JPH10114038A - Aromatic polyamide film, manufacture thereof, and magnetic recording medium using film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a film which is good at surface smoothness and traveling properties and especially suitable for a magnetic recording medium by using an aromatic polyamide film which indicates specified values of root mean square roughness and at least of one side and of maximum height. SOLUTION: In an aromatic polyamide film which is used preferably for a high density magnetic recording medium, a film of 2.0nm or more root mean square roughness at least of one side and of 100nm or less maximum height is used. One in which on its surface, the number of projections of at least 5nm height is 10<6> -10<10> /mm<2> , and at least 30% of the projections is formed from inorganic particles is used. Inorganic and/or organic particles are made to be contained in the film. As the aromatic polyamide which constitutes a base material aromatic polyamide film, para-oriented aromatic polyamide is used, and one in which an aromatic nucleus occupies at least 30% of the total is used in part of hydrogen atoms in the aromatic nucleus in a structural unit.

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, particularly an aromatic polyamide film suitably used for high-density magnetic recording media, and a method for producing the same.
And high-density magnetic recording media.

[0002]

2. Description of the Related Art Aromatic polyamide films and aromatic polyimide films have been studied for various applications by utilizing their excellent heat resistance and mechanical properties. In particular, para-oriented aromatic polyamides are superior to other polymers in mechanical properties such as rigidity and strength, so they are very advantageous for thinning films, and can be used for printer ribbons, magnetic tapes, capacitors, etc. ing. In particular, when used for magnetic tape, it is necessary to improve the surface properties of the film. For example, as an example of improving the surface properties of a film for a magnetic recording medium by adding inorganic particles, see Japanese Patent Application Laid-Open No.
3, JP-A-60-201914.

[0003]

In recent years, with the advancement of digital recording technology and the development of external memories in computers, the demand for a film suitable for a magnetic recording medium having a reduced thickness, higher recording density, and higher durability has been increasing. It is getting stronger. In other words, great progress has been made in the formation of ultra-thin coating type magnetic layers as magnetic layers to achieve high output, or in metal thin film type magnetic layers in which a magnetic layer is formed directly on a film by vapor deposition or sputtering. However, the higher the performance of the magnetic layer, the higher the level of smoothness and running property required for the base film. Particularly, in the case of a metal thin-film type magnetic recording medium, the surface properties of the base film dominate the surface properties of the magnetic surface, so that the requirements are strict, and the problems described below are increased.

As a problem when using an aromatic polyamide film, first, when the surface is to be smoothed in order to improve the output characteristics, the magnetic layer peels off due to friction with the head, or the magnetic powder peels off. The head may be clogged. If the surface is roughened to improve the durability, the output characteristics required for a high-performance magnetic recording medium may not be obtained. Secondly, if the surface is roughened to provide runnability, transfer occurs on the magnetic layer, and data may be lost on the magnetic recording medium. In order to solve such a problem, it has been proposed to change the surface properties of the surface on the magnetic layer side and the surface on the running side, but it is not always sufficient.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention relates to a method for measuring the surface roughness of at least one side of a sheet by means of an atomic force microscope at a root mean square of 2.0 nm or more and a maximum height of 100 nm or less. It is an aromatic polyamide film characterized by having a certain characteristic.

[0006]

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

The 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, Y is _{-O -, - CH 2 -,} - CO -, - SO 2 -, - S -, -
It is selected from C (CH ₃ ) ₂ − and the like, but is not limited thereto. Further, some of the hydrogen atoms on these aromatic rings may be substituted with halogen groups (especially chlorine) such as fluorine, chlorine, and bromine, alkyl groups (particularly methyl groups) such as nitro, methyl, ethyl, and propyl groups, and methoxy. Base. Ethoxy, propoxy,
Also included are those substituted with a substituent such as an alkoxy group such as an isopropoxy group, and those in which hydrogen in an amide bond constituting the polymer is substituted with another substituent. From the characteristic point of view, those in which the above aromatic rings are bonded in the para-oriented position account for 50% or more of the total aromatic rings, preferably 7%.
A polymer occupying 5% or more (hereinafter referred to as a para-oriented aromatic polyamide) is preferred because the film has high rigidity and good heat resistance. The term "para-orientation position" used herein means that the bond position is linear. In addition, 30% or more, more preferably 50% or more, even more preferably 70% or more of the entire aromatic ring in which a part of hydrogen atoms on the aromatic ring is substituted with a halogen group.
Above, moisture resistance is improved, dimensional change due to moisture absorption,
It is preferable because characteristics such as a decrease in rigidity are improved, and adhesion between the aromatic polyamide film and an organic and / or inorganic substance is improved when the organic substance and / or the inorganic substance is applied. Examples of such a halogen include fluorine, chlorine, and bromine, and a particularly preferred halogen is chlorine.

The aromatic polyamide of the present invention contains at least 50 mol% of the repeating units represented by the general formulas (I) and / or (II).
Less than that, other repeating units may be copolymerized or blended.

The aromatic polyamide of the present invention may be blended with additives such as an antioxidant to such an extent that the physical properties of the film are not impaired.

The aromatic polyamide film of the present invention has a root-mean-square (hereinafter abbreviated as Rq) of at least one side (hereinafter abbreviated as A) measured by an atomic force microscope (hereinafter abbreviated as AFM) of 2.0 nm or more. And the maximum height (hereinafter abbreviated as Rm) needs to be 100 nm or less. Rq is 2.
If it is less than 0 nm, the surface may be too smooth and the magnetic layer may be damaged by sliding of the head when used as a magnetic recording medium, resulting in poor durability. On the other hand, if Rm exceeds 100 nm, the spacing loss from the head in a magnetic recording medium increases, and the output characteristics may be insufficient. Rq is preferably at least 2.5 nm, more preferably at least 3.0 nm. Rm is preferably 80n
m, more preferably 60 nm or less.

[0011] The aromatic polyamide film of the present invention comprises A
The number of protrusions having a surface height of 5 nm or more is 10 ⁶ to 10 ¹⁰ / m
m ² is particularly preferable in the case of a vapor deposition type magnetic recording medium since the contact area with the head is reduced and the durability is excellent. Further, it is preferable that the production of a magnetic recording medium can be prevented from causing a change in thermal dimension due to a decrease in the contact area with the cooling can, that is, a so-called "heat loss". It is preferably at least 5 × 10 ⁶ pieces / mm ² , more preferably at least 10 ⁷ pieces / mm ² , and the upper limit is 10
^{When the} number is ¹⁰ / mm ² or less, the adhesion at the interface between the base film and the magnetic layer is not reduced, which is preferable.

Further, when the projections provided on the surface A are formed of inorganic particles at 30% or more of the total number of projections, the surface hardness of the film increases, and the projections are easily formed steeply. It is preferable because the durability when used as a recording medium is improved. Preferably at least 50%,
It is more preferably at least 70%.

In order to achieve the above surface properties, there are a method of incorporating inorganic and / or organic particles into the aromatic polyamide film, a method of coextruding a thin film layer containing the particles with a die and coextruding. However, a method of achieving the above surface properties by applying a coating agent composed of dispersed particles / solvent / polymer binder on an aromatic polyamide film serving as a base material and drying the coating material can be suitably used.

The composition of the coating composition has a particle concentration of 0.00
2 to 10% by weight and at least one polymer is 0.01 to
It is preferable to use a solvent containing 10% by weight in view of applicability and surface formation.

The particles may be either organic particles or inorganic particles, such as cross-linked polyvinyl benzene, acrylic, cross-linked polystyrene, polyester, polyimide,
Polyamide, particles made of an organic polymer such as a fluororesin, colloidal silica, titanium oxide, aluminum oxide, zirconium oxide, calcium carbonate, carbon black, inorganic particles such as zeolite, or the above polymer particles coated with another organic substance, etc. Examples include the above-described organic polymer particles subjected to various treatments, and inorganic particles whose surfaces have been subjected to various treatments such as coating with the organic polymer. Any of these particles may be used, but for the purpose of increasing the hardness of the surface projections, it is more preferable to use inorganic particles or inorganic particles that have been subjected to various treatments such as coating with the above organic polymer. The particle diameter is 5 to 1 as an average particle diameter.
00 nm is preferred, and more preferably 10 to 50 nm.
nm, more preferably 15 to 30 nm, and it is preferable to use monodisperse particles. Further, among these, different kinds and different diameter particles may be used in combination.

Since the aromatic polyamide film of the present invention forms uniform projections, the particle shape is preferably spherical, and it is desirable to use one having a uniform particle size. Specifically, the relative standard deviation σ of the particle size distribution
(Standard deviation / average particle diameter) preferably satisfies σ ≦ 0.3, more preferably σ ≦ 0.15.

The polymer used here is added to improve the adhesion between the particles and the aromatic polyamide, and is, for example, an aromatic or aliphatic polyamide resin, a polyimide or a polyamic acid resin. , A silicone resin, a urethane resin, an epoxy resin, a polyester resin, a cellulose resin, a polysulfone resin such as polyethersulfone, a polyether resin or the like, or a modified product of the above resin, etc., although not particularly limited, aromatic polyamide and Those containing a polar group are preferred from the viewpoint of affinity.

As the solvent, any solvent can be used as long as it dissolves the above-mentioned polymer, but water, alcohols such as isopropanol and methanol, ketones such as methyl ethyl ketone, N-methyl-2-pyrrolidone, dimethylacetamide and the like can be used. An aprotic polar solvent or the like can be suitably used, and a mixture of two or more solvents may be used.

The coating composition may contain a surfactant, a silane coupling agent, etc. in addition to the particles, the polymer binder, and the solvent.

The coating amount should be optimized based on the concentration of the contained particles, the particle diameter, and the target number of projections.
A to 5 g / m ^2, coating method gravure depending on the amount of coating, micro gravure method, Mayer bar method, selected from die coater method or the like. From the viewpoint of uniformity of coating thickness,
The microgravure method and the Meyer bar method are preferred.

The timing of coating may be any time after coating from a die, after a dry process, after a wet process, or after film formation. However, from the viewpoint of reducing unevenness of the coating thickness, After molding, a method of applying off-line is preferable.

The aromatic polyamide film serving as a base material may contain 0.001 to 2.0% by weight of particles selected from the above-mentioned particle group in order to impart an appropriate undulation to the surface. More preferred.

Further, the aromatic polyamide film as a base material has a wetting index of 45 mN / m (45 dyn /
cm) is preferable because the adhesion to the particles / polymer binder is improved. More preferably 55 mN / m
(55 dyn / cm) or more, and more preferably 60
mN / m (60 dyn / cm) or more. In order to make the wetting index 45 mN / m (45 dyn / cm) or more, a discharge treatment using corona, plasma, or the like is effectively used.

The surface of the film of the present invention on the side on which the magnetic layer is provided must be highly defect-free. That is, it is preferable that the number of coarse projections (L; number of pieces / 100 cm ² ) having a height h (nm) on the A side of the film satisfies the following expression.

H ≧ 270 L <100 h> 540 L <70 h> 810 L <15 h> 1080 L <5 In a digital video tape, in terms of many disadvantages exceeding this range, the electromagnetic conversion characteristic is not sufficient. There are many dropouts, which cannot be used for the present invention. In order to satisfy the above expression, it is preferable to remove coarse foreign substances present in the coating material by passing through a filter having a predetermined filtration accuracy when applying the particles. Here, the filtration accuracy is defined as the particle diameter of particles that are just captured on a 95% filter when the particles are dispersed in a polymer or a solvent and passed through a filter. Naturally, the smaller the value of the filtration accuracy, the smaller the removal of foreign matter. The filtration accuracy of the filter of the present invention is 1000 nm or less, preferably 600 nm or less, and more preferably 300 nm or less. It is more preferable that the number of the coarse projections is satisfied also on the surface on the opposite side (hereinafter abbreviated as B surface).

The aromatic polyamide film of the present invention comprises A
It is preferable that the three-dimensional surface roughness SRa1 at a measurement area of 0.002 mm ² and the three-dimensional surface roughness SRa2 at a measurement area of 1.0 mm ² satisfy the following expression.

0.8 ≦ SRa2 / SRa1 ≦ 2.5 When SRa2 / SRa1 exceeds 2.5, uneven undulations are generated on the film surface, and when a magnetic tape is used, head touch becomes unstable and output decreases, Data loss may occur. On the other hand, SRa2 / SRa1 is 0.8
If the amount is less than the above range, the running property of the magnetic tape may be reduced, and blocking may occur when the magnetic tape is wound into a roll. SRa2
/ SRa1 is preferably within the range of the following formula.

1.1 ≦ SRa2 / SRa1 ≦ 1.8 It is more preferable that the above range of SRa2 / SRa1 is satisfied also on the surface on the side opposite to the A surface (hereinafter abbreviated as B surface).

In order to control SRa2 / SRa1 within the above range, for example, the following method is effective. That is, in the production process of the film, a method of mirror-finish the roll surface in contact with the film peeled from the endless belt or the like, or to prevent the solvent extraction and drying of the film from occurring rapidly, for example, the temperature in the solvent extraction process -10
The polymer concentration in the film at the time of peeling from an endless belt or the like is 30 to 70.
%, A method of preheating the film to a temperature of 50 to 100 ° C. before the drying and heat treatment in the tenter, or a combination of the above methods.

The aromatic polyamide film of the present invention may be a single film, but preferably has a particle / polymer-containing thin film layer by a coating method. Moreover, the aromatic polyamide film of the base material may be a single layer or a multilayer. For example, in the case of two layers, the polymerized aromatic polyamide solution is divided into two parts, different particles are added, and then the layers are laminated. The same applies to the case of three or more layers. These laminating methods include well-known methods, for example,
There are a method of laminating in a die, a method of laminating in a composite pipe, and a method of forming one layer once and forming another layer thereon.

The aromatic polyamide film of the present invention preferably has a tensile Young's modulus in at least one direction of 9.8 GPa. The output of the magnetic tape increases with the improvement of the head touch property between the tape and the head. For this purpose, a higher Young's modulus of the base film is required. When the recording method is the fixed head type, the Young's modulus in the longitudinal direction is particularly necessary, and when the recording method is the helical scan type, the Young's modulus in the width direction is particularly necessary. If any direction of the base film is less than 9.8 GPa, any recording is possible. Even if the method is adopted, it is not preferable because a high output cannot be obtained. The aromatic polyamide film of the present invention preferably has a Young's modulus in at least one direction of 11.7 GP.
a or more, more preferably 12.7 GPa or more.
It is needless to say that the Young's modulus in all directions is preferably 9.8 GPa or more.

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 form of the magnetic recording medium is not particularly limited, such as a disk shape, a card shape, and a tape shape. However, in order to cope with the aromatic polyamide film of the present invention, the aromatic polyamide film can be made thinner by utilizing its excellent surface properties and high Young's modulus. The support made of an aromatic polyamide film has a thickness of 6.5 μm or less and a width of 2.3 to 2.3 μm.
13 mm, a length of 100 m / roll or more, a recording density (uncompressed) as a magnetic recording medium of 8 KB / mm ² or more; This is particularly preferable because the excellent effects of having rigidity can be further exhibited. The recording density defined here is obtained by dividing the total recording capacity per cassette by (length × width) of the used magnetic tape. In recent years, magnetic recording media typified by magnetic tapes have been increasingly demanded for miniaturization and high capacity, but there are the following points in implementing high capacity. One is to increase the recording capacity as a whole by reducing the thickness of the support and increasing the length.The other is to reduce the track width, shorten the recording wavelength, etc. These methods generally improve the recording capacity, and generally use these methods in combination. When reducing the thickness of the support,
Of course, it is necessary for the support to have high rigidity, but the contribution of the head surface to the head touch and, consequently, the electromagnetic conversion characteristics becomes larger than when the support is thick. In other words, when the tape is thick, the running tension and the touch pressure to the head can be set high, so that even if the support body surface is unregulated, it can be stably contacted with the head,
When the tape is made thinner, the running tension and the touch pressure of the head must be reduced, and therefore, if the surface of the support is not regulated as in the present invention, the adhesion to the head and the running property are reduced. Since the track becomes non-uniform and unstable, track misalignment and signal dropout are likely to occur. Also, due to the demand for higher data transfer speed, the relative speed between the head and the tape tends to be higher than before,
To avoid generating unnecessary frictional heat,
The aromatic polyamide film of the present invention in which the height and the number of the protrusions are controlled in a specific range is extremely effective. As described above, the aromatic polyamide film of the present invention can be used as a magnetic tape that can suitably meet such a demand for higher capacity. The thickness of the support is preferably 5.5
μm or less, more preferably 4.5 μm or less, and the recording density of the magnetic recording medium is preferably at least 25 kilobytes / mm ^2, more preferably at least 34 kilobytes / mm ² .

The magnetic recording medium of the present invention can be used for consumer, professional, broadcasting stations such as D-1, D-2, D-3, digital video cassettes, DDS-2, 3, 4, data 8 mm,
Although it can be suitably used for data storage applications such as QIC, it can be optimally used for data storage applications where reliability such as data loss is most important.

The magnetic layer is formed by a wet method of kneading a magnetic powder such as iron oxide, metal powder or the like with a binder of thermosetting, thermoplastic or radiation curable, coating and drying, a vapor deposition method, a sputtering method or the like. Any method of a dry method of directly forming a magnetic metal thin film layer on a base film by an ion plating method or the like can be adopted, but when the dry method is adopted, the excellent surface properties of the film of the present invention are further utilized. It is preferable to be.

As the metal thin film type magnetic layer, Co,
Examples thereof include simple substances or alloys of metals such as Fe and Ni, alloys of these simple substances with Cr, Mo, W, V, Nb, Ti, Rh, and Ru, and oxides of these metals or alloys.
If necessary, the same type or different types of magnetic layers can be laminated.

Further, a protective layer such as a diamond-like coating and a lubricating layer are preferably formed on such a magnetic layer for the purpose of further improving the durability of the magnetic recording medium and imparting slipperiness. it can.

Regarding the magnetization method, it can be used for optical recording tapes irrespective of horizontal magnetization or vertical magnetization.

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

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

These polymer solutions may be used directly as a film forming stock solution, or the polymer solution 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. Is also good.

In order to obtain the aromatic polyamide film of the present invention, the intrinsic viscosity of the polymer (measured at 30 ° C. as a 100 ml solution of 0.5 g of the polymer in sulfuric acid) is 0.1.
It is preferably 5 or more. In some cases, an inorganic salt such as calcium chloride, magnesium chloride, lithium chloride, lithium nitrate, or the like is added to the film forming stock solution as a dissolution aid.
The polymer concentration in the stock solution is preferably about 2 to 40% by weight.

As a method for adding the particles, there is a method in which the particles are sufficiently slurried in a solvent in advance and then used as a solvent for polymerization or a solvent for dilution, or a method in which a stock solution for membrane preparation is directly added after preparation.

The membrane-forming stock solution prepared as described above is filtered through a filter having a filtration accuracy of 6000 nm or less, and then formed into a film by a so-called solution casting method. The solution casting method includes a dry-wet method, a dry method, and a wet method. When a film is formed by a wet method, the undiluted solution is filtered and then extruded directly from a die into a film-forming bath, or once extruded onto a support such as a drum or a belt, and introduced together with the support into the wet bath. Is adopted. This bath is generally composed of an aqueous medium, and may contain an organic or inorganic solvent or an inorganic salt in addition to water. The bath temperature is usually from 0 to 100 ° C., and salts and solvents contained in the film are extracted by passing through a wet bath. Here, the film when introduced into the wet bath does not yet have a sufficient surface hardness, so if there is contamination or the like in the wet bath medium, the film surface adheres and the surface properties deteriorate. For this reason, the medium used in the wet bath preferably has a filtration accuracy of 6000 nm or less, more preferably 5000 nm or less, and still more preferably 3000 n.
m. The time required to pass through these wet baths is 10 seconds to 30 minutes, depending on the thickness of the film. Further, if necessary, the film is stretched in the longitudinal direction. Next, drying and heat treatment are performed. These treatments are generally performed at 200 to 500 ° C. for a total of 1
It is preferably performed in seconds to 30 minutes. In this process, transverse stretching is performed as necessary.

When a film is formed by a dry-wet method, the undiluted solution is extruded from a die onto a support such as a drum or an endless belt to form a thin film. Then, the solvent is scattered from the thin film layer and dried until the thin film has a self-holding property. I do. Drying conditions are from room temperature to 2
20 ° C., within 60 minutes, preferably from room temperature to 2
It is in the range of 00 ° C. Further, by controlling the frequency of surface defects of the drum and the endless belt used in the drying step, the surface property of the surface B can be controlled. Preferably 30μ in diameter
0.001 to 0.02 defects / mm
² , more preferably 0.002 to 0.015 particles / mm ² . After the dry process, the film is peeled from the support, introduced into the wet process, subjected to desalting and solvent removal in the same manner as in the above wet process, and further stretched, dried and heat-treated to form a film.

When a dry process is employed, the film which has been dried on a drum or an endless belt or the like and has self-holding properties is peeled off from these supports and stretched in the longitudinal direction of the film. . Further drying, stretching, and heat treatment for removing the residual solvent are performed. These treatments are preferably performed at 200 to 500 ° C. for 1 second to 30 minutes, but are performed at a temperature equal to or lower than the heat resistant temperature of the organic particles. Is more preferred.

The film formed as described above is stretched during the film forming process so that the mechanical properties and the thermal properties fall within the range of the present invention.
It is preferably in the range of 8.0 (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 1 .1 to 5.0.

It is preferable to form surface projections on the final film thus obtained or on the film in the manufacturing process by the above-mentioned coating method.

[0049]

EXAMPLES The characteristic values of the present invention are based on the following measuring methods and evaluation criteria.

(1) Rq, Rm and Number of Projections Using an atomic force microscope (AFM), the measurement was carried out 10 times at different locations under the following conditions, and the average value was obtained.

Apparatus: NanoScope III AFM (manufactured by Digital Instruments) Cantilever: silicon single crystal Scanning mode: tapping mode Scanning range: 5 μm × 5 μm Scanning speed: 0.5 Hz Measurement environment: temperature 25 ° C., relative humidity 55% In addition, the number of protrusions Can be determined by observing an image subjected to shadowing (5 °) with a scanning electron microscope at a magnification of 30,000 or more and counting protrusions having a height of 5 nm or more.

(2) Fraction of number of protrusions by inorganic particles Arbitrary protrusions 10 using a field emission scanning electron microscope-energy dispersive X-ray analyzer (FE-SEM-XMA).
An analysis was performed on 0 protrusions, and the result was defined as a percentage of the number of protrusions from which the inorganic component was detected.

Apparatus Field emission type scanning electron microscope S-800 energy dispersive X-ray analyzer manufactured by Hitachi, Ltd. EMAX-3770 manufactured by Horiba, Ltd. Measurement conditions Acceleration voltage: 15 kV Irradiation current: 0.2 nA Measurement time: 100 sec. Sample preparation Carbon was vapor-deposited on the sample and measured.

(3) Three-dimensional Surface Roughness The surface roughness was measured using a fine shape measuring device ET-30HK manufactured by Kosaka Seisakusho Co., Ltd. For the detection, an optical stylus (HIPOSS, trade name) was used, and the film surface was subjected to aluminum evaporation under vacuum, and then measured. The measurement conditions are described below.

B. SRa1 (measurement area 0.002 mm ² ) ・ Measurement length in the longitudinal direction 0.02 mm ・ Measurement length in the width direction 0.10 mm ・ Cutoff value 0.08 mm b. SRA2 (Measurement area 1.0 mm ²⁾ · longitudinal direction of the measuring length 0.50 mm · width direction of the measuring length 2.00 mm · cutoff value 0.08 mm (4) large protrusions number entity the film surface 50 cm ² or more ranges for Observe under polarized light with a microscope and mark coarse projections such as foreign matter. The height of the protrusion is determined by the multiple interference method, and the number is 100 cm.
^It was converted to the number per ² pieces.

(5) Tensile Young's Modulus The film was cut into a width of 10 mm and a length of 150 mm.
Chart speed 500 mm / min, temperature 23 ° C, relative humidity 6
Under the condition of 5%, it is pulled with an Instron type tensile tester. The tensile Young's modulus is determined from the tangent at the rising portion of the obtained load-elongation curve.

(6) Average Particle Diameter of Containing Particles The particles are observed with an electron microscope, and the image of the particles (shading of light generated by the particles) is linked to an image analyzer (for example, QTM900 manufactured by Cambridge Instrumental Corporation) and observed. The following numerical processing is performed for 5000 or more particles at different locations, and the number average diameter D obtained thereby is defined as the average particle diameter.

D = ΣDi / N where Di is the equivalent circle diameter of the particles and N is the number.

(7) Relative standard deviation of contained particles The standard deviation σ (=) calculated from the particle diameter Di, the average particle diameter D, and the total number N of particles measured by the method of (4) above.
{(Di-D) ² / N}) was divided by the average particle diameter D (σ / D).

(8) Content of Content Particles A solvent that does not dissolve the particles is selected and the film is dissolved.
The particles are centrifuged, and the ratio (% by weight) to the total weight of the particles is defined as the particle content. In some cases, the combined use of infrared spectroscopy is also effective.

(9) Electromagnetic conversion characteristics (initial output characteristics) The obtained film was placed along a cooling can at −10 ° C. in a vacuum of 1 × 10 −5 Torr to form a Co—O alloy (C
(The weight fractions of o and O are 80% and 20%, respectively).
Electron beam evaporation was performed to a thickness of μm to form a magnetic layer. This film was slit into a width of 6.35 mm and a length of 150 m, and after assembling into a cassette, a 6.5 MHz sine wave was recorded at an optimum recording current, and the reproduction output was evaluated based on Example 1.

(10) Durability The tape cassette obtained in the above (9) was run 100 times while being in contact with the head in an environment of a temperature of 40 ° C. and a relative humidity of 30%, and the output characteristics were measured. Was evaluated.

A: Difference from initial output is less than 0.5 dB O: Difference from initial output characteristics is less than 1 dB Δ: Difference from initial output characteristics is 1 dB or more and less than 3 dB X: Difference from initial output characteristics is Next, the present invention will be described based on examples, but the present invention is not limited thereto.

Example 1 2-Chloroparaphenylenediamine corresponding to 80 mol% as an aromatic diamine component and 4,4′-diaminodiphenyl ether corresponding to 20 mol% in N-methyl-2-pyrrolidone (NMP) And dissolve 100
The mole% 2-chloroterephthalic acid chloride was added and stirred for 2 hours to complete the polymerization. This was neutralized with lithium hydroxide to give a polymer concentration of 10% by weight and a viscosity of 300%.
A 0 poise aromatic polyamide solution was obtained.

The polymer solution was filtered with a filtration accuracy of 5000 n.
m, after passing through a 1000 nm filter,
A film with a surface defect of not less than 0.005 m / mm ² is cast on an endless belt and heated with hot air at 180 ° C. for 2 minutes to evaporate the solvent. Peeled off. Next, the film was introduced into a 40 ° C. water tank filtered with a filter having a filtration accuracy of 4000 nm, and water extraction of the residual solvent and the inorganic salt generated by the neutralization was performed. First, preliminary drying was performed at 80 ° C. for 30 seconds with a tenter. After performing, drying and heat treatment of moisture at 280 ° C. for 1.5 minutes,
Slow cooling was performed at a rate of 20 ° C./sec to obtain an aromatic polyamide film having a thickness of 4.2 μm (referred to as film A). During this time, 1.16 times each in the longitudinal direction and width direction of the film,
The film was stretched 1.43 times. The wetting index of this film is 4
3 mN / m (43 dyn / cm) and Young's modulus were 12.1 GPa and 16.8 GPa in the longitudinal direction and the width direction, respectively.

A coating solution prepared according to the following composition was passed through a filter having a filtration accuracy of 0.6 μm on the A side (non-contact surface of the belt) of the film, and then a WET thickness of 1.5 μm was obtained using a microgravure roll. And dried in a hot air oven at 120 ° C. for 10 seconds and wound up to obtain an aromatic polyamide film.

Colloidal silica (particle size: 20 nm) 0.018% by weight Water-soluble polyester resin 1.4% by weight Methylcellulose 0.05% by weight Silane coupling agent 0.1% by weight Solvent: water Rq on the A side of this film is 2 0.4 nm, Rm is 31 nm, and the number of protrusions of 5 nm or more is 15 million / mm.
^{2. The} protrusion fraction of inorganic particles is 94%, SRa2 / SRa1 is 1.
08, which is excellent in both electromagnetic conversion characteristics and durability. Table 1 shows the evaluation results.

Examples 2 and 3 The WET thickness of the film A obtained in Example 1 was 5.0 μm and 0.8 μm, respectively, using the coating solution used in Example 1.
m, and dried in the same manner as in Example 1 to obtain an aromatic polyamide film. Table 1 shows the evaluation results.

Example 4 Film A obtained in Example 1 was coated and dried in the same manner as in Example 1, except that the film A was subjected to a corona discharge treatment to set the surface A wettability index to 72 mN / m (72 dyn / cm). Thus, an aromatic polyamide film was obtained. Table 1 shows the evaluation results.

Example 5 A coating solution prepared in the following composition was passed through a film A obtained in Example 1 through a filter having a filtration accuracy of 0.6 μm, and then a WET thickness of 1.0 was obtained using a microgravure roll.
It was coated continuously to a thickness of μm, dried in a hot air oven at 195 ° C. for 20 seconds, and wound up to obtain an aromatic polyamide film. Colloidal silica (particle diameter: 25 nm) 1.2% by weight Aromatic polyamide resin (*) 2.5% by weight Silane coupling agent 0.3% by weight Solvent: N-methyl-2-pyrrolidone (*) The polymer obtained in Example 1 was reprecipitated in a large amount of water, pulverized, sufficiently washed with warm water, methanol and acetone, and dried, and used as a powder.

Table 1 shows the evaluation results.

Example 6 The average particle size is 50 nm and the relative standard deviation of the particle size distribution is 0.12.
Was subjected to ultrasonic dispersion in NMP for 24 hours, and then sequentially filtered using a filter having a filtration accuracy of 1.0 μm, 0.6 μm, and 0.3 μm. The silica slurry thus obtained was added to the aromatic polyamide solution obtained in Example 1 so that the silica concentration was 0.01% by weight with respect to the polymer, and the mixture was sufficiently stirred. Film formation, application of a coating solution, and drying were performed in the same manner as in Example 1.
Table 1 shows the evaluation results.

Comparative Example 1 An evaporation type magnetic layer was formed on the film A obtained in Example 1 without applying a coating liquid, and evaluation was performed. Table 1 shows the evaluation results.

Comparative Example 2 A coating solution prepared according to the following composition was passed through the film A obtained in Example 1 through a filter having a filtration accuracy of 0.6 μm.
It was applied continuously so as to have a thickness of 5 μm, dried in a hot air oven at 120 ° C. for 10 seconds, and wound up to obtain an aromatic polyamide film.

Colloidal silica (particle size: 20 nm) 15.0% by weight Water-soluble polyester resin 12.0% by weight Methyl cellulose 1.6% by weight Silane coupling agent 1.1% by weight Solvent: water The evaluation results are shown in Table 1.

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[Table 1]

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According to the present invention, an aromatic polyamide film having excellent surface smoothness and running properties can be provided by controlling the height and number of projections on a predetermined surface. The film of the present invention can be suitably used for a flexible printed board, a capacitor, a printer ribbon, etc., but for a magnetic recording medium, among others, a high density, a computer external memory formed with a vapor deposition type magnetic layer required for high precision, Particularly suitable for digital video tapes.

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Claims (11)

[Claims] A root mean square roughness of at least one side measured by an atomic force microscope is 2.0 nm or more, and a maximum height is 1
An aromatic polyamide film having a thickness of not more than 00 nm. 2. The aromatic polyamide film according to claim 1, wherein the number of protrusions having a height of 5 nm or more on the surface is 10 ⁶ to 10 ¹⁰ / mm ² . 3. The aromatic polyamide film according to claim 1, wherein 30% or more of the projections on the surface are projections composed of inorganic particles. 4. The aromatic polyamide film according to claim 1, wherein a layer comprising at least one polymer and inorganic particles is formed on the substrate aromatic polyamide film. 5. The aromatic polyamide film according to claim 1, wherein the aromatic polyamide constituting the base aromatic polyamide film is a para-oriented aromatic polyamide. 6. In the aromatic polyamide constituting the base aromatic polyamide film, at least 30% of the aromatic nuclei in which part of the hydrogen atoms on the aromatic nuclei in the structural units are replaced by halogen groups. Claim 1, characterized in that:
6. The aromatic polyamide film according to 2, 3, 4 or 5. 7. The aromatic polyamide according to claim 1, wherein the base aromatic polyamide film has a wetting index of 45 mN / m (45 dyn / cm) or more. the film. 8. A solvent having a particle concentration of 0.002 to 10% by weight and containing at least one polymer in an amount of 0.01 to 10% by weight is coated on a base aromatic polyamide film, and then dried. The method for producing an aromatic polyamide film according to claim 1, 2, 3, 4, 5, 6, or 7. 9. The method of claim 1, 2, 3, 4, 5, 6, or 7.
A magnetic recording medium comprising a magnetic layer provided on at least one surface of the aromatic polyamide film. 10. The magnetic recording medium according to claim 9, wherein the magnetic layer is a metal thin film type magnetic layer. 11. The magnetic recording medium according to claim 9, wherein the width is 2.3 to 13 mm and the thickness of the support is 6.
5 μm or less, width 3.5 to 13.0 mm, length 100
A magnetic recording medium characterized by being a magnetic tape having a recording density of at least 8 mbytes / mm ^{2 and} a recording density of at least 8 kilobytes / mm ² as a magnetic recording medium.