KR100293595B1 - Optical recording mdium and method for manufacturing for the same - Google Patents

Abstract

PURPOSE: An optical recording medium and a method for manufacturing for the same are provided to suppress the tracking offset to a value or level which is sufficiently low for the practical use and permit efficient disposition of address data even when recording is effected on both the groove and the land. CONSTITUTION: An optical reproducing method using an optical recording medium having an aligned prepit portion straddled on a plurality of tracks in a radial direction;wherein the prepit portion includes first and second prepit portions divided in a track direction; wherein a prepit of the respective first and second prepit portions is arranged on a boundary of the respective tracks; wherein the first prepit portion has an address information prepit and a synchronous information prepit; wherein the second prepit portion has a synchronous information prepit; wherein the prepit of the first prepit portion and the prepit of the second prepit portion are arranged with one track displaced in the radial direction; and wherein a trailing end of an edge prepit of the first prepit portion is aligned in the radial direction; the method comprising the steps of: irradiating an optical spot on the optical recording medium; detecting a reflected beam from the optical recording medium; and reproducing information on the optical recording medium by using a signal obtained by the reflected beam.

Description

OPTICAL RECORDING MEDIUM AND MANUFACTURING METHOD THEREOF

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium, and more particularly to a high density optical recording medium having a track width smaller than the optical spot diameter.

As an example of a medium for performing high density (narrow track) recording, there is disclosed, for example, in JP-A-6-176404. According to this example, in an optical information recording medium having grooves and lands (between grooves) formed on a substrate and information recording areas formed on both of the grooves and lands, on the boundary virtual extension line between the grooves and lands; Prepits are arranged. In particular, the said prepit exists only in one side of arbitrary characteristic positions (place) of the center line of each groove part.

In this structure, the recording information is recorded in both the groove portion and the land portion, while leaving the address information indicating the recording area to the prepit, and sharing address information for a pair of the groove portion and the land portion adjacent to one prepit. have. When the above technique is applied to a phase change type recording medium or a magneto-optical recording medium, the information of adjacent grooves or lands is not mixed due to the optical interference effect in the optical spot (because the interference or leakage prevention can be prevented). Narrow tracks can be achieved.

On the other hand, in the prepit area, since the optical interference effect is eliminated, the effective track pitch is increased and crosstalk (crosstalk) is reduced by sharing address information on the pair of groove portions and land portions.

However, in the example of Japanese Patent Laid-Open Publication No. Hei 6-176404, since the prepit area is disposed to be offset (offset) from the center line of the groove portion or the land portion, the following shift occurs when the light spot follows the groove portion or the land portion. It was difficult to perform high density recording in which (track offset) was increased to narrow the track pitch.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the first object of the present invention is to suppress the track offset to a sufficiently low value or level in practical use even when recording is performed on both the groove portion and the land portion. An optical recording medium capable of efficiently arranging address information is provided.

A second object of the present invention is to provide a high-density optical recording medium capable of demodulation even when a lead error occurs by ensuring simple mastering and easy replica production.

1 is an enlarged partial plan view of Embodiment 1 of an optical recording medium according to the present invention;

2 is a waveform diagram reproduced from the medium of FIG.

3 is a block diagram of a recording / reproducing apparatus of an optical recording medium used in the present invention;

4 is an enlarged partial plan view of Embodiment 2 of an optical recording medium according to the present invention;

5 is a partially enlarged plan view of Embodiment 3 of an optical recording medium according to the present invention;

6 is an enlarged partial plan view of Embodiment 4 of an optical recording medium according to the present invention;

7 is a waveform diagram of a signal reproduced from the optical recording medium of FIG.

7 is an enlarged partial plan view of Embodiment 5 of an optical recording medium according to the present invention;

9 shows an information structure in Embodiment 5 of an optical recording medium according to the present invention;

10 is an enlarged partial perspective view of the prepit and the groove in Example 5;

11 is an enlarged partial plan view showing a detailed positional displacement in an embodiment of an optical recording medium according to the present invention;

12 is an enlarged partial plan view of Embodiment 6 of an optical recording medium according to the present invention;

FIG. 13 shows an example of a modulated code in Embodiment 6 of an optical recording medium according to the present invention.

In order to achieve the above-mentioned first object, the following means was used.

[1] A groove portion and a land portion are formed on a substrate of the recording medium, an information recording area is formed on both the groove portion and the land portion, and prepits are disposed on the virtual extension line of the groove portion and the land portion.

The prepits are arranged to satisfy the following conditions (a)-(c) simultaneously.

(a) The prepits are located on both sides of the virtual extension line of the groove centerline.

(b) The prepits are located on both sides of the virtual extension line of the land center line,

(c) The prepit is absent on either side of any particular location of the centerline of the groove.

(d) The prepits are not present on both sides of any particular place of the land portion.

In such a structure, since the prepits are not disposed to one side with respect to the virtual extension line of the center line of the groove portion or the land portion, a track offset is less likely to occur, and at the same time both at any particular place of the center line of the groove portion or the land portion Since no prepit exists in the reproduction spot, prepit information of adjacent tracks is prevented from interfering with (interfering with) the high density narrow track recording.

[2] When the prepit is arranged in the circumferential direction without distinguishing one side from the other side (left and right) of the groove portion or not distinguishing one side from the other side of the land portion, at least continuous prepits to the groove portion or land portion The two sets are different from each other and the prepits are periodically arranged in two sets.

Or [3] a groove portion having at least one pair of pits arranged on both sides of the center line of the groove portion of the prepit area and an adjacent groove portion not having pits arranged on both sides of the center line of the groove portion of the prepit area in the radial direction. Alternately arranged.

This makes it possible to distinguish whether the prepit is in the groove portion or the land portion by simply reproducing the prepit, thereby improving the reliability of information recording and reproducing.

[4] One of the synchronization information and the address information is represented by a prepit disposed on either side of the groove (left and right).

Or [5] only one of the synchronization information and the address information is represented by the prepit disposed on either side of the groove portion, and both the synchronization information and the address information are represented by the prepit disposed on the other side of the groove portion.

As a result, the address information can be reproduced with reliable synchronization. In addition, the phase margin between both prepits is enlarged, thereby facilitating the manufacture of the recording medium.

[6] The depths of the grooves and the prepits were the same, and the groove depths were 70 nm or less. More preferably, the groove depth is 40 nm or more and 60 nm or less.

With such a structure, an appropriate crosstalk cancellation (crosstalk cancellation) effect is obtained between the groove portion and the land portion, and a good tracking servo signal is obtained. Therefore, the forming and manufacturing of the recording medium can be facilitated. Here, when the groove depth exceeds 70 nm, it is difficult to form the groove. In addition, when the groove depth is about 50 nm, the tracking servo becomes maximum, and even if the groove depth is about 50 nm ± 10 nm, substantially equivalent effects are obtained.

[7] The widths of the groove portions and the land portions are set to be substantially the same, and the width is set between 0.3 µm and 0.7 µm.

This structure makes it possible to achieve both good tracking and high density recording.

If the width of the groove portion and land portion is less than 0.3 µm, two pairs of groove portions and land portions enter simultaneously in one light spot, and a good tracking signal cannot be obtained. In addition, when the width of the groove portion and land portion exceeds 0.7 m, efficient (effective) high density recording cannot be performed.

[8] The diameter of the smallest of the prepits was made smaller than the width of each of the groove portion and the land portion. More preferably, the diameter is in the range of 0.25 μm to 0.55 μm.

As a result, a good prepit signal can be obtained without crosstalk. This is because when the diameter is less than 0.25 µm, the prefinite signal is extremely reduced, and when the diameter exceeds 0.55 µm, crosstalk occurs.

In the present invention, the prepits are arranged on both sides of the virtual extension line of the center line of the groove portion or the land portion in the light spot scanning direction. As a result, the offset (offset) is reduced, making track offset less likely to occur, and at the same time, the prepit information of adjacent tracks in the playback spot is not present at the same time on both sides of any particular place of the center line of the groove portion or the land portion. Since mixing is prevented, high density narrow track recording can be realized.

In addition, even if there is a track offset, the amount of track offset can be accurately detected by comparing the amplitudes of the signals indicated by both (left and right) prepits. Therefore, the track offset can be suppressed by feedback control of the information indicated by the comparison result to the scanning apparatus.

On the other hand, when one prepit column on the boundary virtual extension line between the groove portion and the land portion is shifted to the prepit column on the adjacent virtual extension line, between the groove portion and the prepit region, between the land portion and the prepit region or between the prepit region. The gap is formed in the part. However, the above-described Japanese Patent Laid-Open Publication No. Hei 6-176404 does not take this interval into account. Therefore, when there is no gap or the gap is very short, the mastering of the substrate cannot be processed by one beam cutting, so two beam cutting is required. In addition, in the production of replicas, injection must be performed on steep patterns, leading to a decrease in manufacturing efficiency. In addition, when the signal is reproduced, the tolerance of the distortion of the reproduction spot and the track offset become small, and lead errors are likely to occur.

In order to achieve the above-mentioned second object, the following means was used.

[1] A groove portion and a land portion are formed on the substrate, and prepits are disposed on a virtual extension line between the groove portion and the land portion. In particular, since this prepit is disposed on both sides of the extension line from the center line of the groove portion or the land portion, it is necessary to move the optical axis of the laser beam during cutting. AOD (acoustic optical deflector) is used to change the optical axis. However, since AOD takes a long time to transmit to the desired optical axis position after transmitting a signal for changing the optical axis, if the modulated laser beam is irradiated along the original optical axis as it is, the pits are formed obliquely on the substrate. Therefore, it is assumed that there is nothing in the format between the groove portion or the land portion and the next (following) prepit, while the AOM (acoustic optical modulator) is turned off without irradiating the laser and drawing the pit. Thereby, a board | substrate can be manufactured with a simple cutting machine (cutting machine). In addition, since a large number of irregularities (nonuniformities) are not formed in a narrow area on the substrate, the manufacturing efficiency (efficiency) at the time of replica creation is improved.

[2] The prepits are arranged on the virtual extension line between the groove and the land part, but the arrangement of one prepit row on the virtual extension line between the groove part and the land part is based on the arrangement of the prepit rows on the other side or vice versa. When changed, the trailing edges of each one of the prepit rows are aligned (matched) with each other in the radial direction of the substrate. Subsequent pit rows are spaced from these end positions in the circumferential direction or the recording / reproducing direction, and the ends of the subsequent pit rows are likewise aligned with each other. If the formed gap is made to comply with the recording rules, the format of the entire substrate can be solved without any problems, and the part without pit can be secured by collecting in a specific area on the substrate, so that the above-described cutting (cutting) and The problem of replica production can be solved.

[3] In the pit rows adjacent to each other, only pits having original information cannot radially align ends. Therefore, by adding a new pit, it is possible to align the ends in the radial direction while complying with the rules at the time of recording.

[4] As described in [2] above, when changing the pit row placement from one side to the other, the leading edge of the pit can be radially aligned in the other arrangement. For the same reason as described, the problem with regard to cutting and replicating can be solved. Particularly, in view of signal reproduction, a synchronous signal is assigned to the pit information immediately after the pit string is changed (moved), and the tolerance of the start position can be increased by focusing only on the determination of the channel bit at the specific position. The read error of important data such as the address immediately before the pit row is changed can be reduced.

Example 1 (optical recording medium)

1, which is a partially enlarged plan view of an optical recording medium of the present invention.

In the radial direction of the recording medium, each groove portion 84 having a width of 0.6 mu m and a depth of 50 nm and each land portion (groove portion 85) having a width of 0.6 mu m are alternately arranged, and both regions thereof. The recording mark 81 is formed in the mark. That is, each of the groove portion 84 and the land portion 85 functions as a recording area. No groove is formed in the prepit 83, but the pit 82 is arranged on an extension line of the boundary between the land portion and the groove portion. Each pit has a width of 0.35 μm and a depth of 50 nm. The pit area is divided into a first prepit area 831 and a second prepit area 832. In the first prepit area 83l, the pit 82 is disposed above the center line of the land part 85 in the drawing, and in the second prepit area 832, the pit 82 is the land part ( It is arrange | positioned below in the figure with respect to the center line of 85). For this reason, when the light spot 21 scans the land part 85, for example, only one pit is always reproduced and there is no possibility that crosstalk from adjacent tracks may occur. Therefore, the address information recorded in the prepit format can be satisfactorily reproduced without crosstalk.

In addition, since the pit 82 does not adjoin each other in the radial direction, shaping becomes easy. In addition, since the pits 82 are equally arranged on both tracks (grooves or lands), the influence on the generated tracking servo signal is canceled by the pits 82.

Therefore, the track offset can be suppressed sufficiently small.

For example, when the land portion 85 is reproduced, the address information of the first prepit area 831 and the address information of the second prepit area 832 are continuously reproduced. For this reason, if the information is arranged so that these two areas add up to become address information for one track, the addresses (track numbers) of the land portion and the groove portion can be set independently of each other. In other words, by continuously reproducing the address information in the first and second prepit areas 831 and 832, it is possible to ensure the identification of the land portion and the groove portion. Specifically, when reproducing the groove portion, the address information displayed by the prepit disposed in the first prepit area is arranged to be the same as the address information displayed by the prepit disposed in the second prepit area. When the land portion is reproduced, the address information displayed by the prepits arranged in the first prepit area is arranged to be different from the address information displayed by the prepits arranged in the second prepit area. Even when the addresses indicated by the prepits in the first and second prepit areas are different from each other, there is a correlation between the two addresses, so that the efficiency of the error correction code can be improved by using this correlation. .

Preferably, the synchronization information (VFO) 86 and the address information 87 are preferably arranged in each of the first and second prepit areas.

In this embodiment, the prepit area is divided into first and second prepit areas, but may be divided into a plurality of areas. For example, when the number of divisions is four, the pits of the first and third prepit regions may be arranged on one side of the groove portion, and the pits of the second and fourth prepit regions may be arranged on the other side of the groove portion. By increasing the number of divisions of the prepit area, reliability against defects and the like can be improved.

Here, an image recording material (GeSbTe) was used as the recording film. Thus, the recording mark is formed in the form of an amorphous region (domain).

Hereinafter, a configuration example in which the optical recording medium of the present invention is applied to an optical recording / reproducing apparatus will be described with reference to FIG. In this apparatus, a semiconductor laser having a wavelength of 680 nm and a sighting lance were used as the light source 31. If necessary, beam shaping means such as a prism may be provided. The intensity of the semiconductor laser is controlled by an optical power (light intensity) controller 7l having an automatic light intensity control function. The light beam 22 emitted from the light source 31 is focused (condensed) on the magneto-optical recording medium 8 by the focusing optical system 32. The focusing optical system 32 is composed of at least one lens, and in this embodiment, a beam splitter is also provided. The objective lens for focusing the light beam on the magneto-optical recording medium 8 has an aperture ratio of 0.6. For this reason, the light spot 21 on the magneto-optical recording medium 8 has a diameter of 10 탆. The optical spot-on scanning device 6 can be moved to a desired position on the magneto-optical recording medium 8. In this embodiment, the scanning device 6 is provided with a motor 62 for rotating the disk-shaped optical recording medium 8 and automatic position control means 61 having functions of auto focus control and auto tracking. The automatic position control means 61 executes feedback control to detect the light spot position in the photodetector 33 using the empty light 23 from the optical recording medium 8. The detection of the light spot position is performed by detecting the diffraction light intensity from the groove portion. The photodetector 33 is composed of a lens, a beam splitter, a plurality of photodetectors, and the like. The output signals of the plurality of photodetectors generate reproduction signals and servo signals by calculation.

By using the optical recording medium as shown in Fig. 1, a signal 14 as shown in Fig. 2 is obtained as a prepit signal. Address information is demodulated by inputting this signal to the address detecting apparatus, and at the same time, signal timings of the first and second prepit areas are detected and the first prepit area and the second prepit area according to the timing information. The amplitude of the mean (maximum amplitude) is calculated. The amplitudes thus stored are compared with each other by an amplitude comparator and fed back to the position shifting device (scanning device) as track offset information. In Fig. 2, the magneto-optical reproduction signal 11 and the corresponding prepit signal 14 (upper part in the figure) are generated when the light spot scans the groove portion, and the magneto-optical magnetism is generated when the light spot scans the land portion. The reproduction signal 12 and the corresponding prepit signal 14 (lower in the figure) are generated. In this embodiment, since the light spot is slightly offset as shown in Fig. 1, the amplitude between the prepit signal of the first prepit area 831 and the pypitpit signal of the second prepit area 832 is reduced. The car 13 is occurring. This amplitude difference corresponds to the amount of track offset.

By using the apparatus of FIG. 3, even when various disturbances such as aberrations of light spots are taken into consideration, the track offset can be reduced to ± 0.03 µm or less. In the nominal state with no spot aberration, the track offset was less than ± 0.015 μm.

As described above, in the present invention, the prepits are arranged on both sides of the virtual extension line of the center line of the groove portion or the land portion, as shown in FIG. For this reason, the offset (offset) is reduced, and track offset is less likely to occur. In addition, since both prepits are not present at the same time on both of the center line of the groove portion or the land portion, the prepit information of adjacent tracks is not mixed in the playback spot, so that high density narrow track recording can be performed. Will be.

Also, as shown in Fig. 2, even when a track offset occurs, the amount of track offset can be accurately detected by comparing the signal amplitudes of the prepits located at both (left and right) sides. Therefore, the track offset can be suppressed by feedback control of the information indicating the comparison result with the scanning apparatus.

In addition, it is possible to easily distinguish between the groove portion and the land portion.

By using the optical recording medium of the present invention, not only the track offset can be suppressed to a practically small level (0.03 µm or less), but also address information can be easily obtained even at high density narrow track recording. By using the optical recording / reproducing apparatus of the present invention, the track offset can be easily reduced by feedback control.

Example 2

Embodiment 2 of the present invention will be described with reference to FIG. The difference between the medium of the present embodiment and the first embodiment is that the synchronization information pits 861 to the upper side of the center lines of the grooves 841, 842, 843, 844, and 845 (as seen in the drawing). Only 864 is disposed, and both synchronization information pits 861 to 864 and address information pits 871 to 874 are disposed below the center line of each groove 84 (as seen in the drawing). have. The information feet 861-864 and the address information feet 871-874 for synchronization are preferably arranged in succession. In the case of the land part 85, the relationship of the upper side and the lower side is reversed.

In the present embodiment, unlike in the first embodiment, since the address information is disposed only on one side of the groove portion or the center line of the land portion or above, the same address information is assigned to the land portion and the groove portion. In this embodiment, the prepit areas 831 to 834 are divided into four to improve the reliability of the prepit areas, but the prepit areas are not divided into shapes. In this embodiment, the second to fourth portions are considered by considering the effect of aliasing of the signal after passing the synchronous pit 861 in the first prepit area 831 through the low pass filter (low frequency filter). It is designed to have a length longer than the synchronous feet in the prepit area. It is preferable in the manufacture of the medium that a space of 0.5 m or more is spaced from each other between the pit disposed on the upper side and the pit disposed on the lower side. More preferably, they are spaced apart by a distance of about 1 m, which is the diameter of the reproduction optical disk spot.

Example 3

Embodiment 3 in which the identification mark 88 is used to distinguish the groove portion and the land portion will be described with reference to FIG. In this embodiment, an identification mark 88 for distinguishing the groove portion and the land portion is provided separately from the prepit area in the first or second embodiment.

In this embodiment, a pair of pits (identification marks) 88 are disposed above and below the center line of the grooves 841, 843, or 845 (as seen in the drawing), and the grooves 842 ) Or 844, the pit is not arranged. When the medium on which the identification mark is placed is reproduced, the case where the light spot moves relatively from left to right in the drawing, and the identification mark is indicated (shown) by the light spot is shown. Indicated by "no", the groove portion 841 is referred to as "yes, no", the land portion 851 is kept "no, nothing", and the groove portion 842 is kept "no, nothing" and the land In the section 852, " yes, nothing " In addition, the groove portion 843 is maintained as "Y, Y", the land portion 853 is maintained as "N, Y", and in the groove 844, it is maintained as "N, Y", and the land portion 854 is maintained. In "Yes, nothing" is kept. That is, in the groove portion, one of "Y, Y" and "N, N" is maintained, and in the land portion, "N, Y" and "Y, N" are maintained. Therefore, by using this, identification of the groove portion and the land portion can be performed in accordance with the reproduction signal. In order to secure the reliability, it is preferable to provide several pairs of pit for the identification mark, and the pair of pit (feet between each other) in the information track direction or the circumferential direction of the medium perpendicular to the radial direction is separated by several μm or more. It is more preferable to arrange so that. For example, the prepit area and the identification mark area of the above-described embodiment may be alternately arranged in the circumferential direction.

Example 4

An optical recording medium according to Embodiment 4 of the present invention will be described with reference to FIG. 0.5 μm wide and 40 nm deep grooves and 0.5 μm wide lands 85 are alternately arranged, and recording marks 81 are formed in the two kinds of regions (grooves and lands). That is, both the groove portion 84 and the land portion 85 function as recording regions. The groove portion is not formed in the prepit area 83, and a substantially circular pit 82 (0.3 μm in diameter and 40 nm in depth) is disposed on the boundary extending line between the land portion and the groove portion. This prepit area is divided into a VFO (variable frequency oscillation) area 833 and an address area 834. In particular, in the VFO region, the pits 82 are alternately arranged on the upper side and the lower side of the land center 85 blade center line. In the address area, the pits 82 are alternately arranged at the same period as the VFO. Therefore, pit does not exist at the same time in both the same place of the center line of a land part or a groove part.

Incidentally, in the address area, data for a specific track is coded so as to differ by one foot from data for an adjacent track. That is, the data takes the form of gray codes. With this configuration, for example, when the light spot 21 scans the land portion 85, only one pit is always reproduced, and there is no fear of crosstalk from adjacent tracks. Therefore, the address information disposed in the prepit can be reproduced satisfactorily without crosstalk. In addition, since the pits 82 are not adjacent to each other, this can be easily molded. Further, since the pits 82 are equally arranged on both sides of the track (land or groove), the influence on the tracking servo signal generated by the pits 82 can be canceled out. Therefore, the track offset can be suppressed to the minimum.

When the medium of the embodiment of Fig. 6 is reproduced by the apparatus of Fig. 3, since it is generated in the reproduction signal prepit area 83 as shown in Fig. 7 showing that different data is obtained for each track, it is efficiently and efficiently used as the address information. It is being recorded. In addition, since gray codes are used, addresses can be reproduced even during intertrack access, which is suitable for high-speed access. In addition, since gray codes are used, errors are unlikely to occur even when crosstalk exists, which is suitable for narrow tracking.

Example 5

An optical recording medium according to Embodiment 5 of the present invention will be described with reference to FIG. A groove portion 84 having a width of 0.7 μm and a depth of 70 nm and a land portion 85 having a width of 0.7 μm are alternately arranged in a radial direction, and two kinds of regions (groove and land portion) can form a recording mark. It functions as an information track.

That is, both the groove portion 84 and the land portion 85 function as recording regions. No groove is formed in the prepit area 83, and the pit 82 is disposed on the boundary extending line between the land portion and the groove portion. The prepit area is divided into radially aligned bands (zones) over about 1800 information tracks, or 900 grooves.

This band is arranged concentrically throughout the disk, and has a total of 24 bands in the case of a disk having a radius of 30 mm to 60 mm. That is, in each band, the number of prepits detected per revolution, i.e., the number of sectors, is constant, and the number of sectors is larger in the outer band than the inner band of the disc.

An example of the structure of each sector 41 is shown in FIG. The sector 41 has a prepit area 83 at the head of the data recording area.

As shown in FIG. 8, the prepit area is divided into a first prepit area 831 and a second prepit area 832. In the first prepit area 831, the pit 82 is disposed above the center line of the land portion 85 (as seen in the drawing), and in the second prepit area 832, the pit 82 is land. It is arrange | positioned below the center line of the part 85. FIG. For this reason, when the light spot 21 scans the land part 85, for example, only one pit is always reproduced and there is no fear of crosstalk from the in-point track. Therefore, the address information assigned to the prepit can be reproduced without crosstalk. The address information represented by the prepit is written in the form of a 1-7 modulation code (channel bit length 0.2 mu m) in this example. In other words, the prerecording density is 0.3 탆 / bit.

The relationship between the groove portion and the prepit area of the present invention will be described with reference to FIG. 10, which is a partial cross-sectional perspective view.

In this embodiment, the gap regions 87 are provided at intervals of about 10 μm before and after the first and second prepit regions 831 and 832. In this embodiment, data is recorded according to the 1-7 recording method, so the gap length corresponds to a length of about 5 channel bits. This five channel bit length is the exact intermediate length between the longest mark length (eight channel bit length) and the shortest mark length (two channel bit length). For this reason, the length of the gap area between the first and second prepit areas when the gap is regenerated may be changed in the shape of the pit and the position of the pit when the pit is formed, the shape of the light spot and the change in the dice (servo offset), etc. Even if it is generated, since it is reproduced with the length between the shortest mark length and the longest mark length, very high reliability can be ensured. In this embodiment, the sum of the positional variation of these marks is designed to be suppressed to 0.6 µm (three channel bit length) or less even in the worst case, so that the effective (during playback) length is two channel bits, the longest in the shortest length. Since the length is 8 channel bits in length, no problem occurs during playback in accordance with the rules of 1-7 modulation codes. If the detection bit is longer than the eight-channel bit length, it is not preferable because the detection bit is confused with a special synchronization pattern such as a recording address mark.

In the case where one detection bit becomes shorter than the length of two channel bits, it becomes a micromark below the resolution of the reproduction light spot and cannot be detected. Therefore, as in the present embodiment, it is preferable to suppress the gap length to the middle between the longest mark length and the shortest mark length.

Depending on the specifications (characteristics) of the pit forming apparatus, variations in the mark position can be suppressed to less than one channel bit length. In this case, it is desirable to suppress the nominal gap length to 3 to 7 channel bit lengths, but the pit forming apparatus for this purpose is expensive. In addition, since the possibility of receiving a signal error also increases in track offset during reproduction, etc., it is preferable to have a gap length at an exact intermediate length between the longest mark length and the shortest mark length allowed for the recording method as described above.

In this embodiment, since the pits 82 are equally arranged on both sides of the center line of the tracks (grooves or lands), the influence on the tracking servo signals generated by the pits 82 can be canceled out. Therefore, the track offset can be suppressed to a sufficiently small level. For example, when the land portion 85 is reproduced, address information of the first prepit area 831 and address information of the second prepit area 832 are continuously reproduced. For this reason, when these two areas are totally provided in one area where the information is arranged, and the address information for one track is provided, the address of the home part and the address (track number) of the land part can be set independently of each other. That is, the land portion and the groove portion can be identified by continuously reproducing the address information of the first and second prepit areas 831 and 832.

Specifically, when reproducing the groove portion, the information is arranged so that the address information indicated by the prepit arranged in the first prepit area and the address information indicated by the prepit arranged in the second prepit area are the same. When the land portion is reproduced, the information is arranged so that the address information indicated by the prepit in the first prepit area and the address information indicated by the prepit in the second prepit area are different. Even when the addresses indicated by the prepits in the first and second prepit areas are different from each other, there is a correlation between these two addresses, so that the efficiency of the error correction code can be increased by using the correlation. .

Preferably, both the information VFO 86 and the address information 87 for synchronization are arranged in each of the first and second prepit areas.

In this embodiment, the case where the prepit area is divided into two of the first and second prepit areas has been described, but may be divided into a plurality of areas. For example, as shown in Fig. 5, when the number of divisions is four, the pits in the first and third prepit areas are arranged on one side of the groove portion, and the pits in the second and fourth prepit areas are arranged on the other side of the groove portion. Place it. By increasing the number of divisions of the prepit area, reliability against defects and the like can be improved.

Here, a phase change recording material (GeSbTe) was used as the recording film. Thus, the recording mark is formed in the form of an amorphous region (domain).

Referring to Fig. 11, the position displacement amount 963 between the prepit regions of adjacent tracks of the medium, the position displacement amount 961 between the prepits of adjacent tracks, and the position displacement amount 962 between the groove portions of the adjacent tracks will be described in more detail. In actual media, the pit may sometimes be displaced (displaced) between adjacent tracks due to various causes during pit formation. These positional displacement amounts 961, 962, and 963 effectively increase or decrease the length of the gap regions 86, 87.

In addition to the above-described position displacement amount, the position of the reproduction signal also changes due to various variations (aberration, servo error, etc.) during reproduction. Because of this, positional displacement sometimes causes serious problems. However, in the present invention, since the nominal (nominal) length of the gap region is set to an intermediate length between the shortest mark length and the longest mark length based on the 1-7 modulated code, the positional displacement amount is allowable up to ± 0.6 μm. .

The optical recording medium shown in Fig. 8 can be reproduced by the apparatus shown in Fig. 3 in the same manner as described in connection with Embodiment 1, and the track offset can be reduced to ± 0.3 μm or less even in consideration of various disturbances such as optical aberration. There is an advantage that it can be reduced to ± 0.015μm or less, especially under nominal state without optical aberration.

Example 6

In the embodiment of Fig. 8, the 1-7 modulation code method is used as the recording modulation coding method. In this embodiment, an 8-14 modulation (EFM) system recording method is used. The channel bit length is about 0.2 μm. In this recording method, the shortest mark length is 3 channel bits and the longest microphone length is 11 channel bits. In reality, there are also marks having a length of 12 channel bits or more, but the use thereof is limited to a special use such as a synchronization pattern. Therefore, it should be avoided to include patterns in the data that might be confused with these special patterns. The arrangement of the prepit region, the groove portion and the land portion is the same as that of the fifth embodiment of FIG. 8 except for the following. That is, it is arrange | positioned as shown in FIG. 10, In particular, each groove part and each land part has a width of 0.75 micrometer, and each groove part and each prepit part have a depth of 0.075 micrometer.

In this embodiment, the prepit region and the groove portion are arranged as shown in FIG. Four prepit areas 831, 832, 833, and 834 are allocated (arranged) to the head of one sector. Further, in each pit area, a VFO area for synchronizing with a reproduction signal and an address area in which address information of tracks or sectors are recorded are successively arranged. Further, not only the start position of the pit but also the end position were arranged so as to be aligned almost radially, and a gap region 86 was provided between the end portion of the groove portion and the start end of the pit region. Similarly, gap regions 87, 88, and 89 are provided between adjacent prepit regions.

As described above, the positional displacement between the start position of the pit and the start position of the subsequent pit is described in FIG. If there is a displacement (deviation) as shown in FIG. 11, the gap region 86 is shortened or lengthened effectively as in the fifth embodiment of FIG. In order to align the ends of the pit of the end portions of the prepit areas 831, 832 and 833 in the radial direction, an additional pit pattern 110 as shown in Fig. 13 was used. The additional pattern is selected from four formats (a), (b), (c), and (d) according to the previous data. This makes it possible to align the end 99 of the pit of the end part at the same position at all times without depending on the previous data, and to limit the gap length and the pit length based on the modulation code. This makes it possible to set the gap area between the subsequent prepit area 120 and the end position 99 of the pit of the end portion to be the intermediate length between the longest mark length and the longest mark length based on the modulation code. Similarly, the margins during prepit molding and regeneration are greatly expanded.

In the above embodiment, the phase change type recording material has been described as the medium, but of course, other materials that can achieve the advantages of the present invention can be used. For example, a magneto-optical recording film may be used as the recording film. In addition, although the modulation code was demonstrated as 2-7 and 8/9 code, the form which extended the above-mentioned EFM may be sufficient.

According to the present invention, in an optical recording medium having a land portion and a groove portion, a substrate can be manufactured by a simple mastering device and a replica can be easily produced. As a result, it is possible to secure a sufficiently large medium production margin and lead margin for practical use. There is a number. For this reason, an inexpensive and high density optical recording medium can be provided.

Claims (6)

An optical recording medium having a prepit portion radially aligned over several tracks, The prepit part has first and second prepit parts divided in a track direction and arranged on a boundary line between tracks of the tracks. The first and second prepit portions respectively have address information prepits arranged in two track pitches in a radial direction, and the address information prepits of the first prepit portion and the address information prepits of the second prepit portion are radial directions. One track apart, And an end of the pit of the end of the first prepit portion is aligned in a radial direction. The method of claim 1, And an additional pit pattern at a rear end of said first prepit portion. The method of claim 2, The additional pit pattern is prepared in four kinds and is selected according to previous data. A method of manufacturing an optical recording medium, the method comprising forming a prepit portion radially aligned over several tracks of the optical recording medium. The first and second prepit portions of the prepit portion divided in the track direction are arranged on the boundary line between the tracks of the tracks, The address information prepits of the first and second prepit portions are respectively arranged at two track pitches in the radial direction, and the address information prepits of the first prepit portion and the address information prepits of the second prepit portion are radially arranged. Place one track off And an end of the pit of the end of the first prepit part is aligned in the radial direction. The method of claim 4, wherein And adding an additional pit pattern at the rear end of said first prepit portion such that the ends of said pit are aligned in the radial direction. The method of claim 5, 4. A method for manufacturing an optical recording medium, characterized in that four kinds of additional pit patterns are prepared and selected according to previous data.

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