JP2977618B2 - Magnetic recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for performing digital recording on an in-plane recording type digital recording magnetic recording medium having a ferromagnetic metal thin film composed of columnar crystal grains formed by oblique evaporation as a magnetic layer. .

[0002]

2. Description of the Related Art To put HDTV to practical use, a magnetic tape capable of high-density recording is required to record a huge amount of digital image signals on a small cassette.

[0003] To achieve this, the technical report of the Institute of Television Engineers of Japan, vol. 13, No. 59, PP19-24 (1
989) reports an experimental result of digital image recording using a coating type magnetic tape using metal magnetic powder.

In the IEICE Technical Report (IEICE Technical Report) PP39-44MR90-15, Co-C
Experiments have been conducted using perpendicular magnetic tapes of the r-deposition type.

On the other hand, a magnetic tape containing Co as a main component, further containing Ni or the like, and using a ferromagnetic metal thin film formed by an oblique vapor deposition method as a magnetic layer has a high saturation magnetic flux density, a high coercive force, and is excellent. Shows electromagnetic conversion characteristics.

Therefore, IEICE Technical Report PP43-49MR90
In -7, in order to examine the isolated reproduction wave using this obliquely deposited magnetic tape, a rectangular wave is recorded and an experiment on the running direction dependence and the like are analyzed and the recording mechanism is considered. In this case, in this report, as shown in FIG. 1 on page 43, a single-layer deposited film in which columnar crystal grains grow in one direction by oblique deposition from one direction is used as the magnetic layer.

As a result, in this report, a solitary wave signal is recorded in the forward and reverse directions, and four types of isolated reproduced waveforms in the forward and reverse directions are observed.
As shown in FIG. 4 on page 5, the ratio of the time from the zero-crossing point to the peak point and the time from the peak point to the zero-crossing point is extremely large, 1/5 or less, or 5 times or more.
The asymmetry of the reproduced waveform is extremely large. Also, the overlap of the four types of reproduced waveforms is small, and the overlap of the peaks at zero or more is 60% or less between the most different reproduced waveforms.

As described above, when the isolated reproduction waveform is asymmetric and distorted, and the waveforms become irregular due to the normal / reverse rotation of the recording / reproduction, the error rate increases in the actual recording / reproduction, and the S / N ratio increases.
In addition, a complicated equalization circuit is required, or equalization becomes extremely difficult, and compatibility with a so-called metal tape or the like becomes difficult depending on the degree of distortion of the reproduced waveform.

Furthermore, since the asymmetry of the reproduced waveform differs depending on the reproducing apparatus, the asymmetry varies depending on the reproducing apparatus when viewed as an isolated reproduced waveform. Therefore, in order to achieve compatibility, it is necessary to increase the width (window margin) per unit waveform, and high-density recording becomes impossible.

By the way, it has been proposed that a magnetic tape of an oblique deposition type has a multilayer structure by laminating two or more ferromagnetic metal thin films. In the oblique evaporation method, each layer of the ferromagnetic metal thin film directs a vapor of the ferromagnetic metal at a specific angle to the surface of the non-magnetic substrate by a vapor phase method such as vapor deposition, whereby the columnar crystal grains of the ferromagnetic metal are removed from other layers. It is formed by growing a ferromagnetic metal thin film in a specific direction crossing the growth direction of columnar crystal grains (JP-B-56-26891, 56-4205).
5, 63-21254 and 60-37528, JP-A-54-603, 54-147010, 56-9452.
0, 57-3233, 57-30228, 57-135
19, 57-141027, 57-41028, 57-
141029, 57-143730, 57-14373
1, 57-147129, 58-14324, 58-5
0628, 60-76025, 61-110333, 6
1-187122, 63-10315, 63-1031
5, 63-13117, 63-14317, 63-14
320 and 63-39127, etc.).

When forming a ferromagnetic metal thin film on an obliquely deposited magnetic recording medium, an electron beam or the like is applied to a stationary ferromagnetic metal source while a non-magnetic substrate is conveyed to the surface of a rotating cylindrical cooling drum. To perform vapor deposition.

At this time, the angle between the direction in which the ferromagnetic metal is incident and the normal to the surface of the non-magnetic substrate is called an incident angle, and the vapor deposition is usually performed such that the incident angle gradually decreases from the start to the end of the vapor deposition.

At the start of vapor deposition with the largest incident angle, the vapor deposition rate is the lowest, and as the incident angle increases, the vapor deposition rate sharply increases. For this reason, the columnar crystal grains in the ferromagnetic metal thin film are nearly parallel to the surface of the non-magnetic substrate on the non-magnetic substrate side, and rapidly rise and grow in an arc shape as the distance from the surface of the non-magnetic substrate increases.

The direction of the axis of easy magnetization of such a ferromagnetic metal thin film depends on the inclination of the columnar crystal grains. And since the maximum incident angle is usually 90 °, the inclination of the columnar crystal particles depends on the minimum incident angle.

When the minimum incident angle is reduced, the inclination of the columnar crystal grains with respect to the normal to the substrate is reduced. That is, the columnar crystal particles are in a state of standing against the substrate. In this state, the axis of easy magnetization also stands up with respect to the base,
The coercive force in the in-plane direction of the ferromagnetic metal thin film is reduced.

On the other hand, when the minimum incident angle is increased, the columnar crystal grains are in a state of lying with respect to the substrate, and the axis of easy magnetization is also in a state of lying with respect to the substrate. The coercive force increases. However, in this case, the saturation magnetic flux density becomes small.

Even in a magnetic layer in which two or more ferromagnetic metal thin films are stacked, the relationship between the inclination of the columnar crystal grains and the coercive force and the saturation magnetic flux density is the same as described above.

Since the magnetic recording medium for digital recording is required to have a high recording density as described above, the magnetic layer is required to have a high coercive force and a high saturation magnetic flux density. It has been difficult to realize a high coercive force and a high saturation magnetic flux density in the magnetic layer formed by the method described above.

[0019]

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing circumstances, and has little asymmetry and distortion in an isolated reproduction waveform. Uniform, low error rate, no reduction in S / N,
Equalization is not required or a simple equalization circuit can be used.The window margin can be narrowed, and high coercive force and high saturation magnetic flux density enable high-density digital recording. It is an object of the present invention to provide a method for performing digital recording on a magnetic recording medium for oblique deposition type digital recording.

[0020]

This and other objects are achieved by the present invention which is defined below as (1) to ( 10 ). (1) A magnetic layer is provided on a substrate, and the magnetic layer exists between two or more ferromagnetic metal thin films composed of columnar crystal grains formed by oblique evaporation and an adjacent ferromagnetic metal thin film. The ferromagnetic metal thin film has a configuration in which a non-magnetic thin film is laminated, and the ferromagnetic metal thin film includes a first group and a second group, and includes columnar crystal particles of the ferromagnetic metal thin film belonging to the first group. The average growth direction and the average growth direction of the columnar crystal grains of the ferromagnetic metal thin film belonging to the second group intersect with a normal to the substrate interposed therebetween, and the ferromagnetic metal thin film belonging to the first group And a ferromagnetic metal thin film belonging to the second group and a ferromagnetic metal thin film belonging to the first group exist on at least one side of the ferromagnetic metal thin film belonging to the second group, respectively. For the magnetic metal thin film, the average growth direction of the columnar crystal grains and the main surface of the substrate The angle Nasu θ (where, 0 <θ <
90 °), and when the angle between the direction of the easy axis after demagnetizing field correction and the main surface of the base is E (0 <E <90 °), θ> E, and the surface of the base is Fine particles are arranged
And the center line average of the substrate after disposing the fine particles.
Digital recording is performed on a digital recording magnetic recording medium having a roughness Ra of 40 A or less.
How . (2) The magnetic recording method according to the above (1), wherein θ / E = 1.4 to 5 holds for each ferromagnetic metal thin film. (3) The above (1) or (2), wherein the nonmagnetic thin film mainly contains an oxide of an element contained in the ferromagnetic metal thin film.
3. The magnetic recording method according to item 1 . (4) The magnetic recording method according to any one of (1) to (3), wherein the thickness of the nonmagnetic thin film is 0.12 to 0.5 times the average value of the thickness of the ferromagnetic metal thin film. . (5) The magnetic recording according to any one of (1) to (4), wherein the ferromagnetic metal thin film contains Co as a main component.
How . (6) The magnetic recording method according to any one of the above (1) to (5), wherein the chain ratio of the fine particles is 70% or less. (7) The magnetic recording method according to any one of (1) to (6) above, wherein the coercive force in the plane of the magnetic layer is 1200 Oe or more and the residual magnetic flux density is 4000 G or more.
Law . (8) When the positive and negative solitary wave signals are recorded and reproduced, the time from the zero crossing point to the peak point is 0.5 to 2 times the time from the peak point to the zero crossing point. The magnetic recording method according to any one of 7). (9) The solitary wave signal is recorded by traveling in the forward and reverse directions, and the traveling wave is reproduced in the forward and reverse directions, respectively. When the reproduced waveforms are superimposed on each other, the overlap of the reproduced waveforms occurs. The magnetic recording method according to any one of the above (1) to (8), which is 70% or more. (10) Half width at 50 to 500 nsec, recording wavelength 0.3
The magnetic recording method according to any one of (1) to (9), wherein digital recording is performed with a signal of 5 to 0.80 μm.
Law .

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

The magnetic recording medium used in the magnetic recording method of the present invention comprises two or more ferromagnetic metal thin films formed of columnar crystal grains formed by oblique evaporation and having a non-magnetic thin film interposed therebetween.

In the case of a single-layer ferromagnetic metal thin film, the above θ and E are substantially equal. However, in the present invention, by stacking a ferromagnetic metal thin film via a non-magnetic thin film having a predetermined thickness, the average of columnar crystal grains is reduced. Interaction occurs between the ferromagnetic metal thin films whose growth directions cross each other across the normal of the substrate, and θ> E can be satisfied. That is, the direction of the axis of easy magnetization after the demagnetizing field correction is usually the same as the average growth direction of the columnar crystal grains. However, according to the present invention, the direction of the axis of easy magnetization can be made closer to the base. The above-mentioned interaction mainly occurs between two adjacent ferromagnetic metal thin films.

Therefore, according to the present invention, a coercive force higher than the coercive force according to the inclination of the columnar crystal grains with respect to the substrate can be obtained. The coercive force in this case is a coercive force in the in-plane direction of the magnetic layer.

Further, if the inclination of the columnar crystal grains with respect to the substrate is large, a high saturation magnetic flux density can be obtained, so that a higher saturation magnetic flux density can be obtained while securing a coercive force equivalent to that of the related art.

As described above, by controlling the thickness of the nonmagnetic layer and the inclination of the columnar crystal grains, a value of 1200 Oe or more can be obtained as the coercive force in the in-plane direction, and a value of 4000 G or more can be obtained as the residual magnetic flux density. Can be

In the present invention, by setting the relationship between θ and E as described above, the symmetry of the isolated reproduction waveform is improved, the distortion is reduced, and the forward / reverse of recording / reproduction is further improved. Waveform irregularities due to inversion are reduced. As a result, the error rate is low, the S / N ratio is good, the change in the shape of the reproduced waveform depending on the reproducing device is small, and the window margin required per unit waveform can be narrowed. Recording becomes possible.

Further, in the present invention, when a substrate on which fine particles are provided is used, the friction of the magnetic layer is reduced and the durability is improved. When the center line average roughness Ra of the substrate after the fine particles are provided is 40 A or less and the chain ratio of the fine particles is 70% or less, the columnar crystal particles grow uniformly, so that a high coercive force is obtained. Can be

[0039]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail.

The magnetic recording medium used in the present invention has a magnetic layer on a substrate. The magnetic layer has a configuration in which a ferromagnetic metal thin film formed of columnar crystal grains formed by oblique deposition and a non-magnetic thin film existing between adjacent ferromagnetic metal thin films are stacked.

The ferromagnetic metal thin film in the magnetic layer is composed of a first group consisting of one or more ferromagnetic metal thin films and a second group consisting of one or more ferromagnetic metal thin films. The average growth direction of the columnar crystal grains of the ferromagnetic metal thin film belonging to the first group and the average growth direction of the columnar crystal grains of the ferromagnetic metal thin film belonging to the second group intersect with a normal to the base interposed therebetween. ing.
The magnetic layer having such a configuration can be easily obtained by reversing the running direction of the base between the first group and the second group when a ferromagnetic metal thin film is deposited by an oblique deposition method described later. it can.

In the present invention, at least one side of the ferromagnetic metal thin film belonging to the first group and the ferromagnetic metal thin film belonging to the second group has a ferromagnetic metal thin film belonging to the second group, respectively. There is a ferromagnetic metal thin film belonging to the first group. That is, the ferromagnetic metal thin film in which the average growth direction of the columnar crystal grains is the same direction does not exist continuously in three layers.

For each ferromagnetic metal thin film, the angle between the average growth direction of the columnar crystal grains and the main surface of the substrate is θ, and the angle between the direction of the easy axis after demagnetizing field correction and the main surface of the substrate is θ. Assuming E, θ> E, that is, θ / E> 1, preferably θ / E = 1.4 to 5, more preferably 1.5 to 5. However, 0 <θ <90 °, 0 <E <
90 °.

In the present invention, θ and E are determined by the interaction between two ferromagnetic metal thin films in which the average growth direction of the columnar crystal grains intersects across the normal to the main surface of the substrate, and θ and E have such a relationship. Therefore, the coercive force in the in-plane direction of the magnetic layer can be improved.

By setting θ and E to the above relationship, the symmetry of the isolated reproduction waveform is improved, the distortion is reduced, and the irregularity of the waveform due to the normal / reverse rotation of the recording / reproduction is reduced. .

Specifically, the half width is 50 to 500 ns.
c, when a positive and negative solitary pulse signal train of, for example, a rectangular wave having a recording wavelength of about 0.35 to 0.80 μm is recorded,
The time (rise time) from the zero cross point to the peak point of the reproduced waveform is 0.5 to 2 times, particularly 0.8, the time from the peak point to the zero cross point (fall time).
Approximately 1.5 times.

Further, using a head tester of a fixed head system, the above-mentioned solitary wave signal is recorded in the forward and reverse directions, and is reproduced in the forward and reverse directions, respectively. When superimposed, 70% is defined as the overlapping ratio of the peaks of zero or more points of each reproduced waveform.
As described above, a value of about 80% or more, particularly about 90 to 100% is obtained.

As described above, when the reproduced waveform is symmetrical, distortion is eliminated, and when the recording / reproducing operation is reversed, the error rate is reduced, the S / N ratio is improved, and the equalization is facilitated. May be omitted or omitted, and compatibility with other tapes is also improved. Further, since there is little change in the reproduction waveform due to the difference in the reproduction apparatus, the window margin can be narrowed, and high-density recording can be performed.

The angle θ between the average growth direction of the columnar crystal grains and the main surface of the substrate is measured as follows.

First, the magnetic recording medium is cut along a plane including the growth direction of the columnar crystal grains (usually a plane perpendicular to the main surface of the medium and including the running direction of the magnetic head). In the cross section, the cross section of the columnar crystal particles constituting each ferromagnetic metal thin film appears in an arc shape. The angle formed between the side surface of the columnar crystal grains appearing in this cross section (the boundary line between adjacent columnar crystal grains) and the main surface of the substrate was measured for at least 100 columnar crystal grains for each ferromagnetic metal thin film. The average value of those in the metal thin film is determined. Then, these average values are
The angle θ between the average growth direction of the columnar crystal grains in each ferromagnetic metal thin film and the main surface of the substrate is defined as θ. The measurement position of θ is an intermediate point in the thickness direction of the ferromagnetic metal thin film.

Θ depends on the incident direction of the ferromagnetic metal in the oblique deposition method, and particularly depends on the minimum incident angle θmin.

In the present invention, the range of θ is not particularly limited.
That is, in the present invention, whatever the θ, θ and E
If the above satisfies the above relationship, the effect is realized. Therefore, an appropriate θ may be selected according to the required in-plane coercive force and saturation magnetic flux density, or the position of the ferromagnetic metal thin film in the magnetic layer. In order to obtain θ, it is preferable that θ = 40 to 80 °, particularly θ = 50 to 70 °.

The angle E between the direction of the axis of easy magnetization after the demagnetizing field correction and the main surface of the base is obtained as follows.

The direction of the axis of easy magnetization of the entire magnetic layer can be known by measuring the out-of-plane angle dependence of the squareness ratio of the magnetic layer.

More specifically, the angle between the main surface and the base surface in the plane that is the cutting plane for θ measurement is 0 ° to 180 °.
The squareness ratio is measured within a range of up to °, and the angle between the main surface of the base and the measurement direction is plotted on the horizontal axis, and the squareness ratio is plotted on the vertical axis, and an out-of-plane angle dependence graph of the squareness ratio is created. The measurement may be performed with a vibrating sample magnetometer (VSM) or the like.

From the graph of the out-of-plane angle dependence of the entire magnetic layer prepared in this manner, the direction of the easy axis of magnetization of each of the ferromagnetic metal thin films constituting the magnetic layer is determined as follows.

First, it is assumed that each ferromagnetic metal thin film is laminated with the same thickness as the magnetic layer to be measured to form a magnetic layer, and this magnetic layer is used as a magnetic layer for simulation. For this magnetic layer for simulation, an out-of-plane angle dependence graph of the squareness ratio is created by simulation.

In such a magnetic layer for simulation, the simulation is repeated while changing the direction of the easy axis of magnetization of the ferromagnetic metal thin film at predetermined steps, and an out-of-plane angle dependence graph of the squareness ratio is created. The change in the direction of the easy axis is performed for all the ferromagnetic metal thin films from the lowermost layer to the uppermost layer. And perform a simulation.

Then, from the graphs obtained by these simulations, a graph that substantially matches the out-of-plane angle dependence graph of the squareness ratio obtained from the above-described measured values of the magnetic layer is selected. At this time, the direction of the easy axis of each ferromagnetic metal thin film of the selected magnetic layer for simulation matches the direction of the easy axis of each ferromagnetic metal thin film of the actual magnetic layer. If the demagnetizing field correction described later has been performed on the graph based on the actual measurement and the graph based on the simulation, the angle between the direction of the easy axis of each ferromagnetic metal thin film in the simulation magnetic layer and the main surface of the base body is
This will match the E of each ferromagnetic metal thin film in the actual magnetic layer.

The out-of-plane angle dependence of the squareness ratio is affected by the demagnetizing field in the magnetic layer. The effect of the demagnetizing field increases as the recording wavelength decreases. The recording wavelength when used as a magnetic recording medium is extremely short, so it is hardly affected by the demagnetizing field.However, the wavelength when measuring the out-of-plane angle dependency of the squareness ratio is relatively long, so the effect of the demagnetizing field is large. Is a problem.

The demagnetizing field is generated in the thickness direction of the ferromagnetic metal thin film, and its magnitude Hd is Bmsin ² θ. Therefore, the direction of the easy axis of magnetization determined by the measurement is the direction of the combined vector of the magnetization vector in the actual easy axis direction and the demagnetizing field vector, and the direction closer to the main surface of the base than the actual easy axis. Become. The direction of the actual easy axis may be obtained by utilizing this relationship.

The correction of the demagnetizing field may be made before the graph showing the out-of-plane angle dependence of the squareness ratio, or after the graph is compared with the simulation.

The non-magnetic thin film existing between the ferromagnetic metal thin films has the function of adjusting the magnetic interaction between the ferromagnetic metal thin films on both sides.

The thickness of the nonmagnetic thin film is preferably 0.12 to 0.5 times the average value of the thickness of each ferromagnetic metal thin film. If the thickness exceeds the above range, the interaction between the ferromagnetic metal thin films on both sides hardly occurs, and θ / E becomes extremely small. On the other hand, if the thickness is less than the above range, an interaction different from the above-mentioned interaction occurs between the ferromagnetic metal thin films on both sides, so that θ / E is rather reduced.

The non-magnetic thin film preferably contains an oxide of an element contained in the ferromagnetic metal thin film as a main component. Such a non-magnetic thin film can be formed by, for example, a method of introducing an oxygen gas into a film formation atmosphere when forming a ferromagnetic metal thin film by an oblique deposition method as described below, so that high production is achieved. Property is obtained. Further, by introducing oxygen gas into the film formation atmosphere, a small amount of oxygen is taken in in addition to the nonmagnetic thin film, so that there is an effect that coercive force is improved.

In the non-magnetic thin film containing an oxide formed by such a method, the oxygen concentration gradually changes near the interface with the ferromagnetic metal thin film. The thickness is defined as follows. That is, the average value of the oxygen concentration at the midpoint in the thickness direction of the two ferromagnetic metal thin films present on both sides of the nonmagnetic thin film is defined as Mave,
Assuming that the maximum oxygen concentration of the non-magnetic thin film is Nmax, the maximum oxygen concentration point of the non-magnetic thin film is included (Nmax + Mave) /
The thickness of the region having an oxygen concentration of 2 or more is defined as the thickness of the nonmagnetic thin film.

Although the value of the maximum oxygen concentration Nmax of the non-magnetic thin film is not particularly limited, in order to obtain the above-mentioned θ / E by adjusting the interaction between the ferromagnetic metal thin films, the maximum oxygen concentration Nmax must be set. It is preferable to set it to 20% or more.

The oxygen concentration in the nonmagnetic thin film can be measured by performing elemental analysis by Auger spectroscopy while etching the magnetic layer.

The non-magnetic thin film of the present invention is not limited to the above-described thin film containing an oxide as a main component, but may be a non-magnetic compound other than an oxide or a non-magnetic metal as a main component. Is also good. Various compounds other than oxides are also preferably compounds of elements contained in the ferromagnetic metal thin film. In this case, the thickness of the non-magnetic thin film may be determined by measuring the concentration of nitrogen or carbon in the magnetic layer and measuring the thickness of the non-magnetic thin film containing an oxide as a main component.

The non-magnetic thin film may exist not only between the adjacent ferromagnetic metal thin films, but also between the substrate and the lowermost ferromagnetic metal thin film or on the uppermost ferromagnetic metal thin film. .

The thickness of the magnetic layer composed of the ferromagnetic metal thin film and the non-magnetic thin film as described above is not particularly limited.
It is preferably at least 000A. This makes it possible to sufficiently increase the output in a low band of, for example, about 0.75 MHz.

The thickness of each ferromagnetic metal thin film is about 20
It is preferably from 0 to 1500 A. If the thickness of the uppermost layer is smaller than 200 A, for example, a high-frequency signal of, for example, about 7.0 MHz cannot be sufficiently recorded, and the output decreases. On the other hand, if the thickness is larger than 1500 A, the noise increases and the signal-to-noise ratio decreases.

The number of stacked ferromagnetic metal thin films is not particularly limited, but a configuration of two, three or four or more layers may be appropriately selected in consideration of magnetic properties and productivity.

In the present invention, the ferromagnetic metal thin film is preferably a Co-based alloy containing Co as a main component, and the Co content in the ferromagnetic metal thin film is preferably 60 atomic% or more. As the Co-based alloy, Co and Ni
Or an alloy mainly containing Co, Ni and Cr. The content of each element other than Co may be appropriately selected according to the required magnetic properties and corrosion resistance.

Each ferromagnetic metal thin film is formed by an oblique evaporation method. There is no particular limitation on the oblique vapor deposition apparatus and method, and a normal one may be used.

The oblique vapor deposition method is, for example, oblique vapor deposition from one or more stationary metal sources while feeding a long film-shaped non-magnetic substrate fed from a supply roll along the surface of a rotating cooling drum. It is to be taken up on a take-up roll. In this case, the incident angle is the maximum incident angle θm at the beginning of vapor deposition.
From ax to the final minimum incident angle θmin, columnar crystal grains of a ferromagnetic metal containing Co as a main component are grown and aligned on the surface of the nonmagnetic substrate in an arc shape.

When the magnetic layer has a multilayer structure, this step is repeated.

When forming a two-layered ferromagnetic metal thin film in which the direction of incidence of the ferromagnetic metal intersects across the normal line of the non-magnetic substrate, the traveling direction of the non-magnetic substrate is reversed, and the oblique deposition is performed. Should be performed.

There is no particular limitation on the method of forming the non-magnetic thin film. However, if the deposition is carried out by introducing an oxygen gas into the film-forming atmosphere, the non-magnetic thin film mainly containing an oxide of the element constituting the ferromagnetic metal thin film can be obtained. Can be formed very easily.

In addition, a non-magnetic thin film containing an oxide as a main component can be formed by a method of treating the surface of the ferromagnetic metal thin film with oxygen gas or its plasma.

Further, Al, Cr, A are formed by alternately depositing a ferromagnetic metal thin film and a non-magnetic metal thin film.
A non-magnetic thin film containing g, Au, Pt, Ti, W or the like as a main component can also be formed.

The substrate used in the present invention is not particularly limited in its material as long as it is non-magnetic, and various films that can withstand heat during the deposition of a ferromagnetic metal thin film, for example, polyethylene terephthalate can be used. Also, JP-A-63-1031
Various materials described in No. 5 can be used.

It is preferable that minute projections are provided on the surface of the substrate used in the present invention. Since the magnetic layer is a vapor-deposited film and is extremely thin, the properties of the substrate surface appear directly on the surface of the magnetic layer. Therefore, if minute projections are provided on the surface of the base, minute projections can appear on the surface of the magnetic layer.
The protrusions on the surface of the magnetic layer reduce the friction of the magnetic layer to improve the runnability when taped, and also enhance the durability of the medium.

The properties and forming method of the fine projections on the surface of the base are not particularly limited, but the arrangement pattern of the projections and the surface roughness of the base after the formation of the projections affect the magnetic properties of the magnetic layer, particularly the coercive force. In the present invention, it is preferable that the protrusions are provided by disposing fine particles on the surface of the substrate.

The fine particles used are preferably in the form of particles, in particular, substantially spherical. For example, SiO ₂ , Al ₂
O ₃ , MgO, ZnO, MgCO ₃ , CaCO ₃ , Ca
Inorganic containing one or more of oxides such as SO ₄ , BaSO ₄ , TiO ₂ , sulfates, carbonates, etc., and oxides or salts of metals such as Si, Al, Mg, Ca, Ba, Zn, Mn, etc. Particles or spherical particles of one or more organic compounds such as polystyrene, polyester, polyamide, and polyethylene are preferred. These fine particles may or may not have magnetism.

The average particle size of the fine particles is 100 to 1000
A, particularly preferably 300 to 600A. If the average particle size is less than the above range, the friction reducing effect is small,
The effect of improving durability is also insufficient. Further, when the average particle diameter exceeds the above range, the surface roughness of the magnetic layer becomes large, and it becomes difficult to obtain the center line average roughness Ra described later, and the coercive force decreases and the high frequency characteristics become insufficient. .

The arrangement density of the fine particles is 1 / mm ²
The number is preferably from 100,000 to 100 million, particularly preferably from 1,000,000 to 70,000,000. If the arrangement density is too low, the effect of providing fine particles becomes insufficient. Further, even if the arrangement density is too high, the effect is not improved, and it is difficult to set the chain ratio described later.

It is preferable that the fine particles are arranged as uniformly as possible. If the particles are aggregated or extremely close to each other, they behave as apparently large particles (secondary particles), which is not preferable. The degree of proximity between fine particles is defined herein as a chain ratio. That is, the diameter of the particles disposed on the surface of the substrate is R,
Assuming that the distance between adjacent particles is d, the chain ratio is defined as follows: (the number of particles satisfying d <R per unit area) × 100 / (the number of particles per unit area) (unit is% ). The average particle diameter is adopted as R, and the distance d between particles and the number of particles are measured by an electron micrograph.

In the present invention, such a chain ratio is 70%
Hereinafter, it is particularly preferably 0 to 60%. When the chain ratio exceeds the above range, the fine particles behave as secondary particles, so that the growth directions of the columnar crystal particles are difficult to be uniform, and the coercive force is reduced. In addition, after the formation of the magnetic layer, the diameter and height of the protrusions appearing on the surface of the magnetic layer become extremely large, the surface properties of the magnetic layer are reduced, and the electromagnetic conversion characteristics are reduced due to spacing loss.

Center line average roughness R of the substrate after disposing fine particles
a is preferably 40 A or less, particularly preferably 30 A or less. If Ra exceeds the above range, the growth directions of the columnar crystal grains are difficult to be uniform, and the coercive force tends to decrease. In addition, when Ra is too low, the friction reducing effect is insufficient and the durability is lowered. Therefore, it is preferable that Ra is 10 A or more.

The method for arranging the fine particles on the surface of the substrate is not particularly limited. For example, a method in which fine particles are dispersed in a thin binder in which a synthetic resin is dissolved in a solvent is applied to the substrate, or such a binder is used. A method in which fine particles are adhered after coating is preferably used.

It is preferable that various known topcoat layers are provided on the magnetic layer of the magnetic recording medium used in the present invention in order to protect the magnetic layer and improve corrosion resistance. Also,
In order to secure the running property when the tape is formed, it is preferable to provide various known backcoat layers on the side of the nonmagnetic substrate opposite to the magnetic layer.

In the magnetic recording method of the present invention, digital recording and reproduction may be performed on the magnetic recording medium in various known formats in accordance with the various messages described above. In this case, the half width is usually 50 to 500 nsec and the recording wavelength is 0.35 to
Digital recording is performed at about 0.80 μm.

[0094]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention.

Example 1 0.15% by weight of SiO ₂ (average particle diameter 300A) as fine particles, 0.2% by weight of methyl cellulose as a binder, and a silane coupling agent [N-β (aminoethyl) -γ amino Propylmethyldimethoxysilane] was sufficiently mixed and dispersed with a mixture containing water as a residual solvent, and the resulting suspension was treated with polyethylene terephthalate (P) having a thickness of 7 μm.
ET) Coated on substrate surface and dried.

The arrangement density of the fine particles after drying is 10 million particles /
mm ² , the chain ratio was 50%, and Ra on the substrate surface was 30A.

Next, a ferromagnetic metal thin film was deposited on the substrate surface.

The substrate was unwound from the supply roll, moved along the peripheral surface of the rotating cylindrical cooling drum, and a ferromagnetic metal was obliquely deposited to form a ferromagnetic metal thin film, which was taken up by a take-up roll. .

Next, this take-up roll is used as a supply roll, and a ferromagnetic metal is obliquely deposited in an incident direction intersecting the incident direction at the time of the oblique evaporation with the normal direction of the substrate surface interposed therebetween, and a magnetic recording medium sample is obtained. Created.

When forming the upper and lower ferromagnetic metal thin films, a mixed gas of Ar gas and O ₂ gas was flowed into the vacuum chamber, and the pressure in the vacuum chamber was maintained at 10 ⁻⁴ Torr.
In addition, the mixed gas was caused to flow so as to be sprayed on a portion of the substrate to be deposited near the minimum incident angle.

A plurality of samples were prepared by changing the O ₂ gas concentration in the mixed gas.

For forming the upper layer and the lower layer of each sample, a ferromagnetic metal having a composition of 80 atomic% of Co and 20 atomic% of Ni was used.

Each sample thus formed is:
A nonmagnetic thin film made of an oxide was provided between the lower ferromagnetic metal thin film and the upper ferromagnetic metal thin film.

Table 1 shows the ratio of the thickness of the non-magnetic thin film to the thickness of the non-magnetic thin film (non-magnetic thin film / ferromagnetic metal thin film) in each sample. The thickness of the nonmagnetic thin film was determined by measuring the oxygen concentration distribution in the magnetic layer by Auger spectroscopy, and based on the result, by the method described above. The thickness of the ferromagnetic metal thin film was 1000 A for both the lower layer and the upper layer.

For each ferromagnetic metal thin film of each sample,
Angle θ between average growth direction of columnar crystal grains and main surface of substrate
Was measured by the method described above. The number of columnar crystal particles measured was 100. Table 1 shows the results.

An out-of-plane angle dependence graph of the squareness ratio was prepared for each sample. VSM was used for the measurement. Then, for the simulation magnetic layer as described above, an out-of-plane angle dependence graph of the squareness ratio was created by changing the direction of the easy axis of magnetization of each ferromagnetic metal thin film. These graphs were compared with an out-of-plane angle dependence graph of the squareness ratio of each sample, and the angle E between the easy axis direction and the main surface of the base was obtained for each ferromagnetic metal thin film of each sample. Table 1 shows the results.

For each sample, the coercive force Hc and the residual magnetic flux density Br in the in-plane direction of the magnetic layer were measured. Table 1 shows the results.

Each sample was cut to a width of 8 mm with a slitter and taped to form a video cassette.
Real machine with MIG head (S900 made by Sony Corporation)
, And a 1 MHz positive / negative isolated rectangular wave was recorded, and the zero cross-peak time T ₁ and the peak-zero cross time _Tr of the isolated reproduced wave were measured.

Using a drum-type head tester, the above-mentioned isolated rectangular wave was recorded in the forward and reverse directions, each was reproduced in the forward and reverse directions, and four waveforms were measured with a digital oscilloscope. Averaged and plotted out. These plots were superimposed, and the one with the smallest overlapping area of the peaks of 0 or more points was defined as the degree of overlap.

Table 1 shows the results.

[0111]

[Table 1]

From the results shown in Table 1, the effect of the present invention is clear.

When the above-mentioned composition was applied to the surface of the substrate, the chain ratio of the fine particles was changed to 80% and the Ra of the surface of the substrate was changed to 50 A by changing the application conditions such as the amount of application. Sample No. 1 In the same manner as in No. 3, a ferromagnetic metal thin film was formed. As a result, the coercive force was 1000 Oe and the residual magnetic flux density was 3800 G.

Further, when the error rate was measured using an actual machine using each of the cassettes described above, the sample no. The cassette of Sample No. 2 In comparison with the cassette No. 5, the error rate was improved by two digits or more.

[Example 2] A sample in which three ferromagnetic metal thin films were stacked was also manufactured according to the sample manufacturing method shown in Table 1. The thickness of the ferromagnetic metal thin film for each sample is
The lower layer, the middle layer, and the upper layer were all set to 600A.

The same measurement as in Example 1 was performed on these samples. The results are shown in Table 2 below.

[0117]

[Table 2]

From the results shown in Table 2, it can be seen that the present invention is also highly effective for a magnetic recording medium having a three-layered magnetic layer.

[0119]

According to the magnetic recording medium used in the magnetic recording method of the present invention , a coercive force higher than the coercive force according to the inclination of the columnar crystal grains with respect to the substrate can be obtained. Conversely, a higher saturation magnetic flux density can be obtained while securing a coercive force equivalent to that of the related art.

Since distortion of the reproduced waveform is small and symmetry is good, a window margin per unit waveform can be narrowed, and short-wavelength recording can be performed. Therefore, high-density recording utilizing the high coercive force is possible.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takataka Kobuke 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation (56) References JP-A-57-138035 (JP, A) JP-A-57 -130228 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 5/66

Claims (10)

(57) [Claims] A magnetic layer is provided on a substrate, wherein the magnetic layer comprises:
The ferromagnetic metal has a configuration in which two or more layers of ferromagnetic metal thin films composed of columnar crystal particles formed by oblique vapor deposition and a nonmagnetic thin film existing between adjacent ferromagnetic metal thin films are stacked, The thin film is composed of a first group and a second group, the average growth direction of the columnar crystal grains of the ferromagnetic metal thin film belonging to the first group, and the average thickness of the ferromagnetic metal thin film belonging to the second group. The average growth direction of the columnar crystal grains intersects across the normal of the substrate, and at least one side of the ferromagnetic metal thin film belonging to the first group and the ferromagnetic metal thin film belonging to the second group. In
There is a ferromagnetic metal thin film belonging to the second group and a ferromagnetic metal thin film belonging to the first group, respectively, and for each ferromagnetic metal thin film, an angle formed between an average growth direction of columnar crystal grains and a main surface of the substrate. To θ (where 0 <θ <90
゜), when the angle between the direction of the axis of easy magnetization after demagnetizing field correction and the main surface of the substrate is E (where 0 <E <90 °), θ> E, and the surface of the substrate is fine. Particles are disposed, said fine
The center line average roughness Ra of the substrate after disposing the particles is 40 A or less.
The digital recording to a digital recording magnetic recording medium
Performing a magnetic recording method . 2. For each ferromagnetic metal thin film, θ / E = 1.
The magnetic recording method according to claim 1, wherein 4 to 5 are satisfied. 3. The magnetic recording method according to claim 1, wherein the nonmagnetic thin film mainly contains an oxide of an element contained in the ferromagnetic metal thin film. 4. The magnetic recording method according to claim 1, wherein the thickness of the non-magnetic thin film is 0.12 to 0.5 times the average value of the thickness of the ferromagnetic metal thin film. 5. The magnetic recording device according to claim 1, wherein the ferromagnetic metal thin film contains Co as a main component.
Recording method . 6. The magnetic recording method according to claim 1, wherein a chain ratio of the fine particles is 70% or less.
Law . 7. The coercive force in the plane of the magnetic layer is 120.
7. The magnetic recording method according to claim 1, wherein the magnetic flux is 0 Oe or more and the residual magnetic flux density is 4000 G or more.
Law . 8. The recording apparatus according to claim 1, wherein the time from the zero cross point to the peak point is 0.5 to 2 times the time from the peak point to the zero cross point when the positive and negative solitary wave signals are recorded and reproduced. 8. The magnetic recording method according to any one of items 7. 9. When a solitary wave signal is recorded by traveling in the forward and reverse directions, and reproduction is performed by traveling in the forward and reverse directions, respectively, and the reproduced waveforms are superimposed.
9. The magnetic recording method according to claim 1, wherein an overlap of the reproduced waveforms is 70% or more. 10. The magnetic recording according to claim 1, wherein digital recording is performed with a signal having a half width of 50 to 500 nsec and a recording wavelength of 0.35 to 0.80 μm.
How .