Information storage medium, recording method, and recording apparatus   

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 11/668,835, filed Jan. 30, 2007 and claims the benefit of priority from Japanese Patent Applications No. 2006-023924, filed Jan. 31, 2006; and No. 2006-126241, filed Apr. 28, 2006, the entire contents of each of which are incorporated herein by reference.

1. Field

One embodiment of the invention relates to an information storage medium such as a recordable optical disc, a recording method, and a recording apparatus.

2. Description of the Related Art

In recent years, a digital versatile disc (DVD) has been practically used as a large-capacity optical disc. As a recordable DVD, a recordable DVD-R, a rewritable DVD-RW, and a DVD-RAM have been standardized. Once information is recorded on a recordable disc DVD-R, a recorded area cannot be rewritten. A conventional recordable DVD-R includes a power calibration area (PCA), a recording management area (RMA), and a data recording area (DA) in which an actual recording process is executed from the inner circumference side (for example, see Jpn. Pat. Appin. KOKAI Publication No. 2002-245625 (paragraphs 0041 to 0052, FIG. 1)).

Furthermore, the data recording area DA includes a lead-in area in which recording parameter information and the like to be read when recording data is reproduced from a data area, a data area in which the recording data is recorded, and a lead-out area in which end information or the like to be read when reproducing of the recording data recorded in the data area is ended is recorded. The lead-in area is an area in which recording parameter information or the like is recorded before data is recorded in the data area. The lead-out area is an area in which end information is recorded before recording of recording data on an entire DVD is completed. The capacity of each area is predetermined and unchangeable.

When information is recorded on such a DVD (recording is performed from the inner circumference side of the data area), test recording is performed in the PCA area first. In this test recording, because the characteristics of optical discs of the same type vary depending on manufacturers and because of temperatures of a use environment, an operational environment of a laser, and the like, an optimal recording waveforms vary. Therefore, parameters (intensities, pulse widths, and the like) of the recording waveforms used when information is recorded on the optical disc are adjusted by a result of the test recording.

Thereafter, management information and user data are recorded in the RMA area and the data area, respectively. The management information includes information or the like representing a specific recorded area (record-end position) in the data area. Depending on the progress of recording of user data, the management information is updated into the latest management information. Since the part cannot be rewritten on the recordable DVD once information is recorded, a remaining capacity of the RMA area decreases each time the management information is updated. Depending on a method of updating management information, before recording in the entire area of the data area is completed, the RMA area may not have any more unrecorded areas. When the RMA area does not have an unrecorded area, the management information cannot be updated. Therefore, a recording operation for the data area must be stopped.

On the other hand, in the DVD device described above, a recording waveform changes. Depending on a recording position on a disc, an optimum recording waveform changes due to a change in temperature or aging. In order to adjust the recording waveform depending on these changes, in the DVD device, test recording is performed in the PCA area to adjust parameters of the recording waveform. Like the updating of the management information, each time the test recording is performed, the remaining capacity of the PCA area decreases. Depending on ways of executing the test recording, the PCA area may not have any more unrecorded areas before recording in the entire area of the data area is completed. When there is no unrecorded area in the PCA area, a recording operation must be stopped, or the user data and the management information must be recorded without adjusting the recording waveform. Sufficiently reliable information cannot be reproduced from a part on which the information is recorded with an unadjusted recording waveform.

In order to prevent shortage of the RMA area or shortage of the PCA area, the large capacity of the RMA area or the PCA area may be reserved in advance. However, in this case, the capacity of the data area reduces. As a result, even though the unrecorded areas in the RMA area and the PCA area sufficiently remain, the capacity of the data area may not be large enough.

On the other hand, in order to increase a recording capacity, the standards of a next-generation DVD in which the diameter of a beam spot is narrowed by shortening the wavelength of a laser beam or increasing a numerical aperture NA to increase a recording capacity have been proposed. As a method of increasing a recording capacity, a single-sided multilayer storage medium is also proposed. That is, in addition to the narrowing down of the beam spot, a plurality of recording layers are formed on one side of a disc, an objective lens is moved in an optical-axis direction to focus the beam on the respective layers, so that recording and reproducing can be performed on the respective recording layers (for example, see Jpn. Pat. Appin. KOKAI Publication No. 2004-206849 (paragraphs 0036 to 0041, FIG. 1)).

The single-sided multilayer storage medium has a problem called interlayer crosstalk which does not occur in a single-sided single-layer storage medium. For descriptive simplification, a dual layer medium will be exemplified. On a single-sided dual layer storage medium, a laser beam is focused on the respective layers from a single read surface. A layer which is close to the read surface is called layer 0, and a layer which is far from the read surface is called layer 1. When the beam is focused on each layer, some laser beam is irradiated on a layer except for a target layer. Therefore, a reflected beam from the layer except for the target layer is mixed with a reproducing signal at the time of reproducing, interlayer crosstalk occurs. The interlayer crosstalk causes a problem not only at the time of reproducing but also at the time of recording.

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.

FIGS. 1A and 1B are exemplary views showing a standard phase shift recording film structure and an organic dye recording film structure;

FIG. 2 is an exemplary view showing a specific structural formula of the specific content “(A3) azo-metal complex+Cu” of the information storage medium constituent elements;

FIG. 3 is an exemplary view illustrating an example of optical absorption spectrum characteristics of an organic dye recording material for use in a current DVD-R disc;

FIGS. 4A and 4B are exemplary views each showing comparison of shapes of recording films formed in a pre-pit area or a pre-groove area 10 in the phase shift recording film and the organic dye recording film;

FIGS. 5A and 5B are exemplary views each showing a specific plastic deformation state of a transparent substrate 2-2 at a position of a recording mark 9 in a write-once type information storage medium using a conventional organic dye material;

FIGS. 6A, 6B and 6C are exemplary views relating to a shape or dimensions of a recording film in which a principle of recording is easily established;

FIGS. 7A, 7B and 7C are exemplary views each showing a shape and dimensions of the recording film;

FIG. 8 is an exemplary view illustrating one embodiment of an information recording/reproducing apparatus according to the present invention;

FIG. 9 is an exemplary view showing a detailed structure of peripheral portions including a sync code position sampling section 145 shown in FIG. 8;

FIG. 10 is an exemplary view illustrating polarity of a detection signal detected from the “H-L” recording film and the “L-H” recording film;

FIG. 11 is an exemplary view showing light absorption spectrum characteristics in an unrecorded state of the “L-H” recording film;

FIG. 12 is an exemplary view showing a change of light absorption spectrum characteristics in a recorded state and an unrecorded state of the “L-H” recording film;

FIG. 13 is an exemplary general structural formula of a cyanine dye utilized for a cation portion of the “L-H” recording film;

FIG. 14 is an exemplary view showing an example of an internal structure and dimensions of an information storage medium;

FIGS. 15A, 15B, 15C and 15D are exemplary views each showing an internal data structure of an RMD duplication zone RDZ and a recording management zone RMZ located in a write-once type information storage medium;

FIGS. 16A, 16B, 16C and 16D are exemplary views each showing another embodiment which is different from

FIGS. 17A, 17B, 17C and 17D are exemplary views each illustrating a structure of a border area in the write-once type information storage medium;

FIGS. 18A, 18B, 18C and 18D are exemplary views each showing an internal data structure of a control data zone CDZ and an R physical information zone RIZ;

FIG. 19 is an exemplary view showing a comparison of the contents of detailed information recorded in allocation place information on a data area DTA;

FIG. 20 is an exemplary view showing an update condition of recording position management data RMD;

FIG. 21 is an exemplary view illustrating 180 degree phase modulation and an NRZ technique in wobble modulation;

FIG. 22 is an exemplary view illustrating a relationship between a wobble shape and an address bit in an address bit area;

FIGS. 23A, 23B, 23C and 23D are exemplary views illustrating a comparison in positional relationship between a wobble sync pattern and an inside of a wobble data unit;

FIGS. 24A, 24B, 24C, and 24D are exemplary view relating to an internal data structure of wobble address information in a write-once type information storage medium;

FIG. 25 is an exemplary view illustrating a setting location of a modulation area on the write-once type information storage medium;

FIGS. 26A, 26B, 26C and 26D are exemplary views each illustrating a setting location of a modulation area in a physical segment on the write-once type information storage medium;

FIGS. 27A and 27B are exemplary views each illustrating another embodiment of the detection signal level conforming to the H format in an “L-H” recording film;

FIG. 28 is an exemplary view illustrating a BCA data structure;

FIGS. 29A, 29B, 29C, 29D, 29E, 29F and 29G are exemplary views each illustrating an example of the contents of the BCA information recorded in the BCA data area;

FIGS. 30A, 30B, 30C, 30D and 30E are exemplary views each illustrating a wobble address format in a write-once type information storage medium;

FIG. 31 shows an exemplary sectional view of a dual layer recordable disc according to a second embodiment of the present invention;

FIG. 32 shows an exemplary view showing the ray bundle on the other layer while reading and writing of a layer of the disc;

FIG. 33 shows an exemplary view showing the clearance to prevent the influence of the other layer at the worst case;

FIG. 34 shows an exemplary view showing a physical sector number on Layer 0 and the corresponding recordable physical sectors on Layer 1;

FIG. 35 shows an exemplary view showing the clearance in the number of physical sectors;

FIG. 36 shows an exemplary view showing general parameters of write-once recording medium;

FIG. 37 shows an exemplary view showing the schematic of lead-in area and lead-out area;

FIG. 38 shows an exemplary view showing the schematic of original middle area;

FIG. 39 shows an exemplary view showing the track path;

FIG. 40 shows an exemplary view showing the physical sector layout and numbering;

FIG. 41 shows an exemplary view showing the layout of address field in WAP (Wobble Address in Periodic position);

FIG. 42 shows an exemplary view showing the primary WDU (Wobble Data Unit) in sync field;

FIG. 43 shows an exemplary view showing the primary WDU in address field;

FIG. 44 shows an exemplary view showing the secondary WDU in sync field;

FIG. 45 shows an exemplary view showing the secondary WDU in address field;

FIG. 46 shows an exemplary view showing the WDU in unity field;

FIG. 47 shows an exemplary view showing the structure of the lead-in area;

FIG. 48 shows an exemplary view showing the structure of a control data zone;

FIG. 49 shows an exemplary view showing a structure of a data segment in a control data section;

FIG. 50 shows an exemplary view showing the physical format information;

FIG. 51 shows an exemplary view showing the data area allocation;

FIG. 52 shows an exemplary view showing the layout of the RMD (Recording Management Data) duplication zone;

FIG. 53 shows an exemplary view showing the data structure of the recording management data;

FIG. 54 shows an exemplary view showing the RMD field 0;

FIG. 55 shows an exemplary view showing the data area allocation;

FIG. 56 shows an exemplary view showing the renewed data area allocation;

FIG. 57 shows an exemplary view showing the drive test zone;

FIG. 58 shows an exemplary view showing the RMD field 1 (part 1);

FIG. 59 shows an exemplary view showing the RMD field 1 (part 2);

FIG. 60 shows an exemplary view showing the RMD field 4;

FIG. 61 shows an exemplary view showing the RMD field 5 to RMD field 21;

FIG. 62 shows an exemplary view showing the structure of a physical sector block in a R-physical format information zone;

FIG. 63 shows an exemplary view showing the physical format information;

FIG. 64 shows an exemplary view showing the data area allocation;

FIGS. 65A, 65B and 65C shows exemplary views showing the structure of the middle area before\after the expansion;

FIG. 66 shows an exemplary view showing the structure of the middle area before the expansion;

FIG. 67 shows an exemplary view showing the structure of the middle area after small size expansion;

FIG. 68 shows an exemplary view showing the structure of the middle area after large size expansion;

FIG. 69 shows an exemplary view showing the number of physical sectors in guard track zone;

FIG. 70 shows an exemplary view showing the structure of the lead-out area;

FIGS. 71A and 71B show exemplary views showing the schematic of two adjacent tracks;

FIG. 72 shows an exemplary view showing start PSN and end PSN of the terminator;

FIGS. 73A and 73B show exemplary views showing a type selection for track #i+1;

FIG. 74 shows an exemplary view showing an example of the case that the type3 physical segment is selected;

FIG. 75 shows an exemplary view showing an example of the procedure to select the type of the physical segment;

FIG. 76 shows an exemplary view showing a recording procedure of a blank disc;

FIG. 77 shows an exemplary view showing the example of final area structure for recording user data on Layer 1;

FIGS. 78A and 78B show exemplary views showing the example of final area structure for not recording user data on Layer 1;

FIG. 79 shows an exemplary view showing another recording procedure of a blank disc;

FIG. 80 shows an exemplary view showing still another recording procedure of a blank disc;

FIG. 81 shows an exemplary view showing a terminator recording procedure; and

FIG. 82 shows an exemplary view showing another terminator recording procedure.

DETAILED DESCRIPTION

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, an information recording method which records information on an information storage medium in which layer 0 and layer 1 are sequentially arranged as recording layers from a read surface; a system lead-in area, a data lead-in area, a data area, and a middle area are sequentially arranged from an inner circumference of the layer 0; a system lead-out area, a data lead-out area, a data area, and a middle area are sequentially arranged from an inner circumference of the layer 1; a guard track zone is arranged on a side of the data area in the data lead-out area; and a reference code zone, an R physical format information zone, a recording management zone, and a drive test zone are arranged in the data lead-in area of the layer 0 corresponding to the guard track zone, the method comprises padding of the guard track zone of the data lead-out area is performed after padding of the drive test zone of data lead-in area and recording of the recording management zone, the reference code zone of the data lead-in area, and the R physical format information zone of the data lead-in area.

Hereinafter, embodiments of a recording medium and a method for recording and reproducing the recording medium according to the invention will be described with reference to the accompanying drawings.

1) Relationship Between track Pitch/Bit Pitch and Optimal Recording Power:

Conventionally, in the case of a principle of recording with a substrate shape change, if a track pitch is narrowed, a “cross-write” or a “cross-erase” occurs, and if bit pitches are narrowed, an inter-code crosstalk occurs. As in the present embodiment, since a principle of recording without a substrate shape change is devised, it becomes possible to achieve high density by narrowing track pitches/bit pitches. In addition, at the same time, in the above described principle of recording, recording sensitivity is improved, enabling high speed recording and multi-layering of a recording film because optimal recording power can be lowly set.

2) In Optical Recording With a Wavelength of 620 nm or Less, an ECC Block is Composed of a Combination of a Plurality of Small ECC Blocks and Each Item of Data ID Information in Two Sectors is Disposed in a Small ECC Block Which is Different from Another:

According to the invention, as shown in FIG. 1B, a local optical characteristic change in a recording layer 3-2 is a principle of recording, and thus, an arrival temperature in the recording layer 3-2 at the time of recording is lower than that in the conventional principle of recording due to plastic deformation of a transparent substrate 2-2 or due to thermal decomposition or gasification (evaporation) of an organic dye recording material. Therefore, a difference between an arrival temperature and a recording temperature in a recording layer 3-2 at the time of playback is small. In the present embodiment, an interleaving process between small ECC blocks and data ID allocation are contrived in one ECC block, thereby improving reproduction reliability in the case where a recording film is degraded at the time of repetitive playback.

3) Recording is Carried out by Light Having a Wavelength Which is Shorter than 620 nm, and a Recorded Portion has a Higher Reflection Factor than a Non-Recording Portion:

Under the influence of absorption spectrum characteristics of a general organic dye material, under the control of light having a wavelength which is shorter than 620 nm, the light absorbance is significantly lowered, and recording density is lowered. Therefore, a very large amount of exposure is required to generate a substrate deformation which is a principle of recording in a conventional DVD-R. By employing an “Low to High (hereinafter, abbreviated to as L-H) organic dye recording material” whose reflection factor is increased more significantly than that of an unrecorded portion in a portion (recording mark) recorded as in the present embodiment, a substrate deformation is eliminated by forming a recording mark using a “discoloring action due to dissociation of electron coupling”, and recording sensitivity is improved.

4) “L-H” Organic Dye Recording Rilm and PSK/FSK Modulation Wobble Groove:

Wobble synchronization at the time of playback can be easily obtained, and reproduction reliability of a wobble address is improved.

5) “L-H” Organic Dye Recording Film and Reproduction Signal Modulation Degree Rule:

A high C/N ratio relating to a reproduction signal from a recording mark can be ensured, and reproduction reliability from the recording mark is improved.

6) Light Reflection Factor Range in “L-H” Organic Dye Recording Film and Mirror Section:

A high C/N ratio relating to a reproduction signal from a system lead-in area SYLDI can be ensured and high reproduction reliability can be ensured.

7) “L-H” Organic Dye Recording Film and Light Reflection Factor Range From Unrecorded Area at the Time of On-Track:

A high C/N rate relating to a wobble detection signal in an unrecorded area can be ensured, and high reproduction reliability relevant to wobble address information can be ensured.

8) “L-H” Organic Dye Recording Film and Wobble Detection Signal Amplitude Range:

A high C/N ratio relating to a wobble detection signal can be ensured and high reproduction reliability relevant to wobble address information can be ensured.

<<Table of Contents>>

Chapter 0: Description of Relationship between Wavelength and the Present Embodiment

Wavelength used in the present embodiment.

Chapter 1: Description of Combination of Constituent Elements of Information Storage Medium in the Present Embodiment:

Chapter 2: Description of Difference in reproduction signal between Phase Change Recording Film and Organic Dye Recording Film

2-1) Difference in Principle of Recording/Recording Film and Difference in Basic Concept Relating to Generation of Reproduction Signal . . . Definition of λmax write

2-2) Difference of Light Reflection Layer Shape in Pre-pit/Pre-Groove Area

Optical reflection layer shape (difference in spin coating and sputtering vapor deposition) and influence on a reproduction signal.

Chapter 3: Description of Characteristics of Organic Dye Recording Film in the Present Embodiment

3-1) Problem(s) relevant to achievement of high density in write-once type recording film (DVD-R) using conventional organic dye material

3-2) Description of Basic Characteristics Common to Organic Dye Recording Films in the Present Embodiment:

Lower limit value of recording layer thickness, channel bit length/track pitch in which advantageous effect is attained in the invention, repetitive playback enable count, optimal reproduction power,

Rate between groove width and land width . . . Relationship with wobble address format

Relationship in recording layer thickness between groove section and land section

Technique of improving error correction capability of recording information and combination with PRML

3-3) Recording Characteristics Common to Organic Dye Recording Films in the Present Embodiment

Upper limit value of optimal recording power

3-4) Description of Characteristics Relating to a “High to Low (hereinafter, abbreviated to as H-L)” Recording Film in the Present Embodiment:

Upper limit value of reflection factor in unrecorded layer

Relationship between a value of λmax write and a value of λ1max (absorbance maximum wavelength at unrecorded/recorded position)

Relative values of reflection factor and degree of modulation at unrecorded/recorded position and light absorption values at reproduction wavelength . . . n·k range

Relationship in upper limit value between required resolution characteristics and recording layer thickness

Chapter 4: Description of Reproducing Apparatus or Recording/Reproducing Apparatus and Recording Condition/Reproducing Circuit

4-1) Description of Structure and Characteristics of Reproducing Apparatus or Recording/Reproducing Apparatus in the Present Embodiment: Use Wavelength Range, NA Value, and RIM Intensity

4-2) Description of Reproducing Circuit in the Present Embodiment

4-3) Description of Recording Condition in the Present Embodiment

Chapter 5: Description of Specific Embodiments of Organic Dye Recording Film in the Present Embodiment

5-1) Description of Characteristics Relating to “L-H” Recording Film in the Present Embodiment

Principle of recording and reflection factor and degree of modulation at unrecorded/recorded position

5-2) Characteristics of Light Absorption Spectra Relating to “L-H” Recording Film in the Present Embodiment:

Condition for setting maximum absorption wavelength λmax write, value of Al405 and a value of Ah405

5-3) Anion Portion: Azo Metal Complex+Cation Portion: Dye

5-4) Use of “Copper” as Azo Metal Complex+Main Metal:

Light absorption spectra after recorded are widening in an “H-L” recording film, and are narrowed in an “L-H” recording film.

Upper limit value of maximum absorption wavelength change amount before and after recording:

A maximum absorption wavelength change amount before and after recording is small, and absorbance at a maximum absorption wavelength changes.

Chapter 6: Description Relating to Pre-Groove Shape/Pre-Pit Shape in Coating Type Organic Dye Recording Film and on Light Reflection Layer Interface

6-1) Light Reflection Layer (Material and Thickness):

Thickness range and passivation structure . . . Principle of recording and countermeasures against degradation (Signal is degraded more easily than substrate deformation or than cavity)

6-2) Description Relating to Pre-Pit Shape in Coating Type Organic Dye Recording Film and on Light Reflection Layer Interface:

Advantageous effect achieved by widening track pitch/channel bit pitch in system lead-in area:

Reproduction signal amplitude value and resolution in system lead-in area:

Rule on step amount at land portion and pre-pit portion in light reflection layer 4-2:

6-3) Description Relating to Pre-Groove Shape in Coating Type Organic Dye Recording Film and on Light Reflection Layer Interface:

Rule on step amount at land portion and pre-groove portion in light reflection layer 4-2:

Push-pull signal amplitude range:

Wobble signal amplitude range (combination with wobble modulation system)

Chapter 7: Description of First Next-Generation Optical Disc: HD DVD System (Hereinafter, Referred to as H Format):

Principle of recording and countermeasure against reproduction signal degradation (Signal is degraded more easily than substrate deformation or than cavity):

Error Correction Code (ECC) structure, PRML (Partial Response Maximum Likelihood) System:

Relationship between a wide flat area in the groove and wobble address format.

In the write-once recording, overwriting is carried out in a VFO area which is non-data area.

Influence of DC component change in overwrite area is reduced. In particular, advantageous effect on “L-H” recording film is significant.

Now, a description of the present embodiment will be given here.

As a write-once type optical disc obtained by using an organic dye material for a recording medium, there has been commercially available a CD-R disc using a recording/reproducing laser light source wavelength of 780 nm and a DVD-R disc using a recording/reproducing laser light beam wavelength of 650 nm. Further, in a next-generation write-once type information storage medium having achieved high density, it is proposed that a laser light source wavelength for recording or reproducing, which is close to 405 nm (namely, in the range of 355 nm to 455 nm), is used in either of H format (D1) and B format (D2). In a write-once type information storage medium using an organic dye material, recording/reproducing characteristics sensitively changes due to a slight change of a light source wavelength. In principle, density is increased in inverse proportion to a square of a laser light source wavelength for recording/reproducing, and thus, it is desirable that a shorter laser light source wavelength be used for recording/reproducing. However, for the above described reason, an organic dye material utilized for a CD-R disc or a DVD-R disc cannot be used as a write-once type information storage medium for 405 nm. Moreover, because 405 nm is close to an ultraviolet ray wavelength, there can easily occur a disadvantage that a recording material “which can be easily recorded with a light beam of 405 nm”, is easily changed in characteristics due to ultraviolet ray irradiation, lacking a long period stability. Characteristics are significantly different from each other depending on organic dye materials to be used, and thus, it is difficult to determine the characteristics of these dye materials in general.

As an example, the foregoing characteristics will be described by way of a specific wavelength. With respect to an organic dye recording material optimized with a light beam of 650 nm in wavelength, the light to be used becomes shorter than 620 nm, recording/reproducing characteristics significantly change. Therefore, in the case where a recording/reproducing operation is carried out with a light beam which is shorter than 620 nm in wavelength, there is a need for new development of an organic dye material which is optimal to a light source wavelength of recording light or reproducing light. An organic dye material of which recording can be easily carried out with a light beam shorter than 530 nm in wavelength easily causes characteristic degradation due to ultraviolet ray irradiation, lacking long period stability. In the present embodiment, a description will be given with respect to an embodiment relevant to an organic recording material suitable to use in close to 405 nm. Namely, a description will be given with respect to an embodiment relating to an organic recording material which can be stably used in the range of 355 nm to 455 nm in consideration of a fluctuation of a light emitting wavelength which depends on manufacturers of semiconductor laser light sources. That is, the scope of the present embodiment corresponds to a light beam which is adapted to a light source of 620 nm in wavelength, and desirably, which is shorter than 530 nm in wavelength (ranging from 355 nm to 455 nm in a definition in the narrowest range).

In addition, the optical recording sensitivity due to light absorption spectra of an organic dye material is also influenced by a recording wavelength. An organic dye material suitable for long period stability is easily reduced in light absorbance relevant to a light beam which is shorter than 620 nm in wavelength. In particular, the light absorbance is significantly lowered with respect to a light beam which is shorter than 620 nm in wavelength, and in particular, is drastically reduced with respect to a light beam which is shorter than 530 nm in wavelength. Therefore, in the case where recording is carried out with a laser light beam ranging from 355 nm to 455 nm in wavelength, which is the severest condition, recording sensitivity is impaired because the light absorbance is low, and there is a need for a new design employing a new principle of recording as shown in the present embodiment.

The size of a focusing spot used for recording or reproducing application is reduced in proportion to a wavelength of a light beam to be used. Therefore, from only a standpoint of the focusing spot size, in the case where a wavelength is reduced to the above described value, an attempt is made to reduce a track pitch or channel bit length by a wavelength component with respect to a current DVD-R disc (use wavelength: 650 nm) which is a conventional technique. However, as described later in “3-2-A] Scope requiring application of technique according to the present embodiment”, as long as a principle of recording in a conventional write-once type information storage medium such as a DVD-R disc is used, there is a problem that a track pitch or a channel bit length cannot be reduced. A track pitch or a channel bit length can be reduced in proportion to the above described wavelength by utilizing a technique devised in the present embodiment described below.

In the present embodiment, there exists a great technical feature in that an organic recording medium material (organic dye material) adapted to a light source of 620 nm or less in wavelength has been devised. Such an organic recording medium (organic dye material) has a unique characteristic (Low to High characteristic) that a light reflection factor increases in a recording mark, which does not exist in a conventional CD-R disc or a DVD-R disc. Therefore, a technical feature of the present embodiment and a novel effect attained thereby occurs in a structure, dimensions, or format (information recording format) combination of the information storage medium which produces more effectively the characteristics of the organic recording material (organic dye materials) shown in the present embodiment. The information storage medium in the present embodiment has the following constituent elements:

A] an organic dye recording film;

B] a pre-format (such as pre-groove shape/dimensions or pre-pit shape/dimensions);

C] a wobble condition (such as wobble modulation method and wobble change shape, wobble amplitude, and wobble allocating method); and

D] a format (such as format for recording data which is to be recorded or which has been recorded in advance in information storage medium).

Specific embodiments of constituent elements are as follows:

A1) maximum absorption wavelength Amax

A2) recording mark polarity

A3) azo metal complex+Cu

A4) azo metal complex:anion+dye:cation

A5) arbitrary coat-type recording film

B1) pre-groove shape (for track pitch)

B2) pre-pit shape (for track pitch)

B3) arbitrary groove shape and arbitrary pit shape

C1) PSK

C2) FSK

C3) STW

C4) arbitrary modulation system

C5) wobble amplitude amount

C6) arbitrary amplitude amount

D1) write-once recording method

D2) H format

D3) B format

D4) another format

D5) arbitrary recording method and a format in a write-once medium.

Hereinafter, a description will be given with respect to a combination state of individual embodiments at a stage of explaining the embodiments. With respect to constituent elements, which do not specify a combination, it denotes that the following characteristics are employed:

A5) an arbitrary coat-type recording film;

B3) an arbitrary groove shape and an arbitrary pit shape;

C4) an arbitrary modulation system;

C6) an arbitrary amplitude amount; and

D5) an arbitrary recording method and a format in a write-once medium.

FIG. 1A shows a standard phase change recording film structure (mainly used for a rewritable-type information storage medium), and FIG. 1B shows a standard organic dye recording film structure (mainly used for a write-once type information storage medium). In the description of the present embodiment, a whole recording film structure excluding transparent substrates 2-1 and 2-2 shown in FIGS. 1A and 1B (including light reflection layers 4-1 and 4-2) is defined as a “recording film”, and is discriminated from recording layers 3-1 and 3-2 in which a recording material is disposed. With respect to a recording material using a phase change, in general, an optical characteristic change amount in a recorded area (in a recording mark) and an unrecorded area (out of a recording mark) is small, and thus, there is employed an enhancement structure for enhancing a relative change rate of a reproduction signal. Therefore, in a phase change recording film structure, as shown in FIG. 1A, an undercoat intermediate layer 5 is disposed between the transparent substrate 2-1 and a phase change type recording layer 3-1, and an upper intermediate layer 6 is disposed between the light reflection layer 4-2 and the phase change type recording layer 3-1. In the invention, as a material for the transparent substrates 2-1 and 2-2, there is employed a polycarbonate PC or an acrylic PMMA (poly methyl methacrylate) which is a transparent plastic material. A center wavelength of a laser light beam 7 used in the present embodiment is 405 nm, and refractive index n21, n22 of the polycarbonate PC at this wavelength is close to 1.62.

Standard refractive index n31 and absorption coefficient k31 in 405 nm at GeSbTe (germanium antimony tellurium) which is most generally used as a phase change type recording material are n31≅1.5 and k31≅2.5 in a crystalline area, whereas they are n31≅2.5 and k31≅1.8 in an amorphous area. Thus, a refractive index (in the amorphous area) of a phase change type recording medium is different from a refractive index of the transparent substrate 2-1, and reflection of a laser light beam 7 on an interface between the layers is easily occurred in a phase change recording film structure. As described above, for the reasons why (1) a phase change recording film structure takes an enhancement structure; and (2) a refractive index difference between the layers is great or the like, a light reflection amount change at the time of reproduction from a recording mark recorded in a phase change recording film (a differential value of a light reflection amount from a recording mark and a light reflection amount from an unrecorded area) can be obtained as an interference result of multiple reflection light beams generated on an interface between the undercoat intermediate layer 5, the recording layer 3-1, the upper intermediate layer 6, and the light reflection layer 4-2. In FIG. 1A, although the laser light beam 7 is apparently reflected on an interface between the undercoat intermediate layer 5 and the recording layer 3-1, an interface between the recording layer 3-1 and the upper intermediate layer 6, and an interface between the upper intermediate layer 6 and the light reflection layer 4-2, in actuality, a reflection light amount change is obtained as an interference result between a plurality of multiple reflection light beams.

In contrast, an organic dye recording film structure takes a very simple laminate structure made of an organic dye recording layer 3-2 and a light reflection layer 4-2. An information storage medium (optical disc) using this organic dye recording film is called a write-once type information storage medium, which enables only one time of recording. However, unlike a rewritable-type information storage medium using the phase change recording medium, this medium cannot carry out an erasing process or a rewriting process of information which has been recorded once. A refractive index at 405 nm of a general organic dye recording material is often close to n32≅1.4 (n32≅1.4 to 1.9 in the refractive index range at 405 nm of a variety of organic dye recording materials) and an absorption coefficient is often close to k32≅0.2 (k32≅0.1 to 0.2 in the absorption coefficient range at 405 nm of a variety of organic dye recording materials). Because a refractive index difference between the organic dye recording material and the transparent substrate 2-2 is small, there hardly occurs a light reflection amount on an interface between the recording layer 3-2 and the transparent substrate 2-2. Therefore, an optical reproduction principle of an organic color recording film (reason why a reflection light amount change occurs) is not “multiple interference” in a phase change recording film, and a main factor is a “light amount loss (including interference) midway of an optical path with respect to the laser light beam 7 which comes back after being reflected in the light reflection layer 4-2”. Specific reasons which cause a light amount loss midway of an optical path include an “interference phenomenon due to a phase difference partially caused in the laser light 7” or an “optical absorption phenomenon in the recording layer 3-2”. The light reflection factor of the organic dye recording film in an unrecorded area on a mirror surface on which a pre-groove or a pre-pit does not exist is featured to be simply obtained by a value obtained by subtracting an optical absorption amount when the recording layer 3-2 is passed from the light reflection factor of the laser light beam 7 in the light reflection layer 4-2. As described above, this film is different from a phase change recording film whose light reflection factor is obtained by calculation of “multiple interference”.

Light fastness of a recording film (organic dye recording film) of the disc (High Density recordable DVD (HD DVD-R)) using a blue light laser having a wavelength λ of 405 nm will be described. The light fastness of the HD DVD-R is tested by a device an air cooling xenon lamp which are in accordance with ISO-105-B02. In ISO-105-B02, a temperature of a black panel is not higher than 40° C. and a relative humidity is 70 to 80%. A testing laser beam is irradiated onto the disk in a perpendicular direction from the top. When all conditions after test are satisfied, the disc is regarded as a proofed disc.

First, a description will be given with respect to a principle of recording, which is used in a current DVD-R disc as a conventional technique. In the current DVD-R disc, when a recording film is irradiated with the laser light beam 7, the recording layer 3-2 locally absorbs energy of the laser light beam 7, and becomes hot. If a specific temperature is exceeded, the transparent substrate 2-2 is locally deformed. Although a mechanism, which induces deformation of the transparent substrate 2-2, is different depending on manufacturers of DVD-R discs, it is said that this mechanism is caused by:

1) local plastic deformation of the transparent substrate 2-2 due to gasification energy of the recording layer 3-2; and

2) transmission of a heat from the recording layer 3-2 to the transparent substrate 2-2 and local plastic deformation of the transparent substrate 2-2 due to the heat.

If the transparent substrate 2-2 is locally plastically deformed, there changes an optical distance of the laser light beam 7 reflected in the light reflection layer 4-2 through the transparent substrate 2-2, the laser light beam 7 coming back through the transparent substrate 2-2 again. A phase difference occurs between the laser light beam 7 from a recording mark, the laser light beam coming back through a portion of the locally plastically deformed transparent substrate 2-2, and a laser light beam 7 from the periphery of the recording mark, the laser light beam coming back through a portion of a transparent substrate 2-2 which is not deformed, and thus, a light amount change of reflection light beam occurs due to interference between these light beams. In addition, in particular, in the case where the above described mechanism of (1) has occurred, a change of a substantial refractive index n32 produced by cavitations of the inside of the recording mark in the recording layer 3-2 due to gasification (evaporation), or alternatively, a change of a refractive index n32 produced due to thermal decomposition of an organic dye recording material in the recording mark, also contributes to the above described occurrence of a phase difference. In the current DVD-R disc, until the transparent substrate 2-2 is locally deformed, there is a need for the recording layer 3-2 becoming hot (i.e., at a gasification temperature of the recording layer 3-2 in the above described mechanism of (1) or at an internal temperature of the recording layer 3-2 required for plastically reforming the transparent substrate 2-2 in the mechanism of (2)) or there is a need for a part of the recording layer 3-2 becoming hot in order to cause thermal decomposition or gasification (evaporation). In order to form a recording mark, there is a need for large amount of power of the laser light beam 7.

In order to form the recording mark, there is a necessity that the recording layer 3-2 can absorb energy of the laser light beam 7 at a first stage. The light absorption spectra in the recording layer 3-2 influence the recording sensitivity of an organic dye recording film. A principle of light absorption in an organic dye recording material which forms the recording layer 3-2 will be described with reference to (A3) of the present embodiment.

FIG. 2 shows a specific structural formula of the specific contents “(A3) azo metal complex+Cu” of the constituent elements of the information storage medium. A circular periphery area around a center metal M of the azo metal complex shown in FIG. 2 is obtained as a light emitting area 8. When a laser light beam 7 passes through this light emitting area 8, local electrons in this light emitting area 8 resonate to an electric field change of the laser light beam 7, and absorbs energy of the laser light beam 7. A value converted to a wavelength of the laser light beam with respect to a frequency of an electric field change at which these local electrons resonate most and easily absorbs the energy is called a maximum absorption wavelength, and is represented by λmax. As a range of the light emitting area 8 (resonation range) as shown in FIG. 2 increases, the maximum absorption wavelength λmax is shifted to the long wavelength side. In addition, in FIG. 2, the localization range of local electrons around the center metal M (how large the center metal M can attract the local electrons to the vicinity of the center) is changed by changing atoms of the center metal M, and the value of the maximum absorption wavelength λmax changes.

Although it can be predicted that the light absorption spectra of the organic dye recording material in the case where there exists only one light emitting area 8 which is absolute 0 degree at a temperature and high in purity draws narrow linear spectra in close to a maximum absorption wavelength λmax, the light absorption spectra of a general organic recording material including impurities at a normal temperature, and further, including a plurality of light absorption areas exhibit a wide light absorption characteristic with respect to a wavelength of a light beam around the maximum absorption wavelength λmax.

FIG. 3 shows an example of light absorption spectra of an organic dye recording material used for a current DVD-R disc. In FIG. 3, a wavelength of a light beam to be irradiated with respect to an organic dye recording film formed by coating an organic dye recording material is taken on a horizontal axis, and absorbance obtained when an organic dye recording film is irradiated with a light beam having a respective wavelength is taken on a vertical axis. The absorbance used here is a value obtained by entering a laser light beam having incident intensity Io from the side of the transparent substrate 2-2 with respect to a state in which a write-once type information storage medium has been completed (or alternatively, a state in which the recording layer 3-2 has been merely formed on the transparent substrate 2-2 (a state that precedes forming of the optical reflection layer 4-2 with respect to a structure of FIG. 1B)), and then, measuring reflected laser light intensity Ir (light intensity It of the laser light beam transmitted from the side of the recording layer 3-2). The absorbance Ar (At) is represented by:

Ar≡−log10(Ir/Io)   (A-1)

Ar≡−log10(It/Io)   (A-2)

Unless otherwise specified, although a description will be given assuming that the absorbance denotes absorbance Ar of a reflection shape expressed by formula (A-1), it is possible to define absorbance At of a transmission shape expressed by formula (A-2) without being limited thereto in the present embodiment. In the embodiment shown in FIG. 3, there exist a plurality of light absorption areas, each of which includes the light emitting area 8, and thus, there exist a plurality of positions at which the absorbance becomes maximal. In this case, there exist a plurality of maximum absorption wavelength λmax when the absorbance takes a maximum value. A wavelength of the recording laser light in the current DVD-R disc is set to 650 nm. In the case where there exist a plurality of the maximum absorption wavelengths λmax in the present embodiment, a value of the maximum absorption wavelength λmax which is the closest to the wavelength of the recording laser light beam becomes important. Therefore, only in the description of the present embodiment, the value of the maximum absorption wavelength λmax set at a position which is the closest to the wavelength of the recording laser light beam is defined as “λmax write”; and is discriminated from another λmax (λmax 0).

FIGS. 4A and 4B each show a comparison in shape when a recording film is formed in a pre-pit area or a pre-groove area 10. FIG. 4A shows a shape relevant to a phase change recording film. In the case of forming any of the undercoat intermediate layer 5, the recording layer 3-1, the upper intermediate layer 6, and the light reflection layer 4-1 as well, any of methods of sputtering vapor deposition, vacuum vapor deposition, or ion plating is used in vacuum. As a result, in all of the layers, irregularities of the transparent substrate 2-1 are duplicated comparatively faithfully. For example, in the case where a sectional shape in the pre-pit area or pre-groove area 10 of the transparent substrate 2-1 is rectangular or trapezoidal, the sectional shape of the recording layer 3-1 and the light reflection layer 4-1 each is also rectangular or trapezoidal.

FIG. 4B shows a general recording film sectional shape of a current DVD-R disc which is a conventional technique as a recording film in the case where an organic dye recording film has been used. In this case, as a method for forming the recording film 3-2, there is used a method called spin coating (or spinner coating) which is completely different from that shown in FIG. 4A. The spin coating used here denotes a method for dissolving in an organic solvent an organic dye recording material which forms the recording layer 3-2; applying a coating onto the transparent substrate 2-2; followed by rotating the transparent substrate 2-2 at a high speed to spread a coating agent to the outer periphery side of the transparent substrate 2-2 by a centrifugal force; and gasifying the organic solvent, thereby forming the recording layer 3-2. Using this method, a process for coating the organic solvent is used, and thus, a surface of the recording layer 3-2 (an interface with the light reflection layer 2-2) is easily flattened. As a result, the sectional shape on the interface between the light reflection layer 2-2 and the recording layer 3-2 is obtained as a shape which is different from the shape of the surface of the transparent substrate 2-2 (an interface between the transparent substrate 2-2 and the recording layer 3-2). For example, in a pre-groove area in which the sectional shape of the surface of the transparent substrate 2-2 (an interface between the transparent substrate 2-2 and the recording layer 3-2) is rectangular or trapezoidal, the sectional shape on the interface between the light reflection layer 2-2 and the recording layer 3-2 is formed in a substantially V-shaped groove shape. In a pre-pit area, the above sectional shape is formed in a substantially conical side surface shape. Further, at the time of spin coating, an organic solvent is easily collected at a recessed portion, and thus, the thickness Dg of the recording layer 3-2 in the pre-pit area or pre-groove area 10 (i.e., a distance from a bottom surface of the pre-pit area or pre-groove area to a position at which an interface relevant to the light reflection layer 2-2 becomes the lowest) is larger than the thickness Dl in a land area 12 (Dg>Dl). As a result, an amount of irregularities on an interface between the transparent substrate 2-2 and the recording area 3-2 in the pre-pit area or pre-groove area 10 becomes substantially smaller than an amount of irregularities on the transparent substrate 2-2 and the recording layer 3-2.

As described above, the shape of irregularities on the interface between the light reflection layer 2-2 and the recording layer 3-2 becomes blunt and an amount of irregularities becomes significantly small. Thus, in the case where the shape and dimensions of irregularities on a surface of the transparent substrate 2 (pre-pit area or pre-groove area 10) are equal to each other depending on a difference in method for forming a recording film, the diffraction intensity of the reflection light beam from the organic dye recording film at the time of laser light irradiation is degraded more significantly than the diffraction intensity of the reflection light beam from the phase change recording film. As a result, in the case where the shape and dimensions of irregularities on the surface of the transparent substrate 2 (pre-pit area or pre-groove area 10) are equal to each other, as compared with use of the phase change recording film, use of the conventional organic dye recording film is disadvantageously featured in that: 1) a degree of modulation of a light reproduction signal from the pre-pit area is small, and signal reproduction reliability from the pre-pit area is poor;

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