JPH10279711A - Aromatic polyamide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film using para-oriented aromatic polyamide, excellent in mechanical performance and dimensional stability and especially excellent in durability. SOLUTION: This film contains as a main component a para-oriented aromatic polyamide having an intrinsic viscosity of >=1.5 measured in the form of a solution obtained by dissolving 0.2g of the polymer in 100 ml of 98% concentrated sulfuric acid, has a Young's modulus of >=500 kg/mm<2> on both the longitudinal and latitudinal directions of the film, an elongation of >=8% and a moisture-absorbing expansion coefficient of <=40×10<-6> /%RH, an average density of >=1.38 /cm<3> and a density difference of <=0.01 g/cm<3> between the front and back surfaces of the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film made of para-oriented aromatic polyamide, and more particularly, to a film in a longitudinal direction (hereinafter abbreviated as "MD direction") and a width direction (hereinafter "A" direction). Abbreviated as “TD direction”), which relates to a film exhibiting excellent mechanical performance, and further having excellent dimensional stability and durability.

[0002]

2. Description of the Related Art Para-oriented aromatic polyamides have excellent crystallinity and a high melting point, and have high mechanical strength due to a rigid molecular structure. Used industrially. With respect to the use of polyparaphenylene terephthalamide (hereinafter, referred to as “PPTA”), which is a typical para-oriented aromatic polyamide, as a film, for example, Japanese Patent Publication No. Sho 57-17
As described in JP-A-886, an optically anisotropic dope in which PPTA is dissolved in a strong acid such as concentrated sulfuric acid is heated until it becomes optically isotropic immediately before coagulation, and then coagulated, whereby the transparent and mechanical properties are isotropic. It has been put to practical use by a method of obtaining an excellent film. When a PPTA film is formed, a film solidified as it is without changing the optically anisotropic dope to optically isotropic is generally opaque, and the mechanical properties and dimensional stability in the width direction of the film are poor. Bad, industrial application is difficult.

[0003] A transparent and isotropic film formed from a solution of an organic solvent by solubilizing an organic solvent by copolymerizing a unit in which a halogen is introduced into an aromatic nucleus of a para-oriented aromatic polyamide. (Eg, Japanese Patent Publication No. 56-45421). Such a para-oriented aromatic polyamide film has excellent mechanical properties, heat resistance, chemical resistance, and the like. For example, a recording medium for magnetic recording, a flexible printed wiring board (FPC),
It is expected to be applied to insulating substrates such as carrier tapes for tape automated bonding (TAB), acoustic members such as speaker diaphragms and voice coils, and substrates for solar cells.

However, although the para-oriented aromatic polyamide film has such advantages, it has a problem in that it has a large moisture absorption rate, is apt to undergo dimensional changes due to moisture absorption, and has a high density magnetic recording medium and a high density printed wiring board. However, there is a problem in applications where dimensional stability of the film is required. As a method for improving the moisture absorption characteristics of a para-oriented aromatic polyamide film, an attempt has been made to promote crystallization and orientation by advanced heat treatment and / or stretching.
719, JP-A-6-136156, and the like. For example, JP-A-62-246719 discloses that a film obtained by coagulation and washing is heated to 300 ° C.
A method of heat treatment under tension at 500 ° C. is disclosed. However, the film which has been crystallized by the heat treatment as described above has a problem that a change in physical properties upon repeated changes in humidity is large.

[0005]

An object of the present invention is to provide a film having excellent mechanical performance and dimensional stability using a para-oriented aromatic polyamide, particularly an aromatic polyamide film having excellent durability. To offer.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to obtain a film meeting the above-mentioned object, and as a result, a film having specific mechanical properties and a coefficient of hygroscopic expansion, which has been crystallized by heat treatment. In the above, it was found that the density difference in the thickness direction of the film was large, and further, it was found that by setting this density difference in a specific range, a film having excellent durability against humidity changes could be obtained. As a result of the superposition, the present invention has been completed.

That is, the present invention is a film comprising, as a main component, a para-oriented aromatic polyamide having a logarithmic viscosity of 1.5 or more measured at 30 ° C. in a solution obtained by dissolving 0.2 g of a polymer in 100 ml of concentrated sulfuric acid. The Young's modulus in both the longitudinal and width directions of the film is 500 kg / mm
² or more, elongation 8% or more, hygroscopic expansion coefficient 40 × 10 ^-6 /
% RH or less, the average density is 1.38 g / cm ³ or more, and the density difference between the front and back of the film is 0.01 g / cm ^3.
An aromatic polyamide film characterized by the following. The para-oriented aromatic polyamide which is a main component forming the film of the present invention has the following structural units (1) to (1).
It consists essentially of units selected from the group consisting of (3).

-NH-Ar ₁ -NH- (1) -CO-Ar ₂ -CO- (2) -NH-Ar ₃ -CO- (3) wherein Ar ₁ , Ar ₂ and Ar ₃ are each at least Divalent group containing one aromatic ring, (1) and (2)
Are substantially equimolar when present in the polymer.

In the present invention, in order to ensure good mechanical performance and dimensional stability, Ar ₁ , Ar ₂ and A
Each of r ₃ must be a para-oriented group. Here, the para-oriented type means that the bonding direction of the main chain in the aromatic ring is located at the para-position, or the bonding direction of the main chains at both ends is coaxial or parallel in a residue composed of two or more aromatic rings. It means there is. Representative examples of such a divalent aromatic group include a group represented by the following chemical formula 1.

[0010]

Embedded image

Here, X is -O-, -CH _2- , -S
It is a group selected from O ₂ —, —S—, and —CO—.
Further, some of the hydrogen atoms of these aromatic rings may be substituted with a halogen group, a nitro group, a sulfone group, an alkyl group, an alkoxy group, or the like. Ar ₁ , Ar ₂ and Ar
_Each of ₃ may be two or more kinds, and may be the same or different from each other. The polymer used in the present invention can be produced from a diamine, a dicarboxylic acid, or an aminocarboxylic acid corresponding to each unit by a method known hitherto. Specifically, a method is used in which a carboxylic acid group is first derived into an acid halide, an acid imidazolide, an ester, and the like, and then reacted with an amino group. The type of polymerization is also called a low-temperature solution polymerization method, an interfacial polymerization method, or a melt polymerization method. And a method such as a solid phase polymerization method.

In the aromatic polyamide used in the present invention, groups other than those described above may be copolymerized in an amount of about 10 mol% or less, or other polymers may be blended. The most typical aromatic polyamide used in the present invention is poly-p-phenylene terephthalamide (PPT).
A). If the degree of polymerization of the aromatic polyamide used in the present invention is too low, a film having good mechanical properties aimed at by the present invention cannot be obtained. To be elected.

The logarithmic viscosity ηinh in the present invention is 9
It is a value measured at 30 ° C. for a solution in which 0.2 g of a polymer is dissolved in 100 ml of 8% concentrated sulfuric acid. The film of the present invention,
In order to secure good mechanical properties during processing and during use, the Young's modulus in the longitudinal and width directions needs to be 500 kg / mm ² or more, and preferably 800 kg / mm ² or more. The film of the present invention needs to have an elongation of 8% or more, and more preferably 15% or more, in order to ensure the handling properties during processing and use.

The coefficient of hygroscopic expansion of the film of the present invention is 40
It is necessary to be not more than × 10 ⁻⁶ /% RH, and 35 ×
It is preferably 10 ⁻⁶ /% RH or less.
^-6 /% RH or less. In a film having a coefficient of hygroscopic expansion of more than 40 × 10 ⁻⁶ /% RH, the position of the wiring pattern greatly changes due to humidity in an insulating substrate application, and information recorded due to dimensional change due to humidity in a magnetic recording medium application. Cannot be reproduced, and cannot be used for applications requiring high dimensional accuracy. The heat shrinkage of the film of the present invention is 0.2
%, More preferably 0.1% or less. A film having a large heat shrinkage has problems such as a permanent change in dimensions at the time of processing at a high temperature and a deviation from a design dimension.

The content of the alkali or alkaline earth metal in the film of the present invention is preferably 1000 ppm or less, more preferably 100 ppm or less. If the alkali or alkaline earth metal is abundant in the film,
The moisture absorption dimensional stability and electrical insulation often deteriorate, and in the present invention, it is preferable to use a film having a small content of these metals. The thickness of the film of the present invention,
Usually 3 μm or more and 100 μm or less, 10 μm or more and 7 μm or more
0 μm or less is more preferable.

The average density of the film in the present invention is:
1.38Cm ³ or more, further 1.40Cm ³ or more. Here, the average density is a value obtained by averaging the density in the thickness direction of the film.
It is cut into about square mm and placed in a density gradient tube for measurement. The density of the film is correlated with the crystallinity of the aromatic polyamide. If the average density is less than 1.38 g / cm ³ , the crystallization is insufficient and the dimensional stability of the film is insufficient. The upper limit of the average density of the film is usually 1.50 g / c.
m ³ .

The difference in density between the front and back of the film of the present invention is 0.0
1 g / cm ³ or less, and 0.005
g / cm ³ or less, preferably 0.002 g / c
More preferably, it is not more than m ³ . It is thought that the density difference between the front and back of the film is caused by the non-uniformity of the front and back in the manufacturing process of the film.However, in the production of a practically oriented para-aromatic polyamide film, the process is completely symmetrical. It was virtually impossible to obtain a uniform film on both sides. If the density difference between the front and back surfaces exceeds 0.01 g / cm ³ , there is a problem that the curl changes greatly due to the wet heat condition of the film, and the durability in the wet heat cycle is deteriorated. May cause problems during long-term use.

Next, a method for producing the aromatic polyamide film of the present invention will be described. Since the para-oriented aromatic polyamide has a high melting point and cannot be melt-formed, the film is formed by a wet method, a dry method, or a dry-wet method using a forming solution (hereinafter referred to as “dope”) dissolved in a solvent. In the case of PPTA which is hardly soluble in an organic solvent, a polymer is dissolved in a strong inorganic acid such as concentrated sulfuric acid to form a dope, and a film is formed by a wet method, for example, as disclosed in JP-A-62-174118. As described above, a method of once extruding in a liquid crystal state, optically isotropic, and then solidifying is preferably used. On the other hand, for example, in an aromatic polyamide soluble in an organic solvent such as chloro-substituted PPTA, hydrochloric acid by-produced during polymerization is neutralized and the polymerization reaction mixture is directly used as a molding solution (hereinafter referred to as “dope”).
Called. ), And a method of forming a film by a wet method, a dry method, or a dry-wet method is preferably used.

The method of forming the dope into a film is not particularly limited in practicing the present invention, and may be a method in which the dope is extruded directly from a die into a coagulation bath, a method in which the dope is cast once on an endless belt, or an endless belt. There is a method in which a dope is coated thereon by a doctor knife or other methods, and then the solvent is evaporated on a belt or guided to a coagulation bath together with the belt for wet coagulation. After the film is formed in this manner, the film is washed with water, and then subjected to a neutralization treatment if an acid by-produced during polymerization or an acid used for dissolution remains.

If an acid is contained in the formed film, it is preferable to neutralize the film, because the mechanical properties are reduced by heating during drying and heat treatment. Examples of the alkali used for neutralization include lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium carbonate, sodium carbonate, sodium hydrogen carbonate and the like. The neutralized film is preferably treated with an aqueous solution of carbon dioxide after removing excess alkali and inorganic salts generated by the neutralization by washing. By the treatment with the aqueous carbon dioxide solution, the alkali or alkaline earth metal ions bound to the terminal groups of the aromatic polyamide molecules can be removed, and the metal ion content in the film can be reduced.

The film thus obtained is further washed with water and then dried. If desired, the film can be stretched before drying. That is, the dimensional stability and mechanical properties of the film can be improved by stretching the wet film before drying by about 1.01 to 1.4 times in one or two directions. Drying of the film is usually preferably performed under tension, under constant length, or while slightly stretching. As a method for performing such drying, for example, it can be fixed to a tenter dryer or a metal frame and dried. The drying temperature is usually in the range of 100 ° C to 200 ° C.

In order to obtain the film of the present invention, the dried film thus obtained is usually heat-treated at a temperature of 300 ° C. or more and 500 ° C. or less. This heat treatment can improve mechanical performance and dimensional stability. In the present invention, as a method for obtaining a film having a front and back density difference of 0.01 g / cm ³ or less, in the process from casting the dope to winding up the film, a process is designed so that there is no difference between the front and back surfaces. One of the methods is to perform casting or solidification on a support such as a belt, which is usually performed. However, it is difficult to avoid a difference in structure between the front and back sides. Therefore, it is difficult to avoid a density difference between product films when heat-treated under uniform heating conditions on the front and back when manufactured by a conventional method.

Therefore, in order to obtain the film of the present invention, it is an appropriate method to control the temperature of the heat treatment so that the difference in density between the front and back is 0.01 g / cm ³ or less. The temperature is adjusted so that the density difference of the product film is reduced. When radiant heat is mainly used as the heating method, it is difficult to adjust the difference in density between the front and back surfaces of the film. Therefore, it is preferable to perform a heat treatment by spraying heating fluids having different temperatures on the front and back surfaces. As a fluid,
Heated air, heated nitrogen, heated steam, etc. are usually used,
When the structural difference up to the heat treatment step is large, a heated gas may be blown only on one side, or a heated gas may be blown on one side to cool the other side. The heat treatment can be performed under tension, under a fixed length, or in a relaxed state, and the heat treatment time needs to adopt appropriate conditions in combination with the heat treatment temperature, and is usually performed in about 1 second to 20 seconds. .

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION In order to facilitate understanding of embodiments of the present invention and effects of the present invention, typical PPTA is selected as an aromatic polyamide, and examples are shown below.
These examples do not limit the invention. Further, it will be easily understood that the effects of the present invention will be similarly obtained in other para-oriented aromatic aromatic polyamides. In the examples, unless otherwise specified, parts by weight or% by weight are indicated. Logarithmic viscosity ηinh is 9
A solution prepared by dissolving 0.2 g of the polymer in 100 ml of 8% sulfuric acid was measured at 30 ° C. by a conventional method. The viscosity of the dope was measured using a B-type viscometer at a rotation speed of 0.5 rpm.

The thickness of the film was measured with a dial gauge having a measuring surface having a diameter of 2 mm. The elongation and Young's modulus are obtained by measuring a sample having a size of 200 mm × 10 mm using a constant-speed elongation type elongation tester at a measurement length of 100 mm and a tensile speed of 50 mm / min. The coefficient of hygroscopic expansion is
Dimensional change of the film from when the film was dried in an air oven at 200 ° C. for 2 hours using a sample of 50 mm × 10 mm (measurement length 40 mm) to when the film was sufficiently absorbed in a 23 ° C. and 55% RH atmosphere. Calculated from The dimensions of the film were measured using a reading microscope (Olympus).

The heat shrinkage is 2 cm × 5 cm from the film.
Was cut out with a knife at 4 cm intervals to form a label. After leaving in advance in an atmosphere of 23 ° C. and 55% RH for 72 hours, the distance between the labels was read and measured with a microscope. The sample was left in a hot-air oven at 2 ° C. for 2 hours without restraint, and then left again in an atmosphere of 23 ° C. and 55% RH for 72 hours. The distance between the labels was read and measured with a microscope. The average density of the film is obtained by cutting the film into a square of about 5 mm, placing the film in a density gradient tube using carbon tetrachloride-toluene, and measuring at 30 ° C. by a density gradient tube method. The density difference between the front and back of the film was measured by the following method.

One side of the film was shaved using sandpaper until the film thickness became half of the original thickness, cut into about 5 mm squares, and placed in the above-mentioned density gradient tube to measure the density of one side. . This operation was performed on both the front and back surfaces of the film, the front and back densities were measured, and the difference was defined as the difference between the front and back surfaces of the film. The metal ion content in the film was measured by an inductively coupled plasma emission spectrometer (ICAR-575-II, manufactured by Nippon Jarrell Ash). Reference Example-Production of PPTA PPTA was obtained by a low-temperature solution polymerization method as follows.

In a polymerization apparatus disclosed in Japanese Patent Publication No. 53-43986, 70 parts of anhydrous lithium chloride was dissolved in 1000 parts of N-methylpyrrolidone, and 48.6 parts of paraphenylenediamine were dissolved. After cooling to 8 ° C., 91.4 parts of terephthalic acid dichloride were added at once in powder form. After a few minutes, the polymerization reaction product solidified in a cheese-like manner. Therefore, the polymerization reaction product was discharged from the polymerization apparatus according to the method described in Japanese Patent Publication No. 53-43986, immediately transferred to a twin-screw closed kneader, and polymerized in the kneader. The reaction was milled. Next, the finely pulverized product was transferred into a Henschel mixer, to which an approximately equal amount of water was added and further pulverized, filtered, washed several times in warm water, and dried in hot air at 110 ° C. ηinh is 6.1
95 parts of a pale yellow polymer were obtained.

[0029]

Example 1 ηinh was 6 in concentrated sulfuric acid having a concentration of 99.5%.
Is dissolved at 60 ° C. and the polymer concentration is 12
% Stock solutions were prepared. When the viscosity of this stock solution was measured at 60 ° C., it was 4800 poise. This stock solution had optical anisotropy. This stock solution was degassed under vacuum while maintaining the temperature at 60 ° C. The dope was passed from a tank through a filter, fed by a gear pump, and a dope was cast from a T-die having a slit of 0.4 mm × 700 mm onto a tantalum belt polished to a mirror surface, with a relative humidity of about 25% and a temperature of about 120.
The casting dope was optically isotropic by blowing air at a temperature of ° C, and was introduced into a 57% aqueous sulfuric acid solution at 15 ° C together with a belt to solidify it. Next, the coagulated film was peeled off from the belt, washed in room temperature water for 6 minutes, then in a 2.0% by weight aqueous sodium hydroxide solution for 6 minutes, and further run in room temperature water for 6 minutes. 0.01% aqueous solution (pH =
4.5) was run for 12 minutes, and further washed with water at room temperature for 5 minutes. After washing, the film is roll-stretched in a 1.02-fold lengthwise direction (hereinafter abbreviated as “MD direction”), and then stretched in a width direction (hereinafter abbreviated as “TD direction”) with a 1.08-fold tenter. Then, the film was dried with hot air at 200 ° C. at a constant length while sandwiched between tenters, and further heated at 440 ° C. was blown onto the upper surface of the film while sandwiched between tenters, and 415 ° C. on the lower surface.
Of heated air. The average air velocity of the heated air was 1.5 m / sec both vertically and the heat treatment time was 30 seconds.

The thickness of the obtained film was 48 μm, the average density was 1.402 g / cm ³ , the density difference between the front and back was 0.004 g / cm ³ , and the Young's modulus in the longitudinal and width directions was 1160 kg / cm. mm ² , 1210kg / m
m ² and elongation are 18.2% and 17.6%, respectively, and the coefficient of hygroscopic expansion is 29 × 10 ⁻⁶ /% RH and 26 × 10 ⁻⁶ /%, respectively.
% RH and heat shrinkage are 0.12% and 0.11%, respectively.
It contained 48 ppm of sodium ions as metal ions. The film was subjected to a humidity cycle test of 500 cycles in which the temperature was kept constant at 85 ° C. and the relative humidity was changed between 0% and 85%. The residence time under each condition was 1 hour. The strength and elongation retention after the humidity cycle test were 95% and 92%, respectively, indicating good performance.

[0031]

Comparative Example 1 A PPTA film was produced in exactly the same manner as in Example 1 except that the heat treatment was changed to pass between hot plates heated to 420 ° C. The thickness of the obtained film was 48 μm, and the average density was 1.402 g /
cm ³ , the density difference between the front and back is 0.015 g / cm ³ ,
Young's modulus in the longitudinal and width directions is 1130 kg / m each
m ² , 1150 kg / mm ² , elongation 19.5 each
%, 20.3%, and the coefficient of hygroscopic expansion is 28% and 29, respectively.
%, The thermal shrinkage rates were 0.06% and 0.05%, respectively, and 45 ppm of sodium ions were contained as metal ions. The film was subjected to a humidity cycle test of 500 cycles in which the temperature was kept constant at 85 ° C. and the relative humidity was changed between 0% and 85%. The residence time under each condition was 1 hour. The strength and elongation retention after the humidity cycle test were 38% and 32%, respectively.

[0032]

Comparative Example 2 Example 1 was the same as Example 1 except that the heat treatment was changed such that the upper hot plate temperature was 440 ° C. and the lower hot plate temperature was passed between hot plates heated to 415 ° C. A PPTA film was produced in exactly the same way. The thickness of the obtained film is 49 μm, and the average density is 1.403 g / c.
m ³ , the difference in density between the front and back is 0.013 g / cm ³ , and the Young's modulus in the longitudinal and width directions is 1120 kg / mm, respectively.
² , 1130 kg / mm ² , elongation 19.3 each
%, 20.2%, and the coefficient of hygroscopic expansion is 28 × 10 ^-6 /
% RH, 29 × 10 ⁻⁶ /% RH, and heat shrinkage were 0.09% and 0.10%, respectively, and contained 38 ppm of sodium ions as metal ions. The film was subjected to a humidity cycle test of 500 cycles in which the temperature was kept constant at 85 ° C. and the relative humidity was changed between 0% and 85%. The residence time under each condition was 1 hour. The strength and elongation retention after the humidity cycle test were 48% and 42%, respectively.

[0033]

Example 2 40% colloidal silica particles of 80 nm
The resulting dispersion was mixed with distilled water to prepare a diluent having a silica concentration of 8%, and added to 100.6% concentrated sulfuric acid to prepare concentrated sulfuric acid containing 0.035% silica. Using this concentrated sulfuric acid, PPTA was dissolved so that the polymer concentration became 12.5%, and the dope of PPTA was adjusted. The dope reflects light irregularly during stirring, and when observed under an optical microscope,
The liquid crystal was found to be in a liquid crystal state, such as exhibiting optical anisotropy that makes the dark field of crossed Nicols of a polarizing microscope a bright field.

After the PPTA dope was filtered through a 5 μm-cut filter made of sintered nonwoven fabric of stainless steel, it was cast from a die onto an endless belt at a draft rate of 1.2. Next, the dope is heated and moisture-absorbed simultaneously with the heating to convert the dope from a liquid crystal phase to an isotropic phase, and then coagulated in 30% sulfuric acid at 10 ° C., neutralized, washed with water, and saturated aqueous solution of carbon dioxide. After running through the inside and further washing with water, stretched 1.1 times in the vertical direction, stretched 1.1 times in the horizontal direction with a clip tenter, and dried with hot air at 180 ° C for 10 minutes while maintaining the fixed length state. did. Further, while being held between the tenters, heated air at 470 ° C. was blown to the upper surface of the film, and heated air at 440 ° C. was blown to the lower surface.
The average wind speed of the heated air is 2.0 m / sec both up and down,
The heat treatment time was 20 seconds.

The resulting PPTA film was 4.5μm thick, the average density of 1.415g / cm ^3, the density difference between the front and back is 0.001 g / cm ^3, those containing 45ppm sodium ions as the metal ions Met. The physical properties of the film are strength 4
1, 39 kg / mm ² , elongation 12, 11%, elastic modulus 15
480, 1510 kg / mm ² , coefficient of hygroscopic expansion 27 × 1
It was 0 ^-6 /% RH. The film is heated to 85 ° C
And the relative humidity changes to 0% and 85% 500
A cycle humidity cycle test was performed. The residence time under each condition was 1 hour. Strength after wet heat cycle test,
The elongation retention rates were 97% and 94%, respectively, indicating good performance.

[0036]

Comparative Example 3 Example 2 was repeated except that the hot air temperature during the heat treatment was 455 ° C. for both the upper and lower sides. The obtained PPTA
The film has a thickness of 4.5 μm and an average density of 1.4.
13g / cm ³ , density difference between front and back is 0.012g / cm ³
And 45 pp of sodium ions as metal ions
m. The physical properties of the film were as follows: strength 38, 39 kg / mm ² , elongation 1
2, 13%, elastic modulus 1520, 1490 kg / mm ² ,
The coefficient of hygroscopic expansion was 26 × 10 ⁻⁶ /% RH. The film was kept at a constant temperature of 85 ° C. and a relative humidity of 0% and 85%.
% Humidity cycle test of 500 cycles. The residence time under each condition was 1 hour. The strength and elongation retention after the humidity cycle test are 43%, respectively.
Physical properties were greatly reduced at 34%

[0037]

The film of the present invention is a film having good mechanical performance, heat resistance and dimensional stability of a para-oriented type aromatic polyamide film. And a decrease in physical properties due to a heat cycle is small. Therefore, as a feature in using the product, there is a feature that a decrease in physical properties due to a change in a use environment is small and reliability during long-term use is high. Taking advantage of this feature, high-density recording media, flexible printed wiring boards (FPC),
It can be used as an insulating substrate such as a carrier tape for tape automated bonding (TAB), an acoustic member such as a speaker diaphragm and a voice coil, and a solar cell substrate.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // G11B 5/704 G11B 5/704 B29K 77:00 B29L 7:00

Claims (2)

[Claims] 1. Polymer 100% in 98 ml of 98% concentrated sulfuric acid.
The logarithmic viscosity measured at 30 ° C. of a solution in which 2 g was dissolved was 1.
A film mainly comprising 5 or more para-oriented aromatic polyamides, and having a Young's modulus of 500 kg / mm ² or more and an elongation of 8 in both the longitudinal and width directions of the film.
%, The coefficient of hygroscopic expansion is 40 × 10 ⁻⁶ /% RH or less, the average density is 1.38 g / cm ³ or more, and the difference in density between the front and back of the film is 0.01 g / cm ³ or less. Aromatic polyamide film. 2. The aromatic polyamide film according to claim 1, wherein the content of the alkali or alkaline earth metal in the film is 1000 ppm or less.