JP2010044862A - Optical recording medium, information-recording method, information-reproducing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium which is small in inter-layer crosstalk and stably obtains high-quality recording characteristics. <P>SOLUTION: The optical recording medium includes 100: a first recording part L0 which includes a first recording layer 105 and a first light reflection layer 106 and is arranged on a side near a light reception surface; and a second recording part L1 which includes a second recording layer 107 and a second light reflection layer 108 and is arranged on a side far from the light reception surface; and the second recording layer L1 being laminated on the first recording layer L0. In this case, the thickness (for example, 15-35 nm) of the first light reflection layer 106 is smaller than the thickness (for example, 60-150 nm) of the second light reflection layer 108. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical recording medium in which information can be recorded / reproduced by optical changes such as transmittance and reflectance in a recording layer by irradiating a light beam, and additionally recorded.

  An optical recording medium using a dye material such as CD-R or DVD-R has an organic dye thin film that is used in the recording layer absorbs a part of the recording wavelength, and the recording layer generates heat due to the light absorption. Signal recording is performed by decomposing the thin film and thus causing physical deformation of the recording film. In the past, development has been carried out by shortening the recording laser wavelength in order to increase the recording density. Even when a recent blue laser of around 400 nm is applied, a certain high density is possible, but the limit of the recording capacity is beginning to be seen. In order to achieve a higher recording density, a technique such as multilayering of recording layers is used. For example, a dual-layer DVD-R has been commercialized. However, in order to increase the number of layers, it is necessary to proceed with optimization of the disc structure so that the light transmittance and light absorption rate of the recording layer are strictly controlled to obtain a stable recording / reproducing signal. However, since it is technically difficult, the technology for multilayering dye materials has not yet reached a practically sufficient range. For this reason, the selling price is higher than that of a single-layer disc. Against this background, in order to improve the recording characteristics of multi-layer discs, there have been reports of discs in which the order of the recording film configuration in the back layer as viewed from the light incident surface is reversed from the conventional one.

  For example, in Patent Document 1, a metal oxide layer is introduced between the dye layer and the reflective layer to study improvement in recording / reproducing characteristics. However, in the recording layer configuration, a dye recording film is formed on the reflective film. In order to prevent interference between the adhesive resin used for the intermediate layer and the pigment material, it is necessary to create a new protective layer. In conventional single-layer disc manufacturing processes using pigment materials, it is not easy to handle multi-layer discs, and strict production control is required, so if you try to maintain mass productivity and product yield at a high level, production costs will increase. It can be a factor to increase. In addition, when the recording layer has a multilayer structure, the recording signal quality is likely to change due to slight differences in the optical characteristics of the materials of each layer and mutual optical interference, and in the case of controlling crosstalk between recording layers. There is a possibility that the design margin of the recording layer configuration is narrowed. Multilayer technology is important to achieve high-density recording, but no clear design guideline has been obtained at present, and no reports have been made on methods for suppressing interlayer crosstalk associated with multilayering.

JP 2005-339761 A

  When information is recorded on an optical recording medium having a plurality of (for example, two) recording layers, the power of the light beam incident from the first recording layer (L0) is the presence of the light reflecting layer included in the first recording layer. And the like, and divided into recording / reproduction of the first recording layer (L0) and recording / reproduction of the second recording layer (L1). For this reason, the light reflecting layer included in the second recording layer (L1) needs to efficiently reflect the light beam reduced by half. Therefore, it is necessary to use a highly reflective material such as Ag or an Ag alloy in order to increase the reflectance. However, when the thickness of the light reflection layer of the second light reflection layer (L1) is increased, the amount of reflection increases and optical interference with the recording signal with the first recording layer (L0) increases. Therefore, there is a problem that the interlayer crosstalk between the first recording layer (L0) and the second recording layer (L1) becomes large, and the recording / reproducing signal quality is significantly deteriorated.

  The present invention has been made to solve the problems in studying the recording characteristics of an optical recording medium having a plurality of (for example, two) recording layers.

  That is, one of the problems of the present invention is to provide an optical recording medium that can stably obtain high quality recording characteristics with a small interlayer crosstalk.

  In the optical recording medium according to the embodiment of the present invention, the first recording layer is optimized by adjusting the reflective film material and the reflective film thickness to optimize the reflectance of the light reflecting layer included in the first recording layer. Interlayer crosstalk between the layer and the second recording layer is small, and high quality recording characteristics are obtained stably. In other words, in the optical recording medium according to one embodiment of the present invention, in the optical recording medium having the first recording layer and the second recording layer capable of recording / reproducing information by light, the first recording layer is the first recording layer. The reflective film material and the reflective film thickness of the light reflecting layer included in the recording layer are adjusted.

  In a multi-layer recordable information recording medium, when laser light is focused on a desired layer, generation of interlayer crosstalk due to light irradiated to other than the desired layer is prevented.

The figure explaining the structural example of the multilayer optical disk based on one embodiment of this invention. The figure which shows the specific example of the metal complex part of the organic material for recording layers. The figure which shows an example of the pigment | dye part of the organic material for recording layers. The figure explaining the example of a general parameter setting in a write-once information storage medium. The flowchart figure explaining the recording method using the optical disk which concerns on one embodiment of this invention. The flowchart figure explaining the reproducing method using the optical disk concerning one embodiment of this invention. FIG. 2 is a diagram for explaining an example of a physical sector layout in the optical disc of FIG. 1. FIG. 2 is a diagram for explaining a configuration example of a lead-in area in the optical disc of FIG. The figure explaining the structural example of the control data zone of FIG. FIG. 10 is a diagram illustrating a configuration example of FIG. 9. The figure explaining an example of the physical format information of FIG. FIG. 12 is a diagram for explaining an example of a data area arrangement in the physical format information of FIG. 11. The figure explaining the structural example of a part (L0 relation) of the physical format information of FIG. The figure explaining the structural example of the other part (L1 relation) of the physical format information of FIG. The figure explaining the example of the waveform (write strategy) of a recording pulse. The figure explaining that a burst cutting area (BCA) is formed in the L1 layer of the write-once type single-sided multilayer (2 layers) optical disc concerning one embodiment of this invention. The figure explaining the example of the content of the BCA record recorded on BCA of FIG. The figure explaining the structural example of the apparatus which records the specific information containing the BCA record etc. of FIG. 17 on BCA. The flowchart figure explaining an example of the procedure which records specific information (BCA record etc.) in L1 layer of the write-once type single-sided multilayer (2 layers) optical disk of FIG. FIG. 17 is a flowchart for explaining an example of a procedure for reproducing specific information (such as a BCA record) from the L1 layer of the write once single-sided multilayer (two layers) optical disc of FIG. The figure explaining the example of a manufacturing process of the write-once type single-sided double layer optical disc concerning one embodiment of this invention.

  Hereinafter, various embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining a configuration example of an optical disc (a write-once type single-sided, dual-layer optical disc) 100 according to an embodiment of the present invention. As illustrated in FIGS. 1A and 1B, the optical disc 100 includes a transparent resin substrate 101 formed in a disc shape from a synthetic resin material such as polycarbonate (PC). In the transparent resin substrate 101, grooves (grooves) are formed concentrically or spirally. The transparent resin substrate 101 can be manufactured by injection molding using a stamper.

  Here, a first layer (L0) organic dye recording layer 105 and a light transflective layer 106 are laminated in order on a 0.59 mm thick transparent resin substrate 101 such as polycarbonate, and a photopolymer (2P resin) is formed thereon. 104 is spin coated. Then, the shape of the groove (groove) of the second layer (L1) is transferred thereon, and a second layer organic dye recording layer 107 and a reflective film 108 such as silver or silver alloy are sequentially laminated. Another transparent resin substrate (or dummy substrate) 102 having a thickness of 0.59 mm is bonded to the laminate of the L0 and L1 recording layers via the UV curable resin (adhesive layer) 103. The organic dye recording films (recording layers 105 and 107) have a two-layer structure sandwiching the transflective layer 106 and the intermediate layer 104. The total thickness of the bonded optical disc thus completed is approximately 1.2 mm.

  Here, on the transparent resin substrate 101, for example, spiral grooves having a track pitch of 0.4 μm and a depth of 60 nm are formed (in the respective layers L0 and L1). This groove is wobbled, and address information is recorded on this wobble. Then, recording layers 105 and 107 containing an organic dye are formed on the transparent resin substrate 101 so as to fill the groove.

  As the organic dye for forming the recording layers 105 and 107, an organic dye whose maximum absorption wavelength region is shifted to a longer wavelength side than the recording wavelength (for example, 405 nm) can be used. In addition, the absorption is not extinguished in the recording wavelength region, but it is designed to have a considerable light absorption in the long wavelength region (for example, 450 nm to 600 nm).

  The organic dye (specific examples will be described later) is made into a liquid by dissolving in a solvent, and can be easily applied to the surface of the transparent resin substrate by a spin coating method. In this case, the film thickness can be managed with high accuracy by controlling the dilution rate with the solvent and the number of rotations during spin coating.

  In addition, when the track before information recording is focused or tracked by the recording laser beam, the light reflectance is low. Thereafter, the decomposition reaction of the dye is caused by the laser light, and the light absorptance is lowered, so that the light reflectance of the recording mark portion is increased. Therefore, a so-called Low-to-High (or L to H) characteristic is realized in which the light reflectance of the recording mark portion formed by irradiating the laser light is higher than the light reflectance before the laser light irradiation. is doing.

  In one embodiment of the present invention, examples of physical formats applied to the L0 layer and the L1 layer existing on the transparent resin substrate 101 and the photopolymer (2P resin) 104 include the following. That is, the general parameters of a write once single-sided dual layer disc are almost the same as the general parameters of a single layer disc, but differ in the following points. The recording capacity usable by the user is 30 GB, the inner radius of the data area is 24.6 mm in the layer 0 (L0 layer), 24.7 mm in the layer 1 (L1 layer), and the outer radius of the data area is 58.1 mm (common to layer 0 and layer 1).

  In the optical disc 100 of FIG. 1A, the system lead-in area SLA includes a control data section as illustrated in FIG. 1C, and this control data section is recorded as a part of physical format information or the like. Parameters relating to recording such as power (peak power) and bias power are included for each of L0 and L1.

  Further, mark / space recording is performed on the tracks in the data area DA of the optical disc 100 by a laser having a predetermined recording power (peak power) and bias power as illustrated in FIG. By this mark / space recording, as illustrated in FIG. 1E, for example, object data (VOB, etc.) such as a high-definition TV broadcast program and its management information (VMG) are stored in the data area DA (L0 and (Or L1).

  Examples of organic dyes that can be used in one embodiment of the present invention include cyanine dyes, styryl dyes, and azo dyes. In particular, cyanine dyes and styryl dyes are suitable because the absorptance with respect to the recording wavelength can be easily controlled. The azo dye may be used alone or as a complex of one molecule of azo compound or more and a metal.

  The azo metal complex that can be used in one embodiment of the present invention uses cobalt, nickel, or copper as the central metal M to enhance the light stability. However, not limited thereto, scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, Gold, zinc, cadmium, mercury, or the like may be used as the central metal M of the azo metal complex.

  Azo compounds have an aromatic ring, and not only the structure of the aromatic ring but also various substituents on the aromatic ring can optimize recording characteristics, storage characteristics, and reproduction stability. It becomes. The bulkiness of the substituent tends to improve the reproduction light durability as it is bulky, but the sensitivity at the time of recording also tends to deteriorate. Therefore, it is important to select a substituent that improves both characteristics. This substituent is also involved in the solubility in the solvent.

  Unlike conventional recording mechanisms of dye-based information recording media (recording laser wavelength longer than 620 nm), in short wavelength laser recording (recording wavelength is, for example, 405 nm) related to the present invention, the recording mechanism is the substrate or dye film volume. It is not a physical change. During reproduction, by irradiating the dye with a weaker laser than during recording, the orientation change of the dye molecules in the recording layer or the conformational change in the dye molecules gradually occurs due to heat or light. The presence of a bulky substituent in the dye molecule is considered to have the effect of making these changes difficult to occur. This is the reason why the bulky substituent contributes to the improvement of reproduction light durability.

  The bulky substituent at this time refers to a substituent consisting of three or more carbons substituted on the aromatic ring in the dye molecule. For example, n-propyl, isopropyl, n-butyl, 1-methylpropyl Group, 2-methylpropyl group, n-pentyl group, 1-ethylpropyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1,1-dimethylpropyl group, 1,2-dimethylpropyl group, 2,2-dimethylpropyl group, cyclopentyl group, n-hexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,1-dimethylbutyl group, 1, 2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,2-dimethylbutyl group, 2,3-dimethylbutyl group, 3,3-dimethylbutyl group, 1-ethylbutyl group, 2-ethylbutyl group, cyclohexyl group , Phenyl And the like. Here, the substituent may include atoms other than carbon such as oxygen, sulfur, nitrogen, silicon, fluorine, bromine, chlorine, and iodine.

  In the structural example of FIG. 1B, the thickness of each layer in the area AX on which the laser beam is incident is, for example, as shown in FIG. That is, in this example, the thickness of the L0 reflective layer 106 of Ag or Ag alloy is selected in the range of 15 nm to 35 nm, and the thickness of the L1 reflective layer 108 of Ag or Ag alloy is selected in the range of 60 nm to 150 nm ( That is, L0 reflection layer thickness <L1 reflection layer thickness). The thickness of the intermediate layer 104 is selected in the range of 25 ± 10 μm, and the adhesive layer 103 is managed so that the variation range is 2 μm or less.

  FIG. 2 is a diagram showing a specific example of the metal complex portion of the organic material for the recording layer. A circular peripheral area centering on the central metal M of the azo metal complex shown in the figure is the color development area 8. When the laser beam passes through the coloring region 8, the localized electrons in the coloring region 8 resonate (resonate) with the electric field change of the laser beam and absorb the energy of the laser beam. A value obtained by converting the frequency of the electric field change at which the localized electrons are most resonated (resonant) and easily absorb energy into the wavelength of the laser beam is represented by a maximum absorption wavelength λmax. As the length of the color development region 8 (resonance range) as shown in the figure becomes longer, the maximum absorption wavelength λmax shifts to the longer wavelength side. Further, by changing the atom of the central metal M, the localized range of localized electrons around the central metal M (how much the central metal M can attract the localized electrons to the center) changes, and the maximum absorption wavelength λmax is changed. The value changes. For example, if a material having λmax near 405 nm is selected, an organic material having sensitivity (light absorption) at a wavelength of 405 nm can be obtained.

  As a dye material for a recording layer (for example, L0 or L1) having a light absorption at a wavelength of 405 nm, an organic dye material having a structure in which an organic metal complex part shown in FIG. 2 is combined with a dye material part (not shown) is used. Can be used. The central metal M of the organometallic complex is generally cobalt or nickel (other scandium, yttrium, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, manganese, technetium, rhenium, iron, ruthenium, osmium. Rhodium, iridium, palladium, platinum, copper, silver, gold, zinc, cadmium, mercury, etc.) can be used. Further, although not shown, a cyanine dye, a styryl dye, and a monomethine cyanine dye can be used as the dye material portion.

Here, the recording principle interpreted by the current DVD-R disc will be described. In the current DVD-R disc, when the recording film is irradiated with laser light, the recording layer locally absorbs the energy of the laser light and becomes high heat. When the specific temperature is exceeded, the transparent substrate is locally deformed. The mechanism for inducing the deformation of the transparent substrate differs depending on the DVD-R disc manufacturer,
(1) The transparent substrate is locally plastically deformed by the vaporization energy of the recording layer, and / or (2) Heat is transferred from the recording layer to the transparent substrate, and the transparent substrate is locally plastically deformed by the heat. It is said to be the cause. When the transparent substrate is locally plastically deformed, the optical distance of the laser light that passes through the transparent substrate, is reflected by the light reflecting layer, and returns again through the transparent substrate is changed. Laser light from inside the recording mark returning through the part of the transparent substrate that has been locally plastically deformed, and laser light from the periphery of the recording mark returning through the part of the transparent substrate that is not deformed Since a phase difference occurs between the two, the amount of reflected light changes due to interference between the two. In particular, when the mechanism (1) occurs, a substantial change in the refractive index n ₃₂ caused by cavitation of the recording mark in the recording layer due to vaporization (evaporation), or organic in the recording mark. A change in the refractive index n ₃₂ caused by thermal decomposition of the dye recording material also contributes to the generation of the phase difference. In the current DVD-R disc, the temperature of the recording layer is high until the transparent substrate is locally deformed (the vaporization temperature of the recording layer is the mechanism (1) above, and the transparent substrate is plastically deformed by the mechanism (2)). The internal temperature of the recording layer) or a high temperature in order to thermally decompose or vaporize (evaporate) a part of the recording layer, and in order to form a recording mark, a large power of laser light is required. .

  In order to form a recording mark, the recording layer needs to be able to absorb the energy of the laser beam as a first step. The light absorption spectrum in the recording layer greatly affects the recording sensitivity of the organic dye recording film.

FIG. 2 shows a specific structural formula of the specific content “azo metal complex + Cu” of the constituent elements of the information storage medium described above. A circular peripheral area centering on the central metal M of the azo metal complex shown in FIG. When the laser beam passes through the coloring region 8, the localized electrons in the coloring region 8 resonate (resonate) with the electric field change of the laser beam and absorb the energy of the laser beam. The value converted to the wavelength of the laser beam with respect to the frequency of the electric field change at which the localized electrons resonate most easily and absorb energy is called the maximum absorption wavelength, and is represented by λ _max . As the color developing region 8 (resonance range) as shown in FIG. 2 becomes longer, the maximum absorption wavelength λ _max shifts to the longer wavelength side. Further, in FIG. 2, by changing the atom of the central metal M, the localization range of localized electrons around the central metal M (how much the central metal M can attract the localized electrons to the center) changes, and the maximum absorption. The value of the wavelength λ _max changes.

  An optical disk 100 using a dye represented by the chemical formula of FIG. 3 was produced, and information recording of random data was performed. When the error rate SbER of the L0 layer was measured, it was possible to obtain 5.4e-6, a value sufficiently smaller than the target value (5.0e-5, which is a hurdle higher than the practical level). When a repetitive pattern of the 11T mark 11T space is recorded and reproduced, the waveform distortion is hardly observed, and the difference between the maximum value and the minimum value of the I11L that is the space level (when the 11T space is reproduced) ([I11Lmax -I11Lmin] / I11min) was 2%. Here, the mark length of 11T was 1.12 μm, and 1.2 * Na / λ was 0.74 μm, which was a sufficiently long mark. This dye was analyzed for IR, MS, and NMR before and after recording, but no difference was found.

<General parameters>
FIG. 4 shows general parameters of a write-once single-sided dual-layer disc compared with a write-once single-sided single-layer disc. General parameters of a write once single-sided dual layer disc are almost the same as those of a single layer disc, but differ in the following points. The recording capacity that can be used by the user is 30 GB, the inner radius of the data area is 24.6 mm in the layer 0, 24.7 mm in the layer 1, and the outer radius of the data area is 58.1 mm (common to L0 and L1). ).

  FIG. 5 is a flowchart for explaining a recording method using an optical disk according to an embodiment of the present invention. The recording target layer (L0 or L1) of the disk 100 is irradiated with a modulated laser having a wavelength of 405 nm, for example, from an optical pickup of a disk drive (not shown) to record object data (such as VOB for DVD or HD_DVD) (ST100). ). When this recording is completed (ST102Y), management information (VMG for DVD or HD_DVD) relating to the recorded object data is written to the disc 100 (ST104), and one recording is completed.

  FIG. 6 is a flowchart for explaining a reproducing method using an optical disc according to an embodiment of the present invention. The management information is read from the disk 100 on which the object data and the management information are recorded by the process as shown in FIG. 5 by, for example, a laser having a wavelength of 405 nm (ST200). The read management information is temporarily stored in a work memory of a playback device (not shown). This playback device plays back the recorded object data with reference to the playback procedure information in the stored management information (ST202). This playback ends when the user instructs the end of playback or when the playback proceeds to the point where the playback procedure information in the management information indicates the end of playback (ST204Y).

  FIG. 7 is a diagram for explaining an example of a physical sector layout in the optical disc 100 of FIG. As shown in the figure, information areas provided over two layers are composed of seven areas: a system lead-in area, a connection area, a data lead-in area, a data area, a data lead-out area, a system lead-out area, and a middle area. Become. By providing a middle region in each layer, the reproduction beam can be moved from layer 0 (L0) to layer 1 (L1). The data area DA records main data (management information VMG, object data VOB, etc. in the example of FIG. 1E). The system lead-in area SLA includes control data, a reference code, and the like. The data lead-out area enables continuous and smooth reading.

《Leadout area》
The system lead-in area and the system lead-out area include tracks composed of embossed pits. The layer 0 (L0) data lead-in area, data area, and middle area, and the layer 1 (L1) middle area, data area, and data lead-out area include groove tracks. The groove track is continuous from the start position of the data lead-in area of layer 0 to the end position of the middle area, and is continuous from the start position of the middle area of layer 1 to the end position of the data lead-out area. When a pair of single-sided dual-layer disc substrates are prepared and bonded together, a double-sided, four-layer disc having two readout surfaces is obtained.

  FIG. 8 is a diagram for explaining a configuration example of the lead-in area in the optical disc of FIG. As shown in the figure, the system lead-in area SLA of the layer 0 (L0) is composed of an initial zone, a buffer zone, a control data zone, and a buffer zone in order from the inner circumference side. The data lead-in area of layer 0 is blank zone, guard track zone, drive test zone, disk test zone, blank zone, RMD (Recording Management Data) duplication zone, L-RMZ (recording position management data) in order from the inner circumference side. , R physical format information zone, and reference code zone. The start address (inner circumference side) of the data area of layer 0 (L0) and the end address (inner circumference side) of the data area of layer 1 are shifted by the clearance, and the end of the data area of layer 1 (L1) The address (inner circumference side) is on the outer circumference side than the start address (inner circumference side) of the data area of layer 0.

《Lead-in area structure》
FIG. 8 illustrates the structure of the lead-in region of layer 0 (L0). In the system lead-in area, an initial zone, a buffer zone, a control data zone, and a buffer zone are arranged in order from the inner circumference side. The data lead-in area includes a blank zone, a guard track zone, a drive test zone, a disc test zone, a blank zone, an RMD duplication zone, and a recording position management (recording management) zone (L- RMZ), R physical format information zone, and reference code zone.

<Details of system lead-in area>
The initial zone includes embossed data segments. The main data of the data frame recorded as the data segment of the initial zone is set to “00h”. The buffer zone is composed of 1024 physical sectors from 32 data segments. The main data of the data frame recorded as the data segment of this zone is set to “00h”. The control data zone includes embossed data segments. The data segment includes embossed control data. The control data is composed of 192 data segments starting from PSN 123904 (01 E400h).

  A configuration example of the control data zone is shown in FIG. FIG. 10 shows a configuration example of the data segment in the control data section. The content of the first data segment of the control data section is repeated 16 times. The first physical sector of each data segment includes physical format information. The second physical sector of each data segment contains disk manufacturing information. The third physical sector of each data segment contains copyright protection information. The contents of the other physical sectors of each data segment are reserved for system use.

  FIG. 11 is a diagram for explaining an example of physical format information in the control data section, and FIG. 12 is a diagram for explaining an example of data area arrangement in the physical format information. The description contents of each byte position (BP) of the physical format information are as follows. The values of read power, recording speed, data area reflectivity, push-pull signal, and on-track signal shown in BP132 to BP154 are examples. These actual values can be selected by the disc manufacturer from values satisfying the specifications of emboss information and the characteristics of user data characteristics after recording. The contents of the data area arrangement described in BP4 to BP15 are as shown in FIG. 12, for example.

BP149 and BP152 in FIG. 11 specify the reflectance of the data areas of layer 0 and layer 1. For example, 0000 1010b indicates 5%. The actual reflectivity is specified by the following formula:
Actual reflectance = value × (1/2).

BP 150 and BP 153 specify push-pull signals of layer 0 and layer 1. In each of these BPs, a bit b7 (not shown) designates the track shape of the disk of each layer, and bits b6 to b0 (not shown) designate the amplitude of the push-pull signal:
Track shape: 0b (track on the groove)
1b (track on land)
Push-pull signal: For example, 010 1000b indicates 0.40.

The actual amplitude of the push-pull signal is specified by the following formula:
Actual amplitude of push-pull signal = value × (1/100).

BP151 and BP154 specify the amplitude of the on-track signal of layer 0 and layer 1:
On-track signal: For example, 0100 0110b indicates 0.70.

The actual amplitude of the on-track signal is specified by the following formula:
Actual amplitude of on-track signal = value x (1/100)
It should be noted that BP512 to BP543 of the physical format information can describe the recording related parameters of L0 as exemplified in FIG. 13, and information such as the initial peak power and bias power when recording the L0 layer is as follows: It can be taken from the description of FIG. In addition, in the physical format information BP544 to BP2047, the recording related parameters of L1 as exemplified in FIG. 14 can be described, and information such as the initial peak power and bias power when recording the L1 layer is as follows. It can be taken from the description of FIG.

Explanation of Recording Conditions (Write Strategy Information) A recording waveform (exposure conditions at the time of recording) used when investigating the optimum recording power will be described with reference to FIG. There are four exposure levels, recording power (peak power), bias power 1 (Bias power 1), bias power 2 (Bias power 2), and bias power 3 (Bias power 3). When a long recording mark 9 (4T or more) is formed, modulation is performed in the form of a multipulse between recording power (peak power) and bias power 3 (Bias power 3). In this embodiment, the minimum mark length with respect to the channel bit length T is 2T in both the “H format” and the “B format”. When recording this 2T minimum mark, as shown in FIG. 15, one write pulse at the recording power (peak power) level is used after the bias power 1 (Bias power 1), Immediately after the write pulse, the bias power is 2 (Bias power 2). When recording a recording mark 9 having a length of 3T, two write pulses of the first pulse and the last pulse of the recording power (peak power) level that come after the bias power 1 (Bias power 1) are exposed. After that, the bias power 2 is once set. In the case of recording a recording mark 9 having a length of 4T or more, the bias power 2 (Bias power 2) is obtained after exposure with the multi-pulse and the last pulse.

A vertical broken line in FIG. 15 indicates a channel clock period (T). Rises from a position delayed T _SFP from a clock edge when recording the minimum mark of 2T, it falls at the position of T _ELP from behind the edge of one clock later. The period in which the bias power 2 (Bias power 2) immediately following is defined as _{T LC.} The value of T _SFP and _{T ELP} and _{T LC} are in the case of the H format is recorded in the physical format information PFI in the control data zone CDZ.

In the case of forming a long recording mark of 3T or more, the signal rises from a position delayed by _SFP from the clock edge, and ends with the last pulse. Immediately after the last pulse, the duration bias power 2 of _{T LC} (Bias power 2), but defines a deviation time from the rising / falling timing of the clock edge of the last pulse _{T SLP,} with _{T ELP.} Further, the time measured from the clock edge of the leading edge falling timing is defined as _TEFP , and the interval between one multipulse is defined as _TMP .

Each interval of _{T ELP -T SFP, T MP,} T ELP -T SLP, T LC is defined by a half value width with respect to the maximum value. In this embodiment, the parameter setting range is 0.25T ≦ T _SFP ≦ 1.50T (eq.01)
0.00T ≦ T _ELP ≦ 1.00T (eq.02)
1.00T ≦ T _EFP ≦ 1.75T (eq.03)
−0.10T ≦ T _SLP ≦ 1.00T (eq.04)
0.00T ≦ T _LC ≦ 1.00T (eq.05)
0.15T ≦ T _MP ≦ 0.75T (eq.06)
And

  Furthermore, in this embodiment, the value of each parameter can be changed according to the length of the recording mark (Mark length) and the space length (Leading / Trailing space length) immediately before / after.

  When the optimum recording power of the write-once information recording medium recorded by the recording principle shown in this embodiment is examined, the parameters are bias power 1 (Bias power 1), bias power 2 (Bias power 2), The values of bias power 3 are 2.6 mW, 1.7 mW, and 1.7 mW, respectively, and the reproduction power is 0.4 mW.

  Based on the parameter values calculated as described above, "Optimum recording conditions for the storage medium (write strategy information) on the device (drive) that performed trial writing in the drive test zone" Can be determined.

  Further, as the recording signal data, a repetitive pattern of 11T marks and 11T spaces was used in addition to the above. The physical formats existing in the recording layers (L0, L1) on the transparent resin substrate 101 and the photopolymer resin 104 used in the following examples are as described with reference to FIGS.

  FIG. 16 is a diagram for explaining that a burst cutting area (BCA) is formed in the L1 layer of the write once single-sided multilayer (dual layer) optical disc according to one embodiment of the present invention. Here, the L0 layer is provided on the substrate 101 on the laser light receiving surface side, the L1 layer is provided so as to face the L0 layer, the substrate 102 is disposed on the L1 layer, and two bonded layers having a substrate thickness of 1.2 mm are provided. A disk 100 is configured. On the L1 layer on the inner circumference side of the disc 100, a BCA (Burst Cutting Area) in which information unique to the disc is recorded in a barcode pattern (mark) is provided.

  It is desirable to record disc-specific information in advance on each individual optical disc when the disc is manufactured. The disc-specific information recorded at this time is used, for example, when it is necessary to identify individual discs by copy protection or the like. In an optical disc such as CD, DVD, BD, and HD_DVD, such disc-specific information (BCA record and the like) is preliminarily engraved on the inner periphery of the disc as a barcode-like pattern called BCA (see BCAm in FIG. 16). ). At that time, in the case of a read-only two-layer optical disc, recording is generally performed on the back layer as viewed from the incident surface of the recording / reproducing light.

  In recent years, in response to a demand for an increase in capacity of an optical disc, a single-sided, dual-layer optical disc has been developed for a recording-type optical disc as well as a read-only optical disc. In order to maintain compatibility with the read-only type, it is desirable to record this BCA signal in a layer on the back side as viewed from the incident surface of the recording / reproducing light even in a recording type two-layer optical disc. But there are some problems. The following describes the BCA recording method and the problems associated with the two-layer structure.

  In order to provide the BCA on the disc, there is a method in which a BCA pattern is engraved on a stamper which is a mold for forming an optical disc. However, in order to record individual unique information on each disk, it is necessary to engrave a BCA pattern on the disk after the disk making, for example, with a laser beam. Normally, when recording BCA on a read-only disc, a pattern is produced by burning a reflective film (aluminum, silver or an alloy thereof) with a laser. When recording BCA on a phase change recording disk, a pattern is produced by changing the reflectivity by changing the phase of the recording film with a laser.

  On the other hand, in the case of a write-once type optical disk using an organic dye material, the sensitivity of the dye is very sensitive to the wavelength, so that a next-generation optical disk using a dye corresponding to a short wavelength (for example, 405 nm) (for example, BD or Even when the current BCA recording apparatus using a long wavelength (for example, 650 nm, 680 nm, or 780 nm) laser is applied to HD_DVD, a BCA pattern cannot be recorded satisfactorily. In this case, it is conceivable to increase the laser power of the BCA recording apparatus or change the laser wavelength of the BCA recording apparatus in accordance with the data recording wavelength (for example, 405 nm). However, since the BCA information is recorded in the back layer (L1) through the front layer (L0), this method is coupled with the fact that the BCA recording apparatus has a very deep focal depth (or BCA recording light is parallel light). Then, the pigment in the front layer also reacts. And it becomes noise (interlayer crosstalk signal) when reproducing the BCA signal.

  Therefore, in the embodiment of the present invention, when the wavelength used for data recording / reproduction is A (nm) and the wavelength of the BCA recording apparatus is B (nm), the BCA is more than the previous layer (L0) not recording BCA. The organic material to be used is selected so that the recording sensitivity with respect to the wavelength B is higher in the inner layer (L1) for recording. BCA recording is performed only on the back layer (L1) while the wavelength used for recording actual data (high-definition video data encoded by MPEG4AVC, etc.) and the wavelength used for recording BCA information are kept separate (A ≠ B). By using a dye corresponding to the wavelength of the device (for example, mixing two kinds of dyes having different sensitivities such as a dye having a sensitivity near 405 nm and a dye having a sensitivity near 650 nm to 780 nm) BCA signals can be selectively recorded only in L1).

  In this embodiment, a write-once optical disc having a diameter of 120 mm and a thickness of 1.2 mm (bonding two 0.6 mm polycarbonate molded substrates) and having two recording layers using an organic dye material is used. Illustrated. For recording / reproducing light, an optical system having a wavelength (λ) of 405 nm and a numerical aperture (NA) of 0.65 is used. The track pitch between grooves in the data recording area is, for example, 400 nm, and the position of the BCA area is, for example, between a radius of 22.2 mm to 23.1 mm. Further, the BCA pattern is constituted by a barcode-like pattern having a width (tangential direction) of several tens of μm and a length (radial direction) of several hundreds of μm, for example.

  The embodiment of the present invention is not limited to the above example. For example, an optical disk having a cover layer of 0.1 mm on the surface, an optical disk with a diameter of 80 mm, a higher-density track pitch pattern, or a laser having a shorter wavelength (for example, λ is 400 nm or less) is used. In addition, an optical system (objective lens) having a higher numerical aperture (NA is, for example, 0.8 to 0.9) may be used.

  As a specific material example of the write-once type multilayer optical disc according to the embodiment of the present invention, a molding substrate is polycarbonate; a stamper used for molding is nickel (Ni); a recording layer is azo, diazo, cyanine, phthalocyanine Organic pigment material consisting of styryl, styryl, or a mixture thereof; silver (Ag), aluminum (Al), gold (Au) or metal compounds based on these reflective films; acrylic or epoxy UV Cured resin. These materials are not limited to the above examples. However, the present invention relates to a write-once optical disc having a plurality of recording layers, and a typical method for manufacturing a single-sided dual-layer write-once optical disc will be described later with reference to FIG.

  In the example of the above embodiment, the case where the BCA is formed on the L1 layer over the L0 layer has been described. However, when a reflective layer having the dimensions and configuration illustrated in FIG. 1 (f) is provided, the dummy power can be selected by selecting the L1 layer material corresponding to the power of the laser to be used and its wavelength (which can be selected by trial and error). The BCA information can also be post-cut by irradiating the BCA laser through the substrate 102 (from the dummy substrate side disk surface opposite to the above example). A part of the L1 layer is deformed or changed by a laser irradiated through the dummy substrate 102, and BCA information (the BCA mark in FIG. 16 or the BCA record in FIG. 17) can be cut there with a boss.

  FIG. 17 is a diagram for explaining an example of the contents of a BCA record recorded in the BCA of FIG. As illustrated in FIG. 17A, in this record, a BCA record ID (indicating an HD_DVD book type identifier) is described in relative byte positions 0 to 1, and a version number of an applicable standard is stored in relative byte position 2. The data length is described in the relative byte position 3, the book type and disc type of the standard are described in the relative byte position 4, the extended part version is described in the relative byte position 5, and the relative byte positions 6 to 7 are Reserved for other information descriptions.

  In the BCA record, the book type and disc type fields of the standard document to which the disc conforms are exemplified in FIG. 17B. That is, information indicating that it is a standard for HD_DVD-R can be described in the book type, and a mark polarity flag and a twin format flag can be described in the disc type.

  When the mark polarity flag in FIG. 17B is “0b”, it indicates that the signal from the recording mark is a “Low-to-High” disk that is larger than the signal from the space (between adjacent marks). “1b” indicates that the signal from the recording mark is a “High-to-Low” disk in which the signal from the space is smaller than the signal from the space. When the twin format flag is “0b”, it is not a twin format disk, and when it is “1b”, it can be indicated that the disk is a twin format disk. When it is a twin format disc, the disc (on which the BAC record is recorded) has two recording layers, each of which is a separate format defined by the DVD Forum (eg HD_DVD-Video format and HD_DVD-Video Recording format) Will have.

  Although the twin format disc does not exist in the current DVD, but the twin format disc can exist in the next generation HD_DVD, it is possible to describe the twin format flag in the BCA according to one embodiment of the present invention. This is of great significance for write once multi-layer (two-layer) optical discs (next-generation HD_DVD discs).

  FIG. 18 is a diagram illustrating a configuration example of an apparatus that records specific information including the BCA record and the like in FIG. 17 in the BCA. Recording of a BCA signal (a signal including information such as the BCA record in FIG. 17) by the BCA recording apparatus is performed on the completed disc 100. The laser 210 is modulated in accordance with the BCA signal from the controller 202, and a barcode-like BCA mark is recorded in synchronization with the rotation of the disk 100. As the laser wavelength of the BCA recording apparatus, one in the range of 600 nm to 800 nm (generally, 650 nm to 780 nm or 680 nm to 780 nm) is employed. In the case of a two-layer optical disc, the recording location of the BCA is generally in the vicinity of the inner peripheral radius of 22.2 mm to 23.1 mm of the L1 layer. When performing BCA recording, the L1 layer is irradiated with laser through the L0 layer. In the embodiment of the present invention, the absorbance (sensitivity) at a wavelength of 650 nm to 780 nm (or 680 nm to 780 nm) is adjusted. (Sensitivity of L1 layer> Sensitivity of L0 layer). Therefore, the BCA signal can be accurately and selectively recorded only in the L1 layer in a substantial sense.

  In this way, by adjusting the sensitivity (absorbance at the wavelength used) of each layer, the laser wavelength and laser power of the BCA recording apparatus generally used in the DVD production line are maintained as they are (the laser power is appropriately determined depending on the situation). BCA signal can be recorded on the next generation optical disc. Further, since the BCA signal can be selectively recorded only in the L1 layer, there is no extra crosstalk noise from the L0 layer during reproduction.

  That is, in one embodiment of the present invention, the sensitivity of the dye in each layer (L0, L1, etc.) is adjusted (for example, the sensitivity or absorbance of the L1 layer dye at 600 nm to 800 nm, 650 nm to 780 nm, or 680 nm to 780 nm is L0 layer). Use organic materials that are greater than the sensitivity or absorbance of the dye). By doing so, the BCA signal can be recorded on the next generation optical disc (single-sided dual-layer HD_DVD-R, etc.) while maintaining the laser wavelength and laser power of the BCA recording device generally used in the DVD production line at present. can do. At this time, since BCA information can be selectively recorded only in the L1 layer, extra crosstalk noise from the L0 layer is not mixed when reproducing the BCA signal.

  Also, when BCA information is post-cut by irradiating the BCA laser through the dummy substrate 102, the BCA information can be selectively recorded only in the L1 layer. Extra crosstalk noise is not mixed.

  FIG. 19 is a flowchart for explaining an example of a procedure for recording specific information (BCA postcut) on the L1 layer of the write once single-sided multilayer (two layers) optical disk of FIG. When a BCA signal including specific information such as the BCA record of FIG. 17 is supplied from the controller 202 of FIG. 18 to the laser output control unit 208, the wavelength of 600 nm to 800 nm (or from the laser diode 210 corresponding to the signal content) A laser beam having one wavelength of 650 nm to 780 nm or 680 nm to 780 nm is emitted in a pulsive manner (ST10). The laser light pulse thus emitted is applied to the BCA recording location of the L1 layer through the L0 layer (or the dummy substrate 102) of the disc 100 shown in FIG. 16 (ST12). This irradiation is continued in synchronization with the rotation of the disk 100. When there is no recording information remaining on the BCA (YES in ST14), the BCA postcut to the L1 layer over the L0 layer is completed.

  FIG. 20 is a flowchart for explaining an example of a procedure for reproducing specific information (such as a BCA record) from the L1 layer of the write once single-sided multilayer (two layers) optical disk of FIG. When reproducing the information recorded in the BCA, a laser beam having a predetermined wavelength (for example, 405 nm or 650 nm) is irradiated to the BCA of the L1 layer through the L0 layer (ST20). Specific information (such as the BCA record in FIG. 17) related to the optical disc is read from the reflected light (ST22). This reading is continued in synchronization with the rotation of the disk 100. When there is no remaining read information from the BCA (YES in ST24), the BCA reproduction from the L1 layer over the L0 layer is finished.

  FIG. 21 is a diagram for explaining an example of the manufacturing process of the write once single-sided double layer optical disc according to one embodiment of the present invention. A method for producing this two-layer write-once optical disc will be described below with reference to FIG. First, an L0 layer molded plate is produced by injection molding (block 0301). The molding material is generally polycarbonate. The stamper used for the mold for forming the L0 layer is produced by Ni plating from a laser-exposed photoresist pattern. The dimensions of the molded plate are 120 mm in diameter, 15 mm in inner diameter, and 0.6 mm in thickness. An organic dye material to be a recording layer is applied to the molded plate by a known spin coating method, and a metal film (for example, silver or a silver alloy) to be a reflective film is formed by a known sputtering method (block 0302). . The L0 layer is translucent so that laser light can pass through.

  In parallel with this, a plastic stamper to be a mold of the L1 layer is similarly produced by injection molding (block 0303). The molding material is generally a cycloolefin polymer, but may be polycarbonate or acrylic. The L1 layer Ni stamper is also produced by laser-exposed photoresist plating, but the pattern irregularities are reversed to those of the L0 layer.

  The L0 layer molding plate on which the recording layer is formed and the plastic stamper are bonded together via a photopolymer, and are cured by irradiation with ultraviolet rays (block 0304). Thereafter, the plastic stamper is peeled off to expose the photopolymer layer to which the L1 layer pattern has been transferred (block 0305). Next, an organic dye material to be a recording layer is applied onto the L1 layer photopolymer by spin coating, and a metal film (for example, silver or a silver alloy) to be a reflective film is formed by sputtering or the like (block) 0306).

  In parallel therewith, a dummy plate (the material is polycarbonate or the like) is produced by injection molding (block 0307), and this is bonded with an ultraviolet curable adhesive to complete a two-layer write-once optical disc (block 0308). Although not shown, the dummy plate may be provided with a surface coating for user printing by an inkjet printer or the like, or a pattern such as a brand name or a product name of a disk manufacturer (or sales) manufacturer may be added.

  The dimensions of each layer of the write-once type multi-layer (two-layer) R disc 100 thus completed are as shown in FIG.

  In practicing the present invention, the light reflecting film material and film thickness are set appropriately for the light reflecting layer 106 included in the first recording portion (L0) to strictly control the amount of reflected light with respect to incident light. There is a need to. The film thickness of the light reflecting layer (semi-transmissive reflecting layer using Ag or an Ag alloy) 106 is usually preferably 15 nm to 35 nm. If it is less than 15 nm, the amount of light transmitted through the light reflecting layer increases, making it difficult to obtain a sufficient amount of reflected light. Then, a servo detection signal gain such as a push-pull signal becomes insufficient and stable recording / reproduction becomes difficult, and at the same time, an interlayer caused by the effect of light reflected by the light reflecting layer 108 included in the second recording unit (L1). The influence of crosstalk becomes an unacceptable level, and the recording / reproducing signal characteristics are greatly deteriorated. On the other hand, when it exceeds 35 nm, the amount of reflected light excessively increases. Then, a servo detection signal gain such as a push-pull signal increases and recording / reproduction is possible, but recording / reproduction on the recording layer 107 of the second recording unit (L1) becomes difficult because the light transmittance decreases.

  More specifically, it is as follows. When recording / reproducing the recording layer 105 of the first recording unit (L0), a part of the recording / reproducing light transmitted through the light reflecting layer 106 included in the first recording unit (L0) is included in the second recording unit (L1). Is reflected by the light reflecting layer 108 and returns to the first recording portion (L0). At this time, if the light transmittance of the semi-transmissive reflective layer 106 of the first recording unit (L0) is too high, a part of the leaked light during recording / reproducing is the light reflective layer 108 of the second recording unit (L1). And is added as an unnecessary signal component to the recording / reproducing signal of the first recording unit (L0). For this reason, the quality of the recording / reproducing signal of the first recording unit (L0) is significantly deteriorated.

  Interlayer crosstalk greatly affects the amount of reflected light from the first recording unit (L0) and the second recording unit (L1) and the light transmittance of the semi-transmissive reflective layer 106 included in the first recording unit (L0). Therefore, in order to always perform stable recording and reproduction, it is essential to strictly manage the recording position (see parameters in FIG. 4).

[Example 1a]
When the thickness of the L0 light reflection layer 106 is 25 nm and the thickness of the L1 light reflection layer 108 is 100 nm (L0 reflection layer thickness <L1 reflection layer thickness), an optimum amount of reflection can be obtained and interlayer crosstalk can be kept small. It is done. At the same time, BCA recording from the dummy substrate 102 can be stably performed, and a sufficient signal modulation degree can be obtained in the BCA recording.

[Example 2a]
When the thickness of the L0 light reflection layer 106 is 20 nm and the thickness of the L1 light reflection layer 108 is 80 nm (L0 reflection layer thickness <L1 reflection layer thickness), the optimum reflection amount can be obtained and the interlayer crosstalk is small. It can be suppressed. At the same time, BCA recording from the dummy substrate 102 can be stably performed, and a sufficient signal modulation degree can be obtained in the BCA recording.

[Example 1b]
When the thickness of the light reflecting layer 108 of L1 is 100 nm, an optimum amount of reflection can be obtained and interlayer crosstalk can be suppressed, and at the same time, BCA recording from the dummy substrate 102 can be stably performed. A sufficient degree of signal modulation was obtained.

[Example 2b]
As in Example 1b, the light reflecting layer 108 of L1 was prepared, and the reproduction signal quality in the system lead-out region (the area on the right side of FIG. 7) was evaluated. As a result, it was confirmed that sufficient signal modulation was obtained. .

[Example 1c]
The thickness of the L0 light reflecting layer 106 is 25 nm, the thickness of the L1 light reflecting layer 108 is 100 nm, and the intermediate layer 104 thickness on the entire disk surface is 27 μm ± 2 μm (more specific example within the range of 25 ± 10 μm). As a result, an optimal amount of reflection can be obtained, and interlayer crosstalk can be kept small. At the same time, BCA recording from the dummy substrate 102 can be stably performed, and a sufficient signal modulation degree can be obtained.

[Example 2c]
When the thickness of the L0 light reflecting layer 106 is 20 nm, the thickness of the L1 light reflecting layer 108 is 80 nm, and the intermediate layer thickness is 27 μm ± 2 μm over the entire surface of the disk, the optimum amount of reflection can be obtained and the interlayer crosstalk is small. It can be suppressed. At the same time, BCA recording from the dummy substrate 102 can be stably performed, and a sufficient signal modulation degree can be obtained.

[Comparative Example 1a (Evidence 1 for setting the thickness of the L0 reflective layer 106 to 15 nm to 35 nm)]
When the thickness of the light reflecting layer 106 of L0 is increased to 40 nm and the thickness of the light reflecting layer 108 of L1 is 200 nm, the amount of light transmitted to L1 decreases, so the servo signal gain when not recorded at the time of L1 recording is significantly reduced. As a result, stable recording / reproduction becomes difficult. At the same time, BCA recording from the dummy substrate becomes difficult, the signal modulation degree of the BCA recording portion is reduced, and sufficient signal quality cannot be obtained.

[Comparative Example 2a (Ground 2 for setting the thickness of the L0 reflective layer 106 to 15 nm to 35 nm)]
Even if the thickness of the L0 light reflecting layer 106 is increased to 40 nm and the thickness of the L1 light reflecting layer 106 is set to 100 nm, the light transmission amount to L1 also decreases, so that the servo signal gain at the time of L1 recording is not recorded. Remarkably reduced, making stable recording / reproduction difficult.

[Comparative Example 3a (Ground 3 for setting the thickness of the L0 reflective layer 106 to 15 nm or more and 35 nm or less)]
When the thickness of the L0 light reflecting layer 106 is reduced to 13 nm and the thickness of the L1 light reflecting layer 106 is set to 100 nm, light transmission to the L1 increases, and at the same time, light reflection from the L1 recording layer increases. Thus, unnecessary signal components increased during recording / reproduction of the L0 recording layer, and the characteristics of L0 deteriorated.

[Comparative Example 1b (Ground 1 for making the thickness of the L1 reflective layer 108 60 nm or more and 150 nm or less)]
When the thickness of the light reflecting layer 108 of L1 is made thicker than 150 nm, the amount of reflection at the reflecting layer 108 increases, the interlayer crosstalk increases, and the signal quality of the L0 recording layer 105 tends to deteriorate significantly. At the same time, BCA recording from the dummy substrate 102 becomes difficult, the signal modulation degree of the BCA recording portion is reduced, and sufficient signal quality cannot be obtained for the BCA information (150 nm is considered as a practical upper limit). In practice, it is preferably 100 nm or less).

[Comparative Example 2b (Ration 2 for making the thickness of the L1 reflective layer 108 60 nm or more and 150 nm or less)]
When the thickness of the light reflecting layer 108 of L1 is reduced to 50 nm, the amount of reflected light of L1 is reduced, so that the servo signal gain at the time of unrecording is remarkably reduced, and stable recording / reproduction becomes difficult.

[Comparative Example 1c (Ground 1 for setting the thickness of the intermediate layer 104 to 25 ± 10 μm)]
When the thickness of the L0 light reflecting layer 106 is 25 nm, the thickness of the L1 light reflecting layer 108 is 100 nm, and the thickness of the intermediate layer 104 on the entire disk surface is 35 μm ± 2 μm, the distance from the laser receiving surface of the disk 100 to L1 is as follows. This increases the spot shape of the recording / reproducing laser beam, resulting in a tendency to deteriorate the recording / reproducing signal and make it difficult to perform stable recording / reproducing (35 μm is considered as a practical upper limit).

[Comparative Example 2c (Ground 2 for setting the thickness of the intermediate layer 104 to 25 ± 10 μm)]
When the thickness of the L0 light reflecting layer 106 is 25 nm, the thickness of the L1 light reflecting layer 108 is 100 nm, and the thickness of the intermediate layer 104 on the entire surface of the disk is 15 μm ± 2 μm, the distance from the laser receiving surface of the disk 100 to L1 is as follows. As a result of the decrease, the spot shape of the recording / reproducing laser beam becomes unclear, and the recording / reproducing signal deteriorates and stable recording / reproducing tends to be difficult (15 μm is considered as a practical lower limit).

[Comparative Example 3c (Evidence that the thickness of the L0 reflective layer 106 should be 15 nm or more even if the thickness of the intermediate layer 104 is 25 ± 10 μm)]
When the thickness of the light reflecting layer 106 of L0 is as thin as 13 nm, the thickness of the light reflecting layer 108 of L1 is 100 nm, and the thickness of the intermediate layer 104 on the entire disk surface is 25 μm ± 2 μm,
Light transmission to L1 is increased, and light reflection from the L1 reflection layer 108 is increased at the same time. Unnecessary signal components at the time of recording / reproducing of the L0 recording layer 105 are increased, and the characteristics of L0 are deteriorated. That is, in the embodiment having the configuration as shown in FIG. 1F, the selection of the thickness of the L0 reflection layer 106 is more severe than the selection of the thickness of the intermediate layer 104.

  By implementing any of the embodiments of the present invention, in the optical recording medium having two or more recording layers, the first recording layer and the second recording layer are adjusted by adjusting the reflective film material and the reflective film thickness. Interlayer crosstalk with the layer is small and stable and high quality recording characteristics can be obtained. Further, BCA recording can be stably performed from the dummy substrate to the second recording layer, and a sufficient BCA signal modulation degree can be obtained.

  The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the gist of the present invention or a future implementation stage based on the technology available at that time. It is. For example, the present invention can be applied to an optical disc having three or more layers on one side, and can also be applied to an optical disc using a short wavelength laser having a wavelength of 400 nm or less. In addition, the embodiments may be appropriately combined as much as possible, and in that case, the combined effect can be obtained. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some configuration requirements are deleted from all the configuration requirements shown in the embodiment, a configuration from which these configuration requirements are deleted can be extracted as an invention.

DESCRIPTION OF SYMBOLS 100 ... Optical disk (Specifically two-layer write once optical disk); 101 ... L0 layer side polycarbonate substrate; 102 ... L1 layer side polycarbonate substrate (dummy substrate); 103 ... UV curable resin (adhesive layer); Intermediate layer: 105... L0 recording layer; 106... L0 reflective layer (semi-transparent to laser light); 107... L1 recording layer; 108.

Claims (4)

In a disc-shaped optical recording medium having a recording layer having a spiral track, information can be recorded and reproduced by light of a predetermined wavelength.
The recording layer is provided with a system lead-in area and a data lead-in area,
An optical recording medium in which a track pitch of the system lead-in area is set wider than a track pitch of the data lead-in area.   A disc-shaped optical recording medium having a recording layer having a spiral track capable of recording and reproducing information by light of a predetermined wavelength, wherein the recording layer is provided with a system lead-in area and a data lead-in area And recording information on the recording layer using an optical recording medium in which a track pitch of the system lead-in area is set wider than a track pitch of the data lead-in area.   A disc-shaped optical recording medium having a recording layer having a spiral track capable of recording and reproducing information by light of a predetermined wavelength, wherein the recording layer is provided with a system lead-in area and a data lead-in area And reproducing information from the recording layer using an optical recording medium in which a track pitch of the system lead-in area is set wider than a track pitch of the data lead-in area.   5. A burst cutting area capable of recording a mark polarity flag indicating whether a polarity of a recording mark of the recording layer is low-to-high or high-to-low is formed on an inner peripheral side of the disc-shaped optical recording medium. The optical recording medium described.

Images