This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2006-196217, filed Jul. 18, 2006, the entire contents of which are incorporated herein by reference.
1. Field
One embodiment of the present invention relates to an information recording medium which allows information recording and playback processes using various kinds of laser beams, and a disc apparatus which attains the recording and playback processes.
2. Description of the Related Art
As information storage media that can play back and record a large capacity of video information, DVDs (Digital Versatile Discs) have prevailed. A movie or video content for about two hours is recorded on a DVD, and the recorded information is played back using a player, so that the user can freely enjoy video contents such as movies and the like at home.
In recent years, digitization of television broadcast has been proposed, and practical use of a high-resolution television system called a high-definition television (HDTV) system has been planned. For this reason, the standards of a next-generation DVD which increases the recording capacity by narrowing down a beam spot size by shortening the laser wavelength, increasing the numerical aperture NA, or the like have been proposed.
As disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2004-206849, a method of increasing the recording capacity includes a method using a single-sided, recordable/reproducible, multi-layer information storage medium which can attain recording and playback for respective recording layers by providing a plurality of recording layers on a disc, moving an objective lens in the optical axis direction, and focusing a beam on respective layers from one side, in addition to the method of narrowing down the beam spot size.
On such multi-layer information storage medium, upon focusing a laser beam on a predetermined recording layer, inter-layer crosstalk (inter-layer XT) readily occurs due to irradiation of some light components on a recording layer other than the predetermined recording layer. This inter-layer XT affects not only recording and playback signals, but also a tracking signal and the like. In an actual recording/playback apparatus, since the temperature inside the apparatus rises, a storage playback medium tends to slightly deform. In this case, so-called disc tilt occurs, and has adverse effects such as an increase in error rate and the like upon recording or playing back information. Such disc tilt also affects not only recording and playback signals, but also a tracking signal and the like.
On this single-sided, recordable/reproducible, multi-layer information storage medium, tracks of respective recording layers readily suffer eccentricity due to misregistration upon adhering substrates, eccentricity of a stamper, and the like in the manufacture. The eccentricity means both deviations from a perfect circle and with the corresponding track in other layers. If the eccentricity from the center of rotation of the information recording medium worsens, problems occur in the recording/playback characteristics of the information recording medium, and result in tracking disability in the worst case.
To solve such problems, as disclosed in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2003-263789, a method of determining defectives by measuring the edge of the inner periphery of a disc-shaped information recording medium to inspect the eccentricity amount of a disc, or the like has been proposed.
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.
FIG. 1 is a schematic sectional view for explaining the basic structure of an information recording medium according to the present invention;
FIG. 2 is a schematic sectional view for explaining the structure of an information recording medium according to the first aspect of the present invention;
FIG. 3 is a schematic sectional view for explaining the structure of an information recording medium according to the second aspect of the present invention;
FIG. 4 is a schematic sectional view for explaining the structure of an information recording medium according to the third aspect of the present invention;
FIG. 5 is a schematic diagram showing an example of an inspection apparatus for an information recording medium according to the ninth aspect;
FIG. 6 is a schematic diagram showing an example of an inspection apparatus for an information recording medium according to the 10th aspect;
FIG. 7 is a sectional view showing another example of the layer structure of a write-once information storage medium according to the present invention;
FIG. 8 is a sectional view showing an example of the layer structure of a rewritable information storage medium according to the present invention;
FIG. 9 is a block diagram of a process chamber used in the present invention;
FIG. 10 is a flowchart showing the process procedure upon layer formation;
FIGS. 11A and 11B are schematic views of an inspection method according to the present invention;
FIG. 12 is a schematic view of another inspection method according to the present invention;
FIG. 13 is a graph showing the relationship among the linear velocity, eccentricity amount, and tracking;
FIG. 14 is a block diagram for explaining the arrangement of an embodiment of an information recording/playback apparatus that can be used in the present invention;
FIG. 15 is a block diagram showing a signal processing circuit using a PRML detection method;
FIG. 16 is a block diagram showing the arrangement in a Viterbi decoder 156 ;
FIG. 17 is a chart showing status transition in PR(1, 2, 2, 2, 1) class;
FIG. 18 is a view showing the structure and dimensions of an information storage medium according to one embodiment of the present invention;
FIG. 19 is a view showing the method of setting physical sector numbers on a write-once information storage medium or a read-only information storage medium having a single-layer structure;
FIGS. 20A and 20B are views showing the method of setting physical sector numbers on a read-only information storage medium having a double-layer (or dual-layer) structure;
FIG. 21 is a table showing the physical sector number setting method on a writable information storage medium;
FIG. 22 is a table sowing general parameter values on the writable information storage medium;
FIGS. 23A, 23B, 23 C, 239 , 23 E, and 23 F are views showing comparison between the data structures of data areas DTA and data lead-out areas DTLDO of various types of information storage media;
FIG. 24 is a chart showing the waveform (write strategy) of recording pulses used to make a trial write on a drive test zone;
FIG. 25 is a chart showing the definition of a recording pulse shape;
FIG. 26 is a view showing the data structures in a control data zone CDZ and R-physical information zone RIZ;
FIG. 27 is a table showing the detailed information contents in physical format information PFI and R-physical format information R_PFI;
FIG. 28 is a chart showing an overview of the conversion sequence until a physical sector structure is formed;
FIG. 29 is a view showing the structure in a data frame;
FIG. 30 is an explanatory view of an ECC block structure;
FIG. 31 is an explanatory view of a scrambled frame array;
FIG. 32 is an explanatory view of an interleave method of PO;
FIGS. 33A and 33B are explanatory views of the structure in a physical sector;
FIG. 34 is an explanatory view of sync code pattern contents;
FIG. 35 is a block diagram showing the arrangement of a modulation block;
FIG. 36 is a view showing comparison of data recording formats for various kinds of information recording media;
FIGS. 37A and 37B are comparative explanatory views of the data structure in various kinds of information recording media with the prior art;
FIG. 38 is a comparative explanatory of the data structure in various kinds of information recording media with the prior art;
FIG. 39 is a view showing a data recording method of rewritable data to be recorded on a rewritable information storage medium;
FIG. 40 is an explanatory view of data random shift of rewritable data to be recorded on the rewritable information storage medium;
FIG. 41 is an explanatory view of a write-once method of write-once data to be recorded on a write-once information storage medium;
FIG. 42 is a view showing the detailed structure of ECC blocks after PO interleave shown in FIG. 32;
FIGS. 43A, 43B, and 43 C are tables showing recording condition parameters expressed as a function of the mark length/the preceding space length;
FIG. 44 is an explanatory view of another embodiment associated with a write-once method of write-once data to be recorded on a write-once information storage medium;
FIG. 45 is a block diagram showing the detailed arrangement of a peripheral unit including a sync code position extraction unit 145 shown in FIG. 14;
FIG. 46 is a view showing an example of the structure and dimensions in an information storage medium;
FIG. 47 is an explanatory view of the relationship between the wobble shape and address bit in an address bit area;
FIGS. 48A, 48B, 48 C, and 48 D are comparative explanatory views of the positional relationship between wobble sync patterns and allocations in wobble data units;
FIGS. 49A, 49B, 49 C, and 49 D are explanatory views associated with the data structure in wobble address information on a write-once information storage medium;
FIG. 50 shows a light beam on another layer during recording or playback of a certain layer of a disc;
FIG. 51 is a view for explaining clearance that prevents the influence of the other layer;
FIG. 52 shows a PSN on layer 0 and a corresponding recordable physical sector on layer 1 ;
FIG. 53 is a view showing the configuration of a lead-in area and lead-out area;
FIG. 54 is a view showing the configuration of an initial middle area;
FIG. 55 is a view showing a track path;
FIG. 56 is a view showing the physical sector layout and physical sector numbers;
FIG. 57 is a view showing the configurations of the middle area before and after extension;
FIG. 58 is a view showing the configuration of the middle area before extension;
FIG. 59 is a view showing the configuration of the middle area after small-size extension;
FIG. 60 is a view showing the configuration of the middle area after large-size extension;
FIG. 61 is a view showing an overview of two neighboring tracks to explain the selection sequence of physical segment types;
FIG. 62 is a view showing an example of a terminator recorded upon finalization of layer 1 ;
FIG. 63 is a view showing other examples of the terminator recorded upon finalization of layer 1 ;
FIG. 64 is a flowchart showing a modification example of the recording sequence; and
FIG. 65 is a flowchart showing another modification example of the recording sequence.
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, there is disclosed an information recording medium which includes a first information layer formed on a transparent substrate having tracks of a concentric or spiral shape, and a second information layer formed on the first information layer, and allows optical recording and playback from one surface, and in which eccentricity amounts of the tracks of the information layers fall within the range from 0 to 70 μm.
FIG. 1 is a schematic sectional view for explaining the basic structure of an information recording medium according to the present invention.
As shown in FIG. 1, an information recording medium 20 of the present invention is basically an optically recordable/reproducible information recording medium from one side, which includes a first information layer 22 formed on a transparent substrate 21 having tracks of a concentric or spiral shape (not shown), and a second information layer 23 formed on the first information layer 22 , and is characterized in that the eccentricity amount of tracks of the information layers fall within a range from 0 to 70 μm.
According to the present invention, since the eccentricity amount is 70 μm or less, recording and playback signals and a tracking signal can be stably obtained even under a condition in which inter-layer crosstalk readily occurs.
The information recording medium according to the present invention is roughly classified into the following seven aspects depending on the configurations of the first and second information layers, and the wavelength of its recording/playback light.
FIG. 2 is a schematic sectional view for explaining the structure of an information recording medium according to the first aspect of the present invention.
An information recording medium 30 according to the first aspect of the present invention can undergo recording and playback using light with a wavelength falling within a range from 180 nm to 620 nm. A first information layer 22 of the medium 30 is formed on a transparent substrate 21 , and includes a first organic dye layer 24 and a first reflecting layer 25 formed on the first organic dye layer 24 . A second information layer 23 of the medium 23 is formed on the first reflecting film 25 , and has a second organic dye layer 26 and a second reflecting layer 27 formed on the second organic dye layer 26 .
The information recording medium according to the first aspect can undergo recording and playback using light such as light of a short wavelength of 620 nm or less, e.g., blue-violet laser light of 405 nm or the like, and can be used as a write-once optical recording medium (e.g., DVD-R or the like) since its recording layers include the organic dye layers.
An intermediate layer as an interlayer dielectric layer used to optically separate the first and second information layers can be formed between the first reflecting layer and second organic dye layer.
Note that in the present invention, the eccentricity amount includes deviations from the center of a disc-shaped substrate and from the center of rotation of the substrate, which respectively indicate maximum values of deviations from the tracks on the first and second information layers.
In the present invention, assume that the reflecting layer includes a total reflecting layer and semitransparent reflecting layer.
In the present invention, the multi-layer information recording medium has two or more information layers, and more information layers such as a third information layer, fourth information layer, and the like can be arbitrarily provided.
FIG. 3 is a schematic sectional view for explaining the structure of an information recording medium according to the second aspect of the present invention.
An information recording medium 40 according to the second aspect of the present invention can undergo recording and playback using light with a wavelength falling within the range from 180 nm to 620 nm. A first information layer 22 of the medium 40 is formed on a transparent substrate 21 , and includes a first dielectric layer 31 , first phase change recording layer 34 , second dielectric layer 38 , and first reflecting layer 35 . A second information layer 23 of the medium 40 is formed on the first information layer 22 via an intermediate layer 33 , and has a third dielectric layer 32 , second phase change recording layer 36 , fourth dielectric layer 39 , and second reflecting layer 37 .
The information recording medium according to the second aspect can undergo recording and playback using light such as light of a short wavelength of 620 nm or less, e.g., blue-violet laser light of 405 nm or the like, and can be used as a rewritable optical recording medium (e.g., DVD-RW, DVD-RAM, or the like) since its recording layers include the phase change recording layers.
The dielectric layer can arbitrarily include a protection layer, interface layer, and the like.
The interface layer can be formed to be in contact with one or both of the principal surfaces of the first and second phase change recording layers. The whole dielectric layer may be the interface layer.
The first and second reflecting layers can be formed to be in contact with the corresponding dielectric layers of the respective information layers. Another dielectric layer may be formed above the reflecting layer so as to attain optical enhancement, thermal diffusion, SN ratio improvement, and the like.
FIG. 4 is a schematic sectional view for explaining the structure of an information recording medium according to the third aspect of the present invention.
An information recording medium according to the third aspect of the present invention can undergo recording and playback using light with a wavelength falling within the range from 180 nm to 620 nm. A first information layer 22 of the medium 50 includes a first information pattern 44 embossed on the surface of a transparent resin substrate 21 , and a first reflecting layer 45 formed on this first information pattern. A second information layer 23 of the medium 50 is formed on the first reflecting layer, and has a transparent resin layer 46 or transparent resin substrate on which a second information pattern 47 is embossed, and a second reflecting layer 48 formed on the second information pattern 47 .
The information recording medium according to the third aspect can undergo playback using light such as light of a short wavelength of 620 nm or less, e.g., blue-violet laser light of 405 nm or the like, and can be used as a read-only optical recording medium (e.g., DVD-ROM or the like) since its recording layers include the embossed information patterns.
An information recording medium according to the fourth aspect has the same structure as that according to the first aspect, except that recording and playback are done at a linear velocity of 30 (m/sec) or higher and using light with a wavelength falling within the range from 620 nm (exclusive) to 830 nm (inclusive).
An information recording medium according to the fifth aspect has the same structure as that according to the second aspect, except that recording and playback are done at a linear velocity of 30 (m/sec) or higher and using light with a wavelength falling within the range from 620 nm (exclusive) to 830 nm (inclusive).
An information recording medium according to the sixth aspect has the same structure as that according to the first aspect, except that playback can be done using light of two or more different wavelengths.
An information recording medium according to the seventh aspect has the same structure as that according to the third aspect, except that playback can be done using light of two or more different wavelengths.
An information recording/playback apparatus according to the eighth aspect of the present invention is an apparatus which records and plays back one of the information recording media according to the first to seventh aspects.
An inspection apparatus for an information recording medium according to the present invention is roughly classified into two aspects, i.e., the ninth and 10th aspects.
FIG. 5 is a schematic diagram showing an example of an inspection apparatus for an information recording medium according to the ninth aspect.
As shown in FIG. 5, an inspection apparatus 70 for an information recording medium according to the present invention has a mechanism 74 which clamps a multi-layer information recording medium 71 , which includes first and second information layers having tracks of a concentric or spiral shape, and allows playback from one side using light with a wavelength falling within the range from 180 nm to 620 nm, an illumination system 73 which irradiates the multi-layer information recording medium 71 with an illumination that does not contain light components of wavelengths of 620 nm or less, an image sensing mechanism 72 such as a CCD camera or the like which senses images of the tracks of the first and second information layers, an image processing unit 75 which extracts the paths of the tracks by processing image information obtained from the image sensing mechanism 72 , and an arithmetic and control unit 76 which calculates the eccentricity amounts of the tracks based on the extracted information. The unit is a personal computer or like it.
FIG. 6 is a schematic diagram showing an example of an inspection apparatus for an information recording medium according to the 10th aspect.
As shown in FIG. 6, an inspection apparatus 90 for an information recording medium has the same arrangement as in FIG. 5, except that, in place of the image sensing mechanism 72 , it comprises a light source 79 such as an LD, LED, or the like, a mirror 78 which diffracts light from the light source 79 in a predetermined direction, a lens 91 for focusing the light diffracted by the mirror 78 and radiating the tracks of a desired recording layer with the focused light, and a reflectance measuring device 77 (e.g., photodetector) which receives the light reflected by the recording layer.
An inspection method of an information recording medium according to the present invention can be roughly classified into two aspects, i.e., the 11th and 12th aspects.
An inspection method of an information recording medium according to the 11th aspect is a method using the inspection apparatus according to the ninth aspect, and comprises steps of: irradiating a multi-layer information recording medium, which includes first and second information layers having tracks of a concentric or spiral shape, and allows playback from one surface using light with a wavelength falling within the range from 180 nm to 620 nm, with an illumination that does not contain light components with wavelengths of 620 nm or less, and sensing images for at least one round of the tracks by focusing a light spot on the tracks of the first and second information layers using the image sensing mechanism; and extracting paths of the tracks by processing the obtained image information by the image processing unit and calculating the eccentricity amounts of the tracks based on the extracted information by the arithmetic and control unit.
Furthermore, an inspection method of an information recording medium according to the 12th aspect is a method using the inspection apparatus according to the 10th aspect, and is the same as the method according to the 11th aspect, except that the method comprises steps of: measuring reflectance distributions of reflected light for at least one round of the tracks of the first and second information layers using a reflectance distribution measurement mechanism while irradiating the multi-layer information recording medium with a laser beam using a laser beam irradiation device, in place of the step of irradiating the multi-layer information recording medium with illumination that does not contain light components with wavelengths of 620 nm or less, and sensing images for at least one round of tracks by focusing the light spot on the tracks of the first and second information layers using the image sensing mechanism; and extracting paths of the tracks by applying image processing to the reflectance distributions in place of the obtained image information.
The operation of an optical recording medium according to the present invention will be described in more detail hereinafter.
FIG. 7 shows another example of the layer structure of a write-once information storage medium associated with the first, fourth, and sixth aspects.
The information storage medium has a structure, from the light incidence side, in which an L 0 information layer is prepared by stacking an organic dye recording layer 3 - 3 and reflecting layer 4 - 3 in turn on a transparent substrate 2 - 3 , an L 1 information layer is prepared by stacking an interlayer dielectric layer 7 as an adhesive layer, organic dye recording layer 3 - 4 , and reflecting layer 4 - 4 in turn on the L 0 layer, and another transparent substrate 8 is adhered on the resultant structure. Note that the information storage medium may have a structure in which the reflecting layer 4 - 4 and organic dye recording layer 3 - 4 are stacked in turn on the transparent substrate 8 used for the L 1 information layer, and the resultant structure may be adhered to the L 0 information layer using the interlayer dielectric layer 7 as an adhesive layer.
Note that the structure of the organic dye recording medium according to an embodiment of the present invention is not limited to that shown in FIG. 7. For example, a layer which prevents any reaction between the reflecting layer or semitransparent reflecting layer and the organic dye, or any change or deterioration of the reflecting layer or semitransparent reflecting layer due to a contact of the reflecting layer or semitransparent reflecting layer with the organic dye may be formed between the organic dye recording layer 3 - 3 and reflecting layer 4 - 3 . The reflecting layer may be formed of a plurality of metal layers. More dielectric layers may be formed on a contact portion between the organic dye recording layer and reflecting layer, that between the organic dye and interlayer dielectric layer, that between the semitransparent reflecting layer and interlayer dielectric layer, that between the reflecting layer and transparent substrate, and the like.
In case of a double-layer medium, the first information layer closer to the light incidence surface and the second information layer farther from the light incidence surface, which layers have the above structures, are prepared, and these two information layers may be adhered via an adhesive layer to attain interlayer separation. Basically the same applies to multi-layer media having three or more layers.
Furthermore, the present invention is also applicable to a medium which receives light via a transparent sheet as thin as about 0.1 mm adhered on a substrate on which various layers are formed (assume that such medium uses an objective lens with an NA as high as about 0.85). This is because the characteristics required for the organic dye recording film layer and reflecting layer materials to be used are not much different between a case wherein the transparent cover layer as thin as about 0.1 mm is used on the light incidence side and a case wherein a 0.6-mm thick transparent substrate mainly used in the present invention is used.
FIG. 8 shows an example of the layer structure of a rewritable information recording medium associated with the second and fifth aspects.
The information recording medium has a structure, from the light incidence side, in which an L 0 information layer is prepared by stacking, in turn, a first interference layer 81 (also called a protection layer or dielectric layer; the same applies to the following description), lower interface layer 82 , recording layer 83 , upper interface layer 84 , second interference layer 85 , reflecting layer 86 , and third interference layer 87 on a transparent substrate 80 , an L 1 information layer is prepared by stacking, in turn, a reflecting layer 86 , second interference layer 85 , upper interface layer 84 , recording layer 83 , lower interface layer 82 , and first interference layer 81 on a transparent substrate 80 in the order opposite to the L 0 layer, and the two information layers are adhered using an interlayer dielectric layer 88 .
Note that the structure of a phase change recording medium according to an embodiment of the present invention is not limited to that shown in FIG. 8. For example, another dielectric layer may be formed between the second interference layer 85 and reflecting layer 86 . The interference layers may be replaced by the material of the interface layers, and may be omitted. The reflecting layers may be omitted. Each reflecting layer may be made up of a plurality of metal layers. Another dielectric layer may be formed on the reflecting layer.
The substrate used in this embodiment is roughly classified into two types.
(a) A substrate of one type has a groove pitch of about 0.6 to 0.8 Mm, and uses a so-called land-groove recording method that makes recording on both the land and groove. In the following description, a medium using the substrate of this type will also be referred to as a rewritable type (1) information recording medium.
(b) A substrate of the other type has a groove pitch of about 0.3 to 0.4 μm, and uses a so-called groove recording method which makes recording on either the land or groove (a method that records only on the land will also be referred to as the groove recording method). In the following description, a rewritable medium using this method will also be referred to as a rewritable type (2) information recording medium. Also, a medium that uses organic dye recording layers and allows recording only once will be referred to as a write-once type medium (write-once information storage medium (write-once type medium)). After write, such medium is designed so that the pitch of written pits in the track direction becomes about 0.3 to 0.4 μm as in a read-only storage medium. On a read-only medium, no grooves are formed, and data are recorded using a pit array.
The thickness of the substrate on the light incidence side can range from a thickness as very small as about 0.1 mm to a thickness of 0.6 mm in accordance with the NA value of the objective lens of the optical pickup.
Examples to be described below use these information recording/playback apparatuses and discs (information recording media).
As a result of careful consideration of the aforementioned aspects, the present inventors reached a conclusion that the points to be described below were important. In an information recording/playback medium which is a single-sided, multi-layer medium which has a plurality of information layers that undergo recording or playback using light with a wavelength falling within the range from 620 nm (inclusive) to 180 nm (inclusive) and can access respective layers from one side, and which comprises a transparent substrate, interlayer dielectric layer, organic dye material, and reflecting layer or semitransparent reflecting layer, or in which a layer that prevents any reaction between the reflecting layer or semitransparent reflecting layer and the organic dye material, or a change or deterioration of the reflecting layer or semitransparent reflecting layer due to a contact of the reflecting layer or semitransparent reflecting layer with the organic dye material is formed between the reflecting layer or semitransparent reflecting layer and the organic dye material, an information recording/playback medium in which the eccentricity F amounts of tracks of the respective information layers are, for example, 70 μm or less and, more preferably, 40 μm or less, is preferable.
The eccentricity amounts of the tracks can be precisely presented since a precise evaluation method to be described later has been established. For this reason, establishment of the following evaluation method is one of important prerequisites of the present invention. The characteristics of the information storage medium of the present invention largely depend on the data structure, recording of system information, and the recording method, as described above. Conventionally, the data structure and the like, and improvement and stability of the recording and playback characteristics of an information storage medium could not be examined due to the influences that no accurate evaluation method was established, various variation factors in the manufacturing process of an information storage medium were present, and so forth. The present inventors were dedicated to exploring the physical structure of an information storage medium, and the data structure, recording method, and the like used in that medium, and made studies about points that were not explored conventionally, thus achieving the present invention.
Not only the measurement principle of the method of measuring the eccentricity amount of each track of the present invention is described, but also apparatuses using this method can be used as an inspection apparatus for storage media upon industrially mass-producing them. The conventionally used method has insufficient measurement accuracy, and requires very complicated measurement. Using the evaluation method of the present invention, storage media can be inspected at a rate of one medium per several seconds, i.e., within an equivalent time period required to manufacture one storage medium. Therefore, the evaluation method of the present invention is industrially very useful.
In an information recording/playback medium which is a single-sided, multi-layer medium which has a plurality of information layers that undergo recording or playback using light with a wavelength falling within the range from 620 nm (inclusive) to 180 nm (inclusive) and can access respective layers from one side, and which comprises a transparent substrate, interlayer dielectric layer, phase change recording material, protection layer, interference layer, and reflecting layer or semitransparent reflecting layer and also another protection layer formed on the semitransparent reflecting layer, an information recording/playback medium in which the eccentricity amounts of tracks of the respective information layers are, for example, 70 μm or less and, more preferably, 40 μm or less, is preferable.
In an information recording/playback medium which is a single-sided, multi-layer medium which has a plurality of information layers that undergo playback using light with a wavelength falling within the range from 620 nm (inclusive) to 180 nm (inclusive) and can access respective layers from one side, and which comprises a transparent substrate embossed with information, interlayer dielectric layer, and reflecting layer or semitransparent reflecting layer, an information recording/playback medium in which the eccentricity amounts of tracks of the respective information layers are, for example, 70 μm or less and, more preferably, 40 μm or less, is preferable.
An evaluation method which is a method of measuring the eccentricity amounts of respective track of the respective information layers, and which evaluates the eccentricity amounts of the tracks by focusing a beam spot on the respective information layers using an image processing apparatus, comprising an illumination system which does not include light components with wavelengths of 620 nm or less, a CCD camera, and track extraction mechanism, and an arithmetic and control apparatus, is preferable. Especially, since the material of a medium using an organic dye changes by irradiated light, the inspection method of the present invention selects the wavelength of the light of the illumination system to be used. On the other hand, the wavelength range of a light source used in the illumination system largely influences the sensitivity of the CCD camera as a detection system, the measurement accuracy, and the measurement time. In order to increase the detection accuracy, the wavelength range of the light source to be used is preferably shorter. Conversely, in consideration of the sensitivity of an organic dye, if light with a wavelength of 620 nm or less is used, the organic dye is unwantedly changed by evaluating it.
An evaluation method which is a method of measuring the eccentricity amounts of respective tracks of the respective information layers, and which evaluates the eccentricity amounts of the tracks by focusing on the respective information layers using an image processing apparatus comprising a laser irradiation device, reflectance distribution measurement mechanism, and track extraction mechanism, and an arithmetic and control apparatus, is preferable. Especially, since the material of a medium using an organic dye changes by irradiated light, the inspection method of the present invention can select the wavelength of the light of the illumination system to be used. On the other hand, the wavelength range of a light source used in the illumination system largely influences the sensitivity of the CCD camera as a detection system, the measurement accuracy, and the measurement time. In order to increase the detection accuracy, the wavelength range of the light source to be used is preferably shorter. Conversely, in consideration of the sensitivity of an organic dye, if light with a wavelength of 620 nm or less is used, the organic dye is unwantedly changed by evaluating it.
An evaluation method which is a method of measuring the eccentricity amounts of respective tracks of the respective information layers, and which evaluates the eccentricity amounts of the tracks characterized by using a laser irradiation device whose wavelength exceeds 620 nm, is preferable.
A method which is a method of measuring the eccentricity amounts of respective track of the respective information layers described above, and which measures the eccentricity amounts of the tracks using the tracks which have undergone trial recording for the purpose of learning, optimization, or the like of write strategy is preferable.
A measurement apparatus of the eccentricity amounts of respective track of the respective information layers using the aforementioned evaluation method is preferable.
An information recording/playback apparatus which comprises the aforementioned evaluation method is preferable.
In an information recording/playback medium which is a single-sided, multi-layer medium which has a plurality of information layers that undergo recording or playback using light with a wavelength that exceeds 620 nm and can access respective layers from one side, and which is driven at a linear velocity of 30 m/sec or higher and, more preferably, at a linear velocity of 40 m/sec or higher, and comprises a transparent substrate, interlayer dielectric layer, organic dye material, and reflecting layer or semitransparent reflecting layer, or in which a layer that prevents any reaction between the reflecting layer or semitransparent reflecting layer and the organic dye material, or a change or deterioration of the reflecting layer or semitransparent reflecting layer due to a contact of the reflecting layer or semitransparent reflecting layer with the organic dye material is formed between the reflecting layer or semitransparent reflecting layer and the organic dye material, an information recording/playback medium in which the eccentricity amounts of tracks of the respective information layers are, for example, 70 μm or less and, more preferably, 40 μm or less, is preferable.
In an information recording/playback medium which is a single-sided, multi-layer medium which has a plurality of information layers that undergo recording or playback using light with a wavelength falling within the range from 620 nm (inclusive) to 180 nm (inclusive) and can access respective layers from one side, and which is driven at a linear velocity of 30 m/sec or higher and, more preferably, at a linear velocity of 40 m/sec or higher, and comprises a transparent substrate, interlayer dielectric layer, phase change recording material, protection layer, interference layer, and reflecting layer or semitransparent reflecting layer and also another protection layer, an information recording/playback medium in which the eccentricity amounts of tracks of the respective information layers are, for example, 70 μm or less and, more preferably, 40 μm or less, is preferable.
The present invention is a single-sided, multi-layer medium which has a plurality of information layers that undergo recording or playback using light with a wavelength of 620 nm or less and can access respective layers from one side, and which has been examined. It was found that these techniques are useful even when the wavelength is 620 nm or more. Also, it was found that the effects are especially significant upon recording and playback at a high linear velocity, and these techniques are preferably applied to an information storage medium which is driven at a linear velocity of 40 m/sec or higher. Furthermore, when the above techniques are applied to an information storage medium which is driven at a linear velocity of 50 m/sec or higher, the difference from the prior arts is outstanding. The same effects obtained at a high linear velocity applies to a case of the wavelength of 620 nm or less, and when the present invention is applied to an information storage medium which is driven a linear velocity of 30 m/sec or higher, more preferably, a linear velocity of 40 m/sec or higher and, further more preferably, a linear velocity of 50 m/sec or higher, the difference from the prior arts is outstanding.
In an information recording/playback medium which is a single-sided, multi-layer medium which has a plurality of information layers that undergo recording or playback using light of a plurality of wavelengths and can access respective layers from one side, and which comprises a transparent substrate, interlayer dielectric layer, organic dye material, and reflecting layer or semitransparent reflecting layer, or in which a layer that prevents any reaction between the reflecting layer or semitransparent reflecting layer and the organic dye material, or a change or deterioration of the reflecting layer or semitransparent reflecting layer due to a contact of the reflecting layer or semitransparent reflecting layer with the organic dye material is formed between the reflecting layer or semitransparent reflecting layer and the organic dye material, an information recording/playback medium in which the eccentricity amounts of tracks of the respective information layers are, for example, 70 μm or less and, more preferably, 40 μm or less, is preferable.
In an information recording/playback medium which is a single-sided, multi-layer medium which has a plurality of information layers that undergo playback using light of a plurality of wavelengths and can access respective layers from one side, and which comprises a transparent substrate embossed with information, interlayer dielectric layer, and reflecting layer or semitransparent reflecting layer, an information recording/playback medium in which the eccentricity amounts of tracks of the respective information layers are, for example, 70 μm or less and, more preferably, 40 μm or less, is preferable.
An information recording/playback medium which is the aforementioned information recording/playback medium and is characterized in that any of the radial position where each information layer is formed, the radial positions of a pit forming part and groove forming part, the radial positions of a mirror part and groove forming part, the radial position of a zone boundary, and the radial position where wobble shapes are different, is different depending on the information layers, is preferable.
An information recording/playback medium which is the aforementioned information recording/playback medium and is characterized in that any of the radial position where each information layer is formed, crystalline position, and initialization position is different depending on the information layers, is preferable.
In the following explanation, examples of single-sided, double-layer media will be described.
Also, as measurement data of an optical disc manufactured by way of trial, the worst value of lands (L) and grooves (C) of L 0 and L 1 in each experiment is indicated as a typical value.
The experiments for evaluating the disc characteristics of rewritable information storage media are roughly classified into the following three experiments.
(1) Measurement of Bit Error Rate (SbER: Simulated Bit Error Rate)
One experiment is measurement of the bit error rate (SbER: Simulated bit Error Rate) and PRSNR by which the data error rate is measured. The other experiment is analog measurement for determining the readout signal quality. In the measurement of the SbER and PRSNR, a mark string or train including patterns from 2 T to 13 T at random was overwritten 10 times. Then, the same random patterns were overwritten 10 times on adjacent tracks on the two sides of the former track. After that, the SbER and PRSNR of the middle track were measured.
(2) Analog Measurement
The analog measurement was done as follows.
First, a mark string or train including patterns from 2 T to 13 T at random was overwritten 10 times. Then, a 9 T single pattern was overwritten once on this mark train, and the carrier-to-noise ratio (CNR) of the signal frequency of the 9 T mark was measured by a spectrum analyzer. After that, a laser beam having an erase power level was emitted for one rotation of the disc to erase the recorded marks. In this state, the reduction in carrier intensity of the 9 T mark was measured and defined as the erase ratio (ER). The head was then moved to a sufficiently separated track to measure the cross erase (E-X).
(3) Overwrite (OW) Test
As the third measurement, an experiment about the overwrite (OW) characteristic was conducted. In this experiment, the CNR was measured while a random signal was overwritten (OW) on the same track, thereby checking whether the count of overwrite was 2,000 or more when the CNR was reduced by 2 dB or more from the initial value. This experiment was not conducted to check the limit count of OW. For video recording, the limit count of OW is required to be about 1,000. For data recording of a PC, the limit count of OW is required to be 10,000 or more. However, since the market for video recording is much larger than that for data recording, the evaluation was performed in view of video recording.
As the criteria of evaluation, that for the SbER is 5.0×10 −5 or less, and that for the PRSNR is 15.0 or more. Note that the read power of a single-sided, double-layer medium was selected in consideration of the optical characteristics (L 0 reflectance and transmittance, and L 1 reflectance) and sensitivity of the medium, and the signal amplitudes and SN ratios of playback signals, so that SN ratios and signal amplitudes of L 0 and L 1 playback signals were nearly equal to each other. When all characteristics met target values, that recording medium was determined as “good”, and when at least one characteristic did not meet a target value, it was determined as “rejection”.
On the other hand, in case of a write-once information storage medium (write-once type medium), the following four experiments were conducted:
(a), (b) (1) measurement of the bit error rate conducted for the rewritable medium;
(c) modulation; and
(d) reflectance and playback (read) stability of data part.
As the criteria of evaluation, that for the SbER is 5.0×10 −5 or less, that for the PRSNR is 15.0 or more, that for modulation is 0.4 or more, that for reflectance is 4% or higher for each of L 0 and L 1 media in case of a single-sided, double-layer medium, and that for read stability is that the characteristics (a) to (d) achieve targets even after read of one million or more times when continuous read is made using a satisfactory power of any of 0.4 to 0.8 mW in case of a single-sided, double-layer medium. Note that the read power of a single-sided, double-layer medium was selected in consideration of the optical characteristics (L 0 reflectance and transmittance, and L 1 reflectance) and sensitivity of the medium, and the signal amplitudes and SN ratios of playback signals, so that SN ratios and signal amplitudes of L 0 and L 1 playback signals were nearly equal to each other. When all characteristics met target values, that recording medium was determined as “good”, and when at least one characteristic did not meet a target value, it was determined as “rejection”.
In case of a rewritable medium, the recording film on the entire medium surface of each layer was crystallized by using an initializing apparatus. After the initialization, the layers were adhered by a UV resin such that the surfaces on which the films are formed faced each other, thereby forming an interlayer dielectric layer. A write-once medium was fabricated via the processes of formation of an organic dye recording film by spin-coating, formation of a reflecting layer, and adhesion or bonding. A read-only information storage medium was fabricated by forming a reflecting layer on each of substrates on which information was recorded as pits, and bonding the substrates using a UV resin. The thickness of the interlayer dielectric layer falls within the range from 20 to 30 μm.
Evaluation was performed by using the ODU-1000 disc evaluation apparatus available from Pulstec. This apparatus is comprised of a blue-violet semiconductor laser having a wavelength of 405 nm, and an objective lens having NA=0.65. Recording/playback experiments were conducted under the condition of a linear velocity of 5.6 m/sec or 6.6 m/sec to evaluate rewritable media, and were conducted under the condition of a linear velocity of 6.6 m/sec to evaluate write-once media.
Note that the present invention is also applicable to a medium which receives light via a transparent sheet as thin as about 0.1 mm adhered on a substrate on which various layers are formed (assume that such medium uses an object lens with an NA as high as about 0.85). This is because the characteristics required for the phase change recording layer, interface layer, protection layer, organic dye recording layer, and reflecting layer materials to be used are not much different between a case wherein the transparent cover layer as thin as about 0.1 mm is used on the light incidence side and a case wherein a 0.6-mm thick transparent substrate mainly used in the present invention is used.
The following examples will mainly exemplify single-sided, double-layer media shown in FIGS. 7 and 8 to help understand the effects of the present invention.
As a substrate, a 0.6-mm thick polycarbonate (PC) substrate fabricated by injection molding was used. Grooves are formed on the substrate at a track pitch of 0.4 μm. A single-layer medium is fabricated in such a manner that a dye is applied onto the substrate by spin-coating, a reflecting layer is formed on the dye film by sputtering, and a 0.6-mm thick PC substrate is adhered onto the resultant structure using a UV-curing resin.
On the other hand, a single-sided, double-layer medium can use two different methods. In the first method, the medium is fabricated in such a manner that a dye is applied onto an L 0 substrate by spin-coating, a semitransparent reflecting layer is formed on the dye film by sputtering, an interlayer dielectric layer is formed on the reflecting layer by the 2P method, grooves for L 1 are formed in the interlayer dielectric layer, a dye is applied to the interlayer dielectric layer by spin-coating, a reflecting layer is formed on the dye film by sputtering, and a 0.6-mm thick PC substrate is finally adhered onto the resultant structure using a UV-curing resin. With this method, after formation of the semitransparent reflecting layer of the L 0 layer, another layer can be formed on the reflecting layer for the purpose of adjustment of the optical characteristics. In the second method, an L 0 substrate on which a dye is applied by spin-coating and a semitransparent reflecting layer is formed on the dye film is prepared, and an L 1 substrate on which a reflecting film is formed initially by sputtering, and a dye is applied onto the reflecting layer by spin-coating is prepared. The fabricated L 0 and L 1 layers are adhered using a UV-curing resin so that their semitransparent layer surface and organic dye surface face each other. With this method, another layer can be inserted between the organic dye layer as the L 1 recording layer and the UV-curing resin for the purpose of stabilization of the organic dye as the L 1 recording layer material or adjustment of the optical characteristics. The present invention conducted experiments using media fabricated using these two methods.
Organic dye materials used (to be also simply referred to as “dye” hereinafter) are roughly classified into three types, i.e., (1) anion-cation based, (2) organic metal complex (azo based), and (3) a dye mixture of anion-cation based and organic metal complex (azo based). The reflecting layer used a binary based Ag alloy selected from the group consisting of AgAu, AgBi, AgCa, AgCe, AgCo, AgGa, AgLa, AgMg, AgN, AgNi, AgNd, AgPd, AgY, AgW, and AgZr, and a ternary based Ag alloy selected from the group consisting of AgAlMg, AgAuBi, AgBiGa, AgAuCo, AgAuCe, AgAuNi, AgAuMg, AgBiMg, AgBiN, AgBiPd, and AgBiZr, and the effects upon simultaneously adding additive elements of first and second groups and N (nitrogen) were confirmed. The film formation method used the aforementioned respective Ag alloy targets, multiple-target sputter whose sputter conditions were adjusted to obtain a desired composition, or the like. A reaction with nitrogen was conducted using, as a sputter gas, a gas mixture of Ar and N (nitrogen) in place of normal Ar alone. The composition film thicknesses of the dye and reflecting layer and the substrate shape were respectively adjusted to obtain satisfactory signal characteristics.
The additive amounts of additive elements in Ag alloy reflecting layers used in Examples used four levels, i.e., 0.05, 1, 2, and 5 at. %, and the organic dye materials as the recording layer used three levels, i.e., (1), (2), and (3). Therefore, the total number of samples prepared in Examples is 12.
Tables 1 and 2 below show additive element names of Ag alloy reflecting layers used in Examples. The media were fabricated to have the eccentricity amounts of 70 μm or less of the tracks of the information layers. Note that the media with smaller eccentricity amounts were fabricated from the stage of a stamper, and substrates which were molded using the stamper and had smaller eccentricity amounts were selected. The bonding process was adjusted to reduce the eccentricity amounts. Note that the conditions for smaller eccentricity amounts were explored by improving the reproducibility of the eccentricity amounts by forming a stamper also in consideration of temperature management and the like.
| TABLE 1 | |||
| Example (binary based) | |||
| Reflecting film | Organic | ||
| Additive | Additive element | dye | |
| Example | element | amount at. % | material |
| 1 | Au | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| 2 | Bi | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| 3 | Ga | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| 4 | Mg | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| 5 | N | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| 6 | Nd | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| 7 | Pd | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| 8 | Zr | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| TABLE 2 | |||
| Example (ternary based) | |||
| Reflecting film | Organic | ||
| Additive | Additive element | dye | |
| Example | element | amount at. % | material |
| 9 | AgAuBi | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| 10 | AgBiGa | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| 11 | AgAuMg | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| 12 | AgBiMg | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| 13 | AgBiN | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
| 14 | AgBiZr | 0.05, 1, 2, 5 | {circle around (1)}, {circle around (2)}, {circle around (3)} |
Au was used as an additive element of the Ag alloy reflecting layer, the additive amounts used four levels, i.e., 0.05, 1, 2, and 5 at. %, and the organic dye materials of the recording layer used three levels, i.e., (1), (2), and (3). In order to cover all combinations of the additive element amounts and dye materials, all the combinations, i.e., 12 types of recording media were fabricated, and their recording/playback characteristics were evaluated. Table 3 below lists combinations of the compositions of the reflecting layer and the organic dye materials of the recording layer in practice.
Combination of reflecting layer material (binary based) and composition, and organic dye material of recording layer
| TABLE 3 | |||
| Combination of reflecting film material (binary based) and composition, | |||
| and organic dye material of recording film of Example 1 | |||
| Reflecting film | Organic dye | ||
| material and | material of | ||
| Example | composition | recording film | |
| 1-1 | Ag 99.95 Au 0.05 | {circle around (1)} | |
| 1-2 | Ag 99.95 Au 0.05 | {circle around (2)} | |
| 1-3 | Ag 99.95 Au 0.05 | {circle around (3)} | |
| 1-4 | Ag 99.0 Au 1.0 | {circle around (1)} | |
| 1-5 | Ag 99.0 Au 1.0 | {circle around (2)} | |
| 1-6 | Ag 99.0 Au 1.0 | {circle around (3)} | |
| 1-7 | Ag 98.0 Au 2.0 | {circle around (1)} | |
| 1-8 | Ag 98.0 Au 2.0 | {circle around (2)} | |
| 1-9 | Ag 98.0 Au 2.0 | {circle around (3)} | |
| 1-10 | Ag 95.0 Au 5.0 | {circle around (1)} | |
| 1-11 | Ag 95.0 Au 5.0 | {circle around (2)} | |
| 1-12 | Ag 95.0 Au 5.0 | {circle around (3)} | |
Upon evaluating the characteristics (a) to (d) of the fabricated recording media, the results shown in Table 4 were obtained.
Evaluation Results (binary based) of Example
| TABLE 4 | ||||||
| Evaluation results of Example 1 (binary based) | ||||||
| Eccentricity | ||||||
| Example | SbER | PRSNR | Mod. | R[%] | RS. | amount [μm] |
| 1-1 | 2.0 × 10 −6 | 21.4 | 0.5 | 5.8 | One million times or more | 40-70 |
| 1-2 | 1.0 × 10 −6 | 24.2 | 0.5 | 5.7 | One million times or more | 15-35 |
| 1-3 | 1.3 × 10 −6 | 23.6 | 0.5 | 5.4 | One million times or more | 10-30 |
| 1-4 | 1.1 × 10 −6 | 25.2 | 0.5 | 5.5 | One million times or more | 20-40 |
| 1-5 | 1.1 × 10 −6 | 24.2 | 0.5 | 5.4 | One million times or more | 15-35 |
| 1-6 | 1.2 × 10 −6 | 24.4 | 0.5 | 5.2 | One million times or more | 15-45 |
| 1-7 | 1.9 × 10 −6 | 22.9 | 0.49 | 5.8 | One million times or more | 15-55 |
| 1-8 | 1.9 × 10 −6 | 23.9 | 0.49 | 5.5 | One million times or more | 15-30 |
| 1-9 | 2.1 × 10 −6 | 24.4 | 0.49 | 5.4 | One million times or more | 15-35 |
| 1-10 | 2.3 × 10 −6 | 22.1 | 0.48 | 5.4 | One million times or more | 10-55 |
| 1-11 | 2.2 × 10 −6 | 23.5 | 0.48 | 5.5 | One million times or more | 10-35 |
| 1-12 | 2.4 × 10 −6 | 22.7 | 0.48 | 5.7 | One million times or more | 10-45 |
Mod.: modulation, RS.: read stability, and R: reflectance
As can be seen from these results, the respective recording media achieved, as target values, the SbER of 5.0×10 −5 or less, the PRSNR of 15.0 or more, the modulation of 0.4 or more, the reflectance of 4% or higher, and the read stability of one million times or more. Therefore, “good” characteristics were obtained for the respective recording media.
Bi was used as an additive element of the Ag alloy reflecting layer, the additive amounts used four levels, i.e., 0.05, 1, 2, and 5 at. %, and the organic dye materials of the recording layer used three levels, i.e., (1), (2), and (3). As in Example 1, all the combinations, i.e., 12 types of recording media were fabricated, and their recording/playback characteristics were evaluated. Media having Bi additive amounts of 0.05, 1, 2, and 5 at. % were fabricated, and were evaluated. Table 5 below lists combinations of the compositions of the reflecting layer and the organic dye materials of the recording layer in practice.
| TABLE 5 | |||
| Combination of reflecting film material and composition, and organic | |||
| dye material of recording film of Example (binary based) | |||
| Reflecting film | Organic dye | ||
| material and | material of | ||
| Example | composition | recording film | |
| 2-1 | Ag 99.95 Bi 0.05 | {circle around (1)} | |
| 2-2 | Ag 99.95 Bi 0.05 | {circle around (2)} | |
| 2-3 | Ag 99.95 Bi 0.05 | {circle around (3)} | |
| 2-4 | Ag 99.0 Bi 1.O | {circle around (1)} | |
| 2-5 | Ag 99.0 Bi 1.O | {circle around (2)} | |
| 2-6 | Ag 99.0 Bi 1.O | {circle around (3)} | |
| 2-7 | Ag 98.0 Bi 2.0 | {circle around (1)} | |
| 2-8 | Ag 98.0 Bi 2.0 | {circle around (2)} | |
| 2-9 | Ag 98.0 Bi 2.0 | {circle around (3)} | |
| 2-10 | Ag 95.0 Bi 5.0 | {circle around (1)} | |
| 2-11 | Ag 95.0 Bi 5.0 | {circle around (2)} | |
| 2-12 | Ag 95.0 Bi 5.0 | {circle around (3)} | |
Upon evaluating the characteristics (a) to (d) of the fabricated recording media, the results shown in Table 6 were obtained.
Evaluation Results (binary based) of Example
| TABLE 6 | ||||||
| Evaluation results of Example (binary based) | ||||||
| Eccentricity | ||||||
| Example | SbER | PRSNR | Mod. | R[%] | RS. | amount [μm] |
| 2-1 | 7.4 × 10 −8 | 28.2 | 0.5 | 5.6 | One million times or more | 15-55 |
| 2-2 | 1.6 × 10 −7 | 27.6 | 0.5 | 5.7 | One million times or more | 15-30 |
| 2-3 | 8.0 × 10 −8 | 25.4 | 0.5 | 5.8 | One million times or more | 15-35 |
| 2-4 | 1.2 × 10 −7 | 20.9 | 0.48 | 5.7 | One million times or more | 10-55 |
| 2-5 | 3.2 × 10 −7 | 24.7 | 0.48 | 5.8 | One million times or more | 15-35 |
| 2-6 | 1.6 × 10 −7 | 31.4 | 0.5 | 5.5 | One million times or more | 10-30 |
| 2-7 | 1.6 × 10 −7 | 29.9 | 0.49 | 5.4 | One million times or more | 20-40 |
| 2-8 | 1.8 × 10 −6 | 29.2 | 0.49 | 5.2 | One million times or more | 15-35 |
| 2-9 | 3.9 × 10 −9 | 28.2 | 0.49 | 5.4 | One million times or more | 10-55 |
| 2-10 | 2.2 × 10 −6 | 24.1 | 0.48 | 5.4 | One million times or more | 10-35 |
| 2-11 | 2.1 × 10 −6 | 26.5 | 0.48 | 5.3 | One million times or more | 10-45 |
As can be seen from these results, the respective recording media achieved, as target values, the SbER of 5.0×10 −5 or less, the PRSNR of 15.0 or more, the modulation of 0.4 or more, the reflectance of 4% or higher for both L 0 and L 1 of single-sided, double-layer media, and the read stability of one million times or more. “Good” characteristics were obtained for the respective recording media.
As for other additive elements, the characteristics that met the target values were obtained, and “good” characteristics were obtained for the respective recording media.
By setting the eccentricity amounts of the tracks of the respective information layers of the fabricated media to be 70 μm or less, the characteristics could be improved. By setting the eccentricity amounts of the tracks of the respective information layers of the fabricated media to be 40 μm or less, the characteristics could be further improved. The respective media exhibited satisfactory characteristics. The improved tracking stability largely contributes to such improvements. This also influences the frequency of occurrence of out of tracking during the experiment. When the eccentricity amounts of the tracks are 70 μm or more, out of tracking have occurred several times or more during mere about 10 measurements, and it is difficult to attain stable measurements. The probability of such errors lowers with decreasing eccentricity amounts of the tracks. When the eccentricity amounts of the tracks are 40 μm or less, most of media can stably undergo experiments at higher linear velocities. This fact exerts very large effects in actual recording and playback apparatuses.
FIG. 8 shows an optical recording medium according to one embodiment of the present invention.
This medium will be described in detail below. As substrates, those which were compatible to both the aforementioned methods (a) and (b), i.e., the land-groove recording method and groove recording method were used. That is, in the method (a), a 0.59-mm thick polycarbonate (PC) substrate formed by injection molding were used. Since the substrate on which grooves were formed at a groove pitch of 0.68 μm was used, this corresponds to a track pitch=0.34 μm upon recording on both the lands (L) and grooves (G). In the method (b), a 0.59-mm thick polycarbonate (PC) substrate formed by injection molding were also used, and a groove pitch was set to be 0.4 μm. An information layer L 0 which was formed on the surface formed with the grooves of each of these PC substrate on the side closer to the light incidence side was prepared by forming ZnS:SiO 2 , an interface layer, a recording layer, an interface layer, ZnS:SiO 2 , an Ag alloy, and ZnS:SiO 2 in turn. On the other hand, an information layer L 1 formed on the side farther from the light incidence side using a sputtering apparatus was prepared by forming an Ag alloy, ZnS:SiO 2 , an interface layer, a recording film layer, an interface layer, and ZnS:SiO 2 in turn from the surface on the PC substrate. The sputtering apparatus used is a so-called cluster type sputtering film formation apparatus which forms respective layers by sputtering in different film formation chambers. The cluster type sputtering film formation apparatus comprises a load lock chamber which loads a substrate, a convey chamber, and a process chamber which forms respective layers.
FIG. 9 is a block diagram showing the arrangement of one process chamber. A process chamber 60 is comprised of a device 61 for evacuating the chamber, a vacuum gauge 64 , a pressure sensor 57 , a film gauge 53 , a sputtering target 66 as a material which is to undergo film formation, a loaded substrate 59 , and the like. A rare gas of Ar and the like is mainly used as a sputter gas, and an oxygen or nitrogen gas, or like is used as needed. A discharge mode upon sputtering uses an RF power supply, DC power supply, and the like depending on materials which are undergo film formation, film thicknesses to be obtained, and the like. The process procedure in film formation is as shown in FIG. 10.
When a recording film layer was made up of Ge, Sb, and Te, and its composition was expressed by Ge x Sb y Te z (for x+y+z=100), the recording film layer used a composition selected from those bounded by x=55 and z=45, x=45 and z=55, x=10, y=28, and z=42, and x=10, y=36, and z=54 on a GeSbTe ternary phase diagram. When the recording film was made up of Ge, Sb, Te, and Bi or Sn, and a composition obtained by partially substituting the GeSbTe composition by Bi and/or In and/or Sn was given by (Ge(1-w)Snw)x(Sb(1-v)(Bi(1-u)Inu)v)yTez (for x+y+z=100), the recording film layer used a composition selected from GeSnSbTe, GeSnSbTeIn, GeSbTeIn, GeSbTeBiIn, GeSbSnTeBiIn, GeSbTeBi, GeSnSbTeBi, and GeSnSbTeBiIn in which w, v, and u satisfied 0≦w≦0.5, 0≦v≦0.7, and 0≦u≦1.0. Furthermore, when the recording film layer was made up of Ge, Bi, and Te, and its composition Ge x Bi y Te z (for x+y+z=100), the recording film layer used a composition selected from those bounded by x=55 and z=45, x=45 and z=55, x=10, y=28, and z=42, and x=10, y=36, and z=54 on a GeBiTe ternary phase diagram. Many compositions were examined, and Table 8 shows an example of such compositions. Note that the film thickness of the recording layer was set to be 10 nm or less.
The compositions of the interface layer material and recording layer were selected from Tables 7 and 8.
| TABLE 7 | |
| Interface layer used | |
| No. | Interface layer |
| 1 | GeN |
| 2 | GeCrN |
| 3 | ZrO2 + Y2O3 |
| 4 | ZrO2 + Y2O3 + Cr2O3 |
| 5 | ZrO2 + Y2O3 + SiO2 + Cr2O3 |
| 6 | ZrSiO4 + Cr2O3 |
| 7 | HfO2 |
| 8 | (ZrO 2−x N x ) 1−y ((Y 2 O 3 ) 1−z (Nb 2 O 5 ) z ) y |
| 9 | HfO 2−x N x (0.1 ≦ x ≦ 0.2) |
| 10 | Cr2O3 |
| 11 | ZnO + Ta2O5 |
| 12 | ZnO + Ta2O3 + In2O3 |
| 13 | SnO2 + Sb2O3 |
| 14 | SnO2 + Ta2O5 |
| 15 | SnO2 + Nb2O5 |
Table 8 Composition of Recording Layer
| TABLE 8 | |
| Composition of recording film | |
| No. | Composition of recording film |
| 1 | Ge10Sb2Tel3 |
| 2 | Ge4Sb2Te7 |
| 3 | Ge8Sb2Te13Bi2 |
| 4 | Ge3Sb2Te7Bi |
| 5 | Ge6Sb2Tel3Sn4 |
| 6 | Ge3Sb2Te7Sn |
| 7 | Ge10Bi2Tel3 |
| 8 | Ge2.9BiTe4.4 |
| 9 | Ge11.25BiTel2.75 |
| 10 | Ge10Sb1.5In0.5Te13 |
| 11 | Ge10Sb1.5In0.5Te13 |
| 12 | Ge4Sb1.5In0.5Te7 |
| 13 | Ge2.9Bi0.75In0.25Te4.4 |
A composition range defined by 0<x≦0.2, 0<y≦0.1, and 0≦z≦1 is preferable for (ZrO 2-x N x ) 1-y (Y 2 O 3 ) 1-z (Nb 2 O 5 ) z ) y , and that defined by 0.1≦x≦0.2 is preferable for HfO 2-x N x .
In a medium using GeN on two sides, it was more preferable to use a combination of different composition ratios, as shown in Table 9: for example, Ge 54 N 46 and Ge 47 N 53 , and the like.
Table 9 Composition ratio (at. %) of GeN used in Examples
| TABLE 9 | ||
| Composition ratio of GeN used in Example [at. %] | ||
| No. | Ge | N |
| 1 | 54 | 46 |
| 2 | 52 | 48 |
| 3 | 50 | 50 |
| 4 | 48 | 52 |
| 5 | 47 | 53 |
The interface layer used GeN on the two sides, i.e., the light incidence side and the reflecting layer side. A ZnS:SiO 2 layer was formed using a target prepared by mixing SiO 2 in ZnS. A sputter apparatus used is a so-called cluster type sputter film formation apparatus which forms respective layers by sputtering in different film formation chambers. After fabrication of respective media, their reflectances and transmittances are measured by a spectrophotometer. The media were fabricated to have the eccentricity amounts of 70 μm or less of the tracks of the information layers.
Table 10 Example (Disc Characteristic Measurements)
| TABLE 10 | |||||
| Example (disc characteristic measurement) | |||||
| Eccentricity | |||||
| Example | CNR[dB] | ER[dB] | SbER | PRSNR | amount [μm] |
| Example 1 | 52.9 | 33.8 | 1.8 × 10 −6 | 21.4 | 15-30 |
| Example 2 | 52.6 | 33.1 | 1.5 × 10 −6 | 25.2 | 15-35 |
| Example 3 | 52.8 | 33.1 | 1.6 × 10 −6 | 24.2 | 10-55 |
| Example 4 | 53.7 | 34.8 | 1.9 × 10 −6 | 25.2 | 20-40 |
| Example 5 | 53.6 | 34.9 | 2.2 × 10 −6 | 24.2 | 15-35 |
| Example 6 | 53.7 | 34.8 | 1.8 × 10 −6 | 24.4 | 10-55 |
| Example 7 | 52.0 | 30.9 | 2.6 × 10 −6 | 22.9 | 15-55 |
| Example 8 | 53.2 | 34.6 | 1.9 × 10 −6 | 23.9 | 10-30 |
| Example 9 | 53.6 | 34.7 | 2.2 × 10 −6 | 22.9 | 20-40 |
| Example 10 | 51.9 | 31.3 | 2.6 × 10 −6 | 23.9 | 15-35 |
| Example 11 | 53.8 | 34.8 | 2.0 × 10 −6 | 23.5 | 15-45 |
| Example 12 | 53.7 | 34.9 | 1.9 × 10 −6 | 22.7 | 15-35 |
| Example 13 | 53.1 | 34.9 | 1.4 × 10 −6 | 23.6 | 10-55 |
| Example 14 | 51.9 | 34.6 | 1.5 × 10 −6 | 25.2 | 15-55 |
As can be seen from these results, the respective recording media achieved, as target values, the SbER of 5.0×10 −5 or less and the PRSNR of 15.0 or more. “Good” characteristics were obtained for the respective recording media.
By setting the eccentricity amounts of the tracks of the respective information layers of the fabricated media to be 70 μm or less, the characteristics could be improved. By setting the eccentricity amounts of the tracks of the respective information layers of the fabricated media to be 40 μm or less, the characteristics could be further improved. The respective media exhibited satisfactory characteristics. The improved tracking stability largely contributes to such improvements.
As read-only media, a reflecting layer was formed on a transparent substrate embossed with information, and that structure was adhered to another substrate using a UV-curing resin, thus fabricating single-sided, dual-, triple-, and quadruple-layer media, The media were fabricated to have the eccentricity amounts of 70 μm or less of the tracks of the information layers. Read-only media originally have satisfactory base characteristics. Hence, as evaluations, situations that readily caused errors were created by putting many fingerprints and scratches on the substrate surface on the light incident side, and whether or not to stably play back information was also confirmed, in addition to evaluations of the SbER and PRSNR.
Table 11 Characteristics Measured in Situations that Readily Cause Errors by Putting Many Fingerprints and Scratches on Substrate Surface on Light Incidence Side
| TABLE 11 | ||||
| Characteristics measured in situations that readily cause error by | ||||
| putting fingerprints on substrate surface on liqht incident side | ||||
| Eccentricity | ||||
| Example | SbER | PRSNR | amount [μm] | |
| Single-sided, | 1.1 × 10 −10 | 44.4 | 15-70 | |
| double-layer | ||||
| medium | ||||
| Single-sided, | 1.2 × 10 −10 | 42.2 | 10-30 | |
| triple-layer | ||||
| medium | ||||
| Single-sided, | 1.2 × 10 −10 | 41.6 | 15-30 | |
| quadruple- | ||||
| layer medium | ||||
The respective media exhibited satisfactory playback characteristics, and the stability could be improved compared to the prior art in situations that readily caused errors. The improved tracking stability largely contributes to such improvement.
A method of measuring the eccentricity amounts of the tracks of the information layers in Examples 1 to 3 or Examples to be described hereinafter will be described. FIG. 5 is a block diagram of a measurement system. A measurement system comprises an illumination system that does not include any light components of wavelengths of 620 nm or less, a CCD camera, an image processing apparatus which includes a track extraction mechanism, and an arithmetic and control apparatus. Using this measurement system, the eccentricity amounts of respective tracks could be measured for several seconds, i.e., during the manufacture time period per storage medium. The image processing apparatus with the track extraction mechanism, arithmetic and control apparatus, and the like can be implemented when a so-called personal computer or the like executes predetermined procedures. The capability of an image sensing device such as the CCD camera or the like differs depending on media, and also depends on the accuracy of a lens system and clamp, the stage moving accuracy, and the like. Measurement can be made for media other than those using an organic dye sensitized at a wavelength of 620 nm or less without limiting the wavelength of the illumination system. However, the wavelength of the illumination system preferably fall within the range from 550 nm (inclusive) to 780 nm (inclusive) in consideration of the sensitivity of the CCD and image processing apparatus. In order to implement an apparatus which performs inspection independently of the types of media, an illumination system that does not include any light components of wavelengths of 620 nm or less is preferably used.
A method of measuring the eccentricity amounts of the tracks of the information layers in Examples 1 to 3 or Exa