JP2003160676A - Aromatic polyamide film and magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an aromatic polyamide film which has a good slitting property and which, when used as a base film for a magnetic recording medium, can restrain the deformation at the edges caused by repeated travellings, as well as to provide a magnetic recording medium. <P>SOLUTION: The aromatic polyamide film is the one in which the undermentioned EMD, ETD, and αND simultaneously satisfy formulas (1)-(3): EMD≥ETD (1); ETD≥8 GPa (2); and 10≤αND≤300(×10<SP>-6</SP>/°C) (3), wherein EMD is a Young's modulus in the machine direction; ETD is a Young's modulus in the transverse direction; and αND is a thermal expansion coefficient in the thickness direction. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aromatic polyamide film and a magnetic recording medium using the same.

[0002]

2. Description of the Related Art Conventionally, aromatic polyamide films have been widely used as industrial materials. In particular, due to advances in digital recording technology and the development of external memory for computers, the demand for thinner magnetic tape and higher density recording has become stronger, and aromatic polyamides that have excellent heat resistance, mechanical properties, and dimensional stability. Films are increasingly used as base films for magnetic tapes.

With the recent increase in capacity of magnetic tapes, the recording density of data has dramatically improved. Therefore, a slight dimensional change causes data loss, and the base film is required to have high rigidity and dimensional stability. on the other hand,
From the hardware side as well, attempts have been made to deal with dimensional changes by using servos that record position information. In the process of forming such a servo on the film surface, the guide is strongly regulated in order to prevent the film from swinging in the width direction during running. Also, when used as a magnetic tape, the widthwise fluctuation tends to be designed to be more strongly regulated than in the past so that the servo can be read accurately. Therefore, a strong force is applied to the end portion of the film, and the conventional aromatic polyamide film is deformed, causing problems such as winding and shaving. Upon investigating this cause, it was clarified that the cause was not only the cross-sectional shape due to the slit property but also the thermal deformation due to frictional heat with the guide.

Aromatic polyamide film as a base fill
As an example of use as a system, for example, JP-A-62-62
In Japanese Patent No. 424, the Young's modulus in the width direction is 700 kg / m.
m²Thus, the Young's modulus in the longitudinal direction is
A magnetic recording medium having a recording capacity of 1.2 times or more has been described.
62-70022 discloses a stretched film shape.
In the state, the sum of Young's modulus in the length direction and the lateral direction is 3,500 to 1
1,000 kg / mm ²Aromatic polyamide film
Are listed. But these are all Phil
Focusing on the orientation of the polymer molecular chains that make up the membrane
The slit property is expected to improve, but in the thickness direction
The control of the molecular chain of is not sufficient. Especially, increase the rigidity
Therefore, when the draw ratio is increased, the molecular chains become stronger in the plane direction.
If it is oriented too much and heat is applied, it tends to relax in the thickness direction.
Or neck down (in the direction perpendicular to the stretching
The phenomenon in which the width shrinks) is large and the molecular structure is partially distorted
Deformation in the thickness direction due to the generated heat may easily occur.
It was.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, has good slitting properties, and when used as a base film of a magnetic recording medium, suppresses the deformation of the end portion during repeated running. It is an object to provide an aromatic polyamide film and a magnetic recording medium that can be used.

[0006]

[Means for Solving the Problems] When the Young's modulus in the longitudinal direction (MD) is E _MD , the Young's modulus in the width direction (TD) is E _TD , and the thermal expansion coefficient α _{ND in the} thickness direction is E _MD ,
E _TD and α _ND are achieved by an aromatic polyamide film that simultaneously satisfies the following formulas (1) to (3).

E _MD ≧ E _TD (1) E _TD ≧ 8 GPa (2) 10 ≦ α _ND ≦ 300 (× 10 ⁻⁶ / ° C.) (3)

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The aromatic polyamide used in the present invention is preferably one having a repeating unit represented by the following formula (6) and / or formula (7). Formula (6):

[0009]

[Chemical 1] Formula (7):

[0010]

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

[0011]

[Chemical 3] Etc., and the groups of X and Y are —O—, —CH ₂ —, —
_{CO -, - CO 2 -,} - S -, - SO 2 -, - C (C
H ₃ ) ₂ − and the like, but are not limited thereto.

Further, some of the hydrogen atoms on these aromatic rings are replaced by halogen groups such as fluorine, bromine and chlorine (especially chlorine).
Those substituted with substituents such as nitro groups, alkyl groups (especially methyl groups) such as methyl, ethyl and propyl, and alkoxy groups such as methoxy, ethoxy, and propoxy will lower the moisture absorption rate and cause dimensional changes due to humidity changes. Is preferred, which is preferable. Further, hydrogen in the amide bond constituting the polymer may be replaced with another substituent.

The aromatic polyamide used in the present invention is
It is preferable that the aromatic ring having the para-orientation accounts for 80 mol% or more, more preferably 90 mol% or more, of the total aromatic ring. The para-orientation as used herein means a 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 80 mol%, the film may have insufficient rigidity and heat resistance. Further, the aromatic polyamide has the formula (8)
When the content of the repeating unit represented by is 60 mol% or more, the stretchability and the physical properties of the film are particularly excellent, which is preferable. Formula (8):

[0014]

[Chemical 4] When the aromatic polyamide used in the present invention is obtained from an aromatic diacid chloride and an aromatic diamine, the aromatic polyamide is used in an aprotic organic polar solvent such as N-methyl-2-pyrrolidone, dimethylacetamide or dimethylformamide. It may be synthesized by solution polymerization.

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, 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 by-produced. When neutralizing this, cations and hydroxides of Group I or II of the periodic table are used. It is preferable to use an inorganic neutralizing agent represented by a salt composed of anions such as ions and carbonate ions, and an organic neutralizing agent such as ethylene oxide, propylene oxide, ammonia, triethylamine, triethanolamine and diethanolamine. Further, for the purpose of improving the humidity characteristics of the base film, benzoyl chloride, phthalic anhydride, acetic acid chloride, aniline, etc. are added to the system in which polymerization has been completed,
The terminal functional groups of the polymer may be blocked.

In order to obtain the 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 solution once isolated and then redissolved in a solvent may be used. As the solvent, organic polar solvents such as N-methyl-2-pyrrolidone, dimethylacetamide and dimethylformamide are preferable because they are easy to handle, but strong acidic solvents such as concentrated sulfuric acid, concentrated nitric acid and polyphosphoric acid may be used. The polymer concentration in the film-forming stock solution is preferably in the range of 2 to 20% by weight.

Further, the aromatic polyamide as the surface layer,
It is preferable that a lubricant, an antioxidant and other additives are blended to such an extent that the physical properties of the film are not impaired.

For example, it is preferable that particles are present in the film for the purpose of imparting an appropriate roughness. The types of particles include SiO ₂ , TiO ₂ , Al ₂ O ₃ , CaSO ₄ ,
Inorganic particles such as BaSO ₄ , CaCO ₃ , carbon black, zeolite and other fine metal powders, silicon particles,
There are organic polymers such as polyimide particles, cross-linked copolymer particles, cross-linked polyester particles, cross-linked polystyrene particles, and Teflon (registered trademark) particles, but an inorganic material with excellent heat resistance from the viewpoint of utilizing the heat resistance of the aromatic polyamide film. Particles are more preferred. The particle diameter may be selected depending on the application, but is preferably in the range of 0.01 to 2 μm, more preferably in the range of 0.05 to 1 μm. The content is preferably in the range of 0.01 to 10% by weight, more preferably 0.1 to 5% by weight in order to improve the slippage of the film surface.
For example, when used in a magnetic recording medium, the inorganic particles having an average particle diameter in the range of 0.01 to 0.5 μm are added to 0.1
It is preferable that the content is within the range of 3 wt% to achieve both electromagnetic conversion characteristics, running properties and durability. If the surface of the film is not properly slipped, scratches are likely to occur even when there is a minute foreign substance when the film and the roll come into contact with each other in the film forming process or the processing process. The surface roughness of the final film should be appropriately designed depending on the application in the same manner as the contained particles, but when used for a magnetic recording medium, for example, the center line depth Rp is within a range of 2 to 500 nm,
More preferably in the range of 3 to 300 nm, in the center line average roughness Ra in the range of 0.1 to 100 nm, more preferably in the range of 0.2 to 50 nm, and in the ten-point average roughness Rz of 2 to 5.
It is preferably in the range of 00 nm, more preferably in the range of 3 to 400 nm because the film is less likely to be scratched.

The film-forming stock solution prepared as described above is formed into a film by a dry method, a dry-wet method, a wet method or the like. The dry-wet method is preferable because a high quality film can be obtained.

First, a dry-wet method will be described as an example.

The above stock solution for film formation 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 obtain a polymer sheet which can be peeled from the support. The polymer sheet referred to herein means a film or sheet having a self-supporting property containing a solvent, a dissolution aid, etc. in addition to the polymer. The drying temperature at this time is 80 to 2 because the smoothness of the film surface is improved.
00 ° C is preferred. The solvent content of the polymer sheet is preferably 20 to 70% by weight. If the solvent content exceeds 70% by weight, the self-supporting property of the polymer sheet is insufficient and the stretchability tends to be uneven, and if it is less than 20% by weight, the polymer partially precipitates and the stretchability tends to become uneven. Or
The elongation of the film may decrease. Such uneven stretchability is not preferable because unevenness is likely to occur in the thickness and physical properties of the film. The solvent content of the polymer sheet is more preferably 30 to 70% by weight, and further preferably 30 to 60% by weight, because the thickness and physical properties of the film become more uniform.

Regarding the composition of the solvent contained in this polymer sheet, the above organic polar solvent and / or strongly acidic solvent is 10% by weight or more, more preferably 20% by weight or more,
More preferably, it is contained in an amount of 30% by weight or more because the film is less likely to be broken even when stretched at a high magnification.

The polymer sheet peeled from the support in this manner has a stretched section of 45 ° with respect to the film width.
% To 70% by using a stretching machine set to be less than or equal to
It is heated to 250 ° C. and stretched in the longitudinal direction. When the stretched section exceeds 45%, the structure may be disturbed in the film thickness direction and the slit property may be deteriorated due to a large neck down, or α _ND may exceed the range specified in the present invention. When the heating temperature during stretching is less than 70 ° C, the stretching stress becomes large because the polymer sheet is not sufficiently softened, and when it exceeds 250 ° C, the evaporation of the solvent proceeds too much and the stretching stress increases. Causes a large neck down. Since the neckdown can be further suppressed, the stretched section is preferably 35% or less of the film width, and more preferably 25% or less. The temperature during stretching is more preferably 100 to 200 ° C.,
It is more preferably 0 to 170 ° C. Examples of the heating method include a method using hot air, a method of heating by contact with a high-temperature roll, a method of using infrared rays, and the like. Examples of the stretching method include a method of stretching by changing the peripheral speed between rolls using a roll, a method of stretching by gripping with a chuck, etc., but since the polymer sheet contains a solvent and is easily broken, a roll is used. Is preferred.

Next, the polymer sheet which has undergone the stretching process in the longitudinal direction is introduced into a wet process to undergo desalting, solvent removal and the like. If the heat treatment is performed as it is without passing through the wet process, the surface may be greatly warped or curls may be generated, which is not preferable. Further, when the wet process is introduced, neck down occurs due to the extraction of the solvent, so it is preferable to relax 95 to 98% in the longitudinal direction. The neck-down after the introduction of the wet process (the reduction rate (%) with respect to the die width of the film after the introduction of the wet process) is preferably kept at 30% or less in order to satisfy the requirements of the present invention, and more preferably 25% or less.

The film that has undergone the wet process is dried by moisture and heated.
Processing is performed. The heat treatment temperature is in the range of 200 to 400 ° C.
It is preferable to be surrounded. More preferably 240-3
It is 200 ° C. If the heat treatment temperature is less than 200 ° C,
Decrease in Young's modulus of film _NDMay grow
If the temperature exceeds 400 ° C, the film will crystallize too much.
It is not preferable because it may be a hard and brittle film.

Further, during heat treatment, stretching is performed in the width direction.
U The stretching ratio is the longitudinal stretching ratio R _MD, Longitudinal stretching
Magnification is R_TDAnd when R_TD≤ R_MD/ (1-N / 100) By stretching so that the Young's modulus is
It is preferable to satisfy the requirement (N is the fill after the introduction of the wet process)
(Represents the reduction rate (%) with respect to the width of the mouthpiece). Further surface magnification
(R_MDAnd R_TDThe product of) is preferably 1.3 to 5 times.
Good If it is less than 1.3 times, the rigidity is not sufficient and exceeds 5 times.
If this happens, it tends to be a brittle film.

After stretching or heat treatment, it is effective to gradually cool the film, and it is effective to cool it at a rate of 50 ° C./sec or less.

The dry method is a film-forming method in which the wet step is omitted from the dry-wet method, and the other steps must meet the same requirements as the dry-wet method. However, it is necessary to remove in advance the inorganic salt or the like that cannot be removed in the drying process because there is no wet process, from the stock solution for film formation.

Next, the wet method will be described.

The stock solution for film formation is extruded from a die onto a support such as a drum or an endless belt to form a thin film, which is then introduced into a coagulation bath to remove additives such as a solvent and a dissolution aid. At this time,
In order to desolvate as gently as possible, it is preferable to use a mixed solvent of a good solvent such as a polymerization solvent and a poor solvent such as water in the coagulation bath. Also, calcium chloride as a poor solvent,
A bath prepared by adding an inorganic salt such as magnesium chloride, lithium chloride, lithium bromide or lithium nitrate may be used. The polymer sheet from which the solvent has been extracted is peeled from the support and then formed into a film by a method similar to the dry-wet method. The Young's modulus and the stretching conditions of the polymer sheet at the time of peeling must satisfy the same requirements as in the dry-wet method. Further, in the wet method, a poor solvent is also present as a solvent contained in the polymer sheet, but the organic polar solvent and / or the strongly acidic solvent which is a good solvent is 10% by weight or more, more preferably 20% by weight or more, It is more preferable that the content of 30% by weight or more is less likely to break even when stretched at a high magnification.

The film produced by the method of the present invention may be a laminated film. For example, in the case of two layers, the polymerized aromatic polyamide solution is divided into two, and different particles and the like are added to each and then laminated. The same applies to the case of three or more layers. As a method of stacking these, there are known methods, for example, stacking in a die, stacking in a composite tube, and a method of once forming one layer and then forming another layer thereon.

Next, the physical properties of the aromatic polyamide film obtained by the production method of the present invention will be described.

The thickness of the aromatic polyamide film of the present invention is preferably in the range of 2 to 5 μm. If the thickness of the film is less than 2 μm, it is difficult to handle and it is not practical, and if it exceeds 5 μm, the amount that can be wound per roll is reduced when a high-capacity magnetic tape or the like is used. More preferably in the range of 2 to 4.75 μm, and further 2.5 to
It is within the range of 4.5 μm.

The Young's modulus of the aromatic polyamide film of the present invention, E the Young's modulus in the longitudinal direction _MD, when the Young's modulus in the width direction and E _TD, must satisfy E _MD ≧ E _TD and E _TD ≧ 8 GPa is there. When E _MD is smaller than E _TD , the polymer molecule chains forming the film are oriented in the width direction, so that the slit property is deteriorated and the end portions are easily deformed. From the slit property, the larger the orientation in the longitudinal direction, the better, but
The rigidity in the width direction out of balance of Young's modulus when too large tends salmon or greatly reduced, E _TD ×
It is more preferable to satisfy the relationship of 1.02 ≦ E _MD ≦ E _TD × 1.15, and E _TD × 1.02 ≦ E _MD ≦ E _TD × 1.08
It is more preferable to satisfy the relationship of Also, E _TD is 8G
If it is less than Pa, the rigidity is insufficient and it is not suitable for thinning. Since it is more suitable for thinning, E _TD is more preferably 10 GPa or more, further preferably 12 GPa or more. All Young's modulus is 300m using Tensilon
It was determined from the initial gradient of the curve formed by the elongation and the stretching stress by stretching at m / min.

Thickness of the aromatic polyamide film of the present invention
Coefficient of thermal expansion α_NDIs 10 ≦ α _ND≦ 300 (× 10
^-6/ ° C) is satisfied. α_NDIs 300 (× 10^-6/
℃) exceeds the friction with the guide when used as a magnetic tape
Thermal deformation due to heat is large, which may cause wrapping and the like.
On the other hand, α_NDIs 10 (× 10^-6/ ° C), no winding
It will cause these. The winding appearance when using a magnetic tape is more
Since it improves, 10 ≦ α_ND≦ 100 (× 10^-6/
℃) is more preferable, 50 ≦ α_ND≦ 100 (× 10 ^-6/
C.) is more preferable. α_NDLaser thermal expansion
Using a tensiometer, temperature rise / fall rate: 1 ° C / min, 20-15
The range of 0 ° C. was measured and determined from the amount of change.

The elongation of the aromatic polyamide film of the present invention is preferably 5% or more in all directions. If the elongation is less than 5%, the film may become brittle and may be easily broken, which is not preferable. It is more preferable that the elongation is 10% or more, and particularly 20% or more, since the tape can have appropriate flexibility when processed into a tape.

The moisture absorption rate of the aromatic polyamide film of the present invention is preferably 5% or less, more preferably 3% or less, further preferably 2% or less, since dimensional change due to humidity change can be suppressed.

20 of the aromatic polyamide film of the present invention
The heat shrinkage rate at 0 ° C. for 10 minutes is preferably 0.5% or less, and more preferably 0.3% or less because the dimensional change of the tape due to temperature change is small. This is M
It applies to both D and TD directions. It may be at least one.

The film of the present invention can be used in applications such as flexible printed boards, heat-sensitive transfer ribbons, capacitors, etc., but is particularly useful as a base film for magnetic recording media, and when used as a base film for magnetic recording media. Is provided with a magnetic layer on one side or both sides to form a magnetic recording medium.

Preferable uses of the magnetic recording medium are, for example, 8 mm, for consumer use such as digital video cassette, for professional use, for broadcasting stations such as D-1, 2, 3 and DDS-2, 3,
It is used for data storage such as 4, QIC, data 8 mm, DLT, etc., and can be suitably used particularly for data storage applications where reliability such as data loss is important.

Examples of the method of forming the magnetic layer of the magnetic recording medium of the present invention include coating, vapor deposition, ion plating, sputtering and cluster ion beam.

In the coating method, the coating liquid for the non-magnetic layer is coated on the base film, and then the coating liquid for the magnetic layer is coated thereon while the formed coating layer (non-magnetic layer) is in a wet state. It is preferably formed using a so-called wet-on-wet coating method. Examples of the application method by the wet-on-wet method include the following methods. (1) A non-magnetic layer is first formed on a support using a gravure coating, a roll coating, a blade coating, an extrusion coating device, or the like, and while the non-magnetic layer is in a wet state, the support pressing type extrudate is used. A method for forming a magnetic layer by using a rouge coating apparatus (JP-A-60-23817).
No. 9, Japanese Patent Publication No. 1-46186, Japanese Patent Laid-Open No. 2-2
65672). (2) A method of forming a magnetic layer and a non-magnetic layer on a support almost at the same time by using a coating device comprising a single coating head having two slits for coating liquid (JP-A-63-880).
No. 80, Japanese Unexamined Patent Publication No. 2-17921, and Japanese Unexamined Patent Publication No. 2-
265672). (3) A method of forming a magnetic layer and a non-magnetic layer on a support almost at the same time using an extrusion coating device with a backup roller (see Japanese Patent Laid-Open No. 2-174965).

In the present invention, the non-magnetic layer and the magnetic layer are
It is preferably formed by using a simultaneous multilayer coating method.
The thickness of the nonmagnetic layer is preferably in the range of 1.5 to 1.8 μm. The thickness of the magnetic layer is 0.1 to 0.
It is preferably in the range of 4 μm.

In the magnetic recording medium of the present invention, the non-magnetic layer provided on the non-magnetic support is a substantially non-magnetic layer mainly containing non-magnetic powder and a binder. This non-magnetic layer is required to be substantially non-magnetic so as not to affect the electromagnetic conversion characteristics of the magnetic layer thereabove, but a small amount so as not to affect the electromagnetic conversion characteristics of the magnetic layer. It does not matter in particular even if the magnetic powder of No. 1 is contained. The non-magnetic layer usually contains a lubricant in addition to these components.

Examples of the non-magnetic powder used in the non-magnetic layer include non-magnetic inorganic powder and carbon black. The non-magnetic inorganic powder is preferably relatively hard, and preferably has a Mohs hardness of 5 or more (more preferably 6 or more). Examples of these non-magnetic inorganic powders include α-alumina, β-alumina, γ-alumina,
Silicon carbide, chromium oxide, cerium oxide, α-iron oxide,
Mention may be made of corundum, silicon nitride, titanium carbide, titanium oxide, silicon dioxide, boron nitride, zinc oxide, calcium carbonate, calcium sulphate and barium sulphate. These can be used alone or in combination. Among these, titanium oxide, α-alumina, α-iron oxide, or chromium oxide is preferable. The average particle size of the non-magnetic inorganic powder that can be used in the present invention is 0.01 to
1.0 (preferably 0.01 to 0.5, especially 0.0
It is preferably in the range of 2 to 0.1) μm. In addition, 3 to 25% by weight (preferably 3 to 2) of the non-magnetic powder is used.
It is preferable to use 0% by weight) that has a Mohs hardness of 5 or more (preferably 6 or more) and can function as a so-called abrasive.

The vapor deposition method may be, for example, a diagonal vapor deposition method or a vertical vapor deposition method, and a metal thin film mainly containing Co, Ni, Fe or the like or a metal thin film mainly containing an alloy thereof can be used. For example, ferromagnetic metals such as Co, Ni and Fe, Fe-Co, Co-Ni and Fe-Co-N.
i, Fe-Cu, Co-Au, Co-Pt, Mn-B
i, Mn-Al, Fe-Cr, Co-Cr, Ni-C
r, Fe-Co-Cr, Co-Ni-Cr, Fe-Co
A ferromagnetic alloy such as -Ni-Cr may be used. They are,
It may be a single layer film or a multilayer film.

As a vapor deposition method, a vacuum vapor deposition method in which a ferromagnetic material is heated and vaporized under vacuum and deposited on a film is preferable. However, an ion plating method in which the ferromagnetic material is vaporized in a discharge, and argon is used. A so-called PVD technique such as a sputtering method in which a glow discharge is generated in an atmosphere containing as a main component and atoms on the target surface are knocked out by the generated argon ions may be used. After forming the magnetic thin film,
As a curl countermeasure, heat treatment at 150 ° C. to 250 ° C. is preferably performed. Further, for the purpose of enhancing the durability and weather resistance of the magnetic recording medium on the surface of the magnetic layer formed of a metal magnetic thin film,
If necessary, a hard carbon film may be provided by a sputtering method or a CVD method, and further, by providing a lubricating layer, it is possible to further enhance the running property based on the shape of the particulate projections of the magnetic material. Examples of lubricants include fatty acids and fatty acid esters.

A back coat layer is preferably provided on the other side of the base film of the magnetic recording medium of the present invention. This back coat layer is basically composed of a non-magnetic powder and a binder, and carbon black is preferably contained as the non-magnetic powder. Furthermore, it is preferable that calcium carbonate and inorganic powder having a Mohs hardness of 5 to 9 are contained as the inorganic powder.

In the back coat layer, it is preferable to use two types of carbon black having different average particle sizes. In this case, the average particle size is 10
It is preferable to use fine particle-like carbon black having a particle size of ˜20 mμ and coarse particle-like carbon black having an average particle size of 230-300 mμ. Generally, the surface electrical resistance of the back coat layer can be set low and the light transmittance can also be set low by adding the above-mentioned fine particle carbon black. Depending on the magnetic recording apparatus, many of them use the light transmittance of the tape for the operation signal, and in such a case, the addition of particulate carbon black is particularly effective. In addition, fine particulate carbon black is generally excellent in retaining force of the lubricant, and contributes to reduction of the friction coefficient when used in combination with the lubricant. On the other hand, the particle size is 230-3
The coarse particle carbon black having a particle size of 00 mμ has a function as a solid lubricant, and also forms minute protrusions on the surface of the back layer to reduce the contact area and contribute to the reduction of the friction coefficient. However, the coarse-grained carbon black has a drawback that, in a harsh traveling system, the tape is easily slid to come off from the back coat layer, leading to an increase in error ratio.

The following are specific products of the particulate carbon black that can be used in the present invention. "RAVEN2000B" (18m
μ), “RAVEN1500B” (17 mμ) (above,
Columbia Carbon Co., Ltd., "BP800" (17m
μ) (manufactured by Cabot), "PRINTEX90"
(14 mμ), “PRINTEX95” (15 mμ),
"PRINTEX85" (16mμ), "PRINT
X75 "(17 mμ) (above, manufactured by Degussa), # 395
0 (16 mμ) (manufactured by Mitsubishi Kasei Co., Ltd.). Further, examples of concrete products of coarse particle carbon black include "Thermal black" (270 mμ) (manufactured by Khan Kalb Co.),
"RAVEN MTP" (275 mμ) (manufactured by Columbia Carbon Co.) can be mentioned.

When two kinds of back coat layers having different average particle sizes are used, they are 10 to 20 mμ.
The content ratio (weight ratio) of the fine particle carbon black of No. 2 and the coarse particle carbon black of 230 to 300 mμ is preferably in the range of former: latter = 98: 2 to 75:25, and more preferably 95: 5 to 85: It is 15. In addition, the content of carbon black (in the case of adding fine particles and coarse particles, the total amount thereof) in the back coat layer is usually 30 to 100 parts by weight of the binder described later.
It is in the range of 80 parts by weight, and preferably in the range of 45 to 65 parts by weight.

[0054]

EXAMPLES In the following examples, physical properties were measured and effects were evaluated according to the following methods. (1) Robot Tensilon RT at Young's modulus 25 ° C, 60% RH
It measured using A-100 (made by Orientech).
The test length was set so that the width was 10 mm and the length between the chucks was 50 mm, the tensile speed was 300 mm / min, and the tensile test was performed 5 times to obtain the average value. (2) Coefficient of thermal expansion in the thickness direction The film is divided into three equal parts in the width direction, and each of them is 7
A mm-square piece was cut out and measured under the following conditions to obtain an average value.

Equipment: Vacuum Riko Co., Ltd. Laser thermal dilatometer LIX-1 type Data processing: Toray Research Center data processing system “THADAP-TEX” Measurement mode: Reheating measurement Temperature rising / falling rate: 1 ° C./min Measurement temperature range: 20 to 150 ° C. Measurement atmosphere: in helium Load weight: 17 g Number of measurements n: 2 times (3) Modification of end part The magnetic tape produced by the method described in the example was used as DLT8.
Using the 000 drive, the operation of moving forward for 2 m and returning for 1 m at a running speed of 3.2 m / sec was continued for 50 hours, and then the end was observed. A sample having a length of 10 cm was cut out every 100 m, placed on a horizontal table, and the height of the portion having the largest degree of deformation from the horizontal plane was measured to obtain an average value. The evaluation is performed according to the following criteria, and Δ or more is within the practical range.

◯: Deformation degree is less than 1 mm Δ: Deformation degree is 1 to 2 mm ×: Deformation degree is more than 2 mm (4) Running durability T of the ECMA standard using the DLT8000 drive
An evaluation of 10,000 P (pass) was performed with M1. The number of passes that caused a running stop due to an increase in the error rate was evaluated. The above is the practical range.

◯: No stop up to 10,000P Δ: Stop at 5,000 to 10,000P X: Stop at less than 50,000P The present invention will be described in more detail based on the following examples. Needless to say, is not limited to these. In addition, "part" described in the following examples represents "part by weight". [Example 1] <Preparation of polymer undiluted solution> To dehydrated N-methyl-2-pyrrolidone, 85 mol% of 2-chloroparaphenylenediamine and 15 mol% of 4,4'-diaminodiphenyl ether were added. After being dissolved, 98.5 mol% of 2-chloroterephthalic acid chloride corresponding to this was added, the mixture was stirred for 2 hours, polymerized, and then neutralized with lithium carbonate to obtain an aromatic polyamide solution having a polymer concentration of 11% by weight. Obtained. <Production of Aromatic Polyamide Film> This polymer stock solution was passed through a die with a width of 830 mm to give a mirror-like surface at a speed of 8.0 m.
The final film was cast onto a stainless steel belt rotating at a speed of 1 / min so that the intermediate layer had a thickness of 4 μm. The cast polymer solution was first heated to 160 ° C, then 180 ° C.
Was heated with hot air for 1 minute each to evaporate the solvent and peeled off. The solvent content of the peeled polymer sheet was 40% by weight. This polymer sheet was stretched by 1.25 times in the longitudinal direction while being heated to 80 ° C. by a stretching machine equipped with two sets of nip rolls having a stretching section of 220 mm. The neckdown at this time was 5.1%. Next, 9 in the longitudinal direction into the water tank.
The residual solvent and the inorganic salt generated by neutralization were extracted with water for 2 minutes while applying a relaxation of 8%. The total neckdown up to this step was 13.2%. After this,
TD was stretched 1.44 times and heat-treated in a tenter under hot air at a temperature of 280 ° C. and a wind speed of 5 m / sec. <Production of magnetic tape><Components for forming non-magnetic layer> Non-magnetic powder Titanium oxide TiO ₂ (rutile type) 90 parts (TiO ₂ content: 90% or more, average primary particle diameter: 0.035 μm, ratio by BET method) Surface area: 40 m ² / g, pH: 7.0, DBP oil absorption: 27 to 38 g / 100 g, Mohs hardness: 6.0, surface treatment agent: A1 ₂ 0 ₃ ) Carbon black (manufactured by Mitsubishi Carbon Co., Ltd.) 10 Parts (average primary particle diameter: 16 mμ, DBP oil absorption: 80 ml / 100 g, pH: 8.0, specific surface area by BET method: 250 m ² / g, volatile matter: 1.5%) Polar group (-SO ₃ Na group , 12 parts of an epoxy group-containing) containing vinyl chloride resin (MR-110, Nippon Zeon Co., Ltd.) polar group (-SO ₃ Na group) containing polyester polyurethane resin 5 parts (neopentyl glycol / Kapurora Ton polyol /MDI=0.9/2 .6 / 1 (weight ratio), - SO ₃ Na group content: 1 × 10 ^-4 mol / g) Polyisocyanate 3 parts (Coronate L, Nippon Polyurethane Industry Co., Butyl stearate 1 part Stearic acid 2 parts Oleic acid 1 part Methyl ethyl ketone 150 parts Cyclohexanone 50 parts <Magnetic layer forming component> Ferromagnetic metal powder (composition / Fe: Ni = 70: 80 (atomic ratio)) 100 parts ( Coercive force (Hc): 2,300 oersted (Oe), specific surface area by BET method: 57 m ² / g, crystallite size: 180 Å, saturation magnetization (σs): 141 emu / g, particle size (average major axis diameter) ): 0.08 μm, acicular ratio: 7.5, pH: 9.6, water-soluble Na: 5 ppm, water-soluble Ca: 10 ppm, water-soluble Fe: 10 ppm) Body surface treatment agent (phenylphosphonic acid) 3 parts polar group (-SO ₃ Na group) containing vinyl chloride copolymer 10 parts (-SO ₃ Na group content: 5 × 10 ^-6 mol / g, degree of polymerization 350 , epoxy group content: 3.5% by weight of monomer units, MR-110, manufactured by Nippon Zeon Co.) polar group (-SO ₃ Na group) containing polyester polyurethane resin 2.5 parts (neopentyl glycol / caprolactone polyol /MDI=0.9/2.6/1 (weight ratio), —SO ₃ Na group content: 1 × 10 ⁻⁴ mol / g) Polyisocyanate 2.5 parts (Coronate L, Nippon Polyurethane Industry Co., Ltd.) Made) α-alumina (particle size: 0.3 μm) 10 parts Dichromium trioxide 1 part Carbon black (particle size: 0.10 μm) 3 parts Butyl stearate 1 part Stearic acid 2 parts Oleine Acid 1 part Methyl ethyl ketone 150 parts Cyclohexanone 50 parts The respective components forming the above non-magnetic layer or magnetic layer were kneaded with a continuous kneader and then dispersed using a sand mill. To each of the obtained dispersions, polyisocyanate (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added in an amount of 2.5 parts to the dispersion of the non-magnetic layer and 3 parts to the dispersion of the magnetic layer. Add 40 parts of butyl acetate to
Filtration was performed using a filter having an average pore size of m to prepare a coating liquid for forming a non-magnetic layer and a coating liquid for forming a magnetic layer. <Ingredients for forming back coat layer> 100 parts of fine carbon black powder (manufactured by Cabot, "BP-800", average particle size: 17 mμ) 10 parts of coarse carbon black powder (manufactured by Kahn Kalb, "Thermal Black", Average particle size: 270 mμ) Calcium carbonate 80 parts (manufactured by Shiraishi Industry Co., Ltd., average particle size: 40 mμ) α-alumina 5 parts (Sumitomo Chemical Co., Ltd., “HIT55”, average particle size: 200 mμ, Mohs hardness : 8.5) Nitrocellulose resin 140 parts Polyurethane resin 15 parts Polyisocyanate resin 40 parts Polyester resin 5 parts Dispersant: Copper oleate 5 parts Copper phthalocyanine 5 parts Barium sulfate 5 parts Methyl ethyl ketone 2200 parts Butyl acetate 300 parts Toluene 600 parts Above Form backcoat layer After kneading the components in a continuous kneader and dispersed in a sand mill. The obtained dispersion liquid was filtered using a filter having an average pore size of 1 μm to prepare a coating liquid for forming a backcoat layer. <Formation of Magnetic Layer> The obtained non-magnetic layer forming coating solution and magnetic layer forming coating solution were dried so that the thickness of the non-magnetic layer was 1.7 μm.
Then, simultaneous multilayer coating was performed on the long base film so that the thickness of the magnetic layer after drying was 0.2 μm. Then, while both layers were still in a wet state, orientation treatment was performed using a cobalt magnet having a magnetic flux density of 3,000 gauss and a solenoid having a magnetic flux density of 1,500 gauss. Then, it was dried to provide a non-magnetic layer and a magnetic layer. Then, the other side of the aromatic polyamide support (the side opposite to the magnetic layer) was coated with the above coating solution for forming a backcoat layer so that the thickness after drying was 0.5 μm, and dried. A backcoat layer was provided to obtain a magnetic recording laminate roll in which the non-magnetic layer and the magnetic layer were provided on one surface of the support, and the backcoat layer was provided on the other surface. The obtained magnetic recording laminate roll was a seven-stage calendering machine (temperature 8
It was passed through a calendering process at 5 ° C. and a linear pressure of 300 kg / cm ² ) and then slit into a width of 12.7 mm. The obtained tape (the magnetic tape according to the present invention) was wound around a DLT cartridge for 555 m to manufacture a data storage device.

The characteristics of the base film and the magnetic tape are summarized in Table 1 (the same applies to the following Examples and Comparative Examples). [Example 2] A film and a tape were produced in the same manner as in Example 1 except that the heat treatment temperature was changed to 320 ° C to form a film. [Example 3] In Example 1, the stretching temperature was 130 ° C.
Stretching ratio in longitudinal direction is 1.6 times and stretching ratio in width direction is 2.0.
Films and tapes were produced in the same manner as in Example 1 except that the film was produced by changing the number of times. [Example 4] In Example 1, the stretching temperature was 130 ° C.
Stretching ratio in longitudinal direction is 1.6 times and stretching ratio in width direction is 2.0.
Double, a film and a tape were manufactured in the same manner as in Example 1 except that the heat treatment temperature was changed to 300 ° C. [Example 5] In Example 1, the stretching temperature was 130 ° C.
Stretching ratio in longitudinal direction is 1.6 times, and stretching ratio in width direction is 2.1.
Double, a film and a tape were manufactured in the same manner as in Example 1 except that the heat treatment temperature was changed to 300 ° C. [Comparative Example 1] A film and a tape were produced in the same manner as in Example 1 except that the stretching ratio in the longitudinal direction was changed to 1.15 times and the stretching ratio in the width direction was changed to 1.45 times in Example 1. did.

The orientation in the lateral direction became too strong, and the deformation of the end portion deteriorated. [Comparative Example 2] The same as Example 1 except that the longitudinal stretching ratio was 1.15 times, the transverse stretching ratio was 1.25 times, and the heat treatment temperature was changed to 180 ° C. to form a film. To produce films and tapes.

Α _ND became large, and the deformation of the end portion deteriorated. [Comparative Example 3] In Example 1, the stretching section is 420 m.
A film and a tape were produced in the same manner as in Example 1 except that the film thickness was changed to m, the longitudinal draw ratio was 1.6 times, and the width direction draw ratio was 2.0 times.

As a result of the increased neck down, α _ND increased and the deformation of the end portion deteriorated. [Comparative Example 4] In Comparative Example 4, except that the stretching ratio in the longitudinal direction was 1.6 times, the stretching ratio in the width direction was 2.0 times, and the film was formed by changing the longitudinal stretching ratio to 1.05 times when the water tank was introduced. Films and tapes were prepared as in Example 1.

As a result of the increased neck down, α _ND increased and the deformation of the end portion deteriorated. [Comparative Example 5] A film and a film were prepared in the same manner as in Example 1 except that the amounts of 2-chloroparaphenylenediamine and 4,4'-diaminodiphenyl ether added were changed to 50 mol% respectively. A tape was manufactured.

As a result of the lower Young's modulus, the running durability was lowered.

[0064]

[Table 1]

[0065]

The aromatic polyamide film of the present invention is
By controlling the orientation of the polymer molecular chains that make up the film and the dimensional change in the thickness direction due to heat, the slit properties are good, and when used as the base film of the magnetic recording medium, the deformation of the end part during repeated running is suppressed. It becomes possible to do.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F071 AA54 AF20Y AF62Y AH14                       BA02 BB02 BB06 BC01                 5D006 CB03 CB07 FA02

Claims (3)

[Claims] 1. When the Young's modulus in the longitudinal direction is E _MD , the Young's modulus in the width direction is E _TD , and the thermal expansion coefficient in the thickness direction is α _ND , E _MD , E _TD and α _ND are given by the following formula (1). An aromatic polyamide film which simultaneously satisfies (3) to (3). E _MD ≧ E _TD (1) E _TD ≧ 8 GPa (2) 10 ≦ α _ND ≦ 300 (× 10 ⁻⁶ / ° C) (3) 2. The aromatic polyamide film according to claim 1, wherein E _MD and E _TD satisfy the following formula (4). E _TD × 1.02 ≦ E _MD ≦ E _TD × 1.15 (4) 3. A magnetic recording medium comprising a magnetic layer provided on at least one surface of the aromatic polyamide film according to claim 1.