JP2005243210A - Optical recording method, optical recording apparatus, and optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording method by which successful recording property is acquired even if recording rate is accelerated, and good recording property is maintained even if over-writing is performed one or more times. <P>SOLUTION: The optimal erasure power satisfying the following formula is used for optical recording as the erasure power; formula (1): 1.000<(R1/R0)<1.030, wherein, a reflectivity of non-recorded part is taken as R0, when a non-recorded part in which information on a recording area of a recording layer 3 of an optical recording medium A has never been recorded, is irradiated with reproducing light; and a reflectivity of non-recorded part is taken as R1, when the non-recorded part is irradiated with the reproducing light after the non-recorded part is irradiated once with the light having erasure power. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical recording method, an optical recording apparatus, and an optical recording medium for recording, erasing, and reproducing information by irradiation with light (for example, laser light). In particular, the present invention relates to an optical recording method, an optical recording apparatus, and an optical recording method capable of obtaining good overwrite characteristics when optical recording is performed at a high linear velocity (high double speed) in a rewritable phase change recording medium such as an optical disk and an optical card An optical recording medium is provided.

  The phase change type optical recording medium is, for example, a recent CD-RW, DVD-RW, or DVD-RAM, and is a medium that can rewrite information. Among them, DVD-RW and DVD-RAM are mainly used for recording and rewriting of a large amount of information such as video information. Phase change optical recording media are required to have excellent overwrite characteristics in addition to excellent recording characteristics.

The configuration and recording method of a conventional rewritable phase change type optical recording medium are as follows.
A phase-change optical recording medium has at least a dielectric layer, a recording layer, a dielectric layer, and a reflective layer sequentially on a substrate whose bottom surface is irradiated with laser light having each power for recording / reproducing or erasing. It is a laminated structure. In the phase-change optical recording medium configured as described above, an amorphous recording mark is obtained by applying (irradiating) a recording pulse to the recording layer with a laser beam having a recording power during recording to melt and quench the recording layer. Form. Since the reflectance of the recording mark is lower than that of the crystalline recording layer, the recording mark can be optically read as recorded information. When erasing this recording mark, the recording layer is irradiated with a laser beam having a power smaller than the recording power (erasing power) to bring the recording layer to a temperature not lower than the crystallization temperature and not higher than the melting point, thereby changing from the amorphous state to the crystalline state. The mark is erased and overwriting is possible.

In Japanese Patent Application Laid-Open Nos. 2002-237089 and 2003-200355, for the purpose of excellent jitter characteristics and overwriting characteristics in high-speed recording, light in which the reflectance of an unrecorded part is made lower than the reflectance of a recorded part. Recording methods and optical recording media have been proposed. However, the present inventors have found that sufficient overwriting characteristics (particularly, the characteristics of the first overwriting times) cannot be obtained at a high linear velocity (for example, DVD 4 × speed or more) only with the proposed optical recording method and optical recording medium. It became clear by examination.
JP 2002-237089 A JP2003-200355A

  As described above, the conventional optical recording method in which the reflectance of the unrecorded portion is lower than the reflectance after recording and erasing, or the conventional light in which the reflectance of the unrecorded portion after initialization is lowered in advance. The recording medium has insufficient jitter characteristics after overwriting at high speed recording, and it has been difficult to ensure sufficient overwriting characteristics.

  Therefore, the present invention was devised to solve the above-described problem, and good recording can be achieved even when the recording speed is increased (for example, high linear velocity recording at a DVD quadruple speed (linear velocity: 14 m / s) or more). It is an object of the present invention to provide an optical recording method, an optical recording apparatus, and an optical recording medium capable of obtaining characteristics and maintaining good overwrite recording characteristics at one or more times.

In order to solve the above-described problems, the present invention provides the following optical recording methods (a) to (j), an optical recording apparatus, and an optical recording medium.
(A) In an optical recording method for recording recording information on the recording layer (3) of the phase change optical recording medium (A), a modulation step for modulating the recording information to generate modulation data, and based on the modulation data A mark length generating step for generating a desired mark length, and a recording power (Pw) higher than the erasing power and a bottom power (Pb) lower than the erasing power based on the mark length, rising from the erasing power (Pe). ) And a erasing pulse (Tcl) that rises from the bottom power to the erasing power, and generates a recording light pattern for the recording layer. Recording a recording mark indicating the recording information by irradiating the recording layer according to the recording pulse pattern, and the recording step is performed on the recording layer. R0 is the reflectance of the non-recorded portion when the recording light on which the recorded information has never been recorded is irradiated, and the reproduction is performed after irradiating the unrecorded portion with light having the erasing power once. When the reflectance of the unrecorded portion when irradiated with light is R1,
As the erasing power, the following formula (1): 1.000 <(R1 / R0) <1.030 (1)
An optical recording method using an optimum erasing power satisfying
(B) The recording power is Pw, the erasing power is Pe, and a power ratio ε (ε = Pe / Pw) of the erasing power Pe to the recording power Pw is
0.20 ≦ ε ≦ 0.40
The optical recording method according to (a), wherein
(C) In an optical recording apparatus that records recording information on the recording layer (3) of the phase change optical recording medium (A), an encoder (42) that modulates the recording information to generate modulation data; and the modulation data A mark length generation unit (41) that generates a desired mark length based on the above, a recording power (Pw) that rises from an erasing power (Pe) based on the mark length, and is smaller than the erasing power A recording pulse pattern including a recording pulse (Ttop, Tmp) formed between the bottom power (Pb) and an erasing pulse (Tcl) rising from the bottom power to the erasing power, and generating the recording layer And a recording section (400) for recording a recording mark indicating the recording information by irradiating recording light according to the recording pulse pattern, the recording section comprising the recording layer R0 is the reflectance of the unrecorded portion when the unrecorded portion where the recorded information has not been recorded is irradiated, and the reproduction is performed after the unrecorded portion is irradiated once with the light having the erasing power. When the reflectance of the unrecorded portion when irradiated with light is R1,
As the erasing power, the following formula (1): 1.000 <(R1 / R0) <1.030 (1)
An optical recording apparatus using an optimum erasing power satisfying
(D) A storage unit (451) for storing identification information indicating the optimum erasing power is provided, and the recording unit determines the optimum erasing power based on the identification information stored in the storage unit. The optical recording apparatus according to (c).
(E) a reading unit (34) for reading identification information indicating the optimum erasing power written in a predetermined area of the optical recording medium, wherein the recording unit is configured to perform the identification based on the identification information read by the reading unit. The optical recording apparatus according to (c), wherein an optimum erasing power is determined.
(F) A reflectance detector that obtains R0 and a plurality of R1s corresponding to a plurality of the erasing powers, and selects a combination that satisfies Formula (1) from a combination of R0 and the plurality of R1s. 46), and the recording unit determines the optimum erasing power based on the combination selected by the reflectance detection unit.
(G) The recording power is Pw, the erasing power is Pe, and the power ratio ε (ε = Pe / Pw) of the erasing power Pe to the recording power Pw is
0.20 ≦ ε ≦ 0.40
The optical recording apparatus according to any one of (c) to (f).
(H) The phase change type optical recording medium (A) is formed between the recording power (Pw) that rises from the erasing power (Pe) and is larger than the erasing power and the bottom power (Pb) that is smaller than the erasing power. A recording mark indicating recording information is recorded by irradiating recording light according to a recording pulse pattern consisting of a recording pulse (Ttop, Tmp) and an erasing pulse (Tcl) rising from the bottom power to the erasing power. A recording layer (3), wherein the recording layer has a reflectance of R0 when the reproducing light is irradiated to an unrecorded portion where information in the recording layer has never been recorded, and the erasing power is The non-recorded portion is irradiated with the reproduction light after irradiating the unrecorded portion once with the reproduction light, and the unrecorded portion is irradiated with the light having the erasing power 10 times. When the reflectance of the unrecorded portion when irradiated with the reproduction light after R10 is R10,
As the erasing power, the following formulas (1) and (2): 1.000 <(R1 / R0) <1.030 (1)
0.030 <(R10 / R0)-(R1 / R0) <0.150 (2)
An optical recording medium that is initialized by an initialization laser so that
(I) When the recording power is Pw, the erasing power is Pe, and the power ratio ε (ε = Pe / Pw) of the erasing power Pe to the recording power Pw,
0.20 ≦ ε ≦ 0.40
(H) The optical recording medium according to (h), wherein information for the above is written.
(J) In the recording layer, a value obtained by dividing the power of the initialization laser by the irradiation area of the initialization laser and further dividing the power by the scanning speed of the initialization laser is referred to as initialization laser power density Di. When
1.20 ≦ Di ≦ 1.55
The optical recording medium according to (h) or (i), wherein the optical recording medium is initialized under the following conditions:

  Even if the recording speed is increased, good recording characteristics can be obtained, and even if overwriting is performed once or a plurality of times, the recording characteristics can be maintained well.

FIG. 1 is a diagram showing a manufacturing / initializing process performed in a manufacturing facility 300 or a manufacturing facility 300 for manufacturing a phase change optical recording medium. A phase change optical recording medium is manufactured in the manufacturing apparatus 100 (manufacturing process), and the phase change optical recording medium is initialized in the initialization apparatus 200 (initialization process). The phase change type optical recording medium that has undergone the initialization process is shipped as an optical recording medium A.
Examples of the phase change optical recording medium include media capable of repeatedly overwriting information, such as a phase change optical disk such as a DVD-RW, an optical card, and the like. In the following description, a phase-change optical disk (optical recording medium A) is used as an embodiment of a phase-change optical recording medium. However, a phase-change optical recording medium having a similar configuration such as an optical card other than this is used. Needless to say, the present invention can also be applied.

<< Configuration of optical recording medium >>
FIG. 2 is an enlarged cross-sectional view showing an optical recording medium A that is an embodiment of the present invention. The optical recording medium A has, as its basic structure, a first protective layer 2, a recording layer 3, and a second protective layer on a substrate 1 having an incident surface 1a on which a recording / reproducing or erasing laser beam is incident. 4, the reflective layer 5, and the 3rd protective layer 6 are laminated | stacked one by one.

  As a material of the substrate 1, various transparent synthetic resins, transparent glass, and the like can be used. In order to avoid the influence of dust adhesion and scratches on the substrate 1, the transparent substrate 1 is used, and information is recorded on the recording layer 3 from the incident surface 1 a side of the substrate 1 with the condensed laser light. Examples of the material of the substrate 1 include glass, polycarbonate, polymethyl methacrylate, polyolefin resin, epoxy resin, and polyimide resin. In particular, a polycarbonate resin is preferable because of its small optical birefringence and hygroscopicity and easy molding.

  Although the thickness of the substrate 1 is not particularly limited, it is preferably 0.01 mm to 0.6 mm in consideration of compatibility with the DVD, and most preferably 0.6 mm (the total thickness of the DVD is 1.2 mm). ). This is because if the thickness of the substrate 1 is less than 0.01 mm, even when recording is performed with a laser beam converged from the incident surface 1a side of the substrate 1, it is easily affected by dust. Moreover, if there is no restriction | limiting in the total thickness of an optical recording medium, it should just be in the range of 0.01 mm-5 mm practically. If the thickness is 5 mm or more, it is difficult to increase the numerical aperture of the objective lens, and the spot size of the irradiation laser light is increased, so that it is difficult to increase the recording density.

  The substrate 1 may be flexible or rigid. The flexible substrate 1 is used as an optical recording medium having a tape shape, a sheet shape, or a card shape. The rigid substrate 1 is used as a card-shaped or disk-shaped optical recording medium.

  The first protective layer 2 and the second protective layer 4 protect the substrate 1 and the recording layer 3 from heat, for example, by preventing the substrate 1 and the recording layer 3 from being deformed by heat during recording to deteriorate the recording characteristics. There is an effect, and an effect of improving the signal contrast at the time of reproduction by an optical interference effect.

Each of the first protective layer 2 and the second protective layer 4 is preferably transparent to the recording / reproducing or erasing laser beam and has a refractive index n in the range of 1.9 ≦ n ≦ 2.3. . Further, the materials of the first protective layer 2 and the second protective layer 4 are oxides such as SiO ₂ , SiO, ZnO, TiO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , ZrO ₂ , MgO from the viewpoint of thermal characteristics. ZnS, In ₂ S ₃ , sulfides such as TaS _4, and carbides such as SiC, TaC, WC, and TiC, and mixtures thereof are preferable. Among these, a mixed film of ZnS and SiO ₂ is particularly preferable because deterioration in recording sensitivity, C / N, erasure rate, etc. hardly occurs even when recording and erasing are repeated.
Moreover, the 1st protective layer 2 and the 2nd protective layer 4 do not need to be the same material and composition, and may be comprised from a different material.

  The thickness of the first protective layer 2 is in the range of approximately 5 nm to 500 nm. Furthermore, the thickness of the first protective layer 2 is preferably in the range of 20 nm to 300 nm because it is difficult to peel from the substrate 1 and the recording layer 3 and defects such as cracks are difficult to occur. If it is thinner than 20 nm, it is difficult to ensure the optical characteristics of the disk, and if it is thicker than 300 nm, the productivity is poor. In addition, More preferably, it is the range of 30 nm-80 nm.

  The thickness of the second protective layer 4 is preferably in the range of 5 nm to 40 nm because recording characteristics such as C / N and erasure rate are good and rewriting can be stably performed many times. If the thickness is less than 5 nm, it becomes difficult to secure the heat of the recording layer 3, so that the optimum recording power increases. If the thickness is more than 40 nm, the overwrite characteristic is deteriorated. More preferably, it is the range of 8 nm-20 nm.

  The recording layer 3 includes an Ag—In—Sb—Te alloy, a Ge—In—Sb—Te alloy, or a Ge—In—Sb—Te alloy with at least one of Ag, Si, Al, Ti, Bi, and Ga. It is a kind of alloy layer. The layer thickness of the recording layer 3 is preferably 10 nm to 25 nm. If the layer thickness is less than 10 nm, the crystallization speed decreases and the high-speed recording characteristics deteriorate, and if it is more than 25 nm, a large laser power is required for recording.

An interface layer in contact with one side or both sides of the recording layer 3 may be provided. It is important that the interface layer material does not contain sulfur. Use of a material containing sulfur as the interface layer is not preferable because sulfur contained in the interface layer may diffuse into the recording layer 3 due to repeated overwriting and the recording characteristics may deteriorate. Further, it is not preferable from the viewpoint that the erasing characteristics are not excellent.
As the material of the interface layer, a material containing at least one of nitride, oxide, and carbide is preferable. Specifically, germanium nitride, silicon nitride, aluminum nitride, aluminum oxide, zirconium oxide, chromium oxide, silicon carbide, A material containing at least one kind of carbon is preferable. These materials may contain oxygen, nitrogen, hydrogen, or the like. The aforementioned nitrides, oxides, and carbides do not have to have a stoichiometric composition, and nitrogen, oxygen, and carbon may be excessive or insufficient. This may make it difficult for the interface layer to peel off and improve the properties of the interface layer, such as improved storage durability.

Examples of the material of the reflective layer 5 include metals such as Al, Au, and Ag having light reflectivity, alloys containing these metals as a main component, and an additive element including one or more kinds of metals or semiconductors, and these metals. Examples thereof include a mixture of metal nitrides such as Al and Si, metal oxides, metal chalcogenides, and the like.
Among these, metals such as Al, Au, and Ag, and alloys containing these metals as main components are preferable because they have high light reflectivity and high thermal conductivity. Examples of alloys include a mixture of Al and at least one element such as Si, Mg, Cu, Pd, Ti, Cr, Hf, Ta, Nb, Mn, and Zr, or Au or Ag with Cr, Ag. In general, a mixture of at least one element such as Cu, Pd, Pt, Ni, Nd, In, and Ca is used. However, when high linear velocity recording is considered, a metal or alloy mainly composed of Ag having a high thermal conductivity is preferable from the viewpoint of recording characteristics.
However, when pure silver or a silver alloy is used for the reflective layer 5, it is preferable to use a material that does not contain S for the layer in contact with the reflective layer 5 in order to suppress the formation of an AgS compound.

  The thickness of the reflective layer 5 varies depending on the thermal conductivity of the material forming the reflective layer 5, but is preferably 50 nm to 300 nm. If the thickness of the reflective layer 5 is 50 nm or more, the reflective layer 5 does not change optically and does not affect the reflectance value. However, as the thickness of the reflective layer 5 increases, the effect on the cooling rate increases. . In addition, it takes time in manufacturing to form a thickness exceeding 300 nm. Therefore, the layer thickness of the reflective layer 5 is controlled in the optimum range as much as possible by using a material having high thermal conductivity.

Here, when a compound of ZnS and SiO ₂ is used for the second protective layer 4 and Ag or an Ag alloy is used for the reflective layer 5, a diffusion prevention layer (not shown) is provided between the second protective layer 4 and the reflective layer 5. ) Is preferably inserted. This is to suppress a decrease in reflectance due to an AgS compound generated by a chemical reaction between S in the second protective layer 4 and Ag in the reflective layer 5.
As the material for the diffusion prevention layer, it is important that the material does not contain sulfur as in the interface layer described above, and the specific material is the same as the material for the interface layer.

≪Method for manufacturing optical recording medium≫
Next, a method for manufacturing an optical recording medium in the manufacturing apparatus 100 will be described.
As a method for laminating the first protective layer 2, the recording layer 3, the second protective layer 4, the reflective layer 5, etc. on the substrate 1, a known thin film forming method in a vacuum can be mentioned. For example, vacuum deposition method (resistance heating type or electron beam type), ion plating method, sputtering method (direct current or alternating current sputtering, reactive sputtering), especially because the composition and layer thickness can be easily controlled, A sputtering method is preferred.

  In addition, it is preferable to use a batch method in which a plurality of substrates 1 are simultaneously formed in a vacuum chamber or a single wafer type film forming apparatus that processes the substrates 1 one by one. The thickness of the first protective layer 2, recording layer 3, second protective layer 4, reflective layer 5, etc. to be formed is controlled by controlling the power and time for turning on the sputtering power source or by using a quartz vibration type film thickness meter. It can be easily done by monitoring.

  Further, the formation of the first protective layer 2, the recording layer 3, the second protective layer 4, the reflective layer 5 and the like may be performed in a state where the substrate 1 is fixed, or in a state where it is moved or rotated. Since the in-plane uniformity of the layer thickness is excellent, it is preferable to rotate the substrate 1, and it is more preferable to combine revolution. When the substrate 1 is cooled as necessary, the amount of warpage of the substrate 1 can be reduced.

In addition, after forming the reflective layer 5 and the like within a range not significantly impairing the effects of the present invention, a dielectric layer using ZnS, SiO ₂ or the like, or an ultraviolet curable resin is used for preventing deformation of each layer already formed. The resin protective layer may be provided as the third protective layer 6 as necessary.
Thereafter, another substrate 1 on which each layer is similarly formed may be prepared, and the two substrates 1 may be bonded with an adhesive or the like to form a double-sided optical recording medium.

Next, an optical recording medium initialization method in the initialization apparatus 200 will be described. As described above, in this embodiment, the optical recording medium A is shipped after passing through the initialization process of the initialization apparatus 200. The initialization is to irradiate the recording layer 3 with light such as a laser beam or a xenon flash lamp and heat it to crystallize the constituent material of the recording layer 3. Since there is little reproduction noise, initialization with a laser beam is preferable.
In the present embodiment, there is one feature in the initialization conditions (scanning linear velocity and power of the laser beam for initialization) for obtaining the optical recording medium A. This will be described later.

  FIG. 3 shows a plan view of the optical recording medium A. The optical recording medium A has a center hole 51 and a clamp area 52 on the outer periphery thereof. An information area (lead-in area) 53 is concentrically provided on the outer periphery of the clamp area 52, and the outer peripheral area is a recording area 54 for recording actual data such as video information and audio information. . Here, the lead-in area 53 may be in a ROM state or a RAM state. In addition, there is a method in which high-frequency wobbles or pits are formed in a laser guide groove for obtaining a tracking signal and stored as reproduction-only recording information.

≪Recording method of optical recording medium≫
FIG. 4 shows a recording pulse pattern used when information is recorded on the optical recording medium A. Based on the recording pulse pattern, the laser beam is modulated with a laser intensity of three values (recording power Pw, erasing power Pe, and bottom power Pb), and the number of pulses is increased / decreased according to the mark length of the recording signal. A long recording mark is formed on the recording layer 3. As for the laser intensity, the recording power Pw is the largest, and the erasing power Pe and the bottom power Pb are the smallest in this order.
As shown in FIG. 4, the recording pulse pattern is a first pulse Ttop that rises from the erasing power Pe and first applies laser light to the recording layer 3 at the recording power Pw, and a pulse that follows the first pulse Ttop. And a multi-pulse Tmp that alternately applies the bottom power Pb and an erasing pulse Tcl that rises from the bottom power Pb of the laser beam and is positioned at the end of applying the erasing power Pe. The leading pulse Ttop and the multipulse Tmp are recording pulses for forming recording marks on the recording layer 3. In some cases, the recording pulse is formed only by the top pulse Ttop without the multi-pulse Tmp.

For example, in DVD-RW, there are ten mark lengths of 3T, 4T, 5T, 6T, 7T, 8T, 9T, 10T, 11T, and 14T. When the mark length is nT, the number of multipulses Tmp is generally (n-1) or (n-2). FIG. 4 shows the case of (n-2). Here, T is a unit clock. In DVD-RW, 1T = 38.2 ns at a DVD 1 × speed (recording linear velocity: 3.5 m / s), and 4 × DVD speed (recording linear velocity: 14.0 m / s). ) 1T = 9.6 ns.
Further, since the unit clock T is shortened to the order of several ns with high-speed recording in recent years, the recording pulse pattern based on 2T as shown in FIG. 5 is considered in consideration of the rise / fall response limit of the laser pulse. May be used. In FIG. 5, a recording pulse pattern for forming a recording mark having a mark length of 3T, a recording pulse B of 11T, and a recording pulse C of 14T is shown.

≪Optical recording device≫
FIG. 6 shows an optical recording apparatus according to an embodiment of the present invention for irradiating an optical recording medium A with laser light having a desired recording pulse pattern.

First, the spindle motor 31 rotates the optical recording medium A. The rotation control unit 32 controls the number of rotations of the spindle motor 31 to be a recording linear velocity corresponding to the target recording velocity. Further, a semiconductor laser (LD) 33 used for recording / reproducing or erasing of the optical recording medium A, an objective lens (not shown) for condensing and irradiating the laser light of the LD 33, and, for example, a quadrant light receiving element (not shown) are provided. The optical head 34 is provided so as to be movable in the radial direction of the optical recording medium A.
Note that a light source for recording used in the optical recording apparatus of the present embodiment is preferably a high-intensity light source such as laser light or strobe light. Among these, semiconductor laser light is preferable because the light source can be downsized, power consumption is small, and modulation is easy.

The four-divided light receiving element of the optical head 34 receives the reflected light of the laser light emitted from the LD 33 onto the optical recording medium A. The quadrant light receiving element generates a push-pull signal based on the received light and outputs the push-pull signal to the wobble detection unit 36. The 4-split light receiving element outputs a focus error signal and a tracking error signal to the drive controller 44 based on the received light. Further, a reproduction signal that is a combined signal of the four-divided light receiving element is output to the reflectance detection unit 46.
The drive controller 44 controls the actuator control unit 35 based on the supplied focus error signal and tracking error signal. The actuator controller 35 controls the focusing and tracking of the optical head 34 on the optical recording medium A.
The reflectance detector 46 detects the reflectance based on the supplied reproduction signal and outputs the detection result to the system controller 45. When the identification information indicating the optimum erasing power Pe is not stored in the memory 451, the system controller 45 controls the Pe drive current source 431e based on the reflectance as will be described later.

The wobble detection unit 36 includes a programmable bandpass filter (BPF) 361 and outputs the detected wobble signal to the address demodulation circuit 37. The address demodulation circuit 37 demodulates and outputs the address from the detected wobble signal. The recording clock generation unit 38 to which the demodulated address is input has a PLL synthesizer circuit 381, generates a recording channel clock, and outputs it to the recording pulse generation unit 39 and the pulse number control unit 40.
The recording clock generator 38 is controlled by the drive controller 44. The drive controller 44 also controls the rotation control unit 32, actuator control unit 35, wobble detection unit 36, address demodulation circuit 37, and system controller 45.

The drive controller 44 outputs the wobble signal supplied from the wobble detection unit 36 to the recording clock generation unit 38. The address information supplied from the address demodulation circuit 37 is output to the system controller 45.
The system controller 45 includes a memory 451 and controls the EFM + encoder 42, the mark length counter 41, the pulse number control unit 40, and the LD driver unit 43. The EFM + encoder 42 modulates the input recording information by 8-16 to obtain modulated data, and outputs the modulated data to the recording pulse generator 39 and the mark length counter 41. The mark length counter 41 operates as a mark length generation unit that counts a predetermined mark length based on the modulation data, and outputs the count value to the recording pulse generation unit 39 and the pulse number control unit 40. The pulse number control unit 40 controls the recording pulse generation unit 39 so that the recording pulse becomes a predetermined pulse based on the supplied count value and the recording channel clock.

The recording pulse generator 39 includes a head pulse control signal generator 39t, a multi-pulse control signal generator 39m, and an erasing pulse control signal generator 39c. The start pulse control signal generator 39t generates a start pulse control signal, the multi-pulse control signal generator 39m generates a multi-pulse control signal, and the erase pulse control signal generator 39c generates an erase pulse control signal. The respective control signals are supplied to the LD driver unit 43, and the switching unit 431 receives the control signal supplied with the drive current source 431w of the recording power Pw, the drive current source 431e of the erasing power Pe, and the drive current source 431b of the bottom power Pb. A recording pulse pattern is generated by switching based on this.
The Pw drive current source 431w, Pe drive current source 431e, and Pb drive current source 431b supply current to the optical head 34 based on the recording power Pw, the erasing power Pe, and the bottom power Pb stored in the memory 451 of the system controller 45. Supply. These three values are optimum values for improving the recording characteristics of the optical recording medium A. Identification information indicating the optimum values is stored in the memory 451 in advance, stored by updating, or reflected. It can also be obtained and stored using the rate detector 46. The memory 451 is, for example, a ROM (Read Only Memory) or a recordable RAM (Random Access Memory).
The generated recording pulse pattern is input to the optical head 34. The optical head 34 records the recording information on the optical recording medium A by controlling the LD 33 to output an LD emission waveform having a desired recording pulse pattern and a power ratio ε (Pw / Pe).
The recording pulse generator 39, the LD driver 43, and the optical head 34 rise from the erasing power Pe based on the mark length generated by the mark length counter 41, and the recording power Pw and the erasing power Pe larger than the erasing power Pe. A recording pulse pattern including a recording pulse formed between a lower bottom power Pb and an erasing pulse rising from the bottom power Pb to the erasing power Pe is generated, and recording light is emitted from the LD 33 to the recording layer 3. It operates as a recording unit 400 that records a recording mark indicating recording information by irradiation according to a recording pulse pattern.

≪Study of optimum erasing power≫
The inventor presumes that the erasing power Pe may affect the recording and overwriting characteristics of the optical recording medium, and in the following Examples A-1 to A-3 and Comparative Examples A-4 to A-6, Based on this, it has been found that the estimation is correct and has the optimum erasing power with the best recording and overwriting characteristics.
In each of the following Examples and Comparative Examples, recording is performed using an optical disk drive tester (DDU1000) manufactured by Pulstec Corporation equipped with a laser diode having a wavelength of 658 nm and an optical lens having NA = 0.60 (1 beam / overwrite). And played.
The recording linear velocity was 14 m / s (equivalent to DVD standard quadruple speed), and the recording / reproduction evaluation was performed using an 8-16 (EFM +) modulation random pattern. The unit clock T is 9.6 ns (DVD 4 × speed), and the bit length is 0.267 μm / bit. Recording with the same density as DVD-ROM is performed, and the capacity corresponds to 4.7 Gbytes. The recording was overwritten 10 times including the adjacent track, and then sliced at the center of the amplitude of the reproduced signal, and clock-to-data jitter was measured. Note that the laser power Pr of the reproduction light was fixed at 0.7 mW.
The recording strategy used was a divided pulse sequence according to the DVD-RW Version 1.1 standard as shown in FIG.

(Example A-1)
Each layer described later was formed on a polycarbonate resin substrate 1 having a diameter of 120 mm and a plate thickness of 0.6 mm. The substrate 1 has an empty groove with a track pitch of 0.74 μm. The groove depth was 25 nm, and the ratio of the groove width to the land width was approximately 40:60.

First, after evacuating the inside of the vacuum vessel to 3 × 10 ⁻⁴ Pa, a high frequency magnetron sputtering method is used on the substrate 1 by using a ZnS target to which 20 mol% of SiO ₂ is added in an Ar gas atmosphere of 2 × 10 ⁻¹ Pa. A first protective layer 2 having a layer thickness of 70 nm was formed.
Subsequently, the recording layer 3 is a Ge—In—Sb—Te four-element single alloy target with a layer thickness of 16 nm, and the second protective layer 4 is made of the same material as the first protective layer 2 with a layer thickness of 16 nm. Were stacked sequentially with an Ag—Pd—Cu target with a layer thickness of 120 nm.
After the substrate 1 is taken out from the vacuum vessel, an acrylic ultraviolet curable resin (SK5110 manufactured by Sony Chemical) is spin coated on the reflective layer 5 and cured by ultraviolet irradiation to form a third protective layer 6 having a thickness of 3 μm. Thus, an optical recording medium A shown in FIG. 2 was obtained.

  Initialization of the recording layer 3 is performed using an initialization apparatus 200 (POP120 manufactured by Hitachi Computer Equipment Co., Ltd.) using a laser having a radial laser beam width of 250 μm and a scanning laser beam width of 1.0 μm. s, laser power 1600 mW, feed pitch 220 μm.

  Next, the reflectance of the unrecorded portion when the unrecorded portion where no information has been recorded in the recording area 54 of the optical recording medium A is irradiated with reproduction light (0.7 mW) having the laser power Pr from the LD 33. R0 and R1 were determined by setting R1 as the reflectance of the unrecorded portion when the laser beam for reproduction was irradiated from the LD 33 after the laser beam having the erasing power Pe was irradiated once to this unrecorded portion. .

Subsequently, recording was performed on the optical recording medium A from the substrate 1 side to a groove portion which is a guide groove of the recording layer 3. The groove has a convex shape when viewed from the incident direction of the recording / reproducing or erasing laser beam.
The recording pulse pattern which is a recording condition was Ttop = 0.6 [T], Tmp = 0.5 [T], and Tcl = 0.0 [T] at a linear velocity of 14 m / s (DVD 4 × speed). As the laser intensity of the laser beam, three values of recording power Pw = 17.0 [mW], erasing power Pe = 4.6 [mW], and bottom power Pb = 0.5 [mW] were used.

R0 of the optical recording medium A used in Example A-1 was 17.4, and R1 after one irradiation with a laser beam with an erasing power Pe = 4.6 [mW] was 17.7 ( R1 / R0 = 1.017). The values measured in Example A-1 are collectively shown in Table 1 (Example A-1).
As shown in Table 1, the initial characteristics and overwrite recording characteristics are 6.5% for initial recording (DOW0), 8.0% for overwriting once (DOW1), and 7 for overwriting 9 times (DOW9). .5%. Although not described, the jitter after overwriting (DOW10000) of about 10,000 times was 8.5%, and the characteristics were always stable even after overwriting, and the recording characteristics were good.
The overwrite described here is one-beam overwrite, which means that a previously formed recording mark is erased and a new recording mark is formed by one laser scanning. DOW0 (Direct Over Write) is the first recording to form a recording mark on the unrecorded portion of the initialized optical recording medium A, and DOW1 is the first overwriting to form a recording mark there. Also, the jitter should have a value of 10% or less, which is considered to have little adverse effect on the error rate, and a jitter of 10% or less can be stably obtained from DOW0 to DOW10000 (from the initial recording to 10,000 overwrites). Is defined as a good DOW jitter characteristic.

(Example A-2)
Using the same optical recording medium A as in Example A-1, recording was evaluated under the same conditions as in Example A-1, except that the erasing power Pe was changed to 3.8 [mW]. R0 was 17.4, and R1 after irradiation with a laser beam with an erasing power Pe = 3.8 [mW] once was 17.5 (R1 / R0 = 1.006).
As shown in Table 1, the initial characteristics and overwrite recording characteristics were DOW0 jitter of 6.8%, DOW1 jitter of 8.6%, and DOW9 jitter of 7.9%. Although not described further, the DOW10000 jitter was 9.2%, the characteristics were always stable even when overwritten, and the recording characteristics were good as in Example A-1.

(Example A-3)
Using the same optical recording medium A as in Example A-1, recording was evaluated under the same conditions as in Example A-1, except that the erasing power Pe was changed to 5.6 [mW]. R0 was 17.4, and R1 after irradiation with a laser beam with an erasing power Pe = 5.6 [mW] once was 17.9 (R1 / R0 = 1.029).
As shown in Table 1, the initial characteristics and the overwrite recording characteristics were 7.0% DOW0 jitter, 8.7% DOW1 jitter, and 8.4% DOW9 jitter. Although not described further, the DOW10000 jitter was 9.5%, the characteristics were always stable even when overwritten, and the recording characteristics were good as in Example A-1.

(Comparative Example A-4)
Using the same optical recording medium A as in Example A-1, recording was evaluated under the same conditions as in Example A-1, except that the erasing power Pe was changed to 6.0 [mW]. R0 was 17.4, and R1 after irradiation with a laser beam with an erasing power Pe = 6.0 [mW] once was 18.0 (R1 / R0 = 1.034).
As shown in Table 1, the initial characteristics and overwrite recording characteristics were 8.8% DOW0 jitter, 10.8% DOW1 jitter, and 9.0% DOW9 jitter. Although not described further, the DOW10000 jitter is 12.2%, and in DOW1 and DOW10000, the jitter exceeds 10% which affects the error rate, and the recording characteristics deteriorate.

(Comparative Example A-5)
Using the same optical recording medium A as in Example A-1, recording was evaluated under the same conditions as in Example A-1, except that the erasing power Pe was changed to 3.2 [mW]. R0 was 17.4, and R1 after irradiation with a laser beam with an erasing power Pe = 3.2 [mW] once was 17.4 (R1 / R0 = 1.000).
As shown in Table 1, the initial characteristics and overwrite recording characteristics are 9.8% for DOW0 jitter, 11.1% for DOW1 jitter, 10.8% for DOW9 jitter, and over 10% jitter for DOW1 and DOW9. Characteristics deteriorated.

(Comparative Example A-6)
Using the same optical recording medium A as in Example A-1, recording was performed in the same manner as in Example A-1, except that the erasing power Pe was changed to 6.8 [mW]. R0 was 17.4, and R1 after irradiation with a laser beam with an erasing power Pe = 6.8 [mW] once was 18.2 (R1 / R0 = 1.046).
As shown in Table 1, the initial characteristics and the overwrite recording characteristics are 8.8% DOW0 jitter, 12.3% DOW1 jitter, and 9.8% DOW9 jitter. Was 14.4%, and the DOW 1 and DOW 10000 exceeded 10%, which affects the error rate, and the recording characteristics deteriorated.

  As described above, the reflectance of the unrecorded portion when the laser beam for reproduction is irradiated from the LD 33 to the unrecorded portion in which no information is recorded in the recording area 54 is R0, and the erasing power Pe is present in the unrecorded portion. When the reflectance of the unrecorded portion when the laser beam for reproduction is irradiated from the LD 33 after irradiating the laser beam once is R1, the optimum erasing power Pe1 that satisfies the relationship of the following expression (1) is set as the erasing power Pe. It has been found that the jitter is preferably 10% or less when used for optical recording.

  1.000 <(R1 / R0) <1.030 (1)

Further, it has also been found that the DOW10000 jitter is deteriorated when the erase power Pe is larger than the optimum erase power Pe1 satisfying the expression (1), and the DOW1 jitter is deteriorated when the erase power Pe is small. This is because when the erasing power Pe is large, the load on the recording layer in the phase change optical recording medium in which the layer structure changes reversibly becomes too large, and the composition of the recording layer is easily segregated. This is because when Pe is small, a previously formed mark cannot be completely erased.
As described above, the upper and lower limits of the erasing power Pe are determined depending on the overwrite characteristics. In general, the reflectance R1 tends to increase as the erasing power Pe increases. That is, there is a proportional relationship in which (R1 / R0) increases as the erase power Pe increases. The present inventor has found that (R1 / R0) needs to satisfy the above formula (1) based on this relationship and the experimental results shown in Table 1.

Here, a method of obtaining the ternary value using the reflectance detector 46 when the optimum ternary value is not stored in the memory 451 of the optical recording apparatus shown in FIG. 6 will be described.
First, the optical recording medium A is irradiated with reproduction light having a laser power Pr from the optical head 34, and the reflectance detector 46 outputs R0 based on a reproduction signal supplied from a four-part light receiving element (not shown) of the optical head 34. Is detected. Subsequently, a laser beam with a predetermined erasing power Pe is irradiated to detect R1 in the same manner. Details of R0 and R1 are as described above. Here, the memory 451 has predetermined three values in advance, but these are not optimum three values unique to the optical recording medium. The reflectance detector 46 obtains R1 / R0 based on the detected R0 and R1.
As a method for detecting the reflectance, the reflectance detection unit 46 detects the reflectances R0 and R1 with a voltage value, the voltage value conversion of R0 is V0, the voltage value conversion of R1 is V1, and the reflectance detection unit 46 One example is calculating V1 / V0, that is, R1 / R0.

When the value of (R1 / R0) calculated by the reflectance detection unit 46 is larger than the expression (1), the system controller 45 controls the Pe drive current source 431e so as to reduce the erasing power Pe. If the value is smaller than the expression (1), the system controller 45 controls the Pe drive current source 431e so as to increase the erase power Pe.
Thus, the reflectance detection unit 46 obtains a plurality of R1s for a plurality of erasing powers Pe and (R1 / R0) in each R1, and selects a combination of R1 and R0 that satisfies the expression (1). Then, the erase power Pe that realizes the selected combination of R1 and R0 is stored in the memory 451 as the optimum erase power Pe1. Note that obtaining the optimum erasing power Pe1 in this way is called self-optimization.

≪Study of optimal initialization conditions≫
Next, the present inventor presumes that the initialization conditions in the initialization apparatus 200 may affect the recording and overwrite characteristics of the optical recording medium, and the following Examples B-1 to B-5 and Comparative Examples It has been found that the estimation is correct based on B-6 to B-8, and has an initialization condition that provides the best recording and overwriting characteristics.
FIG. 7 shows the relationship between the initialization laser power density Di and R0 of the optical recording medium A after initialization. The initialization laser power density Di is a value obtained by dividing the laser power of the laser beam used for initialization by the irradiation area of the initialization laser and further dividing by the scanning speed of the initialization laser. The reflectance R0 was an average reflectance for one recording track.
In the region A, the initialization laser power density Di is low, and the amorphous part (As-depo) after sputtering remains, so that the jitter characteristics of DOW0 are very bad, which is not preferable.
When the initialization laser power density Di is increased from the region A, the amorphous portion disappears and the region B has a relatively small reflectance change. When the initialization laser power density Di is further increased, the region C is changed to a region C where the reflectance change is large, a region D where the reflectance change is small, and a disc destruction region. In the disc destruction area, since the laser power input at the time of initialization is too large, physical destruction due to heat occurs in the layer centering on the recording layer.

(Example B-1)
The same optical recording medium A as in Example A-1 was prepared. Similar to Example A-1, the recording layer 3 was initialized under the initialization conditions of a scanning linear velocity of 4.5 m / s, a laser power of 1600 mW, and a feed pitch of 220 μm (initialization power density Di = 1.42 [ mW · s / (μm ² · m)], post-initialization reflectance region = BH).
In addition to the R0 and R1 defined as described above, the reflectance of the unrecorded portion when the laser beam for reproduction is irradiated from the LD 33 after the laser beam having the erasing power Pe is irradiated to the unrecorded portion 10 times. In the case of R10, the difference in reflectance ratio ((R10 / R0) − (R1 / R0)) was 0.092. The respective reflectance values are as shown in Table 2. The method for detecting the reflectance R10 may be the same method as described above.

  Measurements were performed in the same manner as in Example A-1. As shown in Table 2, the initial characteristics and overwrite recording characteristics were 6.5% for DOW0 jitter, 8.0% for DOW1 jitter, and 7.5% for DOW9 jitter. Although not described, the characteristics were always stable even when overwritten with a DOW10000 jitter of 8.5%, and the recording characteristics were good.

(Example B-2)
The recording layer 3 was initialized in the same manner as in Example B-1 except that the same optical recording medium A as in Example B-1 was used and the initialization condition was changed to a laser power of 1700 mW (initialization power density). Di = 1.51 [mW · s / (μm ² · m)], post-initialization reflectance region = BH). The difference in reflectance ratio was 0.043.
When the same measurement as in Example B-1 was performed, the recording characteristics were good as shown in Table 2.

(Example B-3)
The recording layer 3 was initialized in the same manner as in Example B-1 except that the same optical recording medium A as in Example B-1 was used and the initialization condition was changed to a laser power of 1730 mW (initialization power density). Di = 1.54 [mW · s / (μm ² · m)], post-initialization reflectance region = BH). The difference in reflectance ratio was 0.038.
When the same measurement as in Example B-1 was performed, the recording characteristics were good as shown in Table 2.

(Example B-4)
The recording layer 3 was initialized in the same manner as in Example B-1 except that the same optical recording medium A as in Example B-1 was used and the initialization condition was changed to 1400 mW (initialization power density). Di = 1.24 [mW · s / (μm ² · m)], post-initialization reflectance region = BH). The difference in reflectance ratio was 0.124.
When the same measurement as in Example B-1 was performed, the recording characteristics were good as shown in Table 2.

(Example B-5)
The recording layer 3 was initialized in the same manner as in Example B-1 except that the same optical recording medium A as in Example B-1 was used and the initialization condition was changed to laser power of 1360 mW (initialization power density). Di = 1.21 [mW · s / (μm ² · m)], post-initialization reflectance region = BH). The difference in reflectance ratio was 0.144.
When the same measurement as in Example B-1 was performed, the recording characteristics were good as shown in Table 2.

(Comparative Example B-6)
The recording layer 3 was initialized in the same manner as in Example B-1 except that the same optical recording medium A as in Example B-1 was used and the initialization condition was changed to 1300 mW (initialization power density). Di = 1.16 [mW · s / (μm ² · m)], post-initialization reflectance region = BL). The difference in reflectance ratio was 0.160.
When the same measurement as in Example B-1 was performed, as shown in Table 2, the DOW1 jitter was 11.1%, and the overwrite characteristics in a small number of times were not good.

(Comparative Example B-7)
The initial recording layer 3 was the same as in Example B-1, except that the same optical recording medium A as in Example B-1 was used and the initialization conditions were changed to a scanning linear velocity of 4.0 m / s and a laser power of 1600 mW. (Initialization power density Di = 1.60 [mW · s / (μm ² · m)], post-initialization reflectance region = C). The difference in reflectance ratio was 0.037.
When the same measurement as in Example B-1 was performed, as shown in Table 2, the DOW0 jitter was 12.8%, the DOW1 jitter was 10.8%, and the overwrite characteristics in a small number of times were not good.

(Comparative Example B-8)
The initial recording layer 3 was the same as in Example B-1, except that the same optical recording medium A as in Example B-1 was used and the initialization conditions were changed to a scanning linear velocity of 4.0 m / s and a laser power of 1800 mW. (Initialization power density Di = 1.80 [mW · s / (μm ² · m)], post-initialization reflectance region = C). The difference in reflectance ratio was 0.010.
When the same measurement as in Example B-1 was performed, as shown in Table 2, the DOW1 jitter was 16.3%, and the overwrite characteristics at a small number of times were not good.

  From the above, R0, R1 and R10 defined as described above are detected, and the reflectance ratio difference ((R10 / R0) − (R1 / R0)) calculated based on this is the relationship of the equation (2). It has been found that it is preferable to initialize the optical recording medium with an initialization laser power density Di (initialization conditions) that satisfies the above. In this way, good characteristics can be maintained even when overwriting is performed from a small number of times to a large number of times.

  0.030 <(R10 / R0)-(R1 / R0) <0.150 (2)

More preferably,
0.038 ≦ (R10 / R0) − (R1 / R0) ≦ 0.144 (3)
It is.

The initialization laser power density Di satisfying the above equation (2) is preferably in the range of 1.20 ≦ Di ≦ 1.55 from Table 2, and when initialized under this initialization condition, the reflectance R0 is shown in FIG. It falls within the area BH shown.
Further, under the initialization conditions in which the difference in reflectance ratio is less than 0.030 or more than 0.150 as in Comparative Examples B-6 to B-8, the reflectance region after initialization is BL or C. , D was found. In this case, the initialization laser power density Di deviated from 1.20 ≦ Di ≦ 1.55, and the overwrite characteristics in a small number of times also deteriorated. In addition, when the reflectance region is C as in Comparative Example B-7, since the BH and D regions are mixed after initialization, the characteristics of DOW0 are also deteriorated.

FIG. 8 is a DOW jitter characteristic diagram showing the relationship between the number of overwriting (overwrite: DOW) and the jitter value in the reflectance regions B to D.
Under the initialization laser power density in the region D (♦), that is, the initialization condition based on the laser power and scanning speed of the initialization laser, the DOW0 jitter is good, but the DOW1 jitter becomes very bad. In the region D, the difference in reflectance ratio is less than 0.030 and does not satisfy the expression (2).
Under the initialization condition of the region C (●), both the region D and the region BH are mixed and the initial characteristics are not stable, and the jitter of DOW0 is not particularly good as shown in FIG. When the overwrite is repeated a few times, the jitter is improved, but it is not preferable because DOJ9 (overwrite 9th) cannot provide a good jitter. In the region C as well as the region D, the difference in reflectance ratio is less than 0.030 and does not satisfy the expression (2).

As shown in FIG. 7, in the region B, the reflectivity R0 increases gently as the initialization laser power density Di increases. Here, the region on the low reflectance side is further divided into BL, and the region on the high reflectance side is further divided into BH. In FIG. 8, the DOW jitter characteristic in the region BL (□) is good for the DOW0 jitter, but is not preferable because the DOW1 jitter becomes very bad. In the region BL, the difference in reflectance ratio exceeds 0.150 and does not satisfy the expression (2).
On the other hand, the region BH (Δ) is the most desirable initialization condition because good DOW jitter characteristics as shown in FIG. 8 can be obtained. Further, in the region BH, the relationship of the expression (2) is satisfied.
The reason for this good characteristic is considered that the crystallization state formed by applying the optimum erasing power Pe1 during recording is almost the same as the initialization state of the region BH formed by the initialization apparatus 200. .

When Di is smaller than the initialization laser power density Di that satisfies the initialization condition of the region BH, sufficient laser power required for crystallization of the recording layer cannot be irradiated, and an amorphous portion remains, and the reflectance is the region A in FIG. It becomes BL and the DOW characteristic is deteriorated. Further, in the region A, the difference in reflectance ratio exceeds 0.300, and the expression (2) is not satisfied. On the other hand, even if Di is large, there are too few amorphous parts, so regions C and D are formed, or at a high initialization laser power density Di, a disk destruction region is obtained, and the DOW characteristics deteriorate as described above, which is not preferable.
From the above, in order to satisfy the initialization condition of the region BH, the initialization laser power density Di is preferably 1.20 ≦ Di ≦ 1.55.

As can be seen from Table 2, the above-described equation (1) is also satisfied by setting the initialization condition to the region BH. This is because, as described above, the crystallization state formed by applying the optimum erasing power Pe1 during recording is substantially the same as the initialization state of the region BH formed by the initialization apparatus 200.
It should be noted that for an optical recording medium in which the initialization laser power density Di, which is a preferred example of the conditions for satisfying the above expressions (1) and (2), is initialized at 1.20 ≦ Di ≦ 1.55, It is more preferable to use the optimum erasing power that satisfies the expression (1).

≪Study of optimal power ratio ε≫
The optimum recording conditions for recording the optical recording medium A were further examined based on Examples C-1 to C-3 and Comparative Examples C-4 and C-5.
The DOW jitter characteristic of the optical recording medium changes depending on the power ratio ε = (Pe / Pw) between the recording power Pw and the erasing power Pe. FIG. 9 shows the relationship between jitter and power ratio ε in DOW1. The lowest and best jitter is in the vicinity of ε = 0.30, and the jitter increases regardless of whether the power ratio ε is small or large with the vicinity of 0.30 as the base. Note that since it is ε = 0.20 to 0.40 from FIG. 9 that shows a jitter of 10% or less, which is considered to have little adverse effect on the error rate, the preferable range of the power ratio ε is 0.20. ≦ ε ≦ 0.40.
When ε <0.20, the recording power Pw becomes smaller than the erasing power Pe, so that it becomes difficult to form a sufficiently large recording mark, and as a result, a sufficient signal intensity cannot be obtained. When ε> 0.40, the signal characteristics are deteriorated due to cross-erasing because the recording power Pw becomes excessively larger than the erasing power Pe, which is not preferable.

(Example C-1 to Example C-3)
The same optical recording medium A as in Example A-1 was prepared. The initialization conditions were the same as in Example A-1 (scanning line speed 4.5 m / s, laser power 1600 mW, feed pitch 220 μm), and the erasing power Pe during recording was 3.8 to 5 as in each Example A It was changed in the range of 6 [mW]. The recording power Pw was also changed in each Example C, and the power ratio ε (= Pe / Pw) was set to be 0.21 to 0.39. Each value is shown in Table 3.
When the same measurement as in Example A-1 was performed, the initial characteristics and the overwrite recording characteristics of each Example C were 6.5% to 7.0% DOW0 jitter and DOW1 jitter as shown in Table 3. 8.0% to 9.1%, DOW9 jitter is 7.5% to 8.4%, and DOW10000 jitter is 8.0% to 9.8%. The recording characteristics were good.

(Comparative Example C-4)
The same optical recording medium A as in Example A-1 was prepared. Further, the recording layer 3 was initialized under the same initialization conditions as in Example A-1. The same measurement as in Example A-1 was performed except that the recording power Pw was changed to 13.0 mW and the erasing power Pe was changed to 5.8 mW under the recording conditions, and the power ratio ε was set to 0.45. As shown in Table 3, the overwriting characteristics were very inferior at 13.2% or more in overwriting after DOW1.

(Comparative Example C-5)
The same optical recording medium A as in Example A-1 was prepared. In addition, the recording layer 3 was initialized under the same initialization conditions as in Example A-1. The same measurement as in Example A-1 was performed except that the recording power Pw was changed to 21.0 mW and the erasing power Pe was changed to 3.8 mW under the recording conditions to set the power ratio ε to 0.18. As shown in Table 3, the overwrite characteristics were very inferior, with DOW1 having a jitter of 12.2% and DOW10000 having a jitter of 12.4%.

As described above, from each Example C, each Comparative Example C, and FIG. 9, the preferable range of the power ratio ε as the recording condition was found to be 0.20 ≦ ε ≦ 0.40.
FIG. 10 is a DOW jitter characteristic diagram showing the relationship of jitter to the number of DOWs. In FIG. 10, the power ratio ε is 0.3, 0.15 smaller than 0.2, and 0.45 larger than 0.4. When the power ratio ε is smaller than 0.20, the erasing power Pe becomes excessively small with respect to the recording power Pw, so that the previously drawn mark cannot be sufficiently erased. Therefore, as shown by (◇) in FIG. 10, the jitter characteristics after DOW1 are not good, which is not preferable. On the other hand, when the power ratio ε is larger than 0.40, the erasing power Pe is excessively large with respect to the recording power Pw, so that the crystal state is not stable, and the jitter characteristic of DOW1 is shown as (◯) in FIG. Is not good because it is not good.
When the power ratio ε shown in FIG. 10 is 0.30 (Δ), it can be seen that the jitter takes a value of 10% or less at any DOW number. From the above, a power ratio ε in the range of 0.20 ≦ ε ≦ 0.40 is preferable to obtain a jitter of 10% or less.
As shown in FIG. 10 (◇), the jitter characteristics after DOW1 are not good, which is not preferable. On the other hand, when the power ratio ε is larger than 0.40, the erasing power Pe is excessively larger than the recording power Pw, so that the crystal state is not stable, and the jitter characteristics of DOW1 are good as shown in FIG. Since it is not, it is not preferable. The power ratio ε is preferably in the range of 0.20 ≦ ε ≦ 0.40.

The power ratio ε in the range of 0.20 to 0.40 is set as the optimum power ratio ε1, and ε1 is recorded in advance in the lead-in area 53 of the optical recording medium A shown in FIG. The optical recording apparatus reads the optimum recording information such as the optimum erasing power Pe1 and the optimum power ratio ε1 from the lead-in area 53 and performs recording based on the information. Further, recording may be performed using optimum recording information stored in advance in the memory 451 in the system controller 45 of the optical recording apparatus or by updating.
Here, the optimum recording power Pw1 can be obtained from the optimum erasing power Pe1 and the optimum power ratio ε1. The optimum recording power Pw1 may also be included in the optimum recording information.
It can be said that the same effect can be obtained not only in the phase change type optical recording medium such as DVD-RW described above but also in the configuration of the ultra high density phase change type recording medium as shown in FIG. An optical recording medium B shown in FIG. 11 has a first protective layer 12, a recording layer 13, a second protective layer 14, and a reflection layer on a protective layer 17 whose bottom surface is an incident surface 17a for recording / reproducing or erasing laser light. The layer 15 and the substrate 11 are sequentially stacked.

FIG. 5 is a diagram showing a manufacturing / initialization process performed in the manufacturing equipment 300 or the manufacturing equipment 300 of the phase change optical recording medium. It is an expanded sectional view showing one embodiment of the optical recording medium concerning the present invention. 1 is a plan view showing an embodiment of an optical recording medium according to the present invention. It is a figure which shows the 1st example of a recording pulse pattern. It is a figure which shows the 2nd example of a recording pulse pattern. 1 is a block diagram showing an embodiment of an optical recording apparatus according to the present invention. It is a figure which shows the relationship between initialization laser power density Di and R0 of the optical recording medium A after initialization. FIG. 8 is a DOW jitter characteristic diagram showing a relationship between the number of DOWs and jitter in the reflectance regions B to D shown in FIG. 7. It is a figure which shows the relationship between the jitter in DOW1, and power ratio (epsilon). It is a DOW jitter characteristic figure which shows the relationship of the jitter with respect to the DOW frequency | count. It is an expanded sectional view which shows other embodiment of the optical recording medium based on this invention.

Explanation of symbols

A Optical recording medium Pe Erase power Pw Recording power Pb Bottom power ε Power ratio (Pe / Pw)
3 Recording layer 34 Optical head 34 (reading unit, recording unit)
39 Recording pulse generator (recorder)
41 EFM + encoder (encoder)
42 Mark length counter (mark length generator)
43 LD driver section (recording section)
46 Reflectance detection unit 400 Recording unit (recording pulse generation unit 39, LD driver unit 43, optical head 34)
451 memory (storage)

Claims (10)

In an optical recording method for recording recording information on a recording layer of a phase change optical recording medium,
A modulation step of modulating the recording information to generate modulation data;
A mark length generation step for generating a desired mark length based on the modulation data;
Based on the mark length, an erasure rising from the erasing power and a recording pulse formed between a recording power larger than the erasing power and a bottom power smaller than the erasing power, and an erasing rising from the bottom power to the erasing power A recording step of generating a recording pulse pattern consisting of a pulse, and recording a recording mark indicating the recording information by irradiating the recording layer with recording light according to the recording pulse pattern,
In the recording step, the reflectance of the non-recorded part when the reproduction light is irradiated to the non-recorded part in which the recording information in the recording layer has never been recorded is R0, and the light having the erasing power is the unrecorded part When the reflectance of the unrecorded portion when the reproduction light is irradiated after the irradiation is once R1,
As the erasing power, the following formula (1): 1.000 <(R1 / R0) <1.030 (1)
An optical recording method using an optimum erasing power satisfying The recording power is Pw, the erasing power is Pe, and a power ratio ε (ε = Pe / Pw) of the erasing power Pe to the recording power Pw is
0.20 ≦ ε ≦ 0.40
The optical recording method according to claim 1, wherein: In an optical recording apparatus for recording recording information on a recording layer of a phase change optical recording medium,
An encoder that modulates the recording information to generate modulation data;
A mark length generator for generating a desired mark length based on the modulation data;
Based on the mark length, an erasure rising from the erasing power and a recording pulse formed between a recording power larger than the erasing power and a bottom power smaller than the erasing power, and an erasing rising from the bottom power to the erasing power Generating a recording pulse pattern composed of a pulse, and a recording unit that records recording marks indicating the recording information by irradiating the recording layer with recording light according to the recording pulse pattern,
The recording unit has a reflectance of R0 when the reproducing light is irradiated to an unrecorded part in which recording information in the recording layer has never been recorded, and light having the erasing power is the unrecorded part. When the reflectance of the unrecorded portion when the reproduction light is irradiated after the irradiation is once R1,
As the erasing power, the following formula (1): 1.000 <(R1 / R0) <1.030 (1)
An optical recording apparatus using an optimum erasing power satisfying A storage unit for storing identification information indicating the optimum erasing power;
4. The optical recording apparatus according to claim 3, wherein the recording unit determines the optimum erasing power based on the identification information stored in the storage unit. A reading unit for reading identification information indicating the optimum erasing power written in a predetermined area of the optical recording medium;
4. The optical recording apparatus according to claim 3, wherein the recording unit determines the optimum erasing power based on the identification information read by the reading unit. A reflectance detector that obtains the R0 and the plurality of R1s corresponding to the plurality of erasing powers, and selects a combination satisfying the formula (1) from a combination of the R0 and the plurality of R1s.
The optical recording apparatus according to claim 3, wherein the recording unit determines the optimum erasing power based on a combination selected by the reflectance detection unit. The recording power is Pw, the erasing power is Pe, and a power ratio ε (ε = Pe / Pw) of the erasing power Pe to the recording power Pw is
0.20 ≦ ε ≦ 0.40
The optical recording apparatus according to claim 3, wherein the optical recording apparatus is an optical recording apparatus. In the phase change type optical recording medium,
A recording pulse pattern consisting of a recording pulse formed between an erasing power and a recording power larger than the erasing power and a bottom power smaller than the erasing power, and an erasing pulse rising from the bottom power to the erasing power A recording layer for recording recording marks indicating recording information by irradiating recording light according to
The recording layer has a reflectance of R0 when the reproducing light is irradiated to an unrecorded portion where information in the recording layer has never been recorded, and light having the erasing power is applied to the unrecorded portion. The reflectance of the unrecorded portion when irradiated with the reproduction light after being irradiated once and the unrecorded portion when irradiated with the reproduction light after irradiating the unrecorded portion with light having the erasing power 10 times after irradiation. When the reflectance of the recording part is R10,
As the erasing power, the following formulas (1) and (2): 1.000 <(R1 / R0) <1.030 (1)
0.030 <(R10 / R0)-(R1 / R0) <0.150 (2)
An optical recording medium that is initialized by an initialization laser so that When the recording power is Pw, the erasing power is Pe, and the ratio of the erasing power Pe to the recording power Pw is ε (ε = Pe / Pw),
0.20 ≦ ε ≦ 0.40
9. The optical recording medium according to claim 8, wherein information for the following is written. The recording layer is obtained by dividing the power of the initialization laser by the irradiation area of the initialization laser, and further dividing the value by the scanning speed of the initialization laser as an initialization laser power density Di,
1.20 ≦ Di ≦ 1.55
10. The optical recording medium according to claim 8, wherein the optical recording medium is initialized under the following conditions.

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