JPH0628806A - Method for holding magnetic plate on disk substrate - Google Patents

Abstract

PURPOSE:To prevent deterioration of an optical characteristic of the disk substrate formed by molding synthetic resins and to securely and easily hold the magnetic plate on the disk substrate. CONSTITUTION:A vibration impressor 112 is brought with its tip side into contact with several points of a circumferential periphery of a magnetic plate housing recessed part 36 housing the magnetic plate 25 or over the whole circumference. The disk substrate 22 is impressed with an ultrasonic vibration that vibrates in the parallel direction to the main surface of this disk substrate 22 and also in the circumferential direction. The circumferentially peripheral part of the magnetic plate housing recessed part 26 is thermally deformed to form a projecting piece 31 projecting inside the magnetic plate housing recessed part 26, and the magnetic plate 25 disposed to be housed in the magnetic plate housing recessed part 26 is held by this projecting piece 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention holds a magnetic plate disposed on a disk substrate which constitutes an information signal recording disk on which desired information signals are recorded, such as an optical disk or a magneto-optical disk. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, discs for recording information signals, such as optical discs and magneto-optical discs, on which desired information signals are recorded have been proposed. This type of disc is capable of high-density recording of information signals, and therefore has a very small diameter. For example, there has been proposed an optical disk or magneto-optical disk having a diameter of about 64 mm and capable of recording a music signal for about 74 minutes.

The magneto-optical disk having such a small diameter and capable of high-density recording of information signals is mounted on a disk rotation driving device and rotated at a high speed. Then, while being driven to rotate at a high speed, a fine recording track provided on a signal recording layer formed on one main surface of the magneto-optical disk is irradiated with a light beam emitted from an optical pickup and a magnetic field head. A desired information signal is recorded by applying an external magnetic field that is magnetic field modulated according to the information signal to be recorded from an external magnetic field generator such as.

In order to accurately irradiate a fine recording track with a light beam while being rotationally driven at such a high speed,
The magneto-optical disk must be surely integrated with the disk table of the disk rotation driving device and mounted with the rotation center accurately positioned on the axis of the disk table.

By the way, in order to surely integrate the magneto-optical disk into the disk table and to position and mount it with high precision, a magnetic plate for magnetic attraction such as a metal plate made of a magnetic material disposed on the magneto-optical disk side. A disk mounting method has been proposed in which the magneto-optical disk is chucked on the disk table by attracting the magnetic disk with a magnet arranged on the disk table side.

A magneto-optical disk 1 used in a magnet chucking system utilizing the attractive force of this magnet.
As shown in FIGS. 13 and 14, the disk substrate 2 is formed by molding a synthetic resin such as a transparent polycarbonate resin into a disc shape. An information signal recording layer on which a desired information signal is recorded is adhered to one main surface 2a side of the disc substrate 2. In the disc substrate 2, one main surface 2a on which the information signal recording layer is formed is opposite to the other main surface 2b which serves as an information signal writing / reading surface, and the signal recording layer is formed from this writing / reading surface side. A desired information signal is recorded or reproduced by irradiating a light beam on the.

Further, in the central portion of the disc substrate 2,
As shown in FIG. 13, a center hole 3 is formed in which a centering member arranged on the disk rotation drive side engages. Further, one main surface 2 of the disk substrate 2
A metal plate 4, which is a magnetic plate, is disposed in the central portion on the a side so as to close the center hole 3. This metal plate 4
Is the center hole 3 on one main surface 2a side of the disk substrate 2.
It is arranged so as to fit into the metal plate accommodating recess 5 formed so as to surround it, and is joined to the disk substrate 2 with an adhesive 6 such as a double-sided adhesive tape.

As described above, in the magneto-optical disk 1 in which the metal plate 4 is attached to the disk substrate 2 by using the adhesive 6, the metal plate is repeatedly mounted on and removed from the disk table of the disk rotation driving device. 4 may be easily peeled off from the disk substrate 2. That is,
This is because the load at the time of loading and unloading the disk table is applied to the joint portion of the metal plate 4 to the disk substrate 2 and the adhesive 6 is deteriorated.

In order to solve the problems caused by attaching the metal plate using such an adhesive, the applicant of the present application attaches the metal plate to the disc substrate without using the adhesive. Is proposed.
As shown in FIG. 14, this magneto-optical disk 11 has a center hole 13 surrounded by a main surface 12a on one side of which an information signal recording layer of a disk substrate 12 made of a synthetic resin such as transparent polycarbonate resin is adhered and formed. A metal plate accommodating recess 15 is formed so that the metal plate 14 is accommodated therein, and a convex portion 16 for caulking the metal plate 14 is provided on the outer peripheral edge side of the metal plate accommodating recess 15. A plurality of the convex portions 16 are provided at equal intervals on the outer peripheral edge side of the metal plate accommodating concave portion 15.

After the metal plate 14 is accommodated in the metal plate accommodating concave portion 15 and heat is applied to the convex portion 16, as shown in FIG.
As shown in FIG. 5, by thermally deforming the tip side of these convex portions 16 toward the metal plate accommodating concave portion 15 side, the metal plate 1 is projected by the support piece 16 a protruding from the tip of this convex portion 16.
4 is supported in the metal plate accommodating recess 15 and is attached to the disk substrate 12.

In the magneto-optical disk 11 in which the metal plate 14 is mounted by being supported by the support piece 16a protruding from the tip of the convex portion 16 integrally formed with the disk substrate 12, the metal plate is Since 14 is firmly supported by the disk substrate 12, even if the disk rotation driving device is repeatedly mounted on and removed from the disk table, it is possible to securely maintain the state of being mounted on the disk substrate 12 without causing separation or the like. Is possible.

[0012]

However, in order to form the convex portion 16 for supporting the metal plate 14 on the disk substrate 12 as described above, the structure of the mold for molding the disk substrate 12 becomes complicated. , It becomes difficult to process the mold.

When the convex portions 16 are formed intermittently on the outer peripheral edge side of the metal plate accommodating concave portion 15, the disk substrate 12
When molding, the flow of the synthetic resin material melted in the portion where the convex portion 16 is formed is not uniform, further, the curing time of the synthetic resin material is displaced, and so-called weld lines are generated. There is a risk that the uniformly cured disc substrate 12 may not be molded. Further, if the disk substrate 12 is not uniformly hardened, internal stress remains in the disk substrate 12, causing birefringence and the like in the disk substrate 12 and deteriorating the optical characteristics. In particular, if birefringence occurs in the disk substrate 12, writing or reading of an information signal will occur when it is configured as the magneto-optical disk 11.

Therefore, in order to solve the problem caused by intermittently forming the convex portions for supporting the metal plate as described above, a series of ring-shaped convex portions is formed on the outer peripheral edge side of the metal plate accommodating concave portion. A disk substrate adapted to be formed is conceivable. However, it is extremely difficult to perform crimping to support the metal plate arranged in the metal plate accommodating recess by uniformly deforming a series of ring-shaped protrusions by heat, and it is not feasible. Is.

It is also conceivable to partially heat-deform a part of a series of ring-shaped convex portions to perform crimping to support the metal plate, but the metal plate was supported on the disk substrate. After that, the part that was not thermally deformed remains in a protruding shape. Therefore, the thickness of the disc substrate itself becomes thicker only in the above-mentioned protruding portion, and the magneto-optical disc constituted by using this disc substrate also becomes thicker. Then, it becomes difficult to design a disc cartridge for accommodating the magneto-optical disc. That is, since the disc cartridge can be used with versatility, its thickness is regulated to be constant.

Therefore, according to the present invention, the mold for molding the disk substrate can be easily processed, the disk substrate can be easily molded, the deterioration of the optical characteristics of the molded disk substrate can be prevented, and the birefringence can be prevented. It enables the molding of the disc substrate of the information signal recording disc that does not cause the like, maintains the smoothness of the main surface side of the disc substrate, and ensures the holding of the magnetic plate on the disc substrate. It is an object of the present invention to provide a method for holding a magnetic plate on a disk substrate, which makes it possible to suppress the adverse effect on the disk substrate caused by attaching the magnetic plate.

Further, the present invention realizes the simplification of the apparatus used for attaching the magnetic plate to the disk substrate, and the method for holding the magnetic plate to the disk substrate, which makes it possible to quickly and easily hold the magnetic plate. The purpose is to provide.

[0018]

In order to solve the above problems and achieve the above objects, the present invention has a center hole and an information signal recording layer formed on one main surface side. In holding the magnetic plate in the magnetic plate storage recess formed by surrounding the center hole on one main surface side of the disk substrate made of synthetic resin, the tip side of the vibration applicator is attached to the periphery of the magnetic plate storage recess. By contacting and applying ultrasonic vibration in a circumferential direction parallel to the main surface of the disk substrate to the peripheral edge of the magnetic plate storage recess, and thermally deforming at least a part of the peripheral edge of the magnetic plate storage recess, The magnetic plate is held in the plate storage recess.

[0019]

According to the method of the present invention, the disk is inserted through the vibration applicator with the tip of the vibration applicator being in contact with the magnetic plate accommodating concave part accommodating the magnetic plate at several points or the entire circumference thereof. When ultrasonic vibration that vibrates in the circumferential direction in a direction parallel to the main surface of the disk substrate is applied to the substrate,
The peripheral portion of the magnetic plate storage recess, which is in contact with the vibration applicator, is thermally deformed and protrudes so as to project into the magnetic plate storage recess. The magnetic plate accommodated in the magnetic plate accommodating recess is held in the magnetic plate accommodating recess with the outer peripheral edge side being supported by the projecting piece projecting into the magnetic plate accommodating recess.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A concrete embodiment in which the method of the present invention is applied to a magneto-optical disk having a diameter of 64 mm will be described below with reference to the drawings. As shown in FIG. 1, a magneto-optical disk 21 to which the method of the present invention is applied includes a disk substrate 22 formed by molding a synthetic resin material such as a polycarbonate resin having transparency of the present invention. The disk substrate 22 has a diameter R of about 64 mm and a thickness T of about 1.2.
It is formed in a disk shape of mm.

A magneto-optical disk 21 constructed by using this disk substrate 22 is formed by depositing an information signal recording layer on which a desired information signal is recorded on one main surface 2a side of the disk substrate 22. A recording surface is provided, and one main surface 22 on which the information signal recording layer of the disk substrate 22 is adhered and formed
The other main surface 22b facing a is used as an information signal writing / reading surface, and the information signal is recorded / reproduced by irradiating the signal recording layer with a light beam from the writing / reading surface side. Become.

As shown in FIGS. 1 and 2, in the central portion of the disk substrate 22 which constitutes the magneto-optical disk 21, as shown in FIGS.
A center hole 23 is formed to engage with a centering member arranged at the center of a disk table that constitutes a disk rotation driving device arranged in the recording / reproducing apparatus.
The center hole 23 is formed so as to penetrate the disk substrate 22, and is formed so that the center thereof coincides with the center of curvature of a recording track formed in the signal recording layer in a concentric or spiral shape.

Further, as shown in FIG. 2, a circular ring-shaped protrusion 24 is integrally formed at the center of the other main surface 22b of the disk substrate 22 so as to surround the center hole 23. . The protrusion 24 is formed by deepening the depth of the center hole 23 formed in the thin disk substrate 22, so that the center hole of the centering member arranged on the side of the disk table on which the magneto-optical disk 21 is mounted. The protrusion amount with respect to 23 is increased, and the centering operation for mounting the magneto-optical disk 21 with the rotation center of the magneto-optical disk 21 aligned with the axis of the disk table is performed reliably. Further, the tip end surface of the protruding portion 24 functions as a mounting reference surface 24a for mounting on the disc table.

The protrusion 24 is formed at least in the non-signal recording area on the inner peripheral side of the disc substrate 22 where the signal recording layer is not formed, and is formed with a protrusion amount substantially equal to the thickness T of the disc substrate 22. Has been done. Therefore, the portion of the disc substrate 22 on which the protruding portion 24 is formed is twice as thick as the substrate body portion.

An annular metal plate is provided in the center of the one main surface 22a side of the disk substrate 22. A metal plate 25, which is a magnetic plate for attracting magnets, is arranged so as to surround the center hole 23. A storage recess 26 is formed. The metal plate accommodating recess 26 has a diameter smaller than the outer peripheral diameter r of the protrusion 24 and is formed to a depth substantially equal to the thickness T of the disk substrate 22. Further, the opening edge side of the metal plate accommodating recess 26 has a diameter larger than that of the inner part, so that the metal plate 25 can be easily inserted into the metal plate accommodating recess 26.

As described above, the one main surface 22a side of the disk substrate 22 is a smooth surface only with the metal plate accommodating recess 26 formed therein.

Further, the metal plate 2 in the metal plate storage recess 26 is
A step portion 28 is formed on the inner peripheral side of the bottom surface portion that serves as the mounting surface 27 of No. 5. The step portion 28 prevents protrusions such as burrs from being generated on the mounting surface 27 of the metal plate 25 when the metal plate housing recess 26 is formed, and maintains the mounting surface 27 as a smooth surface. To do so.

On the other hand, the metal plate 25 accommodated and arranged in the metal plate accommodating recess 6 has a disk shape made of a metallic material such as a stainless steel plate (SUS-430) having a thickness t of about 0.4 mm. It is formed by punching. As shown in FIG. 1, the metal plate 25 is formed in a disc shape having a size large enough to be housed in the metal plate housing recess 26, and is housed in the metal plate housing recess 26. When installed, the central main surface portion 25a is flush with the one main surface 22a of the disk substrate 22, and the inner peripheral surface 26a of the metal plate housing recess 26 faces the peripheral edge of the metal plate 25. In order to form the eggplant, a step bending process is applied to the outer peripheral edge side. That is, on the outer peripheral edge side of the metal plate 25, the mounting piece 30 on the mounting surface 27 is formed via the bent portion 29 that is bent so as to hang down toward the peripheral edge.
That is, as shown in FIG. 1, the metal plate 25 is formed in a disc shape having a concave shape as a whole.

The metal plate 25 formed as described above is held on the disk substrate 22 by the steps and methods described below.

First, the disc substrate 22 formed as shown in FIGS. 1 and 2 is placed on the suction support table 101. The suction support table 101 is configured to position and support the mounted disk substrate 22 by suction, and the support table body 102.
As shown in FIG. 3, a disk substrate support table 103 for positioning and mounting the disk substrate 22 is provided on the upper surface side of the disk. The disc substrate support table 103 has a fitting protrusion 104 at its center, into which the center hole 23 of the disc substrate 22 fits, and the fitting protrusion 104.
A protrusion fitting recess 105 into which the protrusion 24 of the disk substrate 22 is fitted is provided on the outer periphery of the.

A protective sheet 106 having flexibility such as silicon rubber is attached to the disk substrate mounting surface side which receives the other main surface 22b side of the disk substrate 22 on which the disk substrate supporting table 103 is mounted. And so on. The protective sheet 106 is provided to prevent the other main surface 22b of the mounted disk substrate 22 from being damaged, such as being scratched.

Further, the suction support table 101 has
A suction mechanism is provided that vacuum-sucks and supports the disk substrate 22 placed on the disk substrate support table 103 using a vacuum air pump. This suction mechanism forms a plurality of suction ports 107 in the disc substrate support table 103 and forms a suction air chamber 108 by interposing an escutcheon 110 between the disc substrate support table 103 and the support table body 102. Room 10
8 is sucked by a vacuum air pump (not shown) through an air passage 109 formed in the support table main body 102 to suck and support the disc substrate 22 on the disc substrate support table 103.

The plurality of suction ports 107 are fitted in a position corresponding to the outer peripheral side of the disk substrate 22 placed on the disk substrate support table 103, a position corresponding to the central portion, and a protruding portion fitting with the protruding portion 24. Each of the openings is located in the fitting recess 105. By providing the suction ports 107 at such positions, the entire surface of the disk substrate 22 can be pressed evenly against the disk substrate support table 103 and supported.

An opening 108 communicating with the suction ports 107 is formed at a position corresponding to the suction ports 107 of the protective sheet 106.

As shown in FIG. 4, the disk substrate 22 is mounted on the suction support table 101 having the above-described structure with the metal plate accommodating recess 26 in which the metal plate 25 is disposed facing the upper surface side. To be done. At this time, the disk substrate 22
Fits the metal plate storage recess 26 into the center hole 23 and the projection 10
4 and the projection 24 is fitted into the projection fitting recess 105 to be mounted, whereby the positioning of the mounting position with respect to the suction support table 101 is achieved.

When the disk substrate 22 is thus mounted on the suction support table 101, the vacuum air pump is operated to suck the air in the suction air chamber 108 through the air passage 109, and the disk substrate 2 is then sucked through the suction port 107.
The air between the suction support table 101 and the suction support table 101 is also sucked, and the disk substrate 22 is closely supported by the protective sheet 106 on the suction support table 101.

At this time, in the disk substrate 22, the center hole 23 is fitted in the fitting projection 104, and the projection 24 is fitted in the projection fitting recess 105, so that the suction support table 101 is formed.
Since it is mounted on the suction support table 101,
Accurate positioning of the mounting position with respect to is achieved.

After mounting the disk substrate 22 on the suction support table 101 in this manner, the metal plate 25 is housed in the metal plate housing recess 26. At this time, the metal plate 25
As shown in FIG. 5, the placing piece 10 is placed on the placing surface 27 of the metal plate accommodating recess 26 and accommodated therein.

When the metal plate 25 is placed in the metal plate accommodating recess 26, as shown in FIG. 6, the vibration applying element 112, which is a resonator of the ultrasonic wave applying device, is attached to the suction support table 101.
The contact portion 113 on the front end side is brought into contact with the peripheral edge of the metal plate accommodating recess 26 by lowering it onto the disc substrate 22 placed on the top.

As shown in FIGS. 6 and 7, the contact portions 113 of the vibration applying element 112 used here are first to fourth contact elements which are in contact with each other in the circumferential direction of the metal plate accommodating recess 26 at equal intervals. And 113a to 113d. That is, as shown in FIG. 7, the contact portion 113 is configured by projecting first to fourth contactors 113a to 113d at 90-degree intervals on the tip side of the vibration applying element 112.

Then, as shown in FIG. 6, ultrasonic waves are applied while the first to fourth contactors 113a to 113d forming the contact portion 113 are brought into contact with each other so as to correspond to the peripheral edge of the metal plate accommodating recess 26. The device 111 is driven, and ultrasonic vibration is oscillated from the vibration applicator 112. At this time, the ultrasonic vibration oscillated from the vibration applicator 112 is
This is so-called torsional vibration, which alternately vibrates in the circumferential direction of arrows A and B in FIG. Therefore, when the vibration applicator 112 comes into contact with the peripheral edge of the metal plate accommodating recess 26, ultrasonic vibration in the circumferential direction is applied in parallel with the main surface of the disk substrate 22.

When the ultrasonic vibration is applied in this manner, the first to fourth parts constituting the contact portion 113 of the vibration applicator 112 are formed.
The peripheral portion of the metal plate accommodating concave portion 26 with which the contactors 113a to 113d are in contact is heated and softened. At this time, since the vibration applicator 112 is pressurized with a predetermined pressure, the recess 33 corresponding to the first to fourth contacts 113a to 113d of the vibration applicator 112 is formed in the peripheral edge portion of the metal plate accommodating recess 26. To form the metal plate storage recess 26.
A projecting piece 31 is formed so as to project to the inner peripheral side of the. As shown in FIG. 8, these projecting pieces 31 project on the mounting pieces 30 of the metal plate 25 housed in the metal plate housing recess 26 and support the mounting pieces 30.

The vibration applicator 112 is composed of the first to fourth vibration elements.
After the contactors 113a to 113d are contacted with the peripheral edge of the metal plate accommodating recess 26 for a predetermined time to form the protruding piece 31 as described above, they are separated from the disk substrate 22 and returned to the initial position.

As described above, in the present embodiment, the first to fourth portions are simultaneously formed at four locations on the periphery of the metal plate accommodating recess 26.
The contactors 113a to 113d are contacted to form four protrusions 31 at the same time as shown in FIGS. 9 and 10 to hold the metal plate 25 housed in the metal plate housing recess 26. However, by using the vibration applicator 112 having the contact portions 113 composed of the pair of first and second contact elements at the opposite positions, the protrusions 31 are provided on the periphery of the metal plate accommodating recess 26.
May be formed.

When the protrusion 31 is formed using the vibration applicator 112 having only a pair of contacts in this manner, the peripheral edge of the metal plate accommodating recess 26 is formed by applying ultrasonic vibration once to the disk substrate 22. Since only two projecting pieces 31 are formed at positions opposite to each other, when the projecting pieces 31 are formed at four places as shown in FIG. 10, the vibration applying element 112 is rotated around the axis. Nothing is possible. After forming the pair of projecting pieces 31 by applying ultrasonic vibration once, the vibration applying element 112 is rotated by 90 degrees, and the pair of first and second contact elements are again brought into contact with each other. The pair of projecting pieces 31 are formed.

Further, as shown in FIG. 12, the contact 113e forming the contact 113 of the vibration applying element 112 is formed in a continuous ring shape as shown in FIG. It is possible to form the projecting piece 31 projecting to the inner peripheral side of the metal plate accommodating recess 26 over the entire circumference of the 26.

By the way, the ultrasonic vibration applied to the disk substrate 22 vibrates in the direction parallel to the main surface 22a of the disk substrate 22 and in the circumferential direction thereof. The peripheral portion of the metal plate storage recess 26, which is softened by the contact of the vibration applicator 113, is the metal plate storage recess 26 in the vibration direction of the ultrasonic vibration.
Can be displaced in the circumferential direction of. At this time,
The peripheral portion of the softened metal plate accommodating concave portion 26 projects into the inside of the opened metal plate peripheral portion 26,
A protruding piece 31 protruding inward of the metal plate accommodating recess 26 is formed. The projecting piece 31 formed so as to project inward of the metal plate storage recess 26 has the metal plate storage recess 26.
The mounting plate 31 is supported by protruding on the mounting plate 30 of the metal plate 25 housed and disposed therein, and the metal plate 25 is held in the metal plate storage recess 26.

The vibration applicator 112 is connected to the disk substrate 2
When the ultrasonic wave is applied to the metal plate 2 by bringing the vibration applicator 112 into a pressurized state, the metal plate containing recess 26 is softened by the application of ultrasonic waves. It is possible to reliably perform the inward projection of the metal plate 26, and to reliably form the protruding piece 31 that protrudes inward of the metal plate storage recess 26.

Further, in the method of the present invention, the ultrasonic vibration applied to the disk substrate 22 is a lateral vibration vibrating in a direction parallel to the main surface 22a of the disk substrate 22,
There is little propagation in the thickness direction of the disk substrate 22. Therefore, the heating on the inner side of the disk substrate 22 is controlled, and the inner deformation of the metal plate accommodating recess 26 is restricted. As a result, the thickness of the projecting piece 31 projecting inward of the metal plate accommodating recess 26 is controlled so that the projecting piece 31 can be controlled by the metal plate 2.
It is possible to support the mounting piece 30 of No. 5 without pressing it. That is, the depth d of the metal plate storage recess 26
By making the depth deeper than the thickness of the metal plate 25, a gap w is formed between the projecting pieces 31, 32 and the mounting piece 30, as shown in FIG.
And the metal plate 25 can be loosely fitted and held in the metal plate storage recess 26.

In this way, the metal plate 25 is placed in the metal plate housing recess 2
It is possible to prevent the metal plate 25 from being fixedly attached to the main surface of the disk substrate 22 in a tilted manner by loosely fitting and holding the metal plate 25 in the inside of the disk 6. It is possible to prevent the deformation of the disk substrate 22 caused by the difference in expansion coefficient.

By the way, a disk substrate 2 to which the method of the present invention formed by using a polycarbonate resin as a material is applied.
The ultrasonic vibration applied to 2 is 15 KHz to 50 KH
It is set in the range of z. That is, it is difficult to obtain sufficient heat at a vibration frequency of 15 KHz or less,
When the frequency is 50 KHz or more, heat is generated remarkably and the vibration applying member 112
This is because it becomes difficult to control the softening amount of the portion which is brought into contact with and softened. The ultrasonic vibration applied is preferably about 20 KHz.

In the present embodiment, the metal plate 25 held by the disk substrate 22 is formed in a concave shape having a mounting piece 30 on the periphery, but can be stored in the metal plate storage recess 26. It may also be a flat disc having a size.

Furthermore, in the above-mentioned embodiment, the example applied to the magneto-optical disk has been described. However, the invention is applicable to an information signal recording disk having a disk substrate made of synthetic resin and a magnetic plate for magnet chucking. It is widely applicable.

[0054]

According to the method of the present invention, ultrasonic vibration is applied to the main surface of the disk substrate at the periphery of the recess for storing the magnetic plate, in the direction parallel to the main surface of the disk substrate and in the circumferential direction of the disk substrate. When applied, the peripheral edge of the magnetic plate accommodating recess is thermally deformed to project into the magnetic plate accommodating recess, and the protruding part supports the peripheral edge of the magnetic plate and holds it in the magnetic plate accommodating recess. Therefore, it is possible to form a protrusion for supporting the magnetic plate without generating a protrusion or the like on the main surface of the disk substrate on which the magnetic plate is disposed, and the main surface of the disk substrate can be formed. Sufficient smoothness can be maintained and the molding accuracy of the disk substrate is not hindered.

Since the amount of thermal deformation of the peripheral edge of the magnetic plate accommodating recess can be easily controlled by controlling the ultrasonic vibration applied to the disk substrate, the magnetic plate can be accurately and easily held on the disk substrate. It becomes possible.

Further, since the so-called torsional vibration that vibrates in the direction parallel to the main surface of the disc substrate and in the circumferential direction of the disc substrate is used, it is possible to regulate the deformation inside the disc substrate. Since the magnetic plate can be easily loosely fitted and held in the magnetic plate housing recess, it is possible to prevent the magnetic plate from being fixedly attached to the main surface of the disk substrate while being inclined. Then, it becomes possible to prevent the deformation of the disk substrate caused by the difference in the coefficient of thermal expansion between the disk substrate made of a synthetic resin and the magnetic plate using the metal plate, and the information recording disk configured by using this disk substrate, It can be stably mounted on the disc table of the disc rotation drive mechanism.

Further, since the disk substrate used in the method of the present invention does not need to have protrusions for supporting the magnetic plate on the main surface, the structure of the disk substrate is simplified, and the mold for molding the disk substrate is simplified. Processing becomes easy, and the disk substrate can be easily formed. In particular, since the mold for molding the disk substrate is simplified and the molding of the disk substrate is facilitated, the molding distortion that causes the occurrence of birefringence or the like that deteriorates the optical characteristics of the disk substrate after molding is prevented. Thus, it is possible to construct an information signal recording disk having excellent signal recording / reproducing characteristics which does not cause defective writing or reading of information signals.

Further, by applying ultrasonic vibration once,
Since it is possible to use a vibration applicator capable of thermally deforming the entire circumference or a plurality of points of the peripheral edge of the magnetic plate accommodating concave portion, not only can the magnetic plate be held quickly, but also the configuration of the ultrasonic wave applying device can be realized. To be simplified.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a magneto-optical disk to which the method of the present invention is applied.

FIG. 2 is a cross-sectional view showing a disk substrate and a metal plate that form the magneto-optical disk.

FIG. 3 is a schematic sectional view showing a disk support table used in the method of the present invention.

FIG. 4 is a cross-sectional view showing a state where a disc substrate is mounted on the disc support table.

FIG. 5 is a cross-sectional view showing a state in which a metal plate is housed and disposed in a metal plate housing recess of a disk substrate to which the method of the present invention is applied.

FIG. 6 is a cross-sectional view showing a state where a vibration applicator of an ultrasonic wave application device is brought into contact with the peripheral edge of a magnetic plate housing recess of a disk substrate.

FIG. 7 is a partial perspective view showing a vibration applicator used in the method of the present invention.

FIG. 8 is a cross-sectional view showing a state in which a vibration applicator is brought into contact with the peripheral edge of a magnetic plate accommodating recess of a disk substrate to apply ultrasonic vibration to form a protrusion.

FIG. 9 is a cross-sectional view showing a state in which a metal plate, which is a magnetic material, is attached to the disc substrate.

FIG. 10 is a plan view of a magneto-optical disk to which a metal plate which is a magnetic material is attached by the method of the present invention.

FIG. 11 is a partial perspective view showing another example of the vibration applicator used in the method of the present invention.

FIG. 12 is a plan view of a magneto-optical disk showing another example in which a metal plate which is a magnetic material is attached to a disk substrate by the method of the present invention.

FIG. 13 is a sectional view of a magneto-optical disk in which a metal plate is attached to a disk substrate by a conventional method.

FIG. 14 is an exploded perspective view of a magneto-optical disk applied to another conventional method.

FIG. 15 is a sectional view of a magneto-optical disk in which a metal plate is attached to a disk substrate by another conventional method.

[Explanation of symbols]

 21 Magneto-Optical Disk 22 Disk Substrate 23 Center Hole 25 Metal Plate 26 Metal Plate Storage Recess 31 Protrusion 112 Vibration Applicator of Ultrasonic Wave Applicator 113 Contact Part

Claims (1)

[Claims] 1. A magnetic material formed by surrounding a center hole on one main surface side of a disk substrate made of a synthetic resin in which a center hole is formed and an information signal recording layer is formed on one main surface side. In holding the magnetic plate in the plate accommodating recess, the tip of the vibration applicator is brought into contact with the peripheral edge of the magnetic plate accommodating recess so that the peripheral edge of the magnetic plate accommodating recess is parallel to the main surface of the disk substrate in the circumferential direction. A method for holding a magnetic plate to a disk substrate, wherein the magnetic plate is held in the magnetic plate storage recess by applying sonic vibration to thermally deform at least a part of the peripheral edge of the magnetic plate storage recess.