JP2004319068A - Information recording method, information recording medium, and information recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information recording method in which an overwrite property, especially, an archival overwrite property in which the information is overwritten after a medium is stored for a fixed time in a high temperature environment is good in high speed recording, and to provide an information recording medium and an information recording device. <P>SOLUTION: In an information recording method, a random pattern is overwritten with the light of scheduled recording power and various erasing power, the random pattern is reproduced, the minimum value Pb1 and the maximum value Pb2 of the erasing power when reproduction jitter erases the pattern exceeding the prescribed threshold value are obtained, optimum erasing power Pb is obtained from the minimum value PB1, the maximum value Pb2, and relational expression expressed by Pb=α×Pb1+(1-α)×Pb2, and information is recorded using obtained optimum erasing power Pb. An α value is previously recorded in an information recording medium, a Pb calculation control part of the information recording device reads out the α value when the optimum erasing power Pb is decided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an information recording method and an information recording medium capable of recording information by irradiating a laser beam. More specifically, an information recording method, an information recording medium, and an information recording apparatus capable of improving an overwrite characteristic in high-speed recording, particularly, an archival overwrite characteristic in which a medium is stored in a high-temperature environment for a certain period of time and then information is overwritten. Related.

  In recent years, the market for read-only optical disks such as DVD-ROMs and DVD-Videos has been expanding. In addition, rewritable DVDs such as DVD-RAM, DVD-RW, and DVD + RW have been put on the market, and the market is expanding as a backup medium for computers and a video recording medium instead of a VTR. Further, in recent years, market demands for improving transfer rates and access speeds of recordable DVDs have been increasing.

  In a recordable DVD medium such as a DVD-RAM and a DVD-RW, which is recordable and erasable, a phase change recording method is adopted. In the phase change recording method, information of "0" and "1" is basically recorded in correspondence with crystal and amorphous. By irradiating the crystallized portion and the amorphous portion with a laser beam and reproducing the reflected light, the recorded “0” and “1” can be detected.

  In order to make a predetermined position amorphous, the recording layer is heated by irradiating a laser beam with a relatively high power so that the temperature of the recording layer becomes equal to or higher than the melting point of the material of the recording layer. In order to crystallize a predetermined position, the recording layer is heated by irradiating a laser beam having a relatively low power so that the temperature of the recording layer is close to the crystallization temperature lower than the melting point of the recording layer material. By doing so, the amorphous state and the crystalline state can be reversibly changed. In a normal recording type DVD medium, when overwriting is performed, a recording pulse is modulated between a recording laser power and an erasing laser power lower than the recording laser power, and a new recording is performed while erasing an already recorded amorphous mark. Make a record.

  As an optical recording medium that achieves good overwrite characteristics, for example, as described in Patent Document 1, a recording power level is a value equal to or less than an optimum recording power and an erasing power level is a value higher than the optimum erasing power. An optical recording medium characterized by overwriting with a certain power is known.

  Regarding the method of optimizing the erasing power, assuming a drive of double speed recording (recording speed of 8.2 m / sec, transfer rate of 22 Mbps) of a DVD-RAM as an example, the information of the recording power written on the disc is used. They test write data and seek erasing power. At this time, the values of the erasing power on the low power side and the high power side exceeding the threshold of the error rate are obtained, and the optimum erasing power is set to be exactly at the center between the two.

JP-A-08-007343

  In order to improve the transfer rate and access speed in such a recordable DVD medium, it is necessary to increase the recording speed and perform recording and erasing in a short time. However, a problem in performing high-speed recording is a recording / erasing characteristic when information is overwritten on a medium. When high-speed recording is performed, the time required for the laser beam to pass through the mark position in the amorphous state on which information is recorded becomes shorter, and the time during which the laser beam is kept at the crystallization temperature also becomes shorter. If the time maintained at the crystallization temperature is too short, sufficient crystal growth cannot be achieved, so that in the above-described conventional technique, overwriting characteristics deteriorate when high-speed recording is performed. As a result of further studies by the present inventors, it has been found that when a medium on which high-speed recording is performed is stored in a high-temperature environment for a certain period of time and then taken out at normal temperature and overwritten, the overwrite characteristics are significantly deteriorated. Was. In the present invention, the characteristic of overwriting information after storing the medium in the high-temperature environment for a certain period of time is particularly distinguished from the normal overwrite characteristic, and is called an archival overwrite characteristic.

  The technique of Patent Document 1 mentioned above is intended to improve the deterioration of overwrite characteristics due to uneven crystallization when the initialization process is accelerated, and the recording speed in the embodiment is 7.5 m / sec, which is the current DVD-ROM. This is not a solution that takes into account the problem of high-speed recording that is equal to or less than 8.2 m / sec, which is double speed recording of RAM, and more than 8.0 m / sec, and furthermore, the problem of archival overwrite characteristics. Further, the range of the erasing power is described only as being higher than the optimum erasing power and lower than the maximum power at which the recording layer is not melted. In this method, when high-speed recording is performed, marks are erased by recording on an adjacent track. It has been found that there may be a problem that the reproduction signal leaks from the adjacent track easily occurs.

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to improve overwrite characteristics in high-speed recording, in particular, archival overwrite characteristics in which information is overwritten after storing a medium in a high-temperature environment for a certain period of time. An object of the present invention is to provide an information recording method, an information recording medium, and an information recording device that can be used.

According to a first aspect of the present invention, there is provided a method of recording information by irradiating an information recording medium with light whose power has been modulated to a recording power level and an erasing power level:
Overwriting a random pattern on an information recording medium with light of a predetermined recording power and various erasing powers;
Reproducing the overwritten random pattern to obtain a minimum value Pb1 and a maximum value Pb2 of the erasing power when erasing a pattern in which the reproduction jitter or the reproduction error exceeds a predetermined threshold;
From the obtained minimum value Pb1 and maximum value Pb2 and a relational expression expressed by Pb = α × Pb1 + (1−α) × Pb2, an optimum erasing power Pb for performing recording is obtained;
There is provided an information recording method characterized in that information is recorded using the obtained optimum erasing power Pb.

  The information recording method of the present invention may further include determining the optimum recording power Pp using the obtained optimum erasing power Pb. Further, the value of α is recorded in the information recording medium in advance, and the value of α can be read from the information recording medium during information recording. Assuming that the reproducing power is Pr, Pr <Pb1 <Pb and Pb <Pb2 <Pp may be satisfied. When information is recorded at different recording speeds in the recording method of the present invention, it is preferable that α varies within a range of α ≦ 0.50 according to the recording speed.

According to a second aspect of the present invention, there is provided an information recording medium on which information is recorded and reproduced,
An information recording unit for irradiating a recording beam Pp and a light beam having an erasing power Pb lower than the recording power Pp to record information, and irradiating a light beam having a reproducing power Pr lower than the erasing power Pb to reproduce information; When;
A control data section;
It is assumed that information for obtaining an optimum erasing power Pb from the lowest erasing power Pb1 satisfying Pr <Pb1 <Pb and the highest erasing power Pb2 satisfying Pb <Pb2 <Pp is recorded in advance in the control data portion. An information recording medium is provided.

According to a third aspect of the present invention, there is provided a recording apparatus for recording information by irradiating an information recording medium with light whose power has been modulated to a recording power level and an erasing power level:
An optical head for irradiating the information recording medium with light;
A driver for driving the optical head to output light power-modulated to the recording power level and the erasing power level from the optical head;
A random pattern overwritten by light having a predetermined recording power and various erasing powers is reproduced, and a minimum value Pb1 and a maximum erasing power Pb1 for erasing a pattern having a reproduction jitter or a reproduction error exceeding a predetermined threshold value are erased. The value Pb2 is obtained, and the coefficient α used in the expression Pb = α × Pb1 + (1−α) × Pb2, which is recorded in advance on the information recording medium, is read out. And a Pb calculation control unit for obtaining an optimum erasing power Pb for performing recording.

  The present inventors considered degradation of archival overwrite characteristics in high-speed recording as described below in order to improve the problems of the prior art in high-speed recording. As shown in FIG. 1, as can be seen from the positional relationship between the laser beam passage position and the shape of the mark recorded on the information recording medium, a mark area A near the center of the laser beam passage position and a laser beam It is considered that the temperature history accompanying the passage of the laser beam differs from the mark area B at a location away from the center due to the high-speed recording.

  First, consider the data recording process. FIG. 2 is a schematic diagram of a temperature history with respect to time in the area A and the area B when the recording power is applied. The temperature history in the mark area A near the center of the passage of the laser beam gradually drops from the crystal growth temperature to the crystal nucleation temperature and room temperature after exceeding the melting point. On the other hand, it is considered that the temperature history in the region B distant from the vicinity of the center of the passage of the laser beam is particularly shorter in the time of crystal nucleus generation than the temperature history in the region A. When overwriting is performed, once the mark is erased from the amorphous state to the crystalline state, the mark recording in the amorphous state is performed. It is considered that in the region B, since the number of crystal nuclei in the amorphous phase is smaller than that in the region A, the erasure to return to the crystalline state is not promoted, and as a result, the overwrite characteristics of the entire mark are degraded. In other words, the higher the recording speed, the more the temperature history of the area A and the area B becomes different, and the less the crystal nucleus is formed in the area B. It is considered that the archival overwrite characteristic of overwriting is deteriorated.

  Next, the data erasing process will be considered. FIG. 3 is a schematic diagram of the temperature history with respect to time in the region A and the region B when the erasing power is applied. The temperature history in the mark area A near the center of the passage of the laser beam gradually decreases to room temperature after being kept at the crystallization temperature for a certain time. On the other hand, it is considered that the temperature history in the region B distant from the vicinity of the center of the laser beam passage becomes shorter than the temperature history in the region A to maintain the crystallization temperature. As a result, in the area B, compared with the area A, the data for returning from the amorphous state to the crystallized state is not sufficiently erased. In particular, when information is overwritten after storing the medium in a high-temperature environment for a certain period of time, It is considered that the archival overwrite characteristics of the entire mark deteriorate. That is, it is considered that the decrease in the crystal nucleus generation in the data recording process and the insufficient crystallization in the erasing process cause the archival overwrite characteristics to deteriorate as the recording speed increases.

  The present inventors have completed the information recording method according to the first aspect, the information recording medium according to the second aspect, and the information recording apparatus according to the third aspect based on the above findings. When the information recording method, the information recording medium, and the information recording device of the present invention are used, when each information recording device performs test writing for setting the laser power prior to the information recording, each information recording medium has an archival structure. It is possible to set the erasing laser power level Pb at which the overwrite performance is the best.

  For example, in an information recording apparatus such as an optical disk drive, test writing is usually performed before information is recorded on an optical disk in order to obtain optimum Pp and Pb. At this time, the optical disk drive records information (overwrite) while changing the laser power, and measures the number of errors in the information recorded at this time. For example, when determining the optimum erasing power level Pb, the minimum erasing power level Pb1 and the highest erasing power level Pb2 where the number of errors is equal to or more than a certain reference are measured, and the intermediate power level is set to Pb. . The inventors have clarified that the erase power level determined in this way is not always the optimum erase power level for archival overwrite performance. By previously recording the relationship between Pb1 and Pb2 and the optimum erasing power level Pb, in particular, the coefficient α in Pb = α × Pb1 + (1−α) × Pb2 on the information recording medium, it is possible to store the information after long-term storage. Also, there is provided an information recording medium whose recording performance is less deteriorated. Further, the value of the coefficient α at Pb = α × Pb1 + (1−α) × Pb2 is read out from such an information recording medium to determine an optimum erasing power level Pb, and a suitable erasing power level Pb is set for each recording speed. There is provided a recording method capable of performing recording by using the method. The physical meaning of Pb1 is a laser power level at which the state changes from a crystalline state to an amorphous state, and Pb2 is a laser power level at which the state changes from an amorphous state to a crystalline state. Pb1 and Pb2 can be defined by, for example, a power level using the jitter level of the reproduced signal as a threshold, or can be defined by using the number of information errors as a threshold as described above. In any case, the erasing laser power level Pb at which the archival overwrite characteristics are best is set using the values of Pb1 and Pb2 based on the information reproduced from the information recording medium on which the value of α is recorded. Thus, archival overwrite characteristics can be improved.

  In the information recording medium of the present invention, if the information recording medium in which the information on the relationship between Pb, Pb1, and Pb2 is recorded together with the information on the recording speed is used, as in the case of a CAV (Constant Angular Velocity) type information recording apparatus. If the recording speed changes for each recording radius, the erasing power at which the archival overwrite characteristic is the best can be set according to each recording speed, and the archival overwrite characteristic can be improved.

  Further, in the information recording medium of the present invention, the information on the relationship between Pb, Pb1 and Pb2 is defined as Pb = α × Pb1 + (1−α) × Pb2 by using the ratio α between Pb1 and Pb2. obtain. If this information recording medium is used, the erasing power used when optimizing the erasing power in a drive of a double-speed recording (recording speed 8.2 m / sec, transfer rate 22 Mbps) of a DVD-RAM currently on the market is used. Based on the margin curve, it is possible to set the optimum erasing power for optimizing the archival overwrite characteristics for each recording speed, and the archival overwrite characteristics due to the recording speeds are eliminated. Since no complicated design change of the drive is required, backward compatibility of the drive in increasing the recording speed can be guaranteed.

  Further, in the information recording medium of the present invention, if the value of α is α ≦ 0.50, the value of the erasing power Pb is set to a value of 0.50 × Pb1 + 0.50 × Pb2 or more, thereby enabling high-speed overwriting. By increasing the laser energy at the time of erasing the data, increasing the time to maintain the temperature above the crystallization temperature, and erasing the data from the amorphous state to the crystallized state sufficiently, the archival during high-speed recording Overwrite characteristics can be improved. In particular, if the value of α is 0.25 ≦ α ≦ 0.50, by setting the value of Pb to 0.50 × Pb1 + 0.50 × Pb2 or more and 0.25 × Pb1 + 0.75 × Pb2 or less, Erasure of the mark signal of the adjacent track caused by the increase in the recording mark size can be suppressed. Further, when recording is performed by different information recording devices, the cross power overwrite characteristic, which is the overwrite characteristic assuming that the recording power differs, can be maintained at a favorable value. Here, the cross power overwrite characteristic is a characteristic when recording is performed with 105% power and then overwritten with 90% recording power when the optimum recording power is set to 100%.

  Further, by using the information recording medium of the present invention, high-speed recording such as a recording linear velocity of 9 m / sec or more is possible, and the generation of crystal nuclei at the time of data recording and the crystallization time at the time of data erasure can be maintained. It is possible to improve archival overwrite characteristics during high-speed recording.

  Also, by using an information recording device that records information using the information recording medium of the present invention, when recording is performed by a plurality of information recording devices having different recording speeds using the same information recording medium, The information recording device reads out the information of the recording speed and the erasing power written on the recording medium and records the information, whereby the recording compatibility of the information recording device can be obtained.

  By using the information recording method and the information recording medium of the present invention, recording can be performed with an erasing power optimized according to the recording speed, and the archival overwrite characteristics are optimized. The information recording apparatus of the present invention can read out information on the optimized erasing power from the information recording medium and execute recording with the optimized erasing power.

  Hereinafter, examples of the present invention will be described based on the results of experiments performed by the present inventors.

As an information recording medium, a polycarbonate substrate with a radius of 120 mm and a thickness of 0.6 mm, the surface of which is covered with an uneven guide groove having a track pitch of 1.2 μm and a groove depth of 63 nm based on a 4.7 GB DVD-RAM format. On the above, by a sputtering process, ZnS—SiO ₂ is 100 nm as a first protective layer, GeCrN is 10 nm as a first interface layer, BiGeTe is 10 nm as a recording layer, GeCrN is 10 nm as a second interface layer, and a second protective layer is 10 nm. 50nm the ZnS-SiO _2, 120 nm of Al a GeCr as thermal absorption coefficient control layer layer 50nm, a thermal diffusion layer, are sequentially formed to obtain an information recording medium used in the examples.

  After crystallizing this information recording medium using a laser initialization device, the optical recording medium information recording / reproduction device shown in FIG. 4 was used to examine the recording / reproduction characteristics.

  The operation of the optical recording medium information recording / reproducing apparatus used in this embodiment and the recording / reproducing process will be described below. First, information from the outside of the recording apparatus is transmitted to the 8-16 modulator 47 in units of 8 bits. When information is recorded on the information recording medium 41, a modulation method for converting 8 bits of information into 16 bits, that is, a so-called 8-16 modulation method is used. In this modulation method, information having a mark length of 3T to 14T corresponding to 8-bit information is recorded on an information recording medium. In the figure, an 8-16 modulator 47 performs this modulation. Here, T represents the clock length of data at the time of information recording. In this embodiment, T is 17.1 ns when the recording linear velocity is 8.2 m / sec, and 8 when the recording linear velocity is 16.4 m / sec. 5.7 ns at 0.6 ns and 24.6 m / sec.

  The 3T to 14T digital signal converted by the 8-16 modulator 47 is transferred to the recording waveform generating circuit 45, and the pulse width of the power of the first power level Pp which is the recording power is set to about T / 2, The laser irradiation of the first power level Pp and the second power level Pb, which is the erasing power, having a width of about T / 2 during the laser irradiation time of Pp is performed, and the power level is set between the series of Pp level pulses. A multi-pulse recording waveform in which Pb laser irradiation is performed is generated. Further, in the recording waveform generating circuit 45, signals of 3T to 14T are made to correspond to “0” and “1” alternately in time series, and in the case of “0”, the laser power of the power level of Pb, “ In the case of "1", the laser power of the power level of Pb is applied. At this time, the portion of the information recording medium 41 irradiated with the laser beam of the power level of Pb becomes crystalline, and the portion irradiated with a series of pulse trains including the pulse of the power level of Pp changes to amorphous (mark portion). . Further, when forming a series of pulse trains including a pulse of a power level of Pp for forming a mark portion, the recording waveform generating circuit 45 changes the space length before and after the mark portion as shown in FIG. A multi-pulse waveform table corresponding to a method (adaptive recording waveform control) for changing the width Tfp of the first pulse and the last pulse width Tlp of the multi-pulse waveform. Generates multi-pulse recording waveforms that can minimize the effects of thermal interference.

  The recording waveform generated by the waveform generating circuit 45 is transferred to a laser driving circuit (driver) 46, and the laser driving circuit 46 causes the semiconductor laser in the optical head 43 to emit light based on the recording waveform. The optical head 43 mounted on the optical recording medium information recording / reproducing apparatus uses a semiconductor laser having a wavelength of 655 nm as a laser beam for information recording. The laser light was focused on the recording layer of the information recording medium 41 with an objective lens having an NA of 0.6, and recording was performed by irradiating a laser beam of a laser corresponding to the recording waveform.

  The optical recording medium information recording / reproducing apparatus is compatible with a method of recording information in both a groove and a land (a region between grooves) (a so-called land-groove recording method). In the present optical recording medium information recording / reproducing apparatus, tracking for lands and grooves can be arbitrarily selected by the L / G servo circuit 48. The reproduction of the recorded information was also performed using the optical head 43. A reproduction signal is obtained by irradiating a laser beam onto the recorded mark and detecting reflected light from the mark and a portion other than the mark. The amplitude of the reproduced signal is increased by the preamplifier circuit 44 and transferred to the 8-16 demodulator 49. The 8-16 demodulator 49 converts every 16 bits into 8-bit information. With the above operation, the reproduction of the recorded mark is completed. When recording is performed on the optical information recording medium 41 under the above conditions, the mark length of the shortest mark 3T mark is about 0.42 μm, and the mark length of the longest mark 14T mark is about 1.96 μm.

  When evaluating the jitter, a random pattern signal including 3T to 14T was recorded and reproduced, and the reproduced signal was subjected to waveform equalization, binarization, and PLL (Phase Locked Loop) processing to measure the jitter. The reproduction of the signal was constant at a linear velocity of 8.2 m / sec regardless of the recording speed.

  For evaluation of the characteristics, the following archival overwrite jitter, cross power overwrite jitter, and cross erase jitter were measured.

  First, as an archival overwrite jitter, a random pattern was recorded on a track 10 times, and then an acceleration test was performed at 90 ° C. and 30% R.F. H. After storing in an environment for 20 hours, the temperature was returned to room temperature, a random pattern was overwritten, the reproduction laser power Pr was set to 1.0 mW, and jitter was measured. As a result of the study by the present inventors, the increase in archival overwrite jitter was 90 ° C. and 30% R.F. H. Since it is almost saturated by storing in an environment for 20 hours, it is considered that if the characteristics can be guaranteed in this environment, overwrite characteristics equivalent to 10 years can be guaranteed at room temperature. In this embodiment, recording is performed at an archival overwrite jitter at a linear velocity of 8.2 to 24.6 m / sec, a clock length of 17.1 to 5.7 ns, and a data transfer rate of 22 to 66 Mbps. The target value of the jitter when performing the test is set to 10% or less, and the standard upper limit value is set to 11% or less. Here, the standard upper limit value indicates an upper limit value of a characteristic that can be actually used in a drive without any problem.

  As a cross power overwrite jitter, a random pattern is recorded on a track 10 times at an optimum laser power, then overwritten once at 105% of the optimum laser power, and further overwritten at 90% of the optimum laser power. After overwriting once, the laser power Pr for reproduction was set to 1.0 mW, and the jitter was measured. The cross power overwrite jitter is a characteristic that guarantees the reliability of data when overwriting with different recording powers in different drives, that is, a characteristic that indicates the recording compatibility of the drives. In this embodiment, the target value of the cross power overwrite jitter is set to 11% or less, and the upper limit of the standard is set to 12% or less.

  Further, as a cross erase jitter, after a random pattern is recorded 10 times on the middle track, and after the random patterns are sequentially recorded 10 times from the inner circumference to the outer circumference on both sides of the tracks, and further on both sides of the tracks, At the center of the five tracks, the reproduction laser power Pr was set to 1.0 mW, and the jitter value was measured. The cross erase jitter is a characteristic that indicates the erasure of a mark by recording an adjacent track and the leakage of a reproduction signal from the adjacent track. In this embodiment, the target value of the cross erase jitter is set to 8% or less, and the upper limit of the standard is set to 9% or less.

  Hereinafter, a procedure for recording and reproducing data by changing the configuration (recording strategy) and the linear velocity of the recording pulse train using the optical recording medium evaluation apparatus and examining the value of jitter will be described. In the present embodiment, as the double speed recording, the recording linear velocity is set to 8.2 m / sec, the clock length of the recording data is set to 17.1 ns, and the data transfer rate is set to 22 Mbps. For quadruple speed recording, the recording linear velocity is set to 16.4 m / sec, the clock length of the recording data is set to 8.6 ns, and the data transfer rate is set to 44 Mbps. In addition, for 6 × speed recording, the recording linear velocity is set to 24.6 m / sec, the clock length of the recording data is set to 5.7 ns, and the data transfer rate is set to 66 Mbps.

  The recording strategy, recording power Pp, and erasing power Pb at each linear velocity were determined as follows.

  First, in the land, as temporary laser power, Pp0 = 10.5 mW, Pb0 = 4.0 mW at 2 × speed recording, Pp0 = 13.0 mW, Pb0 = 5.0 mW at 4 × speed recording, 6 × speed recording In this case, Pp0 = 14.0 mW and Pb0 = 5.5 mW. At each recording speed, 3T to 14T marks are recorded using the temporary laser power, and the recording waveform shown in FIG. 5 is set to 3T to 14T so that the thermal interference between marks generated between the marks is minimized. The width Tfp of the first pulse before and after the mark and the pulse width Tlp of the last pulse were determined and used as a recording strategy. At this time, the width Tmp of the multi-pulse was set to half the clock length of each recording speed.

  Next, at each recording speed, using the above-described recording strategy, the recording power was set to the temporary recording power Pp0, the erasing power Pb was set from 2.0 mW to 8.0 mW in 0.2 mW steps, and the random pattern was set. Was recorded 10 times, then the reproduction laser power Pr was set to 1.0 mW, the jitter was measured, and the erasing power dependence of the jitter shown in FIG. 6 was examined. As a method of determining the erasing power Pb used for actually recording data, in the erasing power dependence of the jitter shown in FIG. 6, of the erasing powers at which the jitter is 13%, the lower erasing power is Pb1 and the higher erasing power is Pb1. The erasing power was set to Pb2. In this study, Pb1 = 2.5 mW, Pb2 = 6.1 mW in 2 × speed recording, Pb1 = 3.5 mW, Pb2 = 6.8 mW in 4 × speed recording, and Pb1 = 4.3 mW, Pb2 = in 6 × speed recording. It was 7.4 mW. At this time, the shape of the curve in which the jitter with respect to the recording power at each recording speed is plotted is such that the power levels of Pb1 and Pb2 are shifted differently, the power range in which the jitter is low and stable, The low jitter power range was the center value of Pb1−Pb2 at 2 × speed, but the curve shifted from the center value of Pb1−Pb2 to the higher power side at higher recording speeds. Was. From this, it can be said that merely setting Pb to (Pb1−Pb2) / 2 does not always result in the minimum jitter being obtained depending on the recording speed.

  Further, as a method of determining the erasing power Pb used when recording data at each recording speed, Pb = α × Pb1 + (1−α) × Pb2 is set from the ratio of Pb1 and Pb2, and α is set at the erasing power. = 0.2-0.6 and the value of α was changed to obtain the value of Pb.

  Using the above-mentioned recording strategy, the recording power is set in increments of 0.5 mW from 8.0 mW to 16.0 mW for each of the obtained values of Pb, and after the random pattern is recorded ten times, the reproduction laser power Pr Was set to 1.0 mW, the jitter was measured, and the recording power dependence of the jitter shown in FIG. 7 was examined. In the recording power dependency of the jitter in FIG. 7, for the recording power Ppl at which the jitter is 13%, the optimum recording power Pp was obtained as Pp = K × Ppl as a function of Ppl. Here, the optimum recording power was set to K = 1.25 for 2 × speed recording, K = 1.30 for 4 × speed recording, and K = 1.30 for 6 × speed recording.

  Using the recording strategy, the recording power Pp, and the erasing power Pb obtained in this manner, the qualities of the archival overwrite jitter, the cross power overwrite jitter, and the cross erase jitter are determined as the quality of the recording signal at each land at each recording speed. Measurement was performed to examine the relationship between the value of α when determining the erasing power Pb and the quality of the recording signal.

  By changing the value of α to 0.60, 0.50, 0.40, 0.35, 0.30, 0.25, 0.20 at a linear velocity of 8.2 m / sec which is double speed recording, After determining the recording power at each erasing power, archival overwrite jitter, cross power overwrite jitter, and cross erase jitter at each value of α were examined. Table 1 shows the results.

  When recording at a double speed at a linear velocity of 8.2 m / sec, the archival overwrite jitter is almost constant up to α = 0.60 to 0.25, and slightly when the value of α is smaller than this value. Jitter is getting worse. Further, the cross power overwrite jitter is almost constant from α = 0.60 to 0.35, and when the value of α is smaller than this, the jitter tends to deteriorate. Further, the cross erase jitter is almost constant from α = 0.60 to 0.40, and if the value of α is smaller than this, the jitter becomes worse.

  When the target value of the archival overwrite jitter is 10%, the target value of the cross power overwrite jitter is 11%, and the target value of the cross erase jitter is 8%, at the double speed recording at a linear velocity of 8.2 m / sec. , Α = 0.50, the target value has been reached. When the upper limit of the archival overwrite jitter is 11%, the upper limit of the cross power overwrite jitter is 12%, and the upper limit of the cross erase jitter is 9% as the allowable limits of the characteristics. In the case of recording at a speed of 2 × at 8.2 m / sec, the standard value is satisfied when α = 0.60 to 0.40. However, considering the margin of each characteristic, it can be said that it is most preferable to set α = 0.50 in the recording at a double speed of the linear velocity of 8.2 m / sec.

  By changing the value of α to 0.60, 0.50, 0.40, 0.35, 0.30, 0.25, 0.20 at a linear velocity of 16.4 m / sec, which is quadruple speed recording, After determining the recording power at each erasing power, archival overwrite jitter, cross power overwrite jitter, and cross erase jitter at each value of α were examined. Table 2 shows the results.

  When recording at a quadruple speed at a linear velocity of 16.4 m / sec, the archival overwrite jitter is almost constant from α = 0.40 to 0.20, and when the value of α is larger than this, Is getting worse. Further, the cross power overwrite jitter is almost constant from α = 0.40 to 0.30, and the jitter tends to be worse before and after the value of α. The cross erase jitter is almost constant from α = 0.60 to 0.25, and when the value of α is smaller than this, the jitter tends to deteriorate.

  In quadruple speed recording at a linear velocity of 16.4 m / sec, α = 0.40 to 0.35 satisfies the target value. Further, α = 0.50 to 0.25 satisfies the standard upper limit value. Considering that archival overwrite jitter and cross-erase jitter are minimized in this range, it can be said that it is most preferable to set α = 0.35 for recording at a quadruple speed of a linear velocity of 16.4 m / sec. .

  Compared to the case where recording was performed at a linear velocity of 8.2 m / sec in Example 1, when recording was performed at a higher linear velocity of 16.4 m / sec, when α was smaller than 0.5, obviously, Archival overwrite jitter has been improved. Especially with regard to archival overwrite jitter, not only is the optimal value of α shifted to the smaller one, but the range of α itself is narrowed to about half of that at 2x speed, so it is necessary to set the optimal recording strategy. Become more important.

  By changing the value of α to 0.60, 0.50, 0.40, 0.35, 0.30, 0.25, 0.20 at a linear velocity of 24.6 m / sec, which is 6 × speed recording, After determining the recording power at each erasing power, archival overwrite jitter, cross power overwrite jitter, and cross erase jitter at each value of α were examined. Table 3 shows the results.

  When recording at 6 × speed at a linear velocity of 24.6 m / sec, the archival overwrite jitter is almost constant from α = 0.35 to 0.25, and when the value of α is larger than this, Is getting worse. Further, the cross power overwrite jitter is almost constant from α = 0.35 to 0.20, and when α is larger than this value, the jitter tends to be worse. The cross erase jitter is almost constant from α = 0.60 to 0.25, and when the value of α is smaller than this, the jitter tends to deteriorate.

  In the case of recording at a linear speed of 24.6 m / sec at a 6-times speed, the target value is met at α = 0.35 to 0.25. Further, α = 0.40 to 0.20 satisfies the standard upper limit value. Considering that archival overwrite jitter and cross-erase jitter are minimized within this range, it can be said that α = 0.30 is most preferably set for 6-times recording at a linear velocity of 24.6 m / sec. . In the case of recording at a linear velocity of 8.2 m / sec in Example 1, compared with the case of recording at a high speed of 16.4 m / sec in Example 2, the linear velocity in Example 3 was 24.6 m / sec. In the case of high-speed recording, the archival overwrite jitter is clearly improved when the value of α is made smaller. In addition, the optimal value of α is not only shifted to a smaller value than at the time of 4 × speed, but the range of α itself is further narrowed to about half that at the time of 4 × speed, so that an optimal recording strategy can be set. Become more important.

  As described above, when the results of Examples 1, 2, and 3 are summarized, the erasing power level Pb is set using the value Pb1 larger than the reproduction power Pr and smaller than Pb and the value Pb2 larger than Pb and smaller than the recording power Pp. When Pb = α × Pb1 + (1−α) × Pb2, the most preferable value of α for improving archival overwrite jitter, cross power overwrite jitter, and cross erase jitter is a linear velocity of 8.2 m / sec. Α = 0.50 when recording, α = 0.35 when recording at a linear velocity of 16.4 m / sec, and α = 0.30 when recording at a linear velocity of 24.6 m / sec.

  Table 4 shows a comparison of Examples 1, 2, and 3 with respect to the optimal range of α. Regarding archival overwrite jitter and cross power overwrite jitter, the value and range of α corresponding to the recording speed differ greatly, and all characteristics including cross erase jitter are good and cover all recording speeds. Since there is no possible α, it is necessary to set α according to the recording speed and set the recording power Pp and the erasing power Pb.

  The reason why the optimum α varies depending on the linear velocity of recording in this manner is considered as follows. As the recording speed increases, the generation of crystal nuclei during the recording process decreases, and the crystallization during the erasing process becomes insufficient, resulting in poor archival overwrite characteristics. On the other hand, by changing the definition of the erasing power obtained from the jitter dependency of the erasing power along with the linear velocity of the recording, the recording is performed with the optimum erasing power, thereby generating the crystal nuclei in the recording process and the crystal in the erasing process. We think that it is promoting the conversion.

  However, by increasing the erasing power, archival overwrite jitter, cross-power overwrite jitter, and cross-erase jitter deteriorate, so that an appropriate erasing power setting at each recording speed, that is, an appropriate value of α, Exists. That is, by recording information on the relationship between Pb1, Pb2, and Pb on the medium in advance, recording can be performed with a suitable erasing power, and archival overwrite jitter can be improved. Furthermore, by recording the information on α, which represents the value of Pb by the ratio of the value of Pb1 to the value of Pb2, on the medium in advance, it is possible to perform recording with a suitable erasing power at each recording speed. , Archival overwrite jitter, cross power overwrite jitter, and cross erase jitter can be improved.

  As described above, the information recording medium and the laser beam are relatively scanned at a constant range of linear velocity, and the laser power of the laser beam is set to at least the recording laser power Pp and the erasing laser power lower than the recording laser power level. The information is recorded by power-modulating the level Pb to change the state of the information recording section of the information recording medium, and the information is recorded by a laser beam having a reproduction laser power level Pr lower than the erasing laser power level Pb. An information recording medium on which reproduction is performed, characterized in that information on a relationship between Pb, a value Pb1 larger than Pr and smaller than Pb, a value Pb2 larger than Pb and smaller than Pp, and Pb is recorded. Overwrite characteristics when high-speed recording is performed by using an information recording medium In particular, it is possible to improve the archival overwrite characteristic overwriting information After saving the medium a certain time to a high temperature environment.

  In this embodiment, an information recording medium on which a suitable value of α obtained in the above embodiment is recorded in advance is reproduced by an information recording / reproducing apparatus, and data is read and written using the value of α, and the archival over is performed. The light characteristics were examined.

  A disc having a format of 4.7 GB DVD-RAM, and in the control data portion, information on the recording strategy of 5 × speed and 6 × speed, the information of the recording sensitivity coefficient and the information of α are stored in the same manner as in the case of 2 × speed. A stamper for manufacturing a written disc was manufactured. At this time, the value of α at the time of 5 × speed and 6 × speed recording is α = 0.50 and α = 0.50, respectively, and the value of α at 5 × speed and 6 × speed recording is α = 0.40, respectively. , Α = 0.35 stamper B were produced. Here, α is a coefficient for determining the erasing power Pb from the relational expression Pb = α × Pb1 + (1−α) × Pb2, where Pb1 <Pb2.

Using the stampers A and B, the polycarbonate substrates A and B were formed by injection molding. On the obtained substrate, by sputtering, ZnS—SiO ₂ was 100 nm as a first protective layer, GeCrN was 10 nm as a first interface layer, BiGeTe was 10 nm as a recording layer, GeCrN was 10 nm as a second interface layer, and a second protective layer was formed. the ZnS-SiO ₂ to give 50 nm, 50 nm and GeCr as thermal absorption coefficient control layer layer, 120 nm of Al as a thermal diffusion layer, the successively deposited information recording medium as. FIG. 8 schematically shows the information recording section 75 and the control data section 71 in the obtained information recording medium 1. This information recording medium was initialized to obtain disks A and B. Using the disks A and B thus produced, recording was performed at 5 × speed and 6 × speed with a drive.

  Here, the operation of the used recording / reproducing apparatus (drive apparatus) for performing 5 × speed recording and 6 × speed recording will be described. (1) First, information on the write strategy for each speed and the write power for test writing written in the control data section is read. (2) Next, using the recording waveform and the recording power of the read recording strategy, a random pattern is recorded by changing the erasing power, and the erasing powers Pb1 and Pb2 (Pb1 <Pb2) where the error exceeds a threshold value are obtained. Ask. Here, the threshold of the error was determined based on the power at which the number of errors after error correction suddenly changed from several hundred to several. (3) Using the values of Pb1 and Pb2, the optimum value of the erasing power Pb for actually performing recording is determined from the equation of Pb = α × Pb1 + (1−α) × Pb2. (4) The recording power is changed using the obtained optimum value of the erasing power Pb to record the 6T pattern, and the recording compensation power at which the asymmetry value of the 6T pattern written in the control data portion is obtained is calculated. Ask. (5) The recording strategy is optimized with the recording compensation power and the optimum erasing power. Here, the recording strategy is optimized by changing the width Tfp of the first pulse and the last pulse width Tlp of the multi-pulse waveform according to the space length before and after the mark portion so that the error rate is minimized. Done. (6) Using the optimized recording strategy waveform and the erasing power Pb, the recording power is changed to record a random pattern, and the recording power at which the error exceeds a threshold is obtained. (7) Next, the information of the sensitivity coefficient of the recording power written in the control data section is read, and the obtained recording power is multiplied by the sensitivity coefficient to obtain the optimum recording power. (8) The above-mentioned steps (1) to (7) are performed at 5 × speed recording and 6 × speed recording, respectively, and the data in the recording / reproducing apparatus are obtained by using the obtained optimal strategy, optimal recording power, and optimal erasing power. Record.

  FIG. 4 schematically shows the recording / reproducing apparatus. It is the Pb calculation control unit 410 that reads the coefficient α of the erasing power recorded on the disk and calculates the erasing power Pb from the relational expression of Pb = α × Pb1 + (1−α) × Pb2. The information recording apparatus of the present invention has the same structure as a conventional double-speed or triple-speed recording apparatus (drive apparatus) except that the information recording apparatus mainly includes a Pb calculation control unit 410.

  Next, a procedure for examining the archival overwrite characteristics of the disk A and the disk B at the time of 5 × speed recording and 6 × speed recording by the drive will be described. First, random data is written ten times with the obtained optimum power. The disc on which recording has been completed is 90 ° C., 30% RH. H. After storing in the environment for 20 hours, the temperature is returned to room temperature, and random data is written once again in the same position. Thereafter, using the optical recording medium information recording / reproducing apparatus, the recorded data was reproduced at twice the speed of the recorded data at a reproduction power Pr = 1 mW, and the archival overwrite jitter after the environmental test was examined.

  As the radial position where disk recording is performed by the drive, recording was performed at a radius of 43.30 mm to 44.20 mm for 5 × speed recording and at a radius of 45.23 mm to 46.13 mm for 6 × speed recording. When the jitter was examined after the environmental test, the reproduction jitter was examined every five tracks in the recording area, and the average value was defined as the archival overwrite jitter after the environmental test.

  When writing random data once with the drive after the environmental test, the drive repeats the above-described process of finding the optimal strategy, optimal recording power, and optimal erase power. The strategy, the optimum recording power, and the optimum erasing power did not change.

  Table 5 shows the results of examining the archival characteristics of the discs A and B at the time of 5 × speed recording and 6 × speed recording with a drive.

  As can be seen from the results in Table 5, information α relating to the relationship between Pb1, a value Pb1 larger than Pr and smaller than Pb, a value Pb2 larger than Pb and smaller than Pp, and Pb is recorded. When performing high-speed recording using an information recording medium, by setting α to a suitable value in accordance with the recording speed, the archival overwrite characteristics of overwriting information after storing the medium in a high-temperature environment for a certain period of time can be achieved. You can see that it can be improved.

  In the above embodiment, data is recorded on the land, but the same effect can be obtained when recording is performed on the groove. Further, in the present embodiment, although the recording radial position is not particularly described, the same effect is obtained with an arbitrary radius of 24 to 58 mm. Further, in this embodiment, the signal is reproduced at a linear velocity of 8.2 m / sec. However, since the essence of the present invention lies in the improvement of the high-speed recording process, the effect of the present invention can be obtained irrespective of the reproducing speed. be able to.

  Further, the present invention is characterized in that information on the definition of the erasing power is recorded together with the information on the recording speed on the information recording medium in order to improve the archival overwrite characteristics accompanying the high-speed recording. The effects of the present invention can be obtained irrespective of the structure, composition, crystallization speed, crystallization temperature, crystal nucleus generation temperature, and melting point of.

  Further, in the present embodiment, the threshold value is set to 13% for obtaining the values of Pb1 and Pb2 from the jitter dependency of the erasing power. However, the essence of the present invention is not based on the threshold value of the jitter. When the value is obtained using an arbitrary threshold value instead of jitter, for example, from the error rate dependency of the erasing power or the signal amplitude, S / N, and asymmetry dependency, the effect of the present invention is not lost. .

  Furthermore, in the present specification, the light for recording is expressed as a laser beam, but the present invention is not limited to the present invention as long as the energy beam can change the state of the information recording section of the information recording medium. Since the effect is obtained, the effect of the present invention is not lost even when an energy beam such as an electron beam is used.

  In the embodiment of the present invention, a red laser having a wavelength of 655 nm is used. However, the present invention is not limited to the laser wavelength, but an information recording apparatus using a relatively short wavelength laser such as a blue laser or an ultraviolet laser. Also, the present invention exerts an effect on an information recording medium used for the same.

  In the embodiment of the present invention, a phase change disk is used as the information recording medium. However, the present invention is applicable to any information recording medium on which information is recorded by irradiation of an energy beam. Regardless of the material and structure of the information recording medium or the shape of the information recording medium, the present invention can be applied to information recording media other than the disc-shaped information recording medium such as an optical card.

  The information recording method, the information recording medium, and the information recording apparatus of the present invention improve overwrite characteristics in high-speed recording, particularly, archival overwrite characteristics in which information is overwritten after storing the medium in a high-temperature environment for a certain period of time. be able to. Therefore, the present invention can further improve the reliability of large-capacity and high-speed data recording regardless of the surrounding environment.

FIG. 1 is a diagram schematically showing a laser beam passage position and a shape of a mark recorded on a medium. FIG. 2 is a diagram schematically illustrating a temperature history with respect to time in the area A and the area B when the recording power is applied. FIG. 3 is a diagram schematically showing a temperature history with respect to time in the region A and the region B when the erasing power is applied. FIG. 4 is a schematic diagram of an information recording medium recording / reproducing apparatus used for examining recording / reproducing characteristics in the embodiment of the present invention. FIG. 5 is a diagram for explaining a recording pulse strategy used for examining recording / reproducing characteristics in the embodiment of the present invention. FIG. 6 is a schematic diagram showing the dependence of jitter on the erasing power for explaining the definition of the erasing power used in the embodiment of the present invention. FIG. 7 is a schematic diagram of the recording power dependence of jitter for explaining the definition of the recording power used in the embodiment of the present invention. FIG. 8 is a schematic diagram showing an information recording section and a control data section in the information recording medium according to the present invention.

Explanation of reference numerals

41 Information recording medium 42 Motor
43 optical head 44 preamplifier circuit 45 recording waveform generation circuit 46 laser drive circuit 47 8-16 modulator 48 L / G servo circuit 498 8-16 demodulator

Claims (12)

A method for recording information by irradiating an information recording medium with light whose power is modulated at a recording power level and an erasing power level, comprising:
Overwriting a random pattern on an information recording medium with light of a predetermined recording power and various erasing powers;
Reproducing the overwritten random pattern to obtain a minimum value Pb1 and a maximum value Pb2 of the erasing power when erasing a pattern in which the reproduction jitter or the reproduction error exceeds a predetermined threshold;
From the obtained minimum value Pb1 and maximum value Pb2 and a relational expression expressed by Pb = α × Pb1 + (1−α) × Pb2, an optimum erasing power Pb for recording is obtained;
An information recording method characterized by recording information using the obtained optimum erasing power Pb. 2. The information recording method according to claim 1, further comprising determining an optimum recording power Pp using the obtained optimum erasing power Pb. The information recording method according to claim 1, wherein when information is recorded at different recording speeds, α varies within a range of α ≦ 0.50 according to the recording speed. The value of α is recorded in advance on the information recording medium, and the value of α is read from the information recording medium during information recording. Information recording method. 3. The information recording method according to claim 2, wherein Pr <Pb1 <Pb and Pb <Pb2 <Pp are satisfied when the reproducing power is Pr. An information recording medium on which information is recorded and reproduced,
An information recording unit for irradiating a recording beam Pp and a light beam having an erasing power Pb lower than the recording power Pp to record information, and irradiating a light beam having a reproducing power Pr lower than the erasing power Pb to reproduce information; When;
A control data section;
It is assumed that information for obtaining an optimum erasing power Pb from the lowest erasing power Pb1 satisfying Pr <Pb1 <Pb and the highest erasing power Pb2 satisfying Pb <Pb2 <Pp is recorded in advance in the control data portion. Characteristic information recording medium. 7. The information recording medium according to claim 6, wherein information for obtaining the optimum erasing power Pb from Pb1 and Pb2 is recorded together with information on a recording speed. 8. The method according to claim 6, wherein the information for obtaining the optimum erasing power Pb from Pb1 and Pb2 is α represented by the following equation: Pb = α × Pb1 + (1−α) × Pb2. Information recording medium as described. 9. The information recording medium according to claim 8, wherein the value of α satisfies α ≦ 0.50. 10. The information recording medium according to claim 9, wherein the value of α is 0.25 ≦ α ≦ 0.50. The information according to any one of claims 6 to 10, wherein a linear velocity when the information recording medium is moved relative to the light beam for recording the information is 9 m / sec or more. recoding media. A recording apparatus for recording information by irradiating an information recording medium with light whose power has been modulated to a recording power level and an erasing power level, comprising:
An optical head for irradiating the information recording medium with light;
A driver for driving the optical head so as to output light power-modulated to the recording power level and the erasing power level from the optical head;
A random pattern overwritten with light having a predetermined recording power and various erasing powers is reproduced, and a minimum value Pb1 and a maximum erasing power Pb1 for erasing a pattern having a reproduction jitter or a reproduction error exceeding a predetermined threshold value are erased. The value Pb2 is obtained, and the coefficient α used in the expression Pb = α × Pb1 + (1−α) × Pb2, which is recorded in advance on the information recording medium, is read. From the obtained minimum value Pb1 and maximum value Pb2 and the read coefficient α, A Pb calculation control unit for obtaining an optimum erasing power Pb for performing recording.

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