JPH046213B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention uses a solution of a polyimide precursor (for example, aromatic polyamic acid) obtained from biphenyltetracarboxylic acids and phenylene diamines. , a method of producing an aromatic polyimide film having excellent thermal dimensional stability by forming a film by a solution casting method, etc., and having an average linear expansion coefficient almost the same as that of ceramics, metals, etc. The present invention relates to a thermally stable aromatic polyimide film and a method for producing the same. The aromatic polyimide described above is extremely useful as a base film for printed wiring boards and the like that are normally used in electrical and electronic components. [Description of the 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 the non-oriented state, the average coefficient of linear expansion is approximately 3.5 x 10 ^-5 to 4.5 x 10 ^-5 , so it has the disadvantage of extremely large curling when bonded to copper foil etc. at high temperatures. had. On the other hand, to solve the above problem,
By performing a stretching operation during film formation, the average coefficient of linear expansion of the film is reduced.
In the method proposed in Japanese Patent Publication No. 44-20878, the obtained film is heated from room temperature to approximately 400°C and maintained at that temperature for 2 hours before and after heat treatment. The rate of change in dimensions (thermal dimensional stability) measured at room temperature deteriorated significantly, making it impossible to cope with the recent trend toward finer wiring patterns. [Requirements and effects of the present invention] The inventors have discovered that ceramics, metals (e.g.
To produce 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 the method, we have found that by using a solution of aromatic polyamic acid obtained by polymerizing biphenyltetracarboxylic acids and phenylene diamines, a thin film etc. can be formed on the surface of a support from the polymer solution. By performing drying in two stages: on the support and under low tension in the solidified film after being peeled off from the support, it is possible to simultaneously achieve a specific low coefficient of linear expansion, thermal dimensional stability, etc. They discovered that it is possible to obtain an aromatic polyimide film with excellent properties, and completed this invention. That is, this invention is a film made of aromatic polyimide obtained from a solution of a polymer produced by polymerizing biphenyltetracarboxylic acids and phenylene diamines, and the polyimide film is heated at a temperature of about 50°C to 300°C. The average linear expansion coefficient in the temperature range of approximately 0.1 × 10 ^-5 ~ 2.5 ~ 10 ^-5 cm/cm・
℃, and the ratio of linear expansion coefficients (MD/TD) between the longitudinal direction (MD direction) and the transverse direction (TD direction) of the film is approximately 1/5 to 4, and furthermore, the temperature range from room temperature to 400° C. ℃ and then to a temperature of 400℃ 2
Thermal dimensional stability, which is the rate of change in film dimensions at room temperature before and after heating for a period of time, is approximately 0.3.
% or less, and further relates to a dimensionally stable polyimide film characterized in that the polyimide film has a polyimide film of at least Then, the polymer solution is used to form a thin film of the solution on the surface of the support, and the thin film is dried so that the solvent and the produced moisture are about 27 to 60% by weight.
A remaining solidified film is formed, and the solidified film is peeled off from the surface of the support and dried under a low tension of 100 g/mm ² or less and at a temperature in the range of about 80 to 250°C. to form a solidified film containing the solvent and produced water in a range of about 5 to 25% by weight, and finally, the solidified film is heated at a temperature of 200 to 500°C higher than the drying temperature. The present invention relates to a method for producing a dimensionally stable polyimide film, which is characterized by drying and heat-treating at a temperature with at least a pair of both edges fixed. The aromatic polyimide film of the present invention has a property that its average linear expansion coefficient is almost similar to the linear expansion coefficient of various ceramic materials, conductive metals, magnetic metal alloys, etc. that are normally used in electronic materials. Moreover, it is a new dimensionally stable and heat-resistant aromatic polyimide film that also has properties such as an extremely small thermal dimensional stability, which is indicated by the rate of change in dimensions before and after being heated to high temperatures. be. The aromatic polyimide film of the present invention has an average coefficient of thermal expansion close to that of a conductive metal, and has extremely excellent thermal dimensional stability. When a conductive metal foil is formed on the film of the present invention or when the two are bonded together, problems such as curling do not occur even when exposed to high temperatures. Even if the composite material (laminated material) consisting of the film layer of the invention is subjected to heat history at high temperatures during processing such as etching and soldering of metal layers, it will not curl or deteriorate the performance of the processed product. There is nothing to do. The method of this invention produces a dimensionally stable aromatic polyimide film that simultaneously has each of the above-mentioned properties.
This is an excellent film forming method that allows continuous or continuous production of films with stable properties on an industrial scale with good reproducibility. In the method of this invention, in particular, a solution of a specific aromatic polyamic acid or the like is used to form a film by a solution casting method, and a thin film is formed from the solution on the surface of a support. is dried on a support to form a solidified film containing a high proportion of solvent, and the solidified film is peeled off from the support and further dried under low tension to solidify with a low solvent content. The most distinctive feature lies in the ``specific two-stage drying'' that forms the film. Hitherto, it has not been known that an aromatic polyimide film having excellent performance can be produced by the method of the present invention as described above. [Detailed explanation of each requirement of the present invention] The polyimide film of the present invention has 2, 3,
3',4'- or 3,3',4,4'-biphenyltetracarboxylic acid or its acid dianhydride, or
Biphenyltetracarboxylic acids (aromatic tetracarboxylic acid component), which are acid derivatives such as esterified products or halogenated salts of the acid, and o-, m-,
Alternatively, a polymer solution in which a high molecular weight polymer (polyimide precursor) produced by polymerizing phenylene diamine (aromatic diamine component), which is p-phenylene diamine, is uniformly dissolved in an organic polar solvent. , used as a dope solution for film formation,
It is a heat-resistant and electrically insulating film that has a specific thermal dimensional stability and is formed from an aromatic polyimide obtained by forming a film and imidizing it using a specific dry film forming method. Therefore, the film of this invention has the general formula () about 90 mol% or more, especially 95
It is formed of a high molecular weight aromatic polyimide having a mole % or more. Further, the polyimide film of the present invention is formed of the above-mentioned aromatic polyimide, and has an average linear expansion coefficient of about 0.1×10 ⁻⁵ to
2.5×10 ^-5 cm/cm・℃, preferably 0.5×10 ^-5 ~
It is extremely small at around 2.3×10 ^-5 cm/cm・℃, and the ratio of linear expansion coefficient (MD/TD) between the film's extrusion direction (MD direction) and the film's transverse direction (TD direction) is extremely small. , about 1/5 to 4, preferably 1/3 to 3.0, and the above-mentioned thermal dimensional stability is about 0.3% or less, preferably about 1/3 to 3.0.
It is extremely small, less than 0.25%. The aromatic polyimide of the present invention, which also has the above-mentioned properties, is a polyimide film that has previously been unknown and has new properties. 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. Even when exposed to heat, it does not curl or undergo dimensional changes due to heat. The polyimide film of the present invention substantially contains almost no organic polar solvent in the film-forming dope solution and water generated during imidization, and the content of volatile components such as the solvent is approximately The content is preferably 1% by weight or less, particularly 0.5% by weight or less, and the film is a flexible film having a thickness of about 1 to 150 μm. In the method for producing a polyimide film according to the present invention, first, an aromatic tetracarboxylic acid component containing preferably 90 mol% or more of the above-mentioned biphenyltetracarboxylic acids and preferably 90 mol% or more of the above-mentioned phenylene diamines are added. aromatic diamine component in an organic polar solvent, preferably 100%
A polymer solution in which a polymer (polyimide precursor such as aromatic polyamic acid) produced by polymerization at a polymerization temperature of ℃ or lower, preferably 80℃ or lower is uniformly dissolved in an organic polar solvent is used as a dope for film formation. It is prepared as a liquid. The polyimide precursor is a polymer obtained by polymerizing biphenyltetracarboxylic acid or acid dianhydride with phenylene diamines, and has the general formula () about 50 mol% or more, especially 60 mol% of repeating units represented by
Aromatic polyamic acids which are soluble in organic polar solvents having a mole or more are preferred. The organic polar solvent may be any organic solvent that can be used as a polymerization solvent or a solvent for a dope solution for film formation, and can uniformly dissolve each of the monomer components and the polyimide precursor. For example, N,N-dimethyl sulfoxide,
Amide solvents such as N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, hexamethylenephosphoramide, pyridine, dimethyl Preferred examples include sulfoxide, tetramethylurea, cresol, and phenol. The polyimide precursor used in the method of this invention has a logarithmic viscosity (concentration: 0.5 g/100 ml, 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 may have a polymer concentration of about 2 to 40% by weight, particularly 3 to 30% by weight.
It is preferable that the rotational viscosity (30° C.) is about 10 to 50,000 poise. In the method of the present invention, following the preparation of the dope described above, (a) using the dope, preferably continuously or intermittently, a metal having a smooth surface is cast, such as by a known solution casting method. forming a thin film of said dope of uniform thickness on the surface of a support, such as a drum or belt made of
At a drying temperature of 50 to 150°C, the solvent and produced water of the thin film are gradually evaporated and the thin film is dried on the support, so that the solvent and produced water are about 27 to 60% by weight,
forming a solidified film in which preferably 30 to 50% by weight remains; (b) then peeling off the solidified film from the surface of the support; (i) 100 g/mm ² or less, preferably is 80 g/mm ² or less in a "substantially free state or under low tension up to the above upper limit", and (ii) at a drying temperature in the range of about 80 to 250 °C, preferably 100 to 230 °C, preferably is dried for about 1 to 200 minutes, particularly 2 to 100 minutes, to obtain a solidified film containing the solvent and produced water in a range of about 5 to 25% by weight, preferably 10 to 23% by weight. may form continuously or intermittently. When raising the temperature from the drying temperature of the first stage to the drying temperature of the second stage, it is preferable to raise the temperature in a relatively short time, for example, the temperature raising rate is preferably 10 ° C / min or more. suitable. In the method of the present invention, the final polyimide film obtained by increasing the tension applied to the solidified film during drying after peeling the solidified film from the support The average coefficient of linear expansion can be reduced, and this average coefficient of linear expansion can be adjusted to a desired value within the above-mentioned range. In the method of this invention, the above two-stage drying step
(a) and (b) are extremely important; if the above-mentioned drying method is not adopted or the drying conditions are outside the above-mentioned range, the dimensionally stable polyimide film that is the objective of this invention may not be obtained, or the appearance The resulting film is not completely smooth, but instead has many wrinkles or a roughened surface with many irregularities. In particular, in this invention, the drying step
The tension of the solidified film during drying in (b) is
If it exceeds 100g/ ^mm2 , abnormal thin film deformation,
This is not suitable as it may cause deterioration of flatness, sagging or wrinkles, and furthermore, if the drying temperature in the drying step (b) is higher than 250°C, many large and small wrinkles or fine bubbles may occur in the film. Furthermore, if the temperature is lower than 80°C, the drying step (b) will take a long time, which is not suitable industrially. In the method of the present invention, following the above drying step, at the end, at least one pair of both edges of the solidified film, which is continuously or intermittently supplied, is fixed movably together with the film. While fixed in a device, etc., dry at a high temperature higher than the above-mentioned drying temperature and within the range of 200 to 500°C, preferably within the range of 250 to 450°C, preferably for about 1 to 200 minutes, especially 2 to 100°C. The solidified film is dried and/or heat-treated for 1 minute, so that the solidified film is preferably dried and/or heat-treated so that the volatile content of the solvent and produced moisture in the final polyimide film is approximately 1% by weight or less. The solvent and the like are sufficiently removed and dried from the film, the polymer constituting the film is sufficiently imidized, and the film is further heat-treated sufficiently to obtain a size having all of the above-mentioned properties at the same time. This forms a stable aromatic polyimide film. As the fixing device for the solidified film, for example, a 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 in the longitudinal direction, which is continuously or intermittently supplied. Preferably, a pair of devices are installed along both side edges and can fix the film while moving continuously or intermittently as the film moves.
In addition, the above-mentioned fixing device for the solidified film can maintain the film during heat treatment at an appropriate elongation or shrinkage rate (particularly preferably about 0.5 to 5%) in the width direction or longitudinal direction.
It may be a device that can expand and contract at a certain degree of expansion/contraction magnification. In addition, in the method of the present invention, the aromatic polyimide film produced in the last step is again subjected to a low tension of preferably 400 g/mm ² or less, particularly preferably 300 g/mm ² or less,
At a temperature of about 250-500℃, especially 300-450℃, about 1-
When heat treated for 30 minutes, especially 2 to 20 minutes, a heat-resistant polyimide film with even better thermal dimensional stability can be obtained. Further, the long aromatic polyimide film produced continuously or intermittently by the method of the present invention is
It can be wound into a roll by any suitable known method. [Example] In the Examples and Comparative Examples, the average linear expansion coefficient (α: cm/cm/°C) was measured using a thermomechanical analyzer (physical (manufactured by Denki Co., Ltd.)
Raise the temperature from room temperature to 300°C at a rate of 10°C/min, hold at 300°C for 1 minute, then heat for 5 to 20 minutes.
Cooling down to room temperature at a cooling rate of °C/min, the displacement of the length of the specimen from 300°C to 50°C during cooling (ΔL ₁ ) and the original length of the specimen (L ₁ ; 10
mm) using the following formula. α-(ΔL ₁ /L ₁ )/(300-50) Thermal dimensional stability (A; %) is calculated using a dehydrated sample piece (5 mm x 20
mm) was installed, the temperature was raised from room temperature to 400°C at a rate of 10°C/min, and the temperature was maintained at 400°C for 2 hours.
Next, the specimen was cooled to room temperature at a cooling rate of 5 to 20°C/min, and the displacement of the length of the specimen at room temperature (ΔL ₂ ) before and after heating and the original length of the specimen (L ₂ ;10mm) using the following formula. A=(ΔL ₂ /L ₂ )×100 Example 1 (Preparation of dope solution) 38.1 kg of N,N-dimethylacetamide was added to a cylindrical polymerization tank with an internal volume of 50 mm, and then 3,3',
4,4'-biphenyltetracarboxylic dianhydride
Add 5.2959Kg of paraphenylenediamine, and gradually add 1.9466Kg of paraphenylenediamine while stirring, and heat at 30℃.
The reaction solution was continued to be stirred for about 10 hours, and both components were polymerized to produce polyamic acid. The logarithmic viscosity (30°C) of the polyamic acid produced in the above polymerization reaction is 3.10, and the rotational viscosity (30°C) of the polyamic acid solution is approximately 25000.
It was poise. (Film forming) This polyamic acid solution is used as a dope for film forming, and the dope is extruded into a thin film at approximately 30°C through the slit of a T-die mold (lip interval: 0.5 mm, lip width: 650 mm). Then, a thin film of the dope liquid was continuously placed on a smooth metal belt, and the thin film was dried in the first stage with hot air at about 120°C on the belt to form a solidified film-like body. Then,
Peel the solidified film from the belt, cut it into 200 mm lengths and widths, fix one side of the square piece of the solidified film to the frame with a pin sheet, and fix the opposite side to the frame. Under low tension, a dancer applies a load of approximately 35g uniformly over the entire width (7.0g/ ^mm2 tension in the longitudinal direction of the solidified film)
In that state, raise the temperature to 190℃ in about 30 seconds.
A second stage of drying is performed at a temperature of ℃ for 5 minutes to form a solidified film.Finally, the four square sides of the solidified film are held and fixed with a pin tenter, and the temperature of the solidified film is increased at a rate of about 10℃/min. Raise the temperature at a rapid rate,
Dry and heat treat (imidize) at 450℃ for 30 minutes,
An aromatic polyimide film with a thickness of 25 μm was produced. In the above-mentioned film formation, the solidified film after drying in the first stage, the solidified film after drying in the second stage under low tension, and the volatile content of the solvent and produced water in the aromatic polyimide film, and Table 1 shows the properties of the aromatic polyimide film obtained by the film formation. Comparative Example 1 An aromatic polyimide film was produced in the same manner as in Example 1, except that the square piece of the solidified film was directly dried and heat-treated in a high-temperature heat treatment apparatus without performing the second drying step. The results of the film formation are shown in Table 1. Example 2 A polyamic acid solution produced in the same manner as in Example 1 was used as a dope solution for film formation, and the dope solution was applied to the slits of a T-die mold (rip spacing;
0.5mm, lip width: 650mm) at about 30℃, and then place the thin film of the dope solution continuously on a smooth metal belt, and heat it on the belt at about 120℃.
The thin film is dried in the first stage with hot air to continuously form a solidified film, and then the solidified film is peeled off from the belt and the solidified film is dried under low tension by a dancer. (shown in Table 1) was fed into a vertical furnace (drying temperature 180℃) for about 4 hours.
The solidified film is formed through a second stage of drying, and then the solidified film is fed into a high-temperature heating furnace, where both longitudinal edges of the film are held by a horizontal tenter. The aromatic polyimide film was dried, heat-treated, and imidized with hot air that gradually increased in temperature from about 250 to 450°C while moving the film, forming an aromatic polyimide film.Finally, the film was wound up into a roll while being cooled. . 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 rolled film had a good appearance in the "rolled state". . The aromatic polyimide film obtained by the above-mentioned film forming method has an imidization rate of 95 or more and a heat resistance indicated by the thermal decomposition start temperature of the film.
450℃ or higher, and furthermore, the physical properties of the film in the MD direction (20℃) determined by a tensile test are 55Kg/mm ² , elongation 47%, and initial tensile modulus 870Kg/mm ^{2 .} Ta. Table 1 shows the properties of each film in the above film forming process and the properties of the aromatic polyimide film obtained by the film forming method. Comparative Example 2 An aromatic polyimide film was produced in the same manner as in Example 2, except that the second stage of drying was not performed thoroughly. The results of the film formation are shown in Table 1. Example 3 A film was formed in the same manner as in Example 2, except that the tension on the solidified film was 40 g/mm ² in the second drying stage of the film forming process, and a 25 μm thick aromatic film was formed. A polyimide film was produced. 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 rolled film had a good appearance in the "rolled state". . The aromatic polyimide film obtained by the above-mentioned film forming method has an imidization rate of 95 or more and a heat resistance indicated by the thermal decomposition start temperature of the film.
450℃ or higher, and furthermore, the physical properties of the film in the MD direction (20℃) determined by a tensile test are a tensile strength of 50Kg/ ^mm2 , an elongation rate of 44%, and an initial tensile modulus of 940Kg/ ^mm2. Ta. Table 1 shows the properties of each film in the above-mentioned film formation, such as the content of volatile components and thermal dimensional stability. Example 4 The same procedure as Example 2 was carried out, except that in the second drying stage of the film forming process, both ends of the solidified film in the longitudinal direction were held at regular intervals so that the weight was about 80 g/mm ² . A film was formed using the same method, and the thickness
A 25μm aromatic polyimide film was produced. In the above-mentioned film forming process, when the aromatic polyimide film that has been dried and heat-treated is rolled, no wrinkles occur, and the rolled film has an extremely good appearance in the "rolled state". Ta. The aromatic polyimide film obtained by the above-mentioned film forming method has an imidization rate of 95 or more and a heat resistance indicated by the thermal decomposition start temperature of the film.
450℃ or higher, and furthermore, the physical property values of the film in the MD direction (20℃) determined by a tensile test are a tensile strength of 52Kg/ ^mm2 , an elongation rate of 37%, and an initial tensile modulus of 1010Kg/ ^mm2. Ta. Other results of the film formation are shown in Table 1. Example 5 Example 2 was repeated, except that the width of the horizontal pin tenter in the high-temperature heat treatment furnace was gradually increased to about 1.04 times the width of the furnace inlet in the highest temperature zone of the furnace.
An aromatic polyimide film was produced in the same manner as above. The results of the film formation are shown in Table 1. 【table】

Claims (1)

[Claims] 1. A film made of aromatic polyimide obtained from a solution of a polymer produced by polymerizing biphenyltetracarboxylic acids and phenylene diamines, and the polyimide film can be heated from about 50°C to 300°C.
The average coefficient of linear expansion in the temperature range up to ℃ is approximately 0.1
×10 ^-5 to 2.5 × 10 ^-5 cm/cm・℃, and the ratio of linear expansion coefficients in the longitudinal direction (MD direction) and transverse direction (TD direction) of the film (MD/TD) is
It is about 1/5 to 4, and furthermore, it is 400℃ from room temperature.
Dimensions characterized by a thermal dimensional stability of approximately 0.3% or less, as indicated by the rate of change in film dimensions at room temperature before and after heating to 400°C and maintaining the temperature for 2 hours. Stable polyimide film. 2 Prepare a solution of a polymer obtained by polymerizing biphenyltetracarboxylic acids and phenylene diamines in an organic polar solvent, and then use the polymer solution to coat a thin film of the solution on the surface of a support. is formed, and the thin film is dried until the solvent and generated moisture are approximately 27 to 60% by weight.
A remaining solidified film is formed, and the solidified film is peeled off from the surface of the support and dried under a low tension of 100 g/mm ² or less and at a temperature in the range of about 80 to 250°C. to form a solidified film containing the solvent and produced moisture in a range of about 5 to 25% by weight, and finally, the solidified film is heated at a temperature of 200 to 500% higher than the drying temperature.
1. A method for producing a dimensionally stable polyimide film, which comprises drying and heat-treating at least one pair of edges at a temperature within the range of °C.