JPS62223236A - Production of polyimide laminate - Google Patents

Abstract

PURPOSE:To obtain a laminate having a high bonding strength and scarcely suffering from its decrease even at high temperature and high humidity, by laying a specified modifying layer formed on the surface of a tetrafluoroethylene/fluorocarbon resin copolymer upon the discharge-treated surface of a polyimide resin and heat-sealing them together. CONSTITUTION:The following modifying layer is formed on the surface of a tetrafluoroethylene/fluorocarbon resin copolymer in the production of a laminate comprising a polyimide resin and the tetrafluoroethylene/fluorocarbon resin copolymer. The surface of the modifying layer is laid on the treated surface of the discharge-treated polyimide resin and they are heat-sealed together to obtain the purpose laminate. Said modifying layer is one in which the ratio of the number of fluorine atoms to that of carbon atoms, F/C, is 1.0-1.8 and the ratio of the number of oxygen atoms to that of carbon atoms, O/C, satisfies the relationship of O/C<=0.2-0.09X(F/C).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing a thermally bondable polyimide laminate.

[Conventional technology]

Polyimide resins have various excellent properties, including long-term heat resistance. However, since there is no adhesive that can handle the temperature at which it is used, it is necessary to coat non-melting polyimide resin with a fluororesin such as a copolymer of tetrafluoroethylene and hexafluoropropylene (hereinafter referred to as EP). A laminated type with thermal adhesive properties has been developed.

As a method for producing this fluororesin/polyimide resin laminate, there is a method proposed in Japanese Patent Publication No. 49-12900, in which FEP film and polyimide film subjected to discharge treatment are pressed at high temperature in an acetone atmosphere, or laminated by pressing at high temperature, or 2194, in which the surface of a polyamic acid gel film is coated with an aqueous or organic sol dispersion of an FEP polymer, and then the polyamic acid gel film is converted into a polyimide film.

(Problems to be Solved by the Invention) However, with these techniques, polyimide laminates have insufficient adhesive strength between fluororesin/polyimide resin;
Particularly, it has the disadvantage that its adhesive strength rapidly decreases under high temperature and high humidity conditions.

The present inventors have made extensive efforts to overcome the drawbacks of the prior art, and have discovered that the adhesive strength between the fluororesin and polyimide resin is largely related to the composition of the surface layer of the fluororesin and the surface condition of the polyimide resin. This discovery led to the present invention.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for producing a polyimide laminate in which the adhesive strength between a fluororesin and a polyimide resin is strong and the adhesive strength does not decrease even under high temperature and high humidity.

[Means for solving problems]

In the present invention, when producing a laminate made of a polyimide resin and a tetrafluoroethylene copolymer fluororesin, the ratio F/C of the number of fluorine atoms to the number of carbon atoms is from 1.0 to 1.
8, and the relationship between the ratio of the number of oxygen atoms to the number of carbon atoms 0/C and F/C is O/C≦0.2-0.09X
A modified layer satisfying (F/C) is formed on the surface of the tetrafluoroethylene copolymer fluororesin, and the surface of the modified layer and the treated surface of the discharge-treated polyimide resin are heat-sealed together. A method for producing a polyimide laminate, characterized by:

The tetrafluoroethylene copolymerized fluororesin in the present invention refers to one with an F/C in the range of 1.9 to 2.0, and is not particularly limited as long as it is within this range. These include FEP, copolymers of tetrafluoroethylene and perfluoroalkoxyethylene, and trifluoroethylene, hexafluoropropylene, and perfluoroalkoxyethylene.
Copolymers of tetrafluoroethylene and other hexafluorides, such as original copolymers, are preferred, and FEP is particularly preferred. In addition, if F/C is within the above range, copolymerized with ethylene, chloro-1-lifluoroethylene, etc., pigments for coloring, and various additives such as carbon black, graphite, silica powder, etc. are mixed. It may also be molded.

The fluororesin in the present invention must form a modified layer on at least a part of its surface, and the modified layer has an F/C of 1.0.
and 1.8, and the relationship between O/C and F/C must be O/C≦0.2-0.09X (F/C). When F/C exceeds 1.8, the adhesive strength with the polyimide resin is insufficient, and when F/C becomes less than 1.0, the adhesive strength also decreases. Also, F/C is 1.0 to 1
Even in the range of °8, O/C is (0,2-0,09x
If the value of (F/C)) is exceeded, the adhesive strength will still be insufficient.

The thickness of the modified layer is preferably 100 Å or more and 1 μm or less and 1/2 or less of the thickness of the fluororesin, and more preferably 1000 Å or more and 5000 Å or less to provide sufficient adhesive strength with the polyimide resin. However, it is good in that it does not take away from the excellent characteristics of fluororesins.

Although the method of forming the modified layer of the present invention is not particularly limited, a method of modifying the base resin itself by surface treatment is preferred. This method modifies the extremely thin layer on the surface of the fluororesin, so it can be said to be an extremely excellent method since it can impart only adhesive properties without impairing the excellent properties of the fluororesin.

As a surface treatment method, low-temperature plasma treatment can modify only the surface layer without changing the original properties of the fluororesin, and it can form a layer that will not lose adhesive strength even under high temperature and high humidity conditions. , more preferred.

Low-humidity plasma treatment involves exposing the resin to be treated to plasma generated by a so-called glow discharge, which is a discharge that starts and continues when a high voltage is applied in a low-pressure gas atmosphere.
This is a method of modifying the surface of the resin. Regarding these general plasma treatments, for example, "low temperature plasma chemistry"
(Edited by Keiichi Hozumi, Chemistry Area, Special Edition No. 111, Nankodo Publishing, published in 1976).

By the way, fluorine atoms of fluororesin are extremely easily handled by low-temperature plasma treatment, and the F/C of the surface layer is significantly lowered. In normal low-temperature plasma treatment, the treatment intensity is 5
0 W-sec/- or more is used, but when treated under these conditions, F/C is less than 100, and no sufficient effect of improving adhesive strength is observed. Therefore, in producing the fluororesin of the present invention, the treatment intensity is Q, 'l W-3eC/- or more and 10 W-5ec10+f, preferably 0.2 W-sec/- or more and 5-sec/- or less. It is extremely important to perform intense and low temperature plasma treatment.

By the way, in low-temperature plasma treatment, after fluorine atoms are removed, oxygen atoms are easily incorporated. That is, F
As /C decreases, O/C increases, but as 0/C decreases (0
, 2-0,09x (F/C)) or less, in addition to the above-mentioned treatment intensity, gas selection is also important.

The gas for obtaining plasma must be a gas that is non-polymerizable in the plasma and does not contain 10 mol% or more of oxygen gas, such as CO2, CO1H2, N2, NH.
I, N20. SO2, l-I CD,, H2S.

7 Leon gas such as CF4, or a mixture of these gases can be used by giving due consideration to the processing intensity; however, NH3, CO, J: and a mixture of these gases, or a mixture of these gases with other gases may also be used. It is particularly preferable to use it in a wide range of treatment strengths.

Note that there are no particular limitations on the processing device, power supply, power frequency, etc. for processing.

Next, as the polyimide resin in the present invention, an aromatic polyimide resin is preferable from the viewpoint of heat resistance, and a condensation product of an aromatic tetraacid and an aromatic diamine is particularly preferable. These resins are described in U.S. Patent 3°179.614.3,1.
79.634, etc., extensively and in detail.

Among them, a condensate of pyromellitic dianhydride and 4,4°-diaminodiphenyl ether and 3.4.3'4°
Particularly preferred are resins made of condensates of -biphenyltetracarbonminodiphenyl ether.

The adhesive strength of these polyimide resins can be increased by subjecting them to electrical discharge treatment before being bonded to the fluororesin. This discharge treatment is preferably a low-temperature plasma treatment, but a corona discharge treatment under normal pressure may also be used.

In the case of corona discharge treatment under normal pressure, if a large amount of oxygen exists in the discharge atmosphere, the treatment effect will not be recognized, and the oxygen concentration in the atmosphere gas is preferably 1 mol% or less, more preferably 0.1 mol%. Below, it is better to use as little amount as technically possible. Atmospheric gases for discharge include N2, Ar, To12,
Although it is possible to use organic compounds such as lle, Ne, acetone, ethylene, etc., or mixtures thereof, it is preferable to use Ar, considering the processing effect and the occurrence of drawbacks such as blocking property between resins due to processing. Most preferred.

Next, a method of laminating a polyimide laminate according to the present invention will be explained.

After a modified layer having a specific composition is formed on the surface of the fluororesin by the above method, it is thermally bonded to a polyimide resin that has been subjected to an electric discharge treatment.

Methods for thermal bonding include batch-type P1-press and continuous-type roll lamination-1, but roll lamination is preferred from the viewpoint of productivity.

The temperature of the hot plate or roll when performing this thermal bonding is
In order to prevent thermal deformation of the fluororesin, it is important not to greatly exceed the melting point of the fluororesin, and the range is preferably from 10°C below the melting point to 50°C above the melting point, and more preferably from 5°C below the melting point to 10°C above the melting point. It is in the range of C. For example 2
270-29 for FEP with a melting point of 60-280℃
It is more preferable to carry out thermal bonding at 0°C.

The press pressure during thermal bonding is preferably 1 k11/cnf or more in order to obtain sufficient adhesive strength.

The heat press time or roll lamination speed must be set in consideration of the film thickness so that sufficient heat is transmitted to the modified layer.

In addition to the method described above, the method for producing the laminated film of the present invention includes temporarily adhering at a temperature below the melting point of the fluorine film,
It is also possible to strengthen the adhesive force by subsequently increasing the temperature of the entire laminated film.

By the way, the basic arrangement of the polyimide laminate according to the present invention is fluororesin/modified layer/polyimide resin, but of course, if the resin is in the form of a film, it may be a polyimide film with fluorine films laminated on both sides. Furthermore, if necessary, a modified layer may be formed on the opposite surface of the fluorine film laminated on a polyimide film with a modified layer interposed therebetween. In particular, a type of fluorine film in which a modified layer is formed on the opposite surface of a polyimide film laminated via a modified layer is more preferable because it can be easily thermally bonded to the above material.

In order to obtain a fluorine film with a modified layer formed on the outer surface, it is desirable to form a modified layer once again on the fluorine film side of the laminated films.

[Measurement method of physical properties, evaluation criteria]

(1) Composition analysis of fluorine film C15, Fls and 01. The integrated intensity ratio of each peak is corrected by the detection sensitivity, and the atomic composition ratio F/C and O
/C was calculated.

The measurement conditions are as shown below.

Excitation X-ray: ArL, K ray (1186,6eV)
σ1,2 V for X feeding crab 10, 20mA Temperature: 20℃ Degree of vacuum: 3X10' orr (2) Bonding of fluorine film and polyimide film by thermal adhesion.

They were laminated using a roll laminator at a roll temperature of 275° C., a lamination speed Q of 5 m/min, and a linear pressure of 10 kq/cm.

(3) Measurement of adhesive strength Using universal tensile test Ia (manufactured by Toyo Baldwin, Tensilon), T-peel II $lt (open the test piece at 180°C with the heat-sealed part in the center, and test both ends with the tensile tester) (method of attaching it to both grips and peeling it off) was performed. The tensile speed was 200 mm/min.

Examples 1 to 8, Comparative Examples 1 to 8 An FEP film (Toyoflon FEP manufactured by Toshi Gosei Film Co., Ltd.) with a thickness of 25 μm and a width of 13 cm was placed in an internal electrode type plasma processing device, and initial pressures Q and Q3 were applied. Ding o
Exhaust torr and various gases introduced to Q, 4QTorr
Low-temperature plasma treatment was carried out at a processing speed of 1 m/min by applying high frequency power of 110 KH2.

The composition of the modified layer of the treated film was analyzed by the aforementioned ESCA. Using the same <ESCA, it was confirmed that the F/C of the untreated film (substrate) was in the range of 1.9 to 2°0.

Next, an aromatic polyimide film (E,
1. [) u Pout de Nemours and
Company "KAPTON") was placed in a similar device and Ar plasma treatment was performed. The discharge power is 50-
It is.

This polyimide film and the FEP film on which the modified layer had been formed under the various conditions described above were bonded together with their treated surfaces aligned in the manner described above.

Processing conditions of each example and each comparative example, F/C10/C1
0,2-0,09X (F/C) and adhesive strength as the first
Shown in the table.

As is clear from Table 1, the composition of the modified layer has F/C of 1.
It is in the range of 0 to 1.8, and O/C is 0.2-0.
09X (F/C) or less is necessary in order to provide sufficient initial adhesive strength between the polyimide films of the modified layer. However, sufficient adhesive strength in this case is 25μ
It is defined as an adhesive strength greater than or equal to the extent that a FEP film of m pressure causes necking stretching, that is, greater than or equal to about 0.4 +1/cm.

The bonded samples of Examples 1 to 8 having sufficient initial adhesive strength were left in an atmosphere of 100% RH 160° C. for 240 hours, and then their peel strengths were measured.

Separately, the same sample was placed in an oven at 200°C and the adhesive strength was measured after 480 hours.

These two results are summarized in Table 2.

As is clear from Table 2 and Table 1, the composition of the modified layer has an F/C of 1.0.
Judging from Table 2, it is preferably 1.8.
1 to 1.8, more preferably 1.4 to 1.8
is in the range of , and O/C is 0.2-0.09x (F
/C) Must be below.

Comparative Examples 9-16 "KAPTON" films without low temperature plasma treatment were laminated with the FEP films used in Examples 1-8. All samples showed an initial adhesive strength of less than 0.2-/cm, and the adhesive strengths after 240 hours at 100% R1160℃ and 480 hours at 200℃ were all 0.01.
It became below kq/cm.

In this comparative example, thermal bonding was carried out at 275°C. 300℃
When thermally bonded using the above conditions, some samples did not exhibit an initial adhesive strength of 0.4 kq/cm or more. However, the adhesive strength of all samples rapidly decreased due to changes over time.

Example 9 'KAPTON' film was subjected to a discharge treatment under atmospheric pressure in an Ar atmosphere. The processing speed and discharge power are the same as those for low-temperature plasma processing.

When this "K A P T ON" film was bonded to the FEP used in Example 1, the initial adhesive strength was 1.
00%R1165℃240 hours and 200'C48
The adhesive strength at 0 hours and 1 change all satisfied 0.4 kq/cm or more.

〔Effect of the invention〕

In the polyimide laminate of the present invention, the modified surface of the fluororesin having a specific modified layer on the surface and the treated surface of the polyimide resin whose surface has been subjected to discharge treatment are thermally bonded.
The adhesive strength between each resin is strong, and the adhesive strength can be maintained for a long time even under high temperature and high humidity.

A material with a modified layer formed on the outside of the fluororesin can be easily thermally bonded to other materials.

Therefore, it can be preferably used as an insulating wrapping material for electric wires used under high temperatures, an interlayer insulating material for lead frames, and a substrate for flexible printed circuits and flat cables.

Claims (1)

[Claims] (1) When manufacturing a laminate made of polyimide resin and tetrafluoroethylene copolymer fluororesin, the ratio F/C of the number of fluorine atoms to the number of carbon atoms is in the range of 100 to 1.8, and The ratio of the number of oxygen atoms to the number of carbon atoms 0/
The relationship between C and F/C is 0/C≦0.2-0.09×(F/
A modified layer satisfying C) is formed on the surface of the tetrafluoroethylene copolymerized fluororesin, and the surface of the modified layer and the treated surface of the discharge-treated polyimide resin are heat-sealed together. A method for producing a polyimide laminate.