JPH05342793A - Optical disk - Google Patents

Abstract

PURPOSE:To prevent a distortion and a double refraction of a disk board due to a difference of thermal expansion coefficients, by holding a magnetic member in a state being separated from the board with an ultraviolet ray-curable resin having a high viscosity. CONSTITUTION:A peripheral edge of a recess 27 for containing a metal plate 26 formed of a magnetic material is covered with a ultraviolet ray-curable resin 30 having a high viscosity, and cured. The plate 26 arranged to be contained in the recess 27 has a predetermined interval D2 to a protrusion formed by curing the resin 30 in the recess 27, and held in a state separated from a disk board 21. Accordingly, influence of elongation/contraction due to difference of thermal expansion coefficients because of a variation in an environmental temperature is shut off by the gap between the plate 26 and the board 21, thereby preventing a distortion and a double refraction of the board 21 due to the difference of the thermal expansion coefficients.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk used as a recording medium for information signals, and more particularly to an optical disk chucked on a disk table of a disk rotation drive mechanism by utilizing magnetic attraction.

[0002]

2. Description of the Related Art Conventionally, an optical disk has been used as a recording medium for information signals. This optical disc is capable of high density recording of information signals and has been proposed to have an extremely small diameter. For example, for an optical disc, the diameter is 64
A small diameter of less than or equal to mm has been proposed.

An optical disk having such a small diameter and capable of high-density recording is mounted on a disk rotation drive mechanism and rotated at a high speed. Then, while being rotated at a high speed, a recording track provided on a signal recording layer formed on one main surface of the optical disc is irradiated with a light beam emitted from an optical pickup, and an external magnetic field is generated by a magnetic head. By applying the voltage, a desired information signal is recorded.

In order to accurately irradiate the recording track with the light beam while being rotated at a high speed, the optical disk is surely integrated with the disk table of the disk rotation drive mechanism, and Therefore, it is necessary to position and attach with high accuracy.

By the way, in order to surely integrate the optical disk into the disk table and to position and mount the disk table with high accuracy, the magnetic disk for chucking made of a metal plate or the like arranged at the center of the optical disk. A disk mounting method has been proposed in which a plate is attracted by a magnet disposed on the disk table while the optical disk is placed on the disk table, and the optical disk is mounted on the disk table.

As shown in FIG. 6, the optical disc 1 used in the disc mounting method utilizing the attractive force of the magnet is such that the center hole 2 formed at the center of the optical disc 1 is closed. The metal plate 3, which is a magnetic member, is disposed on one of the main surfaces of the first plate. On the other hand, in the disc rotation drive mechanism 4 that rotationally drives the optical disc 1, the disc table 7 is integrally attached to the rotation drive shaft 6 of the spindle motor 5, and the magnet holder 8 is provided on the tip side of the rotation drive shaft 6. The magnet 9 is integrally attached. Further, in the central portion of the disc table 7, the centering member 11 is biased by the coil spring 12 so as to be accommodated in the accommodating portion 10 formed in the central portion of the disc table 7, and the axis of the rotary drive shaft 6 is thereby. It is mounted so that it can move in any direction.

As shown in FIG. 6, the optical disc 1 is mounted on the disc table 7 while the center hole 2 is inserted into and engaged with the centering member 11 and the peripheral edge of the center hole 2 is supported by the disc table 7. Placed. At this time, the metal plate 3 is attracted by the magnet 9 so that the optical disc 1 is mounted integrally on the disc table 7. In addition, the optical disc 1 is
When the optical disk 1 is placed on the disk table 7, the centering member 11 moves in the axial direction of the rotary drive shaft 6 and enters the center hole 2 to engage with the optical disk 1.
It is mounted on the disc table 7 with its rotation center aligned with the axis of the rotation drive shaft 6.

In this way, the metal plate 3 arranged on the optical disk 1 is attracted by the magnet 9 of the disk table 7, and the optical disk 1 is placed on the disk table 7 by using the centering member 11 for centering. By doing so, the optical disc 1 is surely integrated with the disc table 7 and mounted with high precision positioning with respect to the disc table 7. Further, the chucking mechanism for integrally mounting the optical disc 1 on the disc table by positioning it is also simplified.

The optical disc 1 having a small diameter and capable of high-density recording of information signals is housed in a disc cartridge 13 as shown in FIG. In this state, the disk rotation drive mechanism 4 is mounted.

[0010]

By the way, the metal plate disposed on the previously proposed optical disk is a double-sided adhesive tape or the like for the disk substrate formed of a synthetic resin such as transparent polycarbonate resin of the optical disk. It is fixed and attached using an adhesive material so as not to be displaced on the disk substrate.

However, since the coefficient of thermal expansion of the metal plate and the disk substrate made of synthetic resin are remarkably different, when the metal plate is bonded to the disk substrate using the above-mentioned adhesive material, the environmental temperature changes and When the metal plate and the disk substrate repeatedly expand or contract, there is a problem that the metal plate is separated from the disk substrate. Also, if the metal plate and the disk substrate are firmly joined so that they do not separate even if they repeatedly expand or contract, distortion will occur in the disk substrate due to changes in environmental temperature, and so-called birefringence will occur inside the disk substrate. Therefore, the information signal cannot be recorded / reproduced with good recording / reproducing characteristics on the signal recording layer formed on the disk substrate surface.

Therefore, the present invention makes it possible to attach a magnetic member for chucking, such as a metal plate, to a disk substrate without fixing it with an adhesive such as a double-sided adhesive tape. (EN) Provided is an optical disc which can maintain good recording / reproducing characteristics without causing birefringence due to distortion or the like on the disc substrate and can easily attach a metal plate to the disc substrate to improve productivity. It was proposed for the purpose.

[0013]

In order to achieve the above-mentioned object, an optical disk according to the present invention is provided with a magnetic member such as a metal plate having magnetism and a recess in which the magnetic member is arranged. A disk substrate having a light-transmitting property, and the magnetic member arranged in the recess is separated from the disk substrate by a high-viscosity UV-curable resin applied to the periphery of the recess of the disk substrate. It is configured to be held in the state.

[0014]

The optical disk according to the present invention is a state in which the magnetic member disposed in the recess is separated from the disk substrate by the high-viscosity UV-curable resin which is adhered to the peripheral edge of the recess of the disk substrate and UV-cured. The effect of expansion and contraction due to the difference in the coefficient of thermal expansion due to the change in environmental temperature is blocked between the magnetic member and the disk substrate.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the optical disk according to the present invention will be described below with reference to the drawings. As shown in FIG. 1, an optical disc 20 according to the present invention has a disc-shaped disc substrate 21 formed by molding a synthetic resin having a light transmitting property such as a polycarbonate resin. An information signal recording layer on which a desired information signal is recorded is adhered to one main surface 21a side of the disk substrate 21. The disk substrate 21 has one main surface 21a on which the information signal recording layer is formed and the other main surface 21b opposite to the main surface 21a.
Is referred to as a signal writing / reading surface, and information signals are recorded / reproduced by irradiating the signal recording layer with a light beam from the signal writing / reading surface side.

Then, in the central portion of the disk substrate 21,
As shown in FIGS. 1 and 2, a center hole 22 is formed in which the centering member 11 arranged at the center of the disk table 7 constituting the disk rotation drive mechanism 4 described above engages. On the other main surface side of the disk substrate 21, a cylindrical bulging portion 23 surrounding the center hole 22 is provided so as to project as shown in FIG. The bulging portion 23 is provided to deepen the depth of the center hole 22 formed in the thin optical disk 21 and to ensure a sufficient engagement amount of the centering member 11 with respect to the center hole 22. It will be.

The tip end surface of the bulged portion 23 has a mounting reference surface 2 which is supported by the disk table 7 when the optical disk 21 is mounted on the disk table 7.
It is made 5.

Further, on the other main surface side of the disc substrate 21, when the optical disc 20 is housed in a disc cartridge, a regulating projection provided so as to surround a disc table insertion hole opened in the disc cartridge is engaged. As shown in FIG. 2, a position regulating projection 24 for regulating the storage position of the optical disc 21 in the disc cartridge is provided so as to surround the engaging portion 23.

On the one main surface side of the disk substrate 21 and in the central portion corresponding to the center hole 22,
The disk table 7 is surrounded by the center hole 22.
A recess 27 for housing a metal plate is formed in which a metal plate 26 made of a magnetic material that is a magnetic member attracted by the magnet 9 disposed on the side is housed. The recess 27 is formed with a diameter R ₂ which is slightly larger than the outer diameter R ₁ of the metal plate 26 so that a slight gap is created between the metal plate 26 and the metal plate 26 when the metal plate 26 is housed therein. ing.

Further, the concave portion 27 for accommodating the metal plate is provided.
Is the thickness W _{1 of the} metal plate 26 housed and arranged here.
It is formed with a deeper depth D ₁ compared to. That is, the recess 27 for housing the metal plate is
It is formed with a size and a depth sufficient to allow the 6 to be loosely fitted.

A step portion 28 is formed on the inner periphery of the bottom surface of the recess 27 for housing the metal plate. This step 2
The reference numeral 8 functions as a relief portion for cutting a runner portion generated when the disc substrate 21 is injection molded. That is, by providing the step portion 28, the accuracy of forming the center hole 22 and the recess 27 for housing the metal plate is not affected when the runner portion is cut.

The metal plate 26 accommodated in the recess 27 for accommodating the metal plate formed in the disk substrate 21 is attached to the peripheral edge of the recess 27 so as to project inwardly of the recess 27. It is held in the recess 27 by a high-viscosity UV-curable resin 30 that has been cured by UV rays.

The ultraviolet curable resin 30 is applied to the disk substrate 21 at the periphery of the recess 27 for housing the metal plate.
It is adhered to one main surface side without leaking, and is adhered to the inner peripheral surface 29 of the recess 27. This is because the protrusion of the ultraviolet curable resin 30 is formed on one main surface side of the disk substrate 21 so as not to impair the smoothness on one main surface of the disk substrate 21.

The ultraviolet curable resin 30 is applied so as not to contact the metal plate 26 in the recess 27 for housing the metal plate and to project at least on the outer peripheral edge of the metal plate 26. The ultraviolet curable resin 30 is cured by being irradiated with ultraviolet rays. This irradiation of ultraviolet rays is carried out with the fibers for ultraviolet irradiation facing the adhered portion of the ultraviolet curable resin 30.

As described above, the ultraviolet curable resin 30 is applied to the periphery of the concave portion 27 for accommodating the metal plate and is cured, so that the metal plate 26 accommodated and arranged in the concave portion 27 has the above-mentioned concave portion. A predetermined gap D is formed between the protrusion 27 and the protrusion formed by curing the ultraviolet curable resin 30.
₂ and held in a separated state with respect to the disk substrate 21.

By the way, the ultraviolet curable resin 30 used here does not hang down to the metal plate 26 side in the recess 27 before curing when it is adhered to the inner peripheral surface 29 of the recess 27 for housing the metal plate. A material having a high viscosity is used, for example, a material having a viscosity of about 700,000 cP is used.

Further, in the above-described embodiment, the ultraviolet curable resin 30 forms the ring-shaped protrusion when cured, so that the inner peripheral surface 29 of the recess 27 for accommodating the metal plate is formed.
Although it is applied to the entire circumference of the metal plate 26, it may be applied to several places, such that a plurality of protrusions for supporting the metal plate 26 are formed on the inner peripheral surface 29 of the recess 27. Good.

Furthermore, in the above-mentioned embodiment, the ultraviolet curable resin 30 is applied to the inner peripheral surface 29 of the recess 27 for housing the metal plate, but as shown in FIG. It is also possible to form a step 31 for resin accumulation on the outer peripheral edge of and to apply the ultraviolet curable resin 30 to this step 31. Also in this case, the ultraviolet curable resin 30 is applied so as not to contact the metal plate 26 in the recess 27 and to project at least onto the outer peripheral edge of the metal plate 26.

[0029]

As described above, in the optical disk according to the present invention, since the magnetic member is held in a separated state on the disk substrate made of synthetic resin, the disk substrate made of synthetic resin and chucking, etc. It is possible to prevent distortion of the disk substrate caused by the difference in the coefficient of thermal expansion of the magnetic member, to prevent birefringence of the disk substrate due to this distortion, and to maintain good recording / reproducing characteristics.

Further, since the magnetic member is held by the ultraviolet curable resin which is cured by the irradiation of ultraviolet rays, the magnetic member can be easily attached to the disk substrate and the productivity can be improved.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an optical disc according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a disc substrate and a metal plate that form an optical disc according to the present invention.

FIG. 3 is a cross-sectional view of an optical disc showing a state where a metal plate is attached to a disc substrate.

FIG. 4 is an enlarged sectional view of an essential part of an optical disc showing a state where a metal plate is attached to a disc substrate.

FIG. 5 is a cross-sectional view showing another example of the optical disc according to the present invention.

FIG. 6 is a cross-sectional view showing a state in which a conventional optical disc is mounted on a disc table of a disc rotation drive mechanism.

[Explanation of symbols]

 20 optical disk 21 disk substrate 22 center hole 26 metal plate 27 recessed portion 30 ultraviolet curable resin

Claims (2)

[Claims] 1. A high-viscosity UV-curable film, comprising: a magnetic member; and a light-transmissive disk substrate having a recess in which the magnetic member is disposed. An optical disc in which the magnetic member disposed in the recess is held by the mold resin in a state of being separated from the disc substrate. 2. The optical disk according to claim 1, wherein a step portion for applying an ultraviolet curable resin is formed on the periphery of the concave portion formed on the disk substrate.