JP2000326401A - Aromatic polyamide film and magnetic recording medium using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium suitable for high capacitance, in which electromagnetic conversion characteristics and dimensional stability under high tension are excellent and a reading error at the time of regeneration is difficult to be caused in the case of being used as the magnetic recording medium. SOLUTION: At least unidirectional tensile modulus is >=7 GPa and coefficient of plane orientation is <=0.2 and >=0.8. In a shrinkage factor γ1 in the lateral direction when a film is stretched by 1% in the longitudinal direction and a shrinkage factor γ10 in the lateral direction when the film is stretched by 10%, γ1/γ10<=0.9. The aromatic polyamide which contains a repeating unit shown in formula I and/or formula II at >=50 mol%, is desirable and the aromatic polyamide containing the repeating unit at >= 70 mol% is more desirable. Wherein, for example, Ar1, Ar2 and Ar3 are shown by formula III. X and Y are selected from among -O-, -CH2-, -CO-, -SO2-, -S-, -C(CH3)2- or the like but do not limited by these.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aromatic polyamide film having good dimensional stability. Further, the present invention relates to a magnetic recording medium using the film.

[0002]

2. Description of the Related Art Conventionally, PET (polyethylene terephthalate) or PE has been used as a base film for a magnetic recording medium.
N (polyethylene naphthalate) is used. It has also been proposed to use a highly rigid aromatic polyamide film having better heat resistance as a base film for a magnetic recording medium. In recent years, due to the increase in capacity of magnetic recording media for video tapes and data recording, and the practical use of MR heads and the like, shorter recording wavelengths and narrower track widths have been rapidly advanced, and higher recording densities have been achieved. The recording area has increased dramatically, and high output electromagnetic conversion characteristics are required. For this reason, a change in tension during recording and reproduction while the magnetic tape is running, and a change in dimensions in a minute area of the magnetic recording medium caused by the tension applied at the time of start and stop become serious problems. This is because when a slight dimensional change occurs in the longitudinal direction, if the amount of change in the width direction is large,
This is because an error easily occurs during recording and reproduction. Further, as the magnetic recording medium is made thinner and the recording / reproducing speed is increased, the base film is required to have ever higher dimensional stability.

[0003]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, has high dimensional stability in a minute area, hardly causes errors during recording and reproduction when used as a magnetic recording medium, and has a low electromagnetic conversion characteristic. And a magnetic recording medium using the same.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the plane orientation coefficient of a film is within a certain range, and the value of the shrinkage ratio in the width direction when the film is stretched in the longitudinal direction is determined. It has been found that these problems can be solved by limiting the present invention, leading to the present invention. That is, the present invention
A tensile modulus in at least one direction of 7 GPa or more;
The plane orientation coefficient is 0.2 or more and 0.8 or less, and the shrinkage ratio γ ₁ in the width direction when the film is stretched by 1% in the longitudinal direction and the shrinkage ratio γ in the width direction when the film is stretched by 10% _Ten
Is an aromatic polyamide film satisfying γ ₁ / γ ₁₀ ≦ 0.9.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic polyamide in the present invention preferably contains at least 50 mol% of repeating units represented by the following general formulas (I) and / or (II), and preferably 70 mol%. Those containing the above are more preferable. General formula (I)

[0006]

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General formula (II)

[0008]

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

[0010]

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And X and Y are -O-, -CH
_{2 -, - CO -, -} SO 2 -, - S -, - C (CH 3) 2 -
Etc., but are not limited thereto.
Furthermore, some of the hydrogen atoms on these aromatic rings may be halogens (especially chlorine) such as chlorine, fluorine and bromine, alkyl groups (especially methyl groups) such as nitro, methyl, ethyl and propyl groups, and ethoxy groups. And those substituted with an alkoxy group such as a methoxy group, a propoxy group, or an isopropoxy group, and those in which hydrogen in an amide bond constituting a polymer is substituted with another substituent.

[0012] From the viewpoint of properties, the above aromatic rings bonded at the para position account for at least 50%, preferably 75%, of the total aromatic rings.
% Of the polymer is preferable because a film having good dimensional stability and a high elastic modulus can be obtained. When the aromatic ring in which a part of the hydrogen atoms on the aromatic ring is substituted with halogen (particularly chlorine) is 30% or more, preferably 50% or more, and more preferably 70% or more, the humidity expansion coefficient is small. Is preferred.

The aromatic polyamide contains 50 repeating units represented by the general formula (I) and / or the general formula (II).
It contains not less than 50% by mole, and if it is less than 50% by mole, other repeating units may be copolymerized or blended.

The film of the present invention must have a tensile modulus in at least one direction of 7 GPa or more. When the tensile elastic modulus in one direction is 7 GPa or more, it is easy to handle even if it is made into a thin film, and when a magnetic recording medium is used, the head touch is good and the electromagnetic conversion characteristics are good. Also,
If the tensile elastic modulus in one direction is less than 7 GPa, the running property as a magnetic tape becomes dangerous. More preferably, it is 8 GPa or more in all directions of the film, more preferably 10 GPa or more.

Further, the film of the present invention has a ratio E _TD / E _MD of tensile elastic modulus in the longitudinal direction to the tensile modulus in the width direction of 0.8 ≦ E _TD / E _MD ≦
A value of 3 is preferable because more favorable recording / reproducing characteristics can be obtained, and a value of E _TD / E _MD is more preferably 1 <E _TD / E _MD <2.

The plane orientation coefficient of the present invention is 0.2 to 0.8.
It must be: The plane orientation coefficient herein, when the longitudinal direction of the refractive indices n _x of the film, the refractive index of the width direction n _y, the refractive index in the thickness direction is n _z, (plane orientation coefficient) = (n _x + _Ny ) / 2- _nz .

When the plane orientation coefficient is within this range, a film having a small shrinkage in the width direction in the longitudinal stretching and having good dimensional stability can be obtained. In addition, the electromagnetic conversion characteristics of a magnetic tape are improved. Furthermore, there is also an effect that the slit property of the film is good.

If the plane orientation coefficient is less than 0.2, the shrinkage becomes large and the electromagnetic conversion characteristics are lowered, which is not preferable. The number of outs may increase, and the cut portion may swell to cause deterioration of the rolled shape.

If the plane orientation coefficient exceeds 0.8, the film is liable to be torn or separated into two layers, which is not preferable in practical use. Further, chips may be generated at the time of slitting, and data loss may occur when the magnetic tape is used.

The plane orientation coefficient is preferably from 0.21 to 0.60, more preferably from 0.22 to 0.45.
When the content is less than or equal to the above, the above-mentioned effect is further exhibited.

Further, in the present invention, a film
In the width direction when 1% is stretched in the longitudinal direction.₁
And shrinkage ratio γ in the width direction when stretched by 10%_TenRatio γ
₁/ Γ _TenMust be 0.9 or less.

The shrinkage γ in the width direction tends to increase as the elongation in the longitudinal direction increases. Then, in the longitudinal strain small area, such as gamma _1, since the recording and reproducing mistake hardly occurs due to the small tension fluctuation at the time of recording and reproduction of dimensional change is small data smaller shrinkage in the width direction the film preferable. The value of γ ₁ is preferably 0.008 or less, more preferably 0.007 or less, and even more preferably 0.006 or less.

On the other hand, in the longitudinal direction distortion of a relatively large area, such as shrinkage gamma _10, preferable for it to shrink to some extent in the width direction keeping accurate records reproducing and tape flexibility of data. The value of gamma _10, preferably 0.0
05 or more and 0.09 or less, more preferably 0.01 or more and 0.08 or less.

From the above balance between γ ₁ and γ ₁₀ ,
When γ ₁ / γ ₁₀ is 0.9 or less, the magnetic tape is in a favorable state for accurate recording and reproduction.

When γ ₁ / γ ₁₀ is larger than 0.9, a dimensional change due to a slight change in tension during film running is large, and a recording / reproducing error when a magnetic tape is formed is liable to occur. Also, γ
₁ / gamma ₁₀ as small as good as the range that can be industrially produced, is 0.1 or more. γ ₁ / γ ₁₀ is preferably 0.9 or less, more preferably 0.85 or less, because the above-mentioned effect is further exhibited.

The coefficient of thermal expansion of the film of the present invention is from 0 to 4
0 × 10 ⁻⁶ (cm / cm) / ° C. is preferable because a dimensional change due to a temperature change is small and good recording / reproducing characteristics can be easily obtained when a magnetic recording medium is used.

The heat shrinkage of the film of the present invention at 200 ° C. (5 minutes) is preferably 3% 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 curl is likely to be deteriorated in the processing of the product, and the dimensional change is large when stored or used at a high temperature. This is not preferred.

The coefficient of humidity expansion of the film of the present invention is 0 to 3
When it is 0 × 10 ⁻⁶ (cm / cm) /% RH or less, a dimensional change due to a change in humidity or moisture absorption is small, and it is easy to obtain good recording / reproducing characteristics when a magnetic recording medium is used.
Outside of this range, when used under high humidity, the flatness of the product may be degraded and output characteristics may be reduced.

These tensile modulus, plane orientation coefficient, shrinkage coefficient, thermal expansion coefficient and humidity expansion coefficient act on the film in a complex manner and contribute to the dimensional stability of the film. Is preferred.

The film of the present invention may contain particles for imparting lubricity to the film. The particle size and content of the contained particles should be appropriately selected depending on the application, but the average primary particle size is preferably 0.001 to 2 μm. Further, the content of the particles contained in the film is preferably 0.001 to 5% by weight, and more preferably 0.05 to 3% by weight. If the particle diameter and the content of the particles are larger or larger than the above ranges, the magnetic tape is not preferable because the adhesion between the tape and the magnetic head is poor and the electromagnetic conversion characteristics are deteriorated.
If the particle diameter and the content of the particles are smaller or smaller than the above ranges, the running property of the film deteriorates, which is not preferable from the viewpoint of durability. The types of particles include SiO ₂ , TiO ₂ , Al
Inorganic particles such as ₂ O ₃ , CaSO ₄ , BaSO ₄ , CaCO ₃ , carbon black, zeolite, and other fine metal powders, and organic particles such as silicon particles, polyimide particles, cross-linked copolymer particles, cross-linked polystyrene particles, and Teflon particles Polymers. As a method of imparting slipperiness to the film, besides a method of adding particles, a method of blending a different polymer with a base polymer and forming projections in the film-forming step using the different polymer can also be used.

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 moisture absorption of the film of the present invention is 3.5.
% Or less, and more preferably 2.5% or less. When the moisture absorption exceeds 3.5%, the dimensional stability against a change in humidity is likely to be deteriorated, and the flatness such as curl and wrinkles may be deteriorated, or the electromagnetic conversion characteristics of the magnetic tape may be deteriorated.

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

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

The film of the present invention can be used not only as a base film for a magnetic recording medium but also for applications such as a flexible printed board, a thermal transfer ribbon, and a capacitor.

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 a dry method such as a wet method, a vapor deposition method, a sputtering method, and an ion plating method in which a ferromagnetic powder such as o-Ni, Co-Ni or the like is used as a magnetic paint using various binders and applied on a support film.

Further, 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 thickness of the film used in the present invention is preferably 0.5 to 50 μm, more preferably 1 to 20 μm.
μm, more preferably 2 to 10 μm, and especially for magnetic recording media, the thickness is 6.5 μm or less, preferably 4.5 μm or less, and more preferably 3.5 μm or less. Further, the present invention can be more effectively applied to a magnetic tape having a width of 2.2 to 15 mm and a recording density (uncompressed) of 15 kilobytes / mm ² or more when used as a magnetic recording medium. An embodiment utilizing the effect of (1). The recording density is preferably at least 25 kilobytes / mm ^2, more preferably at least 34 kilobytes / mm ² .

Preferred uses of the magnetic recording medium thus obtained are, for example, 8 mm, for consumer use such as digital video cassettes, for professional use, for broadcasting stations such as D-1, 2, 3, DDS-2, and so on. 3, 4, QIC, data 8mm, DL
For example, T is used for data storage, but the present invention is not limited thereto. In particular, it can be suitably used for data storage applications where reliability such as data loss is important.

Next, the method for producing the film of the present invention will be described, but the present invention is not limited thereto.

As a method for obtaining an aromatic polyamide, for example, when obtaining from an acid chloride and a diamine, N-methylpyrrolidone (NMP), dimethylacetamide (DMA)
c) It is synthesized by solution polymerization in an aprotic organic polar solvent such as dimethylformamide (DMF) or by 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,
Organic neutralizers such as ammonia, triethylamine, triethanolamine, diethanolamine and the like are used. When an aromatic polyamide is obtained from the reaction between an isocyanate and a carboxylic acid, the reaction 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, or the polymer solution may be isolated once and then redissolved in the above organic solvent or 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 η _{inh of the} polymer (0.5 g of
(A value measured at 30 ° C. as a 100 ml solution in 8% sulfuric acid) is preferably 0.5 (dl / g) or more.

As a method for adding the particles, there is 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, or a method in which the stock solution is directly added after preparing a stock solution.

In some cases, an inorganic salt such as calcium chloride, magnesium chloride, lithium chloride or lithium nitrate 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.

The film-forming stock solution prepared as described above is formed into a film by a so-called solution casting method. The solution casting method includes a dry-wet method, a dry method, and a wet method, and any method may be used to form a film.However, when an inorganic salt is contained in the polymer solution, the inorganic salt is extracted. Requires a wet process, and a dry-wet process and a wet process are used.

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 to form a polymer having a self-supporting property. (PC) 35-60w
Dry to t%.

In order to obtain a film having a plane orientation coefficient in a target range in this dry process, first, in the first stage drying, at a low temperature of 50 to 100 ° C. for 5 seconds to 15 minutes in order to suppress rapid in-plane orientation. After drying, dry the second stage 1
It is preferable to carry out at a high temperature of 50 ° C. or more for 5 seconds to 15 minutes. In the drying process, the drying corresponding to the first and second stages may be performed in two or more stages, respectively, or the drying temperature may be continuously changed from a low temperature to a high temperature. .

After the film subjected to the dry process is cooled and peeled from the support, it is preferable to cool the film to room temperature in order to give the film sufficient in-plane orientation and self-supporting property. Thereafter, the mixture is introduced into a wet bath in the next wet process, and is subjected to desalting and desolvation. The wet bath composition is not particularly limited as long as it is a poor solvent for the polymer,
Water or a mixed system of organic solvent / water can be used. The composition ratio of the organic solvent / water mixed system is as follows: organic solvent / water = 70
/ 30 to 0/100, preferably 60/40 to
When the ratio is 30/70, the desired film can be easily obtained. Although the inorganic salt may be contained in the wet bath, it is preferred that the solvent and the inorganic salt contained in the film are finally extracted with a large amount of water. 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
During the film forming process, stretching is performed to improve mechanical properties and dimensional stability in order to obtain desired plane orientation coefficient, contraction rate, thermal expansion coefficient, and humidity expansion coefficient. Stretching is performed by first stretching the film in the longitudinal direction and then in the width direction, or using the sequential biaxial stretching method in which the film is first stretched in the width direction and then in the longitudinal direction, or the simultaneous biaxial stretching method in which the longitudinal direction and the width direction are simultaneously stretched. be able to. These stretching methods are well known as a stretching method in melt film formation performed in the form of a film of polyethylene, polypropylene, polyester, etc., but in the case of a film obtained by solution film formation as in the present invention, A solvent and a wet bath component are contained in the film, and since these are processes including transfer out of the film, a special method is required to obtain a target film. As the stretching method, the sequential biaxial stretching method is preferable from the viewpoint of the apparatus and operability. As the stretching conditions, it is necessary to select appropriate conditions depending on the polymer composition and the like, but the stretching ratio in the longitudinal direction of the film is 1.0%.
It is preferable that the stretching ratio in the width direction is 1.1 to 3.0 times, in order to obtain the desired thermal expansion coefficient and humidity expansion coefficient. The stretching temperature is preferably from 200 to 350 ° C. If the stretching temperature is lower than 200 ° C., the film is likely to be broken during stretching. In addition, the stretching temperature is 350
If the temperature is higher than ℃, the crystallinity is too high, which is not preferable for obtaining a desired shrinkage.

After the stretching, the film is subjected to a heat treatment.
In order to obtain the desired shrinkage, it is important that the film is relaxed before the heat treatment after the stretching and then returned to the same width as after the stretching before the heat treatment. Here, the relaxing ratio is preferably 10% or less of the entire width of the film, and more preferably 5% or less. Although various studies have been made on the temperature of the 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. Furthermore, in order to obtain the desired thermal expansion coefficient and humidity expansion coefficient, 250
It is preferable that the temperature is in the range of from 0C to 350C.

The film of the present invention may be a laminated film. For example, in the case of two layers, a method of dividing the polymerized aromatic polyamide solution into two, adding different particles to each other, and then laminating the solution is mentioned as one example. The same applies to the case of three or more layers. Examples of these lamination methods include lamination in a die, lamination in a composite tube,
There is a method in which one layer is formed once, and another layer is formed thereon.

As described above, the film of the present invention is obtained, but is not limited thereto. Further, in the method for producing the film of the present invention comprising a polymer other than the aromatic polyamide, a method suitable for each polymer is used. [Method for Measuring Physical Properties and Method for Evaluating Effect] The method for measuring physical properties and the method for evaluating effects according to the present invention are as follows. (1) Elastic modulus Using Orientec Tensilon, sample width 10m
m, the sample length was 50 mm, and the tensile speed was 300 mm / min. (2) plane orientation coefficient longitudinal and width directions of the refractive index (n _x, n _y) for the measurement of using Nikon phase difference measuring apparatus NPDM-1000. Using a xenon lamp as a light source and a measurement wavelength of 590 nm, a refractive index was measured from reflected light when a light beam was applied to the sample at an incident angle of 70 °. Also, the refractive index ( _nz ) in the thickness direction
Uses an Atago Abbe refractometer type 4 with sodium D
Line (589 nm) as a light source and a refractive index of 1.79 in the intermediate liquid
Was measured using a methylene sulfur iodide solution, and the plane orientation coefficient was determined from the following equation. In addition, each measurement was performed in an atmosphere at room temperature and 25 ° C.

Plane orientation coefficient = ( _nx + _ny ) / 2- _nz (3) Measurement of shrinkage rate The measurement was performed by the following measurement method.

(I) Cut the film into a dumbbell shape to prepare a sample. The longitudinal direction of the film was defined as the longitudinal direction (tensile direction) of the sample. A 2 mm square grid is printed on the sample with a print gokko (or drawn with a pen).

(Ii) The sample is set on a manual stretching machine and stretched until it breaks in the machine direction (MD).

(Iii) Using a digital microscope (Keyence-6200), check the distortion of the lattice during stretching.
Shoot at 0x and record on Hi-8 VCR.

(Iv) The obtained video is converted into image analysis software (TO
YOBO-V10) performs image analysis, measures the length between lattices, and determines the shrinkage ratio γ in the direction perpendicular to the longitudinal direction (width direction (TD)).
Is measured.

(Iv) The contraction rate γ when stretched by 1% in the longitudinal direction is γ ₁ , and the contraction rate γ when stretched by 10% is γ ₁₀ . (4) Coefficient of thermal expansion To eliminate the effects of heat shrinkage and moisture absorption and 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). (5) Humidity expansion coefficient The sample was set in a high-temperature high-humidity bath so as to have a width of 1 cm and a test length of 15 cm, and was dehumidified to a constant humidity (about 30% RH). % RH), it begins to expand due to moisture absorption. After about 24 hours, the moisture absorption reaches equilibrium and the film elongation reaches equilibrium. The elongation at this time is calculated by the following equation.

Humidity expansion coefficient ((cm / cm) /% RH)
= Elongation / (Test length × Humidity difference) (6) Output characteristics A magnetic paint having the following composition is applied to a film by a gravure roll, magnetically oriented, and dried. In addition, a small test calendar device (steel roll / nylon roll,
(5 steps), and a curing is performed at a temperature of 70 ° C. for 48 hours. The raw tape was slit into 1/2 inch to prepare a pancake.

(Composition of magnetic paint) Co-containing iron oxide: 100 parts by weight Vinyl chloride / vinyl acetate copolymer: 10 parts by weight Polyurethane elastomer: 10 parts by weight Polyisocyanate: 5 parts by weight Lecithin: 1 part by weight Parts-Methyl ethyl ketone: 75 parts by weight-Methyl isobutyl ketone: 75 parts by weight-Toluene: 75 parts by weight-Carbon black: 2 parts by weight-Lauric acid: 1.5 parts by weight A magnetic tape is filled in a tape cassette, and a test tape is used. I got a cassette. Using the obtained test tape cassette and a helical scan type rotary head, a signal having a recording wavelength of 0.45 μm was recorded on the magnetic tape, and the output (reproduced output) when reproducing the signal was measured. The magnetic tape of Comparative Example 1 was used as a reference tape, and its output was expressed as a relative value with the output being 100%. (7) Error rate of tape A helical scan type rotary head is used in which a tape is filled with a magnetic tape and the error rate of the tape during continuous running under conditions of 30 ° C. and 65% RH is used as a magnetic head using an error counter. Using tape running speed of 1
Measured as 00 inch / sec, 200 inch / sec,
The difference between the error rates of 200 inch / second and 100 inch / second is obtained, and the error rate difference is 0.10 (1 / MB).
The following were regarded as good.

[0064]

Next, embodiments of the present invention will be described based on examples.

Example 1 N-methyl-2-pyrrolidone (NMP) contained 2-chloroparaphenylenediamine as an aromatic diamine component in an amount of 85 mol% and 4,4'-diaminodiphenyl ether in an amount of 15 mol%. Is dissolved therein.
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 obtain an aromatic polyamide solution having a polymer concentration of 10.5% by weight and a viscosity of 3500 poise. To this solution, dry silica having a primary particle size of 16 nm was added in an amount of 2.0 wt% per polymer.

This polymer solution was introduced into a dry process, cast from a T-die on an endless belt, heated for 2 minutes with hot air at 90 ° C., and then heated for 2 minutes with hot air at 180 ° C. Was evaporated, and a self-holding film having a polymer concentration of 40 wt% was continuously peeled off from the belt.
After cooling to room temperature, NMP / water = 30 /
70, the film is introduced into a wet bath at a temperature of 50 ° C., and the residual solvent and the inorganic salts and impurities generated by the neutralization are extracted for 5 minutes, and in the meantime, the film is stretched in the longitudinal direction by 1.20 times between nip rolls. Was. Next, the film was introduced into a 50 ° C. water bath for 5 minutes to perform solvent extraction. Next, the film is stretched 1.40 times in the width direction by a tenter and relaxed by 2%. After returning the film to the same width as before the relaxation, the film is dried and heat-treated at 280 ° C. and gradually cooled to a thickness of 4.4 μm. A film was obtained.

The tensile modulus of the film was measured in the longitudinal direction (M
D), width direction (TD) 12.6, 13.8 GPa,
The plane orientation coefficient is 0.254, and the shrinkage ratio γ ₁ / γ ₁₀ is 0.47.
Met. The coefficient of thermal expansion in the longitudinal and width directions is 18
× 10 ⁻⁶ , 16 × 10 ⁻⁶ (cm / cm) / ° C., humidity expansion coefficient: 22 × 10 ⁻⁶ , 18 × 10 ⁻⁶ (cm / cm) /%
RH. The output characteristics of the magnetic tape produced using this film were 108%, which was good. The error rate is 0.20 (/ M at 100 inch / second and 200 inch / second).
B), which was 0.22 (/ MB), which was a good magnetic tape with few reading errors even under high-speed running.

Examples 2 and 3 Using the same polymer solution as in Example 1, the draw ratios were as shown in Table 1.
The film was formed in the same process as in Example 1 except that the relaxation after stretching in the width direction was relaxed by 5% and 8%, respectively, and the heat treatment temperature was set to 280 ° C. and 300 ° C., respectively. . The evaluation results of this film are as shown in Table 1, and both the output characteristics and the error rate of the magnetic tape were good.

Comparative Example 1 The same polymer as in Example 1 was filtered through a filter, introduced into a dry process, cast on a T-die on an endless belt, and the solvent was evaporated with hot air at 160 ° C. to have self-supporting properties. A film having a polymer concentration of 50 wt% was continuously peeled from the belt. Next, NMP / water = 10/9 as a wet bath
0, the film is introduced into a wet bath at a temperature of 40 ° C., and the residual solvent and the inorganic salts and impurities generated by the neutralization are extracted for 5 minutes,
During that time, stretching was performed 1.20 times in the longitudinal direction between the nip rolls. Next, the film was introduced into a 50 ° C. water bath for 5 minutes to perform solvent extraction. Next, after stretching 1.10 times in the width direction with a tenter, relaxing the film by 3%, returning the film to the same width as before the relaxation, performing drying and heat treatment at 250 ° C., and gradually cooling the film to a thickness of 4.4 μm. I got

The tensile modulus of the film was measured in the longitudinal direction (M
D), the width direction (TD) is 11.0, 8.5 GPa, respectively.
The plane orientation coefficient is 0.181, and the shrinkage ratio γ ₁ / γ ₁₀ is 0.44.
Met. The coefficient of thermal expansion in the longitudinal and width directions is 33
× 10 ⁻⁶ , 28 × 10 ⁻⁶ (cm / cm) / ° C., Humidity expansion coefficient: 29 × 10 ⁻⁶ , 38 × 10 ⁻⁶ (cm / cm) /%
RH. The output characteristics of a magnetic tape prepared using this film were set to 100%. The error rate is 10
It was 0.3 (/ MB) at 0 inch / sec, but was 0.47 (/ MB) at 200 inch / sec, indicating a defective magnetic tape with many high-speed reading errors.

Comparative Example 2 N-methyl-2-pyrrolidone (NMP) was used as an aromatic diamine component in 2-chloroparaphenylenediamine corresponding to 50 mol%, and 4,4'-diaminodiphenylmethane corresponding to 50 mol%. Was dissolved, and 98.5 was added thereto.
The mole% isophthalic chloride was added and 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 13% by weight and a viscosity of 3800 poise. This solution has a primary particle size of 1
6 nm of dry silica was added at 2.0 wt% per polymer.

After the polymer solution was filtered with a filter, the polymer solution was introduced into a dry process, cast on an endless belt from a T-die, heated with hot air of 90 ° C. for 2 minutes, and then heated with hot air of 180 ° C. After heating for 2 minutes to evaporate the solvent, a self-supporting film having a polymer concentration of 45 wt% was continuously peeled from the belt. After cooling to room temperature, the film was introduced into a wet bath of NMP / water = 30/70 at a temperature of 50 ° C. as a wet bath, and the residual solvent and the inorganic salts and impurities generated by neutralization were extracted for 5 minutes. And stretched 1.03 times in the longitudinal direction between nip rolls. Next, the film was introduced into a 50 ° C. water bath for 5 minutes to perform solvent extraction. Next, after stretching 1.05 times in the width direction with a tenter, the film is relaxed by 3%, the film is returned to the same width as before relaxation, dried and heat-treated at 380 ° C., and gradually cooled to obtain a film having a thickness of 4.4 μm. Was.

The tensile modulus of this film was measured in the longitudinal direction (M
D) and the width direction (TD) were 5.8 and 6.2 GPa, respectively, the plane orientation coefficient was 0.375, and the shrinkage ratio γ ₁ / γ ₁₀ was 0.79. The coefficient of thermal expansion in the longitudinal and width directions is 52 ×
10 ⁻⁶ , 45 × 10 ⁻⁶ (cm / cm) / ° C., coefficient of humidity expansion: 126 × 10 ⁻⁶ , 103 × 10 ⁻⁶ (cm / cm) /
% RH. The output characteristics of the magnetic tape produced using this film were 91%, which was poor. The error rate was 0.23 (/ MB) at 100 inch / sec, but 0.51 (/ MB) at 200 inch / sec. there were.

Comparative Example 3 The same polymer solution as in Comparative Example 2 was filtered through a filter, introduced into a dry process, cast on a T-die on an endless belt, and heated with hot air at 90 ° C. for 2 minutes. Then 1
The film was heated with hot air at 80 ° C. for 2 minutes to evaporate the solvent, and a self-supporting film having a polymer concentration of 45 wt% was continuously peeled off from the belt. After cooling the film to room temperature,
The film was introduced into a wet bath of NMP / water = 30/70 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 5 minutes. Stretching was performed 20 times in the longitudinal direction. Then 50
The film was introduced into a water bath at 5 ° C. for 5 minutes to perform solvent extraction. Next, after stretching 1.55 times in the width direction with a tenter, 1
After relaxing by 2%, the film was returned to the same width as before relaxation, heat-treated at 200 ° C., and gradually cooled to obtain a film having a thickness of 4.4 μm.

The tensile modulus of the film was measured in the longitudinal direction (M
D), the width direction (TD) was 6.8 and 9.1 GPa, respectively, the plane orientation coefficient was 0.391, and the shrinkage ratio γ ₁ / γ ₁₀ was 0.98. The coefficient of thermal expansion in the longitudinal and width directions is 19 ×
10 ⁻⁶ , 12 × 10 ⁻⁶ (cm / cm) / ° C., coefficient of humidity expansion: 18 × 10 ⁻⁶ , 15 × 10 ⁻⁶ (cm / cm) /% R
There was H. The output characteristics of the magnetic tape produced using this film were 94%, which was poor. Also, the error rate was 0.26 (/ MB) at 100 inch / second,
It was 0.55 (/ MB) at 200 inches / second, indicating a defective magnetic tape with many high-speed reading errors.

[0076]

[Table 1]

[0077]

According to the present invention, by using an aromatic polyamide film having high dimensional stability and having a plane orientation coefficient and a shrinkage ratio in a width direction within a certain range, high-speed recording can be performed when a magnetic recording medium is used. A reading error is less likely to occur even during reproduction, and a magnetic tape having excellent electromagnetic conversion characteristics can be obtained. Furthermore, because of excellent dimensional stability, it is possible to increase the capacity by shortening the recording wavelength and narrowing the track pitch. Further, the film according to the present invention can be used not only for magnetic recording applications but also for applications requiring dimensional stability, such as flexible printed boards, capacitors, and thermal transfer ribbons.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B29L 7:00 F term (Reference) 4F071 AA56 AF15Y AF20Y AF53Y AF54 AH14 BA01 BB06 BB08 BC01 4F100 AA20H AK47A AR00B BA02 BA03 BA06 BA10B BA13 CA23 GB41 GB43 JA02A JA20A JG06B JG10 JK07A JK08A JL04 YY00A 4F210 AA30 AE01 AG01 AG03 AH38 QA02 QA03 QC06 QG01 QG18 QW12 QW17 5D006 CB03 CB07 FA00

Claims (3)

[Claims] 1. A tensile modulus in at least one direction of 7
GPa or more, the plane orientation coefficient is 0.2 or more and 0.8 or less, the shrinkage ratio γ ₁ in the width direction when the film is stretched by 1% in the longitudinal direction, and the width direction when the film is stretched by 10%. aromatic polyamide film satisfying shrinkage gamma ₁₀ is a (1). γ ₁ / γ ₁₀ ≦ 0.9 (1) 2. The thermal expansion coefficient in at least one direction is zero.
~ 40 × 10 ^-6 (cm / cm) / ° C, humidity expansion coefficient is 0
The film according to claim 1, wherein the film has a RH of 30 × 10 ⁻⁶ (cm / cm) /% RH. 3. A magnetic recording medium comprising a film according to claim 1 and a magnetic layer provided on at least one side of the film.