JP2003173579A - Optical disk and optical disk drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin optical disk having a structure for preventing eccentricity to a chucking portion. <P>SOLUTION: A central mirror plane part 2, an eccentricity measurement region 3, a data region (an information recording region) 4, and an outer circumferential mirror plane part 5 are formed in the optical disk 1 in order from the center toward the outer circumference without providing a center hole, a hub, etc., at the central part like a conventional optical disk. The tracks of a groove, a pit row, etc., are formed in the eccentricity measurement region 3 of the inner peripheral part of the optical disk 1 concentrically or spirally. A track pitch in the eccentricity measurement region 3 is formed more widely than an information track formed in the data region 4. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible sheet-like optical disc having an information recording area on its surface, and an optical pickup for irradiating a light spot on the optical disc for recording / reproducing. The present invention relates to an optical disk drive device including a spindle motor that rotationally drives the optical disk.

[0002]

2. Description of the Related Art In recent years, optical discs have been required to record a large amount of digital data as the digitization of television broadcasting has started. Of the methods for increasing the density of optical discs, the basic method is to reduce the spot diameter of light for recording / reproduction.

Therefore, it is effective to shorten the wavelength of light used for recording / reproducing and increase the numerical aperture NA of the objective lens. For the wavelength of light, see CD (comp
actdisk) uses near-infrared light of 780 nm, DVD (digital
A wavelength near 650 nm of red light is used in a versatile disk. Recently, a blue-violet semiconductor laser has been developed, and it is expected that laser light near 400 nm will be used in the future.

Regarding the objective lens, the objective lens for CD is N
Although it was less than A0.5, NA for DVD is about 0.6. In the future, NA will be increased by increasing the numerical aperture (NA).
It is required to be 0.7 or more. However, increasing the NA of the objective lens and shortening the wavelength of light also means that the influence of aberration is increased when the light is stopped down. Therefore, the margin for tilting the optical disc is reduced. In addition, since the depth of focus decreases as the NA increases, the focus servo accuracy must be increased.

Further, since the distance between the objective lens and the recording surface of the optical disk becomes small by using the objective lens having a high NA, the focus servo at the time of start must be made unless the surface deviation of the optical disk is kept small. The objective lens may collide with the optical disc immediately before the optical pickup is pulled in, which causes a failure of the pickup.

As a large-capacity optical disk having a short wavelength and a high NA, for example, O PLUS E (vol. 20 No. 2) is used.
As shown on page 183 of the above, a recording film is formed on a substrate as thick and as rigid as a CD, and recording / reproducing light is passed through the thin cover layer to reach the recording film without passing through the substrate. On the other hand, a system of recording / reproducing has been proposed.

The present inventors have already filed Japanese Patent Application No. 2001-228.
As No. 943, a stabilization technique using Bernoulli's law is applied to an optical disk made of a flexible thin sheet to reduce surface wobbling and to obtain accuracy in a focusing direction required for a high NA lens. Optical disk and optical disk drive system are proposed.

[0008]

However, in the technique disclosed in the above-mentioned Japanese Patent Application No. 2001-228943, chucking of the flexible driving optical disk to the spindle motor is formed at the center of the optical disk. This is done by inserting the center hole into the spindle part of the spindle motor. For this reason, when the optical disk is repeatedly attached to and detached from the spindle motor, the optical disk is made of a thin sheet, so its mechanical strength is weak and changes over time, which lowers the accuracy of the center hole and increases the amount of eccentricity. However, there is a problem that good recording / reproduction cannot be performed.

In order to avoid deformation in the central hole, it is conceivable to provide a chucking hub or attach a reinforcing ring to the center of the optical disk.
The hub or ring increases the overall thickness of the optical disc. However, if the thickness of the thin and flexible optical disk increases, it leads to an increase in the thickness of the disk cartridge or the drive when a large number of data are stored in the disk changer to increase the data capacity, which is not preferable. . Further, bonding the hub to the central portion of the optical disk has a problem that it takes time and effort for centering, the man-hour for manufacturing the disk increases, and the cost increases.

In view of the above-mentioned problems of the prior art, an object of the present invention is to provide an optical disc which is thin and has a structure in consideration of preventing eccentricity with respect to a chucking portion, and using this optical disc during recording / reproduction. An object of the present invention is to provide an optical disk drive device capable of removing the eccentricity of the optical disk.

[0011]

In order to achieve the above object, the invention according to claim 1 is a flexible sheet-like optical disk having an information recording area on the surface thereof, in which the central part of the disk is non-perforated. It features a flat surface, and this structure simplifies disk manufacturing because the center hole does not need to be bored in the center of the disk in consideration of eccentricity as in the past and the hub is not bonded. Further, since the thickness of the entire sheet-shaped disc can be defined only by the sheet itself, it is possible to make the disc cartridge accommodating the optical disc thin.

According to a second aspect of the present invention, in the optical disc according to the first aspect, a groove or a pit row for detecting disc eccentricity correction data is provided at the center of the disc. In addition to the information recording area, there is an area where the tracking error can be detected by the groove or the pit row, so that the signal for disc eccentricity correction can be easily detected.

According to a third aspect of the present invention, in the optical disc according to the first or second aspect, the groove or pit row is formed in the outer peripheral portion and the information recording area at the portion where the clamper member for sandwiching the disc contacts at the central portion of the disc. This configuration is characterized in that it is provided in the inner peripheral portion, and this configuration reduces the amount of cutting the area of the information recording area as compared with, for example, an area in which the eccentricity detection area is on the outer circumference of the disk.

According to a fourth aspect of the present invention, in the optical disc of the second or third aspect, the radial pitches of the concentric circular or spiral grooves or pit rows are formed in the information recording area. In addition to the information recording area, there is an area where a large tracking error can be detected by a groove or a pit row, so that the disk is wider than the pitch between the information tracks. The signal for eccentricity correction becomes easy to detect.

The invention according to a fifth aspect is characterized in that, in the optical disc according to any one of the second to fourth aspects, at least disc management information such as disc identification information is recorded in a groove or a pit row. By recording the management information in the low recording density area according to the configuration, the management information can be read at a low error rate, and highly reliable disk management can be performed.

According to a sixth aspect of the present invention, in the optical disc according to any one of the second to fifth aspects, when the optical disc is a write-once disc or a rewritable disc, at least the directory of the disc in the groove or pit row. It is characterized in that management information such as information is recorded. With this configuration, directory management and the like can be performed in an area of low recording density, so that file management of the disk and the like can be performed with high reliability.

According to a seventh aspect of the present invention, recording and / or reproduction is performed by using a flexible sheet-like optical disc having an information recording area on the surface thereof and having a disc central portion having no hole and a flat surface. In order to achieve this, an optical disc driving device is provided with an optical pickup for irradiating the optical disc with a light spot and a spindle motor for rotating the optical disc. This configuration is characterized in that the optical disc is held between the clamper members at the time of chucking, and it is not necessary to form the center hole in the optical disc as in the conventional case, and the loading operation of the same optical disc can be repeated. Even if the optical disc is not damaged, the durability and reliability are improved.

The invention according to claim 8 is the optical disk drive device according to claim 7, characterized in that it is provided with an arcuate jig which is joined to the outer periphery of the optical disk to perform rough eccentricity correction of 10 μm or more of the optical disk. With this configuration, since imbalance correction and eccentricity removal of the optical disk can be performed at the same time, stable recording / reproduction can be performed when the optical disk rotates at high speed.

According to a ninth aspect of the present invention, in the optical disk drive apparatus according to the seventh or eighth aspect, an alternating current synchronized with the rotation cycle of the spindle motor is applied to a tracking drive current for driving the optical pickup in the tracking direction. Is provided with a means for removing the influence of eccentricity. With this configuration, the tracking operation during high-speed rotation of the optical disk can be further stabilized, and the high-speed limit of recording / reproduction can be increased. In addition, it becomes strong against disturbance such as vibration to the drive device. Further, since the AC current, which is the basis of this eccentricity removal control, has basically the same frequency as the drive current of the spindle motor, the generation of the signal for the eccentricity removal control becomes simple.

According to a tenth aspect of the invention, in order to set the magnitude and phase of the tracking drive current for removing the eccentricity of the optical disc drive apparatus according to the ninth aspect, the groove or the groove in the optical disc according to the second aspect is set. It is characterized by using the tracking error signal detected from the pit train. With this configuration, the signal for eccentricity removal control is obtained independently of the pickup signal from the information recording surface of the optical disc, so the disc rotation speed or recording / reproducing position It contributes to stable tracking without being affected by factors such as.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a flexible sheet-shaped optical disc for explaining an embodiment of the optical disc of the present invention, and FIG. 2 is an optical disc for explaining an embodiment of the optical disc drive of the present invention. It is a schematic block diagram of a drive device.

In FIG. 1, the optical disc 1 is not provided with a central hole, hub, etc. in the central portion unlike the conventional optical disc, and the central mirror surface portion 2, from the central portion toward the outer periphery.
An eccentricity measurement area 3, a data area (information recording area) 4, and an outer peripheral mirror surface portion 5 are sequentially formed. In the eccentricity measurement region 3 on the inner peripheral portion of the optical disc 1, tracks such as grooves and pit rows are formed in a concentric or spiral shape. The track pitch in the eccentricity measurement area 3 is made wider than that of the information tracks formed in the data area 4, and is about 0.7 μm or more. This is because an optical disc using blue light and a high NA lens has an information track pitch of usually 0.6 μm or less, and thus a tracking error signal from the data area 4 may not be sufficiently obtained. For this reason, it may be difficult to detect the eccentricity of the optical disc by the tracking error signal from the data area 4. Therefore, the eccentricity measurement area with the track pitch is provided to surely obtain the tracking error signal. 3 is provided.

In FIG. 2, 10 is a spindle motor,
Reference numeral 11 denotes a lower clamper fixed to an upper portion of a spindle 12 of a spindle motor 10, 13 denotes an upper clamper provided on a support shaft 15 suspended from a main body case 14 so as to be vertically movable, 1
Reference numeral 6 denotes an optical beam having an objective lens 16a, which moves in the radial direction of the optical disc 1 to write (record) information on the data area 4 of the optical disc 1 and / or read (reproduce) the written information. Pickup, 17,
The stabilizing guide member is installed opposite to the optical pickup 16 through the optical disc 1, and when the optical disc 1 is rotating, the stabilizing guide member 18 generates aerodynamic force to prevent surface wobbling of the optical disc 1 according to Bernoulli's law. It is an outer peripheral receiving jig that receives the peripheral edge portion and suppresses the eccentricity from the chucking portion (holding position by the clampers 11 and 13) of the optical disc 1.

FIG. 3 is a configuration diagram of the upper and lower clampers. In the upper clamper 13, a permanent magnet 20 is internally provided, and a spindle 15 is loosely fitted in the central portion. Further, in the lower clamper 11, a permanent magnet 21 is provided on the upper side, and an electromagnet 22 whose magnetic pole is generated by being energized is provided on the lower side.

In the embodiment having the above structure, as shown in FIG. 2, when the optical disc 1 is inserted into the main body case 14 of the drive unit, the electromagnet 22 of the lower clamper 11 is energized,
The upper clamper 13 has a polarity repulsive to the permanent magnet 20, and the upper and lower clampers 11 and 13 are separated from each other to form a gap that allows the optical disc 1 to be inserted. By this insertion, the outermost circular arc portion of the optical disc 1 is received by the outer peripheral receiving jig 18. As a result, positioning (preventing eccentricity during rotation) from the chucking portion of the optical disc 1 is performed. After that, when the energization of the electromagnet 22 of the lower clamper 11 is cut off, the upper and lower clampers 11 and 13 are installed so that the respective permanent magnets 20 and 22 are attracted to each other, so that the central mirror surface portion 2 of the optical disc 1 is removed. Hold (chuck). With this disc clamp, unlike the conventional case, centering is not performed in the central hole formed in the disc, and since each clamper 11 and 13 is a bearing, the stress is dispersed. Therefore, even with a thin sheet-shaped disc, good chucking can be maintained many times and the durability of each part can be maintained for a long time.

After chucking, the spindle motor 10 rotates at a specified rotation speed. At this time, the optical pickup 16 is moved to the eccentricity measurement region 3 on the inner circumference of the optical disc 1 to focus it. Since tracks such as grooves and pit rows in the eccentricity measurement region 3 are formed with a wide track pitch, a tracking error signal having a large amplitude can be obtained. If there is eccentricity, the light spot of the light beam emitted from the optical pickup 16 crosses the track of the eccentricity measurement region 3 many times, so that a tracking error signal as shown in FIG. 4 is obtained. Reducing the eccentricity means lowering the frequency of the tracking error signal.

Since the maximum component of eccentricity is always the component synchronized with the rotation speed of the spindle motor 10, the objective lens 16a provided in the optical pickup 16 is locked at the frequency and phase of the spindle motor 10. ,
By controlling the phase angle to the optimum point, the eccentricity can be reduced.

Therefore, while monitoring the frequency of the tracking error signal, an eccentricity correction AC current is superimposed on the tracking actuator of the optical pickup 16 to eliminate the influence of eccentricity. From the control signal of the spindle motor 10, alternating current completely equal to the spindle motor rotation frequency is used as the eccentricity correction signal.

The eccentricity correction operation will be described with reference to the flowchart of FIG.

First, the eccentricity measurement region 3 on the inner circumference of the optical disc 1
The optical pickup 16 is moved to (S1), focus is applied (S2), and zero cross (the number of times the light spot is crossed) is counted based on the tracking error signal for the track in the eccentricity measurement region 3 (S3). An AC component synchronized with the rotation speed of the spindle motor 10 is superimposed on the tracking drive current (S4).
If the number of zero crosses is a predetermined number (3 times in this example) (Yes in S5), it is determined that there is no eccentricity, and the main tracking servo is applied (S6).

However, when the number of zero crosses is more than the predetermined number (No in S5), the phase of the correction AC signal to be superimposed on the tracking current is divided into arbitrary angles (for example, from 0 ° to 350 ° in steps of 10 °). ), Zero cross is counted at each phase angle in the same manner as described above (S7), and locked to a phase in which the amount of eccentricity is minimized (S8). Thereafter, the amount of the correction current superimposed on the tracking current is arbitrarily divided (for example, 5 μm to 5 μm to 5 μm) so that the amount of eccentricity is minimized.
m increments), and count zero crosses as described above (S
9), the correction current is controlled to minimize the eccentricity (S
10).

Hereinafter, the eccentricity control will be referred to as feedforward. By repeating the loop of the flow chart several times, it is possible to practically eliminate the influence of the eccentricity of the disk on the tracking operation.

The eccentricity does not change unless the optical disk 1 is chucked again. Therefore, as long as the optical disk 1 is chucked first and is used as it is, the eccentricity is changed even if the rotation speed or the radial position used is changed. There is no need to change the value of the correction distance and the phase angle.

When eccentricity detection is performed in the data area 4 of the optical disk 1, the groove pitch of the information track is small and only a small tracking error signal can be obtained in the current optical disk. However, as in the structure of this embodiment, the eccentricity detection is performed. This problem is eliminated by providing the eccentricity measurement region 3 of.

As described above, in this embodiment, firstly, centering (coarse eccentricity removal) by the outer peripheral receiving jig utilizing the outermost peripheral shape of the flexible optical disk 1, second, eccentricity is performed. By using the two-step eccentricity reduction measures of superimposing the eccentricity correction current on the tracking current of the optical pickup 16 by the eccentricity detection signal (tracking error signal) in the measurement area 3, the hub or the disk center of the optical disk 1 is used as in the conventional case. Good tracking without eccentricity is possible even if there is no hole for centering.

Specific examples will be described below as examples. In the following description, the members corresponding to those already described are designated by the same reference numerals, and detailed description thereof will be omitted.

(Embodiment 1) FIG. 6A is a diagram showing the structure of a flexible disk of Embodiment 1, and FIG. 6B is an enlarged cross-sectional view showing the cross-sectional structure at the circled portion of FIG. 6A. It is a figure.

In FIG. 6A, the optical disk 1 has a diameter of 120 mm and a thickness of 75 μm, and the sheet base material 25 is made of polyethylene terephthalate (PET). An information recording area (data area 4 in FIG. 1) is formed within a radius of 24 to 58 mm, and the groove width is 0.3 μm,
Grooves having a groove pitch of 0.6 μm and a groove depth of 65 nm are formed. The groove is formed by a thermal transfer method in which a high temperature stamper is pressed against a PET sheet.

As shown in FIG. 6B, the sheet base material 25
On the PET sheet of No. ₃ , Ag 30 nm, Si ₃ N ₄ 5 nm, Tb ₂₁ Fe are sequentially formed on the sheet by sputtering.
₇₁ Co ₈ (mol%) 10 nm, Si ₃ N _{4 30} n
m recording film 26 was formed, and a DLC protective film was formed thereon by CVD to a thickness of 10 nm to produce a flexible sheet-shaped optical disk.

A radius of less than 22.7 mm is a clamp area (central mirror surface portion 2 in FIG. 1), and a radius of 22.7 mm.
An eccentricity measurement area (eccentricity measurement area 3 in FIG. 1) from 7 mm to 24 mm is provided with an eccentricity detection groove having a groove width of 0.4 μm, a groove pitch of 1.0 μm and a depth of 65 nm. Further, the radius 58 mm to 60 mm is the outer peripheral mirror surface portion in FIG.

The optical disk drive has the structure shown in FIG. 2, and the optical pickup 16 has a wavelength of 405 nm and N wavelength.
A is 0.85. Since the stabilizing guide member 17 does not cause a surface wobbling with a large amplitude of 100 μm or more, the actuator of the optical pickup 16 has a stroke amount of ± 50.
μm, and the spring constant of the actuator is large, the servo stability at high linear velocity is
It is superior to that for VD.

FIGS. 7 (a) and 7 (b) are construction diagrams for explaining the construction and operation of an outer circumference receiving jig for receiving the outer circumference of the optical disk and performing centering in the first embodiment. Three
Reference numeral 1 denotes an outer peripheral receiving jig provided laterally movable in the jig housing 30, 32 a stopper for positioning the outer peripheral receiving jig 31 while preventing the outer peripheral receiving jig 31 from jumping out, and 33 a stopper for the outer peripheral receiving jig 31. Spring biasing in the opposite direction to 3
4 is an outer circumference receiving jig 3 against the biasing force of the spring body 33.
1 is an actuator composed of a solenoid device or the like that operates so as to contact 1 with a stopper 32, and a plurality of units of a spring 33 and an actuator 34 are installed between a jig housing 30 and an outer peripheral receiving jig 31. There is.

The outer peripheral receiving jig 31 is formed so that one side 31a conforms to the outer peripheral shape of the optical disc 1, and when the flexible sheet-shaped optical disc 1 is inserted into the optical disc drive, It is pushed in by a disc loader (not shown) until it contacts one side 31a of the outer circumference receiving jig 31 shown in FIG. 7 (a). Here, the pushing force is once weakened to release the bending of the optical disc 1. Then, the optical disc 1 returns to its original state by its own spring force, eccentricity removal is performed, and thereby, positioning (centering) defined on the outer periphery of the disc is performed.

Incidentally, if the optical disc 1 is rotated in the position shown in FIG. 7A for removing the eccentricity of the outer circumference receiving jig 31, there is a possibility that sliding will occur with the outer circumference receiving jig 31. After the centering of the optical disc 1 is completed, the outer circumference receiving jig 31 is attached to the spindle 12 of the spindle motor 10.
It is preferable to move it to a position as shown in FIG.

In this example, when the disc shown in FIG. 7A is inserted, the actuator 34 is energized to be in the ON state, and the outer peripheral receiving jig 31 is moved to the position where it abuts the stopper 32. The position is regulated by being pushed out. Further, the movement of the outer peripheral receiving jig 31 to the steady position shown in FIG. 7B after the completion of the disc centering is not stopped by turning off the driving force of the actuator 34, but is restored by the urging force of the spring 33. By doing.

Even if the disc eccentricity is removed by performing the centering in this way, the eccentricity due to the residual bending of the optical disc 1 and the error between the groove in the data area 4 and the disc molding outer die remains. Then, in this state, the optical disc 1 is clamped and fixed by a pair of upper and lower clampers 11 and 13.

As shown in FIG. 3, each of the clampers 11 and 13 has a cylindrical upper clamper 13 having a diameter of 19 mm and a height of 4 mm, the outer material is ABS resin, and the permanent magnet 20 is provided inside. There is. The permanent magnet 20 is a disk having a diameter of 15 mm and a thickness of 2 mm, and has a polarity that attracts the permanent magnet 21 provided inside the lower clamper 11 to each other. The lower clamper 11 has the same diameter as the upper clamper 13 and has a diameter of 19 mm. Permanent magnet 2 inside
1 and an electromagnet 22 are provided. In the OFF state where no current is passed through the electromagnet 2, the optical disc 1 is strongly sandwiched by the attraction force of the permanent magnets 20 and 21. By energizing the electromagnet 22, a repulsive force equal to or greater than the attractive force of the permanent magnet 20 and the permanent magnet 21 is generated between the permanent magnet 20.

After chucking the optical disk 1, an eccentricity correction current is superposed on the tracking actuator of the optical pickup 16. The eccentricity correction needs to correspond to the three components of the eccentricity frequency component, phase, and amplitude.

Here, since the main component of the eccentricity is derived from the rotation of the optical disc 1, it is considered that the frequency component of the eccentricity is the disc rotation speed itself. Then, the factors to be considered can be reduced to the two factors of phase and amplitude.

Therefore, an AC signal having the same frequency as the rotation cycle of the spindle motor 10 is applied to the tracking control signal of the optical pickup 16. The amount of eccentricity to be corrected and the amount of current are approximately proportional. The relationship between the absolute value (μm) of the amount to be corrected for each rotation speed and the current (mA) is previously mapped as data (table data) and stored in the CPU (central processing unit) which is the control means. is there. The correction current amount is determined based on this table data.

The same applies to the phase, and the spindle 1
The relationship between the angle 2 and the corrected phase angle is mapped in advance, and which current phase angle is when the spindle 12 is decentered in which angular direction is 1.
Since it is determined to be 1 to 1, it can be determined in advance. This can be obtained by mapping while evaluating a reference disk of known eccentricity on a test spin stand.

After the above process, the optical pickup 16
To seek to the optical disc 1 for focusing,
Perform tracking operation. Since the tracking error signal of the data area 4 is not used in the calculation of the eccentricity amount, the servo operation of the data area 4 can be started after the eccentricity is substantially removed. Therefore, even if the tracking servo margin is small and the tracking servo margin is small in the data area 4, stable servo can be applied.

The loading operation of the optical disk drive device of the present optical disk 1 is summarized as follows. 1. 1. Move the outer circumference receiving jig 31 to the disc receiving position, 2. Insert the optical disc 1 to the outer circumference receiving jig with a disc loader, After abutting the optical disc 1 on the outer circumference receiving jig 31,
3. Once, the holding force of the disk loader is weakened to release the bending of the optical disk 1. The optical disk 1 is clamped on the spindle 12 by the clamper 1
Chucking with 1 and 13; 5. Return the outer circumference receiving jig 31 to the original position, 6. The optical disk 1 is rotationally driven and stabilized by the spindle motor 10. 7. The optical pickup 16 is moved 22.7 mm from the center of the optical disc 1 in the radial direction (to reach the eccentricity measurement region 3), and the focus servo is locked. Based on the tracking error signal of the eccentricity measurement area 3, the amount and direction of the disc eccentricity are obtained, and the optical pickup 1
8. Add correction current to tracking drive current of 6. Lock the track servo, 10. 10. The optical pickup 16 is moved to the vicinity of 22.7 mm, which is the first address portion in the eccentricity measurement region 3, and the disc management information and the like are read. The optical pickup 16 is moved to a desired recording or reproducing position in the data area 4, and the reproducing or recording operation is started while being controlled by the CPU.

In this embodiment, the wavelength is 405 nm, NA0.
Disc speed 600 with 85 optical pickup 16
Recording / reproduction was performed at 0 rpm. As a result, the large eccentricity is removed in advance by the outer circumference receiving jig 31 and the thin flexible disc is light, so the imbalance of the disc is small and 6000 rpm.
Abnormal vibration did not occur even at high speed rotation.

In the eccentricity measurement area 3, only 1 is applied to the groove portion.
Random data was recorded at a density of 0.4 μm / bit by -7 modulation. The recording power was 4.5 mW, which was binary modulation, and the reproducing power was 0.3 mW. In the eccentricity measurement region 3, since the recording / reproducing was performed at a low density, the signal quality was good and the jitter was less than 6%.

In the data area 4, 0.16 μm / bit
Random digital data with a recording density of 1-7
It was modulated and recorded and reproduced. The recording power was 4.5 mW, which was binary modulation, and the reproducing power was 0.3 mW. As a result, good signals for both the land and the groove were obtained, and the jitter of data and clock was 8% or less.

When this optical disk drive is used as a storage device of an actual computer, directory information is recorded in the eccentricity measurement area 3. By this,
After removing the eccentricity, immediately lock the tracking servo,
Since the directory can be played back, the recording / playback is ready immediately.

Further, since the signal quality of the directory is good, the number of retries for reading is reduced, the rising speed of recording or reproduction is fast, and the reliability is improved.

The relationship between the current to be superimposed for the eccentricity correction and the distance of the actual correction amount is a three-dimensional map of the current, the eccentric distance, and the disk rotation speed. Therefore, two-dimensional mapping is performed for each pickup by fixing the rotation speed during the eccentricity correction operation. The eccentricity correction is performed at that rotation speed and then set to the desired reproduction rotation speed. In this example, the eccentricity correction operation was performed at 2000 rpm.

As a final indication of the completion of the eccentricity correction, the zero cross count of the tracking error signal is set to, for example, 3 or less per rotation as shown in FIG. It depends on the pitch. If the track pitch is wide, the eccentricity increases even with the same zero cross count.

In the present embodiment, the track pitch of the eccentricity measurement region 3 is set to 1 μm.
The amount of eccentricity is considered to be 5 μm or less. With this setting,
Tracking with a groove pitch of 0.6 μm can be performed without problems. Since the data recording is land-groove recording, the track pitch of the recording data is 0.3 μm, but since the groove pitch is a problem on the tracking servo, an error signal equivalent to 0.6 μm is obtained and the eccentricity is increased. If it is less than 10 μm, the disk rotation speed will be 7,000.
Stable tracking servo can be applied up to about rpm.

Example 2 As Example 2, the flexible optical disk 1 had a diameter of 96 mm, a thickness of 50 μm, and the base material was polycarbonate. Disk radius 24
Data area (information report recording area) 4 up to 45 mm
In this region, the groove width is 0.12 μm and the groove pitch is 0.
A groove is formed with a thickness of 33 μm and a groove depth of 65 nm. The grooves were formed by a thermal transfer method in which a high temperature stamper was pressed against a polycarbonate sheet.

On the polycarbonate sheet, spatter is
In the ring, from the top of the sheet, Ag 40nm, Z
nS-SiO_Two 8nm, Ag₁In₅Sb₇₀Te
₂₁Ge _Three(Mol%) 10 nm, ZnS-SiO_Two 
A 50 nm recording film is formed, and ultraviolet rays are further formed on it.
Flexible by spin-coating 3μm of cured resin to cure
I made it with a disc.

The area within 21 mm of the disk radius is the clamp area (central mirror surface portion 2). Eccentricity measurement area 3 from radius 22.7 mm to 23.5 mm on the inner circumference side of the disk
Thus, a groove for eccentricity detection having a groove width of 0.6 μm, a groove pitch of 1.2 μm and a depth of 65 nm was formed.

The optical disk 1 having the above structure was placed on a turntable and initialized by a high power laser. Others are the same as in the first embodiment.

The optical pickup 16 has a wavelength of 405 nm,
The NA was 0.85, and recording or reproduction was performed only on the groove portion.

This optical disk 1 also has a rotation speed of 6000 rpm.
However, it rotated stably, and tracking could be performed without any abnormalities. In this embodiment, the groove pitch is narrow.
For example, the first embodiment has a thickness of 0.6 μm, while the second embodiment has a thickness of 0.33 μm, which is about half. Therefore, data area 4
In, the tracking error signal amplitude is extremely small. However, in the second embodiment, as in the first embodiment, in the eccentricity measurement region 3, since the groove pitch is wide and a large tracking error signal is obtained, the eccentricity correction can be performed extremely accurately and stably. Therefore, tracking was stable even after moving to the data area after the eccentricity correction.

In the second embodiment, the disc radius is 40 m.
m, disk rotation speed 3000 rpm, linear velocity 12.5 m
Random digital data was 1-7 modulated and recorded / reproduced at a recording density of 0.13 μm / bit. Recording power is 4.5mW, erasing power is 2.4m
W, bottom power was ternary modulation of 0.1 mW, and reproduction power was 0.25 mW. According to this, a good signal was obtained in the groove, and a good result that the jitter of data and clock was 8% or less was obtained.

(Embodiment 3) An optical disk which is the same as that of the embodiment 2 but is different only in the eccentricity measurement region was prepared.

That is, in the eccentricity measurement region 3 from the disc radius of 22.7 mm to 23.1 mm, the pit width is 0.6 μm, the track pitch is 1.0 μm, and the depth is 65 nm.
It is a phase pit for playback only. In this area, disc management information is recorded in advance as read-only type information.

Further, in the eccentricity measurement region 3, the groove width is 0.6 μ from the disc radius of 23.2 mm to 23.5 mm.
m, groove pitch 1.0 μm, and depth 65 nm for eccentricity detection. This area is an area for recording management information such as directory information of the recorded signal.

By constructing the eccentricity measurement area 3 in this way, the recording conditions are those already recorded as the reproduction pits, so that the signal can be reproduced immediately with good signal quality and low error. When is loaded into the drive device, it becomes possible to immediately determine what number the target optical disc is in the cartridge in which a plurality of sheet-shaped optical discs are accommodated, and the preparation for recording is immediately performed. Can be completed.

Example 4 In Example 4, a flexible sheet-shaped optical disk has a diameter of 30 mm and a thickness of 50 μm.
m, and the material of the base material was PET. On the PET sheet,
By sputtering, from the top of the sheet, Ag 30
nm, Si ₃ N ₄ 5 nm, Tb ₂₁ Fe _{7 1} Co
₈ (mol%) 10 nm, Si ₃ N ₄ 30 nm recording film is formed, and DLC is formed on the recording film by CVD.
A protective film having a thickness of 10 nm was formed to prepare a flexible disk.

In this optical disc 1, there is a data area 4 within a radius of 5 mm to 28.5 mm, and grooves are formed in the data area 4 with a groove width of 0.3 μm, a groove pitch of 0.6 μm and a groove depth of 65 nm. There is. The grooves were formed by a thermal transfer method in which a high temperature stamper was pressed against the PET sheet.

A radius of 3 mm or less is a clamp area (central mirror surface portion 2), and an eccentricity measuring region 3 has a groove width of 0.
A groove for eccentricity detection having a size of 6 μm, a groove pitch of 1.2 μm and a depth of 65 nm was formed.

Then, the optical disc 1 having the above-mentioned structure was stable when subjected to focusing and tracking servo after the Bernoulli stabilization was performed at a position of a radius of 6 mm at a rotation speed of 8000 rpm. Therefore, 0.16 μm at this point
Random digital data was 1-7 modulated and recorded / reproduced at a recording density corresponding to / bit. The recording power was 4 mW and binary modulation was performed, and the reproducing power was 0.2 mW.

Although the rotation speed is as high as 8000 rpm,
Both imbalance and eccentricity were small, and the playback or recording operation was good. Good signals were obtained for both lands and grooves, and the jitter of data and clock was 8% or less.

(Comparative Example) As a comparative example, a diameter of 120 m
An optical disk having a thickness of 75 m and a thickness of 75 μm and a sheet base material of polyethylene terephthalate (PET) was prepared. Further, a data area was formed in the range of a disk radius of 24 to 58 mm, and a through hole having a diameter of 15 mm for chucking was punched and formed at the center with an accuracy of an eccentricity of 5 μm or less. This through hole is the same chucking hole as the conventional CD and DVD. The grooves in the data area were formed by a thermal transfer method in which a high temperature stamper was pressed against a PET sheet.

On the PET sheet, Ag 30 nm and Si ₃ N ₄ 5n were sequentially deposited on the sheet by sputtering.
m, Tb ₂₁ Fe ₇₁ Co ₈ (mol%) 10 nm,
A recording film of Si ₃ N ₄ 30 nm was formed, and a DLC protective film of 10 nm was further formed thereon by CVD to form a flexible sheet-shaped disc.

This sheet-shaped disc was attached to a spin stand having a tapered cone-shaped chuck similar to the DVD standard, and pressed from above to attach a clamp for disc chucking. The disc is clamped by the upper and lower clamps. This is similar to the conventional DVD.

In this state, the sheet-shaped disc is rotated at a rotational speed of 50.
It is rotated at 00 rpm and the part with a radius of 40 mm is stabilized by Bernoulli's theorem using a stabilizing guide member as shown in FIG. 2, and focusing and tracking servo are applied by an optical pickup of 405 nm, NA 0.85. It was In this state, the sheet-shaped disc is in a state with little eccentricity, so that the servo can be applied very stably. At this time, feedforward control was not applied to tracking, and only feedback was performed.

Then, the sheet-shaped disc was withdrawn again from the pickup, the spindle was stopped, and the sheet-shaped disc was removed from the spindle of the spindle motor. This attachment / detachment of the spindle was then repeated 100 times.
Then, again, the radius of the sheet-shaped disc is 40 m.
Focusing and tracking were attempted by an optical pickup at a position of m at a rotation speed of 5000 rpm. As a result,
There was no problem with the focus servo, but there were many residual errors in the tracking servo, and the tracking was unstable and it was likely to come off. The disk eccentricity reached 100 μm. It is considered that this is because the accuracy of the central hole (through hole) for chucking decreased and the amount of eccentricity increased due to repeated chucking. There is a problem with the durability of the disc.

On the other hand, if the feedforward control is used as in the embodiment and examples of the present invention, the disk eccentricity can be increased to some extent, but as in the comparative example, a thin sheet shape having a through hole without a hub is formed. In the disk of No. 2, not only the eccentricity increases but also the part may be broken due to repeated chucking operations.

Therefore, as long as the chucking by the through holes is used, it is considered necessary to provide a hub or the like for the purpose of reinforcement, which complicates the disc manufacturing process and increases the thickness of the sheet-shaped disc as a whole. Will be lost.

[0086]

As described above, according to the optical disc of the present invention, eccentricity correction can be performed without providing a center hole in the center of the optical disc in consideration of eccentricity as in the conventional case. Further, since the hub is not bonded, the disc manufacturing can be simplified, and the thickness of the entire sheet-shaped optical disc can be defined only by the sheet itself, so that the optical disc can be thinned,
It is possible to reduce the thickness of the disc cartridge that houses the optical disc.

Further, according to the optical disk drive device of the present invention, both front and back surfaces in the central portion of the disk can be directly sandwiched by the clamper member for chucking. Therefore, if the optical disk is sandwiched by the clamper member at the time of disk chucking. Of course, it is no longer necessary to form a center hole in the optical disk as in the prior art, and even if the loading operation of the same optical disk is repeated, damage to the optical disk can be prevented, and durability and reliability can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing a flexible sheet-like optical disc for explaining an embodiment of an optical disc of the present invention.

FIG. 2 is a schematic configuration diagram of an optical disk drive device for explaining an embodiment of an optical disk drive device of the present invention.

FIG. 3 is a configuration diagram of upper and lower clampers in the present embodiment.

FIG. 4 is a diagram showing a waveform of an example of a tracking error signal for explaining the present embodiment.

FIG. 5 is a flowchart of an eccentricity correction operation according to this embodiment.

6A is a diagram showing a configuration of a flexible disk in Example 1 of the present invention, and FIG. 6B is an enlarged cross-sectional view showing a cross-sectional configuration at a circle portion in FIG. 6A.

FIG. 7 is a configuration diagram illustrating the configuration and operation of an outer circumference receiving jig that receives the outer circumference of the optical disc and performs centering in the first embodiment of the present invention.

[Explanation of symbols]

1 optical disc 2 Central mirror surface 3 Eccentricity measurement area 4 data areas 5 Peripheral mirror surface 10 Spindle motor 11 Lower clamper 13 Upper clamper 14 body case 16 Optical pickup 17 Stabilization guide member 18 Perimeter receiving jig 20,21 Permanent magnet 22 Electromagnet

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification code FI theme code (reference) G11B 7/007 G11B 7/007 7/095 7/095 C 17/028 17/028 Z (72) Inventor Murata Shozo 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 5D029 KC20 PA01 PA03 PA05 5D090 AA02 BB04 CC01 CC04 CC16 DD01 DD05 FF02 GG16 GG24 GG32 GG33 GG38 5D118 AA19 BA02 BB01 BB01 BB02 BC02 CA09 CA13 CD03 CD12 5D138 RA05 RA11 RA19 SA17 TA08 TA11 TA23 TC22 TC46

Claims (10)

[Claims] 1. A flexible sheet-shaped optical disc having an information recording area on its surface, wherein the central portion of the disc is a non-perforated and flat surface. 2. The optical disc according to claim 1, wherein a groove or a pit row for detecting disc eccentricity correction data is provided in the center portion of the disc. 3. The groove or pit row is provided in an outer peripheral portion of a portion of the central portion of the disc in contact with a clamper member for sandwiching the disc and an inner peripheral portion of the information recording area. Or the optical disc described in 2. 4. The pitch in the radial direction of the groove or pit row formed concentrically or spirally is made wider than the pitch between the information tracks formed in the information recording area. Or the optical disc described in 3. 5. The optical disc according to claim 2, wherein at least disc management information such as disc identification information is recorded in the groove or pit row. 6. If the optical disc is a write-once disc or a rewritable disc, at least management information such as disc directory information is recorded in the groove or pit row. The optical disc according to item 1. 7. A flexible sheet-like optical disc having an information recording area on the surface thereof and having a disc center portion having no hole and a flat surface is used for recording and / or reproducing with respect to the optical disc. An optical disk drive device comprising an optical pickup for irradiating a light spot and a spindle motor for rotationally driving the optical disk, characterized in that both front and back surfaces in a central part of the disk are directly sandwiched by a clamper member for chucking. Optical disk drive. 8. The optical disk drive device according to claim 7, further comprising an arcuate jig which is joined to the outer circumference of the optical disk and performs a rough eccentricity correction of 10 μm or more of the optical disk. 9. A means for removing an influence of eccentricity by applying an alternating current synchronized with a rotation cycle of the spindle motor to a tracking drive current for driving the optical pickup in a tracking direction. 7. The optical disk drive device according to 7 or 8. 10. A tracking error signal detected from a groove or a pit train in the optical disc according to claim 2 is used for setting the magnitude and phase of the tracking drive current for removing eccentricity. The optical disk drive device according to claim 9.