JP2005149545A - Optical information recording method and optical information recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate an unerased mark left when overwriting is performed even when high speed recording corresponding to 6 times to 8 times of a DVD or more is performed, to reduce thermal damage due to repetitive recording and to enable satisfactory repetitive recording. <P>SOLUTION: When shift from mark formation to space formation is performed, light of peak power Pp is modulated into light of erasure power Pe under the condition of high speed specification such as a recording strategy of a 2T period and a strategy is used, wherein at least one pulse of irradiation with light of high erasure power Pe(h) higher than the erasure power Pe and lower than the peak power Pp and having a level at which a mark can be erased is performed within a basic clock period T after modulation into light of the erasure power Pe is started. Thereby, it is not needed that such a high power value that can erase all the marks is incorporated into the erasure power Pe itself, deterioration of jitter characteristics can be prevented, influence on repetitive recording durability can be reduced and the unerased mark left when overwriting is performed can be prevented by using the erasable high erasure power Pe(h). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a recordable optical information recording medium, particularly a phase change type optical information recording medium such as CD-RW, DVD-RAM, DVD-RW, DVD + RW, etc., and an optical information recording method and optical suitable for high-speed recording. The present invention relates to an information recording apparatus.

  In recent years, the demand for high-speed recording of optical information recording media has increased. In particular, in the case of a disk-shaped optical information recording medium, since the recording / reproducing speed can be increased by increasing the rotational speed, the speed has been increased. Among optical discs, optical information recording media that can be recorded by only modulating the intensity of the light irradiated during recording can reduce the cost of the medium and the recording device, and at the same time reproduce the recording medium due to the simplicity of the recording mechanism. Since modulated light is used, high compatibility with playback-only devices can be ensured, and the spread of electronic information has increased the demand for higher density and higher speed recording due to the recent increase in capacity of electronic information. Yes.

  Among such optical discs, those using a phase change material have become mainstream because they can be rewritten many times. In the case of an optical disk using a phase change material, recording is performed by creating a rapid cooling state and a slow cooling state of the recording layer material by intensity modulation of the irradiated light beam. The recording layer material becomes amorphous when it is rapidly cooled, and becomes crystalline when it is slowly cooled. Since optical properties are different between amorphous and crystalline, optical information can be recorded.

  That is, the phase change optical information recording medium irradiates the recording layer thin film on the substrate with laser light to heat the recording layer, and changes the recording layer structure between a crystal and an amorphous layer to change the disk reflectivity. It changes and records and erases information. Normally, information is recorded by forming a non-recorded state as a high-reflectance crystal phase, and forming a mark composed of a low-reflectance amorphous phase and a space composed of a high-reflectance crystal phase.

  Since the recording principle uses such a complicated mechanism of “rapid cooling” and “slow cooling” of the recording layer material, pulse recording is performed as is well known for high-speed recording, and the intensity is modulated into three values. This is done by irradiating the medium with recording light.

  As a waveform light emission pattern (recording strategy) for repeatedly recording data consisting of marks and spaces, there is one used in DVD + RW as shown in FIG. The amorphous mark is formed by pulse irradiation by alternately repeating the peak power (Pw = Pp) light and the bias power (Pb) light, and the crystal space is a medium level erase power (Pe) light. It is formed by continuous irradiation.

  When a pulse train composed of peak power light and bias power light is irradiated, the recording layer repeats melting and quenching to form amorphous marks. When the erasing power light is irradiated, the recording layer is gradually cooled after being melted, or annealed in a solid state and crystallized to form a space. A pulse train composed of peak power light and bias power light is usually divided into a first pulse, an intermediate pulse, and a last pulse, and the shortest 3T mark is recorded only by the first pulse and the last pulse, and a mark of 4T or more is formed. An intermediate pulse is also used. The intermediate pulse is also called a multi-pulse, and is provided in a 1T cycle, and the number of pulses is increased by one every time the mark length becomes 1T longer. That is, the number of pulse trains is (n-1) with respect to the length nT. Also, a pulse train that records a 3T mark with only one pulse of the first pulse, forms 4T with two pulses of the first pulse and the last pulse, and uses an intermediate pulse provided with a 1T cycle when forming a mark of 5T or more. May be (n−2) for the length nT.

  By the way, at the time of high-speed recording exceeding the quadruple speed of DVD, since the time of the basic clock period T is shortened, the load on the light source driving unit is increased. Further, when a pulse train having a 1T period as shown in FIG. 12 is irradiated, both the heating time and the cooling time are shortened, resulting in a problem that an amorphous mark having a sufficiently large size cannot be formed. In order to avoid this, the period of the pulses is longer than 1T to reduce the number of pulses for forming the amorphous mark, and sufficient time for both heating and cooling is ensured. Various proposals have been made that can be formed (for example, see Patent Documents 1 to 4 and many others).

  Among them, in Patent Document 4, every time the mark length increases by 2T, one heating pulse and one cooling pulse are increased, and the level of erasing power for space data is increased or decreased at the beginning of the erasing area after the last cooling pulse. A recording method has been proposed in which an erase pulse for recording marks that defines the recording mark length is added by changing. FIG. 13 shows an example of a pulse train when 4T marks and 5T marks are formed. In the case of a 4T mark, the erase power level at the beginning of the erase region is increased to recrystallize the rear end portion of the amorphous material to shorten the mark length. In the case of the 5T mark, the erase power level is increased. By reducing the length, the mark length is adjusted to be long so that the rear end portion of the amorphous is not recrystallized so much.

  This makes it possible to support high-speed recording on the basis of ensuring a sufficient heating time and cooling time by making the substantial period of the heating pulse and cooling pulse in the multi-pulse train longer than the recording channel clock period, and the multi-pulse train. The trailing edge position of the recording mark can be controlled with high accuracy by the last cooling pulse and the erasing pulse immediately after it without changing each heating pulse.

  Further, according to Patent Document 5, as a recording method for improving the jitter at the trailing edge of the mark particularly during high-speed recording, as shown in FIG. 14, after the final peak power for forming the amorphous mark, the erasing power level Recording methods with higher trailing power levels have been proposed.

JP 2002-237051 A JP 2002-288837 A JP 2001-331936 A JP 2002-334433 A Special table 2003-504783 gazette

  According to Patent Document 4, the position of the trailing edge of the mark can be controlled by relatively simple control, and good recording can be performed at the time of initial recording. However, repetitive recording is not taken into consideration. In the case of adjusting the mark length by subtracting, there is a risk that the previous mark will remain unerased when overwriting.

  In Patent Document 5, the erasing power level stipulates that the mark can be erased by irradiation of the erasing power level. Further, although there is no specific statement regarding the cycle of the multi-pulse, it can be seen from the description of the figure that the cycle is 1T. Needless to say, in the case of high-speed recording that exceeds DVD 4 × speed with a multi-pulse of 1T period, as described above, since the heating and cooling times are short, a sufficiently large amorphous mark cannot be formed. Even if an amorphous mark having a sufficiently large size is formed with a period longer than 1T, all marks are erased at the erasing power level, and if higher trailing power is introduced, Since the load increases, depending on the type of the recording layer material, the repeated recording durability may deteriorate.

  It is an object of the present invention to prevent the previous amorphous mark from being erased at the time of overwriting even at high-speed recording exceeding 4 × speed of DVD and equivalent to 6-8 × speed, and heat generated by repeated recording. It is also possible to reduce the general damage and to perform good repeated recording.

  According to the first aspect of the present invention, information is recorded on the optical information recording medium by a mark length recording method represented by nT in which the time length of the recording mark is n times the basic clock period T (n is a natural number). In the optical information recording method, an amorphous mark having a length of nT by irradiation with an integer number of pulses equal to or less than n / 2 by repeating a peak power light having a relatively high power value and a bias power light having a relatively low power value. And forming a crystal space having a length nT between the amorphous marks by irradiation with an erasing power light having an intermediate power value between the peak power light and the bias power light. Is shifted from the peak power light to the erasing power light, and within the basic clock period T after the start of the modulation to the erasing power light, is shifted from the erasing power light to the formation of the crystal space. The high erasing power light power values erasable levels of the peak power the amorphous mark lower than light, and to use a recording strategy for at least one pulse.

  According to a second aspect of the present invention, in the optical information recording method according to the first aspect, at the time of transition from the formation of the amorphous mark to the formation of the crystal space, a modulation process from the peak power light to the bottom power light is performed once. Modulate to erase power light.

  According to a third aspect of the present invention, in the optical information recording method according to the first or second aspect, the irradiation time of the high erasing power light is 0.2T or more and 2T or less.

  According to a fourth aspect of the present invention, in the optical information recording method according to any one of the first to third aspects, the number of pulses of the high erasing power light is increased by one every time the crystal space length increases by 3T or more.

  A fifth aspect of the present invention is the optical information recording method according to any one of the first to fourth aspects, wherein the level of the power value of the high erasing power light is 1.1 times or more and 2 times that of the erasing power light. It is as follows.

  According to a sixth aspect of the present invention, in the optical information recording method according to any one of the first to fifth aspects, a phase-change optical information recording medium is used as the optical information recording medium.

  According to a seventh aspect of the present invention, in the optical information recording method according to the sixth aspect, the phase change optical recording medium includes at least a first protective layer, a recording layer, a second protective layer, and a reflective layer on a substrate. The formed recording layer contains at least one element selected from Sb and Ge, Ga, In, Zn, Mn, Sn, Ag, Mg, Ca, Ag, Bi, Se, and Te.

  The invention according to claim 8 is the optical information recording method according to claim 7, wherein the Sb content of the recording layer is 50 to 90 atomic%.

  The invention according to claim 9 is the optical information recording method according to claim 7 or 8, wherein the reflective layer is made of Ag or an Ag alloy.

A tenth aspect of the present invention is the optical information recording method according to any one of the seventh to ninth aspects, wherein the first protective layer and the second protective layer are a mixture of ZnS and SiO ₂ .

  An eleventh aspect of the present invention is the optical information recording method according to the ninth or tenth aspect, wherein the phase change optical information recording medium includes an antisulfurization layer between the second protective layer and the reflective layer.

  According to a twelfth aspect of the present invention, in the optical information recording method according to the eleventh aspect, the sulfidation prevention layer contains Si or SiC as a main component.

  According to a thirteenth aspect of the present invention, information is recorded on the optical information recording medium by a mark length recording method represented by nT in which the time length of the recording mark is n times the basic clock period T (n is a natural number). In the information recording apparatus, a laser light source that emits a laser beam to irradiate the optical information recording medium, a light source driving unit that emits light from the laser light source, and a recording strategy relating to an emission waveform of a light beam emitted from the laser light source are set. And a light emission waveform control means for controlling the light source driving means, wherein the light emission waveform control means n is obtained by repeating a peak power light having a relatively high power value and a bias power light having a relatively low power value. An amorphous mark having a length of nT is formed by irradiation with an integer number of pulses equal to or less than / 2, and the power at an intermediate level between the peak power light and the bias power light When forming a crystal space with a length nT between amorphous marks by irradiation of erasing power light, modulation from peak power light to erasing power light is performed at the time of transition from the formation of the amorphous mark to the formation of the crystal space. Then, within the basic clock period T after the start of modulation to the erasing power light, the high erasing power light having a power value higher than the erasing power light and lower than the peak power light and capable of erasing the amorphous mark. A recording strategy for irradiating at least one pulse was used.

  According to a fourteenth aspect of the present invention, in the optical information recording apparatus according to the thirteenth aspect, the light emission waveform control means temporarily changes the peak power light to the bottom power during the transition from the formation of the amorphous mark to the formation of the crystal space. The light is modulated into an erasing power light through a light modulation process.

  According to a fifteenth aspect of the present invention, in the optical information recording apparatus according to the thirteenth or fourteenth aspect, the emission waveform control means sets the irradiation time of the high erasing power light to 0.2 T or more and 2 T or less.

  According to a sixteenth aspect of the present invention, in the optical information recording apparatus according to any one of the thirteenth to fifteenth aspects, the light emission waveform control means increases the number of pulses of the high erasing power light by increasing the crystal space length by 3T or more. Increase by one each time.

  According to a seventeenth aspect of the present invention, in the optical information recording apparatus according to any one of the thirteenth to sixteenth aspects, the emission waveform control means sets the power value level of the high erasing power light to 1 of the erasing power light. .1 to 2 times

  According to an eighteenth aspect of the present invention, in the optical information recording apparatus according to any one of the thirteenth to seventeenth aspects, a phase change optical information recording medium is targeted as the optical information recording medium.

  According to the first and third aspects of the invention, for example, in the case of a high-speed specification condition using an integer number of pulse irradiations of n / 2 or less for forming an nT mark, such as a 2T period recording strategy, At the time of transition from the formation of the mark to the formation of the crystal space, the peak power light is modulated from the erasing power light, and within the basic clock period T after the modulation to the erasing power light is started, the erasing power light is higher than the erasing power light. By using a recording strategy that irradiates at least one pulse of a high erasing power light having a power value that is low and can be erased from the amorphous mark, the erasing power light itself is not necessarily previously emitted at the recording linear velocity. It is not necessary to have a power value that is high enough to erase all the recorded amorphous marks, so that jitter characteristics are not deteriorated and repeated. It is possible to reduce the influence of the recording durability can be prevented unerased mark overwritten during the securely erasable pulsed high erasing power, it is possible to achieve good Naru repetitive recording. In addition, by starting the high erasing power light within 1T from the start of the irradiation of the erasing power Pe light, not only can the previous mark be erased at the time of overwriting but also the trailing edge of the mark even in the first recording. Jitter can be reduced.

  According to the inventions of claims 2 and 14, when shifting from the formation of the amorphous mark to the formation of the crystal space, the modulation is performed from the peak power light to the bottom power light once to the erasing power light. As a result, the temperature condition at the time of shifting to the erasing power light irradiation is made uniform, the variation of the mark tip position is less likely to occur, and the jitter can be further reduced.

  According to the third and fifteenth aspects of the present invention, by setting the irradiation time per pulse of the high erasing power light to 0.2 T or more and 2 T or less, the mark which is partially thick is surely erased. In addition, it is possible to avoid the problem that the jitter at the beginning of the mark becomes high and prevent the repeated recording durability from being deteriorated.

  According to the fourth and sixteenth aspects of the present invention, the number of pulses of the high erasing power light is increased by one every time the space length increases by 3T or more. When there is a part that is partially thick in the middle of forming a long space, it may not be able to be erased. Can do.

  According to the fifth and 17th aspects of the present invention, the mark erasing function by the high erasing power light is surely exhibited by setting the level of the high erasing power light to 1.1 to 2 times the erasing power Pe. In addition, because the power value is not too high, the temperature rises too much, making it difficult to control the mark length and worsening jitter, and repeated recording durability due to excessive temperature rise Can be avoided.

  According to the invention described in claims 6 to 12 and 18, it can be suitably applied to a phase change type optical information recording medium of high speed specification.

  The best mode for carrying out the present invention will be described below with reference to the drawings. This embodiment is an optical information recording medium that can be recorded, erased, or rewritten by intensity modulation of irradiation light, particularly a phase change optical information recording medium, for example, at a high speed equivalent to 6 to 8 times the speed of DVD. The present invention is applied to an optical information recording method and an optical information recording apparatus (including an optical information reproducing apparatus) for performing recording.

[Optical information recording medium]
First, an example of a DVD specification and high-speed phase change optical information recording medium suitable for the optical information recording method of the present embodiment will be described with reference to FIG.

  In the present embodiment, a phase change optical information recording medium 6 in which at least a first protective layer 2, a recording layer 3, a second protective layer 4, and a reflective layer 5 are laminated on a transparent substrate 1 having guide grooves. Is targeted.

  The transparent substrate 1 is preferably polycarbonate from the viewpoints of heat resistance, impact resistance, low water absorption, and the like. The refractive index is preferably 1.5 to 1.65. When the refractive index is higher than this, the reflectivity of the entire disk is lowered, and when it is lower, the modulation factor is insufficient due to the increase in reflectivity. The thickness is preferably 0.59 to 0.62 mm, and if it exceeds this range, a problem occurs in the focus performance of the pickup. Further, if the thickness is too thin, there is a problem that the rotational speed becomes unstable due to the weakness of the clamp of the recording / reproducing apparatus. Furthermore, when the thickness unevenness in the circumferential direction exceeds this range, there arises a problem that the signal intensity varies within the circumference.

  The recording layer 3 is made of a material containing at least one element selected from Sb and Ge, Ga, In, Zn, Mn, Sn, Ag, Mg, Ca, Ag, Bi, Se, and Te. A recording layer based on Sb and suitable for repeated recording of amorphous and crystals when combined with an element having a binary system with Sb and a melting point of about 600 ° C. or a eutectic point or a solid solution. 3 can be formed. Properties such as crystallization speed, recording characteristics, storage stability, and ease of initialization are adjusted according to the type and amount of elements to be combined. There are one or more elements to be combined with Sb, and any number may be used as necessary. Further, another element may be added to the binary alloy of the element and Sb described above.

  When repetitive recording is performed at high speed, it is necessary to crystallize the amorphous mark at high speed. Therefore, when recording at a speed equivalent to 6 to 8 times the speed of DVD as in this embodiment, Sb is 50. ˜90 atomic%, more preferably 60-80 atomic%. If it is less than this, the crystallization speed is too slow, and amorphous marks remain unerased during repeated recording, leading to an increase in jitter and errors. If it is more than this, it will be difficult to form amorphous.

  If the thickness of the recording layer 3 is less than 8 nm, the degree of modulation is small, and the stability of the reproduction light is also reduced. Therefore, the recording layer 3 is 8 nm or more, and if it is thicker than 22 nm, the increase in jitter due to repeated recording is large. To do. More preferably, when the thickness is 11 to 16 nm, the repeated recording durability is particularly improved.

  Conventionally, an alloy mainly composed of Al is used as the reflective layer 5. In addition to high reflectivity and high thermal conductivity, Al is also excellent in stability over time when made into a disk. However, when the crystallization speed of the recording layer 3 material is high, the recording mark is likely to be thin on a disk using an Al alloy that is often used conventionally as the reflective layer 5, and recording with a sufficient degree of modulation is performed. It can be difficult. The reason for this is that if the crystallization speed is high, the recrystallized area of the melted area becomes large during recording, and the formed amorphous area becomes small. In order to reduce the recrystallized region, the second protective layer 4 may be thinned to have a rapid cooling structure, but simply by making the second protective layer 4 thin, the recording layer 3 is sufficiently heated. However, since the melted region becomes small, even if the recrystallized region can be made small, the formed amorphous region eventually becomes small. However, when a metal having a refractive index (n + ik) of n and k smaller than Al is used for the reflective layer 5 at a wavelength of 650 to 670 nm, the absorptance of the recording layer 3 is improved and the degree of modulation can be increased. Examples of metals smaller than Al for both n and k include Au, Ag, Cu, and alloys based on them. Here, the main component means containing 90 atomic% or more, and preferably 95 atomic% or more.

  Au, Ag, and Cu all have a higher thermal conductivity than Al at the same time. When these are used as the reflective layer 5, the light absorption rate of the recording layer 3 is improved, the temperature of the recording layer 3 is increased, and the melting region is increased. At the same time as increasing the cooling rate, the cooling rate is also improved, so that the recrystallization region at the time of cooling becomes small, and it becomes possible to form a larger amorphous region than when an Al alloy is used. The modulation degree of the recording mark is determined by the optical modulation degree and the size of the mark. The optical modulation degree is large, and the larger the mark, the larger the recording mark. Therefore, even when high linear velocity recording is performed using a material having a high crystallization speed as the recording layer 3, if such a reflective layer 5 is used, a large recording mark is formed due to a high absorption rate and a high cooling rate. In addition, since the difference in reflectance between crystal and amorphous is large, recording with a high degree of modulation becomes possible.

  Among Au, Ag, Cu, and alloys based on them, in particular, Ag and Ag alloy are relatively inexpensive, and are less susceptible to oxidation than similarly inexpensive Cu and Cu alloys. Therefore, a medium having excellent stability over time can be formed, which is preferable as the reflective layer.

  If the thickness of the reflective layer 5 is 90 nm or more, the transmitted light is almost eliminated and the light can be used efficiently. The thicker the film, the faster the cooling rate, which is advantageous when using the recording layer 3 having a high crystallization rate. However, the cooling rate is saturated at 200 nm or less, and the recording characteristics change even when the thickness is greater than 200 nm. In addition, since it takes only a long time to form a film, it is preferable to set the thickness to 200 nm or less.

  When Ag or an Ag alloy is used as the reflective layer 5, the sulfuration preventing layer 7 is necessary when a material containing S is used for the second protective layer 4. Properties required for the sulfidation preventing layer 7 include not containing S, not transmitting S, and the like. The inventors of the present invention formed various oxide films, nitride films, and the like as the antisulfurization layer 7 and evaluated recording characteristics and storage reliability. As a result, SiC, Si, or one of them was the main component. It was found that the material has an excellent function. Here, the main component means that 90 mol% or more of SiC or Si is contained in the material, and preferably 95 mol% or more.

  The film thickness of the sulfidation preventing layer 7 is preferably 3 to 22 nm. If the thickness is 3 nm or more, the film formed by sputtering becomes almost uniform and exhibits a function of preventing sulfidation. However, if the thickness is smaller than this, the probability that a defect is partially generated increases rapidly. Further, if the thickness exceeds 22 nm, the reflectivity decreases as the film thickness increases, and the film formation speed is almost the same as that of the recording layer 3 even if estimated to be large. Therefore, it is desirable not to exceed the film thickness of the recording layer 3 at the maximum, and the preferable upper limit is 22 nm after all.

  As the first protective layer 2 and the second protective layer 4, in addition to the function as a protective film such as heat resistance, since the refractive index is high and the heat insulation is high, incident light is efficiently used by adjusting the film thickness. A mixture of ZnS and SiO 2 having a molar ratio of about 8: 2 is used.

  The film thickness of the first protective layer 2 is 40 to 220 nm, more preferably 40 to 80 nm. This is a value mainly determined from the reflectance. Within this range, a film thickness that can achieve both sufficient reflectance and recording sensitivity is selected. If it is thinner than this, the heat resistance is poor, the damage given to the substrate 1 is increased, and the increase in jitter due to repeated recording is increased. If it is thick, the reflectance becomes too high and the recording sensitivity is lowered.

  The thickness of the second protective layer 4 is 2 to 20 nm, more preferably 6 to 14 nm. This is a value mainly determined from heat conduction. Since the reflective layer 5 is further provided on the second protective layer 4, the heat absorbed by the recording layer 3 diffuses to the reflective layer 5 through the second protective layer 4 and is cooled. Therefore, if it is too thin, the thermal diffusion is too fast and the recording layer 3 is not sufficiently heated, and the recording sensitivity is lowered. If it is too thick, the cooling rate will be insufficient and it will be difficult to form amorphous marks.

  A film as described above is formed on the substrate 1 by sputtering in the order of the first protective layer 2, the recording layer 3, the second protective layer 4, the antisulfuration layer 7, and the reflective layer 5, and then an organic protective film on the reflective layer 5. 8 is formed by spin coating. In this state, or after passing through a bonding process, the optical information recording medium 6 is used through an initialization process. Bonding is a process of bonding a plate having the same size and usually the same material as the substrate through the organic protective film 8.

  Initialization is a process of crystallizing the recording layer 3 in an amorphous state immediately after film formation by irradiating laser light of about 1 to 2 W formed to about 1 × (several 10 to several 100) μm. .

[Optical information recording method]
Next, an optical information recording method according to this embodiment for the high-speed optical information recording medium 6 as described above, in particular, its recording strategy will be described with reference to FIG.

  Here, it is assumed that information is recorded by a recording mark length and mark length modulation method in which PWM (Pulse Width Modulation) is applied to the optical information recording medium 6. In this recording method, information can be recorded by controlling the length of the recording mark and the length between the marks in units of the basic clock period T. Since the recording density can be made higher than that of the mark position modulation method which is one of the recording methods of the optical information recording medium, it is characterized in that the recording density can be increased and is adopted in CD and DD (Double Density) CD. This is a modulation method employed in an optical disk such as EFM + employed in EFM and DVD. In the recording mark length and inter-mark length modulation system, it is important to accurately control the recording mark length and the inter-mark length (hereinafter, space length). In these modulation methods, the recording mark length and space length are both nT (n is a natural number of 3 or more) with respect to the basic clock period T.

  Here, in the present embodiment, the number of pulses is set so that sufficient heating and cooling can be performed as a high-speed specification also for a recording strategy using three values of peak power Pp (= Pw), erasing power Pe, and bias power Pb. An amorphous mark having a length of nT is formed by irradiating an integer number of pulses equal to or less than n / 2 by repeating the peak power Pp light and the bias power Pb light, and amorphous by irradiating the erasing power Pe light. It is assumed that a crystal space having a length nT between quality marks is formed. Therefore, 3T, which is the minimum mark formed according to the EFM + modulation method, is formed with one pulse. When the shortest 3T mark is formed with two or more pulses, a sufficient cooling time cannot be taken between the pulses, and the leading edge of the mark is recrystallized by a subsequent pulse, and a mark having a predetermined size cannot be formed. A mark of 4T or more may be formed by one pulse as in 3T, or may be formed by two or more pulses. The number of pulses is mainly determined by the recording linear velocity, and it is better to reduce the number of pulses as the recording linear velocity is faster.

  Under such a high-speed specification condition, the optical information recording method of the present embodiment is such that, at the time of transition from the formation of the amorphous mark to the formation of the crystal space, the erasing power passes from the peak power Pp light to the bottom power Pb light. Modulated to Pe light, or directly modulated from peak power Pp light to erasing power Pe light, and higher than erasing power Pe within the basic clock period T after the start of modulation from peak power Pp light to erasing power light Pe. A recording strategy in which at least one pulse of high erasing power Pe (h) light that is lower than the power Pp and at which the amorphous mark can be erased is used. FIG. 2 shows an example in the case of modulating from the peak power Pp light to the bottom power Pb light and then modulating to the erasing power Pe.

  The erasing power Pe light at this time may be a power value that does not necessarily erase all previously recorded marks when irradiated at the recording linear velocity. As shown in FIG. 3, the recording marks (amorphous marks) are not always uniform in thickness, but are often partially thick. In particular, as shown in FIG. 3, a case where the rear end of the mark is thick is often seen. When crystallization proceeds by crystal growth from the interface with the crystal phase as in the recording layer containing Sb as a main component, the temperature at the interface with the crystal phase is important. FIG. 4 shows the relationship between the crystal growth rate and temperature. The crystal growth rate generally becomes maximum at a temperature just below the melting point, and crystal growth hardly occurs when the temperature is low. If the interface with the crystal phase does not rise to a temperature at which crystal growth can proceed rapidly, that is, close to the melting point, all amorphous marks cannot be crystallized and remain.

  This is shown in FIG. FIG. 5A schematically shows the crystallization when the erasing power on the amorphous mark is irradiated at a constant linear velocity. The region where the temperature is higher than the temperature at which the crystal growth rate proceeds is shown in light gray. If the interface between the amorphous and the crystal enters this region, it can be crystallized at high speed because it crystallizes at high speed, but the amorphous mark partially thickens and the portion protrudes from this region. In this case, the crystal growth rate is slow, and amorphous marks remain in the shape as shown in FIG.

  In order to prevent such unerasing, it is necessary to increase the level of the erasing power and widen the temperature region where the crystal growth rate proceeds at high speed. That is, in order to erase all the amorphous marks that are partially thick, the erasing power must be set higher. However, when the recording speed is increased, there is a problem that the jitter at the head of the mark is increased particularly when the erasing power is set higher. Since this is a high speed, the peak power for forming the amorphous mark is irradiated before the temperature reaches a steady state due to the irradiation of the erasing power for forming the space. This is considered to be because the temperature at the time of irradiation is varied, and the position of the mark head portion also varies. Since the variation in temperature when the first peak power is irradiated becomes larger as the erasing power is higher, the jitter at the head of the mark becomes larger. In addition, when the erasing power is high, the load due to the heat applied to the medium is increased, so that the deterioration of the film quality due to the repeated recording is likely to proceed, and the repeated recording durability is deteriorated.

  However, in the case of the present embodiment, the power value of the erasing power Pe light does not necessarily have to be set so high that all the marks are erased. By irradiating with a pulse of high erasing power Pe (h) light that can be surely erased, marks that are partially thick are also erased, and since the load by heat is small, there is little influence on repeated recording durability, Good repeated recording can be achieved. The pulse irradiation timing of the high erasing power Pe (h) light starts within 1T after the irradiation of the erasing power Pe light is started. As a result, not only can the previous mark be erased satisfactorily during overwriting, but also the effect of reducing the jitter at the trailing edge of the mark even in the case of initial recording.

  The irradiation time per pulse of the high erasing power Pe (h) light is 0.2T or more and 2T or less. If it is shorter than this, the temperature is not sufficiently raised, so that the effect of erasing marks that are partially thick cannot be expected. On the other hand, if the length is longer than this, the value of the erasing power Pe becomes all equivalent to a high erasing power, and the jitter at the head of the mark becomes high or the repeated recording durability deteriorates. .

  In addition, if the pulse of the high erasing power Pe (h) light is irradiated only at the beginning of the space formation, there is a case where there is a part that is partially thick in the middle of forming the long space, and the erasing cannot be completed. Therefore, every time the space length increases by 3T or more, the number of pulses of the high erasing power Pe (h) light is increased by one. Each time the space length increases by 3T, it may be increased by one, or may be increased by one every time 4T or 5T increases. You may combine them. The method of increasing the pulse of the high erasing power Pe (h) varies depending on the characteristics of the recording linear velocity and the shape of the previously recorded mark. However, one pulse is sufficient for forming the 3T to 5T space, and if the number of pulses is more than necessary, repeated recording durability is deteriorated, so care must be taken.

  The level of the high erasing power Pe (h) light is 1.1 to 2 times the erasing power Pe. If the temperature is lower than this, the temperature is not sufficiently raised, and an effect of erasing a mark that is partially thick cannot be expected. If the temperature is higher than this, the temperature will rise too much, and it will be difficult to control the mark length and the jitter will worsen, or if the temperature rises more than necessary, the repeated recording durability will deteriorate. At this time, even if it is less than twice the erasing power Pe, the power value of the peak power Pp light must not be exceeded.

[Optical information recording device]
Next, a configuration example of an optical information recording apparatus for realizing the optical information recording method based on the above-described recording strategy will be described with reference to FIG.

  First, a rotation control mechanism 22 including a spindle motor 21 that rotates the optical information recording medium 6 is provided for the optical information recording medium 6 of DVD + RW, and laser light is applied to the optical information recording medium 6. An optical head 24 provided with an objective lens for condensing irradiation and a laser light source such as a semiconductor laser LD23 is provided so as to be seekable in the disk radial direction. An actuator control mechanism 25 is connected to the objective lens driving device and output system of the optical head 24. A wobble detection unit 27 including a programmable BPF 26 is connected to the actuator control mechanism 25. The wobble detection unit 27 is connected to an address demodulation circuit 28 that demodulates an address from the detected wobble signal. A recording clock generator 30 including a PLL synthesizer circuit 29 is connected to the address demodulating circuit 28. A drive controller 31 is connected to the PLL synthesizer circuit 29.

  The rotation controller 22, the actuator controller 25, the wobble detector 27, and the address demodulator 28 are also connected to the drive controller 31 connected to the system controller 32.

  The system controller 32 has a so-called microcomputer configuration including a CPU and the like. Further, an EFM encoder 34, a mark length counter 35, and a pulse number control unit 36 are connected to the system controller 32. The EFM encoder 34, the mark length counter 35, the pulse number control unit 36, and the system controller 32 are connected to a recording pulse train control unit 37 serving as a light emission waveform control unit. The recording pulse train controller 37 generates a multi-pulse (on pulse for peak power Pp, off pulse for bias power Pb) and an erasing pulse of erasing power Pe or Pe (h) defined by a preset recording strategy. A multi-pulse generation unit 38, an edge selector 39, and a pulse edge generation unit 40 are included.

  On the output side of the recording pulse train controller 37, the optical head is switched by switching the respective drive current sources 41 of the recording power Pw (peak power Pp), the erasing power Pe (including Pe (h)), and the bias power Pb. An LD driver section 42 is connected as a light source driving means for driving the semiconductor laser LD 23 in 24.

  In such a configuration, in order to record on the optical information recording medium 6, the rotation control mechanism controls the rotational speed of the spindle motor 21 under the control of the drive controller 31 so that the recording linear velocity corresponds to the target recording velocity. 22, the address demodulation is performed from the wobble signal separated and detected by the programmable BPF 26 from the push-pull signal obtained from the optical head 24, and the recording channel clock is generated by the PLL synthesizer circuit 29. Next, in order to generate a recording pulse train by the semiconductor laser LD 23, a recording channel clock and EFM + data as recording information are input to the recording pulse train control unit 37, and the multi-pulse generation unit 38 in the recording pulse train control unit 37 performs FIG. A multi-pulse according to the recording strategy as shown in FIG. 6 is generated, and the drive current source 41 set so as to have the irradiation powers of Pw, Pe (including Pe (h)), and Pb described above by the LD driver unit 42. By switching the, the LD emission waveform according to the recording pulse train can be obtained.

  Further, in the recording pulse train control unit 37 configured as in the present embodiment, a mark length counter 35 for counting the mark length of the EFM + signal obtained from the EFM encoder 34 is arranged, and the mark count value is 2T. A multi-pulse is generated via the pulse number control unit 36 so that a set of pulses (an ON pulse based on the recording power Pw (peak power Pp) and an OFF pulse based on the bias power Pb) is generated each time it increases. .

  As another configuration of the multi-pulse generation unit, a recording frequency-divided clock obtained by dividing the recording channel clock by two is generated, an edge pulse is generated using a multi-stage delay circuit, and the front and rear edges are selected by the edge selector. Thus, every time the recording channel clock increases by 2T, one set of pulses (an on-pulse by the recording power Pw (peak power Pp) and an off-pulse by the bias power Pb) can be generated. In the case of this configuration, the substantial operating frequency of the multi-pulse generator is halved, and further high-speed recording operation is possible.

  Examples according to the above-described embodiment will be described below.

[Example 1]
FIG. 7 shows an example of the recording strategy of this embodiment. In the mark formation, every time the mark length increases by 2T, the pulse of the peak power Pp light is increased by one. When moving from the mark formation to the space formation, the peak power Pp light is once modulated to the bottom power Pb light and then the erasing power Pe light. And irradiating a pulse of high erasing power Pe (h) light at the same time as the modulation to erasing power Pe light is started. The pulse of the high erasing power Pe (h) light is only one pulse regardless of the space length.

The optical information recording medium 6 used at this time had a recording layer of ZnS—SiO ₂ with a thickness of 60 nm as a lower protective layer 2 on a polycarbonate disk substrate 1 with a guide groove having a diameter of 12 cm, a thickness of 0.6 mm, and a track pitch of 0.74 μm. Sputtering of In—Sb—Ge 15 nm thick as layer 3, ZnS—SiO ₂ thick 12 nm as upper protective layer 4, SiC 4 nm thick as anti-sulfurization layer 7, Ag 140 nm thick as reflective layer 5 , Overcoated with an organic protective film 8, a polycarbonate disk having a thickness of 0.6 mm is bonded, and is initially crystallized by a large-diameter LD.

  A random pattern having a recording bit length of 0.267 μm / bit was repeatedly recorded at 28 m / s corresponding to DVD 8 × speed using the optical head 24 having a wavelength of 660 nm and NA of 0.65 by the EFM + modulation method. The set values of each power at this time are Pw (= Pp) = 26 mW, Pb = 0.1 mW, Pe = 6 mW, and Pe (h) = 7.5 mW. The pulse irradiation time of the high erasing power Pe (h) light was 1T. FIG. 11 shows the relationship between the number of repeated recordings and jitter at this time.

[Example 2]
FIG. 8 shows an example of the recording strategy of this embodiment. In the mark formation, every time the mark length increases by 2T, the pulse of the peak power Pp light is increased by one. When moving from the mark formation to the space formation, the peak power Pp light is once modulated to the bottom power Pb light and then the erasing power Pe light. The pulse of the high erasing power Pe (h) light is irradiated after 0.8 T from the start of the modulation to the erasing power Pe. The pulse of the high erasing power Pe (h) light is only one pulse regardless of the space length.

  The optical information recording medium 6 and the recording conditions used at this time were all the same as in Example 1, and only the irradiation start time of the high erasing power Pe (h) was changed. FIG. 11 shows the relationship between the number of repeated recordings and jitter at this time.

[Example 3]
FIG. 9 shows an example of the recording strategy of this embodiment. In the mark formation, every time the mark length increases by 2T, the pulse of the peak power Pp light is increased by one. When moving from the mark formation to the space formation, the peak power Pp light is once modulated to the bottom power Pb light and then the erasing power Pe light. And at the same time the pulse of high erasing power Pe (h) light is irradiated. The number of pulses with high erasing power Pe (h) was increased by 1 every time the space length increased by 3T.

  The optical information recording medium 6 and the recording conditions used at this time were all the same as in Example 1, and only the number of pulses of the high erasing power Pe (h) light when the space length was long was changed. Specifically, the number of pulses of the high erasing power Pe (h) light is 1 for 3T-5T space, 2 for 6T-8T space, 3 for 9T-11T space, and 4 for 14T space. The results are shown in FIG.

[Comparative Example 1]
In the mark formation, every time the mark length increases by 2T, the peak power light pulse is increased by one. When moving from the mark formation to the space formation, the peak power light is once modulated to the bottom power light and then modulated to the erasing power light. The high erasing power pulse light was not irradiated.

  Except for not using the phase change recording medium, the recording conditions, and the high erasing power pulse used at this time, all are the same as in the first embodiment. The results are shown in FIG.

[Comparative Example 2]
In the mark formation, every time the mark length increases by 2T, the peak power light pulse is increased by one. When moving from the mark formation to the space formation, the peak power light is once modulated to the bottom power light and then modulated to the erasing power light. The high erasing power pulse light was not irradiated.

  The phase change recording medium and recording conditions used at this time were the same as those in Example 1 except that Pe = 7 mW and no pulse of high erasing power light was used. The results are shown in FIG.

[Comparative Example 3]
In the mark formation, every time the mark length increases by 2T, the peak power light pulse is increased by one. When moving from the mark formation to the space formation, the peak power light is once modulated to the bottom power light and then modulated to the erasing power light. The pulse of the high erasing power light was irradiated 1.2T after the modulation to the erasing power light was started. Only one pulse of the high erasing power light is used regardless of the space length.

  The phase change recording medium and recording conditions used at this time were all the same as in Example 1, and only the start time of the high erasing power was changed. The results are shown in FIG.

[Example 4]
FIG. 10 shows an example of the recording strategy of the present embodiment. In the mark formation, every time the mark length increases by 2T, the pulse of the peak power Pp light is increased by one, and when moving from the mark formation to the space formation, the peak power Pp light is directly modulated to the erase power Pe light, and the erase power Pe light is modulated. At the same time as modulation was started, a pulse of high erasing power Pe (h) light was irradiated. The pulse of the high erasing power Pe (h) light is only one pulse regardless of the space length.

  The optical information recording medium 6 and the recording conditions used at this time are the same as those in Example 1 except that Pe = 5.5 mW and the pulse width of the peak power Pp light at the time of mark formation is optimized. The results are shown in FIG.

[Example 5]
In the mark formation, every time the mark length increases by 2T, the pulse of the peak power Pp light is increased by one, and when moving from the mark formation to the space formation, the peak power Pp light is directly modulated to the erase power Pe light, and the erase power Pe light is modulated. A pulse of high erasing power Pe (h) light is irradiated after 0.8 T from the start of modulation. The pulse of the high erasing power Pe (h) light is only one pulse regardless of the space length.

  The optical information recording medium 6 and the recording conditions used at this time were all the same as in Example 4, and only the irradiation start time of the high erasing power Pe (h) light was changed. The results are shown in FIG.

[Comparative Example 4]
For mark formation, every time the mark length increases by 2T, the peak power light pulse is increased by one. When moving from mark formation to space formation, the peak power light is directly modulated to the erasing power light, and the modulation to the erasing power light is performed. A pulse of high erasing power light is irradiated 1.2T after the start. Only one pulse of the high erasing power light is used regardless of the space length.

  The phase change recording medium and the recording conditions used at this time were all the same as in Example 4, and only the start time of the high erasing power was changed. The results are shown in FIG.

  From these results, it can be seen that the cases of Examples 1 to 5 have a better relationship between the number of repeated recordings and the jitter than the cases of Comparative Examples 1 to 4. Also, among the embodiments, the method of modulating to the erasing power Pe through the process of once modulating to the bottom power Pb (Examples 4 and 5) is the method of directly modulating from the top power Pp to the erasing power Pe (Example 1). , 2, 3), it can be seen that lower jitter can be achieved.

1 is a principle sectional view showing a layer configuration example of an optical information recording medium according to an embodiment of the present invention. It is a wave form diagram which shows the recording strategy of one embodiment of this invention. It is explanatory drawing which shows an example of the mark shape formed. It is a characteristic view which shows the relationship between a crystal growth rate and temperature. It is explanatory drawing which shows a mode that unerasing remains arise. It is a schematic block diagram which shows the example of a control system structure of an optical information recording device. FIG. 3 is a waveform diagram showing a recording strategy of Example 1. 6 is a waveform diagram showing a recording strategy of Example 2. FIG. FIG. 6 is a waveform diagram showing a recording strategy of Example 3. FIG. 6 is a waveform diagram showing a recording strategy of Example 4. It is a characteristic view of the measurement result which shows the relationship between the frequency | count of recording, and a jitter. It is a wave form diagram which shows the conventional general recording strategy. It is a wave form diagram which shows the recording strategy of a patent document 4 system. It is a wave form diagram which shows the recording strategy of a patent document 5 system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 1st protective layer 3 Recording layer 4 2nd protective layer 5 Reflective layer 6 Optical information recording medium 23 Laser light source 37 Light emission waveform control means 42 Light source drive means

Claims (18)

In an optical information recording method for recording information on an optical information recording medium by a mark length recording method represented by nT in which a time length of a recording mark is n times (n is a natural number) a basic clock period T,
An amorphous mark having a length nT is formed by irradiating an integer number of pulses equal to or less than n / 2 by repeating a peak power light having a relatively high power value and a bias power light having a relatively low power value. When a crystal space having a length nT between amorphous marks is formed by irradiating an erasing power light having an intermediate power value between the power light and the bias power light, the formation of the crystal space from the formation of the amorphous marks is performed. Is shifted from the peak power light to the erasing power light, and within the basic clock period T after the start of the modulation to the erasing power light, the amorphous power is higher than the erasing power light and lower than the peak power light. An optical information recording method characterized by using a recording strategy for irradiating at least one pulse of high erasing power light having a power value of a mark erasable level   2. The optical information recording according to claim 1, wherein at the time of transition from the formation of the amorphous mark to the formation of the crystal space, the modulation is performed from the peak power light to the bottom power light and then to the erasing power light. Method.   3. The optical information recording method according to claim 1, wherein the irradiation time of the high erasing power light is 0.2T or more and 2T or less.   4. The optical information recording method according to claim 1, wherein the number of pulses of the high erasing power light is increased by one every time the crystal space length increases by 3T or more.   5. The optical information recording method according to claim 1, wherein the level of the power value of the high erasing power light is 1.1 to 2 times that of the erasing power light. 6.   6. The optical information recording method according to claim 1, wherein the optical information recording medium is a phase change optical information recording medium.   In the phase change optical recording medium, at least a first protective layer, a recording layer, a second protective layer, and a reflective layer are laminated on a substrate, and the recording layer includes at least Sb, Ge, Ga, In, Zn, 7. The optical information recording method according to claim 6, comprising at least one element selected from Mn, Sn, Ag, Mg, Ca, Ag, Bi, Se, and Te.   8. The optical information recording method according to claim 7, wherein the content of Sb in the recording layer is 50 to 90 atomic%.   9. The optical information recording method according to claim 7, wherein the reflective layer is made of Ag or an Ag alloy. The optical information recording method according to claim 7, wherein the first protective layer and the second protective layer are a mixture of ZnS and SiO ₂ .   11. The optical information recording method according to claim 9, wherein the optical information recording medium is a phase change optical information recording medium having a sulfidation prevention layer between the second protective layer and the reflective layer.   The optical information recording method according to claim 11, wherein the anti-sulfurization layer contains Si or SiC as a main component. In an information recording apparatus for recording information on an optical information recording medium by a mark length recording method represented by nT in which the time length of a recording mark is n times (n is a natural number) the basic clock period T.
A laser light source that emits a laser beam for irradiating the optical information recording medium;
Light source driving means for emitting the laser light source;
A light emission waveform control means for controlling the light source driving means by setting a recording strategy related to the light emission waveform of the light beam emitted from the laser light source;
With
The emission waveform control means is an amorphous material having a length of nT by irradiating an integer number of pulses equal to or less than n / 2 by repeating a peak power light having a relatively high power value and a bias power light having a relatively low power value. When forming a mark and forming a crystal space having a length nT between the amorphous marks by irradiating the erasing power light having an intermediate power level between the peak power light and the bias power light, At the time of transition from the formation to the formation of the crystal space, the peak power light is modulated from the peak power light to the erasing power light, and is higher than the erasing power light within the basic clock period T after the start of the modulation to the erasing power light. The use of a recording strategy that irradiates at least one pulse of a high erasing power light having a power value lower than the amorphous mark and erasable. The optical information recording apparatus according to symptoms.   The light emission waveform control means modulates the peak power light to the erasing power light once through the modulation process from the peak power light to the formation of the crystal space from the formation of the amorphous mark. Item 14. An optical information recording apparatus according to Item 13.   15. The optical information recording apparatus according to claim 13, wherein the light emission waveform control means sets the irradiation time of the high erasing power light to 0.2T or more and 2T or less.   16. The optical information recording according to claim 13, wherein the light emission waveform control means increases the number of pulses of the high erasing power light by one every time the crystal space length increases by 3T or more. apparatus.   The light emission waveform control means sets the level of the power value of the high erasing power light to 1.1 times or more and 2 times or less of the erasing power light. Optical information recording device. 18. The optical information recording apparatus according to claim 13, wherein the optical information recording medium is a phase change optical information recording medium.

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