JP4171438B2 - Optical recording medium - Google Patents

Description

  The present invention relates to an optical recording medium. In particular, the present invention can record data as desired, reproduce the recorded data, and prevent long-term storage while preventing an increase in manufacturing cost. The present invention relates to an optical recording medium that can improve the reliability of the recording medium.

  Conventionally, optical recording media represented by CD and DVD have been widely used as recording media for recording digital data. In recent years, the next generation has a larger capacity and a higher data transfer rate. Type optical recording media have been proposed.

  These optical recording media, such as CD-ROMs and DVD-ROMs, can be additionally written to data such as CD-Rs and DVD-Rs, and read-only optical recording media that cannot be additionally written or rewritten. The write-once optical recording medium that cannot rewrite data and the rewriteable optical recording medium that can rewrite data, such as CD-RW and DVD-RW, can be broadly classified.

  Among these, write-once type optical recording media and rewritable type optical recording media irradiate the recording film with an intensity-modulated laser beam so that the organic dye and phase change material contained in the recording film are chemically and / or Or, it is configured to record data by physically changing and forming a recording mark, irradiating the recording film with a laser beam, and detecting the amount of reflected light of the laser beam to reproduce the data. Yes.

  In write-once type optical recording media and rewritable type optical recording media, the recording film is chemically and / or physically protected, the recording film area on which the recording mark is formed, and the recording film on which no recording mark is formed In general, a dielectric film is provided in the vicinity of the recording film so as to increase the difference in reflectance from this area.

As a material for forming such a dielectric film, a mixture of ZnS and SiO ₂ is preferably used from the viewpoints of optical characteristics, film forming characteristics, thermal conductivity, and the like. That is, since the mixture of ZnS and SiO ₂ has a high refractive index, it is possible to increase the difference in reflectance between the region where the recording mark is formed and the region where the recording mark is not formed, and the sputtering rate. Therefore, productivity can be improved. In addition, since the mixture of ZnS and SiO ₂ has low thermal conductivity, even when the dielectric film is formed in the vicinity of the recording film, the heat generated in the recording film is not released excessively, and the recording film is efficiently used. There is an advantage that it is not a harmful effect for heating.

  Further, in the recordable optical recording medium and the rewritable optical recording medium, the difference in reflectance between the region where the recording mark is formed and the region where the recording mark is not formed is further increased, and the recording film In order to appropriately dissipate the heat generated excessively, a reflection film is generally provided.

  As a material for forming the reflective film, metals such as Al, Au, Cu, and Ag, or alloys thereof are preferably used from the viewpoint of reflection characteristics and heat dissipation characteristics. Among these, in an optical recording medium of a type in which a dielectric film and a recording film are sequentially formed on the surface of the reflective film, surface flatness is used as a material for forming the reflective film. Particularly preferred is Ag or an alloy containing Ag that can form a reflective film excellent in thickness.

However, when a reflective film is formed using Ag or an alloy containing Ag, Ag has a property of easily causing a chemical reaction with sulfur, and therefore contains a mixture of ZnS and SiO ₂ as a main component. When used in combination with a dielectric film, there is a problem that the surface of the reflective film is corroded. Such corrosion of the surface of the reflective film progresses over time regardless of whether the optical recording medium is stored for a long period of time under high temperature and high humidity, thus degrading the storage reliability of the optical recording medium. It was a factor to make.

  Thus, as one means for solving such a problem, an optical recording medium in which an intermediate film is formed between a reflective film and a dielectric film has been proposed (for example, see Patent Document 1).

In the optical recording medium proposed in Patent Document 1, an intermediate film formed using a material that does not easily cause a chemical reaction with Ag or sulfur is provided between the reflective film and the dielectric film. Depending on the configuration, the reflective film and the dielectric film are physically separated to prevent a chemical reaction between Ag and sulfur.
JP-A-11-238253

  In the above optical recording medium, although it is possible to improve the storage reliability, it is necessary to add a manufacturing process for forming the intermediate film, which causes a new problem of increasing the manufacturing cost. . Therefore, in order to improve storage reliability without increasing manufacturing costs, it is required to form a dielectric film using a dielectric material that does not contain sulfur.

However, dielectric materials such as TiO ₂ and Ta ₂ O ₅ that do not contain sulfur have a high refractive index and excellent film forming characteristics, but have a high thermal conductivity. For this reason, when a dielectric film is formed using these dielectric materials, there is a problem that heat generated in the recording film easily escapes to the reflective film side and recording sensitivity is deteriorated.

  Therefore, the present invention can record data as desired, reproduce the recorded data, and improve reliability for long-term storage while preventing an increase in manufacturing cost. An object of the present invention is to provide an optical recording medium.

Such an object of the present invention includes a substrate and an information layer formed on the substrate and including a stacked body in which a recording film, a dielectric film, and a reflective film are stacked in this order from the light incident surface side. The reflective film contains Ag or an alloy containing Ag as a main component, and the dielectric film is substantially free of sulfur, and is mainly composed of a Zn oxide or a mixture of Ce oxide and Al oxide. When the dielectric film includes a Zn oxide as a main component, 4 to 7 atomic% of nitrogen is added, and a mixture of a Ce oxide and an Al oxide is the main component. When it is contained, it is achieved by an optical recording medium characterized in that 10 atomic% to 12 atomic% of nitrogen is added.

  In the present invention, the optical recording medium includes a reflective film containing Ag or an alloy containing Ag as a main component. In this specification, including an element as a main component means that the content of the element is the largest among the elements included in a certain film.

  According to the present invention, since the reflection film contains Ag or an alloy containing Ag as a main component, the reflection film having excellent optical characteristics and heat dissipation characteristics and excellent surface flatness is formed. Therefore, it is possible to obtain a reproduction signal having excellent signal characteristics such as C / N ratio.

In the present invention, the optical recording medium includes a dielectric film that is substantially free of sulfur and contains as a main component a Zn oxide or a mixture of a Ce oxide and an Al oxide . In this specification, “substantially not containing sulfur” means that the dielectric film does not contain sulfur except that sulfur is contained as an impurity.

  A dielectric film formed of a dielectric material that does not substantially contain sulfur has a very low possibility of causing a chemical reaction with Ag even if it is formed in the vicinity of a reflective film containing Ag. Corrosion of the film surface can be prevented.

  Further, in the present invention, nitrogen is added as an additive to a dielectric film containing a dielectric material that does not substantially contain sulfur as a main component.

  According to the inventor's research, when a dielectric film is formed by adding nitrogen to a dielectric material that does not substantially contain sulfur, while maintaining excellent optical characteristics and film forming characteristics, It has been found that a dielectric film capable of lowering thermal conductivity can be formed.

  Therefore, according to the present invention, since the thermal conductivity of the dielectric film can be lowered, when recording data, the heat generated in the recording film can be appropriately maintained, and the recording sensitivity can be improved. Is possible.

  In addition, the dielectric film according to the present invention is formed by sputtering using a mixed gas of argon gas and nitrogen gas as a sputtering gas and using a target containing a dielectric material that does not substantially contain sulfur as a main component. Is possible. For this reason, it is possible to form a dielectric layer containing a dielectric material that does not substantially contain sulfur as a main component and to which nitrogen is added in the same manufacturing process. Therefore, it is necessary to add a new manufacturing process. Therefore, it is possible to prevent an increase in manufacturing cost.

  As described above, according to the present invention, it is possible to record data as desired and reproduce the recorded data as desired while preventing an increase in manufacturing cost, and to provide reliability for long-term storage. It becomes possible to raise.

In the present invention, the dielectric film contains, as a main component , a mixture of Zn oxide or Ce oxide and Al oxide as a dielectric material. A dielectric film containing a mixture of Zn oxide or Ce oxide and Al oxide as a main component has a particularly high refractive index with respect to a laser beam having a wavelength of 380 nm to 450 nm. Therefore, when a laser beam having a wavelength of 380 nm to 450 nm is used for data recording / reproduction, it is possible to obtain a reproduction signal having good signal characteristics. In addition, a dielectric material containing a mixture of Zn oxide or Ce oxide and Al oxide as a main component has a high sputtering rate, so that it has excellent film formation characteristics and can improve productivity. Become.

In the present invention, when the dielectric film contains Zn oxide as a main component, the dielectric film contains 4 atomic% to 7 atomic% of nitrogen, and preferably 5.5 atomic% to 6 Contains 5 atomic percent nitrogen .

  When the dielectric film contains a Zn oxide as a main component and the amount of nitrogen added to the dielectric film is less than 4 atomic% or more than 7 atomic%, the thermal conductivity of the dielectric film May not be sufficiently low.

In the present invention, when the dielectric film contains a mixture of Ce oxide and Al oxide as a main component, the dielectric film contains 10 atomic% to 12 atomic% of nitrogen .

When the dielectric film contains a mixture of Ce oxide and Al oxide as a main component and the amount of nitrogen added to the dielectric film is less than 10 atomic%, the heat conduction of the dielectric film The rate may not be sufficiently low.

  In the present invention, it is preferable that data can be recorded on the information layer and data can be reproduced from the information layer with a laser beam having a wavelength of 380 nm to 450 nm.

  In a preferred embodiment of the present invention, the recording film is selected from the group consisting of a second recording film containing Cu as a main component, and the second recording film in the vicinity of Si, Ge, and Sn. And a first recording film containing a kind of element as a main component.

  When the laser beam is irradiated, the first recording film and the second recording film are heated, Cu contained as a main component in the second recording film, and an element contained as a main component in the first recording film, Are mixed to form a mixed region. The mixed region formed in this manner has a significantly different reflectance with respect to the laser beam from the other regions. Therefore, a reproduction signal having good signal characteristics can be obtained by utilizing a large difference in reflectance.

  In a further preferred embodiment of the present invention, the second recording film is added with at least one element selected from the group consisting of Al, Zn, Sn, Mg, and Au. When these elements are added to the second recording film containing Cu as a main component, it is possible to reduce the noise level of the reproduction signal and improve the reliability for long-term storage. It becomes possible.

  According to the present invention, while preventing an increase in manufacturing cost, data can be recorded and reproduced as desired, and reliability for long-term storage can be improved. An optical recording medium can be provided.

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

  FIG. 1 is a schematic perspective view of 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 the present embodiment has a disk shape, and in FIG. 2, the laser beam is irradiated from the direction indicated by the arrow to record and record data. The data is configured to be reproduced.

  As shown in FIG. 2, the optical recording medium 10 according to the present embodiment includes a support substrate 11, an information layer 20 formed on the surface of the support substrate 11, and light formed on the surface of the information layer 20. A transmissive layer 13 is provided.

  The support substrate 11 functions as a mechanical support 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. For example, it can be formed of glass, ceramic, resin, or the like. Of these, a resin is preferably used from the viewpoint of ease of molding. Examples of such a resin include polycarbonate resin, olefin resin, acrylic resin, epoxy resin, polystyrene resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, and urethane resin. Among these, polycarbonate resin and olefin resin are particularly preferable from the viewpoint of processability, optical characteristics, and the like. In the present embodiment, the support substrate 11 is formed of polycarbonate resin.

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

  In the present embodiment, since the laser beam is irradiated through the light transmission layer 13 located on the opposite side to the support substrate 11, the support substrate 11 is not necessarily required to have light transmittance. is not.

  Grooves 11 a and lands 11 b are alternately formed on the surface of the support substrate 11. The grooves 11a and / or lands 11b formed on the surface of the support substrate 11 function as a laser beam guide track when data is recorded on the information layer 20 and when data is reproduced from the information layer 20. The depth of the groove 11a is preferably set to λ / (8n) to λ / (4n) (λ is the wavelength of the laser beam and n is the refractive index of the light transmission layer 13). The pitch of the grooves 11a is preferably set to 0.2 μm to 0.4 μm.

  As shown in FIG. 2, an information layer 20 is formed on the surface of the support substrate 11.

  As shown in FIG. 2, the information layer 20 includes a reflective film 21 formed on the surface of the support substrate 11, a second dielectric film 22 formed on the surface of the reflective film 21, and a second dielectric film 22. Formed on the surface of the second recording film 23b formed on the surface of the dielectric film 22, the first recording film 23a formed on the surface of the second recording film 23b, and the surface of the first recording film 23a The first dielectric film 24 is provided.

  The reflection film 21 reflects the laser beam irradiated to the information layer 20 through the light transmission layer 13 and emits it again from the light transmission layer 13, and the second recording is performed by the laser beam irradiation. It plays a role of effectively dissipating heat generated in the film 23b and the first recording film 23a.

  The reflective film 21 contains Ag or an alloy containing Ag as a main component. In this specification, including an element as a main component means that the content of the element is the largest among the elements included in a certain film.

  When the reflective film 21 has such a composition, it has excellent optical characteristics and heat dissipation characteristics, and can form a reflective film having excellent surface flatness, so that it has excellent signal characteristics such as C / N ratio. A reproduction signal can be obtained.

  When the reflective film 21 contains an alloy containing Ag as a main component, Mg, Al, Ti, Cr, Fe, Co, Ni, Cu, Zn, Ge, Pt, Au, Pd, Nd, In, Sn and The reflective film 21 can be formed by an alloy of a metal such as Bi and Ag, and among these, Al, Cu, Au, Pd, Nd, In, Sn, and Bi having high reflectivity. It is preferable to form the reflective film 21 using an alloy of at least one of these metals and Ag.

  The thickness of the reflective film 21 is not particularly limited, but is preferably 10 nm to 300 nm, and particularly preferably 20 nm to 200 nm. If the thickness of the reflective film 21 is less than 10 nm, it is difficult to make the reflectance of the reflective film 21 sufficiently high, and the heat generated in the second recording film 23b and the first recording film 23a is reduced. It becomes difficult to dissipate heat. On the other hand, if the thickness of the reflective film 21 exceeds 200 nm, it takes a long time to form the reflective film 21, so that productivity is lowered and cracks may occur due to internal stress or the like. is there.

  The second dielectric film 22 physically and chemically protects the second recording film 23b and the first recording film 23a together with the first dielectric film 24 described later, and the second recording film 23b. And has a function of adjusting optical characteristics when data recorded on the first recording film 23a is reproduced. The second dielectric film 22 also plays a role of appropriately releasing the heat generated in the second recording film 23b and the first recording film 23a to the reflective film 21 side.

  In this embodiment, the second dielectric film 22 is mainly composed of an oxide containing at least one metal selected from the group consisting of Zn, Al, Ce, and Zr, that is, a dielectric material that does not substantially contain sulfur. As including. In the present specification, the phrase “substantially not containing sulfur” means that the second dielectric film 22 does not contain sulfur except that sulfur is contained as an impurity.

  A dielectric film containing a dielectric material that does not substantially contain sulfur as a main component has a very low possibility of causing a chemical reaction with Ag even when formed in the vicinity of a reflective film containing Ag. It is possible to prevent the surface of the reflective film from being corroded. In addition, a dielectric film containing as a main component an oxide containing at least one metal selected from the group consisting of Zn, Al, Ce, and Zr has a high refractive index with respect to a laser beam having a wavelength of 380 nm to 450 nm. In addition to having a relatively good sputtering rate, the optical characteristics and film forming characteristics are also excellent.

  However, since the dielectric film has high thermal conductivity, there is a problem that heat generated in the second recording film 23b and the first recording film 23a easily escapes to the reflective film 21 side, and the recording sensitivity is deteriorated. there were.

  Accordingly, the present inventor has conducted extensive research to solve such a problem, and as a result, a dielectric material containing, as a main component, an oxide containing at least one metal selected from the group consisting of Zn, Al, Ce, and Zr. Further, it has been found that by forming a dielectric film by adding nitrogen, it is possible to form a dielectric film capable of reducing the thermal conductivity while maintaining excellent optical characteristics and film forming characteristics.

  Therefore, in this embodiment, nitrogen is added as an additive to the second dielectric film 22, and according to this embodiment, the thermal conductivity of the second dielectric film 22 is lowered. Therefore, the heat generated in the second recording film 23b and the first recording film 23a can be appropriately maintained, and the recording sensitivity can be improved.

  In the present embodiment, for example, when the second dielectric film 22 contains a Zn oxide as a main component, the amount of nitrogen added to the second dielectric film 22 is 4 atomic% or more. It is preferably 7 atomic percent, more preferably 5.5 atomic percent to 6.5 atomic percent.

  When the second dielectric film 22 contains Zn oxide as a main component and the amount of nitrogen added to the second dielectric film 22 is less than 4 atomic% or more than 7 atomic% There is a possibility that the thermal conductivity of the second dielectric film 22 cannot be made sufficiently low.

  In the present embodiment, for example, when the second dielectric film 22 contains a mixture of Ce oxide and Al oxide as a main component, it is added to the second dielectric film 22. The amount of nitrogen added is preferably 9 atomic percent or more, more preferably 10 atomic percent to 12 atomic percent.

  When the second dielectric film 22 contains a mixture of Ce oxide and Al oxide as a main component, the amount of nitrogen added to the second dielectric film 22 is less than 9 atomic%. In some cases, the thermal conductivity of the second dielectric film 22 may not be sufficiently lowered.

  The thickness of the second dielectric film 22 is not particularly limited, but is preferably 10 nm to 100 nm. If the thickness of the second dielectric film 22 is less than 10 nm, the second recording film 23b and the first recording film 23a may not be sufficiently protected. On the other hand, if the thickness of the second dielectric film 22 exceeds 100 nm, the time required for film formation becomes long, which may reduce the productivity of the optical recording medium 10, and further, the second dielectric film 22. The information layer 20 may be cracked by the stress of the.

  The second recording film 23b and the first recording film 23a are recording films on which data is recorded, and one recording layer is constituted by two recording films. The second recording film 23b contains Cu as a main component, and the first recording film 23a contains a kind of element selected from the group consisting of Si, Ge and Sn as a main component.

  Further, in order to improve the storage reliability and the recording sensitivity of the second recording film 23b, the second recording film 23b is further provided with at least one element selected from the group consisting of Al, Zn, Sn, Mg, and Au. May be added. When these elements are added to the second recording film 23b, the noise level of the reproduction signal can be lowered and the reliability for long-term storage can be improved. The addition amount of the element to be added to the second recording film 23b is preferably 1 atomic% or more and less than 50 atomic%.

  The second recording film 23b and the first recording film 23a are preferably formed to have a total thickness of 4 nm to 40 nm. When the total thickness of the second recording film 23b and the first recording film 23a is less than 4 nm, the change in reflectance before and after data recording becomes small, and a reproduction signal having a high C / N ratio is obtained. On the other hand, if the total thickness of the second recording film 23b and the first recording film 23a exceeds 40 nm, the recording sensitivity may be deteriorated.

  The first dielectric film 24, together with the second dielectric film 22, physically and chemically protects the second recording film 23b and the first recording film 23a, and the second recording film 23b and the first dielectric film 23a. It has a function of adjusting optical characteristics when reproducing data recorded on one recording film 23a.

  The material for forming the first dielectric film 24 is not particularly limited as long as it is a transparent dielectric material in the wavelength region of the laser beam, but the first dielectric film 24 is made of Si. , Zn, Al, Ta, Ti, Co, Zr, Pb, Ag, Sn, Ca, Ce, V, oxide, nitride, sulfide containing at least one metal selected from the group consisting of Cu, Fe, Mg , Fluoride, or a composite thereof.

  The first dielectric film 24 may be formed so as to include a dielectric material different from that of the second dielectric film 22 as a main component, or may be formed so as to include the same dielectric material as a main component. Good.

  The thickness of the first dielectric film 24 is not particularly limited, but is preferably 10 nm to 100 nm for the same reason as the second dielectric film 22.

  As shown in FIG. 2, a light transmission layer 13 is formed on the surface of the information layer 20.

  The light transmission layer 13 is a layer that transmits a laser beam, and one surface thereof forms a light incident surface 13a.

  The material for forming the light transmission layer 13 is not particularly limited as long as it is optically transparent, has little optical absorption and reflection, and has low birefringence in the wavelength region of the laser beam used. However, when the light transmission layer 13 is formed by a spin coating method or the like, an ultraviolet curable resin, an electron beam effect resin, or the like is preferably used, and more preferably, the light transmission layer 13 is formed of an ultraviolet curable resin. Is formed. The light transmissive layer 13 may be formed by adhering a sheet formed of a light transmissive resin on the surface of the information layer 20 using an adhesive.

  The optical recording medium 10 having the above configuration is manufactured, for example, as follows.

  First, a support substrate 11 having grooves 11a and lands 11b formed on the surface is produced by injection molding using a stamper (not shown).

  Further, the information layer 20 is formed on the surface of the support substrate 11 on which the grooves 11a and lands 11b are formed. In forming the information layer 20, first, the reflective film 21 is formed on the surface of the support substrate 11. The reflective film 21 is formed by a sputtering method using Ag or an alloy containing Ag as a target.

Next, a second dielectric film 22 is formed on the surface of the reflective film 21. In the present embodiment, the second dielectric film 22 uses a mixed gas of argon gas and nitrogen gas as a sputtering gas, and uses an oxide such as ZnO, CeO ₂ , Al ₂ O ₃ , ZrO ₂ as a target. It is formed by the sputtering method. As a result, the second dielectric film 22 has a composition in which a dielectric material substantially not containing sulfur is contained as a main component and nitrogen is added as an additive. When forming the second dielectric film 22, the nitrogen content in the second dielectric film 22 is adjusted by controlling the ratio of nitrogen gas in the sputtering gas.

  Further, a second recording film 23b, a first recording film 23a, and a first dielectric film 24 are sequentially formed on the surface of the second dielectric film 22. The second recording film 23b, the first recording film 23a, and the first dielectric film 24 can all be formed by a vapor phase growth method such as a vacuum evaporation method or a sputtering method.

  Finally, the light transmission layer 13 is formed on the surface of the first dielectric film 24. The light transmission layer 13 is formed by, for example, applying a viscosity-adjusted acrylic UV curable resin or epoxy UV curable resin to the surface of the first dielectric film 24 by spin coating or the like. It can be formed by forming a film, irradiating it with ultraviolet rays, and curing the coating film.

  The optical recording medium 10 is formed as described above.

In the present embodiment, the second dielectric film 22 uses a mixed gas of argon gas and nitrogen gas as a sputtering gas, and uses an oxide such as ZnO, CeO ₂ , Al ₂ O ₃ , ZrO ₂ as a target. In the same manufacturing process, a dielectric layer containing a dielectric material substantially free of sulfur as a main component and added with nitrogen can be formed in the same manufacturing process. Therefore, it is not necessary to add a new manufacturing process, and it is possible to prevent an increase in manufacturing cost.

  Data is recorded on the optical recording medium 10 according to the present embodiment configured as described above as follows.

  First, as shown in FIG. 2, the information layer 20 is irradiated with a laser beam having a predetermined power through the light transmission layer 13. In order to record data on the optical recording medium 10 at a high recording density, a laser beam having a wavelength of 380 nm to 450 nm is passed through an objective lens (not shown) having a numerical aperture NA satisfying λ / NA ≦ 640 nm. The light is focused on the optical recording medium 10.

  When the information layer 20 is irradiated with the laser beam, the information layer 20 is heated, and the element contained as the main component in the second recording film 23b and the element contained as the main component in the first recording film 23a are mixed. As a result, a mixed region is formed. The mixed region formed in this manner can be used as a recording mark because the reflectance with respect to the laser beam is greatly different from the other regions.

  In the present embodiment, since the second dielectric film 22 has a low thermal conductivity, the heat generated in the second recording film 23b and the first recording film 23a when data is recorded on the information layer 20. Can be held appropriately, and the second recording film 23b and the first recording film 23a can be efficiently heated. Therefore, the element contained as the main component in the second recording film 23b and the element contained as the main component in the first recording film 23a can be quickly mixed, and data can be recorded with high sensitivity. Is possible.

  On the other hand, data recorded on the second recording film 23b and the first recording film 23a is reproduced as follows.

  In reproducing the data recorded on the second recording film 23b and the first recording film 23a, an objective lens having a numerical aperture NA satisfying λ / NA ≦ 640 nm by a laser beam having a wavelength of 380 nm to 450 nm is used. Thus, the recorded data is reproduced by detecting the light quantity of the laser beam irradiated to the information layer 20 and reflected by the information layer 20.

  In the present embodiment, since the second dielectric film 22 has a high refractive index with respect to a laser beam having a wavelength of 380 nm to 450 nm, the region where the recording mark is formed and the recording mark are formed. It is possible to increase the difference in reflectance from the non-existing region. Therefore, the data recorded in the information layer 20 can be reproduced with high sensitivity.

  FIG. 3 is a schematic enlarged cross-sectional view showing the layer structure of an optical recording medium according to another preferred embodiment of the present invention.

  The optical recording medium 100 according to the present embodiment is configured as a rewritable optical recording medium. As shown in FIG. 3, a support substrate 11 and an information layer 200 formed on the surface of the support substrate 11 The light transmission layer 13 is formed on the surface of the information layer 200. The information layer 200 includes a reflective film 21, a first dielectric film 22 formed on the surface of the reflective film 21, and a second A recording film 210 formed on the surface of the dielectric film 22 and a first dielectric film 24 formed on the surface of the recording film 210 are provided.

  Also in this embodiment, a laser beam is irradiated through the light transmission layer 13, data is recorded on the optical recording medium 100, and the recorded data is reproduced.

  The support substrate 11, the reflective film 21, the second dielectric film 22, the first dielectric film 24, and the light transmission layer 13 of the optical recording medium 100 according to this embodiment are the same as the support substrate 11 and the reflective film shown in FIG. The film 21, the second dielectric film 22, the first dielectric film 24, and the light transmission layer 13 have the same functions and are configured similarly.

  That is, also in this embodiment, the reflective film 21 contains Ag or an alloy containing Ag as a main component, and the second dielectric film 22 is at least one selected from the group consisting of Zn, Al, Ce, and Zr. The main component is an oxide containing the above metal, and nitrogen is added as an additive.

  The recording film 210 is formed of a phase change material, and data is recorded on the recording film 210 by utilizing the fact that the reflectance in the crystalline state is different from the reflectance in the amorphous state, Data is reproduced from the recording film 210.

  The material for forming the recording film 210 is not particularly limited, but it requires a phase change from an amorphous state to a crystalline state in order to be able to directly overwrite data at high speed. The time (crystallization time) is preferably short, and examples of such a material include SbTe-based materials.

  As the SbTe-based material, only SbTe may be used, and an additive may be added in order to further shorten the crystallization time and increase the reliability for long-term storage.

Specifically, among SbTe-based materials represented by the composition formula (Sb _x Te _1-x ) _{1- y My} (M is an element excluding Sb and Te), 0.55 ≦ x ≦ 0. 9. Preferably, the recording film 210 is formed of an SbTe-based material satisfying 0 ≦ y ≦ 0.25, and an SbTe-based material satisfying 0.65 ≦ x ≦ 0.85 and 0 ≦ y ≦ 0.25 More preferably, the recording film 210 is formed.

  The element M is not particularly limited. However, in order to shorten the crystallization time and improve the storage reliability, the element M contains In, Ag, Au, Bi, Se, Al, P, Ge, and H. Si, C, V, W, Ta, Zn, Mn, Ti, Sn, Pd, N, O, and one or more elements selected from the group consisting of rare earth elements are preferable. In particular, in order to improve storage reliability, the element M is preferably composed of one or more elements selected from the group consisting of Ag, In, Ge, and rare earth elements.

  The recording film 210 can be formed by a vapor deposition method such as a vacuum deposition method or a sputtering method.

  Data is recorded on the optical recording medium 100 having the above configuration as follows.

  First, the information layer 200 is irradiated with a laser beam having a predetermined power through the light transmission layer 13. Similar to the above-described embodiment shown in FIG. 2, in this embodiment, a laser beam having a wavelength of 380 nm to 450 nm is passed through an objective lens having a numerical aperture NA satisfying λ / NA ≦ 640 nm. It is focused on.

  By irradiating a laser beam, a predetermined region of the recording film 210 is heated to a temperature equal to or higher than the melting point of the phase change material, and rapidly cooled, so that the region becomes an amorphous state. A predetermined region of the film 210 is heated to a temperature equal to or higher than the crystallization temperature of the phase change material and gradually cooled, so that the region is crystallized. A recording mark is formed by the amorphous region of the recording film 210, and data is configured by the length of the recording mark and the length of the blank region between adjacent recording marks. To be recorded.

  In the present embodiment, since the second dielectric film 22 has a low thermal conductivity, the recording film 210 can be efficiently heated when data is recorded on the information layer 200. Therefore, the region of the recording film 210 irradiated with the laser beam can be quickly heated to a temperature higher than the melting point of the phase change material, and data can be recorded with high sensitivity.

  On the other hand, the data recorded on the recording film 210 is reproduced as follows.

  In reproducing the data recorded on the recording film 210, as in the above embodiment shown in FIG. 2, a laser beam having a wavelength of 380 nm to 450 nm is an objective with a numerical aperture NA satisfying λ / NA ≦ 640 nm. The recorded data is reproduced by detecting the light amount of the laser beam irradiated to the information layer 200 and reflected by the information layer 200 through the lens.

  In the present embodiment, since the second dielectric film 22 has a high refractive index with respect to a laser beam having a wavelength of 380 nm to 450 nm, the region where the recording mark is formed and the recording mark are formed. It is possible to increase the difference in reflectance from the non-existing region. Therefore, the data recorded on the recording film 210 can be reproduced with high sensitivity.

  As described above, according to the present embodiment, while preventing an increase in manufacturing cost, data can be recorded as desired, and the recorded data can be reproduced, and for a long time. This makes it possible to increase the reliability of storage of images.

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

Example 1
First, a polycarbonate substrate having a thickness of 1.1 mm and a diameter of 120 mm and having grooves and lands formed on the surface with a groove pitch of 0.32 μm was manufactured by an injection molding method.

  Next, this polycarbonate substrate was set in a sputtering apparatus, and a reflective film containing Ag, Nd, Cu and having a thickness of 100 nm was formed on the surface of the polycarbonate substrate at a ratio of 98: 1: 1.

  Furthermore, the polycarbonate substrate is set in a sputtering apparatus, and sputtering is performed using a ZnO target in a mixed gas atmosphere in which argon gas and nitrogen gas have flow rates of 10 sccm and 5 sccm, respectively. Nitrogen was added to form a second dielectric film having a thickness of 25 nm. The contents of Zn, O, and N in the second dielectric film were 47.9 atomic%, 47.8 atomic%, and 4.3 atomic%, respectively.

  The contents of Zn, O, and N in the second dielectric film were measured using a fluorescent X-ray analysis (XRF) apparatus “RIX2000” (trade name) manufactured by Rigaku Denki Kogyo Co., Ltd. X-rays were generated under the conditions of 50 kV and tube current = 50 mA, and measurement was performed by the FP method.

Next, the polycarbonate substrate was set in a sputtering apparatus, and a thickness of 7.5 nm in which 23 atomic% Al and 13 atomic% Au were added on the surface of the second dielectric film was added. A first recording film containing Si as a main component and having a thickness of 4.5 nm, and a first recording film containing a mixture of ZnS and SiO ₂ as a main component and having a thickness of 30 nm Dielectric films were sequentially formed by a sputtering method to form an information layer. In forming the first dielectric film, a mixture target having a molar ratio of ZnS and SiO ₂ of 80:20 was used.

  Finally, on the surface of the information layer, an ultraviolet curable acrylic resin is applied by a spin coating method so as to cover at least the entire surface of the information layer, and a coating film is formed. Irradiation was performed to cure the ultraviolet curable acrylic resin to form a light transmission layer having a thickness of 100 μm.

  In this way, sample # 1 was produced.

  Next, the flow rates of the argon gas and the nitrogen gas in the mixed gas were changed to 10 sccm and 10 sccm, respectively, and a second dielectric film having a thickness of 28 nm was formed. Sample # 2 was prepared. The contents of Zn, O, and N in the second dielectric film were 47.1 atomic%, 47.0 atomic%, and 5.9 atomic%, respectively.

  Next, the flow rates of argon gas and nitrogen gas in the mixed gas were changed to 10 sccm and 15 sccm, respectively, and a second dielectric film having a thickness of 31 nm was formed. Sample # 3 was produced. The contents of Zn, O, and N in the second dielectric film were 46.8 atomic%, 46.7 atomic%, and 6.5 atomic%, respectively.

  Next, the flow rates of the argon gas and the nitrogen gas in the mixed gas were changed to 10 sccm and 30 sccm, respectively, and the same as sample # 1, except that a second dielectric film having a thickness of 35 nm was formed. Comparative sample # 1 was produced. The contents of Zn, O, and N in the second dielectric film were 46.3 atomic%, 46.2 atomic%, and 7.5 atomic%, respectively.

  Next, the flow rates of the argon gas and the nitrogen gas in the mixed gas were changed to 10 sccm and 50 sccm, respectively, and a second dielectric film having a thickness of 38 nm was formed. Comparative sample # 2 was produced. The contents of Zn, O, and N in the second dielectric film were 46.1 atomic%, 46.0 atomic%, and 7.9 atomic%, respectively.

  Next, the flow rates of argon gas and nitrogen gas in the mixed gas were changed to 10 sccm and 0 sccm, respectively, except that a second dielectric film having a thickness of 22 nm and not containing nitrogen was formed. Comparative sample # 3 was produced in the same manner as sample # 1. The contents of Zn and O in the second dielectric film were 50.0 atomic% and 50.0 atomic%, respectively.

  Next, sample # 1 was set in an optical recording medium evaluation apparatus “DDU1000” (trade name) manufactured by Pulstec Industrial Co., Ltd., and data was recorded under the following conditions.

  A blue laser beam having a wavelength of 405 nm is condensed on an information layer through a light transmission layer using an objective lens having a numerical aperture NA of 0.85, and (1, 7) RLL under the following recording signal conditions: Recording marks having a length of 2T to 8T in the modulation method were randomly combined and formed on the information layer of sample # 1. When recording data, the recording power Pw of the laser beam was set to 6.2 mW, and the base power Pb was set to 2.0 mW.

  Next, the recording power Pw of the laser beam was gradually increased from 6.2 mW within the range of 6.2 mW to 8.6 mW, and data was sequentially recorded on the information layer of sample # 1.

Modulation method: (1,7) RLL
Recording linear velocity: 4.9 m / sec Channel bit length: 112 nm
Channel clock: 66 MHz

  Next, data was recorded on the information layer for Sample # 2 to Comparative Sample # 3 in the same manner as Sample # 1 using the optical recording medium evaluation apparatus described above. When recording data in sample # 2 to comparison sample # 3, the laser beam base power Pb is fixed at 2.0 mW, and the laser beam recording power Pw is in the range of 6.2 mW to 8.2 mW, respectively. The range was gradually increased in the range of 5.8 mW to 8.0 mW, in the range of 5.8 mW to 8.0 mW, in the range of 6.4 mW to 8.2 mW, and in the range of 7.2 mW to 9.8 mW.

  Next, using the above-described optical recording medium evaluation apparatus, data recorded in the information layers of Sample # 1 to Comparative Sample # 3 was reproduced, and jitter was measured. The jitter was calculated by obtaining “fluctuation σ” of the reproduction signal by a time interval analyzer and by σ / Tw (Tw: one cycle of the clock). In reproducing data, a laser beam having a wavelength of 405 nm and an objective lens having a numerical aperture NA of 0.85 were used for all samples, and the reproduction power Pr of the laser beam was set to 0.35 mW.

  The jitter measurement results of sample # 1 to comparison sample # 3 are shown by curves A to F in FIG. 4, respectively, and the minimum jitter and the minimum jitter when data recorded in the information layer is reproduced are obtained. Table 1 shows the recording power Pw of the laser beam when the recorded data is recorded.

  As apparent from FIG. 4 and Table 1, in samples # 1 to # 3 having a nitrogen content of 4 to 7 atomic%, the recording of the laser beam when data with the minimum jitter was recorded. The power Pw was 8.0 mW or less in all cases. On the other hand, in the comparative samples # 1 to # 3 in which the nitrogen content is outside the range of 4 atomic% to 7 atomic%, the recording power Pw of the laser beam when data with the minimum jitter is recorded is , Both exceeded 8.0 mW. From these results, it was confirmed that in samples # 1 to # 3, the recording sensitivity was improved and the recording power Pw of the laser beam when recording data could be reduced.

  Further, as apparent from FIG. 4 and Table 1, in Samples # 1 to # 3, the minimum jitter value was 5.5% or less, whereas in Comparative Samples # 1 to # 3 The minimum value of jitter exceeded 5.5%. From these results, it was found that in samples # 1 to # 3, not only the recording power Pw of the laser beam can be lowered, but also the jitter can be reduced.

Example 2
Sputtering using a CeO ₂ target and an Al ₂ O ₃ target in a mixed gas atmosphere with an argon gas flow rate and a nitrogen gas flow rate of 35 sccm and 10 sccm, respectively, gave a mixture of CeO ₂ and Al ₂ O _3. Sample # 4 was prepared in the same manner as Sample # 1, except that a second dielectric film containing nitrogen as a main component was added. The contents of Ce, Al, O and N in the second dielectric film are 20.9 atomic%, 10.4 atomic%, 57.5 atomic% and 11.2 atomic%, respectively, The thickness of the second dielectric film was 28 nm.

  Next, the flow rates of argon gas and nitrogen gas in the mixed gas were changed to 35 sccm and 15 sccm, respectively, and the same as sample # 4, except that a second dielectric film having a thickness of 31 nm was formed. Sample # 5 was prepared. The contents of Ce, Al, O and N in the second dielectric film were 20.4 atomic%, 10.2 atomic%, 56.0 atomic% and 13.4 atomic%, respectively.

  Next, the flow rates of the argon gas and the nitrogen gas in the mixed gas were changed to 35 sccm and 30 sccm, respectively, and a second dielectric film having a thickness of 38 nm was formed. Sample # 6 was produced. The contents of Ce, Al, O and N in the second dielectric film were 19.5 atomic%, 9.7 atomic%, 53.6 atomic% and 17.2 atomic%, respectively.

  Next, the flow rates of the argon gas and nitrogen gas in the mixed gas were changed to 35 sccm and 50 sccm, respectively, and the same as sample # 4, except that a second dielectric film having a thickness of 38 nm was formed. Sample # 7 was produced. The contents of Ce, Al, O and N in the second dielectric film were 18.9 atomic%, 9.4 atomic%, 52.0 atomic% and 19.7 atomic%, respectively.

  Next, the flow rates of the argon gas and the nitrogen gas in the mixed gas were changed to 10 sccm and 5 sccm, respectively, and the same as sample # 4, except that a second dielectric film having a thickness of 25 nm was formed. Comparative sample # 4 was prepared. The contents of Ce, Al, O and N in the second dielectric film were 21.8 atomic%, 10.9 atomic%, 59.8 atomic% and 7.5 atomic%, respectively.

  Next, the flow rates of argon gas and nitrogen gas in the mixed gas were changed to 35 sccm and 0 sccm, respectively, except that a second dielectric film having a thickness of 22 nm and not containing nitrogen was formed. Comparative sample # 5 was produced in the same manner as # 4. The contents of Ce, Al, and O in the second dielectric film were 23.5 atomic%, 11.8 atomic%, and 64.7 atomic%, respectively.

  Next, in the same manner as in Example 1, data was recorded in the information layers of Sample # 4 to Comparative Sample # 5 using the above-described optical recording medium evaluation apparatus. When recording data in sample # 4 to comparative sample # 5, the laser beam base power Pb is fixed at 2.0 mW, and the laser beam recording power Pw is in the range of 5.2 mW to 7.2 mW, respectively. In the range of 5.2 mW to 7.2 mW, in the range of 5.2 mW to 7.2 mW, in the range of 5.2 mW to 7.2 mW, in the range of 5.4 mW to 7.2 mW, in the range of 5.6 mW to 7.6 mW I raised it little by little.

  Next, in the same manner as in Example 1, the data recorded in the information layer of Sample # 4 to Comparative Sample # 5 was reproduced using the above-described optical recording medium evaluation apparatus, and jitter was measured.

  The jitter measurement results of sample # 4 to comparative sample # 5 are shown by curves G to L in FIG. 5, respectively, and the minimum jitter and the minimum jitter when data recorded in the information layer is reproduced are obtained. Table 2 shows the recording power Pw of the laser beam when the recorded data is recorded.

  As is clear from FIG. 5 and Table 2, in samples # 4 to # 7 in which the nitrogen content is 9 atomic% or more, the recording power Pw of the laser beam when data with the minimum jitter is recorded is , Both were 6.2 mW or less, but in Comparative Samples # 4 and 5 in which the nitrogen content was less than 9 atomic%, the laser beam when recording data with minimum jitter was recorded. Recording power Pw exceeded 6.2 mW. From these results, it was confirmed that in samples # 4 to # 7, the recording sensitivity was improved and the recording power Pw of the laser beam when recording data could be reduced.

  Further, as apparent from FIG. 5 and Table 2, among samples # 4 to # 7, in samples # 4 and 5, the minimum value of jitter is 5.6% or less. It has been found that not only the recording power Pw of the laser beam can be lowered, but also the jitter can be reduced.

  The present invention is not limited to the above embodiments and examples, and various modifications can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. It goes without saying that it is a thing.

  For example, in the embodiment shown in FIGS. 1 to 3, the optical recording medium 10, 100 includes the support substrate 11, the information layers 20, 200, and the light transmission layer 13, and includes only one information layer. However, the present invention is not limited to an optical recording medium having a single information layer, and can be widely applied to an optical recording medium having two or more information layers. In this case, the information layers of two or more layers are all recording films, a dielectric film containing a dielectric material substantially not containing sulfur as a main component, to which nitrogen is added, and Ag or Ag. It is not always necessary that the reflective film containing the alloy containing as a main component includes a laminated body that is laminated in order from the light incident surface of the laser beam, and at least one of the two or more information layers However, what is necessary is just to include this laminated body.

  Further, in the embodiment shown in FIGS. 1 to 3, the optical recording media 10 and 100 have the second dielectric film so as to sandwich the second recording film 23b, the first recording film 23a, and the recording film 210. The body film 22 and the first dielectric film 24 are formed. In the present invention, the recording film is sandwiched between the two dielectric films 22 and the first dielectric film 24. It is not always necessary to omit the first dielectric film 24 when the difference in light reflectance between the region where the recording mark is formed and the region where the recording mark is not formed is sufficiently large. You can also.

  In the embodiment shown in FIGS. 1 and 2, the optical recording medium 10 is formed so that the second recording film 23b and the first recording film 23a are in contact with each other. In the recording film 23b, when the laser beam is irradiated, an element contained as a main component in the second recording film 23b and an element contained as a main component in the first recording film 23a are mixed. Thus, it is sufficient that the mixed region is formed in the vicinity of the first recording film 23a, and a dielectric film or the like is provided between the second recording film 23b and the first recording film 23a. One or more other membranes may be present.

  Further, in the embodiment shown in FIGS. 1 to 3, the optical recording media 10 and 100 include the light transmission layer 13, but instead of the light transmission layer 13 or on the surface of the light transmission layer 13. In addition, a hard coat layer containing the hard coat composition as a main component may be provided, and a lubricant may be included in the hard coat layer in order to impart lubricity and antifouling functions. A lubricating layer containing a lubricant as a main component may be separately provided on the surface of the hard coat layer.

FIG. 1 is a schematic perspective view of 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 showing the layer structure of the optical recording medium according to a preferred embodiment of the present invention. 6 is a graph showing a measurement result of jitter in Example 1. 10 is a graph showing the measurement result of jitter in Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical recording medium 11 Support substrate 11a Groove 11b Land 13 Light transmission layer 20 Information layer 21 Reflective film 22 Second dielectric film 23b Second recording film 23a First recording film 24 First dielectric film 100 Optical recording Medium 200 Information layer 210 Recording film

Claims (1)

A substrate, and an information layer including a stacked body in which a recording film, a dielectric film, and a reflective film are stacked in this order from the light incident surface side, and the reflective film includes Ag, Or an alloy containing Ag as a main component, and the dielectric film contains substantially no sulfur and a Zn oxide or a mixture of Ce oxide and Al oxide as a main component, and the dielectric When the film contains Zn oxide as the main component, 4 to 7 atomic percent of nitrogen is added, and when the film contains a mixture of Ce oxide and Al oxide as the main component, 10 atom% An optical recording medium, wherein 12 atomic% of nitrogen is added.

Images