JP2002324339A - Phase-change recording medium and optical recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase-change recording medium to which recoding and reproduction can be made for every two tracks in a phase-change recording and also provide a recording and reproducing device. SOLUTION: The phase-change recording medium of the present invention has a structure in which at least a substrate, a metal layer and a recording layer are laminated. An information mark is recorded in accordance with a lattice point periodically existing in the recording medium, and the array periods of the lattice points are antiphase to each other between adjacent tracks.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change recording medium and an optical recording / reproducing apparatus, and more particularly, to a phase change recording / reproducing apparatus capable of simultaneously recording and reproducing data on two tracks and improving a data transfer rate in phase change recording. The present invention relates to an optical recording medium and an optical recording / reproducing apparatus.

[0002]

2. Description of the Related Art A problem with phase change recording media is to increase the data transfer speed. In particular, it is necessary to improve the recording speed. In the case of phase change recording, information is recorded using a phase change between crystal and amorphous. The recording speed is particularly affected by the crystallization speed. In order to increase the crystallization speed, the recording layer material and the layer structure of the disk have been improved. Further, as a signal modulation method of phase change recording, 8-16 modulation or 1-7 modulation is adopted. In these modulation methods, a mark length is modulated according to a recording signal. Since the laser beam is pulse-modulated at a high speed and the number of pulses is changed, a predetermined mark length is set. In order to realize high-speed recording, it is necessary to drive a laser beam at high speed and to increase power. As described above, increasing the transfer rate of phase change recording is limited by the recording material and the disk configuration. In addition, there is a limitation due to the characteristics of the laser.

If recording and reproduction can be simultaneously performed on two tracks, the transfer speed in phase change recording can be greatly increased. JP-A-2000-207747
Japanese Patent Application Laid-Open Publication No. H11-139,086 discloses a recording medium and an information recording / reproducing apparatus for reproducing two columns simultaneously in a ROM. R
PRML (Partial Response Maximum Li) combining PR (Radial Partial Response) method and Viterbi composite
A signal of two tracks is reproduced simultaneously by using a signal processing technique called a "kelihood" method. In such a method, the pits need to be aligned in the radial direction of the disk, and high pit position accuracy is required.

[0004]

Conventionally, in the case of the phase change recording modulation system, signals are recorded serially for each track. There is no order in the arrangement of information marks between tracks adjacent in the radial direction. For this reason, the recorded signal cannot be restored even if two rows of tracks are reproduced simultaneously. A method of simultaneously recording and reproducing data on a plurality of tracks using a plurality of laser beams is considered, but this causes an increase in drive cost and an increase in power consumption. Further, in order to simultaneously record and reproduce data on two tracks using one laser beam, it is necessary to accurately record information marks at predetermined positions.

An object of the present invention is to solve these problems, and an object of the present invention is to provide a phase change recording medium and a recording / reproducing apparatus which can record and reproduce information every two tracks in phase change recording. .

[0006]

According to the present invention, there is provided a phase-change recording medium comprising at least a support substrate, a metal layer, and a recording layer. It is recorded so as to coincide with the lattice points periodically existing in the storage medium, and the arrangement period of the lattice points is characterized in that adjacent tracks have mutually opposite phases. Therefore, information is recorded every two tracks in phase change recording,
Can be played.

Further, the recording medium is a disk-shaped recording medium, and the arrangement of the lattice points in the circumferential direction is preferably at a constant period.

Further, the size of the lattice point is preferably smaller than the diameter defined by 1 / e ^ 2 of the laser beam used for recording / reproducing.

It is preferable that the metal layer does not exist at the lattice points.

Further, it is preferable that at least one oxide, nitride, fluoride or sulfide of at least one element constituting the metal layer exists at the lattice point.

It is preferable that the coverage of the metal layer at the lattice points is lower than that at the parts other than the lattice points.

Further, the metal layer is made of Al, Ti, Cu, Zn,
Ge, Pd, Ag, In, Sn, Sb, Te, Pt, A
It is preferable to contain at least one element selected from the group consisting of u, Tl, and Bi.

Further, SbTe used as a composition of the recording layer was used.
Is preferably in the range of 1.5 to 4.

Further, the recording layer is made of Ge, In, Ga, Ag,
It is preferable to contain at least one element selected from the group consisting of Si, Al and B.

An optical recording / reproducing apparatus according to another aspect of the present invention irradiates the above-mentioned phase-change type recording medium with a laser beam so that two tracks are simultaneously included in an irradiation range, and records / reproduces information marks. There is a feature. Therefore, an optical recording / reproducing apparatus capable of recording and reproducing information for every two tracks can be provided.

Further, by modulating the intensity of the laser beam at least at two or more levels at a period of half the arrangement period of the lattice points in the track direction of the phase change recording medium and recording information, the position of the lattice points can be obtained. The recording position of the recording mark can be controlled to the same degree as the accuracy.

Also, an optical pickup having an information reproducing means for reproducing a recorded information sequence recorded on an optical disk by using an optical spot, an information sequence inputted from outside, and an interference code at the time of recording added to the information sequence Then, for each unit information of the information sequence to which the interference code at the time of recording has been added, a precoding means for calculating the remainder of the radix of the first information sequence and converting the information sequence into a recorded information sequence,
The interfering code during recording compensates for the intersymbol interference that occurs when the recorded information sequence is reproduced, so that the mark information read by the beam spot edge interferes with the mark information read by the beam spot center. Thus, the recorded information can be reproduced.

Further, decoding means for calculating the remainder of the unit information of the input information sequence for each unit information of the reproduced information sequence obtained by adding an interference code generated when the recorded information sequence is reproduced to the recorded information sequence. By using the conventional optical pickup, a mark smaller than the beam spot can be written on the recording layer using the conventional optical pickup as it is, and an ultra-high-density optical recording / reproducing apparatus capable of simultaneously recording and reproducing two tracks can be provided.

[0019] Further, the apparatus has decoding means by PRML method for each unit information of the reproduced information sequence obtained by adding an interference code generated when the recorded information sequence is reproduced to the recorded information sequence. By having maximum likelihood decoding means for performing decoding by the maximum likelihood decoding method, S / N can be improved by error correction.

Further, an optical recording / reproducing apparatus according to another aspect of the present invention includes an optical pickup having information reproducing means for reproducing a recorded information sequence recorded on an optical disk using a light spot, and an information sequence inputted from the outside, After adding the interference code at the time of recording to the information sequence, for each unit information of the information sequence to which the interference code at the time of recording is added, 2 units of the first information sequence
A precoding means for calculating a remainder based on a larger radix and converting the information sequence into a recording information sequence, wherein an interference code at the time of recording compensates for intersymbol interference generated when the recording information sequence is reproduced. Therefore, it is possible to reproduce the recorded information by causing the mark information read by the beam spot edge to interfere with the mark information read by the beam spot center.

Further, for each unit information of the reproduced information sequence obtained by adding an interference code generated when the recorded information sequence is reproduced to the recorded information sequence, a remainder by a radix greater than 2 of the input information sequence is calculated. With such a decoding means, it is possible to provide an ultra-high-density optical recording / reproducing apparatus capable of writing a mark smaller than the beam spot on the recording layer using the conventional optical pickup as it is, and capable of simultaneously recording and reproducing two tracks.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The phase-change recording medium of the present invention is composed of at least a support substrate, a metal layer, and a recording layer. The information marks coincide with lattice points periodically present in the storage medium. The arrangement period of the lattice points is opposite to each other between adjacent tracks.

[0023]

FIG. 1 is a diagram showing a configuration of a phase change type recording medium according to an embodiment of the present invention. (A) of the figure is a sectional view, and (a) of the figure is a plan view. In the figure, the phase-change recording medium of the present embodiment includes at least a supporting substrate 10
1, a metal layer 102, and a recording layer 104. Note that a dielectric layer or a protective layer may be provided in addition to these layers. As the support substrate 101, a transparent substrate such as polycarbonate, glass, or quartz can be used. Alternatively, a metal substrate such as aluminum can be used. As the metal layer 102, Al,
Ti, Cu, Zn, Ge, Pd, Ag, In, Sn, S
Metal elements selected from the group consisting of b, Te, Pt, Au, Tl, and Bi can be used alone or in combination. For example, AlTi, AlCu, AlTiCu, AgPd,
InTi, AgTe, SnTe, BiTe, etc. can also be used. Materials with high thermal conductivity are preferred. Also,
A material which deforms or is oxidized, nitrided, fluorinated, or sulfurized by laser heating is preferable. The recording layer 104 has, for example, a composition in which several kinds of additive elements are added to SbTe having a eutectic composition. SbTe was used for the parent phase of the recording layer 104, and SbTe was used.
Of Sb / Te is 1.5-4, more preferably 2-3.
And Ag, I as an additive element using SbTe as a base layer
The composition contains at least one element selected from the group consisting of n, Ge, Ga, B, Si, and Al. Preferably A
gInSbTe, GeAgInSbTe, GeSbT
e, GeInSbTe, GaSbTe, etc. Such a material of the recording layer 104 has good followability of the phase change to the temperature profile, and can change the mark shape finely. It is a material suitable for the phase change recording medium of the present invention. 103 and 105 are ZnS-SiO ₂ , Si for the dielectric or protective layers 103 and 105.
O ₂ , Al ₂ O ₃ , SiN, GeN, BN, SiC, C
Such a material can be used. Laminated substrate 10
As 6, a transparent substrate such as polycarbonate, glass, and quartz can be used.

In FIG. 1B, the recording layer and the dielectric layer are omitted, and the metal layer 102 is emphasized. In the phase change recording medium according to the present invention, lattice points 1021 are periodically present. Here, the lattice point 1021 indicates a unique portion formed in the metal layer 102. At grid point 1021,
No metal layer is present. Alternatively, a compound of an element included in the metal layer 102 exists. Alternatively, the metal layer 102
(Film thickness) is lower than the portion other than the lattice points.

The method of manufacturing a phase change type recording medium having such a structure is described in the following.
Numerals 21 are arranged at a constant period in the circumferential direction (track direction), and have mutually opposite phases between tracks adjacent in the radial direction. Further, the size of the lattice point is smaller than the beam diameter. Preferably, it is set to be equal to or smaller than 1/2 of the beam diameter defined by 1 / e ^ 2. A control area 109 may be periodically provided in addition to the data area 108 in which the grid points 1021 exist. In the control area 109, a pit 1022 serving as a laser beam tracking signal source is provided. The pit 1022 serves as a reference for sample servo control. By the sample servo tracking, the passing position of the laser beam is set at the center of the two tracks.

FIG. 1C is a characteristic diagram showing a temperature distribution in the recording layer when a laser beam passes. The metal layer 102 of the phase change recording medium has a function as a thermal radiation layer in addition to a function as an optical reflection layer. It is known from temperature simulation that much of the heat generated by absorption of the laser beam in the recording layer is diffused, that is, radiated to the metal layer side. Therefore, the temperature of the recording layer greatly differs depending on the presence or absence of the metal layer. For example, a polycarbonate substrate /
Ag thin film _{/ ZnS-SiO 2 / AgInSbTe /} Zn
According to the temperature simulation of the surface recording type configuration is S-SiO _2, and up to the difference between the ultimate temperature is about 700 ° C. calculation results obtained when the DC light in Ag120nm and 0nm has passed. In the present invention, the information mark is formed by the temperature difference depending on the presence or absence of the metal layer. The lattice point 1021 without a metal layer has a higher temperature than its surroundings, and a temperature profile in which the recording layer changes phase can be formed. FIG.
(B) lattice point 1041 immediately after passing the laser beam
As can be seen from FIG. 1C, the temperature profile of the recording layer immediately above the recording layer 1042 has the highest temperature at the lattice point (indicated by a dashed line in the figure), and decreases as the distance from the lattice point increases. That is, a target temperature distribution can be formed around the lattice point. Therefore, when the initial state of the recording layer is a crystal, a portion having a temperature higher than the amorphization temperature becomes an information mark. Also, by processing the metal layer using fine processing technology and periodically changing the heat radiation state in the medium plane,
A temperature profile corresponding to the cycle can be formed.

FIG. 2 is a diagram showing a state of recording / reproducing with respect to the phase change type recording medium of FIG. FIG. 2A shows the timing of modulation of the laser power intensity when the laser beam moves in the illustrated beam movement direction, tracking the center CL of the tracks A and B, and FIG. 2A shows the temperature profile of the recording layer. 2 (b) shows the shape of the information mark (as viewed from above the medium), and FIG. 2 (d) shows the reproduced signal. The period of the lattice point in the circumferential direction is 0.8 μm
And the track pitch is 0.45 μm. The grid points are circular and the diameter is 0.25 um. As shown in FIG. 2A, in the process of moving the beam in the illustrated beam movement direction, when the power level is changed in seven steps at a timing of half the period of the lattice point, FIG.
As shown in (2), if the power level is high, the range in which the temperature is equal to or higher than the amorphization temperature is expanded, and if the power level is low, the range is narrow. FIG.
(B), the solid line is the temperature profile at the track A, and the broken line is the temperature profile at the center of the track B. Since such a temperature profile can be formed, as shown in FIG.
The center of the mark 1043 always coincides with the center of the lattice point 1021. As a result, the recording position of the mark can be controlled to the same degree as the positional accuracy of the lattice point. Since the arrangement of the recording marks is fixed, the RPR method (Radi
al direction Partial Response) or PRML (Pa
rtial ResponseMaximum Likelihood) method can be used. In the case of the method of the present invention, the reflection intensity is changed by changing the mark area. Therefore, the reproduction timing is, as shown in FIG. 2D, the position where the signal becomes maximum, that is, the center of the mark. The change of the sum signal (RF signal) is shown. As shown, eight levels of signal intensity (A0 to A8, B
0 to B8) Can be detected. Since the mark arrangement between two adjacent tracks is determined, two rows of signals can be separated and reproduced by detecting signals at the timings shown in the figure. Therefore, according to the optical recording / reproducing apparatus of the present invention, information marks can be recorded / reproduced by irradiating two tracks simultaneously with a laser beam.

Further, the laser power level at the time of recording is changed according to recording information. The cycle for changing the laser power is
It is set to 点 of the period of the lattice point in the track direction. With the above-described optical recording / reproducing apparatus, two tracks can be simultaneously recorded and reproduced on the above-described phase change recording medium.

Here, the recording medium according to the present invention is DVD
(4.7 GB / φ120 mm). The period of the lattice point in the track direction of the recording medium shown in FIG. 2C is 0.8 μm. In this cycle, the reflected light intensity can be provided with eight gradations. Therefore, 3 bits of data can be recorded at a period of 0.8 μm, and the bit length in the track direction is 0.8 μm / 3 Bit = 0.267 μm / Bit. This bit length is almost the same as that of a DVD recorded by 8-16 modulation. Track pitch is 0.45u in this medium
m, DVD is 0.74 um. Therefore, the areal density of this medium is about 1.6 times that of DVD. When recording / reproducing at the same linear speed as DVD, the data transfer speed of this medium is DV
3.2 times D = 1.6 (capacity contribution) × 2 (simultaneous recording / reproduction of two tracks).

FIG. 3 is a diagram showing steps of a method for manufacturing a phase change recording medium according to a first embodiment of the present invention. FIGS. 3A and 3B show a process for manufacturing a quartz master. First, as shown in FIG. 3A, a resist pattern 3012 corresponding to a lattice point is formed on a quartz substrate 3011. The bottom diameter 3013 of the resist is 0.5 μm in diameter, and the period of the pattern is the same as the period of the lattice points shown in FIG. Then, as shown in FIG. 3B, a depression is provided in the quartz substrate 3011 by wet etching. Note that buffered hydrofluoric acid (BHF) is used for the etching solution. BH
In the case of etching with F, the selectivity between the resist and quartz is very large, and the resist is hardly etched. As a result, a shape as shown in FIG. 3B can be formed.
Next, as shown in FIG. 3C, the resist pattern 3012 is removed after patterning. The resist is removed by acetone ultrasonic waves. The quartz master is completed by the above procedure. The diameter of the width 3031 serving as a lattice point is 0.25 μm. Replication by injection molding is similar to the conventional method. Next, as shown in FIG. 3D, a metal layer 3051 is formed on the molded polycarbonate substrate 3041. Te having a thickness of 50 nm is used for the metal layer 3051. Then, as shown in FIG. 3E, an opening 3062 is formed by irradiating a laser beam 3061 from the substrate side and removing Te on the lattice points. This opening formation process
A so-called "initialization device" used for crystallization of a phase change recording medium is used. After the formation of the lattice points, as shown in FIG. 3G, ZnS—SiO ₂ 2
0 nm is deposited. Ag as the phase change recording layer 3082
A film of InSbTe 20 nm is formed. The composition of the recording layer is
Ag4At% -In 7At% -Sb 61At% -T
e 28 At%. ZnS as the dielectric layer 3083
The formation of the -SiO ₂ 70nm. Finally, a 0.6 mm-thick polycarbonate substrate is bonded as the bonded substrate 3091. Recording and reproduction are performed by irradiating a laser beam 3101 from the bonded substrate side. According to the above manufacturing method, a phase-change recording medium in which lattice points are present at a constant period and no metal layer exists at the lattice points can be formed.

FIG. 4 is a diagram showing the steps of a method for manufacturing a phase change recording medium according to a second embodiment of the present invention. As shown in FIG. 4A, the transfer to the quartz master and polycarbonate is the same as in the first embodiment. As shown in FIG. 4B, an Ag thin film having a thickness of 120 nm is formed on the polycarbonate substrate 4041 as the metal layer 4051. Thereafter, as in the first embodiment, grid points are formed using an "initializing device". As shown in FIG. 4C, a laser beam 4061 is irradiated through polycarbonate. The irradiation with the laser beam is performed in an oxygen atmosphere 4063. In addition, the laser beam is condensed at the convex portion 4062 and becomes higher in temperature than other portions. In the high temperature part, Ag is oxidized and AgO _x 406
It becomes 2. Since AgO _x 4062 has a higher resistance than Ag, the same effect as in the case of removing the metal layer in the first embodiment can be obtained. After lattice point formation, ZnS—SiO ₂ 20 nm is formed as a dielectric layer 4081. GeGaSbTe 20 nm is formed as the phase change recording layer 4082. The composition of the recording layer 4082 is Ge 3 At%
-Ga 7At% -Sb 65At% -Te 25At
%. ZnS—SiO ₂ as the dielectric layer 4083
A 70 nm film is formed. Finally, the bonded substrate 4091
Then, a polycarbonate substrate having a thickness of 0.6 mm is laminated. Recording and reproduction are performed by irradiating a laser beam 4101 from the bonded substrate side.

FIG. 5 is a diagram showing steps of a method for manufacturing a phase change recording medium according to a third embodiment of the present invention. As shown in FIG. 5A, a hole pattern 5042 is transferred to a polycarbonate substrate 5041. The hole diameter is 0.5 μm, the depth is 1.5 μm, and the inclination angle of the side wall is in the range of 70 to 80 °. Al as the metal layer 5051
A Ti thin film is used. A 200 nm thick AlTi film is formed. An RF sputtering apparatus was used for the film formation, the distance between the target and the substrate was 1 cm, and the film formation atmosphere was Ar 5 mTorr.
r. The distance between the target and the substrate is short and the film formation atmosphere is low in vacuum as compared with a sputtering apparatus used for manufacturing an ordinary optical disk. When a film is formed by such an apparatus, the mean free path of the sputtered particles (AlTi particles) is shortened and does not reach the bottom of the hole. As a result, the periphery of the hole has a sectional shape as shown in FIG. If the hole diameter is 0.5 μm and the Ag film thickness is 0.2 μm, a small opening having a diameter of about 100 nm remains. A ZnS—SiO ₂ film having a thickness of 50 nm is formed thereon as a dielectric layer 5061.
To form a film. Next, as the phase change type recording layer 5062, G
eSbTe is deposited to a thickness of 20 nm. Recording layer 5062
Is composed of Ge 3 At% -Sb 72 At% -Te
25 At%. Finally, as the dielectric layer 5063,
ZnS—SiO _{2 is formed} to a thickness of 50 nm. The opening remaining in the hole portion after the Ag film was formed was Zn of the dielectric layer 5061.
The G of the phase-change recording layer 5062 is blocked by S-SiO _2.
The eSbTe thin film is in a bridging state as shown. A state in which no AlTi thin film exists at the lattice point can be formed. Finally, a 0.6 mm-thick polycarbonate substrate is bonded as the bonded substrate 5071. Recording and reproduction are performed by irradiating a laser beam 5081 from the bonded substrate side.

Next, an optical recording / reproducing apparatus according to another invention will be described. First, the operation principle of the optical recording / reproducing apparatus of the present invention will be described with reference to FIG. FIG. 6A is a top view of the phase change recording medium. FIG. 6B is a characteristic diagram showing the detected light intensity when the beam spot passes.

The optical recording / reproducing apparatus according to the present invention is shown in FIG.
As shown in the figure, two tracks, Track 1 and Track 2,
Track so that it irradiates the beam
Perform tuning adjustment. During recording, the grid points on each track
In this case, marks are regularly formed. During playback, two
Load tracks simultaneously. Beams in FIG.
The pot is marked on grid point 1, grid point 2, grid point 3.
Irradiation at the same time. The characteristic diagram of FIG.
This shows the detection signal waveform when the pot is swept in the circumferential direction.
ing. The detection signals from each grid point 1, 2, 3
x₁, X₂, X ₃And it is detected out of alignment. Each grid point 1,
The values of the peaks in the detection signals from 2 and 3 are P
₁, P₂, P₃And Center of spot is above grid point 2
, And x on the graph₂Position.
Beam spot is straddling the grid points
Therefore, the detection signal at this point is the peak of the detection signal from grid point 2.
Ark P ₂Not only from neighboring grid points 1 and 2
No.P₁/ 2, P₃/ 2 is a mixed value. For this reason,
During playback, the mark information located at the center of the beam spot is
At the same time, the mark information before and after the adjacent track is also
Will be read from time to time. Therefore, the beam spot
Mark information read by the edge is in the beam spot
Interfering with the mark information read by the mind, this interference
Can be used to reproduce recorded information.
Become like Furthermore, the marker located at the center of the beam spot
The relative intensity of the read signal is 1 and the
The relative strength of the mark reproduction signal of the adjacent track
When adjusted to 1, PR (1,2,1) partial response
Detection can be performed.

FIG. 7 is a block diagram showing the configuration of an optical recording / reproducing apparatus according to the first embodiment of the present invention. The recording data generation unit 701 applies the pre-code based on the partial response method to the write data transmitted from the controller 702, thereby actually storing the optical disk 703.
Generate recording data to be written to This precode is
The operation of the following equation (1) is performed on the write data.

(1 / G (D)) mod 2 (1) D: delay operator G: transfer function of PR transmission path mod 2: modulo 2

In the optical recording / reproducing apparatus of this embodiment, PR (1,
Since the detection of the partial response method of (2, 1) is performed,
The transfer function G (D) of the PR transmission line is represented by the following equation (2).

G (D) = 1 + 2D + D ² (2)

Therefore, the actual precode is represented by the following (3)
The operation of the expression is performed on the write data.

(1 / (1 + 2D + D ² )) mod 2 (3)

The calculation of the expression (3) is performed by the optical pickup 704.
Is the inverse characteristic 1 of the correlation characteristic G (D) of the intersymbol interference when the data of the mark and the data recorded one bit before and after the mark are read out at a ratio of 2: 1 by the center and the edge of the beam spot. After addition of / G (D), it indicates that a remainder of 2 (radix of bit data) is calculated for this result. When the ratio of the light intensity between the center and the edge of the beam spot is set to one third, the transfer function G (D) is determined by PR (1,3,1) in order to perform the partial response detection. The following equation (4) is obtained.

G (D) = 1 + 3D + D ² (4)

When an isolated mark is recorded on the recording layer of the optical disc 703, the signal output by the photodetector for signal detection has a spot larger than the mark, so that the read waveforms of the marks adjacent to both sides of the read waveform are different from each other. Will be added. Therefore, this optical pickup 704
Will be subject to intersymbol interference from adjacent marks, and this intersymbol interference will enable detection of the partial response method as described above.

As shown in FIG. 7, the optical pickup 704
Is output from the equalizing circuit 705 and the clock extracting unit 706.
Sent to Here, the configuration of the equivalent circuit 705 is shown in FIG. As shown in FIG. 8, the equalizing circuit 705 includes a delay element T
And a transversal filter including a weight coefficient multiplier and an adder. The tap coefficient can be adjusted by changing the gain of each weight coefficient multiplier. The clock extracting unit 706 calculates the signal P from the signal output from the photodetector.
This is a circuit that extracts a sampling clock signal using an LL (Phase Locked Loop). Then, the equalizing circuit 70
The signal output from 5 is sent to A / D converter 707. The A / D converter 707 is a circuit that converts an analog signal output from the equalization circuit 705 into digital data, and performs sampling based on a sampling clock signal extracted by the clock extraction unit 706. Each sampling value is quantized into multi-values according to the PR system to be digital data in order to detect the partial response system. Digital data output from the A / D converter 707 is sent to a decoder 708. The decoder 708 is a circuit that performs a modulo operation on each of the multi-valued digital data, thereby detecting the original write data. The data detected by the decoder 708 is sent to the controller 702. The controller 702 performs the rotation control of the spindle motor 709 for rotating the medium, the servo control of the optical pickup 704, and the like, in addition to the input and output of data as described above.

Although the above embodiment mainly shows a phase change type optical recording system, the present invention can be similarly applied to other rewritable or write-once optical disks or read-only optical disks. In a rewritable or write-once optical disc recording / reproducing apparatus, the same type of recording can be performed by controlling the laser beam intensity of a semiconductor laser similarly to the phase change type. Furthermore, in the case of a read-only optical disk, recording in a similar format is performed when a master for forming pits and the like is created. Further, in each of the above embodiments, a phase-change type optical disk has been described. However, the present invention can be similarly applied to a light modulation type or magnetic field modulation type magneto-optical recording / reproducing apparatus. In the light modulation type magneto-optical recording / reproducing apparatus, the same type of recording can be performed by controlling the laser light intensity of the semiconductor laser for writing, as in the case of the phase change type optical disk recording method. In the case of the magnetic field modulation type, the same type of recording can be performed by controlling the magnetic field of the electromagnet while the semiconductor laser irradiates the perpendicular magnetization film with strong light.

FIG. 9 is a block diagram showing the configuration of an optical recording / reproducing apparatus according to a second embodiment of the present invention. Hereinafter, the recording / reproducing operation of the optical recording / reproducing apparatus of this embodiment will be described with reference to FIG. Here, for example will be described writing the input data sequence {a _m} such as shown in FIG. 10. This input data sequence {a _m } is usually one which has been appropriately modulated in advance.

First, the input data sequence {a _m } is sent from the controller 901 to the recording data generation unit 902,
The data is precoded and converted into a recording data sequence {b _m } by the operation of the above equation (1). (1) computation of the equation adds the inverse characteristic of the correlation characteristic G (D) of the intersymbol interference due to the spread of the beam, since it is assumed to take two of the remainder, to convert the input data a _m are already Converted recording data b
_m−2 , b b that satisfies the following expression 5 using _m−1
An operation for obtaining _m is performed.

[0048] _{b m = (a m -2b m} -1 -b m-2) mod 2 ... (5)

[0049] When converting input data _{a 7} in FIG. 10 for example, since the value of _{a 7} is 0, the recording data _b 5,
2 of which were fitted a value of 1, 1 of b ₆ (0-2 * 1-1)
May be calculated. Thus the recording data _{b 7} 1
Becomes

The pre-recorded recording data sequence {b _m } is sent to the writing LD driver in accordance with the clock signal from the clock generation unit 903, and includes the spread of the light spot in the optical pickup 904. Is recorded on the recording layer of the optical disc 905. The recording layer is a phase change material, and can change the phase state of the recording layer by heat due to light irradiation, thereby forming an amorphous state and a crystalline state. At the time of data writing, since writing is performed using only the portion of the center of the main spot of the LD light where the temperature rises the most, even if the beam spot is spread, it does not contribute to writing. Therefore, it is possible to switch between writing and reading by changing the optical power with the same head, so that it is not necessary to prepare two heads for writing and reading.

The recording data sequence {b _m } recorded on the recording layer of the optical disc 905 is read out by the optical pickup 904, and after the waveform is equalized by the equalization circuit 906,
A / D converter 908 converts the digital data into a reproduced data sequence {x _m }. Since the reproduced data sequence {x _m } is obtained by adding reproduction signals of adjacent bits due to the spread of the spot at a rate of 1/2, the following formula (6) is added to the recorded data sequence {b _m }. Is calculated.

[0052]

(Equation 1)

Specifically, PR (1,2,1), that is, N
= 3, (g ₀ , g ₁ , g ₂ ) = ( ₁ , ₂ , ₁ )

X _m = b _m−4 + 2b _m−2 + b _m (7)

The reproduced data _{x 7} in FIG. 10, for example, since the recording data _{b 5, b 6, b 7} is 1,1,1 respectively, a value of 4 (= 1 + 2 * 1 + 1). That is,
Here, the digital data of 5 values reproduced data sequence {x _m} has a value of 0-4.

It is read out as digital data having a value of 5,
Playback data sequence ｛x_m｝ Is sent to the decoder 909.
You. This reproduced data series ｛x_m｝ Is taken modulo 2,
Binary output data sequence ｛d_mConverted to｝. Therefore,
Output data d₇Is 4mod2 = 0. Recording data system
Column ｛b_m｝ Is the input data sequence ｛a_m｝ Shows the correlation characteristic G
This is obtained by adding the inverse characteristic of (D) and then taking the remainder of 2.
Because of this, the reproduced data series that offset this correlation characteristic
｛X_mAn output data sequence ｛d obtained by taking the remainder of 2 of｝_m｝
Is the original input data sequence ｛a_mMatches｝. And
This output data series ｛d _mIs sent to the controller 901
Can be As a result, the optical recording / reproducing apparatus of this embodiment
Read the data of the mark smaller than the size of the
Read signal of mark of adjacent track generated when
Active use of interference to detect original data
be able to. This allows conventional optical pickups to be used.
Record marks smaller than the beam spot using
Layer, and record and replay two tracks simultaneously.
It is possible to realize an ultra-high-density optical recording / reproducing device.
You.

Next, in a reproduced signal processing system of the PRML system, a Viterbi decoder, which is a typical one of the maximum likelihood decoders, is generally used as a detector arranged after an equalizer. Assuming that the reproduced waveform is equalized to the PR characteristic by the equalizer, the Viterbi decoder selects a sequence having the smallest error from the sample sequence of the equalized waveform from all the sequences satisfying the PR characteristic, and selects the sequence. It outputs binary data (decoded data) corresponding to the sequence. In the PRML method, decoding is performed not from one sample value but from a plurality of sample values, so that the resistance to a signal degradation component having no correlation between the sample values is strong.

The maximum likelihood decoding method using the Viterbi decoder according to the present invention will be described below. FIG. 11 is a block diagram showing a configuration of an optical recording / reproducing apparatus according to a third embodiment of another invention. FIG.
FIG. 2 is a block diagram showing the configuration of the Viterbi decoder of FIG. 11, the same reference numerals as those in FIG. 9 indicate the same components. As a different component, the optical recording / reproducing apparatus of the present embodiment is provided with a Viterbi decoder 1101 instead of the decoder 909 in the optical recording / reproducing apparatus of the second embodiment shown in FIG. In this embodiment, since the PR (1, 2, 1) partial response method is detected, the Vidabi decoder 1
The decoding method in 101 is PR (1, 2, 1), and a Viterbi decoder 1101 that performs Viterbi decoding (maximum likelihood decoding) corresponding to PR (1, 2, 1) is used. Here, consider the reproduced data sequence {x _m } shown in FIG. This reproduced data sequence {x _m } is 3, 3, 2,
.. Are composed of a sequence of five-value data of 2, 1, 1, 3, 4, 3,..., And each sample value can take a value from 0 to 4. However, since each sample value has a PR (1,2,1) correlation with the previously read sample value, when a certain sample value is determined, the next sample value becomes all values of 0 to 4. Cannot transition to This is shown in FIG. 13 by PR (1,
A description will be given with reference to a state transition diagram of (2, 1) (PR2). The eight ellipses in FIG. 13 indicate a data state having eight states, and the three-digit numerical value inside the ellipse represents three bits of the recording data sequence {b _m }. The arrow represents a path that transitions from one state to the next, and cannot transition to a state without an arrow. The numerical values from 0 shown next to the arrows to 4 show the detected sample value x _m. For example, if the detected sample value _{X 0} is 3, the pattern of the recording data series _{{b m}} is (0,1,1) or (1,1,0)
This is one of the cases. Therefore, the pattern of the recording data sequence {b _m } corresponding to the next sample value is (1, 1,
0), (1,1,1), (1,0,0) or (1,0,1)
And the next sample value cannot transition to zero. The next sample value X ₁ is 3, the transition from the sample value 3 to 3 from data state (0,1,1)
(1,1,0) because only can not happen, the recording data B ₁ represents 0 and uniquely determined. The next X ₂ is 2, the next data state is (1, 0, 1), and b ₂ is 1. By performing such decoding sequentially,
The decoding result is 1,0,1,0,0,1,1,1,0..., Which indicates that it matches the recording data sequence {b _m }. Therefore, such a reproduced data sequence {x _m } can be detected by the Viterbi decoding method.

The Viterbi decoder 1101 shown in FIG.
, An addition / comparison / selection unit (hereinafter referred to as an ACS unit) 1101-1 that performs an operation for each state of the trellis transition diagram
And the path (route) selected by the ACS unit 1101-1
And a maximum likelihood path selection circuit (hereinafter referred to as an MLD circuit) 1101-3 for selecting one path from the paths stored in the path memory circuit 1101-2. Have been. Here, a case will be described in which a four-state trellis transition diagram is traced using four ACS units 1101-1. Further, from the state calculated by the ACS unit 1101-1, it is possible to make a transition only to the own state or the state of the ACS unit.
From the status of the CS unit, the status of its own or a specific ACS
It is assumed that transition can be made only to the state of the section.

When decoding by the Viterbi decoding method, A
In general, the / D converter quantizes data not only to five values but also more finely. Ideally, the quantized data output from the A / D converter is quinary data, but it has a width due to the influence of waveform distortion and noise. The quantized data is input to the branch metric calculation circuit 1101-11 of each ACS unit 1101-1. Each branch metric calculation circuit 1101-11 calculates the likelihood (branch metric) for the state transition from the difference between the input quantized data and the value indicated by its own state. This branch metric is added to the certainty (path metric) of the past state transition path by the adding unit. The path metric is the sum of the branch metrics in each past state of the path,
The nearer the pass of the actually read quantized data, the smaller the value. The path metric added here is the path metric up to the previous time stored in the path metric memory of the ACS unit that can transition to the ACS unit.

When one piece of quantized data is input to the Viterbi decoder 1101, the ACS units 1101
Since the path from two directions transitions to −1, the comparison unit compares the two path metrics calculated by these addition units at this time, and the selection unit has a smaller value according to the comparison result. The more (more likely) path metric is stored in the path metric memory. Further, the path selection unit selects a path having a smaller path metric, that is, a path that is most likely, and stores quantized data indicating this path in the path memory. Therefore, the path whose state has changed is stored in the path memory.

When a specified number of quantized data is input, the path with the smallest path metric (the maximum likelihood path) is selected by the maximum likelihood path selection unit from the four paths stored in the path memory. By selecting the maximum likelihood path, the path of the state transition is determined, and a bit data string that causes the state transition is output as a decoded data string. Therefore,
Even if an error is included in the reproduced data sequence {x _m } due to the influence of noise or the like, it can be decoded into the most probable data sequence. The data decoded by the Viterbi decoder as described above is output to the controller as an output data sequence {d _m }.

As a result, according to the optical recording / reproducing apparatus of the present embodiment, the data recorded on the optical disc is
That is, since reproduction can be performed by a method combining the partial response method and the maximum likelihood decoding method (Viterbi decoding method), the S / N can be improved by error correction.

In the optical recording / reproducing apparatus of the present embodiment, as shown in FIG. 6A, tracking adjustment is performed so that a beam is applied so as to extend over two tracks, track 1 and track 2. At the time of recording, the power level of the write pulse is switched to r levels, and multi-value recording of r values is performed.
Marks are regularly formed on grid points on each track. During playback, two tracks are read simultaneously.
The beam spot in FIG. 6A irradiates the marks on the lattice points 1, 2, and 3 at the same time. The graph of FIG. 6B is a diagram showing a detection signal waveform when the beam spot is swept in the circumferential direction. Each grid point 1,
Detection signals from the 2 and 3 are detected offset and positionally _{x 1, x 2, x 3} . The peak values in the detection signals from the lattice points ₁ , ₂ , and ₃ are defined as P1, P2, and P3, respectively. When the center of the spot coincides with the grid point 2, it is located at x ₂ on the graph, but since the beam spot is irradiated over the grid point, the detection signal at this point is not only the peak _{P 2} of the detection signal, a signal _{P 1/2,} the _{value P} 3/2 is mixed from grid points 1 and 2 adjacent. For this reason, at the time of reproduction, the mark information located at the center of the beam spot and the mark information before and after the adjacent track are read at the same time. Therefore, the mark information read by the edge of the beam spot interferes with the mark information read by the center of the beam spot, and the recorded information can be reproduced by positively utilizing the interference. Further, the relative intensity of the mark reproduction signal located at the center of the beam spot is set to 1
When the relative intensity of the mark reproduction signal of the adjacent track due to the beam spot edge is adjusted to half, the PR
(r, 2r, r) partial response detection can be performed.

In FIG. 7, a print data generation unit 701
Generates a record data to be actually written on the optical disc 703 by applying a pre-code by a partial response method to the write data sent from the controller. This precode is for performing an operation of the following equation (8) on write data.

(1 / G (D)) mod r (8) D: delay operator G: transfer function of PR transmission line mod r: remainder of r

In the optical recording / reproducing apparatus of this embodiment, the PR
Since the (r, 2r, r) partial response method is detected, the transfer function G (D) of the PR transmission line is given by the following (9)
It looks like an expression.

G (D) = 1 + 2D + D ² (9)

Therefore, the actual precode is as follows (1)
The operation of expression (0) is performed on the write data.

(1 / (1 + 2D + D ² )) mod r (10)

The calculation of the expression (10) is based on the code when the optical pickup reads the data of the mark and the data recorded one bit before and after the mark at a ratio of 2: 1 by the center and the edge of the beam spot. Interference correlation characteristic G
After adding the inverse characteristic 1 / G (D) of (D), the remainder of r (radix of bit data) is calculated for this result. When the ratio of the light intensity between the center and the edge of the beam spot is reduced to one third, the transfer function G (D) is determined by the PR (r, 3r, r) in order to perform the partial response detection. The following equation (11) is obtained.

G (D) = 1 + 3D + D ² (11)

When an isolated mark is recorded on the recording layer of the optical disk, the signal output from the signal detecting photodetector has a spot larger than the mark. Will be done. Therefore, the signal output from the optical pickup is subject to intersymbol interference from adjacent marks, and the intersymbol interference enables detection of the partial response method as described above.

As shown in FIG. 7, the output signal of the optical pickup is sent to an equalizing circuit 705 and a clock extracting unit 706. As shown in FIG. 8, the equalizing circuit 705 includes a delay element T
And a transversal filter including a weight coefficient multiplier and an adder. The tap coefficient can be adjusted by changing the gain of each weight coefficient multiplier. The clock extracting unit 706 calculates the signal P from the signal output from the photodetector.
This is a circuit that extracts a sampling clock signal using an LL (Phase Locked Loop). Then, the equalizing circuit 70
The signal output from 5 is sent to A / D converter 707. The A / D converter 707 is a circuit that converts an analog signal output from the equalization circuit 705 into digital data, and performs sampling based on a sampling clock signal extracted by the clock extraction unit 706. Each sampling value is quantized into multi-values according to the PR system to be digital data in order to detect the partial response system.

The digital data output from the A / D converter 707 is sent to a decoder 708. The decoder 708 is a circuit that performs the operation of the remainder of r on the multi-valued digital data, thereby detecting the original write data. Then, the data detected by the decoder is sent to the controller 702. The controller 702 performs the rotation control of the spindle motor for rotating the medium, the servo control of the optical pickup, and the like, in addition to the input and output of data as described above.

The recording / reproducing operation of the optical disk recording / reproducing apparatus will be described with reference to FIG. For example, a case where an input data sequence {a _m } as shown in FIG. 10 is written will be described. This input data sequence {a _m } is usually one which has been appropriately modulated in advance.

First, the input data sequence {a _m } is sent from the controller to the recording data generation unit, and is pre-coded by the operation of the above equation (8), and the recording data sequence {b _m }
Is converted to (8) calculating the expression, since it is intended to take the remainder of adding an inverse characteristic of the correlation characteristic G (D) of the intersymbol interference due to the spread of the spot r, to convert the input data a _m are already Converted recording data b _m−2 , b
_An operation for obtaining b _m that satisfies the following equation (12) is performed using _m−1 .

[0078]

(Equation 2)

G _n : weight coefficient of each tap N: data length

The recording data sequence {b _m } thus pre-coded is sent to the writing LD driver in accordance with the clock signal from the clock generation unit, and the optical disk is formed so as to include the spread of the light spot in the optical pickup. Is recorded on the recording layer.

The recording layer is a phase change material, and can change the phase state of the recording layer by heat due to light irradiation to form an amorphous state and a crystalline state. At the time of data writing, since writing is performed using only the portion of the center of the main spot of the LD light where the temperature rises the most, even if the beam spot is spread, it does not contribute to writing. Therefore, it is possible to switch between writing and reading by changing the optical power with the same head, so that it is not necessary to prepare two heads for writing and reading. Recording data series {b _m} recorded in the recording layer of the optical disk is read by an optical pickup, after being equalized waveform equalization circuit, reproducing data series of digital data by the A / D converter {x _m Converted to｝. Since the reproduced data sequence {x _m } is obtained by adding the reproduction signal of the adjacent bit at half the ratio due to the spread of the spot, the recorded data sequence {b _m } can be expressed by the following equation (13). This is the result of the calculation.

[0082]

(Equation 3)

Read as multi-valued digital data
Reproduction data series ｛x_m｝ Is sent to the decoder. this
Reproduction data series ｛x_m｝ Is the remainder of r,
Force data series ｛d_mConverted to｝. Record data series
｛B_m｝ Is the input data sequence ｛a _m｝ Shows the correlation characteristic G (D)
Is obtained by adding the inverse property of and then taking the remainder of r.
Therefore, the reproduced data series ｛x in which the correlation characteristic has been canceled_m｝
Output data series ｛d obtained by taking the remainder of r_m｝
Force data series ｛a_mMatches｝. And this output data
Data series ｛d_m｝ Is sent to the controller.

As a result, the optical disk recording / reproducing apparatus of this embodiment actively utilizes the interference of the read signal of the mark of the adjacent track generated when the data of the mark smaller than the size of the beam spot is read, to recover the original data. It can be used for data detection. As a result, a mark smaller than the beam spot can be written on the recording layer by using the conventional optical pickup as it is, and recording and reproduction can be performed simultaneously on two tracks, so that an ultra-high-density optical recording / reproducing apparatus can be realized.

The present invention is not limited to the above embodiment, and needless to say, various modifications and substitutions can be made within the scope of the claims.

[0086]

As described above, according to the phase change recording medium of the present invention, which is composed of at least a support substrate, a metal layer, and a recording layer, information marks are periodically present on the storage medium. It is characterized in that it is recorded so as to coincide with the lattice points to be arranged, and the arrangement period of the lattice points is opposite to each other between adjacent tracks. Therefore, information can be recorded / reproduced every two tracks in phase change recording.

The recording medium is a disk-shaped recording medium, and the arrangement of lattice points in the circumferential direction preferably has a constant period.

Further, the size of the lattice point is preferably smaller than the diameter defined by 1 / e ^ 2 of the laser beam used for recording / reproducing.

It is preferable that the metal layer does not exist at the lattice points.

Further, it is preferable that at least one oxide, nitride, fluoride or sulfide of at least one element constituting the metal layer exists at the lattice point.

It is preferable that the coverage of the metal layer at the lattice points is lower than that at the parts other than the lattice points.

Further, the metal layer is made of Al, Ti, Cu, Zn,
Ge, Pd, Ag, In, Sn, Sb, Te, Pt, A
It is preferable to contain at least one element selected from the group consisting of u, Tl, and Bi.

The SbTe used as the composition of the recording layer
Is preferably in the range of 1.5 to 4.

Further, the recording layer is made of Ge, In, Ga, Ag,
It is preferable to contain at least one element selected from the group consisting of Si, Al and B.

An optical recording / reproducing apparatus according to another aspect of the present invention irradiates the above-mentioned phase-change type recording medium with a laser beam so that two tracks are simultaneously included in the irradiation range, and records / reproduces information marks. There is a feature. Therefore, an optical recording / reproducing apparatus capable of recording / reproducing information for every two tracks can be provided.

Further, by modulating the intensity of the laser beam at least two levels or more at a period of の of the arrangement period of the lattice points in the track direction of the phase change recording medium and recording information, the positions of the lattice points are recorded. The recording position of the recording mark can be controlled to the same degree as the accuracy.

Also, an optical pickup having an information reproducing means for reproducing a recorded information sequence recorded on an optical disk using an optical spot, and an information sequence inputted from outside, and an interference code at the time of recording added to the information sequence Then, for each unit information of the information sequence to which the interference code at the time of recording has been added, a precoding means for calculating the remainder of the radix of the first information sequence and converting the information sequence into a recorded information sequence,
The interfering code during recording compensates for the intersymbol interference that occurs when the recorded information sequence is reproduced, so that the mark information read by the beam spot edge interferes with the mark information read by the beam spot center. Thus, the recorded information can be reproduced.

Further, for each unit information of a reproduced information sequence obtained by adding an interference code generated when the recorded information sequence is reproduced to the recorded information sequence, a decoding means for calculating a remainder based on a radix of the input information sequence. By using the conventional optical pickup, a mark smaller than the beam spot can be written on the recording layer using the conventional optical pickup as it is, and an ultra-high-density optical recording / reproducing apparatus capable of simultaneously recording and reproducing two tracks can be provided.

Further, the apparatus has a decoding unit based on the PRML system for each unit information of the reproduction information sequence obtained by adding an interference code generated when the recording information sequence is reproduced to the recording information sequence, and By having maximum likelihood decoding means for performing decoding by the maximum likelihood decoding method, S / N can be improved by error correction.

Further, an optical recording / reproducing apparatus according to another aspect of the present invention includes an optical pickup having information reproducing means for reproducing a recorded information sequence recorded on an optical disk by using an optical spot, and an information sequence inputted from the outside, After adding the interference code at the time of recording to the information sequence, for each unit information of the information sequence to which the interference code at the time of recording is added, 2 units of the first information sequence
A precoding means for calculating a remainder based on a larger radix and converting the information sequence into a recording information sequence, wherein an interference code at the time of recording compensates for intersymbol interference generated when the recording information sequence is reproduced. Therefore, the recorded information can be reproduced by the mark information read by the beam spot edge interfering with the mark information read by the beam spot center.

Further, for each unit information of the reproduced information sequence obtained by adding an interference code generated when the recorded information sequence is reproduced to the recorded information sequence, the remainder of the input information sequence by a radix greater than 2 is calculated. With such a decoding means, it is possible to provide an ultra-high-density optical recording / reproducing apparatus capable of writing a mark smaller than the beam spot on the recording layer using the conventional optical pickup as it is, and capable of simultaneously recording and reproducing two tracks.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a phase change recording medium according to one embodiment of the present invention.

FIG. 2 is a diagram showing a state of recording / reproducing with respect to the phase change recording medium of FIG.

FIG. 3 is a diagram showing steps of a method for manufacturing a phase change recording medium according to the first embodiment of another invention.

FIG. 4 is a diagram showing steps of a method for manufacturing a phase change recording medium according to a second embodiment of another invention.

FIG. 5 is a diagram showing steps of a method for manufacturing a phase change recording medium according to a third embodiment of another invention.

FIG. 6 is a diagram illustrating the operation principle of an optical recording / reproducing apparatus according to another invention.

FIG. 7 is a block diagram illustrating a configuration of an optical recording / reproducing apparatus according to a first embodiment of another invention.

FIG. 8 is a diagram illustrating a configuration of an equivalent circuit of FIG. 7;

FIG. 9 is a block diagram showing a configuration of an optical recording / reproducing apparatus according to a second embodiment of another invention.

FIG. 10 is a diagram showing an input data sequence and a reproduced data sequence.

FIG. 11 is a block diagram showing a configuration of an optical recording / reproducing apparatus according to a third embodiment of another invention.

FIG. 12 is a block diagram illustrating a configuration of the Viterbi decoder of FIG. 11;

FIG. 13 is a state transition diagram of PR (1,2,1) (PR2).

[Explanation of symbols]

101; support substrate, 102; metal layer, 103, 105;
Dielectric layer or protective layer, 104; recording layer, 106; bonded substrate, 107; laser beam, 108; data area, 109; control area, 1021;
2: tracking signal generation sources, 1041, 1042; grid points.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 7/0045 G11B 7/005 B 7/005 7/007 7/007 B41M 5/26 X F term (Reference) 2H111 EA23 FA01 FA11 FA23 FB05 FB17 FB20 FB21 5D029 JA01 JB16 MA28 PA03 PA04 5D090 AA01 BB05 CC06 DD01 EE11 FF22 GG22 GG28 HH01 KK01 KK03

Claims (16)

[Claims] At least in a phase change type recording medium composed of at least a support substrate, a metal layer, and a recording layer, information marks are recorded so as to coincide with lattice points periodically existing in the storage medium. Are arranged in opposite phases between adjacent tracks. 2. The phase-change recording medium according to claim 1, wherein the recording medium is a disk-shaped recording medium, and an arrangement of lattice points in a circumferential direction has a constant period. 3. The phase-change recording medium according to claim 1, wherein the size of the lattice point is smaller than a diameter defined by 1 / e ^ 2 of a laser beam used for recording / reproducing. 4. The phase change recording medium according to claim 1, wherein the metal layer does not exist at the lattice points. 5. The phase-change recording medium according to claim 1, wherein at least one oxide, nitride, fluoride, or sulfide of at least one element constituting the metal layer is present at the lattice points. 6. The phase-change recording medium according to claim 1, wherein the coverage of the metal layer at the lattice points is lower than that at a portion other than the lattice points. 7. The metal layer is made of Al, Ti, Cu, Zn,
Ge, Pd, Ag, In, Sn, Sb, Te, Pt, A
The phase-change recording medium according to any one of claims 1 to 6, comprising at least one element selected from the group consisting of u, Tl, and Bi. 8. SbTe used as a composition of the recording layer
2. The phase-change recording medium according to claim 1, wherein the Sb / Te ratio is in the range of 1.5 to 4. 9. The recording layer according to claim 1, wherein the recording layer is Ge, In, Ga, Ag,
The phase-change recording medium according to claim 1, wherein the recording medium contains at least one element selected from the group consisting of Si, Al, and B. 10. A light beam for irradiating a laser beam to the phase change recording medium according to claim 1 or 2 so as to be included in an irradiation range at the same time for two tracks to record / reproduce an information mark. Recording and playback device. 11. The optical recording according to claim 10, wherein the information is recorded by modulating the intensity of the laser beam at least at two levels or more at a half of the arrangement period of the lattice points in the track direction of the phase change recording medium. Playback device. 12. An optical pickup having an information reproducing means for reproducing a recorded information sequence recorded on an optical disk by using an optical spot, receiving an information sequence inputted from the outside, and adding an interference code at the time of recording to the information sequence. Precoding means for calculating the radix of the first information sequence for each unit information of the information sequence to which the interference code at the time of recording has been added, and converting the information sequence into a recording information sequence. The optical recording / reproducing apparatus according to claim 10, wherein the interfering code at the time of recording compensates for intersymbol interference generated when the recorded information sequence is reproduced. 13. For each unit information of a reproduced information sequence obtained by adding an interference code generated when a recorded information sequence is reproduced to the recorded information sequence, a remainder based on a radix of the input information sequence is calculated. 2. The method according to claim 1, further comprising decoding means.
3. The optical recording and reproducing apparatus according to 2. 14. A unit according to a PRML system for each unit information of a reproduced information sequence obtained by adding an interference code generated when the recorded information sequence is reproduced to the recorded information sequence, and 13. The optical recording / reproducing apparatus according to claim 12, wherein the means includes maximum likelihood decoding means for performing decoding by a maximum likelihood decoding method. 15. An optical pickup having an information reproducing means for reproducing a recorded information sequence recorded on an optical disk using a light spot, receiving an information sequence inputted from outside, and adding an interference code at the time of recording to the information sequence. Then, for each unit information of the information sequence to which the interference code at the time of recording has been added, a precoding means for calculating the remainder of the first information sequence by a radix greater than 2 and converting the information sequence into a recording information sequence is provided. The optical recording / reproducing apparatus according to claim 11, wherein the interfering code at the time of recording compensates for intersymbol interference generated when the recorded information sequence is reproduced. 16. For each unit information of a reproduced information sequence obtained by adding an interference code generated when a recorded information sequence is reproduced to the recorded information sequence, a remainder of the input information sequence by a radix greater than 2 is obtained. 16. The optical recording / reproducing apparatus according to claim 15, further comprising: decoding means for calculating the following.