JPH09169860A - Aromatic polyamide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arom. polyamide film which gives a composite which does not undergo the degradation in surface properties, such as the occurrence of curl or wrinkles, nor the degradation in functions even when repeatedly used under severe conditions by imparting a specific degree of orientation respectively to each of the outermost surface layers of both sides of the film. SOLUTION: This polyamide film is obtd. from a polyamide contg. 50mol% or higher repeating units represented by formula I and/or formula II wherein Ar1 to Ar3 are each a group represented by formula III [wherein X and Y are each O, CH2 , CO, SO2 , S, C(CH3 )2 , etc.], etc., provided their H atoms may be partly substd. by other substituents; and H atoms in amide bonds may be substd. by other substituents}. The polyamide may be a blend of polymers and may contain necessary additives. The ratio (PA/PB) of degrees of orientation (PA and PB, provided PA>=PB) obtd. from the ATR spectra of the outermost layers of both sides of the film is 1.10 or lower, and the film has a thermal shrinkage at 220 deg.C of 5% or lower, a coefficient of thermal expansion of -1×10<-6> to 40×10<-6> (cm/cm)/ deg.C, and a coefficient of humidity expansion of -15×10<-6> to 20×10<-6> (cm/cm)/%RH.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aromatic polyamide film. More specifically, it relates to an aromatic polyamide film useful for applications such as base films for magnetic recording media, flexible printed boards, capacitors and the like.

[0002]

2. Description of the Related Art An aromatic polyamide film is a base film for magnetic recording media because of its excellent mechanical properties and heat resistance.
It has been proposed to use it as a composite with other materials such as a flexible printed circuit board, a capacitor and a thermal transfer film. In these applications, the products are often exposed to high temperatures in the process of processing, and the use of products under high temperature or high humidity is increasing. The demands are strict. In order to meet such demands, it is possible to obtain a film excellent in heat resistance and dimensional stability by using a para aromatic polyamide film to regulate the heat shrinkage rate, thermal expansion coefficient, humidity expansion coefficient, etc. Kaihei 06-613,
It is disclosed in Japanese Patent Laid-Open No. 02-84328 and the like.

[0003]

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

The present invention solves the above problems and does not cause curling or wrinkling of the composite even when it is repeatedly used under severe conditions, and does not deteriorate the flatness of the composite or reduce the function of the composite. The purpose is to provide a film.

[0005]

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 arrived at the present invention. That is, according to the present invention, the orientation degrees PA and PB (PA ≧ P) of the outermost layers obtained from the ATR spectra of both surfaces of the film are used.
The aromatic polyamide film is characterized in that 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. Furthermore, some of the hydrogen atoms on these aromatic rings are replaced by halogen groups (especially chlorine) such as chlorine, fluorine and bromine, alkyl groups (especially methyl group) such as nitro group, methyl group, ethyl group, propyl group and ethoxy group. Groups, those substituted with an alkoxy group such as a methoxy group, a propoxy group, an isopropoxy group, etc., and those in which hydrogen in the amide bond constituting the polymer is replaced with another substituent .

From the viewpoint of characteristics, the above-mentioned aromatic ring bonded in the para position is 50% or more, preferably 75% or more of the total aromatic ring.
A polymer that accounts for at least 100% is preferable because it has good thermal dimensional stability and a film having a high elastic modulus can be obtained. When the proportion of the aromatic ring in which a part of hydrogen atoms on the aromatic ring is replaced by a halogen group (especially chlorine) is 30% or more, preferably 50% or more, more preferably 70% or more, the humidity expansion coefficient is It is preferable because it becomes small.

The aromatic polyamide of the present invention contains 50 mol% or more of the repeating unit represented by the general formula (I) and / or the general formula (II), and is 50 mol%.
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 the 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 orientation degrees PA and PB (PA ≧ PB) of the outermost layers on both surfaces of the film obtained from the R spectrum is PA / PB ≦ 1.1.
Must be 0. When the ratio of the degree of orientation of the front and back of the film is 1.10 or less, it 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 orientation ratio in the thickness direction of the film is out of the above range, when the film is exposed to high temperature or high humidity in the processing step, the film itself has a thermal shrinkage coefficient, a thermal expansion coefficient, a humidity expansion coefficient in the thickness direction. Since the film itself is curled because it is different, etc., or when the material such as a metal thin film is compounded in a state where distortion occurs in the thickness direction even if curling does not occur, it is released to the above distortion and the composite material It may curl or deteriorate the flatness. 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 for a long period of time under high temperature or high humidity, or The flatness of the composite material deteriorates. For example, in a magnetic tape, the magnetic layer peels off or the magnetic conversion characteristics deteriorate. 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 during long-term use. Further, if the dimensional stability of the entire film is good, the processability of the film is improved, which 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 in-plane direction, preferably in all directions.
C. is preferred.

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

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

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

Since these thermal expansion coefficient, thermal contraction coefficient and humidity expansion coefficient act on the film in a composite manner, it is preferable that the above ranges are simultaneously satisfied in all directions.

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

The film of the present invention may contain particles in order to impart slipperiness to the film. The particle size and content of the particles 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 0. It is preferably from 01 to 5 wt%, more preferably from 0.05 to 3 wt%. If the particle size or content of the particles is larger or larger than the above range, the adhesiveness with the composite material deteriorates, or when the magnetic tape is used, the adhesiveness between the tape and the magnetic head is poor and the electromagnetic conversion characteristics deteriorate. not good. If the particle size and content of the particles are smaller or smaller than the above range, the running property of the film is poor and it becomes 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, crosslinked copolymer particles, crosslinked polystyrene particles, Teflon particles, etc. Although there are organic polymers and the like, inorganic particles are more preferable from the viewpoint of heat resistance.

The surface roughness of the film should be properly designed depending on the application, but R for magnetic recording 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, Rz 2 to 500 nm, more preferably 3 to 4
00 nm.

The moisture absorption rate of the film of the present invention is 3.5.
% Or less is preferable, and 2.5% or less is more preferable. If the moisture absorption rate exceeds 3.5%, the dimensional stability with respect to changes in humidity will deteriorate, leading to poor flatness such as curls and wrinkles.
It is not preferable because the electromagnetic conversion characteristics of the magnetic tape are deteriorated.

The elongation of the film in the present invention is preferably 10% or more, and more preferably 20% or more because the tape has appropriate flexibility and excellent processability.

The elastic modulus of the film in the present invention is 5.88 GPa or more in both the longitudinal direction and the width direction, preferably 7.
If it is 85 GPa or more, it is easy to handle even if it is thinned,
When using a magnetic tape, the head touch is good,
Good electromagnetic conversion characteristics.

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

The film of the present invention can be used in various applications such as flexible printed boards, heat-sensitive transfer ribbons, condenser applications, and base films for magnetic recording media.

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

The method for forming the magnetic layer of the magnetic tape is 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 to a magnetic coating using various binders on a support film, a vacuum thin film forming method such as a vapor deposition method, a sputtering method and an ion plating method. Although not required, it is particularly effective in a vacuum thin film forming method in which the film is exposed to high temperatures 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.

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

Preferable uses of the magnetic recording medium thus obtained are for consumer use, professional use, D-1, D-2, D-.
For broadcasting stations such as 3, digital video cassette, DDS-
Examples include, but are not limited to, data storage for 2, 3, 4, QIC, data 8 mm, etc.,
It can be optimally used for data storage applications where reliability such as data reproduction is most important.

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

In recent years, magnetic recording media represented by magnetic tapes are increasingly required to be smaller and have higher capacities. For this reason, the support film is thinned, the track width is narrowed,
Higher recording densities are progressing due to shorter recording wavelengths.
Therefore, a slight flatness defect such as curl is likely to cause data recording / reproduction defect and durability defect during repeated use. 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 0.2 or more and 4.5 μm or less, more preferably 0.2 or more and 3.5 μm or less, and the recording density as a magnetic recording medium is preferably 25 kilobytes / mm.
^{It is 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, but when it is obtained from an acid chloride and a diamine, it is used in an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc) or dimethylformamide (DMF). , 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, an inorganic neutralizing agent such as calcium hydroxide, calcium carbonate, lithium carbonate, or ethylene is 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 film forming stock solution, or the polymer may be isolated once and then redissolved in the above organic solvent or an inorganic solvent such as sulfuric acid to prepare a film forming stock solution. Good.

In order to obtain the aromatic polyamide film of the present invention, the intrinsic viscosity of the polymer (value measured at 30 ° C. in a solution of 0.5 g of polymer in 100 ml of sulfuric acid) is 0.
It is preferably 5 or more.

Inorganic salts such as calcium chloride, magnesium chloride, lithium chloride and lithium nitrate may be 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.

The method for adding particles includes a method in which the particles are sufficiently slurried in a solvent in advance and then used as a solvent for polymerization or a solvent for dilution, and a method in which they are directly added after preparing a film-forming stock solution.

The stock solution for film formation prepared as described above is formed into a film by a so-called solution film forming method. The solution film-forming method includes a dry-wet method, a dry method and a wet method, and any method may be used for film formation. As an effective method to obtain a film having no difference in the orientation degree between the front and back of the film, the difference in the solvent extraction rate from both surfaces of the film is reduced, the driving speed of the nip roll used in the manufacturing process, and the difference in the peripheral speed of the free roll. Is preferably carried out, or the difference in heat treatment temperature between both surfaces during heat treatment is reduced. Here, the dry-wet method will be described as an example.

When a film is formed by a dry-wet method, the stock 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-supporting polymer concentration. Dry to 35-60 wt%. In this dry process, in order to obtain a film that is uniform in the thickness direction of interest, the film is dried with hot air at a temperature of 200 ° C. or lower, and the belt surface temperature is (hot air temperature-2
It is preferably performed at 0 ° C.) or higher. By making the belt surface 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 orientation difference in the film thickness direction and the polymer concentration difference at the time of peeling are increased. Can be made smaller.

After the film which has undergone the dry process is cooled, it is peeled from the support and introduced into the wet bath of 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, but water,
Alternatively, it is economical to use a mixed system of organic solvent / water,
It is preferable because it is easy to handle. Composition ratio is organic solvent / water =
70/30 to 0/100, preferably 60/4
When it is 0 to 30/70, the homogeneity is good in the thickness direction of the film. In addition, the wet bath may contain an inorganic salt.

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

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

After stretching, the film is subjected to heat treatment,
The heat treatment is preferably performed at 200 to 450 ° C. for 1 second to 5 minutes. If the heat treatment is below this temperature, crystallization will be insufficient and sufficient mechanical properties will not be obtained. Further, if it exceeds this range, the film becomes brittle and cannot be practically used. At this time, it is preferable that the heat treatment is performed uniformly from both sides of the film within a temperature difference of 3 ° C. in order to reduce the difference in orientation degree 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.

The film of the present invention can be obtained as described above, but the invention 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 of film surface 1
S-polarized ATR spectra were measured in every direction at every 0 ° under the following conditions. From the obtained spectrum, the amide III absorption band based on the amide bond is defined as the π band, the C═O stretching vibration of the amide I absorption band is defined as the σ band, and the infrared dichroic ratio (= π band / σ band) is calculated from the respective peak intensities. It was calculated as an orientation parameter and developed into a polar figure. In this polar figure, the area surrounded by the line connecting the orientation parameters was defined as the orientation degree of the surface. When the degree of orientation obtained from both surfaces of the film in this way is PA and PB (where PA ≧ PB), the ratio PA / PB of the two is taken as the orientation degree ratio. The measurement is 25 ℃,
Performed at 60% RH.

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

(2) Thermal expansion coefficient To remove the effects of heat shrinkage and moisture absorption / desorption, the film was once
80-150 when heated to 0 ℃ and gradually cooled
Calculated from dimensional change at ° C. The amount of dimensional change was measured by a thermomechanical analyzer (TMA).

(3) Thermal shrinkage The film was sampled so that the width was 10 mm and the test length was 200 mm, heated in an oven at 220 ° C. for 10 minutes, the test piece was taken out, and after cooling, it was calculated by the following formula.

Thermal shrinkage (%) = (length after heating−test length)
/ Test length x 100

(4) Humidity expansion coefficient: Set in a high temperature and high humidity tank with a width of 1 cm and a test length of 15 cm, dehumidified to a constant humidity (about 30% RH), and after the film length became constant, humidified. When (about 80% RH), it begins to grow due to moisture absorption. After about 24 hours, the moisture absorption reaches the equilibrium and the film spread reaches the 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 in a vapor deposition machine, and one side was subjected to glow treatment under an Ar atmosphere of 10 ^-2 Torr, and then vacuumed to 10 ^-6 Torr, followed by a drum heated to 100 ° C., Co-Ni alloy (Co80wt%,
20 wt%) was vapor-deposited to a film thickness of 0.1 μm.

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

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

◯: Reduction of RF output is less than 3 dB Δ: Reduction of RF output is 3 dB or more and less than 6 dB × ... Reduction of RF output is 6 dB or more

(Tape status) 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, and ◯ and Δ were evaluated as good.

◯ ... Deterioration of flatness and peeling of the magnetic layer are not observed at all on the tape. B: Deterioration of flatness and a slight peeling of the magnetic layer are observed on the tape. X: Deterioration of flatness and peeling of the magnetic layer are often observed on the tape.

Example 1 N-methyl-2-pyrrolidone (NMP) was added with 2-chloroparaphenylenediamine corresponding to 85 mol% as an aromatic diamine component and 4,4'-diaminodiphenylene corresponding to 15 mol%. -Dissolve tel and 98.
Polymerization was completed by adding 2-chloroterephthalic acid chloride corresponding to 5 mol% and stirring for 2 hours. This is 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 per polymer at a concentration of 0.1.
5 wt% was added.

The polymer solution was filtered through a 5 μm-cut filter and then introduced into a dry process at a belt temperature of 140 ° C.
It is cast on a belt and heated with hot air at 150 ° C to evaporate the solvent and obtain a self-holding property. Polymer concentration 38 wt%
The film 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 inorganic salts and impurities generated by neutralization were extracted for 10 minutes, and then the film was further heated at 50 ° C. The film was introduced into a water bath and extraction was performed for 5 minutes. During this period, the film was stretched 1.2 times in the longitudinal direction between the rolls. Next, while being stretched 1.4 times in the width direction with a tenter, drying and heat treatment were performed from both sides of the film at 280 ° C. and then gradually cooled to obtain a film having a thickness of 4.5 μm.

The orientation ratio PA / PB of this film was 1.
It was 012. The thermal expansion coefficients in the longitudinal direction and the width direction are 11 × 10 ⁻⁶ and 12 × 10 ⁻⁶ (cm / cm) /
C, heat shrinkage rate is 2.5, 2.2%, humidity expansion coefficient is 4.
It was 6 × 10 ⁻⁶ , 5.2 × 10 ⁻⁶ (cm / cm) /% RH. RF of magnetic tape created using this film
The decrease in output was 1.0 dB, and the durability was good under high temperature and high humidity. When the state of the tape after running 500 times was observed, the flatness was not deteriorated and the magnetic layer was not peeled off.

Example 2 In Example 1, the belt temperature in the dry process was 160 ° C.
A film having a thickness of 5.5 μm 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, 1.2 in the width direction, and the heat treatment temperature was 300 ° C.

The orientation ratio PA / PB of this film was 1.
004. Further, the thermal expansion coefficient in each of the longitudinal direction and the width direction is 15 × 10 ⁻⁶ , 17 × 10 ⁻⁶ (cm / cm).
/ ° C., heat shrinkage ratio is 1.3, 1.2%, humidity expansion coefficient is 9.4 × 10 ⁻⁶ , 10.5 × 10 ⁻⁶ (cm / cm) /
There was% RH. The decrease in the RF output of the magnetic tape produced using this film was 0.5 dB, and the durability under high temperature and high humidity was good. When the state of the tape after running 500 times was observed, the flatness was not deteriorated and the magnetic layer was not peeled off.

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 chloride corresponding to 5 mol% was dissolved therein. 2 equivalent to 93.5 mol%
-Chlorterephthalic acid chloride was added and stirred for 2 hours to complete the polymerization. Neutralize this 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, 0.5 wt% of dry silica having a primary particle size of 16 nm was added with respect to the polymer.

The obtained polymer solution was used in Example 1 with a belt temperature of 150 ° C. and a drying temperature of 130 in the dry process.
A film having a thickness of 16 μm was prepared in the same manner as in Example 1 except that the wet bath was water at 50 ° C., and the heat treatment temperature was 320 ° C.

The orientation ratio PA / PB of this film was 1.
It was 008. The thermal expansion coefficients of the longitudinal direction and the width direction are 17 × 10 ⁻⁶ and 19 × 10 ⁻⁶ (cm / cm), respectively.
/ ° C., heat shrinkage rate is 0.8, 0.6%, humidity expansion coefficient is 8.5 × 10 ⁻⁶ , 7.6 × 10 ⁻⁶ (cm / cm) /% R
There was H. The decrease in the RF output of the magnetic tape produced using this film was 1.0 dB, and the durability was good under high temperature and high humidity. When the state of the tape after running 500 times was observed, the flatness was not deteriorated and the magnetic layer was not peeled off.

Example 4 The same polymer as in Example 3 was used to form a film under the conditions of Table 1 in the same manner as in Example 1 to obtain a film having PA / PB = 1.042 and a thickness of 12 μm. When the magnetic tape prepared by using the magnetic tape was evaluated, the decrease in RF output was 2.8 dB, and the state of the magnetic tape was good.

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

There is some curl in this film,
The orientation ratio PA / PB was 1.062. The thermal expansion coefficient of each of the longitudinal direction and the width direction is 10 × 10 ⁻⁶ , 1
2 × 10 ⁻⁶ (cm / cm) / ° C., heat shrinkage rate is 2.7,
2.4%, humidity expansion coefficient 3.5 × 10 ^-6 , 3.8 × 1
It was 0 ⁻⁶ (cm / cm) /% RH. The decrease in the RF output of the magnetic tape made using this film is 4.2d.
It was B, and the 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 observed, which was Δ.

Comparative Example 1 2-chloroparaphenylenediamine corresponding to 40 mol% as an aromatic diamine component and 4,4′diaminodiphenylmethane corresponding to 60 mol% were dissolved in N-methyl-2-pyrrolidone (NMP). Then, 50 mol% of isophthalic acid chloride and 48.5 mol% of terephthalic acid chloride 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, 0.5 wt% of dry silica having a primary particle size of 16 nm was added with respect to the 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 a 20 ° C. water bath, and the stretching ratio was 1.1 times in the longitudinal direction and 1.2 times in the width direction. The film was formed in the same manner to obtain a film having a thickness of 20 μm.

The 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., thermal contraction rate 4.6, 5.1%, humidity expansion coefficient 106 × 10 ⁻⁶ , 123 × 10 ⁻⁶ (cm /
cm) /% RH. This film had the air side curled inward. The decrease in RF output of the magnetic tape produced using this film was 8 dB, and the durability was poor under high temperature and high humidity. Further, when the state of the tape after running 500 times was observed, the flatness was deteriorated and the magnetic layer was often peeled off.

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

The 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. Further, when the state of the tape after running 500 times was observed, the flatness was deteriorated and the magnetic layer was often peeled off.

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 an aromatic polyamide film having excellent heat resistance and mechanical properties is used to produce a magnetic recording medium, a flexible printed circuit board, a condenser, a thermal transfer ribbon, etc. By using a film that is uniform in the thickness direction, which is within a certain range, it is possible to provide a product having excellent durability under high temperature and high humidity when used in the above applications. In particular, when it is used as a base film for a magnetic recording medium, a magnetic recording medium having good electromagnetic conversion characteristics can be obtained even if it is repeatedly used at high temperature for a long time.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H05K 1/03 670 7511-4E H05K 1/03 670A // C08G 69/32 NST C08G 69/32 NST B29K 77:00 B29L 7:00 C08L 77:10

Claims (4)

[Claims] 1. An aromatic polyamide film characterized in that the outermost layers on both surfaces of the film have orientation degrees PA and PB satisfying PA ≧ PB and PA / PB ≦ 1.10. 2. A coefficient of thermal shrinkage at 220 ° C. of 5% or less and a coefficient of thermal expansion of -1 × 10 ^-6 to 40 × 10 ^-6 (cm / cm) /
℃, humidity expansion coefficient -15 × 10 ^-6 ~ 20 × 10 ^-6 (c
m / cm) /% RH, The aromatic polyamide film according to claim 1. 3. An aromatic polyamide film for a magnetic recording medium, which is used by providing a magnetic layer on at least one surface of the film according to claim 1. 4. A support having a thickness of 0.2 or more and 6.5 μm or less,
The width is 2.3 or more and 13.0 mm or less, 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, which is a base film for a magnetic recording medium having a size of ² mm ² or more.