JPH10241209A - optical disk - Google Patents

Abstract

(57) [Problem] To provide a thin disk capable of suppressing warping and deformation due to clamping force and residual stress. An annular plate having a thermal expansion coefficient substantially equal to that of a disk substrate is provided in a non-recording area of a thin disk substrate. By reinforcing with the annular plate, warpage and deformation of the optical disk can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk for recording and reproducing information by irradiating a laser beam, and more particularly to an optical disk capable of suppressing warpage and deformation.

[0002]

2. Description of the Related Art Various types of optical disks for recording and reproducing information by irradiating a laser beam have been put to practical use, and high-density recording has been promoted. High-density recording can be realized by reducing the wavelength d of the beam spot by reducing the wavelength of the semiconductor laser or increasing the numerical aperture NA of the focusing objective lens. However,
Since it is difficult at present to shorten the laser wavelength, attempts have been made to increase the numerical aperture NA of the objective lens as much as possible.

However, when the numerical aperture NA of the objective lens is increased, the aberration caused by the tilt of the disk increases, and the recording / reproducing characteristics deteriorate. The magnitude of the aberration caused by the tilt of the disk is proportional to the thickness of the disk substrate if other conditions are common, so it is necessary to reduce the thickness of the disk substrate to suppress the aberration. Specifically, the thickness of the disk substrate needs to be 1 mm or less.

On the other hand, the bending stiffness of a disk substrate is proportional to the cube of the thickness of the substrate. Therefore, as the thickness of the substrate becomes smaller, it decreases rapidly, and the substrate is easily bent.

FIG. 11 shows a vertical sectional view of a conventional optical disk in a clamped state. As shown in FIG. 11, the optical disk includes a disk substrate 2 and a hub. The clamp is performed by placing the disk substrate 2 on the mounting portion 6 a of the turntable 6 and attracting a magnetic material (or a metal film) formed on the lower surface of the hub 7 to the magnet 6 b provided on the turntable 6. Done. Here, when the disk substrate 2 having a small clamp thickness is used, the optical disk is
The disk substrate 2 is deformed by the clamping force when chucking, and warpage occurs.

Further, an optical recording / reproducing layer is formed in the information recording area, but since this layer has a residual stress, a static warp occurs on the disk substrate as a result, which causes a trouble in signal recording / reproducing. Become.

In order to reduce the thickness of a disk substrate while securing rigidity and strength, Japanese Patent Application Laid-Open No.
A disk substrate described in Japanese Patent Application Publication No. 96-96 is known (conventional example 1). This optical disk substrate has a small substrate thickness in the information recording area and a large substrate thickness in the clamp area so as to ensure rigidity.

As another optical disk substrate, there is known an optical disk in which a hub having a plate-shaped body made of a material having higher rigidity than the disk substrate is provided in a clamp area (Japanese Patent Laid-Open No. 2-310871, a conventional example). 2).

[0009]

However, in the optical disk of the conventional example 1, the thickness of the disk substrate is different in the radial direction, but the thickness is partially changed while maintaining the molding accuracy in the information recording / reproducing area. It is extremely difficult. For this reason, there is a possibility that the accuracy of the disk substrate in the information recording / reproducing area is deteriorated.

Further, in the optical disk of Conventional Example 2, there is a problem that the disk is warped due to a temperature change due to a difference in the thermal expansion coefficient between the hub made of a high-rigidity plate and the disk substrate.

The present invention has been made to solve the above problems, and has a feature to provide an optical disc capable of preventing warpage or deformation due to chucking.

[0012]

According to a first aspect of the present invention, there is provided an optical disk on which information is recorded and / or reproduced by light in an information recording / reproducing area on a disk substrate, An annular plate having substantially the same thermal expansion coefficient as the disk substrate is adhered and fixed concentrically to the disk substrate.

The optical disk according to the second aspect is the optical disk according to the first aspect.
Wherein the annular plate is fixed outside the information recording area of the disk substrate.

The optical disk according to the third aspect is the first aspect.
Alternatively, in the optical disk according to the second aspect, the annular plate is fixed to at least a contact portion with a turntable that rotationally drives the disk.

An optical disk according to a fourth aspect is the optical disk according to the third aspect.
Wherein the annular plate has a flange portion adhered to at least the contact portion of the disc substrate, and a cylindrical portion into which the rotation shaft of the turntable is inserted.

The optical disk according to the fifth aspect is the optical disk according to the third aspect.
Alternatively, in the optical disk according to the fourth aspect, an irregular shape is formed at a portion of the annular plate that contacts the turntable.

The optical disk according to claim 6 is the optical disk according to claim 1
The optical disc according to any one of claims 1 to 5,
An annular plate is fixed to both surfaces of the disk substrate.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described with reference to the drawings.

(Embodiment 1) An optical disc according to Embodiment 1 of the present invention will be described with reference to FIGS.
FIG. 1 is a top view of the optical disc of the present embodiment, and FIG.
Is a vertical sectional view. The optical disc 1 has an optical recording / reproducing layer 4 formed on a translucent disc substrate 2 and a protective resin film (not shown). Disk substrate 2
Is made of polycarbonate, and the thickness is reduced to 0.6 mm for high-density recording.

The optical recording / reproducing layer 4 is made of Al for a read-only medium.
Reflectors such as alloys, amorphous alloys of rare earth and transition metals for magneto-optical recording media, and Se and T for phase transformation recording
It is made of a recording medium of an e-based alloy and a transparent dielectric, and has a thickness of about several tens to several hundreds nm.

Since the optical recording / reproducing layer 4 has a residual stress, the thin disk substrate 2 may be warped and signal recording / reproducing characteristics may be degraded. Since this warp appears more conspicuously in the outer peripheral portion of the disk, in the present embodiment, the annular plate 3 made of polycarbonate and having a thickness of 0.6 mm is attached to the outer peripheral portion on the reading surface side with an adhesive made of an ultraviolet curable resin. Thereby, the static warpage of the optical disk 1 caused by the residual stress of the optical recording / reproducing layer 4 can be improved, and the mechanical characteristics of the thinned disk substrate can be improved.

Next, the effect of the optical disk of the present embodiment will be specifically described by comparing with the comparative example.

Here, a normal optical disk (comparative example) in which an optical recording / reproducing layer is formed on a substrate having a thickness of 0.6 mm and the optical disk of the present embodiment are both rotated at 1800 rpm. The tilt angle in the radial direction was measured, and the maximum value was compared between the inner peripheral portion and the outer peripheral portion. In addition, a temperature test (70
(96 ° C. for 96 hours), and then rotated at 1800 rpm to measure the tilt angle in the radial direction, and the maximum value was compared between the inner and outer peripheral portions. The comparison results are shown in Table 1 (unit is deg).

[0024]

[Table 1]

As shown in the above table, in the comparative example, the tilt angle has a large negative value toward the outer periphery of the disk, and warpage is observed in the direction in which the optical recording / reproducing layer extends due to residual stress. On the other hand, the present disk provided with the annular plate has improved warpage. Further, no change in the warpage after the temperature test is observed in this disk.

In the optical disk of the present embodiment, the attached annular plate 3 is concentric with the disk substrate 2, so that vertical and radial fluctuations during rotation are suppressed, and stability is increased. The reliability as an information recording medium is improved.

(Embodiment 2) Another embodiment of the optical disk of the present invention will be described with reference to FIGS.

FIG. 3 shows a sectional structure of an optical disk to which an annular plate is applied. As shown in this figure, an annular plate 5 made of polycarbonate and having a thickness of 0.6 mm is attached to the inner peripheral portion of the disk substrate 2 on the reading surface side.

FIG. 4 is a sectional view showing a clamped state of the optical disk of the present embodiment. Here, the disk substrate 2
A hub 7 is attached to the hub 7, and a magnetic body 7 a is provided at the tip of the hub 7. And turntable 6
Magnet chucking is performed by the upper magnet 6b. At this time, the clamping unit 6a of the turntable 6
Abuts against the annular plate 5.

In this embodiment, since the clamping portion 6a of the turntable 6 comes into contact with the annular plate 5 as described above, warping and deformation occur as in the case where a clamping force is directly applied to the thin disk substrate 2 conventionally. Does not occur, the rigidity and strength of the optical disc 1 are improved, and the reliability is improved. Here, it is desirable that the annular plate 5 is formed up to about 1 mm inner circumference of the information recording area of the disk substrate 2.

Embodiment 1 Regarding this Disk Warpage
The results of the measurement of the tilt angle and the comparison are shown below. In Table 2 below, a disk without the annular plate 5 as a comparative example, and the embodiments 2-1 and 2-2 and 2-3 are shown.
(Each having a thickness of 0.2 mm on the inner periphery of the disk substrate 2,
0.4mm, 0.6mm disk with annular plate),
And a result of a combination of the first embodiment (in which the annular plate is provided on the outer peripheral portion of the disk) and the second to third embodiments (in which the outer peripheral portion and the inner peripheral portion are provided with the annular plate). (Unit is deg).

[0032]

[Table 2]

As can be seen from Table 2, in the embodiments 2-1, 2-2, 2-3, and 1 + 2-3, the warpage due to the clamping force was improved by using the annular plate 5 as the clamping area. I can say. The warpage of the outer peripheral portion is most improved when the annular plate thickness is 0.6 mm. Although the warpage and deformation tend to be suppressed as the thickness of the annular plate is increased, if the thickness is too large, it is disadvantageous in terms of function and hinders the thinning of the optical disk and the cartridge. In addition, modes 1, 2 and 3
When both are applied, similar improvement results are obtained.

The temperature test performed in the first embodiment was also performed in the second embodiment, but no change in the warpage was observed.

Third Embodiment An optical disc according to a third embodiment of the present invention will be described with reference to FIG. FIG. 5 shows a sectional structure of an optical disk to which a hub is applied. In FIG. 5, a hub 8 having a 0.6 mm-thick annular flange portion 8a made of polycarbonate is attached to the thinned disk substrate 2. The flange portion 8a is attached to the reading surface side of the disk substrate 2, and the whole or a part of the flange portion 8a becomes a clamp area, and the clamping portion comes into contact. The cylindrical portion 8b is provided with a magnetic material and is used for chucking.

In this embodiment, since the annular plate is integrated with the hub, the manufacturing process can be simplified. In addition, the bonding area between the hub 8 and the disk substrate 2 is large, so that the bonding state is good, and the hub 8 is firmly held, so that stable rotation can be realized. Furthermore, the rigidity and strength of the integrated hub 8 are greater than those of the case where only the annular plate is used, so that the rigidity and strength of the optical disk are also improved.

(Embodiment 4) An optical disc according to Embodiment 4 of the present invention will be described with reference to FIG. FIG. 6 shows a sectional structure of an optical disk to which a hub is applied. Here, an annular flange portion 9 made of polycarbonate and having a thickness of 0.6 mm is formed on the thinned disk substrate 2.
A hub 9 having a is mounted. Flange 9a
Is mounted on the reading surface side of the disk substrate 2, and the whole or a part of the flange portion 9a becomes a clamp area, and abuts on the clamping portion. The hub 9 has a cylindrical portion 9c as well as a cylindrical portion 9b used for chucking. Since the cylindrical portion 9c is in contact with the center hole of the disk substrate 2 on the side surface, the bonding area can be increased. As a result, the bonding state with the disk substrate 2 is improved, the peeling of the hub 9 can be prevented, and a stable rotational drive can be realized.

Since the hub 9 has the cylindrical portion 9c,
Easy installation in the center hole of the disc substrate 2, hub 9
Since the rigidity and strength of the optical disc 1 are also increased, there is an advantage that the rigidity and strength of the optical disc 1 are also improved.

Embodiment 5 An optical disk according to Embodiment 5 of the present invention will be described. This optical disk is a double-sided recording type optical disk in which information recording surfaces are faced and bonded to each other, and the annular plate (of the first to fourth embodiments) is applied to both surfaces or one surface thereof.

By providing an annular plate on the outer periphery of the information recording area of the disk, warpage and deformation of the disk can be suppressed, and by providing annular plates or hubs in the clamp areas on both sides of the disk, the chucking time can be reduced. Warpage and deformation due to the clamping force of

Embodiment 6 An optical disc according to Embodiment 6 of the present invention will be described with reference to FIG. FIG. 7 shows a sectional structure of the present optical disc.

Here, an annular flange portion 1 made of polycarbonate and having a thickness of 0.6 mm is formed on the thin disk substrate 2.
A hub 10 having 0a is attached. The flange portion 10a is attached to the reading surface side of the disk substrate 2 and forms a clamp area. The hub 10 is a cylindrical part 1
0b, and is located on the reading surface side of the disk substrate 2 for chucking. Further, an annular plate 11 of the same size as the clamp area is mounted on the information recording surface side, and is bonded to the disk substrate 2 and the hub 10, respectively. Hereinafter, a combination of the hub 10 and the annular plate 11 is referred to as an integral hub 12.

Since the integral hub 12 has a large bonding area with the disk substrate 2, the joint state with the disk substrate 2 is improved. In addition, since the disk substrate 2 is sandwiched and fixed from both sides, stable rotation can be realized. Further, not only the clamp area is formed of an annular plate, but also the area on the information recording surface side corresponding to the clamp area is also formed of an annular plate, and is firmly fixed and held from both sides, so that the disk substrate 2 received by the clamping force Warpage and deformation can be further reduced, and the rigidity and strength of the optical disc are improved. Further, vertical and radial blurs are suppressed, and focusing and tracking characteristics are improved.

The integrated hub of the present embodiment fixes the thin disk substrate 2 by sandwiching the thin disk substrate 2 from both sides with an annular plate, and the internal structure of the integrated hub is not limited to this structure.
Any form may be used.

(Embodiment 7) An optical disc according to Embodiment 7 of the present invention will be described with reference to FIG. FIG. 8 shows a cross-sectional structure of the present optical disk (laminated double-sided optical disk). This optical disk is an integrated hub 15
Is used.

In FIG. 8, the thinned single-plate optical disks 16 and 17 are bonded with an adhesive to form a bonded disk which is read from both sides. However, as in the sixth embodiment, the disk substrate 16 is made of polycarbonate. A hub 13 having an annular flange portion 13a having a thickness of 0.6 mm is attached. The flange portion 13a is attached to the read surface side of the disk substrate 16 and forms a clamp area. An annular plate 14 having the same shape as the flange portion 13a of the hub 13 is attached to the reading surface of the disk substrate 17, and adheres to the disk substrate 17 and the hub 13, respectively. As a result, the hub 13 and the annular plate 14 are fixed by sandwiching the disk substrates 16 and 17 from both sides.

The flange 13a and the annular plate 14 function as a clamp area when reading from both sides. The cylindrical portions 13b and 13c are respectively provided on the disk substrate 1
It is located on the reading surface side of 6, 17 and is used for chucking when reading from both surfaces. Thus, since the clamping area chucking mechanism exists on both sides, stable chucking and clamping from both sides can be performed.

In the meantime, the integrated hub 15 of (Embodiment 7)
The thin disk substrate 2 is fixed by sandwiching the thin disk substrate 2 from both sides with an annular plate 14, and the internal structure of the integrated hub 15 may be any form.

Embodiment 8 An optical disk according to Embodiment 8 of the present invention will be described with reference to FIG. FIG. 9 shows an example of a clamp area and a clamping unit of the present optical disc.

Here, the protrusions and recesses are formed so as to fit into the clamp area 18 and the clamping portion 19 of the turntable. In the present embodiment, the clamp area 18 is used as an annular plate (or a flange portion of a hub) by being adhered to an optical disk. Conventionally, the clamp area 18
Since it was one area of the disk substrate, it was very difficult to form the irregularities. However, in the present embodiment, since the annular plate (or the flange portion of the hub) is used, the irregularities can be formed in advance.

When a disk having such a clamp area 18 is set on a drive device (turntable),
As shown in FIG. 4, the clamping portion 6a comes into contact with a clamp area formed by the annular plate 5. At this time, the irregularities formed in the clamp area 18 of FIG.
The irregularities formed in 9 are fixed by fitting each other. When the disk is set and the turntable is driven, the disk is supported by the turntable and rotates according to the rotation of the spindle.

Here, since the rotation is performed while the unevenness formed in the clamp area 18 and the unevenness formed in the clamping portion 19 are fitted, even if the spindle, that is, the disk is rotated at a high speed, the disk remains on the turntable. As a result, there is no possibility of slipping, and the rotation of the disk faithful to the rotation of the spindle can be obtained, so that the reliability of data signal recording / reproduction is improved. In particular, the effect of the present invention can be expected when the rotation speed must be changed during data signal recording / reproduction. Further, in the present invention, friction and slip due to a difference in speed between start and stop as in the related art do not occur, and displacement of the reference surface and generation of dust do not occur, so that the reliability as an information recording medium is improved. Further, since the clamping force is applied in the direction in which the unevenness is fitted, the fitting is securely fixed, and the rotation can be transmitted more reliably. When the disk is to be removed from the turntable, the fitting state of these irregularities can be easily released, and the disk can be easily removed.

The annular plate in the first to eighth embodiments is not limited to polycarbonate, but may be made of a material having a coefficient of thermal expansion substantially equal to that of the disk substrate (for example, methacrylic resin, epoxy resin, polysulfone when the disk substrate is made of polycarbonate). , Polyamide, acetal resin, P
PO etc.), and the adhesive is not limited to an ultraviolet curable resin. Further, if the coefficient of thermal expansion of the adhesive is equal to that of the disk substrate, the effect of the present invention can be more effectively exhibited.

[0054]

According to the optical disk of the present invention, since an annular plate concentric with the disk substrate is provided in the non-recording area, the warpage of the disk is improved, and the vertical and radial fluctuations during rotation are suppressed and the disk is stabilized. And the reliability as an information recording medium is improved. Further, since the annular plate is formed of a material having substantially the same thermal expansion coefficient as the disk substrate, no difference in thermal expansion occurs due to a temperature change, and warpage can be reduced. As a result, the peeling of the adhesive caused by the environmental change is prevented, and a wide selection of the adhesive is made possible.

By providing the annular plate on the outer periphery of the disk, the effect of the residual stress due to the optical recording / reproducing layer can be effectively removed.

Further, by using at least a part of the annular plate as a clamp area at the time of chucking, warpage and deformation due to a clamping force do not occur, rigidity and strength of the optical disk are improved, and reliability is improved.

Further, by providing the annular plate as a hub on the inner peripheral portion of the disk substrate, the manufacturing process can be simplified. In addition, the bonding area between the hub and the disk substrate is increased, so that the bonding state is improved and the stability is improved. Rotation can be realized. Further, since the rigidity and strength are increased, the rigidity and strength of the optical disk are also improved.

Further, by forming irregularities in the clamp area of the annular plate and fitting the irregularities and the irregularities formed in the clamping portion to each other, the disk can slip on the turntable even when the disk is rotated at high speed. There is no danger of rotation, and the rotation of the disk faithful to the rotation of the spindle can be obtained, and the reliability of data signal recording / reproduction is improved. Further, friction and slip due to a difference in speed between start and stop do not occur, and there is no displacement of the reference surface or generation of dust, so that the reliability as an information recording medium is improved. Furthermore, since the clamping force is applied in the direction in which the unevenness is fitted, the fitting is securely fixed,
More reliable transmission of rotation is possible.

Further, by providing annular plates on both sides of the optical disk substrate, the bonding area with the disk substrate is increased, and the thin disk substrate is sandwiched and fixed from both sides, so that the bonding state with the disk substrate is improved. , And stable rotation can be realized. In addition, the warpage and deformation of the disk substrate caused by the clamping force can be reduced, and the rigidity and strength of the optical disk are improved. Vertical and radial blurs are also suppressed, and focusing and tracking characteristics are improved.

[Brief description of the drawings]

FIG. 1 is a top view showing an optical disc according to a first embodiment.

FIG. 2 is a vertical sectional view showing the optical disc of the first embodiment.

FIG. 3 is a vertical sectional view showing an optical disc according to a second embodiment.

FIG. 4 is a vertical sectional view showing a clamped state of the optical disc according to the second embodiment.

FIG. 5 is a vertical sectional view showing the optical disc of the third embodiment.

FIG. 6 is a vertical sectional view showing an optical disc according to a fourth embodiment.

FIG. 7 is a vertical sectional view showing an optical disc according to a sixth embodiment.

FIG. 8 is a vertical sectional view showing an optical disc according to a seventh embodiment.

FIG. 9 is a perspective view showing a clamp area and a clamping unit of the optical disc according to the eighth embodiment.

FIG. 10 is a vertical sectional view showing a conventional optical disc.

FIG. 11 is a vertical sectional view showing a clamped state of a conventional optical disc.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Disk substrate (thin) 3, 5, 11, 14 Ring plate 6 Turntable 6a Clamping part 7, 8, 9, 10, 13, 20 Hub 8a, 9a, 10a, 13a Flange part (clamp area) 12 , 15 Integrated hub 18 Clamp area 19 Clamping section

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Takahashi Sharp Corporation 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka

Claims (6)

[Claims] 1. An optical disk in which information is recorded and / or reproduced by light in an information recording / reproducing area of a disk substrate, wherein a non-recording / reproducing area of the disk substrate has an annular shape having a thermal expansion coefficient substantially equal to that of the disk substrate. An optical disk, wherein a plate is adhesively fixed concentrically with the disk substrate. 2. The optical disk according to claim 1, wherein the annular plate is fixed outside an information recording area of the disk substrate. 3. The optical disc according to claim 1, wherein the annular plate is fixed to at least a contact portion with a turntable that drives the disc to rotate. 4. The optical disk according to claim 3, wherein the annular plate includes a flange portion bonded to at least the contact portion of the disk substrate, and a cylindrical portion into which a rotation shaft of the turntable is inserted. An optical disc, comprising: 5. The optical disk according to claim 3, wherein an irregular shape is formed in a portion of the annular plate that comes into contact with the turntable. 6. The optical disk according to claim 1, wherein the annular plate is fixed to both surfaces of the disk substrate.