JPS61264027A - Production of polyimide film having high dimensional stability - Google Patents

Abstract

PURPOSE:To obtain a film having high dimensional stability under heat and bondable easily to a metal, etc., at high temperature, by polymerizing a biphenyltetracarboxylic acid and a phenylenediamine compound, forming a thin film from the obtained polymer solution, drying and heat-treating the film, and again heat-treating the product. CONSTITUTION:A biphenyltetracarboxylic acid and a phenylenediamine compound are polymerized in a polar organic solvent to obtain a polymer solution, which is converted to a thin film on the surface of a substrate. The thin film is dried to obtain a solidified film containing about 20-60wt% solvent. The film is peeled off from the substrate, and dried and heat-treated at about 200-500 deg.C fixing at least a pair of opposite side edges. The obtained aromatic polyimide film is heat-treated again at 330-500 deg.C under a low tension, i.e. <=400g/mm<2>.

Description

[Detailed description of the invention] [Field of industrial application] This invention uses a solution of a polyimide precursor (for example, aromatic polyamic acid) obtained from hyphenyltetracarboxylic acids and phenylene diamines. It is produced using a solution casting method, etc., and has a low average linear expansion coefficient that is almost the same as that of inorganic materials (ceramic materials), metal materials, etc., and is also thermally dimensionally stable. The present invention relates to a method for producing an aromatic polyimide film.

The aromatic polyimide film described above is usually extremely useful as a base film for electronic components such as printed wiring boards.

[Description of prior art]

Conventionally, an aromatic polyimide film obtained from pyromellitic dianhydride and an aromatic diamine has been used as a typical aromatic polyimide film. In this state, the average coefficient of linear expansion is approximately 3.5X 10-5 to 4.5X
Since it has a large diameter of about 10-5, it has the disadvantage that it curls extremely when bonded to copper foil or the like at high temperature.

On the other hand, in order to solve the problem described in -F, it was proposed in Japanese Patent Publication No. 44-208 to lower the average coefficient of linear expansion of the film by performing a stretching operation during film formation.
In the above method, the temperature of the obtained film is raised from room temperature to approximately 4.00°C and maintained at that temperature for 2 hours, which is proposed in Japanese Patent No. 78 and other publications. The rate of change in dimensions (thermal dimensional stability) measured at room temperature deteriorated significantly, and it was not possible to respond to the recent trend toward finer wiring patterns.

[Requirements and effects of the present invention]

The inventors have proposed, for example, ceramics, metals (e.g.
A method for producing an aromatic polyimide film that has an average coefficient of linear expansion that does not curl significantly when bonded together with copper foil, copper alloy, etc.) at high temperatures, and also has good thermal dimensional stability. As a result of intensive research on
Using a solution of aromatic polyamic acid obtained by polymerizing biphenyltetracarboxylic acids and phenylenediamines, a thin film formed on the surface of the support from the polymer solution is dried to form a solidified film. Then, with both longitudinal edges of the solidified film fixed, it is further dried and heat-treated to form a polyimide film, and finally, the film is reheated at a high temperature under low tension. discovered that an aromatic polyimide film with excellent thermal dimensional stability could be obtained, and completed this invention.

That is, in this invention, a solution of a polymer obtained by polymerizing biphenyltetracarboxylic acids and phenylene diamines in an organic polar solvent is prepared, and then the polymer solution is used to coat the surface of a support.
forming a thin film of the solution, drying the thin film to form a solidified film in which about 20 to 60% by weight of the solvent remains; further peeling the solidified film from the support; Fix a pair of both edges, about 2
An aromatic polyimide film is formed by drying and heat treatment at a temperature of 00 to 500°C, and finally, the aromatic polyimide film obtained as described above is heated at 400 g/in2.
The present invention relates to a method for producing a dimensionally stable polyimide film, which is characterized by carrying out a reheat treatment under the following low tension and at a temperature of 330 to 500°C.

The aromatic polyimide film produced by the method of this invention has an average coefficient of linear expansion in any direction of approximately 0.1
10-5 to 2.0 x 10-5 cm/cm・℃, which is the linear expansion of metals such as various inorganic materials (ceramic materials, etc.), conductive metals, magnetic metal alloys, etc., usually used in electronic materials, etc. The property is that the value is almost close to the coefficient, and the thermal dimensional stability described below, which is indicated by the rate of change in dimension before and after heating to a high temperature, is about 0.3% or less,
This is a novel dimensionally stable, heat resistant and electrically insulating aromatic polyimide film that has the following properties: extremely small values.

The aromatic polyimide film has an average coefficient of thermal expansion of
The coefficient of linear expansion is close to that of inorganic materials and conductive metals, and it also has extremely excellent thermal dimensional stability, so thin films (foils) of ceramics, conductive metals, etc. When forming or bonding the two together,
Even when exposed to high temperatures, problems such as curling do not occur substantially, and the composite material (laminated material) consisting of a conductive metal and the film layer of the present invention is suitable for metal layer etching, soldering, etc. Even when subjected to high-temperature thermal history during processing, it does not cause curling or deteriorate the performance of the processed product.

The method of the present invention is an excellent film forming method that can continuously and reproducibly produce a dimensionally stable aromatic polyimide film that simultaneously has the above-mentioned properties.

In the method of this invention, in particular, after forming a film by a type of solution casting method using a solution such as a specific aromatic polyamic acid, the obtained polyimide film is reheated at a high temperature under low tension. It has the most characteristics.

Conventionally, it has been difficult to produce an aromatic polyimide film that simultaneously has excellent performance using the method of the present invention as described above.
It was completely unknown.

[Detailed explanation of each requirement of the present invention]

In the method for producing a polyimide film in this invention, first, 2,3.3', 4'- or 3.3', 4.4'-
"Aromatic tetracarboxylic acid component containing preferably 90 mol% or more of biphenyltetracarboxylic acids, acid derivatives such as biphenyltetracarboxylic acid, its acid dianhydride, or its esterified product or halogenated salt"'' and ``aromatic diamine component J containing preferably 90 mol% or more of phenylene diamine, which is 0-1■-1 or p-phenylene diamine, in an organic polar solvent, preferably at 100°C or less, particularly preferably. is 80
A polymer solution in which a polymer (bolyimide such as aromatic polyamic acid, precursor) produced by polymerization at a polymerization temperature of ℃ or lower is uniformly dissolved in an organic polar solvent is used as a membrane-forming solution.
- It is prepared as a liquid.

The polyimide precursor is a polymer obtained by polymerizing biphenyltetracarboxylic acid or acid dianhydride with phenylene diamines, and contains about 50 mol% or more of repeating units represented by general formula (1). In particular, aromatic polyamic acids that are soluble in organic polar solvents having a content of 60 mol% or more are suitable.

The organic polar solvent described above can be used as a polymerization solvent or a solvent for a 1-distillate solution for film formation, and is an organic solvent that can uniformly dissolve each of the monomer components and the polyimide precursor. For example, N,N-dimethylsulfoxide, N,N-dimethylamamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2- Preferred examples include amide solvents such as pyrrolidone and hexamethylene phospolamide.

The polyimide precursor used in the method of this invention has a logarithmic viscosity (concentration: 0.5 g/room R solvent, solvent: N-methyl-2-pyrrolidone, measurement temperature: 30°C)
is preferably about 0.1 to 5, particularly about 0.2 to 4. The polymer solution preferably has a polymer concentration of about 2 to 40% by weight, particularly 3 to 30% by weight, and a rotational viscosity (30°C) of about 10 to 500% by weight.
It is sufficient if it is about 00 poise.

In the method of this invention, following the preparation of the dope solution described above,
Using the dope, preferably continuously or intermittently, by a known solution casting method or the like, a uniform thickness of the dope is applied to the surface of a support such as a metal drum or belt having a smooth surface. Form a thin film of dope, preferably about 40
The thin film is dried on the support by gradually evaporating volatile components such as the solvent in the thin film and water generated by imidization of the polyimide precursor at a drying temperature of ~180°C, particularly preferably 50~150°C. and the volatile component is about 2
A solidified film is formed in which 0 to 60% by weight remains, preferably 25 to 50% by weight.

In the method of this invention, following the above-mentioned drying step,
Further, the temperature is preferably 200 to 500° C. with a pair of longitudinal edges of the solidified film supplied continuously or intermittently fixed by a fixing device or the like that can move together with the film continuously or intermittently. is 250-450
'c and for about 1 to 60 minutes, especially 2 to 60 minutes.
Drying and/or heat treating the solidified film for 30 minutes so that the solvent and product are removed from the solidified film so that the content of solvent in the final polyimide film is preferably about 1% by weight or less. Water is sufficiently removed and dried, the polymer constituting the film is sufficiently imidized, and the film is then sufficiently heat-treated to form an aromatic polyimide film.

As the fixing device for the solidified film, for example, a large belt-like or chain-like device equipped with a large number of pins or grippers at equal intervals may be used to fix the solidified film on both sides of the solidified film that is continuously or intermittently supplied. It is preferable to use a device that can be installed in pairs along the film and fix the film while being moved continuously or intermittently along with the movement of the film.

In the method of this invention, the aromatic polyimide film produced in the previous step is finally heated at about 250 to 500°C under a low tension of 400 g/l or less, preferably 300 g/l or less. .

In particular, heat treatment is performed again at a temperature of 300 to 450° C. for about 1 to 30 minutes, particularly 2 to 20 minutes, to produce a heat-resistant polyimide film with excellent thermal dimensional stability.

Further, the long aromatic polyimide film produced continuously or intermittently by the method of the present invention can be wound into a roll by an appropriate known method.

The polyimide film obtained by the method of the present invention is made of a high molecular weight aromatic polyimide having about 90 mol% or more, particularly 95 mol% or more of repeating units represented by the general formula (IT). be.

Further, the polyimide film of the present invention is formed of the above-mentioned aromatic polyimide, and has an average coefficient of linear expansion of about 0. IXIO-5~2.
OX 10 =cm/cm ・'C1 Preferably, 0.
5×10-5~1.8×10-”cm/cm・'
Moreover, the linear expansion coefficient ratio (MD/TD) between the film's old direction (Mr) direction and the film's transverse direction (1°D direction) is approximately 11.
5 to 4, preferably 1/3 to 3.0, and furthermore, the above-mentioned thermal dimensional stability is extremely small, about 0.3% or less, preferably 0.25% or less.

Aromatic polyimide film that has the above-mentioned properties is a polyimide film that has completely new properties that have not been previously known. exposed to high temperatures when bonded directly or through adhesives with thin sheets (or foils) of metallic materials to form composite materials (laminates), or during further processing or use of the composite material. It does not curl or undergo dimensional changes due to heat.

This polyimide film substantially contains almost no organic polar solvent in the dope solution for film formation, and the content of the solvent is approximately 1% by weight or less, particularly (0.5% by weight or less). It is preferable that the film is flexible and has a thickness of about 1 to 150 μm.

〔Example〕

In Examples and Comparative Examples, the average linear expansion coefficient (α;
cIIl/cm/"C), the sample piece (5 mm x 20 mm) to be measured is placed in a thermomechanical analyzer (manufactured by Rigaku Denki Co., Ltd.) using the tensile load method, and heated at 10 °C/cm from room temperature to 300 °C. After raising the temperature at a heating rate of min and holding it at 300°C for 1 minute, Original length L
+' +, ], Omm) using the following formula.

α-(ΔL+/L'+)/(300-50) Thermal dimensional stability (A; %) was measured using a dehydrated sample piece (5 m x 20') in the same thermomechanical analyzer as above.
fin) was placed, the temperature was raised from room temperature to 400°C at a temperature increase rate of 10°C/min, held at 400'C for 2 hours, and then cooled to 5-5°C. Displacement (Δl, 2) in the length of the sample piece before and after room temperature and the original length of the sample piece I
, 2; 10m1+) using the following formula.

A=(ΔL2/L2)X100 Example 1 (Preparation of dope solution) 507! 38.1 kg of N,N-dimethylacetamide was added to a cylindrical polymerization tank with an internal volume of 3.3', 4.
．． 4'-Biphenyltetracarboxylic dianhydride 5.29
59 kg of para-phenylenediamine was added, and while stirring, 1.946 [i kg of para-phenylenediamine was gradually added, and 30
Stirring of the reaction solution was continued at ℃ for about 10 hours, and both components were polymerized to produce polyamic acid.

The logarithmic viscosity of the polyamic acid produced in the above polymerization reaction (
The polyamic acid solution had a rotational viscosity (at 30°C) of about 25,000 poise.

(Film forming) The polyamic acid solution produced by the method described above was
- Use the tope liquid as a tope liquid, and apply the tope liquid to the slit of the T-die mold (lip interval i 0.5 + n, lip width; 65
(1+n) was extruded into a thin film at about 30°C, and the thin film of the liquid was continuously placed on a smooth metal held 1-1, and heated with hot air at about 120'C in held 7. The thin film is dried to continuously form a solidified film, the solidified film is then peeled off from the heald, and the solidified film is subsequently fed into a high temperature heating furnace where the film is heated in the i+ direction. While holding and moving both edges with a horizontal tenter, the aromatic polyimide film is dried and heat-treated with hot air that gradually increases from about 250 to 450°C to form an aromatic polyimide film, and finally the aromatic polyimide film is A low tension of 100 g/mm2 was applied to the film in the H direction of the film using a dancer, and the film was fed into a high-temperature box heating furnace, heated at a heating temperature of about 350°C for about 4 minutes, and then cooled. Then, it was wound up into a roll.

In the above-mentioned film formation, when the aromatic polyimide film that had been dried and heat treated was rolled, no wrinkles were generated, and the appearance of the rolled film was good. .

The aromatic polyimide film obtained by the above-mentioned film forming method is
The imidization rate of the polymer is 95 or more, the heat resistance indicated by the thermal decomposition start temperature of the film is 450°C or more, and the tensile strength is the MD force direction physical property value (20°C) of the film in a tensile test. is 43 kg/m++2, elongation is 35%, and initial tensile modulus is 100'5
kg/1m2.

The properties of each fill + in the above-mentioned film forming method and the properties of the aromatic polyimide film obtained by the film forming method were first evaluated.
Shown in the table.

Comparative example 1! An aromatic polyimide film was produced in the same manner as in Example 1, except that the V film was not dried and heated in the final high-temperature vertical heating furnace.

The results are shown in Table 1.

Table 1 α Kuchidayo 0 Solidified film (cm/c
m/”C), heat shaving system η incense (g/+m2) (x 10-”) group polyimide film MDTr) MDTD
MD TDl-11 column 1 33 0.01 or less ----0,81,00,470,35 Procedural amendment (voluntary) I/Z, 1985

Claims (1)

[Claims] A solution of a polymer obtained by polymerizing biphenyltetracarboxylic acids and phenylene diamines in an organic polar solvent is prepared, and then the polymer solution is used to apply the solution to the surface of a support. The thin film is dried, and the solvent is about 2
A solidified film remaining at a proportion of 0 to 60% by weight is formed, and the solidified film is further peeled off from the support, and at least one pair of both edges of the solidified film is fixed to form a solidified film that remains at a ratio of 0 to 60% by weight.
The aromatic polyimide film was formed by drying and heat treatment at a temperature of 00 to 500°C, and finally, the aromatic polyimide film obtained as described above was heated to 400g/mm^.
Under low tension of 2 or less and at a temperature of 330 to 500 °C,
A method for producing a dimensionally stable polyimide film characterized by reheat treatment.