JP2007066489A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new multilayer type optical recording medium where a medium identification information recording area can be formed satisfactorily. <P>SOLUTION: The optical recording medium 1 where two or more layers of recording and reproducing function layers 2 and 3 having recording layers 2A and 3A and reflection layers 2B and 3B to perform recording or reproducing with light has a first recording and reproducing function layer 2 where the medium identification information recording area 2X in which medium identification information is recorded is formed; and the second recording and reproducing function layer 3 which is laminated at a position nearer to the incident surface 6 of the light at the optical recording medium than the first recording and reproducing function layer 2 and where at least either of its recording layer 3A and its reflection layer 3B is formed avoiding a section 3X corresponding to the medium identification information recording area 2X. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical recording medium, and more particularly to a multilayer type optical recording medium.

  The medium identification information may be recorded on the optical recording medium for the purpose of distributing the information recorded on the optical recording medium or preventing unauthorized copying. As a specific example, a barcode for recording medium identification information such as copyright information and lot number is formed on the inner diameter side of the main recording / reproducing area (area used for recording or reproduction) of a flat disk-shaped optical recording medium. There is a technique for providing the above-mentioned area ("Burst Cutting Area" or "medium identification information recording area", hereinafter referred to as "BCA area" as appropriate). The bar code is usually formed by burning a recording layer or a reflection layer existing in the BCA area into a predetermined bar coat shape or changing the phase using a laser at the time of manufacturing an optical recording medium. .

  On the other hand, in view of the recent increase in recording capacity, optical recording media having a plurality of recording layers have been developed. Further, even in an optical recording medium having a plurality of such recording layers (hereinafter sometimes referred to as a multilayer type optical recording medium), a BCA region may be formed.

  As a technique for forming a BCA region on such a multilayer optical recording medium, for example, there is Patent Document 1. The information recording apparatus and method in Patent Document 1 is a surface for recording or reproducing user data (that is, information recorded in a recording layer) on an information recording medium (hereinafter referred to as “information recording / reproducing surface” as appropriate). An optical pickup for recording medium information is installed on the opposite side of the surface. The medium identification information is recorded by irradiating a laser beam from the surface opposite to the information recording / reproducing surface.

Japanese Patent Laying-Open No. 2005-13569 (particularly paragraph 0008)

  However, according to the study of the present inventor, the conventional method such as the technique described in Patent Document 1 has a problem that it is difficult to apply to a multilayer optical recording medium formed by a 2P (Photo Polymerization) method. It has been found. This is because in a multilayer optical recording medium formed by the 2P method, a dummy substrate, an adhesive layer, a reflective layer, and a recording layer are laminated from the surface opposite to the information recording / reproducing surface for recording or reproducing user data. This is due to the layered structure.

  Here, in the multilayer type optical recording medium formed by the 2P method, since the recording or reproducing light does not enter the dummy substrate or the adhesive layer, both optically and mechanically are high. Precision is not required. Therefore, in order to reduce costs, the dummy substrate and the adhesive layer are configured to have lower optical accuracy than other layers. Specifically, the accuracy of the thickness of the dummy substrate is relatively low compared to the substrate on the information recording / reproducing surface side. Further, the actual situation is that the dummy substrate does not sufficiently adjust the optical characteristics. In addition, when manufacturing the optical recording medium, the actual situation is that high control is not performed in consideration of the film thickness of the adhesive layer for bonding the dummy substrate and the optical characteristics.

  From the above circumstances, when recording the medium identification information from the dummy substrate side to the BCA area on the multilayer optical recording medium formed by the 2P method using the technique described in Patent Document 1 In this case, the light for recording the medium identification information is transmitted through the dummy substrate and the adhesive layer. However, as described above, since the optical accuracy of the dummy substrate and the adhesive layer is low, the light for recording the medium identification information is attenuated or defocused, and the medium identification information is recorded in the BCA area with high accuracy. Tends to be difficult. In other words, if a BCA region is to be favorably formed by irradiating a laser beam from the surface opposite to the information recording / reproducing surface, dummy substrates and other layers (adhesive layers, etc.) located on this surface side It is necessary to precisely control optical characteristics and thickness characteristics. This means that the cost of the optical recording medium is increased.

A similar problem can occur in a multilayer optical recording medium formed by a method other than the 2P method. For example, a laminated multi-layer optical recording medium has a recording layer, a positive laminate in which a reflective layer is laminated on a substrate on which a guide groove is formed, and a reflective layer on a reverse laminated substrate in which a guide groove is formed, The reverse laminate having the recording layer laminated thereon is bonded with the reflective layer of the normal laminate and the recording layer of the reverse laminate facing each other. Then, a laser beam for recording / reproducing is irradiated from the substrate side of the positive laminate. Even in such a laminated multi-layer optical recording medium, the reverse laminated substrate of the reverse laminated body does not transmit the recording / reproducing laser beam, so that the optical characteristics are not sufficiently adjusted. It is.
Therefore, if an attempt is made to provide a BCA region on the side of the reverse laminate that exists on the side far from the incident surface of the laser beam, the same problem as in the 2P method occurs. That is, it is necessary to match the optical characteristics of the reverse laminated substrate so that the medium identification information recording light can be transmitted and the BCA area can be recorded satisfactorily. This causes an increase in cost.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a new multilayer optical recording medium capable of satisfactorily forming a medium identification information recording area.

  The inventor of the present invention has intensively studied to solve the above problems, and as a result, the BCA region is formed on the recording layer or the reflective layer that is farthest from the surface on which user data is recorded or reproduced (that is, the information recording / reproducing surface). In the multilayer type optical recording medium provided with a laser beam from the information recording / reproducing surface, the recording layer and the reflective layer are formed so as to avoid the portion corresponding to the BCA region between the BCA region and the information recording / reproducing surface. It was found that the medium identification information can be recorded well in the BCA area.

  That is, the gist of the present invention is an optical recording medium having a recording layer and a reflective layer, in which two or more recording / reproducing functional layers that are recorded or reproduced by light are stacked, and on which medium identification information is recorded. A first recording / reproducing functional layer having a medium identification information recording area formed thereon, and a layer closer to the light incident surface of the optical recording medium than the first recording / reproducing functional layer, At least one of the reflective layers includes a second recording / reproducing functional layer formed so as to avoid a portion corresponding to the medium identification information recording area. (Claim 1) .

  At this time, in the optical recording medium of the present invention, the portion corresponding to the medium identification information recording region on the surface of the layer adjacent to the first recording / reproducing functional layer corresponds to the cutoff frequency of the optical transfer function. It is preferable that irregularities with a width smaller than the length are formed (claim 2).

  The optical recording medium of the present invention is preferably capable of recording or reproducing with light having a wavelength of 500 nm or less.

  Further, the recording layer preferably contains an organic dye.

  According to the present invention, it is possible to provide a new multilayer type optical recording medium in which the medium identification information recording area can be satisfactorily formed.

The present invention will be described below. In the description, an embodiment of the present invention will be described as a specific example with reference to the drawings. However, the present invention is not limited to the following embodiment and examples, and the scope of the present invention is not deviated. In the embodiment, the present invention can be implemented with any modification.
1 to 7 illustrate an embodiment of the present invention. FIG. 1 is a schematic cross-sectional view showing an enlarged cross section near the center of the optical recording medium, and FIG. 2 is a schematic diagram of the optical recording medium. FIG. 3 is a schematic diagram for explaining an example of a method for forming a recording layer or a reflective layer in an optical recording medium. FIG. 4 is a schematic diagram for explaining an example of a method for forming a recording layer or a reflective layer in an optical recording medium. FIG. 5 is a schematic diagram for explaining an example of a method for forming a recording layer or a reflective layer in an optical recording medium, and FIG. 6 is a recording / reproducing functional layer in a portion corresponding to the BCA area of a dummy substrate in the optical recording medium. FIG. 7 is a schematic diagram for explaining a method of recording medium identification information in the BCA area of an optical recording medium when an unevenness is formed on the surface of the side, schematically showing an enlarged main part thereof. .

[1. Overview]
As shown in FIG. 1, the optical recording medium 1 has at least recording layers 2A and 3A and reflection layers 2B and 3B, and has two recording / reproducing functional layers 2 and 3 on which recording or reproduction is performed by light. The multilayer optical recording medium. The recording / reproducing functional layers 2 and 3 are usually laminated on the substrate 4. Further, an intermediate layer 5 is usually formed between the recording / reproducing functional layers 2 and 3.

  The optical recording medium 1 includes a first recording / reproducing functional layer 2 in which a BCA area (that is, a medium identification information recording area) 2X in which medium identification information is recorded is formed as the recording / reproducing functional layers 2 and 3 described above. And a layer closer to the light incident surface (that is, the information recording / reproducing surface) 6 in the optical recording medium 1 than the first recording / reproducing functional layer 2, of the recording layer 3A and the reflective layer 3B. At least one of the second recording / reproducing functional layer 3 formed so as to avoid the portion 3X corresponding to the BCA region 2X.

[2. Recording / playback functional layer]
The recording / reproducing functional layers 2 and 3 are layers for performing recording or reproduction by light. The recording / reproducing functional layers 2 and 3 include at least recording layers 2A and 3A and reflecting layers 2B and 3B. In this respect, the recording / reproducing functional layers 2 and 3 in FIG. 1 have the most basic layer configuration of the recording / reproducing functional layer. However, the layer structure of the recording / reproducing functional layer can be variously considered depending on the type of the optical recording medium. Specifically, the layer structure of the recording / reproducing functional layer is such that the optical recording medium is a write-once medium (Write Once medium) that can be recorded only once, and a rewritable medium that can repeatedly perform recording and erasing. Depending on the case of (Rewritable medium), it is possible to adopt a layer structure corresponding to each purpose. The recording / reproducing functional layer can be divided into a substrate surface incident type and a film surface incident type depending on the incident direction of recording / reproducing light (hereinafter referred to as “recording / reproducing light” as appropriate).
The generally used recording / reproducing functional layer will be described below.

(Example 1 of write-once medium)
In the write-once medium, the recording / reproducing functional layer is usually formed of a reflective layer and a recording layer. Further, the order of stacking the reflective layer and the recording layer is set according to the type of medium (light incident direction). Specifically, in a film surface incidence type medium, the recording / reproducing functional layer is usually formed by providing a reflective layer and a recording layer in this order from the side closer to the substrate. On the other hand, in a substrate surface incident type medium, a recording / reproducing functional layer is usually formed by providing a recording layer and a reflective layer in this order from the side closer to the substrate.
Further, in the substrate surface incident type medium, a protective layer may be provided on the reflective layer as necessary.

  Furthermore, the material of the protective layer is arbitrary as long as information can be recorded or reproduced by the recording / reproducing functional layer, but an ultraviolet curable resin is usually used. In addition, the material of a protective layer may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. Moreover, although the formation method of a protective layer is also arbitrary, it forms normally by making it harden | cure after spin-coating.

  As the material of the reflective layer, a material that can reflect the light incident on the recording / reproducing functional layer is used. Any information can be used as long as information can be recorded or reproduced by the recording / reproducing functional layer. Usually, a metal or an alloy such as Al, Ag, or Au is used. In addition, the material of a reflection layer may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  However, since the optical recording medium of the present invention is a multi-layer type (that is, a type having a plurality of recording / reproducing functional layers), a recording / reproducing functional layer (hereinafter referred to as “lowermost recording” as appropriate) existing at the farthest position from the information recording / reproducing surface In FIG. 1, a recording / reproducing functional layer other than the first recording / reproducing functional layer corresponds to the lowest recording / reproducing functional layer (for example, the second recording / reproducing functional layer in FIG. 1). The reflective layer needs to be configured to transmit part of the incident light. This is to allow light used for recording and reproduction to reach the lowermost recording / reproducing functional layer.

The light transmittance of the reflective layer used in such a recording / reproducing functional layer depends on the number of recording / reproducing functional layers provided. For example, when the recording / reproducing functional layer has two layers, the light transmittance is preferably 40% or more and the light reflectance is usually 30% or more. For example, when the recording / reproducing functional layer is formed of four layers, the light transmittance is preferably 70% or more.
In addition, although there is no restriction | limiting in the formation method of a reflection layer, Although it is arbitrary, Usually, it forms by sputtering.

  On the other hand, the material of the recording layer is also arbitrary as long as information can be recorded or reproduced by the recording / reproducing functional layer, but usually an organic dye is used. That is, the recording layer preferably contains an organic dye. Examples of such organic dyes include macrocyclic azaannulene dyes (phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, etc.), polymethine dyes (cyanine dyes, merocyanine dyes, squarilium dyes, etc.), anthraquinone dyes, azurenium dyes, Examples thereof include metal azo dyes and metal-containing indoaniline dyes. In particular, metal-containing azo dyes are preferable because they are excellent in durability and light resistance. The recording layer material may be used alone or in combination of two or more in any combination and ratio.

  Further, the method for forming the recording layer is not limited and is arbitrary. For example, when the recording layer is formed with an organic dye, the recording layer is usually formed by a coating method such as spin coating, spray coating, dip coating, or roll coating using a solution in which the organic dye is dissolved in an appropriate solvent. In this case, the solvent includes ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone, cellosolve solvents such as methyl cellosolve and ethyl cellosolve, and perfluorocarbons such as tetrofluoropropanol and octafluoropentanol. Hydroxyethyl solvents such as alkyl alcohol solvents, methyl lactate and methyl isobutyrate are preferably used.

  In addition, the thickness of the recording layer is not particularly limited because a suitable film thickness varies depending on the recording method or the like, but in order to obtain a sufficient degree of modulation, it is usually 5 nm or more, preferably 10 nm or more, more preferably 20 nm or more. It is. However, since it is necessary to transmit light, it is usually 3 μm or less, preferably 1 μm or less, more preferably 200 nm or less.

Further, when the intermediate layer is formed of a resin and the recording layer is formed of an organic dye, the organic dye may be dissolved when the recording layer and the intermediate layer are in contact with each other. In such a case, in order to suppress the dissolution, a buffer layer made of an inorganic material (for example, ZnS / SiO ₂ ) may be further provided between the recording layer and the intermediate layer.

(Example 2 of write-once medium)
Another example of the recording / reproducing functional layer of the write-once medium is a recording layer, a dielectric layer, and a reflective layer. Further, the recording / reproducing functional layer is formed by providing the reflective layer, the dielectric layer, the recording layer, and the dielectric layer in this order from the side closer to the substrate.

  On the other hand, among the write-once media, another example of the recording / reproducing functional layer of the substrate surface incidence type media includes a recording layer, a dielectric layer, and a reflective layer. Further, the recording / reproducing functional layer is formed by providing a dielectric layer, a recording layer, a dielectric layer, and a reflective layer in this order from the side closer to the substrate.

In this type of recording / reproducing functional layer, the reflective layer may be the same as described above in “(Example of write once medium) 1”.
The material of the recording layer is arbitrary as long as information can be recorded or reproduced by the recording / reproducing functional layer, but is usually an inorganic material (for example, a chalcogen-based alloy such as Ge · Te, Ge · Sb · Te). Is used. The recording layer material may be used alone or in combination of two or more in any combination and ratio.
Moreover, although there is no restriction | limiting in the formation method of a recording layer, Usually, it forms by sputtering.
Furthermore, although there is no restriction | limiting in the film thickness, Usually, it is set as about 1 nm-50 nm.

Further, the material of the dielectric layer is arbitrary as long as information can be recorded or reproduced by the recording / reproducing functional layer. In consideration of heat resistance and mechanical strength, an inorganic material (typically, ZnS / SiO ₂ ) is usually used. In addition, the material of the dielectric layer may be used alone or in combination of two or more in any combination and ratio. Moreover, although the formation method of a dielectric material layer is also arbitrary, it forms normally by sputtering.

  Moreover, you may provide a protective layer as needed. The protective layer is usually provided on the dielectric layer in a film surface incident type medium. On the other hand, the protective layer is usually provided on the reflective layer in the substrate surface incident type medium. The material and manufacturing method of the protective layer may be the same as those described in “Write-once medium example 1”.

(Example 1 of rewritable medium)
In a rewritable medium, the recording / reproducing functional layer is usually formed of a reflective layer, a recording layer, and a dielectric layer. The order of stacking these layers is set according to the type of the medium. Specifically, in a film surface incidence type medium, a recording / reproducing functional layer is usually formed by providing a reflective layer, a dielectric layer, a recording layer, and a dielectric layer in this order from the side closer to the substrate. On the other hand, in a substrate surface incident type medium, a recording / reproducing functional layer is formed by providing a dielectric layer, a recording layer, a dielectric layer, and a reflective layer in this order from the side closer to the substrate. Further, in the film surface incident type medium, a protective layer may be provided on the dielectric layer. Similarly, in the substrate surface incidence type medium, a protective layer may be provided on the reflective layer.

  The reflective layer, the dielectric layer, the recording layer, and the protective layer may be the same as described in “(Examples of write once medium 1 and 2)”. However, the recording layer needs to be made of a material capable of reversible recording / erasing. Examples of such materials include SbTe, GeTe, GeSbTe, InSbTe, AgSbTe, AgInSbTe, GeSb, GeSbSn, InGeSbTe, and InGeSbSnTe. Among these, it is preferable to use a composition containing Sb as a main component in the recording layer in order to increase the crystallization speed.

(Example 2 of rewritable medium)
Another specific example of the rewritable medium is a magneto-optical recording medium (MO disk).

  In the present embodiment, as shown in FIG. 1, the recording / reproducing functional layers 2 and 3 in which the recording layers 2A and 3A and the reflective layers 2B and 3B are formed in this order are formed on the substrate 4 via the intermediate layer 5. The explanation will be made by taking the laminated optical recording medium 1 as an example. Further, this optical recording medium 1 is a substrate surface incident type medium, and information is recorded or reproduced by irradiating light from an information recording / reproducing surface 6 which is the surface of the substrate 4. .

[3. Number of recording / playback functional layers]
In the optical recording medium of the present invention, two or more recording / reproducing functional layers are formed. Although there is no restriction | limiting in the specific number of lamination | stacking, Usually, they shall be 2 layers or more and 10 layers or less. Especially, it is preferably 7 layers or less, more preferably 5 layers or less. Most preferably, the number of recording / reproducing functional layers is two.
In the present embodiment, as shown in FIG. 1, the optical recording medium 1 is an example in which two layers of a first recording / reproducing functional layer 2 and a second recording / reproducing functional layer 3 are used.

[4. substrate]
As a material for the substrate, an appropriate material can be arbitrarily used depending on the type of the optical recording medium 1, but plastic, metal, glass or the like having appropriate processability and rigidity is usually used. However, the substrate of the substrate surface incident type optical recording medium needs to be transparent to incident light (usually laser light). On the other hand, in a film surface incident type optical recording medium, since normal light does not pass through the substrate, the substrate may not be transparent to the light.

  However, when the substrate is formed of metal or glass, a light or thermosetting thin resin layer is provided on the surface, and a guide groove (not shown) described later is often formed there. On the other hand, when the substrate is formed of a plastic material, the shape of the substrate (particularly a disk shape) and the guide groove on the surface can be formed all at once by injection molding. Therefore, it is preferable in manufacturing that the substrate is formed of a plastic material or the like.

As a plastic material that can be injection-molded, for example, polycarbonate resin, polyolefin resin, acrylic resin, epoxy resin, and the like conventionally used in CDs and DVDs can be used.
In addition, the material of a board | substrate may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

Moreover, although the thickness of a board | substrate is also arbitrary, Usually, it is preferable to set it as about 0.5-1.2 mm.
Further, a guide groove for tracking is usually formed on the substrate.
The track pitch of the guide groove differs depending on the wavelength of light used for recording / reproduction of the optical recording medium 1. Specifically, in a CD optical recording medium, the track pitch is usually 1.5 to 1.6 μm. In the DVD optical recording medium, the track pitch is usually 0.7 to 0.8 μm. Furthermore, in the optical recording medium for blue laser, the track pitch is usually 0.2 to 0.5 μm.

  On the other hand, the depth of the guide groove also differs depending on the wavelength of the laser beam used for recording / reproduction of the optical recording medium 1. Specifically, in a CD-based optical recording medium, the groove depth is usually 10 to 300 nm. Further, in the DVD optical recording medium, the groove depth is usually 10 to 200 nm. Further, in the optical recording medium for blue laser, the groove depth is usually 10 to 200 nm.

  In some cases, two or more substrates may be provided on the optical recording medium. For example, in order to reinforce the strength of the optical recording medium on the side opposite to the information recording / reproducing surface side separately from the substrate provided on the information recording / reproducing surface side in the substrate surface incident type optical recording medium. One substrate (hereinafter referred to as “dummy substrate” as appropriate) may be provided. The structure of this dummy substrate is basically the same as that of the substrate, but normally, since this dummy substrate does not need to transmit light for recording or reproducing information, a precise optical structure is necessary. do not do. Further, when a multilayer optical recording medium is formed by the 2P method, it is not necessary to provide a tracking guide groove on the dummy substrate. Therefore, if a predetermined strength can be ensured, it can be formed from a wider range of materials than the substrate.

In the present embodiment, as shown in FIG. 1, the optical recording medium 1 is provided with a substrate 4 on one side and a dummy substrate 7 on the other side. It is assumed that the internal recording / reproducing functional layers 2 and 3 and the intermediate layer 5 are sandwiched between the layers. Specifically, the recording / reproducing functional layer 3, the intermediate layer 5, and the recording / reproducing functional layer 2 are laminated on the substrate 4, and the dummy substrate 7 is disposed on the recording / reproducing functional layer 2 via an adhesive layer (not shown). It is glued.
The substrate 4 is transparent to incident light. Further, a tracking guide groove (not shown) for the recording / reproducing functional layer 3 existing thereon is formed on the substrate 4. On the other hand, no tracking guide groove is formed in the dummy substrate 7.
In addition, although the unevenness | corrugation (illustration omitted in FIG. 1) is formed in the site | part on the dummy substrate 7 corresponding to the BCA area | region 2X, this is mentioned later.

[5. Middle layer]
An intermediate layer is usually provided between the recording / reproducing functional layers. As the material for the intermediate layer, any material can be used as long as it can transmit light used for recording or reproduction, but a photo-curable resin material is usually used.
In general, a photocurable resin material is composed of a mixture of an oligomer, which is a resin main component serving as a resin skeleton, a monomer as a reactive diluent, an initiator, an additive, and the like.

Examples of such a photocurable resin material include an ultraviolet curable resin material.
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 and a photopolymerization initiator as essential components is used. As specific examples thereof, monofunctional (meth) acrylates and polyfunctional (meth) acrylates can be used as the polymerizable monomer component. Here, acrylate and methacrylate are collectively referred to as (meth) acrylate. At this time, the photopolymerization initiator is preferably a photocleavage type or a hydrogen abstraction type.

  On the other hand, examples of the cationic ultraviolet curable resin include an epoxy resin containing a cationic polymerization type photoinitiator. Specific examples of this epoxy resin include bisphenol A-epichlorohydrin type, alicyclic epoxy, long chain aliphatic type, brominated epoxy resin, glycidyl ester type, glycidyl ether type, and heterocyclic type. .

  However, it is preferable to use an epoxy resin having a low content of free chlorine and chlorine ions. Specifically, the amount of chlorine is usually 1% by weight or less, preferably 0.5% by weight or less. Examples of the cationic polymerization type photoinitiator include sulfonium salts, iodonium salts, diazonium salts, and the like.

Furthermore, among the above-mentioned ultraviolet curable resins, it is preferable to obtain an intermediate layer by curing an uncured ultraviolet curable resin precursor mainly composed of radical polymerization type acrylic ester. This is because the radical polymerization type acrylic acid ester has a high curing rate and has a predetermined hardness even in a semi-cured state, and thus has high mass productivity.
In addition, the material of an intermediate | middle layer may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  In addition, the intermediate layer is required to have characteristics such as high hardness, low curing shrinkage, high light transmittance with respect to light for recording and reproduction on an optical recording medium, and little change with time. Therefore, it is preferable to form an intermediate layer having these characteristics.

  In order to increase the hardness, the molecular structure of the oligomer itself is devised, or a monomer having a bifunctional, trifunctional or higher reactive group is used so as to form a three-dimensional crosslink. If the polyfunctional monomer component is too much, curing shrinkage increases. In order to prevent this, it is desirable to devise the structure of the oligomer or to balance by adjusting the composition of each monomer.

  Further, the light transmittance with respect to light for recording and reproduction depends on the skeleton of the oligomer, the type and amount of the photopolymerization initiator. For this reason, it is desirable to devise these designs in order to control the light transmittance.

  Furthermore, changes with time are often caused by volatilization of uncured components, generation of corrosion components due to decomposition, and the like. For this reason, in order to suppress a change with time, it is desirable to devise the composition of the mixture, particularly the type and amount of the polymerization initiator. However, since this polymerization initiator is not incorporated into the cross-linking of the resin, it may be gradually volatilized (eluted). For this reason, it is preferable to stop the said polymerization initiator to the minimum necessary quantity.

The method for forming the intermediate layer is not limited and is arbitrary. Usually, the intermediate layer is formed by applying and curing a photocurable resin material as described above on the recording / reproducing functional layer by a spin coat method or the like.
In particular, when a plurality of recording / reproducing functional layers are stacked by the 2P method, after applying a photocurable resin material on the recording / reproducing functional layer, a transparent stamper (with a tracking guide groove formed) The photo-curing resin material is cured in a state where (not shown) is placed on the coating film. As a result, a tracking guide groove for the recording / reproducing functional layer formed on the intermediate layer can be formed in the intermediate layer.

  The viscosity (viscosity at room temperature (25 ± 5 ° C.)) of the photocurable resin material is not limited, but is usually 30 mPa · s or more, preferably 100 mPa · s or more. This is because when the viscosity of the photocurable resin material is within the above range, the applicability of the photocurable resin material becomes good and the film thickness of the intermediate layer can be easily controlled.

  On the other hand, the viscosity (viscosity at room temperature (25 ± 5 ° C.)) of the photocurable resin material is usually 5000 mPa · s or less, preferably 4000 mPa · s or less. When the viscosity of the photo-curable resin material is set in the above range, the workability is improved because the rotational stretching time can be controlled within a predetermined range. In addition, if the viscosity of the photocurable resin material is set within the above range, generally, it is easy to suppress a change in viscosity due to temperature. For this reason, it is because it is preferable practically.

  In the present embodiment, it is assumed that an intermediate layer 5 is formed between the recording / reproducing functional layer 2 and the recording / reproducing functional layer 3 as shown in FIG. In the intermediate layer 5, a tracking guide groove (not shown) for the recording / reproducing functional layer 2 formed on the intermediate layer 5 is formed.

[6. Shape of optical recording medium]
The shape of the optical recording medium is usually a ring shape. Here, the ring shape represents a broad shape including a planar disk shape. For example, in order to enhance the attractiveness of the design of the optical recording medium, the optical recording medium may be formed into a planar elliptical shape or a planar rectangular shape.
In addition, the optical recording medium is usually formed with a center hole for holding the optical recording medium during rotation.
In the present embodiment, as shown in FIG. 1, the optical recording medium 1 is assumed to be formed in a planar disk shape in which a center hole 8 communicating with the front and back is formed at the center.

[7. Main recording / playback area]
The user data is recorded in the main recording / reproducing area 9 of each recording / reproducing functional layer as shown in FIG. The main recording / reproducing area 9 is usually provided in a donut shape centered on the center hole 8 as an area occupying most of each recording / reproducing functional layer.
Also in the present embodiment, the main recording / reproducing area 9 has a donut shape from the outer peripheral edge of the optical recording medium 1 to the vicinity of the inner peripheral edge (the solid circle of the outer peripheral edge in FIG. It is assumed that information is recorded in the main recording / reproducing area 9 or information is reproduced.

[8. Medium identification information recording area (BCA area)]
The BCA area is formed in the first recording / reproducing functional layer. The BCA area is an area for recording medium identification information of the optical recording medium 1 such as copyright information and a lot number. Usually, the medium identification information is recorded in the BCA area as a barcode pattern formed by burning or phase-changing the first recording / reproducing functional layer with light.

  The first recording / reproducing functional layer having the BCA area is usually formed as the lowest recording / reproducing functional layer. Therefore, at least one recording / reproducing functional layer always exists at a position closer to the information recording / reproducing surface than the first recording / reproducing functional layer in which the BCA area is formed.

  At least one of the recording / reproducing functional layers (collectively referred to as the upper recording / reproducing functional layer) formed at a position closer to the information recording / reproducing surface than the first recording / reproducing functional layer. In the reproducing function layer, at least one of the recording layer and the reflective layer is formed so as to avoid a portion corresponding to the BCA region. A recording / reproducing functional layer in which at least one of the recording layer and the reflective layer is formed so as to avoid a portion corresponding to the BCA region is referred to as a second recording / reproducing functional layer. Of course, among the recording / reproducing functional layers constituting the upper recording / reproducing functional layer, in one or more recording / reproducing functional layers other than the second recording / reproducing functional layer, at least one of the recording layer and the reflective layer corresponds to the BCA region. You may make it form avoiding the site | part to do. In addition, in the upper recording / reproducing functional layer that exists between the first recording / reproducing functional layer and the information recording / reproducing surface, the recording / reproducing functional layer that does not have at least one of the recording layer and the reflective layer in a portion corresponding to the BCA area May be set to be equal to or less than “the number of upper recording / reproducing functional layers−1”.

  Further, in the upper recording / reproducing functional layer, when at least one of the recording layer and the reflective layer of the second recording / reproducing functional layer is formed so as to avoid a portion corresponding to the BCA region, in consideration of productivity, Of the upper recording / reproducing functional layer, the recording / reproducing functional layer closest to the information recording / reproducing surface is preferably the second recording / reproducing functional layer.

  Further, in all the recording / reproducing functional layers constituting the upper recording / reproducing functional layer, it is preferable that the recording layer is formed so as to avoid a portion corresponding to the BCA region. Similarly, in all of the recording / reproducing functional layers constituting the upper recording / reproducing functional layer, it is preferable that the reflective layer is formed so as to avoid a portion corresponding to the BCA region. More preferably, in all of the recording / reproducing functional layers constituting the upper recording / reproducing functional layer, the recording layer and the reflective layer are formed so as to avoid a portion corresponding to the BCA region. When the upper recording / reproducing functional layer is formed as described above, the intensity of the medium identification information forming light (usually a laser beam) irradiated to the first recording / reproducing functional layer when recording the medium identification information. It becomes easy to secure.

  Here, the part corresponding to the BCA area means a part through which light is transmitted when light enters the BCA area from the information recording / reproducing surface. It represents the part facing the side.

Hereinafter, this embodiment will be described as an example.
As shown in FIG. 1, the recording / reproducing functional layer 2 is a first recording / reproducing functional layer in which the BCA region 2X is formed. The recording / reproducing functional layer 2 is formed as the lowermost recording / reproducing functional layer. In the recording / reproducing functional layer 3 that is closer to the information recording / reproducing surface 6 than the recording / reproducing functional layer 2 in which the BCA region 2X is formed, the portion 3X corresponding to the BCA region 2X includes the recording layer 3A and the reflection layer. The layer 3B is not formed.

  As shown in FIG. 10, in the optical recording medium in which the recording / reproducing functional layer 3 (that is, the recording layer 3A and the reflective layer 3B) is formed in the portion 3X corresponding to the BCA region 2X, laser light or the like is emitted from the information recording / reproducing surface 6. When the medium identification information is to be recorded in the BCA area 2X of the recording / reproducing functional layer 2 by irradiation, the recording / reproducing is in front of it (that is, the position closer to the information recording / reproducing surface 6 than the recording / reproducing functional layer 2) Phenomena such as the laser beam being blocked, attenuated, or refracted by the functional layer 3 occur. As a result, a barcode or the like cannot be formed accurately, and it becomes difficult to record the medium identification information in the BCA area 2X. In addition, as described in Patent Document 1, recording of medium identification information in the BCA area 2X by irradiating light from the surface 10 opposite to the information recording / reproducing surface 6 causes an increase in cost. become.

  On the other hand, if the recording / reproducing functional layer 3 is formed so that at least one of the recording layer 3A and the reflective layer 3B avoids the portion 3X corresponding to the BCA region 2X as in the present embodiment (FIG. 1), the BCA It is possible to record the medium identification information precisely while suppressing light shielding, attenuation, and refraction by the recording / reproducing functional layer 3 before the recording / reproducing functional layer 2 in which the region 2X is formed. In this case, since the medium identification information can be recorded by irradiating light from the side of the information recording / reproducing surface 6 that is configured on the premise that light is originally incident, it is described in Patent Document 1. There is no risk of increasing costs as in the case of technology.

In the present embodiment, the position where the BCA area 2X is formed is not limited, but normally, as shown in FIG. 2, it is inside the main recording / reproducing area 9 (that is, the side where the center hole 8 is formed). Formed. That is, normally, the main recording / reproducing area 9 is provided on the outer peripheral side of the BCA area 2X.
Further, since the BCA area 2X is read by rotating the optical recording medium 1 by a reproducing drive of the optical recording medium 1, it is usually formed as an arc-shaped area in the circumferential direction of the optical recording medium 1, and further, it is larger. If it becomes, it will be provided in a ring shape (doughnut shape).

  As described above, in the recording / reproducing functional layer 3 closer to the information recording / reproducing surface 6 than the recording / reproducing functional layer 2 in which the BCA area 2X is formed, at least one of the recording layer 3A and the reflective layer 3B is It suffices that the portion 3X corresponding to the BCA region 2X is avoided, but it is desirable that both the recording layer 3A and the reflective layer 3B are formed so as to avoid the portion 3X.

  Further, as described above, when there are two or more recording / reproducing functional layers closer to the information recording / reproducing surface 6 than the recording / reproducing functional layer 2 in which the BCA area 2X is formed, at least one of those recording / reproducing functional layers is used. In this case, at least one of the recording layer 3A and the reflective layer 3B may be formed so as to avoid the portion 3X corresponding to the BCA region 2X. Preferably, in all of the layers, at least one of the recording layer 3A and the reflective layer 3B is formed so as to avoid the portion 3X corresponding to the BCA region 2X.

The method for forming the recording layer 3A and the reflective layer 3B is not limited and may be arbitrary so as to avoid the portion 3X corresponding to the BCA region 2X. For example, it can be formed by the following method.
For example, when the recording layer 3A and the reflective layer 3B are formed by sputtering, as shown in FIG. 3, a mask 11 that can cover the portion 3X corresponding to the BCA region 2X is formed during the manufacturing process. It may be placed on the recording medium 100 and sputtered in this state. Thereby, since the recording layer 3A and the reflective layer 3B are not formed in the portion covered with the mask 11, the recording layer 3A and the reflective layer 3B can be formed while avoiding the portion 3X. At this time, the outer diameter of the mask 11 to be used is generally preferably the same as the outer diameter of the BCA region 2X.

  For example, when the recording layer 3A and the reflective layer 3B are formed by spin coating, as shown in FIG. 4, the material P for the recording layer 3A and the reflective layer 3B is supplied during spin coating. The position of the outlet 12 may be adjusted so that the dropping position of the material P matches the outer diameter of the BCA region 2X. As a result, the material 3 of the recording layer 3A and the reflective layer 3B is not supplied to the part 3X corresponding to the BCA region 2X, and therefore the recording layer 3A and the reflective layer 3B can be formed while avoiding the part 3X. Become.

  Further, for example, when the recording layer 3A and the reflective layer 3B are formed by a spin coating method, as shown in FIG. 5, a center mask 13 that can cover the portion 3X corresponding to the BCA region 2X is provided. It may be placed on the optical recording medium 100 being manufactured, and in this state, the material P of the recording layer 3A and the reflective layer 3B may be supplied from the ejection port 12 to perform spin coating. This also prevents the material P of the recording layer 3A and the reflective layer 3B from being supplied to the part 3X corresponding to the BCA region 2X, so that the recording layer 3A and the reflective layer 3B can be formed while avoiding the part 3X. It becomes.

  Also in the present embodiment, the inner side of the main recording / reproducing area 9 of the recording / reproducing functional layer 2 which is the first recording / reproducing functional layer (in FIG. 2, the one-dot chain line formed on the inner peripheral edge of the recording / reproducing functional layer 2 The BCA region 2X is formed in a donut shape in the portion shown). Further, it is assumed that the recording layer 3A and the reflective layer 3B of the recording / reproducing functional layer 3 that is the second recording / reproducing functional layer are formed so as to avoid the portion 3X corresponding to the BCA region 2X.

[9. Other configurations]
Further, in order to more easily record the medium identification information in the BCA area, it is preferable to increase the light absorption rate for forming a barcode pattern or the like in the BCA area in the first recording / reproducing functional layer. . Thereby, since it becomes easy to form a barcode pattern or the like, the medium identification information can be efficiently recorded.

  Although the method for increasing the absorption rate is arbitrary as described above, for example, when the first recording / reproducing functional layer is formed on a substrate (including a dummy substrate) (this is the first recording / reproducing function). In the case where the layer is formed as a lowermost recording / reproducing functional layer), there is a method of increasing the thickness of the recording layer in the BCA area. Thereby, the energy of the irradiated light can be effectively absorbed. As a specific example of a technique for realizing this, an optical transfer function (Optical Transfer Function) is provided at a portion corresponding to the BCA area of a layer (substrate, dummy substrate, intermediate layer, etc.) adjacent to the first recording / reproducing functional layer. As appropriate, the formation of unevenness having a width smaller than the length corresponding to the cutoff frequency of “OTF” may be mentioned.

  A specific example is shown using FIG. FIG. 6 is an enlarged view of the main part of the optical recording medium 1 according to the present embodiment in the case where irregularities 14 are formed on the surface of the portion 7X corresponding to the BCA region 2X of the dummy substrate 7 on the recording / reproducing functional layer 2 side. It is sectional drawing shown typically. In FIG. 6, the illustration of the adhesive layer between the reflective layer 2B and the dummy substrate 7 is omitted. As shown in FIG. 6, when the irregularities 14 are formed on the dummy substrate 7, the material for forming the recording layer 2A is accumulated on the irregularities 14, and the amount of the accumulated material (the difference between x and y) ), It is possible to increase the thickness of the recording layer 2A.

  Similarly, the thickness of the recording layer 2A is increased even if the above irregularities are provided on a layer other than the substrate 7 adjacent to the recording / reproducing functional layer 2 on which the BCA region 2X is formed, such as the surface of the intermediate layer 5. Is possible. For example, the optical recording medium 1 may be manufactured through a process of forming a guide groove in the intermediate layer 5, and the recording / reproducing functional layer 2 side of the intermediate layer 5 is used in the same process as the formation of the guide groove. If the above irregularities are formed on the surface of the recording layer 2A, the thickness of the recording layer 2A can be increased.

  Here, OTF refers to how fine a pattern depends on the frequency response of the optical system and circuit of a reproduction drive when a single frequency (record mark of one kind of mark length) is recorded on an optical recording medium. Is an index indicating whether or not can be read. Generally, the resolution of the playback drive system is shown. Therefore, a pattern having a length longer than the length corresponding to the cutoff frequency of the OTF can be detected as a reproduction signal, but a pattern shorter than the length corresponding to the cutoff frequency of the OTF is detected as a reproduction signal. No (usually detected as noise).

  That is, unevenness having a length less than the length corresponding to the cutoff frequency of the OTF is not detected as a signal, and conversely, unevenness exceeding this length is detected as a reproduction signal. For this reason, the guide grooves formed in the substrate 4 and the intermediate layer 5 usually have a width equal to or longer than the length corresponding to the cutoff frequency of the OTF. The servo information of 1 can be read by the reproduction drive.

  If irregularities (grooves or pit rows) having a width greater than or equal to the length corresponding to the cutoff frequency are formed in the BCA area 2X, the medium identification information to be originally recorded in the BCA area 2X Since the uneven signal is carried as noise, the reproduction quality may be deteriorated. Therefore, normally, in order to prevent this, it is preferable that the width of the concave or convex provided in the BCA region is smaller than the length corresponding to the cutoff frequency of the OTF. As a result, the unevenness is not detected by the reproduction drive as representing information related to user data. Therefore, it is possible to form irregularities for increasing the thickness of the recording layer 2A without affecting the recording and reproduction of user data with respect to the recording / reproducing functional layer. In addition, it is preferable that the width | variety of both a recessed part (groove) and a convex part (land) satisfy | fills said conditions, or the width | variety of either a recessed part or a convex part satisfy | fills said conditions. And it is more preferable that the width | variety of a recessed part satisfy | fills said conditions.

  For example, when the numerical aperture NA of the reproduction drive is 0.65 and the laser wavelength λ is 405 nm, the length corresponding to the cutoff frequency of the OTF is about 0.25 μm. Therefore, in order to form irregularities that cannot be detected as signals by the optical pickup of the recording / reproducing drive under the above conditions, in principle, the irregularities having a width of 0.25 μm or less should be formed. That's fine. In particular, it is usually preferable to form a width of about 0.2 μm from the viewpoint of mastering accuracy.

  Also in the optical recording medium 1 of the present embodiment, as shown in FIG. 6, the unevenness having a width smaller than the length corresponding to the cutoff frequency of the OTF is formed on the surface of the dummy substrate 7 on the recording / reproducing functional layer 2 side. As a result, the recording layer 2A in the BCA area 2X is formed thicker than other areas (for example, the main recording / reproducing area 9).

[10. Action]
Since the optical recording medium 1 of the present embodiment is configured as described above, when recording the medium identification information by forming a barcode pattern or the like in the BCA area 2X in the manufacturing process, it is shown in FIG. The medium identification information can be recorded by such a method.
Specifically, when recording the medium identification information in the BCA area 2X, light for recording medium identification information (usually a laser beam) is irradiated from the information recording / reproducing surface 6 side, and the BCA area 2X The recording layer 2A or the reflective layer 2B is burned or phase-changed according to the barcode pattern to be formed, and the medium identification information is recorded.

  At this time, in the optical recording medium 1 of the present embodiment, light can be prevented from being shielded or refracted by the recording / reproducing functional layer 3 before the recording / reproducing functional layer 2, so that it is used when recording the medium identification information. Light attenuation is unlikely to occur, and it is easy to focus accurately. That is, it is possible to accurately form a barcode pattern using light having sufficient power and record medium identification information.

  In addition, the above-mentioned advantage is obtained when an optical recording medium that can be recorded or reproduced with light having a wavelength of 500 nm or less, that is, when a recording layer contains a material capable of recording user data with light having a wavelength of 500 nm or less. In particular, it will be exhibited remarkably. Examples of such a material include organic dyes. The reason why the above advantages can be obtained in such a case is as follows.

  That is, the light used for recording the medium identification information is usually pulse laser light (for example, YAG laser) having a wavelength of 810 nm or 650 nm. This is because a laser device having a wavelength of 500 nm or less still has a short life and is expensive.

  However, materials that can be recorded with light having a wavelength of 500 nm or less (for example, organic dyes) generally do not have large absorption in a long wavelength region of 500 nm or more (that is, low sensitivity to long wavelengths of 500 nm or more). Is. For this reason, in order to record the medium identification information in the BCA area 2X by burning out the recording layer containing a material such as the organic dye, a pulsed laser beam having sufficient power is applied to the recording layer and the reflective layer. Irradiation is desirable. Therefore, the optical recording medium 1 as in the present embodiment is configured, and the first recording / reproducing functional layer 2 is irradiated with the first recording / reproducing functional layer 2 as much as possible without being attenuated as much as possible. Since it becomes possible to irradiate pulsed laser light having a power that compensates for the lack of sensitivity of the material of the functional layer 2, the above advantages can be remarkably exhibited.

[11. Others]
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to said Embodiment, In the range which does not deviate from the summary of this invention, it can change arbitrarily and can implement.
For example, the layers forming the optical recording medium such as the recording layer, the reflective layer, the intermediate layer, the substrate, the dummy substrate, and the adhesive layer, the dielectric layer, and the protective layer are not limited to the above-described embodiments, and are arbitrarily combined. Can be used in a stacked manner. Further, the stacking order is also arbitrary. Furthermore, layers other than the above layers may be used for the optical recording medium.

  Further, in the recording / reproducing functional layer 3 on the information recording / reproducing surface 6 side of the recording / reproducing functional layer 2 in which the BCA area 2X is formed, in addition to the configuration of the above embodiment, for example, an optical recording medium 1 ′ shown in FIG. Alternatively, the recording / reproducing functional layer 3 may be formed so that only the recording layer 3A avoids the portion 3X and the reflective layer 3B does not avoid the portion 3X, and conversely, for example, as in the optical recording medium 1 ″ shown in FIG. Alternatively, the recording / reproducing functional layer 3 may be formed so that only the reflective layer 3B avoids the portion 3X and the recording layer 3A does not avoid the portion 3X.

In the above embodiment, only two recording / reproducing functional layers are provided. However, three or more layers may be received.
Further, what is formed in the BCA area 2X for recording the medium identification information is not limited to the bar code, and other patterns and symbols may be formed.

Furthermore, it is sufficient that at least one of the recording layer 3A and the reflective layer 3B of the recording / reproducing functional layer 3 is formed so as to avoid at least the portion 3X corresponding to the BCA region 2X. It may be formed so as to avoid this.
Further, the BCA area 2X may be provided at a position other than the inner edge (the edge of the center hole 8) of the optical recording medium 1.

  The method for producing an optical recording medium of the present invention can be suitably used in the field of various optical recording media such as CD, DVD, blue laser compatible optical recording medium.

1 is a schematic cross-sectional view showing an enlarged cross section in the vicinity of a central portion of an optical recording medium as one embodiment of the present invention. 1 is a schematic plan view of an optical recording medium as an embodiment of the present invention. It is a schematic diagram explaining an example of the formation method of the recording layer in the optical recording medium as one Embodiment of this invention, or a reflection layer. It is a schematic diagram explaining an example of the formation method of the recording layer in the optical recording medium as one Embodiment of this invention, or a reflection layer. It is a schematic diagram explaining an example of the formation method of the recording layer in the optical recording medium as one Embodiment of this invention, or a reflection layer. FIG. 2 is a cross-sectional view schematically showing an enlarged main part of a case where irregularities are formed on the surface on the recording / reproducing functional layer side of a portion corresponding to the BCA region of a dummy substrate in the optical recording medium as one embodiment of the present invention. is there. FIG. 3 is a schematic diagram illustrating a method for recording medium identification information in a BCA area of an optical recording medium as an embodiment of the present invention. FIG. 6 is a schematic cross-sectional view showing an enlarged cross section near the center of an optical recording medium as a modification of the present invention. FIG. 6 is a schematic cross-sectional view showing an enlarged cross section near the center of an optical recording medium as a modification of the present invention. It is a typical sectional view which expands and shows the section near the central part of the conventional multilayer type optical recording medium.

Explanation of symbols

1, 1 ', 1 "optical recording medium 2 recording / reproducing functional layer (first recording / reproducing functional layer)
2A Recording layer 2B Reflective layer 2X BCA area (medium identification information recording area)
3 Recording / playback functional layer (second recording / playback functional layer)
3A Recording layer 3B Reflective layer 3X Site 4 corresponding to BCA area 4 Substrate 5 Intermediate layer 6 Information recording / reproducing surface 7 Dummy substrate 7X Site corresponding to BCA area of dummy substrate 8 Center hole 9 Main recording / reproducing area 10 Information recording / reproducing surface Surface 11 opposite to the surface 11 Mask 12 Discharge port 13 Center mask 14 Concavity and convexity 100 Optical recording medium in the middle of manufacture

Claims (4)

An optical recording medium having a recording layer and a reflective layer, in which two or more recording / reproducing functional layers that are recorded or reproduced by light are laminated,
A first recording / reproducing functional layer in which a medium identification information recording area in which medium identification information is recorded is formed;
The optical recording medium is laminated at a position closer to the light incident surface than the first recording / reproducing functional layer, and at least one of the recording layer and the reflective layer has a portion corresponding to the medium identification information recording area. An optical recording medium comprising: a second recording / reproducing functional layer formed so as to be avoided. On the surface of the layer adjacent to the first recording / reproducing functional layer, irregularities having a width smaller than the length corresponding to the cut-off frequency of the optical transfer function are formed in the portion corresponding to the medium identification information recording area. The optical recording medium according to claim 1, wherein: The optical recording medium according to claim 1, wherein recording or reproduction is possible with light having a wavelength of 500 nm or less. The optical recording medium according to claim 1, wherein the recording layer contains an organic dye.

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