JPH0931218A - Aromatic polyamide film and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare an aromatic polyamide film which contains basic structural units respectively shoen by the specific formuals, extremely small in the amount of an reduced extract with chloroform such as oligomers and is excellent in heat resistance and mechanical characteristics and useful as a magnetic recording medium due to its smooth surface. SOLUTION: This aromatic polyamide contains ∞50 mole % of basic structural units of formula I (Ar1 and Ar2 are each formula II or like) and 3-30 mole % of basic structural units of formula III [Ar3 and Ar4 are each formula IV or the like (X and Y are O, CH2 , CO, etc.) and the others are formula II] and the extract with chloroform from the polymer is regulated to <=0.5wt.%. When the weight fraction of the aromatic polyamide is regarded as 100, the weight fraction of the substituents in the aromatic ring as S1 and the amide group constituting the main chain of the polyamide as S2, they preferably satisfy the formula: S2/(100-S1)<=0.33.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aromatic polyamide film which has excellent rigidity and heat resistance 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-60-66319.
etc). Japanese Patent Application Laid-Open No. 62-62424 discloses an application example of a film having different Young's moduli in the longitudinal direction and the width direction for the aromatic polyamide. Further, Japanese Patent Application Laid-Open No. 55-41625 discloses a film made of a nuclear chlorine-substituted aromatic polyamide mainly containing para bonds, but it is not necessarily sufficient for a high density magnetic recording medium in terms of rigidity and elongation property. It could not be said.

[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 made of the above polyester film base or aromatic polyamide base has no problem at room temperature and normal humidity, but when used under high temperature and high humidity conditions, the running property and output characteristics are deteriorated. However, there is a problem that dropout occurs during repeated running. It is considered that this is because the heat resistance and moisture resistance of the base film are insufficient, or the surface properties and running properties are insufficient.

The present invention provides an aromatic polyamide having a specific constitution, which is excellent in rigidity and heat resistance, and provides a magnetic recording medium having excellent running properties and output characteristics even under severe conditions such as high temperature and high humidity and repeated running. I found out.

[0006]

That is, according to the present invention, the basic constitutional unit represented by the following general formula (1) is 50 mol% or more, and the basic constitutional unit represented by the following general formula (2) is 3 mol% or more. An aromatic polyamide film containing less than 30 mol%, wherein the chloroform-based extract has a weight fraction of 0.5.
%, Which is an aromatic polyamide film.

The general formula (1)

[Chemical 6] General formula (2)

[Chemical 7] Here, Ar ₁ and Ar ₂ are selected from the group represented by the following general formula (3), and a part of hydrogen atoms of these aromatic rings is a halogen group (especially chlorine), a nitro group, a carbon number of 1 to 3 May be substituted with a substituent such as an alkyl group (especially a methyl group) or an alkoxy group having 1 to 3 carbon atoms.

General formula (3)

Embedded image In the general formula (2), at least one of Ar ₃ and Ar ₄ is selected from the group represented by the following general formula (4), and the other Ar ₃ or Ar ₄ is represented by the general formula (3). Selected from the group

General formula (4)

Embedded image Here, X, Y is _{-O -, - CH 2 -,} - CO -, - C
_{O 2 -, - C (CH} 3) 2 -, - C (CF 3) 2 -,
9,9-fluorenyl _{group, -S -, - SO 2 -} , - Si
Selected from (CH ₃ ) _2-, etc., and some of the hydrogen atoms of these aromatic rings are a halogen group (especially chlorine), a nitro group, an alkyl group having 1 to 3 carbon atoms (especially a methyl group), a carbon number of 1 ~ 3
It may be substituted by a substituent such as the alkoxy group.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION From the viewpoint of characteristics, the aromatic polyamide used in the present invention contains the basic structural unit represented by the general formula (1) in an amount of 50 mol% or more, preferably 70 mol%, of the whole.
It is a polymer occupying the above. That is, the basic constitutional unit represented by the general formula (1) is 50 mol% in the polymer.
For the first time, the rigidity and heat resistance are sufficient. When it is less than 50 mol%, the strength and rigidity are poor and a thin film suitable for a magnetic recording medium cannot be obtained. In addition, the heat shrinkability is also poor. Furthermore, an aromatic ring in which a part of the hydrogen atoms of the aromatic ring is substituted with a halogen group (especially chlorine), a nitro group, an alkyl group having 1 to 3 carbon atoms (especially a methyl group), an alkoxy group having 1 to 3 carbon atoms, or the like. When the group ring content is 30 mol% or more, preferably 50 mol% or more, and more preferably 70 mol% or more, the humidity characteristics are improved, and the characteristics such as dimensional change due to moisture absorption are improved, and the organic solvent is used. It is preferable because the solubility and the film-forming property are improved.

Further, in the aromatic polyamide used in the present invention, the basic constitutional unit represented by the general formula (2) is a polymer.
3 to 30 mol%, more preferably 5 to 20 mol%.
Must be included. Within this range, a film having excellent stretching properties and excellent rigidity and flexibility can be obtained. If it is less than 3 mol%, the physical properties of the film and the process both sides are poorly balanced, and the stability of the solution is insufficient. Furthermore, it becomes a hard and brittle film. Further, if the content exceeds 30 mol%, a flexible film can be obtained, but sufficient rigidity cannot be obtained, which is unsuitable for the present invention.

In the aromatic polyamide film of the present invention, the weight fraction of the extract with chloroform is 0.5% or less. It is more preferably 0.3% or less, still more preferably 0.
2% or less. For example, when the weight fraction of the extract of chloroform such as oligomers exceeds 0.5%, the surface becomes sticky and is easily wrapped around a roll or the like, or the environment after the formation of the magnetic layer changes. The components exude and the magnetic layer peels off.

Further, the weight fraction of the aromatic polyamide used in the present invention is 100, the weight fraction of the substituents of the aromatic ring is S1, and the weight fraction of the amide group constituting the main chain of the aromatic polyamide is S2. Then, it is preferable to satisfy S2 / (100−S1) ≦ 0.33. More preferably S2 / (10
0−S1) ≦ 0.30, more preferably S2 / (100
-S1) ≦ 0.27 is preferable because the solubility in an organic solvent is high and a film without devitrification or void formation can be obtained. Further, the film forming property and the moisture absorption rate of the film are also improved. Such methods include biphenyl, diphenyl ether, diphenylmethane, diphenyl sulfide,
Examples thereof include a method using a diamine component or a dicarboxylic acid component having a structure having a divalent bulky aromatic ring that can be derived from diphenyl sulfone, naphthalene, anthracene, or the like. Of course, a substituent may be introduced into these aromatic rings.

The basic constitutional unit of the aromatic polyamide represented by the general formula (2) has a bent chain structure in the molecule.
As described above, introduction of a bent chain is effective in improving elongation, but excessive introduction results in deterioration of rigidity. However, surprisingly, when the same mole of a monomer containing a plurality of bending chains coaxially with the main chain is used as a monomer having only one, the rigidity decreases despite the increase of the bending component in the main chain. It was found that the elongation property can be suppressed and the elongation property can be improved. Such compounds include 1,4-bis (4-aminophenoxy)
Benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) biphenyl, 2,2-bis [4- Examples thereof include (4-aminophenoxy)] propane and bis [4- (4-aminophenoxy) phenyl] sulfone, but 1,3-bis (4-aminophenoxy) has excellent heat resistance and mechanical properties.
It is preferable to use benzene or 1,3-bis (3-aminophenoxy) benzene.

The aromatic polyamide of the present invention contains 50 mol% or more of the repeating unit represented by the general formula (1),
And containing 3 mol% or more and less than 30 mol% of the repeating unit represented by the general formula (2), the other components are other repeating units such as aromatic polyimide units and other aromatic polyamide units. May be copolymerized or blended.

The aromatic polyamide film of the present invention is usually formed by the solution casting method described below. At this time, the polymerization stock solution is preferably used as it is or as a film-forming stock solution by adding a dissolution aid such as an inorganic salt to form a film from an organic solvent-based solution. Generally, aromatic polyamide can be dissolved in strong acids such as sulfuric acid and trifluoromethanesulfonic acid, but when it is possible to form a film from an organic solvent-based solution, the selection range of cast materials such as belts and drums is wide. Thus, it becomes possible to preferably use, for example, a stainless belt (which can be preferably subjected to anticorrosion treatment) or the like, which has a high processing accuracy and a low frequency of surface defects. Further, it is suitable for film formation by a dry-wet method that can obtain excellent surface characteristics, and can obtain a surface shape suitable for the magnetic recording medium of the present invention. On the other hand, polymers with poor solubility in organic solvents have strong restrictions on the solvent used such as sulfuric acid and trifluoromethanesulfonic acid, and in this case, the castable material does not always have sufficient processing accuracy and the film-forming process for desolvation. Due to the above limitation, it is difficult to obtain a surface shape suitable for a magnetic recording medium as described later. Further, it is difficult to form a thin film, and it is not suitable for a high density magnetic recording medium.

The present invention is suitable for use as a magnetic recording medium by providing a magnetic layer on at least one side of the aromatic polyamide film.

As a method for forming the magnetic layer, there are a dry method such as a wet method in which a ferromagnetic powder is used as a magnetic paint by using various binders and coated on a base film, a vapor deposition method, a sputtering method, an ion plating method and the like. Although not particularly limited, a wet method will be described here as an example.

The type of magnetic powder used as 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. As the binder, a binder made of vinyl chloride / vinyl acetate / vinyl alcohol copolymer, polyurethane prepolymer and polyisocyanate is used. -, A thermosetting resin-based binder, and a radiation-curable resin-based binder can be used. In addition, a dispersant, a lubricant, an antistatic agent, or the like may be used as an additive.

In order for the magnetic recording medium of the present invention to have an appropriate roughness, it is preferable that particles are present in the base film. The types of particles include SiO ₂ , Ti
O ₂ , Al ₂ O ₃ , CaSO ₄ , BaSO ₄ , CaCO
₃ , carbon black, inorganic particles such as carbon black, zeolite, and other fine metal powders, silicone particles, polyimide particles, cross-linked copolymer particles, cross-linked polyester particles, Teflon particles and the like organic polymers. From the viewpoint of heat resistance, inorganic particles are more preferable. Furthermore, the average primary particle size of the particles contained in the film of the present invention is 0.005 to 5 μm.
m, preferably 0.01 to 2 μm, is desirable because both electromagnetic conversion characteristics and running properties are good. The content of the particles contained in the base film of the magnetic recording medium of the present invention is 0.01 to 5 wt%, preferably 0.05 to 3 w.
t%. 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. Further, not only the base film of the magnetic recording medium of the present invention but also a single layer film may be used, but a laminated film may be used. The base film of the magnetic recording medium of the present invention laminated here and the base layer portion (film constituting portion other than the laminated base film of the present invention) may be the same kind or different. Particles may be contained in at least one layer constituting the base layer portion, and the kind of particles, the average primary particle diameter of the particles, and the content are those which are preferably used in the film of the present invention. When the diameter of the particles in the base layer portion is larger than the diameter of the particles in the laminated base material film of the present invention, it is possible to impart an appropriate waviness to the base material film surface and further improve tape running property. Therefore, it is preferable.

In the magnetic recording medium of the present invention, the number H of coarse surface projections on the surface of the base film on which the magnetic layer is formed is H.
2 (pieces / 100 cm ² ) preferably satisfies 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 becomes unsuitable as a high-density magnetic recording medium.

In the magnetic recording medium of the present invention, it is preferable that the number H3 of coarse surface protrusions (number / 100 cm ² ) on the surface of the non-magnetic layer side of the base film is 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 deteriorates. Also H3> 1
If it is 00, the coarse protrusions may affect the surface properties on the magnetic layer side during calendering in the coating step, causing dropout, which is not preferable.

The surface roughness (cutoff value: 0..0) of one surface (A surface) of the substrate film in the magnetic recording medium of the present invention.
08 mm) is the center line surface roughness, RaA = 0.010 μm
It is preferably less than. Here, when the surface A is a magnetic surface, it is preferably a smooth surface in order to improve electromagnetic conversion characteristics. That is, the surface roughness of surface A is RaA = 0.0.
If it is 10 μm or more, the output is lowered, which is not preferable. RaA is preferably less than 0.008 μm, more preferably RaA is less than 0.006 μm. Further, the surface roughness of the B side is the center line surface roughness, RaB
It is preferably less than 0.020 μm. Where B
Since the surface is a running surface, it is preferably a rough surface,
When RaB = 0.020 μm or more, when the base film is rolled or when a magnetic material is provided to make a roll, a recess is formed on the magnetic surface side to cause a reduction in output. Therefore, it is not preferable. More preferably RaB = 0.0
05-0.020 μm, more preferably RaB = 0.
It is in the range of 006 to 0.015 μm.

The thickness of the base film in the magnetic recording medium of the present invention is preferably 0.5 to 50 μm, more preferably 1 to 20 μm, and further preferably 2 to 10 μm. It is desirable because excellent running performance and electromagnetic conversion characteristics that are the effects are realized.

The Young's modulus of the substrate film in the magnetic recording medium of the present invention is preferably 800 kg / mm ² or more in at least one of the longitudinal direction and the width direction. If the Young's modulus is lower than 800 kg / mm ² , stable running properties cannot be obtained and the output also decreases, which is not preferable.
The Young's modulus is more preferably 1000 kg / mm ² or more, and further preferably 1300 kg / mm ² or more.

The elongation of the substrate film in the magnetic recording medium of the present invention is preferably 10% or more, more preferably 20% or more, further preferably 30% or more because the tape has appropriate flexibility.

When the moisture absorption rate of the substrate film in the magnetic recording medium of the present invention is 5% or less, more preferably 3% or less, further preferably 2% or less, the dimensional change of the tape due to humidity change is small and good. It is desirable because it can maintain excellent electromagnetic conversion characteristics.

The heat shrinkage ratio of the base film in the magnetic recording medium of the present invention at 200 ° C. for 10 minutes is preferably 0.5% or less, more preferably 0.3% or less. It is desirable because the dimensional change of the 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.

Next, a method for producing the aromatic polyamide film of the present invention will be described, but the present invention is not limited to this.

First, a method for obtaining an aromatic polyamide includes solution polymerization, interfacial polymerization, solid phase polymerization, etc.
It is synthesized by solution polymerization in an aprotic organic polar solvent such as -methylpyrrolidone (NMP), N, N-dimethylacetamide (DMAc), N, N-dimethylformamide (DMF). Further, there are a method of synthesizing diacid halide and diamine, a method of dicarboxylic acid and diisocyanate, a method of adding a polycondensation agent to dicarboxylic acid and diamine, and the like. However, the method of synthesizing diacid halide and diamine has a high degree of polymerization. It is the most preferable from the viewpoints of productivity and reproducibility. The order of adding the monomers is not particularly limited, but it is preferable to add the diacid halide to the diamine solution because a high polymer can be obtained. Further, calcium chloride, magnesium chloride, lithium chloride, lithium bromide, lithium nitrate, or the like may be added as a dissolution aid. However, in order to reduce the amount of chloroform extract such as oligomers, the water content of these solvents is preferably 100 ppm or less, and the molar ratio of acid chloride and diamine is 97-99% of the other,
It is more preferably adjusted to 98 to 98.5%.

When the hydrogen chloride generated after the polymerization is neutralized, an inorganic neutralizing agent such as calcium hydroxide, calcium carbonate or lithium carbonate, ethylene oxide, propylene oxide, ammonia, triethylamine,
Organic neutralizing agents such as triethanolamine and diethylanol are used. However, it is desirable to use those neutralizing agents in which the salt produced by neutralization is soluble in the solvent.
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 to preferably block the ends of the polymer.

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.

These polymer solutions may be prepared by once isolating the polymer and then re-dissolving it in the above-mentioned organic solvent or an inorganic solvent such as sulfuric acid to prepare a film-forming stock solution. It can also be preferably used.

Inorganic salts such as calcium chloride, magnesium chloride, lithium chloride, lithium bromide and lithium nitrate may be added to the stock solution for film formation as a dissolution aid. The polymer concentration in the stock solution for film formation is preferably about 2 to 40 wt%.

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. There is no particular limitation.

The stock solution for film formation prepared as described above can be formed into a film by a so-called solution film forming method. The solution film-forming method may be a dry-wet method, a dry method, a wet method, or the like, and the film may be formed by any method. 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 until the thin film has a self-holding property. dry. Room temperature ~
220 ° C, within a range of 60 minutes, preferably room temperature to
It is in the range of 200 ° C. If the drying temperature exceeds 220 ° C., the coarse surface protrusions H2 may increase, which is not preferable. Further, it is desirable that surface defects of the drum and the endless belt used in this drying step be small because they may cause coarse protrusions that deteriorate the electromagnetic conversion characteristics.

Next, the film which has undergone the dry process is peeled from the support, introduced into the wet process, desalted, desolvated and the like, and further stretched, dried and heat treated to form a film.

The film formed as described above is stretched in the film-forming process, and the stretching ratio is 0.8 to 8.0 in terms of areal ratio (the areal ratio means the stretched film area after stretching). It is defined as a value divided by the area of the previous film. A value of 1 or less means relaxation.), And more preferably 1.1 to 5.0. It is also effective to gradually cool the film after stretching or heat treatment,
Cooling at a rate of 50 ° C / sec or less is effective.

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, and different particles are added, respectively, and then laminated. The same applies to the case of three or more layers. As a laminating method, there are known methods such as laminating in a die, laminating in a composite tube, and a method in which one layer is once formed and then another layer is formed thereon.

Next, when the magnetic layer is formed by a wet method, a magnetic paint is applied to the 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 this, 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 this magnetic layer is cured and then slit to obtain the magnetic recording medium of the present invention.

[0046]

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

(1) Tensile Young's Modulus Tensilon tensile tester type UTM-III type (manufactured by Tokyo Sokki Co., Ltd.) was used for measurement. The test piece was measured with a width of 10 mm and a length of 50 mm, a pulling speed of 300 mm / min, 20 ° C. and a relative humidity of 60%.

(2) Strength and Elongation It was calculated by the following formula according to JIS Z-1702 using the above tensile tester. The test piece has a width of 10 mm and a test length of 50 mm. Strength = (maximum stress value) / (thickness x test width) (kg / mm
² ) Elongation = (elongation) x 100 / (test length) (%)

(3) Moisture Absorption Rate The film was dried at 200 ° C. for 1 hour, and the weight in an absolutely dried state was W0. 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.

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

[0051]

[Equation 1] (5) Weight Fraction of Extract with Chloroform A film having a weight of 1.5 g was cut and placed in a flask equipped with a cooling tube, and 30 mL of purified chloroform was put therein.
Is added and heat extraction is performed for 24 hours. Next, this liquid was transferred to a rotary evaporator, concentrated while adjusting the degree of vacuum to a constant weight, and the weight W1 (g) of the residue was measured. W1 / 1.5 was multiplied by 100. The weight fraction of the extract was expressed by the value.

(6) Number of rough surface projections (H2, H3) Foreign matter is observed and marked under a polarized light in a range of 100 cm ² of the film surface with 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.

(7) Runnability A slit runnable film having a width of 1/2 inch was used as a tape runnability tester SFT-700 (manufactured by Yokohama System Laboratory Co., Ltd.). The friction coefficient at the 50th pass was determined by the following equation after running in an atmosphere of 40 ° C. and 80% RH.

ΜK = 0.733 log (T2 / T1) Here, T1 is the inlet tension and T2 is the outlet tension. The guide diameter is 6 mmφ, and the guide material is polyoxymethylene (with a surface roughness of about 20 to 40 nm).
The angle is 0 °, the running speed is 3.3 cm / sec, and the repeating stroke is 15 cm. First measurement μ measured by this method
K (1) and the 100th measured value μK (100)

[Equation 2] When the above formula was satisfied, the runnability was evaluated as O, and when the above formula was not satisfied, the runnability was evaluated as X. If the above formula is not satisfied, the handleability in processing magnetic recording media, capacitors, packaging and the like will be poor.

(8) 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. An NV-3700 type video deck manufactured by Matsushita Electric Co., Ltd. was used to record a 4.4 MHz signal at a constant speed on this tape, and a 15 μsec-20 dB dropout during reproduction was manufactured by Okura Industry Co., Ltd. The measurement was carried out for 20 minutes with a drop counter, and the average value (pieces / minute) per minute was calculated. The electromagnetic conversion characteristics were determined to be good when the number of dropouts obtained by this measurement was 1.0 (pieces / minute) or less. This value is necessary for a general magnetic recording medium, and is preferably 0.5 (pieces / minute) or less for a high density magnetic recording medium.

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 terephthaloyl chloride, IPC is isophthalic acid chloride, and CTPC is 2-
Chlorterephthalic acid chloride, TO is o-tolidine, D
A is o-dianisidine, PA is paraphenylenediamine, CPA is 2-chloroparaphenylenediamine, 2,
6-NDC is 2,6-naphthalenedicarboxylic acid chloride, TPE-Q is 1,4-bis (4-aminophenoxy) benzene, TPE-R is 1,3-bis (4-aminophenoxy) benzene, TPE-M. Is 1,3-bis (3
-Aminophenoxy) benzene.

Example 1 CPA corresponding to 85 mol% as an aromatic diamine component and TPE-Q corresponding to 15 mol% were dissolved in NMP dehydrated to 100 ppm or less, and CTPC corresponding to 98.3% was dissolved therein. Was added and stirred for 2 hours to complete the polymerization. This is neutralized with lithium carbonate to give a polymer concentration of 10
A wt% aromatic polyamide solution was obtained.

To this solution, 2 wt% of dry silica having a primary particle size of 16 nm was added per polymer. This polymer solution was passed through a 5 μm-cut filter, cast on a stainless steel belt, heated with hot air at 180 ° C. for 5 minutes to evaporate the solvent, and a film having self-holding property was continuously formed from the belt. Peeled off. Next, the film was introduced into a water tank having a concentration gradient of NMP to extract the residual solvent and the inorganic salt produced by the neutralization with water, and the water was dried and heat-treated with a tenter to obtain a thickness of 6.0 μm. An aromatic polyamide film was obtained. In the meantime, 1.2 each in the longitudinal and width directions of the film.
The film was stretched twice and 1.3 times, dried at 280 ° C. for 1.5 minutes and heat-treated, and then slowly cooled at a rate of 20 ° C./sec.

The number H2 of coarse surface protrusions on the belt non-contact surface of this film was 20/100 cm ² , and the number H3 of coarse surface protrusions on the belt contact surface was 40/100 cm ² . The tensile Young's modulus is 1230, 1250 kg / mm ² , strength 43, 4 in the longitudinal direction and the width direction, respectively.
5 kg / mm ² , elongation 42, 40%, moisture absorption rate 1.4%,
The heat shrinkage rate was 0.3%. The weight fraction of the extract with chloroform was 0.15%.

Next, the running property of the film was measured and it was good. The number of dropouts is 0.3 (pieces / minute)
And the electromagnetic conversion characteristics were also good.

Example 2 TO corresponding to 85 mol% as an aromatic diamine component and TPE-R corresponding to 15 mol% were dissolved in NMP dehydrated to 100 ppm or less, and 98.3 mol% was dissolved therein.
Was added and the mixture was stirred for 2 hours to complete the polymerization. This was neutralized with lithium carbonate to obtain an aromatic polyamide solution having a polymer concentration of 10% by weight.

Thereafter, the thickness is 6.0 in the same manner as in the first embodiment.
A μm aromatic polyamide film was obtained.

The number H2 of coarse surface protrusions on the belt non-contact surface of this film was 25/100 cm ² , and the number H3 of coarse surface protrusions on the belt contact surface was 50/100 cm ² . The Young's modulus is 1250, 1300 kg / mm ² , strength 36, 40 kg in the longitudinal and width directions, respectively.
/ Mm ² , elongation 53, 52%, moisture absorption rate 1.5%, heat shrinkage rate 0.3%. The chloroform extract had a weight fraction of 0.18%.

Next, the running property of the film was measured and found to be good. The number of dropouts is 0.2 (pieces / minute)
And the electromagnetic conversion characteristics were also good.

Example 3 CPA corresponding to 85 mol% and TPE-Q corresponding to 15 mol% as an aromatic diamine component were dissolved in NMP dehydrated to 100 ppm or less, and 98.3 mol% was dissolved therein.
2,6-NDC corresponding to was added and stirred for 2 hours to complete the polymerization. This was neutralized with lithium carbonate to obtain an aromatic polyamide solution having a polymer concentration of 10% by weight.

An aromatic polyamide film having a thickness of 4.5 μm was obtained in the same manner as in Example 1 except that the stretching ratio was 1.4 times and 1.5 times in the longitudinal direction and the width direction of the film, respectively.

The number H2 of coarse surface protrusions on the belt non-contact surface of this film was 15/100 cm ² , and the number H3 of coarse surface protrusions on the belt contact surface was 25/100 cm ² . The Young's modulus is 1420, 1440 kg / mm ² , strength 52, 52 kg in the longitudinal and width directions, respectively.
/ Mm ² , elongation was 32, 30%, moisture absorption was 1.5%, and heat shrinkage was 0.3%. The weight fraction of the extract with chloroform was 0.21%.

Next, the running property of the film was measured and found to be good. The number of dropouts is 0.3 (pieces / minute)
And the electromagnetic conversion characteristics were also good.

Example 4 In NMP dehydrated to 100 ppm or less, DA corresponding to 85 mol% and TPE-M corresponding to 15 mol% as an aromatic diamine component were dissolved, and CTPC corresponding to 98.5 mol% was dissolved in the solution. Was added and stirred for 2 hours to complete the polymerization. This is neutralized with lithium carbonate to give a polymer concentration of 10
A wt% aromatic polyamide solution was obtained.

Thereafter, a thickness of 4.5 is obtained in the same manner as in Example 3.
A μm aromatic polyamide film was obtained.

The number H2 of coarse surface protrusions on the belt non-contact surface of this film was 15/100 cm ² , and the number H3 of coarse surface protrusions on the belt contact surface was 30/100 cm ² . The Young's modulus is 1390, 1430 kg / mm ² , strength 49, 51 kg in the longitudinal and width directions, respectively.
/ Mm ² , elongation 28, 27%, moisture absorption was 1.3%. Furthermore, the heat shrinkage ratio was 0.3%. The weight fraction of the extract with chloroform was 0.17%.

Next, the running property of the film was measured and found to be good. The number of dropouts is 0.3 (pieces / minute)
And the electromagnetic conversion characteristics were also good.

Comparative Example 1 TO corresponding to 70 mol% as an aromatic diamine component, PA corresponding to 30 mol% and lithium bromide as a dissolution aid were dissolved in NMP dehydrated to 100 ppm or less,
When IPC corresponding to 10 mol% and TPC corresponding to 88.3% were added thereto, the mixture was stirred for 2 hours to complete the polymerization. This is neutralized with lithium carbonate to give a polymer concentration of 10
A wt% aromatic polyamide solution was obtained.

To this solution, 2 wt% of dry silica having a primary particle diameter of 16 nm was added per polymer. After passing this polymer solution through a filter of 5 μm cut, it was cast on a stainless steel belt and heated with 180 ° C. hot air for 10 minutes to evaporate the solvent and self-hold because there are many added salts and the drying speed is slow. The film having good properties was continuously peeled off from the belt. Next, the film is introduced into a water tank having a concentration gradient of NMP to extract the residual solvent and the inorganic salt generated by the neutralization with water, and the water is dried and heat-treated with a tenter to obtain a thickness of 6.
A 0 μm aromatic polyamide film was obtained. During this period, the film was stretched 1.2 times and 1.3 times in the width direction and dried at 280 ° C. for 1.5 minutes and heat-treated, and then slowly cooled at a rate of 20 ° C./sec.

The number H2 of coarse surface protrusions on the belt non-contact surface of this film was 30/100 cm ² , and the number H3 of coarse surface protrusions on the belt contact surface was 45/100 cm ² . The Young's modulus is 12 in both the longitudinal and width directions.
20 kg / mm ² , moisture absorption rate 2.0%, heat shrinkage rate 0.3%
Met. However, the strength was 30, 32 kg / mm ² in the longitudinal direction and the width direction, respectively, and the elongation was 5% or less, and the film was hard and brittle. The chloroform extract had a weight fraction of 0.18%.

When the film was slit to measure the running property of the film and the electromagnetic conversion characteristics, the film was torn and the measurement could not be performed.

COMPARATIVE EXAMPLE 2 CMP corresponding to 50 mol% as an aromatic diamine component and TPE-M corresponding to 50 mol% were dissolved in NMP dehydrated to 100 ppm or less, and corresponding to 98.3 mol%. Was added and stirred for 2 hours to complete the polymerization. This was neutralized with lithium carbonate to obtain an aromatic polyamide solution having a polymer concentration of 10% by weight.

Thereafter, a thickness of 6.0 is obtained in the same manner as in Example 1.
A μm aromatic polyamide film was obtained.

The number H2 of coarse surface protrusions on the belt non-contact surface of this film was 20/100 cm ² , and the number H3 of coarse surface protrusions on the belt contact surface was 40/100 cm ² . The Young's modulus of this film is 580 and 620 kg / mm ² in the longitudinal direction and the width direction, respectively, and the strength is 1.
9, 20 kg / mm ² , elongation 65, 60%, moisture absorption 2.
It was 1% and the heat shrinkage rate was 0.4%. The weight fraction of the extract with chloroform was 0.17%.

Next, the running property of the film was measured and found to be good, but after the test, the deformation due to the elongation of the film was large. The number of dropouts is 1.5 (pieces / minute)
And the electromagnetic conversion characteristics were a little inferior.

Comparative Example 3 CMP corresponding to 85 mol% as an aromatic diamine component and TPE-Q corresponding to 15 mol% were dissolved in NMP having a water content of 400 ppm, and CTPC corresponding to 98.3% was dissolved therein. Was added and stirred for 2 hours to complete the polymerization.
This was neutralized with lithium carbonate to obtain an aromatic polyamide solution having a polymer concentration of 10% by weight.

Thereafter, a thickness of 6.0 is obtained by the same method as in the first embodiment.
A μm aromatic polyamide film was obtained.

The number H2 of coarse surface protrusions on the belt non-contact surface of this film was 55/100 cm ² , and the number H3 of coarse surface protrusions on the belt contact surface was 50/100 cm ² . The Young's modulus of this film is 620 and 660 kg / mm ² in the longitudinal direction and the width direction, respectively, and the strength is 1.
7, 18 kg / mm ² , elongation 19, 18%, moisture absorption rate 1.
It was 7% and the heat shrinkage rate was 0.5%. The weight fraction of the extract with chloroform was 2.11%.

Next, the running property of the film was measured and found to be bad. The number of dropouts is 1.3 (pieces /
Min) and electromagnetic conversion characteristics were also poor.

Comparative Example 4 In NMP dehydrated to 100 ppm or less, PA corresponding to 100 mol% as an aromatic diamine component and lithium chloride as a dissolution aid were dissolved, and TPC corresponding to 98.3 mol% was added thereto. Polymerization was carried out. After washing the produced polymer with warm water, the polymer concentration was adjusted to 109.7% with sulfuric acid and the polymer concentration was 10%.
It was dissolved at a weight percentage 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. This polymer solution was passed through a 5 μm-cut filter, cast on a tantalum belt kept at 110 ° C., kept at 20 ° C. in an atmosphere of 68% relative humidity for 40 seconds, and then introduced into a water tank. It solidified and was continuously formed into a film. Next, moisture was dried and heat treatment was performed with a tenter to obtain an aromatic polyamide film having a thickness of 6.0 μm. In the meantime, the film was stretched 1.2 times in both the longitudinal direction and the width direction, and was drawn at 280 ° C for 1.5
After drying for one minute and heat treatment, it was gradually cooled at a rate of 20 ° C./sec.

The number H2 of coarse surface protrusions on the belt non-contact surface of this film was 75/100 cm ² , and the number H3 of coarse surface protrusions on the belt contact surface was 65/100 cm ² . The Young's modulus of this film was 1450 kg / mm ^{2 in} both the longitudinal and width directions, and the strength was 44 and 45 kg.
/ Mm ² , elongation was 20%, moisture absorption was 2.9%, and heat shrinkage was 0.0%. The weight fraction of the extract with chloroform was 0.12%.

Next, the running property of the film was measured and found to be bad. The number of dropouts is 2.4 (pieces /
Min) and electromagnetic conversion characteristics were also poor.

[0090]

[Table 1]

[Table 2]

[0091]

As is apparent from the above, the aromatic polyamide film according to the present invention is excellent in heat resistance and mechanical properties and has a smooth surface. Also, the oligomer
Very little extract with chloroform. For this reason, durability under severe environment (especially under high temperature and high humidity),
It is suitably used as a magnetic recording medium having excellent running properties and output characteristics, and due to these excellent properties, running properties and heat resistance at the time of manufacturing a magnetic recording medium are improved, and processing productivity can be improved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location G11B 5/704 G11B 5/704 // B29K 77:00 B29L 7:00 C08L 77:00

Claims (5)

[Claims] 1. An aromatic polyamide film containing 50 mol% or more of the basic structural unit represented by the following general formula (1) and 3 mol% or more and less than 30 mol% of the basic structural unit represented by the following general formula (2). An aromatic polyamide film, wherein the weight fraction of the extract with chloroform is 0.5% or less. General formula (1) General formula (2) Here, Ar ₁ and Ar ₂ are selected from the group represented by the following general formula (3), and a part of hydrogen atoms of these aromatic rings is a halogen group (especially chlorine), a nitro group, a carbon number of 1 to 3 May be substituted with a substituent such as an alkyl group (especially a methyl group) or an alkoxy group having 1 to 3 carbon atoms. General formula (3) In the general formula (2), at least one of Ar ₃ and Ar ₄ is selected from the group represented by the following general formula (4), and the other Ar ₃ or Ar ₄ is represented by the general formula (3). Selected from the group General formula (4) Here, X, Y is _{-O -, - CH 2 -,} - CO -, - C
_{O 2 -, - C (CH} 3) 2 -, - C (CF 3) 2 -,
9,9-fluorenyl _{group, -S -, - SO 2 -} , - Si
Selected from (CH ₃ ) _2-, etc., and some of the hydrogen atoms of these aromatic rings are a halogen group (especially chlorine), a nitro group, an alkyl group having 1 to 3 carbon atoms (especially a methyl group), a carbon number of 1 ~ 3
It may be substituted by a substituent such as the alkoxy group. 2. When the weight fraction of the aromatic polyamide is 100, the weight fraction of the substituent of the aromatic ring is S1, and the weight fraction of the amide group constituting the main chain of the aromatic polyamide is S2. The aromatic polyamide film according to claim 1, which satisfies the following formula: S2 / (100-S1) ≦ 0.33 3. Ar ₃ in the general formula (2), which is a basic constitutional unit of the aromatic polyamide, is represented by the general formula (5), the general formula (5): The aromatic polyamide film according to claim 1, which is selected from any of the structures shown in. 4. The aromatic polyamide film according to claim 1, which is obtained from an organic solvent-based solution of the aromatic polyamide. 5. The magnetic recording medium according to claim 1, wherein a magnetic layer is provided on at least one surface of the aromatic polyamide film.