JP2003053923A - Aromatic polyamide film, method for manufacturing the same, and magnetic recording medium using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aromatic polyamide film having uniform fine projections on its surface and improved in adhesion, and a magnetic recording medium having good output and output fluctuations and excellent in durability. SOLUTION: The aromatic polyamide film has a resin thin film and fine projections composed of core-shell particles, of which the interiors are softer than the exteriors having a mean particle size of 10-100 nm and provided in the number of 1×10<6> -1×10<8> /mm<2> on its projection forming surface. The center surface average roughness RaA (nm) of the projection forming surface measured by an interatomic force microscope (AFM), the ten score average roughness RzA (nm) thereof satisfy the formula (1): 0.8<=RaA<=5.0 and the formula (2): 10<=RzA<=100, and the number irregularity of fine projections is not more than 20%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has excellent abrasion resistance,
Also, the present invention relates to an aromatic polyamide film having a very uniform surface morphology and a method for producing the same. Furthermore, it relates to a magnetic recording medium using such a film.

[0002]

2. Description of the Related Art Aromatic polyamide films have been developed for various applications by taking advantage of their excellent heat resistance and mechanical properties. Especially para-oriented aromatic polyamide is rigid,
Since mechanical properties such as strength are superior to those of other polymers, it is very advantageous for film thinning, and applications such as printer ribbons, magnetic recording media, and capacitors are considered.

Particularly when used in a magnetic recording medium represented by a magnetic tape, a surface morphology (surface property) suitable for a film.
Is required, for example, a method of incorporating inorganic particles or organic particles in a polymer forming a film (for example, JP-A-60-127523, JP-A-60-201914), film A method of coating a coating liquid containing fine particles during or after film formation (for example, JP-A-3-119512, JP-A-7-241962, JP-A-9-323385, WO99 / 53483). Is a typical example.

These conventional methods have regulated the average surface morphology and structure of the film for the purpose of improving the output characteristics of the magnetic recording medium and, at the same time, improving the running property and durability. .

However, in recent years, it has been unavoidable that the recording density is increased, that is, the recording area per unit bit is miniaturized, and various problems have occurred.
For example, in the 1970's, the recording area per bit was 100 μm ² order, whereas in the 1980's it was 10 μm ² order, in the 1990's it was 1 μm ² order, and those below 1 μm ² are being studied. Therefore, when the recording area is made smaller, it is necessary to improve the reproduction output, and at the same time, it is essential to stabilize the output at each recording position. In other words, just by controlling the average surface morphology and structure of the base film,
There is a concern that it will not be possible to cope with higher and higher densities in the future. Furthermore, as the density of recording increases, the load on the protrusions of the base film increases. That is, since recording / reproducing at a higher speed than before is required, the surface protrusions are exposed to severe rocking, and there is a concern that serious problems such as loss of recording due to scraping or falling of the protrusions may occur. is there.
Further, the processing speed of the magnetic recording medium is also increasing year by year, and the surface protrusions are exposed to severe conditions accordingly, which may cause problems such as chipping and falling of the protrusions. , It was difficult to satisfy these.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and when the magnetic recording medium is used, the output is high and constant, and the aromatic polyamide has excellent durability even under severe conditions. An object is to provide a film and a magnetic recording medium.

[0007]

In order to achieve the above object, the present invention has a resin thin film layer on at least one side, and the surface of the resin thin film layer has 1 × 10 5 projections having an average diameter of 10 to 100 nm. Atomic force microscope (AF) of the surface on which the protrusions are formed with a density of ⁶ to 1 × 10 ⁸ pieces / mm ^2.
M) the center plane average roughness Ra _A (nm) and the 10-point average roughness Rz _A (nm) satisfy the following equations (1) and (2), and the number of protrusions is 20% or less. Features an aromatic polyamide film.

0.8 ≦ Ra _A ≦ 5 (1) 10 ≦ Rz _A ≦ 100 (2)

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the aromatic polyamide of the present invention include the following formula (I) and / or formula (II)
Those having 50 mol% or more of the repeating unit represented by can be used.

Formula (I):

[0011]

[Chemical 1] Formula (II):

[0012]

[Chemical 2] Here, the groups of Ar ₁ , Ar ₂ and Ar ₃ are, for example,

[0013]

[Chemical 3] And so on.

Here, X and Y are aromatic ring-bonding groups, for example, —O—, —CH ₂ —, —CO—, —S—,
-C (CH _{3) 2} - is selected from such as, but not limited thereto. Furthermore, some of the hydrogen atoms on these aromatic rings are halogen groups such as fluorine, bromine and chlorine (especially chlorine), nitro groups, alkyl groups such as methyl, ethyl and propyl (especially methyl groups), methoxy and ethoxy, It may be substituted with a substituent such as an alkoxy group such as propoxy, and hydrogen in the amide bond constituting the polymer may be substituted with another substituent.

In the aromatic polyamide used in the present invention, the aromatic ring having the para orientation is 70 mol% or more, more preferably 90 mol% or more of the total aromatic rings. preferable. Here, the para orientation is
The state in which the divalent bonds constituting the main chain on the aromatic ring are coaxial or parallel to each other. When the para orientation is less than 70 mol%, the film may have insufficient rigidity and heat resistance.

The aromatic polyamide in the present invention is copolymerized or blended if the other repeating units of the above-mentioned repeating units represented by the formula (I) and / or the formula (II) are in a small amount such as less than 50 mol%. It may have been done.

In addition, within the range which does not impair the object of the present invention,
Inorganic or organic additives such as antioxidants, heat stabilizers, UV absorbers and nucleating agents may be blended.

The resin thin film of the present invention refers to a thin film formed of an aqueous resin, that is, a water-soluble resin and / or a water-dispersed resin. Examples of the aqueous resin for forming the resin thin film include cellulose derivatives such as methyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, water-soluble and water-dispersible epoxy resins, acrylic resins, polyester resins, polyurethane resins, and the like. Among these, adhesion with aromatic polyamide film,
From the viewpoint of heat resistance, polyvinylpyrrolidone, water-soluble or water-dispersible acrylic resin and polyester resin are preferable. These aqueous resins may be used in any form of a simple substance, a copolymer and a mixture. The heat resistance of the aqueous resin will be described later.

The above water-soluble or water-dispersible acrylic resin is
It can be obtained by a method of copolymerizing acrylamide or methylol acrylamide with an acrylic resin obtained by copolymerizing monomers such as acrylic acid, methacrylic acid and styrene.

The above water-soluble or water-dispersible polyester resin includes acid components such as terephthalic acid, isophthalic acid, adipic acid, succinic acid, sebacic acid and dodecanedioic acid, ethylene glycol, propylene glycol, 1,4- A polyester resin obtained by a polycondensation reaction with an alcohol component such as butanediol, 1,6-hexanediol or neopentyl glycol can be obtained by a method of copolymerizing a compound having a sulfonic acid group. Examples of the compound having a sulfonic acid group include 5-sulfoisophthalic acid sodium salt and 5-sulfoisophthalic acid ammonium salt. In addition, a polyester resin is copolymerized with a dibasic or higher polybasic acid such as trimellitic anhydride or pyromellitic anhydride to introduce a carboxyl group, which is neutralized with ammonia or amine to be water-soluble or water-dispersed. The water-based polyester resin can also be obtained by the above method.

Among the above, it is particularly preferable to use a resin containing ammonium sulfonate as a hydrophilic component from the viewpoint of recycling of raw materials and recoverability. It is considered that this is because, in the case of a resin having a salt containing an alkali metal such as sodium sulfonate as a hydrophilic component, these metal elements are likely to be a factor to generate coarse particles.
That is, in the case of a resin containing ammonium sulfonate as a hydrophilic component, since there is no metal element that causes such coarse particles, even if recovered and reused a plurality of times, the coarse particles are It is possible to obtain a film having excellent recyclability, which is unlikely to generate foreign matter such as.

Regarding the heat resistance of the above-mentioned aqueous resin, it is preferable that the heat loss at 300 ° C. is 5% by weight or less in order to improve the adhesion between the particles and the film. 30 of the present invention
The thermal loss of 0 ° C. is a value obtained by measuring the thermal loss of the water-based resin in a nitrogen atmosphere under a temperature rising rate of 10 ° C./min using a thermogravimetric measuring device, and using the following formula (3). Yes, the lower this value, the better the heat resistance. Here, the reason why the weight at 120 ° C. is used as a reference is to eliminate the influence of weight change due to moisture absorption of the aqueous resin.

Thermal loss at 300 ° C. (% by weight) = ((weight at 120 ° C.−weight at 300 ° C.) / Weight at 120 ° C.) × 100 (3) The thermal loss at 300 ° C. is 5 When the content exceeds the weight%, the aqueous resin is likely to be thermally decomposed, the adhesion between the aqueous resin and the core-shell particles described later is deteriorated, and the durability of the magnetic tape may be deteriorated. Furthermore, the thermally decomposed water-based resin stains the heat treatment process during film formation, or the heat-decomposed product of the water-based resin deposited in the heat treatment process adheres to the surface of the film to form coarse protrusions. May cause problems such as missing. 300 ° C of water-based resin
The loss on heat is more preferably 4% by weight or less, still more preferably 3% by weight or less.

The thickness of the resin thin film formed from the above-mentioned water-based resin is properly designed depending on the average particle size of the core-shell particles described below, the application, etc., but is 20 to 80 relative to the average particle size of the core-shell particles. It is preferably within the range of%. The thickness of the resin thin film is 20 with respect to the average particle diameter of the core-shell particles.
If it is less than%, the contact area between the core-shell particles and the aqueous resin is small, so that the adhesion is insufficient and the particles are likely to fall off, and the durability when used as a magnetic tape may decrease. When the thickness of the resin thin film exceeds 80% with respect to the average particle diameter of the core-shell particles, the adhesion between the aqueous resin and the core-shell particles is improved, but the slipperiness due to the core-shell particles deteriorates, and when used as a magnetic tape. Driving performance may deteriorate. The thickness of the resin thin film is more preferably in the range of 30 to 70% with respect to the average particle diameter of the core-shell particles, and is 40
The range of -60% is more preferable.

In the present invention, it is preferable to use core-shell particles as the particles for forming the protrusions. The core-shell particles are polymer fine particles having a multilayer structure in which the inside (hereinafter, referred to as the core portion) and the outside (hereinafter, referred to as the shell portion) are composed of polymers having different properties,
Particles that are softer in the shell than in the core are preferred. Here, the multi-layered structure means a two-layered structure or more, and the property may continuously change in the diameter direction of the fine particles. Further, the shell portion, after being disposed on the film surface by coating or the like, reacts with the aqueous resin by heat treatment, or melts, softens, or deforms to increase the affinity with the aqueous resin or the base film, It has a function of strengthening the adhesion between the core-shell particles and the base film, and the core part, together with the shell part, has a function of giving the film an appropriate slidability and an optimal spacing between the magnetic head and the like. In order to impart such a function, the shell part has excellent affinity and adhesion with the water-based resin and the base film, and has appropriate physical, chemical and thermal properties at the film-forming heat treatment temperature. It is required that the core portion has a high hardness with respect to the shell portion and the base film, which is not deformed by pressure or friction.

As the polymer composition of the core-shell particles for realizing the above function, a thermoplastic resin is preferable for the shell portion, and an acrylic resin is particularly preferable. Regarding the core portion, in addition to the thermoplastic resin, a phenol resin,
Thermosetting resins such as epoxy resin, unsaturated polyester resin and urethane resin can be used, but in particular divinylbenzene resin, polystyrene resin, acrylic resin, or the same kind or different kind of these resins for increasing hardness. Copolymers of each other are preferred. Of course, the shell portion and the core portion are not particularly limited as long as they have the above functions.

Further, with respect to the shell portion, a functional group having reactivity or affinity with the aqueous resin or the base film at an arbitrary ratio in the polymer, specifically, for the purpose of enhancing the affinity with the aqueous resin, specifically, Carboxyl group, amide group,
You may introduce an amino group, an epoxy group, etc. These functional groups may be used alone or in combination of two or more depending on the case.

The above-mentioned core-shell particles can be obtained, for example, by the emulsion polymerization method described in "Synthetic Resin Emulsion", pages 26 to 27, issued by Japan Society of Polymer Publishing, January 30, 1978, but is not limited thereto. It is not something that will be done. As an example of the emulsion polymerization method, first, a monomer forming a core portion, an emulsifier and a polymerization initiator are added to an aqueous solvent to carry out emulsion polymerization in the first step, and after the polymerization in the first step is completed, the shell portion is added. The second step emulsion polymerization is carried out by adding the monomer for forming the polymer and the polymerization initiator. Furthermore, particles having a multi-layer structure may be obtained by changing the monomer composition and carrying out the third stage emulsion polymerization or further polymerization.

When the core-shell particles have a two-layer structure, the weight ratio of core-shell (weight of core part / weight of shell part) is appropriately designed depending on the application, but is 1/100 to 3/1.
It is preferably within the range. Core shell weight ratio is 1
When it is smaller than / 100, that is, when the layer thickness of the shell portion is too large, the particles are likely to be deformed by heat or friction. Further, when the weight ratio of the core-shell is larger than 3/1, that is, when the layer thickness of the shell portion is too small, the adhesion to the aqueous resin or the base film is deteriorated, and the particles are apt to fall off, resulting in a magnetic tape. The durability may deteriorate. Core shell weight ratio is 1/80 ~
More preferably within the range of 2/1 and 1/50 to
The range of 1/1 is more preferable.

The average particle diameter of the core-shell particles is 10 to 100.
It must be nm. If the average particle size is less than 10 nm, the particles agglomerate to form coarse protrusions, which lowers the output of the magnetic tape and increases dropouts.
Conversely, if it is too large, the same problem will occur. The average particle diameter of the core-shell particles is more preferably 15 to 80 nm,
More preferably, it is 20 to 50 nm.

When coating the film with the core-shell particles contained in the coating liquid, the addition amount to the coating liquid is the coating thickness,
Although it should be properly designed depending on the application, etc., it is preferably in the range of 0.001 to 0.1% by weight based on the coating liquid. When the addition amount of the core-shell particles is less than 0.001% by weight, the number of core-shell particles is small and thus the number of protrusions is likely to be uneven. When the addition amount exceeds 0.1% by weight, the core-shell particles in the coating liquid form aggregates. May form. The amount of core shell particles added is 0.002 to 0.9 with respect to the coating liquid.
The range of wt% is more preferable, and the range of 0.003 to 0.8 wt% is further preferable.

Depending on the use of the aromatic polyamide film of the present invention, the polymer composition, the core-shell weight ratio,
You may use together several types of core shell particles from which an average particle diameter differs.

The coating liquid may contain a surfactant, and specifically, an anionic surfactant, a cationic surfactant, a nonionic surfactant, a fluorinated surfactant, a reactive surfactant and the like. , Chemical resistance, heat resistance,
A fluorine-based surfactant having excellent surface activity is preferable. Such a surfactant can be expected to be effective in improving the dispersion state of the core-shell particles in the coating liquid and improving the wettability with respect to the base film. The amount of the surfactant added is an arbitrary amount depending on the composition of the coating liquid,
It is preferably 0.01 to 5% by weight with respect to the coating liquid. If the amount of the surfactant added exceeds 5% by weight, the expected surfactant effect cannot be obtained, which is uneconomical, and the core-shell particles in the coating liquid may aggregate. Further, if the addition amount of the surfactant is less than 0.01% by weight, the surfactant effect is low, and when applied to the film surface,
Repelling and coating spots may occur, and the number of protrusions may deteriorate. The amount of surfactant added is 0.05 to 3 with respect to the coating liquid.
It is more preferably in the range of 0.1% by weight, still more preferably 0.1 to 2% by weight.

The surface of the aromatic polyamide film of the present invention on which the projections are formed (hereinafter referred to as the projection formation surface) contains the above-mentioned aqueous resin, core-shell particles and a surfactant on at least one surface of the aromatic polyamide film. It can be formed by applying a water-based coating liquid, and then performing drying, stretching and / or heat treatment.

The aromatic polyamide film of the present invention has a resin thin film and an average diameter of 10 to 100 on the projection forming surface.
nm projections are formed, and the existing density of the projections is 1 × 10 ⁶ to 1 × 10 ⁸ pieces / mm ² . If the density of protrusions is less than 1 × 10 ⁶ pieces / mm ² , the running property of the magnetic tape is poor, and if it exceeds 1 × 10 ⁸ pieces / mm ² , the output of the magnetic tape is reduced. The number of protrusions is more preferably 2 × 10 ^{6 to} 7 × 10 ⁷ pieces / mm ² , and even more preferably 2 × 10 ^{6 to} 5 × 10 ⁷ pieces / mm ² . If the average diameter of the protrusions is less than 10 nm, the running property of the magnetic tape becomes poor, and if it exceeds 100 nm, the output of the magnetic tape decreases. In order to form the protrusions within the above range, for example, when using core-shell particles, it is preferable to use particles having an average particle size within the range of 10 to 100 nm.

In the aromatic polyamide film of the present invention, the center plane average roughness Ra _A (nm) of the projection forming surface and the 10-point average roughness Rz _A (nm) are expressed by the following formula (1),
It is necessary to satisfy (2).

0.8 ≦ Ra _A ≦ 5 (1) 10 ≦ Rz _A ≦ 100 (2) When the center surface average roughness Ra _{A of the} projection forming surface is less than 0.8 nm, the magnetic property is obtained. If the tape runs poorly and the thickness exceeds 5 nm, the smoothness of the entire surface is impaired, and the noise of the magnetic tape increases, which may reduce the output. The center plane average roughness Ra _A is more preferably 0.9 to 4 nm, further preferably 0.9 to 3 nm.

The 10-point average roughness Rz _{A of the} projection forming surface
When the value is less than 10 nm, the running property of the magnetic tape becomes poor, and when it exceeds 100 nm, dropouts increase. The 10-point average roughness Rz _A is more preferably 15 to 80 nm and even more preferably 20 to 50 nm.

Further, in the aromatic polyamide film of the present invention, it is necessary that the number of protrusions on the protrusion forming surface is 20% or less. If the unevenness of the number of protrusions exceeds 20%, the output fluctuation of the magnetic tape becomes large. The number of protrusions is more preferably 15% or less, still more preferably 10% or less.

In the aromatic polyamide film of the present invention, when the agglomeration rate of the protrusions is 20% or less, the dropout when used as a magnetic recording medium is small, and the reliability such as data loss is most important for data storage applications. Can be optimally used, and is particularly preferable. In such applications, the agglomeration rate of protrusions is more preferably 15% or less, and 10
% Or less is more preferable.

The aromatic polyamide film of the present invention is preferably a monolayer film from the viewpoint of easy film formation, but the output and dropout when a magnetic tape is used,
In order to achieve excellent runnability, it is more preferable to use a laminated film by coextrusion. In the case of a laminated film, at least one outermost layer may be used as the protrusion forming surface of the present invention. Therefore, one of the outermost layers satisfies the film requirement of the present invention, but the other one side layer may not satisfy the film requirement of the present invention.

However, in a two-layer laminated film, the inorganic particles and / or organic particles are added to the aromatic polyamide for the purpose of imparting runnability to the layer on the side where the magnetic layer is not formed (hereinafter referred to as layer B). In the case of forming fine projections by a method of incorporating particles or a method of mixing different polymers in an aromatic polyamide and phase-separating the different polymers when the mixed polymer solution is dried, the projection forming surface of the present invention is adversely affected. It is necessary to be careful not to affect. That is, in the B layer, if aggregates or contamination caused by inorganic particles, organic particles and / or different polymers occur, they also adversely affect the surface on which the protrusions are formed, and dropout easily occurs when the magnetic tape is formed. This is because there is something that happens.

In order to suppress the formation of aggregates and contamination in the B layer, the average particle size and content of the inorganic particles, organic particles and / or different polymers to be incorporated in the B layer should be properly designed. It is preferable to increase the laminated thickness on the side where the projections are formed. For example, the average particle size of the inorganic particles, the organic particles and / or the heterogeneous polymer blended in the layer B is preferably 1 to 300 nm, and 5 to 200.
More preferably, it is nm. If the average particle diameter is less than 1 nm, the particles aggregate to form coarse protrusions, which may also cause coarse protrusions on the protrusion forming surface, which may reduce the output of the magnetic tape or increase dropouts. 300
Similar problems may occur even if the thickness exceeds nm. Also,
The content of the inorganic particles, the organic particles and / or the different polymer blended in the B layer is 0.0 with respect to the aromatic polyamide.
It is preferably 1 to 3% by weight, and more preferably 0.02 to 2% by weight. This content is 0.01% by weight
If it is below the range, the running property of the magnetic tape becomes poor, and if it exceeds 3% by weight, the particles agglomerate to form coarse projections, and coarse projections are also generated on the projection forming surface, and the output of the magnetic tape is reduced. It may drop or have more dropouts. Further, in order to further improve the output, running property, and defect-free property of the magnetic tape, in order to reduce the adverse effect of the B layer, the lamination thickness on the projection forming surface side is set to 2.5.
The thickness is preferably at least μm, more preferably at least 3 μm.

The type of particles to be mixed in the B layer is Si
O₂, TiO₂, Al₂O₃, CaSO _Four, BaSO_Four, Ca
CO₃, Carbon black, zeolite, other metals
Inorganic particles such as fine powder, silicone particles, polyimide particles
Particles, cross-linked copolymer particles, cross-linked polyester particles, tefro
Core particles of the present invention.
Particles, etc., using any of these particles
Alternatively, a plurality of types may be used together.

The aromatic polyamide on the side of the projection formation contains the above-mentioned inorganic particles, organic particles and / or a different polymer for imparting lubricity to the extent that the object of the present invention is not impaired. However, it is preferable that these are not included.

Further, the resin thin film of the present invention and, for example, projections of core-shell particles may be provided in the B layer to impart the running property.

Further, the aromatic polyamide film of the present invention preferably has a Young's modulus in at least one direction of 8 GPa or more. Since the output of the magnetic tape increases as the head touchability between the tape and the head improves, the base film is required to have a high Young's modulus. When the recording method is the fixed head type, the Young's modulus in the longitudinal direction is
Further, in the case of the helical scan method, the Young's modulus in the width direction is particularly important, so if the Young's modulus is less than 8 GPa in any direction of the base film, high output will be obtained regardless of which recording method is adopted. Sometimes you can't get it. The Young's modulus is more preferably 9 GPa or more, further preferably 10 GPa or more. It is particularly preferable that the Young's modulus in all directions is 8 GPa or more.
In order to satisfy these characteristics, as described above, the aromatic polyamide used in the present invention having an aromatic ring having para orientation is 70 mol% or more, more preferably 80 mol% of all aromatic rings. % Or more is preferable.

The elongation of the aromatic polyamide film of the present invention is preferably 10% or more, more preferably 20% or more, further preferably 30% or more in order for the tape to have appropriate flexibility.

Further, the moisture absorption rate is preferably 5% or less, more preferably 3% or less, further preferably 2% or less so that the dimensional change of the magnetic tape due to humidity change is small and good output can be maintained.

20 of the aromatic polyamide film of the present invention
The heat shrinkage ratio at 0 ° C. for 10 minutes is preferably 0.5% or less, more preferably 0.3% or less, in order to keep the dimensional change of the magnetic tape due to temperature change small and to maintain a good output.

It is preferable that these characteristics are satisfied regardless of whether it is a monolayer film or a laminated film.

The aromatic polyamide film of the present invention is preferably used for various applications such as flexible printed circuit boards, capacitors, printer ribbons, acoustic diaphragms, base films for solar cells, etc., but it has excellent heat resistance and abrasion resistance. It is particularly preferably used as a base film of a magnetic recording medium by taking advantage of its excellent property.

Next, the magnetic recording medium of the present invention will be described.

The magnetic recording medium of the present invention is one in which a magnetic layer is provided on the protrusion-forming surface of the aromatic polyamide film. At this time, the thickness of the magnetic layer is preferably 0.3 μm or less.

As a ferromagnetic material for forming the magnetic layer, F is
e, Co, Ni and other ferromagnetic metals, Fe-Co, Co
-Ni, Fe-Co-Ni, Fe-Cu, Co-Cu,
Co-Au, Co-Pt, Mn-Al, Fe-Cr, C
o-Cr, Ni-Cr, Fe-Co-Cr, Co-Ni
Examples include ferromagnetic alloys such as —Cr and Fe—Co—Ni—Cr.

The magnetic layer may be a single layer film or a multi-layer film, and after forming the magnetic layer, a sputtering method is applied to the surface of the magnetic layer for the purpose of enhancing the durability and weather resistance of the magnetic recording medium. For example, a DLC (diamond-like coating) film may be provided, and a lubricant may be present to improve the running property. Furthermore, in order to improve the slipperiness and durability, a back coat layer may be provided on the film surface opposite to the magnetic layer.

The form of the magnetic recording medium is not particularly limited, such as a disc, card or tape, but the base film has a thickness of 10 μm or less, a width of 2.3 to 13 mm, a length of 60 m / roll or more, and a recording density. When used as a magnetic recording medium such as a high recording density magnetic tape having a (non-compressed) size of 5 kilobytes / mm ² or more, the film of the present invention has excellent surface resistance with excellent abrasion resistance and smoothness, and high rigidity. It is particularly preferable because the above property can be further utilized. The recording density here is a value calculated by the following equation.

Recording density = Recording capacity / (tape width × tape length) In recent years, magnetic recording media typified by magnetic tapes have been required to have smaller sizes and higher capacities. There are the following points in implementing.
One is to reduce the thickness of the base film and increase the length to increase the overall recording capacity.The other is to narrow the track width and shorten the recording wavelength to reduce the recording area per unit area. This is a method of increasing the recording density, and generally, the capacity is increased in the direction of using them together. As described above, when the recording density is increased by narrowing the track width or shortening the recording wavelength, recording / recording at high speed can be performed.
Regeneration is required, and the surface protrusions of the base film are exposed to harsh conditions, and it is strongly desired to form surface protrusions with better abrasion resistance than before, and it has excellent abrasion resistance. The aromatic polyamide film of the present invention having surface protrusions is extremely effective.

As described above, the aromatic polyamide film of the present invention can be suitably used as a magnetic tape which can meet such a demand for higher capacity.

The thickness of the base film is preferably
It is 7 μm or less, more preferably 5 μm or less, and the recording density as a magnetic recording medium is preferably 8 kilobytes / m.
m ² or more, more preferably 25 kilobytes / mm ² or more.

The magnetic recording medium of the present invention is for consumer use, professional use, digital video cassette use for broadcasting stations such as D-1, D-2 and D-3, DDS-2, 3, 4, data 8 m.
It can be suitably used for data storage applications such as m, AIT, DLT, and LTO, but in particular, it can be optimally used for data storage applications where high capacity and reliability are most important.

The aromatic polyamide film of the present invention can be produced, for example, by the following method, but the invention is not limited thereto.

First, when an aromatic polyamide is obtained from an aromatic diacid chloride and an aromatic diamine, it is synthesized by solution polymerization in an aprotic organic polar solvent such as N-methylpyrrolidone, dimethylacetamide or dimethylformamide. At this time, in order to suppress the production of low molecular weight substances, it is necessary to avoid mixing of water and other substances that hinder the reaction, and it is preferable to employ an efficient stirring means. Further, although the equivalence of the raw materials is important, it can be adjusted appropriately when there is a risk of impairing the film forming property. Further, calcium chloride, magnesium chloride, lithium chloride, lithium bromide, lithium nitrate or the like may be added as a dissolution aid.

When aromatic diacid chloride and aromatic diamine are used as monomers, hydrogen chloride is produced as a by-product. When neutralizing this, cations of Group I or II of the periodic table, hydroxide ions and carbonates are used. Inorganic neutralizing agents represented by salts consisting of anions such as ions, ethylene oxide, propylene oxide, ammonia, triethylamine,
An organic neutralizing agent such as triethanolamine or diethanolamine may be used.

Further, for the purpose of improving the humidity characteristics of the film, benzoyl chloride, phthalic anhydride, acetic acid chloride, aniline and the like may be added to the system in which the polymerization has been completed to block the ends of the polymer.

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

As the membrane-forming stock solution, a polymer solution after neutralization may be used as it is, or a polymer once isolated may be redissolved in an inorganic solvent such as sulfuric acid or an organic solvent.

In order to obtain the aromatic polyamide film of the present invention, it is preferable to remove foreign matters in the polymer before extruding the polymerized polymer from the die in the film forming process.

When the polymer solution is used as it is,
The aprotic organic polar solvent is preferably used in the polymer polymerization as a polymerization solvent after performing a purification operation such as distillation or filtration in advance, and the aromatic diamine and aromatic diacid chloride that are monomers are also used as they are, or It is preferable that the polymer is once dissolved in a polymerization solvent and then filtered to be used for polymer polymerization.

For such filtration, for example, a filter made of polypropylene, stainless steel, fluororesin or the like can be used, and the filtration accuracy is preferably 3 μm or less, more preferably 2 μm or less, still more preferably 1 μm. It is the following. As described above, the smaller the filtration accuracy is, the more preferable it is. However, if the filtration accuracy is too small, the filter is clogged quickly and the solvent cannot be transferred promptly. Therefore, the lower limit is preferably about 0.1 μm.

During the polymerization of the polymer, in order to prevent contamination from entering the polymerization tank, an inert gas filtered by a dust filter having a filtration accuracy of 0.3 μm is used for the polymer solution in the polymerization tank. It is also effective to pour in the solution to raise the pressure in the polymerization tank above atmospheric pressure.

When neutralizing hydrogen chloride produced as a by-product when aromatic diacid chloride or aromatic diamine is used as the monomer, a purified inorganic and / or organic neutralizing agent is used. It is preferable.

At this time, when an inorganic carbonate is used as the neutralizing agent, it is necessary to pay attention to the molar ratio of hydrogen chloride to carbonate. That is, when neutralization is performed with an excessive amount of carbonate with respect to the molar concentration of hydrogen chloride, an excessive amount of carbonate may remain in the polymer, and the residual carbonate may cause contamination. If the amount is too small, neutralization of hydrogen chloride is insufficient and the film forming apparatus is likely to corrode. Further, when neutralization is performed with a carbonate having an equimolar molar concentration with respect to the molar concentration of hydrogen chloride, it takes a long time to complete the neutralization reaction, and the neutralization is performed for a too long time. However, the desired effect cannot be obtained, and on the contrary, productivity is deteriorated, which is not preferable. Neutralization of hydrogen chloride with a carbonate or the like should be appropriately determined, but it is preferable to neutralize with 93 to 99 mol%, particularly 94 to 98.5 mol% of neutralizing agent with respect to hydrogen chloride. The neutralization time is 2 hours or more, especially 3
It is preferably not less than time, and the upper limit is appropriately about 10 hours. When neutralizing the remaining hydrogen chloride, it is preferable to use an organic neutralizing agent.

Also, when the polymerized polymer once isolated is dissolved again in an inorganic solvent such as sulfuric acid or an organic solvent, it is preferable that the same filtering operation is carried out for the solvent.

In addition, as described above, an inorganic and / or organic additive such as an antioxidant, a heat stabilizer, an ultraviolet absorber and a nucleating agent may be added to the aromatic polyamide film within a range that does not impair the object of the present invention. May be blended with the polymerized polymer.

The polymer concentration in the polymer solution is 2
It is preferably ˜40% by weight. This is because when the polymer concentration is less than 2% by weight, problems such as poor productivity and difficulty in obtaining a film having sufficient rigidity are likely to occur, and when the polymer concentration exceeds 40% by weight, the polymer solution This is because the viscosity of the polymer becomes high and the handling property in the polymerization and film forming process is deteriorated.

The polymer solution prepared as above is
In removing the contamination, it is preferable to carry out filtration again immediately before extruding from the die in the film forming process. For the filtration of the polymer solution, it is preferable to use a filter made of a material having excellent corrosion resistance because the solvent is an inorganic solvent such as sulfuric acid or an organic solvent. Examples of such a filter include nickel and titanium. , Zirconium, tantalum, lead simple substance, and "Inconel" and "Monel" containing these simple substances as main components (International
Nickel Co.'s trade name), "Hastelloy" (Haynes Ste
Alloys such as llite Co.), materials made of immobilized metal such as iron or stainless steel, and non-metals such as polyethylene resin, polypropylene resin, Teflon (registered trademark) resin, activated carbon, and glass. Examples include a filter made of a material or a filter made by combining two or more kinds of the above materials.

The filtration accuracy of this polymer solution is preferably 3 μm or less, more preferably 2 μm or less, still more preferably 1 μm or less. As described above, in the filtration of the polymer solution, it is a preferable direction to reduce the filtration accuracy, but if it is too small, the filter may be clogged or the filtration pressure becomes high and the filter may be damaged. The lower limit is appropriately about 0.1 μm.

Examples of the method for forming the polymer solution prepared as described above include a solution method such as a dry method, a dry-wet method, a wet method, and a semi-dry semi-wet method. However, the dry-wet method is preferable in terms of easy control of the surface morphology, and the dry-wet method will be described below as an example.

The polymer solution is extruded from a die onto a support such as a drum or an endless belt to form a thin film, and then the solvent is scattered from the thin film layer to dry the thin film.

At this time, the desolvation rate is 10 to 30% /
Drying in minutes is preferred. When the desolvation rate is less than 10% / min, productivity is poor, and when the desolvation rate exceeds 30% / min, the film surface may be rough due to rapid solvent evaporation. The drying temperature is preferably 100 to 210 ° C, and more preferably 120 to 180 ° C. Also,
The drying time is preferably 2 to 10 minutes, more preferably 3 to 8 minutes.

Next, the film which has undergone the dry process is peeled off from the support and introduced into the wet process for desalting and solvent removal. If the peeled gel film is stretched and heat-treated as it is without passing through the wet process, salt in the polymer may be deposited, resulting in coating unevenness in the subsequent coating process and large coarse protrusions. The solvent for the wet process is generally water-based, but it may contain a small amount of an inorganic or organic solvent or inorganic salt in addition to water. The solvent temperature is usually 0.
Used at ~ 100 ° C. Further, if necessary, the film may be stretched in the longitudinal direction in a wet process.

Here, the step of applying the aqueous coating liquid containing the aqueous resin, the core-shell particles and the surfactant to at least one surface of the film may be during the film forming step or after the film forming. From the viewpoint of surface properties and productivity, it is preferable to apply between the wet process and the heat treatment process. For example, when the water-based coating solution is applied after the polymer solution is cast from the die or after peeled from the support, the film surface is likely to be rough, and the adhesion of the core-shell particles may be decreased even after the heat treatment,
Further, when applying after film formation, it is not economical because a step of drying and heat treating the coating solution again is required.

As a coating method, a metalling bar method,
Die coat method, gravure method, reverse roll method,
Any coating method such as a doctor blade method may be used.

The coating liquid applied by the above coating method is
Before drying, stretching and / or heat treatment. Here, the drying temperature of the coating liquid is preferably 200 ° C. or lower. If the drying temperature exceeds 200 ° C., the core-shell particles in the coating liquid may agglomerate due to a rapid temperature change, and the unevenness in the number of protrusions after drying may worsen, resulting in a large output fluctuation when used as a magnetic tape. Further, if the drying temperature is too low, it takes a long time to dry the coating liquid and the productivity deteriorates. Therefore, the lower limit of the drying temperature is appropriately 100 ° C. The drying temperature of the coating liquid is more preferably 180 ° C or lower, and further preferably 150 ° C or lower.

The temperature unevenness in the film width direction in the coating liquid drying step is preferably 10 ° C. or less, more preferably 7 ° C.
The temperature is below, more preferably 5 ° C or below. When the temperature unevenness in the film width direction in the coating liquid drying step exceeds 10 ° C., the density unevenness of the core-shell particles in the coating liquid occurs in the film width direction, and the unevenness in the number of protrusions after drying may be deteriorated.

When the film is applied through the wet process, it is preferable to remove the solvent on the applied surface as much as possible. The aqueous coating liquid for forming the resin thin film of the present invention has good wettability because it contains the above-mentioned surfactant, but in the state where the solvent of the wet process is attached to the film surface. When application is performed, application unevenness may occur, and unevenness in the number of protrusions may be aggravated. The method of removing the solvent on the film surface is not particularly limited, but, for example,
A method of removing the solvent by bringing the film into contact with a water-absorbing roll having a porous surface is preferable.

Thereafter, stretching and heat treatment are performed to form a film.

The stretching temperature is effective in improving the mechanical properties of the film when it is carried out within the temperature range of 200 to 400 ° C., more preferably 220 to 350 ° C., and further preferably 240.
To 300 ° C., and the draw ratio in the range of 1.2 to 4, more preferably 1.2 to 3.5 in terms of areal magnification, enables stable production of a film having excellent mechanical properties. It is preferable in that a film can be formed. The surface magnification is defined as a value obtained by dividing the film area after stretching by the area of the film before stretching.

Heat treatment is carried out during or after the stretching of the film. The heat treatment temperature is 200 to 300 ° C.
It is preferable that it is within the range from the viewpoint of improving the dimensional stability of the film.

The above stretching and / or heat treatment is generally carried out by blowing hot air onto the film surface from a slit-shaped or cylindrical nozzle. However, in order to control the unevenness of the number of protrusions within the range of the present invention, the film width When the temperature unevenness in the direction is within 10 ° C., unevenness in the number of protrusions due to film stretching unevenness is reduced, which is preferable. The temperature unevenness in the film width direction is more preferably within 7 ° C, further preferably 5 ° C.
Within.

Further, slow cooling of the film after stretching or heat treatment is effective for improving the flatness of the film, and cooling at a rate of 50 ° C./sec or less is effective.

As described above, the aromatic polyamide film of the present invention may be a single layer film or a laminated film. When the aromatic polyamide film is formed into a laminated film, for example, lamination in a die, lamination in a composite pipe, A method of forming one layer and then forming another layer thereon may be used, but it is necessary that at least one of the outermost layers is the projection forming surface of the present invention.

By the method described above, the aromatic polyamide film having the projection forming surface of the present invention can be manufactured.

The magnetic recording medium of the present invention is obtained by forming a magnetic layer on the protrusion forming surface of the aromatic polyamide film obtained by the above method, and the method for forming the magnetic layer is not particularly limited. , For example, a vacuum evaporation method of evaporating a ferromagnetic material under vacuum to deposit it on a non-magnetic support, an ion plating method of evaporating a ferromagnetic material in a discharge, in an atmosphere containing argon as a main component. A physical film deposition method in a vacuum (PVD method: Physical Vapor Depositio) such as a sputtering method in which atoms on the target surface are bombarded by argon ions generated by glow discharge.
n) and the like are preferably used.

Measurement of physical properties and evaluation of effects in the present invention are carried out by the following methods.

(1) Protrusion Density An atomic force microscope (AFM) was used to measure the protrusion formation surface under the following conditions to obtain the number of protrusions having a height of 5 nm or more.
The density of protrusions was converted to m ² . The measurement is 1
The measurement was performed 10 times for each sample, and in order to eliminate the influence of variations due to measurement, the maximum and minimum values were excluded, and the average value was obtained.

Device: NanoScopeIIIa ver3.2 AFM J Scanner used (manufactured by Digital Instruments) Probe: SPM probe NCH-W manufactured by Nanosensors
Type, single crystal silicon Scan mode: Tapping mode Number of samples: 256 Scan range: 5 μm × 5 μm Scan speed: 1.0 Hz Measurement environment: temperature 23 ° C., relative humidity 65%, in air (2) average of protrusions The projection forming surface was observed using a diameter scanning electron microscope (SEM) under the following conditions, the longest diameter of 20 particles in the observed image was determined, and the average value was converted to nm to be the average diameter of the projections.

Apparatus: Ultra-high resolution field emission scanning electron microscope (S-900H manufactured by Hitachi, Ltd.) Accelerating voltage: 2 kV Observation magnification: 50,000 times or more (3) Average particle diameter of core-shell particles of dynamic light scattering method Particle size analyzer MICROTRAC UPA MODEL; 9230 (L
Eeds & Northrup) was used for measurement and rounded to the nearest unit to obtain the average particle diameter of the core-shell particles.

(4) Center plane average roughness Ra _A The center plane average roughness Ra _A was obtained by measuring under the same conditions as the protrusion density in (1) above.

(5) 10-Point Average Roughness Rz _{A The} 10-point average roughness Rz _A was obtained by measuring the projection forming surface under the following conditions using an atomic force microscope (AFM). In addition, the measurement was performed 10 times for each sample, and the average value was determined by taking the maximum and minimum values as the measured values in order to eliminate the influence of variations due to the measurement.

Device: NanoScopeIIIa ver3.2 AFM J Scanner used (Digital Instruments) Probe: Nanosensors SPM probe NCH-W
Type, single crystal silicon Scan mode: Tapping mode Number of samples: 256 Scan range: 30 μm × 30 μm Scan speed: 0.5 Hz Measurement environment: temperature 23 ° C., relative humidity 65%, atmospheric (6) number of protrusions uneven The standard deviation was calculated from the measured value of the protrusion density obtained in the above (1) using the unbiased standard dispersion, and the standard deviation was converted into the number of pieces / mm ² and calculated by the following formula.

Number of protrusions (%) = (standard deviation / protrusion density) × 100 (7) Thermal loss at 300 ° C. Thermogravimetric analyzer (TGA-50 manufactured by Shimadzu Corporation)
H) and analyzer Thermal analyzer (TA-50)
In addition, the measurement was performed using an apparatus in which a personal computer for data processing was combined. Approximately 7 mg of a sample dried at 120 ° C for 12 hours was set in a furnace, the furnace was placed under a nitrogen atmosphere, and the temperature was raised from room temperature to 60 ° C at a temperature increase rate of 10 ° C / min.
Heated to 0 ° C. From the obtained thermogravimetric curve, the heat loss at 300 ° C. was calculated by the following formula.

Thermal loss at 300 ° C. (% by weight) = ((120
Weight at ℃ -Weight at 300 ℃ / Weight at 120 ℃)
× 100 (8) Thickness of resin thin film A small piece of film is fixed and molded with epoxy resin, and an ultrathin section is cut with a microtome (cut parallel to the longitudinal direction of the film).
It was created. The ultrathin section was observed with a transmission electron microscope (H-7100FA manufactured by Hitachi) at an acceleration voltage of 100 kV, and the boundary surface of the resin thin film was searched for the thickness.

(9) Tensile Young's modulus, elongation at break Width 1 using an automatic film strength and elongation measuring device "Tensilon AMF / RTA-100" manufactured by Orientec Co., Ltd.
Set the film cut to 0 mm and length 150 mm in the device with a chuck distance of 50 mm, and pull at a speed of 300 m.
A tensile test was performed under the conditions of m / min, a temperature of 23 ° C. and a relative humidity of 65%, and the tensile Young's modulus was obtained from the tangent line of the rising portion of the obtained load-elongation curve. The elongation was calculated by multiplying the value obtained by subtracting the distance between chucks from the length at the time of film breakage by the distance between chucks and multiplying by 100.

(10) Drying temperature unevenness of coating liquid, heat treatment temperature unevenness Using a thermocouple thermometer, a thermocouple was attached to the film surface on the side where the projections were formed, and the temperature was measured. Measure the temperature at 5 points in the film width direction, find the temperature difference between the highest temperature and the lowest temperature,
The drying temperature unevenness and the heat treatment temperature unevenness were used.

(11) Output characteristics A film having a thickness of 170 nm is formed on the surface on which the protrusions are formed by continuous oblique vapor deposition.
An -O magnetic layer was formed. Then the thickness of 5 by sputtering
A diamond-like coating film having a thickness of 10 nm was formed on the magnetic layer, and a 0.1% by weight solution of an organic rust preventive was applied onto the magnetic layer using a gravure roll and dried in a dryer at 100 ° C. After that, a 0.5 wt% solution mainly containing an organic substance composed of a perfluoropolyether derivative as a lubricant was applied using a gravure roll and dried by a dryer at 100 ° C.

Next, carbon was mainly used on the surface opposite to the magnetic layer, and a vinyl acetate resin was used as a binder to obtain a thickness of 0.1.
A 3 μm back coat layer was formed.

The magnetic recording medium obtained as described above was slit into a width of 8 mm and a length of 250 m and incorporated into a cassette to prepare a magnetic tape.

A commercially available AIT-1 drive was used to record a signal with a recording frequency of 7 MHz, the reproduction output was measured, and the average S / N ratio was compared with a commercially available Hi8 tape as a reference (0 dB). did.

⊚: +2 dB or more O: +1 dB or more, less than +2 dB Δ: -1 dB or more, less than +1 dB x: less than -1 dB (12) Output fluctuation In the measurement of (11) above, fluctuation range of S / N ratio during reproduction. (Maximum value-Minimum value) was measured and the following evaluations were performed.

⊚: Fluctuation width less than 0.2 dB ◯: Fluctuation width of 0.2 dB or more and less than 0.5 dB Δ: Fluctuation width of 0.5 dB or more and less than 1.5 dB ×: Fluctuation width of 1.5 dB or more (13) Durability In the measurement of (11) above, reproduction of 3,000 passes
Rewinding was performed, and the following evaluation was performed by the number of passes attenuated by -1 dB from the S / N ratio of the first pass.

[0113] ○: 1,000 passes or more Δ: 500 or more and less than 1,000 ×: less than 500 passes

[0114]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited thereto. In the examples below, NMP is N-methyl-2-
Pyrrolidone, CTPC is 2-chloroterephthalic acid chloride, CPA is 2-chloroparaphenylenediamine, DP
E represents 4,4'-diaminodiphenyl ether.

Example 1 CPA corresponding to 85 mol% and DPE corresponding to 15 mol% were dissolved in dehydrated NMP, and this solution was filtered through a filter made of polypropylene having a filtration accuracy of 0.6 μm. After that, it was transferred to a polymerization tank and passed through a filter made of polypropylene with a filtration accuracy of 0.6 μm, and CT equivalent to 98.5 mol% was passed.
PC was added and stirred at 30 ° C. or lower for 2 hours to obtain a polymer.

Next, 98.5 mol% of lithium carbonate was added to the hydrogen chloride in the polymer to neutralize for 4 hours to obtain an aromatic polyamide solution A having a polymer concentration of 10.8% by weight. It was

Further, 85 mol% of CPA and 15 mol% of DPE were dissolved in dehydrated NMP, and this solution was filtered through a filter made of polypropylene having a filtration accuracy of 0.6 μm and then polymerized. CTP corresponding to 98.5 mol% transferred to a tank and passed through a filter made of polypropylene with a filtration accuracy of 0.6 μm
C was added and stirred at 30 ° C. or lower for 2 hours to obtain a polymer.

Next, 98.5 mol% of lithium carbonate was added to the hydrogen chloride in the polymer to neutralize for 4 hours, and silica having an average primary particle size of 16 nm was added to the polymer. 1.8% by weight and stirred for 1 hour,
Aromatic polyamide solution B having a polymer concentration of 10.6% by weight
Got

Next, the aromatic polyamide solution A was passed through a metal fiber filter made of stainless steel having a filtration accuracy of 1.2 μm, and the aromatic polyamide solution B was filtered with a filtration accuracy of 3.0.
After passing through a metal fiber filter made of stainless steel having a thickness of μm, it was laminated inside the die. The laminated thickness at this time was 2.5 when the thickness of the aromatic polyamide solution A in the final film was 2.5.
μm, and the aromatic polyamide solution B was laminated so as to have a thickness of 1.5 μm. Next, the laminated polymer solution was cast on a stainless steel belt having a mirror-like surface,
The film having self-holding property was continuously peeled off from the belt by heating at 0 ° C. for 3 minutes to evaporate the solvent. At this time, the polymer concentration of the gel film was 40% by weight, and the desolvation rate was 20% / min.

Next, the gel film was passed through a water tank using water filtered with a polypropylene filter having a filtration accuracy of 0.6 μm for 2 minutes to extract the residual solvent and the inorganic salt produced by neutralization with water. During this time, the film was stretched 1.2 times in the longitudinal direction to obtain a water-containing film.

Next, after removing water on both sides of the water-containing film with a draining roll, a polypropylene filter having a filtration accuracy of 0.6 μm is provided on the side of the aromatic polyamide solution A layer (layer formed by the aromatic polyamide solution A). The coating liquid shown in Table 1 filtered in step 1 was applied by a metering bar method so that the coating thickness was 4.5 μm. Next, the coating liquid was dried with a drier having a temperature unevenness in the film width direction of 1 ° C. and a drying temperature of 120 ° C. Here, the core-shell particles are composed of styrene (15% by weight), butyl acrylate (1
5% by weight) and divinylbenzene (20% by weight) to synthesize the core part, and styrene (15% by weight), butyl acrylate (25% by weight), divinylbenzene (10% by weight) after the middle stage.
Particles having an average particle size of 30 nm in which the shell part was synthesized by using (% by weight) were used. As the aqueous polyester resin, a polycondensation reaction product of terephthalic acid (45 mol%), 5-sulfoisophthalic acid sodium salt (5 mol%) and ethylene glycol (50 mol%) was used. 30 of this water-based polyester resin
The loss on heat at 0 ° C was 0.2%.

Then, stretching and heat treatment were carried out with a tenter to obtain an aromatic polyamide film having a thickness of 4.0 μm.
During this period, the film was stretched 1.4 times in the width direction at 300 ° C., heat-treated at 200 ° C. for 1.5 minutes, and then at 20 ° C.
It was gradually cooled at a rate of / sec. The unevenness of the heat treatment temperature in the film width direction when stretched by the tenter was 3 ° C.

[0123] Tensile Young's modulus of the aromatic polyamide film, 11,700N / mm ² in the longitudinal direction, a 17,200N / mm ² in the width direction and the breaking elongation, 57% in the longitudinal direction, the width direction Was 34%.

Table 2 shows the results of evaluation of the surface characteristics of the protrusion-forming surface of this aromatic polyamide laminated film. In addition, as a result of evaluating a magnetic tape by forming a magnetic layer on the protrusion-formed surface, as shown in Table 2, output characteristics, output fluctuation, and durability were good.

(Examples 2 to 4) Aromatic polyamide laminated films were obtained in the same manner as in Example 1 except that the amount of core-shell particles added was changed as shown in Table 1.

Table 2 shows the evaluation results of the surface characteristics of the protrusion-forming surface of these aromatic polyamide laminated films. In addition, as a result of evaluating a magnetic tape by forming a magnetic layer on the protrusion-formed surface, as shown in Table 2, output characteristics, output fluctuation, and durability were good.

(Example 5) Methyl methacrylate (60 mol%), ethyl acrylate (38 mol%),
An aromatic polyamide laminated film was obtained in the same manner as in Example 2 except that a water-soluble acrylic resin synthesized with acrylic acid (1 mol%) and n-methylolacrylamide (1 mol%) was used. In addition, 300 of the above-mentioned water-based acrylic resin
The loss on heat at ℃ was 3.6%.

Table 2 shows the evaluation results of the surface characteristics of the protrusion-forming surface of this aromatic polyamide laminated film. In addition, as a result of evaluating a magnetic tape by forming a magnetic layer on the protrusion-formed surface, as shown in Table 2, output characteristics, output fluctuation, and durability were good.

Example 6 Polyvinylpyrrolidone "Luviskol K" manufactured by BASF Japan Ltd. was used as an aqueous resin.
An aromatic polyamide laminated film was obtained in the same manner as in Example 2 except that 90 ″ was used. The polyvinyl pyrrolidone had a thermal loss at 300 ° C. of 1.5%.

Table 2 shows the results of evaluation of the surface characteristics of the protrusion-forming surface of this aromatic polyamide laminated film. In addition, as a result of evaluating a magnetic tape by forming a magnetic layer on the protrusion-formed surface, as shown in Table 2, output characteristics, output fluctuation, and durability were good.

Example 7 An aromatic polyamide laminated film was obtained in the same manner as in Example 2 except that polyvinyl alcohol “Poval PVA-117” manufactured by Kuraray Co., Ltd. was used as the aqueous resin. The loss on heat of the polyvinyl alcohol at 300 ° C. was 23.6%.

Table 2 shows the results of evaluation of the surface characteristics of the protrusion-forming surface of this aromatic polyamide laminated film. In addition, as a result of evaluating a magnetic tape by forming a magnetic layer on the protrusion-formed surface, as shown in Table 2, output characteristics, output fluctuation, and durability were good. (Example 8) Styrene (6% by weight) at the initial stage of emulsion polymerization,
Butyl acrylate (6% by weight), divinylbenzene (8% by weight) was used to synthesize the core, and styrene (24% by weight), butyl acrylate (40% by weight)
The aromatic compound was prepared in the same manner as in Example 1 except that core-shell particles having an average particle diameter of 40 nm, the shell portion of which was synthesized with divinylbenzene (16% by weight), were used, and the addition amounts of the core-shell particles and the water-soluble polyester resin were changed. A polyamide laminated film was obtained.

Table 2 shows the results of evaluation of the surface characteristics of the protrusion-forming surface of this aromatic polyamide laminated film. In addition, as a result of evaluating a magnetic tape by forming a magnetic layer on the protrusion-formed surface, as shown in Table 2, output characteristics, output fluctuation, and durability were good.

Example 9 A core portion was synthesized with styrene (6% by weight), butyl acrylate (6% by weight) and divinylbenzene (8% by weight) at the initial stage of emulsion polymerization, and styrene (24% by weight) was added after the middle stage. ), Butyl acrylate (40
%), And a core-shell particle having an average particle size of 50 nm, in which the shell part is synthesized with divinylbenzene (16% by weight),
An aromatic polyamide laminated film was obtained in the same manner as in Example 1 except that the addition amounts of the core-shell particles and the water-soluble polyester resin were changed.

Table 2 shows the results of evaluation of the surface characteristics of the protrusion-forming surface of this aromatic polyamide laminated film. In addition, as a result of evaluating a magnetic tape by forming a magnetic layer on the protrusion-formed surface, as shown in Table 2, output characteristics, output fluctuation, and durability were good.

Example 10 Aqueous solution obtained by polycondensation reaction of terephthalic acid (42.5 mol%), ammonium 5-sulfoisophthalate (7.5 mol%) and ethylene glycol (50 mol%) with an aqueous resin. An aromatic polyamide laminated film was obtained in the same manner as in Example 2 except that the polyester resin was used. In addition, 30 of the above water-based polyester resin
The loss on heat at 0 ° C. was 3.7%.

Table 2 shows the results of evaluation of the surface characteristics of the projection-forming surface of this aromatic polyamide laminated film. In addition, as a result of evaluating a magnetic tape by forming a magnetic layer on the protrusion-formed surface, as shown in Table 2, output characteristics, output fluctuation, and durability were good.

(Comparative Examples 1 and 2) Water on both sides of the water-containing film obtained in the same manner as in Example 1 was removed by a water-removing roll, and then the aromatic polyamide solution A layer side was filtered to a filtration accuracy of 0.6 μm.
The coating liquid shown in Table 1 filtered with a filter made of polypropylene of m.
It was applied to have a thickness of μm. Here, as the core-shell particles and the water-soluble polyester resin, those obtained by the same method as in Example 1 were used. After coating, the coating liquid was dried with a dryer having a temperature unevenness in the film width direction of 7 ° C and a drying temperature of 250 ° C.

Then, an aromatic polyamide laminated film was obtained in the same manner as in Example 1.

Table 2 shows the results of evaluation of the surface characteristics of the projection-forming surface of this aromatic polyamide laminated film. Further, as a result of forming a magnetic layer on the protrusion forming surface and evaluating the magnetic tape, as shown in Table 2, it was not possible to obtain a magnetic tape having good output characteristics, output fluctuation, and durability.

Comparative Example 3 Styrene (15 wt%), butyl acrylate (15 wt%),
A core part was synthesized with divinylbenzene (20% by weight), and a shell part was synthesized with styrene (15% by weight), butyl acrylate (25% by weight), and divinylbenzene (10% by weight) after the middle stage. Comparative Example 1 except that the core-shell particles were used and the addition amounts of the core-shell particles, the water-soluble polyester resin and the surfactant were changed.
An aromatic polyamide laminated film was obtained in the same manner as in.

Table 2 shows the results of evaluation of the surface characteristics of the protrusion-forming surface of this aromatic polyamide laminated film. Further, as a result of evaluating a magnetic tape by forming a magnetic layer on the surface on which the protrusions are formed, as shown in Table 2, the output characteristics and the output fluctuation deteriorated.

(Comparative Example 4) After removing the water on both sides of the water-containing film obtained by the same method as in Example 1 with a draining roll,
On the aromatic polyamide solution A layer side, the coating liquid shown in Table 1 filtered with a filter made of polypropylene having a filtration accuracy of 0.6 μm was applied by a metering bar method to a coating thickness of 4.5 μm.
Was applied so that Here, as the core-shell particles and the water-soluble polyester resin, those obtained by the same method as in Example 1 were used. After coating, temperature unevenness in the film width direction is 5
The coating liquid was dried with a dryer having a temperature of 180 ° C. and a drying temperature of 180 ° C.

Then, an aromatic polyamide laminated film was obtained in the same manner as in Example 1.

Table 2 shows the results of evaluation of the surface characteristics of the protrusion-forming surface of this aromatic polyamide laminated film. Further, as a result of evaluating a magnetic tape by forming a magnetic layer on the surface on which the protrusions are formed, as shown in Table 2, the output characteristics deteriorated.

Comparative Example 5 Styrene (15 wt%), butyl acrylate (15 wt%),
The core part was synthesized with divinylbenzene (20% by weight), and the shell part was synthesized with styrene (15% by weight), butyl acrylate (25% by weight) and divinylbenzene (10% by weight) after the middle stage. An aromatic polyamide laminated film was obtained in the same manner as in Comparative Example 4 except that the core-shell particles were used and the addition amounts of the core-shell particles and the water-soluble polyester resin were changed.

Table 2 shows the results of evaluation of the surface characteristics of the projection-forming surface of this aromatic polyamide laminated film. Further, as a result of evaluating a magnetic tape by forming a magnetic layer on the projection forming surface, as shown in Table 2, the output characteristics and the durability deteriorated.

[0148]

[Table 1]

[0149]

[Table 2]

[0150]

The aromatic polyamide film of the present invention is
Since it has protrusions with less unevenness and strong adhesion, it can be used as a base film to provide a constant output,
It is possible to manufacture a magnetic recording medium having excellent durability even under severe conditions.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4D075 BB05Z BB24Z BB91Z BB93Z                       CA13 CA18 CB33 DA04 DB53                       DC19 DC28 EA06 EA07 EA10                       EB07 EB19 EB22 EB33 EB35                       EB38 EB51 EC07 EC24 EC35                 4F100 AK01B AK21B AK25B AK41B                       AK41K AK47A AR00C BA02                       BA03 BA07 BA10A BA10C                       DD07B EH462 GB41 JB09B                       JG06C JK06 JK15B JL00                       JM01B JM02B YY00B                 5D006 BB07 CB01 CB03 CB07 CB08                       EA03 FA02 FA09

Claims (7)

[Claims] 1. A resin thin film layer is formed on at least one surface, and protrusions having an average diameter of 10 to 100 nm are formed on the surface of the resin thin film layer at a density of 1 × 10 ⁶ to 1 × 10 ⁸ pieces / mm ^2. , Atomic force microscope (AF
M) the center plane average roughness Ra _A (nm) and the 10-point average roughness Rz _A (nm) satisfy the following equations (1) and (2), and the number of protrusions is 20% or less. An aromatic polyamide film. 0.8 ≦ Ra _A ≦ 5 (1) 10 ≦ Rz _A ≦ 100 (2) 2. The resin thin film contains at least one resin selected from the group consisting of a water-soluble or water-dispersible polyester resin, a water-soluble or water-dispersible acrylic resin, and polyvinylpyrrolidone. The aromatic polyamide film described in 1. 3. The aromatic polyamide film according to claim 2, wherein the water-soluble or water-dispersible polyester resin is a resin containing ammonium sulfonate as a hydrophilic component. 4. The aromatic polyamide film according to claim 1, wherein the aggregation rate of the protrusions is 20% or less. 5. An aqueous resin having a heat loss at 300 ° C. of 5% by weight or less on at least one side of an aromatic polyamide film,
A method for producing an aromatic polyamide film, which comprises applying an aqueous coating liquid containing core-shell particles and a surfactant, drying the coating liquid at 200 ° C or lower, and then stretching and / or heat-treating the coating liquid. 6. A magnetic recording medium in which a magnetic layer is provided on the protrusion forming surface of the aromatic polyamide film according to claim 1. 7. The magnetic recording medium according to claim 6, wherein the magnetic layer has a thickness of 0.1 to 0.3 μm.