JP4083667B2 - Optical recording medium - Google Patents

Description

  The present invention relates to a double-sided recording / reproducing type optical recording medium having three recordable recording layers mainly composed of an organic dye.

In addition to optical recording media such as read-only DVDs (digital versatile discs), recordable DVDs (DVD + RW, DVD + R, DVD-R, DVD-RW, DVD-RAM, etc.) have been put into practical use. These DVD + R, DVD + RW, etc. are positioned on the extension of conventional recordable CD-R, CD-RW (recordable compact disc) technology, and are recorded to ensure playback compatibility with playback-only DVDs. The density (track pitch, signal mark length) and substrate thickness are designed to meet the DVD conditions from the CD conditions.
For example, in the case of DVD + R, as in CD-R, an information recording substrate in which a dye is spin coated on a substrate to provide an optical recording layer and a metal reflective layer is provided behind it is formed in the same shape via a bonding material. A configuration in which the substrate is bonded is adopted. In this case, a dye material is used for the optical recording layer. CD-R is characterized by having a high reflectivity (65%) that satisfies the CD standard. In order to obtain a high reflectivity in the above configuration, the light absorption layer has a recording / reproducing light wavelength. This is because a specific complex refractive index needs to be satisfied, and the light absorption characteristics of the dye are suitable. The same applies to DVDs.

By the way, in the prior application (Japanese Patent Application No. 2003-145458), the present applicant has proposed a recordable DVD having two recording layers in order to increase the recording capacity. FIG. 1 is a cross-sectional view showing the structure of a DVD having such two recording layers, and is an example in which both the first recording layer and the second recording layer can be additionally written. DESCRIPTION OF SYMBOLS 1 is 1st board | substrate, 2 is 2nd board | substrate, 3 is 1st recording layer which has organic dye as a main component, 6 is 1st reflection layer, 5 is organic transparent intermediate | middle layer, 4 is mainly organic dye A second recording layer as a component, 7 is a second reflective layer, and 8 is an inorganic protective layer. In these first and second recording layers, recording and reproduction are performed by light from the first substrate surface side. Is called.
A first information substrate having a light guide groove in which a first recording layer and a first reflective layer are sequentially formed on the surface, and a second reflective layer, a second recording layer, and an inorganic protective layer are sequentially formed on the surface. A second information substrate having a light guide groove is bonded to the outside through an organic transparent intermediate layer, and good signal reflectivity can be obtained from the second recording layer. That is, the inorganic protective layer suppresses damage to the second recording layer due to adhesion with the organic transparent intermediate layer, and a high reflectivity is obtained from the second recording layer by the multiple interference effect at both interfaces of the dye recording layer. ing. Since signals can be read from the two recording layers, a maximum storage capacity of about 8.5 GB can be obtained.
The thickness of the first and second substrates is about 0.6 mm, and the thickness of the organic transparent intermediate layer is about 50 μm. The semi-transparent film serving as the first reflective layer is formed so that the reflectance thereof is about 30%, and the laser beam irradiated for recording on the second recording layer is the first reflective layer. After approximately 30% of the total amount of light is reflected and attenuated, it is reflected by the second reflective layer adjacent to the second recording layer, attenuates again by the first reflective layer, and exits the disk. Information recorded on each recording layer can be read by narrowing the reproducing laser beam so that the focal point is positioned on the first recording layer or the second recording layer and detecting the reflected light. In the case of DVD, the laser beam wavelength used for recording / reproduction is about 650 nm.

  In Patent Document 1, a signal layer is formed on at least one surface of a disk substrate, and at least one new signal layer is laminated on the signal layer via an intermediate layer to form a multilayer structure. An optical disc is proposed in which data is recorded or reproduced with respect to two or more signal layers. FIG. 2 is a cross-sectional view showing the structure of a DVD having such a multilayer recording layer. The optical disc 11 has a structure in which a lower signal layer 13 such as a concavo-convex shape or a guide groove is provided on at least one surface of a disc substrate 12, and a multilayer structure 14 is further laminated thereon. In the multilayer structure 14, the pressure-sensitive adhesive sheet layer 15 is formed on the lower signal layer 13, the UV curable resin layer 16 is further laminated thereon, and the upper signal layer 17 is laminated thereon. An optically transparent cover layer 18 is laminated on the substrate. The concave and convex shapes or guide grooves of the lower signal layer 13 and the upper signal layer 17 are formed in advance by applying an ultraviolet curable resin to the stamper and curing it, and thereafter, bonding to the disk substrate 12 or the like using an adhesive sheet. It is a thing. According to this method, it is not necessary to allow the disk substrate 12 or the stamper to transmit ultraviolet rays, and a multilayer optical disk having two or more layers can be easily produced.

JP 2003-91868 A

In Patent Document 1, in an optical disc in which data is recorded or reproduced with respect to two or more signal layers, an intermediate layer is constituted by an ultraviolet curable resin layer and an adhesive sheet layer. A plurality of recording layers or signal layers in which concave and convex shapes or guide grooves forming the recording signal are stacked, and recording is performed on each signal layer by changing the focal position of the laser beam. However, in this case, since the intermediate layer is made of the UV curable resin layer and the adhesive sheet layer by the 2P method (photopolymer method), the production work process is less than the process of bonding the two information substrates through the adhesive layer. There is a concern that it will become more complicated and not only affect the yield, but also costly.
The present invention solves this problem and can be produced by a non-2P method (photopolymer method) based on a dual-layer type optical recording medium having two recording layers, and mainly contains an organic dye. An object of the present invention is to provide a double-sided recording / reproducing type optical recording medium having three recordable recording layers.

The above problems are solved by the following inventions 1) to 5).
1) A first information substrate in which a recordable first recording layer mainly composed of an organic dye, a first reflective layer, and a first protective layer are sequentially formed on a first substrate having a light guide groove. And a recordable third recording layer mainly composed of an organic dye, a second reflective layer, and a second recordable recordable mainly composed of an organic dye on a second substrate having a light guide groove. An optical recording medium in which a substrate and a second information substrate on which an inorganic protective layer are sequentially formed are bonded to each other with an organic transparent intermediate layer (adhesive layer) on the outside. Recording / reproduction of the second recording layer is performed by irradiating laser light from the first substrate direction, and recording / reproduction of the third recording layer is performed by irradiating laser light from the second substrate direction. An optical recording medium comprising:
2) The optical recording medium according to 1), further comprising a second protective layer between the third recording layer and the second reflective layer.
3) The first substrate has a wobble in the groove, and the first recording layer can be recorded / reproduced from the inner periphery to the outer periphery by groove tracking, and the second recording layer is moved from the outer periphery to the inner periphery by land tracking. The optical recording medium according to 1) or 2), wherein the second substrate has wobbles on the land.
4) The optical recording medium according to 3), wherein the third recording layer is recorded and reproduced from the inner periphery to the outer periphery by land tracking.
5) The optical recording medium according to any one of 1) to 4), wherein the inorganic protective layer has a thickness of 500 to 2000 mm.

Hereinafter, the present invention will be described in detail.
The present invention relates to a conventional two-layer optical recording medium in which two substrates are bonded to each other, and a two-layer writable layer mainly composed of an organic dye with a reflective layer interposed therebetween on a second substrate. This is a high-density optical recording medium having three recording layers in which a recording layer is formed so that recording and reproduction can be performed from both sides, and the recording capacity is about three times that of a single-layer optical recording medium.
FIG. 3 shows a configuration example of the optical recording medium of the present invention. 21 is a first substrate, 22 is a second substrate, 23 is a first recordable layer having an organic dye as a main component, 24 is a first reflective layer, 25 is a first protective layer, and 26 is a first protective layer. An organic transparent intermediate layer (transparent adhesive layer), 27 is a second recordable layer mainly composed of an organic dye, 28 is a second reflective layer, 29 is an inorganic protective layer, and 30 is an organic dye. It is a third recording layer that can be additionally recorded as a main component. The first and second recording layers 23 and 27 are recorded and reproduced by irradiating light from the first substrate surface side, and the third recording layer 30 is irradiated from the second substrate surface side. In the following description, a portion on the first substrate side with the organic transparent intermediate layer as a boundary is referred to as a first information substrate, and a portion on the second substrate side is referred to as a second information substrate.

In the optical recording medium of the present invention, a first information substrate having a light guide groove in which a first recording layer, a first reflective layer, and a first protective layer are sequentially formed on the first substrate surface; A second information substrate having a light guide groove in which a third recording layer, a second reflection layer, a second recording layer, and an inorganic protective layer are sequentially formed on the substrate surface of the substrate through an organic transparent intermediate layer Since the substrates are bonded so as to be on the outer side, good signal reflectivity can be obtained from the second recording layer and the third recording layer.
That is, in the present invention, when the laser beam is irradiated from the first substrate direction, the inorganic protective layer can suppress the damage of the second recording layer due to the close contact with the organic transparent intermediate layer, and the multiple layers of the dye recording layer can be multiplexed. A configuration in which high reflectivity can be obtained from the second recording layer due to the interference effect, and high reflectivity can also be obtained from the third recording layer by irradiating laser light from the second substrate direction. It has become. Since the distance between the second recording layer and the third recording layer is short, the laser beam irradiated from the first substrate direction affects the third recording layer, or the laser beam is irradiated from the second substrate direction. In order to prevent light from affecting the second recording layer, a second protective layer may be provided between the second recording layer and the third recording layer in addition to the second reflective layer. preferable.

  The first and second substrates are provided with uneven guide grooves as shown in FIG. One of the characteristics of an optical recording medium that can be reproduced by a CD player such as DVD + R and CD-R is that track information is recorded by wobbling guide grooves or pit rows in a meandering manner. The meandering state of the guide groove can be detected from the track signal as a wobble signal, and track information is recorded on the substrate in advance by FM modulation or phase modulation of a predetermined frequency. The track information is address information, disk rotation frequency information, and the like. When detected from the track signal, the track information is easily separated from the information data signal and has a feature that the ROM signal compatibility is easily obtained.

  In the present invention, in the first recording layer, the first recording layer can be continuously recorded / reproduced from the first and second recording layers by the laser beam irradiated from the first substrate direction. The second recording layer is recorded / reproduced from the outer circumference to the inner circumference, and the third recording layer is recorded / reproduced from the inner circumference to the outer circumference by the laser light irradiated from the second substrate direction. It is preferable to do so. The spiral state of the guide groove when recording / reproducing from the inner periphery toward the outer periphery is clockwise, and the spiral state of the guide groove when recording / reproducing from the outer periphery toward the inner periphery is counterclockwise. Like that. In this case, the tracking method is preferably groove tracking for the first recording layer and land tracking for the second recording layer. Therefore, in the first substrate, the groove (light guide groove) is wobbled, and in the second substrate, the land is wobbled. As a result, in the third recording layer, land tracking is performed because wobbles exist in the lands.

Examples of materials used for the inorganic protective layer include inorganic substances having high light transmissivity such as SiO, SiO ₂ , MgF ₂ , SnO ₂ , ZnS, and ZnS—SiO ₂ . A particularly preferable material is ZnS—SiO ₂ having a low crystallinity and a high refractive index. The film thickness is about 100 to 2000 mm, preferably 500 to 2000 mm. If it is less than 100 mm, it is difficult to obtain a sufficient recording signal modulation degree (contrast).
An organic material such as an ultraviolet curable resin is used for the first and second protective layers. The film thickness of the first protective layer is 2 to 3 μm. The thickness of the second protective layer is about 100 to 400 mm. Since the film thickness of the second reflective layer is usually about 50 to 3000 mm as will be described later, it becomes 150 to 3400 mm together with the second protective layer.
At the DVD recording / reproducing wavelength (about 650 nm), the preferred groove depth of the substrate is 300 to 1400 mm, and the groove width is 0.1 to 0.35 μm. If the groove depth is deeper or wider than this range, the reflectivity tends to decrease, and if the groove depth is shallower or narrower than this range, the shape of the recording mark to be formed is difficult to align and jitter is generated. It is easy to increase.

The optical recording medium of the present invention is configured to obtain a high reflectance due to the multiple interference effect at both interfaces of the dye recording layer as in the case of DVD + R and CD-R. The dye recording layer has a large refractive index n and absorbs k. Is required to have relatively small optical characteristics. Preferred ranges are n> 2, 0.03 <k <0.2. Such optical characteristics can be obtained by utilizing the characteristics of the long wavelength end of the light absorption band of the dye film. Examples of materials that can be used for the first and second dye recording layers include cyanine dyes, phthalocyanine dyes, pyrylium / thiopyrylium dyes, azurenium dyes, squarylium dyes, azo dyes, and formazan chelate dyes. Dyes, metal complex dyes such as Ni and Cr, naphthoquinone dyes / anthraquinone dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, triallylmethane dyes, aminium dyes / diimmonium dyes and nitroso compounds Can be mentioned.
Among them, as a dye compound in which the maximum absorption wavelength of the light absorption spectrum of the film is 550 to 650 nm and desired optical characteristics can be easily obtained at the laser light wavelength (about 650 nm), the film forming property and optical characteristics are adjusted by solvent coating. From the easiness, a tetraazaporphyrazine dye, a cyanine dye, an azo dye, and a squarylium dye can be mentioned.
The organic dye as a main component means that a sufficient amount of the dye is used to ensure good recording / reproduction characteristics, but usually an additive such as a binder or a stabilizer added as necessary. Except for the recording layer.
The film thickness of the recording layer is preferably from 100 to 5000 mm, and particularly preferably from 500 to 2000 mm. When the film thickness is thinner than this range, the recording sensitivity is lowered, and when it is thicker, the reflectance is lowered.

  The substrate used in the present invention can be arbitrarily selected from various materials used as substrates for conventional optical recording media. Examples of substrate materials include acrylic resins such as polymethyl methacrylate, vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers, epoxy resins, polycarbonate resins, amorphous polyolefin resins, polyester resins, and soda lime glass. Mention may be made of glass and ceramics. In particular, polymethyl methacrylate resin, polycarbonate resin, epoxy resin, amorphous polyolefin resin, polyester resin, glass, and the like are preferable from the viewpoints of dimensional stability, transparency, and planarity. Furthermore, polycarbonate resin is preferable because it is easy to mold.

The reflective layer material used in the present invention is a substance having a high reflectivity with respect to laser light. Examples thereof include Mg, Se, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ca, In, Si, Ge, Te, Pb, Po, Sn, Si, Mention may be made of metals such as SiC and metalloids. Among these, Au, Al, and Ag that can provide high reflectivity are preferable. These may be used alone or in combination of two or more or as an alloy.
The thickness of the reflective layer is generally 50 to 3000 mm, but it is necessary to adjust the thickness of the first reflective layer so that the light transmittance is 40% or more. Preferably it is 50-300cm. As the film thickness increases, the light transmittance tends to attenuate. A protective layer may be provided on these reflective layers for chemical and physical protection, and UV curable resin or the like is used as the material thereof.
The organic transparent intermediate layer is preferably used as a permeable adhesive layer, and as the material thereof, an existing acrylate-based, epoxy-based, urethane-based ultraviolet curable or thermosetting adhesive can be used. The thickness is usually about 50 to 65 μm.

Next, the manufacturing method of the optical recording medium of the present invention will be described.
In the case of the layer configuration example shown in FIG. 3, a first recording layer is formed on a first substrate having a groove formed on the surface by a coating film forming means, and a first reflective layer is formed thereon by vacuum film formation. The first information substrate is formed by forming the first protective layer thereon by the coating film forming means.
On the other hand, a third recording layer and a second protective layer are formed by coating film forming means on a second substrate having a groove formed on the surface, and a second reflective layer is formed thereon by vacuum film forming means. Then, a second recording layer is formed thereon by coating film forming means, and further, an inorganic protective layer is formed thereon by vacuum film forming means to form a second information substrate.
Next, when the first information substrate and the second information substrate are bonded together through an organic transparent intermediate layer made of an adhesive, the optical recording medium of the present invention can be easily produced.

That is, the manufacturing method includes the following steps (a) to (ii).
<Manufacture of first information board>
(A) A first recording layer is formed by coating on a first substrate having a groove formed on the surface.
Providing by means.
(B) A step of providing a first reflective layer on the first recording layer by a vacuum film forming means.
(C) A step of providing a first protective layer on the first reflective layer by a coating film forming means.
The manufacturing process of the first information board is the same as that of the conventional DVD + R or DVD-ROM.
<Manufacture of second information board>
(D) A third recording layer is formed by coating on a second substrate having a groove formed on the surface.
Providing by means.
(E) A step of providing a second protective layer on the third recording layer by a coating film forming means.
(F) A step of providing a second reflective layer on the second protective layer by a vacuum film forming means.
(G) A step of providing a second recording layer on the second reflective layer by a coating film forming means.
(H) A step of providing an inorganic protective layer on the second recording layer by vacuum film forming means.
<Lamination process>
(L) A step of bonding the first information substrate and the second information substrate through an adhesive layer.

A process for forming each layer will be briefly described.
<Recording layer forming step>
In the present invention, usually, a recording layer containing an organic dye as a main component is provided by a coating film forming means. That is, it is formed by applying a coating solution in which an organic dye compound is dissolved in a solvent on a substrate. As a solvent for adjusting the coating solution, a known organic solvent (for example, alcohol, cellosolve, halogenated carbon, ketone, ether, etc.) can be used. As the coating method, the spin coating method is desirable because the film thickness can be controlled by adjusting the concentration, viscosity, and solvent drying temperature of the coating solution.
<Reflective layer forming step>
In the present invention, the reflective layer is usually provided by vacuum film forming means. That is, the reflective layer material is formed by, for example, vapor deposition, sputtering, or ion plating.
<Inorganic protective layer forming step>
In the present invention, usually, an inorganic protective layer is provided on the second recording layer by vacuum film forming means. That is, the inorganic protective layer material is formed by, for example, vapor deposition, sputtering, or ion plating.
<Protective layer forming step>
In the present invention, the first and second protective layers are usually provided by coating film forming means. The adjustment of the coating liquid and the coating means are the same as in the recording layer.
<Lamination process>
In the present invention, the first and second information substrates are bonded together via an adhesive layer. That is, an adhesive is dropped on the surface of the inorganic protective layer, the first information substrate is covered from above, and the adhesive is spread uniformly, and then cured by ultraviolet irradiation.

According to the first aspect of the present invention, since there are three recording layers, it is possible to provide an optical recording medium whose recording capacity is about three times that of a single layer.
According to the second aspect of the present invention, information on the second recording layer and the third recording layer can be clearly distinguished and recorded / reproduced.
According to the third to fourth aspects of the present invention, temporally continuous information that extends over two recording surfaces can be continuously recorded and reproduced.
According to the fifth aspect, a good recording signal modulation degree can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited by these Examples.

<Example 1>
A first substrate having a guide groove uneven pattern having a depth of 1600 mm and a track pitch of 0.74 μm on the surface of a polycarbonate disk having a diameter of 120 mm and a thickness of 0.6 mm is prepared. A coating solution in which a squarylium dye compound is dissolved in 2,2,3,3-tetrafluoropropanol is spin-coated to form a first recording layer having a thickness of 700 mm, and Ar is used as a sputtering gas. A first reflective layer made of Ag having a thickness of 110 mm was formed by sputtering, and a first protective layer made of ultraviolet curable resin having a thickness of 3 μm was formed thereon to obtain a first information substrate.
On the other hand, a second substrate having a guide groove uneven pattern having a depth of 900 mm and a track pitch of 0.74 μm on the surface of a polycarbonate disk having a diameter of 120 mm and a thickness of 0.6 mm is prepared. The third recording layer having a thickness of 800 mm is formed by spin-coating a coating solution obtained by dissolving the squarylium dye compound in 2,2,3,3-tetrafluoropropanol, and Ar is sputtered thereon. A second reflective layer made of Ag having a thickness of 1400 mm was formed by the sputtering method described above, and the squarylium dye compound of the following [Chemical Formula 1] was dissolved in 2,2,3,3-tetrafluoropropanol on the second reflective layer. the coating solution was spin-coated to form a second recording layer having a thickness of 1000 Å, on which, made of ZnS · SiO ₂ by sputtering with a sputtering gas of Ar thickness 1 And forming an inorganic protective layer of Å, to give a second information substrate.
Next, the first and second information substrates are bonded to each other with an ultraviolet curable adhesive (KARAYAD DVD003 manufactured by Nippon Kayaku Co., Ltd.), which becomes an organic transparent intermediate layer having a thickness of 50 μm, and the optical recording medium having the layer structure shown in FIG. It was created.
About this optical recording medium, using a DDU1000 of Pulstec Corporation as an evaluation apparatus, irradiating a laser beam having a wavelength of 657 nm from the second substrate direction, under the conditions of NA: 0.65 and linear velocity of 3.49 m / s, The DVD (8-16) signal in the third recording layer was evaluated for recording / reproduction.
As a result, a reflectance (I14H) of 64% and a modulation degree (I3 / I14) of 31% after recording were obtained. These two items are standards of reflectivity (single layer, single layer): 45 to 85%, modulation degree (I3 / I14): 15% or more when compared with the physical format standard of DVD-Video / ROM. And physical compatibility with the playback DVD is ensured.
Next, the first recording layer was evaluated in the same manner as described above except that the laser beam was irradiated from the first substrate direction. As a result, the reflectance (I14H) after recording was 23%, and the modulation factor (I3 / I14). 36% was obtained. Here, the first and second recording layers correspond to a dual layer, and in the DVD-Video / ROM physical format standard, the reflectivity (dual layer) is 18 to 30%. The later reflectivity ensures physical compatibility with the playback DVD.

<Example 2>
Except that the groove depth of the second substrate was changed to 1100 mm, an optical recording medium was prepared in the same manner as in Example 1, and the third recording layer was evaluated in the same manner as in Example 1. The reflectance (I14H) was 58% and the modulation factor (I3 / I14) was 32%.

<Example 3>
An optical recording medium was prepared in the same manner as in Example 1 except that the groove depth of the second substrate was changed to 300 mm and the first reflective layer was changed to Au having a thickness of 110 mm. As a result of evaluation in the same manner as in Example 1 except that the laser beam was irradiated from the first substrate direction with the layer as an evaluation target, the reflectance (I14H) after recording was 20%, and the modulation factor (I3 / I14) was 43%. was gotten.

The figure which shows the structure of the optical recording medium which has the recording layer of two layers which can record additionally which has the organic dye of a prior application as a main component. 6 is a diagram showing a configuration of an optical recording medium having a multilayer structure disclosed in Patent Document 1. FIG. The figure which shows the structural example of the optical recording medium of this invention. Explanatory drawing of the guide groove formed in the 1st and 2nd board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st board | substrate 2 2nd board | substrate 3 The 1st recording layer which can be recorded mainly which has organic dye as a main component 4 The 2nd recording layer which can be recorded which has organic dye as a main component 5 Organic transparent intermediate | middle layer (transmissivity Adhesive layer)
6 First Reflective Layer 7 Second Reflective Layer 8 Inorganic Protective Layer 11 Optical Disc 12 Disc Substrate 13 Lower Signal Layer 14 Multilayer Structure 15 Pressure-Sensitive Adhesive Sheet Layer 16 UV-Curable Resin Layer 17 Upper Signal Layer 18 Optically Transparent Cover Layer 21 First substrate 22 Second substrate 23 First recordable layer 24 having a main component of organic dye 24 First reflective layer 25 First protective layer 26 Organic transparent intermediate layer (adhesive having transparency) layer)
27 Second recordable layer with organic dye as main component 28 Second reflective layer 29 Inorganic protective layer 30 Third recordable layer with organic dye as main component

Claims (5)

  A first information substrate in which a first recordable layer having a main component of an organic dye, a first reflective layer, a first reflective layer, and a first protective layer are sequentially formed on a first substrate having a light guide groove; On a second substrate having a light guide groove, a third recording layer that can be recorded with an organic dye as a main component, a second reflective layer, a second recording layer that can be recorded with an organic dye as a main component, An optical recording medium in which a second information substrate on which an inorganic protective layer is sequentially formed is bonded so that the substrate faces outside via an organic transparent intermediate layer (adhesive layer). Recording / reproduction of the recording layer is performed by irradiating laser light from the first substrate direction, and recording / reproduction of the third recording layer is performed by irradiating laser light from the second substrate direction. An optical recording medium characterized by the above.   2. The optical recording medium according to claim 1, further comprising a second protective layer between the third recording layer and the second reflective layer.   The first substrate has a wobble in the groove, the first recording layer can be recorded and reproduced from the inner periphery to the outer periphery by groove tracking, and the second recording layer is directed from the outer periphery to the inner periphery by land tracking. 3. The optical recording medium according to claim 1, wherein the second substrate has a wobble on the land.   4. The optical recording medium according to claim 3, wherein the third recording layer is recorded and reproduced from the inner periphery toward the outer periphery by land tracking. 5. The optical recording medium according to claim 1, wherein the inorganic protective layer has a thickness of 500 to 2000 mm.

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