JP2964962B2 - Aromatic polyamide film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an aromatic polyamide film. More specifically, the present invention relates to an aromatic polyamide film useful for applications such as a base film for a magnetic recording medium, a flexible printed board, and a capacitor.

[0002]

2. Description of the Related Art Aromatic polyamide films are used as base films for magnetic recording media because of their excellent mechanical properties and heat resistance.
It has been proposed to use it as a composite with other materials such as a flexible printed board, a capacitor, and a thermal transfer film. In these applications, products are often exposed to high temperatures in the processing process, and the use of products is also increasing under high temperature or high humidity. The demands are strict. In response to such demands, it is particularly important to obtain a film having excellent heat resistance and dimensional stability by defining the heat shrinkage, the coefficient of thermal expansion, the coefficient of humidity expansion, and the like using a para-based aromatic polyamide film. Kaihei 06-613,
It is disclosed in JP-A-02-84328 and the like.

[0003]

However, in these methods, there is a problem that the function of the product is deteriorated due to long-term repeated use of the film. That is, when the magnetic recording medium is repeatedly used under high temperature and high humidity, peeling of the magnetic layer and the base film and deterioration of the electromagnetic conversion characteristics are observed. The flexible printed circuit board has problems such as curling and wrinkling when used for a long period of time, and deterioration in adhesiveness to metal.

The present invention solves such a problem, and does not cause curling or wrinkling of the composite, or deterioration of the flatness or deterioration of the function of the composite even under repeated use under severe conditions. It is intended to provide a film.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that these problems can be solved by improving the homogeneity in the film thickness direction, and have reached the present invention. That is, in the present invention, the degree of orientation PA, PB (PA ≧ P) of the outermost layer determined from the ATR spectra of both surfaces of the film.
An aromatic polyamide film, wherein the ratio of B) is PA / PB ≦ 1.10.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic polyamide of the present invention is
Those containing 50 mol% or more of the repeating units represented by the following general formula (I) and / or general formula (II) are preferable, and those containing 70 mol% or more are more preferable.

The general formula (I)

Embedded image General formula (II)

Embedded image

Here, Ar ₁ , Ar ₂ and Ar ₃ are, for example,

Embedded image And the like, X, Y is _{-O -, - CH 2 -,} - CO
_{-, - SO 2 -, -} S -, - C (CH 3) 2 - is chosen from such, but is not limited thereto. Further, some of the hydrogen atoms on these aromatic rings may be substituted with halogen groups (particularly chlorine) such as chlorine, fluorine and bromine, alkyl groups (particularly methyl groups) such as nitro, methyl, ethyl and propyl groups, and ethoxy. Group, methoxy group, propoxy group, isopropoxy group, etc., those substituted with an alkoxy group and the like, and those in which the hydrogen in the amide bond constituting the polymer is substituted by another substituent are also included. .

[0009] From the viewpoint of properties, those in which the above aromatic rings are bonded at the para position account for at least 50%, preferably 75%, of the total aromatic rings.
% Of the polymer is preferable because the film has good thermal dimensional stability and a high elastic modulus film can be obtained. When the aromatic ring in which a part of hydrogen atoms on the aromatic ring is substituted with a halogen group (particularly chlorine) is 30% or more, preferably 50% or more, and more preferably 70% or more of the whole, the humidity expansion coefficient is increased. It is preferable because it becomes smaller.

The aromatic polyamide of the present invention contains at least 50 mol% of the repeating unit represented by the general formula (I) and / or the general formula (II).
Less than that, other repeating units may be copolymerized or blended.

The aromatic polyamide of the present invention may be blended with a lubricant, an antioxidant and other additives to such an extent that the physical properties of the film are not impaired.

In the present invention, the AT on both surfaces of the film
The ratio of the degree of orientation PA, PB (PA ≧ PB) of the outermost layer on both surfaces of the film determined from the R spectrum is PA / PB ≦ 1.1.
Must be 0. The ratio of the degree of orientation between the front and back of the film being 1.10 or less means that the difference in the degree of orientation in the thickness direction of the film is small, that is, the film is homogeneous in the thickness direction. When the ratio of the degree of orientation in the thickness direction of the film is outside the above range, when the film is exposed to high temperature or high humidity in the processing step, the film itself has a heat shrinkage coefficient, a coefficient of thermal expansion, a coefficient of humidity expansion in the thickness direction. If the film itself is curled due to the difference, etc., and if curling does not occur, if a material such as a metal thin film is composited with distortion in the thickness direction and then cooled to room temperature, the distortion is released and the composite material becomes Curling and deterioration of flatness are caused. In the processing step, even if the flatness is not deteriorated, the adhesiveness between the film and the metal thin film and the film is deteriorated due to distortion in the thickness direction when used under a high temperature or high humidity for a long time, The flatness of the composite material is deteriorated. For example, in a magnetic tape, the magnetic layer is peeled off or the magnetic conversion characteristics are deteriorated. Preferably PA / PB ≦ 1.0
5, and more preferably PA / PB ≦ 1.02, the above effect is enhanced.

As described above, the homogeneity in the thickness direction of the film is important for the durability in long-term use. Further, if the dimensional stability of the whole film is good, the processability of the film is further improved, so that it is more preferable.

That is, the coefficient of thermal expansion of the film in the present invention is -1.0 × 10 ⁻⁶ to 40 × 10 ⁻⁶ (cm / cm) / in at least one direction in the plane, preferably in all directions.
C is preferred.

The film of the present invention has a heat shrinkage at 220 ° C. of at least one direction, preferably 5% or less in all directions.

If the thermal dimensional stability is out of this range, the flatness such as curling is deteriorated in the process of processing the product, which is not preferable.

The film of the present invention has a coefficient of humidity expansion of at least one direction, preferably -15 × 1 in all directions.
It is preferably 0 ^{-6 to} 20 × 10 ^-6 (cm / cm) /% RH, and more preferably -10 × 10 ^-6 to 10 × 1.
0 ^-6 (cm / cm) /% RH. If the coefficient of humidity expansion is out of this range, the flatness of the product may deteriorate when used under high humidity, which is not good.

Since these coefficients of thermal expansion, coefficient of thermal shrinkage, and coefficient of humidity expansion affect the film in a complex manner, it is preferable that the above ranges be satisfied in all directions at the same time.

The thickness of the film of the present invention is 0.1 to 15
It is preferably 0 μm, more preferably 1 to 80 μm. If the thickness is larger than this range, it is difficult to keep the thickness direction uniform.

The film of the present invention may contain particles for imparting lubricity to the film. The particle size and content of the particles to be contained should be appropriately selected depending on the application, but the average primary particle size is preferably 0.01 to 2 μm, and the content of the particles contained in the film is preferably 0.1 to 2 μm. It is preferably from 0.01 to 5 wt%, more preferably from 0.05 to 3 wt%. If the particle size and content of the particles are larger or larger than the above range, the adhesion to the composite material is deteriorated, or when a magnetic tape is used, the adhesion between the tape and the magnetic head is poor, and the electromagnetic conversion characteristics are deteriorated. not good. If the particle size and content of the particles are smaller or smaller than the above ranges, the running property of the film is poor and it is difficult to handle. As the type of the particles, SiO ₂ , TiO ₂ , Al ₂
Inorganic particles such as O ₃ , CaSO ₄ , BaSO ₄ , CaCO ₃ , carbon black, zeolite, and other fine metal powders, silicon particles, polyimide particles, cross-linked copolymer particles, cross-linked polystyrene particles, Teflon particles, etc. There are organic polymers and the like, but inorganic particles are more preferable from the viewpoint of heat resistance.

The surface roughness of the film should be appropriately designed depending on the application.
p is 2 to 500 nm, more preferably 3 to 300 nm,
Ra is 0.1 to 100 nm, more preferably 0.2 to 5
0 nm, 2 to 500 nm in Rz, more preferably 3 to 4
00 nm.

The film of the present invention has a moisture absorption of 3.5.
% Or less, and more preferably 2.5% or less. If the moisture absorption exceeds 3.5%, the dimensional stability against a change in humidity becomes poor, and the flatness such as curls and wrinkles is deteriorated,
It is not preferable because the electromagnetic conversion characteristics of the magnetic tape deteriorate.

In the present invention, the elongation of the film is preferably 10% or more, and more preferably 20% or more, since the tape has appropriate flexibility and excellent workability.

The elastic modulus of the film in the present invention is 5.88 GPa or more, preferably 7.88 GPa in both the longitudinal and width directions.
If it is 85 GPa or more, it is easy to handle even if it is made thin,
When using a magnetic tape, the head touch is good,
Electromagnetic conversion characteristics are improved.

The film of the present invention may of course be a single-layer film, but may be a laminated film.

The film of the present invention can be used for various uses such as a flexible printed circuit board, a thermal transfer ribbon, a capacitor, and a base film for a magnetic recording medium.

When used as a base film for a magnetic recording medium, a magnetic layer is provided on one or both sides to form a magnetic recording medium.

The method for forming the magnetic layer of the magnetic tape is as follows: iron oxide, chromium oxide, Fe, Co, Fe--Co, Fe--C
There are limited methods such as a method of applying a ferromagnetic powder such as o-Ni or Co-Ni as a magnetic paint using various binders on a support film, a vacuum thin film forming method such as an evaporation method, a sputtering method, and an ion plating method. It is not particularly effective, but is particularly effective in a vacuum thin film forming method in which the film is exposed to a high temperature during the manufacturing process.

After providing the magnetic layer, a back coat layer may be provided on the surface opposite to the magnetic layer by a known method in order to further improve the running property.

Thus, the film provided with the magnetic layer is slit into a predetermined width to form a magnetic recording medium.

The magnetic recording medium thus obtained is preferably used for consumer, professional, D-1, D-2, D-
3 for broadcasting stations, digital video cassettes, DDS-
2, 3, 4, QIC, data 8mm, etc., for data storage, but are not limited to these.
It can be optimally used for data storage applications where reliability such as data reproduction is most important.

The film of the present invention particularly has a support having a thickness of 0.2 to 6.5 μm and a width of 2.3 to 13 μm.
When a tape-shaped magnetic recording medium having a recording density of 0 mm and a recording density (uncompressed) of 8 KB / mm ² or more as a magnetic recording medium is used, the durability of the present invention when used under severe conditions is used. It is preferable because the effect of the aromatic polyamide film of the present invention having properties is sufficiently exhibited.

In recent years, magnetic recording media represented by magnetic tapes have been increasingly demanded to be smaller and have higher capacity. For this reason, thinner support films, narrower track widths,
Higher recording density is being promoted by shortening the recording wavelength.
For this reason, a slight flatness defect such as curl tends to cause data recording / reproducing defects, or poor durability when repeatedly used. The magnetic recording medium using the film of the present invention can be a magnetic tape that can suitably meet such demands. The thickness of the film is preferably from 0.2 to 4.5 μm, more preferably from 0.2 to 3.5 μm, and the recording density of the magnetic recording medium is preferably 25 kilobytes / mm.
² or more, more preferably 50 kilobytes / mm ² or more.

Next, the manufacturing method of the present invention will be described.

First, an aromatic polyamide. When it is obtained from an acid chloride and a diamine, it is prepared in an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc) or dimethylformamide (DMF). It is synthesized by solution polymerization or interfacial polymerization using an aqueous medium. When acid chloride and diamine are used as monomers in a polymer solution, hydrogen chloride is by-produced.When neutralizing this, inorganic neutralizers such as calcium hydroxide, calcium carbonate, lithium carbonate, and ethylene chloride are used. Oxide, propylene oxide, ammonia,
Organic neutralizers such as triethylamine, triethanolamine, diethanolamine, etc. are used. The reaction between the isocyanate and the carboxylic acid is performed in an aprotic organic polar solvent in the presence of a catalyst.

These polymer solutions may be used directly as a stock solution for film formation. Alternatively, the polymer may be isolated once and then redissolved in the above-mentioned organic solvent or an inorganic solvent such as sulfuric acid to prepare a stock solution for film formation. Is also good.

In order to obtain the aromatic polyamide film of the present invention, the intrinsic viscosity of the polymer (measured at 30 ° C. as a 100 ml solution of 0.5 g of the polymer in sulfuric acid) is 0.1.
It is preferably 5 or more.

In some cases, an inorganic salt such as calcium chloride, magnesium chloride, lithium chloride, lithium nitrate, or the like is added as a dissolution aid to the stock solution for film formation. The polymer concentration in the stock solution is preferably about 2 to 40% by weight.

As a method of adding the particles, there is a method in which the particles are sufficiently slurried in a solvent in advance and then used as a polymerization solvent or a diluting solvent, or a method in which a stock solution is prepared and then directly added.

The film-forming stock solution prepared as described above is formed into a film by a so-called solution casting method. The solution film forming method includes a dry-wet method, a dry method, a wet method, and the like, and any method may be used to form a film. An effective method for obtaining a film having no difference in the degree of orientation between the front and back of the film is to reduce the difference in the solvent extraction rate from both surfaces of the film, to drive the nip roll used in the manufacturing process, and to change the peripheral speed of the free roll. , Or a method of reducing the difference in heat treatment temperature between both surfaces during heat treatment. Here, the dry-wet method will be described as an example.

When a film is formed by a dry-wet method, the undiluted solution is extruded from a die onto a support such as a drum or an endless belt to form a thin film, and then the solvent is scattered from the thin film layer so that the thin film has a self-holding polymer concentration. Dry to 35-60 wt%. In order to obtain a uniform film in the desired thickness direction in this dry process, the film is dried with hot air at a temperature of 200 ° C. or less and the belt surface temperature is reduced to (hot air temperature−2).
0 ° C.) or higher. By raising the belt surface temperature to a temperature higher than (hot air temperature-20 ° C), the evaporation of the solvent on the belt surface side of the cast film, which is difficult to evaporate, is promoted, and the difference in orientation and polymer concentration in the thickness direction of the film at the time of peeling is reduced. Can be smaller.

After the film having been subjected to the dry process is cooled, the film is separated from the support and introduced into a wet bath in the next wet process for desalting and solvent removal. The wet bath composition is not particularly limited as long as it is a poor solvent for the polymer.
Alternatively, using a mixed system of organic solvent / water is economical,
It is preferable because of easy handling. The composition ratio is organic solvent / water =
70/30 to 0/100, preferably 60/4
When the ratio is from 0 to 30/70, the homogeneity is good in the thickness direction of the film. Further, the wet bath may contain an inorganic salt.

The film that has passed through the wet process is subsequently dried and heat-treated in a tenter to form a film.

The film formed as described above is stretched in a wet bath during the film forming process in a tenter to improve mechanical properties and dimensional stability. It is preferably in the range of 0.8 to 4.0 (the area ratio is defined as a value obtained by dividing the area of the film after stretching by the area of the film before stretching).

After the stretching, the film is subjected to a heat treatment.
The heat treatment is preferably performed at 200 to 450 ° C. for 1 second to 5 minutes. If the temperature of the heat treatment is lower than this temperature, crystallization becomes insufficient, and sufficient mechanical properties cannot be obtained. If it exceeds this range, the film becomes brittle and cannot be put to practical use. At this time, it is preferable that the heat treatment is performed uniformly at a temperature difference of 3 ° C. or less from both sides of the film in order to reduce the difference in the degree of orientation between the front and back of the film.

The film of the present invention may be a laminated film. For example, in the case of two layers, the polymerized aromatic polyamide solution is divided into two parts, different particles are added, and then the layers are laminated. The same applies to the case of three or more layers.
These laminating methods include well-known methods such as lamination in a die, lamination in a composite tube, and a method in which one layer is formed once and another layer is formed thereon.

As described above, the film of the present invention can be obtained, but is not limited thereto.

[0048]

EXAMPLES The method for measuring physical properties and the method for evaluating effects according to the present invention are as follows.

(1) Degree of orientation on the film surface
The S-polarized ATR spectrum was measured at every 0 ° in all directions under the following conditions. Based on the obtained spectrum, the amide III absorption band based on the amide bond is a π band, the C = O stretching vibration of the amide I absorption band is a σ band, and the infrared two-color ratio (= π band / σ band) is determined from each peak intensity. It was calculated as an orientation parameter and developed into a polar figure. In this polar figure, the area of a portion surrounded by a line connecting the respective orientation parameters was defined as the degree of orientation of the surface. The ratio PA / PB when the orientation degrees obtained from both sides of the film were PA and PB (where PA ≧ PB) was defined as the orientation degree ratio. The measurement is 25 ° C,
Performed at 60% RH.

Apparatus FTS-55A (Bio Rad)
DIGILB) Attached device Single reflection ATR spectrum measuring device Light source: Ceramics Detector: MCT Resolution: 4 cm ^-1 Accumulation frequency: 500 times IRE: Ge Incident angle: 60 ° Polarizer: Wire grid, S polarized light Detection depth: ~ 0.25μm

(2) Coefficient of thermal expansion To eliminate the effects of heat shrinkage and moisture absorption / desorption, the film was
80-150 when heated to 0 ° C and gradually cooled
It was calculated from the dimensional change at ° C. The dimensional change was measured by a thermomechanical analyzer (TMA).

(3) Heat Shrinkage Film A film was sampled so as to have a width of 10 mm and a test length of 200 mm, heated in an oven at 220 ° C. for 10 minutes, taken out of the test piece, allowed to cool, and calculated by the following equation.

Heat shrinkage (%) = (length after heating−test length)
/ Test length × 100

(4) Coefficient of Humidity Expansion Set in a high-temperature high-humidity chamber so as to have a width of 1 cm and a test length of 15 cm, dehumidify to a constant humidity (about 30% RH), and after the film length becomes constant, humidify (About 80% RH), it begins to expand due to moisture absorption. After about 24 hours, the moisture absorption reaches equilibrium and the film stretch reaches equilibrium. The elongation at this time is calculated by the following equation.

Humidity expansion coefficient ((cm / cm) /% RH)
= Elongation / (Test length x Humidity difference)

(5) Evaluation The film was loaded into a vapor deposition machine, and one side was glow-treated in an Ar atmosphere of 10 ^-2 Torr. Then, the film was evacuated to 10 ^-6 Torr and then heated along a drum heated to 100 ° C. Co-Ni alloy (Co80wt%,
(20 wt%) was deposited to a thickness of 0.1 μm.

The vapor-deposited film was slit to a width of 1/2 inch and assembled into a VTR cassette to form a VTR tape.

(Reduction of RF output) The RF output at 4 MHz was measured using a VHS deck with the optimum recording current with respect to the reference sample for each tape, and the tape was reproduced and run at a high temperature and a high humidity of 60 ° C. and 80% RH. 25 ℃
Returning to a condition of 30% RH was repeated 500 times, and a decrease in RF output before and after 500 times of running was determined and evaluated according to the following criteria.

・ ・ ・: RF output decrease is less than 3 dB Δ: RF output decrease is 3 dB or more and less than 6 dB ×: RF output decrease is 6 dB or more

(Tape state) For each tape, 50
The state of the tape after repeating 0 times was observed using an optical microscope, and evaluated according to the following criteria.

・ ・ ・: No deterioration in flatness or peeling of the magnetic layer was observed on the tape. Δ: Deterioration of flatness and peeling of the magnetic layer are slightly observed in the tape. X: Deterioration of flatness and peeling of the magnetic layer are often observed in the tape.

Example 1 N-methyl-2-pyrrolidone (NMP) contained 2-chloroparaphenylenediamine as an aromatic diamine component in an amount of 85 mol%, and 4,4'-diaminodiphenyleamine in an amount of 15 mol%. -Dissolve ter, and in this 98.
2-Chlorterephthalic acid chloride corresponding to 5 mol% was added and stirred for 2 hours to complete the polymerization. This was neutralized with lithium hydroxide to give a polymer concentration of 11% by weight and a viscosity of 31%.
A 00 poise aromatic polyamide solution was obtained. To this solution, dry silica having a primary particle size of 16 nm was added in an amount of 0.1% per polymer.
5 wt% was added.

This polymer solution was filtered through a filter having a cut of 5 μm, and then introduced into a dry process, where the belt temperature was 140 ° C.
And heated with 150 ° C. hot air to evaporate the solvent and obtain a self-holding polymer concentration of 38% by weight.
Was continuously peeled from the belt. Next, the film was introduced into a wet bath of NMP / water = 50/50 at a temperature of 50 ° C. as a wet bath, and the residual solvent and the inorganic salts and impurities generated by the neutralization were extracted for 10 minutes. The film was introduced into a water bath and extraction was performed for 5 minutes. During this time, the film was stretched 1.2 times in the longitudinal direction between the rolls. Next, drying and heat treatment were performed at 280 ° C. from both sides of the film while stretching it 1.4 times in the width direction with a tenter, and then the film was gradually cooled to obtain a 4.5 μm thick film.

The orientation ratio PA / PB of this film was 1.
012. The thermal expansion coefficients of the longitudinal direction and the width direction are 11 × 10 ⁻⁶ and 12 × 10 ⁻⁶ (cm / cm) /
° C, heat shrinkage ratio 2.5, 2.2%, humidity expansion coefficient 4.
It was 6 × 10 ⁻⁶ , 5.2 × 10 ⁻⁶ (cm / cm) /% RH. RF of magnetic tape made using this film
The output decreased by 1.0 dB, and the durability was good under high temperature and high humidity. Further, when the state of the tape after running 500 times was observed, no deterioration of the flatness or peeling of the magnetic layer was observed, which was good.

Example 2 In Example 1, the belt temperature in the dry process was set to 160 ° C.
A 5.5 μm thick film was obtained in the same manner as in Example 1 except that the hot air temperature was 150 ° C., the stretching ratio was 1.1 in the longitudinal direction, the width direction was 1.2, and the heat treatment temperature was 300 ° C.

The orientation ratio PA / PB of this film was 1.
004. The thermal expansion coefficients of the longitudinal direction and the width direction are 15 × 10 ⁻⁶ and 17 × 10 ⁻⁶ (cm / cm).
/ ° C, heat shrinkage ratio 1.3, 1.2%, humidity expansion coefficient 9.4 × 10 ^-6 , 10.5 × 10 ^-6 (cm / cm) /
% RH. The decrease in RF output of the magnetic tape made using this film was 0.5 dB, and the durability was good under high temperature and high humidity. Further, when the state of the tape after running 500 times was observed, no deterioration of the flatness or peeling of the magnetic layer was observed, which was good.

Example 3 2-chloroparaphenylenediamine corresponding to 100 mol% as an aromatic diamine component was dissolved in N-methyl-2-pyrrolidone (NMP), and 5 mol% of isophthalic acid chloride was dissolved therein. 2 equivalent to 93.5 mol%
-Chlorterephthalic chloride was added and stirred for 2 hours to complete the polymerization. This is neutralized with lithium hydroxide,
An aromatic polyamide solution having a polymer concentration of 10% by weight and a viscosity of 3200 poise was obtained. To this solution was added dry silica having a primary particle size of 16 nm at 0.5 wt% per polymer.

In Example 1, the obtained polymer solution was heated to a belt temperature of 150 ° C. and a drying temperature of 130 ° C.
The film was formed in the same manner as in Example 1 except that the wet bath was set at 50 ° C. and the heat treatment temperature was set at 320 ° C. to obtain a film having a thickness of 16 μm.

The orientation ratio PA / PB of this film was 1.
008. The thermal expansion coefficients of the longitudinal direction and the width direction are 17 × 10 ⁻⁶ and 19 × 10 ⁻⁶ (cm / cm).
/ ° C, heat shrinkage ratio of 0.8 and 0.6%, humidity expansion coefficient of 8.5 × 10 ^-6 , 7.6 × 10 ^-6 (cm / cm) /% R
There was H. The RF output of the magnetic tape produced using this film decreased by 1.0 dB, and the durability was good under high temperature and high humidity. Further, when the state of the tape after running 500 times was observed, no deterioration of the flatness or peeling of the magnetic layer was observed, which was good.

Example 4 Using the same polymer as in Example 3, a film was formed in the same manner as in Example 1 under the conditions shown in Table 1 to obtain a film having a PA / PB of 1.042 and a thickness of 12 μm. Evaluation of the magnetic tape produced by using the same showed that the RF output decreased by 2.8 dB and the state of the magnetic tape was good.

Example 5 A film was formed in the same manner as in Example 1 except that the same polymer solution as in Example 1 was used, the belt temperature in the dry process was adjusted to 50 ° C., and the drying temperature was changed to 180 ° C. A film having a thickness of 6 μm was obtained.

This film has a slight curl,
The orientation ratio PA / PB was 1.062. The thermal expansion coefficients of the longitudinal direction and the width direction are 10 × 10 ⁻⁶ , 1
2 × 10 ⁻⁶ (cm / cm) / ° C., heat shrinkage rate 2.7,
2.4%, coefficient of humidity expansion 3.5 × 10 ^-6 , 3.8 × 1
It was 0 ^-6 (cm / cm) /% RH. The decrease in RF output of a magnetic tape made using this film is 4.2d.
B and durability under high temperature and high humidity was Δ. Also,
When the state of the tape after running 500 times was observed, a part where the flatness was deteriorated was slightly observed, and the evaluation was Δ.

Comparative Example 1 N-methyl-2-pyrrolidone (NMP) was dissolved with 2-chloroparaphenylenediamine corresponding to 40 mol% as an aromatic diamine component and 4,4 ′ diaminodiphenylmethane corresponding to 60 mol% as an aromatic diamine component. Then, isophthalic acid chloride corresponding to 50 mol% and terephthalic acid chloride corresponding to 48.5 mol% were added thereto, and the mixture was stirred for 2 hours to complete the polymerization. This was neutralized with lithium hydroxide to obtain an aromatic polyamide solution having a polymer concentration of 12% by weight and a viscosity of 2900 poise. To this solution was added dry silica having a primary particle size of 16 nm at 0.5 wt% per polymer.

Using this polymer solution, the belt temperature in the drying step was 100 ° C., the drying temperature was 160 ° C., the wet bath was 20 ° C., and the stretching ratio was 1.1 times in the longitudinal direction and 1.2 times in the width direction. In the same manner, a film having a thickness of 20 μm was obtained.

This film was greatly curled, and the orientation ratio was 1.123. The thermal expansion coefficients of the longitudinal direction and the width direction are 45 × 10 ⁻⁶ and 48 × 10 ^{−6, respectively.}
(Cm / cm) / ° C., heat shrinkage ratio 4.6, 5.1%, humidity expansion coefficient 106 × 10 ⁻⁶ , 123 × 10 ⁻⁶ (cm / cm
cm) /% RH. This film had the air side curled inward. The RF output of the magnetic tape produced using this film decreased by 8 dB, and the durability was poor under high temperature and high humidity. When the state of the tape after running 500 times was observed, deterioration of the flatness and peeling of the magnetic layer were often observed.

Comparative Example 2 Using the same polymer as in Example 1, a belt temperature of 80 ° C. in the drying step, a drying temperature of 220 ° C., a wet bath of 20 ° C., a stretching ratio of 1.1 times in the longitudinal direction, and a width direction of 1. 2 times, heat fixation at 300 ° C from the air side of the film, 2 times from the belt side
A film having a thickness of 25 μm was obtained in the same manner as in Example 1 except that the film was formed at 80 ° C.

This film was greatly curled, and the orientation ratio was 1.154.

The decrease in RF output of the magnetic tape produced using this film was 10 dB, and the durability was poor under high temperature and high humidity. When the state of the tape after running 500 times was observed, deterioration of the flatness and peeling of the magnetic layer were often observed.

Table 1 summarizes the physical properties and evaluation results of the examples and comparative examples.

[0080]

[Table 1]

[0081]

According to the present invention, when manufacturing a magnetic recording medium, a flexible printed circuit board, a capacitor, a thermal transfer ribbon, etc. using an aromatic polyamide film having excellent heat resistance and mechanical properties, the ratio of the degree of orientation between the front and back sides is obtained. By using a film that is uniform in the thickness direction, which is within a certain range, it is possible to provide a product that is excellent in durability under high temperature and high humidity when used for the above application. In particular, when used as a base film for a magnetic recording medium, a magnetic recording medium having good electromagnetic conversion characteristics can be obtained even when used repeatedly at a high temperature for a long time.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05K 1/03 670 H05K 1/03 670A // C08G 69/32 C08G 69/32 B29K 77:00 B29L 7:00 C08L 77:10 (58) Field surveyed (Int.Cl. ⁶ , DB name) C08J 5/18 B29C 55/12 G11B 5/704 H01G 4/18 H05K 1/03

Claims (4)

(57) [Claims] 1. An aromatic polyamide film wherein the outermost layers on both surfaces of the film have orientation degrees PA and PB satisfying PA ≧ PB, and PA / PB ≦ 1.10. 2. The heat shrinkage at 220 ° C. is 5% or less, and the coefficient of thermal expansion is −1 × 10 ⁻⁶ to 40 × 10 ⁻⁶ (cm / cm) /
℃, humidity expansion coefficient -15 × 10 ^{-6 to} 20 × 10 ^-6 (c
m / cm) /% RH. 3. An aromatic polyamide film for a magnetic recording medium, wherein a magnetic layer is provided on at least one surface of the film according to claim 1. 4. A support having a thickness of 0.2 to 6.5 μm.
The width is 2.3 to 13.0 mm, the length is 100 m / roll or more, and the recording density as a magnetic recording medium is 8 kilobytes /
The aromatic polyamide film for a magnetic recording medium according to claim 3, wherein the aromatic polyamide film is a base film for a magnetic recording medium having a thickness of ² mm2 or more.