JP2004213859A - Optical recording medium, and method and device for recording/reproducing optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To instantaneously change recording and reproducing conditions, for example, a recording pulse strategy, recording power, reproducing power, etc., in accordance with a recording layer for recording or reproducing information in a one-side incident type optical recording medium. <P>SOLUTION: A control part reads layer information from one recording layer of an optical recording medium where the layer information is respectively recorded on a plurality of recording layers on/from which information can be recorded or reproduced by the irradiation of a laser beam from one side (layer information reading step) and makes control so as to perform recording or reproduction on a recording/reproduction condition that corresponds to a recording layer specified by the layer information (recording control step). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to an optical recording medium having a plurality of recording layers capable of recording or reproducing information by irradiating a laser beam from one side such as a DVD-R, a recording / reproducing method of the optical recording medium, and a recording / reproducing of the optical recording medium. Equipment related.

At present, various types of optical recording media such as CD-R, CD-RW, and MO are widely recognized as external storage devices in information processing devices such as computers because they can store a large amount of information and can be easily accessed at random. It is becoming popular. In such an optical recording medium, it is desired to increase the storage density as the amount of information handled increases.
Among various optical recording media, an optical recording medium (optical disc) having a recording layer containing an organic dye (also referred to as a dye-containing recording layer) such as a CD-R, a DVD-R, and a DVD + R is relatively inexpensive, and It is particularly widely used because it has compatibility with read-only optical disks.

As an example, a medium such as a CD-R, which is a typical optical disk having a dye-containing recording layer, has a dye-containing recording layer and a reflective layer on a transparent disk substrate in this order. It has a laminated structure with a protective layer to cover, and performs recording / reproduction with laser light through the substrate.
A single-sided DVD-R also has a dye-containing recording layer, a reflective layer, and a protective layer covering these layers in this order on a first transparent disk substrate, and further has an adhesive layer on the protective layer. A laminated structure in which a so-called dummy disk having a reflective layer formed on a second disk substrate (which may be transparent or opaque) is provided with or without a laser beam from one side through the first transparent disk substrate. It performs recording and playback. The dummy disk may be a transparent or opaque disk substrate only, or may have a layer other than the reflective layer. It should be noted that DVD + R has almost the same configuration as DVD-R, and will be represented by the description of DVD-R.

  Also, in order to further increase the recording capacity of the optical recording medium, a single-sided DVD-R as described above is bonded to form a medium having two recording layers, and each recording layer is irradiated with laser light from both sides. (I.e., irradiate laser light from one side of the medium and perform recording / reproduction on the recording layer closer to this one side, and irradiate laser light also from the other side of the medium). The recording / reproducing of the recording layer closer to the other surface side) is also known.

In addition, optical recording media (optical disks) having a phase-change recording layer, such as CD-RW and DVD-RW, are also widely used. Generally, in a rewritable optical recording medium having a phase-change recording layer, protective layers are provided above and below the recording layer.
By the way, in recent years, in an optical recording medium having a plurality of recording layers, in order to prevent the recording / reproducing apparatus from becoming large-sized and complicated, and to enable continuous reproduction over a plurality of recording layers, a laser is used from one side. It is desired to realize a single-sided incidence type optical recording medium (for example, single-sided incidence type DVD-R) that can record / reproduce on or from these multiple recording layers by irradiating light.

For this reason, for example, as a single-sided incident type optical recording medium having the following configuration, for example, a dual-layer single-sided incident type DVD-R having two recording layers has been proposed (for example, see Patent Document 1).
For example, a dual-layer single-sided incident type DVD-R has a first recording layer made of an organic dye capable of optically recording information by irradiating a recording laser beam on a first translucent substrate, and a reproduction laser. A first reflective layer composed of a semi-transmissive reflective film capable of transmitting part of light, an intermediate layer having a light-transmitting property with respect to recording laser light and reproduction laser light, and a recording laser light. A second recording layer made of an organic dye capable of optically recording information by irradiation, a second reflection layer for reflecting a reproduction laser beam, and a second light-transmitting substrate are sequentially laminated.
JP-A-11-066662

Meanwhile, for a single-sided optical recording medium having a plurality of recording layers, such as a dual-layer single-sided incident type DVD-R, for example, a recording pulse strategy (recording strategy, write strategy), recording power, etc. Optimal recording / reproduction conditions such as reproduction power and the like are greatly different.
Therefore, in a recording / reproducing apparatus that records or reproduces information on each recording layer of a single-sided incident type optical recording medium having a plurality of recording layers, for example, a recording pulse strategy, a recording power, a reproduction power It is desirable to be able to switch the recording / reproducing conditions, such as, for example, and to record and reproduce information accurately and reliably.

In particular, in order for the recording / reproducing apparatus to perform random access to each recording layer of the optical recording medium to record or reproduce information, it is necessary to switch recording / reproducing conditions instantaneously according to the recording layer. There is.
Also, for example, it is conceivable to attach address information continuously over a plurality of recording layers and determine which layer is based on the read address information in the recording / reproducing apparatus. It is difficult to judge instantly.

  The present invention has been made in view of such a problem, and records or reproduces information on an optical recording medium that records or reproduces information on a plurality of recording layers by irradiating a laser beam from one side. An optical recording medium, a recording / reproducing method for an optical recording medium, and an optical recording medium, wherein recording / reproducing conditions such as a recording pulse strategy, recording power, and reproducing power can be instantaneously switched according to a recording layer to be performed. An object of the present invention is to provide a recording and reproducing apparatus for a medium.

  For this reason, the recording / reproducing method of the optical recording medium of the present invention is characterized in that the control unit controls the optical recording medium to record the layer information on each of a plurality of recording layers capable of recording or reproducing information by irradiating a laser beam from one side. A layer information reading step of reading layer information from one recording layer of the recording medium, and a recording control step of controlling the recording and reproduction to be performed under recording and reproduction conditions according to the recording layer specified by the layer information. (Claim 1).

  The recording / reproducing apparatus for an optical recording medium according to the present invention includes a recording layer of an optical recording medium in which layer information is recorded on each of a plurality of recording layers capable of recording or reproducing information by irradiation of laser light from one side. And a recording / reproducing control unit for controlling recording / reproducing under recording / reproducing conditions corresponding to the recording layer specified by the layer information. Item 2).

An optical recording medium according to the present invention is an optical recording medium recorded or reproduced by the method for recording and reproducing an optical recording medium according to claim 1, wherein a plurality of optical recording media capable of recording or reproducing information by irradiating a laser beam from one side. Wherein the layer information is recorded in each of the recording layers (claim 3).
Preferably, the layer information is recorded on almost the entire surface of each recording layer (claim 4). In particular, it is preferable that the layer information is recorded as a part of the address information (claim 5).

It is also preferable that the layer information is recorded by making the value of the reserve bit included in the address information different in each recording layer.
Furthermore, it is preferable that the layer information is recorded by inverting the sync pattern included in the address information in two adjacent recording layers of the plurality of recording layers (claim 7).

Further, in two adjacent recording layers of the plurality of recording layers, the most significant bit of the address information is inverted, the entire address information of one recording layer is inverted, or the entire address information of one recording layer is inverted. It is also preferable that the layer information is recorded by any one of the two-complement representation methods.
Further, it is preferable to have two recording layers as a plurality of recording layers (claim 9).

  Preferably, each recording layer is a dye-containing recording layer (claim 10).

  As described in detail above, according to the optical recording medium, the recording / reproducing method of the optical recording medium, and the recording / reproducing apparatus of the optical recording medium of the present invention, for example, depending on the recording layer on which information is to be recorded or reproduced, There is an advantage that recording / reproducing conditions such as a recording pulse strategy, recording power, and reproducing power can be instantaneously switched.

Hereinafter, referring to the drawings, an optical recording medium (write-once optical recording medium), a recording / reproducing method for an optical recording medium, and a recording / reproducing apparatus for an optical recording medium according to an embodiment of the present invention will be described with reference to FIGS. explain.
The optical recording medium according to the present embodiment has a plurality of recording layers, and is capable of recording or reproducing information on or from each of the recording layers by irradiating light (laser light) from one side. It is a recording medium.

In the present embodiment, as a single-sided incident type optical recording medium (single-sided incident type DVD-R), for example, a dual layer type single-sided incident type DVD-R (write-once optical recording medium) having two recording layers will be described as an example. .
(1) Structure of Optical Recording Medium First, as an optical recording medium according to the present embodiment, two types of optical recording media (optical disks) having different laminated structures will be described.
(A) Type 1
FIG. 1 is a schematic cross-sectional view showing an optical recording medium (type 1, laminated single-sided incident type optical recording medium) according to the present embodiment.

  The type 1 optical recording medium according to the present embodiment includes a disk-shaped transparent (light-transmitting) first substrate (first substrate, first light-transmitting substrate) 1 on which a first recording containing a dye is performed. Layer (first recording layer, first dye-containing recording layer) 2, translucent first reflective layer (hereinafter also referred to as translucent reflective layer) 3, intermediate resin layer (intermediate layer) 4, and second layer containing dye. It comprises a recording layer (second recording layer, second dye-containing recording layer) 5, a second reflective layer 6, an adhesive layer 7, and a second substrate (second substrate) 8 in this order. The light beam is irradiated from the first substrate 1 side, and recording or reproduction is performed.

  In the present embodiment, being transparent (having optical transparency) means being transparent (having optical transparency) with respect to a light beam used for recording or reproduction of an optical recording medium. Further, the transparent (light-transmitting) layer also includes a layer that slightly absorbs a light beam used for recording or reproduction. For example, if the light beam used for recording or reproduction has a transmittance of 50% or more, preferably 60% or more, it is assumed that the light beam is substantially transparent (transparent).

  Irregularities (lands and grooves) are formed on the transparent first substrate 1 and the intermediate resin layer 4, respectively, and recording tracks are formed by concave and / or convex portions. Here, the recording track 11 on the transparent first substrate 1 is formed by a groove in the first substrate 1, that is, a projection in the light incident direction. The recording track 12 on the intermediate resin layer 4 is also formed of a groove in the intermediate resin layer 4, that is, a projection in the light incident direction. Note that the recording tracks 11 and 12 may be configured with concave portions in the light incident direction, or may be configured with both concave portions and convex portions in the light incident direction. It is preferable that the projections are formed with projections with respect to the incident direction. Unless otherwise specified, the unevenness in the present invention is defined with respect to the incident direction of light used for recording or reproduction.

  These recording tracks 11 and 12 are slightly meandered in the radial direction at a predetermined amplitude and a predetermined frequency (this is called wobble). An isolated pit (address pit) is formed in a land between the recording tracks 11 and 12 according to a certain rule (this is called a land pre-pit, LPP; Land Pre-Pit). Address information is recorded in advance. In addition, it may have a concave and convex pit (pre-pit) if necessary. Also, information can be recorded by reversing the direction of the wobble or modulating the frequency.

Next, each layer will be described.
(A) First substrate 1 The first substrate 1 is desirably excellent in optical characteristics such as being transparent and having a small birefringence. Further, it is desirable that the moldability is excellent, such as easy injection molding. Furthermore, low hygroscopicity is desirable because warpage and the like can be reduced.

Further, it is desirable that the optical recording medium has a shape stability so as to have a certain rigidity. However, as long as the second substrate 8 has sufficient shape stability, the first substrate 1 does not need to have high shape stability.
Examples of such a material include resins made of acrylic resin, methacrylic resin, polycarbonate resin, polyolefin resin (especially amorphous polyolefin), polyester resin, polystyrene resin, epoxy resin, and the like, and those made of glass. Can be used. Alternatively, the first substrate 1 may be composed of a plurality of layers. For example, a substrate in which a resin layer composed of a radiation-curable resin such as a photo-curable resin is provided on a substrate such as glass or resin may be used. Note that radiation is a general term for light (ultraviolet light, visible light, infrared light, etc.), electron beam, and the like.

In addition, polycarbonate is preferable in terms of high productivity such as optical characteristics and moldability, cost, low moisture absorption, shape stability, and the like. Amorphous polyolefin is preferred from the viewpoints of chemical resistance, low hygroscopicity and the like. Further, a glass substrate is preferable in terms of high-speed response and the like.
The first substrate 1 is preferably thinner, and usually has a thickness of preferably 2 mm or less, more preferably 1 mm or less. This is because the smaller the distance between the objective lens and the recording layer and the thinner the substrate, the smaller the coma aberration tends to be and the higher the recording density. However, in order to obtain sufficient optical properties, hygroscopicity, moldability, and shape stability, a certain thickness is required, and it is usually preferably 10 μm or more, more preferably 30 μm or more.

In the present optical recording medium, it is desirable to appropriately adjust the distance between the objective lens and the two recording layers in order to perform good recording or reproduction on both the first recording layer 2 and the second recording layer 5. For example, it is preferable to set the focal point of the objective lens at a substantially intermediate point between the two recording layers, since both the recording layers can be easily accessed.
More specifically, in the DVD-ROM and DVD-R systems, the distance between the objective lens and the recording layer is adjusted to be optimum when the substrate thickness is 0.6 mm.

Therefore, in the case of DVD-ROM compatibility in the present layer configuration, the thickness of the first substrate 1 is most preferably a thickness obtained by subtracting half the thickness of the intermediate resin layer 4 from 0.6 mm. preferable. At this time, the approximate middle point between the two recording layers is about 0.6 mm, and focus servo can be easily applied to both the recording layers.
When there are other layers such as a buffer layer and a protective layer between the second recording layer 5 and the first reflective layer 3, the thickness of these layers and the thickness of the intermediate resin layer 4 is set to 2 mm from 0.6 mm. Most preferably, the thickness is reduced by a factor of one.

  Concavities and convexities are provided spirally or concentrically on the first substrate 1 to form grooves and lands. Usually, information is recorded or reproduced on the first recording layer 2 using such grooves and / or lands as recording tracks. In the case of a so-called DVD-R disc in which recording or reproduction is performed by condensing a laser having a wavelength of 650 nm with an objective lens having a numerical aperture of 0.6 to 0.65, the first recording layer 2 is usually formed by coating. It becomes a thick film in the groove and is suitable for recording or reproduction.

  In the present optical recording medium, it is preferable that the groove of the first substrate 1, that is, the protrusion in the light incident direction be the recording track 11. Here, the concave portion and the convex portion refer to the concave portion and the convex portion with respect to the light incident direction, respectively. Usually, the groove width is about 50 to 500 nm, and the groove depth is about 10 to 250 nm. When the recording track is spiral, the track pitch is preferably about 0.1 to 2.0 μm. In addition, if necessary, a concavo-convex pit such as a land pre-pit may be provided.

From the viewpoint of cost, the substrate having such irregularities is preferably manufactured by injection molding from a stamper having irregularities. When a resin layer made of a radiation curable resin such as a photocurable resin is provided on a substrate such as glass, irregularities such as recording tracks may be formed on the resin layer.
(B) About the first recording layer 2 The first recording layer 2 generally has the same sensitivity as a recording layer used for a single-sided recording medium (for example, CD-R, DVD-R, DVD + R) or the like.

Further, in order to realize good recording / reproducing characteristics, it is desirable that the coloring matter be a low-heat-generation and high-refractive-index dye.
Further, in the combination of the first recording layer 2 and the first reflection layer 3, it is desirable that the reflection, transmission and absorption of light be in appropriate ranges. The recording sensitivity can be increased and the thermal interference during recording can be reduced.

  Such organic dye materials include macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.), pyromethene dyes, polymethine dyes (cyanine dyes, merocyanine dyes, squarylium dyes, etc.), anthraquinone dyes, Examples include azurenium dyes, metal-containing azo dyes, and metal-containing indoaniline dyes.

  Among the various organic dyes described above, metal-containing azo dyes are preferable because they have excellent recording sensitivity and excellent durability and light resistance. In particular, the following general formula (I) or (II)

(Rings A ¹ and A ² are each independently a nitrogen-containing aromatic heterocyclic ring which may have a substituent, and rings B ¹ and B ² may each independently have a substituent X is an alkyl group having 1 to 6 carbon atoms and substituted with at least two fluorine atoms.)
The organic dye used in the recording layer of the present optical recording medium has a maximum absorption wavelength λmax in the visible light to near infrared region of about 350 to 900 nm, and a dye compound suitable for recording with a blue to near microwave laser is preferable. . A near-infrared laser (typically 780 nm or 830 nm or the like) having a wavelength of about 770 to 830 nm used for a normal CD-R or a red laser having a wavelength of about 620 to 690 nm (typically used for a DVD-R) 635 nm, 650 nm, 680 nm, etc.), or a dye suitable for recording with a so-called blue laser having a wavelength of 410 nm or 515 nm is more preferable.

One type of dye may be used, or two or more types of the same type or different types may be mixed and used. Further, a dye suitable for recording in each of the above-mentioned plurality of wavelengths may be used in combination with the recording light to provide an optical recording medium corresponding to recording with laser light in a plurality of wavelength ranges.
In addition, the recording layer is a transition metal chelate compound (eg, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-diketone, etc.) as a singlet oxygen quencher to improve the stability and light resistance of the recording layer. And a recording sensitivity improver such as a metal compound for improving the recording sensitivity. Here, the metal compound refers to a compound in which a metal such as a transition metal is contained in the compound in the form of an atom, an ion, a cluster, or the like.For example, an ethylenediamine-based complex, an azomethine-based complex, a phenylhydroxyamine-based complex, a phenanthroline-based complex, Organometallic compounds such as dihydroxyazobenzene-based complexes, dioxime-based complexes, nitrosoaminophenol-based complexes, pyridyltriazine-based complexes, acetylacetonate-based complexes, metallocene-based complexes, and porphyrin-based complexes are exemplified. The metal atom is not particularly limited, but is preferably a transition metal.

  Further, a binder, a leveling agent, an antifoaming agent and the like can be used in combination in the recording layer of the present optical recording medium, if necessary. Preferred binders include polyvinyl alcohol, polyvinylpyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like.

  The thickness of the recording layer is not particularly limited because a suitable thickness varies depending on a recording method or the like, but is usually preferably 5 nm or more, more preferably 10 nm or more, in order to obtain a sufficient degree of modulation. Particularly preferably, it is 20 nm or more. However, in the present optical recording medium, the thickness is usually not more than 3 μm, preferably not more than 1 μm, more preferably not more than 200 nm because it is necessary that the thickness is not too thick in order to transmit light appropriately. The thickness of the recording layer usually differs between the groove and the land, but in the present optical recording medium, the thickness of the recording layer refers to the thickness in the groove of the substrate.

Examples of the method of forming the recording layer include thin film forming methods generally used such as a vacuum evaporation method, a sputtering method, a doctor blade method, a casting method, a spin coating method, and an immersion method, but from the viewpoint of mass productivity and cost. Spin coating is preferred. From the viewpoint that a recording layer having a uniform thickness can be obtained, the vacuum deposition method is more preferable than the coating method.
In the case of film formation by spin coating, the number of rotations is preferably 10 to 15000 rpm, and after spin coating, treatment such as heating or exposure to solvent vapor may be performed.

  When forming the recording layer by a coating method such as a doctor blade method, a casting method, a spin coating method, and a dipping method, the coating solvent is not particularly limited as long as it is a solvent that does not attack the substrate. For example, ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellosolve solvents such as methyl cellosolve and ethyl cellosolve; chain hydrocarbon solvents such as n-hexane and n-octane A cyclic hydrocarbon solvent such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, tert-butylcyclohexane and cyclooctane; a perfluoroalkyl alcohol such as tetrafluoropropanol, octafluoropentanol and hexafluorobutanol Solvents such as hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate and methyl 2-hydroxyisobutyrate.

In the case of the vacuum evaporation method, for example, an organic dye and, if necessary, recording layer components such as various additives are put into a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is 10 ⁻² to 10 ⁻² . After evacuation to about 10 ^-5 Pa, the crucible is heated to evaporate the components of the recording layer, and the recording layer is formed by vapor deposition on a substrate placed facing the crucible.
(C) First Reflective Layer 3 The first reflective layer 3 is a reflective layer having a certain light transmittance. In other words, it is a reflective layer that absorbs recording / reproducing light little, has a light transmittance of 40% or more, and has an appropriate light reflectivity (generally, 30% or more). For example, an appropriate transmittance can be provided by thinly providing a metal having high reflectance. Also, it is desirable to have some corrosion resistance. Further, it is desirable that the first recording layer 2 has a blocking property so that the upper layer (the intermediate resin layer 4 in this case) of the first reflection layer 3 does not affect the first recording layer 2.

In order to ensure a high transmittance, the thickness of the first reflective layer 3 is usually preferably 50 nm or less. More preferably, it is 30 nm or less. More preferably, it is 25 nm or less. However, since the first recording layer 2 is not affected by the upper layer of the first reflection layer 3, a certain thickness is required, and is usually 3 nm or more. More preferably, the thickness is 5 nm or more.
The material of the first reflective layer 3 has a moderately high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Pd, Mg, Se, Hf. , V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi and rare earth metals It is possible to use a metal alone or as an alloy. Among them, Au, Al and Ag have high reflectivity and are suitable as the material of the first reflection layer 3. In addition to these as main components, other components may be included.

Among them, those containing Ag as a main component are particularly preferable because of their low cost and high reflectivity. Here, the main component means one having a content of 50% or more.
Since the first reflective layer 3 has a small thickness and a large crystal grain of the film causes reproduction noise, it is preferable to use a material having a small crystal grain. Since pure silver tends to have large crystal grains, Ag is preferably used as an alloy.

Above all, it is preferable to contain 0.1 to 15 atomic% of at least one element selected from the group consisting of Ag, Ti, Zn, Cu, Pd, Au and rare earth metal. When containing two or more of Ti, Zn, Cu, Pd, Au and rare earth metals, each may be 0.1 to 15 atomic%, but the total thereof is preferably 0.1 to 15 atomic%. .
A particularly preferred alloy composition is one containing Ag as a main component, containing at least one element selected from the group consisting of Ti, Zn, Cu, Pd, and Au in an amount of 0.1 to 15 atomic%, and at least one rare earth element. Is contained in an amount of 0.1 to 15 atomic%. Among rare earth metals, neodymium is particularly preferred. Specifically, it is AgPdCu, AgCuAu, AgCuAuNd, AgCuNd, or the like.

As the first reflective layer 3, a layer made of Au alone has small crystal grains and is excellent in corrosion resistance and is suitable. However, they are more expensive than Ag alloys.
Also, a layer made of Si can be used as the first reflection layer 3.
It is also possible to form a multilayer film by alternately stacking low-refractive-index thin films and high-refractive-index thin films with a material other than a metal and use it as a reflective layer.

Examples of a method for forming the first reflective layer 3 include a sputtering method, an ion plating method, a chemical vapor deposition method, and a vacuum vapor deposition method. In addition, between the first substrate 1 and the first reflection layer 3, a known inorganic or organic intermediate layer or adhesive layer for improving, for example, reflectance, recording characteristics, and adhesion is provided. It may be provided. For example, by stacking an intermediate layer (or an adhesive layer), a first recording layer 2, an intermediate layer (or an adhesive layer), and a first reflective layer 3 on the first substrate 1 in this order, the first substrate 1 and the first An intermediate layer (or an adhesive layer) may be provided between the recording layer 2 and the intermediate layer (or an adhesive layer) between the first recording layer 2 and the first reflective layer 3.
(D) Intermediate Resin Layer 4 The intermediate resin layer 4 needs to be transparent and need to be able to form grooves and pits due to irregularities. Further, it is preferable that the adhesive strength is high and the shrinkage ratio at the time of curing adhesion is small because the shape stability of the medium is high.

It is desirable that the intermediate resin layer 4 be made of a material that does not damage the second recording layer 5. However, since the intermediate resin layer 4 is usually made of resin, it is easily compatible with the second recording layer 5, and it is desirable to provide a buffer layer described later between both layers to prevent this and suppress damage.
Further, it is desirable that the intermediate resin layer 4 be made of a material that does not damage the first reflection layer 3. However, a buffer layer described later can be provided between the two layers in order to suppress damage.

  In the present optical recording medium, the thickness of the intermediate resin layer 4 is preferably controlled accurately. The thickness of the intermediate resin layer 4 is usually preferably 5 μm or more. In order to separately apply focus servo to the two recording layers, there must be a certain distance between the two recording layers. Although it depends on the focus servo mechanism, it usually needs to be 5 μm or more, preferably 10 μm or more. In general, the higher the numerical aperture of the objective lens, the smaller the distance tends to be. However, if the thickness is too large, it takes time to adjust the focus servo to the two recording layers, and the moving distance of the objective lens becomes long. In addition, since there is a problem such as a long time for curing and a decrease in productivity, the thickness is usually preferably 100 μm or less.

  The intermediate resin layer 4 is provided with irregularities spirally or concentrically to form grooves and lands. Usually, information is recorded or reproduced on the second recording layer 5 using such grooves and / or lands as recording tracks. Usually, since the second recording layer 5 is formed by coating, the second recording layer 5 becomes a thick film at the groove portion and is suitable for recording or reproduction. In the present optical recording medium, it is preferable that the groove of the intermediate resin layer 4, that is, the projection in the light incident direction be the recording track 12. Here, the concave portion and the convex portion refer to the concave portion and the convex portion with respect to the light incident direction, respectively. Usually, the groove width is about 50 to 500 nm, and the groove depth is about 10 to 250 nm. When the recording track is spiral, the track pitch is preferably about 0.1 to 2.0 μm. In addition, if necessary, it may have uneven pits such as land pre-pits.

From the viewpoint of cost, such irregularities are preferably manufactured by transferring and curing a curable resin such as a photocurable resin from a resin stamper having irregularities. Hereinafter, such a method may be referred to as a 2P method (Photo Polymerization method).
Examples of the material of the intermediate resin layer 4 include a thermoplastic resin, a thermosetting resin, an electron beam-curable resin, and an ultraviolet-curable resin (including a delay-curable resin).

  A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in an appropriate solvent to prepare a coating solution, applying the coating solution, and drying (heating). The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, applying the coating solution, and irradiating with ultraviolet light to cure the coating solution. There are various types of ultraviolet curable resins, and any of them can be used as long as they are transparent. These materials may be used alone or as a mixture, or may be used as a multilayer film instead of a single layer.

  As a coating method, a coating method such as a spin coating method or a casting method is used as in the case of the recording layer. Among them, the spin coating method is preferable. Alternatively, a resin having a high viscosity can be applied and formed by screen printing or the like. It is preferable to use a UV-curable resin that is liquid at a productivity of 20 to 40 ° C. because it can be applied without using a solvent. Further, it is preferable to adjust the viscosity to be 20 to 1000 mPa · s.

Now, as the ultraviolet curable adhesive, there are a radical ultraviolet curable adhesive and a cationic ultraviolet curable adhesive, and both can be used.
All known compositions can be used as the radical type ultraviolet curable adhesive, and a composition containing an ultraviolet curable compound and a photopolymerization initiator as essential components is used. As the ultraviolet curable compound, a monofunctional (meth) acrylate or a polyfunctional (meth) acrylate can be used as a polymerizable monomer component. Each of these can be used alone or in combination of two or more. Here, in the present invention, acrylate and methacrylate are collectively referred to as (meth) acrylate.

  Examples of the polymerizable monomer that can be used in the present optical recording medium include the following. Examples of the monofunctional (meth) acrylate include, as a substituent, methyl, ethyl, propyl, butyl, amyl, 2-ethylhexyl, octyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, Nonylphenoxyethyl, tetrahydrofurfuryl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydroxypropyl, dimethylaminoethyl, diethylaminoethyl, nonylphenoxyethyltetrahydrofurfuryl, caprolactone-modified tetrahydrofurfuryl, isobornyl , Dicyclopentenyl, dicyclopentenyl, dicyclopentenyloxyethyl and the like, and a (meth) acrylate having a group.

  Examples of the polyfunctional (meth) acrylate include 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, and 1,6-hexanediol. , Neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecane dimethanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, di (meth) glycol such as polypropylene glycol Acrylate, di (meth) acrylate of tris (2-hydroxyethyl) isocyanurate, di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of neopentyl glycol Di (meth) acrylate of diol obtained by adding 2 moles of ethylene oxide or propylene oxide to 1 mole of bisphenol A, and triol obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of trimethylolpropane Di or tri (meth) acrylate, di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of bisphenol A, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) Acrylates, poly (meth) acrylates of dipentaerythritol, ethylene oxide-modified phosphoric acid (meth) acrylate, ethylene oxide-modified alkylated phosphoric acid (meth) acrylate, and the like. It is.

Examples of those which can be used together with the polymerizable monomer include polyester (meth) acrylate, polyether (meth) acrylate, epoxy (meth) acrylate, and urethane (meth) acrylate as the polymerizable oligomer.
Further, as the photopolymerization initiator used in the present optical recording medium, any known one that can cure an ultraviolet curable compound represented by a polymerizable oligomer and / or a polymerizable monomer to be used can be used. As the photopolymerization initiator, a molecular cleavage type or a hydrogen abstraction type is suitable for the present optical recording medium.

  Such examples include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2-dimethylamino-1- ( 4-morpholinophenyl) -butan-1-one, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide and the like are preferably used. 1-hydroxycyclohexylphenyl ketone, benzoin ethyl ether, benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methyl Propan-1-one and -Methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one and the like may be used in combination, and benzophenone, 4-phenylbenzophenone, and isophthalphenone, which are hydrogen abstraction type photopolymerization initiators , 4-benzoyl-4'-methyl-diphenyl sulfide and the like can also be used in combination.

  Examples of sensitizers for the photopolymerization initiator include, for example, trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N, N-dimethylbenzyl Amines such as amine and 4,4'-bis (diethylamino) benzophenone which do not cause an addition reaction with the above-mentioned polymerizable component can be used in combination. Of course, it is preferable to select and use the photopolymerization initiator and the sensitizer that have excellent solubility in the ultraviolet curable compound and do not inhibit the ultraviolet transmittance.

In addition, all known compositions can be used as the cationic ultraviolet curable adhesive, and an epoxy resin containing a cationic polymerization type photoinitiator corresponds to this. Examples of cationic polymerization type photoinitiators include sulfonium salts, iodonium salts and diazonium salts.
An example of the iodonium salt is as follows. Diphenyliodonium hexafluorophosphate, diphenyliodonium hexafluoroantimonate, diphenyliodonium tetrafluoroborate, diphenyliodonium tetrakis (pentafluorophenyl) borate, bis (dodecylphenyl) iodonium hexafluorophosphate, bis (dodecylphenyl) iodonium hexafluoroantimonate , Bis (dodecylphenyl) iodonium tetrafluoroborate, bis (dodecylphenyl) iodonium tetrakis (pentafluorophenyl) borate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium hexafluorophosphate, 4-methylphenyl-4 -(1-methylethyl) phenyliodonium hexafluoroa Imimonate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium tetrafluoroborate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium tetrakis (pentafluorophenyl) borate, and the like.

The epoxy resin may be any of various types such as bisphenol A-epichlorhydrin type, alicyclic epoxy, long-chain aliphatic type, brominated epoxy resin, glycidyl ester type, glycidyl ether type, and heterocyclic type. It doesn't matter.
As the epoxy resin, it is preferable to use an epoxy resin having a low free chlorine and chlorine ion content so as not to damage the reflective layer. The amount of chlorine is preferably 1% by weight or less, more preferably 0.5% by weight or less.

  The ratio of the cationic polymerization type photoinitiator per 100 parts by weight of the cationic ultraviolet curable resin is usually 0.1 to 20 parts by weight, preferably 0.2 to 5 parts by weight. In order to more effectively use the wavelength in the near-ultraviolet region or the visible region of the wavelength range of the ultraviolet light source, a known photosensitizer can be used in combination. In this case, examples of the photosensitizer include anthracene, phenothiazine, benzylmethyl ketal, benzophenone, acetophenone and the like.

In addition, the UV curable adhesive may further include, if necessary, other additives such as a thermal polymerization inhibitor, an antioxidant represented by a hindered phenol, a hindered amine, and a phosphite, a plasticizer, an epoxy silane, and a mercapto. A silane coupling agent typified by silane, (meth) acryl silane, or the like can be blended for the purpose of improving various characteristics. These are selected from those having excellent solubility in ultraviolet curable compounds and those which do not inhibit ultraviolet transmittance.
(E) Regarding the second recording layer 5 The second recording layer 5 generally has higher sensitivity than the recording layer used for a single-sided recording medium (for example, CD-R, DVD-R, DVD + R) or the like. In the present optical recording medium, since the power of the incident light beam is reduced due to the presence of the first recording layer 2 and the first reflective layer 3, etc., the sensitivity needs to be particularly high in order to record at approximately half the power. It is.

Further, in order to realize good recording / reproducing characteristics, it is desirable that the coloring matter be a low-heat-generation and high-refractive-index dye.
Further, in the combination of the second recording layer 5 and the second reflection layer 6, it is desirable that the reflection and absorption of light be in an appropriate range. The recording sensitivity can be increased and the thermal interference during recording can be reduced.
Since the material of the second recording layer 5, the film forming method, and the like are substantially the same as those of the first recording layer 2, only different points will be described.

  The thickness of the second recording layer 5 is not particularly limited because a suitable thickness varies depending on a recording method or the like, but is usually preferably 10 nm or more, more preferably 30 nm or more in order to obtain a sufficient degree of modulation. And particularly preferably 50 nm or more. However, the thickness is usually 3 μm or less, preferably 1 μm or less, and more preferably 200 nm or less, because it is necessary that the thickness be not too thick in order to obtain an appropriate reflectance.

The materials used for the first recording layer 2 and the second recording layer 5 may be the same or different.
(F) Second Reflective Layer 6 The second reflective layer 6 needs to have a high reflectance. Further, it is desirable to have high durability.
In order to ensure a high reflectance, the thickness of the second reflective layer 6 is usually preferably 20 nm or more. More preferably, it is 30 nm or more. More preferably, it is 50 nm or more. However, in order to shorten the production tact time and reduce the cost, it is preferable that the thickness be somewhat thin, and usually 400 nm or less. More preferably, the thickness is 300 nm or less.

  As a material of the second reflection layer 6, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, a metal of Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta and Pd is used alone or in an alloy. Can be used. Among them, Au, Al and Ag have high reflectivity and are suitable as the material of the second reflection layer 6. In addition to these as main components, the following may be included as other components. Examples of other components include Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Cu, Zn, Cd, Ga, In, Si, Ge, Te, and Pb. , Po, Sn, Bi and rare earth metals.

Above all, those containing Ag as a main component are particularly preferable in that they are inexpensive, easily produce high reflectivity, and when a print accepting layer described later is provided, a white and beautiful ground color can be obtained. Here, the main component means one having a content of 50% or more.
In order to ensure high durability (high corrosion resistance) of the second reflective layer 6, Ag is preferably used as an alloy rather than pure silver.

Above all, it is preferable to contain 0.1 to 15 atomic% of at least one element selected from the group consisting of Ag, Ti, Zn, Cu, Pd, Au and rare earth metal. When containing two or more of Ti, Zn, Cu, Pd, Au and rare earth metals, each may be 0.1 to 15 atomic%, but the total thereof is preferably 0.1 to 15 atomic%. .
A particularly preferred alloy composition is one containing Ag as a main component, containing at least one element selected from the group consisting of Ti, Zn, Cu, Pd, and Au in an amount of 0.1 to 15 atomic%, and at least one rare earth element. Is contained in an amount of 0.1 to 15 atomic%. Among rare earth metals, neodymium is particularly preferred. Specifically, it is AgPdCu, AgCuAu, AgCuAuNd, AgCuNd, or the like.

As the second reflective layer 6, a layer made of only Au is preferable because it has high durability (high corrosion resistance). However, they are more expensive than Ag alloys.
It is also possible to form a multilayer film by alternately stacking low-refractive-index thin films and high-refractive-index thin films with a material other than metal, and use the multilayer film as the second reflective layer 6.
Examples of a method for forming the second reflective layer 6 include a sputtering method, an ion plating method, a chemical vapor deposition method, and a vacuum vapor deposition method. Further, a known inorganic or organic intermediate layer or adhesive layer may be provided above and below the second reflective layer 6 for the purpose of improving the reflectance, improving the recording characteristics, improving the adhesion, and the like.
(G) Adhesive Layer 7 The adhesive layer 7 does not need to be transparent, but preferably has a high adhesive strength and a small shrinkage ratio during curing and bonding, because the shape stability of the medium is high.

It is desirable that the adhesive layer 7 be made of a material that does not damage the second reflection layer 6. However, a known inorganic or organic protective layer may be provided between both layers to suppress damage.
In the present optical recording medium, the thickness of the adhesive layer 7 is usually preferably 2 μm or more. In order to obtain a predetermined adhesive strength, a certain film thickness is required. More preferably, it is 5 μm or more. However, in order to make the optical recording medium as thin as possible, and there is a problem that the curing takes time and the productivity is lowered, the thickness is usually preferably 100 μm or less.

As the material of the adhesive layer 7, the same material as the material of the intermediate resin layer 4 can be used, and a pressure-sensitive double-sided tape or the like can also be used. The adhesive layer 7 can be formed by sandwiching and pressing the pressure-sensitive double-sided tape between the second reflective layer 6 and the second substrate 8.
(H) Second Substrate 8 The second substrate 8 preferably has shape stability so that the optical recording medium has a certain degree of rigidity. That is, it is preferable that the mechanical stability is high and the rigidity is high. Further, it is desirable that the adhesiveness with the adhesive layer 7 is high.

As described above, when the first substrate 1 does not have sufficient shape stability, the second substrate 8 needs to have particularly high shape stability. In this respect, it is desirable that the hygroscopicity is small. However, the second substrate 8 does not need to be transparent. Further, the second substrate 8 may be a mirror-finished substrate, and it is not necessary to form irregularities, so that transferability by injection molding is not necessarily required to be good.
As such a material, the same material as the material that can be used for the first substrate 1 can be used. For example, for example, an Al alloy substrate such as an Al—Mg alloy containing Al as a main component, A Mg alloy substrate such as an Mg-Zn alloy, a substrate made of any of silicon, titanium, and ceramics, a substrate obtained by combining them, and the like can be used.

In addition, polycarbonate is preferable in terms of high productivity such as moldability, cost, low moisture absorption, shape stability, and the like. Amorphous polyolefin is preferred from the viewpoints of chemical resistance, low hygroscopicity and the like. Further, a glass substrate is preferable in terms of high-speed response and the like.
In order to provide the optical recording medium with sufficient rigidity, the second substrate 8 is preferably thick to some extent, preferably 0.3 mm or more. However, a thinner one is advantageous for making the recording / reproducing apparatus thinner, and is preferably 3 mm or less. More preferably, it is 1.5 mm or less.

The second substrate 8 may be a mirror-finished substrate having no irregularities, but is preferably manufactured by injection molding from the viewpoint of ease of production.
In an example of a preferred combination of the first substrate 1 and the second substrate 8, the first substrate 1 and the second substrate 8 are made of the same material and have the same thickness. Since the rigidity is the same and the balance is maintained, it is preferable that the medium does not easily deform as a medium against environmental changes. In this case, it is preferable that the degree and direction of the deformation when the environment changes are the same for both substrates.

An example of another preferable combination is that the first substrate 1 is as thin as about 0.1 mm and the second substrate 8 is as thick as about 1.1 mm. This is preferable because the objective lens can easily approach the recording layer and increase the recording density. At this time, the first substrate 1 may be in a sheet shape.
(I) Other Layers In the above-mentioned laminated structure, any other layers may be interposed as necessary. Alternatively, any other layer may be provided on the outermost surface of the medium. Specifically, an intermediate layer is provided between the first reflective layer 3 and the intermediate resin layer 4, between the intermediate resin layer 4 and the second recording layer 5, between the second reflective layer 6 and the adhesive layer 7, and the like. May be provided as a buffer layer.

The buffer layer prevents mixing of the two layers and prevents compatibility. The buffer layer may also have another function other than preventing the mixing phenomenon. Further, another intermediate layer may be interposed as needed.
The material of the buffer layer must be incompatible with the second recording layer 5 and the intermediate resin layer 4 and have a certain degree of light transmittance, but known inorganic and organic substances can be used. In terms of characteristics, an inorganic substance is preferably used. For example, (i) metal or semiconductor, (ii) oxide, nitride, sulfide, oxysulfide, fluoride or carbide of metal or semiconductor, or (iii) amorphous carbon is used. Above all, a layer made of a substantially transparent dielectric or a very thin metal layer (including an alloy) is preferable.

Specifically, silicon oxides, particularly silicon dioxide, oxides such as zinc oxide, cerium oxide and yttrium oxide; sulfides such as zinc sulfide and yttrium sulfide; nitrides such as silicon nitride; silicon carbide; (Oxysulfide); and alloys described below are preferred. Further, a mixture of silicon oxide and zinc sulfide in a ratio of about 30:70 to 90:10 (weight ratio) is also suitable. Also, sulfur and a mixture of zinc oxide yttrium dioxide _{(Y 2 O 2 S-ZnO} ) is also suitable.

  As the metal or alloy, silver or a material containing silver as a main component and further containing 0.1 to 15 atomic% of at least one element selected from the group consisting of titanium, zinc, copper, palladium, and gold is preferable. is there. Further, those containing silver as a main component and containing at least one kind of rare earth element in an amount of 0.1 to 15 atomic% are also suitable. As the rare earth, neodymium, praseodymium, cerium and the like are suitable.

In addition, a resin layer may be used as long as it does not dissolve the dye in the recording layer during the preparation of the buffer layer. In particular, a polymer film that can be formed by vacuum evaporation or CVD is useful.
The thickness of the buffer layer is preferably 2 nm or more, more preferably 5 nm or more. If the thickness of the buffer layer is too thin, the prevention of the above-mentioned mixing phenomenon may be insufficient. However, it is preferably 2000 nm or less, more preferably 500 nm or less. If the buffer layer is excessively thick, it is not only unnecessary for prevention of miscibility, but also may decrease the light transmittance. In the case of a layer made of an inorganic substance, it takes a long time to form the film, which may lower the productivity or increase the film stress. In particular, in the case of metal, the thickness is preferably about 20 nm or less in order to excessively reduce the light transmittance.

Further, a protective layer may be provided to protect the recording layer and the reflective layer. The material of the protective layer is not particularly limited as long as it protects the recording layer and the reflective layer from external force. Examples of the material of the organic substance include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin. Further, examples of the inorganic substance include silicon oxide, silicon nitride, MgF ₂ , and SnO ₂ .

  A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in a suitable solvent to prepare a coating solution, and applying and drying the coating solution. The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving it in an appropriate solvent, applying the coating solution, and irradiating with UV light to cure the resin. As the ultraviolet curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. These materials may be used singly or as a mixture, or may be used not only as a single layer but also as a multilayer film.

As a method of forming the protective layer, a coating method such as a spin coating method or a casting method, a sputtering method, a chemical vapor deposition method, or the like is used as in the case of the recording layer. Among them, the spin coating method is preferable.
The thickness of the protective layer is generally in the range of 0.1 to 100 μm, but is preferably 3 to 50 μm in the present optical recording medium.

Further, the optical recording medium may be printed on a surface other than the incident surface of the recording light or the reproduction light, if necessary, with various printers such as ink jet and thermal transfer, or various writing tools. A layer may be provided.
Alternatively, a recording layer may be provided in addition to the main layer structure, and three or more recording layers may be provided. Alternatively, two optical recording media having the present layer configuration and the first substrate 1 facing outward may be bonded together to form a larger capacity medium having four recording layers.
(B) Type 2
FIG. 2 is a schematic sectional view showing an optical recording medium (type 2) according to the present embodiment.

  The type 2 optical recording medium (laminated single-sided incident type optical recording medium) according to this embodiment is a disk-shaped transparent (light-transmitting) first substrate (first substrate, first light-transmitting substrate). On a substrate 21, a first recording layer containing a dye (a first recording layer, a first dye-containing recording layer) 22, a translucent first reflective layer (hereinafter also referred to as a translucent reflective layer) 23, and a transparent adhesive Layer (intermediate layer) 24, buffer layer 28, second recording layer containing dye (second recording layer, second dye-containing recording layer) 25, second reflective layer 26, disk-shaped transparent second substrate (second 2 substrates 27) in this order. The light beam is irradiated from the first substrate 21 side, and recording or reproduction is performed. Note that being transparent means being transparent to a light beam used for recording or reproduction of an optical recording medium.

Irregularities are formed on the first substrate 21 and the second substrate 27, respectively, and constitute recording tracks. The recording track 31 on the first substrate 21 is configured by a convex portion in the light incident direction. The recording tracks 32 on the second substrate 27 are formed by concave portions in the light incident direction.
The recording track 31 is formed by a groove in the first substrate 21, that is, a concave portion with respect to the light incident direction, and the recording track 32 is formed by a groove in the second substrate 27, that is, a convex portion with respect to the light incident direction. In general, it is preferable that the recording track 31 is formed by a convex portion in the light incident direction, and the recording track 32 is formed by a concave portion in the light incident direction. In addition, it may have a concave and convex pit as required. Unless otherwise specified, the unevenness in this embodiment is defined with respect to the incident direction of light used for recording or reproduction.

Next, each layer will be described.
The first substrate 21, the first recording layer 22, the first reflection layer 23, the second recording layer 25, and the second reflection layer 26 of the type 2 optical recording medium according to the present embodiment are each a type 1 optical recording medium. It is substantially the same as the first substrate 1, the first recording layer 2, the first reflection layer 3, the second recording layer 5, and the second reflection layer 6.
Further, the transparent adhesive layer 24 as the intermediate layer is substantially the same as the intermediate resin layer 4 of the type 1 optical recording medium except that it is not necessary to form grooves or pits due to unevenness. In the type 2 optical recording medium, the above-described grooves and pits are formed in a second substrate 27 described later.

Further, the buffer layer 28 as the intermediate layer has substantially the same configuration as the buffer layer described in the first embodiment. This buffer layer may be formed as needed.
The second substrate 27 is desirably transparent and has shape stability so that the optical recording medium has some rigidity. That is, it is preferable that the mechanical stability is high and the rigidity is high.

Examples of such a material include resins made of acrylic resin, methacrylic resin, polycarbonate resin, polyolefin resin (especially amorphous polyolefin), polyester resin, polystyrene resin, epoxy resin, and the like, and those made of glass. Can be used.
On the second substrate 27, irregularities are provided spirally or concentrically to form grooves and lands. Usually, information is recorded or reproduced on the second recording layer 25 using such grooves and / or lands as recording tracks. Normally, since the second recording layer 25 is formed by coating, the second recording layer 25 becomes a thick film at the groove portion and is suitable for recording or reproduction. In the present optical recording medium, it is preferable that the groove portion of the second substrate 27, that is, the concave portion in the light incident direction be the recording track 32. Here, the concave portion and the convex portion refer to the concave portion and the convex portion with respect to the light incident direction, respectively. Usually, the groove width is about 50 to 500 nm, and the groove depth is about 10 to 250 nm. When the recording track is spiral, the track pitch is preferably about 0.1 to 2.0 μm. In addition, if necessary, a concavo-convex pit such as a land pre-pit may be provided.

From the viewpoint of cost, the second substrate 27 having such irregularities is preferably manufactured by injection molding using a resin from a stamper having irregularities. When a resin layer made of a radiation curable resin such as a photocurable resin is provided on a substrate such as glass, irregularities such as recording tracks may be formed on the resin layer.
Here, a write-once optical recording medium (here, DVD-R) including a dye-containing recording layer has been described, but the optical recording medium is not limited to this, and information can be obtained by irradiating laser light from one side. Any optical recording medium having a plurality of recording layers capable of recording or reproducing the information may be used. For example, as a recording layer, for example, a rewritable optical recording medium (for example, DVD-RW, DVD + RW, or DVD-RW) including a phase-change recording layer in which a portion in a crystalline state is in an unrecorded state / erased state and a portion in an amorphous state is in a recorded state. A magneto-optical recording medium including a magnetic recording layer as a recording layer may be used.

Here, when the optical recording medium is a DVD-RW, the address information may be recorded in advance by land pre-pits as in the case of the DVD-R described above. When the optical recording medium is DVD + RW, the address information may be recorded in advance by superimposing the address information on the wobble (this is referred to as ADIP; Address in Pre-groove).
When the present invention is applied to a rewritable optical recording medium including a phase-change recording layer, both the first recording layer and the second recording layer of the optical recording medium in the above-described embodiment are the first protective layer. , An information recording layer, and a second protective layer.

  Here, as the material of the information recording layer, it is preferable to use a material whose optical constants (refractive index n, extinction coefficient k) change when irradiated with laser light. Examples of such materials include chalcogenides based on Te and Se, for example, Ge-Sb-Te, Ge-Te, Pd-Ge-Sb-Te, In-Sb-Te, Sb-Te, Ag-In-Sb. -Te, Ge-Sb-Bi-Te, Ge-Sb-Se-Te, Ge-Sn-Te, Ge-Sn-Te-Au, Ge-Sb-Te-Cr, In-Se, In-Se-Co And the like, or an alloy system in which nitrogen, oxygen or the like is appropriately added thereto.

  In addition, as materials of the first protective layer and the second protective layer, the increase in noise due to thermal damage to the protective substrate, the information recording layer, and the like at the time of laser light irradiation, suppression of laser light reflectance, absorptance, and reflected light For the purpose of adjusting the phase and the like, it is preferable to use a material that is physically and chemically stable, has a higher melting point and softening temperature than the information recording layer, and does not form a solid solution with the material of the information recording layer. Examples of such a material include oxides of Y, Ce, Ti, Zr, Nb, Ta, Co, Zn, A1, Si, Ge, Sn, Pb, Sb, Bi, Te, and the like, and Ti, Zr, Nb. , Ta, Cr, Mo, W, B, Al, Ga, In, Si, Ge, Sn, Pb and other nitrides, Ti, Zr, Nb, Ta, Cr, Mo, W, Si and other carbides, Zn, Examples of the dielectric material include a sulfide such as Cd, a selenide or telluride, a fluoride such as Mg or Ca, a simple substance such as C, Si, or Ge, or a mixture thereof, or a material similar to a dielectric. The first protective layer and the second protective layer may be made of the same material, but may be made of different materials as needed.

  By the way, as described above, a plurality of (here, two) recording layers 2, 5 (22, 25) are provided, and each layer 2, 5 (22, 25) is irradiated with laser light from one side. In a single-sided optical recording medium (for example, a dual-layer type single-sided DVD-R) that records or reproduces information on a recording layer, optimum recording and reproducing conditions such as a recording pulse strategy, recording power, and reproducing power are provided for each recording layer. Will be significantly different. The recording / reproducing conditions include a recording condition such as a recording pulse strategy (write strategy) and a recording power, and a reproducing condition such as a reproducing power.

In particular, it is important to optimize the recording conditions. This does not mean that it is not possible to reproduce even if the reproduction conditions are slightly deviated, but if the recording conditions are not optimal, it is impossible to actually write, or even if the information can be reproduced, the information is reproduced. This is because the signal quality is not good.
Therefore, in a recording / reproducing apparatus (drive) for recording or reproducing information on or from each of the recording layers 2, 5 (22, 25) of the single-sided incident type optical recording medium having a plurality of recording layers, the recording layers 2, 5 are used. In accordance with (22, 25), it is desirable to be able to switch recording / reproducing conditions such as a recording pulse strategy, recording power, and reproducing power so that information can be recorded or reproduced accurately and reliably. In particular, since it is important to optimize the recording conditions as described above, it is possible to switch to the optimal recording conditions according to the recording layers 2 and 5 (22, 25), and to record information. I want to be able to do it accurately and reliably.

In this case, for example, it is conceivable to assign address information continuously over a plurality of recording layers 2 and 5 (22, 25), and to determine which layer is based on the read address information in the recording / reproducing apparatus. However, it is difficult to judge instantly which layer this is.
Therefore, in the present embodiment, for example, according to the recording layers 2 and 5 (22 and 25) on which information is to be recorded or reproduced, for example, a recording pulse strategy (recording strategy, write strategy), a recording power, a reproduction power, and the like. Layer information (information on the recording layer number; layer 0, layer 1) is recorded in each of the recording layers 2, 5 (22, 25) of the optical recording medium so that the recording / reproducing conditions can be instantaneously switched. I have.

Here, as a recording method of the layer information, for example, the following methods (i) and (ii) can be considered.
(i) Recording is performed by a prepit (land prepit) or wobble, for example, in a recording management area (RMA; for example, a control track, the innermost periphery) of each recording layer 2, 5 (22, 25).
(ii) Recording is performed over substantially the entire recording area of each of the recording layers 2 and 5 (22, 25) by, for example, pre-pits (land pre-pits) or wobbles. Here, in order to record “substantially all over”, recording is performed over the entire recording area including the recording management area of each of the recording layers 2 and 5 (22, 25) (for example, recording is performed as part of an address in the recording management area). And recording on the entire recording area excluding the recording management area of each of the recording layers 2 and 5 (22, 25). In particular, when the layer information cannot be recorded in the recording management area, it is effective to record the entire area of the recording area excluding the recording management area. It is also effective when recording or reproducing information by random access.

  For example, it may be recorded as part of address information of wobbles and prepits (land prepits). Thus, layer information can be recorded on each of the recording layers 2 and 5 (22, 25) by a simple method. Also, by recording layer information as a part of the address information, when recording or reproducing information by random access based on the address information, the layer can be obtained simply by accessing a desired address and applying focus servo. Since the information can be read, the recording / reproduction conditions such as the recording pulse strategy, the recording power, and the reproduction power can be instantaneously switched based on the information.

Here, as a method of recording the layer information as a part of the address information, for example, the following methods (i) to (v) can be considered.
(i) First, as a method of recording as a part of wobble address information (for example, ADIP; Address in pre-groove), for example, in two recording layers 2, 5 (22, 25), wobble address information (for example, ADIP; There is a method of inverting a sync pattern (synchronous pattern) included in Address in pre-groove.

For example, the direction of the sync pattern (synchronous pattern) included in the ADIP of the second recording layer 5 (25) is opposite to the direction of the sync pattern (synchronous pattern) included in the ADIP of the first recording layer 2 (22). What is necessary is just to make a direction (reversal).
(ii) As a method of recording as a part of address information of wobbles and land prepits formed in the recording area (including the recording management area) of each recording layer 2, 5 (22, 25), There is a method in which the value of the reserved bit differs in 2,5 (22, 25).

For example, the wobble formed in the recording area (including the recording management area) of the first recording layer 2 (22) and the value of the reserved bit of the address information of the LPP are recorded in the recording area (recording) of the second recording layer 5 (25). The value may be different from the value of the reserve bit of the address information of the wobble or land pre-pit formed in the management area (including the management area).
Here, the reserved bit refers to a bit in a part that is not currently used in the area where the address information is recorded. For recording information in the reserved bits, the same modulation method and recording method as the address information may be applied. When a plurality of recording layers are provided, it is necessary to increase the number of reserved bits to be used according to the number of recording layers. For example, in the case of having two recording layers, one bit may be used as a reserved bit, and the value of 0 or 1 may be used to distinguish the first layer from the second layer. If two bits are used as reserved bits, four values of 00, 01, 10, and 11 can be represented by two bits, so that four recording layers can be distinguished. Similarly, if three bits are used as reserved bits, eight values can be represented, so that eight recording layers can be distinguished. That is, if n bits are used as reserved bits, 2 ⁿ recording layers can be distinguished. It should be noted that the number of reserved bits to be used can be reduced by combining with other methods such as the method (i) and the following methods (iii) to (v).
(iii) As a method of recording as a part of address information of wobbles and land pre-pits formed in a recording area (including a recording management area) of each recording layer 2, 5 (22, 25), two recording methods are used. There is a method of bit inverting the entire address information of wobbles and land pre-pits in one of the recording layers in layers 2 and 5 (22 and 25).

For example, when the addresses 3000 to 4FFF (Hex) are put in the first recording layer 2 (22) and the addresses 5000 to 6FFF (Hex) are put in the second recording layer 5 (25), the second recording layer 5 (25) ), The address is AFFF to 9000 (Hex).
Here, for simplicity, the description has been made using only 16 bits (four digits in hexadecimal). However, in practice, there is a margin, for example, in a DVD-R, the address information is 48 bits (12 digits in hexadecimal). Therefore, the address of the first recording layer 2 (22) is 0000000003000-000000004FFF (Hex), and the address of the second recording layer 5 (25) is FFFFFFFFAFFF to FFFFFFFF9000 (Hex).

It is necessary that the drive has information for associating which range of addresses belongs to which layer so that the layer can be determined when the address is read.
(iv) As a method of recording as part of address information of wobbles and land prepits formed in the recording area (including the recording management area) of each recording layer 2, 5 (22, 25), two recording methods are used. There is a method in which the entire address information of wobbles and land prepits in one of the recording layers in layers 2 and 5 (22 and 25) is represented by 2's complement (total bit inversion + 1).

For example, when the addresses 3000 to 4FFF (Hex) are put in the first recording layer 2 (22) and the addresses 5000 to 6FFF (Hex) are put in the second recording layer 5 (25), the second recording layer 5 (25) ) Is represented by two's complement (inverting the whole bit + 1), and the address may be set to B000 to 9001 (Hex).
Here, for simplicity, the description has been made using only 16 bits (four digits in hexadecimal). However, in practice, there is a margin, for example, in a DVD-R, the address information is 48 bits (12 digits in hexadecimal). Therefore, the address of the first recording layer 2 (22) is 0000000003000 to 000000004FFF (Hex), and the address of the second recording layer 5 (25) is FFFFFFFFB000 to FFFFFFFF9001 (Hex).

It is necessary that the drive has information for associating which range of addresses belongs to which layer so that the layer can be determined when the address is read.
(v) Further, as a method of recording as a part of address information of a wobble or a land prepit formed in a recording area (including a recording management area) of each of the recording layers 2 and 5 (22, 25), two recording methods are used. There is a method of recording the wobble of any one of the layers 2 and 5 (22, 25) or the most significant bit of the address information of the land prepit.

For example, the value obtained by inverting the value of the most significant bit of the address information of the wobble or the land pre-pit in one of the first recording layer 2 (22) and the second recording layer 5 (25) is referred to as , The wobble of the other recording layer and the most significant bit of the land prepit address information.
More specifically, for example, when the address 000000000000-000000004FFF (Hex) is put in the first recording layer 2 (22) and the address 00000000000000-000000006FFF (Hex) is put in the second recording layer 5 (25), the second recording is performed. Only the most significant bit of the layer 5 (25) needs to be inverted.

  In this case, "0" becomes "1" when the bit is inverted with a binary number, but "0" becomes "8" when expressed in hexadecimal (Hex). For this reason, the address of the first recording layer 2 (22) is 000000000300-0000000004FFF (Hex), and the address of the second recording layer 5 (25) is 800000000050000 to 80000000006FFF (Hex). It is necessary for the drive to recognize the most significant bit of the address as layer information.

Here, the case where the present invention is applied to an optical recording medium including two recording layers capable of recording or reproducing information by irradiating laser light from one side has been described, but the present invention is not limited to this. For example, the above-described layer information recording method may be applied alone or in combination to an optical recording medium having three or more recording layers and capable of recording or reproducing information by irradiating laser light from one side. it can. In this case, the above-described layer information recording method may be applied to two adjacent recording layers among the plurality of recording layers.
(2) Recording / Reproducing Method of Optical Recording Medium Hereinafter, an outline of the recording / reproducing method of the optical recording medium configured as described above will be described.

For recording on the present optical recording medium (type 1 and type 2) obtained as described above, a laser beam focused on the recording layer to a diameter of about 0.5 to 1 μm is irradiated from the first substrate 21 side. It is done by doing. In the portion irradiated with the laser light, thermal deformation of the recording layer such as decomposition, heat generation, and melting occurs due to absorption of laser light energy, and optical characteristics change.
Reproduction of recorded information is performed by reading the difference in reflectance between a portion where optical characteristics have changed and a portion where optical characteristics have not changed using a laser beam.

  Further, recording or reproduction is individually performed on the two recording layers as follows. The focus position of the focused laser can be distinguished from the first recording layers 2 and 22 and the second recording layers 5 and 25 by a focus error signal obtained by a knife edge method, an astigmatism method, a Foucault method, or the like. That is, when the objective lens that focuses the laser light is moved up and down, the S-shaped curves are obtained at the positions corresponding to the first recording layers 2 and 22 and the positions corresponding to the second recording layers 5 and 25, respectively. can get. Depending on which S-shaped curve is used for focus servo, it is possible to select which of the first recording layers 2 and 22 and the second recording layers 5 and 25 to record or reproduce.

  In the type 1 optical recording medium, preferably, the first substrate 1 and the intermediate resin layer 4 are formed with irregularities as shown in FIG. Recording or reproduction is performed as a recording track. Usually, since the dye recording layer is formed by coating, the dye recording layer becomes a thick film at the groove and is suitable for recording or reproduction. In the type 1 optical recording medium, the groove of the first substrate 1, that is, the convex portion in the light incident direction is used as the recording track 11, and the groove of the intermediate resin layer 4, that is, the convex portion in the light incident direction is recorded. Track 12 is preferred.

  Further, in the type 2 optical recording medium, preferably, as shown in FIG. 2, the first substrate 21 and the second substrate 27 are respectively formed with irregularities, and the convex portions of the first substrate 21 and the concave portions of the second substrate 27 are formed. Recording or reproduction is performed using the as a recording track. The polarity of the tracking servo may be reversed between the first recording layer 22 and the second recording layer 25 in some cases. In the type 2 optical recording medium, the groove of the first substrate 21, that is, the convex portion in the light incident direction is defined as the recording track 31, and the groove of the second substrate 27, that is, the concave portion in the light incident direction is defined as the recording track. It is preferably 32.

The laser light used for the present optical recording medium (type 1 and type 2) includes N ₂ , He—Cd, Ar, He—Ne, ruby, semiconductor, dye laser, and the like. Therefore, a semiconductor laser is preferred because of its ease of handling.
The shorter the wavelength of the laser light used is for high-density recording, the more preferable is the laser light of 350 to 530 nm. Representative examples of such laser light include laser lights having center wavelengths of 405 nm, 410 nm, and 515 nm.

  An example of a laser beam having a wavelength in the range of 350 to 530 nm can be obtained by using a high-power semiconductor laser of 405 nm, 410 nm blue or 515 nm blue-green. Either a semiconductor laser capable of continuous oscillation of 740 to 960 nm or (b) a solid-state laser excited by the semiconductor laser and capable of continuous oscillation having a fundamental oscillation wavelength of 740 to 960 nm is subjected to a second harmonic generation element (SHG). It can also be obtained by wavelength conversion.

The SHG may be any piezo element that lacks inversion symmetry, but is preferably KDP, ADP, BNN, KN, LBO, or a compound semiconductor. As a specific example of the second harmonic, a semiconductor laser having a fundamental oscillation wavelength of 860 nm is a harmonic of 430 nm, and a solid laser excited by a semiconductor laser is a Cr-doped LiSrAlF ₆ crystal (fundamental oscillation wavelength of 860 nm). 430 nm, which is a harmonic of the same.
(3) Recording / reproducing apparatus for optical recording medium By the way, as described above, a light for recording or reproducing information on or from an optical recording medium in which information relating to a recording layer number (layer information) is recorded in each recording layer. The recording / reproducing apparatus for a recording medium is configured as follows.

The recording / reproducing device (drive) may be any device that can record or reproduce information recorded on an optical recording medium. For example, a recording device (writer) that performs only recording and a reproducing device that performs only reproducing (Reader) and a recording / reproducing device (reader / writer) that performs both recording and reproduction.
As shown in FIG. 3, the recording / reproducing apparatus 60 includes a spindle motor 51 for driving the optical recording medium 50 to rotate, a motor driver 52 for driving the spindle motor 51, an optical pickup 53, and an optical drive for driving the optical pickup 53. A pickup driver 54, a servo processor 55 used for performing various servo controls, a signal processing unit (reproduction processing unit) 56 for processing a signal detected by the optical pickup 53, and a signal sent from another computer or the like. A data processing unit (recording processing unit) 57 that processes incoming information (data) and a control unit 58 (for example, a microcomputer that includes a CPU 58A and a memory 58B) that controls each device are configured.

Here, the optical pickup 53 is configured to include, for example, a laser diode, a photodetector (for example, a photodetector), a pickup actuator used for focusing and tracking, and the like.
As shown in FIG. 3, the optical pickup driver 54 includes a laser driver (laser diode driver) 54A that drives a laser diode, a focus driver 54B that drives a pickup actuator, a tracking driver 54C that drives a pickup actuator, and 54C. And is configured to include:

Here, the laser driver 54A is configured to include a reproducing laser driver 54Aa for driving a reproducing laser diode and a recording laser driver 54Ab for driving a recording laser diode.
The servo processor 55 is configured to include a focus servo circuit 55A for performing focus servo and a tracking servo circuit 55B for performing tracking servo.

  The signal processing unit 56 includes a preamplifier 56A that amplifies the signal detected by the optical pickup 53, and a focus error signal, a tracking error signal, an address signal of a wobble or a land prepit [address information ( And a demodulation circuit for demodulating an address signal [address information; including recording layer number (layer information)] generated by the matrix circuit 56B. 56C. The data signal is processed through a binarization circuit and a demodulation circuit (not shown) and then sent to a computer or the like.

When address information including layer information is recorded by pre-pits (ROM pits) when the optical recording medium 50 is manufactured, the signal processing unit 56 includes a matrix circuit, a binarization circuit, and a demodulation circuit. What is necessary is just to comprise as what is provided.
The data processing unit 57 includes a modulation circuit 57A that modulates data transmitted from another computer or the like together with address information, and controls a recording pulse to the recording laser driver 54Ab based on the modulated data. And a write strategy circuit (write strategy circuit) 57B for performing multi-pulse modulation.

Next, processing (recording / reproducing method, recording method, and reproducing method of the optical recording medium) performed by the control unit 58 of the recording / reproducing apparatus 60 for the optical recording medium configured as described above will be described. This will be described with reference to FIG.
Here, a case where information is recorded (or reproduced) on an optical recording medium 50 having two recording layers 2 and 5 (22, 25) and layer information recorded on almost the entire surface of the recording layer. An example is described.

  When a recording command is input from a computer such as a personal computer (or via an input unit such as a button provided on the drive itself), the recording / reproducing apparatus (drive) 60 for the optical recording medium controls the control unit 58. Accesses the table of contents information area included in the recording area of the medium and determines which address can be written. Then, based on the address determined to be writable, it is determined which recording layer is to be recorded (step S10). When the table of contents information area is accessed when the medium is set in the drive and the table of contents information is read in advance, it is determined which address can be written using the previously read table of contents information. What is necessary is just to make a determination.

Here, when layer information is included in the address information, it is possible to determine which recording layer to record on by detecting the layer information included in the address information, and to provide the drive with the address information. In a case where a table in which the information is associated with the layer information is provided, the layer information can be determined from the address information using this table.
On the other hand, when a playback command is input from a computer such as a personal computer (or via an input unit such as a button provided on the drive itself), the control unit 58 performs control based on the address information included in the playback command. Then, which recording layer is to be recorded is determined (step S10).

Here, when the medium is set in the drive, the table of contents information (information on which address is recorded at which address) is read from the medium, and an icon is displayed on a screen of a computer, for example. When clicked, a reproduction command including address information may be input to the drive.
As described above, when the recording command (or the reproduction command) is input, the control unit 58 specifies the recording layer on which the recording (or the reproduction) is performed. The function of the control unit 58 is called a recording layer determining unit (recording layer specifying unit).

  When a recording command (or a reproduction command) is input, the control unit 58 issues a focus servo command to the focus servo circuit 55A, and the focus servo circuit 55A that has received the command issues a focus driver 54B or a pickup driver. By controlling the optical pickup 53 via the actuator, focus servo is applied to any one of the first recording layer 2 (22) and the second recording layer 5 (25) (Step S20). . The function of the control unit 58 is called a focus servo control unit.

  Here, when layer information is recorded as a part of the address information on almost the entire recording layers 2 and 5 (22, 25) of the optical recording medium 50, a desired address is accessed based on the address information. It is only necessary to operate the focus servo in the state where it is set. On the other hand, when layer information is recorded in the recording management area of the optical recording medium 50, focus servo may be performed in this recording management area.

When recording (or reproducing) information on an optical recording medium having a plurality of recording layers, focus servo may be applied to any one of the plurality of recording layers.
Next, the control unit 58 reads out layer information (layer information) recorded on one recording layer on which focus servo has been applied, via the preamplifier 56A, the matrix circuit 56B, and the demodulation circuit 56C as the signal processing unit 56. (Step S30). The function of the control unit 58 is called a layer information reading unit.

Then, the control unit 58 determines whether or not the recording layer specified by the layer information read in step S30 is the recording layer specified as the recording layer to be recorded or reproduced in step S10 (step S40). ). The function of the control unit 58 is called a recording layer determination unit.
As a result of this determination, when it is determined that the recording layer specified by the read layer information is the recording layer specified as the recording layer to be recorded (specific recording layer to be recorded), the control unit 58 A recording command is issued to the optical pickup 53 via the processing unit 57 and the recording laser driver 54Ab, and the laser diode is driven in response thereto, and is specified by the address information of one recording layer on which focus servo has been applied. Tracking is performed via the tracking servo circuit 55B and the tracking driver 54C in the address under recording conditions (recording / reproduction conditions) such as a recording pulse strategy and recording power according to the recording layer (recording layer specified by the layer information). Information (data, etc.) sent from a personal computer or other device The recording is performed (step S50). The function of the control unit 58 is called a recording control unit (recording / reproduction control unit).

  Note that the recording / reproducing conditions may be determined based on the information recorded in advance on the optical recording medium and read out from the optical recording medium, or may be determined based on the information stored in advance in the recording / reproducing apparatus according to the layer information. May be. For example, the recommended recording power or the recommended reproduction power may be recorded on an optical recording medium, and the drive may read the recommended power and determine the recording power or the reproduction power based on the read power.

Also, the drive stores the recommended recording power or the recommended reproduction power according to the layer information, and reads the recommended recording power or the recommended reproduction power corresponding to the layer information based on the stored recommended power or the read recommended recording power or the read recommended power. The recording power or the reproduction power may be determined based on the reproduction recommended power.
Further, in some cases, after reading the recommended recording power, the recording power may be determined by performing OPC (Optimum Power Control).

  On the other hand, as a result of the above determination, when it is determined that the recording layer specified by the read layer information is the recording layer specified as the recording layer to be reproduced (the specific recording layer to be reproduced), the control unit 58 Issues a playback command to the optical pickup 53 via the playback laser driver 54Aa, and sets playback conditions (recording / playback conditions) such as, for example, playback power according to the recording layer (recording layer specified by the layer information). While the tracking is performed via the tracking servo circuit 55B and the tracking driver 54C, the information recorded at the address specified by the address information of one recording layer on which the focus servo is performed is reproduced via the signal processing unit 56. (Step S50). The function of this control unit is called a reproduction control unit (recording / reproduction control unit).

  If the control unit 58 determines in step S40 that the recording layer specified by the read layer information is not the recording layer to be recorded (or reproduced), the process returns to step S20, and another recording is performed. The focus servo is applied to the layer, and thereafter, the same processing (steps S20 to S40) is performed until it is determined that the recording layer specified by the read layer information is the recording layer to be recorded (or reproduced). ) Is repeated.

Therefore, according to the optical recording medium, the recording / reproducing method of the optical recording medium, and the recording / reproducing apparatus of the optical recording medium according to the present embodiment, for example, according to the recording layer on which information is to be recorded or reproduced, for example, the recording pulse strategy There is an advantage that the recording and reproducing conditions such as recording power and reproducing power can be instantaneously switched.
It should be noted that the present invention is not limited to the above embodiment, and can be implemented with various modifications without departing from the spirit of the present invention.

FIG. 1 is a schematic diagram illustrating an overall configuration of an optical recording medium (type 1) according to an embodiment of the present invention. FIG. 1 is a schematic diagram illustrating an overall configuration of an optical recording medium (type 2) according to an embodiment of the present invention. FIG. 1 is a schematic diagram showing an overall configuration of a recording / reproducing apparatus for an optical recording medium according to an embodiment of the present invention. 4 is a flowchart showing a process executed by a control unit of the optical recording medium recording / reproducing apparatus according to one embodiment of the present invention.

Explanation of reference numerals

1,21 1st substrate (1st substrate)
2,22 First recording layer (first recording layer)
3, 23 First reflection layer 4 Intermediate resin layer (intermediate layer)
5,25 Second recording layer (second recording layer)
6, 26 Second reflective layer 7 Adhesive layer 8, 27 Second substrate (second substrate)
28 buffer layer 11, 12, 31 recording track composed of convex portions 24 transparent adhesive layer (intermediate layer)
32 Recording track composed of concave portions 50 Optical recording medium 51 Spindle motor 52 Motor driver 53 Optical pickup 54 Optical pickup driver 54A Laser driver 54Aa Reproduction laser driver 54Ab Recording laser driver 54B Focus driver 55 Servo processor 55A Focus servo circuit 56 Signal processing Unit (reproduction processing unit)
56A Preamplifier 56B Matrix circuit 56C Demodulation circuit 57 Data processing unit (recording processing unit)
57A Modulation circuit 57B Recording strategy circuit 58 Control unit (microcomputer)
58A CPU
58B memory 60 recording / reproducing device (drive)

Claims (10)

A control unit configured to read layer information from one recording layer of an optical recording medium in which layer information is recorded on each of a plurality of recording layers capable of recording or reproducing information by irradiating laser light from one side; Steps and
Recording / reproduction control step of controlling the recording / reproduction to be performed under recording / reproduction conditions corresponding to the recording layer specified by the layer information. Method. A layer information reading unit that reads layer information from one recording layer of an optical recording medium in which layer information is recorded on each of a plurality of recording layers capable of recording or reproducing information by irradiation of laser light from one side,
A recording / reproducing control unit that controls recording or reproduction under recording / reproducing conditions corresponding to the recording layer specified by the layer information. An optical recording medium recorded or reproduced by the recording / reproducing method for an optical recording medium according to claim 1,
With a plurality of recording layers capable of recording or reproducing information by irradiating laser light from one side,
An optical recording medium, wherein layer information is recorded on each of the recording layers.   4. The optical recording medium according to claim 3, wherein the layer information is recorded on substantially the entire surface of each of the recording layers.   The optical recording medium according to claim 3, wherein the layer information is recorded as a part of address information.   The optical recording medium according to any one of claims 3 to 5, wherein the layer information is recorded by making different values of reserved bits included in address information in each of the recording layers. .   6. The layer information is recorded in two adjacent recording layers of the plurality of recording layers by inverting a sync pattern included in address information. The optical recording medium according to the paragraph.   In two adjacent recording layers of the plurality of recording layers, the most significant bit of the address information is inverted, the entire address information of one recording layer is inverted, or the entire address information of one recording layer is changed to 2 bits. The optical recording medium according to any one of claims 3 to 5, wherein the layer information is recorded by any one of the following methods.   9. The optical recording medium according to claim 7, wherein the plurality of recording layers include two recording layers.   The optical recording medium according to any one of claims 3 to 9, wherein each of the recording layers is a dye-containing recording layer.

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