JPH09155970A - Aromatic polyamide film and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film having excellent rigidity and elongation characteristic, and capable of being adapted suitably to a magnetic recording medium. SOLUTION: This film consists mainly of an aromatic polyamide, and the tensile Young's modulus of the film in at least one direction at 20 deg.C and in a relative humidity of 60% is 800kg/mm<2> or more, thus the aromatic polyamide film is made such that the ratio between the strength F1 of a 1% stretch and the strength F5 of a 5% stretch of the film in one direction satisfies a formula of F1/F5>=0.38.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aromatic polyamide film which has excellent rigidity and elongation properties and can be suitably used as a magnetic recording medium.

[0002]

2. Description of the Related Art Conventionally, as a magnetic recording medium, there is known a magnetic recording medium comprising a polyester film provided with an oxide coating type magnetic layer or a metal coating type magnetic layer. (For example, JP-A-61-26933 and JP-A-60-6631.
No. 9). Regarding the aromatic polyamide, an application example of a film having different Young's moduli in the longitudinal direction and the width direction to a magnetic recording medium is disclosed in JP-A-62-62424. Further, Japanese Patent Application Laid-Open No. 55-41625 discloses a film made of a nuclear chlorine-substituted aromatic polyamide mainly containing para bonds. However, as will be described later, the high density magnetic recording medium has rigidity and elongation. It cannot be said that the characteristics are sufficient.

[0003]

In recent years, a thin film is used because the video camera is used outdoors, or is required to be downsized and the recording time is long, and it is used as an external memory of a computer. There is an increasing demand for a magnetic recording medium having excellent durability under severe conditions.

However, a magnetic recording medium composed of the above polyester film base or aromatic polyamide film base has no problem at room temperature and normal humidity, but when used under high temperature and high humidity conditions, running property and output characteristics are improved. And the deterioration of the recording characteristics and dropout due to the deformation of the base material during repeated running occur. Generally, a means for increasing the Young's modulus of the base film is taken as a means for solving such a problem. However, it is not sufficient under high temperature and high humidity or in a situation where a large amount of tension is suddenly applied.

The inventors of the present invention have made extensive studies in order to solve such a problem, and have found that the strength / elongation property in the low elongation region including the elastic recovery region is very important.

That is, the present invention defines the Young's modulus and the strength in the low elongation region of an aromatic polyamide film, so that when it is used as a magnetic recording medium, it can be extremely used under severe conditions such as high temperature and high humidity and repeated running. An object is to provide a magnetic recording medium having stable output characteristics and good running properties.

[0007]

SUMMARY OF THE INVENTION The present invention is a film comprising an aromatic polyamide as a main component.
The tensile Young's modulus in at least one direction at 80 ° C. and 60% relative humidity is 800 kg / mm ² or more, and the ratio of the strength F1 at 1% stretching to the strength F5 at 5% stretching of the film in that direction is: The aromatic polyamide film is characterized by satisfying the following formula.

F1 / F5 ≧ 0.38

[0009]

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

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 substituted with halogen groups (especially chlorine), nitro groups, alkyl groups having 1 to 3 carbon atoms (especially methyl groups), alkoxy groups having 1 to 3 carbon atoms, and the like. And those in which hydrogen in the amide bond constituting the polymer is replaced by another substituent.

From the viewpoint of characteristics, the aromatic polyamide film used in the present invention has a polymer in which the above-mentioned aromatic rings are bonded in the para-position, and the polymer occupies 70% or more, more preferably 80% or more of the total aromatic rings. It is preferable because the film has high rigidity and good heat resistance. Also, some of the hydrogen atoms on the aromatic ring are halogen groups (especially chlorine), nitro groups, and carbon atoms of 1 to 3
If the aromatic ring substituted with the alkyl group (especially methyl group) or the alkoxy group having 1 to 3 carbon atoms accounts for 30% or more of the whole, moisture resistance is improved, and characteristics such as dimensional change due to moisture absorption and rigidity decrease It is preferable because it is improved.

The aromatic polyamide of the present invention contains the repeating unit represented by the general formula (I) and / or the general formula (II) in an amount of 50 mol% or more.
If the amount is less than the above, other repeating units such as aromatic polyimide units and other aromatic polyamide 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.

Further, in the aromatic polyamide film of the present invention, the weight fraction of low molecular weight substances having a molecular weight of 1000 or less is 0.
It is preferably 5% or less, more preferably 0.2% or less. The presence of low molecular weight substances causes internal plasticization and impairs mechanical properties. Furthermore, in the case of a magnetic recording medium, due to a change in environment after the formation of the magnetic layer, exfoliation of the low molecular weight substance or the like may cause peeling of the magnetic layer or the surface of the magnetic layer may become sticky and may be easily wrapped around a roll or the like.

20 of the aromatic polyamide film of the present invention
The tensile Young's modulus in at least one direction at a temperature of 60 ° C. and a relative humidity of 60% must be 800 kg / mm ² or more. It is more preferably 900 kg / mm ² or more, still more preferably 1000 kg / mm ² or more. Since the aromatic polyamide film of the present invention is often used as a thin film in response to the demand for a thinner magnetic recording medium, it has a high Young's modulus in order to withstand the tension applied during tape running or during stop / start. There is a need. If the Young's modulus is lower than this range, the tape is elongated and the recording / reproducing property is deteriorated. Further, since the film has a high Young's modulus, it can withstand tension applied during formation of a magnetic recording medium such as a coating layer forming step and a back coat layer forming step, which is advantageous in processing.

The aromatic polyamide film of the present invention may be stretched in the longitudinal direction and / or the width direction. The degree of stretching is not particularly limited, but the elongation,
Taking into account properties such as tear resistance, the tensile Young's modulus in the longitudinal direction is EMD and the tensile Young's modulus in the width direction is ETD.
Then, it is practical that 0.5 ≦ EMD / ETD ≦ 2.

Further, the aromatic polyamide film of the present invention has a strength F1 at 1% stretching and a strength F at 5% stretching in a direction having a tensile Young's modulus of 800 kg / mm ² or more.
The ratio of 5 should satisfy F1 / F5 ≧ 0.38. More preferably, F1 / F5 ≧ 0.
40, more preferably F1 / F5 ≧ 0.42. In addition, when there are a plurality of directions having a tensile Young's modulus of 800 kg / mm ² or more, one of the directions may satisfy the above relationship. When the aromatic polyamide film of the present invention is used as a magnetic recording medium, it is often used as a thin film. Therefore, it is very important not only to have a Young's modulus but also to have sufficient strength in a low elongation region. . That is, the low elongation region is within the standard range of tape elongation, and the higher the strength of this region is, the less tape elongation is likely to occur in the low load region, and the lowering of the recording / reproducing property can be suppressed. Further, since the toughness is large, the resistance to the deformation stress is large even after repeated use. The ratio F1 / F5 between the strength F5 outside the elastic recovery region and the strength F1 inside the elastic recovery region is a value representing the elongation property in the low elongation region, and F1 / F5 <0.
In the case of No. 38, when used under high temperature and high humidity, the running property and recording / reproducing property are deteriorated due to the elongation of the tape, and dropout occurs during repeated running, so that it is not suitable for a magnetic recording medium.

Further, 80 of the aromatic polyamide film
When the strength at 2% stretching in the direction having a tensile Young's modulus of 0 kg / mm ² or more is F2, F2 / F5 ≧ 0.70, and more preferably F2 / F5 ≧ 0.72 in the low load range. It is preferable because the tape has less elongation.
Also in this case, when there are a plurality of directions having a tensile Young's modulus of 800 kg / mm ² or more, one of the directions may satisfy the above relationship. F2 / F5
In the case of <0.70, elongation of the tape may occur when used under high temperature and high humidity, which is not preferable.

Further, the strength F5 of the aromatic polyamide film of the present invention at 5% stretching in the direction having a tensile Young's modulus of 800 kg / mm ² or more is F5 ≧ 35 kg / mm ² , more preferably F5 ≧ 40 kg / mm. It is preferable to fill ² . Also in this case, when there are a plurality of directions having a tensile Young's modulus of 800 kg / mm ² or more, one of the directions may satisfy the above relationship. When F5 <35 kg / mm ^2, a large dimensional change occurs even under a low load, and it may not be suitable as a magnetic recording medium.

The aromatic polyamide film of the present invention is preferably used for various applications such as flexible printed circuit boards, capacitors, printer ribbons, acoustic diaphragms, base films for solar cells, and the like. When used as a recording medium, the effect of the aromatic polyamide film of the present invention having high output, high durability, and defect-free properties is sufficiently exhibited, which is particularly preferable. Magnetic recording media include consumer use, professional use, D-1,
It can be suitably used for digital video cassette applications for broadcasting stations such as D-2 and D-3, and for data storage applications such as DDS-2, 3, 4 and data 8 mm, and QIC. It can be optimally used for the most important data storage applications.

The form of the magnetic recording medium is not particularly limited, such as a disc form, a card form, and a tape form, but in order to cope with the thinning of the aromatic polyamide film of the present invention, which is excellent in high rigidity and elongation property, The support made of an aromatic polyamide film has a thickness of 6.5 μm or less and a width of 2.3 to
13.0 mm, length 100 m / roll or more, recording density (when not compressed) as a magnetic recording medium is 8 kilobytes / mm ²
The above-mentioned long and high-density magnetic tape is particularly preferable because the excellent effects due to the high rigidity and elongation property of the present invention can be further exhibited. Here, the recording density is calculated by the following equation.

Recording density = Recording capacity / (Tape width × Tape length)

In recent years, magnetic recording media typified by magnetic tapes have been increasingly required to be smaller and have higher capacities, but in order to realize higher capacities, the thickness of the support is reduced to make the media longer. Therefore, it is important to improve the recording capacity as a whole. Therefore, the aromatic polyamide film of the present invention in which the rigidity and the elongation property, especially the elongation property in the low elongation region are controlled is extremely effective, and the magnetic properties of the aromatic polyamide film capable of suitably responding to the demand for such high capacity are high. It can be a tape. The thickness of the support is preferably 5.0 μm or less, more preferably 4.0 μm or less, and the recording density as a magnetic recording medium is preferably 25 kilobytes / mm ² or more,
More preferably, it is at least 34 kilobytes / mm ² . Further, the magnetic recording medium is required to have stronger mechanical properties in the longitudinal direction or the width direction depending on the recording method.
The value specified in the present invention preferably matches the required direction.

However, when the film of the present invention is mainly used for applications other than magnetic materials such as flexible printed circuit boards, capacitors, printer ribbons, etc.
The thickness is preferably 50 μm, more preferably 1 to 20 μm.

The method for forming the magnetic layer includes a wet method in which a ferromagnetic powder is used as a magnetic paint by using various binders and applied on a substrate film, and a dry method such as an evaporation method, a sputtering method and an ion plating method. Although not particularly limited, a wet method will be described here as an example.

The type of magnetic powder to be a magnetic material is not particularly limited, but ferromagnetic powder such as iron oxide, chromium oxide,
Fe, Co, Fe-Co, Fe-Co-Ni, Co-N
i and the like are preferably used.

The magnetic powder can be made into a magnetic paint by using various binders, but thermosetting resin type binders and radiation curing type binders are preferable, and other additives such as dispersants, lubricants and antistatic agents. Etc. may be used.
For example, a binder made of vinyl chloride / vinyl acetate / vinyl alcohol copolymer, polyurethane prepolymer and polyisocyanate can be used.

When the present invention is used for a magnetic recording medium, it is preferable that particles are present in the film in order to impart appropriate roughness to the film. The types of particles include SiO ₂ , TiO ₂ , Al ₂ O ₃ , Ca
SO ₄ , BaSO ₄ , CaCO ₃ , carbon black,
Inorganic particles such as zeolite and other fine metal powders, silicone particles, polyimide particles, crosslinked copolymer particles, crosslinked polyester particles, organic polymers such as Teflon particles, but inorganic particles from the viewpoint of heat resistance Is more preferable. Further, the average primary particle diameter of the particles contained in the film of the present invention is 0.005 to 5 μm, preferably 0.01 to 2 μm.
When it is in the range of m, both the electromagnetic conversion characteristics and the running property are good, which is desirable. The content of the particles contained in the film of the present invention is 0.01 to 5 wt%, preferably 0.05 to
3 wt%. If the content of the particles is less than the above range, the running property of the film tends to be poor, and if it is too large, the electromagnetic conversion characteristics tend to be poor.

The aromatic polyamide film of the present invention can be used not only as a single layer film but also as a laminated film. Further, it may have a laminated structure in which another film or the like is laminated on the single layer film or the laminated film. In the case of a laminated film, the polymers forming each layer may be the same or different.
Further, particles may be contained in at least one layer of each layer, and it is desirable to use the kind of particles, the average primary particle diameter of particles, and the content which are desirably used as described above.
When the diameter of the particles in the base layer is larger than the diameter of the particles in the other laminated film layers, the film surface can have an appropriate undulation, and the tape running property is further improved. desirable.

The number H2 of coarse surface protrusions (number / 100 cm ² ) on the surface of the aromatic polyamide film of the present invention on which the magnetic layer is formed is preferably H2 ≦ 50. More preferably, H2 ≦ 30, and even more preferably H2 ≦ 20. When H2> 50, the surface property of the magnetic recording medium is deteriorated, dropout occurs, and it is often unsuitable as a high-density magnetic recording medium.

Further, the number of coarse surface protrusions H3 (number / 10) on the surface of the aromatic polyamide film of the present invention on the non-magnetic layer side.
0 cm ² ) is preferably 2 ≦ H3 ≦ 100. More preferably, 2 ≦ H3 ≦ 7
0, and more preferably 2 ≦ H3 ≦ 50. When H3 <2, the contact resistance with a guide roll or the like when used as a magnetic recording medium increases, and the running property may deteriorate. Further, when H3> 100, coarse protrusions may affect the surface properties on the magnetic layer side during calendering in the coating step, which is a cause of dropout, which is not preferable.

The elongation of the aromatic polyamide film of the present invention is preferably 10% or more, more preferably 20% or more, further preferably 30% or more, since the tape has appropriate flexibility.

When the moisture absorption rate of the aromatic polyamide film of the present invention is 5% or less, more preferably 3% or less, further preferably 2% or less, dimensional change of the tape due to humidity change is small and good electromagnetic conversion is achieved. It is desirable because the characteristics can be maintained.

20 of the aromatic polyamide film of the present invention
The heat shrinkage ratio at 0 ° C. for 10 minutes is preferably 0.5% or less, and more preferably 0.3% or less, because the tape dimensional change due to temperature change is small and good electromagnetic conversion characteristics can be maintained. .

It is preferable that these characteristics are also satisfied in the laminated film when laminated.

The aromatic polyamide film of the present invention can be produced, for example, by the following method, but the present invention is not limited thereto.

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). It is synthesized by solution polymerization.

At this time, in order to suppress the production of low molecular weight substances, it is necessary to avoid mixing of water and other substances which hinder the reaction, and it is preferable to employ an efficient stirring means. Further, although the equivalence of the raw materials is important, it is preferable to make a slight adjustment when the film-forming property may be impaired. Further, in order to keep the solution uniform during the polymerization, a halogen group (particularly chlorine), a nitro group, an alkyl group having 1 to 3 carbon atoms (particularly a methyl group), an alkoxy group having 1 to 3 carbon atoms, etc. A monomer having a substituent or a monomer having a bent chain such as a biphenyl ether or a biphenylamine skeleton is preferably used as long as the physical properties are not reduced. Also, as a dissolution aid, calcium chloride, magnesium chloride,
You may add lithium chloride, lithium nitrate, etc.

When acid chloride and diamine are used as monomers in these polymer solutions, hydrogen chloride is by-produced. When neutralizing this, inorganic polymers such as calcium hydroxide, calcium carbonate and lithium carbonate are used. Neutralizer, ethylene oxide, propylene oxide, ammonia,
Triethylamine, triethanolamine, dietano-
Organic neutralizing agents such as ruamine are used. Further, in order to reduce the hygroscopicity of the base film, benzoyl chloride, o-phthalic anhydride, acetic acid chloride, aniline or the like may be added to the system in which the polymerization has been completed to block the end of the polymer.

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-mentioned organic solvent or an inorganic solvent such as sulfuric acid to prepare a film-forming stock solution. You may.

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
It is preferably 0.5 or more.

The polymer concentration in the film forming stock solution is 2 to 40% by weight.
The degree is preferred.

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 a film-forming stock solution is prepared and then directly added.

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, a wet method, and the like, and any method may be used. However, the dry-wet method will be described here 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. Then, the solvent is scattered from the thin film layer and dried until the thin film has a self-holding property. I do. Drying conditions are from room temperature to 2
20 ° C., within 60 minutes, preferably from room temperature to 2
It is in the range of 00 ° C. If the drying temperature exceeds 220 ° C., the coarse surface protrusions H2 increase, which may exceed the preferred range of the present invention. Further, H3 can be controlled within the preferable range of the present invention by controlling the frequency of surface defects of the drum and the endless belt used in this drying step. The frequency of surface defects with a diameter of 30 μm or more is preferably 0.1 / mm ²
It is preferable to set the following. The film that has undergone the dry process is peeled from the support, and the condition of the present invention can be satisfied if the concentration of the polymer in the film at this time is 30 to 50 wt%. If the polymer concentration is too high, a part of the polymer is precipitated to form a fragile film. On the other hand, if the polymer concentration is too low, the solvent is rapidly extracted in the wet process to form voids and the like, and the film has a low elongation.

The peeled film is introduced into a wet process to be desalted and desolvated. In this wet process, it is preferable to use a mixed solvent of a coagulation solvent and a good solvent such as a polymerization solvent as the coagulation / desalting / desolvation bath in order to perform desalination and desolvation as gently as possible. In this case, it is preferable to provide a plurality of these coagulation / demineralization / desolvation baths, to provide a gradient in the mixing ratio, and to pass the film in order from the one having a high proportion of good solvent. Further, it is more preferable to provide a gradient in these bath temperatures and pass the film in order from the one having the highest temperature. At this time, stretching in the longitudinal direction is preferable because the molecules are oriented and Young's modulus and F1 / F5 are improved. The proportion of good solvents such as the polymerization solvent in the film after desalting and desolvation is preferably 5 wt% or less. When the proportion of the good solvent is large, crystallization during heat treatment is hindered, and thus Young's modulus and strength are lowered, which is not preferable.

Next, stretching is carried out, and the temperature at this time is preferably within the range of + 20 ° C. from the glass transition temperature of the polymer. If the temperature is lower than this range, the film is easily broken during stretching, and if it is too high, the molecules are difficult to be oriented. The stretch ratio is within a range of 0.8 to 8.0 in terms of areal ratio (the areal ratio is defined as a value obtained by dividing the area of the film after stretching by the area of the film before stretching. 1 or less means relaxing). Is preferable, and more preferably 1.1 to
5.0.

Heat treatment is carried out during or after the stretching of the film, and if the heat treatment temperature is in the range of 200 to 350 ° C., the conditions of the present invention can be satisfied. More preferably, it is 250 to 320 ° C. Heat treatment temperature is 200
When the temperature is lower than 0 ° C, the Young's modulus of the film is lowered and the range of the present invention may not be satisfied. On the other hand, when the temperature exceeds 350 ° C., the crystallization of the film proceeds so much that the film becomes hard and brittle.

Further, it is effective to gradually cool the film after stretching or heat treatment, and it is effective to cool the film at a rate of 50 ° C./sec or less.

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.

Next, when it is used as a magnetic recording medium, a magnetic layer is formed on this film. The method for forming the magnetic layer may be a known method, but the method using a gravure roll is more preferable from the viewpoint of the uniformity of the coating film. The drying temperature after application is preferably from 90C to 150C. The calendering step is preferably performed in the range of 25 ° C to 150 ° C.

After that, 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.

Further, the film coated with the magnetic layer is cured and then slit to obtain the magnetic recording medium of the present invention.

Since the magnetic recording medium thus obtained can be made compact and thin, it is possible to record compact and large-capacity data, and it can be used not only for video and audio, but also for humidity and temperature. Since the dimensional change is small, it is particularly suitable as a digital recording material such as a data tape of a computer. Further, since it is excellent in running property under high temperature and high humidity and electromagnetic conversion characteristics, it can be suitably used for tapes for video cameras for outdoor use.

Since the aromatic polyamide film of the present invention has both excellent heat resistance and dimensional stability, TA
It can also be suitably used for a film substrate such as a B mounting substrate, a transfer material for thermal transfer recording, a film capacitor, and the like.

[0056]

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

(1) Young's modulus in tension, F1, F2, F
5. Elongation Measured at 20 ° C. and 60% relative humidity using Robot Tensilon RTA (manufactured by Orientec). The test piece is 10 mm wide and 50 mm long, and the pulling speed is 300 m.
m / min. However, the weight was 0.
The point of passing 1 kgf was taken as the origin of elongation.

(2) Moisture Absorption Rate The film was dried at 200 ° C. for 1 hour and the weight in an absolutely dry state was W 0, and the film was dried at 20 ° C. and a relative humidity of 75% for 4 hours.
The weight after absorbing moisture for 8 hours is defined as W1 (W1-W0) / W0.
Was multiplied by 100 to represent the moisture absorption.

(3) Heat Shrinkage Rate The heat shrinkage was calculated by the following formula after heating in an oven at 200 ° C. for 10 minutes without load.

[0060]

(Equation 1)

(4) Number of coarse surface protrusions (H2, H3) Foreign matter is observed and marked under polarized light in a range of 100 cm ² of the film surface by a stereoscopic microscope. The height of the marked foreign matter is observed at a wavelength of 546 nm using a multiple interferometer and checked by the number of interference fringes. The number of double rings or more was H2, and the number of triple rings or more was H3.

(5) Weight fraction of low molecular weight substances A gel permeation chromatograph (GPC) showed a low angle laser.
Light scattering photometer (LALLS) and differential refractometer (R
I) is incorporated and the light scattering intensity and the difference in refractive index of the molecular chain solution size-separated by the GPC device are measured over the elution time to sequentially calculate the molecular weight of the solute and its content rate, and finally, The absolute molecular weight distribution and absolute average molecular weight of the polymer substance were determined. The measurement conditions are shown below.

A. GPC device: 244 type gel permeation chromatograph (manufactured by WATERS) Column: TRC-GM (two) (Toray Resarch Center), Shodex KD-802 (one) (Showa Denko) Solvent: NMP (0.01N lithium chloride added) Flow rate: 0.6 ml / min Temperature: 23 ° C. Sample concentration: 0.101% (wt / vol) Solubility: Complete dissolution Filtration: Shodex DT ED-13CR (0.45 μ) (Showa era) Injection amount: 0.2 ml Concentration detector: Differential refractive index detector, R-401 (manufactured by WATERS) B. LALLS device: CMX-100 type low-angle laser light scattering photometer (manufactured by Chromatix) Wavelength: 633 nm (He-Ne) Second virial coefficient (A ₂ ): 0 ml · mole / g Refractive index concentration change (dn) / dc): 0.215 ml / g (actual value) Gain: P0 = 200 mV Temperature: 23 ° C. Filter: 0.45 μ-Fluoro Pore FP-045 (manufactured by Sumitomo Electric Industries, Ltd.) C.I. Data processing: GPC-LALLS data processing system (manufactured by Toray Research Center)

(6) Electromagnetic conversion characteristics On the surface not contacting the metal belt during film formation,
A magnetic coating material having the following composition was prepared and applied by a gravure roll so that the thickness of the magnetic layer was 2 μm, and after curing, calendering was performed.

Magnetic powder (metal powder) 80 parts by weight PVC-based copolymer 10 parts by weight Polyurethane 10 parts by weight Curing agent 5 parts by weight Abrasive 5 parts by weight Toluene 100 parts by weight Methyl ethyl ketone 100 parts by weight A film coated with this magnetic layer is used. It was slit into a 1/2 inch width and incorporated into a VTR cassette to obtain a VTR tape. Using a VHS type domestic VTR for this tape, the chroma S / N after 100 times of running was measured by a color video noise measuring device from a 100% chroma signal by a television test waveform generator. The atmosphere was evaluated under the conditions of 25 ° C. and 55% RH based on a commercially available tape.

(7) Runnability Using the VHS type domestic VTR,
The fluctuation of the screen due to the disturbance of the tape running after repeatedly running 100 times at 5 ° C. and 55% RH was observed. ：: There was no fluctuation in the playback screen due to smooth running. ×: Fluctuation occurs on the playback screen.

(8) Durability Using the VHS type home VTR,
The elongation and slack of the tape were observed after repeatedly running 100 times at 5 ° C. and 55% RH. ○: Growth and sagging X: Elongation and slack are visually observed.

The present invention will be described in more detail based on the following examples, but it goes without saying that the present invention is not limited thereto. In the following examples, NM
P is N-methylpyrrolidone, TPC is terephthalic acid chloride, CTPC is 2-chloroterephthalic acid chloride, D
A is o-dianisidine, PPDA is paraphenylenediamine, CPA is 2-chloroparaphenylenediamine, D
PE is 4,4'-diaminodiphenyl ether, DAM
Represents 4,4′-diaminodiphenylmethane.

Example 1 CPA corresponding to 85 mol% and DPE corresponding to 15 mol% as an aromatic diamine component were dissolved in NMP dehydrated to 100 ppm or less, and CTPC corresponding to 98.3 mol% was dissolved therein. Add and stir for 2 hours to complete the polymerization. After neutralizing this solution with lithium carbonate, the primary particle size is 16n
2 wt% per polymer of dry silica was added.

After passing this polymer solution through a 5 μm-cut filter, the polymer solution was cast on a stainless steel belt having a frequency of surface defects with a diameter of 30 μm or more of 0.05 / mm ² or less, and a temperature of 180 ° C. The film having self-holding property was continuously peeled off from the belt by heating with hot air for 2 minutes to evaporate the solvent. Next, the film was introduced into a water tank having a concentration gradient of NMP, and the residual solvent and the inorganic salt generated by neutralization were extracted with water. During this period, the film was stretched 1.2 times in the longitudinal direction. Thereafter, drying and heat treatment of water were performed by a tenter to obtain an aromatic polyamide film having a thickness of 5 μm. During this period, the film was stretched 1.3 times in the width direction of the film at 280 ° C., dried and heat-treated at 250 ° C. for 1.5 minutes, and then gradually cooled at a rate of 20 ° C./sec.

The physical properties of this film are shown in Tables 1 and 2. In addition, Tables 1 and 2 show the physical properties in the direction having a higher Young's modulus in the longitudinal direction and the width direction. The content of low molecular weight substances in this aromatic polyamide film was 0.5% or less in terms of weight fraction.

Next, the runnability, electromagnetic conversion characteristics and durability of this film were measured, and they were all good.

Example 2 DA corresponding to 50 mol%, PPDA corresponding to 35 mol% and DPE corresponding to 15 mol% as an aromatic diamine component were dissolved in NMP dehydrated to 100 ppm or less, and 98. Polymerization was completed by adding TPC corresponding to 5 mol% and stirring for 2 hours.

Thereafter, the thickness is 5 μm by the same method as in the first embodiment.
Was obtained.

The physical properties of this film are shown in Tables 1 and 2. The content of low molecular weight substances in this aromatic polyamide film was 0.5% or less in terms of weight fraction.

Next, the runnability, electromagnetic conversion characteristics and durability of this film were measured, and they were all good.

Example 3 100 mol% of PPDA as an aromatic diamine component and lithium chloride as a dissolution aid were dissolved in NMP dehydrated to 100 ppm or less, and 100 mol% of TPC was added thereto to carry out polymerization. went. Generated polymer
Was washed with warm water and then added with 99.7% sulfuric acid to a polymer concentration of 1
It was dissolved at 0% by weight to obtain an aromatic polyamide solution.

To this solution, 2 wt% of dry silica having a primary particle size of 16 nm was added per polymer. After passing this polymer solution through a 5 μm-cut filter, the polymer solution was cast on a tantalum belt having a mirror-like surface kept at 110 ° C.
After maintaining in an atmosphere of 0 ° C. and 98% relative humidity for 40 seconds, the film was introduced into a water tank and solidified to continuously form a film. Next, the moisture is dried and heat-treated with a tenter to obtain a thickness of 6 μm.
m was obtained. In the meantime, the film was stretched 1.2 times and 1.2 times in the width direction, respectively, dried and heat-treated at 280 ° C. for 1.5 minutes, and then gradually cooled at a rate of 20 ° C./sec.

The physical properties of this film are shown in Tables 1 and 2. The content of low molecular weight substances in this aromatic polyamide film was 0.5% or less in terms of weight fraction.

Next, the electromagnetic conversion characteristics and running properties of this film were measured and found to be good. However, the processing speed could not be increased because a slight tendency of elongation was observed during the processing of the magnetic layer. Further, although the durability was good, there was a slight dimensional change due to its high moisture absorption rate when stored for a long time in high humidity.

Example 4 After passing the polymer solution of Example 1 through a filter having a cut of 5 μm, the frequency of surface defects having a diameter of 30 μm or more was 0.0.
The film was cast onto a stainless steel belt having 5 pieces / mm ² or less, heated with hot air at 250 ° C. for 80 seconds to evaporate the solvent, and the self-supporting film was continuously peeled from the belt.

Thereafter, a thickness of 5 μm is obtained by the same method as in the first embodiment.
Was obtained.

The physical properties of this film are shown in Tables 1 and 2. The content of low molecular weight substances in this aromatic polyamide film was 0.5% or less in terms of weight fraction.

Next, the runnability and durability of this film were measured and found to be good.

However, although the electromagnetic conversion characteristics were good, a reduction was recognized as compared with Example 1.

Example 5 CPA corresponding to 85 mol% and DPE corresponding to 15 mol% as an aromatic diamine component were dissolved in NMP having a water content of 420 ppm, and CTPC corresponding to 98.3 mol% was added thereto. Then, the mixture was stirred for 2 hours to complete the polymerization. After neutralizing this solution with lithium carbonate, 2 wt% of dry silica having a primary particle size of 16 nm was added per polymer.

Thereafter, a thickness of 5 μm is obtained by the same method as in the first embodiment.
Was obtained.

The physical properties of this film are shown in Tables 1 and 2. The content of low molecular weight substances in this aromatic polyamide film was 0.7% by weight.

Next, the electromagnetic conversion characteristics and durability of this film were measured and found to be good. However, although the runnability was good, a decrease was observed as compared with Example 1.

Example 6 CPA corresponding to 75 mol% and DPE corresponding to 25 mol% as an aromatic diamine component were dissolved in NMP dehydrated to 100 ppm or less, and CTPC corresponding to 98.5 mol% was added thereto. Then, the mixture was stirred for 2 hours to complete the polymerization.

Thereafter, an aromatic polyamide film having a thickness of 5 μm was obtained in the same manner as in Example 1 except that stretching was not performed in the longitudinal direction and the width direction.

The physical properties of this film are shown in Tables 1 and 2. The content of low molecular weight substances in this aromatic polyamide film was 0.5% or less in terms of weight fraction.

Next, the runnability, electromagnetic conversion characteristics and durability of this film were measured and found to be slightly lower than in Example 1, but within the acceptable range.

Comparative Example 1 CMP corresponding to 60 mol% and DPE corresponding to 40 mol% as aromatic diamine components were dissolved in NMP dehydrated to 100 ppm or less, and TPC corresponding to 98.3 mol% was dissolved therein. Add and stir for 2 hours to complete the polymerization.

Thereafter, a thickness of 5 μm is obtained in the same manner as in Example 1.
Was obtained.

The physical properties of this film are shown in Tables 1 and 2. The content of low molecular weight substances in this aromatic polyamide film was 0.5% or less in terms of weight fraction.

Next, the runnability and electromagnetic conversion characteristics of this film were measured and found to be bad. Also, the tape is
It was observed that unilateral stretch occurred in places.

Comparative Example 2 DAM corresponding to 100 mol% as an aromatic diamine component was dissolved in NMP dehydrated to 100 ppm or less, and CTPC corresponding to 98.3 mol% was added thereto, and the mixture was stirred for 2 hours for polymerization. Completed.

Thereafter, a thickness of 5 μm is obtained in the same manner as in Example 1.
Was obtained.

The physical properties of this film are shown in Tables 1 and 2. The content of low molecular weight substances in this aromatic polyamide film was 0.5% or less in terms of weight fraction.

Next, the runnability and electromagnetic conversion characteristics of this film were measured and found to be poor. Also, the elongation and slack of the tape were very large.

Comparative Example 3 Example 1 was repeated except that the polymer solution of Comparative Example 2 was stretched 1.8 times and 1.1 times in the longitudinal direction and the width direction of the film, respectively.
An aromatic polyamide film having a thickness of 5 μm was obtained by the same method as described above.

The physical properties of this film are shown in Tables 1 and 2. The content of low molecular weight substances in this aromatic polyamide film was 0.5% or less in terms of weight fraction.

Next, the runnability and electromagnetic conversion characteristics of this film were measured and found to be bad. Also, the tape is
It was observed that unilateral elongation occurred in places during processing and during each evaluation.

Comparative Example 4 After passing the polymer solution of Example 1 through a filter having a cut of 5 μm, the frequency of surface defects having a diameter of 30 μm or more was 0.0.
The film was cast on a stainless steel belt of 5 pieces / mm ² or less and peeled by hot air at 180 ° C. until the polymer concentration in the film was 50 wt% to evaporate the solvent and obtain self-holding property. The film was continuously stripped from the belt. Then, it was connected to a water bath as a coagulation bath. The proportion of NMP contained in the film at this time exceeded 5 wt% probably because the densification of the surface layer strongly occurred. The film containing this solvent was not stretched in that state, but was stretched and heat-treated after drying. The stretching ratio is 1.2 times and 1.3 times in the longitudinal and width directions of the film, and the thickness is 5
A μm aromatic polyamide film was obtained.

The physical properties of this film are shown in Tables 1 and 2. The content of low molecular weight substances in this aromatic polyamide film was 0.5% or less in terms of weight fraction.

Next, the runnability, electromagnetic conversion characteristics and durability of this film were poor. In particular, when the vehicle was repeatedly run, the elongation was low, so the tape could not withstand the tension applied during stop / start, and the tape was cut off.

[0108]

[Table 1]

[Table 2]

[0109]

INDUSTRIAL APPLICABILITY According to the present invention, by defining the tensile Young's modulus of the aromatic polyamide film and the strength ratio (F1 / F5) in the low elongation region, durability in a severe environment (especially under high temperature and high humidity) The aromatic polyamide film suitable for being used as a magnetic recording medium having excellent properties, running properties and output characteristics was obtained. Further, due to these excellent characteristics, the running property and heat resistance during manufacturing of the magnetic recording medium are improved, and the processing productivity can be improved.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29K 77:00 B29L 7:00

Claims (7)

[Claims] 1. A film comprising an aromatic polyamide as a main component, which has a tensile Young's modulus in at least one direction of 800 kg / mm at 20 ° C. and a relative humidity of 60%.
² or more and 1% of the film in the direction
An aromatic polyamide film, wherein the ratio of the strength F1 at the time of stretching and the strength F5 at the time of 5% stretching satisfies the following formula. F1 / F5 ≧ 0.38 2. The strength at 2% stretching of the film in the direction having a tensile Young's modulus of 800 kg / mm ² or more is F
The aromatic polyamide film according to claim 1, wherein the following formula is satisfied when the number is 2. F2 / F5 ≧ 0.70 3. The strength F5 at 5% stretching of the film in the direction having a tensile Young's modulus of 800 kg / mm ² or more.
Is F5 ≧ 35 kg / mm ² , the aromatic polyamide film according to claim 1 or 2. 4. A molecular weight of the aromatic polyamide of the film is 1
The aromatic polyamide film according to any one of claims 1 to 3, wherein the weight fraction of low molecular weight substances of 000 or less is 0.5% or less. 5. A magnetic recording medium having a magnetic layer formed on at least one surface of the aromatic polyamide film according to any one of claims 1 to 4. 6. The number H2 of coarse surface protrusions on the surface of the aromatic polyamide film on which the magnetic layer is formed and the number H3 of coarse surface protrusions on the surface of the non-magnetic layer are H2 ≦ 50 2 ≦ H3 ≦ The magnetic recording medium according to claim 5, wherein 100 is satisfied. 7. A magnetic tape having a width of 2.3 to 13.0 mm, a support thickness of 6.5 μm or less, a length of 100 m / roll or more, and a recording density as a magnetic recording medium of 8 kilobytes / mm ² or more. 5. The method according to claim 5, wherein
3. The magnetic recording medium according to claim 1.