JP2010092569A - Optical information recording medium and optical information recording medium driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hybrid optical information recording medium from which information is reproduced even with a driving device coping with an optical information recording medium of old standard having less information recording layers, and to improve recording capacity of an optical information recording medium coping with an old standard by adding a read only memory layer (ROM layer) thereto. <P>SOLUTION: The optical information recording medium 200 is constructed by stacking a light transmitting layer 10, a first information recording layer 20, an intermediate layer 30, a second information recording layer 40, and a substrate 50 sequentially from the incident side of reproduction light, wherein the first information recording layer 20 only reads information, and the second information recording layer 40 is a layer including a region in which information is rewritten. Furthermore, in the construction of the first information recording layer 20, an interface between two mutually adjacent light transmitting resin layers forms a projecting and recessing shape corresponding to information to be recorded. Reflectance of the first information recording layer 20 at the wavelength of the reproduction light is >0.4% and ≤2.2%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a multilayer optical information recording medium having two or more information recording layers, and an information recording layer having recording characteristics different from those of other layers among the plurality of information recording layers.

  In recent years, there has been a demand for increasing the information density during recording / reproduction of an optical information recording medium, for enormous information processing such as images. Therefore, in the optical information recording medium that reproduces from one side as disclosed in Patent Document 1, the recording capacity of the optical information recording medium is increased by separating each of the plurality of information recording layers with an intermediate layer made of a transparent resin. A multilayer technology that doubles the number of recording layers has been proposed.

  In the multilayer optical information recording medium manufactured using the multilayer technology described above, the layers other than the information recording layer provided at the position farthest from the reproduction light incident surface are translucent (transmission and reflection) at the reproduction light wavelength. Have both properties. Therefore, in the above multilayer optical information recording medium, the reproduction light can be transmitted through the semi-transparent information recording layer and focused on another information recording layer, so that information reproduction of each information recording layer is possible. It has become.

  In addition, in order to reproduce each information recording layer of the above-described multilayer optical information recording medium manufactured using the multilayer technology, it is necessary for the driving device of this multilayer optical information recording medium to focus on each information recording layer. . As a technique for focusing the information recording layer by the driving device, in Patent Document 2, the driving device focuses on each information recording layer by utilizing S-characteristics obtained by irradiating each information recording layer with reproduction light. Techniques to do this have been proposed.

  As a result of these, at present, multilayer optical information recording media having up to two information recording layers are standardized and sold in DVD (Digital Versatile Disc), BD (Blu-ray Disc; registered trademark), and the like.

  Furthermore, in a multilayer optical information recording medium, in addition to an information rewritable information recording layer, an information recording layer in which various contents are recorded, and a reproduction-only information recording layer that can only be reproduced or additional recording is possible. There is a need for an optical information recording medium (hereinafter referred to as a hybrid optical information recording medium) in which an information recording layer is added to improve the recording capacity. An example of such an optical information recording medium is disclosed in Patent Document 3. Hereinafter, the rewritable information recording layer is referred to as an RE (REwritable) layer, the read-only information recording layer is referred to as a ROM (Read Only Memory) layer, and the additional recordable information recording layer is referred to as an R Called the (Recordable) layer.

Further, in the ROM layer, the shape of the reflective film is fixed by forming the reflective film on the pre-pits made of unevenness provided according to information. Therefore, since information is recorded on the reflective film (including the shape) itself in the optical information recording medium having the ROM layer, even the reflective film is called an information recording layer.
JP 2000-207774 A (released July 28, 2000) Japanese Patent Laid-Open No. 10-188294 (published July 21, 1998) JP 2006-511010 A (published March 30, 2006)

  However, there is a limit to improving the recording capacity by the multilayer technology. As an example, the case of a two-layer BD500 (hereinafter, two-layer RE-BD) in which both the first information recording layer 80 and the second information recording layer 40 are RE layers will be described with reference to FIG. In addition, since each layer 81-86 of the 1st information recording layer 80 has the same function as each layer 61-66 of the below-mentioned 3rd information recording layer 60, the description is abbreviate | omitted here. Further, since the light-transmitting layer 910 (conventional light-transmitting layer), the intermediate layer 930 (conventional intermediate layer), the second information recording layer 40 and the substrate 50 are also described later, description thereof is omitted here.

  The two-layer RE-BD 500 is a kind of the multilayer optical information recording medium described above. For this reason, the reproduction light applied to the two-layer RE-BD 500 needs to pass through the first information recording layer 80 which is an information recording layer on the side close to the reproduction light incident surface. However, the material currently used as the material for the recording films 83 and 43 of each RE layer is actually only a phase change material (GeSbTe, AgInSbTe, etc.). These materials need to absorb the laser beam irradiated at the time of recording and change it into heat, and the property of changing to this heat becomes a factor that impedes the transparency. For this reason, in the two-layer RE-BD 500, it is necessary to obtain a transmittance by reducing the film thickness of the recording film 83. In practice, the recording film 83 is reduced to about 6 nm, and the blue laser which is the reproduction light wavelength is used. A transmittance of about 60% was obtained at the wavelength.

  On the other hand, it is widely known that the reproduction durability is deteriorated by thinning the recording film as described above. This is presumably because the recording film is extremely thin, so that heat generated in the recording film causes thermal degradation to the recording film itself before it is radiated to the adjacent layer. For this reason, it is impossible to make the recording film thinner than the above from the viewpoint of reproduction durability. That is, the improvement of the transmittance by thinning the recording film cannot be expected any more.

  Further, a high reflectance is desired for the second information recording layer 40 which is an information recording layer farther from the reproduction light incident surface. The reason will be described below.

  The reproduction light applied to the second information recording layer 40 is transmitted through the first information recording layer 80, condensed on the second information recording layer 40, reflected there, and transmitted again through the first information recording layer 80. To do. Then, the light (return light) transmitted through the first information recording layer 80 is detected by the optical head of the driving device described above. In this way, information reproduction in the second information recording layer 40 is performed.

  The return light from the second information recording layer 40 to the optical head is transmitted twice through the first information recording layer 80, and the transmittance of the first information recording layer 80 is about 60% as described above. is there. Therefore, the ratio of the light detected by the optical head to the irradiated reproduction light (hereinafter referred to as the return light ratio) is (reflectance of the second information recording layer 40) × 60% × 60%. .

  As described above, the loss caused by the first information recording layer 80 occurs in the reproduction light irradiated to the second information recording layer 40. Therefore, in order to make the amount of light returned from the second information recording layer 40 sufficient for the optical head (that is, the optical head can read information from the second information recording layer 40), reflection is required. It is necessary to increase the rate.

  On the other hand, as described above, since the recording film of the RE layer needs to absorb light, the reflectance of the second information recording layer 40 is determined by eliminating the light transmitted through the second information recording layer 40. However, the current limit is around 16%.

  From the above, when there are three RE layers, the return light rate from the third information recording layer (not shown) provided farthest from the reproduction light incident surface is 2.1% (= 16 % × 60% × 60% × 60% × 60%). This return light rate of 2.1% is a value that is extremely difficult to focus with an optical head mounted on a current optical information recording medium driving device for reasons that will be described later. In the RE layer having a low ratio, the contrast ratio due to the presence or absence of recording can hardly be obtained. Therefore, in practice, it is almost impossible to improve the recording capacity by using three RE layers.

  Furthermore, as described above, optical information recording media are generally standardized so as to be found on DVDs, BDs, and the like. This is essential in order to make the optical information recording medium versatile. And when standardizing up to now, optical information recording media compatible with the old standard can be played back with a drive device compatible with the new standard, but optical information compatible with the new standard There has been a problem that the recording medium cannot be played back by a drive device compatible with the old standard. Therefore, even if the focus or the contrast ratio by the optical head as described above is solved, there remains a problem that reproduction cannot be performed by a drive device that supports the old standard.

  The same problem arises in the case of improving the recording capacity by the combination of the ROM layer or R layer and the RE layer as in Patent Document 3. According to Patent Literature 3, a metal translucent transparent film such as Au is used for the ROM layer or the R layer. These reflectivities are larger than the first information recording layer of a two-layer RE optical information recording medium such as a two-layer RE-BD. In addition, since the S-characteristic depends on the amount of reflected light, a large S-characteristic is detected during focusing. Therefore, in a drive device that supports only the optical information recording medium before the addition of the ROM layer or the R layer, an unknown information recording layer is detected, and a reproduction failure may occur. There is. That is, there is a problem that an optical information recording medium to which a ROM layer or an R layer is added in accordance with the new standard cannot be reproduced by a drive device that supports the old standard.

  As described above, there are many problems in the recording capacity improvement technology by multilayering that requires new standardization.

  The present invention has been made in view of the above-mentioned problems, and the object thereof is to be able to be reproduced by a drive device compatible with an old standard optical information recording medium having a small number of information recording layers. An object of the present invention is to provide a hybrid optical information recording medium capable of improving the recording capacity by adding a read-only layer (ROM layer) to the information recording medium.

  In order to solve the above problems, an optical information recording medium according to the present invention includes a plurality of information recording layers capable of reading information on a substrate by reproducing light, and an intermediate for separating each of the plurality of information recording layers. And a light transmitting layer provided at a position farthest from the substrate, and a first information recording layer provided at a position closest to the reproduction light incident side among the plurality of information recording layers is provided. An optical information recording medium including a plurality of resin layers, which is a layer that can only read information, and is a rewrite layer that includes a region in which at least one of the other information recording layers can rewrite information, The first information recording layer is configured such that an interface between two adjacent resin layers both having translucency forms an uneven shape corresponding to information to be recorded. The reflectance value at the reproduction light wavelength is It is characterized by greater than .4% or 2.2% or less.

  In order to solve the above problems, an optical information recording medium according to the present invention separates a plurality of information recording layers on a substrate from which information can be read by reproduction light, and each of the plurality of information recording layers. A first information recording layer provided at a position closest to the incident side of the reproduction light among the plurality of information recording layers. An optical information recording medium including a plurality of resin layers, wherein the layer is a layer that can only read information, and at least one of the other information recording layers is a rewritten layer that includes a region where information can be rewritten. In addition, the first information recording layer is configured such that an interface between two adjacent resin layers both having translucency forms a concavo-convex shape corresponding to information to be recorded. Of reflectivity at the playback light wavelength of the layer Is a first reproduction light when reproducing the first information recording layer, which is smaller than the return light rate of the rewrite layer and higher in intensity than the second reproduction light when reproducing the rewrite layer. By irradiating the layer, the first information recording layer has such a large value that it can be focused.

  According to the said structure, the 1st information recording layer is comprised because the interface of the two adjacent resin layers which have translucency forms the uneven | corrugated shape according to the information recorded. Therefore, the optical information recording medium according to the present invention does not need to be provided with a ROM layer (metal thin film) formed of metal in order to form the first information recording layer, as compared with the conventional hybrid optical information recording medium. Therefore, vacuum processes such as sputtering and vapor deposition can be reduced by one process. Thereby, the optical information recording medium according to the present invention can reduce the manufacturing cost and the tact time in the manufacturing process.

  The above-mentioned conventional hybrid optical information recording medium improves the recording capacity by additionally providing a ROM layer formed of a metal such as Ag, Al, or Au as the first information recording layer in addition to the rewrite layer. This is an optical information recording medium as shown.

  Furthermore, since the optical information recording medium according to the present invention does not require the provision of a metal thin film as described above, an interface between the metal thin film and a layer adjacent to the metal film is not formed. For this reason, in the optical information recording medium according to the present invention, the generation of film (layer) stress due to temperature change or humidity change can be reduced. Therefore, the optical information recording medium according to the present invention can improve its reliability.

  Further, the reflectance value at the reproduction light wavelength of the first information recording layer is 2.2% or less. For this reason, for the reason described later, the first information recording layer cannot be focused with the second reproduction light when reproducing the rewrite layer, and the second reproduction light when reproducing the first information recording layer. Focus pull-in becomes possible with the first reproduction light having higher intensity.

  Specifically, in the optical information recording medium according to the present invention, the first information recording layer closest to the reproduction light incident surface side among the information recording layers is a layer from which information can be read (ROM layer). In the optical information recording medium including a plurality of resin layers, at least one of the information recording layers is a rewritable layer (RE layer) including an information rewritable region, both of the first information recording layers being transparent. It is a structure comprised by forming the uneven | corrugated shape according to the information recorded on the interface of the two adjacent resin layers which have optical property.

  For this reason, for example, a ROM layer can be further provided in an optical information recording medium having two RE layers, which is difficult to make into three or more layers, without substantially reducing the return light rate of the two RE layers. Therefore, the recording capacity of the optical information recording medium having the RE layer can be improved. Note that having translucency at the reproduction light wavelength means having a transmittance of 80% or more at the reproduction light wavelength. The focus pull-in refers to a state where the focus servo is ON (that is, a state where the focal position of the laser light emitted from the optical system follows an arbitrary information recording layer).

  In the conventional hybrid optical information recording medium in which the recording capacity is improved by providing an additional ROM layer as the first information recording layer, the first information recording layer is an RE layer having a low reflectance in terms of material ( Reflected light from the second and subsequent information recording layers (other information recording layers) produced at a reproduction light wavelength of about 405 nm and a reflectance of about 15% is transmitted. For this reason, in the ROM layer formed of a metal such as Ag, Al, or Au, the transmittance is increased by forming the ROM layer thin.

  However, since the ROM layer is a metal thin film, even if the metal thin film is thinned to the limit at which it is uniformly formed, for example, the reflectivity of the first information recording layer in the two-layer RE-BD is higher than 5%. It has a reflectance of about 8%. For this reason, when reproducing light is irradiated onto the ROM layer, an S-characteristic sufficient for focus pull-in is detected from the ROM layer. Therefore, even in a driving device that does not correspond to the standard of the hybrid optical information recording medium, there is a high possibility that the S-characteristic from the ROM layer is detected. It was not possible to cope with it, and there was a high possibility of causing poor reproduction.

  On the other hand, in the optical information recording medium according to the present invention, the first information recording layer has an uneven shape corresponding to the information recorded on the interface between two adjacent resin layers both having translucency. And the value of the reflectance at the reproduction light wavelength of the first information recording layer is a value that cannot be focused by the second reproduction light when reproducing the rewrite layer. Accordingly, the drive device that does not correspond to the added first information recording layer and that corresponds to the second and subsequent information recording layers (drive device that corresponds to the old standard) is naturally. Since the reproduction light for reproducing the rewrite layer is irradiated, it is possible to reliably focus on the second and subsequent information recording layers. For this reason, the drive device corresponding to the old standard does not need to correspond to the unknown information recording layer, and does not cause a reproduction failure. That is, the optical information recording medium according to the present invention can be reproduced even by a drive device that supports the old standard.

  Further, the first information recording layer is configured such that the interface between two adjacent resin layers both having translucency forms a concavo-convex shape corresponding to the information to be recorded. Therefore, the optical information recording medium according to the present invention does not require a ROM layer (metal thin film) formed of metal for forming the first information recording layer. Therefore, in the optical information recording medium according to the present invention, the translucency of the first information recording layer can be increased. Therefore, in the optical information recording medium according to the present invention, since the first information recording layer hardly inhibits the light incidence to the second and subsequent information recording layers, the light intensity at the time of recording is also compared with the case where the ROM layer is not provided. Almost no increase is required.

  Furthermore, in the optical information recording medium according to the present invention, the first information recording layer is formed with a concavo-convex shape corresponding to information to be recorded at the interface between two adjacent resin layers both having translucency. The first reproduction light that is configured and has a reflectance value at the reproduction light wavelength of the first information recording layer that is higher in intensity than the second reproduction light when reproducing the first information recording layer can be focused. Is a value that becomes For this reason, the drive device corresponding to the first information recording layer irradiates the first reproduction light having higher intensity than the second reproduction light when reproducing the first information recording layer. The recording layer can be focused, and the information recorded on the first information recording layer can be reproduced. Therefore, in this case, in the optical information recording medium according to the present invention, the recording capacity can be improved by the amount corresponding to the first information recording layer.

  In particular, since a ROM layer can be further provided on an optical information recording medium having two RE layers, which is difficult to be formed into three or more layers, the optical information recording medium can be maintained while maintaining the limit value of the recording capacity in the rewritable layer. Recording capacity can be improved.

  Here, when a ROM layer is provided on an optical information recording medium having two RE layers, which is difficult to be formed into three or more layers, the ROM layer is provided at a position different from that of the optical information recording medium according to the present invention. The reason why the problem occurs will be described below.

  First, in the case of an optical information recording medium in which a ROM layer is provided between two RE layers, interlayer crosstalk (noise from information recording layers other than the information recording layer being reproduced) of each of the three information recording layers is generated. It is necessary to provide a ROM layer at a position where there is no problem. For this reason, the addition of the ROM layer widens the distance between the two RE layers, so that the optical head of the driving device corresponding to the old standard can reproduce such an optical information recording medium. I can't.

  Usually, the objective lens of the optical head is designed to focus at a predetermined distance from the reproduction light incident surface which is the surface of the optical information recording medium. However, in the multilayer optical information recording medium, naturally, the distance of each information recording layer from the reproduction light incident surface is different. In this case, spherical aberration occurs in the information recording layer at a position other than the optimum distance, which adversely affects the reproduction signal in the driving device. Therefore, in order to eliminate this spherical aberration, for example, a beam expander is provided in the driving device.

  However, when the allowable range of the beam expander is expanded, an objective lens that more satisfies the sine condition is required. Such an objective lens is expensive because the conditions of tolerances such as eccentricity error and tilt error become very strict. As a result, the optical head becomes expensive. Therefore, in the drive device corresponding to the old standard optical information recording medium having no ROM layer, of course, an optical head provided with a beam expander that can cope with a case where the interval between the two RE layers becomes wide is provided. Often not. For this reason, it is highly possible that each of the two RE layers cannot be reproduced by a drive device that supports the old standard.

  Next, in the case of an optical information recording medium in which the ROM layer is provided after the two RE layers (that is, the ROM layer is provided closest to the substrate), the reflectance of each of the two RE layers is determined by the ROM layer. If it is almost the same as the case without the RE layer, the RE layer as the second information recording layer is likely to have a transmittance of 0% at the reproduction light wavelength (obviously apparent from the example of the two-layer RE-BD). For this reason, in such an optical information recording medium, there is a high possibility that the reproduction light cannot be condensed and irradiated onto the ROM layer.

  Therefore, as in the optical information recording medium according to the present invention, the added ROM layer is located in front of the two RE layers (that is, the position farthest from the substrate among the plurality of information recording layers stacked on the substrate). ) Is preferably provided.

  Further, according to the above configuration, since the reflectance value at the reproduction light wavelength of the first information recording layer is larger than 0.4%, for example, in BD, the reproduction laser power is suppressed to about 3.5 mW. it can. For this reason, in the optical information recording medium according to the present invention, it is possible to prevent the deterioration of the RE layer when counting the information recording layer for the reason described later.

  In order to solve the above problems, an optical information recording medium according to the present invention includes a plurality of information recording layers capable of reading information on a substrate by reproducing light, and an intermediate for separating each of the plurality of information recording layers. And a light transmitting layer provided at a position farthest from the substrate, and a first information recording layer provided at a position closest to the reproduction light incident side among the plurality of information recording layers is provided. An optical information recording medium including a plurality of resin layers, which is a layer that can only read information, and is a rewrite layer that includes a region in which at least one of the other information recording layers can rewrite information, The first information recording layer is configured such that an interface between two adjacent resin layers both having translucency forms an uneven shape corresponding to information to be recorded. The reflectance value at the reproduction light wavelength is The S-characteristic of the first information recording layer obtained by irradiating the second reproducing light when the rewriting layer is reproduced is the S-characteristic of the rewriting layer obtained by irradiating the second reproducing light. In comparison with the second reproduction light, it is necessary to change the gain of the detector that detects the S-characteristics to a certain extent, and the intensity is higher than that of the second reproduction light when reproducing the first information recording layer. The S-characteristic of the first information recording layer obtained by irradiating one reproduction light is such a value as to be the same as the S-characteristic of the rewriting layer obtained by irradiating the second reproduction light. It is characterized by being.

  According to the above configuration, the reflectance value at the reproduction light wavelength of the first information recording layer is the S-characteristic of the first information recording layer obtained by irradiating the second reproduction light when reproducing the rewrite layer. However, compared with the S-characteristics of other information recording layers obtained by irradiating the second reproduction light, it is necessary to change the gain of the detector that detects the S-characteristics to a certain extent. It is such a value. For this reason, a driving device that does not correspond to the added first information recording layer and that corresponds to the second and subsequent information recording layers (a driving device that corresponds to the old standard; hereinafter, the old standard) When the optical information recording medium according to the present invention is reproduced by the corresponding drive device), it is difficult to detect the first information recording layer by the old standard compatible drive device.

  That is, the old standard compliant drive device does not irradiate the first reproduction light for reproducing the first information recording layer that is not supported when counting the number of information recording layers of the optical information recording medium performed at the beginning of reproduction. Therefore, it is difficult for the old standard compliant drive device to detect the first information recording layer of the optical information recording medium according to the present invention without changing the gain of the S-characteristic detector to a predetermined value.

  On the other hand, the driving device (hereinafter referred to as a new standard-compliant driving device) that also supports the first information recording layer corresponds to the first information recording layer count of the optical information recording medium that is performed at the beginning of reproduction. First reproduction light for reproducing the information recording layer is irradiated. Therefore, the new standard compliant drive device can recognize the first information recording layer of the optical information recording medium according to the present invention without changing the gain of the S-characteristic detector.

  Therefore, the optical information recording medium according to the present invention does not cause a reproduction failure even in the old standard compliant drive device, and enables information reading from the second and subsequent information recording layers in the old standard compliant drive device. On the other hand, the optical information recording medium according to the present invention can read information from the first information recording layer when it is reproduced by a new standard compliant driving apparatus, and therefore has a recording capacity corresponding to the first information recording layer. Can be improved.

  Further, according to the above configuration, the reflectance value at the reproduction light wavelength of the first information recording layer is a value at which focus pull-in is impossible with the second reproduction light when reproducing the rewrite layer, When the first information recording layer is reproduced, the first reproduction light having a higher intensity than the second reproduction light can be focused. Therefore, according to the above configuration, the above-described effects can be obtained similarly. In other words, the optical information recording medium according to the present invention can be played back by the drive device corresponding to the old standard, and when it is played back by the drive device complying with the new standard, the recording capacity is improved by the amount of the first information recording layer. It becomes possible to make it.

  When the gain of the S-characteristic detector is not fixed when counting the number of information recording layers of the optical information recording medium performed at the initial stage of reproduction, the driving device can be provided with, for example, AGC. However, the driving device is in a state before focusing and cannot obtain a reference signal amplitude. For this reason, it is extremely difficult to appropriately detect the S-characteristics of the information recording layer other than fixing the drive device to a predetermined gain.

  In order to solve the above problems, an optical information recording medium according to the present invention includes a plurality of information recording layers capable of reading information on a substrate by reproducing light, and an intermediate for separating each of the plurality of information recording layers. And a light transmitting layer provided at a position farthest from the substrate, and a first information recording layer provided at a position closest to the reproduction light incident side among the plurality of information recording layers is provided. An optical information recording medium including a plurality of resin layers, which is a layer that can only read information, and is a rewrite layer that includes a region in which at least one of the other information recording layers can rewrite information, The first information recording layer is configured such that an interface between two adjacent resin layers both having translucency forms an uneven shape corresponding to information to be recorded. The reflectance value at the reproduction light wavelength is The second reproduction light when reproducing the rewritable layer is a value at which focus pull-in is impossible, and when reproducing the first information recording layer, the first reproduction light having higher intensity than the second reproduction light is used. It is a value that enables focus pull-in.

  According to the said structure, the 1st information recording layer is comprised by forming the uneven | corrugated shape according to the information in which the interface of the two adjacent resin layers which have translucency together is recorded, and the said 1st The value of the reflectance at the reproduction light wavelength of one information recording layer is a value that cannot be focused by the second reproduction light when reproducing the rewrite layer. Accordingly, a drive device that does not correspond to the added first information recording layer and that corresponds to the second and subsequent information recording layers (old standard-compliant drive device) naturally has the rewrite layer. Since the reproduction light for reproducing is irradiated, it is possible to reliably focus on the second and subsequent information recording layers. For this reason, the drive device corresponding to the old standard does not need to correspond to an unknown information recording layer and does not cause a reproduction failure. That is, the optical information recording medium according to the present invention can be reproduced even by an old standard compliant drive device.

  Further, the first information recording layer is configured such that the interface between two adjacent resin layers both having translucency forms a concavo-convex shape corresponding to the information to be recorded. Therefore, the optical information recording medium according to the present invention does not require a ROM layer (metal thin film) formed of metal for forming the first information recording layer. Therefore, in the optical information recording medium according to the present invention, the translucency of the first information recording layer can be increased. Therefore, in the optical information recording medium according to the present invention, since the first information recording layer hardly inhibits the light incidence to the second and subsequent information recording layers, the light intensity at the time of recording is also compared with the case where the ROM layer is not provided. Almost no increase is required.

  Furthermore, in the optical information recording medium according to the present invention, the first information recording layer is formed with a concavo-convex shape corresponding to information to be recorded at the interface between two adjacent resin layers both having translucency. The first reproduction light that is configured and has a reflectance value at the reproduction light wavelength of the first information recording layer that is higher in intensity than the second reproduction light when reproducing the first information recording layer can be focused. Is a value that becomes For this reason, the drive device corresponding to the first information recording layer irradiates the first reproduction light having higher intensity than the second reproduction light when reproducing the first information recording layer. The recording layer can be focused, and the information recorded on the first information recording layer can be reproduced. Therefore, in this case, in the optical information recording medium according to the present invention, the recording capacity can be improved by the amount corresponding to the first information recording layer.

In the optical information recording medium according to the present invention, the refractive index at the reproduction light wavelength of the resin layer located on the reproduction light incident side of the two adjacent resin layers is n ₁ , and the resin located on the substrate side. When the refractive index at the reproduction light wavelength of the layer is n ₂ ,

Is preferably satisfied.

  According to the above configuration, the reproduction light wavelength of the first information recording layer configured by forming an uneven shape corresponding to the information to be recorded at the interface between two adjacent resin layers both having translucency. The structure for obtaining the reflectance at can be specified.

Of the two adjacent layers, the refractive index at the reproduction light wavelength of the layer located on the reproduction light incident side is n ₁ , and the refractive index at the reproduction light wavelength of the layer located on the substrate side is n _2. The reflectance of the reproduction light at the interface between the layer positioned on the incident side of the reproduction light and the layer positioned on the substrate side, that is, the reflectance of the reproduction light in the first information recording layer is generally known under normal incidence conditions. It can be represented by the Fresnel equation below.

  In the optical information recording medium according to the present invention, of the two adjacent resin layers, the resin layer positioned on the reproduction light incident side is a light transmitting layer, and the resin layer positioned on the substrate side is an intermediate layer. Preferably there is.

  According to the above configuration, since the interface between the translucent layer and the intermediate layer forms the first information recording layer, the ROM layer (metal thin film) formed of a metal such as Ag, Al, or Au is used as the first information recording layer. The manufacturing process of the metal thin film can be reduced as compared with a conventional hybrid optical information recording medium that is improved in recording capacity by being additionally provided. In addition to the metal thin film manufacturing process, processes similar to the conventional processes can be used, so that it is not necessary to newly consider all the manufacturing processes of the optical information recording medium. As a result, the optical information recording medium according to the present invention can apply the conventional manufacturing know-how and can reduce the manufacturing process of the metal thin film as compared with the conventional one, so that the cost can be reduced.

  In the optical information recording medium according to the present invention, the two adjacent resin layers are preferably made of an ultraviolet curable resin.

  According to the above configuration, since two adjacent resin layers are both made of an ultraviolet curable resin, they can be formed by spin coating, curing with ultraviolet rays, or the like. For this reason, since a vacuum process is not required to form the first information recording layer, manufacturing cost and tact time can be reduced.

  In addition, since the refractive index of the ultraviolet curable resin can be controlled in production, the refractive index can be freely selected to a value of about 1.30 to 1.70, for example. For this reason, it is possible to control the reflectance of the first information recording layer.

  In addition, by appropriately selecting the ultraviolet resin that forms the two adjacent resin layers, the linear expansion coefficient or water vapor transmission rate of each of the two adjacent resin layers can be approximated. Generation of stress due to change can be reduced, and the reliability of the optical information recording medium can be ensured.

  The water vapor transmission rate (also referred to as moisture permeability, water vapor transmission coefficient, and water vapor transmission rate) is a physical property index indicating the degree to which a thin film material transmits moisture (water / water vapor). The water vapor transmission rate is defined as “the amount of water vapor that passes through a test piece of a unit area per unit time under predetermined temperature and humidity conditions”.

  In the optical information recording medium according to the present invention, the two adjacent resin layers are preferably composed mainly of a material having a common functional group.

  In the optical information recording medium according to the present invention, the two adjacent resin layers are preferably composed mainly of the same material having a common functional group.

  According to the above configuration, since the two adjacent resin layers are mainly composed of a material having a common functional group material or the same material having a common functional group, the linear expansion coefficient or the water vapor transmission rate is approximated. be able to. Therefore, in the optical information recording medium according to the present invention, the generation of stress due to temperature change or humidity change can be reduced, and the reliability of the optical information recording medium is ensured.

  An optical information recording medium driving device according to the present invention includes a plurality of information recording layers from which information can be read by reproduction light on a substrate, an intermediate layer separating each of the plurality of information recording layers, A translucent layer provided at a position farthest from the substrate, and among the plurality of information recording layers, at least a first information recording layer provided at a position closest to the incident side of the reproduction light is both translucent The interface between two adjacent resin layers each having a surface is formed by forming a concavo-convex shape corresponding to the information to be recorded, and is a layer that can only read information, and the other information recording layers An optical information recording medium driving apparatus capable of reproducing an optical information recording medium including a plurality of resin layers, wherein at least one layer is a rewriting layer including an area where information can be rewritten, wherein the first information recording layer is Playback light for playback Once again, larger than the reproduction light intensity when playing the rewritable layer, is characterized by small enough not to degrade the rewritable layer.

  According to the above configuration, the reproduction light intensity when reproducing the first information recording layer is larger than the reproduction light intensity when reproducing the rewrite layer. Therefore, the optical information recording medium driving device according to the present invention can reliably focus on the first information recording layer of the optical information recording medium according to the present invention, which can be reproduced even by the driving device corresponding to the above-mentioned old standard. The information recorded on the first information recording layer can be reproduced.

  As described above, the optical information recording medium according to the present invention has, on the substrate, a plurality of information recording layers from which information can be read by reproduction light, an intermediate layer that separates each of the plurality of information recording layers, A light transmitting layer provided at a position farthest from the substrate, and a first information recording layer provided at a position closest to the reproduction light incident side among the plurality of information recording layers reads out information. An optical information recording medium including a plurality of resin layers, wherein the first information recording layer is a rewriting layer including a region in which information can be rewritten among other information recording layers. The information recording layer is configured such that an interface between two adjacent resin layers having translucency forms a concavo-convex shape corresponding to information to be recorded, and the reproduction light wavelength of the first information recording layer Reflectance value at 0.4% A configuration is less than or equal to listen 2.2%.

  Therefore, the optical information recording medium according to the present invention has the versatility that the recording capacity of the rewritable layer can be maintained while maintaining the versatility that it can be applied to a drive device that supports the old standard optical information recording medium with few information recording layers. There is an effect that the recording capacity of the optical information recording medium can be improved while maintaining the limit value.

[Embodiment 1]
Embodiment 1 of the present invention is described below with reference to FIGS.

  As shown in FIG. 1, an optical information recording medium 200 as an example of Embodiment 1 includes a light transmitting layer 10 and a first information recording layer (first information recording layer, information recording layer) in order from the reproduction light incident surface side. Layer) 20, intermediate layer 30, second information recording layer (rewrite layer, information recording layer) 40, and substrate 50. FIG. 1 is a cross-sectional view showing an example of a schematic configuration of the optical information recording medium 200 according to the first embodiment.

  The translucent layer 10 is made of, for example, an ultraviolet curable resin having a thickness of 75 μm. The material of the light transmissive layer 10 may be any material as long as it has a high transmittance (that is, has a light transmitting property) at the wavelength of the reproduction light and satisfies a refractive index condition described later. Examples of the resin material that can be used for the light-transmitting layer 10 include epoxy acrylate, urethane acrylate, polyester acrylate, fluorinated acrylic resin, and epoxy resin. Moreover, the translucent layer 10 is not restricted to a single layer structure, It is good also as a two-layer structure of transparent resin films, such as a polycarbonate film, and a transparent adhesive resin layer. In addition, a structure in which a hard coat layer for surface protection is provided on the light incident surface of the translucent layer 10 may be used. Furthermore, the thickness of the light transmitting layer 10 may be changed according to the optical system of the reproducing device (driving device) of the optical information recording medium 200. The translucent layer 10 may be, for example, a 0.6 mm polycarbonate substrate.

  The intermediate layer 30 is made of, for example, a transparent ultraviolet curable resin having a thickness of 25 μm. The material of the intermediate layer 30 is not limited to this, and may be any material that has high transmittance (that is, has translucency) at the wavelength of the reproduction light and satisfies the refractive index condition described later. Examples of the resin material that can be used for the intermediate layer 10 include, for example, an epoxy acrylate, a urethane acrylate, a polyester acrylate, a fluorinated acrylic resin, and an epoxy resin. The thickness of the intermediate layer 30 is not limited to this, and each information recording layer (here, the first information recording layer 20 and the second information recording layer 40) can be separated, and interlayer crosstalk does not become a problem. It may be an appropriate thickness. Interlayer crosstalk refers to noise from information recording layers other than the information recording layer being reproduced. Further, the intermediate layer 30 may have a multilayer structure.

  The first information recording layer 20 includes an interface between the translucent layer 10 and the intermediate layer 30. As described above, the first information recording layer 20 side of the intermediate layer 30, that is, the surface of the light transmissive layer 10, is provided with prepits having unevenness, and thus the light transmissive formed adjacent to the intermediate layer 30. Information is recorded from the prepits at the interface with the layer 10. That is, the first information recording layer 20 is configured such that an interface between two adjacent resin layers having both translucency forms a concavo-convex shape (pre-pit) corresponding to information to be recorded.

  In order to prevent warpage between the light transmissive layer 10 and the intermediate layer 30, it is desirable to share or approximate characteristics such as thermal expansion of the light transmissive layer 10 and the intermediate layer 30.

  It is considered that the light transmitting layer 10 and the intermediate layer 30 are closer to the same constituent material, and the characteristics such as thermal expansion of the both are closer. Therefore, it is more preferable that the light-transmitting layer 10 and the intermediate layer 30 have a material having a common functional group as a main component of the light-transmitting layer 10 and the intermediate layer 30.

  Here, the refractive index of the translucent layer 10 and the intermediate layer 30 and the reflectance of the first information recording layer 20 will be described.

There are two thin films that are both transparent (having translucency), the refractive indexes are n ₁ and n ₂ , and the two thin films are sufficiently thick and have no optical interference effect. The energy reflectivity of normal incident light at its adjacent interface is the Fresnel equation under normal incidence conditions.

It is represented by

  In reproduction of an optical information recording medium, since the reproduction light is condensed (focused) on a desired thin film or interface and reflected by a beam waist, it is generally considered that the reflectivity is based on the condition of normal incidence. Are known.

Therefore, if the light-transmitting layer 10 and the intermediate layer 30 are the above-described two-layer thin films, the reflectance at the interface is expressed by the above formula when the refractive indexes of the light-transmitting layer 10 and the intermediate layer 30 are n ₁ and n ₂ , respectively. It can be expressed as That is, by appropriately setting the n ₁ and n ₂ , the reproduction light can be reflected at the interface, and the interface functions as the first information recording layer 20.

  It has been described above that the light transmitting layer 10 and the intermediate layer 30 may each have a multilayer structure. In that case, if the refractive index of at least a portion (layer) forming the first information recording layer 20 (that is, the interface) between the light transmitting layer 10 and the intermediate layer 30 satisfies the above condition, the reflection of the first information recording layer 20 is performed. Since the rate can be realized to be greater than 0.4% and 2.2% or less, other portions (layers) other than the above are not restricted by the above conditions. In addition, when each of the translucent layer 10 and the intermediate layer 30 is composed of a plurality of layers, it is difficult to adjust the refractive index and the cost is increased.

  Since the first information recording layer 20 in the present invention is composed of an interface between two adjacent layers, there is actually no layer as a structure. To be precise, the “information recording layer” is referred to as an “information recording surface”. Although it should be expressed, since it functions in the same manner as other information recording layers, it can be functionally expressed as an “information recording layer”.

  The first information recording layer 20 is a read-only layer, that is, a ROM layer. For example, the reflectance of the first information recording layer 20 at a reproduction light wavelength is greater than 0.4% and not more than 2.2%. If it is good. That is, the reflectance value of the first information recording layer 20 is a value at which focus pull-in is impossible with the second reproduction light when reproducing the rewrite layer (second information recording layer 40). The first reproduction light for reproducing the recording layer 20 may be a value that allows focus pull-in.

  Here, the second reproduction light is applied to the optical information recording medium 200 when reproducing the RE layer such as the second information recording layer 40. For example, the driving corresponding to the old standard optical information recording medium is performed. It can be irradiated even with an apparatus. The first reproduction light is higher in intensity than the second reproduction light, and is emitted to the optical information recording medium 200 (or an optical information recording medium 201 described later) when reproducing the first information recording layer 20. It is. The first reproduction light is emitted by a driving device corresponding to an optical information recording medium of a new standard.

  In order for the reflectance value of the first information recording layer 20 at the reproduction light wavelength to be greater than 0.4% and not more than 2.2%, the Fresnel equation under the normal incidence condition must satisfy the above condition. That's fine. That is,

Should be satisfied. For example, when n ₁ = 1.45 and n ₂ = 1.70, the reflectance is 0.63% (that is, 0.0063), and satisfies the above formula. The interface functions as the first information recording layer 20 of the present invention. As can be easily understood from the equation, the same value is obtained when n ₁ = 1.70 and n ₂ = 1.45.

  In general, the refractive indexes of the light-transmitting layer 10 and the intermediate layer 30 are generally used within the range of 1.45 to 1.70. Therefore, the above formula is satisfied by appropriately setting each refractive index within the above refractive index range. For example, when the refractive index of one resin layer is fixed at 1.45, the reflectance value of the first information recording layer 20 at the reproduction light wavelength is larger than 0.4% and not larger than 2.2%. From the above formula, the refractive index of the other resin layer is derived as 1.08 or more and less than 1.28, or greater than 1.65 and 1.96 or less. In consideration of the range of the actual refractive index that the resin having translucency can take, the above formula is satisfied when the refractive index range of the other resin layer is larger than 1.65 and not larger than 1.96.

  For example, when the refractive index of one resin layer is fixed at 1.70, the reflectance value of the first information recording layer 20 at the reproduction light wavelength is larger than 0.4% and not larger than 2.2%. The refractive index of the other resin layer is derived from the above formula to be 1.26 or more and less than 1.50, or more than 1.93 and 2.29 or less. In consideration of the range of the actual refractive index that the resin having translucency can take, the above formula is satisfied when the refractive index range of the other resin layer is 1.26 or more and less than 1.50.

Thus, by solving the above equation, appropriate values of the refractive indexes n ₁ and n ₂ can be easily derived.

  Moreover, for example, the refractive index of an ultraviolet curable resin can be generally adjusted in the range of about 1.30 to 1.70. For this reason, the refractive index of the translucent layer 10 and the intermediate | middle layer 30 can be adjusted as mentioned above by using an ultraviolet curable resin for the translucent layer 10 and the intermediate | middle layer 30, for example.

  Specifically, the adjustment of the refractive index of the ultraviolet curable resin is generally performed by blending another material having a different refractive index with respect to the resin material. As a material to be blended, a material containing a fluorine atom having a low atomic refraction, a sulfur atom having a high atomic refraction, an aromatic ring, a halogen other than fluorine, or the like is used.

  The material of the light transmissive layer 10 and the intermediate layer 30 is not limited to the ultraviolet curable resin, and a resin other than the ultraviolet curable resin may be used as long as the above refractive index condition is satisfied.

The second information recording layer 40 is an RE layer, and is composed of, for example, seven thin films. The seven-layered thin film includes a first protective film 41 (for example, ZnS—SiO _{2 having} a thickness of 35 nm), a second protective film 42 (for example, ZrO _{2 having} a thickness of 5 nm), and a recording layer 43 from the reproducing light incident side. (For example, GeTe—Sb ₂ Te _{3 with} a thickness of 10 nm), a third protective film 44 (for example, ZrO _{2 with} a thickness of 5 nm), a fourth protective film 45 (for example, ZnS—SiO _{2 with} a thickness of 35 nm), 5 protective film 46 (for example, ZrO _{2 having} a thickness of 5 nm) and reflective film 47 (for example, APC (AgPdCu) having a thickness of 20 nm) are sequentially laminated. The material, thickness, and number of layers of the second information recording layer 40 are not limited to this, and any material that functions as an RE layer may be used.

  The substrate 50 is made of polycarbonate having a thickness of 1.1 mm, for example. The material and thickness of the substrate 50 are not limited to this, and a groove is provided on the surface, and it is sufficient that the substrate 50 has a predetermined strength enough to be used as the substrate. Specifically, the substrate 50 may be made of, for example, a polyolefin resin or a metal. Further, the substrate 50 may have a multilayer structure.

  In addition to the groove, the surface of the substrate 50 may be provided with prepits having unevenness corresponding to information recorded as a shape in the second information recording layer 40. In this case, the area where the pre-pits of the second information recording layer 40 are provided is an area where only information can be read. That is, the second information recording layer 40 may include a RE area and a ROM area.

  As shown in FIG. 2, the optical information recording medium 201, which is another example of the first embodiment, has a light transmitting layer 10, a first information recording layer 20, and an intermediate layer 30 in order from the reproduction light incident surface side. The third information recording layer (rewrite layer, information recording layer) 60, the intermediate layer 930, the second information recording layer 40, and the substrate 50 are laminated. FIG. 2 is a cross-sectional view showing an example of a schematic configuration of the optical information recording medium 201 according to the first embodiment.

  The translucent layer 10 is made of, for example, an ultraviolet curable resin having a thickness of 50 μm. The material of the light transmissive layer 10 may be any material as long as it has a high transmittance (that is, has a light transmitting property) at the wavelength of the reproduction light and satisfies a refractive index condition described later. Examples of the resin material that can be used for the light-transmitting layer 10 include epoxy acrylate, urethane acrylate, polyester acrylate, fluorinated acrylic resin, and epoxy resin. Moreover, the translucent layer 10 is not restricted to a single layer structure, It is good also as a two-layer structure of transparent resin films, such as a polycarbonate film, and a transparent adhesive resin layer. In addition, a structure in which a hard coat layer for surface protection is provided on the light incident surface of the translucent layer 10 may be used. Furthermore, the thickness of the light transmitting layer 10 may be changed according to the optical system of the reproducing device (driving device) of the optical information recording medium 201. The translucent layer 10 may be, for example, a 0.6 mm polycarbonate substrate.

  The intermediate layer 30 is made of, for example, a transparent ultraviolet curable resin having a thickness of 25 μm. The material of the intermediate layer 30 is not limited to this, and may be any material that has high transmittance (that is, has translucency) at the wavelength of the reproduction light and satisfies the refractive index condition described later. As the intermediate layer 30, for example, the same material as that of the translucent layer 10 may be used. Further, the thickness of the intermediate layer 30 is not limited to this, and each information recording layer (here, the first information recording layer 20 and the second information recording layer 40) can be separated, and interlayer crosstalk becomes a problem. Any suitable thickness is acceptable. Further, the intermediate layer 30 may have a multilayer structure.

  The first information recording layer 20 includes an interface between the translucent layer 10 and the intermediate layer 30. As described above, the first information recording layer 20 side of the intermediate layer 30, that is, the surface of the light transmissive layer 10, is provided with prepits having unevenness, and thus the light transmissive formed adjacent to the intermediate layer 30. Information is recorded from the prepits at the interface with the layer 10. That is, the first information recording layer 20 is configured such that an interface between two adjacent resin layers having both translucency forms a concavo-convex shape (pre-pit) corresponding to information to be recorded.

The refractive indexes of the light transmitting layer 10 and the intermediate layer 30 and the reflectance of the first information recording layer 20 are the same as those already described with reference to FIG. The reflectance at the interface between the light-transmitting layer 10 and the intermediate layer 30 can be expressed by the formula already described in FIG. 1 when the refractive indexes of the light-transmitting layer 10 and the intermediate layer 30 are n ₁ and n ₂ , respectively. . That is, by appropriately setting the n ₁ and n ₂ , the reproduction light can be reflected at the interface, and the interface functions as the first information recording layer 20.

  Note that the light-transmitting layer 10 and the intermediate layer 30 may each have a multilayer structure. In that case, if the refractive index of at least the first information recording layer 20 of the translucent layer 10 and the intermediate layer 30, that is, the portion (layer) forming the interface satisfies the above condition, the reflectance of the first information recording layer 20 is 0.4. Since it is realizable so that it may become larger than% and 2.2% or less, the other part (layer) other than that is not restricted by the said conditions. In addition, when each of the translucent layer 10 and the intermediate layer 30 is composed of a plurality of layers, it is difficult to adjust the refractive index and the cost is increased.

  The first information recording layer 20 of the optical information recording medium 201 according to the present invention is composed of an interface between two adjacent layers, but functions substantially in the same manner as the other information recording layers. Since it may be expressed as “information recording layer”, it is expressed as “first information recording layer”.

  The first information recording layer 20 is a read-only layer, that is, a ROM layer. For example, the reflectance of the first information recording layer 20 at a reproduction light wavelength is greater than 0.4% and not more than 2.2%. If it is good. That is, the reflectance value of the first information recording layer 20 cannot be brought into focus by the second reproduction light when reproducing the rewrite layer (the second information recording layer 40 and the third information recording layer 60). Any value may be used as long as the focus can be pulled in with the first reproduction light when reproducing the first information recording layer 20.

  In order for the reflectance value of the first information recording layer 20 at the reproduction light wavelength to be greater than 0.4% and not more than 2.2%, the Fresnel equation under the normal incidence condition must satisfy the above condition. That's fine. That is,

Should be satisfied. For example, when n ₁ = 1.45 and n ₂ = 1.70, the reflectance is 0.63%, that is, 0.0063, and the above formula is satisfied, so that the interface between the translucent layer 10 and the intermediate layer 30 is It functions as the first information recording layer 20 of the present invention. As can be easily understood from the above formula, the same value is obtained when n ₁ = 1.70 and n ₂ = 1.45.

  In general, the refractive indexes of the light-transmitting layer 10 and the intermediate layer 30 are generally used within the range of 1.45 to 1.70. Therefore, the above formula is satisfied by appropriately setting each refractive index within the above refractive index range.

  Further, for example, the refractive index of an ultraviolet curable resin can be generally adjusted in the range of about 1.30 to 1.70. For this reason, the refractive index of the translucent layer 10 and the intermediate | middle layer 30 can be adjusted as mentioned above by using an ultraviolet curable resin for the translucent layer 10 and the intermediate | middle layer 30, for example. In addition, the material of the translucent layer 10 and the intermediate | middle layer 30 is not limited to ultraviolet curable resin, You may use resin other than ultraviolet curable resin, if the said refractive index conditions are satisfy | filled.

  The intermediate layer 930 (conventional intermediate layer) is made of, for example, a transparent ultraviolet curable resin having a thickness of 25 μm. The material of the intermediate layer 930 is not limited to this, and any material having a high transmittance at the wavelength of the reproduction light may be used. Further, the thickness of the intermediate layer 930 is not limited to this, and each information recording layer (here, the second information recording layer 40 and the third information recording layer 60) can be separated, and interlayer crosstalk becomes a problem. Any suitable thickness is acceptable.

  Further, the intermediate layer 930 may have a multilayer structure. The intermediate layer 930 may use the same material as the intermediate layer 30, or may use a different material. However, since the intermediate layer 930 does not form the first information recording layer 20 like the intermediate layer 30, the intermediate layer 930 is not restricted by the refractive index condition described above.

  In general, the refractive index of the intermediate layer 930 is often used within the range of 1.45 to 1.70, and can be used in the same manner as the conventional one within the above refractive index range. Further, for example, the refractive index of an ultraviolet curable resin can be generally adjusted in the range of about 1.30 to 1.70. For this reason, an ultraviolet curable resin may be used as the material of the intermediate layer 930. However, the material of the translucent layer 10 and the intermediate layer 30 is not limited to the ultraviolet curable resin.

  Further, if the refractive index of the intermediate layer 930 and the refractive index of the intermediate layer 30 are the same, a common material can be used for the intermediate layer 30 and the intermediate layer 930, which is advantageous in terms of cost. . Furthermore, since the linear expansion coefficient and the water vapor transmission rate can be approximated, it is possible to reduce the generation of stress associated with temperature changes and humidity changes, and to ensure the reliability of the optical information recording medium.

  In the intermediate layer 930 laminated between the second information recording layer 40 and the third information recording layer 60, the intermediate layer 930 (conventional intermediate layer) is provided on the surface on the third information recording layer 60 side. Is provided with a groove. In addition, the intermediate layer 930 may be provided with grooves and prepits having unevenness corresponding to information recorded as a shape in the third information recording layer 60. In this case, the area where the pre-pits of the third information recording layer 60 are provided is an area where only information can be read. That is, the third information recording layer 60 may include a RE area and a ROM area.

The second information recording layer 40 is an RE layer, and is composed of, for example, seven thin films. The seven-layered thin film includes a first protective film 41 (for example, ZnS—SiO _{2 having} a thickness of 35 nm), a second protective film 42 (for example, ZrO _{2 having} a thickness of 5 nm), and a recording layer 43 from the reproducing light incident side. (For example, GeTe—Sb ₂ Te _{3 with} a thickness of 10 nm), a third protective film 44 (for example, ZrO _{2 with} a thickness of 5 nm), a fourth protective film 45 (for example, ZnS—SiO _{2 with} a thickness of 35 nm), 5 protective film 46 (for example, ZrO _{2 having} a thickness of 5 nm) and reflective film 47 (for example, APC (AgPdCu) having a thickness of 20 nm) are sequentially laminated. The material, thickness, and number of layers of the second information recording layer 40 are not limited to this, and any material that functions as an RE layer may be used.

The third information recording layer 60 is an RE layer, and is composed of, for example, six layers of thin films. This six-layered thin film includes a first protective film 61 (for example, ZnS—SiO _{2 having} a thickness of 35 nm), a second protective film 62 (for example, ZrO _{2 having} a thickness of 5 nm), and a recording layer 63 from the reproduction light incident side. (For example, GeTe—Sb ₂ Te _{3 with} a thickness of 6 nm), a third protective film 64 (for example, ZrO _{2 with} a thickness of 5 nm), a translucent film 65 (for example, APC (AgPdCu) with a thickness of 20 nm), and transmission A rate adjusting film 66 (for example, TiO ₂ having a thickness of 19 nm) is sequentially stacked. The material, thickness, and number of layers of the third information recording layer 60 are not limited to this, and any material that functions as an RE layer having a transmittance of about 60% at the wavelength of the reproduction light may be used.

  The substrate 50 is made of polycarbonate having a thickness of 1.1 mm, for example. The material and the thickness of the substrate 50 are not limited to this, and it is sufficient that the groove is provided on the surface and has a predetermined strength that can be used as the substrate. Specifically, the substrate 50 may be made of, for example, a polyolefin resin or a metal. Further, the substrate 50 may have a multilayer structure.

  In addition to the groove, the surface of the substrate 50 may be provided with prepits having unevenness corresponding to information recorded as a shape in the second information recording layer 40. In this case, the area where the pre-pits of the second information recording layer 40 are provided is an area where only information can be read. That is, the second information recording layer 40 may include a RE area and a ROM area.

  The optical information recording medium 201 according to the first embodiment is not limited to the configuration described above, and any of the RE layers may be an R layer or a ROM layer. Further, the optical information recording media 200 and 201 according to the first embodiment are not limited to the two-layer or three-layer structure, and may be an optical information recording medium to which an information recording layer is further added.

〔Example〕
An optical information recording medium 200 according to Embodiment 1 shown in FIG. 1 was produced as Example 1, and an optical information recording medium 202 shown in FIG. 3 was produced as Comparative Example 1 of Example 1. Below, each structure is demonstrated using FIG. 1 and FIG. FIG. 3 is a cross-sectional view showing a schematic configuration of an optical information recording medium 202 that is Comparative Example 1 of the optical information recording medium 200 manufactured as Example 1. FIG.

  As shown in FIG. 1, the optical information recording medium 200 according to Example 1 includes a light transmitting layer 10, a first information recording layer 20, an intermediate layer 30, a second information recording layer 40, and the like in order from the reproduction light incident surface side. The substrate 50 has a stacked structure.

  The translucent layer 10 is made of an ultraviolet curable resin (refractive index of 1.45 at the reproduction light wavelength) having a thickness of 75 μm.

  The intermediate layer 30 is made of a transparent ultraviolet curable resin (refractive index of 1.70 at the reproduction light wavelength) having a thickness of 25 μm. In addition, the surface of the intermediate layer 30 on the first information recording layer 20 side, that is, on the light transmitting layer 10 side, corresponds to information recorded as a shape on the first information recording layer 20 by the 2P method (photo polymerization method). Prepits consisting of irregularities are provided. Here, the 2P method is a method in which an ultraviolet curable resin is filled between a flat plate and a master, and ultraviolet rays are irradiated to cure the ultraviolet curable resin, and then the master is peeled off to transfer the unevenness of the master onto the flat plate. It points out the technique to do. That is, the first information recording layer 20 is configured such that an interface between two adjacent resin layers having both translucency forms a concavo-convex shape (pre-pit) corresponding to information to be recorded.

The second information recording layer 40 is an RE layer, and seven thin films are laminated by sputtering. Specifically, from the reproduction light incident side, a first protective film 41 (ZnS—SiO _{2 with} a thickness of 35 nm), a second protective film 42 (ZrO _{2 with a} thickness of 5 nm), and a recording layer 43 (GeTe with a thickness of 10 nm). -Sb ₂ Te ₃ ), third protective film 44 (ZrO _{2 with a} thickness of 5 nm), fourth protective film 45 (ZnS—SiO _{2 with} a thickness of 35 nm), and fifth protective film 46 (ZrO _{2 with a} thickness of 5 nm). , And a reflective film 47 (APC (AgPdCu) having a thickness of 20 nm) are sequentially stacked.

  The substrate 50 was a polycarbonate disk-shaped substrate having a groove having a diameter of 120 mm and a thickness of 1.1 mm.

  As shown in FIG. 3, the optical information recording medium 202 of Comparative Example 1 includes a light transmitting layer 910, a first information recording layer 920, an intermediate layer 930, a second information recording layer 40, and The substrate 50 has a stacked structure. The first information recording layer 920 of the optical information recording medium 202 is made of a metal translucent film APC (AgPdCu) that has been conventionally used, and is formed to a thickness of 5 nm. The translucent layer 910 and the intermediate layer 930 are both made of an ultraviolet curable resin having a refractive index of 1.50 at the reproduction light wavelength, which has been conventionally used. The other layers (second information recording layer 40 and substrate 50) are produced in the same manner as in Example 1.

  The transmittance of the first information recording layer was 98% in Example 1 and 80% in Comparative Example 1. Further, the reflectance at the reproduction light wavelength of the first information recording layer 20 of Example 1 was 0.6%, and the return light rate of the second information recording layer 40 was 14.4%. On the other hand, the reflectance at the reproduction light wavelength of the first information recording layer 920 of Comparative Example 1 was 8%, and the return light ratio of the second information recording layer 40 was 9.6%.

  Here, the reflectance of the first information recording layer 20 was calculated as follows. The amount of reproduction light when focused on the mirror portion (planar portion) of the first information recording layers 20 and 920 of the optical information recording media 200 and 202 and the first information recording layers 20 and 920 by a disc evaluation machine to be described later. The ratio of the amount of reflected light reflected by and detected by the optical system detector was calculated. Furthermore, the calculated ratio was corrected using the ratio calculated in the same manner as described above for a reference disk with a known absolute reflectance. For this reason, the reflectance of the first information recording layers 20 and 920 is an absolute reflectance from which the influence of the optical system is removed. Similarly, the return light rate of the second information recording layer 40 was obtained from the reproduction light and the reflected light when focused on the mirror part (planar part) in the second information recording layer 40.

  Since it is difficult to measure the transmittance at the interface alone, the transmittances of the first information recording layers 20 and 920 were obtained by the following method.

  Specifically, the first information recording layers 20 and 920 were formed on a glass substrate having a refractive index of 1.53. At this time, in the case of Example 1, the intermediate layer 30 and the translucent layer 10 are arranged in this order on the glass substrate, and in the case of Comparative Example 1, the intermediate layer 930 (conventional intermediate layer) and the first information recording are formed on the glass substrate. Layer 920 (conventional first information recording layer) and translucent layer 910 (conventional translucent layer) were laminated in this order to produce two samples. Light is incident on the two samples from the first information recording layer 20 (first information recording layer 920) side, and the light transmittance is measured with a spectrophotometer. A value obtained by correcting the measured transmittance with the transmittance of the glass substrate alone serving as a reference is set as the light transmittance in the first information recording layer 20 (first information recording layer 920).

  Next, it is possible to emit a laser beam having a wavelength of 406 nm, which is generally used as an evaluation machine for BD, based on the S-characteristics detected when counting the number of information recording layers in the initial stage of reproduction in Example 1 and Comparative Example 1. Semiconductor lasers and N.I. A. (Aperture ratio) It measured with the disk evaluation machine (Pulstec company make ODU-1000) which has an optical system of 0.85. The results obtained by this measurement are shown in FIGS.

  Here, FIG. 4 shows the laser intensity, which is the intensity for reproducing the RE layer (second information recording layer 40), and is the maximum reproduction laser power in the current standardized BD driving apparatus. It is a figure which shows the S character characteristic obtained by setting to 7 mW and irradiating the optical information recording media 200 and 202, respectively. 4A shows S-characteristics obtained by measurement with respect to the optical information recording medium 200 according to Example 1, and FIG. 4B shows measurement with respect to the optical information recording medium 202 according to Comparative Example 1. It is a figure which shows the S-shaped characteristic obtained by these. FIG. 5 shows the S-characteristic obtained by irradiating the optical information recording medium 200 of Example 1 with the laser intensity set to 3.0 mW, which is the intensity for reproducing the ROM layer. FIG.

  As shown in FIG. 4A, the actual measurement value of the S-characteristic in the first information recording layer 20 of Example 1 is 65 mV, and the reference voltage + V1 (230 mV) for focusing in the disk evaluation machine is set. Not exceeded. Therefore, FIG. 4A shows a drive device (first information recording layer 20) that counts the number of information recording layers with a laser beam of 0.7 mW that is the maximum reproduction laser power in the currently standardized BD drive device. This indicates that the first information recording layer 20 cannot be recognized as an information recording layer. That is, it can be seen that the disk evaluation machine cannot detect the S-characteristic in the first information recording layer 20 of Example 1 unless the reference voltage + V1 shown in FIG.

  For this reason, the above-mentioned old standard compliant drive device cannot naturally focus on the first information recording layer 20. Actually, the first information recording layer 20 was focused at the time of measurement, but the above-mentioned disk evaluation machine with high versatility capable of supporting various optical information recording media as compared with a commercially available disk drive device for consumer use. There was no focus. Note that the reference voltage + V1 is a value set as a value by which the information recorded on the two-layer information recording medium can be reproduced and evaluated in the ODU-1000.

  On the other hand, as shown in FIG. 4B, the measured value of the S-characteristic in the first information recording layer 920 of Comparative Example 1 is 847 mV, which exceeds the reference voltage + V1 (230 mV). Therefore, FIG. 4B shows a drive device (first information recording layer 20) that counts the number of information recording layers with a laser beam of 0.7 mW that is the maximum reproduction laser power in the currently standardized BD drive device. It is shown that the first standard recording layer 920 can recognize the first information recording layer 920 as an information recording layer.

  From the above results, the first information recording layer 20 of Example 1 is compared with Comparative Example 1 with information of 0.7 mW laser light, which is the maximum reproduction laser power in the current standardized BD drive device. When counting the number of recording layers, the possibility of being recognized by the old standard-compliant drive device is extremely low. That is, it can be said that the first information recording layer 20 cannot be substantially recognized by the old standard-compliant drive device because it cannot be focused by a disk evaluator that is more versatile than a drive device that is normally used.

  On the other hand, the first information recording layer 920 of Comparative Example 1 has the old standard when counting the number of information recording layers with a laser beam of 0.7 mW which is the maximum reproduction laser power in the currently standardized BD drive device. The possibility of being recognized by the corresponding drive device is high. This is because the old standard-compliant drive device that is normally used at the present time can handle up to two information recording layers. However, since the old standard-compliant drive device recognizes an unknown information recording layer called the first information recording layer 920, there is a possibility of causing a reproduction failure.

  Further, as shown in FIG. 5, the actual measurement value of the S-characteristic in the first information recording layer 20 of Example 1 is 288 mV, which exceeds the reference voltage + V1 (230 mV). Therefore, FIG. 5 shows a drive device that counts the number of information recording layers with a laser beam of 3.0 mW that is the intensity for reproducing the first information recording layer 20 (a new device corresponding to the first information recording layer 20). The standard-compliant drive device) shows that the first information recording layer 20 can be recognized as an information recording layer. In other words, the above-mentioned new standard compliant drive device can naturally focus on the first information recording layer 20 and can reproduce the first information recording layer 20. Actually, the first information recording layer 20 was focused at the time of measurement, and it was confirmed that the focus was applied.

  As shown in FIGS. 4A and 5, the actual measured values of the S-characteristics of the second information recording layer 40 of Example 1 are 1535 mV and 6739 mV, respectively, and both have the reference voltage + V1 (230 mV). Over. For this reason, the second information recording layer 40 can be focused even if the driving device is compatible with any of the old and new standards (that is, the old standard-compliant driving device or the new standard-compliant driving device), and the second information recording is possible. Information can be recorded / reproduced on / from the layer 40.

  As described above, even when the optical information recording medium 200 according to the first embodiment is reproduced by the old standard-compliant drive device, the old standard-compliant drive device as in Comparative Example 1 is used. Information can be recorded / reproduced on the second information recording layer 40 without causing reproduction failure. In addition, since the information recorded on the first information recording layer 20 can be reproduced in the new standard-compliant driving device, the optical information recording medium 200 maintains the limit value of the recording capacity in the second information recording layer 40. It can be said that the recording capacity could be improved. The same applies to the optical information recording medium 201 according to the first embodiment.

  By the way, the limit that can be focused by a normally used driving device depends on the S-characteristic as described above, and thus basically depends on the amount of reflected light. Here, using the plurality of samples, the upper limit value of the reflectance that cannot be focused at each reproduction laser power was measured by the above-described disk evaluator. The measurement result at this time is shown in FIG.

  As shown in FIG. 6, at a maximum reproduction laser power of 0.7 mW in the current standardized BD drive device, the reflectance of 2.2% is the upper limit of the reflectance that cannot be focused (cannot be recognized). I understand that.

  Note that the reproduction laser power is likely to vary depending on the BD drive device, so in reality, the power of the reproduction laser power may be about 20% higher (0.84 mW). In this case (even if the reproduction laser power is 0.84 mW), the upper limit value of the reflectance that cannot be focused (cannot be recognized) was found to be 1.8% from the result shown in FIG.

  Further, the optical information recording media 200 and 201 according to the first embodiment include RE layers (second information recording layer 40 and third information recording layer 60). Therefore, when the number of information recording layers is counted, there is a possibility that reproduction light with high laser power for reproducing the first information recording layer 20 is condensed and irradiated on the RE layer.

  Incidentally, the information recording layer count is usually performed in the lead-in area. Therefore, the reflectance of the lead-in area of a single-layer BD-RE currently on the market can be increased by using a semiconductor laser capable of emitting laser light having a wavelength of 406 nm, which can increase the reproduction laser power from the disk evaluation machine, and N.D. A. (Aperture ratio) It measured with the disk evaluation machine (DDU-1000 by a pulse tech company) which has an optical system of 0.85.

  First, the reflectivity of the lead-in area was measured at 0.35 mW, which is the reproduction laser power of the single layer BD. Next, after irradiation with a higher reproduction laser power, the reflectivity was again returned to 0.35 mW and the lead-in area was Measure the reflectance. By this measurement, the reproduction laser power at which deterioration of the RE layer (reduction in reflectivity of the lead-in area) occurs was measured.

  As a result, it was found that the reflectance did not change until the reproduction laser power was 3.5 mW, but the reflectance decreased by 5% (that is, the RE layer deteriorated) at 4.0 mW. That is, when the number of information recording layers is counted with a laser power higher than 3.5 mW, the lead-in area of the RE layer may be deteriorated. Therefore, from the result shown in FIG. 6, when the upper limit value of the reflectance that is not focused at 3.5 mW is found to be 0.4%, the reflectance of the first information recording film needs to be larger than 0.4%. There will be.

  Therefore, the reflectance at the reproduction light wavelength of the first information recording layer 20 of the optical information recording media 200 and 201 according to Embodiment 1 may be greater than 0.4% and less than or equal to 2.2%, and more preferably. May be larger than 0.4% and 1.8% or less.

  Note that the measurement results by the two disk evaluators do not change as long as the reproduction light wavelength is in the blue laser wavelength range.

  By the way, in a normally used drive device, the information recording layer is recognized when the measured value of the S-characteristic detected from each information recording layer exceeds a predetermined reference voltage. When the information recording layer is recognized by the driving device, the recognized information recording layer is focused, and information can be reproduced from the information recording layer. The reason why information can be reproduced by focusing on the detection result of the S-characteristic will be described below.

  First, a reproduction system 100 for reproducing a general multilayer optical information recording medium will be described. For example, the configuration of the reproduction system 100 that reproduces the four-layer optical information recording medium 400 shown in FIG. 8 will be described below with reference to FIG.

  As shown in FIG. 7, the disk drive motor 101 of the reproduction system 100 rotates and drives a disk-shaped optical information recording medium 400 (see FIG. 8 for a schematic sectional structure) at a predetermined speed. The disk drive motor 101 is controlled by a motor control circuit 109. In addition, reading of information from the optical information recording medium 400 that is rotationally driven in this way is performed by the optical pickup 102.

  The optical pickup 102 is configured to move in the radial direction of the optical information recording medium 400 by the driving force of the feed motor 111. The feed motor 111 is controlled by a feed motor control circuit 108. Further, the feed motor 111 is configured such that the rotational speed thereof is detected by the speed detector 112. Then, the speed detector 112 supplies the detected result as a speed signal to the feed motor control circuit 108.

  The optical pickup 102 includes an objective lens 102a. The objective lens 102a is supported so as to be movable in a focusing direction (optical axis direction) and a tracking direction (radial direction of the optical information recording medium 400). The objective lens 102a is controlled in position in the focus direction by supplying the focus control signal generated by the focus control circuit 105 to the focus drive coil 102c. Similarly, the position of the objective lens 102a in the tracking direction is controlled by supplying the tracking control signal generated by the tracking control circuit 108 to the tracking drive coil 102b.

  Further, the laser control circuit 103 drives the semiconductor laser oscillator 102f in the optical pickup 102, and generates laser light in the semiconductor laser oscillator 102f. The light amount detector 102 g detects the light amount of the laser light generated by the semiconductor laser oscillator 102 f and feeds back the detection result to the laser control circuit 103. With this configuration, the laser control circuit 103 can control the amount of laser light generated by the semiconductor laser oscillator 102f to be constant.

  The laser light generated by the semiconductor laser oscillator 102f passes through the collimator lens 102e, is bent at a right angle by the half prism 102d, and then is recorded on any of the information recording media 400 by the objective lens 102a. Concentrate on the layer. Any one information recording layer of the optical information recording medium 400 refers to the first information recording layer A, the second information recording layer B, the third information recording layer C, or the fourth information recording layer D shown in FIG. The first information recording layer A, the second information recording layer B, the third information recording layer C, and the fourth information recording layer D all have APC ( This is a ROM layer that can only read information in which the shape of APC (AgPdCu) is fixed by forming (AgPdCu).

  Reflected light from the optical information recording medium 400 travels backward through the objective lens 102a and travels straight through the half prism 102d, and then is received by the photoelectric converter 102j via the condenser lens 102h and the cylindrical lens 102i. The photoelectric converter 102j includes four photodetectors 102j1 to 102j4 that generate an electrical signal corresponding to the amount of received light. In the case of the photoelectric converter 102j, the alignment direction of the photodetectors 102j1 and 102j2 and the alignment direction of the photodetectors 102j3 and 102j4 correspond to the tracking direction of the optical information recording medium 400. Similarly, the alignment direction of the photodetectors 102j1 and 102j4 and the alignment direction of the photodetectors 102j2 and 102j3 correspond to the tangential direction of the optical information recording medium 400.

  The electrical signal output from the photodetector 102j1 is supplied to one end of the adder circuits 113a and 113d via the amplifier circuit 114a, and the electrical signal output from the photodetector 102j2 is added to the adder circuit 113b via the amplifier circuit 114b. -It is supplied to one end of 113c. The electrical signal output from the photodetector 102j3 is supplied to the other ends of the adder circuits 113a and 113c via the amplifier circuit 114c, and the electrical signal output from the photodetector 102j4 is added via the amplifier circuit 114d. They are supplied to the other ends of the circuits 113b and 113d, respectively.

  The output signal of the adder circuit 113 a is supplied to the inverting input terminal − of the differential amplifier circuit 104, and the output signal of the adder circuit 113 b is supplied to the non-inverting input terminal + of the differential amplifier circuit 104. The differential amplifier circuit 104 generates a focus error signal by calculating the difference between the output signals of the adder circuits 113 a and 113 b and supplies the focus error signal to the focus control circuit 105. The focus control circuit 105 generates a focus control signal to be applied to the focus drive coil 102c so that the input focus error signal becomes 0 level, and focus servo is performed on the objective lens 102a.

  Here, the focus error signal output from the differential amplifier circuit 104 is obtained by performing focus search processing (that is, the number of information recording layers) by sequentially moving the condensing position of the laser beam by the objective lens 102a from the initial position in the focus direction. Is performed, an S-characteristic is drawn as shown in FIG. Specifically, when the focus search process is performed, the focus error signal indicates that the focus position of the laser beam by the objective lens 102a is the information recording layer (first information recording layer A, fourth information) shown in FIG. Each time it passes through the recording layer D, the third information recording layer C, and the second information recording layer B), an S-characteristic as shown in FIG. 9 is drawn. The initial position is a position before the focus of the objective lens 102a, and is usually below the first information recording layer A of the optical information recording medium 400 and from the optical information recording medium 400 in FIG. The most distant position in the optical axis direction.

  For example, at the start of reproduction of the optical information recording medium 400, the reproduction system 100 first generates reproduction light corresponding to the single-layer optical information recording medium by the semiconductor laser oscillator 102f in the optical pickup 102.

  Next, the condensing position of the laser beam by the objective lens 102a is moved from the initial position upward in FIG. 7 to the drive upper limit position. Then, the reproduction system 100 recognizes the number of information recording layers of the optical information recording medium 400 by counting the number of times that the focus error signal exceeds the predetermined reference voltage + V0.

  Thereafter, the reproduction system 100 changes the reproduction optical power determined based on the number of information recording layers included in the optical information recording medium 400. Then, the reproduction system 100 moves the condensing position of the laser beam by the objective lens 102a from the drive upper limit position downward to the initial position in FIG. 7 with the changed reproduction light power. At that time, the gain of the amplifier included in the focus control circuit 105 or the like is changed so that the voltage value of the focus error signal detected from the information recording layer first subjected to the focus search process becomes an appropriate value.

  For example, when the focus search process is performed on the second information recording layer B, the reproduction system 100 counts the number of times that the focus error signal exceeds a predetermined reference voltage + V0, and after reaching the fourth time, the reproduction system 100 first becomes 0 level. When the value reaches (center level of focus servo operation), the focus servo is turned on. Thereby, the focus search process for the second information recording layer B in the reproduction system 100 is completed.

  FIG. 10 is a diagram showing the transition of the objective lens position and the focus error signal when the focus search process is performed on the second information recording layer 40 by the reproduction system 100, and FIG. FIG. 4B is a diagram showing transition of the objective lens position, and FIG. 4B shows a focus error signal.

  Further, for example, when a layer jump is performed from the fourth information recording layer D to the second information recording layer B, the reproduction system 100 temporarily turns off the focus servo and switches the fourth information recording layer D to the second information recording layer 40. The focal position of the laser beam by the objective lens 102a is sequentially moved. Then, the reproduction system 100 counts the number of times that the focus error signal output from the differential amplifier circuit 104 exceeds a predetermined reference voltage + V0. Level), the focus servo is turned on. As a result, the layer jump process ends. The layer jump process is not shown because it is almost the same process as the focus search process.

  Further, when these focus search processes are performed, the phase difference detection circuit 107 has a phase difference between the sum of the output signals of the photodetectors 102j1 and 102j4 of the photoelectric converter 102j and the sum of the output signals of the photodetectors 102j2 and 102j3. To detect. The phase difference detection circuit 107 supplies the detection result to the tracking control circuit 106 as a tracking error signal.

  The tracking control circuit 106 generates a tracking control signal to be applied to the tracking drive coil 102b based on the input tracking error signal, and applies tracking servo to the objective lens 102a. In the reproduction system 100, the optical information recording medium 400 is reproduced while the tracking servo is being performed. Then, the electrical signals output from the adder circuits 113c and 113d are summed by the adder circuit 113e and converted into a digital signal by the data reproduction circuit 110.

  The laser control circuit 103, the focus control circuit 105, the tracking control circuit 108, the motor control circuit 109, and the data reproduction circuit 110 of the reproduction system 100 are controlled by the control unit 115. The control unit 115 stores information related to recording / reproduction of the optical information recording medium 400 loaded in the reproduction system 100. The control unit 115 controls the circuit according to this information.

  Further, when the reflectance from the information recording layer increases, the voltage value of the focus error signal of the reproduction system 100 also increases.

  Here, a flow of processing in the reproduction system 100 for reproducing a general multilayer optical information recording medium (here, the optical information recording medium 400) will be described. FIG. 11 is a flowchart showing the flow of processing in the reproduction system 100 for reproducing the multilayer optical information recording medium.

  First, after the optical information recording medium 400 is loaded into the reproduction system 100, the optical information recording medium 400 is rotated at a predetermined rotational speed by the disk drive motor 101 (S1). Next, the control unit 115 moves the optical pickup 102 to a position facing the lead-in area of the optical information recording medium 400, and performs a focus search process on a desired layer (S2). This layer refers to any one of the first information recording layer A, the second information recording layer B, the third information recording layer C, and the fourth information recording layer D in the optical information recording medium 400. Then, the tracking control circuit 106 performs tracking processing (S3), and information reproduction processing by the reproduction system 100 is performed (S4).

  As described above, in the reproduction system 100, it is understood that the recognition of the information recording layer and the focus on each information recording layer are all performed based on the S-characteristic obtained from each information recording layer. Therefore, since the reproduction system 100 for the multilayer optical information recording medium as described above is used in the drive device, the drive device recognizes the information recording layer by measuring the S-characteristic of each information recording layer. The presence / absence and the propriety of reproduction can be determined.

[Embodiment 2]
The second embodiment of the present invention will be described with reference to FIG. A reproduction system (optical information recording medium driving apparatus) 600 as an optical information recording medium driving apparatus according to the second embodiment of the present invention includes a control unit 615 instead of the control unit 115 of the reproducing system 100 shown in FIG. It becomes the composition. Since the configuration other than the control unit 615 has the same function as the configuration provided in the reproduction system 100, the description thereof is omitted.

  The control unit 615 stores information for recording / reproduction corresponding to, for example, the optical information recording media 200 and 201 of the first embodiment. This information refers to, for example, reproduction light intensity when counting the number of information recording layers, reproduction light intensity corresponding to each information recording layer, and the like.

  Therefore, for example, when the optical information recording medium 200 is loaded, the laser control circuit 603 is controlled by the control unit 615 at the start of the first information recording layer number count, so that the semiconductor laser oscillator in the optical pickup 602 is provided. 602f is driven. That is, the laser control circuit 603 generates reproduction light (first reproduction light) corresponding to the first information recording layer 20 in the optical information recording medium 200 in the semiconductor laser oscillator 602f.

  That is, in the reproduction system 600, even when the loaded optical information recording medium is, for example, the optical information recording medium 200 or 201 according to the first embodiment, the S-characteristic obtained from the first information recording layer 20 is The value exceeds the reference voltage + V0. For this reason, the reproduction system 600 can recognize and focus on the first information recording layer 20 of the new standard, so that the information obtained from the first information recording layer 20 can be reproduced.

  When focusing on a layer other than the first information recording layer 20, the laser control circuit 603 is controlled by the control unit 615, so that an information recording layer other than the first information recording layer 20 (for example, the second information recording layer 20). The reproduction light (second reproduction light) having a lower intensity corresponding to the layer 40 or the third information recording layer 60) is changed. Therefore, the reproduction system 600 can focus on information recording layers other than the first information recording layer 20, so that information recorded on the information recording layer can also be reproduced.

  Furthermore, when the loaded optical information recording medium is an optical information recording medium of an old standard different from the optical information recording media 200 and 201 (for example, the optical information recording medium 500), the reproduction system 600 includes an information recording layer. After counting several times, the S-characteristic of the first information recording layer 20 corresponding to the new standard is not detected. Therefore, the reproduction system 600 can recognize that the optical information recording medium is not compatible with the new standard.

  Therefore, in the reproduction system 600, similarly to the optical information recording media 200 and 201 described above, the laser control circuit 603 is controlled by the control unit 615, and the intensity corresponding to the information recording layers other than the first information recording layer 20 of the new standard is increased. Is changed to low reproduction light (second reproduction light). As a result, the reproduction system 600 can also reproduce each information recording layer of the old standard optical information recording medium.

  As described above, the reproduction system 600 as the optical information recording medium driving apparatus according to the second embodiment ensures that each information recording layer of the optical information recording medium can be used regardless of the new or old optical information recording medium. Can be played.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. Embodiments are also included in the technical scope of the present invention.

  The optical information recording medium according to the present invention includes various optical information recording media such as CD, DVD, HD-DVD, BD, etc., magneto-optical disc, phase change type disc, etc. and optical information recording medium drive. It can be applied to the device.

It is sectional drawing which shows an example of schematic structure of the optical information recording medium which concerns on Embodiment 1 of this invention. It is sectional drawing which shows another example of schematic structure of the optical information recording medium which concerns on Embodiment 1 of this invention. It is sectional drawing which shows the comparative example of schematic structure of the optical information recording medium shown in FIG. FIG. 4 is a diagram showing the S-characteristic measurement results of Example 1 shown in FIG. 1 and Comparative Example 1 shown in FIG. 3 at a reproduction laser power of 0.7 mW. FIG. The obtained S-characteristic is shown, and FIG. 5B is a diagram showing the S-characteristic obtained by the measurement with respect to Comparative Example 1. It is a figure which shows the S-shaped characteristic measurement result of Example 1 shown in FIG. 1 in reproduction laser power 3.0mW. It is a figure which shows the reproduction laser power dependence of the upper limit of the reflectance which cannot focus. It is explanatory drawing which shows an example of the reproduction | regeneration system which reproduces | regenerates the conventional multilayer optical information recording medium. FIG. 11 is a cross-sectional view showing a conventional multilayer optical information recording medium and a four-layer optical information recording medium. It is explanatory drawing which shows the S-characteristic in the reproduction | regeneration system shown in FIG. FIG. 9A is a diagram showing a transition of an objective lens position and a focus error signal when focus search processing is performed on the second information recording layer shown in FIG. 8 by the reproduction system shown in FIG. It is a figure which shows the transition of a lens position, The same figure (b) shows a focus error signal. It is a flowchart which shows the flow of a process in the reproduction | regeneration system shown in FIG. It is explanatory drawing which shows an example of the reproduction | regeneration system which reproduces | regenerates the multilayer optical information recording medium based on Embodiment 2 of this invention. It is sectional drawing which is a conventional multilayer optical information recording medium, and shows an example of the optical information recording medium of 2 layer structure.

Explanation of symbols

10 translucent layer 20 first information recording layer (first information recording layer, information recording layer)
30 Intermediate layer 40 Second information recording layer (rewrite layer, information recording layer)
50 Substrate 60 Third information recording layer (rewrite layer, information recording layer)
200, 201 Optical information recording medium 600 Playback system (optical information recording medium driving device)

Claims (10)

On the substrate, a plurality of information recording layers from which information can be read by reproduction light, an intermediate layer separating each of the plurality of information recording layers, and a light-transmitting layer provided at a position farthest from the substrate And the first information recording layer provided at a position closest to the reproduction light incident side among the plurality of information recording layers is a layer from which information can only be read, and among other information recording layers An optical information recording medium comprising a plurality of resin layers, wherein the at least one layer is a rewriting layer containing an area where information can be rewritten,
The first information recording layer is configured such that an interface between two adjacent resin layers both having translucency forms a concavo-convex shape corresponding to information to be recorded,
An optical information recording medium, wherein the first information recording layer has a reflectance value at a reproduction light wavelength of more than 0.4% and not more than 2.2%. On the substrate, a plurality of information recording layers from which information can be read by reproduction light, an intermediate layer separating each of the plurality of information recording layers, and a light-transmitting layer provided at a position farthest from the substrate And the first information recording layer provided at a position closest to the reproduction light incident side among the plurality of information recording layers is a layer from which information can only be read, and among other information recording layers An optical information recording medium comprising a plurality of resin layers, wherein the at least one layer is a rewriting layer containing an area where information can be rewritten,
The first information recording layer is configured such that an interface between two adjacent resin layers both having translucency forms a concavo-convex shape corresponding to information to be recorded,
The reflectance value at the reproduction light wavelength of the first information recording layer is:
Smaller than the return light rate of the rewrite layer,
By irradiating the first information recording layer with the first reproduction light having a higher intensity than the second reproduction light when reproducing the rewrite layer, the first information recording layer is irradiated with the first information recording layer. An optical information recording medium having a value large enough to enable focusing of the layer. On the substrate, a plurality of information recording layers from which information can be read by reproduction light, an intermediate layer separating each of the plurality of information recording layers, and a light-transmitting layer provided at a position farthest from the substrate And the first information recording layer provided at a position closest to the reproduction light incident side among the plurality of information recording layers is a layer from which information can only be read, and among other information recording layers An optical information recording medium comprising a plurality of resin layers, wherein the at least one layer is a rewriting layer containing an area where information can be rewritten,
The first information recording layer is configured such that an interface between two adjacent resin layers both having translucency forms a concavo-convex shape corresponding to information to be recorded,
The reflectance value at the reproduction light wavelength of the first information recording layer is:
The S-characteristic of the first information recording layer obtained by irradiating the second reproduction light when the rewrite layer is reproduced is the S-characteristic of the rewrite layer obtained by irradiating the second reproduction light. Compared to the above, it is necessary to change the gain of the detector for detecting the S-characteristics, and it is necessary to be detected to some extent
When reproducing the first information recording layer, the S-characteristic of the first information recording layer obtained by irradiating the first reproduction light having a higher intensity than the second reproduction light has the second reproduction light An optical information recording medium having a value that is the same as the S-shaped characteristic of the rewritten layer obtained by irradiation. On the substrate, a plurality of information recording layers from which information can be read by reproduction light, an intermediate layer separating each of the plurality of information recording layers, and a light-transmitting layer provided at a position farthest from the substrate And the first information recording layer provided at a position closest to the reproduction light incident side among the plurality of information recording layers is a layer from which information can only be read, and among other information recording layers An optical information recording medium comprising a plurality of resin layers, wherein the at least one layer is a rewriting layer containing an area where information can be rewritten,
The first information recording layer is configured such that an interface between two adjacent resin layers both having translucency forms a concavo-convex shape corresponding to information to be recorded,
The reflectance value at the reproduction light wavelength of the first information recording layer is a value at which focus pull-in is impossible with the second reproduction light when reproducing the rewrite layer, and the first information recording layer is reproduced. The optical information recording medium is characterized in that the first reproduction light having a higher intensity than the second reproduction light has a value that enables focus pull-in. Of the two adjacent resin layers, the refractive index at the reproduction light wavelength of the resin layer located on the incident side of the reproduction light is n ₁ , and the refractive index at the reproduction light wavelength of the resin layer located on the substrate side is When n ₂

The optical information recording medium according to claim 1, wherein:   6. The resin layer located on the reproduction light incident side of the two adjacent resin layers is a translucent layer, and the resin layer located on the substrate side is an intermediate layer. The optical information recording medium according to any one of the above.   The optical information recording medium according to any one of claims 1 to 6, wherein each of the two adjacent resin layers is made of an ultraviolet curable resin.   The optical information recording medium according to claim 7, wherein the two adjacent resin layers are mainly composed of a material having a common functional group.   The optical information recording medium according to claim 7, wherein the two adjacent resin layers are mainly composed of the same material having a common functional group. On the substrate, a plurality of information recording layers from which information can be read by reproduction light, an intermediate layer separating each of the plurality of information recording layers, and a light-transmitting layer provided at a position farthest from the substrate The first information recording layer provided at least closest to the incident side of the reproduction light among the plurality of information recording layers has an interface between two adjacent resin layers, both of which are translucent. It is a layer that is configured by forming a concavo-convex shape according to the information to be read and can only read information, and an area in which at least one of the other information recording layers can rewrite information. An optical information recording medium driving device capable of reproducing an optical information recording medium including a plurality of resin layers, which is a rewriting layer including:
An optical information recording medium driving device characterized in that a reproducing light intensity when reproducing the first information recording layer is larger than a reproducing light intensity when reproducing the rewriting layer and is small enough not to deteriorate the rewriting layer. .

Images