JPH11265526A - Disk-shaped recording medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable formation with high accuracy by punching and forming a center hole at a substrate by means of a center punch of a projection height of a specific size with respect to the thickness of the section where the center hole is formed from the mounting reference plane of a disk drive assembly and a disk recording medium. SOLUTION: The projection height of the center punch is specified to 1/3 to 1/2 the thickness size of the forming section from the reference plane. The height of the center punch 28 from the mounting reference plane 5b is set at 0.3 mm. Then, the inner peripheral wall surface of the center hole 4 is directly molded by the center punch 28 at the section 4a up to the height of 0.3 mm from the mounting reference plane 5b with respect to the depth 0.8 mm over the entire part and the remaining section is formed by punching and, therefore, the inner peripheral wall surface of the center hole 4 comprises a shaping surface 4a, a shearing surface 4b and a fracture surface 4c. The shearing surface 4b is set up to 0.6 mm from the mounting reference plane 5b. As a result, the ruggedness degree of the opening section may be formed with the high accuracy approximate to an extremely small roundness as the opening section is directly shaped by the outer peripheral surface of the center punch 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk-shaped recording medium such as an optical disk, a magneto-optical disk or a magnetic disk and a method for manufacturing the same.

[0002]

2. Description of the Related Art For example, an optical disk is used exclusively for reproducing an information signal or the like recorded in advance, and a pit having a concavo-convex pattern corresponding to the information signal and the like is formed on a surface of a disk substrate and a light reflection layer is formed. It becomes. The magneto-optical disk also enables recording while reproducing information signals and the like. A pre-groove forming a recording track on which a desired information signal and the like are recorded is formed on the surface of the disk substrate, and a signal comprising a magnetic film layer is formed. A recording layer and a light reflection layer are formed.

[0003] In these optical disks and magneto-optical disks, a disk substrate is molded by a molding die using a synthetic resin material having optical transparency, for example, a polycarbonate resin. A stamper for transferring and forming the above-mentioned pits and pregrooves to the disk substrate is incorporated in the molding die, and a center hole is formed in the center of the disk substrate by a center punch projecting into the cavity.

[0004] When an optical disc is loaded into a reproducing apparatus,
The center portion is chucked by the disk rotation drive mechanism and driven to rotate, and the information signal and the like recorded by the optical pickup are reproduced. When a magneto-optical disk is loaded into a recording and / or reproducing (hereinafter simply referred to as "recording / reproducing") device, a central portion of the magneto-optical disk is similarly chucked by a disk rotation driving mechanism, and is driven to rotate. The information signal and the like recorded by the pickup are reproduced, and the information signal and the like are recorded by the optical pickup and the magnetic head mechanism.

For example, a magneto-optical disk 100 has a recess 10 having a center hole 101 at the center as shown in FIG.
2 is formed, and a clamping plate 103 made of a magnetic material such as a metal plate is attached to the concave portion 102. When the magneto-optical disk 100 is loaded in the recording / reproducing apparatus, the bottom surface 102a of the recess 102 is magnet-clamped on the disk table 105 of the disk rotation drive mechanism 104. Disk table 105
Is mounted on a rotating shaft 107 of a spindle motor 106 and driven to rotate.

On the disk table 105, a magnet 108 is mounted on a disk mounting surface 105a, and as shown in FIGS.
The positioning balls 110 are assembled. The projection 109 has a diameter slightly smaller than the inner diameter of the center hole 101 of the magneto-optical disk 100. Positioning ball 1
Numerals 10 are arranged at equal intervals in the circumferential direction, and a part of the peripheral surface thereof is exposed from the outer peripheral portion of the convex portion 109 and is attached to the convex portion 109. Two of the positioning balls 110 are provided with a projecting behavior toward the outside by springs (not shown).

The magneto-optical disk 100 includes a magnet 10
The clamping plate 103 is attracted by 8 and is magnet-clamped on the disk table 105 with the bottom surface 102a of the recess 102 as a mounting reference surface. In this state, the projection 109 of the disk table 105 enters the center hole 101 in this state, and the center of rotation is caused by the positioning balls 110 being pressed against the inner peripheral wall of the center hole 101 as shown in FIG. Positioned.

As described above, the magneto-optical disk 100 is
Disk table 105 of disk rotation drive mechanism 104
The center of rotation is positioned by pressing the positioning ball 110 against the inner peripheral wall of the center hole 101. Therefore, in the magneto-optical disk 100, the positioning accuracy of the rotation center is determined by the hole accuracy of the center hole 101, that is, the surface accuracy of the inner peripheral wall (the tolerance of unevenness). When the positioning ball 110 is engaged with the large concave portion 101a formed on the inner peripheral wall of the magneto-optical disk 100 due to the poor hole accuracy of the center hole 101, as shown in FIG. The rotation is driven in a state where the rotation center is eccentric. When recording and reproduction of information signals and the like are performed in this state on the magneto-optical disk 100, a tracking error occurs due to these eccentric components.

In the conventional magneto-optical disk 100,
The specification of the accuracy of the inner peripheral wall surface of the center hole 101 was set to 70 μmpp. Therefore, in the magneto-optical disk 100, even if the center hole 101 is punched and formed by a center punch in a forming die at the time of forming the disk substrate as described above, it is possible to sufficiently conform to this specification.

[0010]

By the way, in the magneto-optical disk 100, high-density recording of information signals and the like is achieved by, for example, reducing the track pitch to 0.6 times that of the conventional specification. I have. This high-density recording magneto-optical disk 100 needs to be rotationally driven in a state where the rotation center is positioned with higher precision, and the surface accuracy specification of the inner peripheral wall of the center hole 101 is also the same as the conventional specification (low-density recording optical disk). The specification is strictly set to, for example, about 40 μmpp for 70 μmpp of the magnetic disk 100.

The high-density recorded magneto-optical disk 100 is formed by punching a center hole by a high-precision center punch on a disk substrate formed with high dimensional accuracy, and the degree of abrasion of the center punch and the like is also determined. It must be strictly managed. High density recording magneto-optical disk 100
In addition, the method involves forming a molding die including a stamper and a center punch with high accuracy, and also requires processes such as management and re-grinding of the center punch, resulting in increased costs and poor productivity.

Meanwhile, in the magneto-optical disk 100, the positioning ball 110 of the disk table 105 is relatively engaged with the center hole 101 at a constant depth position in the axial direction. That is, the disk table 105
The configuration is such that the positioning ball 110 is not pressed against the center hole 101 of the magneto-optical disk 100 at a position, for example, at most 0.6 mm or more from the mounting reference surface 102a. Therefore, the magneto-optical disk 100 has the center hole 1
01, the surface accuracy of the inner peripheral wall
It is sufficient that the portion from the bottom surface 102a of the concave portion 102, which is a reference surface when the magnetic chuck 05 is magnet chucked, to a depth position of 0.6 mm conforms to the above specification.

FIGS. 12 and 13 show that a center punch is assembled into a cavity with its tip protruding by approximately 0.1 mm. In this state, a material resin is injected to form a disk substrate, and then the center punch is driven. FIG. 7 is a diagram showing a result obtained by measuring the accuracy (state of unevenness) of an inner peripheral wall of a center hole 101 formed by punching with a laser measuring machine. FIG.
5 shows a measurement result of the unevenness of the inner peripheral wall surface of the center hole 101 at the opening portion on the bottom surface 102a side of the concave portion 102. FIG. 13 shows the measurement results of the unevenness of the inner peripheral wall of the center hole 101 at a position 0.6 mm from the bottom surface 102a of the recess 102.

As is apparent from FIG. 12, the disk substrate is formed directly by the outer peripheral portion of the center punch, has a small internal stress, and is sharply cut by the center punch to generate a shearing surface. In the vicinity of the opening portion, which is described above, it is manufactured with extremely high precision. On the other hand, as the punching operation by the center punch progresses, the inner surface of the disk substrate gradually increases, and the bottom surface 102 a
In the region from 0.6 mm to 0.6 mm or more, the surface accuracy of the inner peripheral wall of the center hole 101 is deteriorated. Therefore, as is apparent from FIG.
Alternatively, irregularities of 40 μmpp or more are generated as in the part c. Such a disk substrate has almost the same value as the required specification of the above-described high-density recording magneto-optical disk 100. Therefore, in order to maintain quality, it is necessary to perform a 100% inspection process on the molded disk substrate. In addition to lowering the productivity, depending on the change in the molding conditions, there is a possibility that a product having a size outside the specified dimensions is molded and the yield deteriorates.

The above-mentioned numerical values are the specification dimensions of a certain magneto-optical disk, and when the outer diameter and the thickness of the disk substrate are different, they are of course set to appropriate numerical values.

Accordingly, an object of the present invention is to provide a disk-shaped recording medium in which a center hole is formed with high precision at least in a region where the positioning means of the center of rotation relatively engages, and a method of manufacturing the same. It was done.

[0017]

A disk-shaped recording medium according to the present invention, which achieves this object, has a disk substrate formed by a molding die using synthetic resin as a material, and is loaded into a recording / reproducing apparatus. Recording / reproduction of information signals and the like is performed by being rotationally driven by the disk drive mechanism in a state where the rotation center is positioned by the center hole which is chucked by the magnet chucking means and engages with the positioning means. In the disk-shaped recording medium, the center hole is previously projected into the cavity from the mounting reference surface with the disk drive mechanism with a projection amount of 1/3 or more and 1/2 or less with respect to the thickness dimension of the formation portion. It is formed by punching the disk substrate by the center punch.

According to the disk-shaped recording medium of the present invention constructed as described above, at least the portion of the center hole where the positioning means of the recording and / or reproducing apparatus is engaged is directly formed by the outer peripheral portion of the center punch. In addition, since the stress generation is small and formed by the initial part of the punching operation that is sharply cut by the center punch, it is formed with high precision close to a perfect circle. Therefore, the disc-shaped recording medium can use a center punch which has a gradual dimensional tolerance and does not require strict wear control, and the conditions of the punching process by the center punch are relaxed, so that the center hole is formed. It becomes possible. In addition, since the disc-shaped recording medium is positioned and mounted on the recording and / or reproducing apparatus with high precision, tracking control conditions are relaxed, and accurate information signals and the like can be obtained even under high-density specifications or severe use conditions. Recording / reproduction is performed.

Further, in the method for manufacturing a disk-shaped recording medium according to the present invention, which achieves the above-mentioned object, the center punch has a projection amount of not less than に 対 し て and not more than に 対 し て with respect to the thickness dimension of the center hole forming portion. As a result, the disk substrate is previously projected into the cavity, and after the disk substrate is formed in this state, the center punch is operated to punch and form a center hole in the disk substrate.

According to the method of manufacturing a disk-shaped recording medium according to the present invention described above, at least a portion of the center hole where the positioning means of the recording / reproducing device is engaged is directly formed by the outer peripheral portion of the center punch, and stress is generated. Since it is small and formed by the initial portion of the punching operation that is sharply cut by the center punch, it is formed with high precision close to a perfect circle. Therefore, the method for manufacturing a disk-shaped recording medium according to the present invention enables a center hole to be formed by using a center punch which has a gradual dimensional tolerance and does not require strict wear control. It is possible to relax the conditions of the punching process. Further, in the method for manufacturing a disc-shaped recording medium according to the present invention, the disc-shaped recording medium is positioned and mounted on the recording / reproducing apparatus with high accuracy, so that the tracking control conditions are relaxed, and the high-density specification or strict use. Accurate recording / reproduction of information signals and the like is performed even under the conditions.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings. As an embodiment, the disc-shaped recording medium shown in FIGS. 1 and 2 is a magneto-optical recording medium of a high-density recording specification capable of reproducing information signals recorded at high density and recording information signals at high density. Disc 1
It is. The magneto-optical disk 1 includes a disk substrate 2 and a clamping plate 3, and is rotatably housed in a thin box-shaped cartridge (not shown). The disk substrate 2 is made of a light-transmitting synthetic resin material, for example, a polycarbonate resin as a material.
Formed by The disc substrate 2 has a pre-groove forming a recording track on which a desired information signal or the like is recorded, although not described in detail. The pre-groove is formed concentrically at a narrow track pitch, and a signal recording layer and a light reflection layer made of a magnetic film layer are formed. Is formed.

The disk substrate 2 has, for example, a thickness of 0.1 mm.
A concave portion 5 having a center hole 4 formed at the center thereof is bulged to one main surface side and integrally formed. The disk substrate 2 has a clamping plate 3 made of a magnetic material such as a metal plate in an inner space 5 a of the recess 5.
Is stored. The disk substrate 2 has a bottom surface 5 b of the recess 5.
However, when the magneto-optical disk 1 is mounted on the recording / reproducing apparatus as described later, it forms a mounting reference plane. Recess 5
Are formed in the inner peripheral portion where the recording track is not formed.

The center hole 4 is formed in the molding die 2 as described later.
When the disk substrate 2 is molded by the number 0, it is formed in the molding die 20 at the same time. The center hole 4 has an inner peripheral wall whose depth dimension is at least 0.6 from the mounting reference surface 5b.
mm up to about 10μmpp, up to 2
It is formed with a high surface accuracy of 5 μmpp or less.

The outer diameter of the clamping plate 3 is slightly smaller than the inner diameter of the internal space 5a of the concave portion 5, and the flange-like legs 3a are integrally bent around the entire circumference. Be formed. The disk substrate 2 is subjected to a swaging process for applying an ultrasonic wave to the opening edge of the concave portion 5 in a state where the clamping plate 3 is housed in the internal space 5a, so that the disk substrate 2 moves in the center direction as shown in FIG. A plurality of projecting stopper projections 6 are formed by melting. The disk substrate 2 holds the flange-like legs 3a by the stopper projections 6 so that the clamping plate 3
Are combined so as not to fall off from the recessed portion 5 to form the magneto-optical disk 1. Such a magneto-optical disk 1 is
The basic configuration is the same as that of the conventional magneto-optical disk 100.

When the magneto-optical disk 1 is loaded in a recording / reproducing apparatus, it is chucked on a disk table 10 of a disk rotation drive mechanism as shown in FIG. You. The diameter of the disk table 10 is slightly larger than the outer diameter of the concave portion 5 of the magneto-optical disk 1, and although not described in detail, the disk table 10 is mounted on a rotation shaft of a stepping motor and driven to rotate. The disk table 10 is provided with an engagement projection 11 at the center of the main surface 10a, and an annular magnet 12 surrounding the engagement projection 11. Magnet 1
Numeral 2 attracts the clamping plate 3 and magnetically chucks the magneto-optical disk 1 as described later.

The outer diameter of the engaging projection 11 is slightly smaller than the inner diameter of the center hole 4 of the magneto-optical disk 1 and the height is slightly lower than the thickness of the recess 5. In the outer periphery of the engagement protrusion 11, ball attachment recesses 13 (13a to 13c) which are located at regular intervals in the circumferential direction and have a substantially hemispherical shape are formed. Further, the engaging projection 11 is provided with a spring mounting groove 14 (14a, 14b) connected to the bottom of the first ball mounting recess 13a and the second ball mounting recess 13b.

Three positioning balls 15 (15a to 15c) and two coil springs 16 (16a, 16b) are assembled to the engagement convex portion 11. Each of the positioning balls 15 is assembled in each of the ball mounting recesses 13 in such a manner that a part of the peripheral surface is exposed outward and is prevented from coming off. Coil spring 1
As shown in FIG. 2, 6 are assembled in the spring installation grooves 14 in a compressed state, respectively. The coil spring 16 couples the first positioning ball 15a and the second positioning ball 15b assembled to the first ball mounting recess 13a and the second ball mounting recess 13b with the engaging projection 11
Bias in the direction protruding from Therefore, each positioning ball 15 has a state in which the first positioning ball 15a and the second positioning ball 15b are movable in the diametrical direction and the third positioning ball 15c is fixed in the diametrical direction. It is assembled to the engaging projection 11.

When the magneto-optical disk 1 is loaded in the recording / reproducing apparatus, the clamping plate 3 is attracted by the magnet 12 and is magnet-clamped on the main surface 10a of the disk table 10. The rotation center of the magneto-optical disk 1 is positioned on the disk table 10 by engaging the engaging projections 11 with the center hole 4 and pressing the positioning balls 15 against the inner peripheral wall of the center hole 4. Be attached. Magneto-optical disk 1
When the disk rotation drive mechanism is driven in this state,
It is driven to rotate integrally with the disk table 10.

The magneto-optical disk 1 reproduces information signals and the like recorded on recording tracks by an optical pickup (not shown). The magneto-optical disk 1 is applied with an external magnetic field modulated by a magnetic head according to an information signal or the like to be recorded by a magnetic head in a state where a laser beam emitted from an optical pickup irradiates a recording track. Recording of signals and the like is performed. The operation of recording / reproducing such information signals is exactly the same as that of the conventional device. Therefore,
The magneto-optical disk 1 does not require a new configuration for the recording / reproducing device.

In the magneto-optical disk 1, as described above, the inner peripheral wall of the center hole 4 at a position at least 0.6 mm from the mounting reference surface 5b is formed with high surface accuracy with irregularities of about 10 μmpp. On the other hand, the disk table 10
The configuration is such that the positioning ball 15 does not press against the center hole 4 of the magneto-optical disk 1 at a position having an upper limit of 0.6 mm or more in the axial direction. Accordingly, the magneto-optical disk 1 does not have a large eccentric rotation center due to the positioning ball 15 engaging with the large concave portion formed on the inner peripheral wall surface of the center hole 4.
The magnet is chucked by being accurately positioned on the zero.

Since the magneto-optical disk 1 is driven to rotate via the disk table 5 without blurring, the magneto-optical disk 1 is recorded on a recording track formed at a narrow track pitch without performing high-precision tracking control. Accurate reproduction of the information signal or the like or recording of the information signal or the like is performed. In addition, the magneto-optical disk 1 can accurately reproduce an information signal or the like or record an information signal or the like even when vibration or the like is applied.

In the magneto-optical disk 1 described above, the disk substrate 2 is molded by the molding die 20 shown in FIGS. The molding die 20 has the same basic configuration as that of the conventional molding die, and as shown in FIG.
And a movable mold 22 that is arranged opposite to the fixed mold 21 and that is moved toward and away from the fixed mold 21. In the molding die 20, the fixed die 21 is mounted on the fixed die block 23 via mounting bolts and the like, and the movable die 22 is mounted on the movable die block 24 via mounting bolts and the like.
Is attached to the mold attaching portion of the injection molding machine. The molding die 20 has a cavity component on each of the main surfaces of the fixed die 21 and the movable die 22 facing each other. The molding die 20 has a cavity 25 which is a molding space of the disk substrate 2 in a state where the movable die 22 is moved and joined to the fixed die 21 as described later (in a clamped state). You.

A sprue bush 26 is attached to the fixed mold 21 at the center of the cavity 25.
The sprue bush 26 has a nozzle 27 which opens at a portion corresponding to the center hole 4 of the disk substrate 2 which is punched and removed by a center punch 28 on the movable mold 22 side described later.
Is provided. The nozzle 27 injects a molten synthetic resin material, for example, a transparent polycarbonate resin, which is injected and supplied from the injection molding machine side, into the cavity 25.

A stamper 29 for transferring and recording recording tracks on the main surface of the disk substrate 2 formed in the cavity 25 is mounted on the cavity forming surface of the movable mold 22. The movable mold 22 is provided with a center punch 28 and a plurality of eject pins 30. The center punch 28 is positioned so as to face the nozzle 27 on the fixed mold 21 side, and as shown in FIG.
8a is combined with the movable mold 22 in a state where it protrudes into the cavity 25 by a protruding amount x. After the disk substrate 2 is formed, the center punch 28 is protruded into the cavity 25 to punch and form the center hole 4 in the disk substrate 2.

The eject pin 30 is arranged on the outer peripheral portion of the center punch 28 corresponding to the concave portion 5 of the disk substrate 2 and is combined with the movable mold 22. The eject pins 30 are fixed to the fixed mold 2 when the disk substrate 2 is formed.
In the state where the movable mold 22 performs the mold opening operation with respect to
To eject.

FIG. 4 is a view for explaining the molding operation of the disk substrate 2 by the molding die 20 described above. Mold 2
0 denotes a nozzle 2 in a clamped state in which the movable mold 22 is joined to the fixed mold 21 as shown in FIG.
From 7, a molten polycarbonate resin is injected into the cavity 25. In the molding die 20, the fixed state of the fixed die 21 and the movable die 22 is maintained for a predetermined time until the injected polycarbonate resin is slightly cured. The molding die 20 removes the molding distortion generated in the disk substrate 2 which is formed by the movable molding 22 moving to the fixed mold 21 and being subjected to the compression molding operation.

In the molding die 20, the center punch 28 is operated before the injected polycarbonate resin is completely cured, and as shown in FIG. A center hole 4 is punched and formed at the center. In the molding die 20, the fixed state of the fixed die 21 and the movable die 22 is maintained until the polycarbonate resin is completely cured.

After a predetermined curing time has passed, the movable mold 22 is separated from the fixed mold 21 to open the mold 20 as shown in FIG. 4C. The molding die 20 performs an opening operation in a state where the disk substrate 2 is attached to the movable die 22 side, and performs an ejecting operation in which the disk substrate 2 is pushed down from the movable die 22 by a projecting operation of the eject pin 30. Will be Further, in the molding die 20, the runner portion 8 remaining in the nozzle 27 along with the ejecting operation of the disk substrate 2 is cut by an appropriate structure. The disk substrate 2 molded by the molding die 20 as described above undergoes a process such as a process of attaching the clamping plate 3 to the recessed portion 5 and the like.
Manufactured as

Incidentally, in the molding die 20, as described above, the tip portion 28a of the center punch 28 is configured to protrude into the cavity 25 in advance. The center punch 28 is set so that the height dimension x from the mounting reference surface 5b is 0.3 mm, as shown in detail in FIG. Accordingly, the center hole 4 has a portion 4a (depth dimension h = 0.3 mm) from the mounting reference plane 5b to 0.3 mm with respect to the entire depth dimension t = 0.8 mm of the inner peripheral wall surface.
Is formed directly by the center punch 28.

The remaining portion of the center hole 4 is punched and formed by the center punch 28. In this case, the center hole 4
, The inner peripheral wall surface is constituted by the forming surface 4a, the shear surface 4b, and the fracture surface 4c. As shown in FIG. 5, the center hole 4 has a shear surface 4b formed as a sharp cut surface formed at a position at least 0.6 mm from the mounting reference surface 5b.

As described above, with respect to the disk substrate 2 formed by setting the center punch 28 at 0.3 mm from the mounting reference surface 5b, the mounting reference surface of the center hole 4 with respect to the rotation center l as shown in FIG. The unevenness degree k1 of the opening portion on the 5b side and the unevenness degree k at a position of 0.6 mm from the mounting reference plane 5b.
2 was measured by a laser measuring machine. FIG.
FIG. 5 is a diagram showing a measurement result of the degree of irregularity k1 of the opening portion of the center hole 4 on the mounting reference surface 5b side. FIG. 8 shows the unevenness degree k at a position of 0.6 mm from the mounting reference plane 5b of the center hole 4.
FIG. 6 is a diagram showing measurement results of Example 2;

Since the center hole 4 has an opening portion on the mounting reference surface 5b side directly formed by the outer peripheral surface of the center punch 28, as shown in FIG. It is formed with surface accuracy. On the other hand, since the center hole 4 is punched and formed by the center punch 28 at a position of 0.6 mm from the mounting reference surface 5b, the degree of unevenness k2 is slightly larger than that of the opening as is clear from FIG. Has become. However,
Since this portion is the shear surface 4b as described above, the unevenness degree k2 is formed at a maximum value of about 10 μmpp, which is an extremely small value as compared with the conventional magneto-optical disk 100.

FIG. 9 is a diagram showing the relationship between the set position of the center punch 28 projecting into the cavity 25 and the degree of unevenness of the inner peripheral wall surface of the center hole 4 formed by punching. In the magneto-optical disk 1, the tolerance of unevenness generated on the inner peripheral wall surface of the center hole 4 needs to be 25 μmpp or less in order to conform to the required specification (40 μmpp) in consideration of a margin. The disk substrate 2 has a thickness of 0.1 mm.
Although it is 8 mm, as described above, the positioning ball 15 of the disc table 10 is relatively engaged with the center hole 4 with the upper limit of the height of 0.6 mm from the mounting reference surface 5b.

Therefore, the center punch 28 is set at a position set so as to protrude into the cavity 25 up to a height of 0.6 mm from the mounting reference surface 5b as an upper limit. It is possible to form the center hole 4 that meets the required specifications of the disk 1. In the embodiment, since the center punch 28 is set so as to protrude from the mounting reference surface 5b at a position of 0.3 mm, it is obvious that the center hole 4 is formed in conformity with the required specifications. In other words, the center punch 28 has a protrusion amount of not less than の and not more than の of the thickness dimension with respect to the cavity 25 for molding the disk substrate 2 having the thickness dimension of 0.8 mm in consideration of the margin. Is projected in advance.

In the molding die 20, the center punch 28 is assembled in the above-described configuration, so that the dimensional accuracy of the formation portion of the center punch 28 and the center hole 4 is greatly eased, and the center hole 4 is formed by the center punch 28. Can be formed under relatively mild conditions. Further, the molding die 20 includes a center punch 28.
The wear control of the disk substrate 2 is also eased, the productivity of the disk substrate 2 is improved, and the high-precision disk substrate 2 with good yield is obtained.
Is molded.

In the above-described embodiment, the magneto-optical disk 1 has a thickness of 0.8 mm, is magnetically chucked on the disk table 10, and is positioned at the center of rotation by the positioning ball 15. However, the present invention is not limited to the magneto-optical disk 1. The present invention is also applicable to other disk-shaped recording media, such as magnetic disks, which are magnet chucked on a disk table and whose rotation center is positioned by positioning balls.

[0047]

As described above in detail, according to the disk-shaped recording medium of the present invention, the center hole for positioning the center of rotation by the relative engagement of the positioning means can greatly reduce the production process and the size of the molding die. Since it is formed with extremely high accuracy without requiring any change, it is possible to rotate and drive with eccentricity suppressed. Therefore, even when the recording tracks are narrowed to achieve high-density recording of information signals and the like, the disc-shaped recording medium does not require precise tracking control, and the information signals and the like are not affected even when vibration is applied. Is accurately recorded or reproduced.

Further, according to the method of manufacturing a disk-shaped recording medium according to the present invention, a disk substrate in which a center hole for positioning the center of rotation is formed with high accuracy by the relative engagement of the positioning means can be produced in a production process or in a molding process. The production is good and efficient with no significant change of the mold. In addition, the method for manufacturing a disc-shaped recording medium eliminates the need for an inspection process for all the manufactured disk substrates and reduces the wear control process of a center punch for punching and forming a center hole or the dimensional accuracy thereof, thereby reducing the recording track. Is manufactured at a low cost by reducing the pitch of a disk-shaped recording medium in which information signals and the like are recorded at a high density.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part showing a state where a magneto-optical disk shown as an embodiment of the present invention is chucked on a disk table.

FIG. 2 is an explanatory diagram showing details of a chucking state of the magneto-optical disk.

FIG. 3 is a longitudinal sectional view of a main part of a molding die for molding a disk substrate of the magneto-optical disk.

FIG. 4 is an explanatory diagram of a forming process of the disk substrate.

FIG. 5 is a vertical sectional view of an essential part for explaining a configuration of a center hole of the disk substrate.

FIG. 6 is an explanatory diagram of measurement of center hole accuracy of the disk substrate.

FIG. 7 is a view showing a result of measuring hole accuracy of an opening portion with respect to a center hole of the disk substrate.

FIG. 8 is a diagram showing a result of measuring hole accuracy at a position of 0.6 mm from an opening of a center hole of the disk substrate.

FIG. 9 is a relationship diagram between a set position of a center punch and a hole accuracy of a center hole when the disk substrate is formed.

FIG. 10 is a schematic configuration diagram of a disk drive device.

FIG. 11 is an explanatory diagram showing details of a chucking state of a conventional magneto-optical disk.

FIG. 12 is a diagram showing a result of measuring hole accuracy of an opening portion with respect to a center hole of a conventional disk substrate.

FIG. 13 is a view showing a result of measuring hole accuracy at a position of 0.6 mm from an opening of a center hole of a conventional disk substrate.

[Explanation of symbols]

1 magneto-optical disk (disk-shaped recording medium), 2 disk substrate, 3 clamping plate, 4 center hole, 5
Recessed portion, 5b bottom surface (mounting reference surface), 10 disk table, 11 engaging convex portion, 12 magnet, 15 positioning ball (positioning means), 20 disk substrate molding die, 21 fixed die, 22 movable die, 25 cavities, 27 nozzles, 28 center punches, 29
Stamper, 30 eject pins

Claims (2)

[Claims] 1. A center hole in which a disk substrate is molded by a molding die using a synthetic resin as a raw material, and when loaded into a recording and / or reproducing apparatus, is chucked by a magnet chucking means and engages with a positioning means. In the disk-shaped recording medium in which the rotation center is positioned and is rotated and driven by the disk drive mechanism to record and / or reproduce information signals and the like, the center hole is formed from a chucking reference plane with the disk drive mechanism. A disk-shaped member formed by punching out the disk substrate by a center punch previously projected into the cavity with a projection amount of not less than 1/3 and not more than 1/2 with respect to the thickness dimension of the formation portion. recoding media. 2. A center hole in which a disk substrate is molded by a molding die using a synthetic resin as a raw material, and when loaded into a recording and / or reproducing apparatus, is chucked by a magnet chucking means and engages with a positioning means. In the method for manufacturing a disk-shaped recording medium in which the rotation center is positioned and the information is recorded and / or reproduced by being rotationally driven by a disk drive mechanism, the disk substrate has a center punch formed at a center hole forming portion. After being molded in a state of being projected into the cavity with a projection amount of not less than 1/3 and not more than 1/2 with respect to the thickness dimension, the center punch is operated to punch out the center hole. A method for producing a disc-shaped recording medium, characterized by the following.