JP2000344912A - Aromatic polyamide and/or aromatic polyimide film and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject film excellent in electromagnetic transducing characteristics, smoothness, friction characteristics to a magnetic head or the like and handleability, and useful for a magnetic recording media by limiting surface properties within specific values. SOLUTION: A solution dissolving an aromatic polyamide and/or an aromatic polyimide is formed into a film by a film-producing method by using the solution. Voronoi distribution as protrusions formed on the surface of the obtained film is carried out, and a relative standard deviation (σ/Xbar) (Xbar is an average area of the Voronoi polygons; σ is the standard deviation) is regulated so as to be <=1 to provide the objective film suitable for a magnetic recording medium. The aromatic polyamide preferably has >=50 mol.% repeating unit of the formula NH-Ar1-NH-CO-Ar2-CO (Ar1 and Ar2 are each phenylene or the like) or the like, and the polyimide preferably has >=50 mol.% repeating unit of formula I (Ar4 is formula II or the like; Ar5 is phenylene or the like) or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aromatic polyamide and / or aromatic polyimide film which can be particularly suitably used for a magnetic recording medium.

[0002]

2. Description of the Related Art Aromatic polyamides and aromatic polyimides are useful polymers 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) give a molded article excellent in strength and elastic modulus in addition to the above properties due to its rigidity. The utility value is high, and application to a magnetic recording medium is being studied.

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-60-66319, etc.). Generally, the smoothness of the magnetic recording medium is important to obtain high electromagnetic conversion characteristics.However, if the magnetic recording medium is too smooth, it may cause poor running or damage to the magnetic layer due to friction with the head. It is necessary to be. That is, 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, the surface properties of which have been improved by adding inorganic particles are disclosed in JP-A-60-127523 and JP-A-60-2.
01914, JP-A-62-119024,
JP-A-63-268640 is an example.

On the other hand, in recent years, the capacity and performance of magnetic recording media have been further increased, and the need for magnetic recording media using ferromagnetic metal thin films such as Co-Ni has been increasing. However, since the deposited layer is extremely thin, the surface shape of the base film is directly reflected. Therefore, in order to obtain good electromagnetic conversion characteristics, it is more important to design the surface shape.

[0005] Heretofore, there have been thoughts concerning the surface design of a base film used for a magnetic recording medium, for example, focusing on the surface roughness and defining the height and density of the projections.

[0006] However, in recent years, with the progress of higher capacity, the demand for recording and reproduction at higher speeds has been increasing. If the surface roughness is simply specified, the average roughness of the film is not considered. Although it can be grasped as a typical characteristic, it can not grasp coarse projections that cause dropout and wear of the magnetic head,
Since the size or density of the projections is not considered independently, good electromagnetic conversion characteristics may not always be obtained or scratching may be difficult. In this regard, it can be said that what defines the protrusion height and density is effective,
This does not express the dispersion and aggregation state of the projections, and is insufficient for obtaining a film having good electromagnetic characteristics and excellent scratch properties.

On the other hand, aromatic polyamide or aromatic polyimide is generally obtained by solution casting. That is, molding is performed by removing the solvent from the solution state, but during polymerization or film formation, the reaction environment such as temperature, pH, and water content greatly changes, and mass transfer occurs. Particles are generally added for the formation of surface protrusions, but due to such a phenomenon, the particles are aggregated or unevenly distributed, so that a further breakthrough was required for ideal surface formation.
In addition, since aromatic polyamides or aromatic polyimides are generally hard, when coarse projections are formed, there is a concern that the head may be shaved or particles may fall off.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and is excellent in electromagnetic conversion characteristics, smoothness, friction resistance to a magnetic head and the like, handling properties, etc., and particularly a substrate for a magnetic recording medium. An object is to provide an aromatic polyamide and / or aromatic polyimide film suitable for a film.

[0009]

In other words, the present invention relates to a base film mainly composed of an aromatic polyamide and / or an aromatic polyimide, wherein a projection formed on at least one surface of the film is provided. , And the relative standard deviation (σ / Xbar) is 1 or less when the Voronoi polygon area average is Xbar and the standard deviation is σ.
Or it is an aromatic polyimide film.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic polyamide referred to in the present invention refers to a repeating unit represented by the following general formula (I) and / or general formula (II) in an amount of 50 mol% or more, preferably 70 mol% or more. Consists of

[0011]

Embedded image

[0012]

Embedded image Here, Ar ₁ , Ar ₂ , and Ar ₃ each include, for example,

[0013]

Embedded image And the like.

X and 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, hydrogen atoms on these aromatic rings are
R, R 'or R "represents a halogen group, a nitro group, C
An alkyl group of 1 to C3, an alkoxy group of C1 to C3, a trialkylsilyl group, an aryl group, an oxyaryl group,
It may be substituted with a substituent such as a thioaryl group, or hydrogen on the amide group may be substituted with another substituent.

In terms of characteristics, it is preferable that the above aromatic ring bonded at the para position accounts for 50% or more, more preferably 70% or more, and further preferably 75% or more of the total aromatic ring. If it is less than 50 mol%, the film may not be able to fulfill its full functions such as strength, elongation, rigidity and heat resistance. When such a condition is satisfied, the film can be thinned and can be suitably used as a high-capacity magnetic recording medium. Examples of such para-oriented aromatic nuclei include:

[0017]

Embedded image There is.

The substituent for replacing hydrogen on the aromatic nucleus is preferably used because its introduction improves the solubility and hygroscopicity. Particularly in a highly substituted system, it becomes soluble in an organic solvent, and the film-forming property 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), a trimethylsilyl group, The aromatic ring substituted with
An aromatic polyamide which accounts for 50% or more of the whole is preferably used. In addition, a plurality of types of 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 a film with good productivity 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 at least 50 mol%, preferably at least 70 mol%. .

[0020]

Embedded image

[0021]

Embedded image Here, Ar ₄ and Ar _{6 each} include at least one aromatic ring, and two carbonyl groups forming an imide ring are bonded to adjacent carbon atoms on the aromatic ring.

This Ar ₄ is an aromatic tetracarboxylic acid,
Alternatively, it is derived from this anhydride. The following are typical examples

[0023]

Embedded image Is mentioned.

Where 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 an aromatic carboxylic anhydride or its halide. Ar ₅ and Ar ₇ are, for example,

[0026]

Embedded image And the like.

[0027] X ', Y' is _{-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.

Intrinsic viscosity of polymer (measured at 30 ° C. in a solution of 0.5 g of polymer in 100 ml of sulfuric acid)
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 below.

In the aromatic polyamide and / or aromatic polyimide film of the present invention, Voronoi division is performed on the projections formed on at least one surface of the film, and the average area of the Voronoi polygon is Xbar, and the standard deviation is σ. Then, the relative standard deviation (σ / Xbar) is 1 or less.

The Voronoi division can quantitatively grasp the dispersion state of the protrusions. When the projections are solidified, the particles often aggregate three-dimensionally. In such a case, the height of the projections is large, that is, the spacing loss is large, which obviously has an undesirable effect on the electromagnetic conversion characteristics, and is easy to fall off, or the contact with the head is not stable. In addition, there is an unfavorable effect on friction properties such as running properties, scraping properties, scratch resistance, and handling properties. However, even when the heights of the projections are uniform, they may be simply aggregated on a flat surface, and may not be aggregated, but may be unevenly distributed. The stability of the contact is impaired, and this has an unfavorable effect on the electromagnetic conversion characteristics, running properties, scraping properties, and scratch resistance. In addition, the characteristics are also different when they exist randomly and when they have regulated uniformity. Such a situation cannot be grasped by the conventional definition based on the surface roughness or the height-density of the projections, and the definition based on the Voronoi division described in the present invention is effective.

That is, the film of the present invention has a relative standard deviation (σ / Xbar) of 1.0 or less, where Xbar is the area average of the Voronoi polygon and σ is the standard deviation. If it exceeds 1.0, the aggregation (uneven distribution) of the projections is remarkable, and a film suitable for a magnetic recording medium having excellent characteristics cannot be obtained. Preferably it is 0.7 or less, more preferably 0.525 or less. Note that, in theory, when the protrusions exist completely at random, the relative standard deviation is 0.525, and becomes smaller as the tendency to orderly and uniformly increases. The lower limit is not particularly limited, but is practical if about 0.3.

The film of the present invention preferably has 10 ² to ¹⁰ 10 fine protrusions / mm ^{2 with} a height of 5 nm or more, and the lower limit is preferably 10 ³ / mm ^2.
Or more, more preferably 10 ⁴ pieces / mm ² or more;
The upper limit is preferably 10 ⁹ / mm ² or less, more preferably 10 ⁸ / mm ² or less. 10 ² pieces / m
If it is less than m ² , the electromagnetic conversion characteristics are good, but there is concern about running properties and scratching properties. If it exceeds 10 ¹⁰ pieces / mm ² , the running properties and scratching properties are not so much improved. This has an adverse effect on the electromagnetic conversion characteristics and the sharpness.

The height of the projections exceeding 5 nm is 5
The number of protrusions exceeding 0 nm is preferably 10% or less of the whole, more preferably 3% or less, and particularly preferably 1% or less.
% Or less. If the protrusions having a height of 50 nm or more exist in excess of 10%, the electromagnetic conversion characteristics are unfavorably affected, and the abrasion resistance of the head is also unfavorably affected.

The number of coarse projections having a height of 546 nm or more is 100/100 cm ² or less, preferably 50/100 cm ² or less.
It is good to be 100 cm ² or less. Such coarse projections can be prevented from being generated by increasing the dispersibility of the particles. However, in the case of the solution casting system of the present invention, particles that are previously dispersed in a solvent (preferably monodispersed particles) are used. It is preferable to use a method of adding a dispersion of the above. The density of such coarse protrusions can be determined from the observation area by marking a portion where two or more interference fringes occur when a light beam of 546 nm is applied using a differential interference microscope. Such coarse protrusions cause dropout in a magnetic recording medium.

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
≧ 6.9 GPa, more 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 is likely to occur under tension, which causes wrinkles and breaks, which greatly impairs practicality. Also, E20 ≧ 6.9G
If Pa is used, the film can be made thinner, which is advantageous for increasing the capacity of the magnetic recording medium, and the Young's modulus in the width direction is preferably 1.1 times or more that in the longitudinal direction.

The moisture absorption of the film of the present invention is 4% or less,
It is more preferably at most 3%, further preferably at most 2%. If it exceeds 4%, for example, when forming a magnetic layer by a vapor deposition method or the like, bubbles may be generated in the film at the time of heating and the vapor deposition characteristics may be impaired. 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. Further, 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 where the aromatic polyamide is obtained from a diacid chloride and a diamine, for example. Is synthesized in an aprotic organic polar solvent such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF). When acid chloride and diamine are used as monomers in a polymer solution, hydrogen chloride is by-produced.When neutralizing this, inorganic neutralizers such as calcium hydroxide, calcium carbonate, lithium carbonate, and ethylene chloride are 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 a stock solution for obtaining a molded body as they are, or after isolating the polymer once and then re-dissolving it in the above-mentioned organic solvent or an inorganic solvent such as sulfuric acid. May be prepared.

In this polymerization, it is a matter of course to use a raw material of high purity 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 from the beginning to the end of the polymerization so as to decrease the mixing speed in accordance with the increase in the viscosity of the solution. The means can also sharply control the molecular weight distribution of the polymer and have a favorable effect on mechanical properties and moisture absorption.

To 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. May be. Further, the polymerization stock solution may be used as it is, but it may be used after reprecipitation with water or the like and then dissolved in a solvent. The polymer concentration in the stock solution is preferably 2 to 40% by weight, more preferably 5 to 35% by weight. Below this range, it is necessary to take large discharge, which is economically disadvantageous,
If it exceeds, the difficulty in obtaining a thin film is high due to the relationship between the discharge amount and the solution viscosity.

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

Next, SiO ₂ , TiO ₂ , TiN, Al
_The content of inorganic particles such as ₂ O ₃ , ZrO ₂ , zeolite and other fine metal powders and particles such as organic particles is 0.01 to 20% by weight per polymer weight, preferably 0.1 to 20%.
-15% by weight. The method for adding the particles is not particularly limited, but if adjustment of the degree of dispersion and aggregation of the particles is necessary, the adjustment is preferably performed 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, and may be added to the solvent before the polymerization, or after the polymerization, or at the time of preparing the polymer solution. However, in the present invention, for the components forming the projections, for example, pH and temperature, in view of the surrounding environment such as the generation of inorganic ions, it is necessary to minimize the change, the surface of the film of the present invention The polymer solution for forming the layer is formed by first adding a dissolution aid, if necessary, to the solvent dispersion of the projection forming raw material, and then polymerizing the polymer synthesized in advance and removing inorganic substances by washing with water to obtain a desired polymer. It is a preferable method for easily carrying out the present invention to prepare the solution by gradually adding it to a concentration.

Next, the film formation 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.
Dry until the film is self-retaining. Drying can be performed, for example, at room temperature to 220 ° C. for 60 minutes or less. At this time, the residual amount of the solvent as a film after drying is preferably higher, and more preferably 45% or more. In addition, it is necessary to heat gently so as not to form a skin layer or a dense layer (a layer having an extremely low solvent content) on the surface. At this time, an internal heating method such as infrared or electromagnetic heating, or means for 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 the wet process, and desalted.
After the solvent is removed, stretching, drying and heat treatment are performed to form a film. In this process, a wet process,
The stretching and heat treatment steps play an important role.

In the wet process, a poor solvent such as water is usually desolvated. However, when the film surface of the present invention cannot be obtained with only the poor solvent, a mixed medium of a poor solvent and a good solvent is used. 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 coagulating medium is increased as much as possible, that is, the coagulating bath. It is very effective that the coagulating medium in the film comes in contact with the film at a flow rate. The bath temperature can be arbitrarily selected, but a lower temperature is preferred. However, if the temperature is too low, the productivity is affected. For example, when the polymer stock solution is an aprotic polar solvent system such as NMP, setting the temperature at about 40 ° C. can achieve the purpose more easily. .

The stretching can be performed during the wet process or at the time of heating, and the stretching ratio is 1.1 to 8.0 (area ratio is a value obtained by dividing the area of the film after stretching by the area of the film before stretching). Is usually used, but a structure having a crosslinked structure and a cured structure is formed on the surface by a physical means such as an electron beam or a chemical means such as a crosslinking reaction at the stage before stretching. By doing so, the surface of the substrate film of the present invention can be more easily obtained.

The heat treatment is usually carried out at a temperature of 150 to 500 ° C. In the present invention, the polymer is kept at a constant temperature or slightly relaxed for several seconds to several minutes at a temperature of glass transition temperature (Tg) to Tg + 50 ° C. Heat treatment may be performed. Furthermore, slow cooling of the film after stretching or heat treatment is effective in suppressing dimensional fluctuation,
It is effective to cool at a rate of 0 ° C./second or less.

Since the aromatic polyamide film of the present invention has excellent mechanical properties, it exhibits excellent effects not found in other materials, especially when the film is made thin. The preferred thickness is 0.5 to 50 μm, more preferably 1 to 20 μm, and still more preferably 2 to 10 μm,
Particularly for a magnetic recording medium, the thickness is preferably 6.5 μm or less, more preferably 4.5 μm or less, and still more preferably 3.5 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, the width is 2.2 to 15 mm, and the recording density when used as a magnetic recording medium is 15 kilobytes / m.
When a tape-shaped magnetic recording medium having a size of m ² or more (when not compressed) is used, an embodiment utilizing the effects of the present invention can be achieved more effectively. There are two ways to increase the capacity of magnetic tapes: a method of making the support thinner and making it longer, and a method of making the track width narrower and improving the recording capacity per unit area by shortening the recording wavelength. 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. As the recording density,
It is more preferably at least 25 kilobits / mm ^{2, even} more preferably at least 34 kilobits / mm ² . There is no particular upper limit, but the upper limit is regulated by the components constituting the magnetic layer. Then, as a result of the above measures for increasing the capacity, the overall storage capacity is 1 GB or more, preferably 8 GB or more.
More preferably 16 GB or more, particularly preferably 32 GB
I can do that. Although the total storage capacity depends on the size of the housing, the upper limit is about 300 to 1000 GB.

A head scanning method includes a linear method and a helical scanning method. The present invention is excellent in durability and is suitable for recording in a helical scanning method in which sliding is strong. The effective area of the film used for a wide area is suitable 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 a layer constituting a surface on which a magnetic layer is provided has a surface property defined by 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, 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 components constituting each layer may be the same or different. For example, in the case of two layers, a polymerized aromatic polyamide, aromatic polyimide or polyamic acid solution is divided into two, and if necessary, the same or different particles are added and then laminated. The same applies to the case of three or more layers. It is desirable to use those which are desirably used for the film of the present invention as to the kind and content of the particles. Further, when the diameter of the particles used for the inner layer portion is larger than the diameter of the particles in the laminated film of the present invention, a moderate undulation can be provided on the surface of the substrate film, and
It is desirable because the runnability of the head is further improved, and it is preferable to increase the particle size and / or content of the particles contained in the layer on the side opposite to the head than the particles contained in the layer on the side facing the head. It is preferable from the viewpoint of running performance. In addition, regarding the lamination structure, the distribution of the particles in the depth direction in the cross-sectional photograph, or the X-ray microanalyzer analysis of the cross-section,
Secondary ion mass spectrometry or E while etching
In the case of using SCA, infrared spectroscopy, or the like, or in the case of an extremely thin layer, in addition to the above-described method, the surface can be determined by taking into consideration a surface photograph.

The film of the present invention has a surface roughness of R
a is 0.1 to 100 nm, more preferably 0.2 to 50
nm, Rz is 2 to 500 nm, more preferably 3 to 40 nm.
It is preferably designed to be 0 nm. In the case of a magnetic recording medium having a magnetic layer only on one side, it is preferable that the back side of the magnetic recording medium has an appropriate degree in order to ensure running properties.
a 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 heat shrinkage of the film of the present invention at 200 ° C. for 10 minutes is preferably 5% or less, more preferably 2%.
% Is desirable because the dimensional change of the tape due to a temperature change is small and good electromagnetic conversion characteristics can be maintained.

The elongation of the film of the present invention is 10% or more,
It is more preferably at least 20%, more preferably at least 30%, 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 herein 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. When 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 the roller due to bleeding during use.

The metal ions (especially ions of groups IA and IIA of 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. An excellent magnetic recording medium which does not affect the corrosion of the magnetic layer 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 filtered or centrifuged from a solution, such as external particles.

This is, of course, not only to increase the purity of the raw materials including the solvent, but also to prevent 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 preferable to take care to prevent a skin layer or the like from being formed during drying as described above. Also, use multiple baths as a wet bath,
It can be preferably adjusted by 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.

The magnetic layer can be formed by a wet method in which a ferromagnetic powder is formed into a magnetic paint using various binders and applied to a base film, or a dry method such as an evaporation method, a sputtering method, or an ion plating method. Yes, although not particularly limited, the present invention has a highly controlled surface property and excellent adhesion, so it is much thinner than the coating type, and it is hard as a property The effect can be remarkably exhibited in a metal thin film type magnetic layer which requires a surface having more excellent adhesion. Further, when a non-magnetic thin film layer such as an undercoat layer is provided on a base film, it is possible to form an adhesive or a preferable crystal structure on the thin film, and this is preferably employed. 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,
Cr, Mo, W, V, Nb, Ti, R
Examples thereof include alloys with h, Ru, and the like, and oxides of these metals or alloys. If necessary, the same type or different types of magnetic layers can be laminated. On these magnetic layers, a protective layer or a lubricating layer can be preferably formed.

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 running properties.

[0064]

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

(1) Projection Density, Projection Height Surface observation is performed using an atomic force microscope (Nanoscope IIIa) manufactured by Digital Instruments Co., Ltd. The number of protrusions at the time of cutting was determined, and the protrusion density was calculated. The observation conditions and the like are as follows. Scan size: 20 μm, scan speed: 0.5 Hz.

(2) Relative standard deviation obtained by Voronoi division The above-mentioned atomic force microscope observation data is converted into digital data and transferred to a computer. In each measured protrusion, a perpendicular bisector between adjacent protrusions is formed. Then, the area (Ai) surrounded by the vertical bisector for each projection was determined (note: projections not closed by the vertical bisector such as the visual field boundary area are not calculated). . Then,

[0067]

(Equation 1) To determine the relative standard deviation.

Since this item only needs to know the position and distribution information of the particles, it is not impossible to use a scanning electron microscope, an optical microscope, a differential interference microscope or the like for the measurement in addition to the atomic force microscope. It is appropriately selected according to the size and distribution of the particles, and it is preferable to use an atomic force microscope when dealing with fine projections as in the present application. In addition, the measurement area should be appropriately adjusted so that sufficient projections are included in the field of view, and it is recommended that the number of projections to be calculated is about 20/1 field of view. In the present invention, the measurement area is 5 μm.
m × 5 μm.

(3) 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:%).

(4) 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.

(5) S / N Ratio (Electromagnetic Conversion Characteristics) A corona discharge treatment is applied to the surface of the substrate film that satisfies the requirements of the present invention, and then a CoO film is deposited by using a continuous vacuum deposition apparatus. Was formed. 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, and these were slit into a pancake and then incorporated into a cassette to obtain a magnetic tape. Then 6.5 MH
A sine wave of z was recorded at the optimum recording current, and the S / N ratio of the reproduction output was determined for a commercially available standard tape.

(6) Durability and Scratch Resistance The S / N ratio measurement of the above (5) was performed 100 times, and the durability was evaluated based on the following criteria for a decrease in the S / N ratio. A: S / N ratio is hardly reduced. ：: S / N ratio is reduced, but there is no problem in practical use. Δ: S / N ratio is reduced, and there is a problem in practical use. X: The S / N ratio is drastically reduced and is not practical at all.

Further, the scratch resistance is determined by setting the S / N ratio to 10
After the measurement was performed 0 times, the surface of the magnetic layer was observed under a microscope, and the surface state was evaluated according to the following criteria. ◎: No scratches or nicks are observed. ：: Slight scratches are observed. ×: Dropout of the deposited layer is observed.

Examples 1 to 3 and Comparative Example 1 The abbreviations of the respective raw materials used in the following Examples and Comparative Examples are as follows.

Aromatic diamine component: CPA: 2-chloroparaphenylenediamine DPE: 4,4'-diaminodiphenyl ether acid chloride component: TPC: terephthalic acid dichloride CPC: 2-chloroterephthalic acid dichloride acid anhydride component: BTA: 3 , 3 ', 4,4'-Biphenyltetracarboxylic anhydride.

Preparation of Support Layer Components Unless otherwise specified, each polymer raw material was added to N-methylpyrrolidone (hereinafter referred to as NMP) so as to have the same composition as in each of Examples and Comparative Examples, and stirred for 2 hours. To complete the polymerization. Next, the generated hydrogen chloride was neutralized by adding each quarter using lithium hydroxide to obtain a polymer solution having a polymer concentration of 10% by weight. Where the average particle size is 1
Silica particles obtained by adding 50 nm, silica particles having a surface hydrophobic treatment having a relative standard deviation of 0.2 of particle diameter into NMP, performing ultrasonic dispersion for 48 hours, and then filtering using a 1.0 μm filter. The slurry was added to the polymer solution so that the silica concentration was 1 wt% with respect to the polymer, and the slurry was sufficiently stirred to prepare.

Example 1 A dehydrated NMP was placed in a reactor having a cooling jacket having a diameter of 1.8 m and then 80 mol% of CPA and 20 mol% of DPE were dissolved, and the solution was cooled. Then 10
0 mol% of CPC was added, and the peripheral speed was increased from 4 m / sec to 2 m.
The mixture was stirred for 2 hours while changing to / sec, and neutralized with lithium hydroxide to obtain a polymer. Next, the polymer was introduced into water, pulverized while coagulating, and repeatedly washed with water to remove inorganic substances, and dried to obtain a polymer powder.

Next, a substantially monodisperse average primary particle size of 4
0 nm, the above-mentioned polymer powder was gradually added to a lithium chloride-NMP dispersion of colloidal silica having a relative standard deviation of 0.2 of particle diameter while stirring, and was dissolved, so that the content of particles per polymer was 0.8. % By weight and a polymer concentration of 10% by weight.

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 1.0 μm and 3.5 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 gentle evaporation until the solvent content is 56%,
The self-supporting film was peeled off from the belt,
C., with NMP / water (30
/ 70) 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, the film was stretched 1.1 times in the longitudinal direction after the second water tank. Then, it is dried and heat-treated at 300 ° C. in a tenter, and then stretched 1.2 times in the width direction.
After cooling to room temperature at a rate of ° C./sec, an aromatic polyamide film having a thickness of 4.5 μm was obtained.

The physical properties and film properties of this film are as shown in Table 1.

Example 2 In the same manner as in Example 1, 70 mol% of CPA and 30 mol% of DPE were dissolved, and the solution was cooled. Then 10
0 mol% of CPC was added, and the peripheral speed was increased from 4 m / sec to 2 m.
The mixture was stirred for 2 hours while changing to / sec, and neutralized with lithium hydroxide to obtain a polymer. Next, the polymer was introduced into water, pulverized while coagulating, and repeatedly washed with water to remove inorganic substances, and dried to obtain a polymer powder.

A substantially monodisperse average primary particle size of 30 nm,
The above-mentioned polymer powder was gradually added to an NMP dispersion in which colloidal silica particles having a relative standard deviation of 0.1 of particle diameter previously dispersed were stirred and stirred, and the content of particles per polymer was 0.8. Weight%, polymer concentration 1 weight%
It was prepared so that

Next, as a polymer component, 80 mol% of C
A support layer component solution separately prepared as PA, 20 mol% DPE and 100 mol% CPC was passed through a 5 μm cut filter, polished on a mirror surface to a film thickness of 3.5 μm, and preheated to 120 ° C. Can be cast on a stainless steel belt and heated from the upper and lower surfaces of the belt.
After gently evaporating in a dryer with a temperature gradient from 0 ° C. to 170 ° C. until the solvent content becomes 56%, the self-supporting film is peeled off from the belt, and then the peeled film is subjected to After defoaming the previously prepared 30 nm colloidal silica-containing polymer solution, it was applied through a 2 μm-cut filter, and the applied layer was semi-dried with a radiation heater. Next, as a wet process, as a first circulating water tank kept at 40 ° C., water at 20 ° C., and as second, third, and fourth circulating water tanks, NMP / water at 30 ° C., respectively, was 35/35.
The mixture was passed through a water tank having a composition ratio of 65, 15/85, 0/100. At this time, the film was stretched 1.1 times in the longitudinal direction after the second water tank. Then, it is dried and heat-treated at 300 ° C. in a tenter. At this time, the film is stretched 1.2 times in the width direction, and cooled to room temperature at a speed of 20 ° C./second to obtain a 3.5 μm-thick aromatic polyamide film. Obtained.

The physical properties and film properties of this film are as shown in Table 1.

Example 3 A dehydrated NMP was placed in a reactor having a cooling jacket having a diameter of 1.8 m and treated with an amino-terminated silane coupling agent.
m of NMP dispersion of colloidal silica is added so that the content of particles per polymer is 0.7% by weight, then 60 mol% of CPA and 40 mol% of DPE are dissolved and the solution is cooled. Next, 100 mol% of BTA was added, and polymerization was carried out while changing the peripheral speed from 4 m / sec to 2 m / sec, to obtain an aromatic polyamic acid solution having a polymer concentration of 10% by weight.

After defoaming, a catalyst was added to the solution before membrane formation and to the separately prepared support layer component solution, and the polymer solution was passed through a 2 μm-cut filter. After passing through a cut filter, the final film thickness is 2.2 μm and 2.3 μm, respectively, and it is compounded in a laminated tube and cast on a stainless steel belt polished on a mirror surface and preheated to 120 ° C. In a dryer with a temperature gradient from 150 ° C. to 170 ° C., which can be heated from the upper and lower surfaces, the film was gently evaporated while imidizing until the solvent content became 55%. And kept at 40 ° C with a circulation mechanism.
It was first introduced into an NMP / 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, and then stretched 1.2 times in the longitudinal direction and 1.25 times in the width direction.
The cyclization was completed in the above atmosphere, and the mixture was cooled to room temperature at a rate of 20 ° C./sec to obtain an aromatic polyimide film having a thickness of 4.5 μm.

The physical properties and film properties of this film are as shown in Table 1.

Comparative Example 1 A dehydrated NMP and lithium chloride were placed in a reaction vessel having a cooling jacket having a vessel diameter of 1.8 m, and then the colloidal silica used in Example 3 was used in an amount of 0.8 wt. %, And then 80 mol%
Of CPA, 20 mol% of DPE are dissolved and the solution is cooled. Then, 100 mol% of TPC was added, and the mixture was stirred at a peripheral speed of 2 m / sec for 2 hours, and neutralized with lithium hydroxide to obtain a polymer solution having a polymer concentration of 10% by weight.

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 film is cast on a stainless steel belt polished on a mirror surface and preheated to 120 ° C., dried in a hot air drier at 180 ° C. to obtain a self-supporting film. Then, the mixture was separated and introduced into a 40 ° C. water bath to extract the remaining solvent and the like. At this time, the film was stretched 1.1 times in the longitudinal direction in the water tank. Then, it is dried and heat-treated at 300 ° C. in a tenter. At this time, the film is stretched 1.2 times in the width direction, and cooled to room temperature at a speed of 20 ° C./second to obtain a 4.5 μm-thick aromatic polyamide film. Obtained.

The physical properties and film properties of this film are as shown in Table 1.

[0091]

[Table 1]

[0092]

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 recording media, especially for high-density magnetic recording media such as computer memories. Further, the excellent surface properties obtained by the present invention, the relationship between the magnetic tape and the head, for example, the relationship between the thermal head or the recording material and the thermal transfer recording material, and the relationship between the roll and the processing plate and the film. As it is obvious when considering the replacement, 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 It can be suitably used for various uses such as a battery substrate.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI theme coat ゛ (reference) C08L 79:00 F term (reference) 4F071 AA56 AH14 BC01 BC08 BC10 BC15 4F100 AB01B AK47A AK49A AR00B BA02 BA10A BA10B DD07A GB41 JG06B JJ03 JK01 JK07 JM02B YY00A 5D006 BB01 CB02 CB03 CB07 FA02 FA04

Claims (7)

[Claims] 1. A film mainly composed of an aromatic polyamide and / or an aromatic polyimide, wherein a projection formed on at least one surface of the film is subjected to Voronoi division, and the area average value of the Voronoi polygon is obtained. To Xb
ar, standard deviation is σ, relative standard deviation (σ / X
(a) an aromatic polyamide and / or aromatic polyimide film, wherein bar) is 1 or less. 2. The film according to claim 1, wherein the aromatic polyamide is a para-oriented aromatic polyamide. 3. The method according to claim 1, wherein the fine projections having a height of 5 nm or more are 10 ² to 1.
The aromatic polyamide and / or aromatic polyimide film according to claim 1 or 2, wherein the number is 0 ¹⁰ / mm ² . 4. A projection having a height of 50 nm or more among projections having a height of 5 nm or more.
The protrusions exceeding nm are 10% or less of the whole.
4. The aromatic polyamide and / or aromatic polyimide film according to any one of 3. 5. The aromatic polyamide and / or aromatic polyimide film according to claim 1, wherein the relative standard deviation of the height of the projections is 0.5 or less. 6. A magnetic recording medium comprising a magnetic layer provided on at least one surface of the film according to claim 1. 7. The magnetic layer according to claim 6, wherein the magnetic layer is a metal thin film type magnetic layer.
3. The magnetic recording medium according to claim 1.