. 2 is a side view showing the flat cable according to the first embodiment of the present invention.

FIG. 3 is a perspective sectional view showing the flat cable according to the first embodiment of the present invention.

FIG. 4 is a perspective view showing a linear conductor applied to the flat cable according to the first embodiment of the present invention.

FIG. 5 is a perspective view showing the method for manufacturing the flat cable according to the first embodiment of the present invention.

FIG. 6 is a plan view showing a flat cable according to a second embodiment of the present invention.

FIG. 7 is a partially enlarged plan view showing a flat cable according to a second embodiment of the present invention.

FIG. 8 is a sectional plan view showing a flat cable according to a third embodiment of the present invention.

FIG. 9 is a perspective view showing a linear conductor applied to a flat cable according to a third embodiment of the present invention.

FIG. 10 is a perspective view showing a linear conductor applied to a flat cable according to a third embodiment of the present invention.

FIG. 11 is a perspective view showing a linear conductor applied to a flat cable according to a fourth embodiment of the present invention.

FIG. 12 is a sectional view showing an example of a linear conductor applied to a flat cable according to a fourth embodiment of the present invention.

FIG. 13 is a sectional view showing another example of the linear conductor applied to the flat cable according to the fourth embodiment of the present invention.

FIG. 14 is a sectional view showing another example of the linear conductor applied to the flat cable according to the fourth embodiment of the present invention.

FIG. 15 is a sectional view showing another example of the linear conductor applied to the flat cable according to the fourth embodiment of the present invention.

FIG. 16 is a perspective view showing a conventional flat cable manufacturing method.

FIG. 17 is a sectional view showing a conventional flat cable.

[Explanation of symbols]

 11, 13 Insulating film 15 Linear conductor 16 Notch 35 Irregularity

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29K 105: 34 B29K 105: 34 B29L 31:00 B29L 31:00 (72) Inventor Koji Fukumoto Yokkaichi, Mie Prefecture 1-14 Nishi-Suehirocho Sumitomo Wiring Systems Co., Ltd. F-term (reference) 4F211 AA24 AD16 AE03 AG03 AH35 TA04 TA13 TC05 TH06 TN09 TN22 TQ03 5G311 CB01 CD01 CD03 CD10

Claims (7)

[Claims] 1. A flat cable comprising a plurality of linear conductors arranged in parallel at a fixed interval between two insulating films, wherein the linear conductors are intermittently arranged in a longitudinal direction. A plurality of misalignment preventing portions are formed, and at least the insulating films are heat-bonded via a thermoplastic adhesive layer having a thickness of 1 to 3 μm so as to include a region corresponding to the misalignment preventing portion. Flat cable. 2. A flat cable in which a plurality of linear conductors arranged in parallel at a fixed interval are sandwiched between two insulating films, wherein the linear conductors are intermittently arranged in the longitudinal direction. A flat cable in which a plurality of misalignment preventing portions are formed, and the insulating films are ultrasonically welded to each other so as to include a region corresponding to the misalignment preventing portion. 3. The flat cable according to claim 1, wherein the misalignment preventing portion is a cutout portion formed on a side portion of the linear conductor. 4. The flat cable according to claim 1, wherein the displacement prevention part is a hole formed in a part of the linear conductor. 5. The flat cable according to claim 1, wherein the misalignment preventing portion is an unevenness formed on a surface of the linear conductor. 6. The method for manufacturing a flat cable according to claim 1, wherein at least one surface of each of the insulating films has a thickness of 1 to 3.
When a thermoplastic adhesive layer having a thickness of 3 μm is formed in advance and a plurality of linear conductors are interposed between the two insulating films, and when the two insulating films are heated and bonded to each other, the thermoplastic adhesive layer is formed. A method of manufacturing a flat cable, which is filled in the misalignment preventing portion by thermal melting. 7. The method of manufacturing a flat cable according to claim 2, wherein a plurality of linear conductors are arranged between the two insulating films so as to sandwich the two insulating films with each other. A method of manufacturing a flat cable in which, when welding, the insulating film is thermally melted by ultrasonic waves and filled in the displacement preventing portion.