JPH11213373A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium which is made thinner furthermore and secures a sufficient durability and is superior in electromagnetic transduction characteristics and running performance and has a capacity made larger furthermore. SOLUTION: In the magnetic recording medium, a magnetic layer 3 is formed on a long-sized nonmagnetic support body 2. The nonmagnetic support body 2 is an aromatic polyamide film, and the Young's modulus of elasticity in the lengthwise direction is >=1,000 kg/mm<2> , and that in the breadthwise direction is >=1300 kg/mm<2> , and inert particles having 0.02-0.3 μm average particle size are added into the aromatic polyamide film to form 10,00-20,000,000 projections per mm<2> on a surface 2a where the magnetic layer 3 is formed. A back coat layer 4 which contains at least a binder and an acicular nonmagnetic pigment is formed on a surface 2b opposite to the surface of the nonmagnetic support body 2 where the magnetic layer 3 is formed.

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 in which a magnetic layer is formed on a long non-magnetic support,
For example, the present invention relates to a video tape for long-time recording, or a large-capacity tape streamer.

[0002]

2. Description of the Related Art Conventionally, a polyethylene terephthalate film has been mainly used as a non-magnetic support for a metal thin film type magnetic recording medium. Specifically, as a non-magnetic support of a home video cassette tape, for example, an 8 mm tape, a polyethylene terephthalate film having a thickness of about 7 to 10 μm is used. A polyethylene terephthalate film having a thickness of about 5 to 7 μm is used as a non-magnetic support of a tape streamer for data backup of a computer.

[0003] By the way, as for a magnetic recording medium for a video cassette, further downsizing and long-time recording have been desired as the video cassette is downsized. Also, with the recent increase in the amount of information, it is desired to increase the capacity of a magnetic recording medium as a tape streamer. Therefore, in order to meet these demands, studies have been made to reduce the thickness of the magnetic recording medium.

In order to reduce the thickness of a magnetic recording medium,
It is easy to reduce the thickness of the nonmagnetic support. However, when a polyethylene terephthalate film is used as the non-magnetic support, the strength of the magnetic recording medium in the length direction or the width direction decreases when the thickness is reduced. When the strength of the magnetic recording medium in the longitudinal direction decreases, the magnetic recording medium is likely to be deformed when running on a video tape recorder or a drive. Further, the magnetic recording medium has a problem that when the strength in the width direction is reduced, wrinkles and breaks are likely to occur, and furthermore, poor contact with the head is likely to occur.

Therefore, the use of a polyamide film as a non-magnetic support for a metal thin-film type magnetic recording medium has been studied.

[0006] Polyamide films have higher strength than polyethylene terephthalate films. Therefore,
A magnetic recording medium using this polyamide film as a non-magnetic support can be made thinner, and is attracting attention as a magnetic recording medium that can be used for long-term recording of video cassette tapes and large-capacity tape streamers. Have been.

[0007]

In a metal thin film type magnetic recording medium using such a polyamide film as a nonmagnetic support, the magnetic layer is made of a ferromagnetic metal thin film, and the thickness of the magnetic layer is reduced. Since the magnetic layer is thin, the magnetic layer is easily affected by the surface properties of the nonmagnetic support, and the surface shape of the nonmagnetic support is directly reflected on the surface shape of the magnetic layer. Therefore, in this metal thin-film type magnetic recording medium, it is necessary to control the surface shape of the non-magnetic support so that the fine shape of the surface of the magnetic layer is in an appropriate state from the viewpoint of electromagnetic conversion characteristics and running properties.

Accordingly, the present inventors have filed a patent application
In Japanese Patent Application Publication No. 2005534, a polyamide film is used as a long non-magnetic support, and by controlling the Young's modulus in the longitudinal direction and the width direction of the non-magnetic support, deformation such as breakage and wrinkles is hardly caused. In addition, a magnetic recording medium has been proposed in which the electromagnetic conversion characteristics and running properties are improved by setting the fine shape of the surface of the magnetic layer in an optimum state.

In order to cope with a further increase in the capacity of the above-mentioned metal thin film type magnetic recording medium, there is a strong demand for a further reduction in the thickness of the magnetic recording medium. Specifically, in a magnetic recording medium for a tape streamer, 2-3
Since the recording capacity is doubled every year, there is a strong demand for thinner magnetic recording media.

However, even in a metal thin-film magnetic recording medium using this polyamide film as a non-magnetic support, if the non-magnetic support is further thinned to further reduce the thickness of the magnetic recording medium, the following problems occur. There is.

Specifically, when the thickness of the non-magnetic support is reduced, the rigidity, ie, stiffness, is expressed by E × t ³ where E is the Young's modulus and t is the thickness of the non-magnetic support. For this reason, the rigidity of the nonmagnetic support is significantly reduced, the mechanical strength becomes insufficient, and the durability is deteriorated. For example, if the thickness of the non-magnetic support is reduced to half, the rigidity of the non-magnetic support is reduced to 1/8.

As a result, the magnetic recording medium is liable to be deformed when running on a video tape recorder or a drive, and is liable to be wrinkled or broken, and it is not possible to sufficiently secure contact with the magnetic head. .

That is, even in the above-described recording of a metal thin film type magnetic recording medium, in order to achieve further reduction in thickness and increase in capacity, stable running can be achieved when running with a video tape recorder or drive. It is necessary that such rigidity is sufficiently ensured.

Therefore, the present invention has been proposed in view of the conventional situation, and further thinning has been achieved and sufficient durability has been ensured. As a result, the electromagnetic conversion characteristics,
It is an object of the present invention to provide a magnetic recording medium which is excellent in recording / reproducing characteristics and running properties and realizes a further increase in capacity.

[0015]

A magnetic recording medium according to the present invention comprises a long non-magnetic support having a magnetic layer formed thereon, wherein the non-magnetic support comprises an aromatic polyamide film. The non-magnetic support has a Young's modulus in the longitudinal direction of 1000 kg / mm ² or more, and the non-magnetic support has a Young's modulus in the width direction of 1300 kg / mm ² or more. Particle size is 0.
On the surface of the surface on which the magnetic layer is formed by adding inert particles of 02 μm to 0.3 μm, 10,000 particles / mm ^{2 to} 2000
Thousands / mm ² of projections are formed, on the non-magnetic support opposite side on the surface and the surface on which the magnetic layer is formed, the back containing at least binder and acicular nonmagnetic pigment It is characterized in that a coat layer is formed.
Preferably, the thickness of the non-magnetic support is set to 1.0 to 5.0 μm, and the non-magnetic support is applied to the magnetic recording medium.

In the magnetic recording medium according to the present invention constructed as described above, the long non-magnetic support is made of an aromatic polyamide film, and the non-magnetic support has a Young's modulus in the longitudinal direction and the width direction. Since the number of protrusions on the surface of the non-magnetic support on which the ferromagnetic metal thin film is formed is specified, as a result, the fine shape of the surface of the magnetic layer is appropriately adjusted. In this state, good electromagnetic conversion characteristics and good running performance are obtained.

Further, the magnetic recording medium according to the present invention has a backing containing a binder and an acicular nonmagnetic pigment on the surface of the nonmagnetic support opposite to the surface on which the ferromagnetic metal thin film is formed. Since the coat layer is formed, the strength is enhanced not only in the thickness direction of the magnetic recording medium but also in the plane direction, and even if the magnetic recording medium is further thinned, necessary and sufficient mechanical strength is secured. And long-term storage and durability are improved.

Further, since the magnetic recording medium according to the present invention has such a back coat layer formed thereon, the mechanical strength is improved. As much as possible, the contact with the magnetic head is improved.

Further, in the magnetic recording medium according to the present invention, the thickness of the nonmagnetic support made of an aromatic polyamide film is reduced to 1.0 to 5.0 μm, and the thickness is reduced as described above. Since a necessary and sufficient strength is secured, further increase in capacity and recording for a long time are realized.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing a magnetic recording medium to which the present invention is applied.

In the magnetic recording medium 1 according to the present invention, a ferromagnetic metal thin film 3 is formed on one main surface 2a of a long non-magnetic support 2, and the ferromagnetic metal A back coat layer 4 is formed on one main surface 2b opposite to the surface on which the thin film 3 is formed.

The non-magnetic support 2 is made of an aromatic polyamide film. Preferably, the nonmagnetic support 2 is made of an aromatic polyamide film formed using an aromatic polyamide resin comprising the following chemical formula (I) or (II) or a copolymer thereof.

[0023]

Embedded image

The aromatic polyamide has about 20%
Polymers other than the above components may be copolymerized or blended in the following amounts.

When an aromatic polyamide film is prepared from these polymers, for example,
Dimethylacetamide, dimethylformamide, n-methylpyrrolidone, hexamethylphosphoramide, γ-butyrolactone, tetramethylurea, dioxane, etc., or a mixed solvent thereof, or lithium chloride or calcium chloride as a neutralization product of the polymerization stock solution The above-mentioned solvent to which an inorganic salt such as lithium carbonate, lithium nitrate or the like is added is used.

Using such a solvent for film formation, an aromatic polyamide resin is produced by polymerization of an aromatic diamine and an aromatic dicarboxylic acid, and the aromatic polyamide resin is formed by a technique such as solution molding. Produce an aromatic polyamide film.

Here, the aromatic diamines include:
For example, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 2-nitro-p-phenylenediamine, 2-chloro-p-phenylenediamine, 4,4′-diaminobiphenyl, 3,3′-chlorobenzine And the like.

Examples of the aromatic dicarboxylic acids include terephthalic acid chloride, 2-chloroterephthalic acid chloride, terephthalic acid hydrazide, p-aminobenzoic acid hydrazide, p-aminobenzoic acid chloride and the like.

Further, the long aromatic polyamide film obtained as described above is stretched in the longitudinal direction and the width direction, and the Young's modulus in the longitudinal direction is 1000 kg / mm ² or more, and the Young's modulus in the width direction is 1300 kg. / Mm ² or more is obtained. At this time, it is preferable that the thickness of the nonmagnetic support 2 is 1.0 to 5.0 μm.

That is, the nonmagnetic support 2 used in the magnetic recording medium 1 to which the present invention is applied has a Young's modulus in the longitudinal direction of 1000 kg / mm ² or more and a Young's modulus in the width direction of 1300 kg / mm ² or more. Done.

As described above, in the magnetic recording medium 1 to which the present invention is applied, the rigidity and the like of the long non-magnetic support member 2 are defined by defining the Young's modulus in the longitudinal direction and the width direction of the long non-magnetic support member 2 as described above. The mechanical strength of the non-magnetic support 2 can be increased, and the non-magnetic support 2 can be prevented from being deformed such as bent, wrinkled or curled. As a result, the magnetic recording medium 1 manufactured by using the non-magnetic support 2 not only has improved durability but also can sufficiently secure contact with the magnetic head and has good electromagnetic conversion characteristics. And recording / reproducing characteristics.

More specifically, by defining the Young's modulus in the longitudinal direction of the non-magnetic support 2 to be 1000 kg / mm ² or more, the magnetic recording medium 1 in which the non-magnetic support 2 is used
Can reduce off-track. Further, the Young's modulus in the width direction of the nonmagnetic support 2 is set to 1300 kg / mm ^2.
According to the above definition, the magnetic recording medium 1 using the nonmagnetic support 2 can improve the contact with the magnetic head.

If the Young's modulus of the non-magnetic support in the longitudinal direction is too small at 1000 kg / mm ² or less, the magnetic recording medium is likely to be deformed when running on a video tape recorder or a drive. If the Young's modulus in the width direction of the non-magnetic support is too small at 1300 kg / mm ² or less,
The magnetic recording medium is likely to be deformed such as wrinkles, breaks and curls.

The thickness of the non-magnetic support 2 is as follows.
It is preferably from 0 to 5.0 μm. As described above, the magnetic recording medium 1 to which the present invention is applied is made thinner, so that a larger capacity and a longer recording time are realized.

The non-magnetic support 2 in the magnetic recording medium 1 to which the present invention is applied has an average particle size of 0.02 to 0 in the aromatic polyamide film, more specifically, in the material forming the aromatic polyamide film. By adding inert particles of 0.3 μm, the surface 2 a on which the ferromagnetic metal thin film 3 is formed has a size of 10,000 particles / mm ^{2 to} 20 million particles / m ^2.
m ² of projections are formed. As described above, in the magnetic recording medium 1 to which the present invention is applied, since the surface property of the surface of the nonmagnetic support 2 on which the ferromagnetic metal thin film 3 is formed is controlled,
The contact with the magnetic head can be made good, and good electromagnetic conversion characteristics and good running properties can be provided.

As the inert particles in this case, for example,
Silicon dioxide (including hydrate, diatomaceous earth, silica sand, quartz, etc.),
Silicates containing 30% by weight or more of alumina and SiO ₂ (eg, amorphous or crystalline clay minerals, aluminosilicates containing calcined products and hydrates, hot asbestos, zircon,
Fly ash, etc.), sulfates of Mg, Zn, Zr, Ca, Ba, phosphates of Li, Na, Ca (including monohydrogen salts and dihydrogen salts), benzoates of Li, Na, K, Ca , B
a, Zn, Mn terephthalate, Mg, Ca, Ba,
Titanate of Zn, Cd, Pb, Sr, Mn, Fe, Co, Ni, chromate of Ba, Pb, carbon (eg, carbon black, graphite, etc.), carbonate of Ca, Mg, fluorite, ZnS And the like.

More preferably, silicic anhydride, hydrated silicic acid,
Aluminum oxide, aluminum silicate (including calcined products and hydrates), monolithium phosphate, trilithium phosphate, sodium phosphate, barium phosphate, titanium oxide, lithium benzoate, double salts of these compounds (hydration) And clay minerals such as clay, kaolin, bentonite, and clay, talc, diatomaceous earth, and calcium carbonate.

These inert particles may be added and dispersed in a solvent of one monomer before polymerization, or may be added and dispersed in a solvent to be polymerized at the time of polymerization.
Alternatively, it may be added during the step of adjusting the polymer solution.

The inert particles have an average particle size of 0.02 μm
When the number of protrusions is less than 10,000 / mm ² , the number of protrusions is small. In each case, the number of protrusions is small. The effect of preventing clogging, the so-called cleaning effect, cannot be obtained. On the other hand, addition of particles having an average particle size of more than 0.3 μm of inert particles or protrusions of 20 million particles / m
If it exceeds m ² , the electromagnetic conversion characteristics of the magnetic recording medium deteriorate in any case.

Further, in order to improve the handleability of the film, for example, the film of the non-magnetic
The surface 2 on the side where the ferromagnetic metal thin film 3 is not formed has a layer structure.
It is good to make the surface roughness of b relatively rough. Specifically, the center line average roughness Ra of the nonmagnetic support 2 is set to 50 to 250 n.
m, preferably 100 to 200 nm.

At this time, as a method of adjusting the surface roughness,
For example, it is performed by adding the above-mentioned inert particles and controlling the average particle size, the particle size distribution, the added amount, and the like.

The ferromagnetic metal thin film 3 is formed on one main surface 2a of the nonmagnetic support 2 constructed as described above, for example, by oblique evaporation or vertical evaporation. Examples of the material of the ferromagnetic metal thin film 3 include Co, Ni, Fe, and alloys thereof.

The back coat layer 4 has a surface 2 b opposite to the surface on which the ferromagnetic metal thin film 3 of the nonmagnetic support 2 is formed.
Formed on top.

In particular, the back coat layer 4 in the magnetic recording medium 1 to which the present invention is applied is formed of at least a binder and a needle-shaped non-magnetic pigment.

Examples of the binder include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-vinylidene chloride copolymer. Polymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinylidene chloride copolymer, methacrylate-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride , Vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile-methacrylic acid copolymer, polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenol resin, epoxy resin, polycarbonate resin, heat Of polyurethane resins, urea resins, melamine resins, alkyd resins, urea - formaldehyde resins or mixtures thereof. These resins may be those having improved durability by using an isocyanate compound as a cross-linking agent, or those having an appropriate polar group introduced.

Further, as the acicular nonmagnetic pigment contained in the back coat layer 4 in the present invention, it is preferable to use an acicular nonmagnetic pigment having a ratio of the major axis to the minor axis, that is, the aspect ratio of 10 or more.

Thus, it is possible to improve not only the thickness direction of the magnetic recording medium but also the mechanical strength such as the tensile strength and the bending strength in the plane direction such as the longitudinal direction and the width direction. As a result, the magnetic recording medium 1 to which the present invention is applied
However, even if the thickness is reduced, sufficient mechanical strength can be secured, and a further increase in capacity and recording for a long time can be realized.

The material of the acicular non-magnetic pigment is not particularly limited, and examples thereof include hematite, goethite, titanium oxide, aluminum oxide and the like.

When the binder is B and the acicular nonmagnetic pigment is P, the ratio P / B of the binder to the acicular nonmagnetic pigment is preferably 0.5 to 5.0. This P / B
If the ratio is less than 0.5, the content of the acicular nonmagnetic pigment is small, so that the effect of reinforcing the mechanical strength in the planar direction of the magnetic recording medium cannot be obtained. On the other hand, if the P / B ratio is larger than 5, the content of the binder is small, so that the strength of the back coat layer 4 itself is weak, and a powder drop phenomenon occurs, or the durability of the back coat layer 4 itself is deteriorated.

In addition, in addition to the acicular nonmagnetic pigment described above, an inorganic pigment powder may be added to the back coat layer 4 if necessary. As such inorganic pigment powder, for example,
Examples include carbon black, graphite, talc, kaolin and the like. Further, an antistatic agent, a lubricant and the like may be contained in the back coat layer 4 as necessary.

Further, the thickness of the back coat layer 4 is preferably 0.1 to 0.6 μm. If the thickness of the back coat layer 4 is too small, the effect of reinforcing the mechanical strength of the magnetic recording medium will not be exhibited, and if the thickness of the back coat layer 4 is too large, cracks are likely to occur in the magnetic recording medium.

The magnetic recording medium to which the present invention is applied
In addition to a raw material for a magnetic tape, it can be used as a raw material for a magnetic disk, particularly a flexible disk.

Next, the magnetic recording medium 1 to which the present invention is applied
A method of manufacturing the device will be described.

First, a non-magnetic support 2 is prepared as described below. First, an aromatic diamine and an aromatic dicarboxylic acid are added and dissolved in the above-mentioned polymerization solvent, and the above-mentioned inert particles are dispersed in this solution to prepare an aromatic polyamide solution.

Then, the aromatic polyamide solution is cast on a metal drum and dried to obtain an aromatic polyamide film.

After the aromatic polyamide film is peeled off from the metal drum, it is sequentially stretched in the longitudinal direction and the width direction.

Thus, the nonmagnetic support 2 having desired Young's modulus and surface properties is formed. Here, the non-magnetic support 2 thus manufactured is wound up in a roll shape to be a raw material. Hereinafter, the raw material of the non-magnetic support is referred to as a non-magnetic support roll.

Next, this non-magnetic support roll was set in a continuous winding type vacuum evaporation apparatus as shown in FIG.
The ferromagnetic metal thin film 3 is formed on one main surface 6a of the non-magnetic support 2. FIG. 2 is a schematic configuration diagram of a continuous winding type vacuum evaporation apparatus.

This vacuum evaporation apparatus 10 is used for oblique evaporation, and is cooled to, for example, about −20 ° C. and rotated in the direction of arrow A in FIG. The apparatus includes a can 12 and an evaporation source 13 for a metal thin film disposed at a position facing the cooling can 12. The evaporation source 13 is a container in which a ferromagnetic metal material is accommodated in a container such as a crucible.

As shown in FIG. 2, the vacuum evaporation apparatus 10 has a non-magnetic support roll 16 mounted on a rotatable supply shaft 22 and a rotatable drive source (not shown). The magnetic tape roll 17 is mounted on the take-up shaft 23, and the non-magnetic support is run continuously through the cooling can 12.

When the ferromagnetic metal thin film 3 is formed by using the vacuum evaporation apparatus 10 having such a configuration, first, the ferromagnetic metal material in the evaporation source 13 is accelerated from the electron beam source 14. The emitted electron beam 15 is irradiated to heat and evaporate the ferromagnetic metal material.

The heated and evaporated ferromagnetic metal material is supplied to the non-magnetic support roll 16 mounted on the supply shaft 22.
The ferromagnetic metal thin film 3 is formed by being deposited on the non-magnetic support 2 which is fed out in the direction of arrow B in the figure and runs along the peripheral surface of the cooling can 12. Finally, the nonmagnetic support 2 on which the ferromagnetic metal thin film 3 is formed is wound around a magnetic tape roll 17 mounted on a winding shaft 23.

At this time, a deposition-preventing plate 18 is provided between the vapor deposition source 13 and the cooling can 12, and a shutter 19 is provided on the deposition-preventing plate 18 so as to be position-adjustable. Only vapor particles incident at an angle of. The ferromagnetic metal thin film 3 is formed by such an oblique deposition method.

Guide rollers 20 and 21 are arranged between the non-magnetic support roll 16 and the cooling can 12 and between the cooling can 12 and the magnetic tape roll 17, respectively. Is applied with a predetermined tension so that the non-magnetic support 2 runs smoothly.

In the above, the example in which the ferromagnetic metal thin film 3 is formed by the oblique deposition method has been described.
In addition to this example, a known thin film forming method such as a vertical vapor deposition method or a sputtering method can be applied as a method for forming a thin film.

It should be noted that the adhesive strength with the non-magnetic support 2 was improved,
Alternatively, for the purpose of improving the corrosion resistance and abrasion resistance of the ferromagnetic metal thin film 3 itself, it is possible to form the ferromagnetic metal thin film containing oxygen by setting the atmosphere at the time of vapor deposition to an atmosphere in which oxygen gas is dominant. desirable.

Further, in order to heat the evaporation source 13, in addition to the heating means by the electron beam as described above, for example,
Known means such as resistance heating means, high-frequency heating means, and laser heating means may be used.

Next, in order to prevent abrasion of the ferromagnetic metal thin film 3, it is desirable to form a carbon protective film on the ferromagnetic metal thin film 3 using a magnetron sputtering apparatus 30 as shown in FIG.

In this magnetron sputtering apparatus 30, after the inside of the chamber 31 is depressurized by the vacuum pump 32, the angle of the valve 33 to be discarded is reduced toward the vacuum pump 32, whereby Ar gas is introduced from the gas introduction pipe 34. Thus, the degree of vacuum is about 0.8 Pa. In the magnetron sputtering apparatus 30, a cooling can 35 that is cooled to, for example, −40 ° C. and rotates in the direction of arrow C in the drawing, and a target 36 that is arranged to face the cooling can 35 are provided in the chamber 31. I have. The target 36 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.

The magnetron sputtering apparatus 30
The magnetic tape roll 17 on which the ferromagnetic metal thin film 3 is formed is mounted on a rotatable supply shaft 39, and the magnetic tape roll 17 is rotatably driven by a driving source (not shown). The non-magnetic support 2 on which the ferromagnetic metal thin film 3 is formed is mounted on the cooling can 35.
The vehicle is continuously driven in the direction D in FIG.

When a carbon protective film is formed by the magnetron sputtering apparatus 30, first, the gas introduction pipe 34
From the cooling can 35 as an anode and the backing plate 37 as a cathode.
A voltage of 00 V is applied so that a current of 1.4 A flows.

Then, by applying the voltage, the Ar gas is turned into plasma, and the ionized ions collide with the target 36, whereby the atoms of the target 36 are repelled. The atoms repelled from the target 36 are fed out from the magnetic tape roll 17 in the direction of arrow D in the figure, and are deposited on the ferromagnetic metal thin film 3 of the nonmagnetic support 2 running along the peripheral surface of the cooling can 35. Adhering, a carbon protective film is formed. Finally, the non-magnetic support on which the carbon protective film is formed is wound by a magnetic tape roll 42 mounted on a winding shaft 41.

At this time, this carbon protective film has a thickness of 3 to 15 nm so as to minimize spacing loss and to obtain an effect of preventing abrasion of the ferromagnetic metal thin film 3.
Degree, more preferably 5 to 10 nm.

In the above, a method using magnetron sputtering has been described as a method for forming a carbon protective film. In addition to this method, a known thin film forming method such as ion beam sputtering, ion beam plating, or CVD is used. Can be used. Further, it is preferable to apply a lubricant to the surface of the carbon protective film.

Next, a coating for the back coat layer containing a needle-shaped nonmagnetic pigment, a binder and the like was prepared, and the ferromagnetic metal thin film 3 was prepared.
The backcoat layer 4 is formed by applying the coating for the backcoat layer on the surface 2b on the side where the ferromagnetic metal thin film 3 is not formed on the non-magnetic support 2 on which the ferromagnetic metal thin film 3 is not formed. I do.

Finally, the raw material of the magnetic recording medium on which the ferromagnetic metal thin film 3, the carbon protective film and the back coat layer 4 are formed is cut into a predetermined width along the length direction to perform tape-like magnetic recording. The medium 1 is manufactured.

Through the above steps, the magnetic recording medium 1 to which the present invention is applied can be obtained.

[0078]

EXAMPLES Hereinafter, specific examples of the present invention will be described based on experimental results.

In the magnetic recording medium, the Young's modulus in the longitudinal direction and the width direction of the non-magnetic support, the number of protrusions on the surface of the non-magnetic support on which the ferromagnetic metal thin film is formed, and the ferromagnetic metal in the non-magnetic support In order to evaluate the effect of the back coat layer formed on the surface opposite to the surface on which the thin film is formed, a magnetic tape was manufactured by the following method.

Example 1 First, 0.9 mol was added to dehydrated n-methylpyrrolidone.
2-Chloro-p-phenylenediamine corresponding to the ratio and 4,4'-diaminodiphenylsulfone corresponding to the 0.1 mol ratio were dissolved by stirring, cooled, and added thereto.
Terephthalic acid chloride corresponding to the molar ratio was added and stirred for about 2 hours. Thereafter, sufficiently purified calcium hydroxide was added and mixed with stirring. To this, ammonia water is added to complete the neutralization. Then, SiO ₂ having an average particle size of 0.05 μm was added to n-methylpyrrolidone to obtain an aromatic polyamide solution.

Next, this aromatic polyamide solution was uniformly cast at 30 ° C. on a metal drum whose surface was polished,
For about 10 minutes to form an aromatic polyamide film.

Then, the aromatic polyamide film was peeled off from the metal drum and continuously placed in a water bath at 30 ° C. for about 3 hours.
The film was stretched in the longitudinal direction while being immersed for 0 minutes. Furthermore, this aromatic polyamide film was introduced into a tenter,
The film was stretched in the width direction at 20 ° C. to obtain a non-magnetic support having a thickness of about 3.5 μm.

Examples 2 to 6 and Comparative Examples 1 to 4 The same as in Example 1 except that the longitudinal stretching ratio, the width stretching ratio, and the particle size of SiO ₂ were changed, respectively. A support was obtained.

The Young's modulus and the number of surface protrusions in the width direction and the longitudinal direction were measured for the films of the non-magnetic support of each of the examples and comparative examples. The measurement conditions were as follows.

Measurement of Young's Modulus A non-magnetic support was pulled at a temperature of 25 ° C. and a humidity of 55% using a Tensilon type tensile tester, and the tensile strength of the non-magnetic support was 0.05 to 0.05%.
A load giving an elongation of 0.1% was measured, and the Young's modulus was calculated from the value.

Measurement of Number of Surface Protrusions As a scanning electron microscope (SEM), an ultra-high resolution cold FE-SEM [S-900] (trade name) manufactured by JEOL Ltd.
The number of protrusions on the surface of the non-magnetic support on which the ferromagnetic metal thin film was formed was counted and converted to the number per 1 mm ² by setting the acceleration voltage to 20 kV and the magnification to 30,000 or more.

Table 1 shows the results.

[0088]

[Table 1]

Next, with respect to the non-magnetic support of each example, FIG.
A ferromagnetic metal thin film made of Co was formed on a non-magnetic support by a continuous vacuum oblique deposition method using the vapor deposition apparatus shown in FIG.

Specifically, a continuous winding type vapor deposition apparatus as shown in FIG. 2 was evacuated so that the inside thereof was brought into a vacuum state of about 10 ⁻³ Pa, and a non-magnetic support on which a polymer film was formed was formed. The body was set in this deposition apparatus. And by the continuous vacuum oblique deposition method, in the presence of a small amount of oxygen,
A ferromagnetic metal thin film made of Co was formed on the surface of the non-magnetic support. At this time, the incident angle of vapor deposition is 90 to 45 degrees in the normal direction of the non-magnetic support, the traveling speed of the non-magnetic support is 50 m / min, and the thickness of the ferromagnetic metal thin film is 0.
It was manufactured by adjusting the intensity of the electron beam so as to be 18 μm.

Next, the pressure of the magnetron sputtering apparatus as shown in FIG. 3 was reduced to about 10 ⁻⁴ Pa, and then Ar gas was introduced to about ^0.8 Pa. Then, the non-magnetic support on which the ferromagnetic metal thin film 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 to protect the carbon on the ferromagnetic metal thin film. A film was formed.

Next, a coating material for a back coat layer shown below is applied to the surface of the non-magnetic support opposite to the surface on which the ferromagnetic metal thin film is formed, to form a back coat having a thickness of 0.5 μm. A layer was formed.

<Coating for Back Coat Layer> Reinforcing agent: Goethite (major axis: 0.2 μm, aspect ratio: 30) 100 parts by weight Carbon black 50 parts by weight Binder: polyurethane resin 100 parts by weight Solvent: methyl ethyl ketone / toluene = 4/1 300 parts by weight Next, a lubricant composed of perfluoropolyether was applied on the carbon protective film to form a top coat layer, thereby producing a magnetic recording medium.

Finally, the magnetic recording medium was cut into a width of 8 mm to obtain a magnetic tape, and the magnetic tape was stored in a cassette body to obtain a cassette tape.

Comparative Example 4 was a magnetic tape having a back coat layer formed of a material excluding goethite in the above-mentioned back coat layer paint instead of the above back coat layer.

Then, the physical properties of the magnetic tapes manufactured as described above were evaluated as follows.

Evaluation of Tape Characteristics The method of evaluating the characteristics of the magnetic tape includes Sony Corporation's A
The test was performed using a modified version of the IT drive SDX-S300C (trade name). The recording was at a relative speed of 10.04m /
Second, the shortest recording wavelength was 0.35 μm.

As a running durability, a 170 m length was run for 100 passes, and a block error rate after running one pass and a block error rate after running 100 passes were measured.

Further, the squealing state, that is, the slip state of the tape in the rotary head cylinder portion after running 100 passes was measured.

Evaluation of Contact Characteristics with Head The minimum value / maximum value (%) of the output signal during reproduction of the magnetic tape, that is, the output signal when the collision waveform was viewed for one track was measured.

Evaluation of Storage Characteristics As a method for evaluating the storage characteristics of the magnetic tape, a magnetic tape recorded 170 m in length at normal temperature and normal humidity of about 25 ° C. was stored at 45 ° C. and 80% humidity for 3 days. Thereafter, reproduction was performed again under normal temperature and normal humidity, and the increase in the error rate was measured.

Table 2 shows the results of the above physical property evaluation.

[0103]

[Table 2]

As is clear from the results of Tables 1 and 2, Examples 1 to 6 to which the present invention is applied have a Young's modulus in the longitudinal direction of the non-magnetic support of 1000 kg / mm ² or more and a width of The Young's modulus in the direction is defined to be 1300 kg / mm ² or more, and inert particles having an average particle diameter of 0.02 to 0.05 μm are added to the aromatic polyamide film to form a ferromagnetic metal thin film of a nonmagnetic support. Since the protrusions of 10,000 / mm ^{2 to} 20,000,000 / mm ² are formed on the surface on which is formed, the tape characteristics, the contact characteristics with the head, and the storage characteristics are improved.

On the other hand, Comparative Example 1 in which at least one of the Young's modulus in the longitudinal direction, the Young's modulus in the width direction, the average particle size of the inactive particles, and the number of surface protrusions of the nonmagnetic support is not in the above-mentioned range.
In Comparative Example 3, the tape characteristics, head contact characteristics, and storage characteristics are deteriorated.

Specifically, Examples 1 to 6 and Comparative Example 1
In comparison, Comparative Example 1 in which the Young's modulus in the longitudinal direction is smaller than a predetermined value has a particularly high error rate after storage,
Poor storage characteristics. Thus, in the magnetic recording medium, if the Young's modulus in the longitudinal direction of the non-magnetic support is smaller than a predetermined value, the strength in the longitudinal direction becomes insufficient, and the durability deteriorates. In particular, it can be said that in a magnetic recording medium having a reduced strength in the longitudinal direction, the magnetic tape is likely to be deformed during running and storage characteristics are deteriorated.

Further, when Examples 1 to 6 are compared with Comparative Example 2, the Young's modulus in the width direction is smaller than a predetermined value.
Furthermore, Comparative Example 2 in which the number of surface protrusions is smaller than the predetermined value is particularly poor in tape characteristics and head contact characteristics.

Thus, in the magnetic recording medium, if the Young's modulus in the width direction of the non-magnetic support is smaller than a predetermined value, the strength in the width direction becomes insufficient, the durability is deteriorated, and the storage characteristics are deteriorated. Thus, deformations such as wrinkles and breakage are likely to occur, and the contact with the magnetic head is deteriorated, so that the tape characteristics are deteriorated.

Further, when comparing Examples 1 to 6 with Comparative Examples 2 and 3, it is found that the surface of the nonmagnetic support on which the ferromagnetic metal thin film is formed is not in a satisfactory state. Comparative Example 3 has poor tape properties. Thus, it has been found that the magnetic recording medium is required to have appropriate roughness surface properties from the viewpoint of electromagnetic conversion characteristics, recording / reproducing characteristics, and handling.

When Examples 1 to 6 and Comparative Example 4 are compared, it is found that the nonmagnetic support contains the acicular nonmagnetic pigment on the surface of the nonmagnetic support opposite to the surface on which the ferromagnetic metal thin film is formed. In Examples 1 to 6 in which a back coat layer is formed, the strength is further enhanced as compared with Comparative Example 4 in which a back coat layer made of a normal material containing no acicular nonmagnetic pigment is formed,
It was found that the deformation of the magnetic tape was suppressed. As a result, it can be said that the contact with the magnetic head is improved, the durability is improved, and the storage characteristics are improved.

As is clear from the above results, the magnetic recording medium to which the present invention is applied is characterized in that the longitudinal direction and the width direction of the non-magnetic support have a defined Young's modulus and the number of surface protrusions, and the acicular non-magnetic pigment It has been found that since the back coat layer containing is formed, it has excellent electromagnetic conversion characteristics, recording / reproducing characteristics, running properties, and durability.

Furthermore, the magnetic recording medium to which the present invention is applied is extremely thin and has sufficient strength to enable long-time recording and further increase in capacity. You can say that.

[0113]

As described above in detail, the magnetic recording medium according to the present invention has a Young's modulus in the longitudinal direction and the width direction of a long non-magnetic support made of an aromatic polyamide film which is in the above-mentioned range. And the number of protrusions on the surface of the non-magnetic support on which the ferromagnetic metal thin film is formed is specified, so that the surface properties are optimized and good electromagnetic conversion characteristics and It has both running performance.

Further, in the magnetic recording medium according to the present invention, the backcoat layer containing the acicular nonmagnetic pigment is formed on the surface of the nonmagnetic support opposite to the side on which the ferromagnetic metal thin film is formed. Therefore, the strength is enhanced not only in the thickness direction of the magnetic recording medium but also in the plane direction, and even if the magnetic recording medium is made thinner, necessary and sufficient mechanical strength is secured,
Long-term storage and durability are improved.

Further, since the magnetic recording medium according to the present invention has such a back coat layer formed thereon, the mechanical strength is improved. As much as possible, the contact with the magnetic head can be improved.

Further, in the magnetic recording medium according to the present invention, the thickness of the nonmagnetic support made of an aromatic polyamide film is reduced to 1.0 to 5.0 μm, and the thickness is reduced as described above. Since a necessary and sufficient strength is secured, further increase in capacity and recording for a long time are realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a magnetic recording medium to which the present invention is applied.

FIG. 2 is a configuration diagram illustrating an example of a vacuum evaporation apparatus for forming a ferromagnetic metal thin film.

FIG. 3 is a configuration diagram showing an example of a magnetron sputtering apparatus for forming a carbon protective film.

[Explanation of symbols]

1 magnetic recording medium, 2 nonmagnetic support, 3 ferromagnetic metal thin film, 4 back coat layer

Claims (5)

[Claims] 1. A magnetic recording medium in which a magnetic layer is formed on a long non-magnetic support, wherein the non-magnetic support is made of an aromatic polyamide film, and is disposed in a longitudinal direction of the non-magnetic support. Young's modulus is 1000
kg / mm ² or more, and the Young's modulus in the width direction of the nonmagnetic support is 1300 kg / mm ² or more, and the average particle size in the aromatic polyamide film is 0.02 μm or more.
On the surface of the surface on which the magnetic layer is formed by adding 0.3 μm of inert particles, 10,000 particles / mm ^{2 to} 20 million particles / mm ²
The backcoat layer containing at least a binder and an acicular nonmagnetic pigment is formed on a surface of the nonmagnetic support opposite to a surface on which the magnetic layer is formed. A magnetic recording medium characterized in that: 2. The thickness of the non-magnetic support is from 1.0 to 5.
2. The magnetic recording medium according to claim 1, wherein the thickness is 0 μm. 3. The magnetic recording medium according to claim 1, wherein said magnetic layer is a ferromagnetic metal thin film. 4. The thickness of the back coat layer is from 0.1 to
2. The magnetic recording medium according to claim 1, wherein the thickness is 0.6 μm. 5. The magnetic recording medium according to claim 1, wherein the ratio of the major axis to the minor axis of the acicular nonmagnetic pigment is 10 or more.