JP2002212318A - Aromatic polyamide film and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aromatic polyamide film that is useful as a base film for magnetic recording because it has excellent output characteristics and traveling properties and provide a magnetic recording medium. SOLUTION: The objective aromatic polyamide film satisfies the formulas: 0.1<=S5-S10<=10; 2×106<=N5-N10<=50×106; and 0.5×106<=N10, when the film has projections at least on one face; the occupancy of the projection cross section area on the horizontal plane of 5 nm height is defined as S5 in %; the occupancy of the projection cross section area on the horizontal plane of 10 nm height is defined as S10 in %; the projection density of >=5 nm height is defined as N5 in N/mm2 and the projection density of >=10 nm height is defined as N10 in N/mm2, and the thermal shrinkage of the film is in the range of 0.3-5% before and after the heat treatment at 180 deg.C in the widthwise direction for 30 minutes.

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 can be suitably used as a magnetic recording medium.

[0002]

2. Description of the Related Art Aromatic polyamide films are being studied for various uses by taking advantage of their excellent heat resistance and mechanical properties. In particular, the aromatic polyamide film of the para-orientation type has excellent mechanical properties such as rigidity and strength compared to other polymers, so it is very advantageous for thinning, and is useful for printer ribbons, magnetic tapes, capacitors, solar cells, etc. It is considered.

Among them, especially for magnetic recording media, a large capacity of a magnetic tape is required in order to cope with a rapid increase in recording density of a hard disk. It is a more advantageous material than polyethylene terephthalate and polyethylene naphthalate that have been used. However, high-density recording of magnetic tape is indispensable for further increase in capacity.
For that purpose, it is necessary to smooth the surface of the base film to improve the electromagnetic conversion characteristics. However, if the base film is made too smooth, the running properties are poor, and the handling properties in the manufacturing process are reduced, and the life of the magnetic recording medium is reduced. In order to satisfy these conflicting demands, a conventional method of adding particles and forming fine projections on the film surface (JP-A-60-127523, JP-A-60-201914, etc.), To form uniform projections by using the method described in Table 98/0088
No. 92 publication) has been proposed.

[0004]

However, in recent years, there has been an extremely high demand for improvement in the electromagnetic conversion characteristics of magnetic recording media, and it is no longer possible to satisfy the high demand level only with conventional means for improving the surface properties. It is becoming a difficult situation.

Accordingly, an object of the present invention is to provide an aromatic polyamide film and a magnetic recording medium which are excellent in output characteristics and running properties when used as a magnetic recording medium and are useful as a base film for a magnetic recording medium. And

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above object, and as a result, by controlling the difference in cross-sectional area and the difference in the number of protrusions, the smoothness of portions other than high protrusions is controlled, and By controlling the thermal shrinkage ratio of the aromatic resin within a certain range, it is possible to obtain a magnetic recording medium having an appropriate head touch, excellent output, excellent runnability, and an aromatic compound that can be suitably used as a base film for a magnetic recording medium A polyamide film was found.

That is, in order to achieve the above object, the aromatic polyamide film of the present invention has a projection on at least one side, and the occupation ratio of the projection cross-sectional area in the horizontal plane having a height of 5 nm is S5 (%), and the horizontal plane having a height of 10 nm is provided. When the protrusion cross-section area is S10 (%), the protrusion density with a height of 5 nm or more is N5 (pieces / mm ² ), and the protrusion density with a height of 10 nm or more is N10 (pieces / mm ² ), the following formula (1) is used. (3) and an aromatic polyamide film having a heat shrinkage at 180 ° C. in the width direction of 0.3 to 5%.

[0008] 0.1 ≦ S5-S10 ≦ 10 (1) 2 × 10 ⁶ ≦ N5-N10 ≦ 50 × 10 ⁶ (2) 0.5 × 10 ⁶ ≦ N10 (3)

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic polyamide of the present invention is
It has a repeating unit represented by the following formula (I) and / or formula (II). Formula (I)

[0010]

Embedded image Formula (II)

[0011]

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

[0012]

Embedded image And X and Y are -O-, -CH2-, -C
It is selected from O-, -S-, -C (CH3) 2- and the like, but is not limited thereto. Further, some of the hydrogen atoms on these aromatic rings may be replaced by halogen groups (especially chlorine) such as fluorine, bromine and chlorine, nitro groups, methyl, ethyl,
Including those substituted with a substituent such as an alkyl group (especially a methyl group) such as propyl, or an alkoxy group such as methoxy, ethoxy, or propoxy, and hydrogen in an amide bond constituting the polymer is replaced with another substituent Including those replaced by In the aromatic polyamide used in the present invention, the aromatic ring having para-orientation preferably accounts for 80 mol% or more, more preferably 90 mol% or more of the total aromatic ring. . The term "para-orientation" as used herein refers to a state where the divalent bonds forming the main chain on the aromatic ring are coaxial or parallel to each other. If the para-orientation is less than 80 mol%, the film may have insufficient rigidity and heat resistance.

The film of the present invention has protrusions on at least one side, and the occupancy of the cross-sectional area of the protrusion in a horizontal plane having a height of 5 nm is S5 (%), and the cross-sectional area of the protrusion in a horizontal plane having a height of 10 nm is S10 (%). The protrusion density of 5 nm or more is N
5 (pieces / mm ² ), and a protrusion density of 10 nm or more
When 0 (pieces / mm ² ), the following expressions (1) to (3) are simultaneously satisfied.

0.1 ≦ S5−S10 ≦ 10 (1) 2 × 10 ⁶ ≦ N5−N10 ≦ 50 × 10 ⁶ (2) 0.5 × 10 ⁶ ≦ N10 (3) These characteristics are satisfied. In the case of a film, it is possible to achieve both higher output and higher running performance when used as a magnetic recording medium.

The occupation ratio S5 of the projection cross-sectional area here
And S10 are the threshold values (5 nm,
D (μm ² ), the number of protrusions at the threshold value is N (pieces), and the measurement range is H (μm).
m ² ) means the value obtained by the following equation.

S (%) = ((D × N) / H) × 100 When the value of S5−S10 is less than 0.1, the friction is increased due to the small number of high protrusions, and the surface protrusions are scraped off, resulting in an output. May be reduced. Conversely, the value of S5-S10 is 10
In the case where the number of protrusions is more than the above, there is a lower possibility of shaving the projections, but since there are many low projections, the smoothness of the film surface is inferior and the output may decrease. More preferably, it is in the range of 0.2 to 8, more preferably in the range of 0.3 to 7.

The value of N5-N10 is 2 × 10 ⁶ /
When it is less than mm ^{2, the} output is excellent when it is used as a magnetic recording medium, but a problem may occur in the running property and the slit property may be deteriorated. Conversely, the value of N5-N10 is 5
When the density exceeds 0 × 10 ⁶ pieces / mm ² , the running property of the magnetic recording medium is excellent, but the output may be lowered because the film surface other than the high protrusion portions is rough. More preferably, the value of N5-N10 is 4 × 10 ^{6 to} 45 × 1.
0 ⁶ , more preferably 8 × 10 ⁶ to 40 × 10 ⁶ .

Further, the value of N10 is 0.5 × 10 ⁶ /
When the diameter is less than mm ² , the magnetic recording medium has few high protrusions, and the head comes into contact with the low protrusions, so that the contact area increases, and the magnetic layer may peel off due to friction. N
The value of 10 is preferably 1.0 × 10 ⁶ / mm ² or more, more preferably 1.5 × 10 ⁶ / mm ² or more.

The film of the present invention has a width of 1 in the width direction of the film.
Heat shrinkage before and after heat treatment at 80 ° C for 30 minutes is 0.3
５5%. Here, the heat shrinkage refers to a value obtained by the following equation from the film length (L) after the heat treatment and the film length (L ₀ ) before the heat treatment.

Heat shrinkage (%) = ((L ₀ −L) / L ₀ ) × 100 The heat shrinkage is more preferably in the range of 0.4 to 4%, and still more preferably 0.5 to 3%. Is within the range. If the heat shrinkage is less than 0.3%, the film may be curled due to heat during processing, but the curl may not be restored even by the heat treatment again. In particular, in the manufacturing process of the vapor deposition tape, the film curls toward the magnetic layer surface when the magnetic layer is vapor-deposited. If the curl remains in this step, a defect may occur around the head when the magnetic recording medium is used. If the heat shrinkage ratio is larger than 5%, it is difficult to set the heat treatment conditions again, curling in the opposite direction may result in poor head contact when the magnetic recording medium is used, and also may cause temperature change. Dimensional stability may deteriorate.

By satisfying all of the above requirements, it is possible to obtain an aromatic polyamide film having moderately high projections, having excellent smoothness in portions other than the projections, and suppressing curling of the film. Since this aromatic polyamide film has no curl when used as a magnetic recording medium, it can uniformly contact the head, and has moderately high protrusions, and is excellent in smoothness of portions other than the protrusions. It has excellent head contact and can achieve both output and running performance at a high level. Therefore, the film of the present invention can be very suitably used as a base film of a magnetic recording medium, particularly, a magnetic recording medium for vapor deposition in which surface properties are emphasized.

The film of the present invention is preferably a film containing an aromatic polyamide and at least one heteropolymer in order to obtain the film of the present invention having a uniform, fine and high-density projection surface. Although the content of the heteropolymer is appropriately determined for each system, it is preferably more than 0.1% by weight and less than 20% by weight, more preferably 0.5% by weight, based on the aromatic polyamide. %
More than 18% by weight, more preferably more than 1% by weight and 17% by weight or less. When the content of the heteropolymer is 0.1% by weight or less, a sufficient number and height of projections may not be formed on the film surface, and as a result, there is a problem in running properties when used as a magnetic recording medium. There is. When the content is 20% by weight or more, not only the surface of the film becomes rough, but also the mechanical properties may decrease.

The heteropolymer contained in the aromatic polyamide film of the present invention is selected from polymers which are soluble in the solvent of the stock solution for the film formation, but from the viewpoint of the affinity with the aromatic polyamide constituting the film. , A polysulfone polymer, a polyetherimide polymer, a polyphenylene oxide polymer, a polyester polymer, a polyketone polymer, a polycarbonate polymer, a polyimide polymer and a precursor thereof. preferable. Further, it is an aromatic polysulfone polymer having at least one sulfone group -SO2- in a repeating unit represented by polysulfone, and specifically, an aromatic polymer having a repeating unit represented by the formula (III) It is preferable to use a polysulfone polymer in order to obtain a film having a projection distribution according to the present invention. Formula (II)
I)

[0024]

Embedded image Here, n is a positive integer, and a value of 5 or more and 1,000 or less is preferable in terms of heat resistance and solubility in a solvent. In particular,

[0025]

Embedded image Is preferred in that uniform projections can be formed.

The film of the present invention comprises the above composition as a main component, but as long as the object of the present invention is not impaired, an inorganic or organic material such as an antioxidant, a heat stabilizer, a lubricant, an ultraviolet absorber, a nucleating agent, etc. May be blended.

The film of the present invention further comprises SiO 2, Ti
O2, Al2O3, CaSO4, BaSO4, CaCO
3. Inorganic particles such as carbon black, zeolite, and other fine metal powders, and organic polymer particles such as silicone particles, polyimide particles, cross-linked copolymer particles, cross-linked polyester particles, and Teflon (registered trademark) particles. You may use together. At this time, the average primary particle size of the particles is 5 to 100 n.
m is preferably in the range of 0.05 to
Preferably it is in the range of 5% by weight.

The aromatic polyamide film of the present invention has a tensile Young's modulus in the length direction and / or the width direction of preferably 9.8 GPa or more, more preferably 11.7 Gpa.
It is preferably at least Pa, particularly preferably at least 12.7 GPa. In the aromatic polyamide film of the present invention, it is needless to say that the Young's modulus in any of the length direction and the width direction is preferably 9.8 GPa or more. In order to satisfy these properties, as described above, the aromatic polyamide used in the present invention has an aromatic ring having a para-orientation, preferably at least 80 mol% of the total aromatic ring, more preferably Preferably, it accounts for 90 mol% or more.

The film of the present invention is preferably employed as a single-layer film which is easy to form, but may be a laminated film. When forming a laminated film, the film of the present invention is laminated so as to be the outermost layer on at least one surface.

The present invention can be used as a magnetic recording medium by providing a magnetic layer on at least one surface of the film. At this time, it is preferable to provide a magnetic layer on the surface satisfying the requirements of the present invention.

The magnetic layer of the high-density recording medium to which the film of the present invention is applied is not particularly limited, but is preferably a ferromagnetic metal thin film layer. As a means for forming the ferromagnetic metal thin film layer, for example, a vacuum evaporation method, a sputtering method, or an ion plating method is preferably used, but a magnetic layer composed of a ferromagnetic powder and an organic binder may be formed by a coating method. Co, Ni, C
Metals such as r and Fe, alloys containing these as main components, and the like can be used.

After the formation of the magnetic layer, it is preferable to apply a diamond-like coating and / or a lubrication protective layer from the viewpoint of improving the durability of the magnetic recording medium. Further, a back coat layer may be provided in order to improve the running property by the surface opposite to the magnetic layer.

The aromatic polyamide film of the present invention is preferably used for various uses such as a flexible printed circuit board, a capacitor, a printer ribbon, an acoustic diaphragm, and a base film of a solar cell. When used as a medium, the effect of the aromatic polyamide film of the present invention having high output, high durability, and no defect is sufficiently exhibited, which is particularly preferable.

The present invention also relates to a magnetic recording medium for use as a digital video cassette for broadcasting stations such as consumer use, professional use, D-1, D-2 and D-3, DDS-2, 3, 4, data 8 mm, Although it can be suitably used for data storage applications such as AIT and mammoth, it can be optimally used for data storage applications where reliability such as data loss is most important.

The elongation of the film of the present invention is preferably 10% or more, more preferably 20% or more, and further preferably 30% or more, since the tape has appropriate flexibility. However, the upper limit is usually 100% or less, and if too large, the original rigidity of the aromatic polyamide film may be impaired.

The film of the present invention has a moisture absorption of 5% or less,
It is more preferably at most 3%, more preferably at most 2%, because the dimensional change of the tape due to a change in humidity is small, and good electromagnetic conversion characteristics can be maintained. However, the lower limit is usually 0.3% or more, and trying to lower it too much may reduce other physical properties.

It is preferable that these properties be satisfied also in a laminated film when laminated.

The 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. When it is obtained from an aromatic diacid chloride and an aromatic diamine, it is polymerized by solution polymerization in an aprotic organic polar solvent such as N-methylpyrrolidone, dimethylacetamide, and dimethylformamide. Is done.

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 that would hinder the reaction, and it is preferable to use efficient stirring means. In addition, the equivalence of the raw materials is important, but when there is a risk of impairing the film forming property, it can be adjusted appropriately. Further, calcium chloride, magnesium chloride, lithium chloride, lithium bromide, lithium nitrate, or the like may be added as a dissolution aid.

When an aromatic diacid chloride and an aromatic diamine are used as monomers, hydrogen chloride is by-produced. When neutralizing this, cations of Group I or Group II of the periodic table and hydroxide ions are used. An inorganic neutralizing agent represented by a salt composed of an anion such as a carbonate ion and the like, and an organic neutralizing agent such as ethylene oxide, propylene oxide, ammonia, triethylamine, triethanolamine and diethanolamine are used. For the purpose of improving the humidity characteristics of the base film, benzoyl chloride, phthalic anhydride, acetic chloride, aniline, or the like may be added to the system after the polymerization to block the terminal of the polymer.

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

As a film forming stock solution, a polymer solution after neutralization may be used as it is, or a solution obtained by once isolating a polymer and then re-dissolving it in an organic solvent may be used.

The means for forming the projections of the film of the present invention include, for example, particles dispersed in a polymer, coating, addition of a different polymer, and the like. The projections may be formed by any method. From the viewpoint of height uniformity and the number of projections, it is preferable to form by adding a different polymer.

When a heteropolymer is added, it may be dissolved in a solvent together with the monomer before polymerization, mixed with the polymer solution after polymerization, or redissolved with the isolated aromatic polyamide. Immediately before film formation, mixing may be performed using a static mixer or the like. Further, even if it is added in the form of powder or pellets, it may be once dissolved in an organic solvent such as a polymerization solvent and then mixed with a polymer solution.

The concentration of the polymer in the stock solution is preferably from 2% by weight to 40% by weight.

The stock solution prepared as described above is formed into a film by a dry method, a dry-wet method, a wet method, a semi-dry semi-wet method, or the like. The method is preferred, and the dry-wet method will be described below as an example.

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 to dry the thin film. The drying temperature is preferably 100 ° C. or more and 210 ° C. or less, and more preferably 120 ° C. or more and 190 ° C. or less from the viewpoint of uniformly forming projections. The drying time is preferably 0.5 minutes or more and 12 minutes or less, more preferably 1 minute or more and 10 minutes or less.

Next, the film after the dry process is peeled from the support, introduced into a wet process, and subjected to desalting, desolvation and the like. The polymer concentration at the time of peeling the film from the support is preferably 30% by weight or more and 60% by weight or less, more preferably 35% by weight or more and 50% by weight or less. If the polymer concentration is less than 30% by weight, the film may have insufficient self-supporting property and may be easily broken. If it exceeds 60% by weight, stretching may not be performed sufficiently.

The aromatic polyamide film of the present invention is preferably stretched in the longitudinal direction of the film in the state of a gel film while being separated from the support and introduced into a wet process. The stretch ratio is preferably from 1.05 to 4 times, more preferably from 1.05 to 2 times. If the stretching ratio in the longitudinal direction is less than 1.05 times, the Young's modulus in the longitudinal direction may be insufficient, and if it exceeds 4 times, a fragile film having low elongation may be obtained. In addition, it is not preferable to perform stretching and heat treatment on the gel film that has been peeled off without passing through a wet process, since the surface may be largely uneven.

In order to obtain the film of the present invention, the vapor pressure of water (P: kPa) at the time of stretching in the longitudinal direction is 3 kPa
It is preferable that the time (T: seconds) from the peeling to the introduction into the bath is 30 seconds or less. The vapor pressure of water is calculated from the measured temperature (t: ° C) and relative humidity (h:%) based on Antoine's formula (Chemical Engineering Handbook, 5th revised edition, Maruzen, page 18), and the saturated steam pressure (Ps) is calculated as follows. It is calculated by the following equation.

Log (Ps) = 707406-165
7.46 / (227.02 + t) P = Ps × h / 100 gel film when the vapor pressure of water exceeds 3 kPa and / or when the time from separation to introduction into the bath exceeds 30 seconds Absorbs excessive moisture and loses flexibility, and thus an external force due to stretching acts largely on the projections, flattening the projections, and the film surface morphology may not satisfy the range of the present invention.

The film after the wet process is dried after the moisture is dried.
Stretching is performed in the width direction of the film. Stretching temperature is 150
It is preferable that the temperature is not lower than 400 ° C and not higher than 400 ° C. When the stretching temperature is lower than 150 ° C., not only the difference in the cross-sectional area of the projections may exceed the range of the present invention, but also the film may be easily broken at the time of stretching and a stable film formation may not be performed. Also 4
When the temperature is higher than 00 ° C., the number of projections may be below the range of the present invention. The temperature is more preferably 200 ° C or higher and 350 ° C or lower, and further preferably 220 ° C or higher and 320 ° C or lower.

The stretching ratio in the width direction is preferably from 1.05 to 4 times, more preferably from 1.05 to 2 times. The stretching ratio in the width direction is 1.
If it is less than 05 times, the Young's modulus in the width direction may be insufficient, and if it is more than 4 times, the film may be fragile with low elongation or the Young's modulus in the longitudinal direction may be greatly reduced.

In order to keep the heat shrinkage within the range specified by the present invention, the transverse stretching speed is preferably 1% / sec or more and 20% / sec or less. The transverse stretching speed here, between joints adjacent to control the width of the normal tenter is provided, passes between cap side of the joint width W ₀ and winder side of the joint width W, 2 two joints Is a value derived from the time J (seconds) required by the following equation.

Transverse stretching speed (% / sec) = ((W−W ₀ ) /
W ₀ ) × 100 / J When transverse stretching is performed between many joints, it is important to satisfy this condition in the section where the transverse stretching speed is the highest. When the transverse stretching speed is lower than 1% / sec, the heat shrinkage may fall below the range of the present invention. If it is higher than 20% / sec, the heat shrinkage may exceed the range of the present invention.

The stretching ratio is 1.2 times or more and 8 times or less in area ratio (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 relaxed. ), More preferably in the range of 1.2 times to 6 times, from the viewpoint that a film having excellent mechanical properties can be stably formed.

The heat treatment is performed during or after the stretching of the film, and the heat treatment temperature is preferably in the range of 150 ° C. or more and 400 ° C. or less. More preferably, 18
0 ° C or more and 320 ° C or less, more preferably 200 ° C
The temperature is preferably 280 ° C. or lower. If the heat treatment temperature is lower than 150 ° C., the Young's modulus of the film may decrease. If the temperature exceeds 400 ° C., the crystallization of the film proceeds too much to form a hard and brittle film, or the projections become flattened and the magnetic recording medium becomes flat. And the running performance may be inferior.

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.

Although the film of the present invention can realize good surface characteristics even if it is a single-layer film, it may be a laminated film. In the case of forming a laminated film, for example, in the case of two layers, the polymerized aromatic polyamide solution is divided into two, and a heterogeneous polymer is added to at least one, and then laminated. The same applies to the case of three or more layers. These lamination methods include well-known methods, for example, 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.

[0061]

EXAMPLES The methods for measuring physical properties and the methods for evaluating effects in the examples and comparative examples of the present invention are as follows. (1) Occupied area and number of protrusions Measurements were performed ten times using an atomic force microscope (AFM) at different locations under the following conditions, and the average value was obtained.

For the number of protrusions and the average protrusion cross-sectional area, a value displayed by inputting a threshold value in a Grainsize command after performing a flattening process (Flatten Auto) is used.

The occupation rate S (%) of the cross-sectional area of the protrusion is represented by D (μ
m ² ), the number of protrusions at the threshold value was N (pieces), and the measurement range was H (μm ² ), which was obtained from the following equation.

S (%) = ((D × N) / H) × 100 Apparatus NanoScope IIIa ver3.20 AFM (Digital Instrum)
ents) Cantilever: silicon single crystal Scanning mode: tapping mode Scanning range: 5 μm × 5 μm Scanning speed: 1.0 Hz (2) Thermal shrinkage The film is cut out in the width direction into a length of 100 mm and a width of 10 mm, and a film of 1.5 g is cut out. A heat treatment was performed at 180 ° C. for 30 minutes with a weight, and the film length (L) after the heat treatment and the film length (L ₀ ) before the heat treatment were determined by the following formula.

Heat shrinkage (%) = ((L ₀ −L) / L ₀ ) × 100 (3) Temperature and Relative Humidity The film is divided into 10 equal parts in the width direction, and the center line of each is taken as the normal direction of the film. At a distance of 30 cm, the temperature and humidity were measured using a Crimomaster anemometer (model 6511) manufactured by Nippon Kagaku Kogyo Co., Ltd., and the data of these 10 points were averaged to obtain the temperature and humidity. (4) Tensile Young's Modulus Measured at 25 ° C. and 65% relative humidity using a 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. (5) Abrasion resistance One edge is pressed vertically to the aromatic polyamide film slit into a 1/2 inch wide tape and further 2 m
m is run for 200 m with the push-in state (running tension: 1
50 g, running speed: 400 m / min). At this time, the height of the shavings on the film surface adhering to the tip of the single blade was read with a microscope and the shaving amount was used (unit: μm). This shaving amount is 100
If it is less than μm, the abrasion resistance: good (○), and if it exceeds 100 μm, the abrasion resistance: poor (x). (6) Output characteristics The film is 170 nm thick by continuous oblique evaporation.
Was formed. Next, a diamond-like coating film having a thickness of 5 nm is formed on the magnetic layer by a sputtering method, and 0.1% by weight of an organic rust inhibitor is further applied thereon using a gravure roll, and then dried at 100 ° C. with a drier. Let dry. Thereafter, a 0.5% by weight solution mainly composed of an organic substance composed of a perfluoropolyether derivative was applied as a lubricant by a gravure roll and dried. Next, on the opposite surface of the film, a backcoat layer having a thickness of 0.3 μm was formed, mainly using carbon and using a vinyl acetate resin as a binder. The magnetic recording medium raw material obtained as described above was slit into a width of 6.35 mm and a length of 150 m, assembled into a cassette, and then a 6.5 MHz sine wave was recorded at an optimum recording current, and a reproduction output was obtained. Commercially available DVC
And the difference was evaluated according to the following criteria.

◎: Difference from standard tape is +1.5 dB or more ○: Difference from standard tape is +0.5 dB or more +1.5 dB
Less than Δ: Difference from standard tape is −0.5 dB or more +0.5 dB
Less than ×: Difference from the standard tape is less than -0.5 dB (7) Runnability The film on which the magnetic layer is formed by the method of (6) above has a width of 1 /
Using a tape running property tester SFT-700 type (manufactured by Yokohama System Research Institute), the thing slit into a 2-inch tape shape was run at 40 ° C. and 80% RH atmosphere.
The friction coefficient at the 50th pass was determined by the following equation.

ΜK = 0.733 log ₁₀ (T2 / T1) where T1 is the entrance tension and T2 is the exit tension. The guide diameter is 6 mmφ, the guide material is polyoxymethylene (having a surface roughness of about 20 to 40 nm), the winding angle is 90 °, the running speed is 3.3 cm / sec, and the repeated stroke is 15 cm. When the first measurement value measured by this method was μK (1) and the 100th measurement value was μK (100), evaluation was made according to the following criteria.

：: | (μK (100) −μK (1)) / μK (1) |
≦ 0.05 Δ: 0.05 <| (μK (100) −μK (1)) / μ
K (1) | ≦ 1.0 ×: | (μK (100) −μK (1)) / μK (1) |
> 1.0 Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto. In the following examples, NMP is N-methylpyrrolidone, CTP
C represents 2-chloroterephthalic acid chloride, CPA represents 2-chloroparaphenylenediamine, and DPE represents 4,4′-diaminodiphenyl ether. Further, MD means the length direction of the film, and TD means the width direction of the film. (Example 1) A solution of an aromatic polyamide was synthesized as follows. CPA equivalent to 90 mol% in dehydrated NMP and 1
And 0 mol% of DPE.
CTPC equivalent to 5 mol% was added, and polymerization was carried out by stirring for 2 hours, followed by neutralization with lithium carbonate to obtain an aromatic polyamide solution having a polymer concentration of 11% by weight.

On the other hand, dried polyether sulfone manufactured by Sumitomo Chemical Co., Ltd. (grade: 7300P, reduced viscosity: 0.7
3 dl / g, hereafter abbreviated as PES)
After dissolving to 0% by weight, the solution was filtered. The PES was added to the aromatic polyamide solution by adding 3% to the aromatic polyamide.
% By weight.

The polymer solution prepared as described above was cast on a stainless steel belt having a mirror-like surface. The solvent is evaporated from the cast polymer solution with hot air at 160 ° C.
The self-supporting film was peeled from the belt and stretched 1.2 times in the longitudinal direction of the film. At this time, the water vapor pressure (P) was 1.8 kPa, and the time (T) from peeling to entering the bath was 8 seconds. Next, the film was passed through a water tank for 2 minutes to extract the residual solvent and the inorganic salt generated by neutralization with water. Thereafter, the film was stretched 1.6 times in the width direction of the film under hot air at a temperature of 300 ° C. in a tenter, and then heat-treated at 240 ° C. The transverse stretching speed at this time was 6.2% / sec. Thus, an aromatic polyamide film having a total thickness of 4.4 μm was obtained. This film is S5
-The value of S10 is 1.2%, and the value of N5-N10 is 6 × 10
⁶ pieces / mm ² , N10 is 1.8 × 10 ⁶ pieces / mm ² ,
The heat shrinkage in the width direction was 2.1%, the Young's modulus in each of the MD and TD directions was 11.7 GPa and 16.6 GPa, respectively, and the abrasion resistance was ○. The magnetic tape using this film showed good output and good runnability. (Example 2) A film was formed in the same manner as in Example 1 except that the amount of the heteropolymer added was 8% by weight and P was 1.2 kPa, to obtain an aromatic polyamide film. This film is S5-
The value of S10 is 6.3%, and the value of N5-N10 is 25 × 10
⁶ pieces / mm ² , N10 is 6.5 × 10 ⁶ pieces / mm ² , thermal shrinkage rate in the width direction is 2.8%, Young's modulus in MD and TD directions is 11.6 GPa and 16.1 GPa, respectively. The scraping property was ○. The magnetic tape using this film had an output of ◎ and a runnability of ○, which was excellent in both output and runnability. (Example 3) A film was formed in the same manner as in Example 1 except that the amount of the different polymer added was 8% by weight, P was 2.6 kPa, T was 25 seconds, and the transverse stretching speed was 1.5% / second. Thus, an aromatic polyamide film was obtained. This film had a value of S5-S10 of 3.1%, a value of N5-N10 of 12 × 10 ⁶ / mm ² ,
N10 is 8.2 × 10 ⁶ pieces / mm ² , the heat shrinkage in the width direction is 0.5%, and the Young's modulus in each of MD and TD is 1
1.3 GPa, 15.7 GPa, and abrasion resistance were ○. The output of the magnetic tape using this film is ◎
The runnability was excellent and both output and runnability were excellent. (Example 4) A film was formed in the same manner as in Example 1 except that the amount of the heteropolymer was 8% by weight, P was 2.1 kPa, T was 3 seconds, and the transverse stretching speed was 18.2% / second. Thus, an aromatic polyamide film was obtained. This film had an S5-S10 value of 8.2%, an N5-N10 value of 42 × 10 ⁶ / mm ² ,
N10 is 2.1 × 10 ⁶ pieces / mm ² , the thermal shrinkage in the width direction is 4.2%, and the Young's modulus in each of MD and TD is 1
1.9 GPa, 15.9 GPa, and abrasion resistance were ○. The output of the magnetic tape using this film is ○
And the runnability was △, which was a usable level. (Example 5) The amount of the heteropolymer added was set to 10% by weight,
Was formed in the same manner as in Example 1 except that
An aromatic polyamide film was obtained. This film is S5
-The value of S10 is 5.9%, and the value of N5-N10 is 24x1.
0 ⁶ / mm ^2, N10 is 8.1 × 10 ⁶ cells / mm ^2, thermal shrinkage of 2.9% in the width direction, MD, TD each direction Young's modulus, respectively 11.5GPa, 15.6GPa, The abrasion resistance was ○. The magnetic tape using this film had an output of ◎ and a runnability of ○, which was excellent in both output and runnability. (Example 6) The amount of the heteropolymer added was 12% by weight,
Was formed in the same manner as in Example 1 except that
An aromatic polyamide film was obtained. This film is S5
-The value of S10 is 6.5%, and the value of N5-N10 is 29x1.
0 ⁶ / mm ^2, N10 is 9.5 × 10 ⁶ cells / mm ^2, the width direction of the heat shrinkage ratio 3.2%, MD, TD each direction Young's modulus, respectively 11.2GPa, 15.0GPa, The abrasion resistance was ○. The magnetic tape using this film had an output of ◎ and a runnability of ○, which was excellent in both output and runnability. (Example 7) The amount of the heteropolymer added was set to 17% by weight,
Was set to 1.7 kPa and T was set to 8 seconds, and an aromatic polyamide film was obtained in the same manner as in Example 1. This film has an S5-S10 value of 7.8%, an N5-N10 value of 31 × 10 ⁶ pieces / mm ² , an N10 of 10.2 × 10 ⁶ pieces / mm ² , and a heat shrinkage in the width direction of 4 0.3%, Young's modulus in each of MD and TD directions is 10.9 GPa and 14.1 G, respectively.
Pa and abrasion resistance were ○. The magnetic tape using this film showed good output and good runnability. (Example 8) Polycarbonate (grade: FN3000A, weight average molecular weight: 30,200, hereinafter abbreviated as PC) manufactured by Idemitsu Petrochemical Co., Ltd. was used as a heteropolymer, the amount of addition was 12% by weight, and P was 2%. .5 kPa, T = 14
Example 1 except that the second and the transverse stretching speed were 15.2% / sec.
A film was formed in the same manner as described above to obtain an aromatic polyamide film. This film had an S5-S10 value of 4.2%, N5-N1
The value of 0 is 19 × 10 ⁶ pieces / mm ² , and N10 is 1.7 × 10
⁶ pieces / mm ² , heat shrinkage in the width direction 1.6%, MD, TD
Young's modulus in each direction is 10.7 GPa and 14.7, respectively.
GPa and abrasion resistance were ○. The magnetic tape using this film had an output of Δ and a runnability of ○, which was a practical level. (Comparative Example 1) An aromatic polyamide film was obtained by forming a film in the same manner as in Example 1 except that P was set to 4.3 kPa. This film has an S5-S10 value of 0.07%, N5-N1
The value of 0 is 1.7 × 10 ⁶ pieces / mm ² , and N10 is 0.8 × 1
0 ⁶ / mm ^2, thermal shrinkage of 1.0% in the width direction, MD, T
D. Young's modulus in each direction is 11.4 GPa,
5 GPa, the abrasion resistance was x. The magnetic tape using this film had an output of Δ and a running property of ×, and was not practically usable. It can be determined that the various characteristics were lower than in Example 1 because the values of S5-S10, N5-N10, and N10 were low. Comparative Example 2 An aromatic polyamide film was obtained in the same manner as in Example 2 except that P was 2.4 kPa, T was 35 seconds, and the transverse stretching speed was 0.7% / second. This film has a S5-S10 value of 9.1% and an N5-N10 value of 10%.
× 10 ⁶ pieces / mm ² , N10 0.8 × 10 ⁶ pieces / mm ² ,
The heat shrinkage in the width direction was 0.2%, the Young's modulus in each of the MD and TD directions was 11.0 GPa and 15.6 GPa, and the abrasion resistance was x. The characteristics of the magnetic tape using this film were as follows: the output was Δ, and the running property was ×, and it was not practically usable. The reason why the various characteristics were lower than in Example 2 is that N
10 and that the thermal shrinkage was low. (Comparative Example 3) A film was formed in the same manner as in Example 2 except that P was set to 3.9 kPa and T was set to 36 seconds, to obtain an aromatic polyamide film. This film has an S5-S10 value of 12.1
%, The value of N5-N10 is 58 × 10 ⁶ pieces / mm ² , N10
Is 3.1 × 10 ⁶ pieces / mm ² , and the heat shrinkage in the width direction is 2.4.
%, MD, TD Young's modulus in each direction is 10.3G
Pa, 15.4 GPa, and abrasion resistance were ○. The magnetic tape using this film was inferior in smoothness to an output of x and a runnability of △ due to poor smoothness, and was not practically usable as a whole. It can be determined that the various characteristics were lower than in Example 2 because the values of S5-S10 and N5-N10 were high. (Comparative Example 4) A film was formed in the same manner as in Example 2 except that P was 2.4 kPa, T was 10 seconds, and the transverse stretching speed was 22.8% / second, to obtain an aromatic polyamide film. This film has an S5-S10 value of 6.5% and an N5-N10 value of 24%.
× 10 ⁶ pieces / mm ² , N10 is 2.1 × 10 ⁶ pieces / mm ² ,
The heat shrinkage in the width direction was 6.4%, the Young's modulus in each of the MD and TD directions was 10.7 GPa and 15.7 GPa, and the abrasion resistance was x. The magnetic tape using this film has poor head touch due to curl and the output is ×,
The runnability was poor, and was not practical.
It can be determined that the various characteristics were lower than in Example 2 because the value of the heat shrinkage was high. (Comparative Example 5) A film was formed in the same manner as in Example 1 except that P was set to 4.5 kPa to obtain an aromatic polyamide film. This film has an S5-S10 value of 10.7%, N5-N1
The value of 0 is 46 × 10 ⁶ pieces / mm ² , and N10 is 1.3 × 10
⁶ pieces / mm ² , heat shrinkage in width direction 1.2%, MD, TD
Young's modulus in each direction is 11.8 GPa, 16.3 respectively
GPa and abrasion resistance were Δ. The magnetic tape using this film had an output of x and a runnability of △, and was not practically usable. It can be determined that the various characteristics were lower than in Example 1 because S5-S10 was large and the surface smoothness was poor. (Comparative Example 6) A film was formed in the same manner as in Example 6 except that P was changed to 5.3 kPa to obtain an aromatic polyamide film. This film had a value of S5-S10 of 0.05%, N5-N1
The value of 0 is 3.2 × 10 ⁶ pieces / mm ² , and N10 is 7.5 × 1
0 ⁶ / mm ^2, the width direction of the heat shrinkage ratio 3.2%, MD, T
D: Young's modulus in each direction is 10.4 GPa;
1 GPa, scraping resistance was x. The magnetic tape using this film had an output of △ and a running property of △, and was not practically usable. It can be determined that the various characteristics were lower than in Example 6 because S5-S10 was small and the contact area was large. (Comparative Example 7) A film was formed in the same manner as in Example 1 except that P was 2.2 kPa and T was 35 seconds, to obtain an aromatic polyamide film. This film has an S5-S10 value of 8.7%,
The value of N5-N10 is 52 × 10 ⁶ pieces / mm ² , the value of N10 is 2.1 × 10 ⁶ pieces / mm ² , and the heat shrinkage in the width direction is 1.3.
%, MD and TD Young's modulus in each direction is 11.3G
Pa, 16.5 GPa, and abrasion resistance were Δ. The magnetic tape using this film had an output of x and a runnability of △, and was not practically usable. It can be determined that the various characteristics were lower than in Example 1 because N5-N10 was large and the surface smoothness was poor. (Comparative Example 8) A film was formed in the same manner as in Example 6 except that P was set to 2.6 kPa and T was set to 40 seconds, to obtain an aromatic polyamide film. This film has a value of S5-S10 of 0.5%,
The value of N5-N10 is 1.8 × 10 ⁶ pieces / mm ² , the value of N10 is 4.9 × 10 ⁶ pieces / mm ² , and the heat shrinkage in the width direction is 2.9.
%, MD, TD Young's modulus in each direction is 10.6G
Pa, 14.6 GPa, and abrasion resistance were Δ. The magnetic tape using this film had an output of Δ and a running property of ×, and was not practically usable. It can be determined that the various characteristics were lower than in Example 6 because N5-N10 was small and the friction when formed into a tape was increased. (Comparative Example 9) The addition amount of PES was 1% by weight, and P was 3.5 k.
A film was formed in the same manner as in Example 2 except that Pa and T were set to 32 seconds to obtain an aromatic polyamide film. This film has a S5-S10 value of 9.6% and an N5-N10 value of 48.
× 10 ⁶ pieces / mm ² , N10 0.4 × 10 ⁶ pieces / mm ² ,
The heat shrinkage in the width direction was 0.8%, the Young's modulus in each of the MD and TD directions was 11.9 GPa and 17.1 GPa, and the abrasion resistance was x. The magnetic tape using this film had an output of Δ and a running property of ×, and was not practically usable. It can be determined that the various characteristics were lower than in Example 2 because N10 was small and the friction when formed into a tape was increased.

[0071]

[Table 1]

[0072]

As described above, the aromatic polyamide film of the present invention has a large number of projections having a uniform height, controls the smoothness of portions other than the projections within a certain range, and has a heat shrinkage ratio within a certain range. It has excellent running properties and is particularly useful as a base film for a magnetic recording medium.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) (C08L 77/10 (C08L 77/10 81:06) 81:06) F-term (reference) 4F071 AA50 AA56 AA64 AF20 AF20Y AF27 AF61 AF61Y AH14 BA02 BB02 BB08 BC01 BC14 BC15 4J002 CF002 CG002 CH072 CJ002 CL061 CM042 CN032 FD010 GS01 5D006 CB03 CB05 CB07

Claims (5)

[Claims] 1. A projection having at least one surface and a height of 5 n
m is S5 (%),
The protrusion cross-sectional area on the horizontal plane having a height of 10 nm is S10
(%), The density of the protrusions having a height of 5 nm or more was N5 (pieces / m
m ² ) and the density of protrusions having a height of 10 nm or more is N10 (pieces / m ² ).
m ² ), the following formulas (1) to (3) are simultaneously satisfied, and the heat shrinkage before and after the heat treatment at 180 ° C. for 30 minutes in the width direction is in the range of 0.3 to 5%. Aromatic polyamide film. 0.1 ≦ S5-S10 ≦ 10 (1) 2 × 10 ⁶ ≦ N5-N10 ≦ 50 × 10 ⁶ (2) 0.5 × 10 ⁶ ≦ N10 (3) 2. An aromatic polyamide and a heteropolymer, wherein the content of the heteropolymer is more than that of the aromatic polyamide.
The aromatic polyamide film according to claim 1, which is more than 0.1% by weight and less than 20% by weight. 3. The aromatic polyamide film according to claim 2, wherein the heteropolymer has at least one sulfone group in a repeating unit. 4. The aromatic polyamide film according to claim 1, which has a Young's modulus in a length direction and / or a width direction of 9.8 GPa or more. 5. A magnetic recording medium in which a magnetic layer is formed on at least one surface of the aromatic polyamide film according to claim 1.