A general architecture that implements the various feature of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the invention and not to limit the scope of the invention.
Various embodiments according to the invention will be described hereinafter with reference to the accompanying drawings. In general, according to one embodiment of the invention, in a recording medium which has a substrate and a stacked structure including an interference film, a recording film capable of changing an atomic arrangement reversibly, a crystallization enhancing film in contact with the recording film, and a reflecting film and which enables the recording film to be recorded into or erased from reversibly with light, an optical recording medium is characterized by being so configured that the elements constituting the recording film have a segregation or a concentration distribution in the direction of the thickness of the recording film from a region in contact with the recording film, or in the in-plane direction of the recording film.
Hereinafter, referring to the accompanying drawings, embodiments of the invention will be explained.
The stacked structure (19) of the L0 information layer also assumes the role of a dielectric film (ZnS—SiO2 or the like: 17a) where the third interference layer contributes to optical enhancement and/or thermal diffusion.
An ultrathin oxide film 21a is formed to a specific thickness (an average thickness of about 0.1 nm to 1.0 nm) on at least one (preferably both) of the upper and lower surfaces of the L0 recording film 13a. An ultrathin oxide film 21b is formed to a specific thickness (an average thickness of about 0.1 nm to 1.0 nm) on at least one (preferably both) of the upper and lower surfaces of the L1 recording film 13b. These ultrathin oxide films 21a, 21b are made up of the same constituent elements (Ge, Te, and the like) as those of the recording films 13a, 13b.
In
The configuration of the phase-change recording medium of the embodiment is not limited to what is shown in
In the case of a two-layer medium as shown in
Furthermore, the medium may be such that various films are formed on the substrate 1a and/or 1b and, to the resulting film, a thin transparent sheet (not shown) of about 0.1 mm thick is laminated, and light is caused to enter via the transparent sheet (this type of medium is based on the assumption that an objective lens with a high NA of about 0.85 is used). The reason is that, even if a thin transparent cover layer of about 0.1 mm thick is used on the light incident side, this doesn't make much difference to the characteristics required for the recording film, interface layer material, protective film material, and reflecting film material used in the embodiment of
In the embodiment, a preferred optical recording medium (or phase-change optical disk) has the following configuration and/or characteristics.
<1> A recording medium (100) which has a substrate (1a, 1b) and a stacked structure (19, 20) that includes an interference layer (protective film or dielectric film: 11a, 11b), a recording film (13a, 13b) capable of changing an atomic arrangement reversibly, a crystallization enhancing film (12a, 12b/14a, 14b) in contact with the recording film, and a reflecting film (16a, 16b) and which enables the recording film (13a, 13b) to be recorded into or erased from reversibly with light, the recording medium being so configured that the elements (including Ge and Te) constituting the recording film (13a, 13b) have a segregation or a concentration distribution in the direction of the thickness of the recording film (or in the vertical direction of
<2> In the region (place 21a, 21b) in contact with the recording film (13a, 13b), there is provided an ultrathin oxide film (21a, 21b) with an average thickness of 0.1 nm or more and 1 nm or less made up of the constituent elements (including Ge and Te) of the recording film (13a, 13b).
<3> The stacked structure (19) includes a dielectric film (ZnS—SiO2 or the like: 11a, 15a, 17a) which contributes to optical enhancement and/or thermal diffusion.
<4> The interference film (protective film or dielectric film: for example, 11b of
<5> The optical recording medium is so configured that the ratio of the DOS of the crystalline state to the DOS of the amorphous state (the DOS of the crystalline state/the DOS of the amorphous state: for example, au11/au12 in
<6> The optical recording medium is so configured that the ratio of the DOS of the crystalline state to the DOS of the amorphous state (the DOS of the crystalline state/the DOS of the amorphous state: for example, au13/au14, au15/au16 in
<7> The optical recording medium is so configured that the crystallization enhancing film (12a, 12b/14a, 14b) is composed of an upper interface film (14a, 14b) in contact with one face of the recording film (13a, 13b) and a lower interface film (12a, 12b) in contact with the other face of the recording film (13a, 13b) and the upper interface film (14a, 14b) and lower interface film (12a, 12b) are so controlled that the crystallization speed over the recording film (13a, 13b) differs from that under the recording film (13a, 13b).
<8> The optical recording medium is so configured that the crystallization enhancing film (12a, 12b/14a, 14b) is composed of an upper interface film (14a, 14b) in contact with one face of the recording film (13a, 13b) or a lower interface film (12a, 12b) in contact with the other face of the recording film (13a, 13b) and the upper interface film (14a, 14b) and lower interface film (12a, 12b) are so controlled that the crystallization speed over the recording film (13a, 13b) differs from that under the recording film (13a, 13b).
<9> The crystallization enhancing film (12a, 12b/14a, 14b) may be configured to include germanium nitride (GeN), germanium-chrome nitride (GeCrN), zirconium oxide (ZrO2), stabilized zirconia+chrome oxide (ZrO2+Cr2O3), stabilized zirconia+silicon oxide+chrome oxide (ZrO2+SiO2+Cr2O3), zircon+chrome oxide (ZrSiO4+Cr2O3), or hafnium oxide (HfO2). Alternatively, the crystallization enhancing film may be composed of a compound (HfO2-xNx) containing hafnium (Hf), oxygen (O), and nitrogen (N). Alternatively, the crystallization enhancing film may be composed of a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y where z=0) containing zirconium (Zr), oxygen (O), nitrogen (N), and yttria (Y). Alternatively, the crystallization enhancing film may be composed of a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y where z=1) containing zirconium (Zr), oxygen (O), nitrogen (N), and niobium (Nb). Alternatively, the crystallization enhancing film may be composed of a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y where 0≦z≦1) containing zirconium (Zr), oxygen (O), nitrogen (N), yttria (Y), and niobium (Nb). Alternatively, the crystallization enhancing film may be configured to include chrome oxide (Cr2O3), zinc oxide (ZnO), zinc oxide+tantalum oxide (ZnO+Ta2O5), zinc oxide+tantalum oxide+indium oxide (ZnO+Ta2O5+In2O3), tin oxide (SnO2), tin oxide+antimony oxide (SnO2+Sb2O3), tin oxide+tantalum oxide (SnO2+Ta2O5), or tin oxide+niobium oxide (SnO2+Nb2O5).
Here, zirconium oxide (ZrO2) in the embodiment is referred to as stabilized zirconium, usually expressed as ZrO2+Y2O3. The concentration of Y2O3 may be about 3 to 5 mol. %. The stabilized zirconium is not limited to ZrO2+Y2O3. For instance, ZrO2+Nb2O5 or ZrO2+MgO may be used as the stabilized zirconium. Use of only ZrO2 permits a rapid change in the thermal expansion coefficient due to phase transition of the crystal structure caused by temperature change, which causes various problems. Here, zirconium oxide (ZrO2) improved variously to alleviate the problems or virtually avoid them is referred to as stabilized zirconium.
<10> One of the upper interface film (14a, 14b) and lower interface film (12a, 12b) between which the recording film (13a, 13b) is sandwiched may be configured to include germanium nitride (GeN), germanium-chrome nitride (GeCrN), zirconium oxide (ZrO2), stabilized zirconia+chrome oxide (ZrO2+Cr2O3), stabilized zirconia+silicon oxide+chrome oxide (ZrO2+SiO2+Cr2O3), zircon+chrome oxide (ZrSiO4+Cr2O3), or hafnium oxide (HfO2). Alternatively, the upper or lower crystallization enhancing film may be composed of a compound (HfO2-xNx:0.1≦x≦0.2) containing hafnium (Hf), oxygen (O), and nitrogen (N). Alternatively, the upper or lower crystallization enhancing film may be composed of a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y) where z=0) containing zirconium (Zr), oxygen (O), nitrogen (N), and yttria (Y). Alternatively, the upper or lower crystallization enhancing film may be composed of a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y) where z=1) containing zirconium (Zr), oxygen (O), nitrogen (N), and niobium (Nb). Alternatively, the upper or lower crystallization enhancing film may be composed of a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y) where 0≦z≦1) containing zirconium (Zr), oxygen (O), nitrogen (N), yttria (Y), and niobium (Nb).
The other of the upper interface film (14a, 14b) and lower information film (12a, 12b) may be configured to include chrome oxide (Cr2O3), zinc oxide (ZnO), zinc oxide+tantalum oxide (ZnO+Ta2O5), zinc oxide+tantalum oxide+indium oxide (ZnO+Ta2O5+In2O3), tin oxide (SnO2), tin oxide+antimony oxide (SnO2+Sb2O3), tin oxide+tantalum oxide (SnO2+Ta2O5), or tin oxide+niobium oxide (SnO2+Nb2O5).
<11> The recording film (13a, 13b) may be configured to include germanium (Ge), antimony (Sb), and tellurium (Te) and, when its composition is expressed as GexSbyTez where x+y+z=100, to have a composition in (A1 of
<12> 1 to 5 at. % of nitrogen (N) may be added to a GeSbTe-series compound with the above composition.
<13> The recording film (13a, 13b) may be configured to include at least germanium (Ge), bismuth (Bi), and tellurium (Te) and, when its composition is expressed as GexBiyTez where x+y+z=100, to have a composition in (A2 of
<14> 1 to 5 at. % of nitrogen (N) may be added to a GeBiTe-series compound with the above composition.
<15> When a part of the composition of the recording film (13a, 13b) is replaced with bismuth (Bi) and/or indium (In) and/or tin (Sn) and the composition after the replacement is expressed as (Ge(1−w) Snw)×(Sb(1−v)(Bi(1−u)Inu)v)yTez where x+y+z=100, the recording film may be so configured that w, v, and u in the composition satisfy the following: 0≦w≦0.5 and 0≦v≦0.7 and 0≦u≦1.
<16> 1 to 5 at. % of nitrogen (N) may be added to a GeSnSbTe, a GeSnSbTeIn, a GeSbTeIn, a GeSbTeBiIn, a GeSbSnTeBiIn, a GeSbTeBi, a GeSbTeIn, a GeSnSbTeBi, and a GeSnSbTeBiIn series compound with the above composition.
Hereinafter, embodiments of a single-sided, dual-layer medium will be explained. In the measured data on a trial optical disk, the worst experimental values are shown as representative values in each of the lands (L) and grooves (G) of L0 and L1. The transmittance, reflectivity, and others of the trial optical recording medium were measured using a spectrophotometer. The concentration of each element in the thin film was measured using an analytical method, such as ICP (Induced Coupled Plasma), RBS (Rutherford back scattering), SIMS (Secondary Ion Mass Spectroscopy), TOF-SIMS, or XPS (X-ray photoelectron spectroscopy analysis). The atomic binding form in the film was clarified by XPS, IR (infrared spectroscopy) measurement, or the like. The thermal conductivity and thermal diffusivity of the thin film and the interface thermal resistance between stacked thin films were evaluated using a thermoreflectance method. The DOS for the valance band of the recording film can be measured using XPS, UPS, or HX-PES (Hard X-ray Photo Electron Spectroscopy) techniques. Information on the state density can be obtained by measuring the electronic specific heat.
In the embodiment, the DOS for the valance band of the recording film is measured mostly by the HX-PES (Hard X-ray PhotoElectron Spectroscopy) method or XPS method. In measuring the DOS for the valance band of the recording film using the HX-PES method, a sample shown in
The energy of the top of the DOS for the valance band corresponds to Fermi energy in a conductor. In the case of a semiconductor, the Fermi energy lies almost in the middle of the band gap between the valance band and the conduction band. Depending on whether impurities acting as acceptors are doped or impurities acting as donors are doped, a semiconductor may form a localized level, with the result that the Fermi potential goes up and down slightly.
A method of controlling the ratio of the DOS of the crystalline state to the DOS of the amorphous state (the DOS of the crystalline state/the DOS of the amorphous state) at an energy level lower than the top of the DOS for the valence band of the recording film in the crystalline state and amorphous state includes (i) changing slightly the composition of the recording film in the direction of its thickness, (ii) selecting suitably interface layer materials provided over and under the recording film and changing elements doped in minute amounts from the interface layer to the recording film (micro reaction), and (iii) providing an ultrathin oxide film whose average thickness is 0.1 nm or more and 1 nm or less and which is made up of the elements constituting the recording film in a region in contact with the recording film.
Furthermore, the crystallization speed over the recording film can be made different from that under the recording film by (i) changing slightly the composition of the recording film in the direction of its thickness and/or (ii) selecting suitably interface layer materials provided over and under the recording film and changing elements doped in minute amounts from the interface layer to the recording film.
For example, in a micro segregation model, when there is a segregation in the element Ge in a GeSbTe-series film, it is presumed that a part having much Ge and a part having less Ge, or a part having few of the other elements (including Sb and Te) and a part having many of the other elements are at the nucleus of crystallization and the recording film with a segregation has more nuclears than a recording film with no segregation, which contributes to high-speed crystallization. Since as large a segregation as phase separation has no effect, it must be as minute as a size barely found by accurate analysis. Since which of the elements has a minute segregation depends on a recording film and an interface layer to be used and their processes, control can be performed by selecting these suitably.
On the other hand, in the case of a micro reaction model or micro dope model, for example, Te is less liable to be oxidized than Ge and Bi in the GeBiTe series. That is, Ge and Bi are more liable to be oxidized than Te. For example, when a trace of Ge or Bi is oxidized, it is presumed that the unoxidized Te forms the nuclear of crystallization, or a trace of GeOx or BiOx forms the nuclear of crystallization, and therefore the recording film has more nuclears than a conventional recording film, which contributes to high-speed crystallization. Since which of the elements shows a micro reaction or is doped depends on a recording film and an interface layer to be used and their processes, control can be performed by selecting these suitably. By doing this, it is possible to make the crystallization speed over the recording film differ from that under the recording film, which is seemingly difficult to control.
(i) There are several methods of changing the composition of the recording film in the direction of its thickness. One of them is to change the amount of discharge gas and/or the magnitude of discharge power during the time from the beginning to end of sputtering. When the amount of discharge gas is changed, a method of mixing another gas during discharge is possible.
(iii) A method of providing an ultrathin oxide film (21a/21b) whose average thickness is 0.1 nm or more and 1 nm or less and which is made up of the elements (including Ge and Te) constituting the recording film in a region in contact with the recording film (13a/13b) includes a method of using very oxidative materials as materials for the interface layers (12a, 12b/14a, 14b) and a method of oxidizing the surface of the recording film (13a/13b) slightly.
The above-described reaction models from a complicated and microscopic viewpoint hardly considered in the prior art have been realized as a result of combining various analysis methods and accumulating examinations of the mechanism.
Near the lower part of the vacuum container 100A in the figure, an anode plate 104A on which a sputtering source (or target material) is provided so as to face the rotating base 102A. On the underpart of the anode plate 104A, a magnet 111A configured to be rotatable is provided. The rotating base (or cathode plate) 102A is grounded. To the anode plate 104A, a RFpower supply unit 112A is connected in the case of RF sputtering (or a DCpower supply unit 112A is connected in the case of DC sputtering). When sputtering is done, the output voltage of the power supply unit 112A is applied between the grounded cathode plate 102A and the anode plate 104A.
The vacuum container 100A is connected via a gas exhaust port 113A to an exhaust unit 114A. When sputtering is done, a trace of sputtering gas (inert gas, such as argon, and others) is injected from a gas cylinder 116 via a gas introduction port 115A and a control valve 118A into the vacuum container 100A sufficiently evacuated by the exhaust unit 114A. The amount of sputtering gas injected is checked by an inner-pressure sensor (or vacuum gauge) 108A provided on the vacuum container 100A. The substrate rotating motor 110A, magnet 111A, sputtering power supply unit 112A, exhaust unit 114A, and control valve 118 are computer-controlled by a sputtering control unit 120A.
Above the sputtering source provided on the anode plate 104A, there is provided a monitor unit 106A having a film thickness measuring function. The CPU of the control unit 120A causes the monitor unit 106A to monitor the amount of sputtering from the sputtering source to the substrate. Specifically, while monitoring the thin film sputtered on the substrate, the CPU of the control unit 120A is programmed so as to adjust the RF power from the power supply unit 112A to the anode plate 104A so that the thin film layer may have a specific composition (or a specific film thickness). Although not shown, the vacuum container 100A of
Thereafter, sputtering gas is introduced from the gas cylinder 116A into the process chamber (ST110) and the power supply unit 112A is started, thereby starting plasma ignition (ST112). As a result, a thin film corresponding to the composition of the target material is formed uniformly on the substrate (ST114). When the monitor of the film thickness meter 106A has shown that a thin film of a desired thickness has been formed, the introduction of gas into the process gas chamber is stopped (ST116) and the formation of one thin film is completed.
To form another thin film on the substrate (Yes in ST118), the processes in step ST106 to step ST116 are executed again. In that case, when the composition of a thin film to be formed is changed, the target material is changed to the corresponding target material and, if necessary, the components of the gas introduced into the chamber are changed. For instance, depending on the type of a film to be formed, only argon may be used as the gas or a mixed gas of argon and nitrogen may be used.
After all of the films have been formed on the substrate (No in ST118), the rotation of the substrate on the cathode plate 102A side and the rotation of the magnet on the anode plate 104A side are stopped (ST120). Thereafter, the substrate on which the films have been formed is transported to the load lock chamber (ST122), outside nitrogen or air is leaked into the load lock chamber to release the vacuum state, and the substrate 1a/1b after the formation of the films is taken out (manually or with the robot arm) (ST124). Thereafter, the substrates 1a and 1b after the formation of the films are bonded together as shown in
The materials in
Each of
An optical recording medium that has a favorable characteristic (see
Hereinafter, for the sake of convenience, explanation will be given, referring to the energy of the top of the DOS for the valance band as Fermi energy (Fermilevel). The Fermi energy has a fluctuation of about 25 [meV] at room temperature. The inventors of this application used an energy level 0.5 [eV] lower than the top of the DOS for the valance band as a reference. A similar tendency appears from the top of the DOS for the valance band to an energy level about 1.0 [eV] lower than the top (further from the top of the DOS for the valance band to an energy level about 0.25 [eV] lower than the top). However, after having hunted for the condition for a high S/N ratio, the inventors have selected the aforementioned reference (or an energy level 0.5 [eV] lower than the top of the DOS for the valance band) as the most favorable one.
When the ratio of the DOS of the crystalline state to the DOS of the amorphous state (the DOS of the crystalline state/the DOS of the amorphous state) at an energy level 0.5 [eV] lower than the top of the DOS for the valance band of the recording film becomes 2.5 or less, this suggests that the crystalline state and amorphous state are close to each other in terms of electronic state, and that the amorphous state has a higher short-range regularity. As a result, the phase transition from the crystalline state to the amorphous state or vice versa becomes easy, which enables a high-speed phase transition from crystalline to amorphous or vice versa.
When the ratio of the DOS of the crystalline state to the DOS of the amorphous state (the DOS of the crystalline state/the DOS of the amorphous state) at an energy level 0.5 [eV] lower than the top of the DOS for the valance band of the recording film is 1.0, the crystalline state is identical with the amorphous state in terms of electronic state, and therefore the amorphous state has a much higher short-range regularity. As a result, a higher-speed phase transition from crystalline to amorphous or vice versa becomes possible.
On the other hand, when the ratio of the DOS of the crystalline state to the DOS of the amorphous state (the DOS of the crystalline state/the DOS of the amorphous state) at an energy level 0.5 [eV] lower than the top of the DOS for the valance band of the recording film is 2.5 or more, this suggests that the crystalline state and amorphous state differ from each other in terms of both of crystalline state and electronic state and the short-range regularity in the amorphous state decreased greatly. Since there is almost no long-range regularity in the amorphous state, the phase transition from the crystalline state to the amorphous state or vice versa requires considerable energy, which makes it impossible to perform phase transition at high speed.
Accordingly, an optical recording medium is suitable where the ratio of the DOS of the crystalline state to the DOS of the amorphous state (the DOS of the crystalline state/the DOS of the amorphous state) at an energy level 0.5 [eV] lower than the top of the DOS for the valance band of the recording film is 1.0 or more and 2.5 or less. When a film with a crystallization enhancing function (or the interface films 12a, 12b/14a, 14b) is provided so as to be in contact with the recording film, this enables a higher-speed phase transition from crystalline to amorphous or vice versa.
(Interface film)
The interface film which is in contact with the recording film and has a crystallization enhancing function is configured to include germanium nitride (GeN), germanium-chrome nitride (GeCrN), zirconium oxide (ZrO2), stabilized zirconia+chrome oxide (ZrO2+Cr2O3), stabilized zirconia+silicon oxide+chrome oxide (ZrO2+SiO2+Cr2O3), zircon+chrome oxide (ZrSiO4+Cr2O3), or hafnium oxide (HfO2). Alternatively, the interface film may be composed of a compound (HfO2-xNx) containing hafnium (Hf), oxygen (O), and nitrogen (N). Alternatively, the interface film may be composed of a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y where z=0) containing zirconium (Zr), oxygen (O), nitrogen (N), and yttria (Y). Alternatively, the interface film may be composed of a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y where z=1) containing zirconium (Zr), oxygen (O), nitrogen (N), and niobium (Nb). Alternatively, the interface film may be composed of a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y where 0≦z≦1) containing zirconium (Zr), oxygen (O), nitrogen (N), yttria (Y), and niobium (Nb). Alternatively, the interface film may be configured to include chrome oxide (Cr2O3), zinc oxide (ZnO), zinc oxide+tantalum oxide (ZnO+Ta2O5), zinc oxide+tantalum oxide+indium oxide (ZnO+Ta2O5+In2O3), tin oxide (SnO2), tin oxide+antimony oxide (SnO2+Sb2O3), tin oxide+tantalum oxide (SnO2+Ta2O5), or tin oxide+niobium oxide (SnO2+Nb2O5). When such a configuration is used, the characteristic of the embodiment becomes more noticeable.
It is known that, in the process of refining Zr, the homologous elements Hf and Ti are difficult to separate from one another and therefore are inevitably present in the form of a mixture. The same holds true for the homologous elements Zr and Ti in the process of refining Hf. Even if such unavoidable elements are contained in minute amounts, the effect of the embodiment is not impaired significantly.
(Recording Film)
When a recording film is made up of GeSbTe and a so-called pseudo-binary-series linear composition and its vicinity are used which enable a representation of (GeTe)—(Sb2Te3), the effect of the interface film of the invention is noticeable. Preferably, when an alloy recording film material with the (GeTe)—(Sb2Te3) composition and its vicinity, the Ge composition ratio being 30 at. % or more, is used, the effect of the invention is particularly noticeable. Although in the prior art only the composition of the recording film was considered to be important, what the electronic state of the recording film looks like is as important as its composition in the invention as described above. Hereinafter, the composition will be described.
When, on the basis of the composition of GeSbTe, a part of Ge is replaced with Sn, or a part of Sb is replaced with Bi and/or In, and the aforementioned interface film is used, the effect of the invention is more noticeable. In that case, it is desirable that the Ge-to-Sn replacement ratio should be Sn/Ge<0.5 and the Sn-to-Bi replacement ratio should be Bi/(Bi+Sb)<0.7. It is desirable that the ratio of In to Sb or Bi in amount should be 0.7 or less, preferably 0.5 or less, and more preferably 0.25 or less. Not only the amount of these replacement elements but also the crystallization enhancing function is closely related to the crystallization temperature, melting point, and the like. Therefore, although the optimum condition differs depending on the design of a medium, it is preferable to select the amount in the above range.
When a recording film is composed of GeBiTe and a so-called pseudo-binary-series linear composition and its vicinity are used which enable a representation of (GeTe)—(Bi2Te3), the effect of the interface film of the invention is noticeable. Preferably, when an alloy recording film material with the (GeTe)—(Bi2Te3) composition and its vicinity, the Ge composition ratio being 30 at. % or more, is used as the interface film of the invention, the effect of the invention is particularly noticeable.
(Nitriding Each Recording Film)
When the recording film includes nitrogen (N), it can be represented as a composition where nitrogen (N) is added to (GeTe)—(Sb2Te3), or (GeTe)—(Sb2Te3)-N. That is, the composition is such that nitrogen (N) is added to a pseudo-binary series of (GeTe)—(Sb2Te3). It can be represented more simply as GeSbTe—N. When a recording film nitrided this way is used, the effect of the interface film of the invention is remarkable. Preferably, when an alloy recording film material with the (GeTe)—(Sb2Te3) composition and its vicinity, the Ge composition ratio being 30 at. % or more, is used as the interface film of the invention, the effect of the invention is particularly noticeable.
When, on the basis of the composition of GeSbTe—N, a part of Ge is replaced with Sn, or a part of Sb is replaced with Bi and/or In, and the aforementioned interface film is used, the effect of the invention is more noticeable. In that case, it is desirable that the Ge-to-Sn replacement ratio should be Sn/Ge<0.5 and the Sn-to-Bi replacement ratio should be Bi/(Bi+Sb)<0.7. It is desirable that the ratio of In to the amount of Bi should be 0.7 or less, preferably 0.5 or less, and more preferably 0.25 or less. Not only the amount of these replacement elements and the amount of nitrogen but also the crystallization enhancing function is closely related to the crystallization temperature, melting point, and the like. Therefore, although the optimum condition differs depending on the design of a medium, it is preferable to select the amount in the above range.
When the recording film is configured to have a composition where nitrogen (N) is added to (GeTe)—(Bi2Te3), or a so-called pseudo-binary-series linear composition and its vicinity represented as (GeTe)—(Bi2Te3)—N (more simply represented as GeBiTe—N), the effect of the interface film of the invention is remarkable. Preferably, when an alloy recording film material with the (GeTe)—(Bi2Te3) composition and its vicinity, the Ge composition ratio being 30 at. % or more, is used as the interface film of the invention, the effect of the invention is particularly remarkable.
Furthermore, the effect of the invention is produced, regardless of the thickness of the recording film. When the thickness of the recording film is made 20 nm or less, more preferably 10 nm, the effect is more noticeable.
In a recording medium of the type that allows light to enter one side of the medium and enables two different information layers to be accessed (the single-sided, dual-layer type), when the invention is applied to the recording layer closer to the light incident side, the effect of the invention is noticeable. The advantage in that case is that the film thickness of the recording layer can be made 10 nm or less. Use of an interface layer related to the embodiment makes the following advantages noticeable: the transmittance to short-wavelength laser light can be made higher and the contrast can be increased.
The inventors of this application conducted experiments using germanium nitride (GeN), silicon carbide (Si—C), silicon nitride (Si—N), Ta2O5+SiC, and the like which are well known as interface film materials having an effect on the enhancement of crystallization of the recording film. As a result, the following tradeoff was found: using a material with a high crystallization enhancing effect without controlling the state of the recording film resulted in a decrease in CNR and a material with high CNR had a poor crystallization enhancing effect. These materials excluding Si—N present relatively high absorption at a wavelength of λ=405 nm of the blue-violet laser diode used in the next-generation DVD (that is, have a large optical attenuation coefficient), leading to the cause of optical losses. The optical losses require the power of laser light irradiated to be increased that much more. Moreover, the optical losses prevent the transmittance of the L0 recording film from being increased and decrease the sensitivity and contrast of the L1 recording film, causing various problems with the two-layer medium.
However, it has become clear that, when a conventional uniform recording layer and an interface layer material with a crystallization enhancing function, such as GeN, were used, recrystallization was violent particularly at a low linear velocity, preventing a good amorphous mark from being formed. Therefore, the bit pitch couldn't be reduced, which was an obstacle to density growth.
Before the description of embodiments of an experimentally produced optical recording medium, a sample whose recording film was in the crystalline state and a sample whose recording film was in the amorphous state were produced and the DOS for the valance band of each of the recording films was measured using the HX-PES method. Experiments were done on the recording films and interface layers for the following series.
The recording film series on which experiments were conducted:
GeSbTe, GeSnSbTe, GeSnSbTeIn, GeSbTeIn, GeSbTeBiIn, GeSbSnTeBiIn, GeSbTeBi, GeSnSbTeBi, GeSnSbTeBiIn, GeBiTeIn, GeBiTe, GeSbTe—N, GeSbTeBi—N, GeBiTe—N, GeSbInTe—N, GeSbTeBiIn—N, GeBiInTe—N
The interface film series on which experiments were conducted:
germanium nitride (GeN), germanium-chrome nitride (GeCrN), zirconium oxide (ZrO2), stabilized zirconia+chrome oxide (ZrO2+Cr2O3), stabilized zirconia+silicon oxide+chrome oxide (ZrO2+SiO2+Cr2O3), zircon+chrome oxide (ZrSiO4+Cr2O3), hafnium oxide (HfO2), a compound (HfO2-xNx where 0.1≦x≦0.2) containing hafnium (Hf), oxygen (O), and nitrogen (N), a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y where 0≦x≦0.2, 0≦y≦0.1, 0≦z≦1) containing zirconium (Zr), oxygen (O), nitrogen (N), yttria (Y), and niobium (Nb), chrome oxide (Cr2O3), zinc oxide (ZnO), zinc oxide+tantalum oxide (ZnO+Ta2O5), zinc oxide+tantalum oxide+indium oxide (ZnO+Ta2O5+In2O3), tin oxide (SnO2), tin oxide+antimony oxide (SnO2+Sb2O3), tin oxide+tantalum oxide (SnO2+Ta2O5), or tin oxide+niobium oxide (SnO2+Nb2O5)
A substrate compatible with both of the land-groove recording method (a) and groove recording method (b) was used as the substrate of
On the surface of each of the PC substrates in which grooves have been formed, for example, the following films are formed using a sputtering apparatus. In an L0 information layer 19 provided close to the light incident side, an interference film (ZnS—SiO2) 15a, an interface layer 14a, a recording film layer 13a, an interface layer 12a, and an interference film (ZnS—SiO2) 11a are formed in that order. In an L1 information layer 20 provided far away from the light incident side, a reflecting film (Ag alloy) 16b, an interference film (ZnS—SiO2) 15b, an interface layer 14b, a recording film layer 13b, an interface layer 12b, and an interference film (ZnS—SiO2) 11b are formed on the PC substrate in that order.
The sputtering apparatus used is a so-called Cluster sputter film-forming apparatus which forms each layer by sputtering in a different film-forming chamber. The Cluster sputter film-forming apparatus comprises a load-lock chamber in which a substrate is installed, a transport chamber, and a process chamber which forms each film.
In the interface layer, ZrO2 was used on the light incident side and Cr2O3 was used on the reflecting film side. The ZnS—SiO2 film (or interference film) was formed using a target obtained by mixing SiO2 with ZnS. The sputtering apparatus used is a so-called Cluster sputter film-forming apparatus which forms each layer by sputtering in a different film-forming chamber. After each medium is formed, the reflectivity and transmittance of the medium are measured with a spectrophotometer.
Experiments done to evaluate the characteristics of a disk are roughly divided into the following three types:
(1) Bit Error Rate (SbER: Simulated Bit Error Rate) Measurement
One measurement is to measure the bit error rate (SbER: Simulated bit Error Rate) to determine a data error rate. The other is analog measurement to determine the quality of a read-out signal. In SbER measurement, a mark string in which 2T to 13T patterns were included at random was overwritten 10 times. Next, the same random patterns were overwritten 10 times in the adjacent tracks on both sides of the track. Thereafter, the middle track was reached and sbEr was measured.
(2) Analog Measurement
Analog measurements were made as follows. First, a mark string in which 2T to 13 patterns were included at random was overwritten 10 times. Next, in the mark string, a 9T single pattern was overwritten once. Then, the signal-to-noise ratio (hereinafter, CNR) of the signal frequency of the 9T mark was measured with a spectrum analyzer. Next, a laser beam of an erase power level was irradiated as many times as the disk rotation, thereby erasing the recording mark. At that time, the decrease in the magnitude of the signal of the 9T mark was measured. The measured value was defined as an erase ratio (ER). Then, the head was moved to a sufficiently distant track and cross erase was measured.
(3) Overwrite (OW) Test
As a third measurement, experiments were done with overwrite (OW) characteristics. In the experiment, CNR was measured, while a random signal was being overwritten in the same track. A determination was made, depending on whether the number of times CNR became smaller than the initial value by 2 dB or more was 2000 or more. Experiments were not done from a viewpoint of how many times OW was possible. Uses in video recording require about 1000 times and uses in dealing with PC data require 10000 times or more. Since video recording is the main use in the market, evaluations were made giving importance to uses in video recording.
In addition to the measurement of
The optimum power in measuring the SbER was set as the sensitivity of the medium. Here, to measure the sensitivity and transmittance of L0, L0 with the configuration of the embodiment was bonded to a blank disk on which no film had been formed and L1 was bonded to a blank disk on which no film had been formed. Unless otherwise stated, each evaluation was made at a linear velocity of 5.4 m/s (constant velocity) in the land-groove recording method (a) and at a linear velocity of 6.61 m/s (constant velocity) in the groove recording method (b).
All of the embodiments below shared the above conditions. In the examples shown as representative examples, the worst evaluations among the results of the evaluations made as described above are shown. For instance, since the land-groove recording method (a) can increase the recoding density more than the groove recording method (b), the method (b), on the whole, tends to have a better characteristic than the method (a). The tendency is more noticeable in SbER than in CNR or ER. In a certain embodiment, it has been found that SbER in the method (b) was better than in the method (a) by about 1/10 to 1/100, or the former had almost no error.
A disk was made by forming a film configuration of the embodiment on a 1.1-mm-thick polycarbonate (PC) substrate formed by injection molding and providing a 75-μm-thick transparent cover layer on the film. The recording and erasing characteristics of the medium were evaluated with an evaluation unit provided with a blue-violet semiconductor laser with a wavelength of 405 nm and an objective lens with NA=0.85. A substrate with a groove pitch of 0.32 μm was evaluated in groove recording, that is, by the groove recording method (b). CNR was 52 dB or more, the erase ratio was −30 dB or less, and OW characteristic showed 2000 times or more, which were very good results. Accordingly, it is conceivable that the interface layer material of the embodiment is favorable because it is not affected by the thickness of the substrate or the thickness of the cover layer on the light incident side.
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that the recording film had a segregation or concentration distribution as shown in
With the same configuration as that in embodiment 2, a disk was made by using GeCrN on the light incident side of the interface layer and Cr2O3 on its reflecting film side. The same experiment as that in embodiment 2 was conducted. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film.
With the same configuration as that in embodiment 2, a disk was made by using ZrO2+Y2O3+CrO3 on the light incident side of the interface layer and SnO2+Sb2O3 on its reflecting film side. The same experiment as that in embodiment 2 was conducted. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film.
With the same configuration as that in embodiment 2, a disk was made by using ZrSiO4+Cr2O3 on the light incident side of the interface layer and Cr2O3 on its reflecting film side. The same experiment as that in embodiment 2 was conducted. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film.
With the same configuration as that in embodiment 2, a disk was made by using ZrO2+Y2O3+SiO2+Cr2O3 on the light incident side of the interface layer and ZnO+Ta2O5+In2O3 on its reflecting film side. The same experiment as that in embodiment 2 was conducted. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film.
With the same configuration as that in embodiment 2, a disk was made by using (ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y (where (x, y, z)=(0.05, 0.05, 0)) on the light incident side of the interface layer and SnO2+Nb2O5 on its reflecting film side. The same experiment as that in embodiment 2 was conducted. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film.
With the same configuration as that in embodiment 2, a disk was made by using HfO2-xNx (where x=0.1) on the light incident side of the interface layer and GeN on its reflecting film side. The same experiment as that in embodiment 2 was conducted. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film.
With the same configuration as that in embodiment 2, a disk was made by using GeN on the light incident side of the interface layer and Cr2O3 on its reflecting film side. The same experiment as that in embodiment 2 was conducted. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film.
With the same configuration as that in embodiment 2, a disk was made by using HfO2-xNx (where x=0.1) on the light incident side of the interface layer and ZrSiO4+Cr2O3 on its reflecting film side. The same experiment as that in embodiment 2 was conducted. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film.
With the same configuration as that in embodiment 2, a disk was made by using Cr2O3 on the light incident side of the interface layer and ZnO+Ta2O5 on its reflecting film side. The same experiment as that in embodiment 2 was conducted. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film.
With the same configuration as that in embodiment 2, a disk was made by using GeN on the light incident side of the interface layer and SnO2+Ta2O5 on its reflecting film side. The same experiment as that in embodiment 2 was conducted. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film.
With the same configuration as that in embodiment 2, a disk was made by using ZrO2+Y2O3+Cr2O3 on the light incident side of the interface layer and ZnO+Ta2O5+In2O3 on its reflecting film side. The same experiment as that in embodiment 2 was conducted. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film.
A substrate compatible with both the methods (a) and (b), that is, both of the land-groove recording method (a) and groove recording method (b), was used. In the land-groove recording method (a), a 0.6-mm-thick polycarbonate (PC) substrate formed by injection molding was used. Since grooves were formed with a groove pitch of 0.68 μm, when data was recorded to both lands (L) and grooves (G), the pitch corresponded to a track pitch of 0.34 μm. In the groove recording method (b), a 0.59-mm-thick PC substrate formed by injection molding was used. The groove pitch was set at 0.4 μm.
On the surface of each of the PC substrates in which grooves had been formed, the following films were formed using a sputtering apparatus: ZnS—SiO2, SiO2, ZnS—SiO2, an interface layer, a recording film layer, an interface layer, ZnS—SiO2, and Ag alloy in that order, starting from the light incident side. Then, the resulting disk was bonded to a blank disk with no film by UV cured resin. The sputtering apparatus used in the same manner as in embodiment 2 is a so-called Cluster sputter film-forming apparatus which forms each layer by sputtering in a different film-forming chamber.
The recording film layer was made up of Ge, Sb, and Te and was selected from the composition enclosed by x=55·z=45, x=45·z=55, x=10·y=28·z=42, and x=10·y=36·z=54 in the GeSbTe ternary phase diagram, if its composition was expressed as GexSbyTez where x+y+z=100. When the recording film layer was made up of Ge, Sb, Te, and Bi or Sn, a part of the composition of GeSbTe was replaced with Bi and/or In and/or Sn, and the composition after the replacement was expressed as (Ge(1−w)Snw)×(Sb(1−v)(Bi(1−u)Inu)v)yTez where x+y+z=100, GeSnSbTe, GeSnSbTeIn, GeSbTeIn, GeSbTeBiIn, GeSbSnTeBiIn, GeSbTeBi, GeBiTeIn, GeSnSbTeBi, and GeSnSbTeBiIn were used where w, v, and u satisfied the expression 0≦w≦0.5 and 0≦v≦0.7 and 0≦u≦1.0. Moreover, the recording film layer was made up of Ge, Bi, and Te and was selected from the composition enclosed by x=55·z=45, x=45·z=55, x=10·y=28·z=42, and x=10·y=36·z=54 in the GeBiTe ternary phase diagram, if its composition was expressed as GexBiyTez where x+y+z=100.
Many compositions were examined. In this embodiment, a case where a GeSbTeBi-series recording film was used is shown. The thickness of the recording film was set to around 10 nm or less.
In the interface layer, GeN was used on the light incident side and Cr2O3 was used on the reflecting film side. A ZnS—SiO2 film was formed using a target obtained by mixing SiO2 with ZnS. The sputtering apparatus used is a so-called Cluster sputter film-forming apparatus which forms each layer by sputtering in a different film-forming chamber. After each medium was formed, the reflectivity and transmittance of the medium were measured with a spectrophotometer.
The recording film on the entire surface of the medium of each layer was crystallized with an initialization unit (not shown). After the initialization, the mediums were bonded together with UV resin, with the film-formed surfaces inside, thereby forming an interlayer separating layer. The thickness of the interlayer separating layer was 20 μm. Evaluations were made using the aformentioned disk evaluation unit ODU-1000. The unit is provided with a blue-violet semiconductor laser with a wavelength of 405 nm and an objective lens with NA=0.65. A recording experiment was conducted by the land-groove recording method. The experiment was the same as that in embodiment 2. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film. It was found that germanium oxide and antimony oxide as thin as 0.6 nm to 0.1 nm were present at the interface of the layer in contact with the recording film.
A substrate compatible with both the methods (a) and (b), that is, both of the land-groove recording method (a) and groove recording method (b), was used. In the land-groove recording method (a), a 0.6-mm-thick polycarbonate (PC) substrate formed by injection molding was used. Since grooves were formed with a groove pitch of 0.68 μm, when data was recorded to both lands (L) and grooves (G), the pitch corresponded to a track pitch of 0.34 μm. In the groove recording method (b), a 0.59-mm-thick PC substrate formed by injection molding was used. The groove pitch was set at 0.4 μm. On the surface of each of the PC substrates in which grooves had been formed, the following films were formed using a sputtering apparatus: ZnS—SiO2, SiOC, ZnS—SiO2, an interface layer, a recording film layer, an interface layer, ZnS—SiO2, and Ag alloy in that order, starting from the light incident side. Then, the resulting disk was bonded to a blank disk with no film by UV cured resin. The SiOC film was formed by subjecting a SiC-system target to reactive sputtering using a mixed gas of Ar/O2. The SiOC film has almost the same low refractive index as that of SiO2. The same experiment as that in embodiment 2 was conducted. As a result, SbER was on the order of 10−6 in both lands and grooves for any sample as shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film.
With the same configuration as that in embodiment 2, a disk was made by using GeN on the light incident side of the interface layer and Cr2O3 on its reflecting film side, or by using GeN on both the sides. The recording film layer was made up of Ge, Sb, and Te and was selected from the composition enclosed by x=55·z=45, x=45·z=55, x=10·y=28·z=42, and x=10·y=36·z=54 in the GeSbTe ternary phase diagram, if its composition was expressed as GexSbyTez where x+y+z=100. When the recording film layer was made up of Ge, Sb, Te, and Bi or Sn, a part of the composition of GeSbTe was replaced with Bi and/or In and/or Sn, and the composition after the replacement was expressed as (Ge(1−w)Snw)×(Sb(1−v)(Bi(1−u)Inu)v)yTez where x+y+z=100, GeSbTeBi, GeSbTeSn, GeSbTeBiSn, GeSnSbTeIn, GeSbTeIn, GeSbTeBiIn, GeSbSnTeBiIn, GeBiTeIn, and GeSnSbTeBiIn were used where w, v, and u satisfied the expression 0≦w≦0.5 and 0≦v≦0.7 and 0≦u≦1.0. Moreover, the recording film layer was made up of Ge, Bi, and Te and satisfied the condition for the composition enclosed by x=55·z=45, x=45·z=55, x=10·y=28·z=42, and x=10·y=36·z=54 in the GeBiTe ternary phase diagram, if its composition was expressed as GexBiyTez where x+y+z=100. Many compositions were examined. This embodiment shows examples of disks using a GeSbTe-series, a GeSbTeSn-series, and a GeGiTe-series recording film layer whose representative examples are shown in
As shown in
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that Ge, Sb, and Bi were rich and Te was poor in the vicinity of the interface of the recording film. Moreover, it was found that germanium oxide, antimony oxide, and bismuth oxide as thin as 0.4 nm to 0.1 nm were present at the interface of the layer in contact with the recording film.
With the same configuration as that in embodiment 2, a disk was made by using GeCrN on the light incident side of the interface layer and Cr2O3 on its reflecting film side. The recording film layer was made up of Ge, Sb, Te, and N (nitrogen) and was selected from the compounds obtained by adding 1 to 5 at. % of nitrogen (N) to the GeSbTe-series compounds in the composition region enclosed by x=55·z=45, x=45·z=55, x=10·y=28·z=42, and x=10·y=36·z=54 in the GeSbTe ternary phase diagram, if the composition of a compound composed of Ge, Sb, and Te was expressed as GexSbyTez where x+y+z=100. When the recording film layer was made up of Ge, Sb, Te, Bi and/or In and/or Sn, and N (nitrogen), and a part of the composition of GeSbTe was replaced with Bi and/or Sn, and the composition after the replacement was expressed as (Ge(1−w)Snw)×(Sb(1−v)(Bi(1−u)Inu)v)yTez where x+y+z=100, GeSbTeBi, GeSbTeSn, GeSbTeBiSn, GeSnSbTeIn, GeSbTeIn, GeSbTeBiIn, GeSbSnTeBiIn, GeBiTeIn, and GeSnSbTeBiIn each with the addition of 0.1 to 10 at. % of nitrogen (N) were used where w, v, and u satisfied the expression 0≦w≦0.5 and 0≦v≦0.7 and 0≦u≦1. Moreover, the recording film layer was made up of Ge, Bi, and Te and was selected from the compounds obtained by adding 0.1 to 10 at. % of nitrogen (N) to the GeSbTe-series compounds in the composition region enclosed by x=55·z=45, x=45·z=55, x=10·y=28·z=42, and x=10·y=36·z=54 in the GeSbTe ternary phase diagram, if the composition of a compound composed of Ge, Sb, Te was expressed as GexBiyTez where x+y+z=100 and the composition of a compound composed of Ge, Sb, Te, and nitrogen (N) enclosed by x=55·z=45, x=45·z=55, x=10·y=28·z=42, and x=10·y=36·z=54 in the GeBiTe ternary phase diagram, if its composition was expressed as GexBiyTez where x+y+z=100.
Many compositions were examined. In this embodiment, 1 to 5 at. % of nitrogen (N) was added to the compounds of
The result of analyzing a disk produced in the same manner as the evaluated medium has shown that germanium oxide, antimony oxide, and bismuth oxide as thin as 0.9 nm to 0.1 nm were present at the interface of the layer in contact with the recording film.
Next, comparative examples will be explained. With the same configuration as that of embodiment 2, a disk using SiO2 or Y2O3 for an interface layer and a disk with no interface layer were formed.
One of the essential structural requirements in one embodiment of the invention is to set to 1.0 or more and 2.5 or less the ratio of the DOS of the crystalline state to the DOS of the amorphous state (the DOS of the crystalline state/the DOS of the amorphous state) at an energy level 0.5 [eV] lower than the top of the DOS for the valance band of the recording film in a phase-change optical recording medium which records data using a recording film that changes an atomic arrangement reversibly. The other films and others are not limited to the materials explained in the embodiment. Moreover, as for recording film materials, minute amounts of, for example, Co, V, or Ag may be added to GeSbTe in the range that does not ruin the effect of the embodiment. Alternatively, minute amounts of, for example, Co, V, or Ag may be added to GeBiTe.
Furthermore, the embodiment limits neither the thickness of the substrate nor the order in which films are formed. The embodiment may be applied to not only a medium which allows light to enter via a substrate on which films are to be formed but also a medium which allows light to enter via a transparent sheet laminated to a film-formed substrate. For example, it is seen from the above explanation that the effect of the invention is useful for a recording medium whose transparent sheet on the light incident side is designed to be as thin as about 0.1 mm by using an objective lens with a high NA of about 0.85. The wavelength of the laser beam used is not limited to the vicinity of 405 nm. Regarding the optical characteristic of the interface layer materials, it can be said that the interface layer is practically transparent up to a short wavelength range of about 350 nm to 250 nm and therefore the effect of the embodiment is useful.
As described above, in a phase-change optical recording medium which records using a recording film that changes an atomic arrangement reversibly, the phase-change optical recording medium comprises a substrate, a recording film capable of changing an atomic arrangement reversibly, a film which is in contact with the recording film and has a crystallization enhancing function, a protective film or a dielectric film, and a reflecting film. The optical recording film causes the elements constituting the recording film to have a segregation or a concentration distribution in the direction of the thickness of the recording film from a region in contact with the recording film, or in the in-plane direction of the recording film. With this configuration, a high-density, high-speed recording medium achieves a desired mark width without recrystallization in recording. Consequently, it is possible to realize a phase-change recording medium which secures a high CNR and a low bit error rate, assures an excellent erasing ratio, achieves a good cross erase characteristic, and therefore is capable of recording and rewriting at higher speed in higher density than a conventional equivalent.
In
Specifically, the signal reproduced at the information recording and reproducing section 141 is subjected to reproduced waveform correction at a PR equalizing circuit 130. With the timing of a reference clock 198 sent from a reference clock generator 160, an AD converter 169 samples the signal passed through the PR equalizing circuit 130 and converts the signal into a digital amount. The digital amount is then subjected to a Viterbi decoding process at a Viterbi decoder 156. The data after the Viterbi decoding process is treated as data identical with that binarized at a conventional slice level. When PRML techniques are used, a shift in the sampling timing at the AD converter 169 increases the error rate of data after Viterbi decoding. Thus, to increase the accuracy of sampling timing, the information reproducing apparatus or the information recording and reproducing apparatus particularly has a separate sampling timing extracting circuit (a combination of a Schmitt trigger binarizing circuit 155 and a PLL circuit 174).
The Schmitt trigger binarizing circuit 155 has a specific range of slice reference level for binarization (actually the voltage value in the forward direction of the diode). Only when the specific range is exceeded does the binarizing circuit 155 binarize the signal. Therefore, for example, if the pattern “101010101010101010101010” has been input as described above, the signal amplitude is so small that binarization is not performed. If a rougher pattern, for example, “1001001001001001001001” has been input, since the amplitude of the reproduced raw signal becomes larger, the switching between the polarities of a binarized signal is performed with the “1” timing at the Schmitt trigger binarizing circuit 155. In this embodiment, NRZI (Non-Return to Zero Invert) techniques are used and the position of “1” in the pattern coincides with the recording mark or the edge part (boundary part) of the pit.
The PLL circuit 174 detects the difference in frequency and phase between the binarized signal output from the Schmitt trigger binarizing circuit 155 and the reference clock 198 signal sent from the reference clock generator 160 and changes the frequency and phase of the output clock of the PLL circuit 174. Using the output signal of the PLL circuit 174 and decoding characteristic information on the Viterbi decoder 156 (although not shown concretely, information on the convergence length (the distance to convergence) in the path metric memory in the Viterbi decoder 156), the reference clock generator 160 applies feedback to (the frequency and phase of) the reference clock 198 so that the error rate after Viterbi decoding may be decreased. The reference clock 198 generated at the reference clock generator 160 is used as reference timing in processing a reproduced signal.
A synchronizing code position extracting section 145 detects the positions of synchronizing codes (sync codes) mixed in the output data string of the Viterbi decoder 156 and extracts the starting position of the output data. With the starting position as a reference, a demodulation circuit 152 demodulates the data temporarily stored in a shift register circuit 170. In the embodiment, the original bit train is restored by referring to a conversion table recorded in a demodulation conversion table recording section 154 for every 12 channel bits. Thereafter, an ECC decoding circuit 162 carries out an error correction process. Then, a descramble circuit 159 performs descrambling. In a recording-type (rewritable or recordable) information storage medium of the embodiment, address information has been recorded beforehand by wobble modulation. A wobble signal detecting section 135 reproduces the address information (that is, determines the contents of the wobble signal) and supplies information necessary to access a desired location to the control section 143.
The information recording control system above the control section 143 will be explained. A data ID generating section 165 creates data ID information according to the recording location on the information storage medium. When a CPR_MAI data generating section 167 creates copy control information, a data ID, IED, CPR_MAI, EDC adding section 168 adds various pieces of information, including data ID, IED, CPR_MAI, and EDC to the information to be recorded. Thereafter, a descramble circuit 157 performs descrambling. Then, after an ECC encoding circuit 161 constructs an ECC block and a modulation circuit 151 converts the ECC block into a channel bit train, a synchronizing code creating and adding section 146 adds a synchronizing code to the bit train, and the information recording and reproducing section 141 records the data onto the information storage medium. In modulation, a DSV (Digital Sum Value) value computing section 148 calculates DSV values after modulation one after another. The values are fed back to code conversion in modulation.
“Reproduce-only information storage medium” which is for reproduction only and prevents recording
“Recordable information storage medium” which enables additional recording only once
“Rewritable information storage medium” which enables rewriting as many times as necessary
As shown in
In a reproduce-only information storage medium, information is recorded in an emboss (prepit) form in the data lead-in area DTLDI, whereas in a recordable and a rewritable information storage medium, the data lead-in area DTLDI enables new information to be recorded additionally (or rewriting in the rewritable type) by creating recording marks. As described later, in a recordable and a rewritable information storage medium, areas enabling new information to be recorded additionally (or rewriting in the rewritable type) and reproduce-only areas where information is recorded in emboss (prepit) form are mixed in the data lead-out area DTLDO. In the data area DTA, data lead-in area DTLDI, data lead-out area DTLDO, and middle area MDA of
Unlike the present DVD standards, the burst cutting area BCA and the system lead-in area SYLDI do not overlap with each other and are separated from each other spatially in the embodiment of
Another embodiment related to the embodiment is a method of forming a microscopic concavo-convex shape previously in a place where the burst cutting area BCA is provided, when a Low-to-High recording film is used. The polarity of the recording mark (determination of whether the recording film is High-to-Low or Low-to-High) existing at the 192nd byte in
Since the system lead-in area SYLDI is formed in the emboss pit area 211, the reproduced signal from the system lead-in area SYLDI appears in the direction in which the amount of light reflection decreases as compared with the level of light reflection from a mirror surface 210. If the burst cutting area BCA is brought into the state of the mirror surface 210 and a Low-to-High recording film is used, the reproduced signal from the data written in the burst cutting area BCA appears in the direction in which the amount of light reflection increases as compared with the level of light reflection from the mirror surface 210 (in an unrecorded state). This results in a great difference between the positions (amplitude levels) of the maximum and minimum levels of the reproduced signal from the data created in the burst cutting area BCA and the positions (amplitude levels) of the maximum and minimum levels of the reproduced signal from the system lead-in area SYLDI.
The information reproducing apparatus or information recording and reproducing apparatus carries out processes in this order:
(1) Reproducing the information in the burst cutting area BCA
(2) Reproducing the information in the control data zone CDZ in the system lead-in area SYLDI
(3) Reproducing the information in the data lead-in area DTLDI (in the case of a recordable or a rewritable information storage medium)
(4) Readjusting (optimizing) the reproducing circuit constant in the reference code recording zone RCZ
(5) Reproducing the information recorded in the data area DTA or recording new information
Therefore, if there is a great difference between the reproduced signal amplitude level from the data created in the burst cutting area BCA and the reproduced signal amplitude level from the system lead-in area SYLDI, a problem arises: the reliability of information reproduction decreases. In this embodiment, to solve this problem, a microscopic concavo-convex shape is formed beforehand in the burst cutting area BCA when a Low-to-High recording film is used. Forming a microscopic concavo-convex shape in advance makes the light reflection level lower than the light reflection level from the mirror surface 210 because of the effect of light interference, and decreases greatly the difference between the reproduced signal amplitude level (sense level) from the data formed in the burst cutting area BCA and the reproduced signal amplitude level (sense level) from the system lead-in area SYLDI before recording data (barcode data) by local laser exposure, which improves the reliability of information reproduction. Furthermore, the process in moving from (1) to (2) becomes easier.
When a Low-to-High recording film is used, there is a method of using an emboss pit area 211, as in the system lead-in area SYLDI, as a microscopic concavo-convex shape previously formed in the burst cutting area BCA. Another embodiment utilizes a method of using a groove area 214 or a land area and groove area 213, as in the data lead-in area DTLDI or the data area DTA. In the embodiment which arranges the system lead-in area SYLDI and the burst cutting area BCA separately, when the burst cutting area BCA overlaps with the emboss pit area 211, the noise components in the reproduced signal from the data created in the burst cutting area BCA increase because of unwanted interference. When the groove area 214 or land area and groove area 213 is used instead of the emboss pit area 211 as a microscopic concavo-convex shape in the burst cutting area BCA, the noise components in the reproduced signal from the data created in the burst cutting area BCA due to unwanted interference decrease, which improves the quality of the reproduced signal.
If the track pitch of the groove area 214 or the land area and groove area 213 formed in the burst cutting area BCA is caused to coincide with the track pitch of the system lead-in area SYLDI, the productivity of the information storage medium is improved. Specifically, when a matrix of an information storage medium is produced, the feed motor speed at the exposure section of a matrix recording apparatus is made constant, thereby forming emboss pits in the system lead-in area. At this time, the track pitch of the groove area 214 or the land area and groove area 213 formed in the burst cutting area BCA is caused to coincide with the track pitch of the emboss pits in the system lead-in area SYLDI, which enables the feed motor speed to be kept constant over the burst cutting area BCA and the system lead-in area SYLDI. Therefore, the feed motor speed need not be changed, which makes it difficult for pitch irregularity to occur and improves the productivity of the information storage medium.
The data bit length and track pitch of the system lead-in/-out area SYLDI/SYLDO are brought close to the values of the lead-in area of an existing DVD, thereby securing the interchangeability with the existing DVD. In this embodiment, too, as with an existing DVD-R, the step of an emboss in the system lead-in/-out area SYLDI/SYLDO is set shallow. This makes the depth of a pre-groove in a recordable information storage medium shallower, producing the effect of increasing the modulation degree of the reproduced signal from the recording mark formed in additional writing on the pre-groove. Conversely, there arises another problem: the modulation degree of the reproduced signal from the system lead-in/-out area SYLDI/SYLDO becomes smaller. To overcome this problem, the data bit length (and track pitch) of the system lead-in/-out area SYLDI/SYLDO is made rougher, thereby separating (making much lower) the repeat frequency of pits and spaces in the densest position from the optical cut-off frequency of the reproduction objective MTF (Modulation Transfer Function), which makes it possible to increase the amplitude of the reproduced signal from the system lead-in/-out area SYLDI/SYLDO and stabilize reproduction.
As shown in
In a recordable information storage medium or a rewritable information storage medium, a spare area SPA is provided in the innermost part of the data area DTA. If a defective part has occurred in the data area DTA, a substituting process is carried out using the spare area SPA. In the case of a rewritable information storage medium, the substitute history information (defect management information) is recorded into the first and second defect management areas DMA1, DMA2 and into the third and fourth defect management areas DMA3, DMA4. The defect management information recorded in the third and fourth defect management areas DMA3, DMA4 is the same as that recorded in the first and second defect management areas DMA1, DMA2. In the case of a recordable information storage medium, substitute history information (defect management information) when a substituting process is carried out is recorded in the data lead-in area DTLDI and in copy information C_RMZ about the contents of recording into a recording management zone existing in a border zone explained later.
While defect management is not performed on an existing DVD-R disk, there have been strong demands that the reliability of information recorded on a recordable information storage medium should be increased, because an increase in the number of DVD-R disks manufactured has permitted partially defective DVD-R disks to appear on the market. In this embodiment, as shown in
In a rewritable information storage medium or a recordable information storage medium, if many defects have occurred, the information recording and reproducing apparatus on the user side makes a determination and brings the medium into the state immediately after the user purchased the medium as shown in
As shown in
A third guard track zone GTZ3 shown in
A drive test zone DRTZ is secured as an area for the information recording and reproducing apparatus to do trial writing before recording information onto the information storage medium. After the information recording and reproducing apparatus does trial writing in this area beforehand and calculates the optimum recording condition (write strategy), it can record information in the data area DTA under the optimum recording condition.
A disk test zone DKTZ is an area for the information storage medium manufacturer to conduct a quality test (evaluation).
In a recordable information storage medium, a pre-groove area has been formed in the whole data lead-out area DTLDO, excluding the servo calibration zone SCZ. In a rewritable information storage medium, a groove area and a land area have been formed in the same area, thereby enabling recording marks to be recorded (or additionally recorded or rewritten). As shown in
If the information storage medium inclines, an offset occurs in the track shift sense signal amplitude in the DPD method. It is possible to detect the amount of tilt from the magnitude of the offset and the direction of tilt from the offset direction with high accuracy. Using the principle, an emboss pit which enables DPD detection is formed in the outermost edge of the information storage medium (or the outer edge of the data lead-out area DTLDO) in advance, which enables the tilt to be detected inexpensively with high accuracy without adding a (tilt detecting) special part to the optical head existing in the information recording and reproducing section 141 of
In this embodiment, the track pitch in the servo calibration area SCZ is caused to match with another area in the data lead-out area DTLDO, thereby improving the productivity of the information storage medium, which enables the medium to be produced at lower cost as a result of an improvement in the yield. Specifically, in a recordable information storage medium, a pre-groove is formed in the other area of the data lead-out area DTLDO. When a matrix of a recordable information storage medium is manufactured, the pre-groove is made by keeping constant the feed motor speed of the exposure section of the matrix recording apparatus. At this time, the track pitch in the servo calibration area SCS is caused to match with the other area of the data lead-out area DTLDO, thereby keeping constant the feed motor speed also in the servo calibration area SCZ, which makes pitch irregularities less liable to take place and therefore improves the productivity of the information storage medium.
Another embodiment is a method of causing at least one of the track pitch or data bit length in the servo calibration area SCZ to match with the track pitch or data bit length in the system lead-in area SYLDI. As described above, the amount of tilt and the direction of tilt in the servo calibration area SCZ have been measured using the DPD method. Using the result in the data area DTA too, the servo has been stabilized in the data area DTA. In this connection, a method of estimating the amount of tilt in the data area DTA is to measure the amount of tilt and its direction in the system lead-in area SYLDI in advance by the DPD method and estimate the amount of tilt using the relationship with the result of measurements in the servo calibration area SCZ.
When the DPD method is used, the amount of offset of the sense signal amplitude to the tilt of the information storage medium and the direction in which an offset appears change, depending on the track pitch of the emboss pit and the data bit length. Therefore, at least either the track pitch or data bit length in the servo calibration area SCZ is caused to match with the track pitch or data bit length in the system lead-in area SYLDI, thereby causing the amount of offset of the sense signal amplitude and the detection characteristic in the direction in which an offset occurs to coincide with those in the servo calibration area SCZ and system lead-in area SYLDI, which produces the effect of making it easier to correlate them and to estimate the amount of tilt and the direction of tilt in the data area DTA.
As shown in
In the embodiment, the method of setting an extended drive test zone and the method of doing trial writing in the set extended drive test zone are characterized in that:
(1) Extended drive test zones EDRTZ are set (or framed) collectively one after another from the outer edge (closer to the data lead-out area DTLDO) toward the inner edge.
As shown in
(2) Trial writing is done from the inner edge side in the extended drive test zone EDRTZ.
When trial writing is done in the extended drive test zone EDRTZ, it is done along the groove area 214 provided spirally from the inner edge toward the outer edge. Present trial writing is performed in an unrecorded place immediately behind the (recorded) place in which the preceding trial writing was done.
The data area is so configured that additional recording is done along the groove area 214 provided spirally from the inner edge toward the outer edge. Trial writing in the extended drive test zone is done behind the place where the preceding trial writing was done, making it possible to carry out the process of “checking the place where the preceding trial writing was done”→the process of “doing the present trial writing” serially in that order, which not only facilitates the trial writing process but also makes it easier to manage the places where trial writing was done in the extended drive test zone EDRTZ.
(3) Data lead-out area DTLDO including the extended drive test zone EDRTZ can be set again.
Recording pulses are made up of optical pulses as shown in
(Recording Pulse Structure for a 2T Mark)
TSFP after the rising edge of an NRZI signal, the generation of a mono pulse is started. The generation is completed 1T−TELP before the falling edge of the NRZI signal. The period of the mono pulse is 1T−TELP+TSFP. TELP and TSFP are recorded in the control data zone. The period of the second bias power following the mono pulse is TLC. TLC is recorded in the control data zone.
(Recording Pulse Structure for 2T or More Mark)
TSEP after the rising edge of an NRZI signal, the generation of a first pulse is started. TEFP after the falling edge of the NRZI signal, the generation is completed. TEFP and TSFP are recorded in the control data zone. A recording pulse corresponding to 4T to 13T is a multi-pulse train. The multi-pulse train is a repetition of a pulse with a pulse width of TMP and a period of T. 2T after the rising edge of the NRZI signal, the generation of a multi-pulse is started. 2T before the falling edge of the NRZI signal, the generation of the last pulse in the multi-pulse train is completed. TMP is recorded in the control data zone.
1T−TSLP before the rising edge of the NRZI signal, the generation of the last pulse is started. 1T−TELP before the falling edge of the NRZI signal, the generation of the last pulse is completed. TELP and TSLP are recorded in the control data zone. The pulse width of the pulse of the second bias power following the last pulse is TLC. TLC is recorded in the control data zone. TEFP−TSFP, TMP, TELP−TSLP, and TLC are the maximum periods of a full width and a half width. The maximum periods of the full width and half width of each optical pulse are defined in
TSFP, TEFP, TSLP, TELP, TMP, and TLC are recorded in the control data zone in units of (1/32)T. They take the following values:
TSFP is 0.25T or more and 1.50T or less.
TELP is 0.00T or more and 1.00T or less.
TEFP is 1.00T or more and 1.75T or less.
TSLP is −0.10 or more and 1.00T or less.
TLC is 0.00T or more and 1.00T or less.
TMP is 0.15T or more and 0.75T or less.
The following restrictions are imposed on adaptive control parameters TSFP, TELP, and TLC:
The difference between the maximum value and minimum value of TSFP is 0.50T or less.
The difference between the maximum value and minimum value of TELP is 0.50T or less.
The difference between the maximum value and minimum value of TLC is 1.00T or less.
The width of mono pulse 1T−TSFP+TELP is 0.25T or more and 1.50T or less.
These parameters are controlled with a precision of ±0.2 ns. If the peak power period of the first pulse and that of the multi-pulse train overlap with each other, a composite peak power period is the sum total of these consecutive peak power periods. If the peak power period of the first pulse and that of the last pulse overlap with each other, a composite peak power period is the sum total of these consecutive peak power periods. If the peak power period of the end pulse in the multi-pulse train and that of the last pulse overlap with each other, a composite peak power period is the sum total of these consecutive peak power periods.
The recording power has the following four levels: peak power, first bias power, second bias power, and third bias power. These are optical power which are projected onto the reading surface of a disk and used to record marks and spaces.
The peak power, first bias power, second bias power, and third bias power are recorded in the control data zone. The maximum value of the peak power does not exceed, for example, 10.0 mW. The maximum value of each of the first bias power, second bias power, and third bias power does not exceed, for example, 4.0 mW.
The average peak power of each of the mono pulse, first pulse, and last pulse fulfills the following requirement:
|(average peak power)−(peak power)|≦5% of peak power
The average first bias power and average second bias power fulfill the following requirements:
|(average first bias power)−(first bias power)|≦5% of first bias power
|(average second bias power)−(second bias power)|≦5% of second bias power
The average power of the multi-pulse train is the average power of an instantaneous value of the power in the measuring period.
The measuring period includes all of the multi-pulse train and is a multiple of T. The average power of the multi-pulse train fulfills the following requirement:
|(average power of multi-pulse train)−(peak power+third bias power)/2|≦5% of (peak power+second bias power)/2
An instantaneous value of power is an instantaneous value of actual power.
The average power is the average value of an instantaneous value of power in a specific power range.
The power range of the average value of power satisfies the following requirements:
the average value of peak power: |(actual power)−(peak power)|≦10% of peak power
the average value of first bias power:
|(actual power)−(first bias power)|≦10% of first bias power
the average value of second bias power:
|(actual power)−(second bias power)|≦10% of second bias power
the average value of third bias power:
|(actual power)−(third bias power)|≦10% of third bias power
The period required to measure the average power does not exceed the pulse width period of each pulse.
Instantaneous-value power satisfies the following requirements:
|(instantaneous-value peak power)−(peak power)|≦10% of peak power
|(instantaneous-value first bias power)−(first bias power)|≦10% of first bias power
|(instantaneous-value second bias power)−(second bias power)|≦10% of second bias power
|(instantaneous-value third bias power)−(third bias power)|≦10% of third bias power
To control the mark edge position accurately, the timing of the first pulse, last pulse, and mono pulse is modulated.
The mark lengths of NRZI are classified into M2, M3, and M4. The mark lengths M2, M3, and M4 indicate 2T, 3T, and 3T or more, respectively. The space lengths immediately in front of a mark are classified into LS2, LS3, and LS4. The space lengths LS2, LS3, and LS4 indicate 2T, 3T, and 3T or more, respectively. The space lengths immediately behind a mark are classified into TS2, TS3, and TS4. The space lengths TS2, TS3, and TS4 indicate 2T, 3T, and 3T or more, respectively.
TLC is modulated as a function of the category of the mark length of NRZI. Therefore, TLC has the following three values:
TLC(M2), TLC(M3), TLC(M4)
TLC(M) represents the value of TLC when the category of the mark length of the NRZI is M.
The values of these three TLC are recorded in the control data zone.
TSFP is modulated as a function of the category of the mark length of NRZI and the category of the space length of NRZI immediately in front of the mark. Therefore, TSFP has the following nine values:
TSFP(M2, LS2), TSFP(M3, LS2), TSFP(M4, LS2)
TSFP(M2, LS3), TSFP(M3, LS3), TSFP(M4, LS3)
TSFP(M2, LS4), TSFP(M3, LS4), TSFP(M4, LS4)
TSFP(M, LS) indicates the value when the category of the mark length of the NRZI signal is M and the category of the space length of NRZI immediately in front of the mark is LS. These nine values of TSFP are recorded in the control data zone.
TELP is modulated as a function of the category of the mark length of NRZI and the category of the space length of NRZI immediately behind the mark. Therefore, TELP has the following nine values:
TELP(M2, TS2), TELP(M3, TS2), TELP(M4, TS2)
TELP(M2, TS3), TELP(M3, TS3), TELP(M4, TS3)
TELP(M2, TS4), TELP(M3, TS4), TELP(M4, TS4)
TELP(M, TS) indicates the value when the category of the mark length of the NRZI signal is M and the category of the space length of NRZI immediately in front of the mark is TS. These nine values of TELP are recorded in the control data zone.
While in the above example, a multi-pulse train has been used as a write strategy in all of the cases, a so-called block strategy or a write strategy obtained by modifying the block strategy may be used. Under high transfer rate/high linear speed conditions, the block strategy may be easier to control than a multi-pulse train. When data has to be written in less than the limiting value (about one nanosecond) of the rising time of the laser, a multi-pulse train is particularly difficult to use. Therefore, it is necessary to use the block strategy, or a pulse-train whose period is extended (e.g., doubled).
Of the recordable mediums (including the RAM type and RW type), the RW type does additional recording in the same manner as the R type (or the type that prevents rewriting and allows only additional recording to be done in an unrecorded area). Therefore, in an explanation of the RW type, “rewriting” is read as “additional recording” in a similar recording operation to additional reading in the R type (the R type can do only additional recording, whereas the RAM/RW type can do both of additional recording and rewriting). In the disk manufacturing information DMI, information 251 on the name of the country where the medium was manufactured and information 252 on the country to which the medium manufacturer belongs have been recorded. A warning of infringement is often given in a country that has a location of manufacture when a sold information storage medium has committed a patent violation or in a country information storage mediums have been consumed (or used). The recording of the above information is required to be done in the information storage medium, making the location of manufacture (country name) clear and facilitating a warning of patent violation, which guarantees intellectual property and promotes technological advances. Moreover, in the disk manufacturing information DMI, other disk manufacturing information 253 is also recorded.
In physical format information PFI or R physical format information R_PFI, the type of information to be recorded is determined by the recording place (or the byte positions relative to the starting position). Specifically, as the recording place in physical format information PFI or R physical format information R_PFI, common information 261 in the DVD family is recorded in a 32-byte area ranging from the 0th byte to 31st byte, common information 262 in the HD_DVD family to be handled in the embodiment is recorded in a 96-byte area ranging from the 32nd byte to 127th byte, unique information 263 about the types of written standards and part versions is written in a 384-byte area ranging from the 128th byte to 511th byte, and information corresponding to each revision is recorded in a 1536-type area ranging from the 512th byte to 2047th byte. As described above, the information arrangement positions in the physical format information are standardized according to the contents of information, thereby standardizing the places of recorded information, regardless of the type of medium, which enables the reproducing processes in the information reproducing apparatus or information recording and reproducing apparatus to be standardized and simplified.
As shown in
Revision number information that determines the maximum recording speed, revision number table (application revision number), cluster state information, and expanded (part) version are recorded in the 28th byte to 31st byte in that order as common information 261 in the DVD family and information 268 similarly recorded in each of a rewritable and a recordable information storage medium. Revision information corresponding to the recording speed is recorded in the 28th byte to 31st byte of the recording area of physical format information PFI or R physical format information R_PFI.
With the development of a medium with an increased recording speed, such as double speed or quad speed, this has involved an immense amount of time and effort to remake written standards accordingly. In contrast, in this embodiment, written standards are divided into a version book whose version is changed when the contents are changed greatly and a revision book which is revised according to a small change in the recording speed or the like and is issued. Each time the recording speed is improved, only a revision book where only the revision has been updated is issued. This produces the effect of guaranteeing the function of expanding a medium to a future high-speed-recording-compatible medium. In addition, since standards can be dealt with by a simple method of revision, when a new high-speed-recording-compatible medium is developed, this can be coped with at high speed.
Providing separately a field for revision number information that determines the maximum recording speed in the 17th byte and a field for revision number information that determines the minimum recording speed in the 18th byte enables different revision numbers to be assigned to the maximum and minimum values of the recording speed. For instance, when a recording film which enables very high speed recording has been developed, the recording film makes it possible to record data at very high speed, but makes it impossible suddenly to record data when the recording speed is lowered. In addition, such a recording film as enables the minimum possible recording speed to be lowered may be very expensive. In contrast, as in the embodiment, revision numbers are made settable separately using the maximum value and minimum value of the recording speed, making the selection range of the developable recording film wider, which produces the effect of enabling a higher-speed recordable medium and a lower-price medium to be supplied. In the information recording and reproducing apparatus of the embodiment, information on the maximum possible recording speed and the minimum possible recording speed for each revision are known in advance. When an information storage medium is installed in the information recording and reproducing apparatus, the information recording and reproducing section 141 of
Next, explanation will be given about unique information 263 on the types and versions of written standards in the 128th byte to 511th byte and the contents 264 of information uniquely settable in the 512th type to 2047th byte on a revision basis shown in
As shown in
This embodiment is particularly characterized in that information on the polarity of a recording mark (identifying whether it is High-to-Low or Low-to-High) MPD (Mark Polarity Descriptor) is recorded in the 192th byte. In a conventional rewritable or recordable DVD disk, only a High-to-Low recording film where the amount of reflected light in a recording mark was lowered as compared with that in the unrecorded state (the reflection level was relatively high) was allowed. If a request was made for “high-speed recording” and “lower price” or the physical performance, including “the decrease of cross erase” and “an increase in the upper limit of the number of rewritings”, this could not be dealt with only by a conventional High-to-Low recording film. In contrast, since the present embodiment permits the use of not only a High-to-Low recording film but also a Low-to-High recording film where the amount of reflected light increases in a recording mark, this produces the effect of incorporating not only a conventional High-to-Low recording film but also a Low-to-High recording film into standards to widen the recording film selection range and therefore enabling higher-speed recording and the supply of lower-cost mediums.
A method of implementing an information recording and reproducing apparatus will be explained concretely below. In a version book or a revision book, both of the reproduced signal characteristic of a High-to-Low recording film and that of a Low-to-High recording film are written. According to the description, two types of handling circuits are prepared in the PR equalizing circuit 130 and Viterbi decoder 156 of
The embodiment is characterized in that the rim intensity value of the optical system in the radial direction in the 194th byte and the rim intensity value of the optical system in the radial direction in the 195th byte are arranged as optical system condition information in the position that precedes various types of recording condition (write strategy) information included in information content 264 uniquely settable on a revision basis. These pieces of information are condition information on the optical system of the optical head used in determining the recording condition placed behind them. Rim intensity means the distribution of incident light which enters the objective before converging on the recording surface of the information storage medium and is defined as the value of intensity at the periphery of the objective (or at the periphery of the pupil surface) if the central intensity of the intensity distribution of incident light is “1”. The intensity distribution of incident light to the objective is not symmetric with respect to a point, but is an elliptic distribution. Since the value of the rim intensity in the radial direction of the information storage medium differs from that in its circumferential direction, the two values are recorded. The larger the value of the rim intensity, the smaller the condensed spot size on the recording surface of the information storage medium becomes. As a result, depending on the value of the rim intensity, the optimum recording power condition changes greatly.
Since the information recording and reproducing apparatus has known information on the value of the rim intensity of its own optical head, it first reads the value of the rim intensity of the optical system along each of the circumference and the radius recorded on the information storage medium and compares these values with the values of its own optical head. If the result of the comparison has shown no great difference, the recording condition recorded behind can be applied. If the result of the comparison has shown a great difference, the information recording and reproducing apparatus has to ignore the recording condition recorded behind and begins determining the optimum recording condition, while doing trial writing using the drive test zones DRTZ written in
As described above, it is necessary to determine quickly whether to use the recording condition recorded behind or ignore the information and start to find the optimum recording condition while performing trial writing. As shown in
As described above, with the embodiment, the written standards are divided into a version book where the version is changed if the contents have been change greatly and a revision book whose revision is changed according to a small change in the recording speed and then which is issued. Each time the recording speed is improved, only a revision book whose revision alone has been updated is issued. Therefore, since the revision number becomes different, the recording condition in the revision block changes. Information about the recording condition (write strategy) is recorded in information content 264 uniquely settable mainly in the 512th byte to 2047th byte on a revision basis. As seen from
The definitions of peak power, first bias power, second bias power, and third bias power coincide with the power values defined in
A data frame, which is a place in which user data is recorded, is made up of 2048 bytes of main data, a 4-byte data ID, a 2-byte ID error detection code (IED), 6-byte reserved bytes RSV, and a 4-byte error detection code (EDC). First, an IED (ID error detection code) is added to data ID, which is explained later. The 6-byte reserved bytes and data frame are places in which user data is to be recorded. After 2048 bytes of main data are added and an error detection code (EDC) is added, the main data is scrambled. Then, Cross Reed-Solomon Error Correction Code is applied to the scrambled 32 data frames (scrambled frames), thereby carrying out an ECC encoding process, which configures a recording frame.
The recording frame includes outer parity code (Parity of Outer-code) PO and inner parity code (Parity of Inner-code) PI. Each of the parity codes PO and PI is an error correction code created for each ECC block composed of 32 scrambled frames. As described earlier, a recoding frame is subjected to ETM (Eight to Twelve Modulation) in which 8 data bits are converted into 12 channel bits. Then, a sync code SYNC is added to the head in units of 91 bytes, thereby creating 32 physical sectors. This embodiment is characterized in that 32 sectors constitute one error correction unit (ECC block) as written in the frame at the bottom right of
Next-generation DVDs are required to reproduce information accurately by an error correction process, even if as long a flaw as that in the present-generation DVD has been made in the surface of the information storage medium. In this embodiment, the recording density is increased aiming at a larger capacity. As a result, in the case of a conventional ECC block=16 sectors, the length of a physical flaw correctable by error correction becomes shorter than that of the conventional DVD. As in the embodiment, configuring one ECC block using 32 sectors produces the effect of not only lengthening the allowable length of a flaw in the information storage medium which can be corrected by error correction but also securing the interchangeability of the ECC block structure of the existing DVD and the continuity of the format.
Data ID is composed of data frame information 921 and information on data frame number 922. The data frame number represents the physical sector number 922 of the corresponding data frame.
Data frame information 921 is made up of the following information:
Format type 931—0b: represents CLV
Tracking method 932—0b: uses a DPD (Differential Phase Detect) method in a pit-compatible manner in this embodiment
Reflectivity of the recording film 933—0b: 40% or more
1
b: 40% or less
Recording type information 934—0b: General data
1
b: Real-time data (Audio Video data)
Area type information 935—00b: Data area DTA
01
b: System lead-in area SYLDI or data lead-in area DTLDI
10
b: Data lead-out area DTLDO or system lead-out area SYLDO
Data type information 936—0b: Reproduce-only data
1
b: Rewritable data
Layer number 937—0b: Layer 0
The ECC block structure of
PI of a 10-byte size written at right of
Specifically, an ECC block is composed of 32 consecutive scrambled frames. Each row in the left half of an odd-numbered sector is replaced with a row in the right half. 172×2 bytes×192 rows, which are equal to 172 bytes×12 rows×32 scrambled frames, make a data area. A 16-byte PO is added to each set of 172×2 columns to form an outer code for RS (208, 192, 17). A 10-byte PI (RS (182, 172, 11)) is added to each set of 208×2 rows in the right and left blocks. PI is also added to the row of PO. The number in a frame indicates a scrambled frame number. The suffixes R, L mean the right half and left half of a scrambled frame, respectively.
The embodiment is characterized in that the same data frame is distributed over a plurality of small ECC blocks. Specifically, in the embodiment, two small ECC blocks constitute a large ECC block. The same data frame is distributed over the two small ECC blocks alternately. As explained in
As described above, distributing the same data frame over a plurality of small ECC blocks improves the error correcting capability of the data in the physical sector (
In
In this embodiment, a combination of “0-L” and “0-R” is called “0th recording frame” and a combination of “1-L” and “1-R” is called “1st recording frame” in
A small ECC block including data ID in an odd-numbered recording frame differs from a small ECC block including data ID in an even-numbered recording frame (they are provided alternately) (
A part of the left PO shown in
When the physical sector structure shown in each of
As described above, in this embodiment, the same physical sector is caused to belong to two small ECC blocks alternately in units of 2232 channel bits. To put it another way, the data in the right small ECC block and the data in the left small ECC block are distributed alternately in units of 2232 channel bits to form physical sectors, thereby recording data onto the information storage medium. This produces the effect of achieving a structure resistant to burst errors. For example, consider a burst error state where a long flaw has been made in the circumferential direction of the information storage medium and more than 172 bytes of data cannot be read. In this case, since the burst error exceeding 172 bytes is distributed over two small ECC blocks, the burden of error correction in one ECC block is alleviated, assuring higher-performance error correction.
As shown in
(1) A small ECC block (right or left) to which the first 2232 channel bits of data in the physical sector belong differs.
(2) The structure is such that a different PO group of data is inserted alternately on a sector basis.
As a result, even after an ECC block has been configured, the structure that assures the arrangement of data ID at the begin positions of all of the physical sectors is guaranteed, which makes it possible to check the data positions at high speed at the time of accessing. Furthermore, inserting PO belonging to different small ECC blocks into the same sector in a mixed manner simplifies the PO inserting method as shown in
In a method of realizing concretely what has been described above, a structure where PO interleaving and inserting positions at right differ from those at left is used. A part shown by a narrow double line in
X(t)=H{B(t), S(t)}
S(t+1)=G{B(t), S(t)}
where H is a code word output function and G is a next State output function.
A state register 358 inputs next state S(t+1) from the code table 352 and outputs (current) state S(t) to the code table 352. Some 12 channel bits in the code conversion table include not only “0b” and “1b” but also asterisk bit “*” and sharp bit “#”. Asterisk bit “*” in the code conversion table indicates that the bit is a margining bit. Some code words in the conversion table have a margining bit at LSB. A code connector 354 sets the margining bit to either “0b” or “1b” according to the channel bit following the margining bit. If the following channel bit is “0b”, the margining bit is set to “1b”. If the following channel bit is “1b”, the margining bit is set to “0b”. Sharp bit “#” in the conversion table indicates that the bit is a DSV control bit. The DSV control bit is determined as a result of DVC component suppression control performed by a DSV controller 536.
Although the individual ECC blocks 411 to 418 are shown in the same size for comparison, 16 physical sectors constitute one ECC block in a conventional reproduce-only information storage medium DVD-ROM, a conventional recordable information storage medium DVD-R, and a conventional rewritable information storage medium DVD-RW shown in
In a conventional reproduce-only information storage medium DVD-ROM, ECC blocks #1411 to #8418 are recorded consecutively as shown in
The embodiment is characterized in that the length of each of the guard areas 442 to 448 is made equal to the sync frame length 433 of one sync frame size as shown in
Furthermore, in the embodiment, sync codes (sync data) are provided in the guard areas for the purpose of achieving the following:
(1) The frequency of appearances of sync code is made equal even in a place crossing over the guard areas 442 to 448, thereby improving the accuracy of sync code position detection.
(2) The determination of the positions of physical sectors including the guard areas 442 to 448 is made easier.
Specifically, as shown in
In this embodiment, the area of one ECC block #2 (see
Pre-sync areas 477, 478 indicate the positions of the boundary between the VFO areas 471, 472 and the data area 470. The recording channel bit pattern after modulation is a repetition of “100000 100000” (a repeated pattern of 5 consecutive “0s”). The information reproducing apparatus or information recording and reproducing apparatus detects the position of a change in a repeated pattern of “100000 100000” in the pre-sync areas 477, 478 from a repeated pattern of “010001 000100” in the VFO areas 471, 471, thereby realizing the approach of the data area 470. The postamble field 481 indicates not only the end position of the data area 470 but also the starting position of a guard area 443. The pattern in the postamble field 481 coincides with the pattern of “SY1” in a sync code.
An extra area 482 is an area used for copy control and unauthorized copy prevention. When the extra area 482 is not used for copy control and unauthorized copy prevention, all of it is set to “0” in channel bits. In the buffer area, the same data before modulation as in the VFO areas 471, 472 is a repetition of “7Eh” and the actually recorded channel bit pattern after modulation is a repeated pattern of “010001 000100” (a repeated pattern of three consecutive “0s”). To obtain this pattern, the begin byte in each of the VFO areas 471, 472 has to be set to State 2 in modulation.
As shown in
In this embodiment, not only the structure of
In this embodiment, address information on a recording (rewritable or recordable) information storage medium is recorded in advance by wobble modulation. In the wobble modulation method, ±90° (180°) phase modulation is used. Address information is recorded in advance onto the information storage medium by the NRZ (Non-Return to Zero) method.
When a plurality of data segments 529, 530 are recorded consecutively, a plurality of data segments 529, 530 are arranged consecutively in the same recording cluster 531 as shown in
As seen from a correspondence between
To compare physical ranges of rewriting units,
The size of rewritable data in one data segment in the embodiment is:
67+4+77376+2+4+16=77469 data bytes (01)
In addition, as seen from
6+4+6+68=84 wobbles (02)
17 wobble data units constitute one physical segment 550. The length of seven physical segments 550 to 556 coincides with the length of one data segment 531, the length of one data segment 531 includes:
84×17×7=9996 wobbles (03)
Therefore, from equation (01) and equation (03), the following corresponds to one wobble:
77496÷9996=7.75 data bytes/wobble (04)
In the embodiment, the recording film of the rewritable information storage medium uses a phase-change recording film. In a phase-change recording film, since the recording film begins to deteriorate near the rewrite starting and end positions, repeating the recording start and end in the same position limits the number of rewrites due to the deterioration of the recording film. In the embodiment, to alleviate this problem, a shift of (Jm+1/12) data bytes is made in rewriting as shown in
In
A DVD-RAM disk, an existing rewritable information storage medium, also uses a phase-change recording film and shifts the recording start and end positions at random to increase the number of rewrites. The maximum amount of shift in making a random shift on an existing DVD-RAM disk is set to 8 data bytes. The channel bit length (of modulated data recorded on the disk) in an existing DVD-RAM disk is set to 0.143 μm on average.
In the rewritable information storage medium of the embodiment, from
(0.087+0.093)÷2=0.090 μm (05)
When the length of the physical shift range is adapted to the existing DVD-RAM disk, the required minimum length as the random shift range in the embodiment is calculated using the above value as follows:
8 bytes×(0.143 μm÷0.090 μm)=12.7 byte (06)
In the embodiment, to facilitate the reproduced signal detecting process, the unit of the amount of random shift is adapted to a “channel bit” after modulation. In the embodiment, since ETM modulation (Eight to Twelve modulation) that converts 8 bits into 12 bits is used, the amount of random shift is expressed using a mathematical formula with a date byte as a reference:
Jm/12 data bytes (07)
It follows from equation (06) that:
12.7×12=152.4 (08)
Therefore, the values Jm can take are from 0 to 152. For the above reasons, in the range satisfying equation (08), the length of the random shift range agrees with the existing DVD-RAM disk, which assures the same number of rewrites as that of the existing DVD-RAM disk.
In the embodiment, to secure the number of rewrites larger than that of the existing DVD-RAM disk, a small margin is allowed for the value of equation (06) as follows:
The length of the random shift range is set to 14 data bytes (09)
Substituting the value of equation (10) into equation (07) gives 14×12=168. Therefore, it follows that:
The values Jm can take are from 0 to 167 (10)
The amount of random shift is set to a larger range than Jm/12 (0≦Jm≦154), thereby satisfying equation (08) and causing the length of the physical range for the amount of random shift to agree with the existing DVD-RAM, which produces the effect of assuring the same number of repeated recordings as that of the existing DVD-RAM.
In
At this time, there may be rare occasions when a wobble slip (recording done in a position shifted by one wobble period) will occur due to the miscounting of wobbles or uneven rotation of the rotating motor that rotates the information storage medium and therefore the recording position will shift on the information storage medium. In the information storage medium of the embodiment, if a shift in the recoding position has been detected as described above, adjustment is made in a rewritable guard area 461 of
In
In this embodiment, as shown in
a shift of ±1 data bytes (11)
In
In contrast, when a data segment 530 is recorded in the rearmost position and a data segment 531 to be rewritten or additionally recorded later is recorded in the very front position, the begin position of the VFO area 522 may go into the buffer area 537 by up to 15 data bytes because of the values in (09) and (10). In the extra area 534 just in front of the buffer area 537, specific important information has been recorded. Therefore, in the embodiment, the following must be met:
the length of the buffer area 537 has to be 15 data bytes or more (12)
In the embodiment shown in
If a gap occurs between the extended guard area 528 and the VFO area 522 as a result of a random shift, when a single-sided double-recording-layer structure is used, interlayer crosstalk is caused by the gap during reproduction. To overcome this problem, the extended guard field 528 and VFO area 522 are caused to always partially overlap with each other even when a random shift is made, thereby preventing a gap from occurring. Therefore, in the embodiment, from (12), the length of the extended guard field 528 must be set to 15 data bytes or more. Since a subsequent VFO 522 is made as long as 71 data bytes, even if the overlapping area of the extended guard field 528 and VFO area 522 becomes a little wider, this has no adverse effect in reproducing a signal (because the time required to synchronize the reproduction reference clock in the unoverlapped VFO area 522 is secured sufficiently). Therefore, the extended guard field 528 can be set to a larger value than 15 data bytes.
There may be rare occasions when a wobble slip will occur in continuous recording and the recording position will shift by one wobble period. As seen from equation (04), a wobble period corresponds to 7.75 (about 8) data bytes. Thus, taking this into account, (12) is modified as follows in the embodiment:
The length of the extended guard field 528 is set to (15+8)=23 data bytes or more (14)
In the embodiment shown in
In
As shown in
Moreover, in any one of the reproduce-only information storage medium (in
In another embodiment of the invention, as with an existing DVD-R, the step of an emboss in the system lead-in/system lead-out areas SYLDI/SYLDO of the recordable information medium is set shallow. This makes the depth of a pre-groove in the recordable information storage medium shallower, producing the effect of increasing the modulation degree of the reproduced signal from the recording mark formed in additional writing on the pre-groove. Conversely, there arises another problem: the modulation degree of the reproduced signal from the system lead-in/system lead-out areas SYLDI/SYLDO becomes smaller. To overcome this problem, the data bit length (and/or track pitch) of the system lead-in/system lead-out areas SYLDI/SYLDO is made rougher, thereby separating (making much lower) the repeat frequency of pits and spaces in the densest position from the optical cut-off frequency of the reproduction objective MTF (Modulation Transfer Function), which makes it possible to increase the amplitude of the reproduced signal from the system lead-in/system lead-out areas SYLDI/SYLDO and stabilize reproduction.
Although the general parameters of the 30-GB single-sided, dual-layer type (in
<Format of Information Area>
An information area provided over two layers includes seven areas: a system lead-in area, a connection area, a data lead-in area, a data area, a data lead-out area, a system lead-out area, and a middle area. Providing each layer with a middle area enables a reproduction beam to be moved from layer 0 to layer 1. In the data area, main data is recorded. The system lead-in area includes control data and reference code. The data lead-out area enables continuous smooth reading.
<Lead-Out Area>
The system lead-in area and system lead-out area include tracks composed of emboss pits. The data lead-in area, data area, and middle area in layer 0 and the middle area, data area, and data lead-out area in layer 1 include groove tracks. The groove track is continuous from the starting position of the data lead-in area to the end position of the middle area in layer 0 and from the starting position of the middle area to the end position of the data lead-out area in layer 1. Laminating single-sided, dual-layer disks together produces a double-sided, dual-layer disk having two reading surfaces (or a disk having a total of four recording layers).
Each track in the system lead-in area and system lead-out area is divided into data segments.
Each track in the data lead-in area, data area, data lead-out area, and middle area is divided into PS blocks. Each PS block is divided into seven physical segments. Each physical segment contains 11067 bytes.
<Lead-In Area, Lead-Out Area, and Middle Area>
The layout of the middle area can be changed by rearrangement. The boundary between individual zones and between areas in each of the lead-in area, lead-out area, and middle area coincide with the boundary between data segments. On the inner edge side of layer 0, the system lead-in area, connection area, data lead-in area, and data area are provided in that order from the innermost periphery. On the inner edge side of layer 1, the system lead-out area, connection area, data lead-out area, and data area are provided in that order from the innermost periphery.
As described above, since the data lead-in area including a management area is provided only in layer 0, when finalization is performed in layer L1, information on layer L1 is also written in the data lead-in area. This makes it possible to acquire all the management information by reading only layer L0 at the time of start-up, which eliminates the burden of reading layer L0 and layer L1 each time. To record data into layer L1, all of layer L0 has to be written into beforehand. It is at the time of finalization that the management area is filled in.
The system lead-in area in layer 0 is composed of an initial zone, a buffer zone, a control data zone, and a buffer zone in that order from the inner edge side. The data lead-in area in layer 0 is composed of a blank zone, a guard track zone, a drive test zone, a disk test zone, a blank zone, an RMD duplication zone, an L-RMD (recording management data), an R physical format information zone, and a reference code zone in that order from the inner edge side. The starting address (on the inner edge side) of the data area in layer 0 is shifted a clearance from the ending address (on the inner edge side) of the data area in layer 1. The ending address (on the inner edge side) of the data area in layer 1 is closer to the outer edge side than the starting address of the data area in layer 0.
The data lead-out area in layer 1 is composed of a blank zone, a disk test zone, a drive test zone, and a guard track zone in that order from the inner edge side. The blank zone is an area which has grooves but has no data written into. The guard track zone is a zone in which a specific pattern is recorded for testing. In the guard track zone, data “00” before modulation is recorded. The guard track zone in layer 0 is provided to record the disk test zone and drive test zone in layer 1. Therefore, the guard track zone in layer 0 corresponds to a field obtained by adding at least a clearance to the disk test zone and drive test zone in layer 1. The guard track zone in layer 1 is provided to record the drive test zone, disk test zone, blank zone, RMD duplication zone, L-RMD, R physical format information zone, and reference code zone in layer 0. Therefore, the guard track zone in layer 1 corresponds to a field obtained by adding at least a clearance to the drive test zone, disk test zone, blank zone, RMD duplication zone, L-RMD, R physical format information zone, and reference code zone in layer 0.
Like byte positions 197 to 511 in
Furthermore, although not shown, byte position 32 in
Moreover, although not shown, in byte position 33 in
In addition, although not shown, in byte position 133 to byte position 151 in
In byte position 149, the reflectivity of the data area is written. For example, when 00101000b has been written in byte position 149, this means that the reflectivity is 20%. The actual reflectivity is calculated using Value×(1/2)%.
In byte position 150, information on a push-pull signal including a track-shape bit is written. When the track-shape bit is 0b, this means that the track is on a groove. When the bit is 1b, this means that the track is on a land. Moreover, when seven bits representing a push-pull signal is 0101000b, the value of the push-pull signal is, for example, “0.40”. The actual amplitude ((I1-I2)PP/(I1+I2)DC) of the push-pull signal is calculated using Value×(1/100).
In byte position 151, the amplitude of “on-track signal” is written. When the description in byte position 151 is 01000110b, this means that the amplitude of the on-track signal is 0.70. The amplitude value of the actual on-track signal is calculated using Value×(1/100).
In a recordable information storage medium, physical formation information PFI (or a copy of common information on the HD_DVD family) is recorded in R-physical format information recorded in the R physical information zone RIZ in the data lead-in area DTLDI in such a manner that information on the starting position of a border zone (or the outermost address of the first border) is added to the physical format information. In updated physical format information U_PFI in the border-in BRDI, physical format information PFI (a copy of common information on the HD_DVD family) is recorded in such a manner that information on its updated starting position (or the outermost address of its border) is added to the format information. In the example of
There is a possibility that the revision number will be increased and more accurate recording condition be required in the future and therefore, for example, byte position 197 to byte position 207 will be used for information on recording conditions for a rewritable information storage medium. In that case, if information on the starting position of the border zone of R physical format information recorded in the recordable information storage medium as shown in the example of
The contents of concrete information on the starting position of the border zone are as follows. In byte position 133 to byte position 136, “information on the starting position of the border-out BRDO outside the border-in area BRDA currently being used” is written using a physical sector number (PSN) or a physical segment number (PSN). In byte position 137 to byte position 140, “information on the starting position of the border-in BRDI related to the border-in area BRDA to be used next” is written using a physical sector number (PSN) or a physical segment number (PSN).
The contents of concrete information on the updated starting position represent the latest border zone information when a border-in area BRDA has been newly set. Specifically, in byte position 133 to byte position 136, information on the starting position of the border-out BRDO outside the border-in area BRDA currently being used is written using a physical sector number or a physical segment number (PSN). In byte position 137 to byte position 140, information on the starting position of the border-in BRDI related to the border-in area BRDA to be used next is written using a physical sector number or a physical segment number (PSN). When the next border-in area BRDA cannot be recorded into, the area (ranging from byte position 137 to byte position 140) is all filled with “00h”.
In contrast with the example of
Specifically, if the key input is, for example, a key operation of setting timer recording, a program setting process is started (ST20). If the key input is a key operation of starting picture recording, a picture recording process is started (ST22). If the key input is a key operation of starting reproduction, a reproducing process is started (ST24). If the key input is a key operation of outputting a digital signal to a STB or the like, a digital output process is started (ST26). If the key input is a key operation of editing, an editing process is started (ST28).
The processes in step ST20 to ST28 are processed in parallel in each task as needed. For example, during the reproducing process (ST24), the process of outputting a digital signal to the STB (ST26) is carried out in parallel. Moreover, a new program setting process (ST20) may be configured to be processed in parallel, while the process of recording video without timer recording is being carried out (ST22). Alternatively, taking into account the advantage of fast accessible disk recording, a reproducing process (ST24) and a digital output process (ST26) may be configured to be carried out in parallel during the recording process (ST22). The process of editing on a disk (ST28) may be configured to be carried out, while a hard disk drive (HDD) (not shown) is being recorded into.
The optical disk substrates used in the embodiments disclosed in this specification are roughly divided into two types:
(a) One type uses a so-called land-groove recording method that has a groove pitch of about 0.6 to 0.8 μm and records data into both lands and grooves. Hereinafter, this type of information storage medium is also referred to as a rewritable (1) information storage medium.
(b) The other type uses a so-called groove recording method that has a groove pitch of about 0.3 to 0.4 μm and records data into only either lands or grooves (the name is also used when data is recorded into only lands for the sake of convenience). Hereinafter, this type of information storage medium is also referred to as a rewritable (2) information storage medium.
The thickness of the substrate on the light incident side is possible in the range from as thin as about 0.1 mm (with NA=about 0.85) to about 0.6 mm (with NA=about 0.65) according to the size of NA of the objective of the optical pickup. The wavelength λ of the laser beam to be used is assumed to be 405 nm.
Next, a detailed configuration of the information recording and reproducing apparatus and a disk (or information recording medium) when each of the methods is used in this embodiment will be explained. First, a case where the land-groove recording method (a) is used will be described.
The details have been already explained.
For example, when information is additionally recorded into a medium in which certain data has been written, it is necessary to record data immediately behind the backmost part of the previously recorded data to record data into an information storage medium without loss of data. In that case, a part of the data might be overwritten. In such a case, the configuration of an information recording medium of the invention shown in the embodiment below is suitable because the overwrite (OW) erase ratio is particularly high.
The details have been already explained.
As described above, when information is additionally recorded into a medium which has been recorded into halfway, it is necessary to record data immediately behind the backmost part of the already recorded data to record data into the information storage medium without loss of data. In that case, a part of the ending of the recorded data might be overwritten. In such a case, the configuration of an information recording medium shown in an embodiment of the invention below is suitable because the OW erase ratio is particularly high. Since in the age in which next-generation high-capacity mediums are used, the amount of information handled is large, the data recordable characteristic of a rewritable medium is also very important. Use of an optical recording medium according to the embodiment enables a high-density, high-reliability medium to be obtained and information to be recorded and reproduced more stably.
Next, a case where the land or groove method (b) is used will be explained. In the explanation below, what overlaps with the description of the land-groove recording method (a) will be omitted as needed.
The details have been already explained.
The embodiments of the invention are suitable combinations of the apparatus configurations, data structures, and medium configurations disclosed in the present application. Use of optical recording mediums according to the embodiments of the invention enables a high-density, high-reliability medium to be obtained and data to be recorded and reproduced more stably.
<Consequence>
The inventors of this application have come to the realization that the following are important. In a recording medium (100) which has a substrate (1a, 1b), and a stacked structure that includes a protective film or dielectric film (11a, 11b), a recording film (phase-change recording film 13a, 13b) capable of changing an atomic arrangement reversibly, a crystallization enhancing film (12a, 12b and/or 14a, 14b) in contact with the recording film, and a reflecting film (16a, 16b) and which enables the recording film (13) to be recorded into or erased from reversibly with light, an optical recording medium is suitable which is so configured that the elements (including Ge and Te) constituting the recording film (13a, 13b) have a segregation or a concentration distribution (see
In a recording medium capable of being recorded into or erased from reversibly with light, an optical recording medium is suitable which comprises a substrate, a recording film capable of changing an atomic arrangement reversibly, a film having a crystallization enhancing function and in contact with the recording film, a protective film or dielectric film, and a reflecting film, and which has an ultrathin oxide film with an average thickness of 0.1 nm or more and 1 nm or less made up of the constituent elements of the recording film in a region in contact with the recording film.
In a recording medium capable of being recorded into or erased from reversibly with light, an optical recording medium is suitable which comprises a substrate, a recording film capable of changing an atomic arrangement reversibly, a film having a crystallization enhancing function and in contact with the recording film, a protective film or dielectric film, a reflecting film, and a dielectric film that contributes to optical enhancement and/or thermal diffusion, and in which the elements constituting the recording film have a segregation or a concentration distribution in the direction of the thickness of the recording film from a region in contact with the recording film, or in the in-plane direction of the recording film.
In a recording medium capable of being recorded into or erased from reversibly with light, an optical recording medium is suitable which comprises a substrate, a recording film capable of changing an atomic arrangement reversibly, a film having a crystallization enhancing function and in contact with the recording film, a protective film or dielectric film, a reflecting film, and a dielectric film that contributes to optical enhancement and/or thermal diffusion, and which has an ultrathin oxide film with an average thickness of 0.1 nm or more and 1 nm or less made up of the constituent elements of the recording film in a region in contact with the recording film.
In a recording medium capable of being recorded into or erased from reversibly with light, an optical recording medium is suitable which comprises a substrate, a recording film capable of changing an atomic arrangement reversibly, a film having a crystallization enhancing function and in contact with the recording film, a protective film (or dielectric film), and a reflecting film, and in which the ratio of the DOS of the crystalline state to the DOS of the amorphous state (the DOS of the crystalline state/the DOS of the amorphous state) at an energy level 0.5 [eV] lower than the top of the DOS for the valance band of the recording film is 1.0 or more and 2.5 or less.
In a recording medium capable of being recorded into or erased from reversibly with light, an optical recording medium is suitable which comprises a substrate, a recording film capable of changing an atomic arrangement reversibly, a film having a crystallization enhancing function and in contact with the recording film, a protective film (or dielectric film), a reflecting film, and a dielectric film that contributes to optical enhancement and/or thermal diffusion, and in which the ratio of the DOS of the crystalline state to the DOS of the amorphous state (the DOS of the crystalline state/the DOS of the amorphous state) at an energy level 0.5 [eV] lower than the top of the DOS for the valance band of the recording film is 1.0 or more and 2.5 or less.
In a recording medium capable of being recorded into or erased from reversibly with light, an optical recording medium is suitable which comprises a substrate, a recording film capable of changing an atomic arrangement reversibly, a film having a crystallization enhancing function and in contact with the recording film, a protective film (or dielectric film), and a reflecting film, and which has such a configuration as performs control in such a manner that the crystallization speed over the recording film differs from that under the recording film.
In a recording medium capable of being recorded into or erased from reversibly with light, an optical recording medium is suitable which comprises a substrate, a recording film capable of changing an atomic arrangement reversibly, a film having a crystallization enhancing function and in contact with the recording film, a protective film (or dielectric film), a reflecting film, and a dielectric film that contributes to optical enhancement and/or thermal diffusion, and which has such a configuration as performs control in such a manner that the crystallization speed over the recording film differs from that under the recording film.
In the phase-change recording film, an optical recording medium is suitable in which the crystallization enhancing film (upper interface film or lower interface film) is configured to include germanium nitride (GeN), germanium-chrome nitride (GeCrN), zirconium oxide (ZrO2), stabilized zirconia+chrome oxide (ZrO2+Cr2O3), stabilized zirconia+silicon oxide+chrome oxide (ZrO2+SiO2+Cr2O3), zircon+chrome oxide (ZrSiO4+Cr2O3), or hafnium oxide (HfO2). Alternatively, the crystallization enhancing film is composed of a compound (HfO2-xNx) containing hafnium (Hf), oxygen (O), and nitrogen (N). Alternatively, the crystallization enhancing film is composed of a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y where z=0) containing zirconium (Zr), oxygen (O), nitrogen (N), and yttria (Y). Alternatively, the crystallization enhancing film is composed of a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y where z=1) containing zirconium (Zr), oxygen (O), nitrogen (N), and niobium (Nb). Alternatively, the crystallization enhancing film is composed of a film ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y where 0≦z≦1) containing zirconium (Zr), oxygen (O), nitrogen (N), yttria (Y), and niobium (Nb). Alternatively, the crystallization enhancing film is configured to include chrome oxide (Cr2O3), zinc oxide (ZnO), zinc oxide+tantalum oxide (ZnO+Ta2O5), zinc oxide+tantalum oxide+indium oxide (ZnO+Ta2O5+In2O3), tin oxide (SnO2), tin oxide+antimony oxide (SnO2+Sb2O3), tin oxide+tantalum oxide (SnO2+Ta2O5), or tin oxide+niobium oxide (SnO2+Nb2O5).
In the phase-change recording film, an optical recording medium is suitable in which one of the films with the crystallization enhancing function sandwiching the recording film between them (one of the upper interface film and lower information film) is configured to include germanium nitride (GeN), germanium-chrome nitride (GeCrN), zirconium oxide (ZrO2), stabilized zirconia+chrome oxide (ZrO2+Cr2O3), stabilized zirconia+silicon oxide+chrome oxide (ZrO2+SiO2+Cr2O3), zircon+chrome oxide (ZrSiO4+Cr2O3), or hafnium oxide (HfO2). Alternatively, one of the films is composed of a compound (HfO2-xNx) containing hafnium (Hf), oxygen (O), and nitrogen (N). Alternatively, one of the films is composed of a compound ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y) where z=0) containing zirconium (Zr), oxygen (O), nitrogen (N), and yttria (Y). Alternatively, one of the films is composed of a compound ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y) where z=1) containing zirconium (Zr), oxygen (O), nitrogen (N), and niobium (Nb). Alternatively, one of the films is composed of a compound ((ZrO2-xNx)1-y((Y2O3)1-z(Nb2O5)z)y) where 0≦z≦1) containing zirconium (Zr), oxygen (O), nitrogen (N), yttria (Y), and niobium (Nb).
Alternatively, the other of the films with the crystallization enhancing function sandwiching the recording film between them (the other of the upper interface film and lower information film) is configured to include chrome oxide (Cr2O3), zinc oxide (ZnO), zinc oxide+tantalum oxide (ZnO+Ta2O5), zinc oxide+tantalum oxide+indium oxide (ZnO+Ta2O5+In2O3), tin oxide (SnO2), tin oxide+antimony oxide (SnO2+Sb2O3), tin oxide+tantalum oxide (SnO2+Ta2O5), or tin oxide+niobium oxide (SnO2+Nb2O5).
The recording film includes at least Ge, Sb, and Te. When its composition is expressed as GexSbyTez where x+y+z=100, a composition in the area defined by x=55, z=45 and x=45, z=55 and x=10, y=28, z=42 and x=10, y=36, z=54 in a GeSbTe ternary phase diagram is suitable for the recording film. The recording film is obtained by sputtering a sputtering target of the above composition with an inert gas, such as Ar.
Ge in the recording film is relatively liable to get oxidized. A sputtering target serving as a starting material and an inert gas, such as Ar, used in sputtering include a trace of oxygen. Thus, the mixing of a trace of oxygen in the recording film is inevitable. If an oxide thin film is used for a layer in contact with the recording film, a trace of oxygen diffuses into the recording film, resulting in an increase in the amount of oxygen. As described above, even if not only Ge, Sb, and Te but also oxygen (O) or the like has been detected in the recording film, this does not depart from the spirit of the invention. Similarly, it is well known that there is a little difference between the composition of the sputtering target and the composition of the thin film formed under various conditions in the recording film. Generally, compositions with a difference of about ±1 [at. %] are regarded as the same composition except for a special case.
The recording film may include at least Ge, Sb, and Te and, on the basis of the composition within the above-described range, have a part of the composition replaced with bismuth (Bi) and/or indium (In) and/or tin (Sn). When the composition after the replacement is expressed as (Ge(1−w)Snw)x(Sb(1−v)(Bi(1−u)Inu)v)yTez where x+y+z=100, a recording film is suitable in which w, v, and u in the composition satisfy the following: 0≦w≦0.5 and 0≦v≦0.7 and 0≦u≦1. The recording film is obtained by sputtering a sputtering target of the above composition with an inert gas, such as Ar.
As described above, Ge in the recording film is relatively liable to get oxidized. A sputtering target serving as a starting material and an inert gas, such as Ar, used in sputtering include a trace of oxygen. Thus, the mixing of a trace of oxygen in the recording film is inevitable. If an oxide thin film is used for a layer in contact with the recording film, a trace of oxygen diffuses into the recording film, resulting in an increase in the amount of oxygen. As described above, even if not only Ge, Sb, and Sn/Bi/In but also oxygen (O) or the like has been detected in the recording film, this does not depart from the spirit of the invention.
The recording film includes at least Ge, Bi, and Te. When its composition is expressed as GexBiyTez where x+y+z=100, a composition in the area defined by x=55, z=45 and x=45, z=55 and x=10, y=28, z=42 and x=10, y=36, z=54 in a GeSiTe ternary phase diagram is suitable for the recording film. The recording film is obtained by sputtering a sputtering target of the above composition with an inert gas, such as Ar.
As described above, Ge in the recording film is relatively liable to get oxidized. A sputtering target serving as a starting material and an inert gas, such as Ar, used in sputtering include a trace of oxygen. Thus, the mixing of a trace of oxygen in the recording film is inevitable. If an oxide thin film is used for a layer in contact with the recording film, a trace of oxygen diffuses into the recording film, resulting in an increase in the amount of oxygen. As described above, even if not only Ge, Bi, and Te but also oxygen (O) or the like has been detected in the recording film, this does not depart from the spirit of the invention.
The recording film includes at least Ge, Sb, Te, and N (nitrogen). When its composition is expressed as GexSbyTez where x+y+z=100, it is desirable that 1 to 5 at. % of nitrogen (N) should be added to a GeSbTe-series compound in the area defined by x=55, z=45 and x=45, z=55 and x=10, y=28, z=42 and x=10, y=36, z=54 in a GeSiTe ternary phase diagram.
The added nitrogen is not always distributed uniformly in the film and can be distributed inhomogeneously depending on film forming conditions. In that case, it is necessary to analyze and evaluate the amount of nitrogen added using the sum total in the film to which nitrogen is to be added. When the layer in contact with the recording film includes nitrogen, nitrogen can diffuse from the layer in contact with the recording film. The recording film is obtained by sputtering a sputtering target of the above composition with an inert gas, such as Ar.
In this example, too, Ge in the recording film is relatively liable to get oxidized. A sputtering target serving as a starting material and an inert gas, such as Ar, used in sputtering include a trace of oxygen. In addition, when a gas including nitrogen (N2) is used as a sputtering gas, the sputtering gas also includes a trace of oxygen (O). Thus, the mixing of a trace of oxygen in the recording film is inevitable. If an oxide thin film is used for a layer in contact with the recording film, a trace of oxygen diffuses into the recording film, resulting in an increase in the amount of oxygen. As described above, even if not only Ge, Sb, and Te but also oxygen (O) or the like has been detected in the recording film, this does not depart from the spirit of the invention.
The recording film includes at least Ge, Sb, Te, and N (nitrogen). When its composition is expressed as GexSbyTez where x+y+z=100, a part of the composition is replaced with bismuth (Bi) and/or indium (In) and/or tin (Sn) on the basis of a composition in the area defined by x=55, z=45 and x=45, z=55 and x=10, y=28, z=42 and x=10, y=36, z=54 in a GeSbTe ternary phase diagram. When the composition after the replacement is expressed as (Ge(1−w)Snw)x(Sb(1−v)(Bi(1−u)Inu)v)yTez where x+y+z=100, a recording film is suitable in which w, v, and u in the composition satisfy the following: 0≦w≦0.5 and 0≦v≦0.7 and 0≦u≦1. In this case, it is desirable that 1 to 5 at. % of nitrogen (N) should be added to a GeSnSbTe, a GeSnSbTeIn, a GeSbTeIn, a GeSbTeBiIn, a GeSbSnTeBiIn, a GeSbTeBi, a GeSnSbTeBi, and GeBiTeIn, and a GeSnSbTeBiIn series compound with the above composition.
The added nitrogen is not always distributed uniformly in the film and can be distributed inhomogeneously depending on film forming conditions. In that case, it is necessary to analyze and evaluate the amount of nitrogen added using the sum total in the film to which nitrogen is to be added. When the layer in contact with the recording film includes nitrogen, nitrogen can diffuse from the layer in contact with the recording film.
The recording film is obtained by sputtering a sputtering target of the above composition with an inert gas, such as Ar. In this example, too, Ge in the recording film is relatively liable to get oxidized. A sputtering target serving as a starting material and an inert gas, such as Ar, used in sputtering include a trace of oxygen. In addition, when a gas including nitrogen (N2) is used as a sputtering gas, the sputtering gas also includes a trace of oxygen (O). Thus, the mixing of a trace of oxygen in the recording film is inevitable. If an oxide thin film is used for a layer in contact with the recording film, a trace of oxygen diffuses into the recording film, resulting in an increase in the amount of oxygen. As described above, even if not only Ge, Sb, Te, and Sn/Bi/In but also oxygen (O) or the like has been detected in the recording film, this does not depart from the spirit of the invention.
The recording film includes at least Ge, Bi, Te, and N (nitrogen). When its composition is expressed as GexBiyTez where x+y+z=100, it is desirable that 1 to 5 at. % of nitrogen (N) should be added to a GeBiTe-series compound in the area defined by x=55, z=45 and x=45, z=55 and x=10, y=28, z=42 and x=10, y=36, z=54 in a GeBiTe ternary phase diagram.
The added nitrogen is not always distributed uniformly in the film and can be distributed inhomogeneously depending on film forming conditions. In that case, it is necessary to analyze and evaluate the amount of nitrogen added using the sum total in the film to which nitrogen is to be added. When the layer in contact with the recording film includes nitrogen, nitrogen can diffuse from the layer in contact with the recording film.
The recording film is obtained by sputtering a sputtering target of the above composition with an inert gas, such as Ar. Ge in the recording film is relatively liable to get oxidized. A sputtering target serving as a starting material and an inert gas, such as Ar, used in sputtering include a trace of oxygen. In addition, when a gas including nitrogen (N2) is used as a sputtering gas, the sputtering gas also includes a trace of oxygen (O). Thus, the mixing of a trace of oxygen in the recording film is inevitable. If an oxide thin film is used for a layer in contact with the recording film, a trace of oxygen diffuses into the recording film, resulting in an increase in the amount of oxygen. As described above, even if not only Ge, Si, and Te but also oxygen (O) or the like has been detected in the recording film, this does not depart from the spirit of the invention.
Although the material series and compositions of the recording films are selected according to the necessary crystallization speed, the sensitivity of mediums, and the optical characteristics, including the reflectivity, contrast, and transmittance of mediums, those in the above range are suitable.
Practicing any one of the embodiments of the invention makes it possible to realize a phase-change recording medium in which cross erase is less liable to take place, the contrast between crystalloid and amorphous material is high, and the erase ratio at high linear velocity is high, and which is excellent in the overwrite (OW) cycle characteristic and environment resistance and enables high-speed overwriting to be done with high density and high capacity.
This invention is not limited to the above embodiments and, on the basis of available skills in the present or future implementation phase, may be practiced or embodied in still other ways without departing from the spirit or character thereof. For instance, an information storage medium used in the embodiments is not limited to an optical disk obtained by laminating 0.6-mm thick substrates together and may be an optical disk obtained by providing a 0.1-mm-thick protective layer (or transparent sheet) on the surface of a 1.2-mm-thick substrate (that is, an optical disk produced by laminating a 0.1-mm-thick transparent sheet to a 1.1-mm-thick substrate on which a recording layer and others have been formed). Alternatively, the information storage medium may be an optical disk which has a 0.1-mm-thick transparent protective layer (or transparent sheet) provided on one of or both of the surfaces of the substrates of the optical disk obtained by laminating 0.6-mm-thick substrates. While in the embodiments, an ultrathin oxide film whose average thickness is 0.1 nm or more and 1 nm or less has been used, the lower limit may be 0.1 nm or less, provided that necessary values can be controlled in mass production. The upper limit and lower limit representing the average thickness of an ultrathin oxide film have been defined by one effective digit, allowing a certain amount of margin. Specifically, in mass production, a margin of ±20% to ±30% is allowed for an average thickness of 0.1 nm to 1 nm. Some scholarly study has shown that an ultrathin film can present a so-called island like micro-structure and therefore is not a uniform film. However, in the invention, an ultrathin film is used as a film which has an average film thickness. Even if an ultrathin film presents an island texture, this does not impair the effect of the invention.
While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Number | Date | Country | Kind |
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2006-118081 | Apr 2006 | JP | national |