JPH08281818A - Aromatic polyamide film - Google Patents

Abstract

PURPOSE: To provide a film which has satisfactory heat resistance, runnability and cutting resistance and excellent electromagnetic transforming characteristics. CONSTITUTION: An aromatic polyamide film contains aromatic polyamide as a main ingredient, 0.05 to 5wt.% of coherent particles in which the mean coherent particle size of the particle is 5 to 1000nm and the ellipticity of the particle is 0.7 or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium.

[0002]

2. Description of the Related Art Aromatic polyamide films have been investigated for various applications by taking advantage of their excellent heat resistance and mechanical properties. In particular, para-oriented aromatic polyamide is superior to other polymers in mechanical properties such as rigidity and strength, so it is very advantageous for thinning film, and is expected to be used in printer ribbons, magnetic tapes, capacitors, etc. ing. For example, in the case of magnetic recording media, JP-A-58-168655 and JP-A-62.
ー 112218, etc.

[0003]

In recent years, due to an increase in the use of video cameras outdoors, a demand for miniaturization and a long recording time, and for use as an external memory of a computer, they are thin and harsh. There is an increasing demand for magnetic recording media having excellent durability under the conditions.

However, the above-mentioned magnetic recording medium composed of a polyester film base or an aromatic polyamide base has no problem at room temperature, but when used under high temperature conditions, running properties and output characteristics are deteriorated, and dropout occurs after repeated running. There is a problem that occurs. It is considered that this is because the heat resistance of the base film is insufficient, or the surface properties and running properties are insufficient.

The present invention solves the above problems, utilizes the excellent heat resistance and high rigidity of aromatic polyamide, and regulates the particle diameter ratio of particles and the flatness ratio of particles, so that it is difficult to run repeatedly at high temperatures. It is an object of the present invention to provide a magnetic recording medium having excellent running properties, durability and output characteristics even under conditions.

[0006]

According to the present invention, in a film containing an aromatic polyamide as a main component, the film contains 0.05 to 5% by weight of aggregated particles, and the average aggregated particle size of the aggregated particles is 5%. The present invention relates to an aromatic polyamide film, wherein the agglomerated particles have a flatness of 0.7 or more and 1000 nm or less.

The aromatic polyamide of the present invention is preferably one containing 50 mol% or more of repeating units represented by the following general formula (I) and / or general formula (II), and one containing 70 mol% or more. More preferable.

General formula (I)

Embedded image General formula (II)

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

Embedded image And the like, X and Y are —O—, —CH ₂ —, —CO—, —SO ₂ —, —S—,
-C (CH _{3) 2} - is chosen from such, but is not limited thereto. Further, a part of hydrogen atoms on these aromatic rings is a substituent such as a halogen group (especially chlorine), a nitro group, a C ₁ -C ₃ alkyl group (especially a methyl group), a C ₁ -C ₃ alkoxy group 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 above-mentioned aromatic ring bonded in the para position is 50% or more, preferably 75% or more of the total aromatic ring.
%, A polymer having a high rigidity and a good heat resistance is preferable. Further, from the viewpoint of reducing the moisture absorption, a polymer in which a part of hydrogen atoms on the aromatic ring is substituted with a halogen group (particularly chlorine) and the aromatic ring is 30% or more of the whole is preferable.

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, and 50 mol% or more.
If it is less than the above, other repeating units may be copolymerized (for example, aromatic polyimide etc.) or blended, and conductive particles, lubricants, antioxidants and other additives, etc., to the extent that the physical properties of the film are not impaired. May be blended.

In the magnetic recording medium of the present invention, it is necessary for the base film to contain 0.05 to 5 wt% of aggregated particles A. Preferably 0.1 to 4 wt%, more preferably 0.1.
2-3 wt%. If the addition amount is less than 0.05 wt%, the running property when taped becomes poor, and conversely 5 wt%
If it exceeds%, the electromagnetic conversion characteristics deteriorate.

The average agglomerated particle diameter of the agglomerated particles contained in the film constituting the present invention is 5 to 1000 nm, more preferably 10 to 600 nm, still more preferably 20 to 300 nm.
When it is in the range of nm, both electromagnetic conversion characteristics and running properties are good.

When the flatness of the agglomerated particles contained in the film constituting the present invention is 0.7 or more, preferably 1 to 7, more preferably 1.5 to 5, both the electromagnetic conversion characteristics and the running property are improved. It will be good.

Of the agglomerated particles contained in the film constituting the present invention, 10% or less, more preferably 5% or less, of particles having voids (so-called voids) between them and the polymer used for the base film. , The abrasion resistance of the tape becomes good.

The types of the agglomerated particles are SiO ₂ , T
iO ₂ , Al ₂ O ₃ , CaSO ₄ , BaSO ₄ , CaC
Inorganic particles such as O ₃ , carbon black, zeolite, and other fine metal powder, silicone particles, polyimide particles,
Although there are organic polymers such as polyamide particles, crosslinked polymer particles, crosslinked polyester particles, and Teflon particles, inorganic particles are more preferable from the viewpoint of heat resistance.

1 m in the longitudinal direction of the film constituting the present invention
100 ° C when a load of 1 kg per m ² is applied, 10
The dimensional change rate per minute is preferably 2% or less. It is more preferably at most 1.5%, further preferably at most 1.0%. Since the magnetic recording medium of the present invention is often used as a thin film in response to a demand for thinning of the magnetic recording medium, if the dimensional change rate is more than 2%, the tape may run during running or stop when used at high temperature. / The tension at the start causes expansion and contraction of the tape, thereby deteriorating the recording and reproducing properties. In addition, the base film has high dimensional stability (2% or less)
Since the dimensional change of the tape can be suppressed in the drying step after forming the coating layer, it is advantageous in processing.

In order for the magnetic recording medium of the present invention to have an appropriate roughness, it is preferable that spherical particles in which primary particles are not aggregated be present in the base film. As the type of particles, substantially spherical silica particles derived from colloidal silica, particles of a crosslinked polymer (for example, crosslinked polystyrene), and the like are preferable. Further, other particles, for example, particles of calcium carbonate, titanium dioxide, alumina or the like may be used.

The film of the present invention is provided with a magnetic layer on at least one surface thereof and is preferably used as a magnetic recording medium.

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 using various binders and applied 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 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, Co-Cr and the like are preferably used. The particle size (major axis) of the magnetic material is preferably 0.3 μm or less, more preferably 0.2 μm or less.

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

In order to improve the adhesion between the magnetic layer and the film, an intermediate layer may be provided on the film surface.

The back coat layer is formed by dispersing a non-magnetic powder, a binder resin, a lubricant and the like in an organic solvent to prepare a coating material, coating it on a film and drying it. Examples of the non-magnetic powder used for the back coat layer include CaCO ₃ , carbon black, TiO ₂ , α-Fe ₂ CO _{3 and the} like. The same binder resin and organic solvent as those used in the magnetic layer can be used. The backcoat layer preferably has a thickness of 1 μm or less. If it is thicker than 1 μm, the strength of the entire tape becomes insufficient.

The thickness of the film of the present invention is preferably 0.5.
-30 μm, more preferably 1-20 μm, still more preferably 2-10 μm is preferable because the excellent running properties and electromagnetic conversion characteristics which are the effects of the present invention can be realized as a thin film magnetic recording medium. .

The tensile Young's modulus of the film of the present invention in at least one direction is preferably 800 kg / mm ² or more, more preferably 900 kg / mm ² or more, and even more preferably 1000 kg / mm ² or more to form a coating layer,
It is desirable because it can withstand the tension applied during the formation of the magnetic recording medium such as the step of forming the back coat layer and is advantageous in processing.

When the tensile Young's modulus of the film of the present invention in at least one direction is 800 kg / mm ² or more,
It does not matter if it is tempered in the longitudinal direction or in the width direction. The degree of tensilization is not particularly limited, but taking into account characteristics such as elongation and tear resistance, the tensile Young's modulus EMD in the longitudinal direction and the tensile Young's modulus EtD in the width direction are expressed as 0.5 ≦ EMD / ETD ≦ 2. Is practical.

The elongation of the film of the present invention in at least one direction is preferably 10% or less, more preferably 20% or more, still more preferably 30% or more, since the tape has appropriate flexibility.

The moisture absorption rate of the base film in the magnetic recording medium of the present invention is 5% or less, more preferably 3% or less, and further preferably 2% or less. It is desirable because the conversion characteristics can be maintained.

Next, the manufacturing method of the present invention will be explained, but the present invention is not limited to this.

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

These polymer solutions may be used directly as a film forming stock solution, or the polymer may be isolated once and then redissolved in the above organic solvent or an inorganic solvent such as sulfuric acid to prepare a film forming stock solution. Good.

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

Inorganic salts such as calcium chloride, magnesium chloride, lithium chloride and lithium nitrate may be added 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 particles can be added by a method in which the particles are sufficiently slurried in a solvent in advance and then used as a solvent for polymerization or a solvent for dilution, or a method in which the particles are directly added after preparing a stock solution for film formation. The average particle size of the agglomerated particles is controlled by the method of dispersing the particles in the solvent. As a particle dispersion method, a method using an ultrasonic disperser (bath type, circulation type), a jet stream mixer, etc. is known.
When an ultrasonic disperser having an output of 1.2 kW and a resonance frequency of about 1.5 kHz is used, it is preferable to disperse at room temperature for 5 to 50 hours.

The time is controlled by controlling, and the flatness of the agglomerated particles is controlled by controlling the film forming method and the bath temperature in the wet process.

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 may be a dry-wet method, a dry method, a wet method, or the like, and the film may be formed by any method, but 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 spinneret 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. To do. Drying conditions are room temperature to 2
00 ° C., within a range of 60 minutes, preferably room temperature to 1
It is in the range of 80 ° C. If the drying temperature exceeds 200 ° C., voids are generated due to rapid heating and the surface is roughened, and it is difficult to obtain a practical film as an industrial material or a magnetic material.

After the dry process, the film is peeled from the support and introduced into the wet process, where the ionic inorganic compound contained in the film is removed. This bath is generally composed of an aqueous medium, and may contain an organic solvent, an inorganic salt or the like in addition to water. However, in general, the water content is 30% or more, preferably 50% or more, and the bath temperature is usually 0 to 90 ° C.
If the bath temperature exceeds 90 ° C., the solvent in the film is rapidly extracted, and the flatness of the agglomerated particles is reduced due to the shrinkage of the film, making it difficult to obtain a practical film. In this wet process the peeled film is immersed in such a bath under tension and the inorganic compounds in the film are extracted to less than 0.1%, preferably to 0.05% or less. The amount of the inorganic salt as a solubilizer is at most the same as the neutralized salt produced by neutralization, or the amount of the neutralized salt is small and the amount of the inorganic salt is small, so the extraction speed is fast, and the inorganic salt in the bath is also It is also easy to recover the organic solvent.

The film that has undergone the wet process is further stretched, dried and heat-treated to form a film.

The film formed as described above is stretched in the film-forming process so that the mechanical properties are within the range of the present invention, and the stretching ratio is 0.8 to 4.0 in terms of surface magnification.
(The area ratio is defined as a value obtained by dividing the area of the film after stretching by the area of the film before stretching. 1 or less means relaxation.), And more preferably 1.1 to 1.1. 3.0. 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 100 ° C./second or less.

The film of the present invention may be a laminated film. For example, in the case of two layers, two kinds of a film forming stock solution corresponding to the A layer and a film forming stock solution corresponding to the B layer are used by known methods, for example, as described in JP-A-56-162617. It can be formed by laminating with or in a die. The same applies to the case of three or more layers. The viscosity of the stock solution is 100-
It is preferable to adjust it to be 10,000 poise. If it is less than this range, the liquids are easily mixed with each other before the stock liquid comes out of the die, which is not preferable. On the contrary, if it is larger than this range, melt fracture occurs and the surface is easily roughened, which is not preferable.

It is preferable that the viscosity of each layer is the same,
There may be some difference in viscosity, and the difference in viscosity may be targeted within 50%.

When a dry method or a dry-wet method is adopted,
The liquids may mix during the drying process. The undiluted solution cast on the support once decreases in viscosity when heated and then increases as the solvent evaporates.
If it is lower than the poise, it will be easier for each liquid to mix, so 10
Poises It is necessary to adjust the drying conditions sufficiently so that the viscosity does not drop below 50 poises. For example, a method of drying at a drying temperature not exceeding 240 ° C., or a method of raising the drying temperature in at least two stages can be adopted.

Next, a magnetic layer is applied to this film. The method for applying the magnetic layer can be performed by a known method, but a method using a gravure roll is more preferable in terms of the uniformity of the coating film. Drying temperature after coating is 90 ° C-150
C is preferred. The calendering process is at 25 ° C to 150 ° C
It is preferable to carry out within the range.

Thereafter, 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.
For example, DDS-1, 2, 3, 4, QIC, data 8mm
However, the present invention is not limited to this.

[0047]

[Measurement method and evaluation method] The method for measuring the physical properties and the method for evaluating the effect of the present invention are as follows.

(1) Average Particle Size of Particles A cross section of the film is photographically observed with a transmission electron microscope (TEM) to detect particles.

This photograph is numerically processed with an image analyzer for 100 or more particles, and the number average diameter d is taken as the average particle diameter. However, when the particles are aggregated, the aggregate is treated.

D = Σdi / N (where di is the equivalent circle diameter of particles (= (maximum diameter + shortest diameter) / 2), N is the number of particles) (2) Particle flatness ratio OsO ₄ staining ultrathin section method The film cross-section sample is adjusted by the method, and the film cross-section photograph is observed with a transmission electron microscope (TEM) to detect particles (aggregates are one aggregated lump). Numerical processing is performed on 100 or more particles, and the flatness is defined as the ratio of the particle diameter L1 in the film thickness direction to the particle diameter L2 in the direction parallel to the film plane.

Flatness = ΣL2 / ΣL1 (3) Ratio of Particles Having Voids Among the particles contained in the film, the ratio of particles having a void between the film and the base film is the same as in the above item (2). The cross section of the film was photographed with, and the number of particles having voids between the film and the polymer used for the base film was counted for 100 or more particles.

(4) Dimensional change rate Marks are put on the film at intervals of 150 mm, and this is slit into a width of 10 mm to obtain a measurement sample. The thickness is measured with a micrometer, weighted so that the load becomes 1 kg / mm ² , heated in an oven at 100 ° C. for 10 minutes, and the dimensional change is calculated by the following formula.

[0053]

(Equation 1) (5) Electromagnetic conversion characteristics A film coated with a magnetic layer was slit into a 1/2 inch width and incorporated in a VTR cassette to obtain a VTR tape. Chroma S / N was measured from a 100% chroma signal by a television test waveform generator using a household VTR on this tape with a color video noise measuring instrument. The evaluation was made based on a commercially available tape.

(6) Runnability A film slitted into a tape having a width of 1/2 inch was used with a tape runnability tester SFT-700 type (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) where T1 is the inlet tension and T2 is the outlet tension. The guide diameter is 6 mmφ, the guide material is polyoxymethylene (with a surface roughness of about 20-40 nm), and the winding angle is 9
The angle is 0 °, the running speed is 3.3 cm / sec, and the repeating stroke is 15 cm. The μK obtained by this measurement is 0.
When it was 35 or less, the runnability was judged to be good, and when it exceeded 0.35, the runnability was judged to be bad. This μK is a critical point that affects the handling property when processing a film for a magnetic recording medium, a capacitor, packaging, and the like.

(7) Scratch resistance A film was slit into a tape having a width of 1/2 inch, and a single blade was pressed perpendicularly to the film surface.
Run 1.0m with 0mm pushed in. (Running tension: 500 g, running speed: 10 cm / sec). At this time, the height of the shavings on the surface of the film attached to the tip of the single blade was read with a microscope and used as the shaving amount (unit: μm). When the scraped amount is 5 μm or less, it is ◯, when it is 5 to 8 μm, Δ, and 8 μm
When it exceeded, it was marked with x.

The present invention will be described below based on examples, but the invention is not limited thereto.

[0058]

EXAMPLES The present invention will be described below based on examples.
However, the present invention is not limited to these examples.

Example 1 First, dry silica particles having a primary particle size of 0.02 μm were placed in N-methyl-2-pyrrolidone (NMP) using an ultrasonic disperser 20.
A slurry is prepared so as to have an average particle size of 200 nm over time.

The polymerization layer was charged with NMP and the above silica slurry, in which 2-chloroparaphenylenediamine corresponding to 80 mol% as an aromatic diamine component and 4,4'-diaminodiphenylene corresponding to 20 mol% were added. -Then was dissolved, 100 mol% of 2-chloroterephthalic acid chloride corresponding to 100 mol% was added thereto, and the mixture was stirred for 2 hours to complete the polymerization. Furthermore, 9 of hydrogen chloride generated by lithium hydroxide
7 mol% was neutralized, and then 5 mol% of diethanolamine and 10 mol% of triethanolamine were added to obtain a polymer solution. The content of particles is 2 wt% with respect to the aromatic polyamide.

Then, the polymer concentration was adjusted to 11 wt% and the solution viscosity at 30 ° C. was adjusted to 3000 poise to obtain a stock solution for film formation.

These stock solutions for film formation were passed through a 3 μm-cut filter and then cast on a metal belt through a die. The cast film was heated with hot air at 160 ° C. for 2 minutes to evaporate the solvent, and the film having self-holding property was continuously peeled from the belt. Next, the film was introduced into a water tank having an NMP concentration gradient of 50 ° C., and the residual solvent and the inorganic salt produced by neutralization were extracted with water. In this bath, the film was stretched 1.2 times in the machine direction (MD direction).

Next, the mixture was introduced into a tenter and dried at 280 ° C. for 1 minute and subjected to heat treatment.

During this time, the film width direction (TD direction)
The film was stretched 1.3 times and slowly cooled at a rate of 20 ° C./sec to obtain a film.

The flatness of particles in this film is 2.2.
The ratio of particles having voids was 2%, and the dimensional change rate under a load of 1 kg / mm ² was 0.6%. Next, the film running property, electromagnetic conversion property, and abrasion resistance were measured and were good.

Example 2 A polymer solution similar to that of Example 1 was prepared except that a slurry in which colloidal silica particles having a primary particle diameter of 45 nm were dispersed in an NMP with an ultrasonic disperser for 25 hours to have an average particle diameter of 100 nm was used. did. The amount of particles added is 0.2 wt%.

The magnification is the same in the MD direction.
Film formation was carried out by the same process as in Example 1 except that the film was stretched at a speed of 5 times.

The flatness of particles in this film is 3.5,
The ratio of particles having voids was 3%, and the dimensional change rate under a load of 1 kg / mm ² was 0.6%. Next, the film running property, electromagnetic conversion property, and abrasion resistance were measured and were good.

Example 3 As an aromatic diamine component, 60 mol% of para-phenylenediamine and 40 mol% of 4,4'-
Using diaminodiphenyl ether, dry silica particles having a primary particle size of 0.02 μm in NMP were mixed with an ultrasonic disperser 3
A film was prepared in the same manner as in Example 1 except that the slurry was dispersed for 0 hours so that the average particle diameter was 50 nm and the amount of particles added was 4 wt%.

The flatness of particles in this film is 2.0,
The ratio of particles having voids was 3%, and the dimensional change rate under a load of 1 kg / mm ² was 1.1%. Next, the film running property, electromagnetic conversion property, and abrasion resistance were measured and were good.

Example 4 The same polymer solution as in Example 1 except that a dry silica particle having a primary particle size of 0.02 μm was dispersed in an NMP with an ultrasonic disperser for 13 hours to have an average particle size of 500 nm. Polymer A was prepared in the same manner as in Example 1 except that a slurry obtained by dispersing A and dry silica particles having a primary particle diameter of 0.02 nm in an ultrasonic disperser for 17 hours to an average particle diameter of 300 nm was used to prepare three layers. The composite tube for use was laminated in three layers of A / B / A, and a film was formed in the same manner as in Example 1.

The flatness of particles in the layer A on the non-belt surface side of this film was 3.0, the ratio of particles having voids was 3%,
The dimensional change rate under a load of 1 kg / mm ² was 0.6%. Next, the film running property, electromagnetic conversion property, and abrasion resistance were measured and were good.

Comparative Example 1 A film was prepared in the same manner as in Example 1 except that the amount of particles added was 10 wt%.

The flatness of particles in this film is 2.4,
The ratio of particles having voids was 5%, and the dimensional change rate under a load of 1 kg / mm ² was 0.7%. Next, the film running property was measured to be good, but the electromagnetic conversion properties and abrasion resistance were measured to be bad.

Comparative Example 2 A film was prepared in the same manner as in Example 1 except that the amount of particles added was 0.01 wt%.

The flatness of the grains in this film is 2.3,
The ratio of particles having voids was 2%, and the dimensional change rate under a load of 1 kg / mm ² was 0.6%. Next, the electromagnetic conversion characteristics and abrasion resistance of this film were measured to be good, but the runnability was bad.

Comparative Example 3 The same method as in Example 1 was carried out except that a dry silica particle having a primary particle size of 0.05 μm was dispersed in an NMP with an ultrasonic disperser for 4 hours to have an average particle size of 1200 nm. I got a film.

The flatness of particles in this film is 1.5,
The proportion of particles having voids was 7%, and the dimensional change rate under a load of 1 kg / mm ² was 0.7%. Next, the film running property was measured to be good, but the electromagnetic conversion properties and abrasion resistance were measured to be bad.

Comparative Example 4 The same polymer solution as in Example 1 was used, and the solution was directly exposed to
A film was obtained in the same manner as in Example 1 except that the film was introduced into a water tank at ℃.

The flatness of particles in this film is 0.5,
The ratio of particles having voids was 5%, and the dimensional change rate under a load of 1 kg / mm ² was 0.8%. Next, the film running property was measured to be good, but the electromagnetic conversion properties and abrasion resistance were measured to be bad.

Example 5 The same method as in Example 1 was used except that the same polymer solution as in Example 1 was used and the polymer solution cast on the belt was heated with hot air at 220 ° C. for 1 minute to evaporate the solvent. I got a film.

The flatness of particles in this film is 2.3,
The ratio of particles having voids was 15%, and the dimensional change rate under a load of 1 kg / mm ² was 1.0%. Next, it is good to measure the film running property, and the electromagnetic conversion characteristics,
The abrasion resistance was at a satisfactory level.

Example 6 As an aromatic diamine component, which corresponds to 100 mol% 4,
A film was prepared in the same manner as in Example 1 except that 4-diaminodiphenylmethane and 50 mol% of isophthalic acid chloride and 50 mol% of terephthalic acid chloride were used as the aromatic acid chloride components.

The flatness of particles in this film is 2.2,
The proportion of particles having voids was 3%, and the dimensional change rate under a load of 1 kg / mm ² was 2.2%. Next, the film running property and the abrasion resistance were measured, and it was good, and the electromagnetic conversion characteristics were at a satisfactory level.

[0085]

[Table 1]

[0086]

INDUSTRIAL APPLICABILITY The present invention uses a base film made of an aromatic polyamide which is excellent in heat resistance and mechanical properties, and has a particle diameter in the film, an aspect ratio, and a particle having a void between the particles. By specifying the ratio and the rate of dimensional change under load, it is possible to obtain a magnetic recording medium that has excellent durability in harsh environments (especially at high temperatures), running properties, output characteristics, and abrasion resistance. It has been done. Further, due to these excellent characteristics, the running property and heat resistance at the time of manufacturing the magnetic recording medium are improved, and the processing productivity can be improved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B29K 503: 04

Claims (6)

[Claims] 1. A film containing an aromatic polyamide as a main component, wherein the film contains 0.05 to 5% by weight of aggregated particles, and the average aggregated particle size of the aggregated particles is 5 to 1000.
and an aspect ratio of the aggregated particles is 0.7 or more, an aromatic polyamide film. 2. A film containing an aromatic polyamide as a main component, which is a laminated film composed of at least two layers, and 0.05 to 5% by weight of agglomerated particles in at least one outermost layer of the laminated film. An aromatic polyamide film containing the above-mentioned agglomerated particles, wherein the agglomerated particles have an average agglomerated particle diameter of 5 to 1000 nm, and the agglomerated particles have a flatness of 0.7 or more. 3. The aromatic polyamide film according to claim 1, wherein the flatness of the aggregated particles is 1% or more. 4. The aromatic polyamide film according to claim 1, wherein the proportion of particles having voids between the aggregated particles and the polymer used for the base film is 10% or less. 5. The aromatic polyamide film according to claim 1, wherein the dimensional change rate is 2% or less. 6. A magnetic recording medium comprising a magnetic layer provided on at least one surface of the aromatic polyamide film according to claim 1.