JP4922134B2 - Optical recording medium and medium recognition signal recording method - Google Patents

Description

  The present invention relates to an optical recording medium for recording information, and more particularly to a writable optical recording medium and a method for recording a medium recognition signal on the optical recording medium.

  Currently, various optical recording media such as CD-R, CD-RW, and MO can store a large amount of information and are easily recognized as an external storage device in an information processing apparatus such as a computer because they can be easily accessed at random. It is becoming popular. Furthermore, it is desired to further increase the recording density by increasing the amount of information handled. These optical recording media are roughly classified into read-only media (hereinafter sometimes referred to as ROM media), write-once media, and rewritable media. In a ROM medium, information is recorded by concavo-convex pits formed on a substrate, but write-once media and rewritable media are recording layers made of materials whose optical characteristics change by laser irradiation. have. As the recording layer material, inorganic materials such as organic dye materials and phase change materials are generally used.

  On the other hand, the recording density of the optical recording medium depends on the focused spot diameter of the laser beam. For this reason, in an optical recording medium, it is possible to obtain a recording density that is high enough to be focused on a minute region. This condensing spot diameter is known to be proportional to the wavelength of the laser beam, and a higher recording density can be obtained by using a laser beam having a shorter wavelength. In recent years, due to the advancement of laser technology, a blue semiconductor laser having a wavelength of around 400 nm can be used, and optical recording media using this, such as HD-DVD and Blu-ray, have been proposed (for example, Patent Document 1). 2). In this specification, such a laser beam used by a user for recording / reproducing is appropriately referred to as “recording / reproducing light”. The wavelength of “blue recording / reproducing light” is typically 300 to 450 nm.

  Generally, a recording / reproducing drive for an optical recording medium is compatible with a plurality of media including a CD and a DVD. Therefore, when an optical recording medium is reproduced by a drive, the type of the medium is first recognized. There are many cases. For this reason, for example, a simple signal for medium recognition (medium recognition signal) is recorded at the time of shipment on the inner periphery of the disc that is not used by the user for recording information. In addition, a serial number or the like is added to prevent unauthorized copying of information by using a part of the medium recognition signal.

  Such a medium recognition signal is desirably recorded over a wide radius region because it is desirable to reliably reproduce the signal without tracking. For example, the HD-DVD standard determined by the DVD Forum stipulates that a medium identification signal is recorded in a bar code form in an area called a burst cutting area (Burst Cutting Area). The medium recognition signal is usually recorded by a recording device using a laser because a different signal recording method (unique ID) is used for each disk. Hereinafter, in the present invention, the burst cutting area may be referred to as “BCA”. In the present invention, “BCA” means a recorded portion of a layer on which a medium recognition signal is recorded.

  In a ROM medium in which recorded information is recorded mainly by forming concave and convex pits on a substrate, it is practically impossible to record a serial number for each ROM medium because the ROM medium is mass-produced by pressing with a stamper. . Therefore, in a ROM medium, a method of irradiating a metal reflection film with laser light and recording a medium recognition signal including a serial number is common (see, for example, Patent Documents 3 to 5). In this method, a medium recognition signal can be recorded by melting and removing a part of the metal reflective film as BCA. Further, since the write-once medium and the rewritable medium usually have a metal reflection film, the medium recognition signal can be recorded on the BCA by the above method.

JP-A-11-105423 Japanese Patent Laid-Open No. 11-78239 JP 2004-318938 A JP 2006-54032 A JP 2005-196940 A

  However, when the above method is used, corrosion may occur in the defect portion of the metal reflective film which has been melted and removed, and reliability such as storage stability as an optical recording medium may be deteriorated. Therefore, in a write-once medium or a rewritable medium, it is preferable to record a medium recognition signal in the recording layer, as in the case of recording information.

  On the other hand, in HD-DVD and Blu-ray capable of high-density recording, aiming at further higher density, a laminated optical recording medium having a plurality of recording layers has begun to be put into practical use. In these optical recording media, the standard stipulates that the BCA is provided in the recording layer farthest from the surface on which the recording / reproducing light enters the optical recording medium (hereinafter sometimes referred to as “information surface”). Yes. In this case, when the laser beam is irradiated from the information surface side and the medium recognition signal is recorded on the recording layer farthest from the information surface, the most from the information surface, no matter how much the power of the laser light or the focus depth is optimized. There has been a problem that the medium recognition signal is strongly recorded by the near recording layer. That is, the recording / reproducing drive recognizes the recording layer closest to the information surface as the recording layer provided with the BCA, resulting in malfunction of the recording / reproducing drive.

  In order to solve this problem, there is a method in which a medium recognition signal is irradiated with laser light from the back surface opposite to the information surface. However, when laser light is irradiated from the back surface, a reflective layer formed corresponding to this recording layer exists before the recording layer farthest from the information surface on which the BCA is formed. For this reason, the laser beam is almost reflected by the reflective layer, and sufficient laser energy cannot be applied to the recording layer, which makes it very difficult to record a medium recognition signal on the recording layer. It was. Of course, it is possible to record the medium recognition signal by melting and removing the reflective layer instead of the recording layer as described above, but the above-described problem of deterioration in reliability still remains. This problem is not limited to the laminated recording medium when the method of irradiating laser light from the back surface is assumed, and the same applies to a recording medium having a single recording layer.

  As described above, in an optical recording medium that records and reproduces with blue laser light, it is difficult to record a highly reliable medium recognition signal on a recording layer, particularly a medium having a plurality of recording layers. The present invention was devised in view of the above problems, and in an optical recording medium for recording / reproducing with blue laser light, recording is performed from the back side opposite to the information side without impairing the recording characteristics of main information. An object of the present invention is to provide an optical recording medium capable of recording a medium recognition signal on a layer, and a method of recording a medium recognition signal on the optical recording medium.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have made a laser for recording a medium recognition signal from the back surface opposite to the surface (information surface) that irradiates the data area for recording main information with the laser beam. In the light irradiation method, a reflective layer (hereinafter referred to as “specific reflection layer”) formed corresponding to a recording layer having BCA (hereinafter sometimes referred to as “specific recording layer”). The present inventors have found that the above problem can be solved by increasing the value of the reflectance from the information surface side more than the value from the back surface side.

  That is, the gist of the present invention is that a main information recording laser beam having a wavelength of 300 nm to 450 nm is irradiated from the information surface to record the main information, and the medium is recognized from the back surface opposite to the information surface. A specific recording layer having a burst cutting area that is irradiated with a signal recording laser beam to record a medium recognition signal; and a specific reflective layer formed corresponding to the specific recording layer, the specific reflective layer In the optical recording medium, the reflectance from the information surface side at the wavelength of the main information recording laser light is larger than the reflectance from the back surface side.

  At this time, it is preferable that the optical recording medium includes two or more recording layers, and the recording layer farthest from the information surface among the recording layers is the specific recording layer.

  Moreover, it is preferable that the film thickness of this specific reflection layer is 60 nm or more and 200 nm or less.

  Furthermore, it is preferable that the reflectance of the specific reflective layer from the back surface side at the wavelength of the main information recording laser light is 55% or more and 85% or less.

  Moreover, it is preferable that the said specific reflection layer consists of several layers from which a composition differs (Claim 5).

  At this time, it is preferable that the adjacent reflective layer closest to the specific recording layer among the plurality of layers contains 85 atomic% or more of Ag.

Furthermore, among the plurality of layers, the thickness of the closest Itonari contact reflective layer on the specific recording layer is preferably 30nm or more 120nm or less (claim 7).

  The specific recording layer preferably contains an organic dye having a decomposition temperature of 100 ° C. or higher and 350 ° C. or lower and / or an amorphous semiconductor having a phase transition temperature of 100 ° C. or higher and 350 ° C. or lower. .

  Furthermore, a groove having a groove depth of 15 nm to 100 nm, a track pitch of 0.1 μm to 0.6 μm, and a ratio of the land width to the groove width of 0.3 to 1.2 is formed in the burst cutting area. (Claim 9).

  Another gist of the present invention is to record the medium recognition signal in the burst cutting area by irradiating the above-mentioned optical recording medium with the laser light for recording the medium recognition signal having a wavelength of 400 nm to 2000 nm from the back surface. The present invention resides in a method for recording a medium recognition signal (claim 10).

The present invention is described in further detail below.
As described above, as a recording method of the medium recognition signal, there is a method in which the recording light is incident from the surface (information surface) on the recording layer side. Is incident. In the present invention, the reflective layer preferably has a high reflectivity with respect to blue recording / reproducing light in order to satisfactorily record / reproduce main information. However, such a reflective layer usually has a high reflectivity with respect to a red or near-infrared laser wavelength of about 600 to 850 nm used for recording on a BCA.

  Therefore, conventionally, when the recording light of the medium recognition signal is incident from the back side, most of the recording light is reflected and it is difficult to record the medium recognition signal on the recording layer on the opposite side of the reflective layer. It was. For example, in the case of pure silver (Ag), which is often used as a material for a reflective layer in a DVD, 95% or more of light is reflected in the reflective layer, so the energy used for recording a medium recognition signal as heat is 5% or less of the input power. It was. In addition, such a high-reflectivity reflective layer generally has a high thermal conductivity, so the speed of thermal diffusion is high, and it is difficult to increase the temperature required for the recording layer to decompose. It was difficult.

  On the other hand, the present inventors, for example, prepare a layer using a material having a high reflectance by dividing the specific reflection layer into a plurality of layers on the side adjacent to the specific recording layer having BCA, and reflectivity on the back side. By providing a layer using a low material, a layer that maintains a high reflectivity for the laser light for main information recording and has a low reflectivity and a low thermal diffusion for the laser light for medium recognition signal recording It has been found that the above problem can be solved by providing the above.

  As described above, it is common to use a medium recognition signal recording laser beam having a wavelength higher than that of the main information recording laser beam. Since it does not fluctuate greatly, it is possible to predict the influence of the medium recognition signal on recording by defining the reflectance value of the main information recording laser beam. Accordingly, in the present invention, the invention is defined using the reflectance in the main information recording laser beam.

It has also been found that the above problem can be solved more reliably by using a dye and / or an amorphous semiconductor having an appropriate decomposition temperature or phase transition temperature as the recording layer.
As a result, the present invention maintains high reflectivity and good recording / reproduction characteristics for the recording / reproducing light corresponding to the main information, and even if the medium recognition signal is recorded from the back side, the reflective layer is destroyed or lost. Thus, it is possible to record a good medium recognition signal without causing a failure.

According to the optical recording medium of the present invention, the main information can be recorded / reproduced with blue laser light, and the medium recognition signal can be well recorded on the BCA provided in the recording layer.
Further, according to the medium recognition signal recording method of the present invention, the medium recognition signal can be satisfactorily recorded on the BCA of the optical recording medium of the present invention.

  Hereinafter, the present invention will be described in detail with reference to embodiments. However, the present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the invention.

[I. Optical recording medium]
[I-1. Overview〕
The optical recording medium of the present invention comprises one specific recording layer and one specific reflection layer. In addition to the specific recording layer, the optical recording medium of the present invention may include one or two or more other recording layers. In addition to the specific reflecting layer, one or two or more other reflecting layers may be provided. You may have.
The recording layer including the specific recording layer is irradiated with a main information recording laser beam (that is, recording / reproducing light) having a predetermined wavelength from a predetermined surface (information surface), and recording / reproducing of the main information by the recording / reproducing light. Is to be performed. However, among the recording layers, a medium recognition signal is recorded in addition to the main information in the specific recording layer. When this medium recognition signal is recorded, a medium recording signal recording laser beam (hereinafter referred to as “recognition signal recording light” as appropriate) is irradiated from the opposite surface (back surface) to the information surface, and the specific recording layer A medium recognition signal is recorded on the recording medium.

In the present embodiment, a multilayer optical recording medium is taken as an example and described with reference to the drawings.
FIG. 1 is an enlarged cross-sectional view schematically showing a main part of a single-sided two-layer optical recording medium as an embodiment of the present invention. FIG. 2 is a plan view schematically showing the optical recording medium. It is. As such a single-sided two-layer optical recording medium, for example, a dual-layer type single-sided incident type optical recording medium having two recording layers containing an organic dye (single-sided dual-layer HDDVD-R or single-sided dual-layer HDDVD). Recordable disc).
As shown in FIG. 1, an optical recording medium 100 of the present embodiment includes a disk-shaped first substrate 101 that is light transmissive, and a first recording layer 102 containing a dye and a first recording layer 102 on the first substrate 101. A semitransparent first reflective layer 103, a light transmissive intermediate layer 104 made of an ultraviolet curable resin, a second recording layer 105 containing a dye, a second reflective layer 106, an adhesive layer 107, and an outermost layer The second substrate 108 that forms the structure is laminated in order. Further, the surface on the first substrate 101 side of the optical recording medium 100 (this is the surface irradiated with the recording / reproducing light 109 when the main information is recorded in the data area) is the information surface 100A, which is the opposite side of the information surface 100A. The surface on the second substrate side formed in (2) is the back surface 100B.

  In the present embodiment, the second recording layer 105 functions as a specific recording layer, and the second reflective layer 106 functions as a specific reflective layer. In the second recording layer 105, as shown in FIG. 2, a data area 105X in which main information is recorded and a BCA 105Y in which a medium recognition signal is recorded are formed.

Further, as shown in FIG. 1, irregularities are respectively formed on the first substrate 101 and the intermediate layer 104, and these irregularities respectively constitute recording tracks. That is, the uneven shape (that is, the uneven shape described above) on the surface of each of the first substrate 101 and the intermediate layer 104 is the shape of the recording track.
In addition, recording / reproduction of optical information on the optical recording medium 100 is performed by recording / reproducing light 109 applied to the first recording layer 102 and the second recording layer 105 from the information surface 100A.

  In the present embodiment, the “light transmission (or transparency)” means light transmission with respect to the wavelength of light irradiated for recording / reproducing optical information. Specifically, the light transmittance is usually 30% or more, preferably 50% or more, more preferably 60% or more with respect to the wavelength of light for recording / reproducing such as the recording / reproducing light 109 and the recognition signal recording light. Say that there is transparency. On the other hand, the transmittance with respect to the wavelength of light for recording / reproduction is ideally 100%, but normally it is a value of 99.9% or less.

[I-2. First substrate]
The first substrate 101 is usually adjacent to the first recording layer 102 and constitutes the outermost layer. It is desirable that the first substrate 101 has optical properties such as light transmittance and low birefringence. Further, it is desirable that the first substrate 101 is excellent in moldability such as easy injection molding. Furthermore, the first substrate 101 desirably has a low hygroscopic property. Furthermore, it is desirable that the first substrate 101 has shape stability so that the optical recording medium has a certain degree of rigidity.

  Although the material which comprises the 1st board | substrate 101 is not specifically limited unless the effect of this invention is impaired remarkably, For example, acrylic resin, methacryl resin, polycarbonate resin, polyolefin resin (especially amorphous polyolefin), polyester type Examples thereof include resins, polystyrene resins, epoxy resins, and glass. In addition, the material which comprises the 1st board | substrate 101 may be used individually by 1 type, and may be used 2 or more types by arbitrary combinations and ratios.

  The shape of the first substrate 101 is not limited. However, it is usually formed in a disk shape having a center hole H in the center (see FIG. 2). Usually, the shape of the optical recording medium 100 is also determined by the shape of the first substrate 101.

  Further, as shown in FIG. 1, in the present embodiment, the first substrate 101 is provided with irregularities in a spiral shape or a concentric shape. And this unevenness forms a groove and a land. These irregularities coincide with the irregularities formed in the adjacent first recording layer 102, and information is normally recorded in the first recording layer 102 using grooves and / or lands constituted by such irregularities as recording tracks. -Played.

  The groove width is usually 100 nm to 500 nm, and the groove depth is usually 20 to 250 nm. When the recording track is spiral, the track pitch is preferably 0.1 to 0.6 μm.

  The thickness of the first substrate 101 is usually 2 mm or less, preferably 1 mm or less. This is because the coma aberration tends to be smaller as the distance between the objective lens and the recording layer is smaller and the substrate is thinner, and the recording density is easily increased. However, in order to obtain sufficient optical properties, hygroscopicity, moldability, and shape stability, the thickness is usually 10 μm or more, preferably 30 μm or more.

[I-3. First recording layer]
The first recording layer 102 is a recording layer that is provided adjacent to the first substrate 101 and is closer to the first substrate 101. Since the optical recording medium 100 of the present embodiment is a medium for recording main information using laser light having a wavelength of 300 to 450 nm as the recording / reproducing light 109, the first recording layer 102 can be recorded with this laser light. It is configured.
Although the substance which comprises the 1st recording layer 102 is not limited unless the effect of this invention is impaired remarkably, a pigment | dye, an amorphous semiconductor, a partial nitride film, a partial oxide film etc. are mentioned, for example.

  The dye used for the first recording layer 102 is not particularly limited, but an organic dye is used as an example. Examples of organic dyes include macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.), pyromethene dyes, polymethine dyes (cyanine dyes, merocyanine dyes, squarylium dyes, etc.), anthraquinone dyes, and azurenium dyes. Examples thereof include dyes, metal-containing azo dyes, and metal-containing indoaniline dyes. In addition, these pigment | dyes may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The dye used in the first recording layer 102 is preferably a dye compound having a maximum absorption wavelength λmax in a wavelength range of usually 250 nm or more and usually 550 nm or less and suitable for recording with the recording / reproducing light 109. Further, it is necessary to have absorption at the recording laser wavelength of the recording / reproducing light 109.

On the other hand, specific examples of the amorphous semiconductor material used for the first recording layer 102 include SbTe, GeTe, GeSbTe, InSbTe, AgSbTe, AgInSbTe, GeSb, GeSbSn, InGeSbTe, InGeSbSnTe, and the like. Materials. Among these, in order to increase the crystallization speed, it is preferable to use a composition containing Sb as a main component. In addition, these amorphous semiconductor materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.
Specific examples of the partial nitride film and the partial oxide film include partial nitride films such as BiGeN and SnNbN, and partial oxide films such as TeO _x and BiFO _x .

  In addition, it is desirable that a multilayer optical recording medium such as the optical recording medium 100 has higher sensitivity than a recording layer used in an optical recording medium such as a CD-R or a single-sided DVD-R.

  The film thickness of the first recording layer 102 is not particularly limited because a suitable film thickness varies depending on the recording method or the like. However, in order to obtain a sufficient degree of modulation, it is usually 5 nm or more, preferably 10 nm or more, and particularly preferably 20 nm or more. Moreover, in order to transmit light, it is 3 micrometers or less normally, Preferably it is 1 micrometer or less, More preferably, it is 200 nm or less.

[I-4. First reflective layer]
The first reflective layer 103 is a reflective layer adjacent to the first recording layer 102. Here, it is assumed that the first reflective layer 103 and the first recording layer 102 are adjacent to each other. It is desirable that the first reflective layer 103 has a small absorption of the recording / reproducing light 109, a light transmittance of usually 40% or more, and an appropriate light reflectance. As an example of a specific configuration of the first reflective layer 103, a layer having an appropriate transmittance by providing a thin metal with high reflectance can be given. Furthermore, it is desirable that the first reflective layer 103 has a certain degree of corrosion resistance. Further, it is desirable that the first recording layer 102 has a blocking property so that the first recording layer 102 is not affected by leaching of other components from the upper layer of the first reflective layer 103 (the intermediate layer 104 in this embodiment).

  Although the material which comprises the 1st reflective layer 103 is not specifically limited unless the effect of this invention is impaired remarkably, the thing with a moderately high reflectance in the wavelength of reproduction | regeneration light is preferable. Examples of materials constituting the first reflective layer 103 include Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Pd, Mg, Se, Hf, V, Nb, Ru, W, and Mn. , Re, Fe, Co, Rh, Ir, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, rare earth metals and other metals and metalloids, alone or in any combination alloy Can be used.

  Furthermore, the thickness of the 1st reflection layer 103 is 50 nm or less normally, Preferably it is 30 nm or less, More preferably, it is 25 nm or less. By setting it as the above range, the light transmittance is easily set to 40% or more. However, the thickness of the first reflective layer 103 is usually 3 nm or more, preferably 5 nm or more because the first recording layer 102 is not affected by the intermediate layer 104 existing on the first reflective layer 103.

[I-5. (Middle layer)
The intermediate layer 104 is a layer provided between the first reflective layer 103 and the second recording layer 105. The intermediate layer 104 is usually made of a resin that is transparent, can be formed with concave and convex shapes such as grooves and pits, and has high adhesive strength. Furthermore, it is preferable to use a resin having a small shrinkage ratio at the time of curing and bonding because the shape stability of the medium is high.
The intermediate layer 104 may be a single layer film or a multilayer film.

  Further, the intermediate layer 104 is often easily compatible with the second recording layer 105. For this reason, in order to prevent compatibility between the intermediate layer 104 and the second recording layer 105 and to suppress damage to the second recording layer 105, an appropriate buffer layer (not shown) is provided between both layers. desirable. In addition, a buffer layer can be provided between the intermediate layer 104 and the first reflective layer 103.

The intermediate layer 104 is preferably made of a material that does not damage the second recording layer 105. Examples of the material constituting the intermediate layer 104 include curable resins such as thermoplastic resins, thermosetting resins, and radiation curable resins. In addition, the material of the intermediate | middle layer 104 may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.
Among the materials for the intermediate layer 104, radiation curable resins are preferable, and among them, ultraviolet curable resins are preferable. By adopting these resins, it becomes easy to transfer the uneven shape of a stamper (described later).

Examples of the ultraviolet curable resin include a radical (radical polymerization type) ultraviolet curable resin and a cationic (cation polymerization type) ultraviolet curable resin, both of which can be used.
As the radical ultraviolet curable resin, for example, a composition containing an ultraviolet curable compound (radical ultraviolet curable compound) and a photopolymerization initiator as essential components is used. As the radical ultraviolet curable compound, for example, monofunctional (meth) acrylate and polyfunctional (meth) acrylate can be used as the polymerizable monomer component. These may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. Here, acrylate and methacrylate are collectively referred to as (meth) acrylate.
Moreover, although there is no restriction | limiting in a photoinitiator, For example, a molecular cleavage type or a hydrogen abstraction type is preferable. In the present invention, it is preferable to obtain an intermediate layer by curing an uncured ultraviolet curable resin precursor mainly composed of radical polymerization type acrylic ester.

On the other hand, examples of the cationic ultraviolet curable resin include an epoxy resin containing a cationic polymerization type photoinitiator. Examples of the epoxy resin include bisphenol A-epichlorohydrin type epoxy resin, alicyclic epoxy resin, long chain aliphatic type epoxy resin, brominated epoxy resin, glycidyl ester type epoxy resin, glycidyl ether type epoxy resin, complex Examples thereof include cyclic epoxy resins. As the epoxy resin, it is preferable to use a resin having a low content of free chlorine and chlorine ions. The amount of chlorine is preferably 1% by weight or less, more preferably 0.5% by weight or less.
Examples of the cationic polymerization type photoinitiator include a sulfonium salt, an iodonium salt, a diazonium salt, and the like.

  Moreover, when using radiation curable resin as a material of the intermediate | middle layer 104, it is preferable to use what is liquid at 20-40 degreeC. This is because when the resin raw material layer 104a is formed, application can be performed without using a solvent by using the radiation curable resin, so that productivity is improved. Moreover, it is preferable to adjust a viscosity so that it may become 20-4000 mPa * s at normal temperature.

  Further, the intermediate layer 104 is usually provided with irregularities in a spiral shape or a concentric shape. And this unevenness | corrugation forms a groove | channel and a land. These irregularities coincide with the irregularities formed in the adjacent second recording layer 105, and information is normally recorded on the second recording layer 105 using grooves and / or lands constituted by such irregularities as recording tracks. -Played.

The groove width is usually 100 to 500 nm, and the groove depth is usually 20 to 250 nm. When the recording track is spiral, the track pitch is preferably 0.1 to 0.6 μm. In this embodiment, it is assumed that the unevenness of the data area 105X of the second recording layer 105 is formed with this dimension.
Furthermore, the thickness of the intermediate layer 104 is preferably controlled accurately, and is usually 5 μm or more, preferably 10 μm or more. However, it is usually 100 μm or less, preferably 70 μm or less. When the thickness is less than the above range, signals in the first recording layer 102 and the second recording layer 105 are mixed during information reproduction, and signal noise called interlayer crosstalk tends to occur. On the other hand, if the thickness exceeds the above range, the warp due to the resin forming the intermediate layer 104 tends to be severe, or the aberration of the laser beam increases and the reproduced signal quality tends to be impaired.

  Incidentally, in the optical recording medium 100 of the present embodiment, the second recording layer 105 adjacent to the intermediate layer 104 functions as a specific recording layer. For this reason, the second recording layer 105 has a BCA 105Y. Normally, a recording track is not essential for the BCA 105Y because main information is not recorded. Therefore, the concave / convex for the recording track is not essential for the BCA 105Y. However, the BCA 105Y is preferably provided with irregularities. This is because it is easy to change various characteristics of the material of the second recording layer 105 such as a dye or an amorphous semiconductor during recording of the medium recognition signal.

  The uneven shape provided in the second recording layer 105 matches the uneven shape formed in the intermediate layer 104. Therefore, it is preferable to form irregularities in the intermediate layer 104 not only in the portion corresponding to the data area but also in the portion corresponding to the BCA 105Y. At this time, the shape of the unevenness formed on the BCA 105Y may be the same as or different from the unevenness formed on the data area 105X, but the unevenness formed on the BCA 105Y is different from the shape of the data area 105X. Preferably formed. A suitable uneven shape will be described in the description of the second recording layer 105.

[I-6. Second recording layer]
The second recording layer 105 functions as a specific recording layer, and is a recording layer farther from the first recording layer 102 than the first recording layer 102. Since the optical recording medium 100 is a medium for recording main information with the recording / reproducing light 109 having a wavelength of 300 to 450 nm, the second recording layer 105 needs to be able to record the main information with the recording / reproducing light 109.

  Similar to the case of the first recording layer 102 described above, the second recording layer 105 is more sensitive than a recording layer used for an optical recording medium such as a normal CD-R, a single-sided DVD-R, or a single-sided HDDVD-R. It is desirable. The second recording layer 105 is desirably a dye having a low heat generation and a high refractive index in order to realize good recording / reproduction characteristics. Further, in the combination of the second recording layer 105 and the second reflective layer 106, it is desirable that the reflection and absorption of light be in an appropriate range.

A data area 105X and a BCA 105Y are formed in the second recording layer 105, which is a specific recording layer.
As shown in FIG. 2, the data area 105 </ b> X is provided in a donut shape centered on the center hole H as an area occupying most of the second recording layer 105. In the present embodiment, the data area 105X has a donut shape from the outer periphery to the vicinity of the inner periphery of the optical recording medium 100 (a solid line circle in the outer periphery and a one-dot chain line in FIG. 2). It is assumed that it is formed in the enclosed part). For example, in an HD-DVD, grooves are formed in a spiral shape in the area with the above-described track pitch.

  On the other hand, the BCA 105Y can be formed at any position other than the data area 105X of the second recording layer 105, but is usually formed at the inner edge of the second recording layer 105. The BCA 105Y is an area for recording a medium recognition signal of the optical recording medium 1, such as copyright information and a lot number. The medium recognition signal may be recorded in any manner. For example, it may be recorded in the same manner as the main information, may be recorded as a barcode pattern, or may be information (characters, symbols, etc.) that can be recognized visually. Usually, it is preferable that the recorded medium recognition signal can be recognized by a laser.

  The material constituting the second recording layer 105 can be selected from the same substances as the first recording layer 102. The materials used for the first recording layer 102 and the second recording layer 105 may be the same or different.

  By the way, as described in the description of the first reflective layer 103, the first reflective layer 103 is usually formed as a semitransparent reflective layer, and only a certain proportion of the incident recording / reproducing light 109 is incident on the first reflective layer 103. It is not transparent. As a result, the power of the transmitted light incident on the second recording layer 105 causes a corresponding attenuation as compared with the recording / reproducing light 109 before entering the optical recording medium 100. Therefore, since the recording on the second recording layer 105 is performed with the attenuated transmitted light, it is desirable that the second recording layer 105 has particularly high sensitivity.

  Therefore, as the material used for the recording layers 102 and 105, particularly the second recording layer 105, which is the recording layer closest to the back surface 100B, there is a material whose reflectance changes due to decomposition or phase transition due to heat at a relatively low temperature. desirable. The decomposition temperature or phase transition temperature is preferably 350 ° C. or lower, more preferably 300 ° C. or lower, and even more preferably 275 ° C. or lower. However, when the decomposition temperature is too low, the storage stability tends to decrease, and therefore, the temperature is preferably 100 ° C. or higher. Here, the above temperature range is defined by the decomposition temperature when an organic dye is used, and the phase transition temperature when an amorphous semiconductor is used. Note that examples of such organic dyes and amorphous semiconductors can be appropriately selected from those similar to those exemplified in the description of the first recording layer 102.

  The decomposition temperature and the phase transition temperature can be measured with a differential scanning calorimeter (sometimes called DSC). The temperature raising conditions during the measurement may be in accordance with the specifications of the measuring apparatus, or may be raised sufficiently slowly than the time required for thermal diffusion to the entire measurement sample. The standard may be 5 ° C./min to 10 ° C./min.

As described in the description of the intermediate layer 104, the second recording layer 105 is preferably formed with unevenness as shown in FIG. 1, and the BCA 105Y is also preferably formed with unevenness.
When the BCA 105Y has irregularities, the irregularities are usually formed as grooves. At this time, the depth D of the groove is not limited, but is preferably 15 nm or more, preferably 100 nm or less, and more preferably 60 nm or less. If the groove depth D is less than the above range, the medium recognition signal may not be sufficiently recorded in the BCA 105Y. If the groove depth D exceeds the above range, the uneven shape of the intermediate layer 104 during the manufacturing process. May not be sufficiently transferred to the second recording layer 105, and unevenness may not be formed on the BCA 105Y.

  Further, the track pitch P of the grooves formed by the unevenness is not limited, but is preferably 0.1 μm or more, and preferably 0.6 μm or less. When the track pitch P is less than the above range, the track pitch is narrower than the wavelength and exceeds the detectable resolution, so information on adjacent tracks leaks during recording / playback (says that crosstalk occurs). Therefore, there is a possibility that only target information cannot be recorded / reproduced. Further, when the track pitch P exceeds the above range, the recording density tends to be low.

Further, the ratio (WL / WG) of the land width WL to the groove width WG is not limited, but is preferably 0.3 or more, and preferably 1.2 or less. When WL / WG is less than the above range, the land width is narrow, so that the medium recognition signal may not be sufficiently recorded on the BCA 105Y. When WL / WG exceeds the above range, the groove width WG is too wide. For this reason, the difference in reflectance becomes large, which may cause noise in the medium recognition signal recorded in the BCA 105Y.
Note that the land width WL, the groove width WG, and the track pitch P are measured with reference to the half width of the groove as shown in FIG.

  The film thickness of the second recording layer 105 is not particularly limited because the film thickness varies depending on the recording method and the like, but is usually 10 nm or more, preferably 20 nm or more. However, in order to obtain an appropriate reflectance, the film thickness of the second recording layer 105 is usually 3 μm or less, preferably 1 μm or less, more preferably 200 nm or less.

  In an optical recording medium having two recording layers like the optical recording medium 100 of the present embodiment, the laser light for recording main information is usually common, and therefore the energy of the recording / reproducing light 109 (laser Energy) will inevitably be distributed to each layer 102-106. Therefore, it is preferable to adjust the absorption amount, reflection amount, and transmission amount of the recording / reproducing light 109 in each layer.

  When viewed from the viewpoint of recording / reproduction characteristics by a recording / reproduction tester or drive, the reflectance greatly varies greatly from layer to layer, and the recording sensitivity varies greatly from signal to gain, frequency characteristics, recording power, etc. This is not preferable in terms of signal quality. Therefore, the layer located farther away from the information surface 100A is hard to reach the laser energy. For this reason, the optical recording medium 100 preferably has the following configuration.

(Absorptance of the first recording layer 102) <(Absorptance of the second recording layer 105)
(Transmittance of first recording layer 102)> (Transmittance of second recording layer 105)
(Absorptance by first recording layer 102 and first reflection layer 103) <(Absorptance by second recording layer 105 and second reflection layer 106)
(Transmissivity of first recording layer 102 and first reflective layer 103)> (Transmittance of second recording layer 105 and second reflective layer 106)

Moreover, when using a pigment | dye or an amorphous semiconductor as a material of each recording layer 102,105, it is also preferable to set it as the following structures.
(Thermal decomposition temperature of the dye constituting the first recording layer 102 or the phase transition temperature of the amorphous semiconductor)> (The thermal decomposition temperature of the dye constituting the second recording layer 105 or the phase transition temperature of the amorphous semiconductor)
The light absorptance of the recording layers 102 and 105 and the reflective layers 103 and 106 is defined by the refractive index n, the extinction coefficient k, and the film thickness. The extinction coefficient k is within the adjustment range in practical use. The larger, the larger the film thickness.

The same applies to the case of a multilayer optical recording medium (n-layer medium) having three or more recording layers (n layers). That is, the second recording layer 105 and the second reflective layer 106 may be replaced with the nth recording layer and the nth reflective layer as layers closest to the back surface.
More preferably, the following configuration is desirable. However, the second recording layer and the second reflective layer here are not the layers closest to the back surface but the second layer from the side close to the first substrate 101.
(Absorptance of the first recording layer 102) <(Absorptance of the second recording layer) <... <(Absorptance of the nth recording layer)
(Transmittance of the first recording layer 102)> (Transmittance of the second recording layer)>...> (Transmittance of the nth recording layer)
(Absorptance by first recording layer 102 and first reflection layer 103) <(Absorptance by second recording layer and second reflection layer) <... <(Absorptance by nth recording layer and nth reflection layer)
(Transmittance of first recording layer 102 and first reflective layer 103)> (Transmittance of second recording layer and second reflective layer) >>... (Transmittance of nth recording layer and nth reflective layer)

Moreover, when using a pigment | dye or an amorphous semiconductor as a material of each recording layer, it is also preferable to set it as the following structures.
(Thermal decomposition temperature of the dye constituting the first recording layer 102 or the phase transition temperature of the amorphous semiconductor)> (The thermal decomposition temperature of the dye constituting the second recording layer 105 or the phase transition temperature of the amorphous semiconductor) >>. (The thermal decomposition temperature of the dye constituting the nth recording layer or the phase transition temperature of the amorphous semiconductor)

[I-7. Second reflective layer]
The second reflective layer 106 is a reflective layer corresponding to the second recording layer 105, which is a specific recording layer, and functions as a specific reflective layer. Here, in an optical recording medium having a plurality of recording layers and reflective layers, the reflective layer corresponding to a certain recording layer is the most reflective layer among the reflective layers located on the side opposite to the information surface of the recording layer. Refers to a reflective layer close to the layer.

The specific reflection layer according to the present invention is characterized in that the reflectance from the information surface side at the wavelength of the main information recording laser beam is larger than the reflectance from the back surface side.
In the present embodiment, an example in which the second reflective layer 106 has a two-layer structure will be described. The adjacent reflective layer on the information surface side of the second reflective layer 106, that is, the side adjacent to the second recording layer 105 is referred to as the adjacent reflective layer 106a, and the back surface side is referred to as the back reflective layer 106b. Here, the second reflective layer 106 has a two-layer structure, but a plurality of layers made of different materials may be provided between 106a and 106b.

Here, a method for measuring the reflectance of the specific reflective layer will be described.
First, a sample in which only a specific reflective layer is formed on a specular glass substrate is prepared. That is, a layer having the same material and thickness as the specific reflective layer is formed on the mirror glass substrate alone.
Here, when measuring the reflectance from the information surface side, the information surface side of the specific reflective layer is formed so as not to contact the upper surface, that is, the mirror glass substrate. Using this sample, the reflectance value measured by the spectrophotometer after irradiating light from the opposite side of the specular glass substrate to the specific reflection layer is defined as the reflectance from the information surface side of the specific reflection layer To do.
On the other hand, when measuring the reflectance from the back surface, a sample formed so that the back surface side of the specific reflective layer is not in contact with the upper surface, that is, the mirror glass substrate is prepared. Using this sample, the reflectance value measured by a spectrophotometer by irradiating light from the opposite side of the specular glass substrate to the specific reflection layer is defined as the reflectance from the back side of the specific reflection layer. . Here, the wavelength of the light used for the measurement is the wavelength of the main information recording laser beam.
Specifically, the reflectance measured by sequentially forming the surface reflective layer 106b and the adjacent reflective layer 106a on the mirror glass substrate and irradiating light from the adjacent reflective layer 106a side is the reflectance from the information surface side. The reflectance measured by sequentially forming the adjacent reflective layer 106a and the surface reflective layer 106b on the glass substrate and irradiating light from the surface reflective layer 106b side becomes the reflectance from the back surface side.

The reflectance from the information surface side of the second reflective layer 106 is not limited as long as the effect of the present invention is not significantly impaired, but is usually 70% or more, preferably 80% or more with respect to light from a light source having a wavelength of 405 nm. It is preferable. When the reflectance is less than the above range, the reflectance is insufficient particularly in the current single-sided DVD double-layer medium, and there is a possibility that the recording / reproducing apparatus cannot recognize the optical recording medium 100.
Moreover, the reflectance from the back surface side of the 2nd reflection layer 106 which is a specific reflection layer is smaller than the reflectance from the information surface side, Preferably it is 85% or less, More preferably, it is 80% or less. Within this range, the energy of the laser beam for recording the medium recognition signal is easily transmitted to the second recording layer 105, and the medium recognition signal can be favorably recorded on the BCA 105Y. Moreover, 50% or more is preferable, More preferably, it is 55%, More preferably, it is 60% or more. By setting this range, the second reflective layer 106, which is the specific reflective layer, is less likely to be damaged by the medium recognition signal recording laser beam, and the focus servo can be performed stably and easily.

The material constituting the adjacent reflective layer 106a is arbitrary as long as the above reflectance can be realized. For example, a metal such as Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, and Pd is used alone. Alternatively, an alloy can be used.
Among these, it is preferable that Ag is a main component. In particular, it is desirable that Ag is usually 85 atomic% or more, preferably 87 atomic% or more, more preferably 89 atomic% or more, and usually 99.7 atomic% or less, preferably 99.5 atomic% or less, more preferably It is desirable to contain it at 99.0 atomic% or less. By containing Ag in the above range, the material of the adjacent reflective layer 106a has low thermal conductivity, and recording on the BCA 105Y is possible with good sensitivity.

  Examples of elements that can be contained as an alloy with respect to Ag include, for example, O, N, Au, Al, Cu, Ti, Cr, Ni, Ta, Pd, Mg, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, In, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, and rare earth metals are preferable. By containing such an element as an alloy with respect to Ag, high reflectance and good storage stability can be ensured.

  The material constituting the back reflective layer 106b is arbitrary as long as the above reflectance can be realized, but is basically the same as the adjacent reflective layer 106a. Accordingly, it is preferable to use Ag as a main component as in the case of the adjacent reflective layer 106a. However, it is possible to reduce the reflectivity by reducing the Ag content in comparison with the adjacent reflective layer 106a. .

The thickness of the second reflective layer 106 is usually 200 nm or less, preferably 150 nm or less, more preferably 130 nm, usually 60 nm or more, preferably 80 nm or more, and more preferably 90 nm or more. Within the above range, sufficient reliability as an information recording medium can be ensured, and recording of a medium recognition signal onto the BCA 105Y can easily be performed with higher sensitivity.
In order to ensure a high reflectance from the information surface side, the thickness of the adjacent reflective layer 106a is usually 30 nm or more, preferably 40 nm. However, in order to improve the BCA recording sensitivity, it is usually 120 nm or less, preferably 80 nm or less. By setting the range, it is easy to obtain good recording sensitivity in both the medium recognition signal and the main information. By setting the film thickness of the adjacent reflective layer 106a within the above range, the heat capacity of the entire second reflective layer 106, which is the specific reflective layer, is suppressed and the degree of thermal diffusion is reduced while maintaining the reflectance from the information surface high. Because it can.
In order to keep the reflectance from the back side low, the film thickness of the back reflecting layer 106b is usually 5 nm or more, preferably 10 nm. Moreover, it is 170 nm or less normally, Preferably it is 120 nm or less.

Similar to the first reflective layer 103, the second reflective layer 106 is usually formed by sputtering.
The second reflective layer 106 can include a plurality of layers having different compositions as described above, but it is preferable that the second reflective layer 106 has two layers in view of manufacturing process management.

[I-8. Adhesive layer)
The adhesive layer 107 is a layer that adheres the second reflective layer 106 and the second substrate 108. It is preferable that the adhesive layer 107 has a high adhesive force and a small shrinkage rate at the time of curing and adhesion because the shape stability of the optical recording medium 100 is increased. The adhesive layer 107 is preferably made of a material that does not damage the second reflective layer 106. However, a known inorganic or organic protective layer may be provided between the second reflective layer 106 and the adhesive layer 107 in order to suppress damage.

As the material of the adhesive layer 107, the same material as that of the intermediate layer 104 can be used.
The film thickness of the adhesive layer 107 is usually 2 μm or more, preferably 5 μm or more. However, in order to reduce the thickness of the optical recording medium 100 as much as possible and to suppress a reduction in productivity due to the time required for curing, the film thickness of the adhesive layer 107 is usually preferably 100 μm or less. .
As the adhesive layer 107, a pressure sensitive double-sided tape or the like can be used. The adhesive layer 107 can be formed by sandwiching and pressing a pressure sensitive double-sided tape between the second reflective layer 106 and the second substrate 108.

[I-9. Second substrate]
The second substrate 108 is a layer provided facing the back surface 100B. The second substrate 108 preferably has high mechanical stability and high rigidity. Further, it is desirable that the adhesiveness with the adhesive layer 107 is high.
As the material of the second substrate 108, the same material as that used for the first substrate 101 can be used. In addition, as the material, for example, any one of Al alloy substrate such as Al-Mg alloy mainly containing Al, Mg alloy substrate such as Mg-Zn alloy mainly containing Mg, silicon, titanium, ceramics, etc. It is also possible to use a substrate made of these or a combination of them. Moreover, the material of the 2nd board | substrate 108 may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

The material of the second substrate 108 is preferably polycarbonate from the viewpoints of high productivity such as moldability, cost, low hygroscopicity, and shape stability. The material of the second substrate 108 is preferably amorphous polyolefin from the viewpoint of chemical resistance, low hygroscopicity, and the like. The material of the second substrate 108 is preferably a glass substrate from the viewpoint of high-speed response.
Furthermore, in order to give the optical recording medium 100 sufficient rigidity, the second substrate 108 is preferably thick to some extent, and the thickness of the second substrate 108 is preferably 0.3 mm or more. However, it is usually 3 mm or less, preferably 1.5 mm or less.

[II. Manufacturing method of optical recording medium]
Next, a manufacturing method of the multilayer optical recording medium 100 of this embodiment will be briefly described with reference to FIG. 3 (a) to 3 (g) are cross-sectional views schematically showing the cross section of the main part of the method for manufacturing the optical recording medium of the present embodiment.
The manufacturing method of the optical recording medium 100 of the present embodiment includes a first recording layer forming step, a first reflective layer forming step, an intermediate layer forming step (a resin raw material layer forming step, a resin raw material layer curing step, a stamper peeling step). And a second recording layer forming step, a second reflecting layer forming step, and a second substrate forming step.

[II-1. Preparation of substrate]
First, the first substrate 101 is prepared. As the first substrate 101, as shown in FIG. 3 (a), a substrate having an uneven surface and grooves, lands, and pre-pits is prepared. The first substrate 101 can be manufactured by injection molding using a nickel stamper, for example.

[II-2. First recording layer forming step]
Next, in the first recording layer forming step, the first recording layer 102 is formed on the first substrate 101. Although there is no restriction | limiting in the formation method of the 1st recording layer 102, For example, it can form by the following method. That is, a coating solution containing an organic dye is applied to the surface of the first substrate 101 having the unevenness by spin coating or the like. Thereafter, heating or the like is performed to remove the solvent used in the coating solution, and the first recording layer 102 is formed. In the present embodiment, an example in which the first recording layer 102 is formed directly on the first substrate 101 as described above will be described. However, the first recording layer 102 includes the type and configuration of the optical recording medium 100, and the like. Depending on the above, it may be formed on the first substrate 101 via another layer.

  In addition, as a method for forming the first recording layer 102, a generally used thin film forming method such as a vacuum evaporation method, a sputtering method, a doctor blade method, a casting method, an immersion method, or the like can be performed. Among the film formation methods, a wet film formation method such as a spin coating method is preferable from the viewpoint of mass productivity and cost. Moreover, the vacuum evaporation method is preferable from the point that a uniform recording layer is obtained.

[II-3. First reflective layer forming step]
After forming the first recording layer 102, the first reflective layer 103 is formed on the first recording layer 102 in the first reflection forming step. The method for forming the first reflective layer 103 is not limited. For example, the first reflective layer 103 is formed on the first recording layer 102 by sputtering or vapor-depositing an Ag alloy or the like on the first recording layer 102. be able to.
Thus, the data substrate 111 is obtained by sequentially laminating the first recording layer 102 and the first reflective layer 103 on the first substrate 101. In the present embodiment, it is assumed that the data substrate 111 is transparent.

  Moreover, the method of forming the 1st reflection layer 103 can also be performed by the ion plating method, the chemical vapor deposition method, the vacuum vapor deposition method etc., for example.

[II-4. Intermediate layer forming step]
Next, the intermediate layer 104 is formed on the first reflective layer 103. The method of forming the intermediate layer 104 is not limited and is arbitrary, but is usually formed as follows.
The intermediate layer 104 using a thermoplastic resin, a thermosetting resin, or the like is formed by preparing a coating solution by dissolving a thermoplastic resin or the like in an appropriate solvent, applying the coating solution, and drying (heating). can do.
On the other hand, the intermediate layer 104 using a radiation curable resin is formed by preparing a coating solution as it is or dissolving in a suitable solvent, applying the coating solution, and irradiating and curing the appropriate radiation. Can do.

In addition, there is no restriction | limiting in the coating method, For example, methods, such as coating methods, such as a spin coat method and a casting method, are used. Among these, the spin coat method is preferable. In particular, the intermediate layer 104 using a high-viscosity resin can be applied and formed by screen printing or the like.
However, in the optical recording medium 100 of the present embodiment, in order to form irregularities in the second recording layer 105, an intermediate layer is formed by performing a resin raw material layer forming step, a resin raw material layer curing step, and a stamper peeling step. Is more preferable. Hereinafter, this method will be described.

[II-4-1. Resin raw material layer forming process]
After the first reflective layer forming step, in the resin raw material layer forming step, as shown in FIG. 3B, the resin raw material layer 104a is formed on the entire surface of the first reflective layer 103 (that is, the surface of the data substrate 111). Form. That is, the resin material layer 104 a is formed on the first recording layer 102 via the first reflective layer 103.
The resin raw material layer 104a formed here constitutes the intermediate layer 104 when the optical recording medium 100 is completed. The resin raw material layer 104a is a layer formed of a curable resin or a precursor thereof that can be cured by any treatment. It is.

  As said curable resin, curable resin which can be used for an optical recording medium can be used arbitrarily. Examples of the curable resin include a radiation curable resin and a thermosetting resin, and among them, an ultraviolet curable resin which is a kind of the radiation curable resin is preferable. In this specification, “radiation” is used to mean electron beam, ultraviolet light, visible light, and infrared light. Moreover, curable resin may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  However, since the surface of the resin material layer 104a is subsequently formed with a stamper 110 (described later), the resin material layer 104a is in an irregular state (usually predetermined) before being formed in the resin material layer curing step. In a liquid state having a viscosity of

Moreover, there is no restriction | limiting in the formation method of the resin raw material layer 104a. For example, the resin raw material layer 104a can be formed by applying a precursor of a curable resin by spin coating or the like.
In the present embodiment, a precursor of an ultraviolet curable resin that is one of radiation curable resins is applied by spin coating, and a resin raw material layer (hereinafter referred to as an “ultraviolet curable resin raw material layer” for convenience of explanation) ) 104a is formed.

  By the way, in the present embodiment, an example in which the ultraviolet curable resin material layer 104a is formed on the first recording layer 102 through the first reflective layer 103 as described above will be described. The layer 104 a may be directly formed on the first recording layer 102 according to the type and configuration of the optical recording medium 100, and is formed via other layers other than the first reflective layer 103. You may do it.

[II-4-2. Resin raw material layer curing process]
Next, in the resin raw material layer curing step, as shown in FIG. 3C, the stamper 110 is placed on the ultraviolet curable resin raw material layer 104a to cure the ultraviolet curable resin raw material layer 104a. That is, the stamper 110 is placed on the surface of the ultraviolet curable resin material layer 104a opposite to the first recording layer 102.
The stamper 110 is a mold having on the surface irregularities (transfer irregularities) having a shape (uneven shape for transfer) corresponding to the irregular shape (uneven shape) to be formed in the intermediate layer 104. The transfer uneven shape of the transfer unevenness of the stamper 110 is transferred to the ultraviolet curable resin raw material layer 104a, so that the uneven shape of the desired uneven shape is formed in the intermediate layer 104. Is set.

  As the material of the stamper 110, a resin is usually used in consideration of the manufacturing cost of the optical recording medium 100. General-purpose and low-cost resins such as polycarbonate resins and acrylic resins, polyolefin resins, polystyrene trees, and the like are preferable. (Both manufactured by Nippon Zeon Co., Ltd.)).

  Furthermore, the stamper 110 is usually formed in a disc shape in which a central hole penetrating the front and back is formed in the center. Also in this embodiment, it is assumed that the stamper 110 has a disk-like shape having a concavo-convex shape for transfer on the surface and a center hole (not shown) formed in the center.

  When the stamper 110 is manufactured, the manufacturing method is arbitrary. For example, when the stamper 110 is a resin stamper, the stamper 110 has a concave / convex pattern opposite to the transfer concave / convex shape of the stamper 110. It can be produced by injection molding or the like using a metal stamper (for example, a nickel stamper).

  In addition, the thickness of the stamper 110 is generally preferably 0.3 mm or more from the viewpoint of shape stability and ease of handling. However, the thickness is usually 5 mm or less. If the thickness of the stamper 110 is within this range, the stamper 110 has sufficient light transmittance. Therefore, the ultraviolet curable resin or the like can be efficiently cured even when irradiated with ultraviolet rays through the stamper 110 as described later. Yes, productivity can be improved.

  Further, the outer diameter of the stamper 110 is preferably larger than the outer diameter of the first substrate 101 (usually equal to the outer diameter of the optical recording medium 100). If the outer diameter of the stamper 110 is designed to be larger than the outer diameter of the first substrate 101 in advance, when the stamper 110 is manufactured by injection molding, the outer peripheral portion outside the outer diameter of the first substrate 101 of the stamper 110. In addition, the uneven shape for transfer can be formed with a sufficient margin, and a favorable uneven shape for transfer can be formed over the entire surface of the stamper 110.

  Further, by making the outer diameter of the stamper 110 larger than the outer diameter of the first substrate 101, the outer diameter of the stamper 110 becomes larger than the outer diameter of the intermediate layer 104 (and the ultraviolet curable resin raw material layer 104a). If it does in this way, it will become easy to make the shape of the end face of middle class 104 good. That is, if the outer diameter of the stamper 110 is set to be equal to or smaller than the outer diameter of the first substrate 101, the outer periphery of the stamper 110 is cured with ultraviolet light when the stamper 110 is placed on the ultraviolet curable resin material layer 104a. The resin of the conductive resin material layer 104a may adhere. This resin may become a burr when the stamper 110 is peeled off. Therefore, if the outer diameter of the stamper 110 is larger than the outer diameter of the intermediate layer 104 (ultraviolet curable resin raw material layer 104a), the resin present at the end of the ultraviolet curable resin raw material layer 104a that tends to become burrs is removed. It exists outside the outer diameter. As a result, even if burrs are generated, the shape of the end face of the intermediate layer 104 can be improved by removing the burrs.

  Specifically, the outer diameter of the stamper 110 is usually larger than the outer diameter of the first substrate 101 by 1 mm or more, preferably 2 mm or more. However, the difference between the outer diameter of the stamper 110 and the outer diameter of the first substrate 101 is usually 15 mm or less, preferably 10 mm or less.

  By the way, when the stamper 110 is mounted, the stamper 110 is mounted so that the surface on which the unevenness is formed is pressed against the ultraviolet curable resin raw material layer 104a. At this time, the degree to which the stamper 110 is pressed against the ultraviolet curable resin raw material layer 104a is adjusted so that the film thickness of the ultraviolet curable resin raw material layer 104a falls within a predetermined range.

  Then, the ultraviolet curable resin raw material layer 104a is cured in a state where the stamper 110 is placed on the ultraviolet curable resin raw material layer 104a. In order to cure the ultraviolet curable resin raw material layer 104a, the ultraviolet curable resin raw material layer 104a may be irradiated with ultraviolet rays. At this time, the ultraviolet rays may be irradiated through the stamper 110. However, when irradiating ultraviolet rays from the stamper 110 side, it is industrially preferable to use a stamper 110 that can transmit ultraviolet rays (light transmissive one). Moreover, you may make it irradiate from the side surface of the ultraviolet curable resin raw material layer 104a. Further, irradiation may be performed from the first substrate 101 side. However, when irradiating from the first substrate 101 side, it is preferable that the first recording layer 102 is not damaged by the irradiation of ultraviolet rays.

In this embodiment, the ultraviolet curable resin raw material layer 104a is polymerized by irradiating the ultraviolet curable resin raw material layer 104a with ultraviolet rays from the stamper 110 side through the stamper 110 to polymerize the precursor of the ultraviolet curable resin. The description will be made on the assumption that it is cured.
In this way, the resin material layer is cured, and the data substrate 111 (that is, the first substrate 101, the first recording layer 102, and the first reflection layer 103), the ultraviolet curable resin material layer 104a, and the stamper 110 are cured. An adhesive body 112 having the above is obtained.

[II-4-3. Stamper peeling process]
Then, in the stamper peeling step, as shown in FIG. 3D, the stamper 110 is peeled off from the ultraviolet curable resin material layer 104a (see FIG. 3C). Thereby, the uneven shape for transfer of the stamper 110 is transferred to the ultraviolet curable resin raw material layer 104a, and the intermediate layer 104 is formed. In this specification, the ultraviolet curable resin raw material layer 104a refers to a layer that is hardened after coating and before the stamper is peeled off. The intermediate layer 104 refers to the layer after the stamper 110 is peeled off. Therefore, the ultraviolet curable resin raw material layer 104a and the intermediate layer 104 indicate layers formed in the same position, but the states are different.

  Although there is no restriction on the specific method for peeling off the stamper 110, normally, when the optical recording medium has a disk shape, the inner circumference is vacuum-sucked, and a knife edge is put on the inner circumference of the optical recording medium. Peeling is performed by pulling the disc away from the stamper while blowing air.

  Through the above operation, the intermediate layer 104 is formed on the surface of the ultraviolet curable resin raw material layer 104a by transferring the shape of the unevenness for transfer of the stamper 110 (that is, the uneven shape for transfer). An optical recording medium laminate 113 including one recording layer 102, the first reflective layer 103, and the intermediate layer 104 can be obtained (see FIG. 3D).

[II-5. Second recording layer forming step]
Subsequently, in the second recording layer forming step, the second recording layer 105 is formed on the intermediate layer 104 as shown in FIG. Although there is no restriction | limiting in the formation method of the 2nd recording layer 105, For example, it can form by the following method. That is, a coating solution containing an organic dye is applied to the surface of the intermediate layer 104 by spin coating or the like. Then, heating or the like is performed to remove the solvent used in the coating solution, and the second recording layer 105 is formed.
The film forming method of the second recording layer 105 is preferably a wet film forming method when the second recording layer 105 is an organic dye.
In addition, as with the method for forming the first recording layer 102, a generally used thin film forming method such as a vacuum evaporation method, a sputtering method, a doctor blade method, a casting method, or an immersion method can also be performed.

[II-6. Second reflective layer forming step]
Next, in the second reflective layer forming step, the second reflective layer 106 is formed on the second recording layer 105 as shown in FIG. The method for forming the second reflective layer 106 is not limited. For example, the second reflective layer 106 can be formed on the second recording layer 105 by sputtering or vapor-depositing the materials described in the claims.
When the second reflective layer 106 is composed of two layers 106a and 106b having different compositions, for example, a target material corresponding to each composition is prepared, and a film is formed by sequential sputtering, whereby a reflective material composed of a plurality of layers is formed. Layers can be formed. In FIGS. 3F to 3G, the second reflective layer 106 is drawn without distinguishing between the layer 106a and the layer 106b.
In addition, as a method for forming the second reflective layer 106, for example, an ion plating method, a chemical vapor deposition method, a vacuum vapor deposition method, or the like can be employed.

  In the case where an intermediate layer, a recording layer, and, if necessary, a reflective layer are further laminated, [II-2. First recording layer forming step], [II-3. First reflective layer forming step] and [II-4. By repeating the same operation as in the intermediate layer forming step, a multilayer multilayer optical recording medium having three or more recording layers and reflective layers can be efficiently produced.

[II-7. Second substrate forming step]
Thereafter, in the second substrate formation step, the second substrate 108 is formed on the second reflective layer 106 as shown in FIG. There is no limitation on the method for forming the second substrate 108, but for example, the second substrate 108 can be formed by being attached to the second reflective layer 106 with the adhesive layer 107 interposed therebetween. Note that the second substrate 108 is not limited, but here, it is assumed that a mirror substrate obtained by injection molding of polycarbonate is used as the second substrate 108.

Here, the configuration of the adhesive layer 107 is arbitrary. For example, the adhesive layer 107 may be transparent or opaque. Further, the surface may be somewhat rough. Furthermore, even a delayed curing type adhesive can be used without any problem. Further, for example, an adhesive is applied onto the second reflective layer 106 by a method such as screen printing, and after irradiating with ultraviolet rays, the second substrate 108 is placed and pressed to form the adhesive layer 107. May be. Alternatively, the adhesive layer 107 can be formed by pressing a pressure sensitive double-sided tape between the second reflective layer 106 and the second substrate 108.
As described above, the manufacture of the optical recording medium 100 is completed.

[II-8. Other manufacturing methods]
The manufacturing method of the optical recording medium 100 is not limited to the above-described method, and other methods may be adopted.
Moreover, you may implement by adding a change to the manufacturing method mentioned above. For example, you may make it perform other processes other than the process mentioned above before, in the middle of each process mentioned above, and after.

  In the multilayer optical recording medium 100, the resin raw material layer 104 a is made up of a plurality of resin layers in consideration of the warp of the optical recording medium 100 and the recording characteristics of the second recording layer 105 formed on the intermediate layer 104. You may form from. In this case, of the plurality of resin layers constituting the resin raw material layer 104a, the resin layer formed with the uneven shape by the stamper 110 is the outermost resin layer.

  Thus, when the resin raw material layer 104a is comprised from a some resin layer, the number of the resin layers which comprise the resin raw material layer 104a is not restrict | limited in particular. Specifically, the number of the resin layers is usually 10 layers or less, preferably 5 layers or less, more preferably 4 layers or less. On the other hand, the number of the resin layers is two or more. However, from the viewpoint of production efficiency, the number of resin layers constituting the resin raw material layer 104a is preferably 2 or more and 5 or less. From the viewpoint of production efficiency, it is particularly preferable that the number of resin layers constituting the resin raw material layer 104a is a two-layer or three-layer structure.

The method of forming the intermediate layer 104 when the intermediate layer 104 is a multilayer film is as shown in FIGS. 4 (a), 4 (b) and FIG. That is, as shown in FIG. 4A, one resin layer (first resin layer 104a ₁ ) is formed on the first reflective layer 103, and the other is separately formed as shown in FIG. 4B. After the resin layer (second resin layer 104a ₂ ) is formed on the stamper 110, the data substrate 111 and the stamper 110 are bonded so that the first resin layer 104a ₁ and the second resin layer 104a ₂ face each other. Thereafter, ultraviolet rays are irradiated as shown in FIG. Thereby, adhesive body 112 'is obtained.
By forming the intermediate layer 104 from a plurality of resin layers in this manner, a material that easily improves the recording characteristics of the second recording layer 105 is made adjacent to the second recording layer 105 as the second resin layer 104a ₂ and the first A material having good adhesion to the reflective layer 103 is preferable because it can be adjacent to the first reflective layer 103 as the first resin layer 104a ₁ .

[III. Recording method of main information and medium recognition signal]
Next, a method for recording main information and a medium recognition signal on the optical recording medium 100 will be described.
When recording main information on the optical recording medium 100, as shown schematically in FIG. 1, the recording / reproducing light 109 is irradiated from the information surface 100 A to the recording layers 102 and 105, and the recording / reproducing light 109 is used to Record information. In particular, when the main information is recorded on the second recording layer 105, the data area 105X is recorded, so that the recording / reproducing light 109 is also irradiated onto the data area 105X. As the recording / reproducing light 109, a laser beam having a wavelength of 300 to 450 nm is used.

  On the other hand, when recording the medium recognition signal, the second recording layer 105 is irradiated with the recognition signal recording light from the back surface 100B, and the medium recognition signal is recorded on the BCA 105Y. Laser light is usually used as the recognition signal recording light. The wavelength of the recognition signal recording light is not limited, but laser light having a wavelength of usually 400 nm or more, practically 600 nm or more, and usually 2000 nm or less, practically 1200 nm or less is used.

The laser light having a wavelength longer than that of the main information recording laser light is preferably used as the medium recognition signal recording laser light for the following reason.
In general, the medium recognition signal is recorded over a range of about 1 mm in the radial width on the BCA 105Y so that the medium recognition signal can be reliably read. In order to record such a medium recognition signal over a wide radius region with high productivity, it is desirable to use a laser beam source having a large beam spot. However, when the beam spot is enlarged, the power density is lowered. For this reason, in order to perform sufficient recording, it is preferable that the output laser power is very high, for example, 1 W or more. However, such a high power is currently difficult with a blue laser beam used for recording / reproducing main information. Therefore, for recording a medium recognition signal, a red to near-infrared wavelength of about 600 to 850 nm is used separately from the blue laser beam. The laser beam is preferably used.

[IV. advantage]
According to the optical recording medium 100 of the present embodiment, the conventional problems can be solved, recording / reproduction can be performed with blue laser light, and a medium recognition signal can be recorded by forming the BCA 105Y in the second recording layer 105. An optical recording medium configured as described above can be realized.
In addition, according to the optical recording medium 100 of the present embodiment, defects such as large deformation and loss of the second reflective layer 106 do not occur even when a medium recognition signal is recorded on the BCA 105Y. Therefore, it is possible to provide the optical recording medium 100 which does not cause corrosion due to the defect and has excellent long-term storage stability.

  Further, when the medium recognition signal is recorded on the optical recording medium 100 of the present embodiment, the medium recording signal is from the opposite direction (from the top in FIG. 1) to the recording / reproducing light 109 for recording / reproducing the main information. Even when the recording layers 102 and 105 are multi-layered, the medium recognition is performed only on the layer closest to the back surface 100B side, even if the recording layers 102 and 105 are multi-layered. An optical recording medium capable of recording a signal can be provided.

In addition, when the medium is irradiated with a medium recognition signal recording laser from the back side, it is conceivable to simply lower the reflectance of the reflective layer in contact with the specific recording layer. However, according to the optical recording medium 100 of the present invention, since the reflectance from the information surface side of the specific reflective layer is larger than the reflectance from the back surface, the characteristic (reflectance) that allows good reproduction of the main information is achieved. While maintaining, recording on the BCA 105Y can be performed from the back surface with low laser power.
As a result, the life of the laser for BCA recording can be extended, and the equipment cost can be reduced.

[V. Others]
The optical recording medium of the present invention has been described in detail with reference to the embodiment. However, the present invention is not limited to the optical recording medium described above, and can be arbitrarily modified without departing from the gist of the present invention. Can be implemented.

  For example, BCA may be provided in a recording layer other than the second recording layer 105. In an optical recording medium having two or more recording layers, which recording layer is provided with BCA is arbitrary. Moreover, it is also possible to provide BCA in two or more layers as needed. Therefore, in the case of the above-described embodiment, the first recording layer 102 can be provided with BCA. When providing BCA in the 1st recording layer 102, the shape etc. can be provided similarly to BCA105Y described in the 2nd recording layer 105. FIG.

  However, BCA is preferably provided in the recording layer closest to the back surface. That is, when two or more recording layers are formed, it is preferable to form the specific recording layer as the recording layer closest to the back surface among the recording layers. This is to more reliably record and read the medium recognition signal.

Further, for example, it is not necessary to form irregularities on the BCA. Even if the BCA is formed in such a flat shape having no irregularities, the above-described advantages of the present invention can be obtained.
Further, when the optical recording medium is a multilayer optical recording medium having two or more recording layers, the recording / reproducing light having the same wavelength is not used for all the recording layers, and the recording / reproducing light having different wavelengths is mainly used for the recording layer. Information recording and reproduction may be performed. Further, it may be recording / reproducing light having a wavelength other than the blue laser.

  Further, for example, the reflective layer may be provided corresponding to the recording layer, and does not necessarily have to be in contact therewith. For example, in the above-described embodiment, any layer (for example, an intermediate layer or an adhesive layer that appeared in the description of the second recording layer 106) is provided between the reflective layer 103 and the recording layer 102 or between the reflective layer 106 and the recording layer 105. Even if a layer is formed, light (recording / reproducing light and recognizing signal recording light) to the extent that recording and reproduction of main information and recording of a medium recognition signal are possible due to the reason that the layer is very thin. The reflective layer 103 and the recording layer 102 or the reflective layer 106 and the recording layer 105 do not have to be in contact with each other as long as they can transmit and transmit heat.

  In addition, the layer configuration illustrated in FIG. 1 is merely an example, and the optical recording medium 100 may include any other layer as necessary in the above-described stacked structure. Alternatively, any other layer may be provided on the outermost surface of the optical recording medium 100. Further, in the optical recording medium 100, a print receiving layer that can be written (printed) on the back surface 100B, which is not the incident surface of the recording / reproducing light, by various printers such as ink jet and thermal transfer, or various writing tools, if necessary. May be provided. Further, for example, an optical recording medium having another layer not shown in FIG. 1 (for example, a base layer is inserted between the first substrate 101 and the first recording layer 102) may be manufactured.

In FIG. 1, the specific reflection layer 106 is composed of two layers having different compositions. However, this is merely an example, and the reflectance from the information surface and the reflectance from the back surface of the specific reflection layer are the above-described values. If it has a predetermined relationship, it is not limited to a two-layer structure. For example, a composition gradient film in which the composition in the film thickness direction of the specific reflective layer gradually changes may be used. Moreover, even if the specific reflective layer has a uniform composition, for example, if the fine structure of the interface on the information surface side and the interface on the back surface side is different, the reflectance can be controlled to a predetermined relationship. Such a structure can also be adopted.
Further, the specific reflection layer may be composed of three or more layers. By providing a layer made of another material having higher thermal conductivity between the adjacent reflective layer and the reflective layer on the backmost side, the characteristics of the specific reflective layer as a whole are further preferred while maintaining a predetermined reflectivity. Can be.

Furthermore, in the above embodiment, as an example of the optical recording medium 100, a dual layer type single-sided dual layer HDDVD-R having two recording layers containing an organic dye has been described as an example, but the present invention can be applied. The optical recording medium is not limited to this. For example, the present invention can be applied to any optical recording medium having at least a data area for recording main information and a BCA for recording a medium recognition signal and having a reflective layer. The effect is exhibited well.
For example, the present invention can be similarly applied to a Blu-ray disc in which main information recording laser light is incident from the film surface side.

  The present invention can also be applied to an optical recording medium having a single recording layer. In that case, the first recording layer 102 and the first reflective layer 103 may be excluded from the example of the optical recording medium 100 described above. Further, the second recording layer 105 may be laminated directly on the first substrate 101 except for the intermediate layer 104. In the case of an optical recording medium having one recording layer, the second reflective layer 106 is the only reflective layer.

Furthermore, the optical recording medium of the present invention can also be applied to an optical recording medium having three or more recording layers and two or more intermediate layers. In this case, the manufacturing method described above can be applied to form each of the two or more intermediate layers. However, in the case of an optical recording medium having three or more recording layers, the reflective layer is a recording layer closest to the back surface 100B as a specific recording layer, and a reflective layer corresponding to the specific recording layer is a specific reflective layer. The second recording layer 105 and the second reflective layer 106 are desirably formed in the same manner.
Furthermore, in the above-described embodiment, the so-called substrate surface incident type optical recording medium has been described. However, the present invention can naturally be applied to a so-called film surface incident type optical recording medium.

Further, for example, regarding the method for manufacturing an optical recording medium, two optical recording media 100 and the first substrate 101 may be bonded together. By laminating two optical recording media 100, a large-capacity medium having four recording layers can be obtained.
Further, for example, the above-described method for manufacturing an optical recording medium can be applied to a phase change type rewritable compact disc (CD-RW, CD-Rewritable) or a phase change type rewritable DVD / HDDVD. As a layer structure such as a recording layer when applied to a phase change type optical recording medium, a known one can be used as appropriate. A phase change type CD-RW or rewritable type DVD utilizes a reflectance difference and a phase difference change caused by a refractive index difference between an amorphous state and a crystalline state in a recording layer composed of a phase change type recording material. The recording information signal is detected.
In addition, the above-described components can be arbitrarily combined and implemented as appropriate without departing from the gist of the present invention.

  Hereinafter, the present invention will be described more specifically based on examples. In addition, this invention is not limited to a following example, unless it deviates from the summary.

[Example 1] [Example of HD DVDR-DL]
(1) Preparation of optical recording medium (1-1) Preparation of stamper Using an amorphous cyclic polyolefin (APO) as a material, an injection molding method has a central hole with an inner diameter of 15 mm, an outer diameter of 120 mm, and a thickness of 0.6 mm. The disc-shaped stamper (hereinafter sometimes referred to as APO stamper) was formed. The injection molding has a guide groove having a track pitch of 0.40 μm, a groove width of 0.20 μm, and a depth of 65 nm in a region where the BCA can be formed, that is, a region having a radius of 22.0 mm to 23.1 mm. A nickel master having a guide groove with a track pitch of 0.40 μm, a width of 0.26 μm, and a depth of 60 nm was used in an area from a radius of 24.5 mm to 58.5 mm. In addition, it was confirmed by an atomic force microscope (AFM) that the guide groove (unevenness) of the nickel master was accurately transferred to the APO stamper.

-Manufacture of data substrate (1-2) Formation of first recording layer, etc. Diameter in which a polycarbonate was injection molded using a nickel stamper to form a groove having a track pitch of 0.40 μm, a width of 0.26 μm, and a depth of 60 nm. A substrate (first substrate) having a thickness of 120 mm and a thickness of 0.58 mm was obtained. In addition, the groove | channel is provided in 24.0-58.5 mm of radial positions.
Next, a tetrafluoropropanol solution (concentration 1% by weight) of a cyanine dye having a decomposition temperature of 250 ° C. represented by the following chemical formula was prepared, and this was dropped on a substrate and applied by a spinner method. After coating, the first recording layer was formed by drying at 70 ° C. for 30 minutes.
Further, on the first recording layer, a translucent first reflective layer having a thickness of 20 nm was formed by sputtering using an Ag alloy made of Ag-Bi (Bi: 1.0 atomic%).

(1-3) Formation of Intermediate Layer Next, a predetermined ultraviolet curable resin [1] was dropped in a circular shape on the first reflective layer, and a first resin layer having a thickness of about 20 μm was formed by a spinner method. On the other hand, a predetermined UV curable resin [2] was dropped in a circle on the surface of the APO stamper where the guide groove was formed, and a second resin layer (outermost resin layer) having a thickness of about 9 μm was formed by a spinner method. .

Next, the first substrate and the APO stamper were bonded so that the first resin layer and the second resin layer face each other. Subsequently, ultraviolet rays were irradiated from the APO stamper side to cure and bond the first resin layer and the second resin layer to form an adhesive body.
As the ultraviolet curable resins [1] and [2], radical ultraviolet curable resins were used, respectively.

  The APO stamper and the second resin layer (outermost resin layer) are peeled off by inserting a knife edge into the outer periphery of the adhesive and then applying force to peel off the APO stamper from the second resin layer (outermost resin layer). I let you. Through the above process, an intermediate layer having a thickness of about 29 μm was formed by laminating the first resin layer and the second resin layer.

(1-4) Formation of second recording layer, etc. A tetrafluoropropanol solution (concentration 1% by weight) of the same cyanine dye as that used in the first recording layer was dropped onto the intermediate layer and applied by a spinner method. . After coating, the film was dried at 70 ° C. for 30 minutes to form a second recording layer.
Subsequently, the reflective layer adjacent to the recording layer (hereinafter referred to as reflective layer 1) is 50 nm by sputtering, and the reflective layer adjacent to the reflective layer 1 (hereinafter referred to as reflective layer 2) is 50 nm by sputtering. Films were sequentially formed in film thickness. The materials used for the reflective layer 1 and the reflective layer 2 are as shown in Table 1 below.

  Further, an adhesive layer was provided on the second reflective layer by spin coating an ultraviolet curable resin. Then, a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm was placed on the adhesive layer to form a second substrate, which was cured and adhered by irradiation with ultraviolet rays.

In this way, a multilayer optical recording medium having two recording layers was produced.
In this embodiment, the main information recording laser beam is irradiated from the first substrate side, and the medium recognition signal recording laser beam is irradiated from the second substrate side. That is, the first substrate side is the information surface, the second substrate side is the back surface, the second recording layer is the specific recording layer, and the second reflective layer is the specific reflective layer.
With respect to the obtained optical recording medium, main information was recorded in the data area with a laser having a wavelength of 405 nm and reproduced. As a result, the L1 surface (the recording layer closer to the back surface; the second recording layer in this study) and L0. A sufficient reproduction signal was obtained in any layer of the surface (the recording layer on the side close to the information surface. In this study, the first recording layer).

(2) Measurement of reflectivity of second reflective layer Sample in which reflective layer 2 is formed on reflective glass (surface roughness Ra <5 nm) after reflecting layer 1 described in Table 1 is formed, and reflecting layer Samples in which the reflective layer 1 was formed after forming 2 were prepared. About these samples, by measuring the reflectance from the film surface side at a wavelength of 405 nm with an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation), the reflectance and back surface of the specific reflective layer from the information surface side The reflectance from the side was measured. The results are shown in Table 2.

(3) BCA recording characteristics on an optical recording medium A medium recognition signal was recorded on a BCA using a POM120-2R manufactured by Hitachi Computer Equipment Co., Ltd. for a multilayer optical recording medium having two recording layers produced by the method described above. . The laser wavelength was 810 nm, the beam spot diameter was 30 μm, and irradiation was performed from the surface (back surface) opposite to the first substrate. The recording conditions were a rotational speed of 800 rpm, a feed pitch of 18 μm, a duty of 20%, and a recording power of 4600 mW.
The modulation degree obtained from the second recording layer of the optical recording medium in which the medium recognition signal was recorded on the BCA in this way was measured with ODU1000 manufactured by PULSECEC.

The medium recognition signal recorded on the BCA was irradiated with a laser beam from the surface (back surface) opposite to the first substrate, and the L1 surface was read under the following conditions. The maximum potential difference (mV) was measured as IBH, the minimum potential difference was measured as IBL through a filter having a cut-off frequency of 2760 rpm and 550 KHz, and the value of IBL / IBH was taken as the modulation degree. Since the modulation degree means that the amplitude is larger as the value is lower, the sensitivity is better as the value of the modulation degree is lower. In consideration of the characteristic distribution of the optical recording medium and the margin of drive, it is preferable that the IBL / IBH of the medium recognition signal is 0.6 or less.
Further, the reflectance at the time of non-recording (hereinafter referred to as the L1 surface reflectance) when the L1 surface was irradiated with the main information recording laser beam was also measured by the ODU1000 at a read power of 0.6 mW. If the L1 surface reflectivity is too low, the recording characteristics of the main information are adversely affected, and a certain value or more is required. Usually, it is preferably 2.6% or more.
These measurement results are shown in Table 3.

[Example 2, Comparative Example 1-4]
A multilayer optical recording medium having two recording layers was produced in the same manner as in Example 1 except that the materials used for the second reflective layer were as shown in Table 1. Here, in Comparative Examples 1 to 4, the reflective layer 1 and the reflective layer 2 were made of the same material, and as a result, a single specific reflective layer was formed. When the main information was recorded on the data area of the obtained optical recording medium with a laser having a wavelength of 405 nm and reproduced, a good reproduction signal was obtained in any of the examples and comparative examples.

The reflectance of the second reflective layer was also measured in the same manner as in Example 1. The results are shown in Table 2 above. Here, in the comparative example, since the reflective layer 1 and the reflective layer 2 are the same material, the reflectance should not change even if the stacking order is changed. Accordingly, on the mirror glass (surface roughness Ra <5 nm), only the samples in which the reflective layer 1 was formed after forming the reflective layer 1 shown in Table 1 were prepared, and the reflectance was measured.
Table 3 shows the results of measuring the BCA recording characteristics (IBL / IBH) and the L1 surface reflectance by the same method as in Example 1 using the obtained optical recording medium.

In Comparative Example 1, recording to the BCA was attempted by changing the recording power, but no recording was possible.
In the specific reflection layer (Comparative Example 1) of a pure Ag single layer, the L1 surface reflectance is very good at 3.0%, but it is impossible to record on the BCA. On the other hand, by changing the reflective layer 2 to Ag _94.0 Cu _5.0 Nd _1.0 , the reflectance from the back surface can be reduced from 95.5% to 82.6%, and the value of IBL / IBH is also 0. A practically sufficient value of .60 was obtained.
In Comparative Example 4, by using a single layer of Ag _94.0 Cu _5.0 Nd _1.0 , IBL / IBH was 0.49 and good BCA recording characteristics were obtained, but the L1 surface reflectance was as low as 2.5%. This is an insufficient value in terms of the recording characteristics of the main information.

  From these results, by making the reflectance from the back surface side smaller than the reflectance from the information surface side in the specific reflection layer, a good medium recognition signal is maintained while maintaining a high reflectance in recording main information. It was found that the recording characteristics can be realized. In particular, the reflectivity from the back surface side is preferably about 5 to 30% lower than the reflectivity from the information surface side.

  The present invention can be widely used for optical recording media that record main information at a laser wavelength of 300 to 450 nm. As specific examples, it is particularly suitable for use in HD DVD-R, HD DVD-RW, HD DVD-RAM, BD-R, BD-RE media, and the like.

1 is an enlarged cross-sectional view schematically showing a main part of a single-sided, two-layer optical recording medium according to an embodiment of the present invention. 1 is a plan view schematically showing a single-sided two-layer optical recording medium according to an embodiment of the present invention. (A)-(g) is the figure which showed typically the cross section of the principal part, in order to demonstrate the manufacturing method of the optical recording medium as one Embodiment of this invention. (A), (b) is the figure which showed typically the cross section of the principal part, in order to demonstrate the resin raw material layer formation process of the manufacturing method of the optical recording medium as one Embodiment of this invention. is there. In order to explain the resin raw material layer curing step of the method of manufacturing an optical recording medium as one embodiment of the present invention, it is a diagram schematically showing a cross section of the main part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Optical recording medium 100A Information surface 100B Back surface 101 1st board | substrate 102 1st recording layer 103 1st reflection layer 104 Intermediate layer 104a Resin raw material layer (UV curable resin raw material layer)
104a ₁ first resin layer 104a ₂ second resin layer (outermost resin layer)
105 Second Recording Layer 105X Data Area 105Y Burst Cutting Area 106 Second Reflective Layer 106a Adjacent Reflective Layer 106b Backside Reflective Layer 107 Adhesive Layer 108 Second Substrate 109 Recording / Reproducing Light 110 Stamper 111 Data Substrate 112, 112 ′ Adhesive 113 Optical Recording Laminate for medium

Claims (10)

A data area where main information recording laser light having a wavelength of 300 nm to 450 nm is irradiated from the information surface and main information is recorded, and a medium recognition signal recording laser light is irradiated from the back surface opposite to the information surface. And a specific recording layer having a burst cutting area on which a medium recognition signal is recorded, and a specific reflection layer formed corresponding to the specific recording layer, the main information recording laser of the specific reflection layer An optical recording medium, wherein a reflectance from an information surface side at a wavelength of light is larger than a reflectance from a back surface side. The optical recording medium according to claim 1, further comprising two or more recording layers, wherein the recording layer farthest from the information surface is the specific recording layer. The optical recording medium according to claim 1, wherein the specific reflective layer has a thickness of 60 nm to 200 nm. The reflectance from the back surface side in the wavelength of the main information recording laser beam of the specific reflection layer is 55% or more and 85% or less, according to any one of claims 1 to 3. The optical recording medium described. The optical recording medium according to any one of claims 1 to 4, wherein the specific reflective layer includes a plurality of layers having different compositions. 6. The optical recording medium according to claim 5, wherein the adjacent reflective layer closest to the specific recording layer among the plurality of layers contains 85 atomic% or more of Ag. Wherein the plurality of layers, the thickness of the closest Itonari contact reflective layer on the specific recording layer, characterized in that at 30nm or more 120nm or less, the optical recording medium of claim 5 or claim 6. The specific recording layer contains an organic dye having a decomposition temperature of 100 ° C. or higher and 350 ° C. or lower and / or an amorphous semiconductor having a phase transition temperature of 100 ° C. or higher and 350 ° C. or lower. 8. The optical recording medium according to any one of 7 above. Grooves having a groove depth of 15 nm to 100 nm, a track pitch of 0.1 μm to 0.6 μm, and a ratio of land width to groove width of 0.3 to 1.2 are formed in the burst cutting area. The optical recording medium according to claim 1, wherein: The medium recognition signal is irradiated to the burst cutting area by irradiating the optical recording medium according to any one of claims 1 to 9 with the medium recognition signal recording laser light having a wavelength of 400 nm to 2000 nm from the back surface. A method for recording a medium recognition signal, comprising: recording a medium recognition signal.

Images