JP2000276803A - Magneto-optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magneto-optical disk which is capable of maintaining stable rotation and data reliability even at the high-speed rotation, has a central hole and rotates via a hub carried in this central hole. SOLUTION: Material having a thermal conductivity of >=0.05 (cal/ deg.C.cm.s) is used for the hub and material having a thermal conductivity of >=10.3 to 10.6 (cal/ deg.C∼cm.s) Izod strength of >=5 (kgf.cm/cm) is used for a substrate. The relationship between the diameter Y of the hub and the diameter X of the substrate is set at Y/X>=0.28. As a result, even if the magneto-optical disk is rotated at >=720 rpm, the rotation may be stably maintained without the occurrence of a write/read error.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a magneto-optical disk, and more particularly to a structure of a magneto-optical disk having high data reliability and rotational stability even in a high-speed rotation region.

[0002]

2. Description of the Related Art Conventionally, as a method of mounting a magneto-optical disk, a mechanical clamp system and a magnetic clamp system have been adopted. The magnetic clamp method
As shown in FIG. 1, a hub capable of supporting the substrate 1 on the receiving surface of the spindle 2 and attracting by a magnet attached to the center of the substrate 1 does not require a fixing device for the magneto-optical disk unlike the mechanical clamp system. The method of pressing against the disk receiving surface of the spindle 2 by 3 has an advantage that the apparatus can be downsized as compared with the mechanical clamp method. However, this method has a problem of retardation that a strain stress is generated in the substrate due to a change in ambient temperature due to a difference in thermal expansion coefficient between the plastic substrate and the hub. This retardation disturbs the polarization state of the recording / reproducing light of the magneto-optical disk, resulting in deterioration of the recording / reproducing characteristics. On the other hand, FIG. 2 shows a basic configuration diagram which provides one means for solving this disadvantage. One example of this is disclosed in
The structure is described in detail in 2-46446.
This means that the hub 3 for the magnetic clamp is
The substrate 1 and the magnetic clamping hub 3 are released without being fixed to the substrate, and the magnetic clamping hub 3 is attracted by the magnet 4 installed on the spindle 2, and at the same time, the magnetic clamping hub 3 is attached to the substrate 1. Pressing and rotating the disc. In this method, no problem of retardation occurs because the magnetic clamp hub and the substrate are not fixed.

[0003]

However, when this was actually carried out, there was no problem with the conventional rotational speed, but when the rotational speed was increased to realize a high transfer rate, the rotational speed was increased to 720 rpm. At the above rotation speed, a phenomenon was observed in which vibration occurred in the recording / reproducing apparatus, and tracking errors and data write / read errors frequently occurred. Also, this phenomenon was not observed at all below 720 rpm, but beyond that, it became more pronounced as the rotation speed increased. The reason for this is that as a result of various considerations, the rotational force of the disk is larger than the frictional force acting between the substrate and the hub for the magnetic clamp, causing slip, making the rotation of the magneto-optical disk unstable, It is possible that unevenness occurs. Furthermore, it is considered that the surface runout and the turbulence (turbulence) of the air flow caused by the rotation unevenness have an influence.

When the thickness of the substrate is reduced to improve the recording density, the rigidity of the substrate is reduced. It is conceivable that uneven rotation and turbulence may occur due to deformation or deformation.

Further, it is considered that the higher the rotation speed, the more turbulence occurs due to the rotation of the disk inside the cartridge, which affects the rotation stability of the disk. It is also conceivable that the turbulence increases rotation unevenness and surface runout.

Further, due to high-speed rotation and rotation unevenness,
It is also conceivable that the amount of heat generated from the spindle motor increases and a larger amount of heat is transmitted to the substrate.

[0007] Further, it is considered that when a high-speed rotation condition is added to a thin substrate, the influence thereof is further increased due to a synergistic effect.

The present inventors have tried to solve the above problem by changing the magnet of the spindle to a magnet having a large magnetic force and increasing the attraction force between the spindle and the hub for magnetic clamping. A problem occurred. It is considered that this is because the magnetic field of the magnet of the spindle affects the magneto-optical signal. Therefore, the present invention has been made to solve such a problem, and provides a magneto-optical disk that can be rotated at a high speed by a mechanical clamp system or a magnetic clamp system that does not cause retardation. It is in.

[0009]

Means for Solving the Problems The present inventors have conducted various studies to solve this problem. As a result, if the contact area between the spindle receiving surface and the substrate is constant, a magnetic clamp for the substrate is required. It was found that if the area of the hub was secured, the frictional force between the magnetic clamping hub and the substrate was increased to increase the carrying force of the substrate, and the above problem did not occur during recording / reproduction of the magneto-optical disk. is there. In addition, by using a hub with a thermal conductivity of 0.05 cal / ° C · cm · s or more, the area of the magnetic clamp hub with respect to the substrate is secured, and the spindle is inserted through the magnetic clamp hub. It was found that the heat from the car could be efficiently dissipated. Also,
To improve the recording density, the substrate thickness of the recording area should be 0.7 mm
Even if it is set to the following, the substrate thickness outside the recording area is 0.7 mm
By increasing the thickness or fixing a reinforcing member having a tensile strength equal to or higher than the tensile strength of the substrate to a part of the substrate, the rigidity of the entire substrate can be increased, and by suppressing the occurrence of surface runout, It has been found that the synergistic effect of securing the area of the magnetic clamping hub and that of the magnetic clamping hub can reduce the occurrence of uneven rotation and the occurrence of turbulence.
Also, on the substrate projection surface of the inner surface of the cartridge case, at least one of a convex portion and a concave portion for adjusting the flow of air at the time of rotation of the disk is formed, thereby suppressing the occurrence of turbulent flow.
It has been found that the synergistic effect of increasing the rigidity of the entire substrate and securing the area of the magnetic clamping hub with respect to the substrate can improve the increase in surface runout and the effect on the rotation property.

That is, at least a plastic substrate having a center hole, and a layer including a recording layer made of at least a rare earth-transition metal are laminated on the substrate, and a hub supported by the substrate is provided at the center of the substrate. A hub mounted on a spindle of a recording / reproducing apparatus for recording / reproducing while rotating and housed in a cartridge, wherein the hub has a diameter Y and the magneto-optical disc The above problem was solved by setting the relationship between the substrate diameter X and Y / X ≧ 0.28.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magneto-optical disk embodying the means for achieving the object of the present invention will be described below with reference to the drawings.

FIG. 3 shows a magneto-optical disk according to the present invention.
FIG. 2 schematically shows a cross-sectional view of a portion mounted on a spindle of a recording / reproducing apparatus.

The magneto-optical recording medium is formed on a transparent substrate 11 formed by injection molding and having a guide groove on one side for guiding a laser beam to a target position on a disk. 12, a reproducing layer 13, an auxiliary magnetic layer 14,
Second dielectric layer 15, recording layer 16, magnetic capping layer 1
7, a third dielectric layer 18 and a heat dissipation layer 19 are formed in this order, and a protective layer 20 is spin-coated on the uppermost portion.

The transparent substrate 11 is formed of a plastic material such as a polycarbonate resin, an epoxy resin, or PMMA into a desired disk shape. The thermal conductivity of the transparent substrate 11 is 10-3 to 10-6 (cal / C) in order to prevent the transmission of heat from the spindle motor.
· Cm · s) is desirable, and at rotation speeds with a large calorific value of 720 rpm or more, 10−4 to 5 × 10−6 (cal / ° C. · c)
m · s). The Izod strength is 5 kg according to the measurement method ASTM D256 in order to suppress the surface runout of the substrate.
f · cm / cm or more is desirable, and at a rotational speed where the load of the substrate of 720 rpm or more is large, 5.5 kgf · cm / cm or more is desirable.

On one surface of the transparent substrate 11, a pre-format pattern comprising a guide groove for guiding a laser spot and a pre-pit row indicating the address of a recording track defined along the guide groove has a fine unevenness. And a tracking servo signal and a preformat signal can be optically read.

The shape of the substrate will be described with reference to FIGS. The cross-sectional view of FIG. 4A shows the inner region 5a and the outer region 6a.
And their areas and areas 7a where recording and reproduction are performed
Are exaggerated for clarity.

FIG. 4B shows that only the thickness of the outer region 6b is different from that of FIG. 4A in the inner region 5b and the recording / reproducing region 7b.
The case where the thickness is larger than the thickness is shown. 4C is the inner area 5c
Is smaller than the thicknesses of the outer region 6c and the recording / reproducing region 7c. FIG. 4D shows a case where the thickness of the outer area 6d is smaller than the thickness of the inner area 5d and the recording area 7d. FIG. 4E shows the outer region 6 e and the inner region 5.
The case where the thickness of e is smaller than the thickness of the recording / reproducing area 7e is shown.

FIG. 4F shows a case where the outer region 6f, the inner region 5f and the recording / reproducing region 7f have different thicknesses. FIG. 4G also shows a case where the outer region 6g, the inner region 5g, and the recording / reproducing region 7g have different thicknesses.
On the other hand, the relationship of the thickness is reversed.

FIG. 4H shows a cross-sectional structure of a conventional optical disk, in which the disk has a uniform thickness. 4A to 4G, the inclination angle at the step between the regions is 5 °.
~ 80 ° is desirable. The substrate having the cross-sectional structure shown in FIGS. 4A to 4G can be easily manufactured by injection molding a resin such as polycarbonate using a mold having a shape corresponding to the cross-sectional structure. In addition, FIG.
Either the upper surface or the lower surface of the substrate shown in FIG. 4G may constitute the signal surface. In injection molding, a pit group of a preformat pattern is formed on a desired surface using a stamper.

With respect to the substrates shown in FIGS. 4A to 4H, the amount of surface runout during rotation of the substrates was measured. The optical disc substrate according to the present invention shown in FIGS. 4A to 4G has a thickness of 0.7 mm in the recording / reproducing area, but has a different thickness in other areas. Compared with this, the rigidity of the substrate can be improved. Therefore, by using the substrate of the present invention, the rigidity of the substrate is increased, so that the deformation of the substrate during rotation of the disk can be reduced, and the occurrence of surface runout can be suppressed. Further, it is also possible to suppress the occurrence of turbulence in the cartridge case caused by the surface runout and the increase in rotation unevenness.

FIG. 5 shows another example of the structure of the recording medium substrate of the present invention. The substrate 1 has an annular rigid reinforcing member 8a concentric with the substrate 1 fixed to an outer region 6 on the upper surface of a flat polycarbonate substrate for an optical disk by an adhesive or the like. The thickness of the rigid reinforcing member 8a can be adjusted so that the entire thickness of the disk at the portion where the rigid reinforcing member 8a is mounted is about the desired thickness. It is desirable that the inner side wall of the rigid reinforcing member be inclined at an angle of 45 ° or less.
As the material of the rigid reinforcing plate, the same material as the substrate such as polycarbonate, aluminum, iron, aluminum oxide, silicon oxide, titanium oxide, silicon nitride, titanium nitride, silicon carbide and the like are desirable. In order to further increase the rigidity, it is more desirable to use a material having a higher tensile strength than the material of the substrate.

In FIG. 5B, an annular rigid reinforcing member 8b concentric with the substrate 1 is provided in an inner region 5 on the upper surface of the optical disk substrate 1.
Is fixed with an adhesive or the like. In FIG. 5C, annular rigid reinforcing members 8c and 8c 'concentric with the substrate 1 are fixed to the outer region 6 and the inner region 5 of the upper surface of the optical disk substrate 1 by an adhesive or the like. In FIG. 5D, annular rigid reinforcing members 8d and 8d 'concentric with the substrate 1 are fixed to the outer region 6 on the upper surface and the lower surface of the optical disk substrate 1 by an adhesive or the like. In FIG. 5E, an annular rigid reinforcing member 8e concentric with the substrate 1 is fixed to the inner region 6 on the upper surface and the lower surface of the optical disk substrate 1 by an adhesive or the like. In FIG. 5F, an annular rigid reinforcing member 8 concentric with the substrate 1 is provided on the outer region 6 and the inner region 5 on the upper and lower surfaces of the optical disk substrate 1.
f and 8f 'are respectively fixed by an adhesive or the like.

FIG. 5G shows an example of a substrate in which the outermost peripheral portion of the substrate shown in FIG. As the vibration absorbing material, for example, it is preferable that the vibration absorbing material is formed of an elastic member such as a rubber material such as urethane, silicone resin, vinyl chloride, and butyl rubber, and various polymer materials. The substrate structure shown in FIG. 5G is effective for a recording medium housed in a cartridge case described later. In addition, the vibration absorbing material is applied with various shapes and arrangements to the rigid reinforcing member 8 and the inner region 5 used in each of FIGS. It is possible. In addition, an optimum configuration can be obtained by selecting the shape of the substrate shown in each of FIGS. 4A and 4B in combination with the elastic modulus and shape of the vibration absorbing material.

5B to 5G, the material of the reinforcing member 8 and the material and thickness of the substrate 1 are the same as those in FIG. 5A.

As shown in FIGS. 5A to 5G, the rigidity of the substrate 1 can be improved by fixing the rigidity reinforcing member 8 to a region other than the region where recording and reproduction are performed.

With respect to the substrates shown in FIGS. 5A to 5G, the amount of surface runout during rotation of the substrate was measured. As compared with a conventional flat substrate having a thickness of 0.7 mm, it was found that the substrates of FIGS. 5A to 5G have suppressed surface vibration. Therefore, by using the substrate of the present invention, the rigidity of the substrate is increased,
Deformation of the substrate during rotation of the disk can be reduced, and occurrence of surface runout can be suppressed. Furthermore, the occurrence of turbulence in the cartridge case caused by the runout,
An increase in rotation unevenness can also be suppressed.

A plurality of magnetic layers shown in FIG. 6 are laminated on a substrate having a shape selected from FIGS. 4 and 5. A guide groove for guiding a laser spot and a preformat pattern including a prepit array indicating addresses of recording tracks defined along the guide groove are formed on one surface of the transparent substrate 11 in a fine uneven shape. In addition, a tracking servo signal and a preformat signal can be optically read.

The first dielectric layer 12 is provided for causing the light beam to multiply interfere between the recording layer 16 and the transparent substrate 11 to increase the apparent Kerr rotation angle.
It is made of an inorganic dielectric such as i, Al, Zr, Ti, or Ta nitride or oxide having a refractive index larger than that of the transparent substrate 11, and is formed to a thickness of 200 to 1500 °.

The reproduction layer 13 is interposed via the first dielectric layer 12.
Are laminated. As the reproducing layer 13, for example, rare earth
Transition metal amorphous alloys such as GdFeCo, GdF
e, GdCo, or the like, or garnet, or a platinum group-iron group periodic structure film, for example, PtCo, PdCo, or the like, and is formed to a thickness of 100 to 1000 °.

The reproducing layer 13 is in an in-plane magnetization state near room temperature. Then, the temperature changes to a perpendicular magnetization state at a certain critical temperature Tcr or higher. When the temperature near the center of the laser beam spot rises to Tcr or more during reproduction, the area is vertically magnetized.
The magnetization direction at this time matches the magnetization direction of the recording layer 16.
As a result, the outer side of the isotherm of Tcr becomes a mask portion due to in-plane magnetization, and the inner side becomes an opening, so that the reproduction resolution can be improved (FIG. 5).

On the reproducing layer 13, an auxiliary magnetic layer 14 having a function as a mask layer is added. As the auxiliary magnetic layer 14, for example, a rare earth-transition metal amorphous alloy, for example,
GdFe, GdFeCo, GdW or the like, or garnet, or a platinum group-iron group periodic structure film, for example, Pt
It is made of Co, PdCo, or the like, and is formed to a thickness of 50 to 500 °.

The auxiliary magnetic layer 14 is an in-plane magnetic layer having a Curie temperature near Tcr, and has a function of clarifying the boundary between the mask and the opening and improving the S / N.

On the auxiliary magnetic layer 14, a second dielectric layer 15 is laminated. The second dielectric layer is made of Si, Al, Zr, T
i, made of an inorganic dielectric such as a nitride or oxide of Ta,
The reproducing layer 13 and the recording layer 16 are formed to have a thickness of 10 to 500 ° and are magnetostatically coupled.

The recording layer 16 is laminated via the second dielectric layer 15. The recording layer 16 has a large perpendicular magnetic anisotropy and can stably maintain a magnetization state, for example, a rare earth-transition metal amorphous alloy, for example, TbFeCo, DyFeC
o, TbDyFeCo or the like, or garnet, or a platinum group-iron group periodic structure film, for example, PtCo, Pd
It is made of Co or the like, and is formed to a thickness of 100 to 2000 °.

On the recording layer 16, a magnetic capping layer 17 is provided.
Are laminated. As the magnetic capping layer, for example,
Rare earth-transition metal amorphous alloys, for example, GdFeCo,
GdFe, GdCo or the like, or garnet, or a platinum group-iron group periodic structure film, for example, PtCo, PdC
o, etc. and is formed to a thickness of 10 to 200 °.

It is desirable to adjust the magnetic properties of the magnetic capping layer so that the perpendicular magnetic anisotropic energy and the demagnetizing field energy are equal so that the magnetization is easily rotated in the direction of the external magnetic field.

On the magnetic capping layer, a third dielectric layer 1
8 are stacked. The third dielectric layer is made of Si, Al, Zr,
It is made of an inorganic dielectric such as a nitride or oxide of Ti or Ta, and is formed to a thickness of 100 to 1000 °.

The heat radiation layer 19 is laminated on the dielectric layer 18. As the heat radiation layer 19, for example, Al, AlTi, A
A metal such as u, Ag, Cu, AuAl, or AgAl, or a metal alloy is desirable, is formed to a thickness of 200 to 1500 °, and has a role of controlling heat distribution by laser light together with the third dielectric layer 17.

Finally, the entire film from the first dielectric layer 12 to the heat radiation layer 18 is further covered with a protective layer 20 to protect it from chemical corrosion such as oxidation and contact with a magnetic head. Protective layer 2
For example, 0 is formed by spin coating using an organic material such as a photocurable resin.

The hub 3 is a magnetic clamping hub made of a material that can be attracted by a magnet, and is attached to the substrate 1 while being separated from the substrate 1. As a material of the magnetic clamping hub, a metal magnetic material such as Fe, Ni, Co or an alloy containing them, or a plastic magnet is preferable. The magnetic clamping hub 3 is pulled by a magnet 4 attached to the spindle 2. This attractive force is transmitted to the substrate 1, and the substrate 1 is sucked by the disk support of the spindle 2. When the diameter of the substrate at this time is X and the diameter of the magnetic clamping hub is Y, by setting Y / X ≧ 0.28, the frictional force between the substrate and the hub is secured, and the substrate and the hub are rotated by rotation. Can be prevented, and rotation unevenness can be suppressed. Further, the effect of reducing the influence is obtained because the holding force of the substrate is increased even with respect to surface runout caused by uneven rotation and turbulence generated in the cartridge due to rotation.

The hub has a thermal conductivity of 0.05 (cal / ° C.c).
It is desirable to use a material of m.s) or more, and the heat from the spindle motor, whose heat generation has increased due to uneven rotation, can be radiated through the hub.

The magneto-optical recording medium produced in this manner was used for the external shape diagrams 8, 9, and 10, the internal shape diagram 11,
The magneto-optical disk 100 may be housed in the cartridge case shown in FIGS. 12, 13 and 14.

The disk cartridge is a disk-shaped disk (rotary driving body; in this example, a magneto-optical recording medium) 21 for recording information signals, a cartridge case main body 22 for accommodating the disk 21 in a rotatable state, and Consists of The disc 21 can record information signals on one or both sides of the disc main body, and a hub is mounted at the center of the lower surface of the disc main body.

The cartridge case body 22 is composed of a cartridge case having a rectangular shape in plan view, in which an upper cartridge case 22a and a lower cartridge case 22b, each of which is formed by plastic, are joined. A window 23 in the invention is open. The window 23 is slid open and closed by a shutter 24. The shutter 24 is in the closed position and the lock claw 2
5 and is closed and biased by the torsion coil type spring 26. On the upper and lower surfaces of the cartridge case main body 22, a shallow slide concave portion 27 may be formed so as to correspond to the open / close area of the shutter 24.

In the disk cartridge constructed as described above, when the cartridge case main body 22 is loaded into the disk drive in the direction shown by the arrow in FIG.
6 can be slid open against the biasing force. The disc 21 is the cartridge case body 2
2 is held and fixed via a hub by a drive shaft that enters through a drive hole at the center of the lower surface of the drive shaft 2, and is driven to rotate clockwise in FIG. At this time, an opening 30 and a lid 31 for opening and closing the opening 30 are provided in order to effectively escape the flowing air generated due to the rotational driving of the disk 21 to the outside of the cartridge case and thereby reduce the air resistance at the time of driving the disk. May be added.

As shown by the group of broken lines in FIG.
The notch is formed continuously on the side edge 23a on the upper side of rotation. Further, the lid 31 is formed integrally with the main surface wall 24a of the shutter 24 so that the signal read / write window 23 is
It is sufficient that the opening 30 can be closed with the lid 31 in the state where the cover 30 is closed.

At this time, the opening vertical dimension b of the opening 30 is set to be smaller than the opening vertical dimension a based on the opening vertical dimension a of the signal read / write window 23. However, the two dimensions a and b are set with reference to the opening edge of each opening edge on the center side of the cartridge case. Therefore, the reference edges are continuous in a straight line.

In FIG. 9, the shutter 24 can be slid to the position where the signal read / write window 23 is opened and the opening 30 is opened. At this time, the lid 3
1 protrudes from the slide recess 27. Therefore, an escape recess 32 flush with the slide recess 27 is provided on the peripheral wall on the open end side of the slide recess 27 so that the protruding end of the lid 31 can be slid out of the cartridge case via the escape recess 32. I do.

When the opening 30 is provided separately from the signal read / write window 23 as described above, the flowing air generated by the rotation of the disk 21 and the vortex generated on the disk surface are
Since it escapes from each of the signal read / write window 23 and the opening 30, the occurrence of turbulence is suppressed, the air resistance at the time of driving the disk is reduced, and the rotation at the time of driving the disk can be stabilized accordingly.

The opening 30 and the lid 31 can be provided as independent structures separate from the signal read / write window 23 and the shutter 24. For example, as shown in FIG.
Opening openings 30 are opened above and below the side of the cartridge case opposite to the signal read / write window 23, and these are closed by a lid 31.
To be able to slide open and close. Lid 31
Is a pair of upper and lower main surfaces 31a.
31a and an end wall 31b connecting these are formed in a U-shaped cross section. Further, the lock is held in the closed position by the exclusive lock claw 33, and the torsion coil-shaped spring 34 urges the slide to close without permission. The lock claw 33 is configured so that the lock claw 25 for the shutter 24 can be used. In this case, the lid 31 can be opened using the loading operation of the disk cartridge similarly to the shutter 24.

A convex portion or a concave portion is provided on the inner surface of the cartridge to adjust the flow of air during rotation of the disk, and the adjusted air flow urges the signal recording surface of the disk during recording and reproduction to a constant height position. Then, the rotation may be stabilized.

FIG. 11A shows a cartridge case main body 42 in which a convex portion 43a is provided radially from the center of the disk on the inner surface of the cartridge case main body 42 containing the disk 41.
FIG. In FIG. 11A, for convenience of explanation, the disk 41 accommodated in the cartridge case main body 42 is shown.
And the projection 43a on the inner surface of the upper cartridge case are seen through. FIG. 11B is a cross-sectional view of the cartridge case main body 42 taken along the line AA in FIG. 11A. The cartridge case body 42 includes an upper cartridge case 42a and a lower cartridge case 42b.
FIG. 11A is a plan view seen from above the upper cartridge case 42a. Upper cartridge case 42
In a, a signal read / write window 44 is formed so that the optical head can access the disk 41 during recording and reproduction (the shutter is not shown). The disk 41 is stored in the cartridge case body 42.

As shown in FIGS. 11A and 11B, the upper cartridge case 42a
On the inner surface of the lower cartridge case 42b, band-shaped protrusions 43a extending radially from the center of the disk are provided, respectively.
And 43b may be formed symmetrically with respect to the disk 41. The convex portions 43a and 43b have a fan-shaped width that increases radially outward, and may be formed at a desired height from the inner surfaces of the upper cartridge case 42a and the lower cartridge case 42b of the convex portions 43a and 43b. Also,
The protrusion 43a of the upper cartridge case 42a and the disk 4
1 and the distance between the lower cartridge case 42b protrusion 43b and the lower surface of the disk 41 are preferably 50% to 300% of the substrate thickness, and more preferably 50% to 150%. The projections 43a and 43b are formed so that the divergence angle is 5 to 90 ° from the center of the disk.
It may be provided on the circumference of the disk. Convex portions 43a and 43b
May extend from the position of the radius of the disk 41 (the edge of the opening for the hub) to a desired position.

By providing the convex portions 43a and 43b on the inner surface of the cartridge, the flow of air generated in the circumferential direction of the disk during the rotation of the disk is guided in the radial direction, and the pressure at the outer peripheral portion of the disk is increased. By applying pressure evenly from the upper and lower surfaces of the disk, it is possible to stabilize the surface position and the rotational property of the outer peripheral portion of the disk, which vary particularly greatly.

FIGS. 12A and 12B show FIGS. 11A and 11B.
13 shows a modification of the cartridge shown in FIG. The cartridge case main body 52 shown in FIG. 12A and the AA sectional view 12B thereof includes an upper cartridge case 52a and a lower cartridge case 52b similarly to the cartridge case main body 42, and the cartridge case main body 52 To store. This cartridge case body 5
2, the convex portions 53a and 53b are
2a and the inner surface of the lower cartridge case 52b are formed radially from the center of the disk to the outer periphery so as to draw an arc 55 in the rotation direction of the disk. Convex portions 53a, 5
The arc 55 defining the 3b may be drawn with its center on the circumference of the disk. Set the center of the arc 55 on the circumference of the disk
What is necessary is just to set every / 16 round and draw a total of 16 arcs.
The cross-sectional shape of the convex portion defined by the arc 55 is a saw blade shape as shown in FIG. 12B, protrudes at the position of the arc 55, and at that portion, the distance between the inner surface of the cartridge and the disk surface becomes minimum. The distance gradually increases to the arc. That is, a step is generated between the adjacent convex portions at the position of the arc 55, and the convex portion 5
3 and the projections 53a, 53b at that position.
The distance between the disk and the surface of the disk 41 is 50
% To 300% is desirable. The projections 53a, 5 having such a structure
3b on the inner surface of the cartridge case main body 52.
Symmetrically, the air flow generated in the circumferential direction of the disk by the rotation of the disk 41 is guided in the radial direction, the pressure at the outer peripheral portion of the disk is increased, and the increased pressure is applied from the upper and lower surfaces of the disk. By applying evenly,
It is possible to stabilize the surface position and the rotation of the outer peripheral portion of the disk, which has large fluctuations.

FIGS. 13A and 13B show FIGS.
13 shows a modification of the cartridge case body shown in FIG. The cartridge case main body 62 shown in FIG. 13A and FIG. 13B, which is a cross-sectional view taken along line AA of FIG. 13A, has convex portions 63a and 63b having upper cartridge case 62a and lower cartridge case 62b, respectively.
May be formed radially on the inner surface of the disk so as to draw an arc in the rotation direction of the disk from the center of the disk toward the outer periphery. The cross-sectional shape of the convex portions 63a and 63b is
Are symmetrical to each other, but as shown in FIG.
A convex portion is formed only by the drawn arc 65 portion.

FIGS. 13C and 13D show FIGS.
Similarly to the cartridge case main body 62 shown in FIG. 3B, the projections are formed on the inner surface of the upper cartridge case and the lower cartridge case of the cartridge case main body so as to draw an arc from the center of the disk toward the outer circumference in the rotation direction of the disk. 4 shows a cross-sectional structure of a radially formed cartridge. The method of drawing the arc is such that the cross-sectional shapes of the convex portions (or concave portions) defined by the arc are different from each other. In FIG. 13C, the upper cartridge case 62c and the lower cartridge case 62
In d, the center of the arc 65 is set at every 1/16 turn on the outer circumference of the disk, but the arc drawn by the center of the arc set at every 1/8 turn of the outer circumference of the disk has the maximum height and The convex portion 6 is formed so that the adjacent arc portion becomes the lowest.
What is necessary is just to form 3a and the convex part 63b. In FIG. 13D,
In contrast to the case of FIG. 13B, the upper cartridge case 6
The portions of the arc 65 on the inner side surfaces of the inner cartridge 2e and the lower cartridge case 62f form the concave portions 63a and 63b. The distance between the protrusion on the inner surface of the cartridge and the surface of the disk is preferably 50% to 300%, more preferably 50% to 150% with respect to the thickness of the base.

By providing a convex or concave portion having the structure shown in FIGS. 13A to 13D on the inner surface of the cartridge, the flow of air generated in the circumferential direction of the disk by the rotation of the disk 41 is guided in the radial direction, and By increasing the pressure of the portion and applying the increased pressure evenly from the upper and lower surfaces of the disk, it is possible to stabilize the surface position and the rotational property of the disk outer peripheral portion where the fluctuation is particularly large.

FIGS. 14A and 14B show a structure in which the projection is not formed on the cartridge case main body.

Next, the magneto-optical disk 100 was mounted on the recording / reproducing apparatus 71, and the rotational stability of the magneto-optical disk at 360 to 7200 rpm and the occurrence of tracking errors and write / read errors were examined.

The configuration of the recording / reproducing apparatus will be described with reference to FIG. The device 71 shown in FIG.
00: a laser beam irradiating unit for irradiating a pulsed light with a constant period synchronized with the code data; a magnetic field applying unit for applying a controlled magnetic field to the magneto-optical disk 100 during recording and reproduction; And a signal processing system that detects and processes signals from In the laser beam irradiation section, the laser 72 is connected to a laser driving circuit 73 and a recording pulse width / phase adjusting circuit 74 (RC-PPA),
The laser driving circuit 73 receives the signal from the recording pulse width phase adjusting circuit 74 and controls the laser pulse width and phase of the laser 72. Recording pulse width / phase adjustment circuit 7
4 receives a clock signal described later from the PLL circuit 75 and generates a first synchronization signal for adjusting the phase and pulse width of the recording light.

In the magnetic field application section, a magnetic coil 76 for applying a magnetic field is a magnetic coil drive circuit (M-DRIVE) 77.
When recording, the magnetic coil driving circuit 77 receives a signal from the encoder 70 to which data is input, and outputs a phase adjustment circuit (RE-PA).
The magnetic coil 76 is controlled by receiving input data through 78. On the other hand, at the time of reproduction, a reproduction pulse width / phase adjustment circuit (R
A second synchronizing signal for adjusting a phase and a pulse width is generated through a P-PPA (79), and the magnetic coil 76 is controlled based on the second synchronizing signal. Magnetic coil drive circuit 77
The recording / reproduction switch (RC / RPSW) 80 is connected to the magnetic coil drive circuit 77 in order to switch the signal inputted to the recording and reproduction modes.

In the signal processing system, a first polarizing prism 81 is disposed between the laser 72 and the magneto-optical disk 100, and a second polarizing prism 82 and detectors 83 and 84 are disposed on the side of the first polarizing prism 81. . The detectors 83 and 84 are both connected to a subtractor 87 and an adder 88 via I / V converters 85 and 86, respectively. The adder 88 is connected to the PLL circuit 75 via a clock extraction circuit (SCC) 89. The subtracter 87 includes a sample-and-hold (S / H) circuit 90 that holds a signal in synchronization with a clock, an A / D conversion circuit 91 that similarly performs analog-to-digital conversion in synchronization with a clock, and a binary signal processing circuit (BSC). ) 92 to a decoder 93.

In the above device configuration, the light emitted from the laser 72 is made parallel by the collimator lens 94,
The light passes through the polarizing prism 25 and is focused on the magneto-optical disk 100 by the objective lens 95. The reflected light from the disk is directed to the polarizing prism 82 by the polarizing prism 81, passes through the half-wave plate 96, and
2 divides in two directions. The split light is condensed by a detection lens 97 and guided to photodetectors 98 and 99, respectively. Here, pits for generating a tracking error signal and a clock signal may be formed on the magneto-optical disk 100 in advance. After the detectors 83 and 84 detect signals indicating the reflected light from the clock signal generation pits, the clock extraction circuit 89 extracts the signals. Next, the clock extraction circuit 8
9, a data channel clock is generated in the PLL circuit 75 connected to the control circuit 9.

At the time of data recording, the laser 72 is modulated by the laser driving circuit 73 at a constant frequency so as to synchronize with the data channel clock, emits a continuous pulse light having a narrow width, and outputs the data of the rotating magneto-optical disk 100. The recording area is locally heated at equal intervals. In addition, the data channel clock controls the encoder 70 of the magnetic field application unit,
A data signal of a reference clock cycle is generated. The data signal is sent to the magnetic coil driving device 47 via the phase adjusting circuit 78. The magnetic coil driving device 77 controls the magnetic field coil 76 to apply a magnetic field having a polarity corresponding to the data signal to a heated portion of the data recording area of the magneto-optical disk 100.

As a recording method, an optical pulse magnetic field modulation method is used. This method irradiates a pulsed laser beam when the applied recording magnetic field reaches a sufficient magnitude, so that recording in the area where the external magnetic field is switched can be omitted, and as a result, minute magnetic domains can be reduced. This is a technology that allows recording with noise. Using a laser spot of about 1 μm, a magnetic domain of 0.2 μm or less, which cannot be obtained by optical modulation recording, can be stably recorded in a crescent shape.

As a reproducing method, a CAD type (Center)
Aperture detection (center opening detection type) is used. This method utilizes the temperature distribution in the laser beam spot and transfers the magnetic domains of the recording layer only to the central portion of the reproducing layer where the temperature is high, thereby improving the resolution.

[0068]

EXAMPLES Hereinafter, more specific experimental examples and comparative examples will be described.

(Experimental Example 1) This experimental example has the same laminated structure as the magneto-optical recording medium shown in FIG.

Vacuum sputtering is performed on an injection-molded transparent substrate 11 having an outer diameter of 120 mm, a substrate thickness of a recording area of 0.7 mm, and a guide groove formed on one side for guiding a laser beam to a target position on a disk. The first dielectric layer 12, the reproducing layer 13, the auxiliary magnetic layer 14, the second dielectric layer 15, the recording layer 16, the magnetic capping layer 17, the third dielectric layer 18, and the heat radiation layer 19 are formed in this order. The protective layer 20 was spin-coated on the uppermost portion.

The substrate 11 used polycarbonate as a material. The thermal conductivity of the substrate 11 is 4.6 × 10 −4 (cal /
C. cm.s), the tensile strength according to ASTM D638 is 600 kgf / cm2, and the Izod strength according to ASTM D256 is 6 kgf.cm/cm. On one side of the substrate surface, a so-called land / groove substrate having guide grooves formed in a spiral shape at a pitch of 1.2 μm was used.

FIG. 4A is used as the substrate shape. The cross-sectional view of FIG. 4A is exaggerated in order to clarify the positions of the inner region 5a and the outer region 6a and the thickness difference between those regions and the region 7a where recording and reproduction are performed. In FIG. 4A, the inclination angle at the step between the regions is set to 20 °. By making the shape of the substrate thicker in other areas than the recording / reproducing area as described above, even if the thickness of the recording / reproducing area is as thin as 0.7 mm, compared to a conventional substrate having a uniform thickness over the entire substrate. As a result, the rigidity of the substrate could be improved. Therefore, by using the substrate of the present invention, it was possible to reduce the deformation of the substrate during the rotation of the disk and suppress the occurrence of surface runout. Further, it was possible to suppress the occurrence of turbulence in the cartridge case caused by the surface runout and the increase in rotation unevenness.

The substrate has a thermal conductivity of 4.6 × 10 −4 (c
al / ° C · cm · s), the transmission of heat generated by the spindle motor can be suppressed to a level that does not affect the recording / reproducing characteristics even with a thin substrate with a thickness of 0.7 mm. Was.

The first dielectric layer 12 is provided to cause a multiple interference of a light beam between the recording layer 16 and the transparent substrate 11 to increase the apparent Kerr rotation angle.
It was made of iN and had a thickness of 60 nm.

The reproduction layer 13 is formed via the first dielectric layer 12.
Were laminated. The reproducing layer 13 is made of a rare earth-transition metal amorphous film GdFeCo exhibiting in-plane magnetization at room temperature, and has a film thickness of 30.
nm. The film is formed by simultaneous sputtering (co-sputtering) of Gd alone and an Fe80Co20 alloy target, and the critical temperature Tcr at which the easy magnetization direction changes from the in-plane direction to the vertical direction is about 150 ° C., depending on the ratio of the power applied to each target.
The composition was adjusted so that both the compensation temperature and the Curie temperature were 300 ° C. or higher.

The reproducing layer 13 was adjusted so as to be in an in-plane magnetization state near room temperature. Then, the temperature was adjusted so as to change to the perpendicular magnetization state at the critical temperature Tcr or higher. When the temperature near the center of the laser beam spot rises to Tcr or more during reproduction, the area is vertically magnetized. At this time, the magnetization direction is
In the direction of magnetization. As a result, the outer side of the isotherm of Tcr becomes a mask portion due to in-plane magnetization, and the inner side becomes an opening, so that the reproduction resolution can be improved (FIG. 5).

On the reproducing layer 13, an auxiliary magnetic layer 14 having a function as a mask layer was added. The auxiliary magnetic layer 14 is made of a rare earth-transition metal amorphous film GdFe exhibiting in-plane magnetization at room temperature, and has a thickness of 15 nm. The film was formed by co-sputtering a target of Gd alone and Fe alone, and the composition was adjusted so that the Curie temperature was about 150 ° C. The auxiliary magnetic layer 14 plays a role of improving the reproduction resolution by making the change in the magnetization direction of the reproduction layer 13 from in-plane to vertical steep against the temperature gradient caused by the reproduction laser beam.

On the auxiliary magnetic layer 14, the second dielectric layer 15 was laminated. The second dielectric layer 15 is made of SiN, has a thickness of 5 nm, and makes the reproducing layer 13 and the recording layer 16 magnetostatically coupled.

The recording layer 16 was laminated via the second dielectric layer 15. As the recording layer 16, a rare earth element exhibiting perpendicular magnetization is used.
Made of a transition metal amorphous film TbFeCo and having a thickness of 50 nm
And The film is formed by co-sputtering of Tb alone and an Fe90Co10 alloy target. The compensation temperature is about 75 ° C. and the Curie temperature is 2 depending on the ratio of the power applied to each target.
The composition was adjusted to be about 50 ° C.

The magnetic capping layer 17 is formed on the recording layer 16.
Were laminated. The magnetic capping layer 17 was made of a rare earth-transition metal amorphous film GdFeCo exhibiting in-plane magnetization at room temperature, and had a thickness of 5 nm. The film is made of Gd alone and Fe80Co
Co-sputtering was performed on 20 alloy targets, and the composition was adjusted so that the Curie temperature was 300 ° C. or higher according to the ratio of the power applied to each target.

The magnetic properties of the magnetic capping layer were adjusted so that the perpendicular magnetic anisotropic energy and the demagnetizing field energy were equal so that the magnetization could easily rotate in the direction of the external magnetic field.

The third dielectric layer 1 is formed on the magnetic capping layer.
8 were laminated. The third dielectric layer 18 was made of SiN and had a thickness of 20 nm.

The heat radiation layer 19 was laminated on the dielectric layer 18. The heat radiation layer 19 is made of Al97Ti3 and has a thickness of 40 mm.
nm, and plays a role of controlling the heat distribution by the laser light together with the third dielectric layer 18.

Finally, in order to protect the entire film from the first dielectric layer 12 to the heat radiation layer 19 from chemical corrosion such as oxidation and contact with the magnetic head, an acrylic ultraviolet curable resin (UV resin) is used as the protective layer 20. ) Was spin-coated and cured with an ultraviolet exposure device.

The hub 3 is a magnetic clamping hub made of a material that can be attracted by a magnet, and is attached to the substrate 1 while being separated from the substrate 1. SUS430 was used as a material for the magnetic clamp hub. The magnetic clamp hub 3 is pulled by a magnet 4 attached to the spindle 2. This attractive force is transmitted to the substrate 1, and the substrate 1 is sucked by the disk support of the spindle 2. At this time, the diameter Y of the substrate and the hub for magnetic clamping is 33.6 mm (Y / X = 0.2
8). By setting Y / X = 0.28 as described above, it is possible to secure the frictional force between the substrate and the hub, prevent slippage between the substrate and the hub due to rotation, and suppress rotation unevenness. Was. Furthermore, surface run-out caused by uneven rotation,
For turbulence generated in the cartridge by rotation,
Since the holding force of the substrate was increased, an effect of reducing the influence was obtained.

The hub material has a thermal conductivity of 0.06 (cal /
The use of SUS 430 (° C. · cm · s) allowed the heat from the spindle motor, whose heat generation increased due to uneven rotation, to be radiated through the hub.

The magneto-optical recording medium was housed in the cartridge case shown in FIGS. 8 and 9 and the internal structure shown in FIG.

The magneto-optical disk 100 is a disk-shaped disk (rotary driving body; in this example, a magneto-optical recording medium) 21 for recording information signals, and a cartridge case body for accommodating the disk 21 in a rotatable state. 22. The disc 21 can record information signals on one or both sides of the disc main body, and a hub was attached to the center of the lower surface of the disc main body.

The cartridge case body 22 is formed of a cartridge case having a rectangular shape in plan view, in which an upper cartridge case 22a and a lower cartridge case 22b, each of which is formed by plastic, are joined. A window 23 in the present invention was opened. The window 23 is slid open and closed by a shutter 24. The shutter 24 is in the closed position and the lock claw 2
5 and was closed and biased by the torsion coil type spring 26 without permission. On the upper and lower surfaces of the cartridge case main body 22, shallow sliding concave portions 27 are formed corresponding to the opening and closing regions of the shutter 24.

When the disk cartridge constructed as described above is loaded into the disk drive with the cartridge case main body 22 in the direction shown by the arrow in FIG. 8, the lock claw 25 is unlocked, and the shutter 24 is released from the spring 2.
The slide is opened against the urging force of No. 6. Disk 21
Is held and fixed via a hub by a drive shaft which enters through a drive hole at the center of the lower surface of the cartridge case main body 22, and is driven to rotate clockwise in FIG. At this time, in order to effectively escape the flowing air generated due to the rotational drive of the disk 21 to the outside of the cartridge case, thereby reducing the air resistance at the time of driving the disk 21 and suppressing the occurrence of turbulence,
An opening 30 and a lid 31 for opening and closing the opening are added.

As shown by the group of broken lines in FIG.
The notch is formed continuously on the side edge 23a on the upper side of rotation. Further, the lid 31 is formed integrally with the main surface wall 24a of the shutter 24 so that the signal read / write window 23 is
, The opening 30 can be closed by the lid 31.

At this time, the vertical dimension b of the opening 30 was set to be smaller than the vertical dimension a of the opening based on the vertical dimension a of the signal read / write window 23. However, the two dimensions a and b are set with reference to the opening edge of each opening edge on the center side of the cartridge case. Therefore, the reference edges are continuous in a straight line.

In FIG. 9, the shutter 24 opens the signal read / write window 23 and slides to a position where the opening 30 is opened. At this time, the lid 3
1 protrudes from the slide recess 27. Therefore, an escape recess 32 flush with the slide recess 27 is provided on the peripheral wall on the open end side of the slide recess 27 so that the protruding end of the lid 31 can be slid out of the cartridge case via the escape recess 32. did.

As described above, the open port 30 is provided separately from the signal read / write window 23, and the turbulent flow generated by the rotation of the disk 21 and the eddy current generated on the disk surface can be prevented from flowing between the signal read / write window 23 and the open port 30. It was possible to escape from each of them, reduce the air resistance when driving the disk, suppress the occurrence of turbulence, and stabilize the rotation when driving the disk.

A convex portion or a concave portion is provided on the inner surface of the cartridge to adjust the flow of air when the disk is rotated, and the adjusted air flow suppresses the surface deviation of the signal recording surface of the disk during recording and reproduction to a constant height. Energizes the position to stabilize rotation.

FIG. 12A is a sectional view taken along line AA of FIG.
B includes an upper cartridge case 52a and a lower cartridge case 52b.
To store. The cartridge case main body 52 is formed such that the projections 53a and 53b are radially formed on the inner surfaces of the upper cartridge case 52a and the lower cartridge case 52b so as to draw an arc 55 in the rotation direction of the disk from the center of the disk toward the outer periphery. Form. The arc 55 defining the convex portions 53a and 53b is centered on the circumference (diameter 122 mm) of the disk and is drawn with a radius of 61 mm. A total of 16 arcs were drawn by setting the center of the arc 55 every 1/16 of the circumference of the disk. The cross-sectional shape of the convex portion defined by the arc 55 is shown in FIG.
As shown in FIG. 3B, it is saw-toothed and protrudes at the position of the arc 55, at which the distance between the inner surface of the cartridge and the disk surface is minimized, and the distance gradually increases until the next arc. That is, a step is formed between the adjacent convex portions at the position of the arc 55 to form a boundary between the convex portions 53, and the protruding height at the position of the arc is 0.5 mm. The distance between the portions 53a and 53b and the surface of the disk 41 is 0.5 mm. The protrusions 53a and 53b having such a structure are connected to the cartridge case main body 52.
By providing the inner surface symmetrically with respect to the disk 41, the flow of air generated in the circumferential direction of the disk due to the rotation of the disk 41 is guided in the radial direction, and the pressure at the outer peripheral portion of the disk is increased. Is applied evenly from the upper and lower surfaces of the disk, thereby stabilizing the surface position and the rotational property of the outer peripheral portion of the disk with large fluctuations. In addition, the air flow path was formed by the unevenness, and the generation of turbulent flow due to the rotation could be suppressed.

Next, the magneto-optical disk 100 was mounted on the recording / reproducing apparatus 71, and the rotational stability of the magneto-optical disk at 360 to 7200 rpm and the occurrence of tracking errors and write / read errors were examined.

Table 1 shows the results of the recording and reproducing experiments. 720
At rotation speeds higher than rpm, the vibration of the spindle motor itself, the heat generated by the spindle motor, the air flow generated by the rotation of the disk, and the deformation of the substrate due to the rotational force increase as the rotation speed increases. Is affected by these, the magneto-optical disk of the present invention can maintain a stable rotation speed in all rotation regions,
There were no tracking errors and no write / read errors.

(Experimental Example 2) Next, in Experimental Example 1, the diameter Y of the magnetic clamping hub was set to 36 mm (Y / X =
0.150) was mounted on the recording / reproducing apparatus 71, and the rotation speed was increased to 0 to 7200 rpm. The rotation stability and the occurrence of tracking errors and read errors were examined. A stable rotation speed could be maintained in the region, and no tracking error occurred and no write / read error occurred.

Comparative Example 1 Next, in Experimental Example 1, the diameter Y of the magnetic clamping hub was set to 31.2 mm (Y / X
= 0.26) was mounted on the recording / reproducing apparatus 71, and the number of rotations was increased to 0 to 7200 rpm, and the rotation stability and the occurrence of tracking errors and read errors were examined. In the rotation speed region above pm, the rotation became unstable, the rotation speed could not be kept constant, and a tracking error and a read error occurred.

[0101]

As shown in Table 1, even if the magneto-optical disk is rotated at 720 rpm or more, the magneto-optical disk of the present invention maintains a stable rotation without occurrence of a tracking error and a write / read error. This is very suitable as a magneto-optical disk that can be rotated in a high-speed rotation region.

[0102]

[Table 1]

A: Rotational speed variation within ± 1% (no tracking error, no write / read error) B: Rotational speed variation within ± 3% (no tracking error, no write / read error) C: Rotational speed variation ± Within 5% (tracking error, write / read error occurs) D: Rotational speed fluctuation ± 7% or more (tracking error, write / read error occurs)

[Brief description of the drawings]

FIG. 1 is a sectional view showing a conventional example.

FIG. 2 is a sectional view showing another conventional example.

FIG. 3 is a sectional view showing an embodiment of the present invention.

FIG. 4A is a cross-sectional view showing the structure of an optical disc substrate, BG are cross-sectional views showing various structures of an optical disc substrate, and H is a cross-sectional view showing the structure of a conventional optical disc substrate. .

5A to 5G are cross-sectional views showing still another structure of the substrate of the optical disc.

FIG. 6 is a sectional view showing a laminated structure of the magneto-optical recording medium of the present invention.

FIG. 7 is a conceptual diagram of CAD-type magnetic super-resolution reproduction.

FIG. 8 is a plan view of the cartridge case in a state where a shutter of the cartridge is opened.

FIG. 9 is a plan view of the cartridge case in a state where a shutter of the cartridge is closed.

FIG. 10 is a plan view of a cartridge case showing another embodiment of the cartridge.

FIGS. 11A and 11B are a plan view of a cartridge case showing a structure of the cartridge and a cross-sectional view taken along line AA, respectively.

FIGS. 12A and 12B are a plan view of a cartridge case showing a structure of the cartridge and a cross-sectional view taken along line AA, respectively.

FIGS. 13A and 13B are a plan view of a cartridge case showing a structure of the cartridge and a cross-sectional view taken along line AA of the cartridge case, respectively.

14A and 14B are a plan view of a cartridge case showing a structure of the cartridge and a cross-sectional view taken along line AA thereof, respectively.

FIG. 15 is a configuration diagram of a recording / reproducing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Spindle 3 Hub 4 Magnet 5 Inner area 6 Outer area 7 Recording / reproducing area 8 Reinforcement member 9 Vibration absorber 11 Substrate 12 First dielectric film 13 Reproducing layer 14 Auxiliary magnetic layer 15 Second dielectric layer 16 Recording layer 17 Magnetic capping layer 18 Third dielectric layer 19 Heat dissipation layer 20 Protective layer 21 Disk 22 Cartridge case body 23 Signal read / write window 24 Shutter 25 Lock claw 26 Spring 30 Opening opening 31 Lid 32 Escape recess 33 Lock claw 34 Spring 41 Disk 42 cartridge Case main body 43 Convex part 49 Hub opening 52 Cartridge case main body 53 Convex part 55 arc 62 Cartridge case main body 63 Convex part 65 arc 70 Encoder 71 Recording / reproducing device 72 Laser 73 Laser drive circuit 74 Recording pulse width / phase adjustment circuit ( RC-PPA) 75 PL Circuit 76 Magnetic coil 77 Magnetic coil drive circuit (M-DRIVE) 78 Phase adjustment circuit (RE-PA) 79 Reproduction pulse width / phase adjustment circuit (RP-PPA) 80 Recording / reproduction switch (RC / RP SW) 81 First Polarizing prism 82 Second polarizing prism 83 Detector 84 Detector 85 I / V converter 86 I / V converter 87 Subtractor 88 Adder 89 Clock extraction circuit (CSS) 90 Sample hold (S / H) circuit 91 A / D conversion circuit 92 Binary signal processing circuit (BSC) 93 Decoder 94 Collimator lens 95 Objective lens 96 1/2 wavelength plate 97 Detection lens 98 Photodetector 99 Photodetector 100 Magneto-optical disk X Substrate diameter Y Hub diameter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 23/00 601 G11B 23/00 601R 23/03 604 23/03 604F

Claims (8)

[Claims] At least a plastic substrate having a center hole and a layer including at least a recording layer made of a rare earth-transition metal are laminated on the substrate.
A light source for recording / reproducing while being mounted on a spindle of a recording / reproducing apparatus and rotating while being housed in a cartridge case in a rotatable form, the hub comprising a hub carried on the substrate and made of a different material from the substrate. In the magnetic disk, the hub is made of a material having a thermal conductivity of 0.05 (cal / ° C.cm.s) or more, and the substrate has a thermal conductivity of 10-3 to 10-6 (cal / ° C. cm·
s), and the substrate is made of a material having an Izod strength of 5 (kgf · cm / cm) or more, and the relationship between the diameter Y of the hub and the diameter X of the substrate is Y / X. ≧ 0.28, a magneto-optical disk. 2. The magneto-optical disk according to claim 1, wherein the cartridge case has an inner surface portion facing the substrate for adjusting a flow of air inside the cartridge case when the magneto-optical disk rotates. A magneto-optical disk characterized by having irregularities. 3. The magneto-optical disk according to claim 1, wherein the hub carried in the center hole of the substrate is made of a material that can be attracted by a magnet, and is mounted on the spindle to perform recording and reproduction while rotating. A magneto-optical disk characterized by being read. 4. The magneto-optical disk according to claim 3, wherein the material of the hub is made of a metal magnetic material of Fe, Ni, Co or an alloy containing them. 5. The magneto-optical disk according to claim 1, wherein said substrate has a thickness of 0.7 mm or less. 6. The magneto-optical disk according to claim 1, wherein recording and reproduction are performed at a rotational speed of 720 rpm or more. 7. The magneto-optical disk according to claim 1, wherein a relationship between a contact area Y of the hub with the substrate and a projection area X of the substrate is Y / X ≧ 0.30. Magneto-optical disk. 8. The magneto-optical disk according to claim 7, wherein recording and reproduction are performed at a rotation speed of 2400 rpm or more.