JP2000285432A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure both good electromagnetic conversion characteristics and durability even when an aromatic polyamide film of 5 mm thick or less is employed. SOLUTION: The magnetic recording medium is formed by providing a magnetic layer 2 comprising a thin metallic magnetic film on a nonmagnetic support 1A comprising an aromatic polyamide film of 5.0 μm thick or less. A continuous coating 1B of 100 nm thick or less principally comprising a water soluble polymer and fine particles having mean grain of 5-200 nm is formed at least on one side of the nonmagnetic support 1A. The fine particles C form fine protrusions on the surface at a frequency of 5,000,000-50,000,000/mm2 wherein the height of the protrusions is 10-50 nm and the ratio t/d between the thickness t of the continuous coating 1B and the mean grain size d of the fine particles dis in the range of 0.1-4. The nonmagnetic support 1A has Young's modulus of 1000 kg/mm2 or above in the longitudinal direction and Young's modulus of 1300 kg/mm2 or above in the widthwise direction.

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 using a metal magnetic thin film, and more particularly to a magnetic recording medium suitable for use as a video tape for long-time recording or a large-capacity tape streamer.

[0002]

2. Description of the Related Art Conventionally, polyethylene terephthalate films have been mainly used as supports for metal magnetic thin film type magnetic recording media because of their relatively excellent properties such as material strength and dimensional stability. . Especially for home video cassette tapes, for example, 8 mm tape, the thickness is 7 mm.
A polyethylene terephthalate film of about 10 to 10 μm, and a thickness of 5 to 7 μm in a tape streamer or the like.
m is used.

On the other hand, in recent years, among video cassette tapes, especially digital video cassette (DVC) tapes and the like, the size of video cassettes has been reduced, and further long-term recording is desired. Further, in the field of tape streamers, for example, data cartridges called D8 and DDS are desired to have larger capacities.

[0004] In order to achieve long-term recording and large capacity of a magnetic recording medium, it is necessary to make the base film thinner. However, the thinning of the base film causes a problem of lowering the stiffness and deteriorating the skew characteristics of the magnetic recording medium. It is becoming.

In order to satisfy stiffness and skew characteristics, it is necessary to simultaneously satisfy conflicting characteristics such as high strength and low heat shrinkage of the base film. For this reason, measures such as increasing the strength of the polyethylene terephthalate film by a technique such as re-stretching and reducing thermal shrinkage due to aging and the like have been taken. However, the strength of polyethylene terephthalate has reached its limit in recent years as the film thickness has been further reduced, and aromatic polyamide films with high strength and low heat shrinkage have attracted attention as base films for next-generation high-density magnetic recording media. It is becoming.

Further, as long-term recording and large-capacity recording have progressed, the characteristics required for magnetic recording media have become severe. Electromagnetic conversion characteristics are required to be further improved, and requirements for error rates are more severe.

[0007]

In view of the above, it is preferable that the surface of the base film is a mirror surface which is smooth and has no projections. However, since the deposited film formed on such a base film keeps the mirror surface of the base film as it is, the running property of the deposited surface is poor, abrasions are generated, and an error rate frequently occurs due to powder falling of the deposited film. Will be.

The present invention has been made in view of such a conventional situation. When an aromatic polyamide film having a thickness of 5 μm or less is used, the present invention provides a metal magnetic material having both good electromagnetic conversion characteristics and running properties. It is an object of the present invention to provide a magnetic recording medium having a magnetic layer composed of a thin film.

[0009]

The present inventor employs the following means to solve such a problem.

That is, the present invention relates to a magnetic recording medium comprising a magnetic layer comprising a metal magnetic thin film provided on a nonmagnetic support, wherein the nonmagnetic support is an aromatic polyamide film having a thickness of 5.0 μm or less. A water-soluble polymer on at least one side of the non-magnetic support and having an average particle size of 5 to 200.
A continuous film having a thickness of 100 nm or less mainly composed of fine particles of nm is formed.

With the magnetic recording medium according to the present invention having the above-described configuration, long-time recording and large capacity can be achieved.

Further, by controlling the thickness of the continuous film, the average particle size of the fine particles in the continuous film, and the amount added, good characteristics regarding the electromagnetic conversion characteristics and running durability of the magnetic recording medium can be secured.

[0013]

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

In the magnetic recording medium to which the present invention is applied, as shown in FIG. 1, a continuous film 1B is formed on a nonmagnetic support base 1A, and a magnetic layer 2 made of a metal magnetic thin film is formed on the surface of the continuous film 1B. Are formed.

The continuous coating 1B on the nonmagnetic support 1A has a thickness of 100 nm or less and an average particle size of 5 to 2 nm.
Fine surface projections are formed by the fine particles C of 00 nm.

The frequency of the fine surface projections is 5 to 5 million.
It is preferably in the range of 10 million / mm ² , the height is 10 to 50 nm, and the ratio t / d of the thickness t of the continuous coating 1B to the average particle size d of the fine particles C is 0.1. It is preferably in the range of 1-4.

Further, the contact with the magnetic head is improved by setting the Young's modulus in the longitudinal direction of the nonmagnetic support base 1A to 1000 kg / mm ² or more and the Young's modulus in the width direction to 1300 kg / mm ² or more. Can be.

The thickness of the continuous coating 1B is 100 nm or less, and more preferably in the range of 10 to 50 nm. Continuous coating 1
If the thickness of B exceeds 100 nm, the surface roughness becomes coarse, causing an increase in noise and a decrease in electromagnetic conversion characteristics.

The average particle size of the fine particles C is in the range of 5 to 200 nm, more preferably in the range of 10 to 50 nm. When the average particle size of the fine particles C is less than 5 nm, the running property of the magnetic recording medium is deteriorated, and good electromagnetic conversion characteristics cannot be obtained due to generation of scratches, powder falling of a deposited film, etc., and an error rate frequently occurs. Will be. If the average particle size of the fine particles C exceeds 200 nm, the spacing with the magnetic head increases, and the electromagnetic conversion characteristics deteriorate.

As described above, the frequency of the fine surface projections on the surface of the continuous coating 1B is 5 to 50 million / m
formed in the range of m ² , 8 million to 20 million pieces / mm
A range of ² is more preferred. 8 surface protrusions on continuous coating 1B
If the number is less than 100,000 / mm ² , the runnability of the magnetic recording medium deteriorates, and good electromagnetic conversion characteristics cannot be obtained due to generation of scratches, powder fall of a deposited film, and the like, and an error rate frequently occurs. . On the other hand, when the number of surface projections on the surface of the continuous coating 1B exceeds 50 million / mm ² , the spacing with the head increases, and the electromagnetic conversion characteristics deteriorate.

The height of the surface projections on the surface of the continuous coating 1B is formed in the range of 10 to 50 nm,
Is more preferable. When the height of the surface projections of the continuous coating 1B is less than 10 nm, the running property of the magnetic recording medium deteriorates. Also, the height of the surface projections of the continuous coating 1B is 50 nm.
Exceeding this range is not preferable because spacing with the magnetic head increases and electromagnetic conversion characteristics deteriorate.

The ratio t / d of the thickness t of the continuous coating 1B to the average particle size d of the fine particles C is 0.1 to 4.
It is preferably in the range of 0, and more preferably in the range of 1.0 to 3.0. The thickness t of the continuous coating 1B;
If the ratio t / d to the average particle diameter d of the fine particles C is less than 1.0, the fine particles C fall off, resulting in frequent occurrence of an error rate and deterioration of the running property. On the other hand, when t / d exceeds 4.0, the height of the fine surface projections caused by the fine particles C becomes insufficient, and the runnability of the magnetic recording medium deteriorates.

As described above, in the magnetic recording medium to which the present invention is applied, a continuous film 1B mainly composed of a water-soluble polymer and fine particles is formed on a non-magnetic support base 1A, and the thickness of the continuous film 1B and the fine particles C By controlling the average particle diameter, the height and frequency of the fine surface projections on the surface of the continuous coating 1B, and the ratio t / d between the thickness t of the continuous coating 1B and the average particle diameter d of the fine particles to the above-mentioned ranges, excellent results are obtained. Traveling durability and electromagnetic conversion characteristics can be ensured.

Here, the above characteristics are measured by the following method.

A. Surface frequency of surface projections of the projection frequency 5,000,000 to 50,000,000 pieces / mm continuous film 1B formed in ^two ranges, a scanning electron microscope (SE
M), which is an ultra-high resolution cold FE-SEM “S-900” (trade name) manufactured by JEOL Ltd.
Was counted at an acceleration voltage of 20 kV and a magnification of 30,000 or more, and the number was converted to the number per 1 mm ² .

B. Surface protrusion height Digital Instruments
using an atomic force microscope (AFM) manufactured by J. Instruments (Trimants) under the conditions of a scan size of 5 μm × 5 μm, a sampling number of 400 points, and a scan rate of 4.34 Hz, and the height of each of the ten protrusions is measured. Then, an average value of ten protrusions was calculated and used as the protrusion height.

C. The thickness of the continuous coating 1B was calculated from the frequency of the fine surface protrusions and the amount of the water-soluble polymer added.

D. The Young's modulus was measured at a temperature of 25 ° C. and a relative humidity of 55% using a Tensilon type tensile tester.

In the present invention, as the aromatic polyamide film used for the nonmagnetic support substrate 1A, particularly preferred are those having the chemical formula (I) or the chemical formula (II) in the following chemical formula 1, or a copolymer thereof. The film was formed using a polyamide resin.

[0030]

Embedded image

The aromatic polyamide may be copolymerized or friendled with a polymer other than the above components as long as the amount is not more than about 20% by weight.

When a film is produced from these polymers, dimethylacetamide, dimethylformamide, n-methylpyrrolidone, hexamethylsulfonamide, γ-butyrolactone, tetramethylurea, dioxane, etc., or a mixed solvent thereof, or A solvent to which an inorganic salt such as lithium chloride, calcium chloride, lithium carbonate, lithium nitrate or the like is added as a neutralization product of the polymerization stock solution is used.

Using such a film-forming solvent, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 2-nitro-p-phenylenediamine, 2-chloro-p-phenylenediamine, , 4'-
Aromatic diamines such as diaminobiphenyl, 3,3′-chlorobenzine and terephthalic acid chloride, 2-chloroterephthalic acid chloride, terephthalic acid hydrazide;
An aromatic polyamide film is obtained by a technique such as solution molding of an aromatic polyamide resin obtained by polymerization or bonding of aromatic dicarboxylic acids such as p-aminobenzoic acid hydrazide and p-aminobenzoic acid chloride.

The aromatic polyamide film obtained as described above is stretched in the length 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. As a result, a non-magnetic supporting substrate having a thickness of 2.0 to 5.0 μm is obtained. By setting the thickness and strength of the non-magnetic support base to these levels, the thickness of the magnetic recording medium can be reduced, and the recording can be performed for a long time.

On the surface of the nonmagnetic support substrate on which the magnetic layer is formed by the metal magnetic thin film, a continuous coating mainly composed of a water-soluble polymer and fine particles is provided on the nonmagnetic support substrate. 50 surface protrusions with a height of 10 to 50 nm
0 to 50 million pieces / mm ^{2 are} formed.

The fine particles include, for example, silica,
Calcium carbonate, titanium dioxide, alumina, kaolin,
Inorganic particles such as talc, graphite, feldspar, molybdenum dioxide, carbon black, barium nitrate, polystyrene, polymethyl methacrylate, methyl methacrylate copolymer, cross-linked methyl methacrylate copolymer, polytetrafluoroethylene, polyvinylidene fluoride And organic particles such as polyacrylonitrile, benzoguanamine resin, etc., and it is preferable to use particles of colloidal silica or a crosslinked polymer from which spherical particles can be easily obtained.

On the other hand, the water-soluble polymer means a polymer which is dissolved in water or becomes a suspension or an emulsion by adding a surfactant or the like, if necessary. Further, those having a high molecular weight by crosslinking or the like are also included. Examples of these water-soluble polymers include starch, cellulose derivatives such as methylcellulose and hydroxyethylcellulose, alginic acid, gum arabic, gelatin, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, polyethylene oxide,
Examples include polyvinylpyrrolidone, polyvinyl chloride, polystyrene silicone resin, urethane resin, acrylic resin, ether resin, epoxy resin, and ester resin.

The silicone resin contains, as a main component, a polyorganosiloxane in which the siloxane substituent is mainly a methyl group. In addition to the methyl group, a hydroxyl group, α-methylstyrene group, oxyalkylene group, unsaturated group, chlorophenyl group , Trifluoropropyl group, epoxy group,
Those in which a vinyl group, a carboxylic acid group, a phenyl group, an amino group, a cyanoethyl group, an α-olefin group, a hydroxyl group, a mercapto group, a halogenated alkyl group or the like are partially introduced as a substituent can also be used. Those having an epoxy group, amino group, hydroxyl group or other functional terminal group at the terminal are preferred.

The organopolysiloxane can be emulsified or made water-soluble in an aqueous medium, or made water-soluble by a known production method such as an aqueous emulsion obtained by emulsion polymerization of silane or siloxane.

A curing agent can be added to the aqueous polymer used in the present invention, if necessary.

The main components of the urethane resin are as follows:
An aqueous urethane resin comprising a polyisocyanate, a polyol, a chain extender, a crosslinking agent and the like can be used. In making the aqueous solution aqueous, it is a general technique to use a polyisocyanate, a polyol and a chain extender in which a hydrophilic group is introduced. Further, an unreacted isocyanate group of the polyurethane may be reacted with a compound having a hydrophilic group.

Examples of the ether resin include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, a copolymer of ethylene oxide and propylene oxide, and a copolymer of ethylene oxide and tetrahydrofuran.

As the ester resin, terephthalic acid,
Aromatic dicarboxylic acids such as isophthalic acid and their ester-forming derivatives, aliphatic carboxylic acids such as adipic acid, azelaic acid and sebacic acid and their ester-forming derivatives, ethylene glycol, propylene glycol, 1,4- Reaction products with diols such as butanediol, 1,4-cyclohexanedimethanol, diethylene glycol, polyethylene glycol and the like can be used. In making the aqueous solution, it is a well-known method to copolymerize a compound having a sulfonic acid group with the above components, and sulfoisophthalic acid, sulfoterephthalic acid,
Alkali metal salts or alkaline earth metal salts such as 4-sulfonaphthalene-2,7-dicarboxylic acid and ester-forming derivatives thereof are often used.

For the purpose of stabilizing the running of the tape,
An organic substance which is the same as the inert particles or the aromatic polyamide resin used as a raw material of the nonmagnetic support substrate and which is insoluble in the solvent during the solution molding described above may be added to the nonmagnetic support substrate 1A. . The average particle size of the particles is 20 to 300 nm, and the frequency of surface projections formed by the particles is 1 to
The range of 1 million pieces / mm ² is preferable.

In this case, the nonmagnetic support substrate 1 is a single-layer film. However, for the purpose of improving the handling during the film formation and the tape manufacturing process, the two-layer or the three-layer having the roughened back surface is used. It may be a composite film having a layer structure or more.

As the metal magnetic thin film forming the magnetic layer 2 of the magnetic recording medium, for example, a metal magnetic thin film mainly composed of Co, Ni, Fe or the like, or a metal magnetic thin film mainly composed of an alloy thereof is used. .

The thickness of the magnetic layer 2 made of the metal magnetic thin film is preferably 0.05 to 0.2 μm, and 0.1 to 0.2 μm.
μm is more preferable. That is, when the thickness of the magnetic layer 2 is reduced, the self-demagnetization loss and the like are reduced, and as described above, the total thickness of the magnetic recording medium is reduced in addition to the thickness of the nonmagnetic support base. Since the total length of the magnetic recording medium becomes longer, long-time recording and large capacity can be achieved.

As a means for forming the metal magnetic thin film, a vacuum evaporation method or the like in which a ferromagnetic metal material is heated and evaporated under vacuum to deposit on a non-magnetic support substrate is widely used. In addition, a so-called ion plating method in which a ferromagnetic metal material is evaporated in a discharge, a sputtering method in which a glow discharge is caused in an atmosphere containing argon as a main component, and an atom on a target surface is knocked out by generated argon ions, etc. P
VD technology may be used.

Further, in this metal magnetic thin film, an atmosphere in which the film is formed by an oxygen gas dominant film for the purpose of improving the adhesion strength to the non-magnetic support base or improving the corrosion resistance and abrasion resistance of the ferromagnetic thin film itself. It is good to do it below.

A back coat layer may be provided on the surface of the non-magnetic support base 1A opposite to the surface on which the magnetic layer 2 is formed, for the purpose of improving running properties and enhancing durability.
For the back coat layer, conventionally known materials can be used.For example, a material in which a non-magnetic pigment such as carbon or calcium carbonate is dispersed in a binder such as polyurethane or vinyl chloride-vinyl acetate copolymer is used. Can be.

Further, a hard carbon film may be provided on the surface of the magnetic layer 2 made of a metal magnetic thin film for the purpose of improving the durability and weather resistance of the magnetic recording medium. The hard carbon film has a thickness of 6 to 10 that does not affect spacing and tape characteristics by a sputtering method, a chemical vapor deposition (CVD) method, or the like.
It is preferably formed to a thickness of about nm. Further, by allowing the lubricant to be present, it is possible to enhance the running property based on the shape of the particulate protrusions of the magnetic material.

Also, the front and back surfaces of the magnetic recording medium and their vicinity, or in the magnetic layer 2 (voids in the ferromagnetic metal thin film), the interface between the nonmagnetic support base 1A and the magnetic layer 2, the nonmagnetic support base Various additives such as a rust preventive and an antistatic agent may be present in the inside of the device 1 if necessary.

[0053]

EXAMPLES The present invention will be described below with reference to specific examples, but it goes without saying that the present invention is not limited to these examples.

Example 1 First, a nonmagnetic support base was prepared as follows.

0.9 g of dehydrated n-methylpyrrolidone
2-Chloro-p-phenylenediamine corresponding to a molar ratio and 4,4'-diaminophenylsulfone corresponding to a 0.1 molar ratio were dissolved by stirring, cooled, and then dissolved in 0.1 ml.
Terephthalic acid chloride corresponding to a 7 mol ratio was added and stirred for about 2 hours. Thereafter, sufficiently purified calcium hydroxide was added and stirred to obtain an aromatic polyamide solution.

This aromatic polyamide solution was uniformly cast on a surface-polished metal drum at 30 ° C. and dried in an atmosphere at 120 ° C. for about 10 minutes to obtain an aromatic polyamide film.

The film was peeled off from the drum,
The film was stretched 1.1 times in the length direction while continuously immersed in a water tank for about 30 minutes. Further, the film was introduced into a tenter and stretched 1.3 times in the width direction at 320 ° C., and the Young's modulus in the longitudinal direction was 1000 kg / mm ² , the Young's modulus in the width direction was 1300 kg / mm ² , and the thickness was 4 μm. A non-magnetic support base was obtained.

The surface of the non-magnetic support substrate has a particle size of 20 n
A polymer film was formed by applying 4.5 g of a coating solution containing 0.005 parts of m ₂ SiO ₂ per m ² and drying.

Next, a magnetic layer was formed on the non-magnetic support thus manufactured by a continuous oblique evaporation method using a continuous winding evaporation apparatus.

This continuous winding type vapor deposition apparatus has an internal
A crucible containing a metal magnetic thin film deposition source (Co) is disposed in a vacuum chamber in a vacuum state of about 0 ⁻³ Pa, facing the cooling can.

The cooling can is cooled to -20 ° C.
It is rotating in a predetermined direction. Then, the nonmagnetic support base is unwound from the supply roll at a feed speed of 50 m / min.
It moves along the peripheral surface of the cooling can and is taken up by a take-up roll. A guide roller is disposed between the supply roll and the cooling can, a guide roller is disposed between the cooling can and the take-up roll, and the non-magnetic support base is cooled from the supply roll with a predetermined tension. , And between the cooling can and the take-up roll.

The above-mentioned evaporation source is irradiated with an electron beam from an electron beam source at an accelerated rate. The deposition source irradiated with the electron beam at an accelerated irradiation is heated and evaporated, and adheres (deposits) on a non-magnetic support substrate running along the peripheral surface of the cooling can. At this time, since a deposition-preventing plate having a shutter that can be adjusted in position is disposed between the vapor deposition source and the cooling can, vapor-deposited particles enter the nonmagnetic support base at a predetermined angle. It is supposed to. Therefore, a magnetic layer is formed on the surface of the non-magnetic support substrate with the magnetic particles oriented obliquely to the surface of the non-magnetic support substrate. Here, the thickness of the magnetic layer was 180 nm.

Further, when depositing such a metal magnetic thin film, oxygen gas is supplied at a flow rate of 2 L / min from the oxygen gas inlet (not shown) to the surface of the non-magnetic support, so that the magnetic properties and durability of the metal magnetic thin film are improved. Also, the weather resistance is improved.

Next, a hard carbon film was formed on the magnetic layer by a sputtering method. The sputtering conditions were as follows: the degree of vacuum was 0.8 Pa in an Ar gas atmosphere, the tape feeding speed was 5 m / min,
The thickness of the hard carbon film was 5 nm.

Next, a 0.1% by weight solution of an organic rust inhibitor was applied to the hard carbon film using a coating machine using a gravure roll, and dried with a dryer at 100 ° C. Thereafter, a 0.5% by weight solution mainly composed of an organic substance composed of a perfluoropolyether derivative as a lubricant was similarly applied and dried with a gravure roll to form a top coat layer.

Next, a back coat layer (thickness: 0.5 μm) mainly composed of carbon and using a vinyl chloride resin as a binder was formed on the back surface of the nonmagnetic support base.

The magnetic recording medium raw material thus obtained was cut into a width of 8 mm to prepare a sample tape.

Examples 2 to 5 In Examples 2 to 5, the basic structure was the same as in Example 1, and the height and density of the surface projections were adjusted by adjusting the particle size and the amount of SiO ₂ contained in the polymer film. These are different from the first embodiment.

Example 6 In Example 6, the stretching conditions at the time of forming the non-magnetic support substrate were changed so that the Young's modulus in the longitudinal direction was 1200 kg / mm ² and the Young's modulus in the width direction was 1600 kg / mm ^2. A magnetic recording medium was manufactured under the same conditions as in Example 1.

Example 7 In Example 7, a nonmagnetic support was used in which a 100-nm Si
A magnetic recording medium was produced under the same conditions as in Example 1 by adding O ₂ to form 50,000 protrusions / mm ² on the surface.

Examples 8 to 12 In Examples 8 to 12, the basic structure was the same as in Example 1, and the particle size of SiO ₂ contained in the polymer film was 20 nm.
The thickness of the continuous film was different from that of Example 1 by adjusting the addition amount so that the number of surface protrusions became 15 million / mm ² .

Comparative Examples 1 to 5 Comparative Examples 1 to 5 have the same basic structure as that of Example 1, and adjust the particle size and the amount of SiO ₂ contained in the polymer film to increase the height and density of the surface projections. These are different from the first embodiment.

Comparative Example 6 In Comparative Example 6, a magnetic recording medium was produced under the same conditions as in Example 7 except that the polymer coating was not provided on the nonmagnetic support.

Comparative Example 7 In Comparative Example 7, the stretching conditions at the time of forming the non-magnetic support substrate were changed so that the Young's modulus in the longitudinal direction was 400 kg / mm ² and the Young's modulus in the width direction was 600 kg / mm ^2. The magnetic recording medium was manufactured under the same conditions as in Example 1 except for the above.

COMPARATIVE EXAMPLE 8 Comparative Example 8 shows that a non-magnetic support substrate has a Si particle diameter of 100 nm.
In Example 7, in which O ₂ was added to form 50,000 protrusions / mm ² on the surface, the stretching conditions during the formation of the non-magnetic support substrate were changed so that the Young's modulus in the longitudinal direction was 400 kg / mm ^2. ,
The magnetic recording medium was manufactured under the same conditions except that the Young's modulus in the width direction was 600 kg / mm ² .

Evaluation 1. Tape Characteristics The evaluation of the characteristics of the magnetic recording medium in this example was performed by using a modified AIT drive SDX-S300C (trade name) manufactured by Sony Corporation. Recording is relative speed 1
The measurement was performed at 0.04 m / sec and the shortest recording wavelength of 0.35 μm.

2. Durability With respect to the sample tapes of Examples 1 to 12 and Comparative Examples 1 to 8, recording and reproduction were repeated for a tape length of 10 cm, and the number of times until an output could not be obtained was counted. 500
Zero or more was allowed.

3. Error Rate In the magnetic tape for data, a decrease in electromagnetic conversion characteristics due to surface shaving or the like is detected as an error rate. Therefore, the error rates of these sample tapes were evaluated. The number of block error rates was allowed to be 10 ^-2 or less.

4. Friction characteristics The friction coefficient between the initial stage and the guide pin [stainless steel (SUS): 0.2S] after sliding repeatedly 1000 times was examined. The measurement was performed in an environment under normal temperature and normal humidity (25 ° C., 55%) under the conditions of a load of 10 g and a sliding speed of 5 mm / sec. The coefficient of friction after 1000 passes was allowed to be 0.4 or less.

Tables 1 and 2 show the designs of the examples and comparative examples.
Table 3 and Table 4 show the evaluation results of Examples and Comparative Examples, respectively.

[0081]

[Table 1]

[0082]

[Table 2]

[0083]

[Table 3]

[0084]

[Table 4]

From the results shown in Tables 3 and 4, the nonmagnetic support was a film having a thickness of 5.0 μm or less, and had a Young's modulus in the longitudinal direction of 1,000 kg / mm ² or more and a Young's modulus in the width direction of 130.
0 kg / mm ² or more, and fine surface protrusions on the surface forming the magnetic layer are formed by fine particles having an average particle diameter of 5 to 200 nm, and the surface protrusions have a frequency of at least 50 nm.
It is in the range of 100,000 to 50,000,000 pieces / mm ² and the height is 10
In Examples 1 to 7 in which the ratio t / d between the thickness t of the continuous film and the average particle size d of the fine particles is in the range of 0.1 to 4, all of which are excellent. The obtained electromagnetic conversion characteristics, running durability and the like were obtained.

In Example 7, SiO ₂ particles having an average particle diameter of 100 nm were added to a non-magnetic support substrate, and 1 μm was added to the particles.
Although 50,000 protrusions per mm ² are formed on the non-magnetic support, each setting is within an appropriate range, so that it has excellent characteristics such as electromagnetic conversion characteristics and running durability. Understand.

In Examples 8 to 12, the particle size of the fine particles in the continuous film was 20 nm, and the frequency of surface projections was 1 mm ^2.
Although the thickness was set to 5 million and the thickness of the continuous film was changed, since each setting was within an appropriate range, it was found that characteristics such as electromagnetic conversion characteristics and running durability were excellent.

On the other hand, in Comparative Example 1, although the thickness of the continuous film, the frequency of fine surface projections, and t / d were within appropriate ranges, the projection height was insufficient because the average particle size of the fine particles was small. , And good results regarding durability and friction were not obtained. Further, the initial error rate is relatively good, but after 1000 passes, the shaving becomes remarkable and increases.

In Comparative Example 2, the average particle size of the fine particles and the frequency of the fine protrusions were within the appropriate ranges, but the projection height was insufficient due to the thick continuous film, and the durability and friction were poor. ing. Further, since the surface roughness is rough, good results cannot be obtained with respect to the error rate.

Comparative Example 3 is inferior in durability and friction characteristics because the frequency of protrusions is too small. Further, the initial error rate is excellent, but after 1000 passes, the scraping is remarkable and increases.

In Comparative Example 4, since the thickness of the continuous film was small with respect to the average particle size of the fine particles, the fine particles were easily dropped, so that good results were obtained in terms of durability, friction and error rate. Not done.

When the average particle size of the fine particles is large as in Comparative Example 5, the surface becomes rough and the error rate is inferior from the beginning. Further, since the falling of the fine particles becomes remarkable, good results cannot be obtained with respect to durability.

In Comparative Example 6, since no fine surface projections were provided, the durability was extremely poor and the friction was high. Further, the error rate also increases significantly.

In Comparative Example 7, the Young's modulus in the vertical direction was 400 k.
g / mm ² , except that the Young's modulus in the width direction was set to 600 kg / mm ² , but the basic configuration was the same as in Example 1, but the Young's modulus was too small and the contact with the magnetic head was insufficient. Good results cannot be obtained for durability, error rate and the like.

In Comparative Example 8, the Young's modulus in the vertical direction was 400 k.
The basic configuration is the same as that of the seventh embodiment except that g / mm ² and the Young's modulus in the width direction are 600 kg / mm ² .
As in Comparative Example 7, since the Young's modulus in the vertical and width directions is too small, the contact with the magnetic head becomes insufficient, and good results in durability and error rate cannot be obtained.

[0096]

As is apparent from the above description, according to the magnetic recording medium of the present invention, it is possible to achieve both good electromagnetic conversion characteristics and durability, and to satisfy the requirements for the error rate. Can be.

[Brief description of the drawings]

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

[Explanation of symbols]

1A Nonmagnetic support base, 1B continuous coating, 2 magnetic layer (metal magnetic thin film), C fine particles

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C09D 7/12 C09D 7/12 Z 201/00 201/00 G11B 5/73 C08J 5/18 CFG // C08J 5/18 CFG G11B 5/704 C08L 77:00 F-term (reference) 4F071 AA56 AF20Y AH14 BB08 BC01 4F100 AA20H AA37 AB01A AB15 AK01C AK15 AK17 AK47B AK54 BA03 BA05 BA07 BA10A BA10B CA14 CA23C DD07E01 J01 GB01J01 GB01 JM02A YY00A YY00B YY00C YY00H 4J038 BA051 BA111 BA171 BA181 CC032 CD031 CD112 CD122 CE021 CG001 CG111 CG142 CG162 CG171 CH032 CK031 DA172 DB001 DD001 DF001 DF011 DL031 HA026 HA216 CB001 HA03 HA01 HA03 HA01 HA456

Claims (3)

[Claims] 1. A magnetic recording medium comprising a nonmagnetic support and a magnetic layer made of a metal magnetic thin film provided on the nonmagnetic support, wherein the nonmagnetic support is an aromatic polyamide film having a thickness of 5.0 μm or less; A magnetic recording medium comprising a magnetic support and a continuous film having a thickness of 100 nm or less mainly composed of a water-soluble polymer and fine particles having an average particle diameter of 5 to 200 nm formed on at least one surface of the magnetic support. 2. Fine surface projections are formed by the fine particles, and at least the frequency thereof is 5,000,000 to 500,000,000.
It is in the range of 100,000 pieces / mm ² and the height is 10 to 50 n.
2. The magnetic recording medium according to claim 1, wherein a ratio t / d between the thickness t of the continuous film and the average particle diameter d of the fine particles is in a range of 0.1 to 4. 3. . 3. The magnetic recording according to claim 2, wherein the non-magnetic support has a Young's modulus in a longitudinal direction of 1000 kg / mm ² or more and a Young's modulus in a width direction of 1300 kg / mm ² or more. Medium.