WO2012124313A1 - 光学的情報記録装置、光学的情報記録方法及び光学的情報記録媒体 - Google Patents
光学的情報記録装置、光学的情報記録方法及び光学的情報記録媒体 Download PDFInfo
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- WO2012124313A1 WO2012124313A1 PCT/JP2012/001727 JP2012001727W WO2012124313A1 WO 2012124313 A1 WO2012124313 A1 WO 2012124313A1 JP 2012001727 W JP2012001727 W JP 2012001727W WO 2012124313 A1 WO2012124313 A1 WO 2012124313A1
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
- G11B7/0045—Recording
- G11B7/00456—Recording strategies, e.g. pulse sequences
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
- G11B7/126—Circuits, methods or arrangements for laser control or stabilisation
- G11B7/1263—Power control during transducing, e.g. by monitoring
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/004—Recording, reproducing or erasing methods; Read, write or erase circuits therefor
- G11B7/006—Overwriting
- G11B7/0062—Overwriting strategies, e.g. recording pulse sequences with erasing level used for phase-change media
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
- G11B7/125—Optical beam sources therefor, e.g. laser control circuitry specially adapted for optical storage devices; Modulators, e.g. means for controlling the size or intensity of optical spots or optical traces
- G11B7/126—Circuits, methods or arrangements for laser control or stabilisation
- G11B7/1267—Power calibration
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
- G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
- G11B7/2403—Layers; Shape, structure or physical properties thereof
- G11B7/24035—Recording layers
- G11B7/24038—Multiple laminated recording layers
Definitions
- the present invention relates to an optical information recording apparatus and an optical information recording method for recording information on an optical information recording medium by laser beam irradiation, and an optical information recording medium having two or more information layers.
- the recording film When a recording film made of a thin film such as a phase change recording material formed on a substrate is irradiated with a laser beam and subjected to local heating, the recording film can be changed to a state with different optical constants depending on the irradiation conditions. Is possible.
- the optical information recording medium hereinafter also referred to as an optical recording medium
- information is optically recorded, erased, rewritten, or reproduced using a laser beam.
- Optical recording media have been widely researched and developed, and BD (Blu-ray Disc), DVD, CD, and the like have been commercialized.
- phase change type optical recording medium information is recorded by changing the state of a phase change material constituting a recording film between, for example, a crystalline phase and an amorphous phase by heat generated by laser beam irradiation.
- the Information is reproduced by detecting a difference in reflectance between the crystalline phase and the amorphous phase.
- a rewritable optical recording medium can erase or rewrite information by using a phase change recording material that generates a reversible phase change as a recording film.
- the initial state of a recording film is generally a crystalline phase.
- a laser beam with high power is irradiated to melt the recording film, and then the laser irradiation portion is changed to an amorphous phase by rapidly cooling.
- a laser beam having a lower power than that at the time of recording is irradiated to raise the temperature of the recording film, and then slowly cooled to change the laser irradiation portion into a crystalline phase.
- new information can be recorded while erasing the recorded information, that is, rewriting is possible.
- the amorphous part is a mark and the crystal part is a space.
- a metal film having high thermal conductivity is generally used in addition to the recording film for the purpose of efficiently cooling the heat during recording.
- Reproduction of information recorded on the optical recording medium is performed by examining the difference in reflectance between the crystalline phase and the amorphous phase. Specifically, information is reproduced by detecting the intensity of reflected light from the optical recording medium as a signal when the optical recording medium is irradiated with a laser beam set to a certain reproduction power.
- Patent Document 2 discloses a recording control method for optimizing a recording pulse control parameter when recording information by using a PRML system, not a reproduction signal jitter. According to the recording control method of Patent Document 2, the recording pulse control parameter is optimized so that the signal waveform is estimated from the reproduced signal waveform by the PRML method, and the error occurrence probability is minimized.
- an optical recording medium has two information layers
- the recording capacity is doubled.
- information is recorded or reproduced on an information layer (hereinafter referred to as a first information layer) far from the incident surface.
- a first information layer information layer far from the incident surface.
- a second information layer information layer close to the incident surface. That is, when the transmittance of the second information layer is low, the energy of the laser beam reaching the first information layer is attenuated, so that the reflectivity from the first information layer is substantially reduced, and the information at the time of reproduction is reduced. Signal quality deteriorates.
- the reflectance refers to a substantial reflectance including attenuation due to transmission through another information layer. Further, a reflectance that does not include attenuation due to transmission through another information layer is called a film reflectance.
- the second information layer has as high a transmittance as possible.
- the thickness of the metal film having a large extinction coefficient is better in the information layer on the incident surface side of the laser beam.
- the thickness of the metal film is reduced, the cooling rate of the heat generated during recording becomes slower. For this reason, heat propagation outside the laser beam irradiation area is increased, and the boundary between the mark and the space is blurred, so that the reproduction signal is deteriorated. Therefore, when recording information on the information layer close to the incident surface of the laser beam, it has been proposed to use a recording pulse that causes the temperature change to cool more rapidly than when recording information on the information layer farthest from the incident surface. (See Patent Document 3).
- Patent Document 4 discloses recording information on a control parameter of a recording pulse for suitable recording on an optical recording medium in an information unit in a predetermined area of the optical recording medium.
- each power parameter of a recording pulse modulated with a plurality of powers having different levels is calculated for each information layer, and a specific power of each information layer is calculated. And information on the ratio of the highest level of power is recorded in an information unit in a predetermined area of the optical recording medium.
- Patent Document 3 has a problem that the erasing performance deteriorates when information is recorded on an optical recording medium having three or more information layers for further increase in capacity. That is, in order to further increase the transmittance, it is necessary to reduce the thickness of the recording film made of a phase change material having a large extinction coefficient like the metal film.
- the thickness of a recording film made of a phase change material is reduced, the crystallization speed is reduced. Therefore, the phase change from the amorphous phase to the crystalline phase is difficult to occur, and the information erasing performance is deteriorated.
- the transmittance of the information layer (hereinafter referred to as the third information layer) closest to the incident surface side of the laser beam is the transmittance of the second information layer. It must be raised further than. For this reason, the thickness of the recording film of the third information layer becomes thinner than the thickness of the recording film of the second information layer, and it becomes difficult for the erasing performance of the third information layer to satisfy a practically required level. It was.
- the substantial reflectance of the second information layer is low.
- the reflectance ratio of two different information layers be 0.5 or more and 2.0 or less.
- the film reflectance of the second information layer needs to be higher than the film reflectance of the third information layer.
- the ratio between the reflectance of the recording film that is a crystalline phase and the reflectance of the recording film that is amorphous tends to decrease. For this reason, there is a problem that the signal amplitude is reduced and the reproduction signal quality of the second information layer is deteriorated.
- the present invention solves the above problems, and in an optical recording medium having two or more information layers, an optical information recording apparatus and an optical information recording apparatus capable of recording high-quality information on all information layers It is an object to provide an optical information recording method and an optical information recording medium.
- An optical information recording apparatus is an optical information recording apparatus that records information on an optical information recording medium including N information layers (N is an integer of 2 or more), wherein the N Each of the information layers includes a recording film that causes a change in physical state due to a local temperature change caused by the focusing of the laser beam, a light source that emits the laser beam, and a recording mark on the recording film.
- a recording pulse train generating section for generating a recording pulse train for forming, a power setting section for setting the power of each pulse of the recording pulse train, and the laser beam corresponding to the recording pulse train generated by the recording pulse train generating section.
- the power setting unit includes the peak power PwN of the Nth information layer closest to the light incident surface of the optical information recording medium, the Nth information layer Bottom power PbN, peak power PwM of the Mth information layer (M is an integer of N> M ⁇ 1), and bottom power PbM of the Mth information layer satisfy the following formula: Set the power.
- the ratio of the bottom power PbN to the peak power PwN of the Nth information layer closest to the light incident surface of the optical information recording medium among the N information layers is expressed as Mth information layer (M is N> Since the power of each pulse of the recording pulse train is set so as to be higher than the ratio of the bottom power PbM to the peak power PwM of (M ⁇ 1), the temperature change during recording in the Mth information layer is relatively Due to the rapid cooling, a recording mark that is an amorphous phase can be easily formed.
- the signal amplitude is also increased in the M-th information layer in which the ratio of the reflectance of the recording film that is a crystalline phase to the reflectance of the recording film that is amorphous tends to decrease. And the reproduction signal quality can be improved.
- the temperature change during recording in the Nth information layer becomes relatively slow cooling, and the recording mark which is an amorphous phase is formed smaller, so that information rewriting is facilitated. Therefore, the erasing performance required in practice can be ensured even in the Nth information layer in which the thickness of the recording film is reduced to increase the transmittance and the erasing performance is likely to deteriorate.
- 5 is a flowchart for explaining an optical information recording method in the optical recording / reproducing apparatus according to the embodiment of the present invention. It is a figure which shows the example of control of the recording pulse train in the optical information recording method which concerns on embodiment of this invention.
- FIG. 10 is a diagram for explaining an example of a recording pulse in which the number of pulses increases by one when the mark length to be recorded increases by two in the embodiment of the present invention.
- it is a diagram showing an example of a recording compensation table for setting each parameter of the N / 2 recording strategy.
- It is a figure which shows an example of the power information which concerns on embodiment of this invention.
- It is a figure which shows typically the frequency characteristic of the waveform equalizer which concerns on embodiment of this invention.
- 1 is a partial cross-sectional view showing an optical information recording medium according to an embodiment of the present invention. It is a fragmentary sectional view which shows each information layer of the optical information recording medium based on embodiment of this invention further in detail. It is a figure which shows an example of the recording compensation table of the 1st information layer of the optical recording medium which concerns on embodiment of this invention. It is a figure which shows an example of the recording compensation table of the 2nd information layer of the optical recording medium which concerns on embodiment of this invention. It is a figure which shows an example of the recording compensation table before the learning of the 3rd information layer of the optical recording medium which concerns on embodiment of this invention. It is a figure which shows an example of the recording pulse train of each information layer in this Embodiment.
- FIG. 1 is a block diagram showing a configuration of an optical recording / reproducing apparatus according to an embodiment of the present invention.
- the optical recording / reproducing apparatus shown in FIG. 1 includes, as a recording system, an encoder 113, a reference time generator 119, a counter 200, a classifier 201, a recording waveform generator 112, a recording compensator 118, and a laser drive.
- a circuit 111, a power setting unit 114, a laser beam source 110, and a recording optical system including an objective lens 116 and the like are provided.
- the optical recording / reproducing apparatus shown in FIG. 1 includes a reproducing optical system including a detection lens 106 as a reproducing system, a photodetector 100, a preamplifier 101, a waveform equalizer 103, and a binarizer 104. , A decoder 105 and a reproduction shift measuring device 170.
- the recording optical system includes an objective lens 116, a collimating lens 109, and a half mirror 108
- the reproducing optical system includes a detection lens 106, an objective lens 116, and a half mirror 108.
- the optical recording / reproducing apparatus records information on the optical recording medium 11.
- the optical recording medium 11 includes N information layers (N is an integer of 2 or more). Each of the N information layers has a recording film in which a physical state change is caused by a local temperature change caused by focusing of the laser beam. Note that the optical recording medium 11 of the present embodiment includes only three information layers.
- the encoder 113 records the recording data 127 to be recorded into a recording code string (NRZI (Non) that represents the mark length and space length of the mark and space formed on the optical recording medium 11 and the head position information of the mark and space. (Return to Zero Inversion) series) 126.
- the recording code string 126 is transmitted to the classifier 201, the recording waveform generator 112, and the counter 200.
- the classifier 201 determines each mark of the recording code string 126 according to a predetermined rule based on the mark length (code length) of the mark, the space length of the space immediately before the mark, and the space length of the space immediately after the mark. Classify.
- the classifier 201 outputs the classified result to the recording waveform generator 112 as a classification signal 204.
- the counter 200 refers to the recording code string 126, counts the time from the head position of the mark in units of the reference time signal 128 generated by the reference time generator 119, and generates the count signal 205.
- the encoder 113 and the recording waveform generator 112 operate in synchronization with the reference time signal 128, respectively.
- the reference time signal 128 is generated from a signal synchronized by performing PLL (Phase Locked Loop) on the signal read from the wobble on the optical recording medium 11.
- PLL Phase Locked Loop
- the recording compensator 118 reads information recorded in advance in a specific area on the optical recording medium 11 and corresponds to each mark length of each mark, a space length immediately before each mark, and a space length immediately after each mark.
- the recording compensation table data which is the pulse position movement amount of each recording pulse waveform generated by the recording waveform generator 112, is held.
- the recording compensator 118 sends the recording compensation table data to the recording waveform generator 112.
- the recording waveform generator 112 compensates the pulse waveform on the time axis according to the recording code string (NRZI sequence) 126, the classification signal 204, and the recording compensation table data. As a result, the recording code string 126 is converted into a recording pulse signal 125 corresponding to the recording waveform.
- the recording pulse signal 125 is composed of three levels according to the laser power level.
- the recording waveform generator 112 sets the control parameters of the recording pulse train for forming the mark, the mark length of the mark, the first space length of the first space immediately before the mark, and the second space immediately after the mark.
- the second space length is selected in combination.
- the control parameters are the position of the pulse edge at the start of the recording pulse train, the position of the second pulse edge from the start of the recording pulse train, the position of the pulse edge at the end of the recording pulse train, and the position of the second pulse edge from the end of the recording pulse train. At least one of the following.
- the recording compensator 118 stores a recording compensation table related to edge change amounts dTS1, dTS2, dTE1, and dTE2 that change the position of the pulse edge of the recording pulse signal 125, as will be described later.
- the recording compensator 118 sends a recording compensation table to the recording waveform generator 112.
- the recording waveform generator 112 classifies the pulses having the mark lengths according to the classification signal 204, and the position and width of each recording pulse is determined.
- the compensated recording pulse signal 125 is sent to the laser driving circuit 111.
- the recording waveform generator 112 generates a recording pulse train for forming recording marks on the recording film.
- the power setting unit 114 sets the power of each pulse in the recording pulse train.
- the recording pulse train includes at least one write pulse having the highest power, a bottom pulse formed between the plurality of write pulses when there are a plurality of write pulses, and a cooling formed following the last write pulse. Including pulses.
- the power setting unit 114 sets the power of each pulse in the recording pulse train.
- the recording waveform generator 112 generates an erasing pulse between two successive recording pulse trains.
- the power of the erase pulse is assumed to be erase power.
- the power setting unit 114 sets the power of each pulse of the recording pulse train and the erasing pulse.
- the laser driving circuit 111 drives the laser beam source 110 so as to emit a laser beam corresponding to the recording pulse train generated by the recording waveform generator 112 with the power set by the power setting unit 114.
- the laser drive circuit 111 sets the laser power corresponding to each of the three levels (the peak power Pw, the erase power Pe, and the bottom power Pb) of the recording pulse signal 125 at the power level set by the power setting unit 114, and the laser.
- the laser beam source 110 is driven by the drive current 124.
- the laser beam source 110 irradiates the optical recording medium 11 with pulsed light to form a recording mark.
- the laser drive circuit 111 records the mark with a recording pulse train based on the selected control parameter.
- the reading unit 130 includes a preamplifier 101, a waveform equalizer 103, a binarizer 104, and a decoder 105.
- the reading unit 130 reads power information including the peak power of each information layer and the bottom power of each information layer from the optical recording medium 11.
- the optical recording medium 11 records a peak power that represents the power of the write pulse of each information layer and a bottom power that represents the power of the bottom pulse of each information layer.
- the optical recording / reproducing apparatus corresponds to an example of an optical information recording apparatus
- the laser beam source 110 corresponds to an example of a light source
- the recording waveform generator 112 corresponds to an example of a recording pulse train generation unit.
- the power setting unit 114 corresponds to an example of a power setting unit
- the laser driving circuit 111 corresponds to an example of a driving unit
- the reading unit 130 corresponds to an example of a reading unit.
- the recording pulse signal 125 is sent to the laser drive circuit 111.
- the laser driving circuit 111 refers to the recording pulse signal 125 and the power set by the power setting unit 114, generates a laser driving current 124 according to the level of the recording pulse signal 125, and records the laser beam source 110. Light is emitted according to a predetermined recording waveform of the pulse signal 125.
- the laser beam 123 emitted from the laser beam source 110 is condensed on the optical recording medium 11 through the collimating lens 109, the half mirror 108, and the objective lens 116, and the recording film is heated to form marks and spaces.
- the laser beam source 110 emits a laser beam 123 having a low power level that does not destroy the recorded mark, and scans the mark row on the optical recording medium 11.
- the reflected light from the optical recording medium 11 enters the detection lens 106 through the objective lens 116 and the half mirror 108.
- the laser beam is focused on the photodetector 100 through the detection lens 106.
- the condensed light is converted into an electric signal according to the intensity of the light intensity distribution on the photodetector 100.
- the electric signal is amplified by a preamplifier 101 provided in each photodetector 100 to become a reproduction signal 120 corresponding to the presence or absence of a mark at a scanning position on the optical recording medium 11.
- the reproduced signal 120 is subjected to waveform equalization processing by the waveform equalizer 103.
- the reproduction signal 120 subjected to the waveform equalization processing is converted into binary data of “0” or “1” in the binarizer 104 and is synchronized by the PLL, and is then binarized reproduction signal. 121 is converted. Further, the decoder 105 performs reverse conversion of the conversion in the encoder 113 on the binary reproduction signal 121 to generate reproduction data 122.
- the frequency of the reference time signal 128 is 132 MHz, and Tw (channel clock period) is about 7.5 nsec.
- the optical recording medium 11 is rotated at a constant linear velocity of 7.38 m / sec.
- the laser beam source 110 is a semiconductor laser beam source and emits a laser beam having a wavelength of 405 nm.
- the NA of the objective lens 116 is 0.85.
- the optical recording medium 11 is a multilayer disc having a plurality of information layers, and may be a two-layer disc, a three-layer disc or a four-layer disc. Further, the optical recording medium 11 may be a write-once type optical disk medium that can be written once only in addition to a rewritable optical disk medium using a phase change recording material.
- the encoding method is (1-7) modulation. In (1-7) modulation, the shortest code length is 2 Tw.
- FIG. 2 is a diagram for explaining an example of a recording code string mark and space and a recording waveform generation operation for recording the mark and space in the optical recording / reproducing apparatus according to the embodiment of the present invention.
- the reference time signal 128 in FIG. 2 is a signal representing the time reference of the recording operation, and has a cycle of Tw.
- the recording code string 126 in FIG. 2 represents the result of NRZI conversion of the recording data 127 by the encoder 113.
- Tw is the detection window width and is the minimum unit of the change amount of the mark length and the space length in the recording code string 126.
- a mark array 300 in FIG. 2 shows images of marks 301 and spaces 302 actually recorded on the optical recording medium 11.
- the laser beam spot scans the paper surface of FIG. 2 from left to right.
- the mark 301 has a one-to-one correspondence with the “1” level in the recording code string 126 and is formed with a length proportional to the period.
- the count signal 205 in FIG. 2 measures the time from the beginning of the mark 301 and the space 302 in units of Tw.
- the length of the mark and space in units of Tw is generally called the run length.
- the classification signal 204 in FIG. 2 schematically shows the classification signal in the optical recording / reproducing apparatus of the present embodiment.
- “4-5-2” means that for a mark having a mark length of 5 Tw, the space length of the space immediately before the mark is 4 Tw, and the space length of the space immediately after the mark is Represents 2Tw.
- “T” of 4Tw and 2Tw may be omitted and represented as 4T and 2T, respectively.
- the space length is appended with “s” at the end of the run length, such as 4Ts
- the mark length is appended with “m” at the end of the run length, such as 2 Tm.
- the recording pulse signal 125 in FIG. 2 is a recording pulse signal corresponding to the recording code string 126 in FIG. 2, and is an example of an optical waveform that is actually recorded. These recording pulse signals 125 are generated with reference to the count signal 205, the recording code string 126, the classification signal 204, and the recording compensation table data sent from the recording compensator 118.
- FIG. 3 is a schematic diagram showing the relationship between the mark length of the mark and the recording waveform of the recording pulse signal 125.
- the reference time signal 128 in FIG. 3 is a signal that serves as a time reference for the recording operation, and has a cycle of Tw.
- the count signal 205 in FIG. 3 is a signal generated by the counter 200 and measures the time from the beginning of the mark in units of the reference time Tw of the reference time signal 128. The timing when the count signal 205 shifts to 0 corresponds to the head of the mark or space.
- a recording pulse signal 125 in FIG. 3 is a recording pulse signal at the time of recording mark formation. In FIG.
- a recording pulse signal 125 of 2 Tw (Tm) mark, a recording pulse signal 125 of 3 Tw (Tm) mark, a recording pulse signal 125 of 4 Tw (Tm) mark, and a recording pulse signal 125 of 5 Tw (Tm) mark are shown.
- the recording pulse signal 125 is level-modulated and modulated with three values of peak power (Pw), which is the highest level, intermediate power (Pe), and bottom power (Pb), which is the lowest level. Yes.
- Pw peak power
- Pe intermediate power
- Pb bottom power
- a cooling pulse is formed with bottom power.
- the power level is ternary modulation here
- the bottom power of the cooling pulse after the last pulse and the bottom power between the intermediate pulses may be different from each other, and the power level may be quaternary power modulation.
- the power of the cooling pulse is referred to as cooling power (Pc).
- the bottom power is set to a power level lower than the erase power, but the bottom power may be a power level between the erase power and the peak power.
- the recording pulse signal of the 4Tw mark has one intermediate pulse.
- the mark length (code length) is increased by 1Tw, such as 5Tw and 6Tw, the number of intermediate pulses is increased by one accordingly. It will increase.
- each mark is classified according to the mark length of the mark, the space length of the space immediately before the mark, and the space length of the space immediately after the mark. Then, the position of the pulse edge of the recording pulse train for recording each mark is changed by the edge change amounts dTS1, dTS2, dTE1, and dTE2 according to the classification result. Since the recording pulse signal 125 is controlled in this way, the start end position or the rear end position of the mark formed on the optical recording medium 11 can be precisely controlled.
- the pulse edge is controlled not only according to the mark length of the mark to be recorded but also according to the space length of the space immediately before the mark and the space length of the space immediately after the mark, the intersymbol interference is taken into consideration.
- the start position or the rear end position of the mark can be controlled more precisely.
- FIG. 4 is a flowchart for explaining an optical information recording method in the optical recording / reproducing apparatus according to the embodiment of the present invention.
- the encoder 113 encodes the recording data to create encoded data that is a combination of marks and spaces (step S1). This encoded data corresponds to the recording code string 126 of FIG.
- the classifier 201 classifies the mark based on the combination of the mark length of the mark, the space length of the space immediately before the mark, and the space length of the space immediately after the mark (step S2). .
- the 2T mark is classified as “2-2-3”
- the 3T mark is classified as “3-3-4”
- the 5T mark is classified as “4-5-2”.
- the 6T mark is classified as “2-6-2”.
- the classification signals 204 are combined in the order of “front space length”, “mark length”, and “rear space length”.
- the “front space length” represents the space length of the space immediately before the mark
- the “rear space length” represents the space length of the space immediately after the mark.
- the recording waveform generator 112 controls the recording pulse train by changing the position of the pulse edge of the recording pulse train for forming the mark in accordance with the classification result (step S3).
- the recording waveform generator 112 sets the control parameters of the recording pulse train for forming the mark, the mark length of the mark, the first space length of the first space immediately before the mark, and the second space immediately after the mark.
- the second space length is selected in combination.
- the recording waveform generator 112 sets the position of the pulse edge at the start edge as the edge change amount dTS1, the position of the second pulse edge from the start edge as the edge change amount dTS2, and the end pulse amount.
- the position of the pulse edge is changed by the edge change amount dTE1
- the position of the second pulse edge from the end is changed by the edge change amount dTE2.
- the power setting unit 114 sets the power of each pulse in the recording pulse train (step S4).
- the laser driving circuit 111 generates a laser driving current 124 according to the power set by the power setting unit 114 and the recording pulse signal 125 generated by the recording waveform generator 112, and generates the generated laser driving current 124. Output to the laser beam source 110.
- the laser beam source 110 irradiates the optical recording medium 11 with a laser beam corresponding to the recording pulse train to form a mark (step S5).
- FIG. 5 is a diagram showing an example of recording pulse train control in the optical information recording method according to the embodiment of the present invention.
- FIG. 5 shows a case where the position of the pulse edge of the recording pulse train is changed by the edge change amounts dTS1, dTS2, dTE1, and dTE2 when a mark 301 having a mark length of 4T is recorded.
- a reference time signal 128 in FIG. 5 is a signal serving as a time reference for the recording operation, and a count signal 205 in FIG. 5 is a signal generated by the counter 200.
- the recording pulse signal (recording pulse train) 125 in FIG. 5 changes the position of the pulse edge by the edge change amounts dTS1, dTS2, dTE1, and dTE2.
- the mark array 300 in FIG. 5 shows an image of the mark 301 having a mark length of 4T recorded by the recording pulse signal (recording pulse train) 125 in FIG.
- FIG. 5 shows that the starting end position of the mark 301 can be precisely controlled.
- the start edge change amount dTS1 includes the mark length of the mark to be recorded, the space length of the space immediately before the mark (previous space length), and the space length of the space immediately after the mark. It is defined based on the result of classification according to (space length).
- Table 1 is a table showing an example of a recording compensation table related to the edge change amount dTS1 at the starting end.
- the starting edge change amount dTS1 is divided into four mark lengths of 2T, 3T, 4T, and 5T for the mark length to be recorded. Only when the mark length is 2T, the rear space length is 2T and 3T or more.
- the edge change amount dTS1 is the position of the starting pulse edge, the influence of the preceding space (space immediately before the mark) is dominant, but when the mark length is 2T, the trailing space (space immediately after the mark). Since the influence of can not be ignored, it is classified in this way.
- the edge change amount dTS1 is classified into four types for the mark length, four types for the front space length, and two types for the rear space length.
- the mark length may be classified into 2, 3, 5, or 6 or more
- the front space length and the rear space length are respectively 2, 3, 4, 5, or 6 or more. May be classified.
- the mark length is classified into at least four types of k, k + 1, k + 2, and k + 3 or more.
- the mark length may be classified into at least two types of k and k + 1 or more, and the mark length may be classified into at least three types of k, k + 1, and k + 2 or more.
- the k + 1 mark length means the 3T mark length
- the k + 2 mark length means the 4T mark length
- the k + 3 mark length is 5T mark length.
- the first space length (front space length) and the second space length (rear space length) are k and k + 1 or more, respectively.
- the first space length and the second space length may be classified into at least four types of k, k + 1, k + 2, and k + 3 or more.
- the recording waveform generator 112 controls the recording pulse train with reference to the recording compensation table in which the combination of the mark length, the first space length and the second space length, and the control parameter are associated with each other.
- the second edge change amount dTS2 from the start end is the same as the edge change amount dTS1, and as shown in Table 2 below, the mark length of the mark to be recorded and the space length of the space immediately before the mark (previous space length) ) And the space length of the space immediately after the mark (rear space length).
- Table 2 is a table showing an example of a recording compensation table related to the second edge change amount dTS2 from the start end.
- the end edge change amount dTE1 is the mark length of the mark to be recorded, the space length of the space immediately before the mark (previous space length), and the space length of the space immediately after the mark. It is defined based on the result of classification according to (space length).
- Table 3 is a table showing an example of a recording compensation table related to the terminal edge change amount dTE1.
- the edge change amount dTE1 at the end is divided into four types, 2T, 3T, 4T and 5T or more, for the mark length of the mark to be recorded, and only when the mark length is 2T, the previous space length is 2T and 3T or more.
- the edge change amount dTE1 is the position of the terminal pulse edge, the influence of the rear space is dominant. However, when the mark length is 2T, the influence of the front space is not negligible. .
- the edge change amount dTE1 is classified into four types for the mark length, four types for the rear space length, and two types for the front space length.
- the mark length may be classified into 2, 3, 5, or 6 or more
- the front space length and the rear space length are respectively 2, 3, 4, 5, or 6 or more. May be classified.
- the second edge change amount dTE2 from the end is the mark length of the mark to be recorded, the space length of the space immediately before the mark (previous space length), and the space immediately after the mark. It is defined based on the result of classification according to the space length (rear space length).
- Table 4 is a table showing an example of a recording compensation table regarding the second edge change amount dTE2 from the end.
- the edge change amount dTE2 is the position of the second pulse edge from the end.
- the edge change amount dTE2 of the 2T mark is not defined because it matches the second edge change amount dTS2 from the start end.
- the edge change amount dTE2 is classified into three types for the mark length and four types for the rear space length, but the present invention is not limited to this case.
- the mark length may be 2, 4, or 5 or more
- the back space length may be 2, 3, 5, or 6 or more.
- the start position of the mark 301 can be controlled more precisely by changing the position of the pulse edge at the start of the recording pulse signal 125 by the edge change amounts dTS1, dTS2, dTE1, and dTE2. Furthermore, since the pulse edge is controlled not only according to the mark length of the mark to be recorded but also according to the previous space length, the start position of the mark 301 can be controlled more precisely in consideration of intersymbol interference.
- the positions of the pulse edges from the start to the second and from the end to the second are changed, but the positions of the third and subsequent pulse edges from the start and the third and subsequent pulses from the end are changed. It may be.
- Table 5 is a table showing an example of a recording compensation table related to the edge change amount dTS1 at the start end
- Table 6 is a table showing an example of a recording compensation table related to the second edge change amount dTS2 from the start end
- Table 7 is FIG. 8 is a table showing an example of a recording compensation table related to the edge change amount dTE1 at the end
- Table 8 is a table showing an example of a recording compensation table related to the second edge change amount dTE2 from the end.
- the minimum recording mark and space are as small as the light spot. Therefore, due to the influence of optical MTF (Modulation Transfer Function), a signal related to the shortest mark and the shortest space causes intersymbol interference and cannot be recorded or reproduced at an accurate edge position. Therefore, when sufficient recording characteristics can be obtained in consideration of intersymbol interference only by dividing into the shortest 2T space length and other space lengths, the above can be simplified and classified as described above. Since the recording compensation table can be simplified, there is an advantage that the apparatus can be simplified.
- optical MTF Modulation Transfer Function
- the recording compensation table held in the recording compensator 118 is acquired by one of the following two methods.
- the recording compensator 118 reads a recording compensation table recorded in advance in or after manufacturing the disc in an area called a lead-in area of the optical recording medium 11 and stores the read recording compensation table. To do.
- the recording compensator 118 actually performs trial writing in a trial writing area on the optical recording medium 11 using a predetermined recording pulse signal, reproduces the trial written mark and space, and performs edge shift.
- the recording compensation table is acquired from the learning result obtained in the process of searching the condition with the best signal quality by measuring the quantity.
- a recording compensation table recorded in a predetermined area of the optical recording medium 11 is obtained as reproduction data and stored in the recording compensator 118.
- FIG. 6 is a flowchart for explaining a method of creating a recording compensation table in the optical information recording method according to the embodiment of the present invention.
- the optical recording / reproducing apparatus classifies the mark based on the combination of the mark length of the mark, the space length of the space immediately before the mark, and the space length of the space immediately after the mark.
- the test mark is written in a trial writing area on the optical recording medium 11 (step S11).
- the optical recording / reproducing apparatus trial-writes marks having mark lengths of 2T, 3T, 4T, and 5T, and has space lengths of 2T, 3T, 4T, and 5T for each mark. Test-write a front space and a rear space having a space length of 2T, 3T, 4T, and 5T.
- the optical recording / reproducing apparatus reproduces the test written mark and space to obtain a reproduction signal (step S12).
- the optical recording / reproducing apparatus associates the edge change amount with the combination of the mark length of the mark, the space length of the space immediately before the mark, and the space length of the space immediately after the mark based on the reproduction signal.
- a recording compensation table is created (step S13).
- the optical recording / reproducing apparatus creates the recording compensation tables shown in Tables 1 to 4 or the recording compensation tables shown in Tables 5 to 8.
- the electric signal photoelectrically converted by the photodetector 100 is amplified by the preamplifier 101 to become a reproduction signal 120, and then becomes a binarized reproduction signal 121 through the waveform equalizer 103 and the binarizer 104.
- the obtained binarized reproduction signal 121 is sent not only to the decoder 105 but also to the reproduction shift measuring unit 170.
- the reproduction shift measuring unit 170 compares the binarized reproduction signal synchronized by the PLL with the binarized reproduction signal before synchronization, and shifts (edge variation) for each mark and space. And the measurement result is transmitted to the recording compensator 118.
- the optical recording / reproducing apparatus updates the recording compensation table data as needed according to the measured edge change amount, and again described above.
- the recording operation may be repeated to search for a recording compensation table that reduces the edge shift between the PLL clock and the binarized reproduction signal during reproduction.
- the shift component of the MLSE Maximum Likelihood Sequence Estimation
- the recording power is modulated with a ternary laser power level
- a cooling pulse having a power level different from the bottom power in the intermediate pulse is further included.
- the same effect can be obtained when modulation is performed with a four-level laser power level. That is, the recording pulse train is modulated by switching the intensity of the laser beam with a power of three or more values.
- the recording power is temporarily stored in the power setting unit 114.
- the reading unit 130 reads power information recorded in advance in a region called a lead-in area of the optical recording medium 11 at the time of manufacturing the disc or after manufacturing the disc, and temporarily stores the read power information in the power setting unit 114.
- the power setting unit 114 sets the power of each pulse of the recording pulse train based on the value of the power information read by the reading unit 130.
- the power information includes peak power, bottom power, cooling power, and erase power of each information layer. Further, the power information may be information representing the peak power, bottom power, cooling power, and erase power of each information layer as a ratio to the peak power (Pw).
- the power setting unit 114 instructs the laser drive circuit 111 to perform trial writing in the trial writing area on the optical recording medium 11 and searches for an appropriate condition based on the reproduced signal of the trial written signal.
- the peak power may be reset according to the learning result obtained in step (1).
- the power setting unit 114 may reset the erase power, the bottom power, and the cooling power for each information layer using the reset peak power and the ratio to the peak power stored in advance.
- the number of pulses increases by one when the mark length to be recorded increases by one, but the rule of the number of pulses may be different.
- the recording pulse may be one in which the number of pulses increases by one when the mark length to be recorded increases by two, or may have no cooling pulse after the final pulse.
- FIG. 7 is a diagram for explaining an example of a recording pulse in which the number of pulses increases by one when the mark length to be recorded increases by two in the embodiment of the present invention.
- a recording pulse in which the number of pulses increases by 1 when the mark length to be recorded increases by 2 is referred to as an N / 2 recording strategy.
- the recording waveform for recording the shortest mark (2T) and the second shortest mark (3T) consists of only one pulse (top pulse).
- the recording waveform for recording the third shortest mark (4T) and the fourth shortest mark (5T) is composed of two pulses (from the front, the top pulse and the last pulse).
- the recording waveform for recording the fifth shortest mark (6T) and the sixth shortest mark (7T) consists of three pulses (top pulse, intermediate pulse and last pulse).
- the intermediate pulse increases by one every time the mark length increases by two.
- each parameter of the N / 2 recording strategy may be classified and set according to the length of the recording mark as shown in FIG.
- FIG. 8 is a diagram showing an example of a recording compensation table for setting each parameter of the N / 2 recording strategy in the embodiment of the present invention.
- the top pulse rising position dTtop and the top pulse width Ttop are, for example, “2T”, “3T”, “4T, 6T, 8T” and “5T, 7T, 9T” with respect to the length of the recording mark. It may be classified and set in four.
- the last pulse rising position dTlp and the last pulse width Tlp are classified and set to, for example, “4T, 6T, 8T” and “5T, 7T, 9T” with respect to the length of the recording mark. May be.
- the position at which the setting of the cooling power Pc ends (start position of the erase power Pe) dTe is “2T”, “3T”, “4T, 6T, 8T” and “5T, 7T” with respect to the length of the recording mark. , 9T "may be classified and set. Note that the position dTe is set so that the trailing edge of the last pulse coincides with the start position of the erase power Pe, so that the recording pulse train can have no cooling pulse.
- the rising position of the intermediate pulse may be classified into “6T, 8T” and “7T, 9T” with respect to the length of the recording mark.
- the rising edge of the intermediate pulse is matched with the reference clock position.
- the rising edge of the intermediate pulse is shifted by T / 2 from the reference clock.
- the width Tmp of the intermediate pulse may be set to be the same for all of “6T, 7T, 8T, 9T” with respect to the length of the recording mark.
- the parameters classified according to the lengths of these recording marks may be further classified according to the space length before and after the recording marks.
- the position dTtop and the width Ttop may be classified into four “2T”, “3T”, “4T”, and “5T or more” with respect to the length of the previous space (the space immediately before the recording mark). . Further, the position dTtop and the width Ttop may be classified into two, “2T” and “3T or more” with respect to the length of the rear space (the space immediately after the recording mark) in the 2T mark.
- the position dTlp and the width Tlp may be classified into four “2T”, “3T”, “4T”, and “5T or more” with respect to the length of the rear space.
- the position dTe may be classified into four “2T”, “3T”, “4T”, and “5T or more” with respect to the length of the rear space. Further, the position dTe may be classified into “2T” and “3T or more” with respect to the length of the previous space in the 2T mark.
- the width Tmp may be set to be the same for all of “6T, 7T, 8T, 9T” with respect to the length of the recording mark.
- the recording compensation table for setting each parameter of the N / 2 recording strategy is shown in FIG. In the recording compensation table shown in FIG. 8, specific values of each parameter are omitted.
- FIG. 9 is a diagram showing an example of power information according to the embodiment of the present invention.
- the power information may be set by values of peak power Pw, erase power Pe, bottom power Pb, and cooling power Pc, or may be set by a ratio of each power level to the peak power. Good.
- specific values of each power are omitted.
- optical information reproducing method by the optical recording / reproducing apparatus according to the embodiment of the present invention will be described.
- the reflectance of each information layer of the optical recording medium 11 is large, and the ratio between the reflectance of the recording film that is a crystalline phase and the reflectance of the recording film that is amorphous. Is large, and it is important that the laser power during reproduction is large.
- the optical information reproducing method described in this embodiment is characterized by performing waveform equalization having frequency characteristics shown in FIG.
- a mark recorded on the optical recording medium 11 is read with a laser beam, and a reproduction signal 120 is generated using the detection lens 106, the photodetector 100, and the preamplifier 101.
- the reproduction signal 120 is a signal whose frequency characteristic is corrected by the waveform equalizer 103. Further, the reproduction signal 120 whose frequency characteristics are corrected is converted into a binarized reproduction signal 121 by the binarizer 104.
- the decoder 105 performs inverse transformation on the binarized reproduction signal 121 to generate reproduction data 122.
- the equalizer characteristic is set so that the output amplitude is increased as the signal has a higher frequency.
- FIG. 10 is a diagram schematically showing frequency characteristics of the waveform equalizer (equalizer) 103 according to the embodiment of the present invention, and represents the amplitude ratio of the output signal to the input signal.
- the horizontal axis represents the reproduction signal frequency, and schematically shows the frequencies of the 2Tw signal, 3Tw signal, 4Tw signal, and 8Tw signal.
- the vertical axis is a logarithmic display of the output amplitude of the waveform equalizer 103.
- a high pass filter High Pass Filter
- a band pass filter Band Pass Filter
- a combination of amplifiers can be used.
- the difference between the output amplitude when the mark or space is a high frequency signal such as 2Tw signal and the output amplitude when the mark or space is a low frequency signal such as 8Tw, that is, the slope of the characteristic curve Increases as the shortest mark length decreases. Accordingly, for example, the difference between the output amplitude at the frequency of the 4Tw signal and the output amplitude at the frequency of the 8Tw signal also increases.
- the reproduction signal characteristics have characteristics that prevent peak shift of the reproduction frequency characteristics, change the frequency distribution of noise, improve the reproduction signal quality, and improve the error rate of the reproduction signal.
- FIG. 11 is a schematic diagram showing a reproduced signal waveform in the optical information reproducing method according to the embodiment of the present invention.
- FIG. 11 is a schematic diagram showing differences in reproduction signal characteristics due to differences in mark shapes.
- the mark arrays 300a and 300b in FIG. 11 represent the mark shape after the recording spot is formed by scanning the light spot from the left to the right in the drawing.
- Reproduction signals 120a and 120b in FIG. 11 indicate the reproduction signals after the marks are read out with the intensity of light that does not erase the recorded marks after the mark shapes of the mark arrays 300a and 300b are formed.
- a reproduction signal 120a in FIG. 11 is a reproduction signal when the marks in the mark array 300a in FIG. 11 are reproduced.
- the reproduction signal amplitude is the smallest. In this case, I2 is the minimum amplitude.
- the mark array 300b in FIG. 11 shows an example of a mark shape formed in a write-once disc using phase change.
- a reproduction signal 120b in FIG. 11 is a reproduction signal when the marks in the mark array 300b in FIG. 11 are reproduced.
- the 2Tw mark 403 is circular and may be formed narrower in the width direction than other long marks.
- the minimum amplitude I2 of the reproduction signal 120b in FIG. Becomes smaller than the minimum amplitude I2 in the reproduced signal 120a. Therefore, the intersymbol interference of the 2Tw mark 403 increases and a reproduction peak shift occurs.
- the amplitude of the reproduction signal 120 is increased and the noise is increased at the same time.
- the overboost state noise on the higher frequency side than the signal band is increased. In this case, the quality of the reproduction signal 120 is deteriorated.
- the intersymbol interference on the low frequency side (4 Tw to 8 Tw) of the signal components is increased, so that the reproduction characteristics are deteriorated.
- the recording compensation of only the mark length can compensate for the intersymbol interference of the 2Tw mark. Interference remains and deteriorates the characteristics of the reproduced signal.
- the pulse edge of the recording pulse signal 125 is an edge corresponding to the mark length, the front space length, and the rear space length, especially considering 2Tw space.
- the amount of change is changed by dTS1, dTS2, and dTE1, and the start or end edge of the recording pulse signal 125 is compensated.
- the target boost value when performing the recording compensation is also the compensation accuracy of the recording compensation when recording data on an optical recording medium such as a write-once recording medium on which a recording mark such as the mark array 300b in FIG. 11 is formed.
- Dependent For example, when recording compensation is performed with compensation accuracy of about Tw / 32, it is desirable to increase the boost value by about 1 dB to 2 dB for recording.
- recording may be performed in a state where space compensation is not performed first, and a recording operation including space compensation may be performed only when a reproduction signal characteristic such as an error rate does not satisfy a reference value.
- the first trial writing is performed with a code sequence obtained by excluding the shortest mark length from a signal to be recorded in advance, a recording compensation table having a mark length of 3 Tw or more is created, and then a second trial is performed with a code sequence including a 2 Tw signal.
- the recording compensation table including the mark length of 2 Tw may be created by writing.
- a mark having a code length of 3 Tw or more is first recorded, and an edge position of the mark and space of 3 Tw or more is accurately recorded and compensated, and then 2 Tw.
- the signal including the signal is recorded to accurately compensate the recording position of the 2Tw mark and space.
- the boost value of the reproduction equalizer is lowered from 1 dB to 2 dB as compared with the case of recording a normal recording code string including a 2 Tw signal. Recording compensation may be performed.
- the 2Tw signal since the 2Tw signal is not included, the amplitude of the reproduction signal is relatively large and the occurrence of intersymbol interference is gradual. Therefore, a signal with little edge shift can be recorded by adjusting the edge position of a mark having a long mark length with a boost value slightly lower than the normal boost value.
- a rewritable optical recording medium must be able to correctly reproduce a signal recorded by a plurality of rewrites.
- the error rate is at a level that causes no practical problem if the symbol error rate (SER) is 2.0 ⁇ 10 ⁇ 4 or less.
- FIG. 12 is a partial sectional view showing the optical recording medium 11 according to the embodiment of the present invention.
- the optical recording medium 11 is assumed to be a three-layer multilayer optical recording medium capable of recording or reproducing information by irradiating a laser beam 31 condensed by an objective lens 32.
- the wavelength ⁇ of the laser beam 31 is preferably in the range of 350 nm to 450 nm.
- the optical recording medium 11 includes three information layers, a first information layer 41, a second information layer 42, and a third information layer 43, which are sequentially stacked on the substrate 21 via separation layers 22 and 28, and The transparent layer 23 is provided in this order.
- the objective lens 32 focuses the laser beam 31 on each information layer from the transparent layer 23 side, and information is recorded or reproduced.
- the laser beam reaching the information layer closer to the substrate 21 than the third information layer 43 and the reflected light are transmitted through the information layer on the incident surface side of the laser beam 31 from the information layer. Will be attenuated. Therefore, the first information layer 41 and the second information layer 42 need to have high recording sensitivity and high reflectance, and the second information layer 42 and the third information layer 43 need to have high transmittance.
- the substrate 21 has a disk shape and is used to hold each layer from the first information layer 41 to the transparent layer 23.
- a guide groove for guiding the laser beam 31 may be formed on the surface of the substrate 21 on the first information layer 41 side.
- the surface of the substrate 21 opposite to the first information layer 41 side is preferably smooth.
- a polycarbonate resin, a polymethyl methacrylate resin, a polyolefin resin, a norbornene resin, glass, a material obtained by appropriately combining these, or the like can be used.
- a polycarbonate resin is preferable as a material for the substrate 21 because it is excellent in transferability and mass productivity and is low in cost.
- the separation layer 22 and the separation layer 28 are layers provided to distinguish the focus positions of the first information layer 41, the second information layer 42, and the third information layer 43 of the optical recording medium 11.
- the thicknesses of the separation layer 22 and the separation layer 28 are desirably equal to or greater than the depth of focus determined by the numerical aperture NA of the objective lens 32 and the wavelength ⁇ of the laser beam 31.
- the separation layer 22 and the separation layer 28 are too thick, the distance from the incident surface of the laser beam 31 of the optical recording medium 11 to the first information layer 41 becomes long, and coma aberration when the optical recording medium 11 is tilted is increased. Therefore, the light cannot be condensed correctly on the first information layer 41. In that respect, the separation layer 22 and the separation layer 28 should be thin. If the wavelength ⁇ of the laser beam 31 is 405 nm and the numerical aperture NA of the objective lens 32 is 0.85, the thicknesses of the separation layer 22 and the separation layer 28 are in the range of 5 ⁇ m to 50 ⁇ m. Is preferred.
- the separation layer 22 and the separation layer 28 have small light absorption with respect to the laser beam 31.
- Guide grooves for guiding the laser beam 31 may be formed on the surfaces of the separation layer 22 and the separation layer 28 on the irradiation side of the laser beam 31.
- a polycarbonate resin, a polymethyl methacrylate resin, a polyolefin resin, a norpollene resin, an ultraviolet curable resin, a slow-acting thermosetting resin, glass, a material obtained by appropriately combining these materials, or the like is used. Can do.
- the transparent layer 23 is on the incident surface side of the laser beam 31 of the third information layer 43 and protects the third information layer 43.
- the transparent layer 23 preferably has a small light absorption with respect to the laser beam 31.
- polycarbonate resin, polymethyl methacrylate resin, polyolefin resin, norbornene resin, ultraviolet curable resin, slow-acting thermosetting resin, glass, or a material obtained by appropriately combining these materials can be used. Further, as the material of the transparent layer 23, a sheet made of these materials may be used.
- the thickness of the transparent layer 23 is preferably in the range of 5 ⁇ m to 150 ⁇ m, and more preferably in the range of 40 ⁇ m to 110 ⁇ m. .
- FIG. 13 is a partial sectional view showing each information layer of the optical recording medium 11 according to the embodiment of the present invention in more detail.
- the first information layer 41 is provided with a metal film 412, a first dielectric film 414, a recording film 416, and a second dielectric film 418 in this order from the side close to the substrate 21. ing. Further, if necessary, a metal film side interface film 413 may be provided between the metal film 412 and the first dielectric film 414, and the first dielectric film 414 and the recording film 416 may be provided between the first dielectric film 414 and the recording film 416. One interface film 415 may be provided, or a second interface film 417 may be provided between the second dielectric film 418 and the recording film 416. Note that illustration of the metal film side interface film 413, the first interface film 415, and the second interface film 417 is omitted.
- the transmittance adjustment film 421, the metal film 422, the first dielectric film 424, the recording film 426, and the second dielectric film 428 are arranged on the second information layer 42 in this order from the side close to the substrate 21. Is provided. Further, if necessary, a metal film side interface film 423 may be provided between the metal film 422 and the first dielectric film 424, and the first dielectric film 424 and the recording film 426 may be provided between the first dielectric film 424 and the recording film 426. One interface film 425 may be provided, or a second interface film 427 may be provided between the second dielectric film 428 and the recording film 426. The illustration of the metal film side interface film 423, the first interface film 425, and the second interface film 427 is omitted.
- a transmittance adjusting film 431, a metal film 432, a first dielectric film 434, a recording film 436, and a second dielectric film 438 are arranged in this order from the side closer to the substrate 21.
- a metal film side interface film 433 may be provided between the metal film 432 and the first dielectric film 434, and the first dielectric film 434 and the recording film 436 may be provided with a first film.
- One interface film 435 may be provided, or a second interface film 437 may be provided between the second dielectric film 438 and the recording film 436.
- the illustration of the metal film side interface film 433, the first interface film 435, and the second interface film 437 is omitted.
- the recording film 416 is a film that causes a reversible phase change between a crystalline phase and an amorphous phase by irradiation with the laser beam 31.
- As the material of the recording film 416 (Ge—Sn) Te, GeTe—Sb 2 Te 3 , (Ge—Sn) Te—Sb 2 Te 3 , GeTe—Bi 2 Te 3 , GeTe—In 2 Te 3 , (Ge -Sn) Te-Bi 2 Te 3 , GeTe- (Sb-Bi) 2 Te 3 , (Ge-Sn) Te- (Sb-Bi) 2 Te 3 , GeTe- (Bi-In) 2 Te 3 , (Ge —Sn) Te— (Bi—In) 2 Te 3 , Sb—Te, Sb—Ge, (Gb—Te) —Ge, Sb—In, (Sb—Te) —In, Sb—Ga and (Sb—Te
- the recording film 416 can easily change from an amorphous phase to a crystalline phase when irradiated with a laser beam during recording and does not change from an amorphous phase to a crystalline phase when not irradiated with a laser beam.
- the thickness of the recording film 416 is preferably in the range of 6 nm to 15 nm, and more preferably in the range of 8 nm to 12 nm.
- the metal film 412 has an optical function of increasing the amount of light absorbed by the recording film 416 and a thermal function of diffusing heat generated in the recording film 416.
- a material of the metal film 412 a material containing at least one element of Ag, Au, Cu, and Al can be used.
- an alloy such as Ag—Cu, Ag—Ga—Cu, Ag—Pd—Cu, Ag—Nd—Au, AlNi, AlCr, Au—Cr, or Ag—In is used. it can.
- an Ag alloy is preferable as a material for the metal film 412 because of its high thermal conductivity. The thicker the metal film 412, the higher the heat diffusion function.
- the thickness of the metal film 412 is preferably in the range of 30 nm to 200 nm, and more preferably 70 nm to 140 nm.
- the first dielectric film 414 is located between the recording film 416 and the metal film 412, and adjusts the thermal function for adjusting the thermal diffusion from the recording film 416 to the metal film 412, the reflectance, the absorptance, and the like. With optical functions.
- the material of the first dielectric film 414 include ZrO 2 , HfO 2 , ZnO, SiO 2 , SnO 2 , Cr 2 O 3 , TiO 2 , In 2 O 3 , Ga 2 O 3 , and Y 2 O 3.
- An oxide such as CeO 2 or DyO 2
- a sulfide such as ZnS or CdS
- a carbide such as SiC, or a mixture thereof can be used.
- Examples of the mixture include ZrO 2 —SiO 2 , ZrO 2 —SiO 2 —Cr 2 O 3 , ZrO 2 —SiO 2 —Ga 2 O 3 , HfO 2 —SiO 2 —Cr 2 O 3 , ZrO 2 —SiO 2 —.
- ZnS—SiO 2 , or SnO 2 —SiC can be used.
- ZnS—SiO 2 is excellent as a material for the first dielectric film 414.
- ZnS—SiO 2 has a high deposition rate, is transparent, and has good mechanical properties and moisture resistance.
- the thickness of the first dielectric film 414 is preferably in the range of 5 nm to 40 nm, and more preferably in the range of 8 nm to 30 nm.
- the metal film side interface film 413 has a function of preventing the metal film 412 from being corroded or broken by the material of the first dielectric film 414. Specifically, the metal film side interface film 413 uses a material containing silver (Ag) for the metal film 412 and a material containing sulfur (S) for the first dielectric film 414 (eg, ZnS— When SiO 2 ) is used, corrosion of Ag due to reaction with S is prevented.
- a material containing silver (Ag) for the metal film 412 and a material containing sulfur (S) for the first dielectric film 414 eg, ZnS— When SiO 2 ) is used, corrosion of Ag due to reaction with S is prevented.
- a metal other than Ag for example, Al or an Al alloy can be used.
- a dielectric material not containing sulfur (S), for example, ZrO 2 , HfO 2 , ZnO, SiO 2 , SnO 2 , Cr 2 O 3 , TiO 2 , In 2 is used as a material of the metal film side interface film 413.
- An oxide such as O 3 , Ga 2 O 3 , Y 2 O 3 , CeO 2 , or DyO 2 , a single substance of carbide such as SiC, or a mixture thereof can be used.
- Examples of the mixture include ZrO 2 —SiO 2 , ZrO 2 —SiO 2 —Cr 2 O 3 , ZrO 2 —SiO 2 —Ga 2 O 3 , HfO 2 —SiO 2 —Cr 2 O 3 , ZrO 2 —SiO 2 —.
- 2 O 3 or SnO 2 —SiC can be used.
- carbon (C) or the like can be used as a material for the metal film side interface film 413.
- the thickness of the metal film side interface film 413 is preferably in the range of 1 nm to 100 nm, and more preferably in the range of 5 nm to 40 nm.
- the first interface film 415 has a function of preventing mass transfer that occurs between the first dielectric film 414 and the recording film 416 due to repeated recording.
- the first interface film 415 is preferably a material having a high melting point that does not melt during recording and good adhesion to the recording film 416.
- Examples of the material of the first interface film 415 include ZrO 2 , HfO 2 , ZnO, SiO 2 , SnO 2 , Cr 2 O 3 , TiO 2 , In 2 O 3 , Ga 2 O 3 , Y 2 O 3 , CeO 2, DyO oxides such as 2, ZnS, or sulfides such as CdS, single carbides such as SiC, or may be a mixture thereof.
- Examples of the mixture include ZrO 2 —SiO 2 , ZrO 2 —SiO 2 —Cr 2 O 3 , ZrO 2 —SiO 2 —Ga 2 O 3 , HfO 2 —SiO 2 —Cr 2 O 3 , ZrO 2 —SiO 2 —.
- ZnS—SiO 2 , or SnO 2 —SiC can be used.
- carbon (C) or the like can be used as a material for the first interface film 415. Particularly including Ga 2 O 3, ZnO or In 2 O 3, preferably as the material for the first interface film 415. This is because Ga 2 O 3 , ZnO, or In 2 O 3 has good adhesion to the recording film 416.
- the thickness of the first interface film 415 is preferably in the range of 0.3 nm to 15 nm, and more preferably in the range of 1 nm to 8 nm.
- the second dielectric film 418 is closer to the laser beam incident surface than the recording film 416, and functions to prevent corrosion and deformation of the recording film 416, and an optical function to adjust reflectivity or absorptance. And have. Further, as the material of the second dielectric film 418, a material similar to that of the first dielectric film 414 can be used. In particular, ZnS—SiO 2 is excellent as a material for the second dielectric film 418. ZnS—SiO 2 has a high deposition rate, is transparent, and has good mechanical properties and moisture resistance.
- the thickness of the second dielectric film 418 satisfies the condition that the change in the amount of reflected light between the recording film 416 which is a crystalline phase and the recording film 416 which is an amorphous phase becomes large by calculation based on a matrix method. Can be determined strictly.
- the thickness of the second dielectric film 418 is preferably in the range of 20 nm to 80 nm.
- the second interface film 417 has a function of preventing mass transfer that occurs between the second dielectric film 418 and the recording film 416 due to repeated recording. Therefore, the material of the second interface film 417 is preferably a material having the same performance as that of the first interface film 415.
- the thickness of the second interface film 417 is preferably in the range of 0.3 nm to 15 nm, and more preferably in the range of 1 nm to 8 nm.
- the first information layer 41 includes a metal film 412, a first dielectric film 414, a recording film 416, and a second dielectric film 418, and further includes a metal film side interface film 413 and a first interface as necessary. A film 415 and a second interface film 417 are added.
- the same material as the recording film 416 of the first information layer 41 can be used.
- the thickness of the recording film 426 is preferably 10 nm or less, and more preferably in the range of 5 nm to 9 nm, in order to increase the transmittance of the second information layer 42.
- the metal film 422 has the same function as the metal film 412 of the first information layer 41. That is, the metal film 422 has an optical function of increasing the amount of light absorbed by the recording film 426 and a thermal function of diffusing heat generated in the recording film 426. Therefore, as the material of the metal film 422, the same material as that of the metal film 412 of the first information layer 41 can be used. In particular, an Ag alloy is preferable as a material for the metal film 422 because of its high thermal conductivity.
- the thickness of the metal film 422 is preferably 20 nm or less, and more preferably in the range of 6 nm to 14 nm in order to increase the transmittance of the second information layer 42. When the thickness of the metal film 422 is in the range of 6 nm to 14 nm, the optical and thermal functions of the metal film 422 are sufficient.
- the first dielectric film 424 has a function similar to that of the first dielectric film 414 of the first information layer 41. That is, the first dielectric film 424 has a thermal function for adjusting thermal diffusion from the recording film 426 to the metal film 422 and an optical function for adjusting reflectivity or absorption rate. Therefore, as the material of the first dielectric film 424, the same material as that of the first dielectric film 414 of the first information layer 41 can be used.
- the thickness of the first dielectric film 424 is preferably in the range of 1 nm to 40 nm, and more preferably in the range of 4 nm to 30 nm so that the optical and thermal functions are sufficient. .
- the second dielectric film 428 has the same function as the second dielectric film 418 of the first information layer 41. That is, the second dielectric film 428 has a function of preventing corrosion and deformation of the recording film 426 and an optical function of adjusting reflectance or absorption rate. Therefore, as the material of the second dielectric film 428, the same material as that of the second dielectric film 418 of the first information layer 41 can be used.
- the thickness of the second dielectric film 428 satisfies the condition that the change in the amount of reflected light between the recording film 426 which is a crystalline phase and the recording film 426 which is an amorphous phase becomes large by calculation based on the matrix method. It can be strictly determined.
- the transmittance adjusting film 421 is made of a dielectric and has a function of adjusting the transmittance of the second information layer 42.
- the transmittance adjusting film 421 allows the transmittance Tc (%) of the second information layer 42 when the recording film 426 is in a crystalline phase and the second information layer 42 when the recording film 426 is in an amorphous phase. Both the transmittance Ta (%) can be increased.
- the material of the transmittance adjustment film 421 TiO 2, ZrO 2, HfO 2, ZnO, Nb 2 O 5, Ta 2 O 5, Al 2 O 3, SiO 2, Cr 2 O 3, CeO 2, Ga 2 O 3 or oxides such as Bi 2 O 3 , nitrides such as Ti—N, Zr—N, Nb—N, Ge—N, Cr—N, or Al—N, sulfides such as ZnS, or these Can be used.
- the refractive index nt and extinction coefficient kt of the transmittance adjusting film 421 are preferably nt ⁇ 2.4 and kt ⁇ 0.1 in order to increase the transmittance Tc and the transmittance Ta.
- the thickness of the transmittance adjusting film 421 is approximately ⁇ / 8 nt (where ⁇ is the wavelength of the laser beam 31 and nt is the refractive index of the material of the transmittance adjusting film 421), the transmittance Tc and the transmission The effect of increasing the rate Ta is great. If the wavelength ⁇ of the laser beam 31 is 405 nm and the refractive index nt of the material of the transmittance adjusting film 421 is 2.6, the thickness of the transmittance adjusting film 421 depends on other conditions such as reflectance. In view of the above, it is preferable to be within the range of 5 nm to 36 nm.
- the metal film side interface film 423, the first interface film 425, and the second interface film 427 are the metal film side interface film 413, the first interface film 415, and the second interface film 417 of the first information layer 41, respectively. Has the same function. Further, the metal film side interface film 423, the first interface film 425, and the second interface film 427 are the metal film side interface film 413, the first interface film 415, and the second interface film of the first information layer 41, respectively. A material similar to that of 417 can be used.
- Each film constituting the third information layer 43 has a function equivalent to each film constituting the second information layer 42 corresponding thereto.
- each film constituting the third information layer 43 can be made of the same material as each film constituting the second information layer 42 corresponding to each film.
- the third information layer 43 is required to have a higher transmittance than the second information layer 42, a film using a material having a large extinction coefficient such as a recording film and a metal film needs to be thin. Therefore, the thickness of the recording film 436 of the third information layer 43 is preferably made thinner than the thickness of the recording film 426 of the second information layer 42.
- the optical recording medium 11 can be manufactured by the method described below.
- the first information layer 41 is laminated on the substrate 21 having a thickness of, for example, 1.1 mm.
- the first information layer 41 is formed of a multilayer film, but each film of the first information layer 41 can be formed by sequentially sputtering.
- the substrate 21 has a high hygroscopic property. Therefore, if necessary, a substrate annealing step for removing moisture may be performed before sputtering.
- Each film of the first information layer 41 is in a rare gas atmosphere such as Ar gas, Kr gas, or Xe gas or in a mixed gas atmosphere of a rare gas and a reactive gas (at least one gas selected from oxygen gas and nitrogen gas).
- a rare gas atmosphere such as Ar gas, Kr gas, or Xe gas
- a mixed gas atmosphere of a rare gas and a reactive gas at least one gas selected from oxygen gas and nitrogen gas.
- the sputtering method a DC sputtering method and an RF sputtering method are properly used as necessary.
- the DC sputtering method is preferable because the film formation rate can be increased, but a material having low conductivity such as a dielectric material may not be sputtered by the DC sputtering method.
- a film containing a material having low conductivity is sputtered by an RF sputtering method.
- a dielectric material can be sputtered by a DC sputtering method or a pulsed DC sputtering method, such as a highly conductive material or a material whose conductivity is improved by preparing a sputtering target.
- the composition of each film formed by sputtering may not completely match the composition of the original sputtering target.
- oxygen deficiency is likely to occur by sputtering.
- oxygen vacancies can be compensated by using oxygen gas as the reaction gas.
- the composition of the sputtering target is determined so that the film formed by sputtering has a desired composition. Note that the composition of the sputtering target and the film formed by sputtering can be confirmed, for example, by analyzing with an X-ray microanalyzer.
- a metal film 412 is first formed on the substrate 21.
- the metal film 412 can be formed by DC sputtering a sputtering target made of a metal or an alloy constituting the metal film 412 in a rare gas atmosphere or a mixed gas atmosphere of a rare gas and a reactive gas.
- the metal film side interface film 413 can be formed by sputtering a sputtering target made of a material constituting the metal film side interface film 413 in a rare gas atmosphere or a mixed gas atmosphere of a rare gas and a reactive gas.
- a sputtering target made of a material constituting the metal film side interface film 413 in a rare gas atmosphere or a mixed gas atmosphere of a rare gas and a reactive gas.
- a DC sputtering method may be used, and when the material is a low conductivity material such as an oxide, an RF sputtering method may be used.
- a first dielectric film 414 is formed on the metal film side interface film 413 or the metal film 412.
- the first dielectric film 414 is formed by sputtering a sputtering target made of a material constituting the first dielectric film 414 mainly in an RF sputtering method in a rare gas atmosphere or a mixed gas atmosphere of a rare gas and a reactive gas. Can be formed.
- the reason why the RF sputtering method is used is that the material constituting the first dielectric film 414 is often a material having low conductivity and is not suitable for DC sputtering.
- the first interface film 415 is obtained by sputtering a sputtering target made of a material constituting the first interface film 415 mainly in an RF sputtering method in a rare gas atmosphere or a mixed gas atmosphere of a rare gas and a reactive gas. Can be formed.
- a recording film 416 is formed on the first interface film 415 or the first dielectric film 414.
- the recording film 416 can be formed by sputtering a sputtering target made of a material constituting the recording film 416 mainly in a rare gas atmosphere by a DC sputtering method.
- the second interface film 417 is obtained by sputtering a sputtering target made of a material constituting the second interface film 417 mainly in an RF sputtering method in a rare gas atmosphere or a mixed gas atmosphere of a rare gas and a reactive gas. Can be formed.
- a second dielectric film 418 is formed on the second interface film 417 or the recording film 416.
- the second dielectric film 418 is formed by sputtering a sputtering target made of the material constituting the second dielectric film 418 mainly in an RF sputtering method in a rare gas atmosphere or a mixed gas atmosphere of a rare gas and a reactive gas. Can be formed.
- the separation layer 22 can be formed as follows. First, an ultraviolet curable resin (for example, an acrylic resin or an epoxy resin) or a slow-acting thermosetting resin is applied on the first information layer 41. Next, the whole is rotated to uniformly extend the resin (spin coating), and then the resin is cured.
- the separation layer 22 includes a guide groove for the laser beam 31, first, the substrate (mold) on which the groove is formed is brought into close contact with the resin before being cured. In this state, the whole is rotated and spin-coated, and after the resin is cured, the substrate (mold) is peeled off. In this way, a guide groove can be formed in the separation layer 22.
- the recording film 416 of the first information layer 41 is normally in an amorphous state as it is formed (as-depo state). Therefore, an initialization process for crystallizing the recording film 416 may be performed by irradiating a laser beam as necessary. Note that the initialization process may be performed after the formation of the other information layers.
- the film thickness of the recording film may become thin due to the recording film changing from an amorphous state to a crystalline state by initialization.
- the film thickness of the recording film is reduced by about 2% to 9% as compared with the original film thickness by the initialization.
- the second information layer 42 is formed on the separation layer 22.
- a transmittance adjusting film 421 is first formed on the separation layer 22.
- the transmittance adjusting film 421 is obtained by sputtering a sputtering target made of a material constituting the transmittance adjusting film 421 in a rare gas atmosphere or a mixed gas atmosphere of a rare gas and a reactive gas by an RF sputtering method or a DC sputtering method. Can be formed.
- a metal film 422 is formed on the transmittance adjusting film 421.
- the metal film 422 can be formed by the same method as the metal film 412 of the first information layer 41.
- a metal film side interface film 423 is formed on the metal film 422 as necessary.
- the metal film side interface film 423 can be formed by the same method as the metal film side interface film 413 of the first information layer 41.
- a first dielectric film 424 is formed on the metal film side interface film 423 or the metal film 422.
- the first dielectric film 424 can be formed by the same method as the first dielectric film 414 of the first information layer 41.
- a first interface film 425 is formed on the first dielectric film 424 as necessary.
- the first interface film 425 can be formed by the same method as the first interface film 415 of the first information layer 41.
- a recording film 426 is formed on the first interface film 425 or the first dielectric film 424.
- the recording film 426 can be formed by the same method as the recording film 416 of the first information layer 41.
- a second interface film 427 is formed on the recording film 426 as necessary.
- the second interface film 427 can be formed by the same method as the second interface film 417 of the first information layer 41.
- a second dielectric film 428 is formed on the second interface film 427 or the recording film 426.
- the second dielectric film 428 can be formed by the same method as the second dielectric film 418 of the first information layer 41.
- the second information layer 42 is laminated on the separation layer 22, and then the separation layer 28 is formed on the second information layer 42.
- the separation layer 28 can be formed by the same method as the separation layer 22.
- an initialization process for crystallizing the recording film 426 may be performed by irradiating a laser beam, if necessary. good. Note that the initialization process may be performed after the formation of the other information layers.
- the third information layer 43 is laminated on the separation layer 28.
- the transmittance adjusting film 431, the metal film 432, the first dielectric film 434, the recording film 436, and the second dielectric film 438 are formed on the separation layer 28 in this order.
- a metal film side interface film 433 is formed between the metal film 432 and the first dielectric film 434, and a first film is formed between the first dielectric film 434 and the recording film 436.
- the first interface film 435 may be formed, and the second interface film 437 may be formed between the second dielectric film 438 and the recording film 436.
- Each film of the third information layer 43 can be formed by the same method as each film of the second information layer 42.
- the transparent layer 23 is formed on the third information layer 43.
- the transparent layer 23 can be formed as follows. First, an ultraviolet curable resin (for example, acrylic resin or epoxy resin) or a slow-acting thermosetting resin is applied on the third information layer 43 and spin-coated, and then the resin is cured. Further, the transparent layer 23 may be formed using a disk-shaped polycarbonate resin, polymethyl methacrylate resin, polyolefin resin, or norbornene resin. The transparent layer 23 may be formed using a disk-shaped plate or sheet made of glass or the like. In this case, the transparent layer 23 is coated with an ultraviolet curable resin or a slow-acting thermosetting resin on the third information layer 43, and after the plate or sheet is brought into close contact with the applied resin, the transparent layer 23 is cured. It can be formed by curing the functional resin. As another forming method, after the adhesive resin is uniformly applied to the plate or sheet in advance, the plate or sheet can be brought into close contact with the second dielectric film 438.
- an ultraviolet curable resin for example, acrylic resin or epoxy resin
- an initialization process for crystallizing the recording film 436 is performed by irradiating a laser beam as necessary. May be.
- the initializing step of crystallizing the recording film 416 of the first information layer and the recording film 426 of the second information layer is an initial step of crystallizing the recording film 436 of the third information layer after the transparent layer 23 is formed. It may be performed before the conversion step.
- the optical recording medium 11 can be manufactured.
- the sputtering method is used as a method for forming each film constituting the information layer.
- the present invention is not limited to this, but a vacuum evaporation method, an ion plating method, or MBE (Molecular Beam Epitaxy). It is also possible to use a method or the like.
- the optical recording medium 11 including three information layers has been described. However, the same applies to the case where the number of information layers is two or the number of information layers is four or more. It can manufacture by the method of.
- the transmittance of each information layer needs to be higher for the information layer on the incident surface side of the laser beam.
- the diameter is 12 cm and the recording capacity per surface is 33.4 GB.
- the transmittance of the second information layer is preferably 40% to 55%
- the transmittance of the third information layer is preferably 45% to 65%.
- the recording film made of a phase change material having a large extinction coefficient In order to obtain high transmittance, it is necessary to thin the recording film made of a phase change material having a large extinction coefficient.
- the crystallization speed is slowed down. Therefore, the phase change from the amorphous phase to the crystalline phase is difficult to occur, and the information erasing performance is deteriorated.
- the thickness of the recording film of the third information layer is made thinner than the thickness of the recording film of the second information layer. At this time, in order to satisfy the practically required level of the erasing performance of the third information layer, it is necessary to devise a recording method.
- the substantial reflectance of each information layer is calculated by multiplying the film reflectance that does not include attenuation due to transmission through the other information layers by the transmittance of each information layer twice.
- the reflectance of the information layer far from the incident surface tends to be low.
- the film reflectance needs to be considerably higher (about three times) than the film reflectance of the third information layer.
- the inventors produced the optical recording medium 11 of FIG. 12, and examined the recording characteristics and the reproduction characteristics of each information layer of the first information layer 41, the second information layer 42, and the third information layer 43. .
- the sample of the optical recording medium was manufactured as follows. First, a polycarbonate substrate (diameter 120 mm, thickness 1.1 mm) on which a guide groove (depth 20 nm, track pitch 0.32 ⁇ m) for guiding the laser beam 31 was formed was prepared as the substrate 21.
- an Ag—Ga—Cu film (thickness: 100 nm) as the metal film 412, a ZrO 2 —Cr 2 O 3 film (thickness: 18 nm) as the first dielectric film 414, a recording film GeTe—Sb 2 Te 3 film (thickness: 10 nm) as 416, ZrO 2 —Cr 2 O 3 film (thickness: 5 nm) as second interface film 417 (not shown), and second dielectric film 418
- ZnS—SiO 2 films (thickness: 65 nm) were sequentially laminated by sputtering.
- an ultraviolet curable resin was applied on the second dielectric film 418, and a substrate on which a guide groove (depth 20 nm, track pitch 0.32 ⁇ m) was formed was covered and adhered, and rotated. Thereby, a uniform resin layer is formed. Then, after the resin was cured, the substrate was peeled off. As a result, a separation layer 22 having a thickness of 25 ⁇ m in which a guide groove for guiding the laser beam 31 was formed on the second information layer 42 side was obtained.
- a TiO 2 film (thickness: 20 nm) as the transmittance adjustment film 421
- an Ag—Pd—Cu film thickness: 10 nm
- a first dielectric film 424 are formed.
- ZrO 2 —Cr 2 O 3 film (thickness: 11 nm), GeTe—Sb 2 Te 3 film (thickness: 8 nm) as recording film 426, and ZrO 2 —Cr 2 as second interface film 427 (not shown)
- a ZnS—SiO 2 film (thickness: 35 nm) was sequentially laminated by sputtering as an O 3 film (thickness: 5 nm) and a second dielectric film 428.
- an ultraviolet curable resin was applied on the second dielectric film 428, and a substrate on which a guide groove (depth 20 nm, track pitch 0.32 ⁇ m) was formed was covered and brought into close contact with the substrate and rotated. Thereby, a uniform resin layer is formed. Then, after the resin was cured, the substrate was peeled off. As a result, a separation layer 28 having a thickness of 18 ⁇ m in which a guide groove for guiding the laser beam 31 was formed on the third information layer 43 side was obtained.
- a TiO 2 film (thickness: 18 nm) as the transmittance adjusting film 431
- an Ag—Pd—Cu film thickness: 8 nm
- a first dielectric film 434 are formed on the separation layer 28.
- ZrO 2 —Cr 2 O 3 film (thickness: 10 nm), GeTe—Sb 2 Te 3 film (thickness: 7 nm) as recording film 436, and ZrO 2 —Cr 2 as second interface film 437 (not shown)
- a ZnS—SiO 2 film (thickness: 33 nm) was sequentially laminated by sputtering as an O 3 film (thickness: 4 nm) and a second dielectric film 438.
- an ultraviolet curable resin was applied on the second dielectric film 438 and rotated to form a uniform resin layer. Thereafter, the resin was cured by irradiating ultraviolet rays to form a transparent layer 23 having a thickness of 57 ⁇ m. Thereafter, an initialization process for crystallizing the recording film 416, the recording film 426, and the recording film 436 with a laser beam was performed. A sample was manufactured as described above.
- the reflectance of each information layer was measured, and it was confirmed that the ratio of the reflectance of two different information layers was 0.5 or more and 2.0 or less.
- the recording film thickness DN of the Nth information layer closest to the light incident surface of the optical recording medium 11 is the thickness DM of the recording film of the Mth information layer (M is an integer of N> M ⁇ 1). Smaller than. Further, the reflectance RN from the Nth information layer is smaller than twice the reflectance RM from the Mth information layer.
- the symbol error rate (SER) of each information layer was measured using the optical recording / reproducing apparatus of FIG.
- recording was performed by a recording method in which the capacity per layer was 33.4 GB, and the shortest mark length (2T) was 0.112 ⁇ m.
- the linear velocity of the sample during recording and measurement was 7.38 m / s.
- the reproduction power was switched according to the information layer.
- the reproduction power was 1.44 mW when reproducing the first information layer and the second information layer, and the reproduction power was 1.00 mW when reproducing the third information layer.
- the reproduction signal was PRML processed with PR (1, 2, 2, 2, 1).
- SER was measured.
- the SER is preferably not more than a reference value (2.0 ⁇ 10 ⁇ 4 ).
- the optical recording / reproducing apparatus determines the position of the pulse edge of the recording pulse by trial writing.
- the optical recording / reproducing apparatus first performs trial writing using parameters of recording pulses recorded in advance in a region called a lead-in area of the optical recording medium 11 at the time of manufacturing the disc or after manufacturing the disc. If there are other optimum parameters, the optical recording / reproducing apparatus may learn the position of the pulse edge, for example, obtain a recording compensation table for the new edge change amount, and determine the position of the pulse edge. Good.
- recording is performed by the recording compensation table of the N / 2 recording strategy shown in FIG. 8 and the power information shown in FIG.
- FIG. 14 is a view showing an example of a recording compensation table of the first information layer of the optical recording medium according to the embodiment of the present invention
- FIG. 15 is a second diagram of the optical recording medium according to the embodiment of the present invention
- FIG. 16 is a diagram illustrating an example of a recording compensation table for an information layer
- FIG. 16 is a diagram illustrating an example of a recording compensation table before learning for the third information layer of the optical recording medium according to the embodiment of the present invention.
- the control parameter is changed in units of Tw / 32.
- the recording / reproducing characteristics when the power ratio of the recording power is changed are measured, and the recording compensation table may be optimized according to the power ratio.
- the start position dTe of the erase power Pe of the 2T mark in the first information layer is set so as not to have a cooling pulse. This is because in the first information layer with a thick metal film, if the recording pulse has a cooling pulse, the mark becomes too large, making it difficult to record so that the shortest mark length (2T) is 0.112 ⁇ m. Because it becomes. Note that the recording pulse for forming a mark of 3T or more is set to have a cooling pulse.
- Table 9 is a table showing an example of the recording power for recording information on the first information layer and the SER of the signal recorded with the recording power. SER was measured for each of DOW0 and DOW10. The determination in Table 9, if the SER is the reference value (2.0 ⁇ 10 -4) or less is set to "Yes", if the SER is greater than the reference value (2.0 ⁇ 10 -4) "No "
- Tables 10 and 11 are tables showing examples of recording power for recording information on the second information layer and the third information layer, and SER of signals recorded with the recording power.
- Tables 10 and 11 the results of the first information layer shown in Table 9 are also shown for reference.
- the SER was measured for each of state DOW0 and state DOW10.
- the determinations in Table 10 and Table 11 are “OK” when the SER is less than or equal to the reference value (2.0 ⁇ 10 ⁇ 4 ), and when the SER exceeds the reference value (2.0 ⁇ 10 ⁇ 4 ). Was “impossible”.
- the overall determination is “OK” when all the determinations of each information layer are “OK”, and “No” when there is even one “NO”.
- the SER of the second information layer exceeds the reference value in both the state DOW0 and the state DOW10.
- the SER of the second information layer satisfies the reference value in both the state DOW0 and the state DOW10. That is, at the recording power shown in Table 11, since the bottom power Pb2 of the second information layer is high, the temperature change at the time of recording is rapidly cooled, and the mark portion that is an amorphous phase is easily formed.
- the signal amplitude is increased even in the second information layer in which the ratio of the reflectance of the recording film that is a crystalline phase and the reflectance of the recording film that is amorphous tends to be reduced by increasing the reflectance.
- the playback signal quality can be improved.
- the SER of the third information layer is not more than the reference value in the state DOW0, but exceeds the reference value in the state DOW10.
- the SER of the third information layer satisfies the reference value in both the state DOW0 and the state DOW10. That is, with the recording power shown in Table 11, since the bottom power Pb3 of the third information layer is high, the temperature change during recording is gradually cooled, and the mark portion that is an amorphous phase is formed to be small, so that rewriting is easy. The effect of making is obtained.
- the erasing performance required in practice can be ensured and the reproduction signal quality can be improved. it can.
- FIG. 17 is a diagram showing an example of a recording pulse train of each information layer in the present embodiment.
- FIG. 17 shows recording pulse trains of the first to third information layers.
- Each power shown in FIG. 17 is preferably set as shown in Table 11. That is, the peak power Pw3 of the third information layer, the bottom power Pb3 of the third information layer, the peak power Pw2 of the second information layer, and the bottom power Pb2 of the second information layer satisfy the following expressions.
- the peak power PwN of the Nth information layer closest to the light incident surface of the optical recording medium the bottom power PbN of the Nth information layer
- the peak power PwM of the Mth information layer M is an integer of N> M ⁇ 1
- the bottom power PbM of the Mth information layer satisfies the following formula.
- the bottom power Pb3 of the third information layer becomes larger than the cooling power Pc3 of the third information layer, and the bottom power Pb2 of the second information layer becomes equal to the cooling power Pc2 of the second information layer.
- the bottom power PbN of the Nth information layer becomes larger than the cooling power PcN of the Nth information layer, and the bottom power PbM of the Mth information layer becomes equal to the cooling power PcM of the Mth information layer.
- the bottom power Pb1 of the first information layer farthest from the light incident surface of the optical recording medium is equal to the cooling power Pc1 of the first information layer.
- a recording pulse train not including a cooling pulse is generated.
- Table 12 shows an example of the recording power for recording information in the second information layer and the third information layer, and the ratio of the bottom power to the peak power is 0.100 for both the second information layer and the third information layer. It is a table
- the determination method is the same as in Table 10 and Table 11.
- the ratio of the bottom power Pb3 to the peak power Pw3 of the third information layer is made larger than the ratio of the bottom power Pb2 to the peak power Pw2 of the second information layer. It can be seen that it is necessary for high quality reproduction.
- an N / 2 recording strategy is used, which is a recording pulse characterized by the fact that the number of pulses increases by one when the mark length to be recorded increases by two.
- a recording pulse in which the number of pulses increases by one when the number increases by one may be used.
- the optical recording medium includes three information layers, that is, a first information layer, a second information layer, and a third information layer.
- the optical recording medium may include four information layers. The same effect as this embodiment can be obtained.
- FIG. 18 is a diagram showing an example of a recording pulse train of each information layer in the first modification of the present embodiment.
- the optical recording medium according to the first modification of the present embodiment includes four information layers.
- FIG. 18 shows recording pulse trains of the first to fourth information layers. As shown in FIG. 18, in the first modification of the present embodiment, the recording pulse train of the second information layer and the recording pulse train of the third information layer are the same.
- the recording pulse train of the first information layer in the first modification is the same as the recording pulse train of the first information layer shown in FIG. 17, and the second information layer and the third information layer in the first modification are the same.
- the recording pulse train is the same as the recording pulse train of the second information layer shown in FIG. 17, and the recording pulse train of the fourth information layer in the first modification is the same as the recording pulse train of the third information layer shown in FIG. It is.
- the peak power Pw4 of the fourth information layer, the bottom power Pb4 of the fourth information layer, the peak power Pw3 of the third information layer, and the bottom power Pb3 of the third information layer satisfy the following expressions: .
- Pb3 / Pw3 is equal to Pb2 / Pw2.
- FIG. 19 is a diagram showing an example of a recording pulse train of each information layer in the second modification of the present embodiment.
- the optical recording medium according to the second modification of the present embodiment includes four information layers.
- FIG. 19 shows recording pulse trains of the first to fourth information layers. As shown in FIG. 19, in the second modification of the present embodiment, the recording pulse train of the third information layer and the recording pulse train of the fourth information layer are the same.
- the recording pulse train of the first information layer in the second modification is the same as the recording pulse train of the first information layer shown in FIG. 17, and the recording pulse train of the second information layer in the second modification is shown in FIG. 17 is the same as the recording pulse train of the second information layer, and the recording pulse train of the third information layer and the fourth information layer in the second modification is the same as the recording pulse train of the third information layer shown in FIG. It is.
- the peak power Pw4 of the fourth information layer, the bottom power Pb4 of the fourth information layer, the peak power Pw2 of the second information layer, and the bottom power Pb2 of the second information layer satisfy the following expressions: .
- Pb4 / Pw4 is equal to Pb3 / Pw3.
- the bottom power Pb3 of the third information layer and the bottom power Pb4 of the fourth information layer are the same.
- the bottom power Pb3 of the information layer may be smaller than the bottom power Pb4 of the fourth information layer. That is, the peak power Pw4 of the fourth information layer, the bottom power Pb4 of the fourth information layer, the peak power Pw3 of the third information layer, the bottom power Pb3 of the third information layer, the peak power Pw2 of the second information layer, and the second information
- the bottom power Pb2 of the layer may satisfy the following formula.
- FIG. 20 is a diagram showing an example of a recording pulse train of each information layer in the third modification of the present embodiment.
- the optical recording medium in the third modification example of the present embodiment includes two information layers.
- FIG. 20 shows recording pulse trains of the first and second information layers. As shown in FIG. 20, the recording pulse train of the first information layer in the third modification is the same as the recording pulse train of the second information layer shown in FIG. 17, and the second information layer in the third modification is the same.
- the recording pulse train and the recording pulse train of the third information layer shown in FIG. 17 are the same.
- the peak power Pw2 of the second information layer, the bottom power Pb2 of the second information layer, the peak power Pw1 of the first information layer, and the bottom power Pb1 of the first information layer satisfy the following equations: .
- the optical recording medium includes N information layers (N is an integer of 2 or more).
- each of the N information layers has a recording film that causes a physical change in state due to a local temperature change caused by the focusing of the laser beam.
- a recording mark is formed on the recording film by irradiation with a laser beam corresponding to the recording pulse train.
- FIG. 21 is a block diagram showing a configuration of an optical recording / reproducing apparatus according to the fourth modification of the present embodiment. In FIG. 21, the same components as those in FIG.
- the memory 131 stores in advance peak power representing the power of the write pulse of each information layer and bottom power representing the power of the bottom pulse of each information layer.
- the memory 131 stores not only peak power and bottom power but also cooling power and erase power.
- the memory 131 stores peak power, bottom power, cooling power, and erase power as power information.
- the power information stored in the memory 131 may be stored in advance when the optical recording / reproducing apparatus is manufactured. Further, the power information stored in the memory 131 may be stored in association with the identification information for identifying the optical recording medium, the power information read from the optical recording medium by the reading unit 130. In the present embodiment, the memory 131 corresponds to an example of a storage unit.
- the power setting unit 114 sets the power of each pulse of the recording pulse train based on the peak power of each information layer and the bottom power of each information layer stored in the memory 131.
- the materials and film thicknesses mentioned in the above embodiments and examples are examples of various materials and film thicknesses for realizing the present invention, and the present invention is not limited thereto.
- the optical information recording medium according to the present invention may use materials other than those mentioned in the above embodiments and examples, and may have a thickness other than the thickness of each layer mentioned in the above embodiments and examples. You may set it.
- An optical information recording apparatus is an optical information recording apparatus that records information on an optical information recording medium including N information layers (N is an integer of 2 or more), wherein the N Each of the information layers includes a recording film that causes a change in physical state due to a local temperature change caused by the focusing of the laser beam, a light source that emits the laser beam, and a recording mark on the recording film.
- a recording pulse train generating section for generating a recording pulse train for forming, a power setting section for setting the power of each pulse of the recording pulse train, and the laser beam corresponding to the recording pulse train generated by the recording pulse train generating section.
- the power setting unit includes the peak power PwN of the Nth information layer closest to the light incident surface of the optical information recording medium, the Nth information layer Bottom power PbN, peak power PwM of the Mth information layer (M is an integer of N> M ⁇ 1), and bottom power PbM of the Mth information layer satisfy the following formula: Set the power.
- the light source emits a laser beam.
- the recording pulse train generation unit generates a recording pulse train for forming a recording mark on the recording film.
- the power setting unit sets the power of each pulse of the recording pulse train.
- the driving unit drives the light source so as to emit a laser beam corresponding to the recording pulse train generated by the recording pulse train generating unit with the power set by the power setting unit.
- the recording pulse train includes at least one write pulse having the highest power, a bottom pulse formed between the plurality of write pulses when there are a plurality of write pulses, and a cooling formed following the last write pulse. Including pulses.
- the power setting unit When the power of the write pulse is the peak power and the power of the bottom pulse is the bottom power, the power setting unit has the peak power PwN of the Nth information layer closest to the light incident surface of the optical information recording medium, the Nth information layer
- the power of each pulse of the recording pulse train is set so that the bottom power PbN of the recording medium, the peak power PwM of the M-th information layer (M is an integer of N> M ⁇ 1), and the bottom power PbM of the M-th information layer satisfy the above formula.
- the ratio of the bottom power PbN to the peak power PwN of the Nth information layer closest to the light incident surface of the optical information recording medium among the N information layers is expressed as Mth information layer (M is N> M ⁇ 1). Since the power of each pulse of the recording pulse train is set so as to be higher than the ratio of the bottom power PbM to the peak power PwM of (integer), the temperature change during recording in the Mth information layer becomes relatively rapid cooling, Recording marks that are in an amorphous phase can be easily formed. Therefore, by increasing the reflectance, the signal amplitude is also increased in the M-th information layer in which the ratio of the reflectance of the recording film that is a crystalline phase to the reflectance of the recording film that is amorphous tends to decrease. And the reproduction signal quality can be improved.
- the temperature change during recording in the Nth information layer becomes relatively slow cooling, and the recording mark which is an amorphous phase is formed smaller, so that information rewriting is facilitated. Therefore, the erasing performance required in practice can be ensured even in the Nth information layer in which the thickness of the recording film is reduced to increase the transmittance and the erasing performance is likely to deteriorate.
- the power setting unit is configured such that the bottom power PbN of the Nth information layer is the Nth information layer. It is preferable that the power of each pulse of the recording pulse train is set so that the cooling power PcN of the Mth information layer is equal to the cooling power PcM of the Mth information layer. .
- the power setting unit when the power of the cooling pulse is the cooling power, the power setting unit has the bottom power PbN of the Nth information layer larger than the cooling power PcN of the Nth information layer, The power of each pulse of the recording pulse train is set so that the bottom power PbM is equal to the cooling power PcM of the Mth information layer.
- the temperature change during the shortest mark recording can be rapidly cooled. Therefore, it becomes easy to form the shortest mark, and the signal quality can be improved.
- the laser beam is modulated at the three power levels of the peak power, the bottom power, and the erase power that is the power of the erase pulse. be able to.
- the power setting unit is configured to transmit the optical information.
- the power of each pulse of the recording pulse train is set so that the bottom power Pb1 of the first information layer farthest from the light incident surface of the recording medium is equal to the cooling power Pc1 of the first information layer, and the recording pulse train
- the generator preferably generates a recording pulse train that does not include the cooling pulse when the shortest recording mark is formed on the recording film of the first information layer.
- the optical information recording medium includes three or more information layers.
- the power setting unit makes the bottom power Pb1 of the first information layer farthest from the light incident surface of the optical information recording medium equal to the cooling power Pc1 of the first information layer.
- the power of each pulse of the recording pulse train is set.
- the recording pulse train generator generates a recording pulse train that does not include a cooling pulse when the shortest recording mark is formed on the recording film of the first information layer.
- the N information layers include only three information layers.
- the signal amplitudes of the first and second information layers can be increased, and the reproduction signal quality can be improved.
- the erasing performance required for practical use of the information layer can be ensured.
- the optical information recording medium records a peak power indicating the power of the write pulse in each information layer and a bottom power indicating the power of the bottom pulse in each information layer,
- a reading unit that reads the peak power of each information layer and the bottom power of each information layer from the optical information recording medium; and the power setting unit includes the peak of each information layer read by the reading unit. It is preferable to set the power of each pulse of the recording pulse train based on the power and the bottom power of each information layer.
- the optical information recording medium records the peak power indicating the power of the write pulse of each information layer and the bottom power indicating the power of the bottom pulse of each information layer.
- the reading unit reads the peak power of each information layer and the bottom power of each information layer from the optical information recording medium.
- the power setting unit sets the power of each pulse of the recording pulse train based on the peak power of each information layer read by the reading unit and the bottom power of each information layer.
- the power of each pulse of the recording pulse train can be set based on the peak power of each information layer read from the optical information recording medium and the bottom power of each information layer.
- the optical information recording apparatus may further include a storage unit that stores in advance a peak power that represents the power of the write pulse of each information layer and a bottom power that represents the power of the bottom pulse of each information layer.
- the setting unit sets the power of each pulse of the recording pulse train based on the peak power of each information layer and the bottom power of each information layer stored in the storage unit.
- the storage unit stores in advance peak power indicating the power of the write pulse of each information layer and bottom power indicating the power of the bottom pulse of each information layer.
- the power setting unit sets the power of each pulse of the recording pulse train based on the peak power of each information layer and the bottom power of each information layer stored in the storage unit.
- the power of each pulse of the recording pulse train can be set based on the peak power of each information layer read from the storage unit and the bottom power of each information layer.
- An optical information recording method is an optical information recording method for recording information on an optical information recording medium having an information layer of N layers (N is an integer of 2 or more), Each of the N information layers has a recording film that causes a change in physical state due to a local temperature change caused by the focusing of the laser beam, and generates a recording pulse train for forming a recording mark on the recording film.
- a recording pulse train generating step, a power setting step for setting the power of each pulse of the recording pulse train, and the laser beam corresponding to the recording pulse train generated in the recording pulse train generating step is set in the power setting step.
- the recording pulse train includes at least one write pulse having the highest power, a bottom pulse formed between a plurality of write pulses when there are a plurality of the write pulses, and a last write pulse.
- the power setting step is closest to the light incident surface of the optical information recording medium when the power of the write pulse is a peak power and the power of the bottom pulse is a bottom power.
- the peak power PwN of the Nth information layer, the bottom power PbN of the Nth information layer, the peak power PwM of the Mth information layer (M is an integer of N> M ⁇ 1), and the bottom power PbM of the Mth information layer are as follows:
- the power of each pulse of the recording pulse train is set so as to satisfy the following equation.
- the recording pulse train generation step a recording pulse train for forming recording marks on the recording film is generated.
- the power setting step the power of each pulse of the recording pulse train is set.
- the driving step the light source is driven so that the laser beam corresponding to the recording pulse train generated in the recording pulse train generating step is emitted with the power set in the power setting step.
- the laser beam emission step the laser beam is emitted from the light source.
- the recording pulse train includes at least one write pulse having the highest power, a bottom pulse formed between the plurality of write pulses when there are a plurality of write pulses, and a cooling formed following the last write pulse. Including pulses.
- the power of each pulse of the recording pulse train is such that the bottom power PbN of the recording medium, the peak power PwM of the Mth information layer (M is an integer satisfying N> M ⁇ 1), and the bottom power PbM of the Mth information layer satisfy the following expression: Is set.
- the ratio of the bottom power PbN to the peak power PwN of the Nth information layer closest to the light incident surface of the optical information recording medium among the N information layers is expressed as Mth information layer (M is N> M ⁇ 1). Since the power of each pulse of the recording pulse train is set so as to be higher than the ratio of the bottom power PbM to the peak power PwM of (integer), the temperature change during recording in the Mth information layer becomes relatively rapid cooling, Recording marks that are in an amorphous phase can be easily formed. Therefore, by increasing the reflectance, the signal amplitude is also increased in the M-th information layer in which the ratio of the reflectance of the recording film that is a crystalline phase to the reflectance of the recording film that is amorphous tends to decrease. And the reproduction signal quality can be improved.
- the temperature change during recording in the Nth information layer becomes relatively slow cooling, and the recording mark which is an amorphous phase is formed smaller, so that information rewriting is facilitated. Therefore, the erasing performance required in practice can be ensured even in the Nth information layer in which the thickness of the recording film is reduced to increase the transmittance and the erasing performance is likely to deteriorate.
- An optical information recording medium includes N information layers (N is an integer of 2 or more), and each of the N information layers is locally formed by focusing a laser beam.
- N is an integer of 2 or more
- a recording film that has a physical state change caused by a temperature change, and a recording mark is formed on the recording film by being irradiated with a laser beam corresponding to a recording pulse train, and a light incident surface of the optical information recording medium
- the recording film thickness DN of the Nth information layer closest to is smaller than the recording film thickness DM of the Mth information layer (M is an integer of N> M ⁇ 1).
- the reflectance RN is smaller than twice the reflectance RM from the Mth information layer, and the recording pulse train includes a plurality of write pulses when there are at least one write pulse having the highest power and a plurality of the write pulses.
- Bot formed during the pulse And a cooling pulse formed subsequent to the last write pulse, and at least one information layer of the N information layers has a peak power representing the power of the write pulse of each information layer And the bottom power representing the power of the bottom pulse of each information layer, the peak power PwN of the Nth information layer, the bottom power PbN of the Nth information layer, the peak power PwM of the Mth information layer, and the The bottom power PbM of the M information layer satisfies the following formula.
- the recording film thickness DN of the Nth information layer closest to the light incident surface of the optical information recording medium is recorded in the Mth information layer (M is an integer of N> M ⁇ 1).
- the film thickness is smaller than DM.
- the reflectance RN from the Nth information layer is smaller than twice the reflectance RM from the Mth information layer.
- the recording pulse train includes at least one write pulse having the highest power, a bottom pulse formed between the plurality of write pulses when there are a plurality of write pulses, and a cooling formed following the last write pulse. Including pulses.
- At least one information layer among the N information layers records a peak power indicating the power of the write pulse of each information layer and a bottom power indicating the power of the bottom pulse of each information layer.
- the peak power PwN of the Nth information layer, the bottom power PbN of the Nth information layer, the peak power PwM of the Mth information layer, and the bottom power PbM of the Mth information layer satisfy the above expressions.
- the ratio of the bottom power PbN to the peak power PwN of the Nth information layer closest to the light incident surface of the optical information recording medium among the N information layers is Mth information layer (M is N> M ⁇ 1). Since the ratio of the bottom power PbM to the peak power PwM of (integer) is higher, the temperature change at the time of recording in the Mth information layer is relatively rapidly cooled, and a recording mark that is an amorphous phase can be easily formed. it can. Therefore, by increasing the reflectance, the signal amplitude is also increased in the M-th information layer in which the ratio of the reflectance of the recording film that is a crystalline phase to the reflectance of the recording film that is amorphous tends to decrease. And the reproduction signal quality can be improved.
- the temperature change during recording in the Nth information layer becomes relatively slow cooling, and the recording mark which is an amorphous phase is formed smaller, so that information rewriting is facilitated. Therefore, the erasing performance required in practice can be ensured even in the Nth information layer in which the thickness of the recording film is reduced to increase the transmittance and the erasing performance is likely to deteriorate.
- An optical information recording apparatus, an optical information recording method, and an optical information recording medium according to the present invention can record high-quality information on all information layers in an information recording medium including two or more information layers.
- the optical information recording apparatus and the optical information recording method for recording information on the optical information recording medium by laser beam irradiation are useful for an optical information recording medium having two or more information layers.
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Abstract
Description
以下、具体的な実施例により本発明をさらに具体的に説明する。
Claims (8)
- N層(Nは2以上の整数)の情報層を備える光学的情報記録媒体に情報を記録する光学的情報記録装置であって、
前記N層の情報層のそれぞれは、レーザビームの集光による局所的な温度変化によって物理的な状態の変化を生じる記録膜を有し、
前記レーザビームを出射する光源と、
前記記録膜に記録マークを形成するための記録パルス列を生成する記録パルス列生成部と、
前記記録パルス列の各パルスのパワーを設定するパワー設定部と、
前記記録パルス列生成部によって生成された前記記録パルス列に応じた前記レーザビームを、前記パワー設定部によって設定されたパワーで出射するように前記光源を駆動する駆動部とを備え、
前記記録パルス列は、最も高いパワーを有する少なくとも1つのライトパルスと、前記ライトパルスが複数ある場合に複数のライトパルスの間に形成されるボトムパルスと、最後尾のライトパルスに後続して形成されるクーリングパルスとを含み、
前記ライトパルスのパワーをピークパワーとし、前記ボトムパルスのパワーをボトムパワーとしたとき、
前記パワー設定部は、前記光学的情報記録媒体の光入射面に最も近い第N情報層のピークパワーPwN、前記第N情報層のボトムパワーPbN、第M情報層(MはN>M≧1の整数)のピークパワーPwM及び前記第M情報層のボトムパワーPbMが下記の式を満たすように、前記記録パルス列の各パルスの前記パワーを設定する光学的情報記録装置。
PbN/PwN>PbM/PwM - 前記クーリングパルスのパワーをクーリングパワーとしたとき、
前記パワー設定部は、前記第N情報層のボトムパワーPbNが、前記第N情報層のクーリングパワーPcNよりも大きくなり、前記第M情報層のボトムパワーPbMが、前記第M情報層のクーリングパワーPcMと等しくなるように、前記記録パルス列の各パルスの前記パワーを設定する請求項1記載の光学的情報記録装置。 - 前記光学的情報記録媒体は、3層以上の情報層を備え、
前記クーリングパルスのパワーをクーリングパワーとしたとき、
前記パワー設定部は、前記光学的情報記録媒体の光入射面から最も遠い第1情報層のボトムパワーPb1が、前記第1情報層のクーリングパワーPc1と等しくなるように、前記記録パルス列の各パルスの前記パワーを設定し、
前記記録パルス列生成部は、前記第1情報層の記録膜に、最も短い記録マークを形成する場合、前記クーリングパルスを含まない記録パルス列を生成する請求項1又は2記載の光学的情報記録装置。 - 前記N層の情報層は、3層の情報層のみを含む請求項1~3のいずれかに記載の光学的情報記録装置。
- 前記光学的情報記録媒体は、各情報層の前記ライトパルスのパワーを表すピークパワー及び各情報層の前記ボトムパルスのパワーを表すボトムパワーを記録し、
前記光学的情報記録媒体から各情報層の前記ピークパワー及び各情報層の前記ボトムパワーを読み出す読出部をさらに備え、
前記パワー設定部は、前記読出部によって読み出された各情報層の前記ピークパワー及び各情報層の前記ボトムパワーに基づいて、前記記録パルス列の各パルスの前記パワーを設定する請求項1~4のいずれかに記載の光学的情報記録装置。 - 各情報層の前記ライトパルスのパワーを表すピークパワー及び各情報層の前記ボトムパルスのパワーを表すボトムパワーを予め記憶する記憶部をさらに備え、
前記パワー設定部は、前記記憶部に記憶されている各情報層の前記ピークパワー及び各情報層の前記ボトムパワーに基づいて、前記記録パルス列の各パルスの前記パワーを設定する請求項1~4のいずれかに記載の光学的情報記録装置。 - N層(Nは2以上の整数)の情報層を備える光学的情報記録媒体に情報を記録する光学的情報記録方法であって、
前記N層の情報層のそれぞれは、レーザビームの集光による局所的な温度変化によって物理的な状態の変化を生じる記録膜を有し、
前記記録膜に記録マークを形成するための記録パルス列を生成する記録パルス列生成ステップと、
前記記録パルス列の各パルスのパワーを設定するパワー設定ステップと、
前記記録パルス列生成ステップにおいて生成された前記記録パルス列に応じた前記レーザビームを、前記パワー設定ステップにおいて設定されたパワーで出射するように光源を駆動する駆動ステップと、
前記レーザビームを前記光源から出射するレーザビーム出射ステップとを含み、
前記記録パルス列は、最も高いパワーを有する少なくとも1つのライトパルスと、前記ライトパルスが複数ある場合に複数のライトパルスの間に形成されるボトムパルスと、最後尾のライトパルスに後続して形成されるクーリングパルスとを含み、
前記ライトパルスのパワーをピークパワーとし、前記ボトムパルスのパワーをボトムパワーとしたとき、
前記パワー設定ステップは、前記光学的情報記録媒体の光入射面に最も近い第N情報層のピークパワーPwN、前記第N情報層のボトムパワーPbN、第M情報層(MはN>M≧1の整数)のピークパワーPwM及び前記第M情報層のボトムパワーPbMが下記の式を満たすように、前記記録パルス列の各パルスの前記パワーを設定する光学的情報記録方法。
PbN/PwN>PbM/PwM - N層(Nは2以上の整数)の情報層を備え、
前記N層の情報層のそれぞれは、レーザビームの集光による局所的な温度変化によって物理的な状態の変化を生じる記録膜を有し、
記録パルス列に応じたレーザビームが照射されることで前記記録膜に記録マークが形成され、
前記光学的情報記録媒体の光入射面に最も近い第N情報層が有する記録膜の厚さDNは、第M情報層(MはN>M≧1の整数)が有する記録膜の厚さDMより小さく、
前記第N情報層からの反射率RNは、前記第M情報層からの反射率RMの2倍よりも小さく、
前記記録パルス列は、最も高いパワーを有する少なくとも1つのライトパルスと、前記ライトパルスが複数ある場合に複数のライトパルスの間に形成されるボトムパルスと、最後尾のライトパルスに後続して形成されるクーリングパルスとを含み、
前記N層の情報層のうちの少なくとも1つの情報層は、各情報層の前記ライトパルスのパワーを表すピークパワー及び各情報層の前記ボトムパルスのパワーを表すボトムパワーを記録し、
前記第N情報層のピークパワーPwN、前記第N情報層のボトムパワーPbN、前記第M情報層のピークパワーPwM及び前記第M情報層のボトムパワーPbMは下記の式を満たす光学的情報記録媒体。
PbN/PwN>PbM/PwM
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CN1248201C (zh) | 2001-10-02 | 2006-03-29 | 松下电器产业株式会社 | 光学信息记录方法以及再生装置 |
JP2003242644A (ja) * | 2002-02-14 | 2003-08-29 | Tdk Corp | 光記録媒体への情報記録方法、情報記録装置及び光記録媒体 |
JP2003242643A (ja) * | 2002-02-14 | 2003-08-29 | Tdk Corp | 光記録媒体への情報記録方法、情報記録装置及び光記録媒体 |
JP2006209935A (ja) * | 2004-12-28 | 2006-08-10 | Victor Co Of Japan Ltd | 光記録方法、光記録装置及び光記録媒体 |
JP2007080463A (ja) * | 2005-09-16 | 2007-03-29 | Ricoh Co Ltd | 多層相変化型光記録媒体とその記録方法 |
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JP2006031936A (ja) * | 2001-10-02 | 2006-02-02 | Matsushita Electric Ind Co Ltd | 光学的情報記録方法 |
JP2004171642A (ja) * | 2002-11-19 | 2004-06-17 | Tdk Corp | 光記録媒体、光記録方法及び光記録装置 |
WO2010061557A1 (ja) * | 2008-11-26 | 2010-06-03 | パナソニック株式会社 | 情報記録媒体、記録装置、再生装置および再生方法 |
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WO2020202765A1 (ja) * | 2019-03-29 | 2020-10-08 | パナソニックIpマネジメント株式会社 | 記録状態評価方法、記録補償方法及び情報記録再生装置 |
US11475918B2 (en) | 2019-03-29 | 2022-10-18 | Panasonic Intellectual Property Management Co., Ltd. | Recording state evaluation method, recording compensation method, and information recording/playback device |
JP7442100B2 (ja) | 2019-03-29 | 2024-03-04 | パナソニックIpマネジメント株式会社 | 記録状態評価方法、記録補償方法及び情報記録再生装置 |
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CN103189918A (zh) | 2013-07-03 |
US20130215731A1 (en) | 2013-08-22 |
JPWO2012124313A1 (ja) | 2014-07-17 |
US8824263B2 (en) | 2014-09-02 |
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