JP2003157532A - Information recording and reproducing device, information recording and reproducing method and phase change type recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording and reproducing device, a recording and reproducing method and a phase variable recording medium in which the dispersion of a phase change mark size within a disk surface and between disks can be reduced and a mark in the shape of no trailing can be recorded. SOLUTION: In the information recording and reproducing device composed of a pickup part, a laser power modulation part, a medium drive part and a signal processing part, the laser power modulation part is provided with a means for controlling the power level of a laser beam between P1 and P2 in the relation of P1>P2 at least and a means for changing time T to keep the power level P1 on the basis of a signal from the medium drive part or signal from a signal detecting part in accordance with an input signal. In the information recording and reproducing method, information is recorded while changing the size of the recording mark by controlling the power level of the laser beam between P1 and P2 in the relation of P1>P2 and changing the time T (nsec) to keep the power level P1 corresponding to the recording information within the range of 0.05×λ/NA/v<=T<=1.0×λ/NA/v when a wavelength of the laser beam is defined as λ (nm), the numerical aperture of an objective lens is defined as NA and a recording velocity is defined as (v) (m/sec).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing apparatus for recording / reproducing information using a laser beam, an information recording / reproducing method, and a phase change recording medium. In particular, an information recording / reproducing apparatus for recording multi-valued information by changing the area of a recording mark (hereinafter referred to as mark area modulation multi-valued recording), an information recording method (hereinafter referred to as a recording strategy),
The present invention relates to a phase change recording medium. The tracking method is sample servo.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No. 2001-84591 discloses
A recording strategy used in mark area modulation multi-value recording is disclosed. FIG. 1 shows a multi-pulse recording strategy (101) used in a conventional rewritable DVD.
And a recording strategy (102) disclosed in Japanese Patent Laid-Open No. 2001-84591. In the case of multi-pulse, the mark size is controlled by the number of pulses. In FIG. 1, the power level is changed among Pw, Pb, and Pe, and the number of pulses is 1.
The state is shown in which the number is increased from 7 to 7. In this case, one pulse width (Tw, T
b) must be made very short, and Tw and Tb are several n
Since it is about sec, a high-speed laser beam modulating means is required, and the information recording apparatus becomes expensive. Further, there is a limit to the high speed modulation of the laser beam, and the recording density is limited. In the method disclosed in Japanese Patent Laid-Open No. 2001-84591, laser power is modulated between Pw and Pb (hereinafter referred to as a cooling pulse). Here, Pb is a level close to the reproduction power. In this recording strategy, one mark is recorded by one pulse, and the mark size is controlled by the pulse width. Conventional 8-16 modulation or 1-7
Compared with mark edge recording such as modulation, the mark length modulation width is narrower in mark area modulation multilevel recording.
The recording strategy disclosed in Japanese Patent Publication No. 1-84591 can be applied. However, there are some problems in achieving a high recording density with this recording strategy.

In order to realize high-density recording with the recording strategy disclosed in Japanese Unexamined Patent Publication No. 2001-84591, the shape of the phase change mark to be recorded and the in-plane variation of the disk become problems.
FIG. 2 shows the shape of the phase change mark recorded by the cooling pulse (102). This figure shows the recording strategy and the recorded phase change marks. The holding time Tb of the Pb level is changed to make seven marks (M1 to M) of different sizes.
7) is recorded. As you can see, the short marks are very thin crescent-shaped and the long marks are head-shaped. When recording is performed with a cooling pulse, the rear end of the phase change mark (the rear side in the beam scanning direction) is formed by recrystallization. That is, the part that has once become amorphous is recrystallized to become a mark. In the vicinity of the track center where the maximum temperature is reached in the recording process, recrystallization is delayed compared to the peripheral portion and the trailing edge of the mark occurs. Therefore, if large marks continue, the marks are connected at the trailing portion. In the case of such a mark shape, a mark with or without trailing is formed due to a slight change in the recording condition, and the mark size varies within the disc surface.

Further, in the mark area modulation method, it is necessary to reduce the unit size (mark pitch) in order to increase the linear density. However, if the mark pitch is reduced, the reproduced signal includes the information of the preceding and following marks, so that intersymbol interference occurs. Occurs. Therefore, the situation in which intersymbol interference occurs is reproduced, and the recording signal is restored using signal processing technology.However, the mark shape that is asymmetric in the front-rear direction in the disc tangential direction complicates the state of intersymbol interference. Since various signal processing is required, the recording / reproducing apparatus becomes expensive. In mark area modulation multi-value recording, variations in mark size within the disc surface cause variations in reproduction signal level. Further, if the mark shape is complicated, signal processing becomes difficult.
Therefore, it is possible to suppress variations in the mark size within the disc surface,
A recording strategy that can record a mark with a simple shape is required.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and reduces the in-plane variation of the phase change mark size and the inter-disc variation in the mark area modulation multilevel recording. An object of the present invention is to provide an information recording / reproducing device, an information recording / reproducing method, and a phase change recording medium capable of recording a mark having a shape without tailing, that is, a mark such as a ROM pit that is symmetrical in the longitudinal direction in the disc tangential direction. To do.

[0006]

[Means for Solving the Problems] The above problems are solved in the following 1) to
It is solved by the invention of 10) (hereinafter, referred to as the inventions 1 to 10). 1) An information recording / reproducing apparatus comprising a pickup section, a laser power modulation section, a medium driving section, and a signal processing section, for recording / reproducing multi-valued information on / from a phase change recording medium, wherein the laser power modulation section , P1 to P having at least the power level of the laser beam in the relationship of P1> P2
And a means for changing the time (pulse width) T held at the power level P1 based on the signal from the medium driving unit or the signal from the signal detecting unit according to the input signal. Characteristic information recording / reproducing apparatus. 2) An information recording / reproducing method for recording / reproducing multi-valued information on / from a phase change recording medium, wherein the power level of the laser beam is controlled between P1 and P2 in the relationship of P1> P2. As the wavelength λ (nm), the numerical aperture NA of the objective lens, and the recording linear velocity v (m / sec), the time (pulse width) T (nsec) for holding at the power level P1
0.05 × λ / NA / v ≦ T ≦ 1.0 × λ / NA /
The information is recorded by changing the size of the recording mark by changing the size of the recording mark by changing it in the range of v, and the recorded information is reproduced by detecting the change of the reflected light amount level accompanying the change of the size of the recording mark. Information recording / playback method. 3) To obtain the power level ratio P2 / P1 at which the reflected light intensity difference between the unrecorded state and the maximum mark recorded state becomes a predetermined value for each recording medium, and record the information of the power level ratio on the recording medium. (2) The information recording / reproducing method described in 2). 4) The information recording / reproducing method according to 2) or 3), wherein the recording medium is a disc, and at least one of the power levels P1 and P2 is changed according to the radial position. 5) It has a structure in which at least a phase-change recording layer, a dielectric layer, and a metal layer are laminated in this order as viewed from the laser beam incident side, and the electrical resistivity of the phase-change recording layer material in the crystalline state is 1 × 10 5. It is in the range of ⁻⁵ to 1 × 10 ⁻³ (Ω · cm), and the electrical resistivity of the metal layer material is 1 × 10 ⁻⁶ to.
A phase change recording medium characterized by being in the range of 1 × 10 ⁻⁴ (Ω · cm). 6) The sheet resistance of the metal layer is 1 × 10 ⁻³ to 1 (Ω /
The phase change recording medium according to 5), which is in the range of □). 7) The phase-change recording medium according to 6), wherein the metal layer material contains at least one metal element selected from the group consisting of Ag, Cu, Au, and Al as a main component. 8) The recording layer materials are SbTe having an Sb / Te ratio in the range of 1 to 4, Ag, In, Ge, Ga, B, Si and A.
8. The phase change recording medium according to any one of 5) to 7), which contains at least one element selected from the group consisting of 1 and Sn. 9) The phase change according to any one of 5) to 8), wherein a data recording area and a servo area including at least prepits for sample servo tracking are alternately arranged in the track direction. Type recording medium. 10) At least one pre-pit aligned in the radial direction of the disk exists in the servo area, and if the recording period of the mark is P, the distance from the pre-pit to the recording start position differs by P / 2 between adjacent tracks. Characteristic 9)
The described phase change recording medium.

The present inventions 1 to 10 will be described in detail below. In the case of phase change recording, there are two methods for forming the trailing end of the recording mark. The first method is a method of forming the trailing edge of the mark by crystallizing the part that has once been made amorphous (method by recrystallization). In this case, the shapes of the front and rear ends of the phase change mark are asymmetric, and a crescent-shaped mark or a head-shaped mark is recorded. The second method is a method of controlling the amount of temperature change. In the case of phase change recording, the portion where the temperature change amount per unit time exceeds the threshold value becomes amorphous, so by controlling the temperature change amount by the laser power level and pulse width, the mark trailing edge does not depend on recrystallization. Can be formed. In this case, the front and rear ends of the phase change mark are symmetrical, and a mark close to a circle or an ellipse can be recorded. The conventional cooling pulse method records a phase change mark by the first method (recrystallization method), whereas the present invention records a phase change mark by the second method (temperature change amount control method). To do. Therefore, an information recording / reproducing apparatus for recording a phase change mark by the second method, a recording strategy, and a phase change recording medium will be described.

FIG. 3 shows the configuration of the information recording / reproducing apparatus according to the first embodiment of the present invention. The information recording / reproducing apparatus includes a pickup unit 30.
1, a laser power modulator 302, a medium driver 303,
It is composed of the signal processing unit 304. Pickup part 30
Reference numeral 1 records information on the phase-change recording medium 305 with a laser beam, reproduces the recorded information, and detects a signal from a reference pit provided on the medium. The medium driving unit 303
The rotation speed of the medium is controlled. The signal processing unit 304 processes the reproduced signal from the pickup unit and the signal from the reference pit. The present invention 1 is characterized by the laser power modulator 302. That is, the laser power modulator 302 has means for controlling the power level between P1 and P2 in the relationship of P1> P2 according to the input signal. Further, it is provided with means for changing the time (pulse width) T held at the power level P1 based on the control signal 307 of the medium rotation speed from the medium driving unit 303 or the reference pit signal 308 from the signal processing unit 304. Using such an information recording / reproducing apparatus, recording / reproducing of multi-valued information is performed by the information recording / reproducing method according to the second to fourth aspects of the present invention.

FIG. 4 shows an example of the recording strategy according to the present invention 2 and the shape of the phase change mark. The power level of the laser is modulated between two levels P1 and P2 which are in the relationship of P1> P2. Preferably the power level ratio P2 / P1 =
Set in the range of 0.1 to 0.8. The condition range in which the phase change mark can be recorded by controlling the temperature change amount is the laser beam diameter (wavelength λ and the numerical aperture N of the objective lens N) as in the present invention 2.
The ratio of A = proportional to λ / NA) and the recording linear velocity. The time (pulse width) T1 (nsec) held at the power level P1 is the recording linear velocity v (m / se).
c), where the wavelength λ (nm) of the laser beam and the numerical aperture NA of the objective lens are in the range of 0.05 × λ / NA / v at the shortest to 1.0 × λ / NA / v at the longest. A more preferable range is 0.1 × λ / NA / v to 0.8 × λ / NA / v
Is. The power levels P1 and P2 are kept constant within this range, and the pulse width T1 is changed according to the recording information. The area of the mark changes by changing the pulse width T1 (M1 to M7). As shown in FIG. 4, the phase change mark recorded by this method has a mark shape close to a circle or an ellipse without the trailing edge of the mark rear end occurring unlike in the conventional case. Details will be described in Examples.

The present invention 3 is an OPC (Optimum po)
wer control), that is, trial writing for obtaining the optimum recording condition. In the case of area modulation multi-level recording, it is necessary to increase the amount of change in the reflected light intensity depending on the mark size in order to reduce the determination error of the multi-valued level, and the reflected light intensity between the unrecorded state and the maximum mark recorded state. The difference becomes important. Specifically, the optimum P2 / P for each medium
By obtaining the 1 ratio, it is possible to suppress the variation of the reflected light intensity difference due to the variation of the recording characteristics between the media. in this case,
The P2 / P1 ratio is adjusted so that the reflected light intensity difference between the unrecorded state and the maximum mark recorded state becomes a predetermined value. P2 found
Information about the / P1 ratio is recorded at a predetermined position on the disc.

FIG. 5 shows an example of a recording strategy according to the present invention 4. FIG. 5 shows the CAV (Consta
nt Angular Velocity) recording strategy, the pulse width is changed according to the linear velocity within the condition range defined by the present invention 2 according to the disk radial position, and at least one of the power levels P1 and P2 is set. Change. Preferably, as shown in FIG. 5, the P2 level is lowered as the linear velocity increases toward the outer peripheral direction of the disc (changes from P21 → P22 → P23 toward the outer periphery of the disc). As the linear velocity increases, the unrecorded portion (the P2 level power irradiation portion) becomes amorphized, and the difference in reflected light intensity between the recorded and unrecorded states decreases. However, lowering the P2 level can suppress the amorphization. . The P2 level may be changed stepwise between zones or continuously depending on the radial position.

The present inventions 5 to 8 relate to a phase change recording medium. The present invention 5 indicates the range of electric resistivity of the recording layer material and the metal layer material. The phase-change recording medium consists of a phase-change recording layer / dielectric layer /
It has a layer structure called a metal layer. The dielectric _{layer, ZnS-SiO 2, SiO 2} , Al 2 O 3, AlN
A general material such as can be used. The film thickness is 5
The range is 50 nm. The thermal conductivity of the recording layer material and the metal layer material is correlated with the electrical resistivity. In the fifth aspect of the invention, the electrical resistivity range of the phase change recording layer material and the metal layer material is limited. The electrical resistivity of the phase change recording layer material in the crystalline state is in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁻³ (Ω · cm). Further, the electric resistivity of the metal layer material is 1 × 10 ⁻⁶ to 1
The range is × 10 ⁻⁴ (Ω · cm). Here, the electrical resistivity may be a value obtained by measuring and converting a thin film material by a four-terminal resistance measuring method, and in the case of forming a film by a sputtering method,
It may be a value obtained by measuring the sputtering target. By using the phase change recording layer material and the metal layer material having an electric resistivity in the above range to prepare a medium having the above layer structure,
The heat generated in the recording layer due to the absorption of the laser beam diffuses into the metal layer, and the metal layer functions as a heat dissipation layer. As described above, by providing the metal layer with a function as a heat dissipation layer, the temperature change amount per unit time in the recording layer can be controlled by the recording strategy according to the second to fourth aspects of the present invention, and the size of the phase change mark can be accurately measured. Can be changed.

The sixth aspect of the present invention defines the physical properties of the metal layer in the fifth aspect by the sheet resistance value, and sets the sheet resistance of the metal layer in the range of 1 × 10 ⁻³ to 1 (Ω / □). To do. By setting the film thickness and material of the metal layer so as to fall within this range, the heat generated in the recording layer due to absorption of the laser beam is more efficiently diffused into the metal layer, and the metal layer functions as a heat dissipation layer. The present invention 7 is a metal layer material which can satisfy the sheet resistance range of the present invention 6,
It is an invention in which one containing at least one metal element selected from Ag, Cu, Au, and Al as a main component is selected. Here, the main component means an element having a content of 80 atomic% or more. In addition to the main element, Ti, Pd, Si
You may use the alloy which added etc. As a specific example, Ag, AgPdCu, AgAuCu, AgCu, A
gZn, AgCuAl, AgRuZr, AgNi, A
l, AlTi, AlCu, AlSiCu, Cu, CuT
i, Au, and the like. Since these metal materials have low resistance, they satisfy the above range of sheet resistance with a thin film thickness and have a function as a heat dissipation layer. Moreover, corrosion resistance can be improved by alloying.

As described in Invention 8, the recording layer of the phase change recording medium contains SbTe as a main component. Where Sb
The Te content ratio Sb / Te is set in the range of 1 to 4. Preferably, Sb / Te = 2 to 3 is set. In addition, the SbTe
In addition to Ag, In, Ge, Ga, B, Si, Al, S
At least one element selected from the group of n may be contained, and Ge and / or Si and Ag, In, Ge, G
Those containing one element selected from the group consisting of a, B, Si, Al and Sn are preferable. Specific examples of preferable compositions include AgInSbTe, GeSbTe, and GeInSb.
Te, GeGaSbTe, GaSbTe, etc. are mentioned. When the phase change recording layer material has such a composition, the resistivity range according to the present invention 5 is satisfied, and the followability of the phase change with respect to the temperature change amount is improved. Further, the phase change mark can be recorded with a size close to the recording pulse width (T1 in FIG. 4), and the mark size can be changed accurately according to the pulse width.

The present inventions 9 and 10 relate to a disk format of a phase change recording medium. In the present invention 9, a data recording area and a servo area are provided in the track direction.
Although not shown in the figure, a data area and a servo area are alternately present in the track direction. At least a servo signal source for sample servo tracking is provided in the servo area. The servo signal source is previously formed as a pit on the support substrate of the phase change recording medium. The data recording area is a mirror surface (flat) and has no groove. In the case of area modulation multi-level recording, it is necessary to expand the mark in the radial direction as well in order to increase the amount of change in reflected light. The groove step in groove recording or land / groove recording also acts as a thermal barrier. That is, when the groove is deepened, the mark does not spread in the radial direction and becomes a recording mark having a constant width. If the groove is made shallow so as not to become a thermal barrier, the signal amplitude of the tracking signal will be reduced, and the tracking servo will become unstable or the servo will not be applied. Further, if there is a step, the laser beam is diffracted and scattered and the amount of light received decreases. According to the ninth aspect of the present invention, the sample servo tracking is used as the medium structure to limit the expansion of the recording mark in the radial direction, thereby eliminating the groove step which causes the decrease in the reflected light amount.

FIG. 8 is an explanatory view of the present inventions 9 and 10. Reference numeral 801 in the drawing is a top view showing the relative positional relationship between the pits previously formed on the polycarbonate substrate and the phase change marks existing in the recording layer. Reference numeral 802 is a reproduction signal. 8011
Is a servo area, and 8012 is a data area. In the servo area, wobble pits 8013 and clock pits 8
014 exists. The clock pits are aligned in the radial direction. A tracking error signal is detected from the wobble pit, and a reference clock signal is generated from the interval T1 between the wobble pit and the clock pit. The timing of power level modulation according to the present invention 2 to 4 is determined based on T1. Further, the recording start timing T2 is determined based on the clock pit. The recording period P of the phase change mark in the data area 8012 is constant in the track direction. In the tenth aspect of the invention, the recording position on the adjacent n + 1 and n−1 tracks is P / with reference to the n track.
Two different. That is, the recording cycles of the adjacent tracks are in opposite phases. By recording in reverse phase,
Crosstalk can be suppressed. In order to achieve such a recording state, the recording start timing T in the adjacent track
2 is changed by a time corresponding to P / 2.

[0017]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Embodiment 1 This embodiment will be described with reference to FIG. The recording strategy 601 using the conventional cooling pulse and the recording strategy 602 according to the present invention 2 were compared. The layer structure of the recording medium is Z
nS-SiO ₂ (thickness of 20nm) / AgInSbTe
(Film thickness 17 nm) / ZnS—SiO ₂ (film thickness 20 nm)
/ Ag (film thickness 140 nm) / polycarbonate substrate. The electrical resistivity of AgInSbTe, which is the phase-change recording layer, in the crystalline state is 1.7 × 10 ⁻⁴ (Ω · c).
m), and the electrical resistivity of Ag, which is the metal layer, is 1.6 ×
It is 10 ⁻⁶ (Ω · cm). Further, the sheet resistance at the Ag film thickness in the above medium structure is 1.5 × 10 ⁻¹ (Ω /
□). The recording wavelength is 405 nm, the numerical aperture NA of the objective lens is 0.65, and the recording linear velocity is 3.5 m / sec. FIG. 6 shows the recording strategy and the phase change mark shape. In the case of the conventional recording strategy 601 using the cooling pulse, the recording power ratio Pb / Pw = 0.0
8, and in the case of the recording strategy 602 in this embodiment, P2 / P1 = 0.5 is set. As shown in FIG. 6, five marks (M1 to M5) were recorded with different sizes, and the mark size (the length between the front and rear ends in the disc tangential direction) was measured. The set values of the pulse width are as shown in Table 1 below.

[0019]

[Table 1]

FIGS. 7A and 7B show the in-plane variation of the mark size represented by the average value and the standard deviation of the actually measured mark size. As shown in FIG. 7A, in both recording strategies 601 and 602, the mark size changes according to the pulse width. In the figure, the solid line indicates the set value calculated from the pulse width and the recording linear velocity. The deviation from the set value is smaller in the recording strategy 602 of this embodiment than in the conventional recording strategy 601. As can be seen from the standard deviation shown in FIG. 7B, in the case of the conventional recording strategy 601,
The variation increases as the mark size decreases (M
1-M3). This is because the trailing portion of the trailing edge of the mark fluctuates in the disc surface, and some marks are trailing and some are not trailing. With the recording strategy according to the present invention, the variation can be suppressed even if the mark size is reduced. Thus, the recording strategy 6 according to the present invention 2
02, it is possible to record a phase change mark close to an elliptical shape without trailing. In the case of such a mark shape, variations due to size reduction can be reduced.

Embodiment 2 This embodiment will be described with reference to FIG. 4 and Table 2, and this embodiment shows the effect of optimizing the P2 / P1 ratio by trial writing according to the third embodiment of the present invention. The layer structure of the recording medium is the same as that of the first embodiment. In the case of area modulation multi-value recording, it is necessary to increase the amount of change in reflected light intensity depending on the mark size in order to judge the multi-value level. That is, it is necessary to increase the difference in reflected light intensity between the unrecorded state and the maximum mark recorded state. When the marks M1 to M7 are recorded as shown in FIG. 4, the reflected light amount level when the maximum mark M7 is recorded,
If the difference in the reflected light level in the unrecorded state is ΔL7, then ΔL
It can be said that the larger the value of 7 and the smaller the variation of ΔL7 between discs and within the disc surface, the more suitable the recording strategy is for the mark area modulation multilevel recording. Table 2 is a result of comparing ΔL7 in different disks A to C. Table 2
As can be seen from the above, when recording is fixed at P2 / P1 = 0.5, ΔL7 varies slightly between discs. On the other hand, if P2 / P1 that maximizes ΔL7 is obtained in advance for each disc and then recorded, the variation between discs can be improved.

[Table 2]

Embodiment 3 This embodiment will be described with reference to FIG. 5 and Table 3. FIG. 5 shows a recording strategy according to the fourth embodiment of the present invention, which is an example of CAV recording in which the P2 level is changed depending on the radial position. The figure is
P21, P22, P2 from the inner circumference to the outer circumference
3 and P2 to reduce the power level. Table 3 shows a comparison result of the recording strategy of the related art (102 of FIG. 1), the recording strategy of the present invention 2 (401 of FIG. 4), and the recording strategy of the present invention 4 (501 of FIG. 5). Similar to Example 2, ΔL7 was compared. The recording / reproducing wavelength is 405 nm, and the numerical aperture of the objective lens is 0.65. Recording was done by CAV. The recording linear velocity at the innermost circumference of 21 mm is 3.5 m / sec. The layer structure of the medium is the same as in Example 1, and the disk size is φ120 mm. Table 3 shows the disk radial positions of 21 mm, 40 mm,
The ΔL7 at 59 mm was shown. ΔL7 of the conventional recording strategy 102 is 1 at a radius of 21 mm, but decreases to 0.3 at a radius of 40 mm. Recording strategy 10
In the case of 2, since the high power level (Pw) is maintained,
As the linear velocity increases toward the outer circumference, the unrecorded portion becomes amorphous and the difference in reflected light intensity between the recorded mark and the unrecorded portion decreases. Also in the recording strategy 401 according to the second aspect of the invention, in the case of CAV recording, the variation ΔL7 decreases toward the outer periphery. On the other hand, in the recording strategy 501 according to the fourth embodiment of the present invention, as described above, P2 is set according to the radial position.
By lowering the level, the reduction of ΔL7 can be suppressed. Even in CAV recording, Δ within the disc surface
No change in L7 occurs.

[Table 3]

Embodiment 4 This embodiment will be described with reference to FIG. As described above, reference numeral 801 in the drawing is an upward view showing the relative positional relationship between the pre-pits previously formed on the polycarbonate substrate and the phase change marks existing in the recording layer. The structure of the medium is the first embodiment.
Is the same as. Reference numeral 8016 denotes a laser beam. The wavelength of the laser beam is 405 nm, and the N
A is 0.65. Reference numeral 8011 denotes a servo area. The servo area has a wobble pit 8013 and a clock pit 8014. In the wobble pits, two pits are arranged in a zigzag pattern with respect to one track in a state in which the wobble pits are shifted from the center of the track toward the inner and outer circumferences of the quarter track pitch. The clock pit 8014 is arranged at the center of the track. The track pitch is 400 nm. 801
2 is a data area. The data area is flat and has no steps. 8015 shows the recorded phase change mark. The recording period P is constant in the track direction. D (n), D
(N ± 1) indicates the mark recording start position. D (n) and D (n ± 1) are different from each other by P / 2, and the mark recording periods are opposite in phase between adjacent tracks. As a result, cross writing does not occur even when the maximum marks are adjacent to each other. Reference numeral 802 indicates a reproduction signal. Reference numeral 8021 denotes a tracking error signal from the wobble pit.
22 is a clock signal. Reference numeral 8023 is a reproduced signal of n tracks, and the reflected light level is L depending on the mark size.
The state which changes between 7-L0 level is shown. Table 4 shows the results of comparison of the reproduction signal level between the medium of this example and the case of recording on the groove substrate shown in FIG. The recording strategy is 401 in FIG. 4, and P1 / P2 is 0.
It is 5. As shown in Table 4, the L0 level (reproduction signal level in the unrecorded state) of the groove substrate was set to 1 for comparison. As can be seen from Table 4, in the medium of this example, the spread of the mark in the radial direction is larger than that of the groove substrate, and
7 (reproduction signal level in maximum mark recording state) is lowered. As a result, .DELTA.L7 (signal change amount in unrecorded-maximum mark recorded state) is larger than that in the case of the groove substrate.

[Table 4]

[0024]

According to the first and second aspects of the invention, by using the recording / reproducing apparatus of the first aspect of the invention and recording with the recording strategy of the second aspect of the invention, it is possible to reduce variations in the mark size within the disc surface. Further, since it is a simple recording strategy that changes the mark size with a single pulse, it can be applied to high density recording. According to the recording strategy of the third aspect of the invention, it is possible to suppress variations in recording characteristics between recording media. According to the recording strategy of the fourth aspect of the invention, it is possible to suppress the change in recording characteristics due to the recording linear velocity. Also, CAV recording becomes possible. According to the configuration of the phase change recording medium of the present inventions 5 and 6, the heat generated in the recording layer by the absorption of the laser beam diffuses into the metal layer, and the metal layer functions as a heat dissipation layer. Therefore, the recording strategy of the present invention 2 Can be applied. According to the seventh aspect of the present invention, the metal layer can be thinned by selecting the metal layer material, so that the process time for producing the disk can be shortened and the manufacturing cost can be reduced. According to the present invention 8, by selecting the material of the recording layer, the phase change mark can be recorded with a size according to the recording pulse, and high density recording becomes possible. According to the present invention 9, the mark size can be modulated without being affected by the groove step, and as a result, unrecorded-
It is possible to increase the difference in reflected light intensity when recording the maximum mark. According to the tenth aspect of the present invention, even in the state where the mark is expanded in the radial direction, cross-write and cross-erase can be suppressed and the track pitch can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a conventional recording strategy.

FIG. 2 is a diagram showing the shape of a phase change mark recorded by a cooling pulse (102).

FIG. 3 is a diagram showing a configuration of an information recording / reproducing apparatus according to the first invention.

FIG. 4 is a diagram showing an example of a recording strategy and a phase change mark shape according to the present invention 2;

FIG. 5 is a diagram showing an example of a recording strategy according to the present invention 4;

FIG. 6 is an explanatory diagram of Example 1 (recording strategy and phase change mark shape). (A) In the case of the conventional recording strategy 601 by the cooling pulse (b) In the case of the recording strategy 602 of the first embodiment

FIG. 7 is a diagram showing a recording result of Example 1. (A) Shows the average value of the actually measured mark sizes. (B) Shows the in-plane variation of the mark size represented by the standard deviation.

FIG. 8 is a diagram for explaining a phase change recording medium of the present inventions 9 and 10.

[Explanation of symbols]

101 Mark Strategy for Mark Area Modulation by Multi-Pulse 102 Recording Strategy for Mark Area Modulation by Cooling Pulse 301 Pickup Section 302 Laser Power Modulation Section 303 Medium Driving Section 304 Signal Processing Section 305 Phase Change Recording Medium 306 Input Signal 307 From Medium Driving Section Signal 308 output from the signal processing unit 409 output signal 401 recording strategy 402 phase change mark shape 501 recording strategy 601 conventional recording strategy (cooling pulse) 602 recording strategy 801 of the present embodiment medium upper view 8011 servo area 8012 data area 8013 Wobble pit 8014 clock pit 8015 phase change recording mark 8016 laser beam 802 reproduction signal 8021 tracking error signal 8022 clock signal 8023 Raw signal Pw Laser power level Pb Laser power level Pe Laser power level P1 Laser power level P2 Laser power level P21 Laser power level P22 Laser power level P23 Laser power level Tw Pulse width Tb Pulse width T1 Pulse width M1 Phase change mark with different size M2 different size phase change marks M3 different size phase change marks M4 different size phase change marks M5 different size phase change marks M6 different size phase change marks M7 different size phase change marks P mark recording period D (n ) Mark recording start position D (n ± 1) Mark recording start position

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 7/24 511 G11B 7/24 522A 522 538L 538 571B 571 B41M 5/26 X F term (reference) 2H111 EA04 EA12 EA23 EA32 EA37 FA01 FA11 FA18 FA21 FA23 FB04 FB05 FB06 FB09 FB12 FB17 FB20 FB21 FB30 5D029 JA01 JB18 JC09 MA13 MA17 PA03 5D090 AA01 BB05 CC01 CC14 DD01 EE02 FF12 GG16 GG22 GG38 JJ12 KK03 KK05 5D119 AA22 AA23 BA01 BB04 DA01 EA02 HA19 HA60 5D789 AA22 AA23 BA01 BB04 DA01 EA02 HA19 HA60

Claims (10)

[Claims] 1. An information recording / reproducing apparatus comprising a pickup section, a laser power modulating section, a medium driving section and a signal processing section for recording / reproducing multi-valued information on / from a phase change recording medium. The modulator is a means for controlling at least the power level of the laser beam between P1 and P2 having a relationship of P1> P2, and a power is supplied based on a signal from the medium driving unit or a signal from the signal detecting unit according to an input signal. An information recording / reproducing apparatus comprising means for changing a time (pulse width) T held at the level P1. 2. An information recording / reproducing method for recording / reproducing multi-valued information on / from a phase-change recording medium, wherein the power levels of laser beams are P1> P2.
The laser beam wavelength λ (nm), the objective lens numerical aperture NA, and the recording linear velocity v (m / sec) are held at the power level P1 (pulse width) T.
(Nsec) is 0.05 × λ / NA / v ≦ T ≦ 1.0
By changing the size of the recording mark to record the information by changing the recording mark in the range of λ / NA / v, and detecting the change in the reflected light amount level accompanying the change in the recording mark size. An information recording / reproducing method for reproducing the recorded information. 3. A power level ratio P2 / P at which the reflected light intensity difference between the unrecorded state and the maximum mark recorded state becomes a predetermined value.
3. The information recording / reproducing method according to claim 2, wherein 1 is obtained for each recording medium, and the information on the ratio of the power levels is recorded on the recording medium. 4. The information recording / reproducing method according to claim 2, wherein the recording medium is in the form of a disk, and at least one of the power levels P1 and P2 is changed according to its radial position. 5. A structure in which at least a phase-change recording layer, a dielectric layer, and a metal layer are laminated in this order when viewed from the laser beam incident side, and the electrical resistivity of the phase-change recording layer material in the crystalline state is: 1 × 10 ⁻⁵ to 1 × 10 ⁻³ (Ω · c
m), and the electric resistivity of the metal layer material is 1 ×
A phase-change recording medium having a range of 10 ⁻⁶ to 1 × 10 ⁻⁴ (Ω · cm). 6. The sheet resistance of the metal layer is 1 × 10 ⁻³ or more.
The phase change recording medium according to claim 5, wherein the phase change recording medium is in the range of 1 (Ω / □). 7. The metal layer material is Ag, Cu, Au, Al
7. The phase change recording medium according to claim 6, which contains at least one metal element selected from the group consisting of as a main component. 8. The recording layer material comprises SbTe having an Sb / Te ratio in the range of 1 to 4, Ag, In, Ge, Ga, B,
At least one selected from the group consisting of Si, Al, and Sn
The phase change recording medium according to any one of claims 5 to 7, wherein the phase change recording medium contains a seed element. 9. A data recording area and a servo area including at least pre-pits for sample servo tracking are alternately arranged in the track direction. Phase change recording medium. 10. In the servo area, at least one prepit aligned in the disk radial direction exists, and when the mark recording period is P, the distance from the prepit to the recording start position is P / 2 between adjacent tracks. 10. The phase change recording medium according to claim 9, which is different.