JP2000339662A - Magnetic recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out flattening with high precision even when a nonmagnetic substrate comprising a polyamide film is used. SOLUTION: At least, a metallic magnetic film 4 is formed on one principal face of a nonmagnetic substrate 1 to obtain the objective magnetic recording medium. The nonmagnetic substrate 1 comprises an aromatic polyamide film having 1.5-2.5% heat shrinkage percentage at 200 deg.C in the width direction. The metallic magnetic film 4 is prepared by etching an oxidized surface layer formed on the surface of the metallic magnetic film 4. A metallic thin film 5 for reinforcement is formed on the other principal face of the nonmagnetic substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having a metal magnetic film formed on one main surface of a non-magnetic support, and more particularly to a magnetic recording medium suitable for use as a large-capacity tape streamer. .

[0002]

2. Description of the Related Art In recent years, with the spread of office computers such as minicomputers and personal computers, magnetic tapes (so-called tape streamers) for recording computer data as external storage media have been actively studied. . When a magnetic tape for such a purpose is put into practical use, an increase in the recording capacity is strongly required in order to achieve a large-capacity recording and a miniaturization, particularly in conjunction with the downsizing of the computer and the increase in the information processing capability.

On the other hand, as for a magnetic recording medium for a video cassette, further downsizing and long-time recording are desired with the downsizing of the video cassette.

In addition, the magnetic tape can be used under a wide range of environmental conditions (especially, in a highly fluctuating temperature and humidity condition) due to the spread of the usage environment, reliability in data storage, and in repeated running at high speed, can be used many times. There has also been a demand for reliability of performance such as stable recording and reading of data.

In general, a magnetic tape has a structure in which a magnetic layer is provided on a non-magnetic support made of a flexible material such as a synthetic resin. In order to achieve the above-mentioned large recording capacity (volume recording capacity), the recording density of the magnetic layer itself is increased by making the magnetic layer a ferromagnetic metal thin film, and the total thickness of the magnetic tape is reduced. It is said that this is an effective method. That is, as the magnetic tape, a so-called vapor deposition tape formed by forming a metal magnetic thin film on a non-magnetic support is effective.

In this vapor-deposited tape, a polyester, mainly a polyethylene terephthalate film, is used as a nonmagnetic support. In particular, a non-magnetic support used for a home video cassette tape, for example, an 8 mm tape is a polyethylene terephthalate (PET) film of about 7 to 10 μm, and a tape streamer for data backup of a computer is about 5 to 7 μm. Polyethylene terephthalate (PE
T) Film is used.

As a method for extending the recording time of a magnetic recording medium used for a video tape, for example, as described in JP-A-6-215350, polyester is mainly used as a non-magnetic support. It is said that it is desirable to use polyethylene naphthalate as a component, more specifically.

On the other hand, studies have been made to use an aromatic polyamide film having higher strength than the above-mentioned polyethylene terephthalate or polyethylene naphthalate film. The magnetic recording medium using this polyamide film as a non-magnetic support has high strength and can be reduced in thickness, and is suitable for long-time recording of video cassette tapes and large capacity of tape streamers. Attention has been paid to magnetic recording media.

[0009]

However, since the polyamide film usually has a different heat shrinkage from the polyester used as the non-magnetic support, it reacts differently to the heat history generated in the process of manufacturing the vapor-deposited tape. Cupping and curling occur. As described above, when the cupping or curling occurs and the amount exceeds a predetermined limit, there is a problem that the contact state between the magnetic recording medium and the head, that is, the so-called head contact is deteriorated.

Further, in recent years, when a magnetic recording medium is used for a video cassette or the like, further downsizing and recording for a long time are required as the video cassette or the like is downsized. Also, with the recent increase in the amount of information, the tape streamer is also required to have a large capacity, and there is a strong demand for a thinner non-magnetic support. However, in a magnetic recording medium, when a thin nonmagnetic support is used, it is difficult to achieve a high degree of flatness.

In particular, when manufacturing a magnetic recording medium,
In order to correct cupping and curling, so-called hot roll treatment is performed in which heat of several tens to 200 ° C. is intentionally applied with a predetermined pressure. However, even with this hot roll treatment, it was difficult to obtain the desired flatness, and there was almost no effect particularly when a thin nonmagnetic support was used.

Accordingly, the present invention has been made based on such a technical background, and even when a non-magnetic support made of a polyamide film is used, a highly precisely flattened magnetic material is used. It is an object to provide a recording medium, and also to provide a method for manufacturing a magnetic recording medium that can be flattened with high accuracy even when a nonmagnetic support made of a polyamide film is used. .

[0013]

A magnetic recording medium according to the present invention is a magnetic recording medium comprising at least a metal magnetic film formed on one main surface of a nonmagnetic support. Made of an aromatic polyamide film and having a heat shrinkage in the width direction of 200 ° C. of 1.5 to 2.5%
Wherein the metal magnetic film is formed by etching a surface oxide layer formed on the surface of the metal magnetic film, and the other main surface of the non-magnetic support opposite to the side on which the metal magnetic film is formed. A metal thin film for reinforcement is formed.

In the magnetic recording medium according to the present invention configured as described above, the coefficient of thermal expansion at 200 ° C. in the width direction of the non-magnetic support is defined as described above, so that a predetermined thermal history is added. Also in this case, curling and cupping in the width direction are prevented.

Further, the magnetic recording medium according to the present invention has excellent electromagnetic conversion characteristics because the surface oxide layer formed on the surface of the metal magnetic film is etched.

In the magnetic recording medium according to the present invention, the reinforcing metal thin film is formed on the other main surface of the non-magnetic support opposite to the side on which the metal magnetic film is formed. Curling and cupping are reliably prevented.

Therefore, the magnetic recording medium according to the present invention has excellent electromagnetic conversion characteristics and shape stability.

Further, according to a method of manufacturing a magnetic recording medium according to the present invention, there is provided a method of manufacturing a magnetic recording medium comprising at least a metal magnetic film formed on one main surface of a nonmagnetic support.
Heat shrinkage at 200 ° C in the width direction is 1.5 to 2.5%
Using a non-magnetic support made of an aromatic polyamide film, and forming the metal magnetic film on one main surface of the non-magnetic support; and forming the metal magnetic film after forming the metal magnetic film. Etching a surface oxide layer formed on the surface, forming a reinforcing metal thin film on the other main surface of the non-magnetic support opposite to the side on which the metal magnetic film is formed, Adding a thermal history after forming the reinforcing metal thin film.

According to the method of manufacturing a magnetic recording medium according to the present invention as described above, since the thermal shrinkage at 200 ° C. in the width direction is defined as described above, even when a predetermined thermal history is applied. In the magnetic recording medium, curling and cupping in the width direction are prevented.

Further, according to the method of manufacturing a magnetic recording medium of the present invention, since the surface oxide layer formed on the surface of the metal magnetic film is etched, the magnetic recording medium has excellent electromagnetic conversion characteristics.

According to the method of manufacturing a magnetic recording medium of the present invention, the reinforcing metal thin film is formed on the other main surface of the nonmagnetic support opposite to the side on which the metal magnetic film is formed. ,
The magnetic recording medium is reliably prevented from curling and cupping in the width direction.

A magnetic recording medium according to the present invention is a magnetic recording medium in which at least a metal magnetic film is formed on one main surface of a nonmagnetic support, wherein the nonmagnetic support is made of an aromatic polyamide film. 2 in the width direction
The heat shrinkage at 00 ° C. is 1.5 to 2.5%, and the metal magnetic film is formed by etching a surface oxide layer formed on the surface of the metal magnetic film, and the metal magnetic film of the nonmagnetic support is An organic plasma polymer film is formed on the other main surface opposite to the side on which the magnetic film is formed.

In the magnetic recording medium according to the present invention configured as described above, since the coefficient of thermal expansion at 200 ° C. in the width direction of the nonmagnetic support is defined as described above, a predetermined thermal history is added. Also in this case, curling and cupping in the width direction are prevented.

Further, the magnetic recording medium according to the present invention has excellent electromagnetic conversion characteristics because the surface oxide layer formed on the surface of the metal magnetic film is etched.

In the magnetic recording medium according to the present invention, the organic plasma polymer film is formed on the other main surface of the non-magnetic support opposite to the side on which the metal magnetic film is formed. Curling and cupping are reliably prevented.

Therefore, the magnetic recording medium according to the present invention has excellent electromagnetic conversion characteristics and shape stability.

[0027] The method for manufacturing a magnetic recording medium according to the present invention is a method for manufacturing a magnetic recording medium comprising at least a metal magnetic film formed on one main surface of a nonmagnetic support.
Heat shrinkage at 200 ° C in the width direction is 1.5 to 2.5%
Using a non-magnetic support made of an aromatic polyamide film, and forming the metal magnetic film on one main surface of the non-magnetic support; and forming the metal magnetic film after forming the metal magnetic film. A step of etching a surface oxide layer formed on the surface, and a step of forming an organic plasma polymer film on the other main surface of the nonmagnetic support opposite to the side on which the metal magnetic film is formed, Adding a thermal history after forming the organic plasma polymer film.

According to the method of manufacturing a magnetic recording medium according to the present invention as described above, since the thermal shrinkage at 200 ° C. in the width direction is defined as described above, even when a predetermined thermal history is applied. In the magnetic recording medium, curling and cupping in the width direction are prevented.

Further, according to the method for manufacturing a magnetic recording medium of the present invention, since the surface oxide layer formed on the surface of the metal magnetic film is etched, the magnetic recording medium has excellent electromagnetic conversion characteristics.

According to the method of manufacturing a magnetic recording medium of the present invention, the organic plasma polymer film is formed on the other main surface of the non-magnetic support opposite to the side on which the metal magnetic film is formed. Therefore, the magnetic recording medium is reliably prevented from curling or cupping in the width direction.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a magnetic recording medium according to the present invention will be described below in detail with reference to the drawings.

First Embodiment As shown in FIG. 1, a magnetic recording medium according to the present embodiment has a non-magnetic support 1 and a film formed on one main surface 1a of the non-magnetic support 1. And a reinforcing metal thin film 5 formed on the other main surface 1b of the nonmagnetic support 1. In this magnetic recording medium, the non-magnetic support 1 is made of an aromatic polyamide film.

The aromatic polyamide film has a heat shrinkage of 1.5 to 2.5% at 200 ° C. in a direction perpendicular to the longitudinal direction, that is, in the width direction.

In order to further improve the running property of the magnetic recording medium of the present invention, a back coat layer 6 is formed on the reinforcing metal thin film 5.
May be formed.

Hereinafter, the non-magnetic support 1, the metal magnetic film 4, the reinforcing metal thin film 5, the back coat layer 6, and the binder and additives used for these layers will be described in detail.

Non-magnetic support 1 First, the non-magnetic support 1 is made of an aromatic polyamide film as described above. The non-magnetic support 1 is made of an aromatic polyamide film,
It is excellent in physical properties such as tensile strength, and has sufficient strength to withstand even a very thin overall thickness.

The aromatic polyamide film contains, for example, an aromatic polyamide represented by the following formula (I) and / or (II) in an amount of 50% by mole or more, preferably 70% by mole or more.

[0038]

Embedded image

In the above formula, X and Y represent -O
_{-, - CH 2 -, -} CO -, - SO 2 -, - S -, - C
(CH ₃ ) ₂ — or the like, but is not limited thereto. Further, in the above formula, part of the hydrogen atoms on the aromatic ring is a halogen group (particularly chlorine), a nitro group, an alkyl group having 1 to 3 carbon atoms (particularly methyl group),
And may be substituted with a substituent such as an alkoxy group from 1 to 3, or hydrogen in an amide bond constituting the polymer may be substituted with another substituent.

From the viewpoint of increasing rigidity, the aromatic polyamide film is a polymer in which aromatic rings are bonded at the para-position and occupies 60% or more, more preferably 80% or more of the total aromatic rings. Is preferred. In addition, from the viewpoint of reducing the hygroscopicity, a part of the hydrogen atoms on the aromatic ring is a halogen group (particularly a chlorine atom), a nitro group, an alkyl group having 1 to 3 carbon atoms (particularly a methyl group), It is preferable that the aromatic ring substituted with the alkoxy group 3 or the like occupies 30% or more of the whole.

Further, the aromatic polyamide film contains at least 50 mol% of the repeating unit represented by the above formula (I) and / or the above formula (II).
Less than mol% of other repeating units, for example, a polymer obtained by copolymerizing or blending an aromatic polyimide unit or another aromatic polyamide unit can be used,
It is preferable to use wholly aromatic polyamide (aramid).

Further, in the non-magnetic support 1, the configuration of the aromatic polyamide film may be a composite structure. That is, the non-magnetic support 1 may be such that a plurality of aromatic polyamide films are laminated.

In this case, as long as the aromatic polyamide film constituting each layer is mainly composed of the polymer represented by the above formula, each layer may have the same composition or may be different. However, from the viewpoint of productivity, it is advantageous that each layer has the same composition. For example, FIG. 2 shows a configuration example in which the nonmagnetic support 1 has a two-layer structure of a first aromatic polyamide film 2 and a second aromatic polyamide film 3.

In order to laminate a plurality of aromatic polyamide films, a plurality of stock solutions constituting each layer are laminated by a known method, for example, as described in JP-A-56-162617, by lamination. Can be formed by laminating in a die.

When the aromatic polyamide film is produced, first, a solution obtained by dissolving an aromatic polyamide in N-methyl-2-pyrrolidone (NMP) is placed on a belt at a temperature of 100 ° C. to 200 ° C. And cast 10
The film is heated with hot air at 0 ° C. to 250 ° C. to evaporate the solvent to obtain a film having self-holding properties. afterwards,
This film, in the longitudinal direction, width direction each 1.0 ~
By performing drying and heat treatment while stretching 2.0 times, an aromatic polyamide film is produced.

At this time, in the aromatic polyamide film, the Young's modulus and the heat shrinkage in the longitudinal direction and the width direction are controlled by adjusting the stretching ratio and the heat treatment conditions when the film is stretched in the longitudinal direction and the width direction. be able to.

Specifically, the nonmagnetic support 1 has a thickness of 2.
5 μm to 5.0 μm, and the Young's modulus in the length direction is 10
And at 00kg / mm ² or more, and the Young's modulus in the transverse direction thereof is at most 1300 kg / mm ² or more. As described above, by defining the thickness and the Young's modulus of the nonmagnetic support 1, a desired strength can be obtained, and the thickness of the magnetic recording medium can be reduced. It is possible to cope with an increase in the recording amount.

The non-magnetic support 1 is provided with inert particles in order to make it easier to handle or to make the surface of the magnetic layer moderate in the manufacturing process of the magnetic recording medium and to obtain high running durability of the magnetic recording medium. Is desirably added.

The inert particles added to the non-magnetic support 1 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, and silicon particles, polyimide particles, and organic polymers such as polymer particles, cross-linked polyester particles, and Teflon particles. Can be used. Above all, from the viewpoint of heat resistance,
It is preferable to use the above-mentioned inorganic particles.

Examples of the method of adding the inert particles include a method in which particles are sufficiently slurried in a solvent in advance and then used as a solvent for polymerization or a solvent for dilution, or a method in which a stock solution is prepared and then directly added. .

When the non-magnetic support 1 is composed of a plurality of aromatic polyamide films, it is preferable to add inert particles having a different average particle size to each layer. Specifically, inert particles having a relatively small average particle diameter are added to the aromatic polyamide film constituting the surface on which the metal magnetic film 4 is formed, and the surface on which the metal magnetic film 4 is formed is added. It is preferable to add inert particles having a relatively large average particle size to the aromatic polyamide film constituting the surface on the opposite side from the above.

As described above, by adding inert particles having a relatively small average particle size to the aromatic polyamide film on which the metal magnetic film 4 is formed, the surface on which the metal magnetic film 4 is formed can be formed. Surface roughness can be kept low. As a result, the metal magnetic film 4 has a desired surface property, and excellent electromagnetic conversion characteristics of the magnetic recording medium can be secured. Also, since coarse projections on the surface of the metal magnetic film 4 are hardly formed, dropout Etc. can be suppressed,
The running stability of the magnetic recording medium can be ensured.

On the other hand, by adding inert particles having a relatively large average particle size to the aromatic polyamide film on the side opposite to the surface on which the metal magnetic film 4 is formed,
The surface roughness of the surface on which the back coat layer 6 is formed can be made relatively large. Thereby, the back coat layer 6
Can have relatively large surface roughness, and the handling characteristics in the manufacturing process can be improved.

More specifically, the average particle size of the inert particles contained in the aromatic polyamide film on which the back coat layer 6 is formed is preferably 0.05 to 1.5 μm. Further, the addition amount of the inert particles contained in the aromatic polyamide film is preferably 0.05 to 2.0% by weight, and more preferably 0.1 to 1.0% by weight.

The inert particles contained in the aromatic polyamide film on which the metal magnetic film 4 is formed have an average particle diameter of 0 in order to improve the smoothness and lubricity of the surface of the metal magnetic film 4. 0.03 to 0.15 μm, the amount added is 0.01 wt.
% To 1% by weight.

Further, in the non-magnetic support 1, one main surface on which the metal magnetic film 4 is formed has a surface roughness (SRa) of 1.
It is preferably from 5 nm to 5.0 nm, and
More preferably, it is 0 to 3.5 nm. This surface roughness (SRa) is adjusted by the size and amount of inert particles added to the aromatic polyamide film, or the layer structure of the nonmagnetic support 1. As described above, by setting the surface roughness (SRa) of one main surface on which the metal magnetic film 4 is formed to 1.5 nm to 5.0 nm, good electromagnetic conversion characteristics and running durability of the magnetic recording medium can be obtained. Can be secured.

Further, in the non-magnetic support 1, the surface roughness (SRa) of the surface on the side where the back coat layer 6 is formed is:
It is controlled by the size and amount of inert particles added to the aromatic polyamide film, and is preferably as large as possible from the viewpoint of handleability in the production process. However, if the surface roughness (SRa) is too large, the influence of set-off when the metal magnetic layer 4 is formed and then wound up into a roll becomes large, so that the surface roughness (SRa) is 4 nm to 4 nm.
It is 15 nm, preferably 5 nm to 10 nm.

Further, by setting the thickness of the non-magnetic support 1 to 2.5 μm to 5.0 μm, the required strength can be obtained, and the thickness of the magnetic recording medium can be reduced to cope with an increase in capacity. Can be done.

Further, the non-magnetic support 1 has a surface on the one main surface side on which the metal magnetic film 4 is formed, with 10 ³ to 10 ⁵ pieces / piece.
The protrusions are preferably formed at a density of mm ² .

As described above, the surface on the one main surface side has a density of 10 ³ -1.
By forming projections at a density of 0 ⁵ / mm ² ,
The surface property of the metal magnetic film 4 can be brought into a desired state. In other words, 10 ³ to 10 ⁵ pieces /
By forming protrusions with a density of mm ² , the surface of the metal magnetic film 4 has a desired surface roughness.
This makes the magnetic recording medium excellent in running durability and electromagnetic conversion characteristics.

Metal Magnetic Film 4 Next, the metal magnetic film 4 is formed on the second aromatic polyamide film 3 in the non-magnetic support 1 described above.

At this time, the metal magnetic film 4 is formed, for example, as shown in FIG.
It is formed using a continuous winding type vacuum evaporation apparatus as shown in FIG.

This vacuum evaporation apparatus 11 is configured for so-called oblique evaporation, and is, for example, −20 ° C. in a vacuum chamber 12 in which the inside is in a vacuum state of, for example, about 10 ⁻³ (Pa).
Cooled to the extent, counterclockwise direction in the figure (arrow A direction)
The evaporation source 14 for the metal magnetic film 4 is disposed so as to face the cooling can 13 that rotates.

The evaporation source 14 is a container such as a crucible in which a ferromagnetic metal material such as Co is accommodated.
(Ferromagnetic metal material) is heated with an electron beam 16 accelerated from an electron beam source 15 to heat the ferromagnetic metal material.
This is evaporated from the supply roll 18 rotating in the counterclockwise direction in the figure and is fed in the direction of arrow B in the figure, and adheres to the non-magnetic support 1 running along the peripheral surface of the cooling can 13 (evaporation). ) To form the metal magnetic film 4. Then, the non-magnetic support 1 on which the metal magnetic film 4 is formed
Is taken up by a take-up roll 19.

At this time, a deposition-preventing plate 20 is provided between the vapor deposition source 14 and the cooling can 13, and a shutter 21 is provided on the deposition-preventing plate 20 so as to be adjustable in position. Only vapor particles incident at an angle of. Thus, the metal magnetic film 4 is formed by the oblique deposition method.

Note that guide rollers 22 and 23 are disposed between the supply roll 18 and the cooling can 13 and between the cooling can 13 and the take-up roll 19, respectively. A predetermined tension is applied to the non-magnetic support 1 running from the cooling can 13 according to the take-up roll 19 so that the non-magnetic support 1 runs smoothly.

Further, when such a metal magnetic film 4 is deposited, the non-magnetic support 1 is supplied through an oxygen gas inlet (not shown).
Oxygen gas is supplied to the surface of the metal magnetic film 4, whereby the magnetic properties, durability and weather resistance of the metal magnetic film 4 are improved. In addition, in order to heat the evaporation source 14, in addition to the above-described heating means using an electron beam, known means such as a resistance heating means, a high-frequency heating means, and a laser heating means can be used.

In the above, an example in which a film is formed by using a ferromagnetic metal material made of Co or the like by the oblique vapor deposition method has been described. Known thin film forming methods such as a vapor deposition method and a sputtering method can be applied, and as the ferromagnetic metal material,
In addition to Co, Ni, Fe, or an alloy thereof can be used. However, the adhesive strength with the non-magnetic support 1 is improved,
Alternatively, for the purpose of improving the resistance and abrasion resistance of the metal magnetic film itself, it is desirable to use the metal magnetic film 4 containing oxygen obtained when the atmosphere at the time of vapor deposition is an atmosphere in which oxygen gas is dominant. The thickness of the metal magnetic film 4 is 0.0
About 5 to 0.25 μm, preferably 0.1 to 0.2 μm
m.

In the metal magnetic film 4, it is preferable to etch the surface oxide film formed on the surface in order to improve the electromagnetic conversion characteristics. This surface oxide film is a non-magnetic film formed on the surface of the metal magnetic film 4 formed as described above, and causes a spacing loss.
That is, the surface oxide film is non-magnetic and causes deterioration of electromagnetic conversion characteristics. Therefore, by removing the surface oxide film by etching, the electromagnetic conversion characteristics of the metal magnetic film 4 can be significantly improved in the magnetic recording medium.

For this etching, any method may be applied. For example, it is preferable to use a reverse sputtering method, an ion etching method, an ECR plasma etching method, or the like. In this etching, A
It is preferable that the pressure be about 0.4 (Pa) in an r gas atmosphere.

Further, the magnetic recording medium has a metal magnetic film 4
It is desirable to form a carbon protective film on the metal magnetic film 4 using a magnetron sputtering apparatus 30 as shown in FIG.

The outside of the magnetron sputtering apparatus 30 is covered with a chamber 31. After the pressure in the chamber 31 is reduced to about 10 ^-4 (Pa) by the vacuum pump 32, the exhaust speed is reduced by reducing the angle of the valve 33 to be discarded to the vacuum pump 32 side from the fully opened state to 10 degrees. Ar gas is introduced from the gas introduction pipe 34, and the degree of vacuum is set to about 0.8 Pa.

The magnetron sputtering apparatus 30 has a cooling can 35 which is cooled to, for example, about -40 ° C. and rotates in a counterclockwise direction (direction of arrow A) in FIG. A target 36 to be arranged is provided.

The target 36 is a material for the carbon protective film, and is supported by a backing plate 37 constituting a cathode electrode. On the back side of the backing plate 37, a magnet 38 for forming a magnetic field is provided.
Are arranged. This magnetron sputtering apparatus 30
When the carbon protective film is formed by the gas introduction pipe 34,
From the cooling can 35 as an anode and the backing plate 37 as a cathode.
A voltage of 000 (V) is applied so that a current of 1.4 A flows.

The application of this voltage turns the Ar gas into plasma, and the ions of the target 36 are repelled by the ionized ions colliding with the target 36.
At this time, a magnet 38 is provided on the back side of the backing plate 37, and a magnetic field is formed near the target 36.
Will be concentrated near.

The atoms repelled from the target 36 are fed in the direction of arrow B in the figure from the supply roll 39 rotating counterclockwise in the figure, and travel along the peripheral surface of the cooling can 35. 4 adheres to the non-magnetic support 1 on which the film is formed, and a carbon protective film is formed. Then, the non-magnetic support 1 on which the carbon protective film is formed is taken up by a take-up roll 41.

This carbon protective film has a thickness of about 3 to 15 nm so that the spacing loss can be reduced and the effect of preventing the metal magnetic film 4 from being worn can be obtained.
In particular, the thickness is preferably about 5 to 10 nm.

While the above description has been given of the example in which the carbon protective film is formed by magnetron sputtering, other methods of forming the carbon protective film include ion beam sputtering, ion beam plating, and CV.
A known thin film forming method such as a method D can be used.

In this magnetic recording medium, it is desirable that a lubricant is present on the surface of the carbon protective film. Thereby, the magnetic recording medium can further improve the effect of improving the running property based on the shape of the fine protrusion.

Further, the magnetic recording medium has a front surface, a back surface, or their vicinity or a carbon protective film, a gap in the metal magnetic film 4, an interface between the carbon protective film and the metal magnetic film 4, Various additives such as a rust preventive, an antistatic agent, and a fungicide can be added to the interface with the non-magnetic support 1, in the non-magnetic support 1, and the like, if necessary, by known means.

The metal thin film 5 for reinforcement is disposed on the surface of the non-magnetic support 1 opposite to the surface on which the metal magnetic film 4 is formed, and the mechanical thin film 5 for the non-magnetic support 1 is provided. It serves to reinforce the mechanical strength and suppress the occurrence of cupping.

Examples of the metal used for the reinforcing metal thin film 5 include Al, Cu, Ni, Cr and alloys thereof. Further, the thickness of the reinforcing metal thin film is 0.1
０．５0.5 μm is preferred. If the thickness of the reinforcing metal thin film 5 is too thin, the effect of reinforcing the mechanical strength is not exhibited, and if it is too thick, cracks are likely to occur in the reinforcing metal thin film 5.

The reinforcing metal thin film 5 does not need to be composed of a single layer, but may have a multilayer structure of two or more layers.

The reinforcing metal thin film 5 is formed as a continuous film by a PVD method such as vacuum evaporation or sputtering, or a CVD method.

Backcoat Layer 6 The backcoat layer 6 is provided on the reinforcing metal thin film 5 formed on the surface of the nonmagnetic support 1 opposite to the surface on which the metal magnetic film 4 is formed. ing. This back coat layer 4 is mainly composed of a binder, carbon black and inorganic powder. Specifically, examples of the inorganic powder include calcium carbonate and inorganic powder having a Mohs hardness of 5 to 9.

In the back coat layer 6, 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-grained carbon black having a particle size of 20 to 20 nm and coarse-grained carbon black having an average particle size of 230 to 300 nm.

In general, the surface electric resistance of the back coat layer 6 can be set low and the light transmittance can be set low by adding the above-mentioned fine particle carbon black.
Some magnetic recording devices use the light transmittance of the tape and use it as an operation signal. In such a case, the addition of fine carbon black is particularly effective.

In addition, since fine carbon black particles generally have excellent holding power to a lubricant, a lubricant can be used in combination, and as a result, the friction coefficient can be reduced.

On the other hand, coarse carbon black having a particle size of 230 to 300 nm has a function as a solid lubricant and forms fine projections on the surface. It is possible to reduce the coefficient of friction. However, coarse carbon black
In a severe running system, the tape may slide off from the back coat layer 6 easily, which may increase the error ratio.

Specifically, the following can be cited as the particulate carbon black. RAVEN2
000B (18 nm), RAVEN 1500B (17n
m) (above, manufactured by Columbia Carbon Co., Ltd.), BP800
(17 nm) (Cabot), PRINTEX90
(14 nm), PRINTEX95 (15 nm), PR
INTEX85 (16 nm), PRINTEX75 (1
7 nm) (all manufactured by Degussa), # 3950 (16 n
m) (Mitsubishi Chemical Industries, Ltd.). Thermal black (270 nm) is used as coarse carbon black.
(Manufactured by Khancarb), RAVEN MTP (275n
m) (manufactured by Columbia Carbon Co., Ltd.).

In the case of using two kinds of back coat layers 6 having different average particle sizes, 10 to 20 n
m of the fine carbon black and the coarse carbon black of 230 to 300 nm (weight ratio) is as follows: fine carbon black: coarse carbon black =
The ratio is preferably from 98: 2 to 75:25, and more preferably from 95: 5 to 85:15. Further, the content of carbon black (in the case of adding fine particles and coarse particles, the total amount thereof) in the back coat layer 6 is usually in the range of 30 to 80 parts by weight with respect to 100 parts by weight of a binder described later. And preferably in the range of 45 to 65 parts by weight.

On the other hand, inorganic powders having a Mohs hardness of 5
By using one of Nos. 1 to 9, the magnetic recording medium can be repeatedly provided with running durability, and the backcoat layer 6 can be strengthened. When these inorganic powders are used together with the above-described carbon black and calcium carbonate, the back coat layer 6 becomes a strong back coat layer 6 with little deterioration even by repeated sliding due to its filler effect.

When the inorganic powder used in the back coat layer 6 has a relatively high Mohs hardness of 5 to 9, an appropriate polishing force is generated on the surface of the back coat layer 6, and the surface of the back coat layer 6 adheres to guide poles and the like. Is reduced. As a magnetic recording medium, when calcium carbonate and an inorganic powder are used in combination for the back coat layer 6, the sliding characteristics with respect to a guide pole having a rough surface are improved, and the friction coefficient of the back coat layer 6 is stabilized. Can also be achieved. The inorganic powder preferably has an average particle size in the range of 80 to 250 nm, more preferably 100 to 210 nm.
Of the range.

Examples of the inorganic powder include α-iron oxide, α-alumina, and chromium oxide (Cr ₂ O ₃ ). These inorganic powders may be used alone or in combination. Among these, α-iron oxide or α-alumina is preferred. The content of the inorganic powder having a Mohs' hardness of 5 to 9 is usually 3 to 30 parts by weight, preferably 3 to 20 parts by weight, based on 100 parts by weight of carbon black. In particular, the back coat layer 6 preferably contains two types of carbon black having different average particle sizes, calcium carbonate having the above particle size, and the inorganic powder having the specific Mohs hardness.

The back coat layer 6 can contain a lubricant. The lubricant, as described above, for example,
Fatty acids or fatty acid esters can be mentioned. As fatty acids, for example, acetic acid, propionic acid, octanoic acid, 2-ethylhexanoic acid, lauric acid, myristic acid, stearic acid, palmitic acid, behenic acid, arachinic acid, oleic acid, linoleic acid, linolenic acid, elaidic acid, And aliphatic carboxylic acids such as palmitoleic acid or mixtures thereof.

The fatty acid esters include, for example,
Butyl stearate, sec-butyl stearate, isopropyl stearate, butyl oleate, amyl stearate, 3-methylbutyl stearate, 2-ethylhexyl stearate, 2-hexyldecyl stearate, butyl palmitate, 2-ethylhexylmilli State, a mixture of butyl stearate and butyl palmitate, oleyl oleate, butoxyethyl stearate, 2-butoxy-1-propyl stearate, dipropylene glycol monobutyl ether acylated with stearic acid, diethylene glycol dipalmitate, Hexamethylenediol is acylated with myristic acid to form a diol, and various ester compounds such as oleate of glycerin. These can be used alone or in combination.

In the back coat layer 6, the lubricant is preferably added in an amount of usually 1 to 5 parts by weight based on 100 parts by weight of the binder resin.

The binder used for the back coat layer 6 includes, for example, a thermoplastic resin, a thermosetting resin, a reactive resin, and a mixture thereof.

Examples of the thermoplastic resin include vinyl chloride,
Polymer containing vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, and vinyl ether as constituent units Or a copolymer. Examples of the copolymer include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, and acrylate-vinylidene chloride copolymer. Polymer, acrylate-styrene copolymer, methacrylate-acrylonitrile copolymer, methacrylate-vinylidene chloride copolymer, methacrylate-styrene copolymer, vinylidene chloride-acrylonitrile copolymer , Butadiene-
An acrylonitrile copolymer, a styrene-butadiene copolymer, and a chlorovinyl ether-acrylate copolymer can be exemplified. In addition to the above, polyamide resins, cellulose resins (cellulose acetate butyrate,
Cellulose diacetate, cellulose propionate, nitrocellulose, etc.), polyvinyl fluoride, polyester resin, polyurethane resin, various rubber resins and the like can also be exemplified.

The thermosetting resin or the reactive resin includes, for example, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic reaction resin, formaldehyde resin, silicon resin, epoxy resin -Polyamide resins, mixtures of polyester resins and polyisocyanate prepolymers, mixtures of polyester polyols and polyisocyanates, mixtures of polyurethane and polyisocyanates.

Additives Examples of the additives include dispersants which are added to the coating solution for forming the back coat layer 6 in order to favorably disperse carbon black, non-magnetic powder, and the like in the binder. Examples of the additive include a plasticizer, conductive particles other than carbon black (antistatic agent), and a fungicide, which are added as necessary.

Examples of the dispersant include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid,
Stearic acid, behenic acid, oleic acid, elaidic acid,
1 carbon atom such as linoleic acid, linolenic acid, stearic acid
2 to 18 fatty acids (RCOOH, R represents 11 to 1 carbon atoms)
A metal soap comprising an alkali metal or an alkaline earth metal of the fatty acid, a fluorine-containing compound of the fatty acid ester,
Amides of the above fatty acids, polyalkylene oxide alkyl phosphates, lecithin, trialkylpolyolefinoxy quaternary ammonium salts (alkyl has 1 carbon atom)
~ 5, olefins are ethylene, propylene, etc.),
Sulfate, copper phthalocyanine and the like can be used. These may be used alone or in combination.
In particular, it is preferable to use a combination of copper oleate, copper phthalocyanine, and barium sulfate for the back coat layer 6. The dispersant is added in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the binder resin.

Second Embodiment As shown in FIG. 5, a magnetic recording medium according to a second embodiment has a non-magnetic support 1 and a film formed on one main surface 1a of the non-magnetic support 1. And an organic plasma aggregate film 7 formed on the other main surface 1b of the metal magnetic film 4 and the nonmagnetic support 1. In this magnetic recording medium, the non-magnetic support 1 is made of an aromatic polyamide film.
FIG. 6 shows another configuration example of the magnetic recording medium to which the present invention is applied. In the magnetic recording medium shown in FIG. 6, the nonmagnetic support 1 has a two-layer structure.

The aromatic polyamide film has a heat shrinkage of 1.5 to 2.5% at 200 ° C. in a direction perpendicular to the longitudinal direction, that is, in the width direction.

The second embodiment will be described below. The nonmagnetic support 1 and the metal magnetic film 4, and the binder and additives used for these layers are the same as those in the first embodiment. The description will be omitted, and the organic plasma assembly film 7 will be described in detail.

Organic Plasma Polymer Film 7 The organic plasma polymer film 7 is a strong structure having a dense three-dimensional structure. And the organic plasma polymer film 7
Can be adhered very thinly and uniformly, and by adhering it to the non-magnetic support,
Can be reinforced and the occurrence of cupping can be suppressed.

The organic plasma polymer film 7 is produced by a plasma polymerization method. Plasma polymerization methods include Ar, He, H
₂ , a method in which a discharge plasma of a carrier gas such as N ₂ and a monomer gas are mixed, and the mixed gas is brought into contact with the surface of a non-treated substrate to form a plasma polymer film on the surface of the substrate. Hereinafter, the principle of the plasma polymerization method will be described.
When the substrate is kept at a low pressure and an electric field is applied, the free electrons present in the gas in a small amount have a much larger intermolecular distance than normal pressure, so they undergo electric field acceleration and have a velocity energy of 5 to 10 eV (electron temperature). To win. When this free electron collides with an atom or molecule, it breaks the atomic orbital or molecular orbital and dissociates into a chemical species that is unstable in a state such as an electron, an ion, or a neutral radical. The dissociated electrons are again subjected to electric field acceleration to dissociate other atoms and molecules, but the chain action immediately turns the gas into a highly ionized state, which is called a plasma gas. Gas molecules do not absorb much energy because they have little chance of collision with electrons, and are kept at a temperature close to room temperature. A system in which electron velocity energy (electron temperature) and molecular thermal motion (gas temperature) are separated in this way is called low-temperature plasma, where chemical species are kept relatively intact and undergo additive processes such as polymerization. Create situations where chemical reactions can proceed.

In the present invention, a plasma polymer film is formed on a gas utilizing this situation. In the present invention, since low-temperature plasma is used, there is no thermal effect on the substrate.

The monomer gas which can be used in the present invention includes a plasma-polymerizable carbon-hydrogen system, carbon-hydrogen-oxygen system, carbon-halogen system, carbon-oxygen-halogen system, carbon-hydrogen-halogen system. Organic compounds including organic metals and the like. Among them, organic compounds having an unsaturated bond such as ethylene, acetylene, styrene, acrylonitrile, methyl methacrylate, butadiene, and benzene are particularly preferable. In addition, organic silicon compounds such as various silanes having a siloxane bond, and various organic compounds containing sulfur or nitrogen can also be used.

As the plasma generation source, high-frequency discharge, microwave discharge, DC discharge, AC discharge and the like can be used. The degree of vacuum during plasma polymerization is preferably about 1 to 1000 Pa.

The thickness of the organic plasma polymer film 7 is 0.1
It is preferably from 1.0 to 1.0 μm. When the thickness of the organic plasma polymer film 7 is less than 0.1 μm, the effect of reinforcing the mechanical strength is not exhibited, and the cupping cannot be reduced. Further, when the thickness of the organic plasma polymer film 7 is 1.0
If it exceeds μm, the cupping in the direction opposite to the conventional one becomes large, and the thickness of the magnetic recording medium itself becomes thick.

[0112]

EXAMPLES Hereinafter, the present invention will be described more specifically by describing specific examples and comparative examples of the above-described magnetic recording medium. Examples 1 to 5 and Comparative Examples 1 to 5
Corresponds to the first embodiment, and corresponds to a sixth embodiment.
Example 10 to Comparative Example 6 to Comparative Example 10 correspond to the second embodiment. The various physical properties and characteristics in this example were measured by the following methods.

<Measurement of Heat Shrinkage of Aromatic Polyamide Film> When measuring the heat shrinkage of an aromatic polyamide film, first, a sample to be measured was 10 mm wide and 3 mm long.
Cut to 00mm, 200m on the cut sample surface
Mark at m intervals. Next, at 150 ° C or 20
The sample is thermally contracted for 10 minutes under a load of 1 kgf / mm ² in a hot-air circulation furnace set at 0 ° C. After the heat shrinkage, the interval between the markings on the sample surface was measured, and the heat shrinkage was calculated.

<Measurement of Young's Modulus of Aromatic Polyamide Film> The aromatic polyamide film has a Young's modulus of 25.
It measured using the Tensilon type | mold tensile test apparatus under conditions of 65 degreeC and 65% RH.

<Measurement of Cupping> The measurement of cupping was performed using a cupping measurement device having an optical microscope 40 as shown in FIG. In this cupping measuring device, first, a magnetic tape 4 to which a predetermined tension is applied
1 is wound over a pair of rolls 42. Next, the optical microscope 4
0 (100 × magnification) by the driving means 43
1 is positioned at the center or both ends in the width direction. Then, in this cupping measurement device, the optical microscope 40 is driven in the vertical direction, so that the magnetic tape 41 is focused at the center or both ends in the width direction. At this time, in the cupping measurement device, the micrometer 44 interlocked with the vertical driving of the optical microscope 40,
The difference in height between the center and both ends in the width direction of the magnetic tape 41 is measured.

At this time, a state where the metal magnetic film is convex is defined as negative cupping, and a state where the metal magnetic film is concave is defined as positive cupping.

<Tape Characteristics> The characteristics of the magnetic recording media in Examples and Comparative Examples were evaluated using AIT manufactured by Sony Corporation.
The test was performed using a modified drive SDX-S300C (trade name). The recording was performed at a relative speed of 10.04 m / sec.
c, recording was performed at the shortest recording wavelength of 0.35 μm.

[0118] In evaluating the running durability running durability, first, the length is 1000 pass running the magnetic tape 170m, it was measured error rate and 1000 the error rate after the path running after one pass running. The running durability was evaluated by comparing these measured values.

Contact Characteristics with Head When evaluating the contact characteristics with the head, first, the output signal when the output signal (collision waveform) during reproduction of the magnetic tape was viewed for one track was measured. Then, by calculating the value (%) of the minimum value (MIN) / maximum value (MAX) of the output signal, the hitting characteristic with the head was evaluated.

First, Examples 1 to 5 and Comparative Example 1
Hereinafter, Comparative Example 5 will be described.

Example 1 First, a slurry was prepared by dispersing dry silica particles having an average particle diameter of 0.1 μm in N-methyl-2-pyrrolidone (NMP).

Next, NMP and the above slurry were charged into a polymerization tank, and 2-chloroparaphenylenediamine corresponding to 80 mol% as an aromatic diamine component and 4,4′-diamino equivalent corresponding to 20 mol% were added thereto. The diphenyl ether was dissolved, and 2-chloroterephthalic acid chloride corresponding to 100 mol% was added thereto, followed by stirring for 2 hours to complete the polymerization. This was neutralized with lithium hydroxide to obtain a polymer solution. The content of the particles was 0.1 wt% with respect to the aromatic polyamide.

This polymer solution has a polymer concentration of 10
The solution viscosity at 30% by weight was adjusted to 3000 poise to obtain a stock solution.

Then, after passing these membrane-forming stock solutions through a 5 μm-cut filter, they were cast on a metal belt set to 150 ° C., heated with hot air at 150 ° C. to evaporate the solvent, The obtained film was continuously peeled off from the belt.

Next, the film was introduced into a water tank having a concentration gradient of NMP, and the residual solvent and the inorganic salt generated by the neutralization were extracted with water, followed by drying of the water with a tenter and heat treatment.
During this time, 1.2 times each in the film longitudinal direction and width direction,
After stretching by a factor of 1.4, drying and heat treatment at 300 ° C. for 1.5 minutes, the film was gradually cooled at a rate of 20 ° C./sec to a thickness of 3.5
A μm non-magnetic support was obtained.

Next, using the non-magnetic support thus produced, an original magnetic tape was produced in the following manner.

That is, the continuous winding type vapor deposition apparatus 11 as shown in FIG. 3 is evacuated so that the inside thereof becomes a vacuum state of about 10 ⁻³ (Pa), and the above-mentioned nonmagnetic support is This was set in this vapor deposition apparatus. Then, a metal magnetic film 4 made of Co was formed on one main surface 1a of the nonmagnetic support in the presence of a small amount of oxygen by a continuous vacuum oblique deposition method. The incident angle of the vapor deposition is 90 to 45 degrees in the normal direction of the nonmagnetic support, and the traveling speed of the nonmagnetic support is 5 °.
The electron beam intensity was adjusted such that the thickness of the metal magnetic film was 0.18 μm at 0 m / min.

Next, the inside of the ECR plasma etching apparatus was adjusted to about 0.4 Pa with Ar gas. And E
The non-magnetic support on which the metal magnetic film was formed was set in a CR plasma etching apparatus, and ECR plasma etching was performed to reduce the surface oxide layer formed on the ferromagnetic metal thin film to about 5 nm. At this time, E
The input power of CR plasma etching equipment is 300K
w.

Next, the pressure of the magnetron sputtering apparatus as shown in FIG. 4 was reduced to about 10 ⁻⁴ (Pa), and then Ar gas was introduced to about 0.8 Pa. Then, the non-magnetic support having the metal magnetic film formed thereon is set in this magnetron sputtering apparatus, and is run at a speed of 5 m / min on a cooling can cooled to −40 ° C. to form a carbon protective film on the metal magnetic film. Formed.

Next, the raw material on which the ferromagnetic metal thin film and the carbon protective film were formed was set in a continuous winding type evaporation apparatus as shown in FIG. 3, and the inside thereof was vacuumed to about 10 ⁻² Pa. The reinforcing metal thin film made of Al was formed on the surface of the nonmagnetic support opposite to the surface on which the ferromagnetic metal thin film and the carbon protective film were formed. The incident angle of vapor deposition is 0 to 25 degrees, and the feed rate of the non-magnetic support is 6
The electron beam intensity was adjusted such that the thickness of the reinforcing metal thin film was 0.2 μm at 0 m / min.

Next, a back coating was prepared according to the following composition.

<Back coating composition> 100 parts by weight of carbon black (manufactured by Asahi Corporation, # 50) 100 parts by weight of polyester polyurethane (manufactured by Nippon Polyurethane Co., Ltd., trade name N-2304) Solvent: 500 parts by weight of methyl ethyl ketone 500 parts by weight of toluene Then, the prepared back coating was applied to the surface of the non-magnetic support opposite to the surface on which the metal magnetic film 4 was formed, and dried to form a 0.4 μm-thick back coat layer 6. .

Next, after forming the back coat layer 6,
The metal magnetic film 4 was run at a speed of 100 m / min while being in contact with the roll heated to 00 ° C.

Thereafter, a top coat layer of a lubricant made of perfluoropolyether was formed on the carbon protective film by 10.
mg / m ² .

[0135] The raw tape obtained by forming the metal magnetic film 4, the reinforcing metal thin film 5, and the back coat layer 6 on the non-magnetic support 1 in this way is slit into an 8 mm width and then stored in the cassette body. To produce a cassette tape.

Example 2 In Example 2, a cassette tape was produced in the same manner as in Example 1 except that the heat treatment temperature for producing an aromatic polyamide film was 290 ° C.

Example 3 In Example 3, a cassette tape was produced in the same manner as in Example 1, except that the heat treatment temperature for producing the aromatic polyamide film was 280 ° C.

Example 4 In Example 4, the heat treatment temperature after forming the back coat layer was set to 2
A cassette tape was produced in the same manner as in Example 2 except that the temperature was changed to 50 ° C.

Example 5 In Example 5, the stretching ratio in the width direction at the time of producing an aromatic polyamide film was 1.6 times, and the heat treatment temperature was 32 times.
A cassette tape was produced in the same manner as in Example 1 except that the temperature was set to 0 ° C.

Comparative Example 1 In Comparative Example 1, a cassette tape was produced in the same manner as in Example 1 except that the reinforcing metal thin film 5 was not formed.

Comparative Example 2 In Comparative Example 2, a cassette tape was produced in the same manner as in Example 2 except that the reinforcing metal thin film 5 was not formed.

Comparative Example 3 In Comparative Example 3, a cassette tape was produced in the same manner as in Example 3 except that the reinforcing metal thin film 5 was not formed.

Comparative Example 4 In Comparative Example 4, a cassette tape was produced in the same manner as in Example 4 except that the reinforcing metal thin film 5 was not formed.

Comparative Example 5 In Comparative Example 5, a cassette tape was produced in the same manner as in Example 5, except that the reinforcing metal thin film 5 was not formed.

Evaluation of Characteristics Regarding Examples 1 to 5 and Comparative Examples 1 to 5 as described above, the evaluation of physical properties and the evaluation of characteristics were performed as described above. Table 1 shows the results.

[0146]

[Table 1]

As shown in Table 1, a reinforcing metal thin film 5 was formed using an aromatic polyamide film having a heat shrinkage in the width direction at 200 ° C. of 1.5% to 2.5%.
In the samples of Examples 5 to 5, the cupping was suppressed as low as possible, and the head contact was good. In the first to fifth embodiments, the error rate after traveling 1000 passes is also kept low.

Thus, as shown in Examples 1 to 5, the heat shrinkage in the width direction at 200 ° C. was 1.5 to 1.5.
By using the 2.5% aromatic polyamide film and forming the reinforcing metal thin film 5, the main surface can be flattened with high precision, and the contact state with the head is good, and the running durability is high. It has become possible to obtain a magnetic recording medium having the property.

[0149] When Examples 1 to 4 and Example 5 are compared, Examples 1 to 4 have better results than Example 5. Thus, in the aromatic polyamide film, by defining the heat shrinkage in the width direction at 150 ° C. in the range of 0.5% or more, the main surface is further flat and the contact state with the head is good. It turned out that the magnetic recording medium had high running durability.

Next, Examples 6 to 10 and Comparative Examples 6 to 10 will be described.

Example 6 First, a slurry was prepared by dispersing dry silica particles having an average particle diameter of 0.1 μm in N-methyl-2-pyrrolidone (NMP).

Next, NMP and the above slurry were charged into a polymerization tank, and 2-chloroparaphenylenediamine corresponding to 80 mol% as an aromatic diamine component and 4,4′-diamino equivalent corresponding to 20 mol% were added thereto. The diphenyl ether was dissolved, and 2-chloroterephthalic acid chloride corresponding to 100 mol% was added thereto, followed by stirring for 2 hours to complete the polymerization. This was neutralized with lithium hydroxide to obtain a polymer solution. The content of the particles was 0.1 wt% with respect to the aromatic polyamide.

This polymer solution has a polymer concentration of 10
The solution viscosity at 30% by weight was adjusted to 3000 poise to obtain a stock solution.

Then, after passing these membrane-forming stock solutions through a 5 μm-cut filter, they were cast on a metal belt set at 150 ° C., heated with hot air at 150 ° C. to evaporate the solvent, The obtained film was continuously peeled off from the belt.

Next, the film was introduced into a water tank having a concentration gradient of NMP, and the residual solvent and the inorganic salt generated by the neutralization were extracted with water, and the moisture was dried and heat-treated with a tenter.
During this time, 1.2 times each in the film longitudinal direction and width direction,
After stretching by a factor of 1.4, drying and heat treatment at 300 ° C. for 1.5 minutes, the film was gradually cooled at a rate of 20 ° C./sec to a thickness of 3.5
A μm non-magnetic support 1 was obtained.

Next, using the non-magnetic support 1 thus manufactured, an original magnetic tape was manufactured by the following method.

That is, the continuous winding type vapor deposition apparatus 11 as shown in FIG. 3 is evacuated so that the inside thereof becomes a vacuum state of about 10 ⁻³ (Pa),
Was set in this vapor deposition apparatus. Then, a metal magnetic film 4 made of Co was formed on one main surface 1a of the nonmagnetic support in the presence of a small amount of oxygen by a continuous vacuum oblique deposition method. The incident angle of vapor deposition is 90 to 45 degrees in the normal direction of the nonmagnetic support 1, the traveling speed of the nonmagnetic support 1 is 50 m / min, and the thickness of the metal magnetic film 4 is 0.18 μm. It was manufactured by adjusting the intensity of the electron beam so as to be as follows.

Then, the pressure inside the ECR plasma etching apparatus was reduced to about 10 ⁻³ Pa, and Ar gas was introduced to about 0.4 Pa. Then, the nonmagnetic support 1 on which the metal magnetic film 4 is formed in the ECR plasma etching apparatus
Was set, and the surface oxide layer formed on the ferromagnetic metal thin film was thinned to about 5 nm by performing ECR plasma etching. At this time, the input power of the ECR plasma etching apparatus was set to 300 Kw.

Next, the inside of the magnetron sputtering apparatus as shown in FIG. 4 was depressurized to about 10 ⁻⁴ (Pa), and then Ar gas was introduced to about 0.8 Pa. Then, the nonmagnetic support 1 on which the metal magnetic film 4 is formed is set in the magnetron sputtering apparatus, and is run on a cooling can cooled to -40 ° C. at a speed of 5 m / min. A protective film was formed.

Next, the surface of the non-magnetic support 1 opposite to the surface on which the ferromagnetic metal thin film is formed has a thickness of 0.3 μm under the following conditions.
m of the plasma polymer film 7 was formed.

Monomer gas: ethylene Monomer gas flow rate: 30 ml / min Carrier gas: argon Carrier gas flow rate: 70 ml / min Degree of vacuum: 70 Pa High frequency power supply: 13.56 MHz, 300 W Next, the metal magnetic film 4 was heated on a roll heated to 200 ° C. Was run at a speed of 100 m / min.

Then, a top coat layer of a lubricant composed of perfluoropolyether was formed on the carbon protective film by 10.
mg / m ² .

The raw tape having the metal magnetic film 4 and the organic plasma polymer film 7 formed on the non-magnetic support 1 in this manner is slit into a width of 8 mm and then housed in the cassette main body to cut the cassette tape. Produced.

Example 7 In Example 7, a cassette tape was produced in the same manner as in Example 6, except that the heat treatment temperature for producing the aromatic polyamide film was 290 ° C.

Example 8 In Example 8, a cassette tape was produced in the same manner as in Example 6, except that the heat treatment temperature for producing the aromatic polyamide film was 280 ° C.

Example 9 In Example 9, a cassette tape was produced in the same manner as in Example 7, except that the heat treatment temperature after the formation of the organic plasma polymer film was 250 ° C.

Example 10 In Example 10, the stretching ratio in the width direction when producing an aromatic polyamide film was 1.6 times, and the heat treatment temperature was 3 times.
A cassette tape was produced in the same manner as in Example 6, except that the temperature was changed to 20 ° C.

Comparative Example 6 In Comparative Example 6, the following ordinary back coat paint was prepared in place of the organic plasma polymer film 7, and the back coat layer 6 having a dry thickness of 0.4 μm was formed. In the same manner as in Example 6, a cassette tape was produced.

<Backcoat coating composition> 100 parts by weight of carbon black (manufactured by Asahi Corporation, # 50) 100 parts by weight of polyester polyurethane (product name: N-2304 manufactured by Nippon Polyurethane Co.) Solvent: 500 parts by weight of methyl ethyl ketone 500 parts by weight of toluene Comparative Example 7 In Comparative Example 7, the back coat paint used in Comparative Example 6 was prepared in place of the organic plasma polymer film 7, and 6 layers of the back coat having a dry thickness of 0.4 μm were formed. In the same manner as in 7, a cassette tape was produced.

Comparative Example 8 In Comparative Example 8, instead of the organic plasma polymer film 7, the back coat paint used in Comparative Example 6 was prepared, and the back coat layer 6 having a dry thickness of 0.4 μm was formed. Except for the above, a cassette tape was produced in the same manner as in Example 8.

Comparative Example 9 In Comparative Example 9, the back coat paint used in Comparative Example 6 was prepared in place of the organic plasma polymer film 7, and the back coat layer 6 having a dry thickness of 0.4 μm was formed. Except for the above, a cassette tape was produced in the same manner as in Example 9.

Comparative Example 10 In Comparative Example 10, instead of the organic plasma polymer film 7,
A cassette tape was produced in the same manner as in Example 10, except that the back coat paint used in Comparative Example 6 was prepared and the back coat layer 6 having a dry thickness of 0.4 μm was formed.

Evaluation of Characteristics For the above-described Examples 6 to 10 and Comparative Examples 6 to 10, the physical properties and the characteristics were evaluated as described above. Table 2 shows the results.

[0174]

[Table 2]

As shown in Table 2, organic plasma polymer films were formed using aromatic polyamide films having a heat shrinkage in the width direction at 200 ° C. of 1.5% to 2.5%. Regarding the sample of Example 10, the cupping was suppressed as low as possible, and the head contact was good. In the sixth to tenth embodiments, the error rate after traveling 1000 passes is also low.

Thus, as shown in Examples 6 to 10, the heat shrinkage in the width direction at 200 ° C. was 1.5%.
By using an aromatic polyamide film of about 2.5% and forming an organic plasma polymer film, the main surface can be flattened with high precision, and a good running state with good contact with the head can be achieved. It has become possible to obtain a durable magnetic recording medium.

When Examples 1 to 7 are compared with Examples 8 and 9, better results are obtained in Examples 1 to 7 than in Examples 8 and 9. It has become. Thus, in the aromatic polyamide film, by defining the heat shrinkage in the width direction at 150 ° C. in the range of 0.5% or more, the main surface is further flat and the contact state with the head is good. It turned out that the magnetic recording medium had high running durability.

[0178]

As described above in detail, in the magnetic recording medium according to the present invention, heat treatment and the like can be performed by defining the thermal expansion coefficient at 200 ° C. in the width direction of the aromatic polyamide film to a predetermined value. Even in the case where it is applied, it has excellent shape stability without causing curling, cupping and the like. Therefore, the magnetic recording medium has good contact with the head and has excellent running stability.

Further, the method for manufacturing a magnetic recording medium according to the present invention has a thermal shrinkage at 200 ° C. in the width direction of 1.5 to 1.5.
Since a non-magnetic support having a concentration of 2.5% is used,
Even when heat history is added, the surface of the magnetic recording medium can be formed with high precision and flatness without causing curling or cupping.

Further, by forming the reinforcing metal thin film, the strength of the thin magnetic recording medium is improved, and the durability and the reliability can be improved without causing the deterioration of the error rate and the hit characteristics even after repeated running. An excellent thin magnetic recording medium can be obtained.

In the magnetic recording medium according to the present invention, an organic plasma polymer film may be formed instead of the reinforcing metal thin film, and even when the organic plasma polymer film is formed, the reinforcing metal thin film may be formed. As a result, a thin magnetic recording medium having excellent durability and reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a configuration example of a magnetic recording medium according to the present invention using a reinforcing metal thin film.

FIG. 2 is a cross-sectional view of a main part of another configuration example of the magnetic recording medium according to the present invention using a reinforcing metal thin film.

FIG. 3 is a schematic configuration diagram of a continuous winding type vacuum evaporation apparatus used for forming a metal magnetic film.

FIG. 4 is a schematic configuration diagram of a magnetron sputtering apparatus used when forming a carbon protective film.

FIG. 5 is a cross-sectional view of a main part of a configuration example of a magnetic recording medium according to the present invention using an organic plasma polymer film.

FIG. 6 is a cross-sectional view of a main part of another configuration example of the magnetic recording medium according to the present invention using an organic plasma polymer film.

FIG. 7 is a schematic configuration diagram of a cupping measurement device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Non-magnetic support, 4 Metal magnetic film, 5 Metal thin film for reinforcement, 6 Back coat layer, 7 Organic plasma polymer film

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinichi Matsumura 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Hiroshi Yatakai 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F term (reference) 5D006 BB07 CB02 CB04 CB07 CB08 CC01 CC03 CC04 FA02 5D112 AA02 AA05 AA08 AA11 AA22 BA01 BD01 BD03 BD04 FA07 GA02 GA27 GB03

Claims (19)

[Claims] 1. A magnetic recording medium having at least a metal magnetic film formed on one main surface of a non-magnetic support, wherein the non-magnetic support is made of an aromatic polyamide film and has a temperature of 200 ° C. in the width direction. Has a heat shrinkage of 1.5 to 2.
5%, wherein the metal magnetic film is formed by etching a surface oxide layer formed on the surface of the metal magnetic film, and the other side of the non-magnetic support opposite to the side on which the metal magnetic film is formed is formed. A magnetic recording medium comprising a reinforcing metal thin film formed on a main surface. 2. The non-magnetic support according to claim 1, wherein the non-magnetic support is one in the width direction.
2. The magnetic recording medium according to claim 1, wherein the heat shrinkage at 50 ° C. is 0.5% or more. 3. The magnetic recording medium according to claim 1, wherein the non-magnetic support has a multilayer structure. 4. The method according to claim 1, wherein the metal magnetic film has a thickness of 0.05 to 0.05.
2. The magnetic recording medium according to claim 1, wherein the thickness is 0.25 [mu] m. 5. The thickness of the nonmagnetic support is 2.5 to 2.5.
2. The magnetic recording medium according to claim 1, wherein the thickness is 5.0 [mu] m. 6. The nonmagnetic support according to claim 1, wherein the Young's modulus in the length direction is 1000 kg / mm ² or more, and the Young's modulus in the width direction is 1300 kg / mm ² or more. Magnetic recording medium. 7. The reinforcing metal thin film has a thickness of 0.1 to 0.1.
2. The magnetic recording medium according to claim 1, wherein the thickness is 0.5 μm. 8. The reinforcing metal thin film is made of Al, Cu, N
2. The magnetic recording medium according to claim 1, comprising at least one metal thin film composed of a metal selected from the group consisting of i, Cr and an alloy of these metals. 9. A method for manufacturing a magnetic recording medium comprising at least a metal magnetic film formed on one main surface of a non-magnetic support, wherein the heat shrinkage at 200 ° C. in the width direction is 1.5 to 2. 5%
Using a non-magnetic support made of an aromatic polyamide film, and forming the metal magnetic film on one main surface of the non-magnetic support; and forming the metal magnetic film on the non-magnetic support, Etching a surface oxide layer formed on the film surface; forming a reinforcing metal thin film on the other main surface of the nonmagnetic support opposite to the side on which the metal magnetic film is formed; and Adding a thermal history after forming the reinforcing metal thin film. 10. A heat treatment at 100 ° C. to 250 ° C. after forming the reinforcing metal thin film on the other main surface of the nonmagnetic support opposite to the side on which the metal magnetic film is formed. The method for manufacturing a magnetic recording medium according to claim 9, wherein: 11. A magnetic recording medium in which at least a metal magnetic film is formed on one main surface of a nonmagnetic support, wherein the nonmagnetic support is made of an aromatic polyamide film and has a temperature of 200 ° C. in the width direction. Has a heat shrinkage of 1.5 to 2.
5%, wherein the metal magnetic film is formed by etching a surface oxide layer formed on the surface of the metal magnetic film, and the other side of the non-magnetic support opposite to the side on which the metal magnetic film is formed is formed. A magnetic recording medium comprising an organic plasma polymer film formed on a main surface. 12. The magnetic recording medium according to claim 11, wherein the nonmagnetic support has a thermal shrinkage at 150 ° C. in the width direction of 0.5% or more. 13. The magnetic recording medium according to claim 11, wherein the non-magnetic support has a multilayer structure. 14. The thickness of the metal magnetic film is 0.05 to
The magnetic recording medium according to claim 11, wherein the thickness is 0.25 µm. 15. The thickness of the nonmagnetic support is from 2.5 to
The magnetic recording medium according to claim 11, wherein the thickness is 5.0 µm. 16. The non-magnetic support according to claim 11, wherein the Young's modulus in the length direction is 1000 kg / mm ² or more, and the Young's modulus in the width direction is 1300 kg / mm ² or more. Magnetic recording medium. 17. The thickness of the organic plasma polymer film is as follows:
12. The structure according to claim 11, wherein the thickness is 0.1 to 1.0 [mu] m.
The magnetic recording medium according to the above. 18. A method for manufacturing a magnetic recording medium comprising a nonmagnetic support having at least a metal magnetic film formed on one main surface thereof, wherein a thermal shrinkage at 200 ° C. in the width direction is 1.5 to 2. 5%
Using a non-magnetic support made of an aromatic polyamide film, and forming the metal magnetic film on one main surface of the non-magnetic support; and forming the metal magnetic film on the non-magnetic support, Etching a surface oxide layer formed on the film surface; forming an organic plasma polymer film on the other main surface of the nonmagnetic support opposite to the side on which the metal magnetic film is formed; Adding a thermal history after forming the organic plasma polymer film. 19. After the organic plasma polymer film is formed on the other main surface of the non-magnetic support opposite to the side on which the metal magnetic film is formed, a heat treatment at 100 ° C. to 250 ° C. is performed. 19. The method for manufacturing a magnetic recording medium according to claim 18, wherein: