JP3121376B2 - Polyimide laminate and cable insulated with the laminate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide laminate and a cable insulated by the laminate, and more particularly to a method for improving the stripping property of an insulation coating without adversely affecting mechanical strength and dielectric breakdown voltage. A polyimide laminate having a specific heat seal strength and a cable insulated with the laminate. The laminate of the present invention is usually wound into a conductor such as copper in the form of a tape, and is used for a coil, a cable for a motor, an electric wire for an aircraft, or the like.

[0002]

2. Description of the Related Art As described above, a polyimide laminate is used as an insulating coating for electric wires and the like. The electric wire is usually manufactured by winding the tape-shaped laminate on a conductor wire and then fusing a fluororesin by a predetermined heat treatment. When the electric wires manufactured in this way are electrically connected to each other, the end portions of the electric wires are stripped of an insulating coating and connected by soldering or the like. However, if the adhesive strength between the conductor and the fluororesin is larger than the adhesive strength between the polyimide film and the fluororesin, when the electric wire is stripped, a part of the fluororesin remains on the conductor (defective stripping property), There is a problem that an electrical connection failure occurs.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyimide laminate which has solved the above-mentioned problem of strip failure and a cable insulated by the laminate.

[0004]

SUMMARY OF THE INVENTION In view of the above circumstances, the present inventors have dealt with the problem of the poor insulation coating strip property in a polyimide laminate, specifically, the adhesive force between a conductor and a fluorine-based resin and the polyimide film and a fluorine-containing resin. As a result of intensive studies on a method of controlling the adhesive force with the resin, the present invention has been achieved. That is, the present invention is a laminate obtained by laminating a fluorine-based resin on both sides or one side of a polyimide film, and used as an insulating coating of a conductor,
The heat sealing strength between the fluororesin surface of the laminate and the polyimide film surface is 1.5 times or more the heat sealing strength between the fluororesin surface of the laminate and the shine surface of the copper foil. The content is a polyimide laminate characterized by being improved. Further, the present invention provides a cable characterized in that the polyimide laminate is coated with an insulating material.

[0005] If the adhesive strength between the polyimide film and the fluororesin is smaller than the adhesive strength between the fluororesin and the conductor, stripping failure occurs as described above. The adhesive strength is expressed as the product of the adhesive strength per unit area and the contact area. When the cross section of the manufactured electric wire is observed, it is as shown in FIG. The contact area between the fluororesin and the contact area between the fluororesin and the conductor are different. That is, in the actual manufacturing process, after the tape-shaped laminate is wound around the conductor, heat treatment is performed at a temperature equal to or higher than the melting point of the fluorine-based resin. Is in contact with the conductor surface having a large surface area due to the uneven shape, so that the contact area between the fluororesin and the conductor is larger than the contact area between the polyimide film and the fluororesin.

Therefore, heat seal strength is generally used as an index of adhesive strength. However, heat seal strength is an index indicating the adhesive strength per unit area. It is necessary to consider the contact area. However, it is difficult to estimate the contact area between the conductor and the fluororesin. Therefore, as a result of evaluating the strippability using a polyimide laminate having various heat seal strengths, the heat seal strength between the fluororesin surface and the polyimide film surface of the laminate was determined by the shine between the fluororesin surface of the laminate and the copper foil. It has been found that when the heat seal strength with the surface is 1.5 times or more, the poor stripping property is improved. The heat seal strength can be controlled by adjusting the firing conditions or the thickness of the fluorine-based resin when producing the polyimide laminate.

[0007] The heat sealing strength measuring method applied to the present invention is a method of measuring the fluororesin surface of a polyimide laminate of 8 cm x 15 cm and the shine surface of a copper foil, or the fluororesin surface of a polyimide laminate and a polyimide film surface. After superimposing and heat-sealing at a pressure of 20 psi, a heat-sealing time of 20 seconds and a heat-sealing temperature of 350 ° C., 1 cm × 1
Cut out 5 pieces of 5cm sample and use INSTRON TENSILE tester
100mm / min by 180 degree peeling with TESTER)
The peel strength is measured at a speed of. The average of the measured values of n = 5 is defined as the heat seal strength.

The polyimide film applied to the present invention is obtained from a resin solution of polyamic acid, which is a precursor of polyimide. Polyamic acid is the following (1)

Embedded image Which is obtained from an aromatic diamine such as 4,4-diaminodiphenyl ether and an aromatic tetracarboxylic dianhydride such as pyromellitic dianhydride. As an organic solvent for forming the polyamic acid resin solution, N, N─dimethylformamide, N, N
N─dimethylacetamide and the like are typical.

The above-mentioned resin solution of polyamic acid is first mixed with a dehydrating agent or a catalyst for accelerating imidization. Acetic anhydride is preferred as a typical dehydrating agent, and a tertiary amine is preferred as a catalyst. Typically, isoquinoline, β
-There is picolin. As the mixing ratio, 1 to 8 mol of the dehydrating agent and 0.05 to 1 mol of the catalyst are suitable for 1 mol of the polyamic acid. Mix the above mixture with a slit die 4
Extruded onto a support such as a casting drum or belt at 0 to 120 ° C., formed a self-supporting polyamic acid gel film on the support in 5 seconds to 5 minutes, and then peeled off from the support, Gel film is pre-dried at 100-200 ° C in a pin tenter, 300-
After drying and curing (curing) at 500 ° C., a polyimide film is obtained. The thickness of the polyimide film applied to the present invention is preferably 7 to 125 μm.

The fluororesin applied to the present invention is preferably an aqueous dispersion. Specifically, polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FEP),
An aqueous dispersion containing a fluororesin such as tetrafluoroethylene / perfluoroalkylvinyl ether (PFA), tetrafluoroethylene / ethylene copolymer (ETFE) and chlorine-containing polychlorotrifluoroethylene, which may be used alone or It is used in combination of two or more.

The solid content concentration of this dispersion is 10
~ 70% by weight is appropriate, but is determined in relation to the final product thickness, dispersion viscosity and the like. The viscosity of this dispersion is 1 cp (centipoise) to 1 cp (centipoise).
00p (poise) is preferable, and 50 cp is more preferable.
５5p.

On the other hand, a thickener for adjusting the viscosity, a solvent such as methanol, an antifoaming agent for eliminating bubbles generated at the time of application, a pigment for coloring the dispersion, and the like are added to the dispersion. That is no problem. In the production of a laminate of a polyimide film and a fluororesin, an aqueous dispersion is applied to both sides or one side of the polyimide film to a predetermined thickness, and dried and fired under predetermined conditions.

[0013]

The present invention will be described below with reference to examples.
The present invention is not limited to these. Example 1 A polyimide film (Apical AH, Kanegabuchi Chemical Industry Co., Ltd.) having a thickness of 25 μm and a width of 1020 mm was coated on both sides with F
An aqueous dispersion was applied so that each of the EP layers had a thickness of 2.5 μm after firing, and was then dried at 150 ° C. for 1 minute, and then fired. Here, the firing conditions and the heat seal strength and the strippability of the laminates manufactured under the respective firing conditions were evaluated. The copper foil for measuring the heat seal strength (assuming a stranded copper wire as the conductor) was 35 μm thick (3EC, Mitsui Kinzoku Kogyo Co., Ltd.). Table 1 shows the firing conditions and the thickness of the fluororesin, and Table 2 shows the results of the evaluation of the heat seal strength and the strippability at each level. In addition, among the heat seal strengths in the following table, “laminate / copper foil” means the heat seal strength of “the fluorinated resin surface of the laminate and the shine surface of the copper foil”.
The “laminate” means the heat sealing strength of the “fluorine resin surface and polyimide film surface of the laminate”.

The strip property was evaluated by using a microscope to determine whether or not the fluororesin remained on the conductor when the insulating coating layer of the cable produced under the following conditions was stripped by a manual stripper. (Magnification: 50 times) and evaluated. The conditions for producing the cable were as follows: a copper wire 1 having a diameter of 0.2 mm;
A 10 mm tape was wound around 9 strands with 50% wrap and heat treated at 350 ° C. for 3 minutes. Further, the mechanical strength and dielectric breakdown voltage of the polyimide laminate did not depend on the firing conditions.

[0015]

[Table 1]

[0016]

[Table 2]

Example 2 The procedure of Example 1 was repeated except that the firing time was changed to 30 seconds. Table 3 shows the firing conditions and the thickness of the fluororesin, and Table 4 shows the results of evaluating the heat sealing strength and stripping properties at each level. Further, the mechanical strength and dielectric breakdown voltage of the polyimide laminate did not depend on the firing conditions.

[0018]

[Table 3]

[0019]

[Table 4]

Example 3 The procedure of Example 1 was repeated except that the firing time was changed to 45 seconds. Table 5 shows the firing conditions and the thickness of the fluorine-based resin, and Table 6 shows the results of the heat seal strength and stripability evaluation at each level. Further, the mechanical strength and dielectric breakdown voltage of the polyimide laminate did not depend on the firing conditions.

[0021]

[Table 5]

[0022]

[Table 6]

Example 4 The procedure of Example 1 was repeated, except that the firing time was changed to 60 seconds. Table 7 shows the firing conditions and the thickness of the fluororesin, and Table 8 shows the results of the evaluation of the heat seal strength and the strippability at each level. Further, the mechanical strength and dielectric breakdown voltage of the polyimide laminate did not depend on the firing conditions.

[0024]

[Table 7]

[0025]

[Table 8]

Example 5 A polyimide film (Apical AH, Kanegabuchi Chemical Industry Co., Ltd.) having a thickness of 25 μm and a width of 1020 mm was placed on both sides of a polyimide film.
An aqueous dispersion was applied so that each EP layer had a thickness of 1.5 μm after firing, and was dried and fired. Drying and cable preparation conditions were the same as in Example 1. Table 9 shows the firing conditions and the thickness of the fluororesin, and Table 10 shows the results of the evaluation of the heat seal strength and the strippability at each level. Further, the mechanical strength and dielectric breakdown voltage of the polyimide laminate did not depend on the firing conditions.

[0027]

[Table 9]

[0028]

[Table 10]

Example 6 The procedure of Example 5 was repeated, except that the firing time was changed to 30 seconds. Table 11 shows the firing conditions and the thickness of the fluorine-based resin, and Table 12 shows the evaluation results of the heat seal strength and the strippability at each level. Further, the mechanical strength and dielectric breakdown voltage of the polyimide laminate did not depend on the firing conditions.

[0030]

[Table 11]

[0031]

[Table 12]

Example 7 The procedure of Example 5 was repeated, except that the firing time was changed to 45 seconds. Table 13 shows the firing conditions and the thickness of the fluororesin, and Table 14 shows the results of the evaluation of the heat seal strength and the strippability at each level. Further, the mechanical strength and dielectric breakdown voltage of the polyimide laminate did not depend on the firing conditions.

[0033]

[Table 13]

[0034]

[Table 14]

Example 8 The procedure of Example 5 was repeated, except that the firing time was changed to 60 seconds. Table 15 shows the firing conditions and the thickness of the fluorine-based resin, and Table 16 shows the results of evaluating the heat seal strength and the strippability at each level. Further, the mechanical strength and dielectric breakdown voltage of the polyimide laminate did not depend on the firing conditions.

[0036]

[Table 15]

[0037]

[Table 16]

Example 9 A polyimide film (Apical AH, Kanegabuchi Chemical Industry Co., Ltd.) having a thickness of 25 μm and a width of 1020 mm was coated on both sides with F
The aqueous dispersion was applied so that each of the EP layers had a thickness of 3.5 μm after firing, and was dried and fired. Drying and cable preparation conditions were the same as in Example 1. Table 17 shows the firing conditions and the thickness of the fluorine-based resin, and Table 18 shows the results of the evaluation of the heat seal strength and the strippability at each level. The mechanical strength and dielectric breakdown voltage of the polyimide laminate are as follows:
It did not depend on the firing conditions.

[0039]

[Table 17]

[0040]

[Table 18]

Example 10 The procedure of Example 9 was repeated, except that the firing time was changed to 30 seconds. Table 19 shows the firing conditions and the thickness of the fluororesin, and Table 20 shows the results of evaluating the heat seal strength and the strippability at each level. Further, the mechanical strength and dielectric breakdown voltage of the polyimide laminate did not depend on the firing conditions.

[0042]

[Table 19]

[0043]

[Table 20]

Example 11 The procedure of Example 9 was repeated, except that the firing time was changed to 45 seconds. Table 21 shows the firing conditions and the thickness of the fluororesin, and Table 22 shows the results of evaluating the heat seal strength and the strippability at each level. Further, the mechanical strength and dielectric breakdown voltage of the polyimide laminate did not depend on the firing conditions.

[0045]

[Table 21]

[0046]

[Table 22]

Example 12 The procedure of Example 9 was repeated, except that the firing time was changed to 60 seconds. Table 23 shows the firing conditions and the thickness of the fluororesin, and Table 24 shows the results of the evaluation of the heat seal strength and the strippability at each level. Further, the mechanical strength and dielectric breakdown voltage of the polyimide laminate did not depend on the firing conditions.

[0048]

[Table 23]

[0049]

[Table 24]

[0050]

By using the polyimide laminate having a specific heat seal strength of the present invention, it is possible to improve the stripping defect of the insulating coating without affecting the mechanical strength and the dielectric breakdown voltage.

[Brief description of the drawings]

FIG. 1 is a sectional view of an electric wire.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-223236 (JP, A) JP-A-62-162543 (JP, A) JP-A-4-303652 (JP, A) JP-A-4- 303651 (JP, A) JP 49-12900 (JP, B1) WO 90/9853 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35 / 00

Claims (3)

(57) [Claims] 1. A laminate comprising a polyimide film laminated on both surfaces or one surface with a fluororesin, and used as an insulating coating of a conductor, the heat seal strength between the fluororesin surface of the laminate and the polyimide film surface is increased. A polyimide laminate characterized in that the heat sealing strength between the fluorine resin surface of the body and the shine surface of the copper foil is 1.5 times or more, and the stripping property of the insulation coating is improved. 2. The polyimide laminate according to claim 1, wherein the fluororesin is an aqueous dispersion. 3. A cable having an insulation coating with the polyimide laminate according to claim 1.