JP2000082221A - Optical recording medium and tracking controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent reliability from lowering even when a pitch is narrowed by recording track discriminative information discriminating whether a groove track is a projected or recessed groove track on the top of respective groove tracks of the projected and recessed groove tracks and using a prescribed sector as the track discriminative information. SOLUTION: A spiral groove track 102 is constituted of alternately and repeatedly forming a recessed groove track 106 and a projected groove track 105 at every one round of an optical recording medium 101. The discriminative information for detecting that the projected groove track 105 is switched with the recessed groove track 106 is recorded on a switch detection area 103 provided on its boundary area. Pits 108 are provided on both tops of the projected groove track 105 and the recessed groove track 106, and their sizes and intervals, that is, spacial frequencies are changed in the projected groove track 105 and the recessed groove track 106. Thus, whether the track scanned next by a light beam is the projected groove or the recessed groove is beforehand discriminated simply by the switch detection area 103.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium for irradiating a converged light beam and recording information by heat generated by the light beam, and more particularly to an optical recording medium having an uneven groove track.

[0002]

2. Description of the Related Art In recent years, optical recording media on which information can be recorded are:
Because it can hold a large amount of data, voice information data
It is occupying an important position to store video information data and various information device data. However, further increase in capacity is required, and in order to satisfy this demand, it is necessary to further improve the information recording density on the optical recording medium.

[0003] As a conventional optical recording medium, a groove pattern having minute irregularities having a width of 0.8 µm and a pitch of 1.6 µm is spirally formed on a disk-shaped resin substrate surface, and a method such as sputtering is formed on the substrate surface. It is known that a thin film of a ternary phase-change recording material mainly composed of Te, Sb, and Ge is formed and a protective layer is provided on the thin film. For this resin substrate, a stamper is manufactured based on a master on which concave and convex groove tracks are cut, and a large amount of the resin substrate is copied by a technique such as injection using the stamper.

A phase change type recording material becomes crystalline when heated and then gradually cooled, and becomes amorphous when melted and rapidly cooled. Utilizing this property, a phase-change recording medium reversibly changes between a crystalline state and an amorphous state, and overwrites information in the same place as many times as a magnetic recording medium such as a floppy disk or hard disk. it can. When recording information on a phase change type recording medium, the recording medium is rotated at a predetermined speed, and tracking control is performed so that the light beam is positioned on the groove track, and the intensity of the light beam is adjusted according to a signal to be recorded. The modulation is performed between the non-crystallization level and the crystallization level. For example, when recording so that the recording mark is in an amorphous state, an amorphous mark is formed by irradiating a light beam with an amount of light enough to melt the thin film, and the mark is not melted during a period other than the recording mark. It is crystallized by irradiating a light beam with an amount of light. Therefore, during a period other than the recording mark, whether the previous state is amorphous or crystalline, the state becomes a crystalline state, and overwriting can be performed even at a place where information has already been recorded.

[0005] Information recorded on the phase-change recording medium is reproduced by utilizing the fact that the reflectance or transmittance differs between the amorphous state and the crystalline state. For example, a weak constant light beam is irradiated, light reflected from the recording medium is received by a photodetector, and information is reproduced by a change in the amount of reflected light.

[0006]

The information density of this type of optical recording medium is determined by the pitch of information tracks and the information density in the track direction, that is, the linear density of information. Narrow the pitch,
It is necessary to increase the linear density. However, the conventional optical recording medium is configured to record information on either the concave or convex groove track. Therefore, when the track pitch is reduced, the track width is reduced, and the duplication of the master or the resin substrate is performed. Becomes difficult. Further, when reproducing information recorded on the groove track, there is a problem that the quantity of light reflected or transmitted from the groove track is reduced, so that the quality of a reproduced signal is deteriorated. Further, when detecting the position shift between the light beam and the groove track on the optical recording medium, that is, the track shift signal by the push-pull method, the magnitude and dynamic range of the track shift signal are determined by the width and pitch of the groove track, When the width of the groove track is reduced to reduce the pitch, the amplitude of the track shift signal decreases, and the dynamic range also decreases. Therefore, there is a problem that the tracking control becomes unstable because the quality of the track shift signal deteriorates, and the track jump easily occurs due to disturbance such as vibration and shock.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an optical recording medium suitable for high-density recording that can be easily manufactured without reducing the reliability of the device even if the pitch is reduced.

[0008]

In order to solve the above-mentioned problems, an optical recording medium according to the present invention comprises a recording thin film formed on a substrate having an uneven groove track, and a convex groove track and a concave groove track. In a disc-shaped optical recording medium in which groove tracks are alternately arranged to form one spiral groove track, it is identified that the track form switches to the top of a convex groove track and a concave groove track. To provide track identification information.

In the optical recording medium according to the second aspect of the present invention, one spiral groove track is formed by alternately arranging the convex groove tracks and the concave groove tracks for each circumference, and the convex groove tracks are formed. And a track address for identifying a recording area is provided at the head of the concave groove track.

According to a third aspect of the present invention, a recording thin film for recording information by heat generated by a light beam is formed on a substrate having an uneven groove track, and the recording thin film is formed on the convex groove track and the concave groove track. In a disk-shaped optical recording medium on which information is recorded on both sides, the width of the concave groove track is smaller than the width of the convex groove track.

The optical recording medium according to a fourth aspect of the present invention is arranged such that the center of the identification information for identifying the recording area is located between the center of the concave groove track and the center of the convex groove track. It was done.

The operation will be described below. According to the recording media of the first and second aspects of the present invention, the boundary between the convex groove track and the concave groove track can be detected based on the identification information. Can be done.

According to the optical recording medium of the third aspect of the present invention, since the width of the concave groove track is narrower than the width of the convex groove track, the heat radiation conditions are substantially equal, and the convex groove track is formed. The conditions for recording information on the top and the conditions for recording information on the concave groove track are almost the same.

According to the fourth aspect of the present invention, the center of the identification information for identifying the recording area is located between the center of the concave groove track and the center of the convex groove track. , The width of the identification information can be widened, the identification information can be cut with the same light beam as the light beam for cutting the groove track, and the configuration of the cutting machine is simplified.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical recording medium according to one embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view showing an optical recording medium according to an embodiment of the present invention. FIG. 1A is a plan view of an optical recording medium 101, and shows a concave or convex groove track 10.
2 are provided in a spiral shape. The spiral groove track 102 is formed such that a concave groove track and a convex groove track are alternately repeated for each round of the optical recording medium 101. A switching detection area 103 is provided in the boundary area, and identification information for detecting switching between the concave groove track and the convex groove track is recorded in the switching detection area 103. An information area 104 records information or records information. FIG. 1B is a partially enlarged view of the switching detection area 103. Reference numeral 105 denotes a convex groove track, reference numeral 106 denotes a concave groove track, and reference numeral 107 denotes a center of the groove track 102. Reference numeral 108 denotes identification information pits recorded in the switching detection area 103 in the form of irregularities. As shown, the pit 108 is provided at the head of both the convex groove track 105 and the concave groove track 106, and the size and the interval between the convex groove track 105 and the concave groove track 106, that is, the spatial frequency Are different. Therefore, in the switching detection area 103, it can be easily identified in advance whether the track to be scanned next by the light beam is the convex groove track 105 or the concave groove track 106.

The track width of a conventional optical recording medium is 0.8 μm.
Assuming that m and the track pitch are 1.6 μm, in order to reduce the track pitch to ０．８ of 0.8 μm, it is necessary to make the track width extremely small, for example, 0.4 μm. It is difficult to cut such narrow tracks, and it is also difficult to duplicate them. However, in the present invention, since the convex groove tracks 105 and the concave groove tracks 106 are alternately arranged in the radial direction of the optical recording medium 101, if the width of the groove track 102 is 0.8 μm, the track pitch is also 0. .8 μm. Therefore, the master can be easily cut, and the duplication can be simplified.

Further, for example, if a continuous convex groove track is formed in a spiral shape, a continuous concave groove track is formed between the convex groove tracks. When the groove track is formed in this manner, two spiral tracks are formed, and continuous recording and reproduction become difficult. For example, information is recorded on a groove track that is continuously convex from the inner periphery to the outer periphery of the optical recording medium, and then returns to the inner periphery of the optical recording medium again, and is continuously concave from the inner periphery to the outer periphery. It is necessary to record information on the groove track. Therefore, information cannot be recorded while returning from the outer circumference to the inner circumference. Further, even if the convex groove track and the concave groove track are alternately recorded every one rotation of the optical recording medium, for example, the convex groove track is changed from the convex groove track to the concave groove track every one rotation of the optical recording medium. It is necessary to scan the light beam by interlaced scanning, and information cannot be recorded during the interlaced scanning. However, in the above-described optical recording medium 101 of the present invention, since the groove track 102 is a single spiral track, information can be recorded or reproduced continuously.

Since heat radiation conditions are generally different between the convex groove track 105 and the concave groove track 106, it is necessary to change recording conditions such as the recording light amount or irradiation pulse width of a light beam for recording information. When the width of the convex groove track 105 and the width of the concave groove track 106 are different, the amount of reflected light is different, and the magnitude of the reproduction amplitude is different. Furthermore, for example, when tracking control is performed by detecting a track shift signal by the push-pull method, the polarity of the track shift signal is opposite between the convex groove track 105 and the concave groove track 106. In the optical recording medium 101 of the present invention, the track identification information for identifying the form of the track is recorded in the switching detection area 103, so that the recording / reproducing condition or tracking is performed by the convex groove track 105 and the concave groove track 106. The control polarity can be easily switched.

FIG. 2 is an enlarged and exaggerated cross-sectional view of the optical recording medium 101 cut in the radial direction. A convex groove track 105 and a concave groove track 106 are formed on one surface of a substrate 201 made of polycarbonate resin or the like. Then, a dielectric film 202 such as SiO ₂ , a recording material film 203, and a dielectric film 204 are sequentially provided thereon, and the dielectric film 204 and the protective layer 206 are bonded by an adhesive. Reference numeral 205 denotes an adhesive layer made of an adhesive. The recording material film 203 is formed, for example, by a method such as sputtering of a phase-change recording material containing Te (tellurium), Sb (antimony), and Ge (germanium) as main components. The dielectric films 202 and 204 are for protecting the recording material film 203 from humidity or thermal shock, and can be omitted.

An apparatus to which the above-described phase change type optical recording medium 101 is applied will be briefly described with reference to FIG. In FIG. 6, an optical recording medium 101 is attached to a rotating shaft of a motor 601 and is rotated at a predetermined rotation speed. An optical beam generated from a light source 602 such as a semiconductor laser is converted into parallel light by a coupling lens 603,
The light passes through a polarizing beam splitter 604 and a quarter-wave plate 605, is reflected by a total reflection mirror 606, and is converged by a converging lens 607.
The light is converged on the optical recording medium 101 and is irradiated.
The light reflected by the optical recording medium 101 passes through the converging lens 607, is reflected by the total reflection mirror 606, and
After passing through the wave plate 605, the polarizing beam splitter-6
The light is reflected at 04 and is irradiated on the photodetector 608. The converging lens 607 is attached to a movable part of the actuator 609. The actuator 609 is composed of a tracking coil provided in the movable part and a permanent magnet attached to the fixed part. Therefore, when a current is applied to this coil, the converging lens 607 moves in the radial direction of the optical recording medium 101, that is, across the groove track on the optical recording medium 101 due to the electromagnetic force applied to the coil. A focusing coil is also attached to the movable part of the actuator 609. When a current flows through the coil, the converging lens 607 is perpendicular to the surface of the optical recording medium 101 by the electromagnetic force received by the coil. It is configured to be able to move in the direction. The converging lens 607 is focus-controlled so that the light beam irradiated on the optical recording medium 101 always has a predetermined converging state.

The transfer table 610 includes a light source 602, a coupling lens 603, a polarizing beam splitter 604,
A fixed part of a quarter-wave plate 605, a total reflection mirror 606, a photodetector 608, and an actuator 609 is attached, and the transfer table 610 is configured to move in the radial direction of the optical recording medium 101 by a linear motor 611. Have been. The photodetector 608 has a two-part structure, and its output is an I / V converter 612, 613 for converting current to voltage.
Are entered respectively. I / V converters 612, 61
The output signal of No. 3 is input to the differential amplifier 614, and the differential amplifier 614 outputs a signal corresponding to the difference between the two signals.
The output signal of the differential amplifier 614 is a signal representing the positional deviation between the optical beam converged on the optical recording medium 101 and the groove track, that is, a track deviation signal. It is called the pull method.

The signal of the differential amplifier 614 is supplied to a polarity switching circuit 61 for switching the polarity of tracking control.
5, applied to the tracking coil of the actuator 609 via a phase compensation circuit 616 for compensating the phase of the tracking control system and a drive circuit 617 for power amplification, and converged on the optical recording medium 101. Light beam
The tracking control is performed so that the system is always positioned on the groove track. Further, the signal of the differential amplifier 614 is applied to the linear motor 611 via the polarity switching circuit 615, the phase compensation circuits 616 and 618, and the drive circuit 619 for power amplification, and the convergent lens 607 is focused on the natural state. The transfer is controlled to move. An addition circuit 620 outputs a signal obtained by adding the signals of the I / V converters 612 and 613. The adder circuit 620 outputs a signal corresponding to the difference between the reflectance in the amorphous state and the reflectance in the crystalline state, and reads information recorded on the optical recording medium 101 from the signal. The addition circuit 620 outputs a signal corresponding to the pit 108 in the switching detection area 103. The discrimination circuit 621 discriminates from the output signal of the addition circuit 620 whether the groove track 102 where the light beam is next located is the convex groove track 105 or the concave groove track 106, and sends this identification signal to the polarity switching circuit 615. The polarity switching circuit 615 switches the polarity of the input signal in response to the output signal of the identification circuit 621. For example, polarity switching circuit 6
The differential amplifier 101 receives a low-level signal indicating the convex groove track 105 from the identification circuit 621.
4 and outputs a signal of the opposite phase when a high-level signal representing the concave groove track 106 is sent. Therefore, the polarity of the tracking control is inverted each time the optical recording medium 101 makes one rotation, so that the light beam is projected to the convex groove track 105 and the concave groove track 106.
Are continuously tracked on one spiral track formed by alternately repeating the process for each round.

When information is recorded, the intensity of the light beam generated from the light source 602 is modulated according to the information to be recorded. This will be described with reference to FIG. FIG. 7 shows the light intensity of the light beam on the vertical axis and the time on the horizontal axis.
P0 is a reproduction light amount when reading information recorded on the optical recording medium 101, P1 is a crystallization light amount for bringing the phase change material into a crystalline state, and P2 is an amorphous light amount for bringing the phase change material into an amorphous state. is there. The recording material in the portion irradiated with the amount of amorphization light P2 is melted, and becomes amorphous regardless of whether the state before the irradiation is a crystalline state or an amorphous state. Also, the amount of crystallization light P
The portion of the recording material irradiated with 1 is in a crystalline state whether the state before the irradiation is a crystalline state or an amorphous state.

In the embodiment of the present invention shown in FIG. 1, the switching area 103 has a convex groove track 105 and a concave groove track 1.
In step 06, the concavo-convex signals having different spatial wavelengths are recorded, but the present invention is not limited to this. For example, the switching area 10
3 can be used as a track address. In this case, for example, if continuous track numbers are recorded from the inner circumference to the outer circumference of the optical recording medium 101, it is determined whether the track number is an even or odd number and whether the groove track is a convex groove track 105 or a concave groove track 106. Can be.

Further, one spiral track is formed by alternately repeating the convex groove tracks 105 and the concave groove tracks 106 for each rotation of the optical recording medium 101, but the optical recording medium surface is radially formed. Even if the groove track is divided into an odd number and the convex groove track and the concave groove track are alternately switched a plurality of times per circumference, one spiral groove track can be formed. In this case, it is not necessary to divide the optical recording medium at an equal angle. When n is a positive integer, (2n + 1) is set so that convex groove tracks and concave groove tracks are alternately arranged in the radial direction of the optical recording medium. What is necessary is just to divide. And
When tracking control is performed by detecting a track shift signal by the push-pull method, if the polarity of the track shift signal is reversed at a switching point between the convex groove track and the concave groove track, a light beam having one spiral shape is obtained. It can follow continuously so as to be located on the groove track.

An embodiment in which one spiral groove track is formed by alternately switching the convex groove track and the concave groove track a plurality of times per rotation will be described with reference to FIG. FIG. 3A is a plan view of an optical recording medium 301 in which a concave or convex groove track 302 is provided in a spiral shape. 303 is an ID in which identification information for identifying the position of the information area is recorded in the form of uneven pits
An area 304 is an information area where information is recorded or information is recorded. One spiral track is divided into a plurality of odd sectors, ie, three sectors 305 of 0, 1, and 2 in FIG.
Is composed of a pair of ID area 303 and information area 304. FIG. 3B is a partially enlarged view in which the ID area 303 is enlarged. Reference numeral 306 denotes a convex groove track, and 307 denotes a concave groove track. Identification information including pits 308 is provided corresponding to each information area. ID area 3
In 03, a track number and a sector number are recorded.
Depending on whether the track number and the sector number are odd or even, the groove track 302 to be scanned next by the light beam has a convex groove track 30.
6 or concave groove track 307.

In the embodiment of the present invention shown in FIG.
3, a track number and a sector number are recorded, but the present invention is not limited to this. For example, a continuous sector number may be recorded in the ID area 303 from the inner circumference to the outer circumference of the optical recording medium 301. For example, 0 to 2 on the innermost first track track 302 and second track 3 on the innermost track.
02, a sector number of 3 to 5 is recorded, and similarly, a continuous sector number is recorded in the same manner. By recording the continuous sector numbers in this manner, it is possible to identify whether the groove track 302 to be scanned next by the light beam is the convex groove track 306 or the concave groove track 307 by the odd or even sector number.

In the embodiment of the present invention shown in FIG. 3, similarly to the embodiment shown in FIG. 1, the convex groove tracks 306 and the concave groove tracks 307 are alternately repeated every rotation of the optical recording medium 301. One spiral groove track 302 can be formed. For example, the convex groove track 306 and the concave groove track 307 are switched with the sector 0 as a boundary. In this case, the number of sectors per round is an even number,
Depending on whether the track number is odd or even, it is possible to identify whether the groove track 302 to be scanned next by the light beam is the convex groove track 306 or the concave groove track 307.

An optical recording medium having two spiral groove tracks, a continuous convex groove track and a concave groove track, for recording information on both the convex groove track and the concave groove track. Preferred identification information will be described with reference to FIG. FIG. 4A is a plan view of the optical recording medium 401, and shows a spiral convex groove track 402 and a concave spiral groove track 4 between the convex groove tracks 402.
03, two groove tracks 404 are provided. 40
Reference numeral 5 denotes an ID area, 406 denotes an information area, and a spiral groove track 404 around one circumference is divided into four sectors 407. FIG. 4B is a partially enlarged view in which the ID area 405 is enlarged. The identification information provided in the ID area 405 includes a convex groove track 402 and a concave groove track 4.
03 is located almost on the boundary line. That is, the center of the convex groove track 402 and the concave groove track 40
The center of the pit 408 constituting the identification information is located between the three centers, and the information areas of the adjacent convex groove track 402 and concave groove track 403 are identified based on one identification information. It is formed as follows. In FIG. 4B, the convex groove track 402a and the concave groove track 403a, and the convex groove track 402b and the concave groove track 403b are respectively identified based on the same identification information. In the information area of the convex groove track 402 and the concave groove track 403, when the tracking control is performed by detecting the track shift signal by the push-pull method, the polarity of the track shift signal becomes opposite. Therefore, even if the identification information of the information area of the convex groove track 402 and the concave groove track 403 is the same, the convex groove track 402 and the concave groove track 403 can be determined from the polarity of the tracking control. Can be identified.

When cutting two spiral tracks, for example, by cutting a continuous convex groove track 402 in a spiral shape, the convex groove track 40 can be cut.
The groove track 403 is a continuous concave groove track between the two. When the identification information is separately provided to the convex groove track 402 and the concave groove track 403, at least the concave groove is provided in addition to the light beam for cutting the identification information for the convex groove track 402 and the convex groove track 402. A light beam for cutting the identification information for the track 403 is required. However, if the identification information is shared between the convex groove track 402 and the concave groove track 403 as in the embodiment of FIG. 4, only the light beam cutting the convex groove track 402 and the identification information is used. be able to. Further, when the identification information is provided in this manner, the width W3 of the pit 408 of the identification information can be made substantially the same as the width of the groove track. Therefore, it is necessary to perform recording by slightly moving the optical recording medium 401 in the radial direction using an optical deflector or the like. However, the identification information is recorded by the same light beam as the light beam for cutting the convex groove track 402. This makes the cutting machine simpler, and the pits can be made larger so that they can be easily formed.

In FIG. 4, W1 is a convex groove track 4
A width 02 and a width W2 indicate the width of the concave groove track 403, respectively. Since the identification information of the convex groove track 402 and the concave groove track 403 is also used, if the width W3 of the pit 408 is excessively small, it becomes difficult to read the identification information. Therefore, if W3 ≧ W1 or W3 ≧ W2, the convex groove track 402 or the concave groove track 4
Since almost half of the light beam spot scans over the pit 408 while the light beam scans over the pit 403, high-quality identification information can be obtained. Also, the width W of the pit 408 is excessively large.
When 3 is increased, crosstalk from adjacent identification information increases, and reading of the identification information becomes difficult due to the crosstalk. According to the experiment, W3 ≦ (W1 + W
2) When x is set to 0.8, the result is that the identification information can be read with high reliability.

The optical recording medium 401 of the embodiment shown in FIG. 4 has a continuous convex groove track 402 and a concave groove track 403.
The two spiral groove tracks 404 are formed. Similar to the embodiment of FIG. 1, the convex groove tracks and the concave groove tracks are alternately repeated every one rotation of the optical recording medium. A spiral groove track of a book can be formed. In this case, since the tracking polarity is opposite between the convex groove track and the concave groove track, the polarity of the tracking control is automatically inverted every rotation of the optical recording medium, for example, every time sector 0 is detected. I just need. Needless to say, in the embodiment of FIG.
The number of sectors per round may be an odd number, and a concave groove track and a convex groove track may be switched for each sector.

Next, a convex groove track and a concave groove track are used.
The width of the loop will be described with reference to FIG. Figure 5 is light
Enlarged sectional view when the recording medium 501 is cut in the radial direction
To improve thermal sensitivity and improve heat dissipation
Of the dielectric film 505 to protect the recording material film 504.
A structure in which a reflective layer 506 made of aluminum or the like is further provided thereon
And That is, a convex groove track on one surface
509, the port where the concave groove track 510 is formed.
SiO 2 on a substrate 502 such as a carbonate resin _Two Invitation
The dielectric film 503, the recording material film 504, the dielectric film 505,
A reflective layer 506 and a protective layer 5
08 is bonded with an adhesive.

From the viewpoint of reproduction signal quality, it is desirable that the amount of light reflected from the convex groove track 509 is equal to the amount of light reflected from the concave groove track 510. To satisfy this condition, the width W1 of the convex groove track 509 and the width W2 of the concave groove track 510 may be made substantially equal.

However, when a material on which information is recorded by heat, such as a phase-change recording material, is used as the recording material, the convex groove track 509 and the concave groove track 5 are used.
The 10 width relationship requires recording considerations.

The thermal conductivity of the substrate 502 depends on the recording material film 50.
4. The thermal conductivity of the reflective layer 506 is smaller than that of the reflective layer 506 by an order of magnitude, and the thermal conductivity of the reflective layer 506 is larger than the thermal conductivity of the recording material film 504. Therefore, heat generated by the light beam irradiated on the convex groove track 509 or the concave groove track 510 is radiated through the reflection layer 506, the recording material film 504, or the dielectric films 503 and 505. As shown in FIG. 5, the concave groove track 510 is configured to be surrounded by the reflective layer 506 and the dielectric films 503 and 505, but the convex groove track 509 is not surrounded. Therefore, the optical recording medium 5
In the radial direction 01, the concave groove track 510 has better heat radiation than the convex groove track 509, and the sensitivity is reduced. It is desirable that the recording sensitivity of the convex groove track 509 and the concave groove track 510 be equal, and in order to equalize the heat radiation, the width W2 of the concave groove track 510 should be smaller than the width W1 of the convex groove track 509. Good.
Further, the convex groove track 509 and the concave groove track 51
In the case of detecting a track deviation by the push-pull method, the step d having a value of 0 has the best step d substantially at λ / (8n).
Here, λ is the wavelength of the light beam, and n is the refractive index of the substrate 501.

Some devices rotate the optical recording medium at a rotational speed inversely proportional to the radius so that the peripheral speed is constant, and other devices rotate so that the angular speed is constant. There is no problem when rotating so that the peripheral speed becomes constant, but when rotating so that the angular velocity becomes constant, it is necessary to consider the peripheral speed dependency. As described above, the phase-change recording material has the property of becoming crystalline when gradually cooled after being heated, and becomes amorphous when rapidly cooled after being melted, but the crystallization speed and the peripheral speed are closely related. . That is, it is necessary to increase the crystallization speed as the speed in the track direction between the light beam and the optical recording medium (referred to as linear speed) increases. For example, Te, S
In the case of a phase-change recording material containing b and Ge as main components, Sb
Increasing the amount of C will slow the crystallization rate. Therefore, in an optical recording medium used by rotating at a constant angular velocity,
If the recording material is formed such that the amount of Sb increases as the radius decreases, the peripheral speed dependency can be reduced.

The peripheral speed dependency can be reduced by changing the width of the groove track between the inner circumference and the outer circumference of the optical recording medium. For example, in the case of an optical recording medium in which the crystallization speed is set to be optimal for the linear velocity on the outer circumference and the information is recorded in the amorphous state as a recording mark, when information is recorded at a lower linear velocity on the inner circumference. In addition, it is less affected by the heat before and after the recording mark, whereby a cooling effect is generated, and the size of the amorphous recording mark is reduced. Accordingly, in this case, an amorphous mark having a predetermined size can be formed by increasing the width of the groove track on the inner circumference so that heat is easily radiated in the radial direction of the optical recording medium. Further, in the case of an optical recording medium in which the crystallization speed is set to be optimal for the linear velocity on the inner periphery, when information is recorded at a faster linear velocity on the outer periphery, a rapid cooling effect occurs due to the higher linear velocity, It is difficult to crystallize. In this case, if the width of the groove track on the outer periphery is narrowed so that heat is not easily dissipated in the radial direction of the optical recording medium, the erasure residue can be reduced. As described above, the peripheral speed dependency can be reduced by changing the width of the groove track according to the radius of the optical recording medium.

Although the present invention has been described in detail, the present invention is not limited by the above-described embodiments. For example, a magneto-optical material may be used as the optical recording material without any problem.

[0041]

According to the optical recording medium of the present invention, one spiral groove track is formed by alternately arranging the convex groove tracks and the concave groove tracks, and the convex groove tracks and the concave grooves are formed. Since track identification information is provided at the beginning of the track to identify that the track type is switched, the boundary between the convex groove track and the concave groove track can be detected based on the identification information, and the recording / reproduction conditions can be switched. Alternatively, the polarity of the tracking control can be easily switched. Further, since the track width can be increased even if the track pitch is reduced, the manufacture of the optical recording medium is simplified.

Further, in the optical recording medium of the present invention, since the width of the concave groove track is smaller than the width of the convex groove track, the heat radiation conditions of the concave groove track and the convex groove track are almost equal. Thus, high-quality information can be easily recorded on both the convex and concave groove tracks. Also,
In the optical recording medium of the present invention, since the identification information for identifying the recording area is provided substantially on the boundary between the concave groove track and the convex groove track, the width of the identification information can be increased, and the cutting can be performed. The configuration of the machine is simplified, and the crosstalk between adjacent identification information can be reduced, so that the identification information can be easily read.

[Brief description of the drawings]

FIG. 1A is a schematic front view of an optical recording medium according to a first embodiment of the present invention. FIG. 1B is a partially enlarged view of the surface of the optical recording medium according to the first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the optical recording medium according to the first embodiment of the present invention.

FIG. 3A is a schematic front view of an optical recording medium according to a second embodiment of the present invention; FIG. 3B is a partially enlarged view of the surface of the optical recording medium according to the second embodiment of the present invention;

FIG. 4A is a schematic front view of an optical recording medium according to a third embodiment of the present invention, and FIG. 4B is a partially enlarged view of the surface of the optical recording medium according to the third embodiment of the present invention.

FIG. 5 is an enlarged cross-sectional view for explaining a width and a step of a groove track of the optical recording medium.

FIG. 6 is a block diagram of an apparatus suitable for the optical recording medium according to the first embodiment of the present invention.

FIG. 7 is an explanatory diagram of a light beam irradiation light amount when information is recorded on a phase change recording medium.

[Explanation of symbols]

 Reference Signs List 101 optical recording medium 102 groove track 103 switch detection area 104 information area 105 convex groove track 106 concave groove track 107 center of groove track 108 pit

Claims (5)

[Claims] 1. A disk-shaped optical recording medium in which one spiral groove track is formed in which a convex groove track and a concave groove track are alternately arranged for each circumference. Track identification information for identifying whether the groove track is the convex groove track or the concave groove track is recorded at the head of each of the groove grooves and the concave groove tracks, Using a predetermined sector as the track identification information,
Optical recording medium. 2. The apparatus according to claim 1, wherein the identification information is arranged so that a center of the identification information for identifying a recording area is located between a center of the concave groove track and a center of the convex groove track. The optical recording medium according to claim 1, wherein: 3. The optical recording medium according to claim 2, wherein a width of said identification information is substantially equal to said convex groove track width or said concave groove track width. 4. The width of the identification information is wider than the convex groove track width or the concave groove track width, and
3. The optical recording medium according to claim 2, wherein the sum of the convex groove track width and the concave groove track width is 80% or less. 5. A tracking control device for performing tracking control so that a light beam converged on an optical recording medium according to claim 1 is positioned on a groove track, wherein the tracking control apparatus is recorded on the optical recording medium. An identification circuit that identifies whether the groove track is the convex groove track or the concave groove track based on the track identification information, and performs tracking control in accordance with a signal output from the identification circuit. A tracking control device, comprising: a polarity switching circuit for switching polarity.