JP2007157219A - Multilayer optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer optical information recording medium which is free from degradation of an SN ratio, degrading of precision of tracking control and restriction in processing of a control layer due to increase of noise caused by a wavelength and angular change of incident light and has a small change of a light quantity in recording and reading a signal. <P>SOLUTION: On a substrate 1, repeating an intermediate layer 2, a recording layer 3, an intermediate layer 2, furthermore, a recording layer 3, an intermediate layer 2, ... from the side of the substrate 1, five recording layers 3 and six intermediate layers 2 are laminated with a multilayer structure of the recording layers 3 and the intermediate layers 2 as a single unit. Moreover, a separation layer (spacer layer) 4 is laminated, and another single unit is laminated in order across the separation layer 4. The single unit laminated next is obtained similarly by laminating five recording layers 3 and six intermediate layers 2 repeating an intermediate layer 2, a recording layer 3, .... On each recording layer 3, a recording mark is formed by convergence spot which is obtained by condensing light of a light source wavelength with an objective lens. In laminating of two or more single units, even when reflectivity is high at single units on and under the separation layer 4, transmittance of the whole is prevented from being degraded, so that transmittance is improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical information recording / reproducing apparatus and recording medium for recording an optical file system and video information, and more particularly to an information recording / reproducing apparatus for a multi-layer optical recording medium and a multilayer optical information recording medium capable of increasing its use efficiency. It is.

  As a conventional multilayer optical information recording medium, Patent Document 1 discloses a method and apparatus for optically writing information to an optical recording medium having at least two recording surfaces and a guide surface, and reading and / or erasing the written information. Are listed. The structure of the recording medium described in Patent Document 1 shown in FIG. 14 is configured by providing one track layer (control layer) 5 for a plurality of recording layers 3.

  Patent Document 2 describes a configuration of a recording medium in which a tracking control layer and a photosensitive material are stacked in layers as an optical recording medium, an optical pickup device, and a recording / reproducing device. An optical memory element in which a recordable recording layer is provided adjacent to a resin core layer or a resin clad layer, in order to prevent mixing between the recording layer and the resin core layer or the resin clad layer. A configuration in which a barrier layer is provided is described.

Patent Document 4 discloses a pressure-sensitive adhesive sheet for optical recording media, a multilayer structure for optical recording media, and a multilayer recording medium, in which an optical recording layer containing a photosensitive material and an adhesive layer are laminated. An optical recording medium having a multilayer structure in which recording layers and non-recording layers are alternately laminated using an adhesive sheet is described.
Japanese Patent No. 3110532 JP 2003-36537 A JP 2003-141739 A JP 2005-259192 A

  However, the multi-layered optical information recording medium having such a configuration has a wavelength dependency due to an increase in the amplitude of the reflectance of the reflected return light under a specific wavelength or incident angle condition when the multilayer structure is multistaged. Getting stronger. For this reason, the amount of light at the time of signal recording and reading changes due to changes in wavelength and angle of incident light, so that noise increases and the S / N ratio deteriorates.

  As shown in FIG. 14, when a tracking control layer is added to an optical recording medium for multi-layer recording, the distance between each multi-layer recording layer and the control layer can be increased by increasing the number of layers. Therefore, it becomes difficult to ensure the accuracy of control.

  In addition, since the multi-layered recording layer and the control layer are in close contact with each other, when the recording layer and the control layer are sequentially stacked, there is a problem that the processing process of the control layer is limited and the degree of freedom in design is reduced. It was.

  The present invention is directed to solving the above-described problems of the prior art, and in a multi-layered optical recording medium, the change in the amount of light during signal recording and reading is small, and noise due to the change in wavelength and angle of incident light. The S / N ratio does not deteriorate due to the increase in the number of recording layers, and even if the number of recording layers is multi-layered, the tracking control accuracy is ensured to reduce the decrease in accuracy, and each recording layer is controlled. An object of the present invention is to provide a multilayer optical information recording medium in which, when the layers are sequentially laminated, there is no restriction on the processing process of the control layer and the degree of freedom in design is not limited.

  In order to achieve the above object, a multilayer optical information recording medium according to claim 1 of the present invention has a multilayer structure composed of two or more layers of a recording layer and an intermediate layer as one unit, and one unit of the multilayer structure is By having a structure in which a plurality of layers are stacked in the depth direction via the spacer layer, the optical phase change between one unit of the multilayer structure can be adjusted and optimized by the spacer layer, and the reflectance of the reflected return light In addition, it is possible to weaken fluctuations in amplitude due to wavelength fluctuations and incident angle changes.

  Further, in the multilayer optical information recording medium described in claims 2 and 3, the plurality of spacer layers in the multilayer optical information recording medium according to claim 1 have different layer thicknesses or refractive indexes. In the unit, the arrangement period of the recording layer and the intermediate layer, the refractive index of the recording layer, and the refractive index of the intermediate layer are constant within one unit, and the arrangement period, the refractive index of the recording layer, or the refractive index of the intermediate layer is 1. Due to the difference in units, the relative phase during propagation of light between each unit of the multilayer structure changes, and the reflectance and amplitude of reflected return light fluctuate due to changes in wavelength and incident angle. Can be weakened by interference.

  The multilayer optical information recording medium according to any one of claims 4 to 7 is a multilayer structure in which a control layer for generating a tracking control signal provided for each unit in the multilayer optical information recording medium according to claims 1 to 3 is formed as one unit. And laminated adjacent to the first recording layer, laminated in the middle part of the multilayer structure constituting one unit, and further adhered to the control layer for generating the tracking control signal provided for each unit. Alternatively, the adhesive layer is provided, or the control layer is recorded with the order information of the combination of the recording layer and the intermediate layer configured as one unit and the information indicating the position in the multilayer optical information recording medium. Tracking control can be performed based on the control layer, and it can be formed without being restricted by the control layer when one unit of the multilayer structure is stacked in the depth direction.

  A multilayer optical information recording medium according to claim 8 or 9 is characterized in that a spacer layer laminated between one unit and one unit of the multilayer structure in the multilayer optical information recording medium of claims 1 to 7 is an adhesive layer or an adhesive layer. Furthermore, by providing a barrier layer between the recording layer and the intermediate layer that constitute one unit in one unit of the multilayer structure, a configuration in which one unit of the multilayer structure is sequentially laminated can be facilitated. When the recording layer and the intermediate layer are formed, the solvent of one layer can be formed without affecting the other layer.

  The multilayer optical information recording medium according to claim 10 is characterized in that one unit is a recording layer in which a plurality of recording spots formed by changing the surroundings and optical properties are periodically arranged and arranged in layers. Since the recording layer has a structure in which a plurality of layers are stacked in the depth direction via the spacer layer, the optical phase change between one unit of the multilayer structure can be adjusted and optimized by the spacer layer, and the reflected return light can be optimized. It is possible to weaken fluctuations in the reflectivity and amplitude thereof due to changes in wavelength and changes in incident angle.

  Further, in the multilayer optical information recording medium described in claims 11 and 12, each of the plurality of spacer layers in the multilayer optical information recording medium according to claim 10 has a different layer thickness or refractive index. In the unit, the layered period in which the recording spot is arranged is constant within one unit, and the layered period in which the recording spot is arranged is different for each unit. It is possible to weaken the reflectance and amplitude of the reflected return light due to the change in wavelength and the change in incident angle due to mutual interference.

  The multilayer optical information recording medium according to any one of claims 13 to 16 is a recording layer comprising one unit of a control layer for generating a tracking control signal provided for each unit in the multilayer optical information recording medium according to claims 10 to 12. Laminated adjacent to each other, laminated in the middle of the recording layer constituting one unit, and further provided an adhesive layer or adhesive layer adjacent to the control layer for generating the tracking control signal provided for each unit. Or by recording configuration information relating to a plurality of periodic arrangements and layered arrangements of recording spots and information representing positions in the multilayer optical information recording medium in the recording layer configured as one unit in the control layer, Tracking control can be performed for each unit based on the control layer, and when one unit of a multilayer structure is stacked in the depth direction, it can be formed without being restricted by the control layer.

  The multilayer optical information recording medium according to claim 17 or 18 is characterized in that a spacer layer laminated between one unit and one unit of the recording layer in the multilayer optical information recording medium according to claims 10 to 16 is an adhesive layer or an adhesive layer. Furthermore, through a recording layer in which a plurality of recording spots whose optical properties change with the surroundings are periodically arranged and arranged in layers, and an intermediate layer that does not form a recording spot in place of the spacer layer By having a structure in which a plurality of layers are stacked in the depth direction, a configuration in which one unit is sequentially stacked can be facilitated.

  According to the present invention, a multi-layer light that suppresses changes in the amount of reflected light during signal recording and reading due to changes in the wavelength and angle of incident light, reduces noise and S / N ratio degradation, and improves tracking accuracy. There is an effect that an information recording medium can be provided.

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

  FIG. 1 is a diagram showing a configuration of a multilayer optical information recording medium according to Embodiment 1 of the present invention. The first embodiment will be described with reference to FIG. As shown in FIG. 1, the first intermediate layer 2, the first recording layer 3, the second intermediate layer 2, the second recording layer 3, and the third intermediate layer 2 are repeated on the substrate 1. For example, 5 layers of the recording layer 3 and 6 layers of the intermediate layer 2 are laminated with a multilayer structure including the recording layer 3 and the intermediate layer 2 as one unit. Furthermore, a separation layer (spacer layer) 4 is laminated thereon. As described above, a multilayer optical information recording medium is constructed by laminating a single unit of multilayer recording medium on the substrate 1 with the spacer layer 4 interposed therebetween.

  As another unit, the intermediate layer 2, the recording layer 3, and the intermediate layer 2 are repeated, and similarly, the recording layer 3 has five layers and the intermediate layer 2 has six layers. Here, light of the light source wavelength is condensed by the objective lens on the recording layer 3 of the optical recording medium, and a recording mark is formed by the condensed spot.

  In the first embodiment, a material in which the refractive index of the recording mark increases with respect to the surroundings may be used. Conversely, a material in which the refractive index decreases with respect to the surroundings may be used. Further, it is desirable that the thickness of the recording layer 3 is smaller than the size of the focused spot in the depth direction. On the contrary, it is desirable that the thickness of the intermediate layer 2 is about the size of the focused spot in the depth direction or larger.

  In addition, since reading of recorded information differs depending on whether the recording layer 3 has a refractive index or not, the reflectance at the interface between the intermediate layer 2 and the recording layer 3 differs depending on the presence or absence of the recording mark. Using the, read by the intensity of reflected light.

  As the substrate 1, a material transparent to the light source wavelength such as glass, oxide crystal, polycarbonate, and polyolefin can be applied. The intermediate layer 2 is made of a material that is transparent with respect to the light source wavelength, and the recording layer 3 is set so as to absorb a part of light having the light source wavelength. Further, as the intermediate layer 2, a resin such as polyvinyl alcohol or ethylene vinyl alcohol is applied and laminated. For example, a transparent resin such as polycarbonate, polystyrene, polyamide, epoxy, or urethane resin and its film are fused. It can also be formed by lamination by extrusion, lamination, vapor deposition, or the like.

  Furthermore, the material is not limited to an organic material, and can be formed by a method such as vapor deposition of glass or oxide, sputtering, or the like. As the recording layer 3, a mixture of a resin such as polymethyl methacrylate and polystyrene and a photochromic dye that absorbs light of a specific light source wavelength such as spiropyran, diarylethene, and fulgide and changes its absorption wavelength and refractive index is applied or mixed. The layers are stacked by vapor deposition. In a recording medium using these dyes, a recording method such as multiphoton absorption including two-photon absorption can be used by using a laser light source with a short pulse and high output. The separation layer (spacer layer) 4 can be formed by the same method using the same material as the intermediate layer 2.

  In addition, a barrier layer (not shown) is provided between the recording layer 3 and the intermediate layer 2 constituting one unit, and when the multilayer structure of the recording layer 3 and the intermediate layer 2 is formed by this barrier layer, Even in the case where the solvent of the layer dissolves the other layer, there is a barrier layer of another material between them, so that each layer can be formed by a simple method such as application of a solvent. Further, in the configuration of the recording layer 3 and the intermediate layer 2 to be described later, it is possible to easily cope with the case where each layer is thinned to increase the transmittance.

  Next, the characteristics of the multilayer optical information recording medium of the first embodiment will be described with reference to FIGS. FIG. 2 shows the relative reflectance of the multilayer optical information recording medium shown in FIG. 1 when viewed from the opposite side of the substrate 1 when the combination of the intermediate layer 2 and the recording layer 3 is 5 layers and 50 layers. It is a figure which shows the relationship between the number of layers and the reflectance which were compared. Here, the effect of the spacer layer 4 and the substrate 1 is not considered, and the combination of the intermediate layer 2 and the recording layer 3 is simply repeated to change only the number of layers.

  This calculation example shows a calculation example of the reflectance of the multilayer structure when the refractive index n2 of the recording layer 3 is 1.6, the refractive index n3 of the intermediate layer 2 is 1.5, and the light source wavelength λ is 0.66 μm. ing. When the recording layer 3 has a thickness of λ / 4n2 and the intermediate layer 2 has an odd multiple of λ / 4n3 (solid line shown in FIG. 2), or slightly deviates from this condition (broken line shown in FIG. 2). Two conditions are shown.

  As can be seen from FIG. 2, when the thickness of the intermediate layer 2 is an odd multiple of λ / 4n3, it can be seen that the reflectance increases rapidly as the number of layers increases. This indicates that the light does not reach the back when the substrate 1 of the optical recording medium is viewed from the opposite side and should be avoided.

  FIG. 3 is a diagram showing the relationship between the thickness of the intermediate layer of the multilayer structure and the reflectance as in FIG. Here, the thickness of the recording layer 3 is fixed to λ / 4n2, and the reflectance when the layer thickness of the intermediate layer 2 is changed is 50 (the solid line shown in FIG. 3) and 5 (see FIG. 3). The broken line shown in FIG. The configuration of the multilayer optical information recording medium here is an example in which the number of layers is one unit and ten layers are stacked. It can be seen that when the number of layers is large, the reflectivity is high depending on the thickness of the intermediate layer 2 and the conditions to be avoided periodically exist depending on the thickness of the intermediate layer 2.

  Therefore, a combination condition of the layer thickness and refractive index of the intermediate layer 2 (optical path length determined by the product of the refractive index and the layer thickness) as shown in FIG. There is a need.

  From this point of view, the arrangement period of the recording layer 3 and the intermediate layer 2 and the refractive index of the intermediate layer are constituted by a plurality of one unit with a multilayer structure composed of two or more layers of the recording layer 3 and the intermediate layer 2 as one unit. It is not necessary to be constant in the set of multilayer optical information recording media, and it is preferable that the information is changed. Furthermore, regarding the layer thickness and the refractive index of the spacer layer 4, it is desirable that the optical path length, which is the product of the layer thickness and the refractive index, be an integral multiple of λ / 2.

  Under this condition, when the multilayer structure described above is one unit and there are a plurality of these, it is possible to prevent the overall transmittance from being lowered even if one unit above and below the spacer layer 4 has a high reflectance. The transmittance can be increased.

  FIG. 4 is a diagram showing the configuration of the multilayer optical information recording medium in Embodiment 2 of the present invention. The second embodiment will be described with reference to FIG. As shown in FIG. 4, the first recording layer 3 is formed on the substrate 1, in which a plurality of recording marks 3 a that are recording spots having different refractive indexes from the surroundings are periodically arranged, and the substrate 1 Are arranged in a layered manner with a certain period (interval) in a direction perpendicular to.

  A recording layer 3 in which a plurality of recording marks 3a are periodically arranged and arranged in layers is taken as one unit, and a spacer layer 4 is laminated thereon. Further, the second recording layer 3 is laminated on the spacer layer 4, and like the first recording layer 3, a plurality of recording marks 3 a having different refractive indices from the surroundings are periodically arranged, and It is formed in layers. Further, a spacer layer 4 is laminated thereon, and a multilayer optical information recording medium is constituted by repeating this.

  In the multilayer optical information recording medium, light of the light source wavelength is condensed on the recording layer 3 by an objective lens, and a row of recording marks 3a is formed by the condensed spot. Here, a material in which the refractive index of each recording mark 3a increases with respect to the surroundings may be used, and conversely, a material in which the refractive index decreases with respect to the surroundings may be used. In reading the recorded information, since the refractive index of the row of the recording marks 3a is different from the surroundings, the reflectance when the recording mark 3a is irradiated with the condensing spot is different between where the recording mark 3a is present and where it is not. Reading is performed using the intensity of reflected light.

  The material of the substrate 1 is the same as that in the first embodiment. As the recording layer 3, a mixture of a resin such as polymethyl methacrylate or polystyrene and a photochromic dye that absorbs light of a specific light source wavelength such as spiropyran, diarylethene, or fulgide and changes its absorption wavelength or refractive index is applied. The layers are laminated by a method such as mixed vapor deposition. In recording using these dyes, it is possible to use a recording method such as multiphoton absorption including two-photon absorption using a laser light source with a short pulse and high output. The separation layer (spacer layer) 4 can also be formed by the same method using the same material as the intermediate layer of the first embodiment.

  Furthermore, the second embodiment has characteristics similar to those of the multilayer optical information recording medium of the first embodiment shown in FIGS. That is, the cycle of the combination of the intermediate layer 2 and the recording layer 3 in the configuration of the first embodiment corresponds to the layered cycle of the recording mark 3a in the second embodiment. Also in this case, the layered period of the recording mark 3a as shown in FIGS. 2 and 3 is an odd multiple of λ / 4n2, where λ is the light source wavelength and n2 is the refractive index of the recording layer 3. There is a phenomenon in which the reflectivity increases rapidly with an increase in the number of layers of the recording mark 3a. This indicates that it is difficult for light to reach the back when the substrate 1 of the multilayer optical information recording medium is viewed from the opposite side, and should be avoided.

  In addition, when the number of layers is large, the reflectivity is high depending on the period of the recording mark 3a, and it can be seen that conditions for avoiding this periodically exist according to the layered period of the recording mark 3a. Such a combination condition of the layered period of the recording mark 3a and the refractive index of the recording medium (the optical path length determined by the product of the refractive index and the period) needs to be avoided.

  From this point of view, the layered period of the recording mark 3a and the refractive index of the recording layer 3 do not have to be constant in a set of multilayer optical information recording media constituted by a plurality of units as one unit of the recording layer. It is desirable to do. Furthermore, regarding the layer thickness and the refractive index of the spacer layer 4, it is desirable that the optical path length, which is the product of the layer thickness and the refractive index, is an integral multiple of λ / 2.

  Under these conditions, a plurality of recording marks 3a having different optical properties from the surroundings are periodically arranged and arranged in layers, and the recordable recording layer 3 is defined as one unit. Even when the reflectance of one unit of the recording layer 3 above and below 4 is high, the overall transmittance can be prevented from decreasing and the transmittance can be increased.

  FIG. 5 is a diagram showing the configuration of the multilayer optical information recording medium in Embodiment 3 of the present invention. The third embodiment will be described with reference to FIG. As shown in FIG. 5, the structure of the third embodiment is similar to that of the first embodiment shown in FIG. 1, but the first adhesive layer 6 and the control layer are interposed between the substrate 1 and the intermediate layer 2. 5 and 2 in that the second adhesive layer 6 is formed. Here, a tracking groove is formed in the control layer 5, and its refractive index needs to be different from that of the adhesive layer 6. However, the refractive index of the control layer 5 may be higher or lower than the refractive index of the adhesive layer 6.

  On the second adhesive layer 6, the intermediate layer 2, the recording layer 3, the intermediate layer 2, the recording layer 3, the same layer as in the first embodiment, and the spacer layer 4 are further formed. ing. Thereafter, the layers described above are periodically repeated to constitute a multilayer optical information recording medium.

  Further, as the configuration of the recording layer 3 and the intermediate layer 2 in the third embodiment, an example in which the control layer 5 is provided in one unit of the number of layers of 5 layers and 6 layers is shown. It is not limited to. For example, when the value of (layer thickness of the recording layer 3) × number of layers + (layer thickness of the intermediate layer 2) × number of layers increases, the distance from the farthest recording layer 3 in the control layer 5 increases, and a signal described later When the tracking position control method using the light beams from the two light sources is performed as in the recording / reproducing apparatus, the tracking position accuracy is deteriorated at the condensing spot of the recording light beam, and the control layer 5 is adjacent to one unit. The effect to provide becomes small. From this point of view, practically, each layer has a level of 100 layers or less.

  In FIG. 5, the control layer 5 has a groove formed on the substrate 1 side for detection by the push-pull method. However, it may be formed on the side opposite to the substrate 1. Further, not only the groove shape but also the refractive index modulation type can be configured. Furthermore, the groove pattern of the control layer 5 can be any pattern such as concentric circles or spirals.

  Other configurations and operations are the same as those of the first embodiment. Regarding the material, for example, a method of applying a UV curable resin to the control layer 5 and bringing a transparent uneven stamper into contact with the control layer 5 can be applied. The adhesive layer 6 can be applied with various resin adhesives and pressure-sensitive adhesives.

  FIG. 6 is a diagram showing a configuration of a multilayer optical information recording medium according to Embodiment 4 of the present invention. The fourth embodiment will be described with reference to FIG. In the fourth embodiment, the control layer 5 and the adhesive layer 6 of the third embodiment shown in FIG. 5 are provided in the configuration of the second embodiment shown in FIG. 4 described above. As shown in FIG. 6, an adhesive layer 6, a control layer 5, and an adhesive layer 6 are formed between the substrate 1 or the spacer layer 4 and the recording layer 3 to constitute a multilayer optical information recording medium. Other configurations, operations, etc. are the same as those in the second and third embodiments.

  FIG. 7 is a diagram showing a configuration of a multilayer optical information recording medium in Embodiment 5 of the present invention. The fifth embodiment will be described with reference to FIG. In the fifth embodiment, spacer layers 4-1 and 4-2 having different thicknesses of the spacer layer 4 are formed in the configuration of the first embodiment shown in FIG. In the spacer layer 4, the refractive index of the spacer layer 4 may be changed in order to change the optical path length. Other configurations, operations, and the like of the fifth embodiment are the same as those of the first embodiment described above. Further, it is sufficient that the thickness of the spacer layer 4 is changed as long as the optical path length is about 0 to λ / 2 or more.

  FIG. 8 is a diagram showing a configuration of a multilayer optical information recording medium in Embodiment 6 of the present invention. The sixth embodiment will be described with reference to FIG. In the sixth embodiment, spacer layers 4-1 and 4-2 having different thicknesses of the spacer layer 4 are formed in the configuration of the second embodiment shown in FIG. 3 described above. In the spacer layer 4, the refractive index of the spacer layer 4 may be changed in order to change the optical path length. Other configurations, operations, and the like of the sixth embodiment are the same as those of the second embodiment described above. Further, it is sufficient that the thickness of the spacer layer 4 is changed as long as the optical path length is about 0 to λ / 2 or more.

  FIG. 9 is a diagram showing a configuration of a multilayer optical information recording medium according to Embodiment 7 of the present invention. The seventh embodiment will be described with reference to FIG. In the seventh embodiment, the intermediate layer 2-1, 2-2, 2-3 in which the layer thickness of the intermediate layer 2 or the intermediate layer 2 and the recording layer 3 is different from the configuration of the first embodiment shown in FIG. The recording layers 3-1, 3-2, and 3-3 are formed by changing the layer thickness. Further, the refractive index of the intermediate layer 2 or the intermediate layer 2 and the recording layer 3 may be changed in order to change the optical path length of the intermediate layer 2 or the intermediate layer 2 and the recording layer 3. Other configurations, operations, and the like of the seventh embodiment are the same as those of the first embodiment described above. Further, it is sufficient that the thickness of the intermediate layer 2 and the recording layer 3 is changed from 0 to λ / 2 or more as the optical path length, but it may be arbitrary. Furthermore, it is desirable that the method of variation has as little periodicity as possible.

  FIG. 10 is a diagram showing a configuration of a multilayer optical information recording medium in Embodiment 8 of the present invention. The eighth embodiment will be described with reference to FIG. In the eighth embodiment, in the configuration of the second embodiment shown in FIG. 5 described above, the layered period of the recording marks 3a in the recording layer 3 is changed to that of the recording layers 3-1, 3-2 and 3-3. Further, the thickness of the recording marks 3a is changed to 3b-1, 3b-2, 3b-3. Further, the refractive index of the recording layer 3 may be changed in order to change the optical path length without changing the layered period of the recording mark 3a in the recording layer 3. Other configurations, operations, and the like are the same as those in the second embodiment described above. It is sufficient that the thickness of the recording layer 3 and the thickness between the recording marks 3a are changed as long as the optical path length is about 0 to λ / 2 or more. Furthermore, it is desirable that the method of variation has as little periodicity as possible.

  FIG. 11 is a diagram showing a configuration of a multilayer optical information recording medium in Embodiment 9 of the present invention. The ninth embodiment will be described with reference to FIG. The structure of the ninth embodiment is similar to that of the third embodiment shown in FIG. 5 described above, but the first adhesive layer 6 and the control layer 5 located between the substrate 1 and the intermediate layer 2 in FIG. The second adhesive layer 6 is different in structure in that it is formed between the intermediate layer 2 and the recording layer 3 that are periodically laminated as one unit. However, as shown in FIG. 11, the first adhesive layer 6 and the second adhesive layer 6 next to the control layer 5 are omitted in FIG. In this case, the intermediate layer 2 can be formed and laminated directly on the control layer 5. Other configurations, operations, and the like in the ninth embodiment are the same as those in the second embodiment described above.

  FIG. 12 is a diagram showing the configuration of the multilayer optical information recording medium in Embodiment 10 of the present invention. The tenth embodiment will be described with reference to FIG. The structure of the tenth embodiment is similar to that of the fourth embodiment shown in FIG. 6 described above. However, the structure of FIG. 6 is the first adhesion between the substrate 1 or the spacer layer 4 and the recording layer 3. The difference is that the layer 6, the control layer 5, and the second adhesive layer 6 are formed between the recording layer 3 and the recording layer 3. However, the second adhesive layer 6 is omitted in the configuration shown in FIG. In this case, the recording layer 3 can be formed directly on the control layer 5. Other configurations, operations, and the like are the same as those of the fourth embodiment described above.

  FIG. 13 is a block diagram showing an apparatus for recording and reproducing signals on a multilayer optical information recording medium in Embodiment 11 of the present invention. Here, an example in which signals are recorded / reproduced on / from the multilayer optical information recording medium described in the third embodiment shown in FIG. 5 is shown.

  The eleventh embodiment will be described with reference to FIG. In the signal recording / reproducing apparatus shown in FIG. 13, the light emitted from the light source 11 (first light source) is an optical recording medium via the lens 12, the polarization beam splitter 13, the dichroic prism 14, the quarter wavelength plate 15, and the objective lens 16. The light is condensed on the track portion of the control layer 5 inside. Reflected light from the track portion of the control layer 5 passes through the objective lens 16, the quarter-wave plate 15, and the dichroic prism 14 and is reflected by the polarization beam splitter 13, and the condenser lens 17 and the pinhole 18 (first pinhole). Then, the light passes through the condenser lenses 19 and 20, passes through the cylindrical lens 21, and is condensed on the quadrant photodetector 22.

  Light rays collected by the condensing lens 20 and the cylindrical lens 21 have astigmatism and have two focal points. A quadrant photodetector 22 is disposed between the two focal positions. A pinhole 18 is disposed between the condensing lenses 17 and 19, and the diameter of the pinhole 18 is set slightly larger than the condensing spot diameter of the condensing lens 17, for example. Therefore, the return light can pass through the pinhole 18 even if the light beam from the light source 11 is not focused on the control layer 5 of the optical recording medium.

  Next, light emitted from a light source 23 (second light source) different from the light source 11 passes through the lens 24, is reflected by the polarization beam splitter 25, passes through the condenser lenses 26 and 27, and then passes through the dichroic prism 14. The reflected light passes through the quarter-wave plate 15 and is condensed on the recording layer 3 in the optical recording medium by the objective lens 16. The objective lens 16 is provided with a position control mechanism such as a coil, and the position can be controlled.

  The reflected light from the recording layer 3 of the optical recording medium is reflected through the objective lens 16, the quarter-wave plate 15, and the dichroic prism 14, passes through the condenser lenses 27 and 26, and further passes through the polarizing beam splitter 25. The light is condensed on the photodetector 30 through the condenser lens 28 and the pinhole 29 (second pinhole).

  Here, the positions of the light source 23 and the pinhole 29 are optically confocal. Further, the condenser lenses 26 and 27 form a beam expander, function as a position control device, and change the focal position to be focused in the optical recording medium by changing each other's position along the optical axis. be able to. That is, by controlling the distance between the condenser lenses 26 and 27, the condensing position of the light beam from the light source 23 can be adjusted along the optical axis. In addition, the pinhole 29 needs to have a diameter adjusted to the same level as the condensing spot diameter of the condensing lens 28 or to a level before and after that.

  In such a configuration, the light beam from the light source 11 is relatively focused on the track on the control layer 5 while the light beam from the light source 11 is focused on the track on the control layer 5. If the distance between the condenser lenses 26 and 27 is controlled and adjusted so as to be separated by a certain distance on the optical axis, the light can be condensed on an arbitrary recording layer 3. The emitted light from the light source 11 can obtain a focus error signal by the astigmatism method and a track error signal by the push-pull method from the signal of the quadrant photodetector 22. For this reason, the objective lens 16 can be controlled.

  As a configuration other than this, a plurality of detection systems of the light source 23 and the photodetector 30 can be provided, and information can be recorded / reproduced to / from the multi-layer recording layer 3 by a multi-beam. Further, instead of the detection system of the light source 23 and the photodetector 30, a plurality of optical systems of the light source 11 and the four-divided photodetector 22 can be provided, and the plurality of recording layers 3 can be simultaneously subjected to focus servo. In this case, it is necessary to add dynamic focus adjusting means such as a liquid crystal focus adjusting element.

  Next, an embodiment 12 of the invention will be described. In the twelfth embodiment, the order information of the combination of the recording layer 3 and the intermediate layer 2 configured as one unit in the control layer 5 in the third, fourth, ninth, tenth, and eleventh embodiments described above, or the recording layer 3 Among them, configuration information relating to a plurality of periodic arrangements and layered arrangements of the recording marks 3a and information representing positions in the multilayer optical information recording medium are recorded in the control layer 5.

  The method for recording these information in the control layer 5 can be formed in the control layer 5 in an uneven shape by changing the shape at the same time when the track groove of the control layer 5 is created. Other configurations, operations, and the like are the same as those in each embodiment.

  In the multilayer optical information recording medium of the present invention, regarding the numerical values such as the number of layers and the thickness of each layer such as the recording layer 3 and the intermediate layer 2, the total number of the recording layers 3 is several tens to several hundreds. The number of layers per unit is assumed to be a range of several layers to 100 layers as described above. Specifically, when considering the specifications of materials and products that can be actually used, the film thickness of the recording layer 3 and the intermediate layer 2 is in the range of about 0.1 μm to several tens of μm. The recording layer 3 is preferably equal to or thicker than the recording layer 3, and the spacer layer 4 is also preferably in the range of about 1 μm to 100 μm.

  The multilayer optical information recording medium according to the present invention suppresses changes in the amount of reflected light at the time of signal recording and reading due to changes in wavelength and angle of incident light, reduces increase in noise and S / N ratio, and improves tracking accuracy. It is useful for an optical file system, an optical information recording / reproducing apparatus for recording video information, and a multilayer optical recording medium used for a recording medium.

The figure which shows the structure of the multilayer optical information recording medium in Embodiment 1 of this invention. Diagram showing the relationship between the number of layers and reflectance Diagram showing the relationship between interlayer thickness and reflectance The figure which shows the structure of the multilayer optical information recording medium in Embodiment 2 of this invention. The figure which shows the structure of the multilayer optical information recording medium in Embodiment 3 of this invention. The figure which shows the structure of the multilayer optical information recording medium in Embodiment 4 of this invention. The figure which shows the structure of the multilayer optical information recording medium in Embodiment 5 of this invention. The figure which shows the structure of the multilayer optical information recording medium in Embodiment 6 of this invention. The figure which shows the structure of the multilayer optical information recording medium in Embodiment 7 of this invention. The figure which shows the structure of the multilayer optical information recording medium in Embodiment 8 of this invention. The figure which shows the structure of the multilayer optical information recording medium in Embodiment 9 of this invention. The figure which shows the structure of the multilayer optical information recording medium in Embodiment 10 of this invention. Configuration diagram showing an apparatus for recording and reproducing signals on a multilayer optical information recording medium in Embodiment 11 of the present invention The figure which shows the structure of the conventional multilayer optical information recording medium

Explanation of symbols

1 Substrate 2, 2-1, 2-2, 2-3 Intermediate increase 3, 3-1, 3-2, 3-3 Recording layer 3a Recording marks 3b-1, 3b-2, 3b-3 Thickness 4, 4-1, 4-2 Spacer layer 5 Control layer 6 Adhesive layer 11 Light source (first light source)
12, 24 Lens 13, 25 Polarizing beam splitter 14 Dichroic prism 15 1/4 wavelength plate 16 Objective lens 17, 19, 20, 26, 27, 28 Condensing lens 18 Pinhole (first pinhole)
21 Cylindrical lens 22 Quadrant photodetector 23 Light source (second light source)
29 pinhole (second pinhole)
30 photodetectors

Claims (18)

  A multilayer light comprising a multilayer structure composed of two or more layers of a recording layer and an intermediate layer as one unit, and one unit of the multilayer structure having a structure in which a plurality of layers are stacked in the depth direction through a spacer layer Information recording medium.   2. The multilayer optical information recording medium according to claim 1, wherein each of the plurality of spacer layers has a different layer thickness or refractive index.   In one unit of the multilayer structure, the arrangement period of the recording layer and the intermediate layer, the refractive index of the recording layer, and the refractive index of the intermediate layer are constant within the one unit, and the arrangement period or the recording layer 2. The multilayer optical information recording medium according to claim 1, wherein a refractive index or a refractive index of the intermediate layer is different for each unit.   4. The tracking control signal generation control layer provided for each unit is laminated adjacent to the first recording layer in a multilayer structure forming the one unit. The multilayer optical information recording medium described in 1.   The multilayer optical information according to any one of claims 1 to 3, wherein a control layer for generating a tracking control signal provided for each unit is laminated in an intermediate portion of the multilayer structure constituting the unit. recoding media.   6. The multilayer optical information recording medium according to claim 4, wherein an adhesive layer or an adhesive layer is provided adjacent to the control layer for generating a tracking control signal provided for each unit.   7. The information on the order of the combination of the recording layer and the intermediate layer constituting one unit and the information indicating the position in the multilayer optical information recording medium are recorded on the control layer. The multilayer optical information recording medium described.   The multilayer optical information recording medium according to any one of claims 1 to 7, wherein a spacer layer laminated between one unit of the multilayer structure and the one unit is an adhesive layer or an adhesive layer.   9. The multilayer optical information recording medium according to claim 1, wherein a barrier layer is provided between the recording layer and the intermediate layer constituting the unit in one unit of the multilayer structure. .   A recording layer in which a plurality of recording spots whose optical properties change with the surroundings is periodically arranged and arranged in layers is defined as one unit, and the recording layer of one unit is defined in the depth direction via a spacer layer. A multilayer optical information recording medium characterized by having a structure in which a plurality of pieces are laminated.   The multilayer optical information recording medium according to claim 10, wherein each of the plurality of spacer layers has a different layer thickness or refractive index.   The laminar period in which recording spots are arranged in one unit of the recording layer is constant within the one unit, and the laminar period in which recording spots are arranged is different for each unit. Item 11. The multilayer optical information recording medium according to Item 10.   The multilayer optical information according to any one of claims 10 to 12, wherein a control layer for generating a tracking control signal provided for each unit is laminated adjacent to the recording layer forming one unit. recoding media.   The multilayer optical information recording according to any one of claims 10 to 12, wherein a control layer for generating a tracking control signal provided for each unit is laminated in the middle of the recording layer forming one unit. Medium.   15. The multilayer optical recording medium according to claim 13, wherein an adhesive layer or an adhesive layer is provided adjacent to a control layer for generating a tracking control signal provided for each unit.   Configuration information relating to a plurality of periodic arrangements of recording spots and layered arrangements and information representing positions in a multilayer optical information recording medium are recorded in the recording layer configured as one unit in the control layer. The multilayer optical information recording medium according to any one of claims 13 to 15.   The multilayer optical information recording medium according to any one of claims 10 to 16, wherein a spacer layer laminated between one unit of the recording layer and the one unit is an adhesive layer or an adhesive layer.   A plurality of recording spots having different optical properties from the surroundings are arranged periodically and in a layered manner in a depth direction through a recording layer arranged in layers and an intermediate layer that does not form the recording spots in place of the spacer layer The multilayer optical information recording medium according to claim 10, wherein the multilayer optical information recording medium has a structure in which a plurality of layers are stacked.

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