JP3971401B2 - Information recording method, information recording medium, and information recording apparatus - Google Patents

Description

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

  In recent years, the market for read-only optical discs such as DVD-ROM and DVD-Video is 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 replacing a VTR. Furthermore, in recent years, market demands for improving the transfer rate and access speed of recordable DVDs have increased.

  A recordable DVD medium such as DVD-RAM and DVD-RW that can be recorded and erased employs a phase change recording method. In the phase change recording method, recording is basically performed with information of “0” and “1” corresponding to crystal and amorphous. The recorded “0” and “1” can be detected by irradiating the crystallized portion and the amorphous portion with a laser beam and reproducing the reflected light.

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

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

  Regarding the method for optimizing the erasing power, taking a DVD-RAM double speed recording (recording speed 8.2 m / sec, transfer rate 22 Mbps) as an example, using the recording power information written on the disk, Trial writing of data is performed and erasing power is demanded. At this time, the values of the erasing power on the low power side and the high power side that exceed the threshold of the error rate are obtained, and the optimum erasing power is set to be exactly the center of both.

Japanese Patent Laid-Open No. 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 erasure 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 performing high-speed recording, the time required for the laser beam to pass through the amorphous mark position where information is recorded is shortened, and the time during which the laser beam is held at the crystallization temperature is also shortened. If the time for which the crystallization temperature is maintained is too short, sufficient crystal growth cannot be achieved. Therefore, in the above-described conventional technique, overwriting characteristics deteriorate when high-speed recording is performed. As a result of further investigation by the present inventors, it was found that the overwriting characteristics deteriorated remarkably when a medium on which high speed recording was performed was stored in a high temperature environment for a certain period of time and then overwritten at room temperature. It was. In the present invention, the characteristic when information is overwritten after the medium is stored in this high temperature environment for a certain period of time is particularly distinguished from the normal overwrite characteristic and is called the archival overwrite characteristic.

  The technique of Patent Document 1 described above is to improve deterioration of the overwrite characteristics due to uneven crystallization when the initialization process is speeded up, and the recording speed in the embodiment is 7.5 m / sec, which is the current DVD- This is not a solution that takes into account the problem in high-speed recording, which is 8.2 m / sec or less, which is the double speed recording of RAM, and in particular exceeds 8.0 m / sec, and also the problem of archival overwrite characteristics. In addition, it is only described that the range of the erasing power is higher than the optimum erasing power and lower than the maximum power at which the recording layer does not melt. In this method, when high-speed recording is performed, the mark is erased by recording on the adjacent track. It has been found that there may be a problem that a reproduction signal from an adjacent track is likely to leak.

  Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art and improve the overwrite characteristic in high-speed recording, particularly the archival overwrite characteristic for overwriting information after storing the medium in a high temperature environment for a certain period of time. An information recording method, an information recording medium, and an information recording apparatus are provided.

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 modulated to a recording power level and an erasing power level:
A random pattern is overwritten on the information recording medium with light having a predetermined recording power and various erasing powers;
Reproducing the overwritten random pattern to obtain the minimum value Pb1 and the maximum value Pb2 of the erasing power when the pattern whose reproduction jitter or reproduction error exceeds a predetermined threshold is erased;
An optimum erasing power Pb for recording is obtained from the obtained minimum value Pb1 and maximum value Pb2 and a relational expression represented by Pb = α × Pb1 + (1−α) × Pb2.
An information recording method is provided, wherein information is recorded using the determined 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 advance on the information recording medium, and the value of α can be read from the information recording medium at the time of information recording. When the reproduction power is Pr, Pr <Pb1 <Pb and Pb <Pb2 <Pp can be satisfied. When information is recorded at different recording speeds in the recording method of the present invention, α varies in the range of α ≦ 0.50 depending on 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 in which information is recorded by irradiating a light beam having a recording power Pp and an erasing power Pb lower than the recording power Pp, and information is reproduced by irradiating a light beam having a reproducing power Pr lower than the erasing power Pb. When;
A control data section;
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 the control data portion in advance. A featured information recording medium is provided.

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

  In order to improve the problems of the prior art in high-speed recording, the present inventors considered the deterioration of archival overwrite characteristics in high-speed recording as follows. As shown in FIG. 1, as can be seen from the positional relationship between the laser beam passage position and the mark shape recorded on the information recording medium, the mark region A near the center of the laser beam passage position, and the laser beam It is considered that the temperature history associated with the passage of the laser beam differs between the mark region B away from the center and the speed of recording.

  First, consider the data recording process. FIG. 2 is a schematic diagram of the temperature history with respect to the time of the area A and the area B when the recording power is irradiated. The temperature history in the mark region A in the vicinity of the center of the laser beam passage gradually decreases 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 far from the vicinity of the center of the laser beam passage is particularly shorter than the temperature history in the region A in terms of crystal nucleation time. When overwriting is performed, the mark is erased once from the amorphous state to the crystalline state, and then the mark recording in the amorphous state is performed. In the region B, since there are fewer crystal nuclei in the amorphous region than in the region A, erasure to return to the crystalline state is not promoted, and as a result, the overwrite characteristics of the entire mark are deteriorated. In other words, the higher the recording speed, the more the difference in the temperature history between the region A and the region B and the less the generation of crystal nuclei in the region B. In particular, after the medium is stored in a high temperature environment for a certain period of time, information is stored. It is thought that the archival overwrite characteristic of overwriting will deteriorate.

  Next, consider the data erasing process. FIG. 3 is a schematic diagram of the temperature history with respect to the time of the region A and the region B when the erasing power is irradiated. The temperature history in the mark area A in the vicinity of the center of the laser beam passage is kept at the crystallization temperature for a certain time and then gradually decreases to room temperature. On the other hand, the temperature history in the region B far from the vicinity of the center of the laser beam passage is considered to be shorter than the temperature history in the region A. As a result, compared with the region A, the data in the region B is not sufficiently erased to return from the amorphous state to the crystallized state. In particular, when information is overwritten after the medium is stored in a high temperature environment for a certain time, We think that the archival overwrite characteristics of the entire mark will deteriorate. That is, the decrease in crystal nucleation in the data recording process and the insufficient crystallization in the erasing process are considered to be causes of the phenomenon that the archival overwrite characteristics deteriorate as the recording speed increases.

  Based on the above findings, the present inventors have completed the information recording method according to the first aspect of the present invention, the information recording medium according to the second aspect, and the information recording apparatus according to the third aspect. By using the information recording method, information recording medium, and information recording apparatus of the present invention, when each information recording apparatus performs trial writing for laser power setting prior to information recording, the information recording medium is archived. It is possible to set the erasing laser power level Pb that provides the best overwrite performance.

For example, in an information recording apparatus such as an optical disk drive, trial writing is generally performed to obtain optimum Pp and Pb before recording information on an optical disk. 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 lowest erasing power level Pb1 and the highest erasing power level Pb2 at which the number of errors is equal to or greater than a certain reference are measured, and the intermediate power level is set as Pb. . The inventors have thus clarified that the determined erase power level is not necessarily the optimum erase power level for the archival overwrite performance. 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 is recorded on the information recording medium in advance, after long-term storage. However, an information recording medium with little deterioration in recording performance is provided. Further, the value of the coefficient α at Pb = α × Pb1 + (1−α) × Pb2 is read from such an information recording medium, an optimum erasing power level Pb is determined, and an erasing power level Pb suitable for each recording speed is determined. There is provided a recording method capable of performing recording using the. The physical meaning of Pb 2 is a laser power level that starts to change from a crystalline state to an amorphous state, and Pb 1 is a laser power level that starts to change from an amorphous state to a crystalline state. Pb1 and Pb2 can be defined by, for example, a power level with the jitter level of the reproduction signal as a threshold value, or can be defined with the number of information errors as a threshold value as described above. In any case, the erase laser power level Pb that provides the best archival overwrite characteristics 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. And 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 CAV (Constant Angular Velocity) type information recording apparatus. When the recording speed changes for each recording radius, it is possible to set an erasing power that provides the best archival overwrite characteristics according to each recording speed, and to improve the archival overwrite characteristics.

  In the information recording medium of the present invention, the information relating to the relationship between Pb, Pb1, and Pb2 is defined as Pb = α × Pb1 + (1−α) × Pb2 using the ratio α of Pb to Pb1 and Pb2. obtain. If this information recording medium is used, the erasing power used when optimizing the erasing power with a double-speed recording (recording speed 8.2 m / sec, transfer rate 22 Mbps) of a commercially available DVD-RAM. Based on the margin curve, it is possible to set the optimum erasing power that optimizes the archival overwrite characteristics for each recording speed, and there is no variation in the archival overwrite characteristics depending on the recording speed. Since no complicated design change of the drive is required, it is possible to guarantee backward compatibility of the drive in increasing the recording speed.

  Further, in the information recording medium of the present invention, if the value of α is α ≦ 0.50, the erasing power Pb is set to a value of 0.50 × Pb1 + 0.50 × Pb2 or higher so that high-speed overwriting is performed. Archiving during high-speed recording by increasing the laser energy during erasing, relatively increasing the time to maintain the temperature above the crystallization temperature, and sufficiently erasing the data from the amorphous state to the crystallization state. 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, It is possible to suppress the erasure of the mark signal of the adjacent track caused by the increase in the recording mark size. In addition, when recording is performed using different information recording apparatuses, the cross power overwrite characteristic, which is an overwrite characteristic assuming that the recording power is different, can be maintained at a good value. Here, the cross power overwrite characteristic is a characteristic when overwriting is performed with 90% recording power after recording with 105% power when the optimum recording power is 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 generation of crystal nuclei at the time of data recording and retention of crystallization time at the time of erasing data can be maintained. As a result, it is possible to improve the archival overwrite characteristic during high-speed recording.

  In addition, by using an information recording apparatus that records information using the information recording medium of the present invention, information is recorded in advance when recording is performed using a plurality of information recording apparatuses having different recording speeds using the same information recording medium. The information recording apparatus reads out the information on the recording speed and the erasing power described in the recording medium and records the information, whereby the recording compatibility of the information recording apparatus can be obtained.

  By using the information recording method and information recording medium of the present invention, recording can be performed with an erasing power optimized in accordance with the recording speed, and the archival overwrite characteristic is the best. The information recording apparatus of the present invention can read information on the optimized erasing power from the information recording medium and execute recording with the optimized erasing power.

  Examples of the present invention will be described below based on the results of experiments conducted by the present inventors.

A polycarbonate substrate having 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 the 4.7 GB DVD-RAM format as an information recording medium. Then, by sputtering process, ZnS-SiO ₂ is 100 nm as the first protective layer, GeCrN is 10 nm as the first interface layer, BiGeTe is 10 nm as the recording layer, GeCrN is 10 nm as the second interface layer, and the second protective layer is used. ZnS—SiO ₂ was deposited in a thickness of 50 nm, GeCr as a heat absorption rate correction layer layer was deposited in a thickness of 50 nm, and Al as a thermal diffusion layer was deposited in a thickness of 120 nm, thereby obtaining an information recording medium used in the examples.

  After this information recording medium was crystallized using a laser initialization apparatus, the optical recording medium information recording / reproducing apparatus shown in FIG. 4 was used to examine the recording / reproducing characteristics.

  The operation and recording / reproducing process of the optical recording medium information recording / reproducing apparatus used in this embodiment 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 recording information on the information recording medium 41, a modulation system that converts 8 bits of information into 16 bits, a so-called 8-16 modulation system, 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 the present embodiment, 17.1 ns when the linear velocity of recording is 8.2 m / sec and 8 when the linear velocity is 16.4 m / sec. It was set to 5.7 ns at 0.6 ns and 24.6 m / sec.

  The digital signal of 3T to 14T converted by the 8-16 modulator 47 is transferred to the recording waveform generation circuit 45, and the width of the pulse of the power of the first power level Pp which is the recording power is set to about T / 2. Laser irradiation of the power of the first power level Pp and the second power level Pb, which is the erasing power, having a width of about T / 2 in the laser irradiation time of Pp, and the power level between the series of pulses of the Pp level. A multi-pulse recording waveform in which Pb laser irradiation is performed is generated. Further, in the recording waveform generating circuit 45, the 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 irradiated. At this time, the portion irradiated with the laser beam with the Pb power level on the information recording medium 41 becomes a crystal, and the portion irradiated with a series of pulse trains including a pulse with the power level of Pp changes to amorphous (mark portion). . Further, when the recording waveform generation circuit 45 forms a series of pulse trains including pulses of Pp power level for forming the mark portion, as shown in FIG. 5 according to the space length before and after the mark portion. 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, thereby generating a mark interval between marks. A multi-pulse recording waveform that can eliminate the influence of thermal interference as much as possible is generated.

  The recording waveform generated by the recording waveform generation 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 this 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. This laser beam was focused on the recording layer of the information recording medium 41 with an objective lens of NA 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 system (so-called land / groove recording system) for recording information on both grooves and lands (areas between grooves). In the present optical recording medium information recording / reproducing apparatus, the L / G servo circuit 48 can arbitrarily select tracking for lands and grooves. The recorded information was also reproduced 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 reproduction signal is increased by the preamplifier circuit 44 and transferred to the 8-16 demodulator 49. The 8-16 demodulator 49 converts the information into 8-bit information every 16 bits. 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 3T mark, which is the shortest mark, is about 0.42 μm, and the mark length of the 14T mark, which is the longest 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, and the jitter was measured. Note that the signal reproduction was constant at a linear velocity of 8.2 m / sec regardless of the recording velocity.

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

  First, as archival overwrite jitter, a random pattern was recorded 10 times on a track, and then an acceleration test was performed at 90 ° C. and 30% R.D. H. After storing in the environment for 20 hours, the temperature was returned to room temperature, the random pattern was overwritten, the reproduction laser power Pr was set to 1.0 mW, and jitter was measured. As a result of studies by the present inventors, the increase in archival overwrite jitter is 90 ° C. and 30% R.D. H. Since it is almost saturated when stored in the environment for 20 hours, if the characteristics can be guaranteed in this environment, it is considered that the overwrite characteristics equivalent to 10 years can be guaranteed at room temperature. In this embodiment, as archival overwrite jitter, recording is performed 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 as 2 to 6 times speed recording. The target value of jitter when it is performed 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 characteristics that can actually be used in a drive without problems.

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

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

  A procedure for recording and reproducing data by using the optical recording medium information recording / reproducing apparatus and changing the recording pulse train configuration (recording strategy) and the linear velocity and examining the jitter value will be described below. In the present embodiment, as the double speed recording, the recording linear velocity is set to 8.2 m / sec, the recording data clock length is set to 17.1 ns, and the data transfer rate is set to 22 Mbps. In quadruple speed recording, the recording linear velocity is set to 16.4 m / sec, the recording data clock length is set to 8.6 ns, and the data transfer rate is set to 44 Mbps. In 6 × speed recording, the recording linear velocity is set to 24.6 m / sec, the recording data clock length 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 a temporary laser power, Pp0 = 10.5 mW, Pb0 = 4.0 mW at 2 × speed recording, Pp0 = 13.0 mW, Pb0 = 5.0 mW, 6 × speed recording at 4 × speed recording. In this case, Pp0 = 14.0 mW and Pb0 = 5.5 mW were set. At each recording speed, 3T to 14T marks are recorded using this temporary laser power, and 3T to 14T in the recording waveform shown in FIG. 5 so that thermal interference between marks generated between the marks is minimized. A leading pulse width Tfp and a trailing pulse width Tlp before and after the mark are determined and used as a recording strategy. At this time, the multi-pulse width Tmp was set to half the clock length of each recording speed.

  Next, at each recording speed, using the above recording strategy, the recording power is set to the temporary recording power Pp0, the erasing power Pb is set from 2.0 mW to 8.0 mW in increments of 0.2 mW, and the random pattern Was recorded 10 times, the reproduction laser power Pr was set to 1.0 mW, jitter was measured, and the dependency of jitter on erasing power shown in FIG. 6 was examined. As a method of determining the erasing power Pb used when actually recording data, in the erasing power dependence of jitter in FIG. The erasing power was 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. Further, the shape of the curve plotting the jitter against the recording power at each recording speed at this time is not only shifted with different power levels of Pb1 and Pb2, but also a power range where the jitter is low and stable, The low jitter power range was the center value of Pb1-Pb2 at double speed, but when the recording speed was increased, the curve shifted from the center value of Pb1-Pb2 to the higher power side. It was. From this, it can be said that the minimum jitter is not always obtained depending on the recording speed only by setting Pb to (Pb1-Pb2) / 2.

  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 The value of Pb was determined by changing the value of α to 0.2 to 0.6.

  For each of the obtained values of Pb, the recording power is set in steps of 0.5 mW from 8.0 mW to 16.0 mW using the above recording strategy, and after recording a random pattern 10 times, the reproduction laser power Pr Was set to 1.0 mW, jitter was measured, and the recording power dependence of jitter shown in FIG. 7 was examined. With respect to the recording power dependence of jitter in FIG. 7, the optimum recording power Pp was determined as Pp = K × Ppl as a function of Ppl with respect to the recording power Ppl at which the jitter is 13%. Here, the optimum recording power is 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 thus obtained, the archival overwrite jitter, the cross power overwrite jitter, and the cross erase jitter are recorded as the recording signal quality for each recording speed in the land. 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.

  At a linear velocity of 8.2 m / sec, which is a double speed recording, the value of α is changed to 0.50, 0.40, 0.35, 0.30, 0.25, 0.20, and each erasing power is changed. After obtaining the recording power, archival overwrite jitter, cross power overwrite jitter, and cross erase jitter at each value of α were examined. For comparison, archival overwrite jitter, cross power overwrite jitter, and cross erase jitter were also examined when α was 0.60. The results are shown in Table 1.

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

  When the target value of archival overwrite jitter is 10%, the target value of cross power overwrite jitter is 11%, and the target value of cross erase jitter is 8%, in double speed recording at a linear velocity of 8.2 m / sec, The target value is reached at α = 0.50. In addition, when the upper limit value of the archival overwrite jitter is 11%, the upper limit value of the cross power overwrite jitter is 12%, and the upper limit value of the cross erase jitter is 9%. In the double speed recording at 8.2 m / sec, the standard value is satisfied at α = 0.60 to 0.40. However, in consideration of the margin of each characteristic, it is most preferable to set α = 0.50 in the double speed recording at the linear velocity of 8.2 m / sec.

  At a linear velocity of 16.4 m / sec, which is quadruple speed recording, the value of α is changed to 0.50, 0.40, 0.35, 0.30, 0.25, and 0.20, and each erasing power is changed. After obtaining the recording power, archival overwrite jitter, cross power overwrite jitter, and cross erase jitter at each value of α were examined. For comparison, archival overwrite jitter, cross power overwrite jitter, and cross erase jitter were also examined when α was 0.60. The results are shown in Table 2.

  When quadruple speed recording is performed at a linear velocity of 16.4 m / sec, the archival overwrite jitter is substantially constant from α = 0.40 to 0.20, and jitter when the value of α is larger than this. Is getting worse. Further, the cross power overwrite jitter is substantially constant from α = 0.40 to 0.30, and it can be seen that the value of α tends to deteriorate the jitter before and after this value. Regarding the cross erase jitter, α = 0.60 to 0.25 is almost constant, 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. In this range, considering that the archival overwrite jitter and the cross erase jitter are minimized, it is most preferable to set α = 0.35 in the quadruple speed recording at the linear velocity of 16.4 m / sec. .

  Obviously, when recording at a higher linear velocity of 16.4 m / sec than when recording at a linear velocity of 8.2 m / sec, the archival overwrite was observed when α was made smaller than 0.5. Jitter is improved. In particular, with regard to archival overwrite jitter, not only is the optimum value of α shifted to a smaller value, but the range of α itself is narrowed to about half that at double speed, so that an optimum recording strategy can be set. Become more important.

  At a linear velocity of 24.6 m / sec, which is 6 × speed recording, the value of α was changed to 0.50, 0.40, 0.35, 0.30, 0.25, 0.20, and After obtaining the recording power, archival overwrite jitter, cross power overwrite jitter, and cross erase jitter at each value of α were examined. For comparison, archival overwrite jitter, cross power overwrite jitter, and cross erase jitter were also examined when α was 0.60. The results are shown in Table 3.

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

In 6 × speed recording at a linear velocity of 24.6 m / sec, the target value is found at α = 0.35 to 0.25. Further, α = 0.40 to 0.20 satisfies the standard upper limit value. In view of the fact that archival overwrite jitter and cross erase jitter are minimized within this range, it is most preferable to set α = 0.30 for 6 × speed recording at a linear velocity of 24.6 m / sec. . When recording at a linear velocity of 8.2 m / sec, clearly when recording at a higher linear velocity of 24.6 m / sec than when recording at a higher linear velocity of 16.4 m / sec, α When the value is made smaller than the value of α when the linear velocity is 2 × (linear velocity 8.2 m / sec) or 4 × (linear velocity 16.4 m / sec) , the archival overwrite jitter is improved. Yes. In addition, the optimum value of α is not only shifted to a value smaller than that at 4 × speed, but the range of α itself is further narrowed to about half that at 4 × speed, so that an optimum recording strategy can be set. Become more important.

  The results of Example 1 are summarized as follows. The erase power level Pb is set to Pb = α × using a value Pb1 larger than the reproduction power Pr and smaller than Pb and a value Pb2 larger than Pb and smaller than the recording power Pp. When defining Pb1 + (1-α) × Pb2, the most preferable value of α that improves archival overwrite jitter, cross power overwrite jitter, and cross erase jitter is when recording at a linear velocity of 8.2 m / sec. When recording at α = 0.50 and a linear velocity of 16.4 m / sec, α = 0.35, and when recording at a linear velocity of 24.6 m / sec, α = 0.30.

  A comparison of the optimal range of α in Example 1 is shown in Table 4. For 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 all recording speeds are covered. Since there is no α that can be set, it is necessary to set α according to the recording speed and set the recording power Pp and the erasing power Pb.

  Thus, the reason why the optimum α differs depending on the linear velocity of recording can be considered as follows. As the recording speed is increased, the generation of crystal nuclei in the recording process and the insufficient crystallization in the erasing process occur, resulting in poor archival overwrite characteristics. On the other hand, by changing the definition of the erasing power obtained from the jitter dependence of the erasing power according to the linear velocity of recording, recording with the optimum erasing power enables the generation of crystal nuclei in the recording process and the crystal in the erasing process. We think that we promote promotion.

  However, by increasing the erase power, the archival overwrite jitter, the cross power overwrite jitter, and the cross erase jitter are deteriorated. Therefore, an appropriate erase power setting, that is, an appropriate value of α is set at each recording speed. Exists. That is, by recording information on the relationship between Pb1, Pb2, and Pb in advance on the medium, recording can be performed with a suitable erasing power, and archival overwrite jitter can be improved. Furthermore, by recording on the medium in advance information relating to the above α, which expresses the value of Pb as the ratio of the value of Pb1 to the value of Pb2, recording can be performed at a suitable erasing power at each recording speed. , Archival overwrite jitter, cross power overwrite jitter, cross erase jitter can be improved.

  As described above, the information recording medium and the laser beam are relatively scanned at a linear velocity within a certain range, and the laser power of the laser beam is at least the recording laser power Pp and the erasing laser power lower than the recording laser power level. Information is recorded by power-modulating the level Pb and changing the state of the information recording portion of the information recording medium. Information is recorded by a laser beam having a reproduction laser power level Pr lower than the erase laser power level Pb. An information recording medium on which reproduction is performed, wherein a value Pb1 larger than Pr and smaller than Pb, a value Pb2 larger than Pb and smaller than Pp, and information relating to the relationship between Pb are recorded. Overwrite characteristics when performing high-speed recording 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 first embodiment is recorded in advance is reproduced by an information recording / reproducing apparatus, data is read / written using the value of α, and archival is performed. The overwrite characteristics were examined.

  The disc has a 4.7 GB DVD-RAM format, and the control data section contains information on the recording strategy of 5 × speed and 6 × speed, the recording sensitivity coefficient, and the information of α as in the case of 2 × speed. A stamper for producing the written disc was produced. At this time, the value of α at 5 × and 6 × recording is stamper A with α = 0.50 and α = 0.50, respectively, and the value of α at 5 × and 6 × recording is respectively α = 0.40. Two types of stamper B with α = 0.35 were produced. Here, α is a coefficient for obtaining the erasing power Pb from the relational expression of Pb = α × Pb1 + (1−α) × Pb2, Pb1 <Pb2.

Using the stamper A and the stamper B, the polycarbonate substrate A and the substrate B were formed by injection molding. By sputtering on the obtained substrate, ZnS-SiO ₂ is 100 nm as the first protective layer, GeCrN is 10 nm as the first interface layer, BiGeTe is 10 nm as the recording layer, GeCrN is 10 nm as the second interface layer, and the second protective layer As an information recording medium, ZnS—SiO ₂ was deposited in a thickness of 50 nm, GeCr as a heat absorption rate correction layer layer was deposited in a thickness of 50 nm, and Al as a thermal diffusion layer was deposited in a thickness of 120 nm. An information recording unit 75 and a control data unit 71 in the obtained information recording medium 1 are schematically shown in FIG. This information recording medium was initialized as Disk A and Disk B. Using the produced disc A and disc B, 5 × speed recording and 6 × speed recording were performed with a drive.

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

  FIG. 4 shows an outline of the recording / reproducing apparatus. The Pb calculation control unit 410 reads the erase power coefficient α recorded on the disk and calculates the erase power Pb from the relational expression 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 it mainly includes a Pb calculation control unit 410.

  Next, a procedure for examining the archival overwrite characteristics at the time of 5 × speed recording and 6 × speed recording on the disk A and the disk B by the drive will be described. First, random data is written 10 times with the obtained optimum power. The disc on which recording was completed was recorded at 90 ° C. and 30% R.D. H. After storing in the environment for 20 hours, the temperature is returned to room temperature, and random data is written once again at the same position. Thereafter, the recorded data was reproduced at a double speed reproduction of the recorded data at a reproduction power Pr = 1 mW using the optical recording medium information recording / reproducing apparatus, and the archival overwrite jitter after the environmental test was examined.

  As radial positions for disk recording with the drive, 5 × speed recording was performed from a radius of 43.30 mm to 44.20 mm, and 6 × recording was performed from a radius of 45.23 mm to 46.13 mm. Further, when the jitter was examined after the environmental test, the reproduction jitter was examined every 5 tracks in the recording area, and the average value was taken as the archival overwrite jitter after the environmental test.

  Note that when writing random data once with the drive after the environmental test, the drive performs the above-described process for obtaining the optimum strategy, optimum recording power, and optimum erasing power again. The strategy, optimum recording power, and optimum erasing power did not change.

  Table 5 shows the results of examining the archival characteristics at the time of 5 × speed recording and 6 × speed recording with the drive using the above-mentioned disc A and disc B.

  As can be seen from the results in Table 5, the value Pb1 larger than Pr and smaller than Pb, the value Pb2 larger than Pb and smaller than Pp, and information α relating to the relationship between Pb are recorded. When performing high-speed recording using an information recording medium, by setting α to a suitable value according to the recording speed, the archival overwrite characteristic that overwrites information after the medium is stored 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 even when recording is performed on the groove. In the present embodiment, the recording radial position is not particularly described, but the same effect is obtained at 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 is to improve the high-speed recording process, the effect of the present invention is obtained regardless of the reproduction speed. be able to.

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

  In this embodiment, 13% is used as the threshold value to obtain the values of Pb1 and Pb2 from the jitter dependence of the erasing power. However, the essence of the present invention is not based on the jitter threshold value, and Pb1 and Pb2 For example, the effect of the present invention is not lost even when the threshold value is determined using an arbitrary threshold value based on the error rate dependency of the erasing power or the signal amplitude, S / N, and asymmetry dependency instead of the jitter. .

In the embodiments of the present invention, a red laser having a wavelength of 655 nm is used. However, the present invention is not particularly based on the wavelength of the laser, and an information recording apparatus using a relatively short wavelength laser such as a blue laser or an ultraviolet laser. The present invention is also effective for information recording media used therefor.

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

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

Explanation of symbols

41 Information recording medium
42 Motor
43 Optical head
44 Preamplifier circuit
45 Recording waveform generator
46 Laser drive circuit
47 8-16 modulator
48 L / G servo circuit
49 8-16 Demodulator

Claims (7)

A method of recording information on a phase change recording type information recording medium by irradiating light modulated to a recording power level and an erasing power level:
Overwriting the random pattern on the information recording medium with light of predetermined recording power and various erasing powers;
Replaying the overwritten random pattern to obtain a minimum value Pb1 and a maximum value Pb2 of erasing power when a pattern whose reproduction jitter or reproduction error exceeds a predetermined threshold value;
Obtaining an optimum erasing power Pb for recording from the obtained minimum value Pb1 and maximum value Pb2 and a relational expression represented by Pb = α × Pb1 + (1−α) × Pb2;
Recording information using the determined optimum erasing power Pb; and when information is recorded at different recording speeds, α varies in the range of 0 <α ≦ 0.50 according to the recording speed and An information recording method characterized in that α decreases as the recording speed increases. 2. The information recording method according to claim 1, further comprising determining an optimum recording power Pp using the obtained optimum erasing power Pb. 3. The information recording method according to claim 1, wherein 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 at the time of information recording. 3. The information recording method according to claim 2, wherein Pr <Pb1 <Pb and Pb <Pb2 <Pp are satisfied when the reproduction power is Pr. An information recording medium of the phase-change recording method in which information is recorded by information recording method according to any one of claims 1 to 4,
An information recording unit in which information is recorded by irradiating a light beam having a recording power Pp and an erasing power Pb lower than the recording power Pp, and information is reproduced by irradiating a light beam having a reproducing power Pr lower than the erasing power Pb. When;
A control data section;
In the control data portion, Pb = α × Pb1 + (1 as information for obtaining the optimum erase power Pb from the minimum erase power Pb1 satisfying Pr <Pb1 <Pb and the maximum erase power Pb2 satisfying Pb <Pb2 <Pp. -Α) x represented by the formula of Pb2 is recorded in advance, the α is recorded together with information on the recording speed, and the α is in the range of 0 <α ≦ 0.50 depending on the recording speed. An information recording medium, which is different and has a smaller α as the recording speed increases. 6. The information recording medium according to claim 5, wherein the value of α satisfies 0.25 ≦ α ≦ 0.50. An information recording apparatus for recording information by irradiating the information recording medium according to claim 5 or 6 with light 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 modulated to a recording power level and an erasing power level from the optical head;
A minimum pattern Pb1 and a maximum value of erasing power when a random pattern overwritten with light of predetermined recording power and various erasing power is reproduced and a pattern in which reproduction jitter or reproduction error exceeds a predetermined threshold is erased. The value Pb2 is obtained, the coefficient α used in the expression Pb = α × Pb1 + (1−α) × Pb2 recorded in advance on the information recording medium is read, and the obtained minimum value Pb1 and maximum value Pb2 and the read coefficient α are read out. A Pb calculation control unit for obtaining an optimum erasing power Pb for recording.

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