JP2010205327A - Optical recording medium and recording method of optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium which is manufactured by suppressing an increase in cost and is compatible with both rewritable type recording and write-once type recording, and to provide a recording method of the optical recording medium. <P>SOLUTION: The optical recording medium 1 to/from which data is recorded and reproduced by irradiation with a laser beam L, includes: a substrate 10 having grooves and lands formed on the surface thereof; a first recording film 23 formed on the surface of the substrate 10 and made of a material reversibly changing by irradiation with the laser beam L; and a second recording film 24 made of a material irreversibly changing by irradiation with the laser beam L. The first recording film 23 is formed on the grooves and lands, and the second recording film 24 is formed on only the grooves. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical recording technique, and more particularly to an optical recording medium capable of rewritable recording and write-once recording, and a recording method for the optical recording medium.

  There is a demand for further increasing the capacity of optical recording media, such as compact discs (CD) and digital versatile discs (DVD), in which a recording layer is formed on a substrate. The optical recording medium records data corresponding to a change in optical state detectable by light in the recording layer. In recent years, Blu-ray discs and the like that can increase the capacity several times that of DVDs have attracted attention due to the development of blue lasers and lenses with a high numerical aperture NA.

  Currently, optical recording media such as Blu-ray discs are roughly classified into two types according to the data recording method. One is a rewritable disc used for rewritable recording using a reversibly changing material for the recording layer, and the other is a write once used for write once recording that can be recorded only once using an irreversible changing material. Type disc. Further, write-once discs include a recording medium using an organic dye as a recording layer material and a recording medium using an inorganic material.

  In the case of using an organic dye as the recording layer material and when using an inorganic material, the recording medium using the organic dye as the recording layer material records data in the groove of the guide groove, In a recording medium using an inorganic material, data can be recorded on the groove portion (land) of the guide groove.

  In addition to a single layer structure rewritable optical recording medium and a write once optical recording medium having a single recording layer, the recording layer includes a recording layer used for rewritable recording and a recording layer used for write once recording. A two-layer optical recording medium has been proposed (see, for example, Patent Document 1).

JP 2007-109369 A

  Although the rewritable optical recording medium has an advantage that the recorded data can be erased and new data can be recorded, there is a risk that the data will be tampered with or erased. On the other hand, the write-once type dedicated optical recording medium cannot tamper with data, but cannot correct data recorded by mistake. Further, the two-layer optical recording medium has a problem that the structure is very complicated and the manufacturing cost increases.

  In view of the above problems, an object of the present invention is to provide an optical recording medium and a recording method for the optical recording medium that can be used for both rewritable recording and write-once recording while suppressing an increase in manufacturing cost.

  According to one aspect of the present invention, there is provided an optical recording medium on which data is recorded / reproduced by laser light irradiation, (a) a substrate having grooves and lands formed on the surface, and (b) on the surface of the substrate. A first recording film made of a material that reversibly changes when irradiated with laser light, and a second recording film made of a material that changes irreversibly when irradiated with laser light, and the first recording film is formed on the grooves and lands. An optical recording medium in which the second recording film is formed only on the groove is provided.

  According to another aspect of the present invention, a substrate having grooves and lands formed on the surface, a first recording film made of a material that is formed on the grooves and lands and reversibly changes when irradiated with laser light, and formed on the grooves. A recording method for an optical recording medium comprising a second recording film made of a material that changes irreversibly upon irradiation with laser light, wherein: (a) the first recording film formed on the land is irradiated with laser light; A first recording step for forming a recording mark based on information on one recording film; (b) an erasing step for erasing the recording mark formed on the first recording film; and (c) after the erasing step, And a second recording step of forming a recording mark based on information on the second recording film by irradiating the second recording film with a laser beam.

  ADVANTAGE OF THE INVENTION According to this invention, the increase in manufacturing cost is suppressed and the optical recording medium which can be used for both rewritable recording and write-once recording, and the recording method of an optical recording medium can be provided.

1 is a schematic cross-sectional view showing a configuration of an optical recording medium according to an embodiment of the present invention. It is process sectional drawing for demonstrating the manufacturing method of the optical recording medium which concerns on embodiment of this invention (the 1). It is process sectional drawing for demonstrating the manufacturing method of the optical recording medium which concerns on embodiment of this invention (the 2). It is process sectional drawing for demonstrating the manufacturing method of the optical recording medium which concerns on embodiment of this invention (the 3). 3 is a flowchart for explaining a recording method of an optical recording medium according to an embodiment of the present invention. It is a flowchart for demonstrating the comparative example of the recording method of an optical recording medium. It is typical sectional drawing which shows the structure of the optical recording medium of a comparative example. It is a flowchart for demonstrating the other comparative example of the recording method of an optical recording medium.

  Embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the embodiments described below exemplify apparatuses and methods for embodying the technical idea of the present invention, and the embodiments of the present invention include the material, shape, structure, The layout is not specified as follows. Various modifications can be made to the embodiment of the present invention within the scope of the claims.

  An optical recording medium according to an embodiment of the present invention is an optical recording medium 1 on / from which data is recorded / reproduced by irradiation with a laser beam L, and a substrate having guide grooves formed on the surface thereof as shown in FIG. 10 and a first recording film 23 formed on the substrate 10 made of a material reversibly changed by the irradiation of the laser light L and a second recording film 24 made of a material irreversibly changed by the irradiation of the laser light L. A body 20.

  The substrate 10 is formed with a groove (groove) and an inter-groove (land). Here, the land formed on the substrate 10 is a convex portion as seen from the incident direction of the laser beam L, and the groove is a concave portion as seen from the incident direction of the laser beam L, as shown in FIG. On the surface of the substrate 10 on which the grooves and lands are formed, a reflective film 21, a first protective film 22, and a first recording film 23 are sequentially laminated. Furthermore, the second recording film 24 is formed only on the first recording film 23 formed on the groove. A second protective film 25 is formed on the groove and the land so as to cover both the first recording film 23 and the second recording film. A cover film 26 is formed on the second protective film 25.

  Therefore, on the groove of the substrate 10, the reflective film 21, the first protective film 22, the first recording film 23, the second recording film 24, the second protective film 25, and the cover film 26 are formed in this order. On the land of the substrate 10, a reflective film 21, a first protective film 22, a first recording film 23, a second protective film 25, and a cover film 26 are formed in this order. In the laminate 20 formed on the substrate 10, a recording area including the first recording film 23 formed on the land and not including the second recording film 24 is defined as a first recording area 101, and the first recording area is formed on the groove. A recording area including the first recording film 23 and the second recording film 24 is defined as a second recording area 102. The reflective film 21, the first protective film 22, the first recording film 23, the second protective film 25, and the cover film 26 are formed in common in the first recording area 101 and the second recording area 102.

The “guide groove” is a groove formed on the surface of the optical recording medium as a tracking guide for recording / reproducing laser light. Groove portions (grooves) and inter-groove portions (lands) are alternately arranged on the surface of the substrate 10 on which the guide grooves are formed. The width of one unit composed of one groove and one land is the tracking width in recording / reproducing of the optical recording medium 1 by irradiation with the laser beam L. For example, the sum of the groove width w _IN and the land width w _ON is about 320 nm. At this time, if the land width w _ON is made wider than the groove width w _IN , the optical recording medium 1 in which the second recording film 24 is not formed on the land can be easily formed. _{Therefore, w IN: w ON = 140nm} : 180nm, or _w IN: _{w ON} = 120nm: may be as 200nm.

  As shown in FIG. 1, the laser beam L used for recording / reproducing data is applied to the optical recording medium 1 from the cover film 26 side. In FIG. 1, the position of the laser beam L when data is recorded on the recording film formed on the land of the guide groove (hereinafter referred to as “on-groove recording”) is indicated by a solid line, and the data is recorded on the groove of the guide groove. The position of the laser beam L when data is recorded on the formed recording film (hereinafter referred to as “in-groove recording”) is indicated by a broken line.

  The first recording area 101 has a structure capable of rewritable recording. In the first recording area 101, the first recording film 23 is used as a recording layer for rewriting. The first protective film 22 and the second protective film 25 suppress heat from escaping from the first recording film 23 when irradiated with the laser light L. For this reason, the first recording film 23 is kept at a temperature at which data is efficiently recorded. As described above, the first recording area 101 is used as a rewritable recording area.

  The second recording area 102 has a structure capable of non-rewritable write-once recording. The structure of the second recording area 102 is different from the first recording area 101 in that the structure of the first recording area 101 further includes a second recording film 24. In the second recording area 102, the second recording film 24 is used as a recording layer for additional recording. The first recording film 23 in the second recording area 102 is not used as a recording layer, and improves the heat radiation from the second recording film 24 when irradiated with the laser beam L.

  Therefore, in the optical recording medium 1, rewritable recording is performed in the case of on-groove recording, and data is recorded on the first recording film 23 in the first recording area 101. On the other hand, write-once recording is performed in the case of in-groove recording, and data is recorded on the second recording film 24 in the second recording area 102.

  Since the substrate 10 does not need to transmit the laser beam L, a material may be appropriately selected in consideration of physical strength and manufacturing cost. As the material of the substrate 10, for example, glass, polycarbonate, polymethyl methacrylate, polyolefin resin, epoxy resin, polyimide resin, or the like can be used. Among these, polycarbonate is suitable for the material of the substrate 10 because it can be easily molded and has low hygroscopicity.

  The reflective film 21 is a layer for reflecting the laser light L irradiated from the cover film 26 side and improving the efficiency of data recording / reproducing on the optical recording medium 1. The reflective film 21 is made of a light-reflective metal film such as aluminum (Al), gold (Au), silver (Ag), or the like, and an additive element made of one or more kinds of metals or semiconductors mainly composed of these metals. An alloy film including the above, or a film obtained by mixing a metal compound such as metal nitride such as Al or silicon (Si), metal oxide, or metal chalcogenide with the above metal can be used. Examples of alloys include Si, magnesium (Mg), copper (Cu), palladium (Pd), titanium (Ti), chromium (Cr), hafnium (Hf), tantalum (Ta), niobium (Nb), manganese ( Mn), zirconium (Zr), etc., an alloy in which at least one element is mixed with Al, or Cr, Ag, Cu, Pd, platinum (Pt), nickel (Ni), neodymium (Nd), indium (In In general, an alloy in which at least one element is mixed with Au or Ag. Among them, Ag and an alloy containing Ag as a main component have high light reflectivity with respect to a blue-violet wavelength, can increase thermal conductivity, and can increase signal intensity when the optical recording medium 1 is a Blu-ray disc. preferable.

  The film thickness of the reflective film 21 is appropriately set according to the thermal conductivity of the material of the reflective film 21. If the thickness of the reflective film 21 is 20 nm or more, the reflective film 21 does not change optically and does not affect the reflectance value. However, as the thickness of the reflective film 21 increases, the influence on the cooling rate increases. The thickness of the reflective film 21 is preferably about 20 nm to 300 nm, for example.

  The refractive index n of the first protective film 22 and the second protective film 25 is preferably in the range of 1.9 ≦ n ≦ 2.5. This is to clarify the contrast when the optical recording medium 1 is irradiated with the laser light L in the area where the data of the optical recording medium 1 is recorded and the area where the data is not recorded. When n is small, it is necessary to increase the film thickness in order to clarify the contrast. An appropriate refractive index n for satisfying the thicknesses of the first protective film 22 and the second protective film 25 as an optical recording medium is 1.9 ≦ n ≦ 2.5. In addition, the film thickness and refractive index n of the 1st protective film 22 and the 2nd protective film 25 are set arbitrarily, and the optical path length of the laser beam L is adjusted to a desired value. The second protective film 25 is made of a material that transmits the laser light L.

The first protective film 22 and the second protective film 25 have an effect of maintaining the temperature of the first recording film 23 made of an inorganic material when irradiated with the laser light L. From the viewpoint of thermal characteristics, the materials of the first protective film 22 and the second protective film 25 include silicon dioxide (SiO ₂ ), silicon monoxide (SiO), zinc oxide (ZnO), titanium oxide (TiO ₂ ), and oxidation. Simple substance of oxide such as tantalum (Ta ₂ O ₅ ), niobium oxide (Nb ₂ O ₅ ), zirconia oxide (ZrO ₂ ), magnesium oxide (MgO), zinc sulfide (ZnS), indium sulfide (In ₂ S ₃ ) A simple substance of sulfide such as tantalum sulfide (TaS ₄ ), a simple substance of carbide such as tantalum carbide (TaC), tungsten carbide (WC), titanium carbide (TiC), or a mixture thereof is preferable. Among these, a mixed film of ZnS and SiO ₂ is particularly preferable because it has a good C / N ratio, which is one of recording sensitivity and reliability characteristics, and has a high film formation rate and high productivity.

  For the first recording film 23, an inorganic material or the like that reversibly changes when irradiated with the laser beam L can be used. For example, a phase change material can be used for the first recording film 23. Here, the “phase change material” is a material that reversibly changes between a crystal and an amorphous state when irradiated with the laser beam L. Specifically, based on the three elements of germanium-antimony-tellurium (Ge-Sb-Te), an alloy material containing any one of Ag, In, Ti, Al, and Cu is the first phase change material. Used for the recording film 23.

  For the second recording film 24, for example, a material mainly containing an organic dye that absorbs the laser light L and changes irreversibly upon irradiation with the laser light L can be used. Specifically, methine-based, azo-based, pyrone-based, porphyrin-based compounds, or a mixture of these organic dyes can be employed as the main organic dye of the second recording film 24. In addition, as a material used for the second recording film 24, it is preferable to select a material that does not absorb light having a wavelength other than the wavelength of the laser light L. For example, when the optical recording medium 1 is a Blu-ray disc and the laser light L is blue laser light, a material that hardly absorbs light having a wavelength other than 405 nm is used for the second recording film 24.

  Further, considering the sensitivity at the time of recording, the second recording film 24 is preferably a material that has a decomposition start temperature in the differential thermal analysis (IG-DTA) between 150 ° C. and 400 ° C. and causes an exothermic reaction as a reaction. . This is because the portion of the organic dye irradiated with the laser beam L during recording gasifies and expands, and mainly deforms toward the second protective film 25, thereby causing a phase difference between the unrecorded portion and the recorded portion. It is for generating. Due to the phase difference, the reflectance of the laser beam L changes between the unrecorded portion and the recorded portion, the contrast becomes clear, and the recorded data can be easily read.

  The cover film 26 is a layer that protects the surface of the optical recording medium 1 and adjusts the distance from the surface to the recording layer. The thickness of the cover film 26 is adjusted so that the distance from the surface of the optical recording medium 1 irradiated with the laser light L to the first recording film 23 and the second recording film 24 is optimal at the time of pickup or the like.

  The cover film 26 is formed by a spin coating method, a roller bonding method, or the like. When the cover film 26 is formed using the spin coating method, urethane, epoxy, acrylic resin, or the like is used as the material of the cover film 26. After these resins are applied by a spin coating method, ultraviolet rays or the like are irradiated to accelerate radical polymerization or cationic polymerization to cure the resins, thereby forming the cover film 26. When the cover film 26 is formed by using the roller bonding method, for example, the center position of a polymer sheet such as a pressure-sensitive adhesive polycarbonate having a film thickness of about 0.1 mm is aligned with the center position of the optical recording medium 1. Then, the cover film 26 is formed by applying pressure with a roller from above the polymer sheet superimposed on the optical recording medium 1.

  In general, a two-layer optical recording medium is manufactured by superimposing a substrate having a rewritable recording layer used for rewritable recording and a substrate having a write-once recording layer used for write-once recording. Further, the production yield of the two-layer optical recording medium depends on both the production yield of the substrate having the rewritable recording layer and the production yield of the substrate having the write-once recording layer, so that the manufacturing cost of the two-layer optical recording medium increases. To do.

  However, in the optical recording medium 1 shown in FIG. 1, the first recording film 23 and the second recording film 24 are not separated by a separation layer or the like, and the second recording film 24 is directly formed on the first recording film 23. Has been. For this reason, the process for forming the separation layer is unnecessary, and the process for overlaying the rewritable recording layer and the write-once recording layer is also unnecessary, so that an increase in manufacturing period and manufacturing cost is suppressed.

  As described above, the optical recording medium 1 shown in FIG. 1 includes the first recording film 23 made of rewritable recording made of, for example, an inorganic material, and the second recording made of write-once recording made of, for example, an organic material. The membrane 24 is provided together. The second recording film 24 is disposed only on the groove. That is, according to the optical recording medium 1 according to the embodiment of the present invention, the rewritable recording is performed by on-groove recording, and the write-once recording is performed by in-groove recording, thereby suppressing an increase in manufacturing cost and rewriting. An optical recording medium that can be used for both mold recording and write-once recording can be realized.

  A method for manufacturing the optical recording medium 1 according to the embodiment of the present invention will be described with reference to FIGS. The optical recording medium manufacturing method described below is an example, and it is needless to say that the optical recording medium can be realized by various other manufacturing methods including this modification.

  (A) A substrate 10 having a thickness of about 1.1 mm and having guide grooves formed on the surface thereof is prepared. As shown in FIG. 2, a reflective film 21 having a thickness of about 20 nm to 300 nm, a first protective film 22 having a thickness of about 5 nm to 50 nm, and a first recording film 23 having a thickness of about 5 nm to 50 nm are formed on the surface of the substrate 10. Are sequentially laminated by a sputtering method or the like.

  (B) Next, an organic dye is dissolved in tetrafluoropropanol at a concentration of 0.3 wt% and applied onto the first recording film 23 by a spin coating method to form the second recording film 24. At this time, as shown in FIG. 3, the spin coating conditions are set so that the organic dye is accumulated only in the groove, so that the organic dye does not remain on the land. The film thickness of the second recording film 24 is adjusted to about 10 nm to 60 nm.

  (C) As shown in FIG. 4, a second protective film 25 having a thickness of about 10 nm to 200 nm is formed on the upper surfaces of the first recording film 23 and the second recording film 24 by sputtering. That is, in the first recording area 101 on the land, the second protective film 25 is disposed on the first recording film 23, and in the second recording area 102 on the groove, the second protective film 25 is disposed on the second recording film 24. Is done.

  (D) The cover film 26 is formed on the second protective film 25 by using the spin coating method or the roller bonding method described above. Thus, the optical recording medium 1 shown in FIG. 1 is completed.

  The film thickness of the laminate 20 from the reflective film 21 to the cover film 26 is about 0.1 mm. The depth of the guide groove formed on the surface of the substrate 10 is set to about 30 nm to 100 nm, for example. For example, the depth of the guide groove is determined according to the material and film thickness of each of the reflective film 21, the first protective film 22, the first recording film 23, and the second recording film 24 disposed in the groove.

  As described above, the second recording film 24 is formed by using the spin coating method, but each film other than the second recording film 24 uses a sputtering method, a vacuum deposition method, a chemical vapor deposition (CVD) method, or the like. Can be formed.

  When the organic dye is applied by spin coating to form the second recording film 24, as described above, conditions are set so that the organic dye accumulates only in the groove, and the organic dye is formed on the land. It is necessary not to remain. This is because if the organic dye is on the land, the organic dye reacts when recording on the first recording film 23 on the land, and adversely affects the subsequent reproduction / erasure of the first recording film 23. It is because it exerts. Among them, the solubility x of the organic dye with respect to tetrafluoropropanol is preferably 0.3 weight percent (wt%) ≦ x ≦ 0.5 wt% in view of maintaining good recording characteristics. It has been experimentally obtained that the rotation speed of the substrate in the method is preferably 2000 rpm or more.

  If the second recording film 24 is formed on the first recording film 23 formed on the land, the second recording film 24 also reacts when data is recorded on the first recording film 23 by on-groove recording. End up. For this reason, subsequent rewritable recording becomes impossible. Therefore, it is very important that the first recording film 23 is formed on the land but the second recording film 24 is not formed.

  According to the method for manufacturing an optical recording medium according to the embodiment of the present invention as described above, the first recording area 101 disposed on the land and including the first recording film 23 but not including the second recording film 24 is provided. The optical recording medium 1 can be provided including the second recording region 102 which is disposed on the groove and has a structure in which the second recording film 24 is disposed on the first recording film 23.

  Next, a result of manufacturing the optical recording medium 1 according to the embodiment of the present invention and evaluating recording / reproduction will be described. Here, a case where the optical recording medium 1 is a Blu-ray disc and the laser light L is 405 nm blue laser light, which is a wavelength that causes an irreversible change in the second recording film 24, will be described as an example. When recording / reproducing / erasing is performed in the first recording area 101 by irradiating the laser beam L, the land is tracked, and recording / reproducing is performed in the second recording area 102 by irradiating the laser beam L. When reproducing, the groove is tracked.

<Example 1>
A method for manufacturing the optical recording medium according to Example 1 will be described below. That is, after the reflective film 21, the first protective film 22, and the first recording film 23 are formed on the substrate 10 by the sputtering method, the organic dye as the second recording film 24 is added to the tetrafluoropropanol at a concentration of 0.3 wt%. And dissolved on the first recording film 23 by spin coating. Thereafter, the second protective film 25 was formed by a sputtering method. Finally, the ultraviolet (UV) curable resin applied on the second protective film 25 was cured to form the cover film 26.

  The optical recording medium manufactured as described above was evaluated according to the flowchart shown in FIG. In step S11, the first recording film 23 is initialized using laser light having a wavelength of 600 nm to 800 nm, for example, red laser light having a wavelength of 680 nm, and then in step S12, the first recording region 101 is irradiated with the laser light L. Recording / reproducing / erasing was performed five times on the first recording film 23. Thereafter, in step S13, the recording mark of the first recording film 23 recorded for the fifth time was erased. In step S14, the second recording area 102 was irradiated with laser light L, and recording / reproduction was performed on the second recording film 24.

  During the reproduction of the first recording film 23 in step S12, it was possible to read the recording mark from the first recording film 23. Furthermore, it was possible to read the recording mark from the second recording film 24 during the reproduction of the second recording film 24 in step S14.

<Example 2>
The optical recording medium according to Example 2 manufactured in the same manner as Example 1 was evaluated according to the flowchart shown in FIG. In step S11, the land was tracked and the first recording film 23 on the land was initialized using blue laser light. In step S12, recording / reproducing / erasing was performed five times on the first recording film 23. Thereafter, in step S13, the recording mark of the first recording film 23 recorded for the fifth time was erased. In step S14, recording / reproduction was performed on the second recording film 24.

  During the reproduction of the first recording film 23 in step S12, it was possible to read the recording mark from the first recording film 23. Furthermore, it was possible to read the recording mark from the second recording film 24 during the reproduction of the second recording film 24 in step S14.

  In Example 1 and Example 2, the first recording film 23 was initialized before data was recorded on the first recording film 23. Here, “initialization” is to make the first recording film 23 in the first recording area 101 in a state where data can be recorded / reproduced after the optical recording medium 1 is manufactured. For example, when the first recording film 23 includes a phase change material, the first recording film 23 that is in an amorphous state at the time of manufacture is crystallized.

  When the optical recording medium 1 is a Blu-ray disc as described above, the first recording film 23 is initialized by irradiating the laminate 20 with laser light having a wavelength of 600 nm to 800 nm, for example, red laser light. Alternatively, tracking is performed on the land, and blue laser light (laser light L may be used) is applied only to the first recording area 101 to initialize the first recording film 23 in the first recording area 101. .

  Even when the optical recording medium 1 is not a Blu-ray disc, the initialization of the first recording film 23 is similarly performed. That is, the first recording film 23 is initialized by irradiating the stacked body 20 with a laser beam having a wavelength that does not cause an irreversible change in the second recording film 24. Alternatively, the first recording film 23 in the first recording area 101 may be initialized by irradiating only the first recording area 101 with laser light L having a wavelength that causes irreversible changes in the second recording film 24.

  The data recorded on the first recording film 23 in the first recording area 101 can be erased by tracking the land and irradiating only the first recording area 101 with the laser beam L.

  Comparative Examples 1 to 4 below are examples in which a recording mark could not be correctly read from the first recording film 23 and the second recording film 24 during reproduction.

<Comparative Example 1>
The optical recording medium according to Comparative Example 1 manufactured in the same manner as Example 1 was evaluated according to the flowchart shown in FIG. In step S21, the first recording film 23 was initialized using a red laser beam having a wavelength of 680 nm, and in step S22, recording / reproduction was performed on the second recording film 24. Thereafter, in step S23, recording / reproducing / erasing was performed five times on the first recording film 23.

  During the reproduction of the second recording film 24 in step S22, it was possible to read the recording mark from the second recording film 24. However, at the time of recording / reproduction of the first recording film 23 in step S23, the leakage of the signal from the second recording film 24 in the second recording area 102 adjacent to the first recording area 101 to be read is severe. The recording mark could not be read from the first recording film 23. “Signal leakage” refers to, for example, a signal obtained by irradiating the adjacent recording area adjacent to the recording area to be read with the laser beam L and reading the recording mark recorded in the recording area to be read, This means that the signal read from the recording mark recorded in the recording area is mixed during reproduction. When signal leakage occurs, the recording mark recorded in the recording area to be read cannot be read accurately.

  In addition, when the second recording film 24 is reproduced after data is recorded on the first recording film 23, the leakage of the signal from the first recording film 23 is severe, and the recording recorded on the second recording film 24 is performed. The signal based on the mark could not be reproduced.

  That is, in order to correctly read the recording mark formed on the second recording film 24, after the write-once recording is performed on the second recording film 24, the rewritable recording on the first recording film 23 is performed. Can not. Therefore, in the optical recording medium 1 according to the embodiment of the present invention, when rewritable recording is performed in the first recording area 101, the first recording area is recorded before the write-once recording in the second recording area 102 is performed. It is necessary to perform rewritable recording at 101.

<Comparative example 2>
A method for manufacturing an optical recording medium according to Comparative Example 2 will be described below. The structure of the optical recording medium according to Comparative Example 2 is shown in FIG. After the reflective film 21 and the first protective film 22 are formed on the substrate 10 by the sputtering method, the organic dye as the material of the second recording film 24 is dissolved in tetrafluoropropanol at a concentration of 0.3 wt%, and spin coating is performed. The first protective film 22 was applied by the method. Thereafter, a first recording film 23 and a second protective film 25 were formed on the second recording film 24 by sputtering. Finally, the UV curable resin applied on the second protective film 25 was cured to form the cover film 26. The optical recording medium according to Comparative Example 2 is different from the optical recording medium 1 shown in FIG. 1 in that the first recording film 23 is formed on the second recording film 24 as shown in FIG.

  The optical recording medium of Comparative Example 2 produced as described above was evaluated according to the flowchart shown in FIG. During the reproduction of the first recording film 23 in step S12, it was possible to read the recording mark from the first recording film 23. However, data could not be recorded on the second recording film 24 in step S14. This is because when the data is recorded on the second recording film 24, the laser light L is absorbed by the first recording film 23, and the energy of the laser light L is not efficiently transmitted to the second recording film 24. It is estimated to be.

  Therefore, in the second recording area 102, the second recording film 24 needs to be formed on the first recording film 23.

<Comparative Example 3>
The optical recording medium according to Comparative Example 3 manufactured in the same manner as Example 1 was evaluated according to the flowchart shown in FIG. In step S31, the first recording film 23 was initialized using a red laser beam having a wavelength of 680 nm, and then recording / reproduction was performed on the first recording film 23 in step S32. After that, in step S33, recording / reproduction was performed on the second recording film 24 with the recording mark recorded on the first recording film 23. As a result, at the time when data was recorded only on the first recording film 23 in step S32, it was possible to reproduce the signal based on the reading of the recording mark. However, in the state where the recording mark remains in the first recording film 23 in step S33, the signal leakage from the first recording film 23 is severe and based on the reading of the recording mark on the second recording film 24. It was difficult to reproduce the signal.

  Therefore, before reproducing the data recorded on the second recording film 24 (or reading the recording marks recorded on the second recording film 24), the recording marks recorded on the first recording film 23 are erased. is required.

<Comparative example 4>
The optical recording medium according to Comparative Example 4 was changed in the same manner as the optical recording medium according to Example 1 except that the dissolution concentration of the organic dye used for the second recording film 24 was changed from 0.3 wt% to 2.0 wt%. Manufactured. The optical recording medium according to Comparative Example 4 was evaluated in the same manner as Example 1 according to the flowchart shown in FIG. As a result of the evaluation, in recording / reproducing / erasing with the first recording film 23, erasing was insufficient, and as a result, rewriting could not be performed. This is due to the fact that the organic dye is applied not only on the groove but also on the land when the second recording film 24 is applied by the spin coating method because the dissolution concentration of the organic dye is too high. If an organic dye is applied on the land, when data is recorded on the first recording film 23, the organic dye applied on the land reacts to form a recording mark. The formation of the recording mark by the decomposition of the organic dye is an irreversible change. As a result, erasing with the first recording film 23 could not be performed. Therefore, the dissolution concentration of the organic dye used for the second recording film 24 is preferably about 0.3 wt% to 0.5 wt% obtained by experiments.

  As described above, in the optical recording medium 1 according to the embodiment of the present invention, when write-once recording using the second recording film 24 as a recording layer is performed, a recording mark is formed on the first recording film 23. It is necessary not to. That is, recording is performed on the second recording film 24 in the second recording area 102 without recording on the first recording film 23 in the first recording area 101, or rewritable recording using the first recording film 23 as a recording layer is performed. When write-once recording is performed using the second recording film 24 as a recording layer after the recording, the recording marks recorded on the first recording film 23 must be erased.

  Therefore, the recording method of the optical recording medium 1 is performed as follows. That is, the recording mark recorded on the first recording film 23 after performing rewritable recording using the first recording film 23 as a recording layer by irradiating the first recording area 101 disposed on the land with the laser beam L. Erase. Then, after erasing the recording mark recorded on the first recording film 23, the second recording area 102 disposed on the groove is irradiated with the laser beam L to use the second recording film 24 as a recording layer. Make a record. Thereby, rewritable recording at the land and write-once recording at the groove can be performed without causing leakage of the signal during reproduction.

  Further, as shown in the first comparative example, after the write-once recording with the second recording film 24 is performed, the rewritable recording with the first recording film 23 cannot be performed. For this reason, after write-once recording is performed on the optical recording medium 1 according to the embodiment of the present invention, rewritable recording cannot be performed, and unauthorized erasure or alteration of recorded data is prevented in advance. can do.

(Other embodiments)
As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the description of the embodiment described above, an example in which the main component of the second recording film 24 is an organic dye has been described. However, other materials that can be recorded on once, for example, an inorganic material are used for the second recording film 24. May be.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  INDUSTRIAL APPLICABILITY The optical recording medium and the optical recording medium recording method of the present invention can be used in industries that use technology for recording and reproducing data using an optical recording medium.

L ... Laser beam 1 ... Optical recording medium 10 ... Substrate 20 ... Laminated body 21 ... Reflective film 22 ... First protective film 23 ... First recording film 24 ... Second recording film 25 ... Second protective film 26 ... Cover film 101 ... First recording area 102 ... second recording area

Claims (10)

An optical recording medium on / from which data is recorded / reproduced by irradiation with laser light,
A substrate having grooves and lands formed on the surface;
A first recording film formed on a surface of the substrate and made of a material that reversibly changes when irradiated with the laser beam; and a second recording film made of a material that changes irreversibly when irradiated with the laser beam. An optical recording medium, wherein one recording film is formed on the groove and the land, and the second recording film is formed only on the groove.   The optical recording medium according to claim 1, wherein the second recording film is directly formed on the first recording film formed on the groove.   The optical recording medium according to claim 1, wherein the first recording film is an inorganic material.   4. The optical recording medium according to claim 1, wherein the first recording film includes a phase change material that causes a phase change between a crystal and an amorphous phase. 5.   5. The optical recording medium according to claim 1, wherein the second recording film contains an organic dye that absorbs the laser light as a main component.   The optical recording medium according to claim 5, wherein the organic dye is gasified by irradiation with the laser light, and the shape of the second recording film is changed. A substrate having grooves and lands formed on the surface, a first recording film formed on the grooves and lands and made of a material reversibly changed by laser light irradiation, and formed on the grooves by laser light irradiation. A recording method of an optical recording medium comprising a second recording film made of a material that changes irreversibly,
Irradiating the first recording film formed on the land with the laser beam to form a recording mark based on information on the first recording film; and
An erasing step of erasing a recording mark formed on the first recording film;
After the erasing step, a second recording step of irradiating the second recording film formed on the groove with the laser light to form a recording mark based on information on the second recording film. An optical recording medium recording method.   8. The method of recording an optical recording medium according to claim 7, further comprising a step of initializing the first recording film before the first recording step.   9. The optical recording according to claim 8, wherein the first recording film is initialized by irradiating the groove and the land with the laser beam having a wavelength that does not cause an irreversible change in the second recording film. Media recording method.   9. The optical recording medium according to claim 8, wherein the first recording film is initialized by irradiating only the land with the laser beam having a wavelength that causes an irreversible change in the second recording film. Recording method.

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