JP2001344736A - Magnetic recording medium and magnetic recording method - Google Patents

Abstract

[PROBLEMS] To provide a large-capacity magnetic recording medium and a magnetic recording method suitable for high-density recording used in audio equipment, video equipment and various information equipment. SOLUTION: In a magnetic recording medium having a non-magnetic substrate, a magnetic layer and a reinforcing layer, the magnetic layer is a ferromagnetic metal thin film having a thickness of 120 nm or less, and the reinforcing layer is a non-magnetic metal film having a thickness of 480 nm or less. By using a magnetic metal oxide layer, a magnetic recording medium suitable for recording signals using a magnetic head having a gap length of 0.10 to 0.25 μm is obtained.

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 used in information equipment, audio equipment and video equipment, which requires a high recording density, and a magnetic recording method for recording a signal on the magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, the technical development of highly functional thin films has been remarkable, and their application fields have been diversified. A magnetic recording medium is an example in which a highly functional thin film is used. In a magnetic recording medium, a magnetic layer (that is, a recording layer) is regarded as a kind of a high-performance thin film, and its properties are closely related to an improvement in magnetic recording density.

A magnetic recording medium in which the magnetic layer is a highly functional thin film is referred to as a metal thin film type magnetic recording medium or a high density magnetic recording medium in which the magnetic layer is formed of a metal thin film formed by depositing a ferromagnetic metal. Magnetic recording media. This magnetic recording medium is more suitable for high-density recording than a conventional coating type magnetic recording medium because the magnetic layer has no inclusion such as a binder.

[0004] A conventional coating type magnetic recording medium is, specifically, a method of applying a γ-Fe ₂ O ₃ powder, a CrO ₂ powder, a pure iron powder, etc. together with a binder such as a resin on a polymer film to obtain a magnetic recording medium. It refers to a layer formed. The coating type magnetic recording medium is generally used as an audio or video tape.

On the other hand, a metal thin film type magnetic recording medium is made of Fe, Co, Ni by vacuum evaporation, ion plating, sputtering or cluster ion beam evaporation.
And / or a magnetic metal such as Cr alone or in the form of an alloy is deposited on a polymer film or a glass substrate to form a magnetic layer. Metal thin-film magnetic recording media have already been put into practical use as video tapes having a magnetic layer formed by oblique incidence evaporation and hard disks having a magnetic layer formed on a glass substrate by sputtering.

An example of a method for manufacturing a metal thin film type magnetic recording medium will be described with reference to FIG. FIG. 8 schematically shows a method of forming a magnetic metal thin film as a recording layer on a non-magnetic substrate by a vacuum evaporation method. The vacuum evaporation method shown in FIG. 8 is also called a continuous winding vacuum evaporation method, is excellent in productivity, and is an effective production method as a practical mass production method. In FIG. 8, the non-magnetic substrate is a polymer film (40
1). Generally, fine particles made of SiO ₂ or the like are dispersed and fixed to one surface of a polymer film.
The fine particles impart irregularities to the surface of the magnetic recording medium on the side of the magnetic layer, thereby improving the running property of the magnetic recording medium.

[0007] The polymer film (401) is set on a feed shaft (402), is continuously fed therefrom, passes through a cooling drum (406), and is taken up by a take-up shaft (410). At this time, the ferromagnetic metal (414) is dissolved and evaporated by the electron beam (412), and deposited on the surface of the polymer film (401) from below. Unnecessary magnetic metal is shielded during deposition (416, 42
Cut at 0). When oxygen is contained in the magnetic layer, oxygen is supplied from the nozzle (418). After the vacuum deposition of the magnetic layer is completed, if necessary, a protective layer and a lubricant layer are formed on the magnetic layer, and a back coat is formed on the surface of the polymer film opposite to the surface on which the magnetic layer is formed. Form a layer. Then, slitting is performed to obtain a tape-shaped magnetic recording medium.

FIG. 9 schematically shows a sectional view in the thickness direction of a tape-shaped magnetic recording medium (hereinafter, also referred to as a “vapor-deposited tape” or “ME tape”) obtained by this method. In the illustrated magnetic recording medium, fine particles (2) are dispersed and fixed on one surface of the nonmagnetic substrate (1), and a magnetic layer (3) is formed on the surface where the fine particles (2) are present. A protective layer (4) and a lubricant layer (5) on the magnetic layer (3).
Are formed. Therefore, the surface of the magnetic recording medium (the surface of the lubricant layer (5)) has irregularities provided by the fine particles (2). A back coat layer (7) is formed on the surface of the non-magnetic substrate opposite to the surface on which the magnetic layer is formed.

In general, a metal thin film type magnetic recording medium is thinner than a coating type magnetic recording medium, so that a magnetic recording medium product (for example, ME tape) having a large recording capacity can be provided. However, there is a strong demand for performance improvement of magnetic recording media, and it is still desired to be able to accommodate more magnetic recording media (for example, magnetic tape) in a case of a predetermined size and record more information. . Therefore, attempts have been made to reduce the thickness of the magnetic recording medium.

An effective method of reducing the thickness of a magnetic recording medium is to reduce the thickness of a non-magnetic substrate (for example, a polymer film) which occupies a large part of the thickness of the magnetic recording medium. However, when the thickness of the non-magnetic substrate is reduced, the rigidity (stiffness) tends to decrease, which may cause a practical problem.

The rigidity of a non-magnetic substrate is determined by its Young's modulus as E,
When the thickness is t, it is represented by E × t ³ . Therefore, when the thickness of the non-magnetic substrate is reduced, the rigidity of the non-magnetic substrate, and eventually the entire magnetic recording medium, is significantly reduced.

For example, when the magnetic recording medium is a tape,
If the rigidity is low, the head contact of the tape tends to be poor. If the head contact is poor, the electromagnetic conversion characteristics are degraded, the reproduction output is degraded, the linear characteristics are degraded, and the like, and a problem that good recording and reproduction cannot be performed may occur.

[0013] The rigidity of the magnetic recording medium also affects the durability against repeated use. In a magnetic recording medium having low rigidity, deformation, elongation, wrinkling, and breakage are apt to occur during repeated use, and as a result, the reproduction output decreases or fluctuates, and stable recording / reproduction characteristics cannot be obtained. Sometimes.

Further, in the case where the magnetic recording medium is a magnetic tape, if the thickness of the polymer film as the non-magnetic substrate is reduced, the surface of the polymer film is subjected to a thermal load at the time of vapor deposition, so that thermal contraction is likely to occur. Become. The heat shrinkage of the polymer film deforms the magnetic tape, causing the magnetic tape to bend, curl, and the like. Deformation of the magnetic tape also causes the head of the tape to deteriorate, leading to deterioration in electromagnetic conversion characteristics, reduction in reproduction output, reduction in linear characteristics, and the like.

In order to solve such problems, for example, Japanese Patent Application Laid-Open No. H10-105944 discloses a backcoat layer comprising at least two thin films on a surface of a non-magnetic substrate opposite to the surface on which the magnetic layer is formed. Is formed by vacuum film formation,
By tilting the columns of the layer farthest from the non-magnetic substrate and the layer adjacent to the non-magnetic substrate in the back coat layer in opposite directions, the running performance of the magnetic recording medium can be stabilized and the head touch can be improved. I'm trying.

In JP-A-11-283234, a magnetic layer is formed on a long polyethylene naphthalate film (PEN) in which Young's modulus and heat shrinkage are regulated, and a binder and a needle are provided on the opposite side of the magnetic layer. There has been proposed a magnetic recording medium having a back coat layer, a metal thin film, a plasma polymer layer, or an electron beam polymer layer containing a non-magnetic pigment. In this magnetic recording medium, even if the thickness of the magnetic recording medium is small, mechanical strength such as rigidity is sufficiently ensured by the back coat layer or the like. Thereby, the deformation of the magnetic recording medium is suppressed as much as possible, and the contact between the magnetic recording medium and the magnetic head is maintained in a good state.

[0017]

As described above, various attempts have been made to increase the recording capacity by reducing the thickness of the non-magnetic substrate constituting the magnetic recording medium. However, there is a limit to the increase in capacity that depends only on thinning, and improving the recording density of the magnetic recording medium itself, that is, making the magnetic recording medium suitable for higher-density recording, is also required to increase the capacity. Is essential. Improvement of the recording density of the magnetic recording medium is also required from the viewpoint of recording and reproducing with good sound quality and image quality.

The recording density of the magnetic recording medium is increased by increasing the recording frequency and decreasing the track width. If the relative speed between the magnetic head and the magnetic recording medium is constant, the recording frequency can be made higher by shortening the recording wavelength. High-density recording performed at a high recording frequency can be performed by using a high-sensitivity head. For example, a gap length of 0.1 to
When a 0.25 μm MR type (Magnetoresistance) head is used, a recording frequency of about 1 kHz and a 50 M
It is possible to record in the range up to the recording frequency of Hz.

When the recording wavelength is shortened, a change occurs in the thickness loss of the reproduction output, which may have an undesirable effect on the quality of the reproduction signal. The thickness loss refers to a decrease in reproduction output caused by the thickness of the magnetic layer being larger than the recording wavelength. In general, when the thickness of the magnetic layer is the same, the thickness loss tends to increase as the recording wavelength decreases. Therefore, it can be said that it is necessary to reduce the thickness of the magnetic layer in order to improve the recording density. For example, when the above-described MR head is used, the thickness of the magnetic layer is equal to the thickness of the magnetic layer (about 180
nm) or less is preferred for obtaining a good reproduction output (for example, CN ratio).

However, reducing the thickness of the magnetic layer also reduces the rigidity of the entire magnetic recording medium. In a magnetic recording medium, the magnetic layer functions as a recording layer and also functions as a kind of reinforcing layer. Therefore, the thickness of the magnetic layer affects the rigidity of the entire magnetic recording medium, as does the thickness of the nonmagnetic substrate. Therefore, for example, when the magnetic recording medium is a magnetic tape, if the thickness of the magnetic layer is small,
The contact between the head and the tape becomes poor, and the sliding of the tape at the head becomes insufficient.

The present invention has been made in view of the above circumstances, and is intended to provide a magnetic recording medium having a thin magnetic layer and a thin magnetic layer suitable for high-density recording using an MR head or the like having a small gap length. It is an object of the present invention to provide the overall rigidity (stiffness) without lowering it.

[0022]

According to the present invention, there is provided a magnetic recording medium having a non-magnetic substrate, a magnetic layer, and a reinforcing layer, wherein the magnetic layer has a thickness of 120 nm or less. Is a ferromagnetic metal thin film having
Provided is a magnetic recording medium which is a nonmagnetic metal oxide layer having a thickness of not more than nm.

In the magnetic recording medium of the present invention, the magnetic layer is a thin ferromagnetic metal thin film having a thickness of 120 nm or less. Therefore, by using the magnetic recording medium of the present invention, it is possible to use a magnetic head having a narrow gap length (for example, 0.1 to 0.25 μm) to record a signal with a short recording wavelength and a small track width (that is, a signal). High-density recording). The magnetic recording medium of the present invention is provided with a nonmagnetic metal oxide layer having a thickness of 480 nm or less as a reinforcing layer. The reinforcing layer compensates for a decrease in mechanical strength (for example, a decrease in rigidity) caused by the thin nonmagnetic substrate and the magnetic layer. Since the mechanical strength of the non-magnetic metal oxide layer is 1.2 to 2 times as large as that of a layer made of a metal that has not been oxidized, a sufficient reinforcing effect can be obtained even with a thickness of 480 nm or less. Therefore, when the magnetic recording medium of the present invention is a magnetic tape, the contact with the head is improved, and the durability is improved. Is obtained.

In the magnetic recording medium of the present invention, at least the gap end face is made of a ferromagnetic material, and the gap length is 0.1.
It is particularly preferably used as a magnetic recording medium for recording signals using a magnetic head of 0 to 0.25 μm. Specifically, such a magnetic recording medium is a magnetic recording medium for data backup used in information equipment and a digital video tape that requires high image quality and high reliability.

According to the magnetic recording medium of the present invention, a magnetic recording method for recording signals using a magnetic head having at least a gap end face made of a ferromagnetic material and having a gap length of 0.10 to 0.25 μm. May be implemented. The magnetic recording medium of the present invention recorded by the method exhibits a high CN ratio and a high SN ratio, and gives a high-quality reproduced signal.

[0026]

Embodiments of the present invention will be described below. In the present specification, regarding the configuration of the magnetic recording medium, the “surface” of each layer constituting the magnetic recording medium is:
The surface exposed when each layer is formed, that is, the surface of each layer remote from the nonmagnetic substrate. Regarding the configuration of the magnetic recording medium, the term “above” each layer constituting the magnetic recording medium also means the surface of each layer farther from the nonmagnetic substrate unless otherwise specified, and conversely, the “lower” of each layer. "" Means the surface of each layer closer to the nonmagnetic substrate. Therefore, for example, when saying “on the magnetic layer”,
"At the position adjacent to the surface of the magnetic layer far from the nonmagnetic substrate" means "under the magnetic layer", and "at the position adjacent to the surface of the magnetic layer near the nonmagnetic substrate" Means.

The “magnetic layer side surface” of the magnetic recording medium refers to the exposed surface of the magnetic recording medium on the side where the magnetic layer is formed with reference to the two surfaces of the nonmagnetic substrate. For example, as shown in FIG. 9, when a protective layer and a lubricant layer are formed on a magnetic layer formed on one surface of a non-magnetic substrate, the exposed surface of the lubricant layer is Surface ".

The magnetic recording medium of the present invention is a magnetic recording medium having a non-magnetic substrate, a magnetic layer, and a reinforcing layer, wherein the magnetic layer is a ferromagnetic metal thin film having a thickness of 120 nm or less, A magnetic recording medium in which the reinforcing layer is a non-magnetic metal oxide layer having a thickness of 480 nm or less.

The non-magnetic substrate is preferably a flexible polymer film. The polymer film is made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyamide (P) depending on the rigidity and strength to be obtained in the final magnetic recording medium.
A), one or a plurality of materials are appropriately selected from polyimide, polyvinyl chloride, polycarbonate and the like. For example, a thickness of 5 μm made of PA, PEN, PET
PEN is 1.4% of PET.
Times, PA has 1.7 times the strength of PET. Also, P
A magnetic tape was manufactured using films of the same thickness consisting of A, PEN, and PET, and the SN ratio at the time of reproduction was compared.
Those using PA are the highest and those using PET are the lowest. Therefore, for example, when a thinner magnetic recording medium is to be obtained, a PA film is preferably used.

On the surface of the non-magnetic substrate on which the magnetic layer is formed (that is, the surface in contact with the magnetic layer), SiO ₂ , Ti is used to improve the running property of the magnetic layer side surface of the magnetic recording medium.
Fine particles made of an inorganic substance such as O ₂ , Al ₂ O ₃ or ZrO ₂ or an organic substance such as polysulfone are 1 μm, for example.
It is preferable that ³ to 150 particles per ² are dispersed and fixed. The fine particles have a height of, for example, 5
It is preferable to have a shape and dimensions to form surface protrusions of ５０50 nm. In general, if the height of the projection is less than 5 nm, it is difficult to secure good running properties,
If it exceeds, the spacing loss of the reproduction output increases, and it cannot be used as a magnetic recording medium.

The surface projections of the non-magnetic substrate are formed, for example, by mixing the fine particles with a polymer resin (for example, when the non-magnetic substrate is a polymer film, the same resin as the resin forming the polymer film). The mixture can be formed by coating the mixture on a polymer substrate. Alternatively, a nonmagnetic substrate having protrusions on the surface can be obtained by producing a film from a polymer material containing fine particles. Non-magnetic substrates having surface projections are disclosed in
644 and JP-A-10-261215.

The thickness of the non-magnetic substrate used in the present invention can be made smaller than that of a non-magnetic substrate used in a conventional magnetic recording medium by forming a reinforcing layer. The thickness of the non-magnetic substrate is determined in consideration of the mechanical strength (for example, rigidity) of the non-magnetic substrate and the thickness of the magnetic layer and the reinforcing layer so that the total thickness of the magnetic recording medium is 2.0 to 5.3 μm. It is preferable to determine it. The thinner the non-magnetic substrate, the more easily it loses heat during evaporation, wrinkles during winding and elongation, and the total thickness of the magnetic recording medium is 2 μm.
If the thickness of the non-magnetic substrate is reduced so as to be smaller than the above, those problems cannot be ignored. On the other hand, a magnetic recording medium having a total thickness exceeding 5.3 μm cannot be said to be thin enough to effectively increase the recording capacity.

The thickness of the non-magnetic substrate is, for example, 1.4 to 5 μm depending on the material and mechanical strength (for example, rigidity).
It is preferable to select within the range. For example, when manufacturing a magnetic recording medium having the same degree of rigidity using each of the PET, PEN, and PA films exemplified above, the thickness of the PA film can be minimized.

The rigidity of the non-magnetic substrate is preferably larger than the combined rigidity of the magnetic layer and the non-magnetic metal oxide layer. If the rigidity of the non-magnetic substrate is smaller than the combined rigidity of the magnetic layer and the non-magnetic metal oxide layer, it is necessary to increase the thickness of the reinforcing layer to secure the rigidity of the entire magnetic recording medium. When the reinforcing layer is thickened, the following problem occurs. First, when the reinforcing layer is formed by vapor deposition,
When the reinforcing layer is formed thick, the non-magnetic substrate is thermally damaged, causing the non-magnetic substrate to lose heat, and the quality of a reproduced signal from the obtained magnetic recording medium is disadvantageously deteriorated. Second, there is a problem that when the reinforcing layer is thickened, cracks are easily generated in the reinforcing layer. When a crack occurs in the reinforcing layer, its reinforcing effect decreases.

The rigidity of the magnetic layer and the non-magnetic metal oxide is as follows:
When the respective Young's moduli are Em and Eb and the thicknesses are tb and tm, they are expressed by Em × tm ³ and Eb × tb ³ . The Young's modulus and the thickness may be expressed in any units. In this specification, the Young's modulus and
Expressed in Pa (Pascal) and μm, their rigidity is therefore indicated in N · μm.

In the magnetic recording medium of the present invention, the magnetic layer is a ferromagnetic metal thin film having a thickness of 120 nm or less. Ferromagnetic metals suitable for the magnetic layer include Fe-based metals, Co-based metals, and Ni-based metals. In the present invention, it is particularly preferable to form the magnetic layer with a Co-based metal. Here, "Co
The “base metal” refers to cobalt and an alloy containing cobalt as a main component and preferably at least 50 atomic%. The same applies to “Fe-based metal” and “Ni-based metal”.

The ferromagnetic metal thin film is specifically composed of Fe, C
o and Ni, and Co-Ni, Co-Fe, Co
-Cr, Co-Cu, Co-Pt, Co-Pd, Co-
Sn, Co-Au, Fe-Cr, Fe-Co-Ni, F
e-Cu, Ni-Cr, Fe-Co-Cr, Co-Ni
-Cr, Co-Pt-Cr and Fe-Co-Ni-C
It is formed of one or more materials selected from alloys such as r. The ferromagnetic metal film may include oxygen, which may be included in the form of oxides of these metals or alloys.

The ferromagnetic metal thin film may be in the form of a single-layer film or a multilayer film. In any case, the thickness of the ferromagnetic metal thin film is preferably 120 nm or less. By setting the thickness of the ferromagnetic metal thin film (that is, the recording layer) to this level, the gap length becomes 0.1
0-0.25 μm magnetic head (for example, MR head)
, High-density recording can be optimally performed at a high recording frequency (for example, 20 MHz or higher). When the thickness of the magnetic layer increases, the output is saturated, the noise component increases, and the CN ratio of the reproduction output decreases. The thickness of 150 to 120 nm substantially corresponds to the thickness at which the output is saturated when a magnetic head having a gap length in the above range is used.

In order to obtain a magnetic recording medium suitable for recording with a magnetic head having the above-mentioned gap length, the thickness of the ferromagnetic metal thin film is generally preferably from 20 to 100 nm. The preferred lower limit of the thickness of the ferromagnetic metal thin film is determined according to the characteristics of the magnetic head to be used, the recording wavelength, and the like. it can. Therefore, the thickness of the ferromagnetic metal thin film is equivalent to the average diameter of the magnetic particles, and the thickness at which thermal fluctuation cannot be ignored (about 5 nm)
It is also possible to make it as thin as possible.

The ferromagnetic metal thin film is preferably formed by vacuum evaporation, particularly preferably by oblique evaporation. The oblique deposition is performed by depositing a magnetic metal vapor stream having a predetermined high incident angle component to a low incident angle component on a non-magnetic substrate moving on a suitable support in a vacuum evaporation tank. The non-magnetic substrate is moved on a can-shaped rotating support or a belt-shaped support. When oxygen is present in the ferromagnetic metal thin film, the deposition is performed in an atmosphere in which oxygen is slightly introduced.

On the magnetic layer which is a ferromagnetic metal thin film and / or
Alternatively, a nonmagnetic layer not involved in recording may be present below. The nonmagnetic layer is preferably a layer made of a ferromagnetic metal oxide forming a ferromagnetic metal thin film. For example,
When the ferromagnetic metal thin film is mainly composed of cobalt, it is preferable that a non-magnetic layer made of cobalt oxide be present above and / or below the magnetic layer.

When a magnetic layer is formed on a non-magnetic layer by vacuum evaporation, the magnetic particles constituting the magnetic layer tend to be small, and as a result, the electromagnetic conversion characteristics of the magnetic recording medium are improved. When a non-magnetic layer made of a metal oxide is present on the magnetic layer, the non-magnetic layer protects the magnetic layer and effectively suppresses abrasion of the magnetic layer.

The thickness of the nonmagnetic layer is preferably 3 to 50 nm. When the reinforcing layer is formed on the side of the nonmagnetic substrate on which the magnetic layer is formed, as described later, the reinforcing layer may also serve as the nonmagnetic layer, or the nonmagnetic layer may be included in the reinforcing layer. In such a case, the thickness of the nonmagnetic layer is not limited to the above range.

The nonmagnetic layer can be formed, for example, by vacuum-depositing a metal in an oxygen atmosphere.

In the magnetic recording medium of the present invention, the reinforcing layer is a non-magnetic metal oxide layer having a thickness of 480 nm or less. The reinforcing layer is provided to increase the rigidity of the entire magnetic recording medium.
The magnetic recording medium of the present invention is characterized in that the reinforcing layer is a non-magnetic metal oxide layer.

In the magnetic recording medium of the present invention, the phrase that the reinforcing layer is a nonmagnetic metal oxide layer means that the ratio of the number of oxygen atoms to the number of metal atoms present in the reinforcing layer (also simply referred to as “oxygen ratio”) is zero. Larger, and means that the entire reinforcing layer is substantially non-magnetic (ie, not substantially magnetized in a magnetic field). That is, the metal present in the reinforcing layer does not need to be entirely oxidized, and may be partially unoxidized.

Examples of the non-magnetic metal oxide layer include: 1) a mixture of a non-oxidized metal and a metal oxide;
2) A mixture of oxygen not bonded to a metal, a non-oxidized metal and a metal oxide, and 3) a mixture of a metal oxide alone are conceivable. The metal oxide contained in the non-magnetic metal oxide layer may be a double oxide containing two or more metals. Further, the nonmagnetic metal oxide layer may include a plurality of types of metal oxides (including multiple oxides). Mechanical strength (for example, rigidity) of such a nonmagnetic metal oxide layer
Is as large as 1.2 to 2 times as large as a layer made of only a substantially non-oxidized metal (that is, a layer having an oxygen ratio close to 0), so that an excellent reinforcing effect can be obtained even with a small thickness.

The reinforcing layer is specifically made of aluminum,
It is preferable to include an oxide of one or more metals selected from copper, titanium, tin, iron, nickel, cobalt and chromium. Particularly, aluminum is preferably used because it is a non-magnetic substance itself, and has a low melting point, so that when a reinforcing layer is formed by vapor deposition, thermal damage to a non-magnetic substrate or the like can be small.

The oxygen ratio of the reinforcing layer can be selected so that the reinforcing layer exhibits a high rigidity. Such an oxygen ratio depends on the metal and can be determined experimentally. For example, when the reinforcing layer is a non-magnetic metal oxide layer containing aluminum oxide, the rigidity of this layer increases as the oxygen ratio increases, becomes maximum when it is 1, and does not change even if it exceeds 1.
Therefore, when the nonmagnetic metal oxide layer is formed of Al, the oxygen ratio is preferably set to 1 or more. Even if the oxygen ratio to Al is about 0.5, the rigidity is sufficiently higher than that of the case where the oxygen ratio is 0. Therefore, if necessary, the oxygen ratio may be in the range of 0.5 to 1. Good. When the oxygen ratio to Al is larger than 0, it is considered that the nonmagnetic metal oxide layer is composed of a mixture of Al, Al ₂ O ₃ , and oxygen not bonded to Al.

The non-magnetic metal oxide layer is preferably made of Al
Is formed by vacuum-depositing a metal such as on a nonmagnetic substrate in an oxygen atmosphere. The oxygen ratio of the reinforcing layer can be changed by changing the oxygen supply during the deposition.

In the magnetic recording medium of the present invention, since the reinforcing layer is a highly rigid layer containing a metal oxide, sufficient rigidity is imparted to the magnetic recording medium even if the thickness of the reinforcing layer is as small as 480 nm or less. obtain. When the thickness of the reinforcing layer exceeds 480 nm, when the reinforcing layer is formed by vapor deposition, thermal damage to the non-magnetic substrate is increased, and the non-magnetic substrate is likely to lose heat. The quality of the reproduced signal is deteriorated, cracks occur in the reinforcing layer and the reinforcing effect cannot be obtained, the reinforcing layer cannot be formed efficiently,
There is a problem that the production efficiency of the magnetic recording medium is reduced.

The thickness of the reinforcing layer is appropriately selected within a range of 480 nm or less according to the rigidity of the non-magnetic substrate and the thickness of the magnetic layer so that the desired rigidity is finally imparted to the magnetic recording medium. You. Specifically, the thickness of the reinforcing layer is preferably selected so that the sum of the thicknesses of the magnetic layer and the reinforcing layer is 0.1 to 0.6 μm. If the sum of the two layers is less than 0.1 μm, the rigidity of the magnetic recording medium becomes insufficient, and it becomes difficult to obtain good electromagnetic conversion characteristics. The greater the sum of the two layers, the greater the stiffness, and when the magnetic recording medium is a magnetic tape, the better the contact with the head, resulting in excellent electromagnetic conversion characteristics. However, when the sum of the two layers exceeds 0.6 μm, the thickness of the magnetic layer and / or the reinforcing layer increases, and as described above, a problem arises due to the respective layers being thick, which is not preferable. More preferably, the nonmagnetic metal oxide layer has a thickness of 95 nm or more so that the magnetic recording medium has sufficient mechanical strength.

The reinforcing layer is preferably formed such that the magnetic layer and the reinforcing layer face each other with a non-magnetic substrate interposed therebetween. Specifically, the reinforcing layer is preferably formed on the surface of the non-magnetic substrate opposite to the surface on which the magnetic layer is formed.

When the reinforcing layer is formed on the surface of the non-magnetic substrate on which the magnetic layer is formed, it is preferable to dispose the reinforcing layer below the magnetic layer. Such an arrangement can be realized by forming a reinforcing layer on a nonmagnetic substrate by vapor deposition or the like, and then forming a magnetic layer on the reinforcing layer by vapor deposition or the like.

The non-magnetic substrate, magnetic layer, and reinforcing layer constituting the magnetic recording medium of the present invention have been described above.
Elements not specifically mentioned above may be constructed using commonly employed materials and methods.

For example, a protective layer is formed on the magnetic layer (on the non-magnetic layer when a non-magnetic layer is formed on the magnetic layer), and further lubricated on the protective layer if necessary. An agent layer may be formed.

The protective layer is made of, for example, an amorphous, graphite, or diamond-like carbon thin film obtained by a method such as sputtering or plasma CVD, or a carbon film formed by mixing and / or laminating those carbons. It can be formed using a thin film.

In the present invention, in particular, diamond-like carbon, that is, diamond-like carbon (Diamond Like Car)
bon; DLC). D
Since LC has an appropriate hardness, it is the most preferable material because it can suppress damage to the magnetic recording medium and also prevent damage to the magnetic head. When the protective layer is formed using any material, the thickness of the protective layer is 1
Preferably it is ~ 50 nm.

The lubricant forming the lubricant layer can be arbitrarily selected from those commonly used as lubricants for magnetic recording media. The lubricant is preferably, for example, a fluorine-based lubricant such as perfluoropolyether or a hydrocarbon-based lubricant. The lubricant layer may contain, for example, an extreme pressure agent, a rust preventive, and the like as components other than the lubricant. The lubricant layer is formed, for example, by applying a coating solution obtained by dissolving or dispersing a lubricant in an appropriate solvent to a protective layer (or a magnetic layer if no protective layer is formed).
Can be formed by evaporating the solvent. The thickness of the lubricant layer is generally 0.05 to 50 nm.

The magnetic recording medium of the present invention may be provided with a back coat layer so as to face the magnetic layer via a non-magnetic substrate in order to improve the running property in the recording / reproducing apparatus. When the reinforcing layer is formed on the surface of the non-magnetic substrate opposite to the surface on which the magnetic layer is formed, the back coat layer is formed on the reinforcing layer. The back coat layer is made of one or more materials selected from a polyurethane resin, a nitrocellulose resin, a polyester resin (for example, Byron), carbon and calcium carbonate, and a suitable solvent (for example, toluene and methyl ethyl ketone). A coating solution dissolved and / or dispersed in a mixed solvent) on the surface of the non-magnetic substrate opposite to the surface on which the magnetic layer is formed (if the reinforcing layer is formed on the surface, the surface of the reinforcing layer) , And then can be formed by a wet coating method of drying and evaporating the solvent. When the back coat layer is formed in this manner, the thickness is preferably set to 100 to 500 nm.

FIGS. 1 to 4 illustrate embodiments of the magnetic recording medium of the present invention. 1 to 4, the same reference numerals represent the same elements.

In the magnetic recording medium shown in FIG. 1, a magnetic layer (3) is formed on one surface of a non-magnetic substrate (1) which is a polymer film having fine particles (2) dispersed and fixed on the surface, and the other is formed. A nonmagnetic metal oxide layer is formed as a reinforcing layer (6) on the surface. On the magnetic layer (3), a protective layer (4) and a lubricant layer (5) are formed in this order.

In the magnetic recording medium shown in FIG. 2, a non-magnetic metal oxide layer as a reinforcing layer (6) and a ferromagnetic metal thin film as a magnetic layer (3) are formed on one surface of a non-magnetic substrate in this order. The protective layer (4) and the lubricant layer (5) are formed on the magnetic layer (3). A back coat layer (7) is formed on the surface of the non-magnetic substrate opposite to the surface on which the reinforcing layer (6) and the magnetic layer (3) are formed.

The magnetic recording medium shown in FIG. 3 has a magnetic layer (3) formed on a non-magnetic layer (8), and the other configuration is the same as that of the magnetic recording medium shown in FIG. The magnetic recording medium shown in FIG. 4 has a back coat layer (7) formed on the surface of a reinforcing layer (6), and other configurations are the same as those of the magnetic recording medium shown in FIG.

In the magnetic recording medium of the present invention, the magnetic layer is a ferromagnetic metal thin film having a thickness suitable for high-density recording.
Using a magnetic head with a narrow gap length, a signal can be recorded with a short recording wavelength and a short track width. In addition, even when the magnetic recording medium of the present invention is reduced in thickness, the same rigidity as that of a conventional magnetic recording medium is ensured by the reinforcing layer. Therefore, according to the magnetic recording medium of the present invention, it is possible to obtain a magnetic recording medium product (for example, a magnetic tape housed in a case) whose recording capacity has been greatly improved by increasing the recording density and reducing the thickness. .

The magnetic recording medium of the present invention has at least a gap end face made of a ferromagnetic material, and has a gap length of 0.1.
It is optimally recorded using a magnetic head of 0 to 0.25 μm. When the gap length is reduced, the processing accuracy of the head itself is deteriorated, and signal reproduction processing becomes difficult. Therefore, when a magnetic head having a gap length of less than 0.10 μm is used, the output during reproduction is reduced, the noise is increased, and the CN ratio is reduced. On the other hand, when the gap length is 0.2
If it exceeds 5 μm, high density recording cannot be performed.

The head is, specifically, an MR head, a GM
R (Giant Magneto Resistive) head, TMR (Tunne
A magnetic head used in a large-capacity recording device, such as a ling magnetoresistive head, is preferable. Each of these heads is further classified into various types. In the present invention, any type can be preferably used. For example, MR heads include a SAL bias type, a dual stripe type, and a vertical type, and any type can be used as long as the head gap length satisfies the above range.

As described above, when the magnetic recording medium of the present invention is used, at least a gap end face is made of a ferromagnetic material, and a signal is recorded using a magnetic head having a gap length of 0.10 to 0.25 μm. A magnetic recording method can be preferably implemented. According to this method, a large amount of signals can be recorded so that a high-quality reproduced signal can be obtained.

[0069]

Next, the present invention will be described in more detail with reference to examples.

Example 1 A magnetic recording medium having the cross-sectional structure shown in FIG. 1 was manufactured. As shown in FIG. 5, a ferromagnetic metal thin film was formed on a non-magnetic substrate. In this embodiment, a 4.5 μm-thick polyester (PE
T) Film was used. On one side of this film, S
50 particles of iO _{2 having a} diameter of 15 nm were dispersed and fixed per 1 μm ² . In addition, Co metal was prepared as a ferromagnetic metal.

The upper and lower cooling rotary drums (106a, 1
The set temperature of the refrigerant for cooling 06b) was -20 ° C. The non-magnetic substrate (101) is set on the feed shaft (102), the line speed at the time of vapor deposition is set to 200 m / min, and the nip roller (104), the upper cooling rotary drum (106a), the plate belt (108), Winding was performed by a winding shaft (110) via a lower cooling rotary drum (106b). Endless belt (10
The inclination angle (θ) of 8) was set to 55 ° with respect to the melting surface (corresponding to the horizontal plane in this embodiment) of the magnetic metal (114).

The vacuum deposition is performed by using Co (11) which is a ferromagnetic metal.
4) was irradiated with an electron beam (112) to melt and evaporate the alloy, thereby performing oblique evaporation from below. Spread of metal vapor flow is two shielding plates (116, 120)
, And components from the maximum incident angle (β) of 87 ° to the minimum incident angle (α) of 38 ° are deposited. At this time, the solid angle (ω) was 34 °. Here, the solid angle (ω) is an angle formed between two line segments that define the minimum incident angle (α) and the maximum incident angle (β) of the magnetic metal vapor flow, and Shows the spread.

During vapor deposition, oxygen gas was supplied at a flow rate of 4 liter /
The gas pressure was set to 156 kPa (1.6 kgf / cm ² ), and the nozzle (11) provided close to the shielding plates (116, 120) was set.
8, 122) into a metal vapor stream so that oxygen is contained in the ferromagnetic metal thin film. Oxygen was introduced from the nozzle (122) toward the nonmagnetic substrate (11) in a direction at an angle of 90 ° with the nonmagnetic substrate. Oxygen was introduced from the nozzle (118) in a direction parallel to the nonmagnetic substrate in a direction opposite to the direction of travel of the nonmagnetic substrate (101). The vapor deposition was performed so that the thickness of the ferromagnetic metal thin film became 100 nm.

After the formation of the magnetic layer, a reinforcing layer was formed using Al on the surface of the non-magnetic substrate opposite to the surface on which the magnetic layer was formed. The reinforcing layer was formed by vacuum deposition using the apparatus shown in FIG. The non-magnetic substrate (101) is set on the feed shaft (202) such that the surface of the non-magnetic substrate opposite to the surface on which the magnetic layer is formed is the deposition surface, and the line speed during the deposition is set to 50.
The speed was set to m / min, and the film was wound on the winding shaft (210) via the cooling rotary drum (206). During vapor deposition, the set temperature of the cooling medium for cooling the cooling rotary drum (206) was 0 ° C. The aluminum metal (215) in the crucible was dissolved and evaporated by the electron beam (212) irradiated from the electron gun, and was deposited on the non-magnetic substrate from below. The spread of the aluminum metal vapor flow is limited by two shielding plates (216a, 216b),
The solid angle (ω) was 30 °.

The vapor deposition was performed in an oxygen atmosphere so that the reinforcing layer contained aluminum oxide. The oxygen has a flow rate of 5 L / min and a gas pressure of 156 kPa (1.6 kgf / cm ² ).
And introduced from nozzles (218a, 218b) provided near the shielding plates (216a, 216b). The vapor deposition was performed so that the thickness of the reinforcing layer was 400 nm.

After forming the magnetic layer (ferromagnetic metal thin film) and the reinforcing layer, a DL is formed as a protective layer on the surface of the ferromagnetic metal thin film.
A C film was provided, and a lubricant layer was further formed on the DLC film to obtain a magnetic recording medium. Then, this magnetic recording medium was slit into a tape and assembled into a cassette to prepare a sample for performance evaluation.

Example 2 A magnetic recording medium having the cross-sectional structure shown in FIG. 2 was manufactured. Using the apparatus shown in FIG. 7, a reinforcing layer and a magnetic layer were formed in this order on one surface of the non-magnetic substrate. In this embodiment, the non-magnetic substrate has a thickness of 4.2 μm.
m of polyethylene naphthalate (PEN) film was used. On one side of this film, 70 fine particles of polysulfone having a diameter of 10 nm were dispersed and fixed per 1 μm ² .

The non-magnetic substrate (301) was set on the feed shaft (302), and the line speed during vapor deposition was set to 50 m / min.
The winding shaft (31) passes through the cooling rotary drums (306a, 306b).
0). During deposition, cooling rotating drum (3
06a, 306b) The set temperature of the refrigerant for cooling both is 0 ° C.
And

The reinforcing layer was formed while the non-magnetic substrate (301) passed through the first cooling rotary drum (306a). The reinforcing layer was formed by depositing cobalt in an oxygen atmosphere to contain cobalt oxide. As in Example 2, the reinforcing layer
The cobalt metal (315) in the crucible was dissolved and evaporated by an electron beam (312a) irradiated from an electron gun, and was formed by vapor deposition from below on a non-magnetic substrate (301). The spread of the cobalt metal vapor stream was limited by two shielding plates (316, 317) and the solid angle (ω) was 30 °. Oxygen has a flow rate of 5 L / min and a gas pressure of 156 kPa (1.6 kgf).
/ Cm ² ) and introduced from nozzles (318a, 318b) provided near the shielding plates (316, 317). The thickness of the reinforcing layer was 400 nm.

The non-magnetic substrate on which the reinforcing layer is formed passes through the rollers (304a, 304b) and then passes through the cooling drum (306b).
Was moved along. The magnetic layer was formed while the non-magnetic substrate (301) passed along the second cooling drum (306b). In this example, cobalt was prepared as a ferromagnetic metal. The magnetic layer was formed by dissolving and evaporating the cobalt metal (314) in the crucible with an electron beam (312b), and vapor-depositing the non-magnetic substrate (301) from below. The spread of the cobalt metal vapor flow is limited by two shielding plates (319, 320), and the maximum incident angle (β) is 85 ° to the minimum incident angle 40 °.
The components up to (α) were deposited. The solid angle (ω) was 20 °. During the deposition, oxygen and a flow rate of 1.
8 liter / min, gas pressure 156 kPa (1.6 kgf / cm
² ) Set the nozzle (32) near the shielding plate (320).
It was introduced from 2) so that oxygen was contained in the magnetic layer.
The thickness of the magnetic layer was 100 nm.

After forming the reinforcing layer and the magnetic layer (ferromagnetic metal thin film), a DL is formed as a protective layer on the surface of the ferromagnetic metal thin film.
A C film was provided, and a lubricant layer was further formed on the DLC film.
On the other hand, a backcoat layer having a thickness of 200 nm was formed on the surface of the nonmagnetic substrate opposite to the surface on which the reinforcing layer and the magnetic layer were formed. The back coat layer was formed by applying a coating solution prepared by dissolving a polyurethane resin in methyl ethyl ketone, drying and evaporating methyl ethyl ketone. The magnetic recording medium thus obtained was slit into a tape, and the tape was assembled into a cassette to produce a sample for performance evaluation.

Example 3 A magnetic recording medium having the cross-sectional structure shown in FIG. 3 was manufactured. In this example, a 4 μm thick polyaramid (PA) film was prepared as a nonmagnetic substrate. One side of this film has a diameter of 1 made of SiO _2.
50 particles of 5 nm were dispersed and fixed per 1 μm ² . Using the same apparatus as used in Example 2, a flow rate of 1 liter / min and a gas pressure of 156 were applied to this film.
By depositing cobalt while introducing oxygen at a setting of kPa (1.6 kgf / cm ² ), a non-magnetic layer made of cobalt oxide and having a thickness of 10 nm is formed. By depositing Co in the same manner as in Example 2, a 100 nm thick ferromagnetic metal thin film was formed.

Next, a nonmagnetic metal oxide layer having a thickness of 400 nm was formed as a reinforcing layer on the surface of the nonmagnetic substrate opposite to the surface on which the magnetic layer was formed. The nonmagnetic metal oxide layer was formed by vapor deposition of aluminum in an oxygen atmosphere in the same manner as in Example 1.

After forming the non-magnetic layer, the magnetic layer and the reinforcing layer, a protective layer and a lubricant layer were formed in the same manner as in Example 1 to obtain a magnetic recording medium. Then, this magnetic recording medium was slit into a tape and assembled into a cassette to prepare a sample for performance evaluation.

Example 4 A magnetic recording medium having the sectional structure shown in FIG. 3 was manufactured. In this embodiment, a 3.2 μm thick polyaramid (PA) film was used as the nonmagnetic substrate. On one side of this film, 50 fine particles of SiO _{2 having a} diameter of 15 nm were dispersed and fixed per 1 μm ² . The magnetic layer and the reinforcing layer were the same as those in Example 1 except that the line speed in the step of forming the reinforcing layer was 30 m / min in order to make the thickness of the nonmagnetic metal oxide layer as the reinforcing layer 300 nm. Formed using the same materials and methods.
Further, on the surface of the nonmagnetic metal oxide layer, a backcoat layer having a thickness of 300 nm was formed using the same material and method as in Example 2. Then, the obtained magnetic recording medium was slit into a tape and assembled into a cassette to produce a sample for performance evaluation.

Comparative Example 1 A conventional magnetic recording medium having a sectional structure shown in FIG. 9 was manufactured. Using the apparatus shown in FIG. 8, a ferromagnetic metal thin film was formed on a non-magnetic substrate. In this example, the same polyester (PET) film as that used in Example 1 was used as the nonmagnetic substrate, and Co metal was used as the ferromagnetic metal. The non-magnetic substrate (401) is set on the feed shaft (402), and the line speed during evaporation is 60
The speed was set to m / min, and the film was wound on the winding shaft (410) via the cooling rotary drum (406).

The set temperature of the refrigerant for cooling the cooling rotary drum (406) was set at 0 ° C. Vacuum deposition uses an electron beam (41
This was carried out in the same manner as in Example 1 using 2). The spread of the metal vapor flow is limited by the two shielding plates (416, 420), and the maximum incident angle (β) is 90 ° to the minimum incident angle (α) is 40 °.
The components up to ° were deposited. The solid angle (ω) was 15 °.

During the vapor deposition, oxygen gas was introduced from the nozzle (418) in a direction parallel to the direction of travel of the non-magnetic substrate (401) and in a direction opposite to the direction of travel. The pressure of oxygen gas was the same as in Example 1. The vapor deposition was performed so that the thickness of the ferromagnetic metal thin film became 150 nm.

After forming the magnetic layer, a protective layer and a lubricant layer were formed in the same manner as in Example 1, and a 500 nm-thick backcoat layer was formed in the same manner as in Example 2. I got Then, this magnetic recording medium was slit into a tape and assembled into a cassette to prepare a sample for performance evaluation.

Comparative Example 2 A magnetic recording medium and a sample for performance evaluation were produced in the same manner as in Comparative Example 1, except that the thickness of the magnetic layer (ferromagnetic metal thin film) was 100 nm.

The performance of the samples obtained in each of the examples and comparative examples was evaluated. The performance evaluation was performed after observing the fractured surface of each magnetic recording medium with an electron microscope and confirming that it had a desired sectional structure. The performance of the sample was evaluated according to the following method.

[Total thickness of magnetic recording medium] Using a commercially available thickness gauge (trade name: Millitron, manufactured by FEINPRUH), the thickness was measured with 10 magnetic recording media stacked, and the total thickness was determined from the thickness. I asked.

[Thickness of Magnetic Layer and Reinforcing Layer] A transmission electron microscope (TEM) photograph (magnification: 50) of the fracture surface of the tape
0000). For some magnetic recording media, the relationship between the thickness and the deposition rate was determined from a TEM photograph of the magnetic recording medium having the magnetic layer and / or the reinforcing layer formed by the same method, and the thickness of the magnetic layer and the reinforcing layer was determined based on the relationship. Was calculated.

[Rigidity] From the Young's modulus E and the total thickness t of the magnetic recording medium, an equation E × t ³ was used, and a relative comparison was made based on the rigidity of the magnetic recording medium of Example 1.

The Young's modulus was determined by cutting a magnetic recording medium into appropriate dimensions so that the width (TD) direction of the magnetic recording medium was in the tensile direction of the sample, preparing a sample, and performing a tensile test on the sample. . The Young's modulus is defined as the load (stress) acting on the cross section of the sample, the elongation of the sample, and the cross-sectional area of the sample in the width direction. From the equation, E = (W · L) / (A · △)
l) (where E is Young's modulus (Pa), W is load within elastic limit (N), L is distance between marked lines before tensile test (m), A is cross-sectional area of sample before tensile test ( m ² ) and Δl indicate the inter-mark line elongation (m) under the load W).

As a tensile tester, RTM-25 manufactured by Orientec was used, and the tensile length (distance between marked lines) was 20.
0 mm and the pulling speed were set at 10 mm / min. The load within the elastic limit was a load when the sample was elongated by 0.05 to 0.1%. The cross-sectional area in the width direction of the sample was determined from the width and thickness of the sample.

[Electromagnetic Conversion Characteristics per Head] An MR head having a gap length of 0.2 μm is mounted on a DV cylinder, the relative speed is 10.2 m / s, the track width is 6 μm, the maximum recording frequency is 50 MHz (the minimum recording wavelength is 0. 2 μm), and the output, noise, and envelope waveform of the recorded signal were measured. The head contact was evaluated from the flattening rate of the envelope and the waveform, and those with good head contact were represented by ○ and those with bad head contact were represented by x. The electromagnetic conversion characteristics are based on the CN ratio of the sample of Example 1 (carrier 21 MHz) (0
dB), and the electromagnetic conversion characteristics were evaluated by comparing the relative values (values corresponding to the differences from the reference values) of the respective examples and comparative examples.

Table 1 shows the performance of the samples obtained in each example and each comparative example.

[0099]

[Table 1]

As shown in Table 1, the magnetic recording medium of the present invention had better contact with the head and a higher CN ratio than Comparative Example 1 (corresponding to a conventional product). The conversion characteristics were shown. The magnetic recording medium of Comparative Example 2 did not have a layer corresponding to the reinforcing layer (non-metal oxide layer) of the magnetic recording medium of the present invention, and had the lowest rigidity due to the reduced thickness of the magnetic layer. small. Therefore, the head contact of the comparative example was poor. This indicates that the reinforcing layer greatly contributes to improving the rigidity of the magnetic recording medium.

Each of the tape-shaped magnetic recording media obtained in each of the examples is a commercially available D-type magnetic recording medium having a total thickness of about 7.0 μm.
ME tape for V (non-magnetic substrate: PET with a thickness of 6.4 μm)
Film, magnetic layer: 180 nm thick, back coat layer: 0.4 μm thick) and LP (Long Pla
y) ME tape (non-magnetic substrate: PE with a thickness of 4.7 μm)
N film, magnetic layer: thickness 180 nm, back coat layer:
It had the same degree of rigidity as 0.4 μm in thickness, and could be used in a commonly used recording / reproducing apparatus. Therefore, when the thin tapes of Examples 1 to 4 are used, the length of the tape (that is, the winding length) that can be accommodated in a case having a predetermined size can be increased, so that a longer recording time (for example, a longer recording time) than a commercially available product can be obtained. Possible magnetic recording media products may be provided.

Although not shown in Table 1, when the output and SN ratio during reproduction were compared, the higher the relative rigidity, the higher the output and SN ratio, and the better the electromagnetic conversion characteristics. For example, Example 1 and Comparative Example 2, in which the non-magnetic substrate and the magnetic layer are the same, showed a difference of 4 dB in the SN ratio at 21 MHz, corresponding to the different rigidities of the magnetic recording media. This is probably because the greater the rigidity, the better the head contact. In addition, when the electromagnetic conversion characteristics were evaluated using an amorphous laminated head used in a conventional digital video system, all the samples of the examples exhibited good electromagnetic conversion characteristics.

[Measurement of Frequency Characteristics] An MR head having a gap length of 0.2 μm was mounted on a DV cylinder on the magnetic recording medium of Example 1, Comparative Example 1, and Comparative Example 2, and the relative velocity was 10.2 m / m. s and a track width of 6 μm, a signal was recorded by changing the recording wavelength (frequency), and the CN ratio (carrier of 21 MHz) of reproduction of the recorded signal was measured. FIG. 10 shows the obtained results.

As shown in FIG. 10, the playback CN ratio of Comparative Example 1 corresponding to the conventional product reaches a peak at 10 MHz, but the playback CN ratio of Example 1 corresponding to the present invention is about 2%.
It reaches a peak at 0 MHz and shows a practical value up to 50 MHz. Since the thickness of the magnetic layer of the magnetic recording medium of Comparative Example 2 is smaller than that of Comparative Example 1, the CN ratio in the short wavelength region is higher than that of Comparative Example 1. However, C shown in Comparative Example 2
The N ratio is smaller than the CN ratio shown in Example 1 at any wavelength. This is presumably because the rigidity of the tape of Comparative Example 2 was low, and the contact between the tape and the head was insufficient. This can also be understood from the fact that the drop in the CN ratio of Comparative Example 2 in the high frequency range is larger than that of Example 1.

[Effect of Magnetic Layer Thickness on Electromagnetic Conversion Characteristics] A plurality of magnetic recording media having the same configuration as that of the magnetic recording medium of Example 1 were manufactured by changing the thickness of the magnetic layer, and signals were recorded on each of them. And the CN ratio during reproduction (carrier at 21 MHz) was measured. The signal was obtained at a relative speed of 10.2 m using an MR head with a gap length of 0.2 μm mounted on a DV cylinder.
/ S, track width 6 μm, maximum recording frequency 50 MHz (shortest recording wavelength 0.2 μm). FIG. 11 shows the evaluation results.
Shown in

FIG. 11 shows that the magnetic recording medium having a magnetic layer having a thickness of about 100 nm shows a peak of the CN ratio, and that the CN ratio decreases as the thickness of the magnetic layer increases. This is considered to be because the output becomes saturated and the noise component increases as the thickness increases.

On the other hand, the thickness of the magnetic layer is small (in particular, about 50 nm).
Below), the CN ratio also decreases. This is considered to be due to the fact that the output decreases more than the noise component does. As the thickness of the magnetic layer becomes smaller, C
The decrease in the N ratio largely depends on the characteristics of the MR head used. Therefore, when different MR heads are used, a sufficiently large CN ratio can be obtained even if the magnetic layer is thinned.

The same evaluation was performed using an MR head having a gap length of 0.22 μm.
At nm or more, the noise was higher than the output, and the CN ratio tended to deteriorate. This tendency was remarkably recognized as the recording frequency was increased. The CN ratio of the conventional example having a thick magnetic layer is further reduced by 10 to 20 several dB.

[Relationship Between Oxygen Ratio and Rigidity] A plurality of magnetic recording media having the same configuration as that of the magnetic recording medium of Example 1 were manufactured so that the oxygen ratio in the reinforcing layer was different, and the rigidity of each obtained magnetic recording medium was reduced. It was measured. The oxygen ratio was changed by changing the supply amount of oxygen when depositing aluminum. The oxygen ratio was determined by the amount of oxygen introduced during vapor deposition and Auger electron spectroscopy. FIG. 12 shows the relationship between the oxygen ratio (O / Al) and the rigidity in the reinforcing layer.

FIG. 12 shows that the non-magnetic metal oxide formed by vapor deposition of aluminum has the highest rigidity in a state where about half of the aluminum atoms are oxidized (oxygen ratio 1), and the oxygen ratio becomes higher. It can be seen that the stiffness does not change. The relationship shown in FIG. 12 is for aluminum, and the oxygen ratio at which the rigidity is maximized differs depending on the metal.

Although the magnetic recording medium of the present invention has been mainly described in the case where the aspect is a magnetic tape, the present invention is also applicable to magnetic recording media of other aspects, for example, a magnetic disk.

[0112]

The magnetic recording medium of the present invention has a magnetic layer of 12
It is a ferromagnetic metal thin film having a thickness of 0 nm or less, and the reinforcing layer is a non-magnetic metal oxide layer having a thickness of 480 nm or less. The magnetic recording medium of the present invention has the same rigidity as the conventional magnetic recording medium even when both the nonmagnetic substrate and the magnetic layer are thin, by using the nonmagnetic metal oxide layer having high rigidity for the reinforcing layer. It is possible to be. When the magnetic layer is thinned, a signal with high output and low noise can be reproduced even when a signal is recorded at a short recording wavelength, so that the recording density of the magnetic recording medium is improved. Therefore, according to the magnetic recording medium of the present invention, the improvement of the recording density provided by the thin magnetic layer and the increase in capacity provided by the reduction in thickness of the entire magnetic recording medium are combined, so that the magnetic recording medium is more than the conventional one. A magnetic recording medium product having a significantly increased recording capacity can be provided.

The magnetic recording medium of the present invention is suitable for high-density recording using a magnetic head having a gap length of 0.1 to 0.25 μm. Further, by using the magnetic recording medium of the present invention, a magnetic recording method for recording a signal using such a magnetic head having a narrow gap length can be advantageously implemented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a magnetic recording medium of the present invention.

FIG. 2 is a cross-sectional view schematically showing one example of the magnetic recording medium of the present invention.

FIG. 3 is a cross-sectional view schematically showing one example of the magnetic recording medium of the present invention.

FIG. 4 is a cross-sectional view schematically showing one example of the magnetic recording medium of the present invention.

FIG. 5 is a schematic diagram of an example of a vacuum evaporation apparatus.

FIG. 6 is a schematic view of an example of a vacuum evaporation apparatus.

FIG. 7 is a schematic diagram of an example of a vacuum evaporation apparatus.

FIG. 8 is a schematic diagram of an example of a vacuum evaporation apparatus.

FIG. 9 is a cross-sectional view schematically illustrating an example of a conventional magnetic recording medium.

FIG. 10 is a graph showing frequency characteristics of the magnetic recording media of Example 1, Comparative Examples 1 and 2.

FIG. 11 is a graph showing an example of the relationship between the thickness of a magnetic layer and electromagnetic conversion characteristics.

FIG. 12 is a graph showing the relationship between the oxygen ratio to aluminum and the rigidity of the magnetic recording medium when the nonmagnetic metal oxide layer is formed of aluminum.

[Explanation of symbols]

1 ... Polymer film (non-magnetic substrate) 2 ... Particles 3 ... Magnetic layer (ferromagnetic metal film) 4 ... Protective layer 5 ... Lubricant 6 ... Reinforcing layer (non-magnetic) Metal oxide layer) 7. Back coat layer 8. Non-magnetic layer 101, 301, 401 ... Non-magnetic substrate (polymer film) 102, 202, 302, 402 ... Feed shaft 104 .. . Nip rollers 304a, 304b ... Rollers 106a, 106b, 306a, 306b ... Cooling rotating drums 206, 406 ... Cooling rotating drums (can-like rotating support) 108 ... Belts 110, 210, 310, 410 ... winding shaft 112,212,312a, 312b, 412 ... electron beam 114,215,314,315,414 ... metal (evaporation source) 116,120,216a, 216b, 316,317,319 , 320,416,4
20 ... Shielding plates 118, 122, 218a, 218b, 318a, 318b, 418, 322 ...
nozzle

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01F 10/30 H01F 10/30

Claims (14)

[Claims] 1. A magnetic recording medium comprising a non-magnetic substrate, a magnetic layer and a reinforcing layer, wherein the magnetic layer is a ferromagnetic metal thin film having a thickness of 120 nm or less, and the reinforcing layer is 480 nm.
A magnetic recording medium which is a nonmagnetic metal oxide layer having the following thickness. 2. The magnetic recording medium according to claim 1, wherein the non-magnetic substrate is a polymer film. 3. The magnetic recording medium has a total thickness of 2.0 to 5.3 μm.
3. The magnetic recording medium according to claim 1, which is within a range of m. 4. The magnetic recording medium according to claim 1, wherein the rigidity of the nonmagnetic substrate is higher than the combined rigidity of the magnetic layer and the nonmagnetic metal oxide layer. 5. The magnetic layer according to claim 1, wherein the magnetic layer is a ferromagnetic metal thin film containing cobalt as a main component, and further includes a nonmagnetic layer made of cobalt oxide above and / or below the magnetic layer. Item 7. The magnetic recording medium according to Item 1. 6. The sum of the thicknesses of the magnetic layer and the reinforcing layer is from 0.1 to 0.1.
The magnetic recording medium according to claim 1, wherein the magnetic recording medium is within a range of 0.6 μm. 7. A non-magnetic metal oxide layer comprising Cu, Al, T
The magnetic recording medium according to any one of claims 1 to 6, comprising an oxide of one or more metals selected from i, Sn, Fe, Ni, Co, and Cr. 8. The magnetic recording medium according to claim 1, wherein the reinforcing layer is formed by vacuum-depositing a metal in an oxygen atmosphere. 9. The magnetic recording medium according to claim 1, wherein the magnetic layer and the reinforcing layer face each other via a non-magnetic substrate. 10. The magnetic recording medium according to claim 1, wherein a carbon film is formed as a protective layer on the magnetic layer, and a lubricant layer is formed on the carbon film. 11. The magnetic recording medium according to claim 1, further comprising a backcoat layer facing the magnetic layer via a nonmagnetic substrate. 12. The method according to claim 1, wherein at least a gap end face is formed of a ferromagnetic material, and is used for recording a signal using a magnetic head having a gap length of 0.10 to 0.25 μm. The magnetic recording medium according to claim 1. 13. The magnetic recording medium according to claim 12,
A magnetic recording method for recording a signal using a magnetic head having at least a gap end face made of a ferromagnetic material and having a gap length of 0.10 to 0.25 μm. 14. The magnetic recording medium according to claim 12, wherein at least a gap end face is made of a ferromagnetic material and a magnetic head having a gap length of 0.10 to 0.25 μm is mounted. Magnetic recording and reproducing device.