JP2005216462A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium having super-resolution reproduction characteristics and high reproduction durability.
A reproduction layer 3, a heat dissipation layer 4, a dielectric layer 2, and a cover are formed on a substrate 5 for super-resolution reproduction of a signal having a minute mark length exceeding the optical system resolution limit of the optical laser. An optical information recording medium 10 provided with the layer 1 is used. By using the optical information recording medium 10, when performing super-resolution reproduction, the heat radiation layer 4 can dissipate heat generated by the reproduction layer 3, and high super-resolution reproduction characteristics and high reproduction durability are achieved. Can be realized.
[Selection] Figure 1

Description

  The present invention relates to an optical information recording medium, and more specifically, can reproduce a signal having a short mark length exceeding the optical system resolution limit of a reproducing apparatus (super-resolution reproduction), and is durable. The present invention relates to a high optical information recording medium.

  In recent years, in optical information recording media, in order to record enormous information such as images, it is increasingly required to increase the information density during recording and reproduction. As a technology for improving the information density during reproduction of an optical information recording medium, a recording mark having a minute mark length exceeding the optical system resolution limit of the reproducing apparatus was recorded as the recording mark from the recorded optical information recording medium. A technique for reproducing a signal (information signal), that is, a so-called super-resolution technique has been developed. The minute mark length exceeding the optical system resolution limit of the reproducing apparatus is determined by the laser wavelength of the reproducing optical laser and the numerical aperture of the optical system.

  An optical information recording medium (hereinafter referred to as a super-resolution optical information recording medium) capable of reproducing (super-resolution reproduction) a signal with a short mark length exceeding the optical system resolution limit of the reproducing apparatus will be described below.

  In general, many super-resolution optical information recording media are provided with a mask layer, which is a layer that causes a super-resolution phenomenon based on the principle described later, and a reflective layer. The optical laser spot formed on the mask layer by the reproducing optical laser output from the reproducing apparatus has a light intensity distribution, and thus a temperature distribution is generated at the same time. In the mask layer, this temperature distribution causes a distribution in optical characteristics such as transmittance in the optical laser spot. For example, in the case of an optical information recording medium using, as a mask layer, a material having a property of increasing the transmittance when the temperature is increased, only the transmittance at a high temperature portion is increased, and a laser spot generated on the mask layer surface is generated. It is reduced in size. Thereby, in this optical information recording medium, a signal having a mark length shorter than the optical system resolution limit can be reproduced (super-resolution reproduction).

  As an optical information recording medium that enables super-resolution reproduction by combining the mask layer and the reflective layer as described above, an optical information recording is provided with a thermochromic dye layer whose optical characteristics (transmittance) change with temperature as a mask layer. A medium is disclosed in Patent Document 1. Specifically, super-resolution reproduction is performed by irradiating the mask layer closer to the reproducing light beam entrance surface than the reflective layer with the optical characteristic distribution in the optical laser spot on the mask layer. To do.

Further, the optical information recording medium disclosed in Patent Document 2 realizes super-resolution reproduction characteristics only by a reproduction layer that causes a super-resolution phenomenon. Although the principle of this optical information recording medium has not been elucidated for the most part at present, by providing a thin metal film or the like as a reproducing layer on a substrate having irregularities as recording information (signals) on its surface, The signal due to the unevenness of the mark length below the resolution limit can be reproduced.
JP 2001-35012 A (publication date: February 9, 2001) JP 2001-250274 A (publication date: September 14, 2001)

  However, the optical information recording medium according to the prior art as described above has a problem in the durability of the mask layer and the reproducing layer. As a result, super-resolution reproduction is possible as the optical information recording medium, but the reproduction durability is low. This causes a drawback.

  Specifically, it is as follows. In the case of the optical information recording medium of Patent Document 1 described above, a thermochromic dye is provided as a mask layer. That is, since the material of the mask layer is an organic compound, the durability of the material itself is low. Further, when super-resolution reproduction is performed, information is reproduced with a power larger than a normal reproduction laser power, so that the mask layer itself is in a very high temperature state. For this reason, it is considered that the organic compound itself used as the mask layer undergoes thermal decomposition and deteriorates the super-resolution reproduction characteristics.

  Similarly, in the case of an optical information recording medium that realizes super-resolution reproduction characteristics only by the reproduction layer disclosed in Patent Document 2 described above, a very thin metal film such as about 15 nm is used for the reproduction layer. Yes. In the optical information recording medium disclosed in Patent Document 2, the mechanism of the super-resolution phenomenon has not yet been elucidated. For this reason, it is difficult to clarify the cause of the strict degradation, but because the reproduction layer is very thin, the reproduction layer itself is not durable and the super-resolution reproduction characteristics are degraded during reproduction. It is considered that there is a problem in the reproduction durability of the optical information recording medium. In addition to the structure of the optical information recording medium that achieves super-resolution reproduction characteristics only with the reproduction layer, this document also describes a structure in which the reproduction layer is sandwiched between dielectric layers. However, it cannot be said that the reproduction durability of the optical information recording medium is improved.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical information recording medium having high super-resolution reproduction characteristics and high reproduction durability.

  In order to solve the above problems, an optical information recording medium according to the present invention includes a substrate on which information is recorded or provided with an information recording surface on which information can be recorded. The reproduction that causes the super-resolution phenomenon by itself in the optical information recording medium in which the super-resolution phenomenon that enables the reproduction of the information recorded as the recording mark having the mark length smaller than the optical system resolution limit of the reproducing apparatus occurs. A layer, a dielectric layer, and a heat dissipation layer having higher thermal conductivity than the dielectric layer for releasing heat from the reproduction layer are provided on the substrate. It is characterized by being sandwiched between a body layer and the heat dissipation layer.

  With the above configuration, when reproducing information (information signal) recorded as a recording mark having a minute mark length exceeding the optical system resolution limit of the reproducing apparatus (super-resolution reproduction), particularly high power When super-resolution reproduction is performed using an optical laser, heat generated in the reproduction layer can be radiated by the heat radiation layer, and deterioration due to excessive temperature rise of the reproduction layer can be prevented. Therefore, the optical information recording medium of the present invention can improve the durability of the reproducing layer with respect to heat generated by repeatedly performing super-resolution reproduction, and can improve the durability of the optical information recording medium itself. Become. As a result, an optical information recording medium having high super-resolution reproduction characteristics and high reproduction durability can be provided.

  Specifically, it is as follows. When trying to reproduce a signal with a very small mark length exceeding the optical system resolution limit of the optical laser, reproduction is performed with a power larger than the normal optical laser power for reproduction. The layer generates a relatively large amount of heat by the optical laser. If the generated heat is not dissipated, the reproducing layer will be excessively heated. The characteristics of the reproduction layer that has been excessively heated deteriorate due to oxidation or the like. As a result, the super-resolution reproduction characteristics of the optical information recording medium itself are lost.

  Therefore, the optical information recording medium of the present invention includes a heat dissipation layer having a higher thermal conductivity than the dielectric layer for releasing heat from the reproducing layer. As a result, heat generated by the optical laser in the reproducing layer and deteriorating the characteristics of the reproducing layer can be released from the reproducing layer by the heat dissipation layer. Thereby, since the temperature of the reproducing layer does not excessively increase, the characteristics of the reproducing layer can be maintained even when the super-resolution reproduction is repeatedly performed.

  The optical information recording medium of the present invention further includes a dielectric layer on one side of the reproducing layer. Thereby, it is possible to prevent deterioration of the characteristics of the reproduction layer due to chemical changes such as oxidation of the reproduction layer. Therefore, it is possible to prevent deterioration of the super-resolution reproduction characteristics of the optical information recording medium itself.

  Chemical changes such as oxidation of the reproduction layer are likely to occur when the reproduction layer is heated. Therefore, it is not possible to prevent chemical changes such as oxidation of the reproducing layer only by providing the dielectric layer. In the optical information recording medium of the present invention, in addition to preventing a chemical change such as oxidation of the reproduction layer by the dielectric layer, by preventing the temperature of the reproduction layer from being increased by the heat dissipation layer, oxidation of the reproduction layer or the like can be performed. Prevents chemical changes. Therefore, the durability of the reproducing layer can be configured by providing the dielectric layer and the heat dissipation layer.

  As described above, the optical information recording medium having the configuration of the present invention solves the problems of deterioration of characteristics due to excessive temperature rise of the reproduction layer and deterioration of characteristics due to chemical changes such as oxidation of the reproduction layer, and is a super solution. Super-resolution reproduction can be performed without degrading image reproduction characteristics.

  Here, the “reproduction layer” is a layer that can reproduce a signal with a minute mark length that exceeds the optical system resolution limit of the optical laser by itself. It is a layer that causes a super-resolution phenomenon such as narrowing down to itself.

  The optical information recording medium of the present invention is characterized in that the dielectric layer, the reproducing layer, and the heat dissipation layer are laminated on a substrate in order from the light incident direction.

  By providing the above configuration, in addition to the above effects, the heat dissipation can be effectively performed by the heat dissipation being laminated adjacent to one side of the reproduction layer. Further, the dielectric layer is laminated adjacent to the reproduction layer on the side opposite to the substrate, so that chemical changes such as oxidation of the reproduction layer can be effectively prevented. Therefore, by providing the above laminated structure, it is possible to improve the durability of the reproducing layer, and as a result, the durability of the optical information recording medium can be improved.

  The optical information recording medium of the present invention is characterized in that the reproducing layer is composed of a single substance (that is, composed of a single element).

  As a result, compared with an optical information recording medium in which the reproduction layer is made of an organic compound, characteristic deterioration due to heat of the reproduction layer hardly occurs. That is, when the reproducing layer is composed of an organic compound, when the optical laser having a higher power than usual irradiated for super-resolution reproduction is irradiated, heat is generated in the reproducing layer, and the organic compound is generated by the heat. Causes thermal decomposition, and super-resolution characteristics deteriorate. In contrast, a single reproduction layer is unlikely to deteriorate super resolution characteristics due to heat.

  Therefore, by providing the above configuration, it is possible to further improve the reproduction durability of the optical information recording medium.

  Furthermore, with the above configuration, the optical information recording medium of the present invention can realize excellent super-resolution reproduction characteristics.

  The optical information recording medium of the present invention is characterized in that the reproducing layer is made of either silicon or germanium.

  As a result, the optical information recording medium of the present invention can realize excellent super-resolution reproduction and high reproduction durability.

  The optical information recording medium of the present invention is characterized in that the reproducing layer is made of an inorganic compound.

  As a result, compared with an optical information recording medium in which the reproduction layer is made of an organic compound, characteristic deterioration due to heat of the reproduction layer hardly occurs. That is, when the reproducing layer is composed of an organic compound, when the optical laser having a higher power than usual irradiated for super-resolution reproduction is irradiated, heat is generated in the reproducing layer, and the organic compound is generated by the heat. Causes thermal decomposition, and super-resolution characteristics deteriorate. On the other hand, in the reproducing layer made of an inorganic compound, the super-resolution characteristics are hardly deteriorated by heat.

  Therefore, by providing the above configuration, it is possible to further improve the reproduction durability of the optical information recording medium.

  In the optical information recording medium of the present invention, the dielectric layer is a transparent dielectric layer.

  As a result, since the dielectric layer is a transparent dielectric layer, it is possible to prevent chemical changes such as oxidation of the reproducing layer without reducing the amount of reflected light due to optical laser irradiation in signal recording and reproduction. It becomes possible.

  In the present specification, the “transparent dielectric layer” refers to a dielectric layer having a light transmittance of 80% or more with reproduction wavelength light.

  The optical information recording medium of the present invention is characterized in that the heat dissipation layer is made of a metal.

  Thereby, the reproducing layer of the optical information recording medium according to the present invention can efficiently transfer heat to the heat dissipation layer. As a result, it is possible to more efficiently prevent deterioration of the characteristics of the reproduction layer, which has been thought to occur due to heat, by efficiently radiating the heat of the reproduction layer. . Therefore, by providing the above configuration, it is possible to further improve the reproduction durability of the optical information recording medium.

  As described above, the optical information recording medium according to the present invention includes a substrate on which information is recorded or provided with an information recording surface on which information can be recorded. In an optical information recording medium in which a super-resolution phenomenon that enables reproduction of information recorded as a recording mark having a mark length smaller than the optical system resolution limit of the device occurs, a reproduction layer that causes the super-resolution phenomenon by itself, A dielectric layer and a heat dissipation layer having higher thermal conductivity than the dielectric layer for releasing heat from the reproduction layer are provided on the substrate, and the reproduction layer includes the dielectric layer and the dielectric layer. It is characterized by being sandwiched between the heat dissipation layer.

  With the above configuration, when reproducing information (information signal) recorded as a recording mark having a minute mark length exceeding the optical system resolution limit of the reproducing apparatus (super-resolution reproduction), particularly high power When super-resolution reproduction is performed using an optical laser, heat generated in the reproduction layer can be radiated by the heat radiation layer, and deterioration due to excessive temperature rise of the reproduction layer can be prevented. Therefore, the optical information recording medium of the present invention can improve the durability of the reproducing layer against heat generated by repeatedly performing super-resolution reproduction, and as a result, the durability of the optical information recording medium itself is improved. Is possible.

  An embodiment of the present invention will be described with reference to FIG. In the present embodiment, a read-only optical information recording medium will be described. FIG. 1 is a diagram showing a configuration of an optical information recording medium according to an embodiment of the present invention. An optical information recording medium 10 according to this embodiment includes a cover layer 1, a dielectric layer 2, a reproduction layer 3, a heat dissipation layer 4, and a substrate 5. Further, these layers are stacked on the substrate 5 in the order of the heat dissipation layer 4, the reproduction layer 3, the dielectric layer 2, and the cover layer 1. In particular, it is preferable that the heat dissipation layer 4 is laminated adjacent to one side of the reproduction layer 3 and the dielectric layer 2 is laminated adjacent to the other side of the reproduction layer 3.

  The cover layer 1 is usually configured to be thinner than the thickness of the substrate 5, but is not limited thereto. According to the above configuration, when recording or reproducing information by making an optical laser incident from the dielectric layer 2 side, a lens for condensing the optical laser is prevented from colliding with the dielectric layer 2. In addition, the environmental durability can be enhanced. The cover layer 1 is preferably made of a transparent material so as not to reduce the amount of light emitted from the laser beam and the reflected light, and for example, glass is preferably used.

The dielectric layer 2 is provided to prevent oxidation of the reproducing layer 3 described later. The optical information recording medium 10 of the present embodiment is an optical information recording medium that performs super-resolution reproduction by the reproduction layer 3, and the dielectric layer 2 is provided, so that deterioration of the reproduction layer 3 due to oxidation can be suppressed. Become. The dielectric layer 2 is preferably made of a transparent dielectric so as not to reduce the amount of reflected light due to irradiation with an optical laser during signal recording and reproduction. More specifically, the dielectric layer 2 is preferably a transparent dielectric layer having a transmittance of 80% or more with reproduction wavelength light. For example, SiN, AlN, ZnS—SiO used in the following examples are used. _A transparent dielectric layer made of an inorganic compound such as ₂ is more preferable. Although the thickness of the dielectric layer 2 varies depending on the constituent material, it is usually preferable that the thickness is in the range of 20 nm to 200 nm, for example, about 140 nm, which is the minimum thickness for preventing oxidation.
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The reproduction layer 3 itself enables reproduction of a signal with a minute mark length exceeding the optical system resolution limit of the reproduction apparatus.

  When the thermochromic dye described in Patent Document 1 described above is used as the constituent material of the reproduction layer 3, the thermochromic dye is an organic compound, so that the durability is inferior compared to the inorganic material. Is fully expected. Therefore, the constituent material of the reproducing layer 3 of the optical information recording medium according to the present invention is preferably an inorganic compound or a simple substance. In the embodiment described below, Si is used for the reproducing layer 3, but the present invention is not limited to this. Even when the reproducing layer 3 is made of TbFeCo as in Example 2 described below, for example, super-resolution characteristics can be seen (see FIG. 4). Furthermore, as described in Patent Document 2 described above, it is generally known that a certain amount of inorganic compound or a single layer exhibits super-resolution characteristics. Therefore, even a layer composed of a single element of Mo, W, Mn, Pt, C, Zr, Ge, In or the like or a compound thereof is sufficiently expected to exhibit super-resolution characteristics in the structure of the present application. The reproducing layer 3 can be used. In general, Si and Ge are known to exhibit particularly excellent super-resolution characteristics as the reproducing layer 3. For example, when Si is used for the reproducing layer 3, better super-resolution characteristics can be obtained than when the reproducing layer 3 is made of TbFeCo. Therefore, the reproducing layer 3 is more preferably made of Si or Ge.

  The thickness of the reproduction layer 3 varies depending on the constituent material. However, when Si is used for the reproducing layer 3 as described above, super-resolution characteristics appear even when the thickness of the reproducing layer 3 is increased to at least 100 nm, as described in Example 3 described later. (See FIG. 4). Also, in the case of using the super-resolution medium having only the reproducing layer of Patent Document 2, it is said that the limitation of the thickness of the reproducing layer made of Si is wider than that of the reproducing layer made of other substances. For these reasons, Si is preferably used for the reproducing layer 3. Therefore, in the configuration of the optical information recording medium of the present application, it can be sufficiently predicted that the limitation on the thickness of the reproducing layer 3 can be expanded by forming the reproducing layer 3 with Si.

  The preferable thickness of the reproduction layer 3 when composed of a single metal or metalloid is, for each constituent element, Nb: 100 nm or less, Mo: 70 nm or less, particularly 45 nm or less, W: 70 nm or less, particularly 40 nm or less, Mn: 100 nm In particular, 70 nm or less, Pt: 40 nm or less, particularly 30 nm or less, C: 100 nm or less, Si: 100 nm or less, Ge: 100 nm or less, Ti: 100 nm or less, Zr: 100 nm or less, particularly 25 to 100 nm, V: 100 nm or less, Cr: 30 nm or less, particularly less than 15 nm, Fe: 80 nm or less, particularly 50 nm or less, Co: 70 nm or less, particularly 45 nm or less, Ni: 70 nm or less, particularly 50 nm or less, Pd: 40 nm or less, particularly 30 nm or less, Sb: 100 nm or less, Especially 60 nm or less, Ta: 100 nm or less, particularly 60 nm or less, Al: 20 nm or less, particularly less than 15 nm, In: 100 nm or less, especially less than 10 nm, Cu 10nm or less, Sn: 40 nm or less, Te: 70 nm or less, Zn: 40~90nm, Bi: a 25～70Nm. In addition, those having sufficiently high C / N (Nb, Mn, C, Si, Ge, Ti, Zr, V, Sb, Ta, In) even with a thickness of 100 nm are not thicker in terms of characteristics. Although there is no need to set the upper limit to 100 nm, it is usually preferable to set the thickness to 100 nm or less in order to prevent a decrease in productivity. Moreover, it is preferable that the thickness of the reproducing layer 3 is 2 nm or more when it is composed of any element. If the reproducing layer 3 is too thin, the reflectance becomes low and it becomes difficult to perform tracking servo, and it becomes difficult to obtain sufficient C / N.

  The heat radiating layer 4 is laminated so as to be adjacent to the other side of the reproducing layer 3 in which the dielectric layer 2 is laminated on one side, so that the heat generated in the reproducing layer 3 by super-resolution reproduction is efficiently Heat can be released. As a result, it is possible to solve the problem that has been considered that the durability of the reproducing layer 3 is lost by raising the temperature of the reproducing layer 3 so far by laminating the heat radiation layer 4 on the reproducing layer 3.

  The constituent material of the heat dissipation layer 4 may be any material as long as it has a higher thermal conductivity than the dielectric constituting the dielectric layer 2 laminated on the other side of the reproduction layer 3, but is a metal. It is preferable. This is because the heat of the reproducing layer 3 is efficiently radiated. As the constituent material of the heat dissipation layer 4, for example, Al, Ag, Au, or the like used in Examples 1, 2, and 3 shown below is used, but is not limited thereto. Further, the layer thickness of the heat dissipation layer 4 is different depending on the material constituting the layer, as in the above-described reproducing layer 3, but it is usually more preferably in the range of 20 to 100 nm, for example, about 30 nm.

  The substrate 5 may be made of a resin conventionally used as a substrate for an optical information recording medium. Specifically, for example, a polycarbonate resin or a polyolefin resin can be used. Moreover, it is preferable that the thickness of the board | substrate 5 shall also be normal 0.5 mm-1.2 mm.

  In the optical information recording medium of the present invention, an information signal is recorded as unevenness composed of pits and / or grooves, an information signal can be recorded as a recording mark, or an information signal can be recorded with the above unevenness. It has an information recording surface. In other words, in FIG. 1, the reproduction-only optical information recording medium is used. However, the present invention is not limited to this, and the reproduction-only optical information recording medium and the write-once or rewritable optical information recording medium can be used. It can be applied to both. In the read-only optical information recording medium, the pits provided on the surface of the substrate 5 constitute the recording surface, whereas in the case of a write-once or rewritable optical information recording medium, for example, the reproduction layer has a recording layer. It also constitutes an information recording surface. When the reproducing layer also serves as the recording layer, for example, Si is used for the reproducing layer. The recording mark may be any one having a different optical constant such as a reflectance relative to the surroundings, a concave one, or a convex one.

  The optical information recording medium of the present invention includes a CD (Compact Disc), a CD-ROM (Compact Disc Read-Only Memory), a CD-R (Compact Disc Recordable), a CD-RW (Compact Disc ReWritable), and a DVD (Digital Versatile). Disc), DVD-ROM (Digital Versatile Disc Read-Only Memory), DVD-R (Digital Versatile Disc Recordable), DVD-RW (Digital Versatile Disc ReWritable), BD (Blu-ray Disc), BD-ROM (Blu- a disc-shaped optical information recording medium such as ray disc), but is not limited thereto.

  The optical information recording medium of the present invention shown in FIG. 1 will be described in more detail based on the following examples and comparative examples, but the present invention is not limited to these.

  As the optical information recording medium 10 having the configuration shown in FIG. 1, a cover layer 1, a dielectric layer 2, a reproducing layer 3, a heat radiation layer 4, and a substrate 5 having the following configurations were used. Specifically, as the optical information recording medium 10 of the present invention, on a substrate 5 made of a polyolefin resin of 0.5 mm, a heat dissipation layer 4 that is a 30 nm Al layer, a reproduction layer 3 that is a 50 nm Si layer, A dielectric layer 2 that is a 140 nm SiN layer and a cover layer 1 that is a 0.5 mm glass layer are laminated in this order. As described above, the optical information recording medium 10 shown in FIG. 1 is for reproduction only.

[Comparative Example 1]
Instead of the optical information recording medium having the configuration described in the first embodiment, an optical information recording medium 100 shown in FIG. 2 was used. The optical information recording medium 100 of FIG. 2 is configured by removing the dielectric layer 2 and the heat dissipation layer 4 from the optical information recording medium 10 in Example 1, that is, the cover layer 101, the reproducing layer 103, and the substrate 105. is there. That is, in the optical information recording medium 100, a reproduction layer 103 which is a 50 nm Si layer and a cover layer 101 which is a 0.5 mm glass layer are laminated in this order on a substrate 105 made of a polyolefin resin of 0.5 mm. It will be.

  Super-resolution performance was compared using the optical information recording medium 10 having the configuration described in Example 1 and the optical information recording medium 100 described above. The mark lengths of the optical information recording medium 10 and the optical information recording medium 100 were set appropriately between 0.1 μm and 4.0 μm, respectively. As a comparison method of super-resolution performance, reproduction of these optical information recording media is performed by using a reproduction optical laser wavelength of 408 nm, an optical system numerical aperture (NA) of 0.65, and a linear velocity of 3.0 m / second. Measured with However, the reproduction laser output was performed at the optimum laser output for each mark length of each medium.

  With such a method, the OTF for comparing the super-resolution performance of Example 1 and Comparative Example 1 was measured. Note that OTF means the dependency of C / N, which is an evaluation standard representing signal quality, on the recording mark length. FIG. 4 is a diagram showing the results of measuring the OTF of Example 1 and Comparative Example 1. Thus, it was shown that Example 1 can reproduce a signal having a larger super-resolution characteristic, that is, a shorter mark length, with a higher signal quality than Comparative Example 1. Specifically, even if the signal has a mark length of 0.13 μm shorter than the optical system resolution limit mark length (0.16 μm) of the optical laser, the optical information recording medium of Example 1 has a C / N of 30 dB. I found out.

  That is, the optical information recording medium 10 of the present invention (Example 1) has a shorter mark length signal on the optical information recording medium than the optical information recording medium 100 (Comparative Example 1) having the conventional configuration. Indicates that it can be played.

  In this specification, reproduction is possible when C / N of 25 dB or more is obtained. However, practically, it is necessary to obtain C / N of preferably about 30 dB or more, more preferably about 40 dB or more.

  An optical information recording medium having the same configuration as that of the optical information recording medium having the configuration described in Example 1 and having a reproducing layer as a TbFeCO layer was used. That is, on a substrate that is a 0.5 mm polyolefin resin layer, a heat dissipation layer that is a 30 nm Al layer, a reproduction layer that is a 50 nm TbFeCO layer, a dielectric layer that is a 140 nm SiN layer, and a 0.5 mm glass A layer formed by laminating a cover layer as a layer in this order was used.

  An optical information recording medium having the same structure as the optical information recording medium having the structure described in Example 1 and a reproducing layer thickness of 100 nm was used. That is, on a substrate that is a 0.5 mm polyolefin resin layer, a heat dissipation layer that is a 30 nm Al layer, a reproduction layer that is a 100 nm Si layer, a dielectric layer that is a 140 nm SiN layer, and a 0.5 mm glass A layer formed by laminating a cover layer as a layer in this order was used.

  Super resolution performance (OTF) was measured for the optical information recording media of Example 2 and Example 3 by the same method as described above, and compared with Comparative Example 1.

  The results are shown in FIG. Thus, it can be seen that the signals of the shorter mark length can be reproduced in the second and third embodiments than in the optical information recording medium of the first comparative example. Among them, the optical information recording medium of Example 3 has the best super-resolution reproduction compared to the optical information recording media of Example 1 and Example 2, and has a mark length of 0.11 μm. C / N was found to be 30 dB.

  FIG. 4 shows that the super-resolution characteristics are better when Si is used as the reproducing layer (Example 1) than when the reproducing layer is TbFeCO (Example 2). Further, from Example 3, it was found that the super-resolution characteristics appeared even when the thickness of the Si layer was increased to at least 100 nm.

[Comparative Example 2]
An optical information recording medium 200 shown in FIG. 3 was used in place of the optical information recording medium having the configuration described in the first embodiment. Patent Document 2 discloses an optical information recording medium having a structure in which both sides of a reproducing layer are sandwiched between dielectric layers and further provided with a metal film as an optical information recording medium having another structure. In order to clarify the difference from the optical information recording medium 10 of the present invention, the optical information recording medium 200 shown in FIG. 3 is obtained by changing the heat dissipation layer 4 in the optical information recording medium 10 of Example 1 to a dielectric layer. That is, the cover layer 201, the first dielectric layer 202, the reproducing layer 203, the second dielectric layer 204, and the substrate 205 are configured. That is, the optical information recording medium 200 includes a second dielectric layer 204, which is a 140 nm SiN layer, a reproducing layer 203, which is a 50 nm Si layer, and a 140 nm thick layer on a substrate 205 made of a polyolefin resin of 0.5 mm. The first dielectric layer 202, which is a SiN layer, and the cover layer 201, which is a 0.5 mm glass layer, are laminated in this order.

  The reproduction durability performance was compared between Example 1 and Comparative Example 1. FIG. 5 is a diagram comparing the reproduction durability performance. The reproduction durability performance comparison method was performed under the same conditions as the above-described super-resolution performance measurement method except for the output of the reproduction optical laser, and the reproduction signal mark length was set to 0.14 μm below the resolution limit. Is an optical laser output for reproduction that can obtain substantially the same C / N (near 25 dB). Specifically, Example 1: 3.5 mW, Comparative Example 1: 2.0 mW, Comparative Example 2: 3.5 mW. These reproduction optical lasers were used for reproduction as shown in FIG.

  However, it was confirmed that the reproduction characteristics of the optical information recording medium 200 deteriorated during the measurement of C / N. That is, the reproduction characteristics of the optical information recording medium 200 in Comparative Example 2 deteriorated more rapidly than those in Comparative Example 1. Therefore, the measured value could not be determined and could not be shown in FIG.

  In other words, in the optical information recording medium 200 having the structure in which the reproducing layer 203 is sandwiched between the dielectric layers 202 and 204, at least when the reproducing laser is a blue laser, the reproduction durability is not achieved, and the reproduction is remarkable compared to the first embodiment. It turns out that durability is inferior.

  On the other hand, as shown in FIG. 5, in the optical information recording medium 10 of Example 1, the C / N hardly decreased even when the number of reproductions was 20,000.

  From the above, according to the optical information recording medium (Examples 1 to 3) of the configuration of the present invention, compared with the optical information recording medium 100 that does not include the dielectric layer and the heat dissipation layer as in Comparative Example 1, it is a super solution. It was found that the image performance can be improved and the reproduction durability can be remarkably improved as compared with the optical information recording media 100 and 200 having no heat dissipation layer as in Comparative Examples 1 and 2.

  The present invention is generally applicable to optical information recording media such as CD, CD-ROM, CD-R, CD-RW, DVD, DVD-ROM, DVD-R, DVD-RW, BD, and BD-ROM.

1 is a diagram showing an embodiment of an optical information recording medium according to the present invention. 6 is a diagram showing an optical information recording medium of Comparative Example 1. FIG. 6 is a diagram showing a structure of an optical information recording medium of Comparative Example 2. FIG. 4 is a graph showing a comparison between the optical information recording medium according to the present invention and the super-resolution reproduction capability of a conventional optical information recording medium. 6 is a graph showing the reproduction durability of the optical information recording medium according to the present invention and the conventional optical information recording medium in comparison.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cover layer 2 Dielectric layer 3 Reproduction layer 4 Heat dissipation layer 5 Substrate 10 Optical information recording medium

Claims (7)

As a recording mark having a mark length that is smaller than the optical system resolution limit of the reproducing apparatus when reproducing information by the reproducing apparatus, the information recording surface is provided or a substrate provided with an information recording surface on which information can be recorded. In an optical information recording medium in which a super-resolution phenomenon that enables reproduction of recorded information occurs,
A reproduction layer that causes a super-resolution phenomenon by itself, a dielectric layer, and a heat dissipation layer having higher thermal conductivity than the dielectric layer for releasing heat from the reproduction layer are provided on the substrate. And
An optical information recording medium, wherein the reproducing layer is sandwiched between the dielectric layer and the heat dissipation layer.   2. The optical information recording medium according to claim 1, wherein the dielectric layer, the reproducing layer, and the heat dissipation layer are laminated on a substrate in order from the light incident direction.   The optical information recording medium according to claim 1, wherein the reproduction layer is made of a single substance.   The optical information recording medium according to claim 3, wherein the reproducing layer is made of silicon or germanium.   The optical information recording medium according to claim 1, wherein the reproduction layer is made of an inorganic compound.   The optical information recording medium according to claim 1, wherein the dielectric layer is a transparent dielectric layer.   The optical information recording medium according to claim 1, wherein the heat dissipation layer is made of a metal.

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