JP3062220B2 - Optical disc for simultaneous double-sided recording and reproduction, method of manufacturing the same, and optical disk apparatus using the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an optical disk, and more particularly to a double-sided simultaneous recording / reproduction suitable for a recording / reproduction method for simultaneously accessing a recording medium having a recording film on both sides. The present invention relates to an optical disc for use, a method for manufacturing the same, and an optical disc apparatus using the same.

[Conventional technology]

Conventional optical discs have been developed assuming use only for access from one side. Therefore, when the back surface of the optical disk on the opposite side is used, the optical disk is once removed, turned over, and mounted on the optical disk device. Therefore, the structure of the optical disk has been adapted to the above specifications. That is, an optical disk is formed by bonding disk substrates having address signals of the same pattern so that the recording films face each other. Therefore, address pit arrangements such as address signals recorded in advance on both sides of an optical disk have been used simply by recording them in the order of reading (Japanese Patent Publication No. 60-48806, JP-A-60-48806, 1962
No. 75948).

However, there is a problem that it is almost impossible to apply a conventional optical disk when recording / reproducing and erasing both sides simultaneously by arranging optical heads on both sides of the optical disk.

Further, as a method capable of reproducing both sides of an optical disk, a method of electrically discriminating the front and back of the optical disk surface and operating the disk (Japanese Patent Application Laid-Open No. 64-23424) has been proposed, but the circuit configuration of the optical disk device becomes complicated. However, there is a problem that the disk device becomes expensive.

[Problems to be solved by the invention]

As described above, in the prior art, there is a problem that it is extremely difficult and almost impossible to achieve high-speed access by simultaneously recording and reproducing both sides of the optical disk due to the structure of the optical disk. Also, the method of discriminating the front and back of the optical disk surface and operating it by an electric circuit has a complicated circuit configuration, which leads to an increase in the cost of the optical disk device and cannot be said to be the best method.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks in the prior art, and to dispose optical heads on both the front and back surfaces of an optical disk.
An object of the present invention is to provide an optical disk capable of simultaneously reading and writing data on both sides, a method of manufacturing the same, and an optical disk device using the same.

[Means for solving the problem]

In order to achieve the object of the present invention, in the present invention, an array of address pits or the like to be formed in advance on a disk substrate such as a magneto-optical disk, a phase-change optical disk, a hole- or bubble-formed optical disk, or a read-only optical disk is provided. This can be realized by providing them in a symmetrical form so that they have the same contents regardless of whether they are reproduced from the forward direction or the reverse direction.

An example of the specific means will be described below. An initial process of manufacturing an optical disk substrate includes a process of manufacturing a master (master stamper) for manufacturing a disk substrate. In the process of manufacturing the master stamper, an array of address pits and the like is formed by the following method. That is, a photoresist is applied on a disk-shaped glass substrate, and a high-power laser beam is applied to the photoresist to form a pattern such as address pits. At this time, by modulating the light intensity of the laser light in accordance with the information such as the desired address pits, the same pattern as the information such as the previous address pits is formed on the resist. Then, when modulating the light intensity of the laser light, an end mark is written at the end of the address pit information, and then the address pit information is written in reverse order, thereby achieving the object of the present invention. . Then, the master exposed by the above-described means is developed to produce a master,
By using this master and passing through each process of a stamper and a replica, a large amount of optical disc substrates can be manufactured.

The present invention relates to an optical disk for double-sided simultaneous recording / reproduction having recording films on both front and back surfaces of the optical disk and simultaneously performing recording (writing), reproduction (reading) or erasing on both surfaces of the optical disk using a laser beam. An address pit array such as a track number or a sector number to be pre-recorded on the disk substrate constituting the disk is formed in a symmetrical form so that the same content is obtained even if the address pit array is read from either the forward or reverse direction of the rotating optical disk. The two disk substrates are arranged and preferably arranged so as to be aligned with each other.

In the optical disk for double-sided simultaneous recording / playback of the present invention, an end mark indicating the end of the address pit array such as a track number or a sector number is arranged at the center of the address pit array, and after the end mark, the address pit is placed. The address pits are arranged in the reverse order of the arrangement, and it is preferable that the address pits are arranged concentrically or spirally on the disk.

In the optical disk for simultaneous recording / reproduction of both sides of the present invention, a part of an optical disk cartridge accommodating the optical disk may be provided with a mechanism for discriminating the front and back of the optical disc and a means for preventing incorrect insertion of the front and back when the optical disc is mounted on the optical disc device. it can. Further, it is also possible to read (reproduce) the front / back discrimination information of the optical disc from the forward direction or the reverse direction of the rotating optical disc at a position during or before or after the writing of the address information to be recorded on the disk substrate constituting the optical disk. You may make it record so that it may become the same content.

The present invention also relates to a method for manufacturing an optical disk for double-sided simultaneous recording / reproduction, which has recording films on both front and back surfaces of the optical disk and simultaneously performs recording (writing), reproduction (reading) or erasing on both surfaces of the optical disk by using a laser beam. At the stage of manufacturing a master stamper for an optical disk substrate using photolithography technology, at least three signals, an address signal, a separation signal, and a signal in the reverse order of the address signal, are placed in a preformat area, which cannot be used by a user. A master stamper on which an address pit array is recorded as one address signal is manufactured, and an optical disk for simultaneous double-sided recording / reproduction including a process of manufacturing an optical disk substrate by an injection molding method or a photopolymer method using the master stamper. And a method for producing the same.

Further, the present invention uses the above-described optical disk for simultaneous recording and reproduction on both sides of the present invention, and arranges optical heads on both sides of the optical disk to simultaneously record, reproduce, or erase on both sides of the optical disk, thereby increasing the access speed. The present invention relates to an optical disk device having measuring means. Also, in the optical disk device of the present invention, when accessing and recording / reproducing by accessing the back surface of the optical disk, the address signal read by the optical head is demodulated in reverse order so that the address signal has the same content as the address signal viewed from the front surface of the optical disk. Function can be provided.

[Action]

Even if the address pit information recorded in advance on the optical disk substrate is reproduced from the forward direction and the reverse direction, the same address can be obtained. Thus, an optical disk is manufactured by bonding the optical disks, and the optical disk is rotated to prepare optical heads on both sides, so that both sides can be simultaneously accessed and reproduced. With this configuration, two types of disk substrates, front and rear, were conventionally required to achieve high-speed optical disk access. Since it is possible to improve the production yield of optical discs, it is not necessary to classify and manage two types of disc substrates for front and back.
The working efficiency in the manufacture of optical discs is further improved.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a schematic view showing an example of an address pattern on the surface of an optical disk for simultaneous recording and reproduction on both sides according to the present invention. An optical head guide groove (not shown) and markings 1 indicating a track number, a sector number, a synchronization signal, and the like are spirally formed on the surface of the optical disk. The marking 1 is displayed in a digital code. As shown in FIG. 2 (enlarged view of a portion D in FIG. 1), when viewed from the left to the right, for example, the sector mark start signal 5, "A. B
C ", the left digital information 3 arranged as" C ", the sector mark end signal 6 as viewed from right to left, and" AB
The right digital information 4 arranged as "C" is integrated with the separation information 2 arranged in the middle. Two such disc substrates are bonded together so that the recording films face each other. An optical head is placed on both sides of this optical disk, and information is recorded / reproduced simultaneously from both sides, in which case, for example, the marking 1 shown in FIG. become,
The track and sector information can be read from the left digital information 3 arranged to the left of the separation information 2. Similarly, the marking 1 shown in FIG. 1 is read from the right side on the back surface of the optical disk, and the track and sector information can be read from the right digital information 4 arranged to the right of the separation information 2.

FIG. 3 shows an example of information of the marking 1. Separation information 2 is placed at the center, and on the left side, a sector mark start signal 5 and left digital information 3 are arranged so as to be read from the left and become track and sector information.
The sector mark end signal 6 and the right digital information 4 are arranged on the right side of the data so as to be read from the right side and become track and sector information.

The optical disk substrate having the above-described marking can be easily manufactured. Hereinafter, the manufacturing method will be described.

First, the surface of a disk-shaped glass substrate is polished smoothly, and then a photosensitive resin (for example, a positive photoresist) is applied to the polished glass substrate through a cleaning process to dry and improve adhesion to the glass substrate. A baking process is performed to cause the baking process. Next, the intensity of argon laser light or the like is modulated (or turned on or off) by an AO (acousto-optic) optical modulator or the like using an address signal indicating a track number, a sector number, a synchronization signal, or the like as shown in FIG. 2, for example. Off-modulation), concentrically (or spirally) exposed on the photoresist on the surface of the rotating glass substrate, and a digital code corresponding to the address signal is recorded. That is, the digital code is, for example, first “= AB
C "and the left digital information 3 in order, and then the separation information 2"-"is exposed, and then the left digital information 3" = ABC "is reproduced in the reverse order, and" = AB
Exposure of the right digital information 4 so that it is correctly aligned with C ". Next, the exposed photoresist surface is developed and the exposed portion is melted to form an address pit array such as track numbers and sector numbers. Before transferring the glass master on which the address pit array is formed to the electroforming step, electrodes are formed by electroless plating, and a master stamper (master) having a predetermined thickness is manufactured from the glass master by electroforming. Set this master stamper on an injection molding machine to produce a transparent plastic disk substrate (about 1.2 mm thick), or place plastic particles on the master stamper and raise the temperature. By pressing, the disk substrate of the present invention can be manufactured by the same compression method as the so-called record. Then, a recording film is formed on the disk substrate manufactured by the above-described method, and a protective film, an adhesive film, and the like are adhered on the recording film, so that the recording film is formed inside. By bonding the two disks together, the optical disk for simultaneous double-sided recording and reproduction of the present invention can be obtained.

In the double-sided simultaneous recording / playback optical disc of the present invention,
In order to form the address pit array in a preformat area that cannot be used by the user, it is conceivable that the user area of the optical disk is reduced, but this can be sufficiently covered by the coding of the data array such as address pits.

Further, in the above-described embodiment, the case where the recording surface (address pit array surface) of the disk substrate is assembled with the recording surface facing outward in the production of the optical disk for double-sided simultaneous recording / reproduction has been described. Substrates may be assembled back-to-back, and when recording, reproducing and erasing with an optical head,
The structure may be such that its performance does not decrease.

In order to obtain the same effect as the double-sided simultaneous recording / reproducing optical disk of the present invention, the address signals reproduced and correctly arranged from the front surface of the optical disk are reproduced by an optical head for recording / reproducing on the rear surface of the optical disk. By temporarily storing the address signal in a memory and using means for demodulating the address signal in the reverse order, the address signal can be correctly read even if it is reproduced from the back surface.

In addition, by providing an optical disc front / back discrimination mechanism in the cartridge containing the optical disc and taking measures to prevent erroneous insertion into the optical disc device, the optical disc recorded on the front side can always be read and written correctly without being reproduced from the back side. it can. Alternatively, when writing (recording) the address information,
The discrimination signal of the front and back of the optical disc is recorded symmetrically so that the same content is obtained even if the signal is read (reproduced) from the forward or reverse direction of the optical disc. In the event that recording occurs on the front side of the optical disk and playback is performed on the back side, one sector of information before the address information is reproduced is stored in the memory, and the address information is read out. By reproducing the information as important information before that and extracting the information stored in the memory, it is possible to always read and write correctly.

〔The invention's effect〕

As described in detail above, both-sided simultaneous recording /
The playback optical disk is a simple combination of two disk substrates in which the address pit array such as the track number or the sector number has the same contents when read from either the forward or reverse direction of the optical disk. With such a simple method, the optical head can be obtained easily and inexpensively, and the optical head can be arranged on both sides of the disk so that recording and reproduction can be simultaneously performed on both sides, and the access can be speeded up. Furthermore, in the manufacture of the optical disk of the present invention, since one type of disk substrate is manufactured, handling of the disk substrate is simplified in terms of manufacturing and product management, and an improvement in product yield can be expected.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the surface configuration of an optical disk for simultaneous double-sided recording and reproduction exemplified in an embodiment of the present invention, FIG. 2 is an enlarged view of a portion D in FIG. 1, and FIG. 3 is an optical disk shown in FIG. FIG. 4 is a schematic diagram showing an example of marking information in FIG. 1 ... Marking 2 ... Separation information 3 ... Left digital information 4 ... Right digital information 5 ... Sector mark start signal 6 ... Sector mark end signal

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Motoyasu Terao 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B 20/12 G11B 7/007

Claims (9)

(57) [Claims] A double-sided simultaneous recording / playback optical disc having recording films on both front and back surfaces of an optical disc and simultaneously performing recording (writing), reproduction (reading), or erasing on both sides of the optical disc using a laser beam. Symmetrical configuration so that the address pit array such as the track number or sector number to be prerecorded on the disk substrate constituting the disk has the same contents when read from either the forward or reverse direction of the rotating optical disk. An optical disk for simultaneous double-sided recording / reproduction characterized by being arranged in a matrix. 2. The double-sided simultaneous recording / reproducing optical disk according to claim 1, wherein two disk substrates are assembled with the address pit arrangement surfaces of the disk substrates facing each other. 3. An address pit according to claim 1, wherein an end mark indicating the end of the address pit array such as a track number or a sector number is arranged at the end of the address pit array, and after the end mark, the address pit is arranged. An optical disk for simultaneous double-sided recording / reproduction, wherein address pits are arranged in a reverse order to the arrangement. 4. A double-sided optical disk according to claim 1, wherein the address pits such as track numbers or sector numbers are arranged concentrically or spirally on the disk. Optical disk for simultaneous recording and reproduction. 5. An optical disk cartridge for storing an optical disk for double-sided simultaneous recording / reproduction according to claim 1, wherein a part of said optical disk cartridge is provided with an optical disk front / back discrimination mechanism. An optical disk for simultaneous double-sided recording / reproduction, comprising means for preventing incorrect insertion of the front and back sides when the optical disk is mounted on a device. 6. The double-sided simultaneous recording / reproducing optical disk according to claim 1, wherein address information to be recorded on a disk substrate constituting said optical disk is located at a position before or after writing address information. An optical disc for simultaneous double-sided recording / reproduction, characterized in that the discrimination information of the front / back of the optical disc is read out (reproduced) from the forward or reverse direction of the rotating optical disc so as to have the same contents. 7. A method for manufacturing an optical disk for double-sided simultaneous recording / reproduction, which has recording films on both front and rear surfaces of the optical disk and simultaneously performs recording (writing), reproduction (reading) or erasing on both surfaces of the optical disk by using a laser beam. At the stage of manufacturing the master stamper of the optical disk substrate using the photolithography technique, at least three signals of an address signal, a separation signal, and a signal in the reverse order of the address signal are provided in a preformat area, which is an area that cannot be used by a user. A step of producing a master stamper on which an address pit array in which a signal is one composite address signal is recorded, and producing an optical disc substrate by an injection molding method or a photopolymer method using the master stamper. A method for manufacturing an optical disk for simultaneous recording and reproduction on both sides. 8. The double-sided simultaneous recording / reproducing optical disk according to claim 1, wherein an optical head is disposed on both sides of the optical disk, and recording / reproducing or simultaneous recording / reproduction on both sides of the optical disk is performed. An optical disk apparatus for performing simultaneous double-sided recording / reproduction, comprising means for performing erasing and speeding up access. 9. The optical disk device according to claim 8, wherein
When recording / reproducing by accessing the back side of the optical disc,
An optical disk device having a function of demodulating an address signal read by an optical head in the reverse order to make the same content as an address signal viewed from the surface of the optical disk.