JPH0773430A - Magnetic recording medium and its recording method - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium which is free from the waveform distortion of a reproduced waveform and has a small spacing loss. CONSTITUTION:The direction 30 of the axis of effective easy magnetization in the part of an upper layer 5 of a magnetic layer 19 is upward inclined to the plane of a nonmagnetic substrate 7 at a first inclination angle alpha1 which is 25 to 45 deg. on the average. The direction 31 of the axis of effective easy magnetization in the whole of the magnetic layer 19 including this part of the upper layer 5 is inclined to the plane of the nonmagnetic substrate 7 in the same direction as the first inclination angle at a second inclination angle alpha2 which is 15 to 40 deg. on the average. The first inclination angle alpha1 is made larger than the second inclination angle alpha2.

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 and a recording method therefor, and in particular, it is excellent in high density recording / reproducing characteristics.
The present invention also relates to a magnetic recording medium suitable for recording and reproducing digital signals and a recording method thereof.

[0002]

2. Description of the Related Art A perpendicular magnetic recording system is known as a magnetic recording system having excellent short-wavelength recording / reproducing characteristics. According to this method, by using a Co-Cr perpendicular magnetic recording medium and a perpendicular recording head, theoretically high density recording of 500 kFCI or more is possible. However, this method has not yet reached a practical level because mass production technology and stable system construction technology for Co-Cr perpendicular magnetic recording media and perpendicular recording heads have not yet been established.

On the other hand, in this perpendicular magnetic recording system, attempts have been made to avoid the technical problems caused by the perpendicular recording head by using a conventional ring-type recording head instead of the perpendicular recording head. However, with the use of a ring-type recording head ,. Larger reduction in output (spacing loss) due to spacing between the recording head and recording medium ,. Low reproduction output in the low-density recording area ,. The output waveform becomes a waveform (dipulse) in which a sub-peak is generated, and there is a problem that a waveform process for eliminating the sub-peak is required.

Recently, in order to alleviate the above-mentioned problems that occur when a ring type recording head is used, the easy axis of magnetization of a thin film recording medium such as a Co--Cr recording film or a Co--O recording film is in-plane from the perpendicular direction. The use of a quasi-perpendicular magnetic recording medium tilted slightly in the direction has been proposed, for example, by Japanese Patent Laid-Open No. 183014/1993.

FIG. 17 is an explanatory diagram showing a manufacturing process of the quasi-perpendicular magnetic recording medium, and FIG. 18 is an explanatory diagram showing a magnetized state when a signal is recorded on the quasi-perpendicular magnetic recording medium using a ring type recording head. FIG. 19 is a reproduction waveform diagram of this quasi-perpendicular magnetic recording medium.

The quasi-perpendicular magnetic recording medium is manufactured using a continuous vacuum vapor deposition apparatus as shown in FIG. In the figure, 101 is a film-shaped non-magnetic substrate, 102 is a supply roll of the non-magnetic substrate 101, 103 is a winding roll of the non-magnetic substrate 101, 104 is a cylindrical can, 105 is a mask,
106 is an introduced gas, 107 is an evaporation source, 108 is a crucible,
Reference numeral 109 is a shield plate, and R is the rotation direction of the can 104.

As shown in the figure, the non-magnetic substrate 101 is applied to the peripheral surface of the can 104 and travels with the rotation of the can 104, and the magnetic layer 110 is formed on the non-magnetic substrate 101 by vacuum deposition.

At this time, the position of the mask 105 provided along the peripheral surface of the can 104 is adjusted to set the incident angle of the vaporized atoms to the non-magnetic substrate 101 at the vapor deposition start position and the vapor deposition end position. The magnetic layer 110 in which the easy axis direction 114 is inclined with respect to the normal line 111 (see FIG. 18) of the surface of the magnetic substrate 101 is formed.

To explain this in detail, the non-magnetic substrate 1
Between the vapor deposition start position where the angle of incidence of vaporized atoms is 01 to 01 and the vapor deposition end position where the angle of incidence of vaporized atoms is θ12, the shield plate 1 is located at a position where the angle of incidence of vaporized atoms is θ13.
Install 09. The inert gas 106 (for example, argon) is introduced on the downstream side of the shield plate 109 in the rotation direction.

Then, in the first formation process while the incident angle changes from θ11 to θ13, as shown in FIG.
2 and subsequently, the upper layer 113 is formed by a single vapor deposition process in the second formation process while the incident angle changes from θ13 to θ12.

The incident angle θ11 is 70 ° or less, the incident angle θ12 is 0 ° or more, and the incident angle θ13 is regulated in the range of 10 ° to 40 °.
11>θ13> θ12.

By thus controlling the incident angle θ of the vaporized atoms to the non-magnetic substrate 101, at least the lower layer 112 of the magnetic layer 110 is inclined with respect to the normal line 111 to the surface of the non-magnetic substrate as shown in FIG. Easy magnetization axis 11
Have 4. Further, by introducing the inert gas 106 when forming the upper layer 113, the vaporized atoms are scattered to disturb the crystal orientation, and as a result, the magnetic anisotropy of the upper layer 113 is changed to that of the lower layer 112. A weaker quasi-perpendicular magnetic recording medium can be obtained.

As described above, FIG. 18 is a diagram showing a magnetized state when a signal is recorded on this quasi-perpendicular magnetic recording medium by using the ring type recording head, and 115a and 115b in the figure are head cores of the ring type recording head. , 116 are head gaps of the ring type recording head, 117 is a relative moving direction of the ring type recording head with respect to the magnetic recording medium, 118 is a magnetization direction in the lower layer 112, and 119 is a magnetization direction in the upper layer 113.

FIG. 19A is an isolated reproduction waveform of the upper layer 113 when a rectangular waveform signal is recorded and reproduced by a ring type recording head, and FIG. 19B is an isolated reproduction waveform of the lower layer 112.
FIG. 6C shows a reproduced waveform of the entire magnetic layer.

As shown in these figures, by adding the isolated reproduction waveform of FIG. 9A and the isolated reproduction waveform of FIG. 9B, the sub-peak 120 of FIG.
Are offset by the portion 121 in FIG. 7B, the sub-peak 122 in FIG. 2B is offset by the portion 123 in FIG. 1A, and as a result, the sub-peaks as shown in FIG. It is possible to obtain a reproduction signal having a single peak that is almost nonexistent.

[0016]

The above-mentioned proposal makes it possible to obtain a unimodal reproduction waveform having almost no sub-peaks, but the pulse width of the reproduction waveform cannot be sufficiently narrowed.
The problem of spacing loss still remains.

Particularly in a VTR in which the magnetic recording medium and the recording head are always in sliding contact with each other, wear and deterioration of the magnetic layer, recording head, lubricant, etc. cannot be avoided. Therefore, if you use a recording medium with a large spacing loss,
The substance generated by the above-mentioned wear and deterioration adheres to the surface of the head, resulting in a large reduction or fluctuation of the reproduction output, which causes a problem in reliability.

An object of the present invention is to solve the above drawbacks of the prior art and to provide a magnetic recording medium having a small spacing loss and high reliability, and a recording method therefor.

[0019]

To achieve the above object, the first aspect of the present invention provides a magnetic recording medium in which a magnetic layer is formed on a non-magnetic substrate directly or via an underlayer. The independent reproducing waveform of the upper layer side portion of the magnetic layer and the independent reproducing waveform of the portion other than the upper layer side of the magnetic layer are opposite to each other when a rectangular waveform signal is recorded and reproduced by a 0.2 μm ring-shaped magnetic head. It is characterized by being a phase.

In order to achieve the above-mentioned object, a second aspect of the present invention is a recording method of a magnetic recording medium in which a magnetic layer is formed on a non-magnetic substrate directly or via an underlayer, the upper layer side of the magnetic layer. The effective easy axis direction of the portion rises and inclines at a first inclination angle (α1) in the range of 25 ° to 45 ° on average with respect to the plane of the non-magnetic substrate, and includes the upper layer side portion. The effective easy axis direction of the entire magnetic layer is in the same direction as the first tilt angle, and the second tilt angle (α in the range of 15 ° to 40 ° on average with respect to the plane of the non-magnetic substrate).
2), the first tilt angle (α1) is larger than the second tilt angle (α2) (α1> α2), and a ring-shaped recording head is used.
The direction of the relative motion between the magnetic layer and the ring-shaped recording head is the same as the direction of the magnetic field in the vicinity of the leading core of the ring-shaped recording head and the easy axis of magnetization of the entire magnetic layer with respect to the normal line of the non-magnetic substrate. Independent reproduction waveform of the upper layer side portion of the magnetic layer and independent reproduction waveform of the portion other than the upper layer side of the magnetic layer when the predetermined signal is recorded and reproduced by scanning so as to face the direction. Are opposite in phase to each other.

[0021]

As a result of various studies on the reason why the pulse width of the reproduced waveform cannot be sufficiently narrowed in the above-proposed magnetic recording medium, the present inventors have found that the main peak 124 of the isolated reproduced waveform of FIG. Since the main peaks 125 of the isolated reproduction waveform of (b) are both on the same upper side, that is, in the same phase, the effect of canceling the isolated reproduction waveform of (a) and (b) is insufficient and the pulse width is sufficient. It was clarified that a narrow reproduction waveform could not be obtained.

Therefore, according to the present invention, the independent reproduction waveform of the upper layer side portion of the magnetic layer and the independent reproduction waveform of the portion other than the upper layer side of the magnetic layer when a rectangular waveform signal is recorded and reproduced by the ring-shaped recording head. By configuring so that they have mutually opposite phases, the effect of canceling the independent playback waveform of the upper layer side portion and the independent playback waveform of the portion other than the upper layer side is sufficiently exerted, and a playback waveform with a sufficiently narrow pulse width is obtained. can get.

Thus, it is possible to provide a highly reliable magnetic recording medium with a small spacing loss and a recording method therefor.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. 1 is an enlarged cross-sectional view of a magnetic recording medium according to an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a continuous vacuum vapor deposition apparatus for producing the magnetic recording medium, and FIG. 3 uses the magnetic recording medium according to the embodiment. FIG. 4 to FIG. 12 are reproduction waveform diagrams of respective examples, showing a state in which a signal is recorded.

First, a method of manufacturing a magnetic recording medium according to an embodiment of the present invention will be described with reference to FIG. The long film-shaped non-magnetic substrate 7 is wound from the supply roll 15 through the two cylindrical cans 16 and 17 onto the winding roll 18.

An evaporation source 24 is provided obliquely below the can 16 via an opening 20 and an opening 2 is provided obliquely below the can 17.
The evaporation sources 25 are respectively installed via 1. An electron gun 27 is provided for the evaporation source 24, an electron gun 28 is provided for the evaporation source 25, a gas introduction pipe 22 is arranged near the opening 20, and a gas introduction pipe 23 is arranged near the opening 21. ing. A plasma oxidation chamber 26 is provided between the cans 16 and 17.

The angle of incidence θ1 at the vapor deposition start position and the angle of incidence θ2 at the vapor deposition end position of the vaporized atoms forming the lower layer 6 (see FIG. 1) are restricted by the position and size of the aperture 20 and the position of the aperture 21. The angle of incidence θ3 at the vapor deposition start position and the angle of incidence θ4 at the vapor deposition end position of the vaporized atoms forming the upper layer 5 (see FIG. 1) are restricted by the size.

While the non-magnetic substrate 7 fed from the supply roll 15 passes near the opening 20, the vaporized atoms from the evaporation source 24 are attached to the non-magnetic substrate 7 by electron beam heating, as shown in FIG. The lower layer 6 is formed, and at that time, a magnetic property adjusting gas such as oxygen gas is supplied from the gas introduction pipe 22.

After being formed by the can 16, the surface of the lower layer 6 is oxidized by passing through the plasma oxidation chamber 26, so that the non-magnetic film 29 is formed.

While the lower layer 6 whose surface has been oxidized passes near the opening 21, the evaporation source 25 is heated by electron beam heating.
The vaporized atoms from the upper layer 5 shown in FIG.
Is formed, and at that time, a magnetic property adjusting gas such as oxygen gas is supplied from the gas introducing pipe 23. In this way, the magnetic recording medium having the magnetic layer 19 having the two-layer structure of the upper layer 5 and the lower layer 6 is sequentially wound on the winding roll 18.

In this embodiment, the magnetic layers 5 and 6 are laminated by using two cans 16 and 17 and two vapor deposition openings 20 and 21, respectively. However, only one can is used to provide two vapor deposition openings. A method of stacking a magnetic layer by partitioning one vapor deposition opening into two or more, a method of providing a can and a vapor deposition opening, vapor depositing once, rewinding, and then vapor depositing again to laminate the magnetic layer, A method in which one can and one evaporation opening are provided and the angle between the upper and lower sides of the magnetic layer in the easy axis of magnetization is changed by one evaporation while changing the evaporation conditions can be applied.

As described above, in the method of laminating two or more magnetic layers, the angle in the direction of the easy axis of magnetization can be changed stepwise, but in the method of forming the magnetic layer by one deposition, the easy axis of magnetization can be changed. The angle of the direction will change continuously.

As the non-magnetic substrate 7, for example, polyethylene terephthalate (PET) or polyimide is used, and the surface of the non-magnetic substrate 7 is made of SiO having a diameter of 180Å.
_Two particles are dispersed and attached at a density of about 10 particles per 1 μm ² . By dispersing and adhering the fine particles in this way, when the magnetic layer 19 is formed thereon, fine irregularities are formed on the surface of the magnetic layer 19 to improve the slipperiness of the magnetic recording medium with respect to the recording head. There is. Since the magnetic recording medium of the present invention has a small spacing loss as will be described later, even if fine irregularities are formed on the surface of the magnetic layer 19 as described above, there is almost no adverse effect due to the spacing loss.

As the evaporation sources 24 and 25, for example, C
o, Co-Cr, Co-Cr-Ni, Co-O, Co-
Ni—O or a material containing a trace amount of impurities can be used, and the evaporation source 24 and the evaporation source 25 may be the same material or different materials.

In this embodiment, the nonmagnetic layer 29 is formed on the surface of the lower layer 6 by plasma oxidation. However, a method of locally blowing oxygen gas to a portion to be oxidized, a method of temporarily exposing the surface of the lower layer 6 to the atmosphere, a method of lower layer 6 It is also possible to use a method of implanting oxygen ions on the surface of the. Also, Ti, C
Metals such as r, Al, Mn, Sn, B, C, Si and Ge, semimetals, semiconductors, oxides, nitrides thereof, Co,
Oxides such as Ni, nitrides and mixtures thereof,
It is also possible to form a thin film of a substance which is non-magnetic and does not disturb the magnetic characteristics of the upper layer side portion of the magnetic layer.

The thickness of the non-magnetic layer 29 is 30Å-100.
The range of 0 Å is appropriate, and if it is less than 30 Å, the upper layer side portion (upper layer 5 in this embodiment) of the magnetic layer 19 and the other portion (lower layer 6 in this embodiment) interact with each other to cause isolation as described later. The reproduced waveform cannot be obtained reliably. On the other hand, when it exceeds 1000 Å, the non-magnetic layer 29 becomes a spacing, and the non-magnetic layer 2
It becomes difficult for the recording head to pick up the magnetic flux from the magnetic layer below 9 (the lower layer 6 in this embodiment).

The film thicknesses of the upper layer 5 and the lower layer 6 are the same as those of the electron gun 2.
It is possible to control by the output of 7, 28 and the feeding speed of the non-magnetic substrate 7. The film thickness of the upper layer 5 is regulated to 2500 Å or less, preferably in the range of 200 Å to 1500 Å. Upper layer 5
If the film thickness exceeds 2500 Å, the portion other than the upper layer 5 is too far away from the recording head, and it becomes difficult for the recording head to pick up the magnetic flux from this portion.

The film thickness of the portion other than the upper layer 5 is 500 Å or more,
It is preferably regulated in the range of 800Å to 2000Å.
If the thickness of the portion other than the upper layer 5 is less than 500 Å, the magnetic flux picked up by the recording head from that portion becomes too small, and the effect of superposition with the reproduced waveform of the upper layer 5 cannot be sufficiently obtained.

The total thickness of the magnetic layer 19 is limited to 3500 Å or less, preferably 1000 Å to 2500 Å. If the film thickness of the entire magnetic layer 19 exceeds 3500Å, noise increases and C / N characteristics deteriorate.

The coercive force of the magnetic layer 19 depends on the type of magnetic material,
It is controlled by the kind of the blowing gas, the blowing method, the blowing amount, the temperature of the non-magnetic substrate, the surface property of the non-magnetic substrate, the crystal orientation control film, the degree of vacuum at the time of film formation, and the like.

By using these methods, the coercive force in the vertical direction of the upper layer 5 is regulated within the range of 700 to 2000 Oe. If the coercive force of this portion exceeds 2000 Oe, writing with a ring-shaped recording head becomes difficult, while if the coercive force is less than 700 Oe, it becomes difficult to keep the magnetization state stable.

The coercive force in the in-plane direction of the portion other than the upper layer 5 is 5
It is regulated in the range of 00 to 2000 Oe. When the coercive force of this portion exceeds 2000 Oe, writing with the ring-shaped recording head becomes difficult as in the case of the upper layer portion, while when the coercive force is less than 500 Oe, it becomes difficult to keep the magnetization state stable. .

The square shape in the in-plane direction of the portion other than the upper layer 5 is
It is regulated within the range of 0.4 to 0.9.

The direction of the easy axis of magnetization of the magnetic layer is determined by the angle of incidence of vapor-deposited atoms on the non-magnetic substrate, the type of magnetic material, the type of spraying gas, the spraying method, the spraying amount, the temperature of the non-magnetic substrate, and the surface property of the non-magnetic substrate. , The crystal orientation control film, and the degree of vacuum during film formation.

For example, when adjusting the vapor deposition incident angle, if the same magnetic material is used and other film forming conditions are made constant,
The larger the angle of incidence, the easier the axis of magnetization of the magnetic layer rises from the surface of the non-magnetic substrate. By utilizing this tendency, the vapor deposition incident angle is made large in the upper layer portion of the magnetic layer and the vapor deposition incident angle is made small in other portions, whereby the magnetic recording medium of the present invention can be easily manufactured.

The crystal orientation control film will be briefly described. For example, a first control film such as chromium is formed on the surface of a non-magnetic substrate, a magnetic lower layer made of cobalt is provided on the first control film, and titanium is provided on the lower layer. When a second control film made of, for example, germanium or silicon is formed and a magnetic upper layer made of a cobalt-chromium alloy is further provided thereon,
The control film and the second control film serve as crystal orientation control films, respectively. That is, the first control film has a function of controlling the in-plane crystal orientation of the magnetic lower layer, and the second control film has a function of controlling the vertical crystal orientation of the magnetic upper layer. Easy axial direction can be adjusted.

As shown in FIG. 1, the effective magnetic easy axis direction 30 of the upper layer portion of the magnetic layer is in the range of 25 ° to 45 °, preferably 30 ° to 40 ° on average with respect to the plane of the nonmagnetic substrate 7. Is inclined (first inclination angle α1). Moreover, the effective magnetic easy axis direction 31 of the entire magnetic layer including this upper layer portion
Is in the same direction as the easy axis direction of magnetization of the upper layer portion, that is, if the easy axis direction 30 of the upper layer portion is leftward as shown in FIG. Direction, and 15 ° to 40 ° on average with respect to the plane of the non-magnetic substrate 7, preferably 20 ° to 35 °.
Is inclined in the range of (second inclination angle α2). Moreover, the first inclination angle α1 is larger than the second inclination angle α2 (α1>
α2). In the figure, α3 is the inclination angle (third inclination angle) of the lower layer 6 in the easy magnetization axis direction 31, and the third inclination is such that the second inclination angle α2 is within the above range with respect to the first inclination angle α1. The angle α3 is set.

The term "effective easy magnetization axis direction" used in the specification of the present invention means that a predetermined magnetic layer is formed and the magnetization easy determined finally under the influence of a demagnetizing field. It means the axial direction.

By satisfying the above conditions of the first inclination angle α1 and the second inclination angle α2, when the rectangular waveform signal is recorded and reproduced by the ring-shaped recording head, the independent reproduction waveform of the upper layer portion of the magnetic layer is obtained. , The main peak becomes negative, the independent reproduction waveforms of the portions other than the upper layer of the magnetic layer become positive, and the phases are opposite to each other.

FIG. 3 is a diagram showing the recording state of the magnetic recording medium according to this embodiment. In the figure, 1 and 2 are the head core of the ring-shaped recording head, and 3 is the relative moving direction of the recording head with respect to the magnetic recording medium. 4 is a head gap, 8 is a magnetic layer 19
Of the recording magnetization as a whole, 9 is the recording magnetization direction of the lower layer 6, 10 is the recording magnetization direction of the upper layer 5, and 11 is the magnetic field generated from the ring-shaped recording head.

As shown in the figure, when the ring-shaped recording head is moved in the direction of arrow 3, the head core 1 is on the leading side, recording is performed for the entire thickness of the magnetic layer 19, and the direction of magnetization is the direction of arrow 8. Then, only the upper layer 5 is re-recorded on the trading (head core 2) side of the ring-shaped recording head. As a result, the magnetization directions of the upper layer 5 and the lower layer 6 are opposite to each other (see arrows 9 and 10). Further, as described above, the first inclination angle α1 of the upper layer 5 in the easy axis of magnetization is set to the lower layer 6
Is larger than the third inclination angle α3 in the easy axis direction of
The angle of the magnetization direction of the upper layer 5 is higher than the angle of the magnetization direction of the lower layer 6.

FIG. 4 shows an example of reproduction waveform of the magnetic layer magnetized in this way. FIG. 3A shows an isolated reproduction waveform of the upper layer,
The figure (b) shows the isolated reproduction waveform of the lower layer, and the figure (c) shows the reproduction waveform of the entire magnetic layer. Since the magnetization direction 10 of the upper layer and the magnetization direction 9 of the lower layer are opposite to each other as described above, the main peak 33 of the isolated reproduction waveform is negative and the sub-peak 34 is positive in the upper layer as shown in FIG. In the lower layer, the main peak 35 of the isolated reproduction waveform is negative and the sub-peak 36 is positive, as shown in FIG.

The area S1 occupied by the upper main peak 33 is smaller than the area S2 occupied by the lower main peak 35 (S1 <S2).

Then, the front parts of the main peak 33 and the main peak 35 cancel each other out, the front part of the sub-peak 34 and the rear part of the main peak 35 are added, and further the sub-peak 3
Since the rear part of 4 and the sub-peak 36 cancel each other, there is almost no phase distortion as shown in FIG. 7C, the pulse width is narrow, the left and right symmetry of the reproduced waveform is good, and the waveform processing is unnecessary. It has a single peak waveform.

Next, specific examples of the magnetic recording medium (Examples 1 to 8 of the present invention and Comparative Examples 1 to 4) will be described. (Example 1) The incident angle θ in the continuous vapor deposition apparatus shown in FIG.
1 for 50 °, θ2 for 40 °, θ3 for 90 °, θ4 for 60
And Co was used as the vapor deposition sources 24 and 25, and oxygen gas was introduced from the gas introduction pipes 22 and 23 to perform vapor deposition.

A polyethylene terephthalate film having a thickness of 10 μm is used as a non-magnetic substrate, and SiO ₂ particles having an average particle diameter of 180 Å are dispersed and adhered to the surface thereof at a density of about 10 particles per 1 μm ² .

The degree of vacuum during vapor deposition was set to 1 × 10 ^-5 Torr, and after depositing the lower layer, a non-magnetic layer of about 200 Å was formed on the surface through the plasma oxidation chamber, and the upper layer was vapor deposited thereon. The film thickness of the upper layer is 350Å, the film thickness of the lower layer is 1650Å
Therefore, the total magnetic layer becomes 2000 Å. The effective easy axis of the upper layer is inclined by 25 ° with respect to the plane of the non-magnetic substrate (α1 = 25 °), and the easy axis of magnetization of the entire magnetic layer is inclined by 23 ° in the same direction as the upper layer. Cage (α2 = 2
3 °), α1 is 2 ° larger than α2. The reproduced waveform of the magnetic recording medium obtained in this example is shown in FIG.

Example 2 A magnetic recording medium was manufactured in the same manner as in Example 1 except that the incident angle θ1 was 50 °, θ2 was 30 °, θ3 was 90 °, and θ4 was 55 °.

The effective easy axis of the upper layer is inclined by 30 ° with respect to the plane of the non-magnetic substrate (α1 = 30 °), and the easy axis of the entire magnetic layer is 23 ° in the same direction as the upper layer.
Inclined (α2 = 23 °), α1 is 7 ° more than α2
It is getting bigger. The reproduced waveform of the magnetic recording medium obtained in this example is shown in FIG.

Example 3 A magnetic recording medium was manufactured in the same manner as in Example 1 except that the incident angle θ1 was 35 °, θ2 was 20 °, θ3 was 80 °, and θ4 was 48 °.

The effective easy axis of the upper layer is inclined by 40 ° with respect to the plane of the nonmagnetic substrate (α1 = 40 °), and the easy axis of the entire magnetic layer is 23 ° in the same direction as the upper layer.
Inclined (α2 = 23 °), α1 is 17 more than α2
° It's getting bigger. The reproduced waveform of the magnetic recording medium obtained in this example is shown in FIG.

Example 4 A magnetic recording medium was manufactured in the same manner as in Example 1 except that the incident angle θ1 was 30 °, θ2 was 15 °, θ3 was 80 °, and θ4 was 43 °.

The effective easy axis of the upper layer is inclined by 45 ° with respect to the plane of the non-magnetic substrate (α1 = 45 °), and the easy axis of the entire magnetic layer is 23 ° in the same direction as that of the upper layer.
Inclined (α2 = 23 °), α1 is 22 more than α2
° It's getting bigger. The reproduction waveform of the magnetic recording medium obtained in this example is shown in FIG.

(Example 5) Example 5 except that the incident angle θ1 was 50 °, θ2 was 30 °, θ3 was 90 °, θ4 was 70 °, the upper layer had a thickness of 400 Å, and the lower layer had a thickness of 1200 Å. A magnetic recording medium was manufactured in the same manner as in 1.

The effective easy axis of the upper layer is inclined by 30 ° with respect to the plane of the non-magnetic substrate (α1 = 30 °), and the easy axis of the entire magnetic layer is 15 ° in the same direction as that of the upper layer.
It is inclined (α2 = 15 °), and α1 is 15 more than α2.
° It's getting bigger. The reproduced waveform of the magnetic recording medium obtained in this example is shown in FIG.

Example 6 A magnetic recording medium was manufactured in the same manner as in Example 5 except that the incident angle θ1 was 50 °, θ2 was 30 °, θ3 was 90 °, and θ4 was 65 °.

The effective easy axis of the upper layer is inclined by 30 ° with respect to the plane of the non-magnetic substrate (α1 = 30 °), and the easy axis of the entire magnetic layer is 20 ° in the same direction as the upper layer.
It is inclined (α2 = 20 °), and α1 is 10 more than α2.
° It's getting bigger. The reproduction waveform of the magnetic recording medium obtained in this Example 6 is shown in FIG.

Example 7 A magnetic recording medium was manufactured in the same manner as in Example 5 except that the incident angle θ1 was 30 °, θ2 was 15 °, θ3 was 70 °, and θ4 was 45 °.

The effective easy axis of the upper layer is inclined by 45 ° with respect to the plane of the non-magnetic substrate (α1 = 45 °), and the easy axis of the entire magnetic layer is 35 ° in the same direction as that of the upper layer.
It is inclined (α2 = 35 °), and α1 is 10 more than α2.
° It's getting bigger. The reproduction waveform of the magnetic recording medium obtained in this example is shown in FIG.

Example 8 A magnetic recording medium was manufactured in the same manner as in Example 5 except that the incident angle θ1 was 30 °, θ2 was 15 °, θ3 was 70 °, and θ4 was 40 °.

The effective easy axis of the upper layer is inclined by 45 ° with respect to the plane of the non-magnetic substrate (α1 = 45 °), and the easy axis of the entire magnetic layer is 40 ° in the same direction as that of the upper layer.
Inclined (α2 = 40 °), α1 is 5 ° more than α2
It is getting bigger. The reproduced waveform of the magnetic recording medium obtained in this example is shown in FIG.

Comparative Example 1 A magnetic recording medium was manufactured in the same manner as in Example 1 except that the incident angle θ1 was 70 °, θ2 was 30 °, θ3 was 20 °, and θ4 was 10 °.

The effective easy axis of the upper layer is inclined by 51 ° with respect to the plane of the non-magnetic substrate, and the easy axis of magnetization of the entire magnetic layer is inclined by 42 ° in the same direction as the upper layer. The reproduced waveform of the magnetic recording medium obtained in this comparative example is as shown in FIG. 13, and the inclination angle of the easy axis of magnetization of both the upper layer and the entire magnetic layer is too large, so that the reproduction output is very small.

Comparative Example 2 A magnetic recording medium was manufactured in the same manner as in Example 1 except that the incident angle θ1 was 90 °, θ2 was 65 °, θ3 was 60 °, and θ4 was 50 °.

The effective easy axis of the upper layer is inclined by 21 ° with respect to the plane of the non-magnetic substrate, and the easy axis of the entire magnetic layer is inclined by 12 ° in the same direction as the upper layer. The reproduction waveform of the magnetic recording medium obtained in this comparative example is as shown in FIG. 14, and since the inclination angle of the easy axis of magnetization of both the upper layer and the entire magnetic layer is too small, the isolated reproduction waveform (a) and the isolated reproduction waveform (a) are isolated. By canceling the reproduced waveform (b),
This is not preferable because the reproduction output of the entire magnetic layer decreases.

Comparative Example 3 A magnetic recording medium was manufactured in the same manner as in Example 1 except that the incident angle θ1 was 40 °, θ2 was 30 °, θ3 was 90 °, and θ4 was 65 °.

The effective easy axis of the upper layer is tilted by 11 ° with respect to the plane of the non-magnetic substrate, and the easy axis of magnetization of the entire magnetic layer is tilted by 30 ° in the same direction as the upper layer. The reproduction waveform of the magnetic recording medium obtained in this comparative example is as shown in FIG. 15. Since the inclination angle of the easy axis of magnetization of the upper layer is too small, the perpendicular magnetization component is small and a sufficient reproduction output can be obtained. Absent.

(Comparative Example 4) The incident angle θ1 is set to 90 by using only the first can without using the second can.
The magnetic recording medium was manufactured without forming plasma oxidation by forming a magnetic layer consisting of a 2100Å-thick Co single layer with θ and θ2 set to 55 °. The easy axis of magnetization is inclined by 30 ° with respect to the plane of the non-magnetic substrate.

FIG. 16 shows the reproduced waveform of the magnetic recording medium obtained in this comparative example. As shown in FIG. 16, the reproduced output is large, but the reproduced waveform has poor left-right symmetry. If the right and left symmetry of the reproduced waveform is poor in this way, there is a need for waveform processing.

In the above-mentioned embodiment, the case of a magnetic layer having a substantially two-layer structure has been described, but a laminated structure of three or more layers may be used, or an isolated reproduction waveform of the upper layer portion and the other portions with one magnetic layer. However, the inclination angle of the easy axis of magnetization in the upper layer portion and other portions can be continuously made different.

In the present invention, for example, in order to prevent corrosion of the magnetic layer due to invasion of water from the nonmagnetic substrate side,
It is also possible to form an underlayer of aluminum or the like between the non-magnetic substrate and the magnetic layer. The underlayer can also be formed with a film having another composition for other purposes.

[0082]

EFFECTS OF THE INVENTION Each magnetic recording medium described above is slit into a tape shape, and a gap length of 0.2 μm is used for an 8 mm VTR MIG.
Using the head, a rectangular waveform signal was recorded and reproduced at a relative speed of 3.8 m / sec between the magnetic recording medium and the recording head.

As a result, the recording medium of the above embodiment is shown in FIGS.
As shown in FIG. 12, there is almost no waveform distortion of the isolated reproduction waveform, and a sharp reproduction waveform is obtained. On the other hand, the recording media of Comparative Examples 1 to 3 have a small reproduction output as shown in FIGS. 13 to 15, and particularly the reproduction outputs of Comparative Examples 1 and 3 are very small. This is probably because recording could not be performed in the lower layer.

The spacing dependence of the reproduction output when a non-magnetic layer having a predetermined thickness is formed on each of the above-mentioned tape-shaped magnetic recording media by vapor deposition and a rectangular waveform signal is recorded and reproduced is shown. The results were investigated and shown in comparison with the following Table 1.

The spacing loss Ls in the table is a numerical value represented by the following equation. The larger this value, the larger the spacing loss.

Ls = K · S / λ K: Spacing loss coefficient S: Spacing amount λ: Recording wavelength Table 1 Spacing loss Ls Example 1 125 Example 2 128 Example 3 133 Example 4 135 Example 5 115 Example 6 118 Example 7 138 Example 8 141 Comparative Example 4 120 Co—O quasi-perpendicular magnetization film 210 Generally, spacing when recording and reproducing a signal on a perpendicular magnetization recording medium using a ring-shaped recording head. It is considered that the increase in loss is caused by difficulty in saturated recording because the vertical magnetic field generated by the ring-shaped recording head is strong only in the vicinity of the head core and sharply decreases when it is separated from the head core. Magnetic recording medium of the present invention (Examples 1 to 8)
Is considered to have a low spacing loss because the perpendicular magnetization component in the medium that causes the spacing loss is locally present in the portion having a strong vertical magnetic field near the head core, that is, in the upper layer portion of the magnetic layer.

As is clear from the above table, the magnetic recording media of the present invention (Examples 1 to 8) have a small spacing loss which is almost equal to that of Comparative Example 4. The magnetic recording medium of Comparative Example 4 has poor symmetry of the reproduced waveform as apparent from FIG. 16, but the magnetic recording medium of the present invention does not have such a problem.

The evaluation results are summarized in Table 2 below. As is apparent from this table, the present invention in which α1 is 25 ° to 45 °, α2 is 15 ° to 40 °, and α1> α2 has an excellent reproduced waveform.

Table 2 α1 (°) α2 (°) Evaluation Example 1 25 23 Good reproduction waveform Example 2 30 23 〃 Example 3 40 23 〃 Example 4 45 23 〃 Example 5 30 15 〃 Example 6 30 20 〃 Example 7 45 35 〃 Example 8 45 40 〃 Comparative Example 1 51 42 Small playback output Comparative Example 2 21 12 〃 Comparative Example 3 11 30 30 〃 Comparative Example 4 30-Playback waveform symmetry problem (EN) A magnetic recording medium and a recording method therefor having almost no waveform distortion, good waveform symmetry, a sharp reproduced waveform, a small spacing loss, and high reliability. be able to.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a magnetic recording medium according to an example of the present invention.

FIG. 2 is a schematic configuration diagram of a continuous vapor deposition apparatus used in an example of the present invention.

FIG. 3 is an explanatory diagram showing a state when a signal is recorded on the magnetic recording medium according to the example of the present invention.

FIG. 4 is a diagram showing an example of a reproduction waveform of a magnetic recording medium according to the present invention.

FIG. 5 is a reproduction waveform diagram of the magnetic recording medium according to the first embodiment of the present invention.

FIG. 6 is a reproduction waveform diagram of the magnetic recording medium according to the second embodiment of the present invention.

FIG. 7 is a reproduction waveform diagram of a magnetic recording medium according to Example 3 of the present invention.

FIG. 8 is a reproduction waveform diagram of a magnetic recording medium according to Example 4 of the present invention.

FIG. 9 is a reproduction waveform diagram of a magnetic recording medium according to Example 5 of the invention.

FIG. 10 is a reproduction waveform diagram of a magnetic recording medium according to Example 6 of the invention.

FIG. 11 is a reproduction waveform diagram of the magnetic recording medium according to Example 7 of the present invention.

FIG. 12 is a reproduction waveform diagram of a magnetic recording medium according to Example 8 of the invention.

13 is a reproduction waveform diagram of the magnetic recording medium according to Comparative Example 1. FIG.

FIG. 14 is a reproduction waveform diagram of a magnetic recording medium according to Comparative Example 2.

15 is a reproduction waveform diagram of the magnetic recording medium according to Comparative Example 3. FIG.

16 is a reproduction waveform diagram of the magnetic recording medium according to Comparative Example 4. FIG.

FIG. 17 is a schematic configuration diagram of a continuous vapor deposition apparatus for manufacturing a conventionally proposed magnetic recording medium.

FIG. 18 is an explanatory diagram showing a state when a signal is recorded on a conventionally proposed magnetic recording medium.

FIG. 19 is a reproduction waveform diagram of a conventionally proposed magnetic recording medium.

[Explanation of symbols]

 1, 2 Head core 3 Head movement direction 4 Head gap 5 Upper layer 6 Lower layer 7 Nonmagnetic substrate 8, 9, 10 Direction of recording magnetization 19 Magnetic layer 29 Nonmagnetic layer 30 Easy axis of upper layer 31 Easy axis of entire magnetic layer 32 Easy axis of lower layer 33 Main peak of upper layer 34 Sub peak of upper layer 35 Main peak of lower layer 36 Sub peak of lower layer α1 First tilt angle α2 Second tilt angle α3 Third tilt angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryo Yano 1-88, Tora, Ibaraki, Osaka Prefecture Hitachi Maxell Co., Ltd. (72) Inventor Naoki Kitagaki 1-88, Tora, Ibaraki, Osaka Hitachi Maxel Co., Ltd.

Claims (11)

[Claims] 1. A magnetic recording medium in which a magnetic layer is formed on a magnetic substrate directly or via an underlayer, a rectangular waveform signal is recorded and reproduced by a ring-shaped magnetic head having a gap length of 0.2 μm. In this case, the independent reproduction waveform of the upper layer side portion of the magnetic layer and the independent reproduction waveform of the portion other than the upper layer side of the magnetic layer have opposite phases to each other. 2. The area S1 occupied by the main peak in the independent reproduction waveform of the upper layer side portion of the magnetic layer according to claim 1, the area S2 occupied by the main peak in the independent reproduction waveform of portions other than the upper layer side of the magnetic layer. A magnetic recording medium characterized by being smaller than 3. The first tilt angle (wherein the effective easy axis direction of the upper layer side portion of the magnetic layer is in the range of 25 ° to 45 ° on average with respect to the plane of the nonmagnetic substrate according to claim 1. α1) rises and is inclined, and the effective easy axis direction of the entire magnetic film including the upper layer side portion is in the same direction as the first inclination angle and is 15 on average with respect to the plane of the non-magnetic substrate. The second tilt angle (α1) is larger than the second tilt angle (α2) (α1> α2). Magnetic recording medium. 4. The magnetic recording medium according to claim 1, wherein the first inclination angle (α1) is restricted to a range of 30 ° to 40 °. 5. The magnetic recording medium according to claim 1, wherein the second inclination angle (α2) is regulated within a range of 20 ° to 35 °. 6. The magnetic recording medium according to claim 1, wherein the magnetic film is composed of a plurality of laminated bodies, and an uppermost layer of the magnetic layer includes the upper layer side portion. 7. The third tilt according to claim 6, wherein the effective easy axis directions of layers other than the uppermost layer of the magnetic layer are in the range of 10 ° to 30 ° on average with respect to the plane of the nonmagnetic substrate. A magnetic recording medium, characterized in that it rises and is inclined at an angle (θ3). 8. The magnetic recording medium according to claim 1, wherein a nonmagnetic film is formed between the uppermost layer of the magnetic layer and a layer other than the uppermost layer. 9. A recording method of a magnetic recording medium in which a magnetic layer is formed on a non-magnetic substrate directly or via an underlayer, wherein an effective easy axis direction of an upper layer side portion of the magnetic layer is the non-magnetic substrate. Is inclined and rises at a first inclination angle (α1) in the range of 25 ° to 45 ° on average, and the effective easy axis direction of the entire magnetic layer including the upper layer side portion thereof is Inclining with a second inclination angle (α2) in the same direction as the first inclination angle and in the range of 15 ° to 40 ° on average with respect to the plane of the non-magnetic substrate, and the first inclination angle (α1) is Greater than the second tilt angle (α2) (α1
> Α2) A magnetic recording medium is used. A ring-shaped recording head is used, and the direction of relative movement between the magnetic layer and the ring-shaped recording head is determined by the magnetic field direction in the vicinity of the leading core of the ring-shaped recording head and the magnetic layer. When a predetermined signal is recorded and reproduced by scanning so that the direction of the easy axis of magnetization is oriented in the same direction with respect to the normal line of the non-magnetic substrate, the independent reproduction waveform of the upper layer of the magnetic layer becomes independent. A recording method for a magnetic recording medium, wherein the reproduction waveform and the independent reproduction waveform of the portion other than the upper layer side of the magnetic layer have mutually opposite phases. 10. The recording method for a magnetic recording medium according to claim 9, wherein the first inclination angle (α1) is restricted to a range of 30 ° to 40 °. 11. The recording method for a magnetic recording medium according to claim 9, wherein the second inclination angle (α2) is restricted to a range of 20 ° to 35 °.