JP3196684B2 - Film and magnetic recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to severe use conditions,
Particularly under high temperature and high humidity, it has good recording / reproducing characteristics even in a high stress state, and a film and a film which can be suitably used for a high-density magnetic recording medium such as a metal-deposited magnetic layer. The present invention relates to a magnetic recording medium.

[0002]

2. Description of the Related Art Aromatic polyamides and aromatic polyimides are useful as industrial materials because of their high heat resistance and electrical insulation. In particular, aromatic polyamides composed of para-oriented aromatic nuclei, such as polyparaphenylene terephthalamide (PPTA), provide molded articles having excellent strength and elastic modulus in addition to the above-mentioned properties due to their rigidity, and thus their utility value. Is expensive.

Conventionally, as a magnetic recording medium, a magnetic recording medium in which an oxide coating type magnetic layer, a metal coating type magnetic layer, and a metal thin film type magnetic layer are provided on a polyester film has been known (for example, Japanese Patent Application Laid-Open No. Sho 61 (1986)). -26933, JP-A-60
However, the smoothness of the magnetic recording medium is important in order to obtain high electromagnetic conversion characteristics. However, if it is too smooth, it may cause poor running due to friction with the head or damage to the magnetic layer. It must be rough. In other words, in such applications, it is particularly important to improve the surface properties. For example, as a film for a magnetic recording medium using an aromatic polyamide in which the surface properties are improved by adding inorganic particles, see JP-A-60-127523.
JP, JP-A-60-201914, JP-A-60-201914
JP-A-1119024 and JP-A-63-268640.

On the other hand, in recent years, demands for higher capacity and higher performance of magnetic recording media have been increasing. Higher tape capacity is being studied mainly by means of thinning the tape thickness to make it a long tape, or by means of improving the recording capacity per unit area by narrowing the track width or shortening the recording wavelength. However, if the recording / reproducing speed is not enough, it cannot be said that the function is insufficient even if the recording capacity is high.

To improve the recording / reproducing speed, there is a signal compression technique in software, but it is necessary to increase the sliding speed between the head and the recording material. For example, a helical scan method is used as a recording / reproducing method. In this method, a drum-shaped head contacts a tape surface at a fixed angle and reads and writes a signal while rotating. Increase the rotation speed. That is, the friction between the head and the recording material is increasing. For high-density magnetic recording, a metal thin-film type magnetic layer is preferably used as a magnetic layer. However, the magnetic layer is fragile and has poor adhesion to an organic substrate surface, so that a mat layer is provided or the surface is modified. Attempts have been made to improve the adhesiveness of the surface by texture or the like. For example, in the case of an aromatic polyamide film, JP-B-6-87298 can be mentioned.

[0006]

[Problems to be Solved by the Invention] However, in recent years, demands for high-speed recording and reproduction have been increased with the progress of higher capacity. For this reason, the method of providing the mat layer described above increases the number of steps, which is economically unfavorable and impairs thinning (high capacity).
In addition, the surface treatment as disclosed in Japanese Patent Publication No. 6-87298 requires a large-scale apparatus, has a low processing speed, and is inferior in productivity.

The present invention solves the above problems, that is, the adhesiveness or adhesion without impairing the excellent heat resistance, mechanical properties, etc. inherent to aromatic polyamide, and without affecting the improved surface properties. With high-density recording media or recording / reproducing methods,
In particular, it is an object of the present invention to provide a film which does not cause detachment of an upper structure including a magnetic layer even in a high temperature and high stress state, and can be suitably used especially for a high density magnetic recording medium.

[0008]

Means for Solving the Problems] The present invention is mainly composed of an aromatic polyamide-de, two projection group on at least one surface of the film, [1]: height from the flat surface of the film 1 × 10 ² to 1 × 10 ⁸ micro-projections / mm ² having a maximum diameter of 20 nm or more and a maximum diameter of 10 nm or more, [2]: 5 × 10 ultra-fine projections having a height of less than 10 nm and a maximum diameter of 3 nm or more ⁸ / mm ² or more, have a, and protrusions of [1]
Is formed by the particles contained in the film, [2]
The gist of the present invention is a film characterized in that the projections are formed irrespective of the added particles .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic polyamide of the present invention is
50 mol% or more, preferably 70 mol% of the repeating unit represented by the following general formula (I) and / or general formula (II)
It is composed of the above.

Formula (I)

Embedded image General formula (II)

Embedded image Here, Ar ₁ , Ar ₂ , and Ar ₃ (where l, m, and n are integers of 0 or more) respectively include, for example,

Embedded image Etc. can be mentioned, X, Y _{are, -O -, - CH 2 -} , - CO
_{-, - SO 2 -, -} S -, - C (CH 3) 2 -, - C
It is selected from (CF ₃ ) _2- and the like, but is not limited thereto.

Further, a hydrogen atom on these aromatic rings is R,
R ′ or R ″ represents a halogen group, a nitro group, C1 to
It may be substituted with a substituent such as a C3 alkyl group, a C1-C3 alkoxy group, a trialkylsilyl group, an aryl group, an oxyaryl group, a thioaryl group,
Hydrogen on the amide group may be substituted with another substituent.

From the viewpoint of characteristics, it is preferable that the above aromatic ring bonded at the para position accounts for 50% or more, preferably 70% or more, more preferably 75% or more of the total aromatic ring. If it is less than 50 mol%, the film cannot fulfill its functions such as strength, elongation, rigidity and heat resistance. When such conditions are satisfied, the film can be made thinner and can be suitably used as a high-capacity magnetic recording medium. Examples of such para-oriented aromatic nuclei include the following.

[0013]

Embedded image

The substituent for replacing hydrogen on the aromatic nucleus is preferably used because of its improved solubility and hygroscopicity. Particularly in a highly substituted system, it becomes soluble in an organic solvent, and the film-forming properties and surface properties are greatly improved. In order to obtain such an effect, a part of the hydrogen atoms of the aromatic ring may be a halogen group (particularly chlorine), a C1 to C3 alkyl group (particularly a methyl group), a C1 to C3 alkoxy group (particularly a methoxy group),
An aromatic ring substituted with a trimethylsilyl group represents 50
% Or more is preferably used.
In addition, a plurality of types of the above-described para-bonded aromatic nuclei may be used, and a combination of aromatic nuclei having different numbers of aromatic rings (for example, a phenylene group and a biphenylene group or a naphthylene group) has excellent solubility in a solvent and is produced. A good film can be obtained.

The aromatic polyimide of the present invention is one in which a repeating unit represented by the following general formula (III) and / or general formula (IV) comprises 50 mol% or more, preferably 70 mol% or more. .

Formula (III)

Embedded image General formula (IV)

Embedded image

Here, Ar ₄ and Ar ₆ contain at least one aromatic ring, and two carbonyl groups forming an imide ring are bonded to adjacent carbon atoms on the aromatic ring. This A
r ₄ is derived from an aromatic tetracarboxylic acid or its anhydride. The following are typical examples.

[0018]

Embedded image Wherein Z is _{-O -, - CH 2 -,} - CO -, - SO 2 -, - S-,
—C (CH ₃ ) ₂ — and the like, but is not limited thereto.

Ar ₆ is derived from carboxylic anhydride or its halide. Ar ₅ and Ar ₇ are, for example,

Embedded image And X ′ and Y ′ are —O—, —CH ₂ —, —CO—, —SO ₂ —, —S—,
—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 a substituent such as a halogen group (especially chlorine), a nitro group, an alkyl group having 1 to 4 carbon atoms (especially a methyl group), or an alkoxy group having 1 to 3 carbon atoms. And those in which the hydrogen in the amide bond constituting the polymer is substituted by another substituent.

The intrinsic viscosity of the polymer (measured at 30 ° C. as a 100 ml solution of 0.5 g of polymer in sulfuric acid) is
It is preferably 0.5 or more.

As the polymer constituting the base film, an aromatic polyamide is preferable because it is easy to obtain a high Young's modulus and the surface can be formed relatively easily as described later.

At least one surface of the film of the present invention has the following two protrusion groups: [1]: 1 × 10 ² fine protrusions having a height from the flat surface of the film of 20 nm or more and a maximum diameter of 10 nm or more. １1 × 10 ⁸ / mm ² , [2]: Ultra-fine projections having a height of less than 10 nm and a maximum diameter of 3 nm or more have 5 × 10 ⁸ / mm ² or more.

First, the group of projections [1] mainly has a running property,
This has the effect of improving durability and maintaining good electromagnetic conversion characteristics. In other words, the presence of the projection group of [1] makes it possible to obtain a good contact with the head, for example, when a magnetic recording medium is used, and it is possible to obtain a deviation from the magnetic layer or the head and stable running properties. In addition, since it has appropriate smoothness, it can have excellent electromagnetic conversion characteristics. It is effective that the projection has a height from the flat surface of the film of 20 nm or more, preferably 20 nm or more and 500 nm or less. A projection having a height of less than 20 nm cannot sufficiently obtain the above-described effects. Further, those having a height of 500 nm or more are effective for improving running properties, but are not preferable because electromagnetic conversion characteristics are deteriorated. The maximum diameter of the projection is 10 nm or more. Since the projections of less than 10 nm are steep, the effects of the present invention cannot be sufficiently obtained. The upper limit of the maximum diameter is not particularly limited.
It is at most 00 nm, more preferably at most 500 nm.
If it is too large, the function as a projection cannot be fully exhibited,
Further, there is a concern that generation of modulation noise and adverse effects on electromagnetic conversion characteristics may occur. Next, regarding the density, the lower limit of the projection density is 1 × 1
0 ² pieces / mm ² or more, preferably 1 × 10 ³ pieces / mm
² or more. When it is less than this range, driving performance,
Little effect of improving durability. The upper limit is 1 × 10 ⁸ / mm ² or less, preferably 1 × 10 ⁷ / mm ² or less. When the amount is large, the running property is good, but the effect is not as high as expected, and the magnetic recording medium has poor electromagnetic conversion characteristics. The number of coarse projections having a height of 546 nm or more is 100/100 cm ² or less.
Preferably, the number is 50/100 cm ² or less. Such coarse projections can be avoided by increasing the dispersibility of the particles, but in the solution casting system of the present invention, the dispersion of particles (preferably monodispersed particles) dispersed in a solvent in advance is required. It is preferable to use a method of adding John. The density of such coarse protrusions can be determined from the observation area by using a differential interference microscope to mark a portion where two or more interference fringes occur when a light beam of 546 nm is applied. Such coarse protrusions cause dropout in a magnetic recording medium.

Next, the projection group [2] mainly contributes to improving the adhesion and improving the durability of the upper structure. In other words, the presence of a large number of such ultra-fine projections increases the surface area substantially without affecting the function of the projections in the above-mentioned semi-microscopic dimension in a semi-microscopic dimension or forms an anchor effect on the substrate surface. Adhesion to the structure of the magnetic layer or the like is greatly improved. In addition, since it does not impair the smoothness, good electromagnetic conversion characteristics can be obtained. The height of the projection is less than 10 nm, preferably less than 5 nm, more preferably less than 2 nm.
The lower limit is preferably 0.01 nm or more. The maximum diameter of the projection is 3 nm or more, preferably 5 nm or more. When the thickness is less than 3 nm, the effect of improving the adhesion is not seen, probably because the projections do not have sufficient strength as a whole. The projection density is 5 × 10 ⁸ / mm ² or more, preferably 1 × 10 ⁹ / mm ² or more, and more preferably 1 × 10 ¹⁰ / mm ^2.
Pieces / mm ² or more. There is no particular upper limit, but if it is too large, the size of each one will not be sufficient and the effect will be diminished, so that about 1 × 10 ²⁰ pieces / mm ² is a standard. Here, it is extremely preferable that a large number of low protrusions exist, and a protrusion higher than the above range causes unfavorable characteristics relating to the protrusion density of the protrusions in [1]. If the projection density is less than the above range, it is difficult to obtain sufficient adhesion. When the magnetic layer is used for a magnetic recording medium, it is preferable that a magnetic layer is provided on the surface having the protrusion [2].

The aromatic polyamide and / or aromatic polyamide film used in the present invention may be blended with particles, lubricants, antioxidants and other additives to such an extent that the physical properties of the film are not impaired.

Here, in the film of the present invention, it is preferable that the projections [1] are formed by added particles, and the projections [2] are formed independently of the particles. As described above, the protrusion [1] has an effect on running properties and durability. Therefore, a strong effect can be expected if the protrusion is reinforced by particles. Conversely, if there are no particles, sufficient action cannot be expected due to deformation or shaving. Also,
If the projection group of [2] is made of added particles, the surface of the entire film becomes hard, and the structure of the facing surface such as the head and the roll is cut off, which may adversely affect the life of the head.
In order to form protrusions independent of these particles, for example, as described in the production of the base film of the present invention described below, microvoids or polymer concentration irregularities are formed near the surface, and then the surface is stretched and dried in a drying step or the like. There is a method of forming the shape. At this time, although irregularities are formed on the film surface, the projections in [2] count the relatively convex portions.

The tensile Young's modulus (20 ° C., relative humidity 60%) E20 of at least one direction of the film of the present invention is E20 ≧ E20.
6.9 GPa, preferably E20 ≧ 7.8 GPa, more preferably E20 ≧ 8.8 GPa. If the Young's modulus is less than 6.9 GPa, it means that deformation tends to occur under tension, and wrinkles and breaks are caused, which greatly impairs practicality. If E20 ≧ 6.9 GPa, the film can be made thinner, which is advantageous for increasing the capacity of a magnetic recording medium, and the Young's modulus in the width direction is 1.1 times or more that in the longitudinal direction. It is preferred that

The film of the present invention has a moisture absorption of 4% or less, preferably 3% or less, more preferably 2% or less. 4
If the content exceeds%, for example, when a magnetic layer is to be formed by a vapor deposition method or the like, bubbles may be generated in the film when heated, which may impair the vapor deposition characteristics. This moisture absorption can be achieved by a method of introducing a substituent into the molecular structure or increasing the crystallinity by heat treatment or the like. In the case of the aromatic polyamide of the present invention, it is preferable to treat the terminal with aniline, phthalic anhydride, benzoyl chloride or the like, since the moisture absorption can be further reduced.

Next, a method for obtaining the film of the present invention will be described. Of course, the present invention is not limited to the following description.

The method for obtaining an aromatic polyamide includes, for example, a low-temperature solution polymerization method, an interfacial polymerization method, a melt polymerization method, and a solid-phase polymerization method. In the case of obtaining the aromatic polyamide from a diacid chloride and a diamine, for example, , N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), and dimethylformamide (DMF). 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 as such as a stock solution for obtaining a molded product, or a 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 stock solution. May be.

In this polymerization, it is a matter of course to use a high-purity raw material and to use a solvent from which impurities such as water have been removed. It is extremely important to provide shear stress and mix efficiently. The reaction for forming an aromatic polyamide is accompanied by a very exothermic reaction at the beginning of the reaction. The reaction heat causes a reaction with the solvent molecule and deactivation of the active terminal, thereby generating an oligomer molecule. Therefore, it is preferable to control the mixing speed to decrease from the beginning to the end of the polymerization in accordance with the increase in the viscosity of the solution. Said means can also sharply control the molecular weight distribution of the polymer and have a favorable effect on mechanical properties and moisture absorption.

In the stock solution for obtaining the aromatic polyamide used in the present invention, an inorganic salt such as calcium chloride, magnesium chloride, lithium chloride, lithium nitrate or the like is added as a solubilizing agent within a range not to impair the object of the present invention. Is also good. Further, the polymerization stock solution may be used as it is, but may be used after reprecipitation with water or the like and then dissolving in a solvent. The polymer concentration in the stock solution is preferably from 2 to 40% by weight, more preferably from 5 to 35% by weight. Below this range, it is necessary to take a large amount of ejection, which is economically disadvantageous. If it exceeds this range, it is difficult to obtain a thin film due to the relationship between the amount of ejection and the viscosity of the solution.

On the other hand, a solution of an aromatic polyimide or a polyamic acid is prepared by dissolving tetracarboxylic acid in an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc) or dimethylformamide (DMF) as a polyamic acid. It can be obtained by a method such as reacting an acid dianhydride or a tricarboxylic anhydride chloride with an aromatic diamine. The aromatic polyimide can be prepared by heating a solution containing the above-mentioned polyamic acid or adding an imidizing agent such as pyridine to form a polyimide, and after reprecipitation, dissolving in a solvent.

Next, SiO ₂ , TiO ₂ , TiN, Al
_The content of particles such as inorganic particles and organic particles such as ₂ O ₃ , ZrO ₂ , zeolite and other fine metal powders is 0.01 to 20% by weight per polymer weight, preferably 0.1 to 20%.
Add 15% by weight. The method of adding the particles is not particularly limited, but if adjustment of the degree of dispersion and aggregation of the particles is necessary, the dispersion is preferably adjusted using a stirring disperser, a ball mill, an ultrasonic disperser, a high-pressure disperser, or the like.

The dispersed particles are mixed with the polymer solution. The particles may be added to the solvent before polymerization, added after polymerization, or added at the time of preparing the polymer solution, or may be added immediately before ejection.

Next, the formation of a film will be described. The film forming stock solution prepared as described above is formed into a film by a so-called solution film forming method. The solution casting method is a dry-wet method,
Although there are a dry method and a wet method, in the present invention, it is appropriate to apply a dry-wet method or a wet method. Here, the dry-wet method will be described as an example.

When a film is formed by a dry-wet method, the stock solution is extruded from a die onto a support such as a drum or an endless belt to form a thin film, and then the solvent is scattered from the thin film layer until the thin film has a self-holding property. I do. Drying conditions are, for example,
The reaction can be performed at room temperature to 220 ° C. for 60 minutes or less. At this time, it is preferable that the residual amount of the solvent as a film after drying is large, and it is preferable that the amount is 45% or more. In addition, it is necessary to heat gently so that a skin layer or a dense layer (a layer having an extremely low solvent content) is not formed on the surface. At this time, means such as taking an internal heating method such as infrared or electromagnetic heating, or preheating the casting medium and heating from the casting medium side after casting is effective in obtaining the present invention. The film after the dry process is peeled from the support, introduced into a wet process, subjected to desalination, solvent removal, and the like, and further subjected to stretching, drying, and heat treatment to form a film. In this process, the wet process, the stretching, and the heat treatment process play an important role.

In this step, a poor solvent such as water is usually used to remove the solvent. However, when the film surface of the present invention cannot be obtained (usually the projections of the above [2] are rough), a poor solvent and a good solvent are mixed. Use a medium. In the wet process, with the progress of desolvation, the vicinity of the film is in a solvent-rich state, but in order to obtain the surface of the present invention, the relative speed between the film and the coagulation medium is increased as much as possible, and the coagulation medium in the coagulation bath is increased. It is extremely effective to force the film to come into contact with the film. Further, the bath temperature can be arbitrarily selected, but a lower bath temperature is preferable because the height of the projections in the above [2] can be kept low. However, if it is too low, productivity will be affected.
When the polymer stock solution is an aprotic polar solvent system such as NMP, the purpose can be more easily achieved by setting the temperature around 40 ° C. as a standard. In addition, the shrinkage of the film is limited during the wet process, and when the film is stretched, the projections of the above [2] can be easily formed.

The stretching can be performed during the wet process or at the time of heating, but the stretching ratio is 1.1 to 8.0 (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). )) Is usually used, but it is easier to form a structure having a crosslinked structure and a cured structure on the surface by physical means such as electron beam or chemical means such as a crosslinking reaction before stretching. The substrate film surface of the present invention can be obtained.

The heat treatment is performed at 150 ° C. to 500 ° C.
C. is usually used. In the present invention, the heat treatment may be preferably performed at a temperature of glass transition temperature (Tg) to Tg + 50 ° C. of the polymer for a few seconds to a few minutes or with a slight relaxation. Furthermore, slow cooling of the film after stretching or heat treatment is effective in suppressing dimensional fluctuation, and cooling at a rate of 50 ° C./sec or less is effective.

Since the aromatic polyamide film used in the present invention has excellent mechanical properties, when it is made into a thin film, it exhibits an excellent effect not found in other materials. The preferred thickness is from 0.5 to 50 μm, more preferably from 1 to 20 μm, and still more preferably from 2 to 10 μm. Particularly for magnetic recording media, the thickness is at most 6.5 μm, preferably at most 4.5 μm, more preferably at most 3 μm. 0.5 μm or less. The lower limit depends on the Young's modulus of the film and the design of the traveling system, and is about 0.5 μm. Thinning can be preferably achieved by using a para-oriented aromatic polyamide. Further, when a tape-shaped magnetic recording medium having a width of 2.2 to 15 mm and a recording density of 15 kilobytes / mm ² or more (when uncompressed) when used as a magnetic recording medium, the present invention is more effectively used. An embodiment utilizing the effects of the invention can be obtained. To increase the capacity of a magnetic tape, there are a method of making the support thinner and making it longer, a method of making the track width narrower, and a method of improving the recording capacity per unit area by shortening the recording wavelength, and these are shared. In many cases, however, an increase in recording density requires an improvement in the amount of magnetization per unit area and output characteristics, and high-speed sliding with the head also occurs during recording and reproduction. Since the film of the present invention is highly controlled in surface properties and excellent in the adhesion of the magnetic recording layer, it can be said that the film exactly meets this demand. The recording density is preferably 25 kbit / mm ² or more, more preferably 34 kbit / mm ^2.
That is all. There is no particular upper limit, but it is finally regulated by the components constituting the magnetic layer. As a result of the above measures for increasing the capacity, the storage capacity as a whole can be at least 1 GB, preferably at least 8 GB, more preferably at least 16 GB, particularly preferably at least 32 GB. The overall storage capacity depends on the case size, but the upper limit is about 300 to 1000 GB.

As a method of scanning the head, there are a linear method and a helical scan method. However, the present invention is excellent in durability and is suitable for recording in a helical scan method in which sliding is strong. This method is used for recording. Large effective film area for high capacity.

The film of the present invention may of course be a single-layer film or a laminated film.

When forming a laminated film, one of the outermost layers has the surface defined in the present invention. When a magnetic recording medium is used, it is preferable that the layer constituting the surface on which the magnetic layer is provided has the surface properties specified in the present invention. With such a configuration, the electromagnetic conversion characteristics, the durability of the magnetic layer, and the running property can be excellent. These laminating methods include well-known methods such as lamination in a die, lamination in a composite tube, and a method in which one layer is formed once and another layer is formed thereon. The components constituting each layer may be the same or different. For example, in the case of two layers, a polymerized aromatic polyamide or aromatic polyimide or polyamic acid solution is divided into two, and the same or different particles are added as necessary, and then laminated. The same applies to the case of three or more layers. Particle type,
It is desirable to use those which are desirably used for the film of the present invention. Further, when the diameter of the particles used in the inner layer portion is larger than the diameter of the particles in the laminated film of the present invention, the surface of the base film can have an appropriate undulation, and the tape running property can be further improved. Therefore, it is preferable from the viewpoint of running properties to increase the particle size and / or the content of the particles contained on the surface opposite to the surface facing the head. In addition, regarding the lamination structure, the distribution of particles in the cross-sectional photograph in the depth direction or X-ray microanalyzer analysis of the cross section, secondary ion mass spectrometry, or ESC while etching is performed.
In the case of using A or infrared spectroscopy, or in the case of an extremely thin layer, it can be determined by referring to the surface photograph in addition to the above method.

The surface roughness of the surface of the film of the present invention having the projections [1] and [2] is 2 to 500 nm, preferably 3 to 300 nm in Rp.
0.1 to 100 nm in Ra, preferably 0.2 to 50 n
It is preferably designed so that m and Rz are 2 to 500 nm, preferably 3 to 400 nm. Further, in a magnetic recording medium having a magnetic layer on only one side, the back side is preferably appropriately adjusted from the viewpoint of ensuring running properties, and Ra is preferably about 0.5 to 50 nm. The definition of each parameter is shown in, for example, "Method for Measuring Surface Roughness" by Jiro Nara (Tokyo Gijutsu Center, 1983).

The film has a three-dimensional surface roughness SRa at a measurement area of 0.002 mm ² on a specified surface.
1 and three-dimensional surface roughness SRa2 at a measurement area of 1.0 mm ²
It is preferable that the following relationship be satisfied.

0.8 ≦ SRa2 / SRa1 ≦ 4.5 SRa2 / SRa1 is preferably 3.5 or less, more preferably 2.5 or less. SRa2 / SRa1 is 4.5
If the magnetic recording medium is exceeded, undulations on the surface of the base material are remarkable, and when a magnetic recording medium is used, head touch becomes unstable, and there is a concern that output may be reduced and data may be lost. Also, S
Ra2 / SRa1 is preferably 0.9 or more, more preferably 1.2 or more. When SRa2 / SRa1 is less than 0.8, the running property of the magnetic tape is reduced and blocking on the roll is liable to occur, which adversely affects the durability.

The heat shrinkage of the film of the present invention at 200 ° C. for 10 minutes is preferably 5% or less, more preferably 2%.
It is preferable that the ratio is less than the above because the dimensional change of the tape due to the temperature change is small and good electromagnetic conversion characteristics can be maintained.

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.

The content of the oligomer having a molecular weight of 1,000 or less in the film of the present invention is preferably less than 1% by weight, more preferably less than 0.5% by weight. The oligomer referred to here includes at least a part of the aromatic polyamide or aromatic polyimide structural unit of the present invention, and includes, for example, a reaction product with a solvent. If the content of the oligomer exceeds 1% by weight, the mechanical and thermal properties of the film may be impaired, or the film may be wrapped around by rollers or the like during use, or the heat-sensitive transfer recording layer may peel off. is there.

The metal ions (especially ions of Group IA and IIA in the periodic table) in the film of the present invention are preferably 3000 ppm or less, more preferably 100 ppm or less, and particularly preferably 30 ppm or less, if the head or magnetic layer is 30 ppm or less. An excellent magnetic recording medium that does not have an influence of corrosion or the like can be obtained. The metal ion referred to here is an ionized metal component, and excludes a metal component constituting a solid that can be separated from a solution by filtration or centrifugation, such as external particles.

This not only increases the purity of the raw materials including the solvent, but also prevents the formation of a dense layer on the surface in the step of extracting the film-forming solvent and the inorganic salt during film formation. It is necessary to take care to prevent a skin layer or the like from being formed during drying as described above. Also, the wet bath can be preferably adjusted by using a plurality of baths and providing a temperature gradient or a concentration gradient.

The film of the present invention can be suitably used for magnetic recording media. The recording method is arbitrary, and a known recording method such as horizontal magnetic recording, vertical magnetic recording, and magneto-optical recording can be used.

As a method for forming the magnetic layer, there are a dry method such as a wet method, a vapor deposition method, a sputtering method, and an ion plating method in which a ferromagnetic powder is formed into a magnetic paint using various binders and is applied on a base film. Although not particularly limited, the present invention has a highly controlled surface properties and is excellent in adhesion, so it is much thinner than the coating type, and is harder in properties. The effect can be remarkably exhibited in a metal thin film type magnetic layer which requires a surface having excellent adhesion. When a non-magnetic thin film layer such as an undercoat layer is provided on a substrate film, the effect is exerted on the thin film. At this time, in order to further improve the adhesiveness with the magnetic layer or the like, the surface of the film may be subjected to ultraviolet light, radiation, discharge treatment or the like in advance.

As the metal thin film type magnetic layer, Co, F
e, Ni, or a simple substance or alloy of a metal such as Cr, Mo, W, V, Nb, Ti, Rh, Ru
And oxides of these metals or alloys. If necessary, magnetic layers of the same type or different types may be laminated. Further, a protective layer or a lubricating layer can be preferably formed on these magnetic layers.

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 further processed to obtain the magnetic recording medium of the present invention.

[0059]

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

(1) Projection density and projection height Hitachi Field Emission Scanning Electron Microscope (S90
No. 0) with a magnification of 10,000 times or more (preferably 5 times).
The substrate surface was observed at a magnification of 0000 or 100,000), and the number of protrusions having a diameter of 3 nm or more was counted (the number of protrusions at this time is defined as N1). When the projections were so small that observation was difficult, the sample surface was inclined at about 45 degrees for observation.

The height of each projection can be obtained by calculation from the length of the shadow when observed at an angle of 45 degrees.

The observation conditions are as follows.

Acceleration voltage: 10 kv. Sample preparation: Pt sputter coating.

[0064]

B. The surface is observed using an atomic force microscope (Nanoscope IIIa) manufactured by Digital Instruments, and the number of protrusions when the protrusions having a diameter of 10 nm or more are cut from a flat surface to a threshold surface (20 nm) is obtained. (The number of projections at this time is N2).

The number of projections when the maximum diameter of the projections exceeding 3 nm was cut on the threshold surface (10 nm) from the flat surface was defined as N3.

The observation conditions are as follows.

Scanning size: 20 μm, scanning speed: 0.5 Hz At this time, the projection density at each height can be obtained by cutting at an arbitrary threshold plane.

When the number of protrusions is obtained by the methods A and B,
The projection density of the above [1] is obtained by N2, and the projection density of the above [2] is obtained by, for example, (N1−N3) (where N1 >> N3).
In this case, the projection density in the above [2] was N1. ).

Whether or not each protrusion is formed by particles can be determined by, for example, obtaining an element distribution by focusing on elements caused by particles on an observation surface with an electron microscope equipped with an electron beam microanalyzer or the like. In microscopic observation such as AFM, the protrusion can be confirmed or sampled or marked with a probe and analyzed by elemental analysis.

(2) Moisture Absorption A few grams of the substrate film is dried in a vacuum dryer under a condition of 100 Pa or less and 180 ° C. until a constant weight is obtained, and its weight is defined as W1. Then, the film was heated at 25 ° C., 75%
After placing in the environment of RH for 48 hours, the measured weight is
Let it be 2. The moisture absorption was determined as (W2−W1) / W1 × 100 (unit:%).

(3) Young's modulus and elongation Tensilon manufactured by Orientec Co., Ltd.
The test was performed at a test length of 50 mm and a tensile speed of 300 mm / min. In the measurement, the sample was placed in an atmosphere of 20 ° C. and a relative humidity of 60% for 24 hours or more, and the measurement was performed under the same conditions.

(4) Weight fraction of oligomer The film was dissolved in a solvent, and a low-angle laser light scattering photometer (LALL) was applied to a gel permeation chromatograph (GPC).
S) and a differential refractometer (RI) are incorporated, and the molecular weight and the content of the solute are sequentially determined by measuring the light scattering intensity and the refractive index difference of the molecular chain solution size-separated by a GPC device according to the elution time. After calculating, the absolute molecular weight distribution of the high molecular weight substance was finally calculated. Diphenylmethane was used for calibration of the absolute molecular weight.

As a simple method, it can be obtained by simply collecting fractions having a molecular weight of 1,000 or less from a solution obtained by size separation and removing the solvent.

(5) Metal ion content The base film is dissolved in a solvent, and particles and the like are removed by a centrifuge or filtration. Next, components other than the particles were recovered from the solution, quantified, burned, incinerated, dissolved in nitric acid and hydrofluoric acid, and then solubilized with dilute nitric acid.

Next, quantification was performed using an atomic absorption spectrometer based on a previously prepared calibration curve. Here, the unit ppm is (μg / g).

(6) 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 measurement was performed after aluminum evaporation was performed on the surface of the specimen under vacuum. Detailed measurement conditions are shown below.

B. SRa1 (measurement area 0.002 mm ² ) ・ Measurement length in the longitudinal direction 0.02 mm ・ Measurement length in the width direction 0.1 mm ・ Cutoff value 0.08 mm b. SRa2 (measurement area: 1.0 mm ² ) ・ Measurement length in the longitudinal direction: 0.5 mm ・ Measurement length in the width direction: 2.0 mm ・ Cutoff value: 0.08 mm

(7) Electromagnetic Conversion Characteristics A CoO film was vapor-deposited on the surface of the substrate film opposite to the support using a continuous vacuum vapor deposition device to form a magnetic layer. Next, a carbon protective film was formed on the surface of the vapor-deposited layer, and a back coat layer was formed on the opposite surface by a known means. Then, a 6.5 MHz sine wave was recorded at the optimum recording current, and the reproduction output was represented by a difference from a commercially available standard tape.

(8) Durability Aluminum was vapor-deposited on the surface of the present invention using a continuous vacuum vapor deposition apparatus on a substrate film, and the tape was run by slitting into a tape having a width of 1/2 inch. Tester SFT-700
Using a mold (Yokohama System Laboratory Co., Ltd.)
The device was run 200 times in an atmosphere with a relative humidity of 80% such that the surface of the present invention faced the guide.

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 degrees, and the running speed is 3.3 cm /
The second, repeated stroke is 15 cm. In addition, in order to eliminate the influence of static electricity, static electricity was removed from the film during each run.

Thereafter, the surface of the magnetic layer was observed under a microscope, and the surface condition was evaluated according to the following criteria.

A: No flaws or scratches are observed. ：: Slight scratches are observed. ×: Dropout of the deposited layer is observed.

Examples 1 to 5 and Comparative Examples 1 to 3 Abbreviations of the respective raw materials used in the following Examples and Comparative Examples are as follows.

Aromatic diamine component: CPA: 2-chloroparaphenylenediamine DPX: 2,5-dimethylparaphenylenediamine DMB: 3,3′-dimethylbenzidine DPE: 4,4′-diaminodiphenyl ether acid chloride component: TPC: Terephthalic dichloride CPC: 2-chloroterephthalic dichloride Anhydride component: BTA: 3,3 ', 4,4'-biphenyltetracarboxylic anhydride

Preparation of Support Layer Components Each of the polymer raw materials was added to N-methylpyrrolidone (NMP) so as to have the same composition as in the examples and comparative examples.
The polymerization was completed by stirring for 2 hours. Then, the generated hydrogen chloride was neutralized by adding one quarter at a time using lithium hydroxide to obtain a polymer solution having a polymer concentration of 10% by weight. To this polymer solution, silica particles having an average particle diameter of 150 nm and a surface hydrophobic treatment having a relative standard deviation of 0.2 were added into NMP, and ultrasonic dispersion was performed for 48 hours, followed by filtration using a 1.0 μm filter. The obtained silica slurry was added to the polymer solution so that the silica concentration was 2 wt% with respect to the polymer, and then the mixture was sufficiently stirred and prepared.

Example 1 Dehydration of N into a reactor having a cooling jacket with a diameter of 1.8 m was carried out.
Add MP, the content of particles per polymer is 0.8wt
%, And a substantially monodisperse average primary particle size of 40 nm.
N-methylpyrrolidone (hereinafter referred to as NM)
P) (abbreviated as P) and then 80 mol% of CP
A. Dissolve 20 mol% of DPE and cool the solution.
Then, 100 mol% of CPC was added and the peripheral speed was increased to 4 m / cm.
After stirring for 2 hours while changing the speed from 2 m / sec to 2 m / sec, the mixture was neutralized with lithium hydroxide to obtain a polymer.

After defoaming, the polymer solution was passed through a 2 μm-cut filter, and the separately prepared support layer component solution was passed through a 5 μm-cut filter, and the final film thickness was 2.2 μm and 2.3 μm, respectively. In a dryer with a temperature gradient from 150 ° C to 170 ° C, which can be heated from the upper and lower surfaces of the belt, and then cast on a stainless steel belt polished on a mirror surface and preheated to 120 ° C. After gently evaporating the solvent content to 56%, the self-supporting film was peeled off the belt and kept at 40 ° C., first with NMP / water (30/7) with circulation mechanism.
0) The solution was successively introduced into a bath and then into a plurality of water baths to extract residual solvents and the like. At this time, after the second water tank, 1.
The film was stretched by one time. Then, drying at 300 ° C. in a tenter,
After heat treatment, the film was stretched 1.2 times in the width direction and cooled to room temperature at a rate of 20 ° C./sec to obtain an aromatic polyamide film having a thickness of 4.5 μm.

The height of the film from the flat surface is 20 nm.
As described above, the number of fine projections having a maximum diameter of 10 nm or more and 2000 nm or less (hereinafter, abbreviated as [1]) is 1 × 10 ⁶ / mm ² ,
The number of ultrafine projections having a height from the flat surface of the film of less than 10 nm and a maximum diameter of 3 nm or more (hereinafter abbreviated as projection [2]) was 5 × 10 ⁹ / mm ² . At this time, the projection [2]
In most cases, the height was not less than 0.01 nm and less than 5 nm (that is, in the frequency distribution of the protrusion height, the fine protrusion and the ultrafine protrusion in a range of less than 5 nm appeared as two peaks). . Further, as a result of the analysis, it was found that the protrusion [1] was formed by the particles, but the protrusion [2] was formed irrespective of the particles. In addition, height 5
The number of coarse projections of 46 nm or more was 20/100 cm ² .

The moisture absorption of this film is 1.5%,
The elongation and Young's modulus were 45% in both the longitudinal and width directions, and 1
2 GPa, the metal ion content was 25 ppm, the oligomer content was less than 0.5%, and SRa2 / SRa1 was 1.2.

The electromagnetic conversion characteristics and durability of this film were as shown in Table 1.

Example 2 A substantially monodispersed NMP slurry in which titania particles having an average primary particle size of 50 nm were previously dispersed was added so that the particles became 1.2% by weight per polymer. Polymerization was carried out in the same manner, and a film having a thickness of 4.5 μm was obtained in the same manner as in Example 1 except that the stretching ratio in the wet process was changed to 1.15 times.

The protrusion [1] of the film was 5 × 10 ⁶ / mm ² , and the protrusion [2] was 5 × 10 ⁹ / mm ² . At this time, the height of the projection [2] was almost 0.01 nm or more and less than 5 nm. Further, as a result of the analysis, it was found that the protrusion [1] was formed by the particles, but the protrusion [2] was formed irrespective of the particles. The number of coarse projections having a height of 546 nm or more was 120/100 cm ² .

The moisture absorption of this film is 1.5%,
The elongation and Young's modulus were 45% in both the longitudinal and width directions, and 1
2 GPa, the metal ion content was 25 ppm, the oligomer content was less than 0.5%, and SRa2 / SRa1 was 1.3.

The electromagnetic conversion characteristics and durability of this film were as shown in Table 1, but dropouts were slightly larger than those of the other examples.

Example 3 A substantially monodispersed NMP slurry in which colloidal silica particles having an average primary particle size of 25 nm were previously dispersed was added so that the particles became 0.8% by weight per polymer. Polymerization was carried out in the same manner as described above, and after gently evaporating until the solvent content became 55% in a dryer at 150 ° C. capable of heating from the upper and lower surfaces of the belt, the film having self-supporting properties was peeled off from the belt, and the wet process As the first circulating water tank
0 ° C water, 2nd, 3rd and 4th circulating water tanks each 3
35/65, 15/85, 0/10 NMP / water at 0 ° C
The mixture was passed through a water tank having a composition ratio of 0. At this time, the film was stretched 1.15 times in the longitudinal direction after the second water tank. Then, it is dried and heat-treated at 290 ° C. in a tenter, and at this time, 1.35 in the width direction.
Stretched twice, re-stretched about 1% after heat treatment at 300 ° C,
The film was cooled to room temperature at a rate of ° C./sec to obtain a film having a thickness of 4.5 μm.

The protrusion [1] of this film was 7 × 10 ⁶ / mm ² , and the protrusion [2] was 1 × 10 ¹¹ / mm ² . At this time, the height of the projection [2] was almost 0.01 nm or more and less than 5 nm. Further, as a result of the analysis, it was found that the protrusion [1] was formed by the particles, but the protrusion [2] was formed by the particles. The number of coarse projections having a height of 546 nm or more is 5/1.
00 cm ² .

The moisture absorption of this film is 1.5%,
The elongation and Young's modulus are 45% each in the longitudinal and width directions,
25%, 11 GPa, 16 GPa, metal ion content is 15 ppm, oligomer content is less than 0.5%, SRa
2 / SRa1 was 1.0.

The electromagnetic conversion characteristics and durability of this film are as shown in Table 1, and the film had properties which were extremely superior to those of the films of Examples 1 to 3.

Example 4 N dehydrated in a reactor having a cooling jacket with a diameter of 1.8 m was provided.
An NMP slurry in which colloidal silica particles having a substantially monodispersed average primary particle diameter of 40 nm are previously dispersed in MP is added so that the particles become 1.2% by weight per polymer, and then 40 mol% of DPX, 40 mol% DMB, 20 mol%
Is dissolved and the solution is cooled. Subsequently, 100 mol% of TPC was added thereto, the mixture was stirred at a peripheral speed of 2 m / sec for 2 hours, and neutralized with lithium hydroxide to obtain a polymer.

After defoaming, the polymer solution was passed through a 2 μm-cut filter, and the separately prepared support layer component solution was passed through a 5 μm-cut filter, and the final film thickness was 2.2 μm and 2.3 μm, respectively. Combine in a laminated tube so that it is cast on a stainless steel belt polished on a mirror surface and preheated to 120 ° C. until the solvent content becomes 55% in a dryer at 160 ° C. that can be heated from the upper and lower surfaces of the belt. After gentle evaporation, a film having a thickness of 4.5 μm was obtained in the same manner as in Example 3 except that the film having self-supporting property was peeled off from the belt and the stretching ratio in the width direction was changed to 1.25 times. .

The protrusion [1] of the film was 2 × 10 ⁶ / mm ² , and the protrusion [2] was 1 × 10 ¹⁰ / mm ² . In this case, the height of the projection [2] was almost 0.01 nm or more and less than 5 nm. Further, as a result of the analysis, it was found that the protrusion [1] was formed by the particles, but the protrusion [2] was formed irrespective of the particles. The number of the coarse projections having a height of 546 nm or more is 20 /
It was 100 cm ² .

The moisture absorption of this film was 1.8%,
The elongation and Young's modulus are 35% each in the longitudinal and width directions,
30%, 12 GPa, 13 GPa, metal ion content 25 ppm, oligomer content 0.8%, SRa2 /
SRa1 was 1.1.

The electromagnetic conversion characteristics and durability of this film were as shown in Table 1. However, in the durability test, deposits were found on the transport roll.

Example 5 N dehydrated in a reactor having a cooling jacket with a diameter of 1.8 m was provided.
MP was added, and the content of particles per polymer was 1.2 wt.
% Of a substantially monodisperse average primary particle size of 80 nm.
Of a colloidal silica NMP dispersion,
Dissolve 0 mol% CPA, 40 mol% DPE and cool the solution. Then, 100 mol% of BTA was added, and the peripheral speed was changed from 4 m / sec to 2 m / sec to carry out polymerization.
An aromatic polyamic acid solution was obtained.

After defoaming, a catalyst was added to the solution before film formation and to the separately prepared support layer component solution, and the polymer solution was added to the solution.
After passing through a filter having a cut of .mu.m and the component solution of the support layer having been passed through a filter having a cut of 5 .mu.m, they are combined in a laminated tube to have a final film thickness of 2.2 .mu.m and 2.3 .mu.m, respectively. It is cast on a stainless steel belt polished and preheated to 120 ° C, and gently imidized in a dryer with a temperature gradient from 150 ° C to 170 ° C, which can be heated from the upper and lower surfaces of the belt, until the solvent content becomes 55%. After evaporation, the self-supporting film was peeled off from the belt and kept at 40 ° C.
It was introduced sequentially into an MP / water (30/70) bath and then into a plurality of water baths to extract residual solvents and the like. Then, it is dried and heat-treated at 300 ° C. in a tenter.
The film is stretched 1.25 times in the width direction, and the cyclization is completed in an atmosphere at 340 ° C., and cooled to room temperature at a rate of 20 ° C./sec to produce an aromatic polyimide film having a thickness of 4.5 μm. The obtained film had protrusions [1] of 3 × 10 ⁶ protrusions / mm ² and protrusions [2] of 1 × 10 ¹⁰ protrusions / mm ² . In this case, the height of the projection [2] was almost 0.01 nm or more and less than 5 nm. Further, as a result of the analysis, it was found that the protrusion [1] was formed by the particles, but the protrusion [2] was formed irrespective of the particles. The number of coarse projections having a height of 546 nm or more was 50/100 cm ² .

The moisture absorption of this film was 2.1%,
Elongation and Young's modulus are 30% in both longitudinal and width directions, 7G
Pa and metal ions were hardly detected, the oligomer content was less than 0.5%, and SRa2 / SRa1 was 1.5.

The electromagnetic conversion characteristics and durability of this film were as shown in Table 1.
At the time of evaluation, slight deformation of the tape was observed.

Comparative Example 1 In an NMP dispersion of colloidal silica, the content of particles per polymer was 0.05 wt%, and the average primary particle size was 25%.
Polymerization was carried out in the same manner as in Example 1 except that the thickness was changed to nm.

After defoaming, the polymer solution was passed through a 2 μm-cut filter, and the separately prepared support layer component solution was passed through a 5 μm-cut filter. The final film thickness was 2.2 μm and 2.3 μm, respectively. In a dryer with a temperature gradient from 150 ° C to 170 ° C, which can be heated from the upper and lower surfaces of the belt, and then cast on a stainless steel belt polished on a mirror surface and preheated to 120 ° C. After gently evaporating until the solvent content becomes 62%, the self-supporting film is peeled off from the belt and sequentially introduced into a plurality of water baths having a circulation mechanism maintained at 60 ° C. to remove residual solvent and the like. Extracted. Then, at 290 ° C in a tenter
And stretched 1.25 times in the longitudinal direction and 1.3 times in the width direction, and cooled to room temperature at a rate of 20 ° C./sec to obtain an aromatic polyamide film having a thickness of 4.5 μm. Was.

The protrusion [1] of the film was 1 × 10 ²
Pcs / mm ^2, and the projection of [2] is 5 × 10 ⁸ pcs / m
m ² . At this time, many of the projections [2] had a height exceeding 5 nm. Further, as a result of the analysis, it was found that the protrusion [1] was formed by the particles, but the protrusion [2] was formed irrespective of the particles. Also, almost no coarse protrusions having a height of 546 nm or more were observed.

The moisture absorption of this film was 1.6%.
The elongation and Young's modulus are 40% in both the longitudinal and width directions, and 1
3 GPa, the metal ion content was 20 ppm, the oligomer content was less than 0.5%, and SRa2 / SRa1 was 1.3.

The electromagnetic conversion characteristics and durability of this film were as shown in Table 1.

Comparative Example 2 90 mol% of CPA and 10 mol% of DP as monomers
After dissolving E, the solution was cooled and then 100 mol% of C
Except for the addition of PC, the addition of particles and the polymerization operation were performed in the same manner as in Example 1 to obtain a polymer solution.

After defoaming, the polymer solution was passed through a 2 μm-cut filter, and the separately prepared support layer component solution was passed through a 5 μm-cut filter, and the final film thickness was 2.2 μm and 2.3 μm, respectively. The composite is mixed in a laminated tube so as to be cast on a stainless steel belt polished on a mirror surface, and hot air of 190 ° C. is blown from the upper surface of the belt to evaporate until the solvent content becomes 43%. The obtained film was peeled off from the belt and introduced into a plurality of water baths maintained at 60 ° C. to extract residual solvent and the like. Then
It is dried at 300 ° C. in a tenter and heat-treated. At this time, it is stretched 1.25 times in the longitudinal direction and 1.3 times in the width direction. An aromatic polyamide film was obtained.

The protrusions of [1] on this film were 2 × 10 ⁵
Pieces / mm ^2, the projection of [2] was 2 × 10 ⁵ cells / mm ^2. At this time, the protrusions [1] and [2] were obtained in one peak in the frequency distribution of the protrusion height. As a result of the analysis, it was found that not only the protrusion [1] but also the protrusion [2] were substantially formed by the particles. In addition, height 546
The number of coarse protrusions of not less than nm was 15 protrusions / 100 cm ² .

The moisture absorption of this film was 1.5%,
The elongation and Young's modulus were 35% in the longitudinal and width directions, and 1
4 GPa, the metal ion content was 35 ppm, the oligomer content was less than 0.5%, and SRa2 / SRa1 was 4.7.

The electromagnetic conversion characteristics and durability of this film were as shown in Table 1. The film had severe undulation and the magnetic tape had periodic noise.

[0119]

[Table 1]

[0120]

The present invention is directed to a film made of an aromatic polyamide or an aromatic polyimide having excellent heat resistance and mechanical properties, and having excellent surface properties. It is suitable for a medium, particularly for a high-density magnetic recording medium such as a computer memory. In addition, the excellent surface properties obtained by the present invention are considered by replacing the relationship between the magnetic tape and the head with, for example, the relationship between a thermal head or a recording material and a recording material for thermal transfer, and the relationship between a roll or a processing plate and a film. As is obvious, optical recording media, recording materials for thermal transfer, flexible printed wiring boards, capacitors, coating materials, insulating materials for high-speed rotating electrical equipment, plate making materials, photographic films, acoustic diaphragms, solar cell substrates, etc. It can be suitably used for various applications.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FI B29L 7:00 B29L 7:00 C08L 67:03 C08L 67:03 (58) Investigated field (Int.Cl. ⁷ , DB name) C08J 5/18 B29C 55/12 C08J 7/02 G11B 5/66 C08L 67/03

Claims (9)

(57) [Claims] [Claim 1] as a main component an aromatic polyamide-de, two projection group on at least one surface of the film, [1]: height from the flat surface of the film is 20nm or more, a maximum diameter of 1
1 × 10 ² to 1 × 10 ⁸ fine protrusions of 0 nm or more / mm
^2, [2]: with less than 10nm height, maximum diameter than 3nm ultrafine projections 5 × 10 ⁸ pieces / mm ² or more, have a, or
First, the protrusions of [1] are caused by the particles contained in the film.
Formed, and the projections of [2] are formed regardless of the added particles
A film characterized by being made . 2. The maximum diameter of the fine projections of the projection group [1] is 200.
The film according to claim 1, wherein the thickness is 0 nm or less. 3. The height of the ultrafine projections of the projection group [2] is 0.0.
The film according to claim 1, wherein the thickness is 1 nm or more and less than 5 nm. 4. The film has a Young's modulus in at least one direction of 6.9 GPa or more, and 100/100 cm of coarse projections having a height of 546 nm or more on a surface having the projection group.
The film according to any one of claims 1 to 3 , wherein the film thickness is ² or less. 5. A three-dimensional surface roughness SRa1 at a measurement area of 0.002 mm ² and a three-dimensional surface roughness SRa2 at a measurement area of 1 mm ² on the surface having the projection group satisfy the following expression. The film according to any one of claims 1 to 4 , wherein 0.8 ≦ SRa2 / SRa1 ≦ 4.5 6. A magnetic recording medium formed by providing a magnetic layer on at least one surface of the film according to any one of claims 1-5. 7. The magnetic recording medium according to claim 6 , wherein the magnetic layer is a metal thin film type magnetic layer. 8. A magnetic recording medium according to claim 6 or 7, characterized in that a non-magnetic thin layer between the magnetic layer and the substrate film. 9. A tape-shaped medium having a base film having a thickness of 6.5 μm or less, a width of 2.2 mm to 15 mm, a recording density of 15 KB / mm ² or more, and a recording capacity of 1 GB or more. The magnetic recording medium according to any one of claims 6 to 8 , wherein: