JP2006202447A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium which is provided with a plurality of information layers laminated on a supporting substrate via at least a transparent intermediate layer and enables data to be recorded and recorded data to be reproduced desirably in and from any information layer. <P>SOLUTION: The optical recording medium is provided with the plurality of information layers laminated on the supporting substrate via the transparent intermediate layer, wherein at least one information layer of the information layers other than the information layer the furthest from a light incident plane of a laser beam includes a recording film 34 formed by using a eutectic-based phase transition material, a reflection film 32 formed on the supporting substrate 11 side with respect to the recording film 34, a first heat radiation film 38 formed on the light incident plane 13a side with respect to the recording film 34 and formed by using a material containing Al<SB>2</SB>O<SB>3</SB>or SiO<SB>2</SB>as a main component and a second heat radiation film 37 formed between the recording film 34 and the first heat radiation film 38 and formed by using a material containing AlN as a main component. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical recording medium. More specifically, the present invention includes a plurality of information layers stacked on a support substrate through at least a transparent intermediate layer, and any information layer has a desired shape. Further, the present invention relates to an optical recording medium capable of recording and reproducing data.

  Conventionally, optical recording media represented by CD and DVD have been widely used as recording media for recording digital data, and recorded data can be rewritten as CD-RW or DVD-RW. Such rewritable optical recording media are known.

  In such a rewritable optical recording medium, generally, the power of a laser beam applied to an information layer including a recording film formed of a phase change material corresponds to the recording power Pw, the base power Pb, and the erasing power Pe. By modulating to a plurality of levels, data can be recorded in the information layer, and data recorded in the information layer can be reproduced or erased.

  For example, when data is recorded on the information layer, a laser beam whose power is set to the recording power Pw is irradiated to the recording film included in the information layer, and the region of the recording film irradiated with the laser beam is When heated to a temperature equal to or higher than the melting point of the phase change material, the phase change material contained in the region is melted. Next, the recording film is irradiated with a laser beam whose power is set to the base power Pb, and the melted phase change material is rapidly cooled. As a result, the melted phase change material in the region changes from a crystalline state to an amorphous state, a recording mark is formed on the recording film, and data is recorded on the information layer.

  In recent years, in order to increase the recording capacity of optical recording media and realize a very high data transfer rate, the development of next-generation optical recording media capable of recording data at high density on the information layer has been developed. A next-generation rewritable optical recording medium has also been proposed.

  On the other hand, in order to increase the recording capacity of the optical recording medium, a technique for increasing the number of information layers and increasing the area of the recording area has also been developed, and a structure in which two or more information layers are stacked. A rewritable optical recording medium having the above has also been proposed.

  Such an optical recording medium having two or more information layers records data on the information layer by irradiating one of the information layers with a laser beam, reproduces the recorded data, or Since it is configured so that it can be erased, the data is recorded on the information layer far from the light incident surface, and the data recorded on the information layer far from the light incident surface is reproduced or erased. The information layer far from the light incident surface is irradiated with the laser beam through the information layer close to.

  Therefore, in order to record data in an information layer far from the light incident surface and reproduce or erase data recorded in the information layer far from the light incident surface, information close to the light incident surface is desired. It is necessary that the layer has a high light transmittance for the laser beam.

  Here, in order to increase the light transmittance of the information layer, it is effective to make the information layer thin. In particular, among various films included in the information layer, the metal layer is included as a main component. It is effective to form a thin reflective film having a low light transmittance.

  However, if the reflective film included in the information layer close to the light incident surface is thinly formed, the heat dissipation of the reflective film itself is reduced, and the heat dissipation of the information layer as a whole is also reduced. Therefore, it is difficult to dissipate heat, and when data is recorded on the information layer and the recorded data is reproduced, the jitter of the reproduced signal may be deteriorated. Therefore, when the reflective film included in the information layer close to the light incident surface is thinly formed, the data is recorded on the information layer far from the light incident surface, and the recorded data is reproduced, as desired, or However, there is a problem that it is difficult to record data as desired in the information layer close to the light incident surface.

  Accordingly, an object of the present invention is to provide a plurality of information layers stacked on a support substrate through at least a transparent intermediate layer, and record and record data in any information layer as desired. An object of the present invention is to provide an optical recording medium capable of reproducing data.

  As a result of extensive research on the heat dissipation of the information layer close to the light incident surface of the laser beam, the present inventor has found from the support substrate side that the fourth dielectric film, the reflective film, the third dielectric film, Optical recording in which an information layer close to the light incident surface of a laser beam is formed by laminating a recording film, a second dielectric film, a first dielectric film, and a heat dissipation film formed of a crystal phase change material In the medium, when the heat dissipation film is formed of a material such as AlN having a high thermal conductivity, the heat dissipation of the information layer can be sufficiently enhanced, while the reflective film included in the information layer is formed thin. After all, it was found that the heat dissipation of the reflective film itself was lowered, the heat dissipation of the information layer as a whole was also lowered, and it was difficult to effectively dissipate the heat generated in the recording film. .

  Such a decrease in heat dissipation is considered to be solved by forming a thick heat dissipation film included in the information layer near the light incident surface and improving the heat dissipation performance of the entire information layer.

  However, since the information layer close to the light incident surface is required to have a property of reflecting the laser beam as desired when reproducing the data recorded in the information layer, the reflectance of the information layer is required. In order to form the information layer so as to have the desired reflectance, the reflectance of the information layer also depends on the thickness of the heat dissipation film. It was found that the thickness is limited to a certain range, and it is difficult to increase the thickness of the heat dissipation film.

  Therefore, in an optical recording medium provided with a plurality of information layers, by maintaining heat characteristics such as reflectance and light transmittance of the information layer close to the light incident surface, it is possible to add any information layer. However, it was usually considered difficult to record data and reproduce the recorded data as desired.

However, as a result of further earnest research to achieve the above object of the present invention, the inventor has found that the recording film, the recording film, the reflective film formed on the support substrate side, and the recording film And an information layer formed at a position close to the light incident surface, and further with respect to the heat radiating film. When a film formed of a material mainly composed of Al ₂ O ₃ or SiO ₂ is provided on the incident surface side, the optical characteristics of the information layer are deteriorated even if the reflective film is formed thin. It has been found that it is possible to improve the heat dissipation of the information layer as a whole.

The present invention is based on such knowledge. According to the present invention, the object of the present invention includes a plurality of information layers stacked on a support substrate through at least a transparent intermediate layer. And at least one information layer other than the information layer farthest from the light incident surface of the laser beam is a recording film formed of a eutectic phase change material, and the recording film The first heat radiation formed of the reflective film formed on the support substrate side and the recording film is formed on the light incident surface side and formed of a material mainly composed of Al ₂ O ₃ or SiO _2. An optical recording medium comprising: a film; and a second heat dissipation film formed between the recording film and the first heat dissipation film and formed of a material mainly composed of AlN. Is done.

In the present invention, the material having a compound as a main component means that the content of the compound is the largest among the compounds contained in the material, and Al ₂ O ₃ or SiO ₂ is the main component. Then, in addition to the case where Al ₂ O ₃ is the main component and the case where SiO ₂ is the main component, the case where Al ₂ O ₃ and SiO ₂ are the main components is also included.

  According to the present invention, the entire information layer can be obtained without degrading optical characteristics such as high reflectance and light transmittance of at least one information layer other than the information layer farthest from the light incident surface of the laser beam. Since the heat dissipation can be improved, when recording data on this information layer, the laser beam is irradiated onto the recording film and the melted area can be surely quenched and included in the melted area. Effectively preventing a part of the phase change material from recrystallizing and forming a recording mark smaller than the recording mark that should be formed, and forming the recording mark in a desired size Is possible. Furthermore, according to the present invention, when reproducing data recorded in an information layer other than the information layer farthest from the light incident surface of the laser beam, the irradiated laser beam can be reflected as desired. Therefore, when reproducing the data recorded in this information layer, it becomes possible to prevent the reproduction signal from deteriorating and to prevent the excellent optical characteristics of this information layer from deteriorating. It becomes possible to do. Therefore, it is possible to record data as desired in an information layer other than the information layer farthest from the light incident surface of the laser beam, and to reproduce the recorded data as desired.

  Further, according to the present invention, the reflective film included in the information layer is thinly formed while improving the heat dissipation of at least one information layer other than the information layer farthest from the light incident surface of the laser beam. Therefore, it is possible to improve the heat dissipation of the information layer and increase the light transmittance. Therefore, when the laser beam is transmitted through the information layer, it is possible to minimize the decrease in the light amount of the laser beam, so that the laser is passed through the information layer to the information layer farthest from the light incident surface. By irradiating the beam, it is possible to record data on the information layer farthest from the light incident surface as desired, and to reproduce or erase the recorded data as desired. .

  In the present invention, the first heat dissipation film is preferably formed adjacent to the second heat dissipation film. When the first heat dissipation film is formed adjacent to the second heat dissipation film, it is possible to further improve the heat dissipation performance of the information layer as a whole without degrading the excellent optical properties of the information layer. become.

  According to further studies by the inventors, when the first heat dissipation film is formed to have a film thickness of less than 10 nm, there is a possibility that a sufficient heat dissipation effect may not be obtained. If the heat dissipation film is formed so as to have a film thickness of 75 nm or more, the heat dissipation performance on the first heat dissipation film side is excessively improved, and the amount of heat radiated from the first heat dissipation film is significantly increased. It has been found that the amount of heat dissipated from the reflective film side is reduced and the heat dissipation performance on the reflection film side is reduced, and as a result, the heat dissipation performance of the information layer as a whole tends to decrease. Therefore, in the present invention, the first heat dissipation film is preferably formed so as to have a film thickness of 10 nm or more and less than 75 nm, and in particular, formed so as to have a film thickness of 25 nm or more and 50 nm or less. Preferably it is.

  In the present invention, the reflective film preferably contains Ag as a main component and has a thickness of 5 nm to 25 nm. When the reflective film includes Ag as a main component and has a film thickness of 5 nm to 25 nm, the heat dissipation from the reflection film can be improved, and the heat dissipation of the entire information layer can be further increased. It becomes possible to increase.

  In the present invention, it is more preferable that the reflective film has a thermal conductivity of 50 W / mK or more. When the reflective film has a thermal conductivity of 50 W / mK or more, the heat dissipation from the reflective film can be further enhanced, and the heat dissipation as the entire information layer can be further enhanced. become.

  According to the present invention, a plurality of information layers stacked on at least a transparent intermediate layer are provided on a support substrate, and data can be recorded and reproduced in any information layer as desired. It is possible to provide an optical recording medium that can be used.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a partially cutaway schematic perspective view showing an optical recording medium according to a preferred embodiment of the present invention, and FIG. 2 is a schematic enlarged sectional view of a portion indicated by A in FIG.

  As shown in FIG. 1, the optical recording medium 10 according to this embodiment is formed in a disc shape, and has an outer diameter of about 120 mm and a thickness of about 1.2 mm.

  The optical recording medium 10 according to the present embodiment is configured as a rewritable optical recording medium, and as shown in FIG. 2, a support substrate 11, a transparent intermediate layer 12, a light transmission layer 13, a support substrate 11, and the like. The L0 information layer 20 provided between the transparent intermediate layer 12 and the L1 information layer 30 provided between the transparent intermediate layer 12 and the light transmission layer 13 are provided. A light incident surface 13a on which the laser beam L is incident is configured.

  In this embodiment, the L0 information layer 20 constitutes an information layer far from the light incident surface 13a, and the L1 information layer 30 constitutes an information layer close to the light incident surface 13a.

  The optical recording medium 10 according to this embodiment is an objective lens (FIG. 2) in which a laser beam L having a wavelength λ of 380 nm to 450 nm has a numerical aperture NA of about 0.85 from the direction indicated by the arrow L in FIG. The light transmitting layer 13 is configured to be irradiated via a not-shown).

  The support substrate 11 functions as a support for ensuring the mechanical strength required for the optical recording medium 10.

  The material for forming the support substrate 11 is not particularly limited as long as it can function as a support for the optical recording medium 10, but a resin is preferably used. Such a resin is particularly preferably a polycarbonate resin or a polyolefin resin from the viewpoint of processability, optical characteristics, and the like. In this embodiment, the support substrate 11 is formed of a polycarbonate resin.

  In the present embodiment, the support substrate 11 has a thickness of about 1.1 mm.

  In the present embodiment, the laser beam L is irradiated through the light transmission layer 13 located on the side opposite to the support substrate 11, so that the support substrate 11 does not necessarily have optical transparency. Not necessary.

  As shown in FIG. 2, the support substrate 11 has a groove 11a formed on the surface thereof. The groove 11a serves as a guide track for the laser beam L when data is recorded on the L0 information layer 20 and data is reproduced from the L0 information layer 20.

  The support base 11 having the groove 11a on the surface is manufactured by, for example, an injection molding method using a stamper (not shown).

  The transparent intermediate layer 12 has a function of separating the L0 information layer 20 and the L1 information layer 30 physically and optically with a sufficient distance.

  As shown in FIG. 2, a groove 12 a is formed on the surface of the transparent intermediate layer 12. The groove 12a formed on the surface of the transparent intermediate layer 12 functions as a guide track for the laser beam L when data is recorded on the L1 information layer 30 and data is reproduced from the L1 information layer 30.

  The transparent intermediate layer 12 needs to have a sufficiently high light transmittance since the laser beam L passes when data is recorded on the L0 information layer 20 and data is reproduced from the L0 information layer 20. .

  Therefore, the material for forming the transparent intermediate layer 12 is required to have little optical absorption and reflection in the near-infrared to ultraviolet wavelength region and a small birefringence. The material for forming the transparent intermediate layer 12 is not particularly limited as long as it satisfies these conditions, but an ultraviolet curable resin composition containing an ultraviolet curable resin such as an ultraviolet curable acrylic resin. It is preferable that the transparent intermediate layer 12 is formed by an object.

  The transparent intermediate layer 12 is formed by applying a solution of an ultraviolet curable resin composition on the L0 information layer 20 by a spin coating method to form a coating film, and preparing the support substrate 11 on the surface of the coating film. It is preferably formed by irradiating with ultraviolet rays through a stamper in a state of covering a stamper (not shown) on which a concave and convex pattern similar to the stamper used in the above is formed.

  The light transmission layer 13 is a layer through which the laser beam L is transmitted, and a light incident surface 13a is constituted by one surface thereof.

  The material for forming the light transmission layer 13 is required to have low absorption and a low birefringence in the near-infrared to ultraviolet wavelength region. The material for forming the light transmission layer 13 is not particularly limited as long as the material satisfies these conditions, but a resin composition containing an ultraviolet curable resin, an electron beam curable resin, or the like may be used. In order to form the light transmission layer 13, a resin composition containing an ultraviolet curable acrylic resin is more preferably used.

  The light transmission layer 13 is preferably formed to have a thickness of 30 μm to 200 μm.

  The light transmission layer 13 is preferably formed by applying a solution of the resin composition on the surface of the L1 information layer 30 by spin coating, but the sheet formed of the light transmission resin is bonded. The light transmission layer 13 can also be formed by adhering to the surface of the L1 information layer 30 using an agent.

  FIG. 3 is a schematic enlarged cross-sectional view of the L0 information layer 20.

  As shown in FIG. 3, in this embodiment, the L0 information layer 20 includes the reflective film 21, the second dielectric film 22, the L0 recording film 23, and the first dielectric film 24 from the support substrate 11 side. In addition, the heat dissipation film 25 is laminated.

  The reflective film 21 reflects the laser beam L applied to the L0 recording film 23 via the light transmitting layer 13 and the L1 information layer 30 and emits the light again from the light transmitting layer 13. Is used to effectively dissipate heat generated in the L0 recording film 23.

  The material for forming the reflective film 21 is not particularly limited, and Mg, Al, Ti, Cr, Fe, Co, Ni, Cu, Zn, Ge, Ag, Pt, Au, Nd, and the like are used. However, among these, metal materials such as Al, Au, Ag, Cu, or an alloy containing at least one of these metals, such as Al, Au, Ag, Cu, or an alloy of Ag and Cu, which have high reflectivity, reflect It is preferably used for forming the film 21. In particular, when the reflective film 21 contains Ag, the reflective film 21 having excellent surface smoothness can be formed, and the noise level of the reproduction signal can be reduced, which is preferable.

  The reflective film 21 may be configured by a single film or may be configured by stacking two or more films, but in the present embodiment, the reflective film 21 is formed by a metal material containing Ag. The first film 212 and the second film 211 are laminated.

  The thickness of the reflective film 21 is not particularly limited, but is preferably 10 nm to 300 nm, and particularly preferably 40 nm to 200 nm.

  The reflective film 21 is formed by, for example, a sputtering method.

  The second dielectric film 22 and the first dielectric film 24 physically and chemically protect the L0 recording film 23, dissipate the heat generated in the L0 recording film 23, and further, the laser beam L Has a function of increasing the change in optical properties before and after irradiation.

  The material for forming the second dielectric film 22 and the first dielectric film 24 is not particularly limited as long as it is a transparent dielectric material in the wavelength region of 380 nm to 450 nm that is the wavelength region of the laser beam L. Although not intended, the second dielectric film 22 and the first dielectric film 24 are made of Si, Zn, Al, Ta, Ti, Co, Zr, Pb, Ag, Sn, Ca, Ce, V, Cu. It is preferably formed from an oxide, nitride, sulfide, carbide, fluoride, or composite containing at least one metal selected from the group consisting of Fe, Mg.

Each of the second dielectric film 22 and the first dielectric film 24 may be configured by a single film or may be configured by stacking two or more films. In the present embodiment, The second dielectric film 22 is configured by laminating a first film 222 formed of a mixture of ZnS and SiO ₂ and a second film 221 formed of an oxide of Ce and Al. The first dielectric film 24 is constituted by a single film.

  The thickness of the second dielectric film 22 and the first dielectric film 24 is not particularly limited, but the thickness of the second dielectric film 22 is preferably 5 nm to 35 nm. The thickness of one dielectric film 24 is preferably 10 nm to 80 nm.

  The second dielectric film 22 and the first dielectric film 24 are formed by, for example, a sputtering method.

  The L0 recording film 23 is a film for recording data by forming recording marks, is formed of a phase change material, and is formed of a single film. Since the phase change material has a reflectance different from that in the crystalline state and the reflectance in the amorphous state, data is recorded by using this, and the recorded data is reproduced.

  The phase change material for forming the L0 recording film 23 is not particularly limited, but the L0 recording film 23 is at least one element selected from the group consisting of Sb, Te, Ge, Ag, Tb, and Mn. It is preferably formed including a phase change material containing

  The thickness of the L0 recording film 23 is not particularly limited, but is preferably 8 nm to 25 nm.

  The L0 recording film 23 is formed by, for example, a sputtering method.

  The heat dissipation film 25 plays a role of radiating heat transferred from the L0 recording film 23 via the first dielectric film 24.

The material for forming the heat dissipation film 25 is not particularly limited as long as it has high light transmittance with respect to the laser beam L and can dissipate heat generated in the L0 recording film 23. A material having a thermal conductivity higher than that of the first dielectric film 24 is preferable. Specifically, AlN, Al ₂ O ₃ , SiN, ZnS, ZnO, SiO ₂ or the like is used as the heat dissipation film 25. Is preferably used to form

  The heat dissipation film 25 is preferably formed to have a thickness of 10 nm to 120 nm.

  The heat dissipation film 25 is formed by, for example, a sputtering method.

  FIG. 4 is a schematic enlarged cross-sectional view of the L1 information layer 30.

  As shown in FIG. 4, in the present embodiment, the L1 information layer 30 includes the fourth dielectric film 31, the reflective film 32, the third dielectric film 33, and the L1 recording film 34 from the support substrate 11 side. The second dielectric film 35, the first dielectric film 36, the second heat radiation film 37, and the first heat radiation film 38 are laminated.

  The fourth dielectric film 31 plays a role of effectively dissipating heat generated in the L1 recording film 34 by irradiation of the laser beam L together with a reflection film 32 described later.

  The material for forming the fourth dielectric film 31 is not particularly limited, and is selected from the group consisting of Ti, Zr, Hf, Ta, Si, Al, Mg, Y, Ce, Zn, and Cr. An oxide, nitride, sulfide, carbide, fluoride, or a composite thereof containing at least one metal is used to form the fourth dielectric film 31.

The fourth dielectric film 31 may be composed of a single film or may be composed of two or more films laminated. In the present embodiment, the fourth dielectric film 31 is composed of A first film 312 formed by a mixture of ZrO ₂ and Y ₂ O ₃ with a ratio of 97: 3, and a second film 311 formed by a mixture of ZnS and SiO ₂ with a molar ratio of 80:20; Are stacked and configured. When the first film 312 is formed of a mixture of ZrO ₂ and Y ₂ O ₃ having a molar ratio of 97: 3, the heat generated in the L1 recording film 34 by the irradiation of the laser beam L is generated. It is possible to quickly dissipate heat, and it is possible to prevent the surface of the reflective film 32 from being corroded by sulfur contained in the second film 311 and to ensure high storage reliability. Become. On the other hand, when the second film 311 is formed of a mixture of ZnS and SiO ₂ having a molar ratio of 80:20, the light transmittance of the L1 information layer 30 with respect to the laser beam L can be increased. Become.

  The fourth dielectric film 31 is preferably formed to have a thickness of 3 nm to 30 nm. When the thickness of the fourth dielectric film 31 is less than 3 nm, the heat dissipation effect decreases, and when it exceeds 30 nm, the productivity decreases.

  The fourth dielectric film 31 is formed by, for example, a sputtering method.

  The reflection film 32 reflects the laser beam L applied to the L1 recording film 34 via the light transmission layer 13 and emits the laser beam L from the light transmission layer 13 again, and is irradiated with the laser beam L. Thus, the heat generated in the L1 recording film 34 is effectively dissipated.

  As a material for forming the reflective film 32, Mg, Al, Ti, Cr, Fe, Co, Ni, Cu, Zn, Ge, Ag, Pt, Au, Nd, etc. are used, and among these, high In order to form the reflective film 32, a metal material such as Al, Au, Ag, Cu having a reflectivity, or an alloy containing at least one of these metals, such as an alloy of Ag and Cu, is used. Preferably used. In particular, when the reflective film 32 contains Ag as a main component, the heat dissipation of the L1 information layer 30 can be improved, and the reflective film 32 having excellent surface smoothness can be formed. The noise level can be reduced, which is preferable.

  In the present embodiment, the reflective film 32 preferably has a thermal conductivity of 50 W / mK or more. When the reflective film 32 has a thermal conductivity of 50 W / mK or more, the heat dissipation from the reflective film 32 can be further increased, and the heat dissipation as the entire L1 information layer 30 can be further improved. It becomes possible to increase.

  The reflective film 32 needs to have a high light transmittance with respect to the laser beam L and a desired reflectance, and considering these, the reflective film 32 has a thickness of 5 nm to 25 nm. Preferably, it has a thickness of 7 nm to 18 nm. In particular, when the reflective film 32 contains Ag as a main component, the reflective film 32 is preferably formed to have a thickness of 10 nm to 15 nm. When the reflective film 32 contains Ag as a main component and has a film thickness of 10 nm to 15 nm, the heat dissipation from the reflective film 32 can be improved, and the heat dissipation of the L1 information layer 30 as a whole can be further increased. It becomes possible to increase.

  The reflective film 32 is formed by, for example, a sputtering method.

  The third dielectric film 33, together with the second dielectric film 35, plays a role of physically and chemically protecting the L1 recording film 34, and is generated in the L1 recording film 34 by the irradiation of the laser beam L. It has a function of radiating heat to the reflective film 32 side.

The material for forming the third dielectric film 33 is not particularly limited, and the same material as that for forming the fourth dielectric film 31 is used. In this embodiment, the third dielectric film 33 is formed of a mixture of ZrO ₂ and Y ₂ O ₃ having a molar ratio of 97: 3, like the first film 312 of the fourth dielectric film 31. Has been. In this case, the heat generated in the L1 recording film 34 by the irradiation of the laser beam L can be quickly dissipated.

  The third dielectric film 33 is preferably formed to have a thickness of 3 nm to 15 nm. If the thickness of the third dielectric film 33 is less than 3 nm, it is difficult to form the third dielectric film 33 as a continuous film, and if it exceeds 15 nm, the heat of the recording film It is difficult to effectively escape to the reflective film.

  The third dielectric film 33 is formed by, for example, a sputtering method.

  The L1 recording film 34 is a film for recording data by forming recording marks, and is formed of a phase change material (Sb eutectic phase change material) having an Sb eutectic composition. It is constituted by. Since the phase change material has a different reflectance in a crystalline state and a reflectance in an amorphous state, data is recorded using this, and the recorded data is reproduced.

  The Sb eutectic phase change material for forming the L1 recording film 34 is not particularly limited, but a eutectic system containing Sb and at least one element having a eutectic with Sb as a main component. Are preferably used, in particular, a phase change material comprising 79 atomic% to 95 atomic% Sb, 5 atomic% to 21 atomic% Ge, and 70 atomic% to 95 atomic% Sb. A phase change material containing more than 0 atomic% and 30 atomic% or less of Ge and more than 0 atomic% and 25 atomic% or less of Mg is preferable. In this embodiment, the L1 recording film 34 is formed of a phase change material containing 79 atomic% to 95 atomic% of Sb and 5 atomic% to 21 atomic% of Ge. When the L1 recording film 34 is formed of such a phase change material, the storage characteristics of the L1 information layer 30 are improved regardless of the film thickness of the L1 recording film 34.

  Here, the element having an eutectic with Sb is not particularly limited as long as it can have an eutectic with Sb. For example, Ge, Mg, Ga, As, Pb, Bi, Cr, Mn Ni, Cu, Zn, Pd, Ag, In, and other elements are preferably used.

  When the film thickness of the L1 recording film 34 is 2 nm to 15 nm, particularly when the film thickness of the L1 recording film 34 is 4 nm to 9 nm, the storage characteristics of the L1 information layer 30 are further improved. Therefore, the L1 recording film 34 is preferably formed to have a thickness of 2 nm or more and 15 nm or less, preferably 4 nm to 9 nm.

  The L1 recording film 34 can be formed on the surface of the third dielectric film 33 by, for example, a vapor phase growth method using chemical species including the constituent elements of the L1 recording film 34. Examples of the vapor phase growth method include a vacuum evaporation method and a sputtering method, but it is preferable to form the L1 recording film 34 by a sputtering method.

  The second dielectric film 35, together with the third dielectric film 33, plays a role of physically and chemically protecting the L1 recording film 34, and is generated in the L1 recording film 34 by the irradiation of the laser beam L. It has a function of radiating heat to the heat radiating film 37 described later. The second dielectric film 35 also serves as a barrier film that prevents the elements constituting the first dielectric film 36 from diffusing into the L1 recording film 34.

The material for forming the second dielectric film 35 is not particularly limited, and the same material as the material for forming the fourth dielectric film 31 and the third dielectric film 33 is used. Thus, the second dielectric film 35 can be formed. In the present embodiment, the second dielectric film 35 is composed of ZrO ₂ and Y having a molar ratio of 97: 3, like the first film 312 and the third dielectric film 33 of the fourth dielectric film 31. It is formed by a mixture of ₂ O _3. In this case, the heat generated in the L1 recording film 34 by the irradiation of the laser beam L can be quickly dissipated.

  The second dielectric film 35 is preferably formed to have a thickness of 3 nm to 15 nm. When the thickness of the second dielectric film 35 is less than 3 nm, it becomes difficult to sufficiently fulfill the role as a barrier film, and the heat dissipation effect is reduced, while it exceeds 15 nm. In the case where the second dielectric film 35 is formed, the internal stress generated when the second dielectric film 35 is formed is increased, and the second dielectric film 35 is easily cracked.

  The second dielectric film 35 is formed by, for example, a sputtering method.

  The first dielectric film 36 has a function of improving the adhesion between the second dielectric film 35 and the heat dissipation film 37.

The material for forming the first dielectric film 36 is a material having high light transmittance with respect to the laser beam L and having high adhesion to the second dielectric film 35 and the heat dissipation film 37. The first dielectric film 36 is preferably formed of a mixture of ZnS and SiO ₂ , although not particularly limited. The first dielectric film 36, when formed by a mixture of ZnS and SiO _2, the molar ratio of ZnS and SiO ₂ is 60: 40 to 95: is preferably 5. When the ZnS molar ratio is less than 60%, the refractive index of the first dielectric film 36 is lowered, and the region of the L1 recording film 34 where the recording mark is formed and the recording mark is not formed. There is a possibility that the difference in reflectance from the area of the L1 recording film 34 is lowered. On the other hand, when the molar ratio of ZnS exceeds 95%, it is difficult to form the first dielectric film 36 as a complete transparent film, and there is an adverse effect such as a decrease in signal output. come.

  The first dielectric film 36 is preferably formed to have a thickness of 5 nm to 50 nm. If the thickness of the first dielectric film 36 is less than 5 nm, cracks are likely to occur in the heat dissipation film 37, and if it exceeds 50 nm, the heat dissipation effect may be reduced.

  The first dielectric film 36 is formed by, for example, a sputtering method.

  The second heat radiation film 37 plays a role of radiating heat transferred from the L1 recording film 34 through the second dielectric film 35 and the first dielectric film 36 together with the first heat radiation film 38. .

  As a material for forming the second heat radiation film 37, AlN having high light transmittance with respect to the laser beam L and higher thermal conductivity than that of the first dielectric film 36 is used. A material having a main component is preferably used. When the second heat dissipation film 37 is formed of a material mainly composed of AlN, the light transmittance of the L1 information layer 30 is increased and the heat dissipation is improved.

  The second heat dissipation film 37 is preferably formed to have a thickness of 20 nm to 70 nm. When the thickness of the second heat dissipation film 37 is less than 20 nm, there is a possibility that a sufficient heat dissipation effect may not be obtained. On the other hand, when the thickness of the second heat dissipation film 37 exceeds 70 nm, Since it takes a long time to form the second heat radiation film 37, the productivity of the optical recording medium 10 may be reduced.

  The second heat radiation film 37 is formed by, for example, a sputtering method.

  The first heat radiation film 38 plays a role of radiating heat transmitted from the L1 recording film 34 through the second dielectric film 35 and the first dielectric film 36 together with the second heat radiation film 37. .

  In the present embodiment, the first heat dissipation film 38 is formed adjacent to the second heat dissipation film 37. In this way, when the first heat dissipation film 38 and the second heat dissipation film 37 are formed adjacent to each other, the L1 information layer 30 is not deteriorated without deteriorating the excellent optical characteristics of the L1 information layer 30. It becomes possible to further improve the heat dissipation as a whole.

The material for forming the first heat dissipation film 38 has high light transmittance with respect to the laser beam L, a refractive index lower than the refractive index of the second heat dissipation film 37, and high thermal conductivity. A material mainly composed of Al ₂ O ₃ or SiO ₂ is preferably used. When the first heat dissipation film 38 is formed of a material mainly composed of Al ₂ O ₃ or SiO ₂ , both the light transmittance and heat dissipation of the L1 information layer 30 can be improved, and the information layer The heat dissipation of the L1 information layer 30 as a whole can be improved without degrading optical characteristics such as high reflectance and transmittance.

  The thickness of the first heat dissipation film 38 is not particularly limited, but is preferably 10 nm or more and less than 75 nm, and particularly preferably 25 nm or more and 50 nm or less. When the film thickness of the first heat dissipation film 38 is less than 10 nm, there is a possibility that a sufficient heat dissipation effect may not be obtained. On the other hand, when the film thickness of the first heat dissipation film 38 is 75 nm or more, Since it takes a long time to form the heat dissipation film 37, the productivity of the optical recording medium 10 may be reduced.

  The first heat dissipation film 38 is formed by, for example, a sputtering method.

  When data is recorded on the L0 information layer 20 or the L1 information layer 30 of the optical recording medium 10 according to the present embodiment configured as described above, the recording power Pw, the erasing power Pe, and the base power Pb are used. When the laser beam L whose power is modulated and reproducing the data recorded in the L0 information layer 20 or the L1 information layer 30, the laser beam L whose power is set to the reproduction power Pr is The light is focused on the L0 recording film 23 included in the L0 information layer 20 or the L1 recording film 34 included in the L1 information layer 30 via the light transmission layer 13.

  In this embodiment, the L0 recording film included in the L0 information layer 20 of the optical recording medium 10 is irradiated with a laser beam L having a wavelength of 405 nm using an objective lens (not shown) having a numerical aperture of 0.85. 23 or the L1 recording layer 34 included in the L1 information layer 30 is configured to be focused.

  When recording marks are formed on the L1 recording film 34 included in the L1 information layer 30 of the optical recording medium 10 and data is recorded on the L1 information layer 30, a laser beam whose power is set to the recording power Pw. L is irradiated onto the L1 recording film 34, and the region of the L1 recording film 34 irradiated with the laser beam L is heated to a temperature equal to or higher than the melting point of the phase change material, and the phase change material contained in the region is melted. The Next, the laser beam L whose power is set to the base power Pb is irradiated to the L1 recording film 34 through the light transmission layer 13, and the power is melted by the laser beam L whose power is set to the recording power Pw. The phase change material is rapidly cooled, the phase change material changes from a crystalline state to an amorphous state, a recording mark is formed on the L1 recording film 34, and data is recorded on the L1 information layer 30.

In the present embodiment, the L1 information layer 30 includes the L1 recording film 34, the reflective film 32 formed on the support substrate 11 side with respect to the L1 recording film 34, and the light incident surface with respect to the L1 recording film 34. The first heat dissipation film 38 is formed between the L1 recording film 34 and the first heat dissipation film 38 and the first heat dissipation film 38 formed of a material mainly composed of Al ₂ O ₃ or SiO _2. A second heat dissipating film 37 formed of a material having AlN as a main component and formed adjacent to the film 38, and further includes a second dielectric film 35, a third dielectric film 33, and a fourth dielectric film. Each of the dielectric films 31 is formed of a mixture of ZrO ₂ and Y ₂ O ₃ having a molar ratio of 97: 3. In such a case, the excellent optical characteristics of the L1 information layer 30 are deteriorated. Without increasing the heat dissipation of the L1 information layer 30 as a whole Since bets can be, when recording the data in the L1 information layer 30, a recording mark in the L1 recording film 34 can be formed to a desired size. Therefore, it becomes possible to prevent the jitter of the reproduction signal from deteriorating when the data recorded in the L1 information layer 30 is reproduced. As a result, the data is transferred to the L1 information layer 30 as desired. It becomes possible to record.

  On the other hand, when reproducing data recorded on the L1 information layer 30 of the optical recording medium 10, the laser beam L whose power is set to the reproduction power Pr is transmitted through the light transmission layer 13 to the L1 information layer 30. The amount of the laser beam L focused on the L1 recording film 34 and reflected by the reflective film 32 or the like is detected.

  In the present embodiment, as described above, since the heat dissipation of the L1 information layer 30 as a whole can be improved without deteriorating the excellent optical characteristics of the L1 information layer 30, it is recorded in the L1 information layer 30. When reproducing data, the irradiated laser beam L can be reflected as desired. Therefore, it is possible to prevent the jitter of the reproduction signal from deteriorating when the data recorded in the L1 information layer 30 is reproduced. As a result, the data recorded in the L1 information layer 30 is changed to a desired value. So that it can be played.

  On the other hand, when recording marks are formed on the L0 recording film 23 included in the L0 information layer 20 of the optical recording medium 10 and data is recorded on the L0 information layer 20, the power becomes the recording power Pw. The set laser beam L is applied to the L0 recording film 23 via the light transmission layer 13 and the L1 information layer 30, and the region of the L0 recording film 23 irradiated with the laser beam L is equal to or higher than the melting point of the phase change material. And the phase change material contained in the region is melted. Next, the laser beam L whose power is set to the base power Pb is irradiated to the L0 recording film 23 via the light transmission layer 13 and the L1 information layer 30, and the laser beam whose power is set to the base power Pb. By L, the melted phase change material is rapidly cooled, the phase change material changes from a crystalline state to an amorphous state, a recording mark is formed on the L0 recording film 23, and data is recorded on the L0 information layer 20.

  In the present embodiment, as described above, the heat radiation property of the L1 information layer 30 as a whole can be improved, and the reflection film 32 included in the L1 information layer 30 can be formed thin, so that the laser beam L is L1. When the light passes through the information layer 30, it is possible to minimize the reduction in the amount of light of the laser beam L. Therefore, the L0 information layer 20 is irradiated with the laser beam L via the L1 information layer 30. Thus, data can be recorded in the L0 information layer 20 as desired.

  On the other hand, when data recorded on the L0 information layer 20 of the optical recording medium 10 is reproduced, the laser beam L whose power is set to the reproduction power Pr is transmitted through the light transmission layer 13 and the L1 information layer 30. The light quantity of the laser beam L focused on the L0 recording film 23 included in the L0 information layer 20 and reflected by the reflecting film 21 or the like is detected.

  In the present embodiment, as described above, when the laser beam L passes through the L1 information layer 30, it is possible to minimize the decrease in the light amount of the laser beam L. Then, by irradiating the L0 information layer 20 with the laser beam L, the data recorded in the L0 information layer 20 can be reproduced as desired.

  Examples are given below to clarify the effects of the present invention.

Example 1
Optical recording medium sample # 1 was produced as follows.

  First, a polycarbonate substrate having a thickness of 1.1 mm, a diameter of 120 mm, and grooves formed on the surface with a groove pitch of 0.32 μm was manufactured by an injection molding method.

Next, the polycarbonate substrate was set in a sputtering apparatus, and a thickness of 40 nm made of 98.4 atomic% Ag, 0.7 atomic% Nd, 0.9 atomic% Cu and N was formed on the surface on which the groove was formed. And a first film having a thickness of 60 nm made of 98.4 atomic% Ag, 0.7 atomic% Nd, and 0.9 atomic% Cu. A second film having a thickness of 10 nm made of a mixture of CeO ₂ and Al ₂ O ₃ with a molar ratio of 80:20 and a mixture of ZnS and SiO ₂ with a molar ratio of 50:50 as main components, A second dielectric film composed of a first film having a thickness of 10 nm, a phase change material comprising 77.1 atomic% Sb, 18.7 atomic% Te and 4.2 atomic% Ge Containing L as a main component and having a thickness of 10 nm It includes a recording film, a mixture of ZnS and SiO ₂ in a molar ratio of 80:20 as the main component, the first dielectric film having a thickness of 40 nm, and includes AlN as a main component, having a thickness of 30nm A heat dissipation film was sequentially formed by a sputtering method to form an L0 information layer.

  Here, the first film constituting the reflective film, the first film and the second film constituting the second dielectric film, the L0 recording film and the first dielectric film are in an argon gas atmosphere. It formed by the sputtering method using the target which has a composition corresponding to each film | membrane.

  On the other hand, the second film and the heat dissipating film constituting the reflective film were formed by reactive sputtering in an argon and nitrogen gas atmosphere using an AgNdCu or Al target, respectively.

  Next, the polycarbonate substrate on which the L0 information layer is formed is set in a spin coater, a solution of an ultraviolet curable acrylic resin composition is applied on the L0 information layer, and a groove is formed on the transparent substrate. The UV curable acrylic resin composition is cured by irradiating ultraviolet rays while developing the UV curable acrylic resin composition solution while rotating the polycarbonate substrate and rotating the polycarbonate substrate, and has a thickness of 25 μm. An intermediate layer was formed. The groove formed in the transparent intermediate layer had a groove pitch of 0.32 μm.

  Further, using a semiconductor laser having a wavelength of 810 nm, the L0 recording film was initialized at an output of 500 mW to crystallize the L0 recording film.

Next, the polycarbonate substrate on which the L0 information layer and the transparent intermediate layer are formed is set in a sputtering apparatus, and contains a mixture of ZnS and SiO ₂ having a molar ratio of 80:20 as a main component on the surface of the transparent intermediate layer. , A second film having a thickness of 15 nm, and a first film having a thickness of 4 nm containing a mixture of ZrO ₂ and Y ₂ O ₃ having a molar ratio of 97: 3 as a main component. A fourth dielectric film, a reflective film comprising an alloy of 98 atomic% Ag, 1 atomic% Pd and 1 atomic% Cu, and having a thickness of 15 nm, ZrO ₂ having a molar ratio of 97: 3, and A phase change material containing a mixture of Y ₂ O ₃ as a main component and having a thickness of 6 nm and comprising a third dielectric film, 87.0 atomic% Sb and 13.0 atomic% Ge is mainly used. L1 notation containing as component and having a thickness of 6 nm Film, the molar ratio of 97: comprises a mixture of ZrO ₂ and _Y 2 _{O 3} of 3 as a main component, a second having a thickness of 6nm dielectric film, the molar ratio of 80:20 ZnS and SiO ₂ A first dielectric film having a mixture as a main component and having a thickness of 12.5 nm, a second heat dissipation film having AlN as a main component and having a thickness of 35 nm, and Al ₂ O ₃ as a main component And a first heat dissipation film having a thickness of 50 nm was sequentially formed by a sputtering method to form an L1 information layer.

  Here, the second heat dissipation film is formed by a reactive sputtering method using an Al target in an argon gas and nitrogen gas atmosphere, and the first heat dissipation film is an Al target in an argon gas and oxygen gas atmosphere. It was formed by the reactive sputtering method using.

  In addition, the first and second films, the reflective film, the third dielectric film, the L1 recording film, the second dielectric film, and the first dielectric film constituting the fourth dielectric film Was formed by a sputtering method using a target having a composition corresponding to each film in an argon gas atmosphere.

  Next, on the surface of the heat dissipation film of the L1 information layer, a solution of an ultraviolet curable acrylic resin composition is applied by a spin coating method to form a coating film, and the coating film is irradiated with ultraviolet rays. The curable acrylic resin composition was cured to form a light transmission layer having a thickness of 75 μm.

  Further, using a semiconductor laser having a wavelength of 810 nm, the L1 recording film was initialized at an output of 500 mW to crystallize the L1 recording film.

  Thus, an optical recording medium sample # 1 was produced.

  Next, an optical recording medium comparison sample # 1 was produced in the same manner as the optical recording medium sample # 1 except that the first heat dissipation film was not formed on the L1 information layer.

Further, a second heat dissipation film mainly composed of Al ₂ O ₃ is formed on the surface of the first dielectric film of the L1 information layer, and a first layer mainly composed of AlN is formed on the surface of the second heat dissipation film. An optical recording medium comparative sample # 2 was produced in the same manner as the optical recording medium sample # 1 except that one heat dissipation film was formed.

Next, a film having a thickness of 5 nm, further including a mixture of ZnS and SiO ₂ with a molar ratio of 80:20 as a main component between the first heat dissipation film and the second heat dissipation film of the L1 information layer. An optical recording medium comparison sample # 3 was produced in the same manner as the optical recording medium sample # 1 except that the film was formed.

  The optical recording medium sample # 1 and the optical recording medium comparison samples # 1 to # 3 thus produced were set in an optical recording medium evaluation apparatus “DDU1000” (trade name) manufactured by Pulstec Industrial Co., Ltd. While rotating at a linear velocity of 10.5 m / sec, the channel clock frequency is 132 MHz, the channel bit length is 0.12 μm / bit, the wavelength is 405 nm, and the power is between the recording power Pw and the base power Pb. The L1 recording film of each sample is irradiated with a laser beam modulated according to a predetermined pattern through a light transmission layer using an objective lens having a numerical aperture NA of 0.85, and a 1,7RLL modulation method A recording mark having a length corresponding to the 2T signal to the 8T signal is formed, and a random signal is recorded on the L1 information layer.

  Here, when a random signal is recorded on the L1 information layer of each sample, the recording power Pw, the erasing power Pe, the reproducing power Pr, and the base power Pb of the laser beam are respectively 9.6 mW, It was set to 3.8 mW, 0.7 mW, and 0.3 mW.

  Next, the random signals thus recorded were reproduced in the same manner as described above, and the clock jitter (%) of the reproduced signal was measured.

  Here, the clock jitter was calculated from σ / Tw (Tw: one cycle of the clock) by obtaining the fluctuation σ of the reproduction signal with a time interval analyzer.

  Next, each of the L1s of the optical recording medium sample # 1 and the optical recording medium comparison samples # 1 to # 3 is the same except that the recording power Pw is sequentially changed from 0.2 mW to 12.6 mW. A recording mark having a length corresponding to 2T signal to 8T signal in the 1,7RLL modulation system is formed on the recording film, a random signal is recorded on the L1 information layer, and the recorded random signal is reproduced, The clock jitter (%) of the reproduced signal was measured.

  The jitter measurement result for optical recording medium sample # 1 is shown by curve A in FIG. 5, and the jitter measurement result for optical recording medium comparison sample # 1 is shown by curve B in FIG. The jitter measurement results for the optical recording medium are shown by the curve C in FIG. 5, and the jitter measurement results for the optical recording medium comparative sample # 3 are shown by the curve D in FIG.

  Next, the power of the laser beam is set to the recording power Pw at which the smallest jitter is obtained, and each L1 of the optical recording medium sample # 1 and the optical recording medium comparison samples # 1 to # 3 is processed in the same manner as described above. A random signal was recorded on the information layer, the recorded random signal was reproduced, the reflectance was measured, and the degree of modulation was calculated.

  Here, the reflectance was measured by irradiating a laser beam onto a region where no recording mark was formed, and the modulation factor was calculated by (La−Lb) / La.

  Here, La is a level of a reproduction signal obtained by irradiating a laser beam to an area where no recording mark is formed, and Lb is a recording mark having a length of 2T to 8T formed at random. This is the level of a reproduction signal obtained by irradiating a region with a laser beam.

  The reflectance measurement results and the modulation degree calculation results are shown in Table 1, respectively.

  Next, the power of the laser beam is set to the recording power Pw at which the smallest jitter is obtained, and each of the optical recording medium sample # 1 and the optical recording medium comparison samples # 1 to # 3 is set in the same manner as described above. A recording mark having a length corresponding to a 2T signal in the 1,7RLL modulation system is formed on the L1 recording film, and a single signal is recorded on the L1 information layer, and each L1 recording film corresponds to an 8T signal. A recording mark having a length was formed, a single signal was recorded on the L1 information layer, a recording mark having a length corresponding to a 2T signal was formed on each L1 recording film, and recorded on the L1 information layer A recording mark having a length corresponding to the 8T signal is formed on each L1 recording film and the C / N ratio of the reproduction signal obtained by reproducing the single signal, and the single signal recorded on the L1 information layer is reproduced. C of the playback signal obtained N ratio, respectively, were measured.

  Here, the C / N ratio of the reproduction signal was measured using a spectrum analyzer “Spectrum Analyzer XK180” (trade name) manufactured by Advantest Corporation.

  Table 1 shows the measurement results of the C / N ratio of the reproduction signal.

  Further, in the same manner as recording a random signal on the L1 information layer, a laser beam is irradiated to the L0 recording film of the optical recording medium sample # 1 through the light transmission layer and the L1 information layer, The recording signal is formed, the random signal is recorded on the L0 information layer, and the random signal is reproduced in the same manner as the random signal recorded on the L1 information layer is reproduced. A random signal was recorded on the layer, and the random signal recorded on the L0 information layer could be reproduced.

  As apparent from FIG. 5 and Table 1, in the optical recording medium sample # 1 in which the first heat dissipation film is provided in the L1 information layer, the deterioration of jitter can be prevented, and high recording of 11 mW or more is possible. In the power Pw, it becomes possible to prevent the deterioration of jitter particularly effectively, and even if the first heat dissipation film is provided, the optical characteristics such as the reflectance and the degree of modulation are prevented from being lowered. However, it was found that it was difficult to prevent deterioration of jitter in the optical recording medium comparative samples # 1 to # 3. Therefore, in the optical recording medium comparison samples # 1 to # 3, it is difficult to record data in the L1 information layer and reproduce the recorded data as desired. In the recording medium sample # 1, it has been found that data can be recorded in the L0 information layer and the L1 information layer as desired, and the recorded data can be reproduced.

Example 2
In the same manner as in Example 1, the prepared polycarbonate substrate on which the L0 information layer and the transparent intermediate layer were formed was set in a sputtering apparatus, and ZrO ₂ and Y having a molar ratio of 97: 3 were formed on the surface of the transparent intermediate layer. _A fourth dielectric film comprising a mixture of ₂ O ₃ as a main component and having a thickness of 5 nm, comprising an alloy of 98 atomic% Ag, 1 atomic% Pd and 1 atomic% Cu, A reflective film having a thickness, a third dielectric film having a thickness of 4 nm, comprising a mixture of ZrO ₂ and Y ₂ O ₃ having a molar ratio of 97: 3 as a main component, 84.1 atomic% of Sb And an L1 recording film comprising a phase change material containing 14.0 atomic% Ge and 1.9 atomic% Mg as a main component and having a thickness of 6 nm, ZrO ₂ having a molar ratio of 97: 3, and a mixture of Y ₂ O ₃ comprises as a main component, 5 nm Wherein the second dielectric film having a thickness, a mixture of ZnS and SiO ₂ in a molar ratio of 80:20 as the main component, wherein the first dielectric film having a thickness of 10 nm, an AlN as a main component, A second heat dissipating film having a thickness of 36 nm and a first heat dissipating film containing Al ₂ O ₃ as a main component and having a thickness of 50 nm are sequentially formed by sputtering to form an L1 information layer. Except for the above, optical recording medium sample # 2 was produced in the same manner as optical recording medium sample # 1.

Further, the thickness of the second heat radiating film containing AlN as a main component was set to 40 nm, and the first heat radiating film containing Al ₂ O ₃ as a main component was not formed. In the same manner as in # 2, optical recording medium comparison sample # 4 was produced.

  Next, the optical recording medium sample # 2 and the optical recording medium comparison sample # 4 are set in the above-described optical recording medium evaluation apparatus, respectively, and the recording power Pw is increased from 8.5 mW to 0.5 mW in increments of 12.0 mW. 2T signal or 8T signal in the 1,7RLL modulation system is applied to each of the L1 recording films of the optical recording medium sample # 2 and the optical recording medium comparison sample # 4 in the same manner as in Example 1 except that the points are sequentially changed. A recording mark having a length corresponding to is formed, a random signal is recorded on each L1 information layer, the recorded random signal is reproduced, and clock jitter (%) of the reproduced signal is measured.

  The jitter measurement result for the optical recording medium sample # 2 is shown by a curve A in FIG. 6, and the jitter measurement result for the optical recording medium comparison sample # 4 is shown by a curve B in FIG.

  Next, in the same manner as in Example 1, the power of the laser beam is set to the recording power Pw at which the smallest jitter is obtained, and each L1 information layer of the optical recording medium sample # 2 and the optical recording medium comparison sample # 4 In addition, a random signal was recorded, the recorded random signal was reproduced, the reflectance was measured, and the degree of modulation was calculated.

  The reflectance measurement results and the modulation degree calculation results are shown in Table 2, respectively.

  Further, in the same manner as in Example 1, the power of the laser beam is set to the recording power Pw at which the smallest jitter is obtained, and the respective L1 recording films of the optical recording medium sample # 2 and the optical recording medium comparison sample # 4 In addition, a recording mark having a length corresponding to a 2T signal in the 1,7RLL modulation system is formed, a single signal is recorded on the L1 information layer, and each L1 recording film has a length corresponding to an 8T signal. A single signal is recorded on the L1 information layer by forming a recording mark having a length corresponding to the 2T signal on each L1 recording film. A recording mark having a length corresponding to the 8T signal is formed on each L1 recording film and the C / N ratio of the reproduction signal obtained by reproducing the signal, and a single signal recorded on the L1 information layer is reproduced. C / N ratio of the reproduced signal It is, was measured.

  Table 2 shows the measurement results of the C / N ratio of the reproduction signal.

  Next, in the same manner as recording a random signal on the L1 information layer, a laser beam is irradiated to the L0 recording film of the optical recording medium sample # 2 through the light transmission layer and the L1 information layer, When a recording mark is formed, a random signal is recorded on the L0 information layer, and the recorded random signal is reproduced, a random signal is recorded on the L0 information layer and recorded on the L0 information layer as desired. It was possible to reproduce the random signal.

As apparent from FIG. 6 and Table 2, in the optical recording medium sample # 2 in which the first heat dissipation film is provided on the L1 information layer, the reflection film and the fourth dielectric film of the L1 information layer are thinned. Even when formed, it is possible to prevent the deterioration of jitter, and even if the first heat dissipation film is provided, it is possible to prevent a decrease in optical characteristics such as reflectance and modulation factor. However, it was found that it is difficult to prevent the deterioration of jitter in the optical recording medium comparative sample # 4. Therefore, in the optical recording medium comparison sample # 4, it is difficult to record data in the L1 information layer and reproduce the recorded data as desired. In # 2, it was found that it was possible to record data in the L0 information layer and the L1 information layer as desired, and to reproduce the recorded data.
Example 3
It contains a mixture of ZnS and SiO ₂ with a molar ratio of 80:20 as a main component, and instead of the second film having a thickness of 15 nm, it contains TiO ₂ as a main component and has a thickness of 12.5 nm. Optical recording was performed in the same manner as in optical recording medium sample # 1, except that the second film was formed and the thickness of the first heat dissipation film containing Al ₂ O ₃ as a main component was set to 25 nm. Media sample # 3 was made.

Further, a mixture of ZnS and SiO ₂ with a molar ratio of 80:20 is included as a main component, and instead of the second film having a thickness of 15 nm, TiO ₂ is included as a main component and the thickness is 12.5 nm. An optical recording medium sample # 4 was produced in the same manner as the optical recording medium sample # 1 except that a second film having a thickness of 2 was formed.

Next, a mixture of ZnS and SiO ₂ with a molar ratio of 80:20 is included as a main component, and instead of the second film having a thickness of 15 nm, TiO ₂ is included as a main component and the thickness is 12.5 nm. In the same manner as in the optical recording medium sample # 1, except that the thickness of the first heat dissipation film containing Al ₂ O ₃ as a main component is set to 75 nm. Optical recording medium sample # 5 was produced.

Further, a mixture of ZnS and SiO ₂ with a molar ratio of 80:20 is included as a main component, and instead of the second film having a thickness of 15 nm, TiO ₂ is included as a main component and the thickness is 12.5 nm. An optical recording medium comparison sample # 5 was produced in the same manner as the optical recording medium comparison sample # 1 except that a second film having a thickness of 2 was formed.

  Next, the optical recording medium samples # 3 to # 5 and the optical recording medium comparison sample # 5 are set in the above-described optical recording medium evaluation apparatus, respectively, and in the same manner as in the first embodiment, the optical recording medium samples # 3 to ## 5 and a recording mark having a length corresponding to 2T to 8T signals in the 1,7RLL modulation system are formed on the L1 recording film of the optical recording medium comparison sample # 5, and a random signal is recorded on each L1 information layer. The recorded random signal was reproduced, and the clock jitter (%) of the reproduced signal was measured.

  The jitter measurement result for the optical recording medium sample # 3 is shown by curve A in FIG. 7, and the jitter measurement result for the optical recording medium sample # 4 is shown by curve B in FIG. The measurement result is shown by the curve C in FIG. 7, and the jitter measurement result for the optical recording medium comparison sample # 5 is shown by the curve D in FIG.

  As is apparent from FIG. 7, in order to prevent the jitter from deteriorating, it is necessary to form the first heat dissipation film in the L1 information layer, but in order to reliably prevent the jitter from deteriorating. It has been found that it is effective to set the thickness of the first heat dissipation film formed in the L1 information layer to 10 nm or more and less than 75 nm.

  Next, in the same manner as in Example 1, the power of the laser beam is set to the recording power Pw at which the smallest jitter is obtained, and each of the optical recording medium samples # 3 to # 5 and the optical recording medium comparison sample # 5 is set. When a random signal is recorded on the L1 information layer, the recorded random signal is reproduced, the reflectance is measured, and the modulation factor is calculated, the reflectance and the modulation factor of the optical recording medium samples # 3 to # 5 are calculated. The reflectance and the modulation degree of the optical recording medium comparative sample # 5 were almost the same.

  Further, in the same manner as in Example 1, the power of the laser beam is set to the recording power Pw at which the smallest jitter is obtained, and each of the optical recording medium samples # 3 to # 5 and the optical recording medium comparison sample # 5 is set. A recording mark having a length corresponding to a 2T signal in the 1,7RLL modulation system is formed on the L1 recording film, and a single signal is recorded on the L1 information layer, and each L1 recording film corresponds to an 8T signal. A recording mark having a length is formed, a single signal is recorded on the L1 information layer, a recording mark having a length corresponding to a 2T signal is formed on the L1 recording film, and a single signal recorded on the L1 information layer is recorded. A recording mark having a length corresponding to the 8T signal is formed on the L1 recording film and the C / N ratio of the reproduced signal obtained by reproducing one signal, and a single signal recorded on the L1 information layer is reproduced. C / N ratio of the reproduced signal obtained Each place was measured, and the measured values of the optical recording medium sample # 3 to # 5, the measured values of the optical recording medium comparative sample # 5 were similar.

  Therefore, it has been found that even if the first heat dissipation film is provided, it is possible to prevent a decrease in optical characteristics.

  Further, in the same manner as recording a random signal on the L1 information layer, a laser beam is irradiated to each L0 recording film of the optical recording medium samples # 3 to # 5 through the light transmission layer and the L1 information layer, When a recording mark is formed on the L0 recording film, a random signal is recorded on the L0 information layer, and the recorded random signal is reproduced, each of the random signals is recorded on the L0 information layer as desired. Thus, the random signal recorded in the L0 information layer could be reproduced.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

  For example, in the optical recording medium 10 according to the embodiment, the L1 information layer 30 includes the fourth dielectric film 31, the reflective film 32, the third dielectric film 33, the L1 recording film 34, and the second dielectric material. The film 35, the first dielectric film 36, the second heat dissipation film 37, and the first heat dissipation film 38 are laminated, and the L1 information layer of the optical recording medium includes a recording film, a recording film, On the other hand, the reflective film formed on the support substrate side, the first heat radiation film formed on the light incident surface side with respect to the recording film, and the recording film and the first heat radiation film are formed between The second heat dissipation film only needs to be included, and the other configurations are not particularly limited. For example, either the second dielectric film or the first dielectric film can be omitted. .

  Further, in the optical recording medium 10 according to the embodiment, the first heat dissipation film 38 and the second heat dissipation film 37 are formed adjacent to each other, but the first heat dissipation film and the second heat dissipation film are adjacent to each other. It is not always necessary to form the other film formed between the first heat dissipation film and the second heat dissipation film by a material having a refractive index lower than that of the second heat dissipation film 37. May be interposed.

Furthermore, in the optical recording medium 10 according to the embodiment, the second dielectric film 35, the third dielectric film 33, and the fourth dielectric film 31 or the first film of the fourth dielectric film 31 are used. 312 are all formed of a mixture of ZrO ₂ and Y ₂ O ₃ with a molar ratio of 97: 3, but the second dielectric film, the third dielectric film, and the fourth dielectric film Alternatively, it is not always necessary that the first film of the fourth dielectric film is formed of a mixture of ZrO ₂ and Y ₂ O ₃ having a molar ratio of 97: 3.

  In the optical recording medium 10 according to the above embodiment, the fourth dielectric film 31 is formed by laminating the first film 312 and the second film 311. It is not always necessary that the body film 31 is formed by laminating the first film 312 and the second film 311, and the fourth dielectric film is composed of a single film. Also good.

  Furthermore, in the optical recording medium 10 according to the above embodiment, the third dielectric film 33 is configured by a single film, but the third dielectric film 33 is configured by a single film. It is not always necessary, and the third dielectric film may be formed by laminating two or more films.

  The optical recording medium 10 according to the embodiment includes the support substrate 11, the L0 information layer 20, the transparent intermediate layer 12, the L1 information layer 30, and the light transmission layer 13, and is provided with two information layers. However, it is not always necessary for the optical recording medium to include two information layers, and the optical recording medium includes three or more information layers stacked via a transparent intermediate layer. May be. When the optical recording medium has three or more information layers, all the information layers other than the information layer farthest from the light incident surface of the laser beam are all on the support substrate side with respect to the recording film and the recording film. A reflective film formed on the recording film, a first heat radiation film formed on the light incident surface side with respect to the recording film, and a second heat radiation film formed between the recording film and the first heat radiation film. It is not necessary to include at least one information layer formed on the light incident surface side with respect to the recording film, the reflective film formed on the support substrate side with respect to the recording film, and the recording film. It is only necessary to include one heat dissipation film and a second heat dissipation film formed between the recording film and the first heat dissipation film.

  Further, in the optical recording medium 10 according to the embodiment, the L0 information layer farthest from the light incident surface of the laser beam includes the L0 recording film 23 formed of a phase change material, and is configured as a rewritable information layer. However, it is not always necessary that the L0 information layer farthest from the light incident surface of the laser beam is configured as a rewritable information layer. The L0 information layer may be a read-only information layer or a write-once information layer. May be configured. For example, when the L0 information layer is configured as a read-only information layer, the information layer as the L0 information layer is not particularly provided, and the support substrate functions as the information layer farthest from the light incident surface of the laser beam. Then, prepits are formed on the surface of the support substrate, and data is recorded by such prepits.

FIG. 1 is a partially cutaway schematic perspective view showing an optical recording medium according to a preferred embodiment of the present invention. FIG. 2 is a schematic enlarged cross-sectional view of a portion indicated by A in FIG. FIG. 3 is a schematic enlarged cross-sectional view of the L0 information layer. FIG. 4 is a schematic enlarged cross-sectional view of the L1 information layer. FIG. 5 is a graph showing jitter of the optical recording medium sample # 1 and the optical recording medium comparison samples # 1 to # 3. FIG. 6 is a graph showing jitter of the optical recording medium sample # 2 and the optical recording medium comparison sample # 4. FIG. 7 is a graph showing the jitter of the optical recording medium samples # 3 to # 5 and the optical recording medium comparison sample # 5.

Explanation of symbols

10: Optical recording medium 11: Support substrate 12: Transparent intermediate layer 13: Light transmission layer 20: L0 information layer 21, 32: Reflective film 22: Second dielectric film 23: L0 recording film 24: First dielectric Film 25: Heat dissipation film 30: L1 information layer 31: Fourth dielectric film 33: Third dielectric film 34: L1 recording film 35: Second dielectric film 36: First dielectric film 37: First Second heat radiation film 38: first heat radiation film 311: second film 312: first film

Claims (4)

A plurality of information layers laminated on at least a transparent intermediate layer on a support substrate, and at least one of information layers other than the information layer farthest from the light incident surface of the laser beam among the plurality of information layers. An information layer is formed of a eutectic phase change material, a reflective film formed on the support substrate side with respect to the recording film, and the light incident surface side with respect to the recording film is formed, a first heat radiation film formed of a material mainly composed of Al ₂ O ₃ or SiO _2, is formed between the first heat radiation film and the recording film, composed mainly of AlN An optical recording medium comprising: a second heat dissipation film formed of a material. The optical recording medium according to claim 1, wherein the first heat dissipation film is formed adjacent to the second heat dissipation film. The optical recording medium according to claim 1, wherein the first heat dissipation film is formed to have a film thickness of 10 nm or more and less than 75 nm. 4. The optical recording medium according to claim 1, wherein the reflective film includes Ag as a main component and has a film thickness of 5 nm to 25 nm.

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