JPH11213375A - Magnetic recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make accurately reproducible an information signal at a high speed by facilitating movement of a magnetic barrier in a magnetic barrier movement layer constituting a recording track. SOLUTION: This magnetic recording medium is provided with a first base body 2 and a band-shaped recording track consisting of a magnetic material layer formed on the surface of this first base body 2. In this case, the magnetic material layer constituting the recording track 9 consists of at least a magnetic recording layer 5 and a magnetic barrier movement layer 7 which has a magnetic wall coercive force smaller than that of the magnetic recording layer 5 and has a high magnetic barrier movement speed, and areas on both sides of the recording track 9 are so constituted that the magnetic barrier movement layer 7 is not formed there.

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 capable of recording information signals at high density. Especially,
The present invention relates to a magnetic recording medium capable of reproducing a recorded information signal by a domain wall motion reproducing method.

[0002]

2. Description of the Related Art Conventionally, there are known magnetic recording media for recording information signals at high density and various systems for reproducing information signals recorded on the magnetic recording media. In particular, the reproducing method proposed by the present applicant in Japanese Patent Application Laid-Open No. 6-290496 is a method for reproducing an information signal from a magneto-optical recording medium, which is a magnetic recording medium in which an information signal is recorded by a domain wall formed on a recording track. It is characterized by reproducing the information signal by moving the domain wall at high speed by applying a driving force to the domain wall and detecting the movement, enabling the reproduction of the information signal recorded at a very high recording density. (Domain wall moving reproduction method).

A configuration of a magnetic recording medium used in a conventionally known domain wall displacement reproducing system will be described. FIG.
8A is a partially enlarged view showing a cross section parallel to a recording track of a magneto-optical recording medium 20 which is a magnetic recording medium, FIG. 8B is a partially enlarged view seen from a lower surface direction, and FIG. FIG. 4 is a partially enlarged view showing a cross section perpendicular to FIG.

Here, the magneto-optical recording medium 20 is composed of a base material 21 made of a transparent material such as polycarbonate and a base material 2.
1 is composed of a magnetic layer 25 formed on the first magnetic layer.

[0005] On a substrate 21, grooves (grooves) 22 each having a side wall 24 on both sides are formed in parallel at a constant pitch. The magnetic layer 25 is composed of three stacked layers of magnetic material, that is, a magnetic recording layer 26, a switching layer 27, and a domain wall displacement layer 28. Here, the domain wall motion layer 28 is a perpendicular magnetization film having a smaller domain wall coercive force and a larger domain wall mobility than the magnetic recording layer 26, and
Reference numeral 7 denotes a film of a magnetic material having a lower Curie temperature than the domain wall displacement layer 28 and the magnetic recording layer 26, and the magnetic recording layer 26 is a perpendicular magnetization film. The magnetic layer 25 is formed on the bottom surface and the side surface 24 of the groove 22 and on the upper surface of the land 23 between the grooves 22. Magnetic layer 25 formed on upper surface of land 23
Constitutes a band-like recording track 29.

[0008] Q1, Q2,..., Q9 in FIG. 8 are domain walls formed on the recording track 29 corresponding to the information signals. Using a magneto-optical recording / reproducing apparatus, the magnetic head applies a magnetic field modulated by an information signal to a recording track 29 of the magneto-optical recording medium 20 and irradiates a recording light beam through the base 21 with the optical head. When the recording track 29 is scanned while scanning, the magnetic layer 25 constituting the recording track 29 has a row of magnetization regions having an upward or downward magnetization corresponding to the direction of the applied magnetic field as shown by the up and down arrows. It is formed. A domain wall Q1, which is an information signal mark, is provided at a boundary between the magnetization region and the front and rear magnetization regions.
, Q9 are formed in a line. These domain walls are exchange-coupled between the domain wall displacement layer 28, the switching layer 27, and the magnetic recording layer 26.

Next, the magneto-optical recording / reproducing apparatus shown in FIG.
Magneto-optical recording medium 2 on which information signals are recorded in the state shown in FIG.
A method of reproducing an information signal from 0 using the domain wall displacement reproduction method will be described.

The optical head of the magneto-optical recording and reproducing apparatus scans the recording track 29 while converging and irradiating a reproducing light beam on the recording track 29 of the magneto-optical recording medium 20. 9A and 9B are diagrams for explaining the principle of signal reproduction. FIG. 9A is a cross-sectional view showing an enlarged portion of the magneto-optical recording medium 20 irradiated with a reproducing light beam, and FIG. FIG.

The reproducing light beam is transmitted through the base material 21 of the magneto-optical recording medium 20 and applied to the recording track 29 so as to converge on a minute light spot 30. The light spot 30 of the reproducing light beam scans the recording track 29 in the direction of arrow B. The recording track 2 is irradiated by the reproduction light beam.
9 is heated, and a temperature distribution having a peak at a position Xp slightly behind the center of the light spot 30 is formed. Here, reference numeral 31 denotes an isotherm indicating a region where the temperature reaches Ts which is a temperature near the Curie temperature of the switching layer 27.

[0010] The temperature of a certain point on the recording track 29 is increased by the isotherm 31 during the passage through the irradiation area of the light spot 30.
Rises above the temperature Ts at the position Xf, which is the front end of the isotherm, turns to fall after reaching the peak at the position Xp, passes through the position Xr which is the rear end of the isotherm 31, and falls below the temperature Ts again.

At a position far from the light spot 30 of the reproducing light beam, the temperature of the recording track 29 is sufficiently low. At this position, the magnetic recording layer 26, the switching layer 27, and the domain wall displacement layer 28 are exchange-coupled to each other. And
Therefore, the domain wall transferred to the domain wall displacement layer 28 is restrained. In addition, since the temperature distribution around the domain wall is substantially uniform, no driving force for moving the domain wall transferred to the domain wall moving layer 28 acts, and the domain wall does not move.

On the other hand, in a region of the switching layer 27 surrounded by the isotherm 31, that is, a portion between the position Xf and the position Xr, the temperature is higher than Ts and the magnetization has disappeared. The switching layer 27, the switching layer 27, and the domain wall displacement layer 28 are not exchange-coupled to each other, and the domain wall is not restricted. Moreover, the domain wall (Q5 in FIG. 9) that has reached the position Xf receives a driving force due to the temperature gradient. For this reason,
This domain wall is located at a position Xp where the temperature is high and the domain wall energy is low from the position Xf as indicated by the arrow C in the domain wall displacement layer 28.
Start moving towards. With the movement of the domain wall, a magnetized region Rex having a magnetization in one direction (upward in the illustrated example) is formed while extending. At this time, since the magnetic recording layer 26 is made of a material having a small domain wall mobility, the domain wall does not move in the magnetic recording layer 26. In FIG. 9B, the magnetic recording layer 2 located between the position Xf and the position Xr where the magnetization of the switching layer 27 has disappeared is shown.
The domain walls Q1 to Q5 of No. 6 are indicated by broken lines. Thus, the domain wall Q
Each of 1, Q2,..., Q9 sequentially moves toward the position Xp each time it reaches the position Xf, and each time, the magnetization regions Rex having the upward and downward magnetizations are alternately formed. The polarization plane of the reflected light of the reproducing light beam from the magnetization region Rex is:
Due to the magneto-optical effect (Kerr effect), the magnetization region Rex rotates according to the direction of magnetization. Such rotation of the polarization plane is detected by the optical head. Since this detection signal includes a change in the signal corresponding to the movement of the domain wall, if the domain wall is formed at a position corresponding to the information signal, the information signal can be reproduced from the timing of the signal change. is there.

[0013]

In the reproduction of the information signal by the domain wall displacement reproducing method described above, the recording track 29 is magnetically connected to the regions on both sides of the domain wall displacement layer 28 so that the domain wall can move easily. Desirably, the coupling is reduced.

If the magnetic layer 25 is formed on the side wall 24 of the groove 22,
Is not formed at all, the magnetic layer 25 and the groove 22 on the upper surface of the land 23 constituting the recording track 29 are formed.
Is separated from the magnetic layer 25 on the bottom surface by the side wall 24, so that the magnetic coupling between the two can be cut off.

However, in the above-mentioned conventional magneto-optical recording medium 20, the inclination α of the side wall 24 of the groove 22 of the substrate 21 is at most about 70 degrees, and the magnetic layer is formed on the substrate 21 by a sputtering film forming method or the like. When the magnetic layer 25 is formed, the thickness of the magnetic layer 25 formed on the side wall 24 of the groove 22 is at least about 40% of the thickness of the magnetic layer 25 formed on the top surface of the land 23 and the bottom surface of the groove 22. It is. This is not thin enough to reduce the magnetic coupling between the recording track 29 and the regions on both sides thereof.

For this reason, by the action of magnetic coupling between the recording track 29 and the regions on both sides of the recording track 29, in the reproduction of the information signal by the above-mentioned domain wall displacement reproduction method, the domain wall displacement layer 28
In this case, the domain wall movement is hindered, and as a result, the domain wall movement speed becomes slow.As a result, it is difficult to reproduce the information signal at high speed. There is a problem that it becomes impossible.

An object of the present invention is to provide a magnetic recording medium which facilitates movement of a domain wall in a domain wall moving layer forming a recording track, and can reproduce an information signal at high speed and accurately, and a method of manufacturing the same.

[0018]

The present invention provides a first substrate,
And a magnetic recording medium having a band-shaped recording track formed of a magnetic material layer formed on the surface of the first base material, wherein the magnetic material layer forming the recording track includes at least a magnetic recording layer; A magnetic recording medium (I) comprising a domain wall displacement layer having a smaller domain wall coercive force and a larger domain wall mobility than the magnetic recording layer, and the domain on both sides of the recording track is not formed with the domain wall displacement layer. About.

The present invention also relates to a first base material and the first base material.
In a magnetic recording medium provided with a band-shaped recording track composed of a magnetic material layer formed on the surface of a base material, the magnetic material layer constituting the recording track is at least a magnetic recording layer and a magnetic recording layer. The magnetic material layers formed on both sides of the recording track are formed of a domain wall moving layer having a small domain wall coercive force and a large domain wall mobility. The present invention relates to a magnetic recording medium (II), which is different from the layer in magnetic properties.

The present invention also relates to the method of manufacturing the magnetic recording medium (I), wherein the step of forming the magnetic material layer on the surface of the first base material includes the step of forming a photoresist on the surface of the magnetic material layer. Forming a film, projecting the pattern of the recording track onto the photoresist film and exposing the film,
Removing only the exposed or unexposed portions of the photoresist film by a development process, and removing all of the exposed layer of the magnetic material, or removing a portion so that the domain wall motion layer does not remain, The present invention relates to a method for manufacturing a magnetic recording medium, comprising:

The present invention also relates to the above magnetic recording medium (II)
Forming the magnetic material layer on the surface of the first base material, forming a photoresist film on the surface of the magnetic material layer, and forming the recording track on the photoresist film. Projecting and exposing the pattern, removing only the exposed or unexposed portions of the photoresist film by a developing process, and changing the magnetic properties by injecting charged particles into the exposed layer of the magnetic material. And a method of manufacturing a magnetic recording medium.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A magnetic recording medium according to a first embodiment of the present invention and a method for manufacturing the same will be described below.

FIGS. 1 and 2 show the configuration of the magneto-optical recording medium 1, respectively, and are partially enlarged views showing a cross section perpendicular to the recording track 9 of the magneto-optical recording medium 1. FIG. Here, the magneto-optical recording medium 1 has a disk shape with a diameter of 64 mm, and is bonded to the first substrate 2, the magnetic layer 4 formed on the first substrate 2, and the first substrate 2. It is composed of the second base material 3. Reference numeral 8 denotes an adhesive layer for bonding.

The first substrate 2 is formed of a flexible sheet having a uniform thickness, and examples of the material include resin materials such as polyethylene terephthalate, polyimide, polycarbonate, and polyester. The thickness of the first base material 2 is preferably 200 μm or less, and the thickness distribution (unevenness) is 3 μm or less at maximum (± 1.5 μm or less).
It is preferred that The second substrate 3 is made of a transparent resin material such as polycarbonate and polymethyl methacrylate, and preferably has a thickness of 0.3 to 1.2 mm.

The magneto-optical recording medium 1 is provided with a recording track 9 formed in a concentric band shape or a spiral band shape and constituted by the magnetic layer 4. In the example shown in FIG. 1, the magnetic layer 4 forming the recording track 9 is composed of three layers made of laminated magnetic materials, that is, a magnetic recording layer 5, a switching layer 6, and a domain wall displacement layer 7, and the recording track 9
The magnetic layer 4 is not formed in the region 10 (between recording tracks) on both sides of the magnetic recording medium.

In the example shown in FIG. 2, the magnetic layer 4 forming the recording track 9 is made of a laminated magnetic material.
Layers, that is, a magnetic recording layer 5, a switching layer 6, and a domain wall displacement layer 7, and regions 10 on both sides of the recording track 9 (between recording tracks) do not include the domain wall displacement layer 7 and are separated from the magnetic recording layer 5 and the switching layer 6. And a magnetic layer 4. The thickness of the magnetic layer 4 (total of three layers) is 100 to 20.
Desirably, it is 0 nm.

As described above, the magnetic layer 4 constituting the recording track 9 has at least the domain wall moving layer 7, and the regions 10 between the recording tracks 9 (between the recording tracks) include the domain wall moving layer 7. Therefore, the domain wall displacement layer 7 forming the recording track 9 is not magnetically coupled to the regions 10 on both sides of the recording track 9.

Here, the domain wall motion layer 7 constituting the magnetic layer 4 is a perpendicular magnetization film having a smaller domain wall coercive force and a larger domain wall mobility than the magnetic recording layer 5, and the switching layer 6 is composed of the domain wall motion layer 7 and the magnetic field. It is a film of a magnetic material having a lower Curie temperature than the recording layer 5, and the magnetic recording layer 5 is a perpendicular magnetization film.

When a magnetic field modulated by an information signal is applied to the recording track 9 of the magneto-optical recording medium 1 using a magneto-optical recording / reproducing apparatus and a recording light beam is irradiated through the second base material 3, the recording track 9 In 9, a domain wall is formed and an information signal is recorded.

After that, a reproducing light beam is irradiated through the second base material 3 to form the domain wall moving layer 7 constituting the recording track 9.
According to the domain wall movement reproduction method in which the domain wall is moved in and the movement of the domain wall is detected from the reflected light of the reproduction light beam,
The recorded information signal can be reproduced. here,
Since the domain wall motion layer 7 forming the recording track 9 is not magnetically coupled to the regions (between the recording tracks) 10 on both sides of the recording track 9, the motion of the domain wall in the domain wall motion layer 7 forming the recording track 9 does not occur. It will be easier.

On the surface of the first substrate 2, a preformat signal mark (for example, an address) composed of the magnetic layer 4 is formed regardless of the uneven structure of the first substrate 2 itself such as pits (recesses). Marks of information signals and synchronization signals). Alternatively, a preformat signal mark can be formed by partially removing the magnetic layer 4. Such a preformat signal mark can be detected from the reflected light of the reproducing light beam by utilizing the difference in reflectance with the surrounding area.

A tracking mark for controlling the tracking of a recording or reproducing light beam can be provided on the surface of the first substrate 2. Such a tracking mark can be constituted by the magnetic layer 4 similarly to the above-mentioned preformat signal mark, without depending on the uneven structure provided on the first base material 2 itself such as pits and grooves. Alternatively, it can be formed by partially removing the magnetic layer 4.

Next, a method for manufacturing the magneto-optical recording medium 1 will be described. As shown in FIGS. 4 and 5, the manufacturing process of the magneto-optical recording medium according to the present embodiment includes (a) a magnetic layer forming process, (b) a photoresist coating process, (c) an exposing process, and (d). Development step, (e) etching step,
It comprises (f) a photoresist removal step, (g) a bonding step, and (h) a cutting step. Hereinafter, each step will be described in order.

(A) Step of Forming Magnetic Layer First, a long sheet-shaped roll 11 of the first base material 2 made of a resin material is prepared. The surface of the first base material 2 is flat, and no uneven structure such as pits (recesses) or grooves is formed on the surface.

Next, the first base material 2 is sent out by rotating the roll 11, and while being transported in the direction of arrow A, the magnetic material is continuously formed on the upper surface thereof by sputtering using the film forming apparatus 12 or the like. , A switching layer 6 and a domain wall motion layer 7 are sequentially laminated to form a magnetic layer 4.

(B) Photoresist Coating Step A positive or negative photoresist film 14 is formed on the surface of the magnetic layer 4 using the coating device 13 while the first substrate 2 is being conveyed.

(C) Exposure Step The photoresist film 14 formed on the first substrate 2 is exposed using the exposure device 15 in the following procedure.

First, the lower surface of the first substrate 2 (the surface on which the photoresist film 14 is not formed) is placed on the stage 1 of the exposure apparatus 15.
6 and fixed to the surface thereof by vacuum suction or the like. The surface of the stage 16 is processed with a high flatness of, for example, 2 μm or less, and the first base material 2 has flexibility, so that it is sufficiently adhered to the surface of the stage 16. As a result, the upper surface of the first substrate 2 (the surface on which the photoresist film 14 is formed)
Is the sum of the flatness of the stage 16 and the thickness distribution (unevenness) of the first base member 2, for example, 5 μm or less.

Next, light generated by a light source (not shown) of the exposure device 15 is applied to a mask 17 having a concentric or spiral band-like recording track pattern formed on a surface of a glass substrate 18 by a metal film 19 such as Cr. To the first substrate 2 to project an image of a pattern of a recording track, thereby exposing the photoresist film 14. Here, it is desirable that the wavelength of the light to be irradiated be short, since the exposure can be performed with high resolution. For this purpose, for example, a high-pressure mercury lamp is used as a light source, and the generated g-line (wavelength 436 n
m), h-line (wavelength 405 nm) or i-line (wavelength 365)
nm). Alternatively, a KrF excimer laser (wavelength 248 nm) or an ArF excimer laser (wavelength 1
93 nm).

The irradiation light is parallel light, and the pattern of the recording tracks formed on the mask 17 is changed to the photoresist film 1.
4 may be projected as a 1 × image, or the irradiation light may be focused light, and the pattern of the recording track formed on the mask 17 may be reduced to about 10 to 80% and projected. In particular, the method of reducing exposure is suitable for manufacturing a magneto-optical recording medium having a diameter of 80 mm or less and a recording track pitch of 1 μm or less because the exposure area is small but the resolution is high. Further, the depth of focus of the exposure device 15 is larger than the flatness of the upper surface of the first base material 2, for example, 6 μm (± 3 μm).
Then, since the projected image is not blurred, a recording track with high dimensional accuracy can be formed.

When the exposure is completed, the first base member 2 is released from being fixed to the stage 16 by suction, is conveyed a predetermined distance in the direction of arrow A, and then the above-described exposure operation is repeated.

(D) Developing Step The exposed portion of the photoresist film 14 by the developing process,
Alternatively, only the non-exposed portion is removed to expose a part of the magnetic layer 4. Here, the portion of the magnetic layer 4 where the photoresist film 14 is not removed serves as a recording track.

(E) Etching Step The exposed portion of the magnetic layer 4 by the development, that is, the portion between the recording tracks is removed by wet etching or dry etching such as plasma etching, RIE (reactive ion etching), or ion milling. I do. When manufacturing the magneto-optical recording medium 1 shown in FIG. 1, all of the magnetic recording layer 5, the switching layer 6, and the domain wall motion layer 7 are removed. Magneto-optical recording medium 1 shown in FIG.
Is manufactured, only the domain wall motion layer 7 is removed as shown. A portion where the photoresist film 14 is formed,
That is, the portion of the magnetic layer 4 that will be the recording track is not removed.

(F) Photoresist Removal Step When the remaining photoresist film 14 is removed, a strip-shaped recording track 9 composed of the magnetic layer 4 including the domain wall displacement layer 7 is formed. Has no magnetic layer or a magnetic layer not including the domain wall motion layer 7 is formed.

(G) Laminating Step The second substrate 3 formed into a disk shape is laminated to the portion of the first substrate 2 where the recording tracks 9 are formed, using an adhesive.

(H) Cutting Step When the first substrate 2 is cut in accordance with the outer shape of the second substrate 3, the magneto-optical recording medium 1 is completed. The cutting step may be performed before the bonding step (g).

The recording track 9 and the preformat signal mark or tracking mark composed of the magnetic layer 4 or the preformat signal mark or tracking mark formed by partially removing the magnetic layer 4 are formed on the surface of the first base material 2. To form a mark, in the exposure step (c) of the above-described manufacturing method, a pattern of a recording track, a pattern of a preformat signal mark and a pattern of a tracking mark are formed on the mask 17 by the metal film 19, and these are formed. May be projected onto the photoresist film 14. If the exposed magnetic layer 4 is removed after the development processing, the magnetic layer 4 between the recording tracks 10 is removed, and at the same time, a preformat signal mark or tracking mark made of the magnetic layer 4 or a portion of the magnetic layer 4 is formed. A pre-format signal mark and a tracking mark are formed by mechanical removal.

[Second Embodiment] Hereinafter, a magnetic recording medium according to a second embodiment of the present invention and a method of manufacturing the same will be described.

FIG. 3 shows the configuration of the magneto-optical recording medium 1 and is a partially enlarged view showing a cross section perpendicular to the recording tracks 9 of the magneto-optical recording medium 1. Here, the magneto-optical recording medium 1 is in the form of a disk having a diameter of 64 mm,
Magnetic layer 4 formed on first base material 2 and first base material 2
And a second base material 3 bonded to the base material. Reference numeral 8 denotes an adhesive layer for bonding.

The first substrate 2 is made of a flexible sheet having a uniform thickness, and examples of the material include resin materials such as polyethylene terephthalate, polyimide, polycarbonate, and polyester. The thickness of the first base material 2 is preferably 200 μm or less, and the thickness distribution (unevenness) is 3 μm or less at maximum (± 1.5 μm or less).
It is preferred that The second substrate 3 is made of a transparent resin material such as polycarbonate and polymethyl methacrylate, and preferably has a thickness of 0.3 to 1.2 mm or less.

The magnetic layer 4 is made of a laminated magnetic material.
Layers, that is, a magnetic recording layer 5, a switching layer 6, and a domain wall displacement layer 7, and the thickness (total of the three layers) is 100 to
Desirably, it is 200 nm.

The magnetic layer 4 forms a recording track 9 formed in a concentric band shape or a spiral band shape. The areas 10 (between the recording tracks) on both sides of the recording track 9 are also formed of the magnetic layer 4.

The domain wall motion layer 7 of the magnetic layer 4 constituting the recording track 9 is a perpendicular magnetization film having a smaller domain wall coercive force and a larger domain wall mobility than the magnetic recording layer 5, and the switching layer 6 is composed of the domain wall motion layer 7 and the magnetic field. It is a film of a magnetic material having a lower Curie temperature than the recording layer 5, and the magnetic recording layer 5 is a perpendicular magnetization film.

Charged particles are injected into the magnetic layer 4 constituting the regions 10 (between the recording tracks) on both sides of the recording track 9 so that the magnetic properties of the domain wall motion layer 7, especially the perpendicular magnetic anisotropy, are recorded. Domain wall displacement layer 7 constituting track 9
Has been reduced.

With such a configuration, the recording track 9
The magnetic coupling between the magnetic domain wall moving layer 7 and the magnetic layer 4 forming the regions 10 on both sides of the recording track 9 is reduced.

When a magnetic field modulated by an information signal is applied to the recording track 9 of the magneto-optical recording medium 1 using a magneto-optical recording / reproducing apparatus and a recording light beam is irradiated through the second base material 3, the recording track In 9, a domain wall is formed and an information signal is recorded.

After that, a reproducing light beam is irradiated through the second base member 3 to form the domain wall moving layer 7 forming the recording track 9.
According to the domain wall movement reproduction method in which the domain wall is moved in and the movement of the domain wall is detected from the reflected light of the reproduction light beam,
The recorded information signal can be reproduced. here,
The magnetic domain wall movement layer 7 constituting the recording track 9 has reduced magnetic coupling with the regions (between the recording tracks) 10 on both sides of the recording track 9, so that the movement of the domain wall in the domain wall movement layer 7 constituting the recording track 9 is reduced. Becomes easier.

When charged particles are injected into the magnetic layer 4 constituting the regions 10 (between the recording tracks) on both sides of the recording tracks 9 by the manufacturing method described later, the optical characteristics (reflectance and magneto-optical characteristics) change at the same time. I do. Therefore, if this is used, the optical characteristics of the magnetic layer 4 are partially changed without depending on the uneven structure of the first base material 2 itself such as pits (recesses) on the surface of the first base material 2. Thereby, a pre-formatted signal mark (for example, a mark of an address information signal or a synchronization signal) can be formed. Such a preformat signal mark can be detected from the reflected light of the reproducing light beam by utilizing the difference in the optical characteristics from the surroundings.

A tracking mark for tracking control of a recording or reproducing light beam can be provided on the surface of the first base material. Such a tracking mark does not depend on the concavo-convex structure of the first base material 2 itself, such as pits (recesses) on the surface of the first base material 2, but similarly to the above-described preformat signal mark. Can be formed by a partial change in the optical characteristics of

Next, a method for manufacturing the above-described magneto-optical recording medium will be described. As shown in FIGS. 6 and 7, the manufacturing process of the magneto-optical recording medium according to the present embodiment includes (a) a magnetic layer forming process, (b) a photoresist coating process, (c) an exposing process, and (d). Development step, (e) ion implantation step,
It comprises (f) a photoresist removal step, (g) a bonding step, and (h) a cutting step. Hereinafter, each step will be described in order.

(A) Step of Forming Magnetic Layer First, a long sheet-like roll 11 of the first base material 2 made of a resin material is prepared. The surface of the first base material 2 is flat, and no uneven structure such as pits (recesses) or grooves is formed on the surface.

Next, the first base material 2 is sent out by rotating the roll 11, and while being transported in the direction of arrow A, the magnetic material is continuously formed on the upper surface thereof by sputtering using a film forming apparatus 12 or the like. The magnetic recording layer 5, the switching layer 6, and the domain wall motion layer 7 are sequentially laminated to form the magnetic layer 4.

(B) Photoresist Coating Step A positive or negative photoresist film 14 is formed on the surface of the magnetic layer 4 using the coating device 13 while the first substrate 2 is being conveyed.

(C) Exposure Step The photoresist film 14 formed on the first base material 2 is exposed using an exposure device 15 in the following procedure.

First, the lower surface of the first substrate 2 (the surface on which the photoresist film 14 is not formed) is placed on the stage 1 of the exposure apparatus 15.
6 and fixed to the surface thereof by vacuum suction or the like. The surface of the stage 16 is processed with a high flatness of, for example, 2 μm or less, and the first base member 2 has flexibility, so that it is sufficiently adhered to the surface of the stage. As a result, the flatness of the upper surface of the first base material 2 (the surface on which the photoresist film 14 is formed) is the sum of the flatness of the stage 16 and the distribution (unevenness) of the thickness of the first base material 2, for example. It becomes 5 μm or less.

Next, light generated by a light source (not shown) of the exposure device 15 is applied to a mask 17 having a concentric or spiral band-like recording track pattern formed on the surface of a glass substrate 18 by a metal film 19 of Cr or the like. To the first substrate 2 to project an image of a pattern of a recording track, thereby exposing the photoresist film 14. Here, it is desirable that the wavelength of the light to be irradiated be short, since the exposure can be performed with high resolution. For this purpose, for example, a high-pressure mercury lamp is used as a light source, and the generated g-line (wavelength 436 n
m), h-line (wavelength 405 nm) or i-line (wavelength 365)
nm). Alternatively, a KrF excimer laser (wavelength 248 nm) or an ArF excimer laser (wavelength 1
93 nm).

The irradiation light is parallel light, and the pattern of the recording track formed on the mask 17 is changed to the photoresist film 1.
4 may be projected as a 1: 1 image, but the irradiation light may be focused light, and the pattern of the recording tracks formed on the mask 17 may be reduced to about 10 to 80% and projected. In particular, the method of reducing exposure is suitable for manufacturing a magneto-optical recording medium having a diameter of 80 mm or less and a recording track pitch of 1 μm or less because the exposure area is small but the resolution is high. The depth of focus of the exposure device 15 is
Is larger than the flatness of the upper surface of, for example, 6 μm (± 3 μ
If m), the projected image is not blurred, and a recording track with high dimensional accuracy can be formed.

When the exposure is completed, the first base member 2 is released from being fixed to the stage 16 by suction, is conveyed a predetermined distance in the direction of arrow A, and the above-described exposure operation is repeated again.

(D) Developing Step The exposed portion of the photoresist film 14 by the developing process,
Alternatively, only the non-exposed portion is removed to expose a part of the magnetic layer 4. Here, the portion of the magnetic layer 4 where the photoresist film 14 is not removed serves as a recording track.

(E) Step of Injecting Charged Particles Charged particles (for example, ionized atoms and molecules such as Ti ions) are exposed as shown by arrows in the exposed portions of the magnetic layer 4 by the development, that is, the portions between the recording tracks. Inject at high speed. The structure of the exposed magnetic layer 4 is destroyed by the collision of the charged particles, and the magnetic properties of the domain wall displacement layer 7,
In particular, perpendicular magnetic anisotropy decreases. Here, the domain wall displacement layer 7
In order to sufficiently reduce the magnetic characteristics of the magnetic domain wall moving layer 7, it is desirable that the depth of the charged particle injection be at least equal to or greater than the thickness of the domain wall displacement layer 7. Since the charged particles are shielded by the photoresist film 14, the charged particles are not injected into a portion to be a recording track.

(F) Photoresist Removal Step When the remaining photoresist film 14 is removed, a band-shaped recording track 9 composed of the magnetic layer 4 into which charged particles are not injected, and charged particles are injected to form the domain wall moving layer. The magnetic characteristics 7, in particular, the interval 10 between the recording tracks with reduced perpendicular magnetic anisotropy are formed.

(G) Laminating Step The second substrate 3 formed into a disk shape is laminated to the portion of the first substrate 2 where the recording tracks 9 are formed, using an adhesive.

(H) Cutting Step When the first substrate 2 is cut in accordance with the outer shape of the second substrate 3, the magneto-optical recording medium 1 is completed. The cutting step may be performed before the bonding step (g).

In order to form a preformat signal mark and a tracking mark on the surface of the first base material 2 together with the recording tracks 9 by a partial change in the optical characteristics of the magnetic layer 4, the above-described manufacturing method is used. In the exposure step (c), a pattern of a preformat signal mark and a pattern of a tracking mark are formed on the mask 17 together with the recording track pattern by the metal film 19, and images of these patterns are projected on the photoresist film 14. do it. After the development process, the charged magnetic particles are injected into the exposed magnetic layer 4 to obtain optical characteristics (reflectance and magneto-optical characteristics) of the magnetic layer 4.
Changes, the magnetic characteristics between the recording tracks 10 are reduced, and at the same time, preformat signal marks and tracking marks with partially changed optical characteristics are formed.

In each of the embodiments described above, when the first base material 2 is made of a resin material, the thickness of the first base material 2 is 200 μm.
If the thickness is larger than m, the flexibility is reduced and deformation such as warpage is likely to occur. In this case, in the exposure step (c) of the above-described manufacturing method, it is difficult to correct deformation such as warpage of the first base material 2 and bring the first base material 2 into close contact with the flat stage 16 of the exposure apparatus 15. First substrate 2 fixed to
Of the upper surface of the exposure device 15 becomes larger than the depth of focus of the exposure device 15. As a result, the projected image of the pattern of the recording track is blurred, and a recording track with high dimensional accuracy cannot be formed. Therefore, it is desirable that the thickness of the first base material 2 be 200 μm or less.

However, when the thickness of the first base material 2 is 20
Even if it is larger than 0 μm, the temperature of the first base material is set to 80 to 80 in the exposure step (c) of the above manufacturing method.
If the flexibility is improved by heating to about 150 ° C., the first substrate 2 can be brought into close contact with the stage 16.

In the manufacturing method of each of the above embodiments, in the exposure step (c), the lower surface of the first substrate 2 (the surface on which the photoresist film 14 is not formed) is placed on the stage 16 of the exposure apparatus 15. The upper surface of the first substrate 2 (the surface on which the photoresist film 14 is formed)
Exposure may be performed in a state where the mask is fixed to the mask 17 in close contact. Also in this case, the thickness of the first base material 2 is set to 200 μm.
It is desirable to make it adhere to the mask 17 as follows.

In the production of the magnetic recording medium of the present invention,
A pit (recess) of a preformat signal mark is formed on a base material on which a magnetic layer is formed as in a conventional magneto-optical recording medium.
It is also conceivable to previously form pits or tracking grooves of tracking marks. However, if the pits of the preformat signal mark, the pits of the tracking mark, or the tracking groove are formed on the first base material 2 in advance, in the exposure step (c) of the above manufacturing method, Of the preformat signal mark, the pit of the tracking mark or the tracking groove
The pattern of the recording track must be projected (with an accuracy of the order of μm). However, since the first base material 2 made of a resin material can easily change its dimensions due to the influence of tension, thermal expansion, or the like, such alignment is very difficult. For this reason, as described in each of the above embodiments, the surface of the first base material 2 is flat, and an uneven structure such as a pit of a preformat signal mark, a pit of a tracking mark, or a tracking groove is provided. Without
Partial removal of the magnetic layer 4 (first embodiment)
It is desirable to form a preformat signal mark and a tracking mark by a partial change in optical characteristics (second embodiment).

When recording or reproducing a signal on the magneto-optical recording medium 1 of the present invention by a magneto-optical recording / reproducing apparatus, if the base material of the magneto-optical recording medium 1 is only the first base material 2, In some cases, the rigidity of the magnetic recording medium 1 is insufficient, causing deflection. Therefore, it is desirable that the second base material 3 be bonded to have sufficient rigidity. At this time, it is desirable that the second base material 3 be thicker or have higher rigidity than the first base material 2. However, when the magneto-optical recording / reproducing apparatus is provided with means for preventing the bending of the magneto-optical recording medium 1, for example, means for holding the magneto-optical recording medium 1 from above and below, the second base material is not always required. 3 is not required.

The magnetic recording medium of each of the above-described embodiments irradiates the recording track 9 with the recording or reproducing light beam through the second base material 3 to record or reproduce the information signal. The magnetic recording layer 5, the switching layer 6, and the domain wall moving layer 7 are sequentially formed from the side of the first base material 2 in the order of lamination of the magnetic layer 4; In order to irradiate the recording track 9 with a reproducing light beam through the first base material 2 to record or reproduce an information signal, the first base material 2 is made of a transparent material, The lamination order may be the domain wall displacement layer 7, the switching layer 6, and the magnetic recording layer 5 in this order from the first base material 2 side.

The present invention is not limited to a magneto-optical recording medium capable of reproducing an information signal by utilizing the magneto-optical effect as shown in the above embodiment, but a magnetic flux generated by an elongated magnetized region. Is detected by a magnetic head provided with a coil or a magnetoresistive effect (MR) element, whereby the movement of the domain wall can be detected, and the present invention can also be applied to a magnetic recording medium.
In any case, according to the present invention, the domain wall motion layer forming the recording track is formed so that the magnetic coupling with the regions on both sides of the recording track is sufficiently reduced or not magnetically coupled. Therefore, the movement of the domain wall in the domain wall displacement layer becomes extremely easy.

[0082]

According to the configuration of the magnetic recording medium of the present invention as described above, the magnetic coupling between the recording track and the regions on both sides thereof is sufficiently reduced or the coupling is broken. In the reproduction of the information signal by the domain wall motion reproducing method, the motion of the domain wall in the domain wall motion layer is facilitated. As a result, the moving speed of the domain wall is increased, and the information signal can be reproduced at a high speed, and the information signal can be accurately reproduced without reproducing the erroneous information signal due to the non-movement of the domain wall.

According to the method of manufacturing a magnetic recording medium of the present invention, the first substrate on which the layer of the magnetic material is formed has flexibility, so that the first substrate is closely fixed to the stage of the exposure apparatus in the above-described exposure step. Thus, a recorded track with high dimensional accuracy can be formed without blurring the projected image of the pattern of the recorded track.

If the pattern of the preformat signal mark and the tracking mark are formed on the mask of the exposure apparatus together with the pattern of the recording track, the preformat signal mark and the tracking mark formed of the magnetic material layer can be used. Alternatively, it is possible to form a preformat signal mark and a tracking mark by partially removing the magnetic material layer, and a preformat signal mark and a tracking mark by partially changing the optical characteristics of the magnetic material layer. For this reason, it is not necessary to provide an uneven structure such as a pit of a preformat signal mark, a pit of a tracking mark, or a tracking groove on the first base material. There is no need to accurately align the pits (concave portions) or tracking grooves of the tracking mark with the position of the image of the pattern of the recording track to be projected, which facilitates manufacturing.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view illustrating a configuration of a magnetic recording medium according to a first embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing another configuration of the magnetic recording medium according to the first embodiment of the present invention.

FIG. 3 is a partial cross-sectional view illustrating a configuration of a magnetic recording medium according to a second embodiment of the present invention.

FIG. 4 is a diagram illustrating a manufacturing process of the magnetic recording medium according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a manufacturing process of the magnetic recording medium according to the first embodiment of the present invention.

FIG. 6 is a diagram illustrating a manufacturing process of the magnetic recording medium according to the second embodiment of the present invention.

FIG. 7 is a diagram illustrating a manufacturing process of the magnetic recording medium according to the second embodiment of the present invention.

FIG. 8 is a diagram showing a configuration of a conventional magnetic recording medium.

FIG. 9 is a diagram illustrating the principle of information signal reproduction by the domain wall motion reproduction method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 20 Magneto-optical recording medium 2 1st base material 3 2nd base material 4, 25 Magnetic layer 5, 26 Magnetic recording layer 6, 27 Switching layer 7, 28 Domain wall displacement layer 8 Adhesive layer 9 Recording track 10 Areas on both sides of recording track (between recording tracks) 11 Roll 12 Film forming device 13 Coating device 14 Photoresist film 15 Exposure device 16 Stage 17 Mask 18 Glass substrate 19 Metal film 21 Base material 22 Groove 23 Land

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G11B 11/10 541 G11B 11/10 541A

Claims (13)

[Claims] 1. A magnetic recording medium comprising a first base material and a band-like recording track formed of a magnetic material layer formed on a surface of the first base material, wherein a magnetic material forming the recording track is provided. The material layer includes at least a magnetic recording layer and a domain wall motion layer having a smaller domain wall coercive force and a larger domain wall mobility than the magnetic recording layer. A magnetic recording medium characterized by the above-mentioned. 2. A magnetic recording medium comprising a first base material and a band-like recording track formed of a magnetic material layer formed on a surface of the first base material, wherein a magnetic material constituting the recording track is provided. The material layer includes at least a magnetic recording layer and a domain wall displacement layer having a smaller domain wall coercive force and a larger domain wall mobility than the magnetic recording layer. Wherein the magnetic properties of the recording track are different from those of the magnetic material layer constituting the recording track. 3. The magnetic recording medium according to claim 1, wherein the surface of the first base material is flat, and no uneven structure is formed. 4. The method according to claim 1, wherein the first base material is made of a resin material, and has a thickness of 200 μm or less.
4. The magnetic recording medium according to 2 or 3. 5. A pre-format signal mark or tracking mark formed from the magnetic material layer or a pre-format signal mark or tracking mark formed by partially removing the magnetic material layer. 4. The magnetic recording medium according to claim 1, 2 or 3. 6. The magnetic device according to claim 2, further comprising a preformat signal mark or a tracking mark formed by injecting charged particles into the magnetic material layer to partially change optical characteristics. recoding media. 7. The magnetic recording medium according to claim 1, wherein the first base is made of a material that transmits light. 8. The magnetic recording medium according to claim 1, further comprising a second base material bonded to the first base material. 9. The magnetic recording medium according to claim 8, wherein the second base is made of a material that transmits light. 10. The magnetic recording medium according to claim 8, wherein the second base is thicker than the first base. 11. The magnetic recording medium according to claim 8, wherein the second base has higher rigidity than the first base. 12. The method for manufacturing a magnetic recording medium according to claim 1, wherein the step of forming the magnetic material layer on the surface of the first base material includes the step of forming a photoresist film on the surface of the magnetic material layer. Forming, exposing the pattern of the recording track to the photoresist film by exposing, exposing only the exposed or unexposed portions of the photoresist film by a development process, and exposing the magnetic material Removing the entirety of the layer or partially removing the domain wall displacement layer so as not to remain. 13. The method for manufacturing a magnetic recording medium according to claim 2, wherein the step of forming the magnetic material layer on the surface of the first base material includes the step of forming a photoresist film on the surface of the magnetic material layer. Forming, exposing the recording track pattern onto the photoresist film by exposing, exposing only the exposed or unexposed portions of the photoresist film by a developing process, and exposing the magnetic material A step of injecting charged particles into the layer to change magnetic properties.