JPH04351548A - Polyimide laminate - Google Patents

Abstract

PURPOSE:To improve poor stripping properties of insulation coating without affecting mechanical strength and dielectric breakdown voltage by making heat seal strength between a fluororesin and a polyimide film to be 1.5-fold or larger of heat seal strength between the fluororesin and a conductive material. CONSTITUTION:A laminate is prepd. by laminating a fluororesin on both faces or one face of a polyimide film. In this case, heat seal strength between the fluororesin and the polyimide film is made 1.5-fold or larger of heat seal strength between the fluororesin and a conductive material. It is possible thereby to solve failure of stripping properties of insulation coating without having a bad effect on mechanical strength and dielectric breakdown voltage.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a polyimide laminate, and more particularly, it has a specific heat sealing strength that improves poor stripability of insulation coating without adversely affecting mechanical strength or dielectric breakdown voltage. This invention relates to a polyimide laminate. The laminate of the present invention is usually wound in the form of a tape around a conductor such as copper, and is used for motor coils, cables, aircraft wires, and the like.

0002

BACKGROUND OF THE INVENTION As mentioned above, polyimide laminates are used as insulating coatings for electric wires and the like. Electric wires are usually manufactured by winding the above tape-shaped laminate around a conductor wire, and then fusing a fluororesin through a predetermined heat treatment. When electrically connecting the wires manufactured in this manner, the insulation coating at the ends of the wires is stripped and the wires are connected by soldering or the like. However, if the adhesive strength between the conductor and the fluororesin is greater than the adhesive strength between the polyimide film and the fluororesin, when the wire is stripped, a portion of the fluororesin will remain on the conductor (poor stripping property). A problem arises in that poor electrical connections occur.

0003

SUMMARY OF THE INVENTION The present invention provides a polyimide laminate that solves the above problem of strip defects.

0004

[Means for Solving the Problems] In view of the above-mentioned circumstances, the present inventors have solved the problem of poor insulation stripping properties in polyimide laminates by specifically focusing on the adhesive strength between the conductor and the fluorine-based resin, and the adhesive strength between the polyimide film and the fluorine-based resin. The present invention was developed as a result of intensive research into methods for controlling the adhesive force with resins. That is, in the present invention, in a laminate in which a fluororesin is laminated on both sides or one side of a polyimide film, the heat seal strength between the fluororesin and the polyimide film is 1.5 times the heat seal strength between the fluororesin and the conductor. The content is a polyimide laminate characterized by the above.

If the adhesive strength between the polyimide film and the fluororesin is smaller than the adhesive strength between the fluororesin and the conductor, poor stripping properties will occur as described above. Adhesive force is expressed as the product of the adhesive force per unit area and the contact area, and when observing the cross section of the manufactured electric wire, it looks like the one shown in Figure 1, which shows that the polyimide film and the polyimide film in the manufactured electric wire The contact area between the fluororesins and the contact area between the fluororesin and the conductor are different. That is, in the actual manufacturing process, a tape-like laminate is wrapped around a conductor and then heat treated at a temperature higher than the melting point of the fluororesin, but at this time, the innermost layer of fluororesin becomes molten and the outer peripheral surface Since the conductor surface has an uneven shape and a large surface area, the contact area between the fluororesin and the conductor becomes larger than the contact area between the polyimide film and the fluororesin.

[0006] Therefore, heat seal strength is generally used as an index of adhesive strength, but heat seal strength is an index that expresses 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 strip properties using polyimide laminates having various heat seal strengths, we found that the heat seal strength between the fluororesin and the polyimide film was 1.5 times or more than the heat seal strength between the fluororesin and the conductor. It has been found that stripping defects can be improved if there is. The heat seal strength can be controlled by adjusting the firing conditions or the thickness of the fluororesin when producing the polyimide laminate.

[0007] The heat seal strength measurement method applied to the present invention is to measure the fluororesin surface of a polyimide laminate of 8 cm x 15 cm and the shine surface of copper foil, or the fluororesin surface of a polyimide laminate and the polyimide film surface. After overlapping and heat sealing at a pressure of 20 psi, heat sealing time of 20 seconds, and a heat sealing temperature of 350°C, 1 cm x 1
Cut out five 5cm samples and test them with an INSTRON TENSILE tester.
100mm/m with 180 degree peeling with TESTER
The peel strength is measured at a speed of in. 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 as follows (1)

It has the structural formula: [Image Omitted] It is obtained from an aromatic diamine such as 4,4-diaminodiphenyl ether and an aromatic tetracarboxylic dianhydride such as pyromellitic dianhydride. Organic solvents used in forming the polyamic acid resin solution include N,N-dimethylformamide, N,
A typical example is N-dimethylacetamide.

The polyamic acid resin solution is first mixed with a dehydrating agent and a catalyst to promote imidization. A typical dehydrating agent is acetic anhydride, and a preferred catalyst is a tertiary amine, typically isoquinoline, β
-There is picoline. The appropriate mixing ratio is 1 to 8 moles of dehydrating agent and 0.05 to 1 mole of catalyst per mole of polyamic acid. The mixture with the above composition was passed through a slit die.
It is extruded onto a support such as a casting drum or belt at 0 to 120°C, becomes a self-supporting polyamic acid gel film on the support for 5 seconds to 5 minutes, and then peeled off from the support. Pre-dry the gel film in a pin tenter at 100-200°C, 300-200°C.
A polyimide film is obtained through drying and solidification (curing) at 500°C. The thickness of the polyimide film applied to the present invention is preferably 7 to 125 μm.

The fluororesin used in the present invention is preferably an aqueous dispersion. Specifically, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP),
Examples include aqueous dispersions containing fluororesins such as tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), and chlorine-containing polychlorotrifluoroethylene, which may be used alone or in combination. Two or more types are used in combination.

[0011] The solid content concentration of this dispersion is 10
~70% by weight is suitable, but is determined in relation to final product thickness, dispersion viscosity, etc. In addition, the viscosity of this dispersion is 1 cp (centipoise) to 1
00p (poise) is preferable, more preferably 50cp
~5p.

On the other hand, a thickener for adjusting the viscosity or a solvent such as methanol, an antifoaming agent for eliminating foam generated during application, a pigment for coloring the dispersion, etc. are added to this dispersion. There is absolutely no problem with that. To manufacture a laminate of a polyimide film and a fluororesin, an aqueous dispersion is applied to both or one side of the polyimide film to a predetermined thickness, and then dried and fired under predetermined conditions.

[0013]

[Examples] The present invention will be explained below with reference to Examples.
The present invention is not limited to these. Example 1 A polyimide film with a thickness of 25 μm and a width of 1020 mm (
Apical AH, Kanebuchi Chemical Industry Co., Ltd.), double-sided FE
An aqueous dispersion was applied so that the P layer had a thickness of 2.5 μm after firing, and then dried at 150° C. for 1 minute, and then fired. Here, the firing conditions and the heat seal strength and stripability of the laminates produced under each firing condition were evaluated. Note that the copper foil (assuming stranded copper wire as the conductor) used for the heat seal strength measurement had a thickness of 35 μm (3EC, Mitsui Kinzoku Kogyo Co., Ltd.). Table 1 shows the firing conditions and the thickness of the fluororesin, and Table 2 shows the heat seal strength and stripability evaluation results for each level.

[0014] In the evaluation of stripping property, when the insulation coating layer of the cable produced under the conditions shown below is stripped using a manual stripper, it is checked with a microscope ( It was observed and evaluated at a magnification of 50 times. The cable manufacturing conditions are as follows: 1 copper wire with a diameter of 0.2 mm.
A 10 mm wide tape was wrapped around nine stranded wires using 50% wrap, and heat treatment was performed at 350° C. for 3 minutes. Furthermore, 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 same procedure as in Example 1 was carried out 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 heat seal strength and stripability evaluation results for each level. Furthermore, 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 same procedure as in Example 1 was carried out except that the firing time was changed to 45 seconds. Table 5 shows the firing conditions and the thickness of the fluororesin, and Table 6 shows the heat seal strength and stripability evaluation results for each level. Furthermore, 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 same procedure as in Example 1 was carried out 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 heat seal strength and stripability evaluation results for each level. Furthermore, 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 with a thickness of 25 μm and a width of 1020 mm (
Apical AH, Kanebuchi Chemical Industry Co., Ltd.), double-sided FE
An aqueous dispersion was applied so that the P layer had a thickness of 1.5 μm after firing, dried, and fired. The drying and cable manufacturing 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 heat seal strength and stripability evaluation results for each level. Furthermore, 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 In Example 5, the same procedure as in Example 1 was carried out except that the firing time was changed to 30 seconds. Table 11 shows the firing conditions and the thickness of the fluororesin, and Table 12 shows the heat seal strength and stripability evaluation results for each level. Furthermore, 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 In Example 5, the same procedure as in Example 1 was carried out 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 heat seal strength and stripability evaluation results for each level. Furthermore, 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 same procedure as in Example 1 was carried out in Example 5, except that the firing time was changed to 60 seconds. Table 15 shows the firing conditions and the thickness of the fluororesin, and Table 16 shows the heat seal strength and stripability evaluation results for each level. Furthermore, 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 with a thickness of 25 μm and a width of 1020 mm (
Apical AH, Kanebuchi Chemical Industry Co., Ltd.), double-sided FE
An aqueous dispersion was applied so that each P layer had a thickness of 3.5 μm after firing, dried, and fired. The drying and cable manufacturing conditions were the same as in Example 1. Table 17 shows the firing conditions and the thickness of the fluororesin, and Table 18 shows the heat seal strength and stripability evaluation results for each level. Furthermore, the mechanical strength and dielectric breakdown voltage of the polyimide laminate did not depend on the firing conditions.

[0039]

[Table 17]

[0040]

[Table 18]

Example 10 The same procedure as in Example 1 was carried out in Example 9, 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 heat seal strength and stripability evaluation results for each level. Furthermore, 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 same procedure as in Example 1 was carried out in Example 9 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 heat seal strength and stripability evaluation results for each level. Furthermore, 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 same procedure as in Example 1 was carried out in Example 9, 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 heat seal strength and stripability evaluation results for each level. Furthermore, 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]

Effects of the Invention By using the polyimide laminate of the present invention having a specific heat sealing strength, it is possible to improve stripability defects of the insulation coating without affecting the mechanical strength and dielectric breakdown voltage.

[Brief explanation of the drawing]

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

Claims (2)

[Claims] Claim 1: In a laminate in which a fluororesin is laminated on both sides or one side of a polyimide film, the heat seal strength between the fluororesin and the polyimide film is at least 1.5 times the heat seal strength between the fluororesin and the conductor. A polyimide laminate characterized by: 2. The polyimide laminate according to claim 1, wherein the fluororesin is an aqueous dispersion.