JP4238170B2 - Optical recording medium - Google Patents

Description

  The present invention relates to an optical recording medium including a plurality of recording layers for recording or reproducing information by making light incident from one side, such as a DVD-R.

Currently, various optical recording media such as CD-R, CD-RW, and MO can store a large amount of information and are easily accessible at random, so that they are widely recognized as external storage devices in information processing apparatuses such as computers. It is becoming popular. Furthermore, it is desired to increase the storage density by increasing the amount of information handled.
Among various optical recording media, an optical disc having a recording layer containing an organic dye (also referred to as a dye-containing recording layer) such as CD-R, DVD-R, and DVD + R is relatively inexpensive and is a reproduction-only optical disc. In particular, it is widely used.

As an example, a medium such as a CD-R that is representative of an optical disk having a dye-containing recording layer has a dye-containing recording layer and a reflective layer in this order on a transparent disk substrate. It has a laminated structure having a protective layer for covering, and performs recording / reproduction with a laser beam through a substrate.
Similarly, a typical single-sided DVD-R (single-sided single-layer DVD-R) has a dye-containing recording layer, a reflective layer, and a protective layer covering them in this order on the first transparent disk substrate, and further protection. 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 formed on a second disk substrate (which may be transparent or opaque) with or without an adhesive layer on the layer. Recording / reproduction is performed with laser light from one side through the transparent disk substrate. The dummy disk may be only a transparent or opaque disk substrate, or a layer other than the reflective layer may be provided.

Since DVD + R has almost the same configuration as DVD-R, it is represented in the description of DVD-R.
In order to further increase the recording capacity of the optical recording medium, the above single-sided DVD-R 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 record / reproduce the recording layer closer to this one side, while irradiating laser light from the other side of the medium) A double-sided DVD-R (double-sided dual-layer DVD-R) is also known which records and reproduces the recording layer closer to the other side.

  By the way, in recent years, in an optical recording medium having a plurality of recording layers, the recording / reproducing apparatus is not enlarged and complicated, and a laser is applied from one side to enable continuous reproduction over a plurality of recording layers. It is desired to realize a single-sided incident type optical recording medium (for example, single-sided incident double-layer DVD-R) that can perform recording / reproduction on these plural 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 type single-sided incident type DVD-R (single-sided dual-layer DVD-R) having two recording layers has been proposed. (For example, see Patent Document 1).
For example, a bonded dual layer type single-sided incidence DVD-R has a first recording layer made of an organic dye capable of optically recording information by irradiation with a recording laser beam on a first translucent substrate. A first reflective layer composed of a semi-transparent reflective film capable of transmitting a part of the reproduction laser beam, an intermediate layer having transparency to the recording laser beam and the reproduction laser beam, and recording The second recording layer is made of an organic dye capable of optically recording information by irradiation with the laser beam for use, the second reflection layer for reflecting the reproduction laser beam, and the second substrate.
Japanese Patent Laid-Open No. 11-066662

Incidentally, in general, guide grooves (concave portions) for guiding recording light or reproducing light are provided in a spiral shape or a concentric shape on a substrate of an optical recording medium such as a CD or a DVD.
For example, in an optical recording medium having a dye-containing recording layer (hereinafter referred to as a recording layer) such as CD-R and DVD-R, the depth of the guide groove is generally about 150 nm, for example.
Further, in order to produce an optical recording medium such as a CD or a DVD having a recording layer, when the material for forming the recording layer is applied on the substrate, the recording layer is formed so as to fill the recess on the substrate. Then, the recording layer becomes thick. In general, when a recording track is provided in such a thick portion (thick film portion; concave portion), recording / reproducing characteristics (for example, reflectance, maximum signal amplitude, polarity, etc.) are considered good. .

Here, the maximum signal amplitude is a value obtained by normalizing the signal amplitude of the longest mark / longest space (14T mark / 14T space in the case of a DVD-based medium) by the reflectance.
For this reason, all commercially available optical recording media are provided with a recording track in the thick film portion (concave portion).
The guide grooves (concave portions) provided on the substrate are convex portions when viewed from the incident side of the light irradiated during recording or reproduction. That is, the dye-containing recording layer becomes a convex portion in the concave portion of the substrate.

Currently, development of a single-sided incident type optical recording medium having a plurality of dye-containing recording layers (for example, a dual-layer type single-sided incident type DVD-R) is in progress.
For example, in a single-sided incident type optical recording medium having two dye-containing recording layers, the first dye-containing recording layer on the side closer to the light incident side (light incident side, one side) and the second dye-containing recording on the far side And a layer. In such a single-sided incident type optical recording medium, information is recorded or reproduced on the second dye-containing recording layer by making light incident through the first dye-containing recording layer.

In such a single-sided incident type optical recording medium, as in a general optical recording medium, if the depth of the guide groove formed on the substrate opposite to the side on which light is incident is about 150 nm, for example, the second dye In some cases, the reflectance necessary for recording or reproducing information in the contained recording layer cannot be obtained.
The present invention has been devised in view of such a problem, and in an optical recording medium having a plurality of dye-containing recording layers for recording or reproducing information by making light incident from one side, from the light incident side. When recording or reproducing information on the dye-containing recording layer located on the far side, or recording or reproducing information on the dye-containing recording layer by making light incident from the opposite side of the substrate, sufficient reflectivity (even better It is an object of the present invention to provide an optical recording medium in which a good recording characteristic is obtained.

For this reason, the optical recording medium of the present invention includes at least a first substrate having a guide groove, a first dye-containing recording layer, a translucent reflective layer, a second dye-containing recording layer, a reflective layer, and a second substrate having a guide groove. And an optical recording medium for recording or reproducing information on the first dye-containing recording layer and the second dye-containing recording layer by making light incident from the first substrate side, wherein the depth of the guide groove of the second substrate is The recording / reproducing wavelength is in a range of 1/100 × λ to 1/8 × λ, where λ is (claim 1).

The optical recording medium of the present invention is a first information recording body in which at least a first dye-containing recording layer containing a first dye and a translucent reflective layer are sequentially laminated on a first substrate having a guide groove. And a second information recording body in which at least a reflective layer and a second dye-containing recording layer containing a second dye are sequentially laminated on a second substrate having a guide groove, and a first information recording The body and the second information recording body are bonded to each other with the opposite surface of the substrate facing each other through an optically transparent adhesive layer, and information is recorded or reproduced by making light incident from the first substrate side. In the optical recording medium to be performed, the depth of the guide groove of the second substrate is in the range of 1/100 × λ to 1/8 × λ, where λ is the recording / reproducing wavelength. 2).

The optical recording medium of the present invention is characterized in that the depth of the guide groove of the second substrate is shallower than the depth of the guide groove of the first substrate .

The optical recording medium of the present invention is an optical recording medium having a plurality of dye-containing recording layers for recording or reproducing information by making light incident from one side, and the dye located on the side far from the light incident side The depth of the guide groove used for recording or reproducing information in the contained recording layer is in the range of 1/100 × λ to 1/8 × λ, where λ is the recording / reproducing wavelength. 4).
The optical recording medium of the present invention includes at least a substrate having a dye-containing recording layer, a reflective layer, and a guide groove, and records or reproduces information on the dye-containing recording layer by making light incident from the opposite side of the substrate. The depth of the guide groove of the substrate is in the range of 1/100 × λ to 1/8 × λ, where λ is the recording / reproducing wavelength.

  According to the optical recording medium of the present invention, in an optical recording medium having a plurality of dye-containing recording layers for recording or reproducing information by making light incident from one side, the dye located on the side far from the light incident side There is an advantage that sufficient reflectivity (further good recording characteristics) can be obtained when recording or reproducing information in the recording layer. In addition, there is an advantage that sufficient reflectance (further good recording characteristics) can be obtained when light is incident from the opposite side of the substrate to record or reproduce information in the dye-containing recording layer.

Hereinafter, an example of an optical recording medium (write-once type optical recording medium) according to an embodiment of the present invention will be described with reference to FIG. 1 and FIG.
The optical recording medium of the present invention is a single-sided incident type optical recording medium that has a plurality of recording layers and can record or reproduce information on each recording layer by irradiating laser light from one side.

In the optical recording medium of the present invention, for example, a dual-layer type single-sided DVD-R (single-sided dual-layer DVD) having two recording layers is used as a bonded single-sided optical recording medium (single-sided DVD-R). -R, single-sided dual-layer DVD recordable disc) will be described as an example.
FIG. 1 is a schematic cross-sectional view showing an optical recording medium (optical disk) according to the present embodiment.
As shown in FIG. 1, the optical recording medium of the present invention has a first recording layer (first recording layer) containing a dye on a disk-shaped transparent (light-transmitting) first substrate (first light-transmitting substrate) 21. 1 dye-containing recording layer) 22, translucent reflective layer (hereinafter referred to as translucent reflective layer) 23, transparent adhesive layer (intermediate layer) 24, buffer layer 28, and second recording layer containing dye (second dye-containing recording) Layer) 25, a reflective layer 26, and a disk-shaped second substrate 27 in this order. The light beam is irradiated from the first substrate 21 side, and recording or reproduction is performed.

  That is, the optical recording medium of the present invention is formed by sequentially laminating at least the first dye-containing recording layer 22 containing the first dye and the translucent reflective layer 13 on the first substrate 21 having the guide groove. A second information recording body in which at least a reflective layer 26 and a second dye-containing recording layer 25 containing a second dye are sequentially laminated on a first information recording body and a second substrate 27 having a guide groove. The first information recording body and the second information recording body are bonded to each other with an optically transparent adhesive layer facing the opposite surface of the substrate.

  In the optical recording medium of the present invention, being transparent (having light transmission) means being transparent (having light transmission) to a light beam used for recording or reproduction of the optical recording medium. Further, the transparent (light-transmitting) layer includes a layer that absorbs a light beam used for recording or reproduction to some extent. For example, if the wavelength of a light beam used for recording or reproduction is 50% or more (preferably 60% or more), it is substantially light transmissive (transparent).

Next, each layer will be described.
(A) About the 1st board | substrate 21 It is desirable for the 1st board | substrate 21 to be excellent in optical characteristics, such as being transparent and low birefringence. The refractive index of the first substrate 21 (refractive index with respect to the wavelength of recording light or reproducing light) is usually 1.40 or more, preferably 1.45 or more. However, it is usually 1.70 or less, preferably 1.65 or less. Furthermore, it is desirable to have excellent moldability such as easy injection molding. Furthermore, it is desirable that the hygroscopicity is small because warpage can be reduced.

Furthermore, it is desirable to provide shape stability so that the optical recording medium has a certain degree of rigidity. However, if the second substrate 27 has sufficient shape stability, the first substrate 21 may not have high shape stability.
Examples of such materials include those made of resins such as acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, epoxy resins, and the like. Can be used. Or the 1st board | substrate 21 may consist of a several layer, for example, what provided the resin layer which consists of radiation curable resins, such as photocuring resin, on base | substrates, such as glass and resin, etc. can be used.

Polycarbonate is preferable from the viewpoints of high productivity such as optical characteristics and moldability, cost, low hygroscopicity, and shape stability. Amorphous polyolefin is preferred from the standpoint of chemical resistance and low hygroscopicity. Moreover, a glass substrate is preferable from the viewpoint of high-speed response.
The first substrate 21 is preferably thin, and the thickness is usually preferably 2 mm or less, more preferably 1 mm or less. This is because the coma aberration tends to decrease as the distance between the objective lens and the recording layer decreases and the substrate becomes thinner, and the recording density is easily increased. However, in order to obtain sufficient optical properties, hygroscopicity, moldability, and shape stability, a certain amount of thickness is necessary, and is usually preferably 10 μm or more, more preferably 30 μm or more.

In the optical recording medium of the present invention, it is desirable to appropriately adjust the distance between the objective lens and both recording layers in order to perform good recording or reproduction on both the first recording layer 22 and the second recording layer 25. For example, it is preferable that the focal point of the objective lens is approximately at the midpoint between the two recording layers so that both recording layers can be easily accessed.
More specifically, in DVD-ROM and DVD-R systems, the distance between the objective lens and the recording layer is adjusted to be optimal when the substrate thickness is 0.6 mm.

Therefore, in the case of DVD-ROM compatibility in this layer structure, the thickness of the first substrate 21 is a thickness obtained by subtracting one half of the thickness of the transparent adhesive layer 24 as an intermediate layer from 0.6 mm. Most preferably it is. At this time, the substantially middle point between both recording layers is about 0.6 mm, and it is easy to apply focus servo to both recording layers.
In the case where there are other layers such as a buffer layer and a protective layer between the second recording layer 25 and the translucent reflective layer 23, the sum of the thicknesses of these layers and the transparent adhesive layer 24 is 0.6 mm. Most preferably, the thickness is reduced by a factor of one.

  A groove (guide groove) 31 used for guiding recording / reproducing light (recording / reproducing beam; for example, laser light) at the time of recording or reproducing information is provided on the first substrate 21 in a spiral shape or a concentric shape. It is done. Thus, when the groove | channel 31 is provided in the 1st board | substrate 21, an unevenness | corrugation will be made on the surface of the 1st board | substrate 21, the recessed part (groove) is called a groove, and a convex part is called a land. Information is recorded or reproduced on the first recording layer 22 using these grooves and / or lands as recording tracks. In addition, the groove | channel 31 on the 1st board | substrate 21 becomes a convex part with respect to the incident direction of light.

  For example, 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 22 is usually the first substrate. Since the film is thickly formed by the grooves (concave portions) of the first substrate 21 and is thicker and more suitable for recording or reproduction, the groove is preferably used as a recording track.

  Here, the depth of the groove 31 provided on the first substrate 21 (groove depth; the height of the convex portion of the first dye-containing recording layer) is 1/10 × λ or more, where λ is the recording / reproducing wavelength. It is preferable to ensure sufficient reflectivity. More preferably, it is 1/8 × λ or more. More preferably, it is 1/6 × λ or more. For example, when the wavelength of recording / reproducing light (recording / reproducing wavelength) is λ = 650 nm, the depth of the groove 31 of the first substrate 21 is preferably 65 nm or more. More preferably, it is 81 nm or more. More preferably, it is 108 nm or more.

  However, the depth of the groove 31 of the first substrate 21 is preferably 2/4 × λ or less because the groove shape transferability can be improved. More preferably, it is 2/5 × λ or less, and further preferably 2/6 × λ or less. For example, when the recording / reproducing wavelength is λ = 650 nm, the depth of the groove 31 of the first substrate 21 is preferably 325 nm or less. More preferably, it is 260 nm or less, More preferably, it is 217 nm or less.

  In addition, the width of the groove 31 (groove width, G width; width of the convex portion of the first dye-containing recording layer; half-value width) of the first substrate 21 is 1/10 × T or more, where T is the track pitch. Is preferable because sufficient reflectivity can be secured. More preferably, it is 2/10 × T or more, and further preferably 3/10 × T or more. For example, when the track pitch is 740 nm, the width of the groove 31 of the first substrate 21 is preferably 74 nm or more. More preferably, it is 148 nm or more, and further preferably 222 nm or more.

  However, it is preferable that the width of the groove 31 of the first substrate 21 is 9/10 × T or less because the transferability of the groove shape can be improved. More preferably, it is 8/10 × T or less, and further preferably 7/10 × T or less. For example, when the track pitch is 740 nm, the width of the groove 31 of the first substrate 21 is preferably 666 nm or less. More preferably, it is 592 nm or less, and more preferably 518 nm or less.

  For example, in the case of groove recording, the groove 31 of the first substrate 21 is wobbled by slightly meandering in the radial direction with a predetermined amplitude and a predetermined frequency. In addition, isolated pits (address pits) according to a certain rule are formed in the land between the grooves 31 of the first substrate 21 (this is called a land pre-pit, LPP; Land Pre-Pit), and an address is generated by the land pre-pit. Information may be recorded in advance. In addition, it may have uneven pits (pre-pits) as necessary.

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 1st recording layer 22 The 1st recording layer 22 is sensitivity comparable as the recording layer normally used for a single-sided type recording medium (for example, CD-R, DVD-R, DVD + R).

In order to realize good recording / reproducing characteristics, it is desirable to use a dye having low heat generation and high refractive index.
Here, the refractive index (refractive index with respect to the wavelength of recording light or reproducing light) of the dye used for the first recording layer 22 is usually 1.00 or more, preferably 1.50 or more. However, it is usually 3.00 or less.

  Further, the extinction coefficient of the dye used for the first recording layer 22 (extinction coefficient with respect to the wavelength of recording light or reproducing light) is usually 0.50 or less, preferably 0.30 or less. If the extinction coefficient is too large, the absorption by the dye-containing recording layer becomes too large, and the reflectance becomes low. However, in order to perform recording, it is preferable that there is some absorption, and there is no particular lower limit, but it is usually 0.001 or more.

Further, in the combination of the first recording layer 22 and the translucent reflective layer 23, it is desirable that the reflection, transmission and absorption of light be in an appropriate range. The recording sensitivity can be increased and the thermal interference during recording can be reduced.
Examples of 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 azulenium dyes, metal-containing azo dyes, and metal-containing indoaniline dyes.

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

(Ring A ¹ and A ² are each independently a nitrogen-containing aromatic heterocyclic ring that may have a substituent, and Ring B ¹ and B ² may each independently have a substituent. X is an alkyl group having 1 to 6 carbon atoms which is substituted with at least two fluorine atoms.
The organic dye used for the recording layer of the optical recording medium of the present invention has a maximum absorption wavelength λmax in the visible light to near infrared region of about 350 to 900 nm, and is suitable for recording with a blue to near microwave laser. Is preferred. A near-infrared laser having a wavelength of about 770 to 830 nm (typically 780 nm, 830 nm, etc.) used for a 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 about 340 to 530 nm represented by a wavelength of 410 nm or 515 nm is more preferable.

One kind of dye may be used, or two or more kinds of the same kind or different kinds may be used in combination. Furthermore, it is also possible to use an optical recording medium corresponding to recording with laser light in a plurality of wavelength regions by using a combination of dyes suitable for recording in each of the recording light with the plurality of wavelengths.
The first recording layer 22 has a transition metal chelate compound (for example, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-) 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 atoms, ions, clusters, etc., for example, an ethylenediamine complex, an azomethine complex, a phenylhydroxyamine complex, a phenanthroline complex, Organic metal compounds such as dihydroxyazobenzene complex, dioxime complex, nitrosoaminophenol complex, pyridyltriazine complex, acetylacetonate complex, metallocene complex and porphyrin complex can be mentioned. Although it does not specifically limit as a metal atom, It is preferable that it is a transition metal.

  Furthermore, a binder, a leveling agent, an antifoaming agent, etc. can be used in combination with the first recording layer 22 of the optical recording medium of the present invention, if necessary. Preferable binders include polyvinyl alcohol, polyvinyl pyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like.

  The film thickness of the first recording layer 22 is not particularly limited because it varies depending on the recording method and the like. However, in order to obtain a sufficient degree of modulation, it is usually preferably 5 nm or more, more preferably 10 nm or more. And particularly preferably 20 nm or more. However, in the optical recording medium of the present invention, it is not necessary to be too thick in order to transmit light moderately, so that it is usually 3 μm or less, preferably 1 μm or less, more preferably 200 nm or less. The film thickness of the first recording layer 22 is usually different between the groove part and the land part. In the optical recording medium of the present invention, the film thickness of the first recording layer 22 is the film thickness in the groove part of the substrate.

Examples of the film formation method for the first recording layer 22 include commonly used thin film formation methods such as a vacuum deposition method, a sputtering method, a doctor blade method, a cast method, a spin coating method, and an immersion method. From the viewpoint of spin coating, spin coating is preferred. From the viewpoint that a recording layer having a uniform thickness can be obtained, the vacuum vapor deposition method is preferable to the coating method.
In the case of film formation by spin coating, the rotation speed is preferably 10 to 15000 rpm, and after spin coating, treatment such as heating or application to solvent vapor may be performed.

  A coating solvent for forming the first recording layer 22 by a coating method such as a doctor blade method, a casting method, a spin coating method, or a dipping method may be any solvent that does not attack the substrate and is not particularly limited. For example, ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellosolv solvents such as methyl cellosolve and ethyl cellosolve; chain hydrocarbon solvents such as n-hexane and n-octane Cyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, tert-butylcyclohexane and cyclooctane; perfluoroalkyl alcohols such as tetrafluoropropanol, octafluoropentanol and hexafluorobutanol Examples of the solvent include hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate.

In the case of the vacuum deposition method, for example, an organic dye and, if necessary, recording layer components such as various additives are put in a crucible installed in a vacuum vessel, and the inside of the vacuum vessel is 10 ⁻² to After evacuating to about 10 ⁻⁵ Pa, the crucible is heated to evaporate the recording layer components and vapor deposited on the substrate placed facing the crucible to form the first recording layer 22.
(C) Translucent reflective layer 23 The translucent reflective layer 23 is a reflective layer having a certain degree of light transmittance. That is, the reflective layer has a small absorption of recording / reproducing light, a light transmittance of 40% or more, and an appropriate light reflectance (usually 30% or more). For example, an appropriate transmittance can be provided by providing a thin metal with high reflectivity. Moreover, it is desirable that there is some degree of corrosion resistance. Furthermore, it is desirable that the first recording layer 22 be blocked by the seepage of the upper layer of the translucent reflective layer 23 (here, the transparent adhesive layer 24).

In order to ensure high transmittance, the thickness of the translucent reflective layer 23 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 22 is not affected by the upper layer of the translucent reflective layer 23, a certain thickness is required, and usually 3 nm or more. More preferably, it is 5 nm or more.
As a material of the translucent reflective layer 23, a material having 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 and semi-metals It is possible to use a metal alone or as an alloy. Among these, Au, Al, and Ag have high reflectivity and are suitable as materials for the translucent reflective layer 23. In addition to these as main components, other components may be included.

Among these, those containing Ag as a main component are particularly preferable from the viewpoint of low cost and high reflectance. Here, the main component means one having a content of 50% or more.
The translucent reflective layer 23 is thin, and if the crystal grains of the film are large, it may cause reproduction noise. Therefore, it is preferable to use a material with small crystal grains. Since pure silver tends to have large crystal grains, Ag is preferably used as an alloy.

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

As the translucent reflective layer 23, a layer made only of Au is suitable because of its small crystal grains and excellent corrosion resistance. However, it is more expensive than Ag alloy.
It is also possible to use a layer made of Si as the translucent reflective layer 23.
It is also possible to form a multilayer film by alternately stacking a low refractive index thin film and a high refractive index thin film using a material other than metal, and use it as a reflective layer.

Examples of the method for forming the translucent reflective layer 23 include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition. In addition, a known inorganic or organic intermediate layer or adhesive layer is provided between the first substrate 21 and the translucent reflective layer 23, for example, in order to improve reflectivity, improve recording characteristics, and improve adhesion. It may be provided. For example, an intermediate layer (or adhesive layer), a first recording layer 22, an intermediate layer (or adhesive layer), and a translucent reflective layer 23 are laminated on the first substrate 21 in this order, so that the first substrate 21 and the first substrate 21 are stacked together. An intermediate layer (or adhesive layer) may be provided between the recording layer 22 and an intermediate layer (or adhesive layer) may be provided between the first recording layer 22 and the translucent reflective layer 23.
(D) Transparent Adhesive Layer 24 The transparent adhesive layer 24 needs to be transparent, and has a high adhesive force and a low shrinkage rate during curing and adhesion is preferable because the shape stability of the medium is high.

The refractive index (refractive index with respect to the wavelength of recording light or reproducing light) of the transparent adhesive layer 24 is usually 1.40 or more, preferably 1.45 or more. However, it is usually 1.70 or less, preferably 1.65 or less.
The transparent adhesive layer 24 is preferably made of a material that does not damage the second recording layer 25. However, since the transparent adhesive layer 24 is usually made of a resin, it is easily compatible with the second recording layer 25. In order to prevent this and prevent damage, it is desirable to provide a buffer layer 28 described later between the two layers.

Furthermore, the transparent adhesive layer 24 is preferably made of a material that does not damage the translucent reflective layer 23. However, a known inorganic or organic protective layer may be provided between both layers in order to suppress damage.
In the optical recording medium of the present invention, the film thickness of the transparent adhesive layer 24 is preferably controlled accurately. The film thickness of the transparent adhesive layer 24 is usually preferably 5 μm or more. In order to separately apply focus servo to the two recording layers, it is necessary to have a certain distance between the two recording layers. Although it depends on the focus servo mechanism, it is usually required 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 it is too thick, it takes time to adjust the focus servo to the two recording layers, and the moving distance of the objective lens becomes long, which is not preferable. Moreover, since there are problems such as requiring time for curing and lowering productivity, the thickness is usually preferably 100 μm or less.
Examples of the material of the transparent adhesive layer 24 include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, an ultraviolet curable resin (including a delayed curable type), and the like.

  A thermoplastic resin, a thermosetting resin, or the like can be formed by dissolving in an appropriate solvent to prepare a coating solution, coating it, 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, and then applying the coating solution and curing it by irradiating with ultraviolet light. There are various types of ultraviolet curable resins, and any of them can be used as long as it is transparent. These materials may be used alone or in combination, and may be used not only as a single layer but also as a multilayer film.

  As a coating method, a method such as a spin coating method or a casting method is used as in the recording layer, and among these, the spin coating method is preferable. Alternatively, a resin having a high viscosity can be formed by screen printing or the like. It is preferable to use an ultraviolet curable resin that is liquid at 20 to 40 ° C. because it can be applied without using a solvent. The viscosity is preferably adjusted to 20 to 1000 mPa · s.

In addition, an adhesive layer can also be formed by using a pressure-sensitive double-sided tape and sandwiching and pressing the tape between laminated structures.
As the ultraviolet curable adhesive, there are a radical ultraviolet curable adhesive and a cationic ultraviolet curable adhesive, both of which can be used.
As the radical ultraviolet curable adhesive, all known compositions can be used, and a composition containing an ultraviolet curable compound and a photopolymerization initiator as essential components is used. As the ultraviolet curable compound, monofunctional (meth) acrylate or polyfunctional (meth) acrylate can be used as the polymerizable monomer component. 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 optical recording medium of the present invention include the following. Examples of the monofunctional (meth) acrylate include 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, nonylphenoxyethyl tetrahydrofurfuryl, caprolactone modified tetrahydrofurfuryl, isobornyl , (Meth) acrylate having a group such as dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl and the like.

  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. Di (meth) such as neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecane dimethanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol Di (meth) acrylate of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of acrylate, tris (2-hydroxyethyl) isocyanurate di (meth) acrylate, neopentyl glycol Diol di (meth) acrylate obtained by adding 2 mol of ethylene oxide or propylene oxide to 1 mol of bisphenol A, triol obtained by adding 3 mol or more of ethylene oxide or propylene oxide to 1 mol 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) Acrylate, poly (meth) acrylate of dipentaerythritol, ethylene oxide modified phosphoric acid (meth) acrylate, ethylene oxide modified alkylated phosphoric acid (meth) acrylate, etc. It is.

Moreover, what can be used together with the polymerizable monomer includes polyester (meth) acrylate, polyether (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate and the like as polymerizable oligomers.
Furthermore, as the photopolymerization initiator used in the optical recording medium of the present invention, any known one that can cure an ultraviolet curable compound represented by the polymerizable oligomer and / or 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 optical recording medium of the present invention.

  Examples of such 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, etc. are preferably used, and other molecular cleavage types 1-hydroxycyclohexyl phenyl 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 or the like may be used in combination, and hydrogen extraction photopolymerization initiators such as benzophenone, 4-phenylbenzophenone, and isophthalphenone 4-benzoyl-4′-methyl-diphenyl sulfide and the like can be used in combination.

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

Further, as the cationic ultraviolet curable adhesive, all known compositions can be used, 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 an 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 Ntimonate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium tetrafluoroborate, 4-methylphenyl-4- (1-methylethyl) phenyliodonium tetrakis (pentafluorophenyl) borate, and the like.

The epoxy resin can be any of various types such as bisphenol A-epichlorohydrin 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. A known photosensitizer can be used in combination in order to use the near-ultraviolet region and the visible region of the ultraviolet light source more effectively. Examples of the photosensitizer at this time include anthracene, phenothiazine, benzylmethyl ketal, benzophenone, and acetophenone.

In addition, UV curable adhesives include, as necessary, other additives such as thermal polymerization inhibitors, antioxidants typified by hindered phenols, hindered amines, phosphites, plasticizers and epoxy silanes, mercapto. Silane coupling agents represented by silane, (meth) acrylic silane and the like can also be blended for the purpose of improving various properties. These are selected from those having excellent solubility in ultraviolet curable compounds and those that do not impair ultraviolet transparency.
(E) Second Recording Layer 25 The second recording layer 25 is usually more sensitive than the recording layer used for single-sided recording media (for example, CD-R, DVD-R, DVD + R). In the optical recording medium of the present invention, since the power of the incident light beam is reduced due to the presence of the first recording layer 22 and the semitransparent reflection layer 23, etc., recording is performed with about half of the power, so the sensitivity is particularly high. There is a need.

In order to realize good recording / reproducing characteristics, it is desirable to use a dye having low heat generation and high refractive index.
Here, the refractive index of the dye used for the second recording layer 25 (refractive index with respect to the wavelength of the recording light or reproducing light) is usually 1.00 or more, preferably 1.50 or more. However, it is usually 3.00 or less.

  Further, the extinction coefficient of the dye used for the second recording layer 25 (extinction coefficient with respect to the wavelength of recording light or reproducing light) is usually 0.50 or less, preferably 0.30 or less. If the extinction coefficient is too large, the absorption by the dye recording layer becomes too large and the reflectance becomes low. However, in order to perform recording, it is preferable that there is some absorption, and there is no particular lower limit, but it is usually 0.001 or more.

Further, in the combination of the second recording layer 25 and the reflective layer 26, 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 25, the film forming method, and the like are described in substantially the same manner as in the first recording layer 22, only different points will be described.
The film thickness of the second recording layer 25 varies depending on the recording method and the like, and is not particularly limited. However, in order to obtain a sufficient degree of modulation, it is usually preferably 10 nm or more, and more preferably 30 nm or more. And particularly preferably 50 nm or more. However, since it is not necessary to be too thick in order to obtain an appropriate reflectance, it is usually 3 μm or less, preferably 1 μm or less, more preferably 200 nm or less. Here, the film thickness of the second recording layer 25 usually refers to the film thickness in the thick film portion.

The materials used for the first recording layer 22 and the second recording layer 25 may be the same or different.
(F) About the reflective layer 26 The reflective layer 26 needs to have a high reflectance. Moreover, it is desirable that it is highly durable.
In order to ensure high reflectivity, the thickness of the reflective layer 26 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 to be thin to some extent, and is usually 400 nm or less. More preferably, it is set to 300 nm or less.

  As the material of the reflective layer 26, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, and Pd are used alone or as an alloy. It is possible. Among these, Au, Al, and Ag have high reflectivity and are suitable as materials for the reflective layer 26. In addition to these as main components, the following components 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, Pb Mention may be made of metals and metalloids such as Po, Sn, Bi and rare earth metals.

Among them, those containing Ag as a main component are particularly preferred because they are low in cost, easily exhibit high reflectivity, and when a print receiving 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), the reflective layer 26 is preferably used as an alloy rather than pure silver.

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

As the reflective layer 26, a layer made only of Au is preferable because of its high durability (high corrosion resistance). However, it is more expensive than Ag alloy.
It is also possible to form a multilayer film by alternately stacking a low refractive index thin film and a high refractive index thin film using a material other than metal, and use it as the reflective layer 26.
Examples of the method for forming the reflective layer 26 include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition. In addition, a known inorganic or organic intermediate layer or adhesive layer may be provided above and below the reflective layer 26, for example, in order to improve reflectivity, improve recording characteristics, and improve adhesion.
(G) Regarding the second substrate 27 The second substrate 27 preferably has shape stability so that the optical recording medium has a certain degree of rigidity. That is, it is preferable that mechanical stability is high and rigidity is large.

Examples of such materials include those made of resins such as acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, epoxy resins, and the like. Can be used.
Or the 2nd board | substrate 27 may consist of a several layer, for example, what provided the resin layer which consists of radiation curable resin, such as photocuring resin, on the board | substrates, such as glass and resin, is 2nd. Can be used as a substrate.

As described above, when the first substrate 21 does not have sufficient shape stability, the second substrate 27 needs to have particularly high shape stability. In this respect, it is desirable that the hygroscopicity is small.
The second substrate 27 does not need to be transparent, but when it is transparent, the refractive index of the second substrate 27 (refractive index with respect to the wavelength of recording light or reproducing light) is usually 1.40 or more, preferably Is 1.45 or more. However, it is usually 1.70 or less, preferably 1.65 or less.

As such a material, the same material as that which can be used for the first substrate 21 can be used. For example, an Al alloy substrate such as an Al-Mg alloy containing Al as a main component, or an Mg alloy as a main component, for example. An Mg alloy substrate such as an Mg—Zn alloy, a substrate made of any of silicon, titanium, and ceramics, a substrate that combines them, and the like can be used.
In addition, from the viewpoints of high productivity such as moldability, cost, low hygroscopicity, and shape stability, the above-described resins are preferable, and polycarbonate is particularly preferable. Amorphous polyolefin is preferred from the standpoint of chemical resistance and low hygroscopicity. Moreover, a glass substrate is preferable from the viewpoint of high-speed response.

In order to give the optical recording medium sufficient rigidity, the second substrate 27 is preferably thick to some extent, and the thickness is preferably 0.3 mm or more. However, the thinner one is advantageous for thinning the recording / reproducing apparatus, and it is preferably 3 mm or less. More preferably, it is 1.5 mm or less.
As an example of a preferable combination of the first substrate 21 and the second substrate 27, the first substrate 21 and the second substrate 27 are made of the same material and have the same thickness. Since the rigidity is equal and balanced, it is preferable that the medium is difficult to be deformed against environmental changes. In this case, it is preferable that the degree and direction of deformation when the environment changes are the same for both substrates.

As an example of another preferable combination, the first substrate 21 is as thin as about 0.1 mm, and the second substrate 27 is as thick as about 1.1 mm. The objective lens is preferable because it easily approaches the recording layer and easily increases the recording density. At this time, the 1st board | substrate 21 may be a sheet form and does not need to have a guide groove.
The second substrate 27 is provided with a groove (guide groove) 32 used to guide recording / reproducing light (recording / reproducing beam; for example, laser light) in recording or reproducing information in a spiral shape or a concentric shape. It is done. Thus, when the groove | channel 32 is provided in the 2nd board | substrate 27, an unevenness | corrugation will be made on the surface of the 2nd board | substrate 27, the recessed part (groove) is called a groove, and a convex part is called a land. In addition, the groove | channel 32 on the 2nd board | substrate 27 becomes a recessed part with respect to the incident direction of light.

Here, since the second recording layer 25 is applied and formed on the reflective layer 26 formed on the second substrate 27, the film thickness is increased by the groove (concave portion) of the second substrate 27 (this portion is thick). The film thickness is reduced at the land (convex portion) of the second substrate 27 (this portion is referred to as a thin film portion).
In the present embodiment, as will be described later, since the depth of the groove 32 is shallow, information can be recorded or reproduced on the second recording layer 25 using the groove and / or land as a recording track.

  For example, in the case of groove recording, the wobble is provided by slightly meandering the groove 32 of the second substrate 27 with a predetermined amplitude and a predetermined frequency in the radial direction. In addition, isolated pits (address pits) according to a certain rule are formed in the land between the grooves 32 of the second substrate 27 (this is called a land pre-pit, LPP; Land Pre-Pit), and an address is generated by the land pre-pit. Information may be recorded in advance. In addition, it may have uneven pits (pre-pits) as necessary.

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.
(I) Buffer Layer 28 Here, a buffer layer 28 as an intermediate layer is provided between the transparent adhesive layer 24 and the second recording layer 25.

The buffer layer 28 prevents the two layers from being mixed and prevents compatibility. The buffer layer 28 may also serve other functions than preventing the mixing phenomenon. Further, another intermediate layer may be interposed as required.
The material of the buffer layer 28 is incompatible with the second recording layer 25 and the transparent adhesive layer 24 and needs to have a certain degree of light transmission, but known inorganic and organic materials can be used. In view of characteristics, an inorganic material is preferably used. For example, (a) metal or semiconductor, (b) metal or semiconductor oxide, nitride, sulfide, oxysulfide, fluoride or carbide, or (c) amorphous carbon is used. Among them, a layer made of a substantially transparent dielectric or a very thin metal layer (including an alloy) is preferable.

Specifically, silicon oxide, particularly silicon dioxide, oxides such as zinc oxide, cerium oxide, yttrium oxide; sulfides such as zinc sulfide and yttrium sulfide; nitrides such as silicon nitride; silicon carbide; oxide and sulfur A mixture thereof (oxysulfide); and alloys described later are suitable. Further, a mixture of about 30:70 to 90:10 (weight ratio) of silicon oxide and zinc sulfide is also suitable. A mixture of sulfur, yttrium dioxide and zinc oxide (Y ₂ O ₂ S—ZnO) is also suitable.

  As the metal or alloy, silver or a material containing 0.1 to 15 atomic% of at least one element selected from the group consisting of titanium, zinc, copper, palladium, and gold, which is mainly composed of silver, is preferable. is there. Further, those containing silver as a main component and containing 0.1 to 15 atomic% of at least one rare earth element are also suitable. As this 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 when the buffer layer is produced. In particular, a polymer film that can be produced by vacuum deposition or CVD is useful.
The thickness of the buffer layer 28 is preferably 2 nm or more, more preferably 5 nm or more. If the thickness of the buffer layer 28 is excessively thin, there is a possibility that the prevention of the above mixing phenomenon is insufficient. However, it is preferably 2000 nm or less, more preferably 500 nm or less. If the buffer layer 28 is excessively thick, it is not only necessary for preventing mixing but also may reduce the light transmittance. In the case of a layer made of an inorganic material, it takes a long time to form a film, and the productivity may be lowered or the film stress may be increased. In particular, in the case of a metal, about 20 nm or less is preferable because the light transmittance is excessively lowered.

In addition, a buffer layer as an intermediate layer may be provided between the translucent reflective layer 23 and the transparent adhesive layer 24.
(J) Other layers In the above laminated structure, any other layers may be sandwiched as necessary. Alternatively, any other layer may be provided on the outermost surface of the medium.

Specifically, 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 can protect 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. Examples of the inorganic substance include silicon oxide, silicon nitride, MgF ₂ , SnO _{2 and the} like.

  A thermoplastic resin, a thermosetting resin, etc. can be formed by dissolving in an appropriate 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 a suitable solvent, and then applying the coating solution and curing it by irradiation with UV light. 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 alone or in combination, and may be used not only as a single layer but also as a multilayer film.

As a method for forming the protective layer, a coating method such as a spin coating method and a casting method, a sputtering method, a chemical vapor deposition method, and the like are used as in the recording layer. Among these, a 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 1 to 50 μm in the optical recording medium of the present invention.

Furthermore, the above optical recording medium can be printed on a surface that is not the incident surface of recording light or reproducing light as required by various printers such as inkjet 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 configuration, and the recording layer may be three or more layers. Alternatively, two optical recording media having this layer structure and two first recording layers 21 may be bonded to form a larger capacity medium having four recording layers.

  Incidentally, as described above, in the single-sided incident type optical recording medium having the two dye-containing recording layers 22 and 25, the first dye-containing recording layer 22 on the side closer to the light incident side (one side) and the second on the far side. And a dye-containing recording layer 25. For this reason, information recording or reproduction on the second dye-containing recording layer 25 located on the side far from the light incident side is performed by making light incident through the first dye-containing recording layer 22. Become.

In such a single-sided incident type optical recording medium, the depth of the groove (guide groove, concave portion) 32 formed in the second substrate 27 on the side opposite to the light incident side is set in the same manner as a general optical recording medium. For example, if the thickness is about 150 nm, the reflectance necessary for recording or reproducing information in the second dye-containing recording layer 25 may not be obtained.
Therefore, in the optical recording medium according to the present embodiment, the groove shape of the second substrate 27 is made shallower in a specific range, unlike the groove depth of a general dye-based optical recording medium. Therefore, the reflectance sufficient to record or reproduce information of the second dye-containing recording layer 25 is obtained. When a sufficiently high reflectance can be obtained in this way, compatibility with a DVD-ROM can be easily obtained. Moreover, if the depth of the groove of the second substrate 27 is small, the productivity of the second substrate 27 having the guide groove is improved, and the mass productivity is improved.

  In this way, unlike the conventional general dye-based optical recording medium, the depth of the groove 32 of the second substrate 27 is reduced to a specific range, so that the second dye-containing recording layer 25 is reduced. Therefore, the reflectance sufficient for recording or reproducing the information can be obtained, so that both the thin film portion and the thick film portion of the second dye-containing recording layer 25 can be used as the recording track. That is, information can be recorded or reproduced by making light incident (irradiated) on the land (convex portion) of the second substrate 27, that is, the concave portion (thin film portion) of the second recording layer 25, or the second. Information can be recorded or reproduced by making light incident (irradiated) on the groove (concave portion) of the substrate 27, that is, the convex portion (thick film portion) of the second recording layer 25.

Specifically, the depth of the groove 32 of the second substrate 27 is set as follows.
First, the depth (groove depth) of the groove 32 of the second substrate 27 is preferably 1/100 × λ or more, where λ is the recording / reproducing wavelength. More preferably, it is 2/100 × λ or more, and further preferably 3/100 × λ or more. This is because it is preferable to have such a depth in order to ensure sufficient reflectivity and to stably perform tracking.

For example, when the recording / reproducing wavelength is λ = 650 nm, the depth of the groove 32 of the second substrate 27 is preferably 7 nm or more. More preferably, it is 13 nm or more, and further preferably 20 nm or more.
However, the depth of the groove 32 of the second substrate 27 is preferably 1/6 × λ or less. More preferably, it is 1/8 × λ or less, and further preferably, 1/10 × λ or less. This is because it is desirable not to make the grooves too deep in order to reduce the shape change of the reflective layer to ensure the amount of reflected light and to obtain a high reflectance.

For example, the depth of the groove 32 of the second substrate 27 is preferably 108 nm or less when the recording / reproducing wavelength is λ = 650 nm. More preferably, it is 81 nm or less, More preferably, it is 65 nm or less.
The width (groove width, G width; half width) of the groove 32 of the second substrate 27 is preferably 1/10 × T or more, where T is the track pitch. More preferably, it is 2/10 × T or more, and further preferably 3/10 × T or more. This is because if the groove width is too narrow, tracking tends to be difficult.

For example, when the track pitch is 740 nm, the width of the groove 32 of the second substrate 27 is preferably 74 nm or more. More preferably, it is 148 nm or more, and further preferably 222 nm or more.
However, the width of the groove 32 of the second substrate 27 is preferably 9/10 × T or less. More preferably, it is 8/10 × T or less, and further preferably 7/10 × T or less. This is because if the groove width is too wide, tracking is difficult to be performed and it is difficult to perform recording well.

For example, when the track pitch is 740 nm, the width of the groove 32 of the second substrate 27 is preferably 666 nm or less. More preferably, it is 592 nm or less, and more preferably 518 nm or less.
As described above, in this embodiment, the depth of the groove 32 of the second substrate 27 is made shallower than the depth of the groove of a general dye-based optical recording medium. The depth 32 is preferably shallower than the depth of the groove 31 of the first substrate 21.

  For example, it is preferable to set the recording / reproducing wavelength to 650 nm, the depth of the groove 32 of the second substrate 27 to 65 nm or less, and the depth of the groove 31 of the first substrate 21 to 108 nm or more, for example. The combination of setting the groove depths of the first substrate 21 and the second substrate 27 is not limited to this, and the depth of the groove 32 of the second substrate 27 is greater than the depth of the groove 31 of the first substrate 21. Should be shallower.

Usually, the depth of the groove 32 of the second substrate 27 is made shallower than the depth of the groove 31 of the first substrate 21, and preferably 90% or less, more preferably 80% or less. Preferably it is 70% or less. However, it is usually 5% or more of the depth of the groove 31 of the first substrate 21, and preferably 10% or more.
Therefore, according to the optical recording medium of the present invention, in the optical recording medium having the plurality of dye-containing recording layers 22 and 25 for recording or reproducing information by making light incident from one side, it is far from the light incident side. There is an advantage that a reflectance sufficient for recording or reproducing information of the dye-containing recording layer 25 located on the side can be obtained. As a result, good recording / reproducing characteristics can be obtained in any of the plurality of dye-containing recording layers 22 and 25.

In the present embodiment, an example in which the present invention is applied to a bonded dual layer type single-sided incident DVD-R has been described. However, the present invention is not limited to this, and information is obtained by making light incident from one side. As long as the optical recording medium has a dye-containing recording layer for recording or reproducing the above, the present invention can be applied to optical recording media having other configurations.
For example, as shown in FIG. 2, a first recording layer (first dye-containing recording layer) containing a dye on a disk-shaped transparent (light-transmitting) first substrate (first light-transmitting substrate) 1 2, translucent reflective layer (translucent reflective layer) 3, intermediate resin layer (intermediate layer) 4, second recording layer containing dye (second dye-containing recording layer) 5, reflective layer 6, second substrate 78 ( The present invention can also be applied to a laminated dual layer type single-sided incident type DVD-R having an adhesive layer 7 and a substrate 8 in this order. Reference numerals 11 and 12 are guide grooves (grooves and recesses).

  In this case, a guide groove provided on the second substrate 78 (substrate opposite to the light incident side) is used for recording or reproducing information on the second recording layer 5 located on the side far from the light incident side. Since (grooves, recesses) 12 are used, in order to obtain a sufficient reflectance, the depth of the guide groove 12 is set to 1/100 × λ˜1 / It may be within a range of 6 × λ.

  However, the present invention is particularly effective when applied to a bonded dual layer type single-sided incident optical recording medium. That is, a first information recording body in which at least a first dye-containing recording layer containing a first dye and a translucent reflective layer are sequentially laminated on a first substrate having a guide groove, and a guide groove are provided. A second information recording body formed by sequentially laminating at least a reflective layer and a second dye-containing recording layer containing a second dye on the second substrate, the first information recording body and the second information recording; Applied to an optical recording medium in which information is recorded or reproduced by allowing light to enter from the first substrate side, with the body facing the surface opposite to the substrate and being bonded via an optically transparent adhesive layer Then, the effect is high.

In such a medium, since the two information recording bodies are bonded in the opposite direction, when viewed from the incident light side, the guide groove is filled with the dye-containing recording layer and the optical path between the groove portion and the land portion Since the difference in length tends to be different between the two recording layers, the optimum groove depth of the second substrate is different from that of the first substrate, and it is considered that the shallower groove tends to be the optimum value.
Further, for example, the present invention can be applied not only to a so-called substrate surface incident type optical recording medium but also to a so-called film surface incident type optical recording medium. That is, for example, a substrate (including a protective layer and a substrate), a dye-containing recording layer, a reflective layer, and a substrate having a guide groove are provided, and light is incident from the substrate side (opposite side of the substrate). The present invention can also be applied to an optical recording medium for recording or reproducing information (an optical recording medium having one dye-containing recording layer).

In this case, the depth of the guide groove of the substrate is recorded in order to obtain sufficient reflection in the guide groove (groove, recess) provided on the substrate (substrate opposite to the light incident side). The reproduction wavelength may be in the range of 1/100 × λ to 1/6 × λ, where λ is the reproduction wavelength.
Thus, there is an advantage that sufficient reflectance can be obtained when light is incident from the opposite side of the substrate to record or reproduce information in the dye-containing recording layer. As a result, good recording / reproducing characteristics can be obtained.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

Next, the present invention will be described in more detail by way of examples. The present invention is not limited to the following examples.
(Production of optical recording medium)
In the optical recording media of this example and the comparative example, for example, at least a first dye-containing recording layer containing a first dye and a translucent reflective layer are sequentially laminated on a first substrate having a guide groove. And a second information recording body in which at least a reflective layer and a second dye-containing recording layer containing a second dye are sequentially laminated on a second substrate having a guide groove. The first information recording body and the second information recording body are bonded to each other through an optically transparent adhesive layer with the opposite surfaces of the substrate facing each other.

Hereinafter, the production of the second information recording body will be mainly described.
First, a polycarbonate second substrate (refractive index 1) having a guide groove having a track pitch of 740 nm, a predetermined groove depth and a groove width by injection molding using a mother stamper (negative stamper). .56).
Next, a silver alloy containing 97 atom% or more of Ag was sputtered on the second substrate to form a reflective layer.

Next, an octafluoropentanol solution of a metal-containing azo dye was spin-coated on the reflective layer under predetermined coating conditions (dye concentration) and dried at 100 ° C. for 30 minutes to form a second dye-containing recording layer. . Here, the film thickness of the second dye-containing recording layer was set to a predetermined film thickness by changing the coating conditions. The recording layer had a refractive index of 2.25 and an extinction coefficient of 0.02.
Next, a buffer layer is formed on the second dye-containing recording layer by sputtering one of Ag alloy containing 97 atomic% or more of Ag, (ZnS) ₈₀ (SiO ₂ ) ₂₀ , and SiO _2. A protective layer was formed by spin coating an ultraviolet curable resin (SPC-920, manufactured by Nippon Kayaku Co., Ltd.) to a thickness of about 5 to 7 μm.

Then, usually, a radical ultraviolet curable resin (adhesive) is applied onto the protective layer by spin coating, and bonded to the reflective layer side of the first substrate including the separately prepared recording layer (first recording layer). Thus, an optical recording medium is manufactured.
However, the thickness of the first information recording body does not include the recording layer and the translucent reflective layer so that the influence of the first information recording body can be eliminated and the characteristics of the second recording layer can be accurately evaluated. A 0.6 mm grooveless polycarbonate substrate (refractive index 1.56) was used. The refractive index of the adhesive layer after curing was 1.53.
(Measuring method)
The reflectivity of the unrecorded second recording layer was measured using an evaluation machine (DDU-1000 manufactured by Pulse Tech Co., Ltd., maximum recording power 15 mW) equipped with a semiconductor laser having a wavelength of 657 nm (NA = 0.65).

  In this example, the reflectance of 25% or more was considered excellent, and the reflectance of 30% or more was considered superior. Usually, in order to maintain compatibility with the DVD-ROM, the reflectance of the unrecorded portion of the second recording layer may be 10% or more. Since this embodiment does not have the first recording layer and the translucent reflective layer, the reflectance tends to be higher than the actual one. However, if the reflectance of 25% or more is obtained in this embodiment, the actual first Even if the influence of the information recording medium is taken into consideration, it is considered that a reflectance of 10% or more can be obtained.

  The measurement results of each example and comparative example are as shown in Table 1 below.

Example 1
In Example 1, guide grooves were formed on the second substrate so as to have a groove depth of 65 nm (equivalent to approximately λ / 10), a groove width (G width) of 320 nm, and a land width (L width) of 420 nm.
The buffer layer was formed by sputtering an Ag alloy. Then, the second recording layer was formed by spin-coating the metal-containing azo dye with the dye concentration as the coating condition being 3.55 wt%.

The film thickness (thick film portion, G film thickness) of the groove portion of the second recording layer thus formed was 85 nm, and the film thickness (thin film portion, L film thickness) of the land portion was 70 nm.
When the reflectance of the groove part was measured on the optical recording medium thus produced under the conditions as described above, the reflectance was 30.7% as shown in Table 1.
(Example 2)
In Example 2, the reflectance of the land portion was measured on the optical recording medium manufactured in the same manner as in Example 1 under the above conditions. As a result, as shown in Table 1, the reflectance was 40.0%.

Thus, it has been found that the reflectance required for recording / reproducing can be obtained even when the groove recording is replaced with land recording.
(Example 3)
In Example 3, the reflectance was measured in the same manner as in Example 2 except that the buffer layer was made of SiO _2. As shown in Table 1, the reflectance was 28.1%.

Thus, it has been found that the reflectance required for recording / reproduction can be obtained even if the buffer layer is changed from Ag alloy to SiO ₂ .
(Example 4)
In Example 4, the film thickness of the groove portion (thick film portion, G film thickness) of the second recording layer is set to 100 nm by setting the dye concentration as the coating condition to 4.43 wt%, and the film thickness of the land portion ( Reflection is performed in the same manner as in Example 2 except that the thin film portion (L film thickness) is 80 nm (that is, the thickness difference between the thick film portion of the second recording layer and the thin film portion is 20 nm). When the rate was measured, as shown in Table 1, the reflectivity was 27.4%.

Thus, it was found that the reflectance required for recording / reproduction can be obtained even if the film thickness of the second recording layer is changed.
(Example 5)
In Example 5, the reflectance was measured in the same manner as in Example 4 except that the buffer layer was changed to ZnS—SiO _2. As shown in Table 1, the reflectance was 26.7%.

Thus, it was found that the reflectance required for recording / reproduction can be obtained even when the buffer layer is changed from an Ag alloy to ZnS—SiO ₂ .
(Example 6)
In Example 6, by setting the dye concentration as the coating condition to 4.43 wt%, the film thickness of the groove portion (thick film portion, G film thickness) of the second recording layer is set to 100 nm, and the film thickness of the land portion ( Reflection is performed in the same manner as in Example 3 except that the thin film portion (L film thickness) is 80 nm (that is, the thickness difference between the thick film portion of the second recording layer and the thin film portion is 20 nm). When the rate was measured, as shown in Table 1, the reflectivity was 29.7%.

Thus, it was found that the reflectance required for recording / reproduction can be obtained even if the film thickness of the second recording layer is changed.
(Example 7)
In Example 7, guide grooves were formed on the second substrate so as to have a groove depth of 50 nm (equivalent to approximately λ / 13), a groove width (G width) of 410 nm, and a land width (L width) of 330 nm.

The buffer layer was formed by sputtering an Ag alloy. Then, the second recording layer was formed by spin-coating the metal-containing azo dye with the dye concentration as the coating condition being 3.55 wt%.
The film thickness (thick film portion, G film thickness) of the groove portion of the second recording layer thus formed was 105 nm, and the film thickness (thin film portion, L film thickness) of the land portion was 75 nm.

When the reflectance of the groove part was measured on the optical recording medium thus produced under the conditions as described above, the reflectance was 40.1% as shown in Table 1.
Thus, it has been found that the reflectance increases as the groove depth of the second substrate is reduced as compared with Example 1 described above.
(Example 8)
In Example 8, the reflectance was measured in the same manner as in Example 7 except that the buffer layer was made of SiO _2. As shown in Table 1, the reflectance was 30.9%.

Thus, it has been found that the reflectance required for recording / reproduction can be obtained even if the buffer layer is changed from Ag alloy to SiO ₂ .
Example 9
In Example 9, by setting the dye concentration as the coating condition to 4.43 wt%, the film thickness of the groove portion (thick film portion, G film thickness) of the second recording layer is set to 130 nm, and the film thickness of the land portion ( Reflection is performed in the same manner as in Example 7 except that the thin film portion (L film thickness) is 95 nm (that is, the film thickness difference between the thick film portion and the thin film portion of the second recording layer is 35 nm). When the rate was measured, as shown in Table 1, the reflectivity was 29.1%.

Thus, it was found that the reflectance required for recording / reproduction can be obtained even if the film thickness of the second recording layer is changed.
(Example 10)
In Example 10, when the reflectance was measured in the same manner as in Example 9 except that the buffer layer was ZnS—SiO ₂ , the reflectance was 31.3% as shown in Table 1.

Thus, it was found that the reflectance required for recording / reproduction can be obtained even when the buffer layer is changed from an Ag alloy to ZnS—SiO ₂ .
(Example 11)
In Example 11, by setting the dye concentration as the coating condition to 4.43 wt%, the film thickness of the groove portion (thick film portion, G film thickness) of the second recording layer is set to 100 nm, and the film thickness of the land portion ( Reflection is performed in the same manner as in Example 8 except that the thin film portion (L film thickness) is 80 nm (that is, the film thickness difference between the second recording layer and the thin film portion is 20 nm). When the rate was measured, as shown in Table 1, the reflectance was 31.2%.

Thus, it was found that the reflectance required for recording / reproduction can be obtained even if the film thickness of the second recording layer is changed.
Example 12
In Example 12, the reflectance of the land portion was measured on the optical recording medium manufactured in the same manner as in Example 7 under the conditions described above. As a result, as shown in Table 1, the reflectance was 45.3%.

Thus, it has been found that the reflectance required for recording / reproducing can be obtained even when the groove recording is replaced with land recording.
(Example 13)
In Example 13, the reflectance was measured in the same manner as in Example 12 except that the buffer layer was changed to ZnS—SiO _2. As shown in Table 1, the reflectance was 29.0%.

Thus, it was found that the reflectance required for recording / reproduction can be obtained even when the buffer layer is changed from an Ag alloy to ZnS—SiO ₂ .
(Example 14)
In Example 14, the reflectance of the land portion was measured on the optical recording medium manufactured in the same manner as in Example 8 under the conditions described above. As a result, as shown in Table 1, the reflectance was 36.4%.

Thus, it has been found that the reflectance required for recording / reproducing can be obtained even when the groove recording is replaced with land recording.
(Example 15)
In Example 15, the reflectance of the land portion was measured on the optical recording medium manufactured in the same manner as in Example 9 under the above conditions. As a result, as shown in Table 1, the reflectance was 31.1%.

Thus, it has been found that the reflectance required for recording / reproducing can be obtained even when the groove recording is replaced with land recording.
(Example 16)
In Example 16, the reflectance of the land portion was measured on the optical recording medium manufactured in the same manner as in Example 10 under the conditions described above. As a result, as shown in Table 1, the reflectance was 38.2%.

Thus, it has been found that the reflectance required for recording / reproducing can be obtained even when the groove recording is replaced with land recording.
(Example 17)
In Example 17, the reflectance of the land portion was measured on the optical recording medium manufactured in the same manner as in Example 11 under the above-described conditions. As a result, as shown in Table 1, the reflectance was 36.1%.

Thus, it has been found that the reflectance required for recording / reproducing can be obtained even when the groove recording is replaced with land recording.
(Example 18)
In Example 18, guide grooves were formed on the second substrate so as to have a groove depth of 30 nm (approximately equivalent to λ / 20), a groove width (G width) of 220 nm, and a land width (L width) of 520 nm.

The buffer layer was formed by sputtering an Ag alloy. Then, the second recording layer was formed by spin coating the metal-containing azo dye with the dye concentration as the coating condition being 3.10 wt%.
The film thickness (thick film portion, G film thickness) of the groove portion of the second recording layer thus formed was 110 nm, and the film thickness (thin film portion, L film thickness) of the land portion was 70 nm.

When the reflectance of the groove part was measured on the optical recording medium thus produced under the conditions as described above, the reflectance was 43.0% as shown in Table 1.
Thus, it has been found that the reflectance increases as the groove depth of the second substrate is reduced as compared with Example 7 described above.
Example 19
In Example 19, the reflectance was measured in the same manner as in Example 18 except that the buffer layer was changed to ZnS—SiO _2. As shown in Table 1, the reflectance was 39.0%.

Thus, it was found that the reflectance required for recording / reproduction can be obtained even when the buffer layer is changed from an Ag alloy to ZnS—SiO ₂ .
(Example 20)
In Example 20, the reflectance was measured in the same manner as in Example 18 except that the buffer layer was made of SiO _2. As shown in Table 1, the reflectance was 43.2%.

Thus, it has been found that the reflectance required for recording / reproduction can be obtained even if the buffer layer is changed from Ag alloy to SiO ₂ .
(Example 21)
In Example 21, by setting the dye concentration as the coating condition to 3.55 wt%, the film thickness of the groove portion (thick film portion, G film thickness) of the second recording layer was set to 135 nm, and the film thickness of the land portion ( Reflection is performed in the same manner as in Example 18 except that the thin film portion (L film thickness) is 90 nm (that is, the film thickness difference between the second recording layer and the thin film portion is 45 nm). When the rate was measured, as shown in Table 1, the reflectivity was 30.2%.

Thus, it was found that the reflectance required for recording / reproduction can be obtained even if the film thickness of the second recording layer is changed.
(Example 22)
In Example 22, the reflectance was measured in the same manner as in Example 21 except that the buffer layer was changed to ZnS—SiO _2. As shown in Table 1, the reflectance was 41.7%.

Thus, it was found that the reflectance required for recording / reproduction can be obtained even when the buffer layer is changed from an Ag alloy to ZnS—SiO ₂ .
(Example 23)
In Example 23, the film thickness of the groove portion (thick film portion, G film thickness) of the second recording layer was set to 135 nm by setting the dye concentration as the coating condition to 3.55 wt%, and the film thickness of the land portion ( Reflection is performed in the same manner as in Example 20 except that the thin film portion (L film thickness) is 90 nm (that is, the thickness difference between the thick film portion and the thin film portion of the second recording layer is 45 nm). When the rate was measured, as shown in Table 1, the reflectivity was 38.9%.

Thus, it was found that the reflectance required for recording / reproduction can be obtained even if the film thickness of the second recording layer is changed.
(Example 24)
In Example 24, the reflectance of the land portion was measured on the optical recording medium manufactured in the same manner as in Example 18 under the above conditions. As shown in Table 1, the reflectance was 49.1. %Met.

Thus, it has been found that the reflectance required for recording / reproducing can be obtained even when the groove recording is replaced with land recording.
(Example 25)
In Example 25, the reflectance of the land portion was measured on the optical recording medium manufactured in the same manner as in Example 19 under the above conditions. As shown in Table 1, the reflectance was 43.9. %Met.

Thus, it was found that the reflectance required for recording / reproduction can be obtained even when the buffer layer is changed from an Ag alloy to ZnS—SiO ₂ .
(Example 26)
In Example 26, the reflectance of the land portion was measured on the optical recording medium manufactured in the same manner as in Example 20 under the above conditions. As shown in Table 1, the reflectance was 49.5. %Met.

Thus, it has been found that the reflectance required for recording / reproducing can be obtained even when the groove recording is replaced with land recording.
(Example 27)
In Example 27, the reflectance of the land portion of the optical recording medium manufactured in the same manner as in Example 21 was measured under the conditions described above. As shown in Table 1, the reflectance was 33.9. %Met.

Thus, it has been found that the reflectance required for recording / reproducing can be obtained even when the groove recording is replaced with land recording.
(Example 28)
In Example 28, the reflectance of the land portion of the optical recording medium manufactured in the same manner as in Example 22 was measured under the above conditions. As shown in Table 1, the reflectance was 47.9. %Met.

Thus, it has been found that the reflectance required for recording / reproducing can be obtained even when the groove recording is replaced with land recording.
(Example 29)
In Example 29, the reflectance of the land portion of the optical recording medium manufactured in the same manner as in Example 23 was measured under the above conditions. As shown in Table 1, the reflectance was 44.2. %Met.

Thus, it has been found that the reflectance required for recording / reproducing can be obtained even when the groove recording is replaced with land recording.
(Comparative Example 1)
In Comparative Example 1, guide grooves were formed on the second substrate so as to have a groove depth of 120 nm (corresponding to approximately λ / 5.5), a groove width (G width) of 330 nm, and a land width (L width) of 410 nm.

The buffer layer was formed by sputtering an Ag alloy. Then, the second recording layer was formed by spin-coating the metal-containing azo dye with the dye concentration as the coating condition being 1.90 wt%.
The film thickness (thick film portion, G film thickness) of the groove portion of the second recording layer thus formed was 70 nm, and the film thickness (thin film portion, L film thickness) of the land portion was 30 nm.

When the reflectance of the groove portion was measured on the optical recording medium thus produced under the conditions as described above, the reflectance was 9.0% as shown in Table 1.
As described above, it was found that when the groove depth of the second substrate is deeper than the above-described embodiments, the reflectance necessary for recording / reproduction cannot be obtained.
(Comparative Example 2)
In Comparative Example 2, the reflectance was measured in the same manner as in Comparative Example 1 except that the buffer layer was made of SiO _2. As shown in Table 1, the reflectance was 6.5%.

Thus, it has been found that even when the buffer layer is changed from an Ag alloy to SiO ₂ , the reflectance necessary for recording / reproduction cannot be obtained.
(Comparative Example 3)
In Comparative Example 3, guide grooves were formed on the second substrate so as to have a groove depth of 160 nm (equivalent to approximately λ / 4), a groove width (G width) of 310 nm, and a land width (L width) of 430 nm.

The buffer layer was formed by sputtering an Ag alloy. Then, the second recording layer was formed by spin-coating the metal-containing azo dye with the dye concentration as the coating condition being 1.90 wt%.
The film thickness (thick film portion, G film thickness) of the groove portion of the second recording layer thus formed was 75 nm, and the film thickness (thin film portion, L film thickness) of the land portion was 20 nm.

When the reflectance of the groove portion was measured on the optical recording medium thus produced under the conditions as described above, the reflectance was 12.9% as shown in Table 1.
As described above, it was found that when the groove depth of the second substrate was increased as compared with Comparative Example 1 described above, the reflectance required for recording / reproduction could not be obtained although the reflectance increased.
(Comparative Example 4)
In Comparative Example 4, the reflectance was measured in the same manner as in Comparative Example 3 except that the buffer layer was made of SiO _2. As shown in Table 1, the reflectance was 19.9%.

Thus, it has been found that even when the buffer layer is changed from an Ag alloy to SiO ₂ , the reflectivity is high, but the reflectivity necessary for recording / reproduction cannot be obtained.
(Summary)
As in the comparative examples 1 to 4, when the depth of the groove of the second substrate is set to 120 nm and 160 nm, for example, the recording of information on the second dye-containing recording layer located on the side far from the light incident side or While the reflectance required for reproduction cannot be obtained, the land recording and groove recording can be performed by reducing the depth of the groove of the second substrate to 65 nm or less, as in each of the first to 29th embodiments. In any case, it has been found that the reflectance necessary for recording or reproducing information of the second dye-containing recording layer located on the side far from the light incident side can be obtained.

In each of the above embodiments, in order to eliminate the influence of the first information recording body and evaluate the characteristics of the second recording layer as precisely as possible, the recording layer and the translucent reflective layer are used as the first information recording body. Although the substrate having no groove is used, the use of the normal first information recording body does not significantly affect the evaluation of the second recording layer.
In the media of Examples 1 to 29, sufficient reflectivity, which is the most important requirement for recording / reproducing, is obtained. However, by appropriately selecting a configuration other than the groove depth, other recording / reproducing characteristics can be obtained. It seems that an excellent optical recording medium can be obtained.

1 is a schematic diagram showing an overall configuration of an optical recording medium according to an embodiment of the present invention. It is a schematic diagram which shows the whole structure of the other optical recording medium concerning one Embodiment of this invention.

Explanation of symbols

1,21 First substrate 2,22 First recording layer (first dye-containing recording layer)
3,23 Translucent reflective layer 4 Intermediate resin layer (intermediate layer)
5,25 Second recording layer (second dye-containing recording layer)
6,26 Reflective layer 7 Adhesive layer 8 Substrate 27 Second substrate 28 Buffer layer 11, 12, 31, 32 Groove (guide groove)
22A, 25A Thick film part 22B, 25B Thin film part 24 Transparent adhesive layer (intermediate layer)
78 Second substrate

Claims (5)

At least a first substrate having a guide groove, a first dye-containing recording layer, a translucent reflective layer, a second dye-containing recording layer, a reflective layer, and a second substrate having a guide groove, and incident light from the first substrate side An optical recording medium for recording or reproducing information of the first dye-containing recording layer and the second dye-containing recording layer,
An optical recording medium characterized in that the guide groove depth of the second substrate is in the range of 1/100 × λ to 1/8 × λ, where λ is a recording / reproducing wavelength. A first information recording body in which at least a first dye-containing recording layer containing a first dye and a translucent reflective layer are sequentially laminated on a first substrate having a guide groove, and a second having a guide groove. A second information recording body comprising at least a reflective layer and a second dye-containing recording layer containing a second dye sequentially laminated on the substrate, the first information recording body and the second information recording An optical recording medium in which information is recorded or reproduced by making light incident from the first substrate side, which is bonded to the body with the opposite surface of the substrate facing each other through an optically transparent adhesive layer. There,
The depth of the guide groove of the second substrate is in the range of 1/100 × λ to 1/8 × λ, where λ is the recording / reproducing wavelength . The optical recording medium according to claim 1, wherein a depth of the guide groove of the second substrate is shallower than a depth of the guide groove of the first substrate . An optical recording medium having a plurality of dye-containing recording layers for recording or reproducing information by making light incident from one side,
The depth of the guide groove used for recording or reproducing information in the dye-containing recording layer located on the side far from the light incident side is 1/100 × λ to 1/8 × λ, where λ is the recording / reproducing wavelength. An optical recording medium characterized by being in the range. An optical recording medium comprising at least a substrate having a dye-containing recording layer, a reflective layer, and a guide groove, and recording or reproducing information on the dye-containing recording layer by making light incident from the opposite side of the substrate,
The depth of the guide groove of the substrate is in the range of 1/100 × λ to 1/8 × λ, where λ is a recording / reproducing wavelength.

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