JP2005129154A - Optical disk and manufacturing method thereof, optical disk recording device, and optical disk reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an optical disk for providing satisfactory recording and reproduction characteristics at low casts by improving the productivity of the optical disk having a plurality of recording surfaces on which information is recorded. <P>SOLUTION: In the optical disk 1 having a plurality of disk sheets 6 having the recording surface on which information is recorded, a positioning region 4 is formed on each of the disk sheets 6 and is used as a reference when the disk sheets 6 are laminated, thus providing the optical disk in which the plurality of disk sheets each having an equal thickness can be laminated at the same time with the positioning region as the reference, which is simple, and has an equal interval in the plurality of recording surfaces. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical disc having a plurality of recording surfaces, a method for manufacturing the same, and an optical disc recording apparatus and an optical disc reproducing apparatus that realize recording or reproduction of high-density information.

  In recent years, development of optical discs capable of reproducing, recording, and erasing information has progressed, and researches that satisfy further demands for higher density and larger capacity have been earnestly advanced. Among them, development of an optical disc having a plurality of recording surfaces is progressing as development of an optical disc that realizes a large capacity.

  Hereinafter, a conventional method for forming an optical disk having a plurality of recording surfaces (see, for example, Patent Document 1) will be described with reference to FIG. FIGS. 21A to 21D each show a process of forming an optical disk having a plurality of recording surfaces, using a cross-sectional view of the optical disk.

  First, as shown in FIG. 21A, the first pit 101 is covered with respect to the first substrate 100 having the first pit 101 (concave or convex) formed by injection molding or 2P method. Thus, the first reflective film 102 is formed.

  Next, as shown in FIG. 21B, after the ultraviolet curable resin 103 is applied on the first reflective film 102 of the first substrate 100, information different from the first pit 101 is recorded. The master 104 having the second pit 105 is disposed on the ultraviolet curable resin 103. Thereafter, the ultraviolet curable resin is cured by irradiating the ultraviolet light, and the first ultraviolet curable resin layer 103 to which the second pit pattern is transferred is formed.

  Next, as shown in FIG. 21C, after the master 104 is removed, a second reflective film 106 is formed on the first ultraviolet curable resin layer 103 to which the second pit 105 is transferred. To do.

  Next, as shown in FIG. 21D, the second substrate 107 having the third pit 108 and the third reflective film 109 and the first substrate 100 are made of the second ultraviolet curable resin 110. Used together. Here, the first substrate 100 and the second substrate 107 are bonded so that the second reflective film 106 and the third reflective film 109 face each other.

Here, a method for forming an optical disk having a three-layer structure having the first pit 101, the second pit 105, and the third pit 108 is shown. However, by repeating the above transfer process, more recording layers can be formed. It is also possible to form an optical disc having
JP 2001-134981 A (published on May 18, 2001)

  However, when an optical disc is formed in accordance with the above-described conventional forming process, there are a problem that the flatness of the optical disc cannot be maintained, and a throughput of optical disc formation is reduced, leading to an increase in the cost of the optical disc.

  This will be described with reference to FIG. The first pit 101, the second pit 105, and the third pit 108 are each formed in a spiral shape or a concentric shape on the substrate 100 of the optical disk, and constitute a recording track. However, if the position of the spiral center or concentric circle center of the recording track is shifted between the respective layers, the recording track is decentered, and tracking disturbance during recording / reproduction increases.

  In order to suppress this increase in eccentricity, when forming the pits of each layer, a step of aligning the spiral center or concentric circle center of the pit (recording track) between the layers is necessary (so-called centering step). In other words, the conventional forming process has the problems that the optical disk forming throughput decreases due to the necessity of the above steps, leading to an increase in the cost of the optical disk.

  The present invention has been made in view of the above problems, and an object of the present invention is to improve the productivity of an optical disc having a plurality of signal recording layers, and to provide a multilayer optical disc having good recording and reproducing characteristics at low cost. It is to provide.

  An optical disc according to the present invention is formed by laminating a plurality of disc sheets having a recording surface including spiral or concentric tracks or pits on one side on a disc substrate, and each disc sheet is a disc. It has a positioning area for positioning between sheets.

  The “recording surface” in the specification of the present application is a surface on which information is recorded, and is generally a reflective film or recording film provided on the surface on which the concavo-convex pattern is formed. In addition, “optical disk”, “disk sheet”, “disk substrate”, and “disk sheet substrate” (described later) in the present specification are not limited to the shape of a disc, but other plate shapes For example, a rectangular plate shape such as a business card type may be used.

  Further, the optical disc according to the present invention has the above-described configuration, wherein the positioning region includes a convex portion provided on one of mutually facing surfaces of an adjacent disc sheet and a concave portion provided on the other side. Is fitted in the recess. The positioning region is not limited to a pair of a convex portion and a concave portion, and may be a pair of a step portion and a concave portion, a pair of a hole and a convex portion, a mark, or the like.

  In addition, you may combine the structure described as this invention arbitrarily with each structure described as said invention as needed.

  By the way, normally, the first UV curable resin layer 103 and the second UV curable resin layer 110 need to have a layer thickness of about 10 μm or more in order to eliminate interlayer crosslight and interlayer crosstalk generated during recording and reproduction. is there.

  When forming the first ultraviolet curable resin layer 103, a liquid ultraviolet curable resin is filled between the reflective film 102 formed on the first substrate 100 and the second pit 105 formed on the master 104. Then, the first ultraviolet curable resin layer 103 is formed by irradiating ultraviolet rays to cure the ultraviolet curable resin. When the cured resin has a layer thickness of 20 μm, the shrinkage force is ultraviolet curing having a layer thickness of 10 μm. Here, the ultraviolet curing resin is slightly contracted with curing by ultraviolet irradiation. Therefore, for example, it becomes larger than that obtained when the ultraviolet resin is cured, and the flatness of the substrate 100 cannot be maintained. When the shrinkage occurs, a large tilt occurs in the substrate 100 as a result. When a plurality of ultraviolet curable resin layers 103 are formed, the shrinkage force is further increased, and the tilt of the substrate 100 is increased according to the number of stacked layers.

  The increase in the tilt causes an increase in coma aberration of the light beam for recording / reproducing, and a good light beam spot shape cannot be obtained, which causes deterioration in recording / reproducing characteristics.

  In addition, the reflective film 102 and the second pit 105 are arranged with an interval of about 10 μm or more, and an ultraviolet curable resin is filled between them, and the reflective film 102 and the second pit 105 are partially Distortion tends to occur. This partial distortion causes variations in the distance between the reflective film 102 and the second pit 105, that is, the layer thickness of the first ultraviolet curable resin layer 103. Such a variation in the layer thickness causes a spherical aberration in the light beam for recording / reproducing, increases the diameter of the focused spot, and causes a deterioration in recording / reproducing characteristics.

  Next, in the bonding process in FIG. 21D, the second ultraviolet curable resin layer 110 is cured in a state different from that in FIG. That is, in FIG. 21B, between the first substrate 100 (generally plastic) and the master 104 (generally a metal plate or a glass plate) (precisely, the reflective film 102). In FIG. 21D, the first substrate 100 and the second substrate 107 (generally plastic are used), whereas the ultraviolet curable resin filled between the first and second pits 105 is cured. In other words, the ultraviolet curable resin filled in the second reflective film 106 and the third reflective film 109 is cured, and the ultraviolet curable resin is cured in such a different state. If this is the case, the curing conditions such as temperature rise during curing change, making it difficult to obtain the same layer thickness.

  As described above, the conventional process has a problem that the recording surface interval cannot be accurately controlled.

  Further, in order to solve the above problems, the optical disk according to the present invention has a recording surface on one side and a recording surface on the other side in order to solve the above problems. It is characterized by not. Here, in the case of an optical disc having a configuration in which two disc sheets are laminated, the “adjacent disc sheets” simply refers to these two disc sheets.

  In addition, you may combine the structure described as this invention arbitrarily with each structure described as said invention as needed.

  The disk sheet is preferably a molded body formed by molding a molding material such as resin into a sheet shape, or a sheet mainly composed of the molded body. A molded body formed by molding a molding material such as a resin into a sheet shape has a uniform thickness as compared with a resin layer formed by applying and curing an ultraviolet curable resin by ultraviolet irradiation. Therefore, by using the disk sheet having the above configuration, it is possible to suppress variations in the recording surface interval. Even when the disk sheet having the above-described configuration is used, there is a resin layer formed by applying and curing an ultraviolet curable resin by ultraviolet irradiation as an adhesive layer formed between a part of the disk sheets or between the disk sheets. However, the thickness of the resin layer is much thinner than the thickness of the resin layer formed between the recording surfaces of the conventional multilayer optical disc, and can be set to about 1 μm, for example. Therefore, the shrinkage that occurs when the ultraviolet curable resin is cured by ultraviolet irradiation is much smaller than the shrinkage that occurs during the production of a conventional multilayer optical disk, and does not substantially affect the smoothness of the optical disk.

  The optical disk according to the present invention is characterized in that, in the above configuration, the disk substrate is thicker than the plurality of disk sheets.

  In addition, you may combine the structure described as this invention arbitrarily with each structure described as said invention as needed.

  The optical disc according to the present invention is characterized in that, in the above configuration, the disc substrate has a positioning region for positioning between the disc substrate and the disc sheet.

  In addition, you may combine the structure described as this invention arbitrarily with each structure described as said invention as needed.

  The optical disk according to the present invention is characterized in that, in the above configuration, adjacent disk sheets are bonded via a pressure-sensitive adhesive film.

  In addition, you may combine the structure described as this invention arbitrarily with each structure described as said invention as needed.

  In the optical disk according to the present invention, in the above configuration, the disk sheet is composed of a disk sheet substrate and an ultraviolet curable resin layer provided on the disk sheet substrate, and an uneven pattern is formed on the surface of the ultraviolet curable resin layer. It is characterized by being formed.

  In addition, you may combine the structure described as this invention arbitrarily with each structure described as said invention as needed.

  The optical disc according to the present invention is characterized in that, in the above-described configuration, the disc sheet is formed by directly forming an uneven pattern on the surface of the disc sheet substrate.

  In addition, you may combine the structure described as this invention arbitrarily with each structure described as said invention as needed.

  The disk sheet substrate is preferably a molded body formed by molding a molding material such as a resin into a sheet shape. A molded body formed by molding a molding material such as a resin into a sheet shape has a uniform thickness as compared with a resin layer formed by applying and curing an ultraviolet curable resin by ultraviolet irradiation. Therefore, by using the disk sheet substrate having the above-described configuration, it is possible to suppress variations in the recording surface interval. Even when the disk sheet having the above-described configuration is used, a resin layer formed by application and curing of an ultraviolet curable resin by ultraviolet irradiation may exist as an adhesive layer formed between the disk sheets. The thickness of the layer is much thinner than the thickness of the resin layer formed between the recording surfaces in the conventional multilayer optical disc, and can be set to about 1 μm, for example. Therefore, the shrinkage that occurs when the ultraviolet curable resin is cured by ultraviolet irradiation is much smaller than the shrinkage that occurs during the production of a conventional multilayer optical disk, and does not substantially affect the smoothness of the optical disk.

  The optical disk according to the present invention is characterized in that, in the above-described configuration, a protective layer is provided on a surface of the disk sheet farthest from the disk substrate opposite to the surface on the disk substrate side.

  In addition, you may combine the structure described as this invention arbitrarily with each structure described as said invention as needed.

  The optical disk according to the present invention is characterized in that, in the above-described configuration, the protective layer is made of an ultraviolet curable resin.

  In addition, you may combine the structure described as this invention arbitrarily with each structure described as said invention as needed.

  In the optical disk according to the present invention, the protective layer is a protective sheet bonded onto the disk sheet in the above configuration.

  In addition, you may combine the structure described as this invention arbitrarily with each structure described as said invention as needed.

  An optical disk recording apparatus according to the present invention is characterized by comprising a recording irradiation means for condensing and irradiating a light beam for recording information on each recording surface of the optical disk having the above-described configuration. Yes.

  An optical disk reproducing apparatus according to the present invention is characterized by comprising reproduction irradiating means for condensing and irradiating a light beam for reproducing information on each recording surface of the optical disk having the above-described configuration. Yes.

  The method of manufacturing an optical disk according to the present invention also includes a disk sheet having a recording surface including spiral or concentric tracks or pits on one surface and having a positioning area. It is characterized in that a plurality of layers are stacked on a substrate.

  By the way, when the process of FIGS. 21B and 21C is repeated many times to provide a plurality of first ultraviolet resin layers 103 and second reflective layers 106 to form a multilayer optical disk, After the first ultraviolet curable resin layer 103 is formed, the second reflective layer 106 is formed using a vacuum apparatus such as a vapor deposition apparatus or a sputtering apparatus, and the optical disk on which the second reflective layer 106 is formed is removed from the vacuum apparatus. Then, it is necessary to repeat the formation of the ultraviolet curable resin layer 103 and the formation of the reflective layer 106 after that.

  Therefore, in the above conventional forming process, it is necessary to repeatedly carry in and out of the vacuum apparatus in order to form an optical disk, which causes a problem that the forming process becomes complicated. Furthermore, when the evacuation time for carrying in / out becomes long, there is a problem that the throughput of forming the optical disk is lowered and the cost of the optical disk is increased.

  The optical disk manufacturing method according to the present invention is characterized in that a plurality of disk sheets are laminated on a disk substrate at one time in order to solve the above-described problems.

  In the optical disk of the present invention, the recording surface may be provided on the surface of the disk substrate. However, when the recording surface is provided on the surface of the disk substrate, the recording surface forming process is different from the process of providing the recording surface on the disk sheet. is required. Therefore, in order to realize cost reduction of the optical disk by simplifying the disk manufacturing process, it is desirable not to provide a recording surface on the surface of the disk substrate.

  As described above, the optical disk according to the present invention is formed by laminating a plurality of disk sheets having a recording surface including spiral or concentric tracks or pits on one surface on a disk substrate. Since it has a positioning area for positioning between disk sheets, it is manufactured by a method of laminating a plurality of disk sheets having a recording surface on one side and having positioning areas on a disk substrate. Therefore, each disk sheet can be manufactured by a method of laminating on the disk substrate while accurately positioning the relative positions of the disk sheets with reference to the positioning region. Therefore, according to the above configuration, it is possible to provide a multilayer optical disc (an optical disc having a plurality of recording surfaces) in which the relative positions of the disc sheets are accurately positioned. Thereby, the position of the spiral center or concentric circle center of the track or pit can be easily matched between the recording surfaces of the respective disk sheets at low cost. As a result, it is possible to easily and inexpensively provide a multi-layer optical disk with a small track or pit eccentricity (deviation of the spiral center or concentric circle center of the track or pit with respect to the rotation center of the optical disk) and small tracking disturbance during recording and reproduction. Is possible.

  Further, as described above, the optical disc according to the present invention includes the convex portion provided on one of the mutually opposing surfaces of the adjacent disc sheet and the concave portion provided on the other, as described above. Since a plurality of disc sheets having a positioning region can be positioned between the disc sheets only by fitting the convex portions into the concave portions without using a special jig for positioning. However, the disk sheets can be stacked while being stacked. Therefore, the optical disk having the above configuration is easy to manufacture.

  Further, since the disk sheet is relatively weak in mechanical strength, if a center hole is provided and positioning is performed with reference to the center hole, the center hole is mechanically deformed and positioning with high accuracy cannot be performed.

  On the other hand, the convex portion and the concave portion as the positioning region are provided on the surface of the disc sheet, so that mechanical deformation does not occur and positioning with high accuracy is possible. As a result, the spiral centers or concentric circle centers of the tracks or pits on the recording surface are more consistent between the respective disk sheets, and an optical disk with less eccentricity can be realized.

  Further, as described above, since the optical disk according to the present invention has one recording surface and the other does not have a recording surface, the surfaces of adjacent disk sheets facing each other, The interval is substantially equal to the thickness of the disk sheet interposed between these recording surfaces. Therefore, by using a disc sheet having a uniform thickness as a disc sheet interposed between these recording surfaces, it is possible to suppress variations in the interval between the recording surfaces. As a result, the configuration described above has an effect of providing an optical disc having excellent recording characteristics and reproduction characteristics by suppressing fluctuations in coma and spherical aberration of a light beam used for recording and reproduction.

  When the optical disk having the above configuration has three or more recording surfaces, the interval between the recording surfaces adjacent to each other is substantially equal to the thickness of the disk sheet interposed between these recording surfaces. Therefore, by using disc sheets having the same thickness as the plurality of disc sheets interposed between these recording surfaces, the interval between adjacent recording surfaces can be made equal. As a result, when moving the focused light beam spot to a different recording layer, that is, when performing an interlayer jump, the distance to the recording layer to be moved is equalized because the distance between adjacent recording surfaces is equal. Can be predicted in advance. Therefore, by moving the objective lens for condensing the light beam by a predetermined amount predicted in advance, it becomes possible to condense the light beam onto the target recording layer, with simpler control, In addition, there is an effect that a high-speed interlayer jump can be realized.

  In addition, as described above, the optical disk according to the present invention has a thickness of the disk substrate larger than the thickness of the plurality of disk sheets, so that the optical disk according to the present invention is compared with a stacked disk composed of only stacked disk sheets. Thus, the mechanical strength can be increased and the degree of freedom of the number of stacked disk sheets can be increased.

  That is, for example, when a 20-μm-thick plastic disk sheet is stacked in a stacked disk composed of only stacked disk sheets, the total thickness is 400 μm. A laminated disk having such a total thickness is difficult to maintain sufficient mechanical strength as an optical disk, and deformation occurs due to rotational driving for recording and reproduction during recording and reproduction. As a result, the focus servo becomes unstable, and in the worst case, the focus servo is lost. In order for a laminated disc formed by laminating only disc sheets to maintain sufficient mechanical strength as an optical disc, it is necessary to have a total thickness of 600 μm or more. Therefore, when using a plastic disk sheet having a thickness of 20 μm, it is necessary to stack at least 30 disk sheets in order for the laminated disk to maintain sufficient mechanical strength as an optical disk. The degree of freedom of the number of stacked disc sheets is greatly limited.

  On the other hand, the optical disk having the above-described configuration in which a plurality of disk sheets are stacked on a disk substrate thicker than the disk sheet is formed by stacking 20 layers of 20 μm thick disk sheets on a 300 μm thick disk substrate, for example. In this case, since the total thickness of the disk substrate and the disk sheet is 700 μm, it has sufficient mechanical strength as an optical disk. Furthermore, the optical disk having the above configuration has sufficient mechanical strength as an optical disk because the total thickness is 600 μm even when the number of stacked disk sheets is 10, for example. Therefore, it is possible to freely set the number of stacked disc sheets in accordance with a desired recording capacity.

  In addition, as described above, the optical disk according to the present invention has a positioning area for positioning the disk substrate between the disk substrate and the disk sheet. The sheet can be manufactured by a method of laminating on the disk substrate while accurately positioning the relative positions of the disk sheet and the disk substrate with reference to the positioning area of the disk sheet and the positioning area of the disk substrate. Therefore, according to the above configuration, it is possible to provide a multilayer optical disc (optical disc having a plurality of recording surfaces) in which both the disc sheet and the relative position of the disc substrate are accurately positioned. Thereby, the center position of the disk sheet can be made coincident with the center position of the disk substrate easily and at low cost.

  As a result, it is possible to easily and inexpensively provide a multi-layer optical disc with small track or pit eccentricity and disc substrate eccentricity (displacement of the center of the disc substrate with respect to the center of rotation of the optical disc) and little tracking disturbance during recording and reproduction. Is possible.

  That is, when the optical disk is rotated for recording or reproduction, if the center position of the disk substrate and the center position of the disk sheet do not coincide with each other, the rotation drive is performed when the center of the disk substrate is aligned with the rotation drive center. As a result, eccentricity of the disk sheet (track or pit eccentricity) occurs, and tracking becomes unstable. Also, if the center of the disk sheet is aligned with the rotational drive center, the disk substrate will be decentered with the rotational drive, and the disk substrate will be rotationally vibrated with the eccentric rotation of the disk substrate, resulting in focusing servo and tracking. Servo will be adversely affected.

  On the other hand, since the center position of the disk substrate coincides with the center position of the track or pit, the eccentricity associated with the rotational drive is suppressed, and stable focusing servo and tracking servo can be realized.

  Further, as described above, the optical disk according to the present invention has the adjacent disk sheets bonded together via the pressure-sensitive adhesive film, so that the optical disk having the above-described configuration has the disk sheets stacked via the pressure-sensitive adhesive film. They can be manufactured by simply applying pressure. Therefore, the manufacturing method of the optical disk having the above-described configuration is for curing such as ultraviolet irradiation as compared with an optical disk manufactured by a method in which an adhesive made of an ultraviolet curable resin or the like is applied between the disk sheets and cured. Since this process is not required, adhesion in a short time is possible, and an apparatus for curing such as an ultraviolet light source is not necessary. Therefore, the optical disk having the above configuration can be manufactured at a low cost with a simple process.

  In the optical disk according to the present invention, as described above, the disk sheet is composed of a disk sheet substrate and an ultraviolet curable resin layer provided on the disk sheet substrate, and an uneven pattern is formed on the surface of the ultraviolet curable resin layer. Since the ultraviolet curable resin is disposed on the disk sheet substrate, the concave / convex pattern is transferred, and the concave / convex pattern is formed by irradiating the ultraviolet curable resin with ultraviolet rays to cure the ultraviolet curable resin. Is possible. Therefore, a concave / convex pattern for tracking can be formed on the disk substrate in a short time. Therefore, the productivity of the multilayer optical disk is increased, and the cost can be reduced.

  In addition, as described above, the optical disc according to the present invention has a concave / convex pattern for tracking on the surface of the molded sheet substrate because the disc sheet is formed directly on the surface of the disc sheet substrate. Since it can manufacture by forming directly, the process of providing an additional layer like the said ultraviolet curing resin layer becomes unnecessary. Therefore, it becomes possible to further increase the productivity of the multilayer optical disc, and realize further cost reduction.

  Further, in the above configuration, when one of the adjacent disk sheets has a recording surface and the other does not have a recording surface, it is not necessary to form an ultraviolet curable resin layer. Compared with the case where the concave / convex pattern is formed by curing the resin, the shrinkage of the ultraviolet curable resin that affects the uniformity of the spacing between the recording surfaces can be suppressed, so that the spacing between the recording surfaces can be made more uniform.

Further, as described above, the optical disk according to the present invention is provided with the protective layer on the surface opposite to the disk substrate side of the disk sheet farthest from the disk substrate, so that it is the furthest from the disk substrate. It is possible to protect the surface of the disk sheet opposite to the disk substrate side. As a result, it is possible to prevent damage to the disk sheet and recording surface due to external impact, dust, etc., and to prevent deterioration of recording characteristics and reproduction characteristics due to damage to the disk sheet and recording surface. As described above, since the protective layer is made of an ultraviolet curable resin, in addition to the above effects, the protective layer can be formed by a simple process and at a low cost. That is, after laminating a plurality of the disk sheets on the disk substrate, an ultraviolet curable resin is applied onto the disk sheets by a simple method such as a spin coating method, and the ultraviolet rays are irradiated. By this process, a protective layer (ultraviolet curable resin layer) having a uniform layer thickness can be formed.

  In addition, when recording or reproducing information by inputting a light beam from the protective layer side using an objective lens having a high NA (aperture) of 0.8 or more, light for recording and reproducing is used as the ultraviolet curable resin layer. By using an ultraviolet curable resin layer that is transparent to the beam, a protective layer corresponding to a high NA objective lens can be obtained.

  Further, as described above, since the protective layer is a protective sheet bonded on the disk sheet, the optical disk according to the present invention can be easily obtained by using a sheet having a uniform thickness as the protective sheet. It becomes possible to make the thickness of the protective layer more uniform.

  When using an optical disc recording device or optical disc reproducing device that records or reproduces by entering a light beam from the protective layer side, coma aberration or spherical aberration occurs in the light beam if the layer thickness of the protective layer varies. Gets worse.

  On the other hand, in the structure of the said invention, the dispersion | variation in the layer thickness of a protective layer can be suppressed using the protective sheet which has uniform thickness. Therefore, it is possible to prevent coma aberration and spherical aberration from occurring in the light beam and to realize good recording / reproducing characteristics.

  In addition, the optical disk recording apparatus according to the present invention includes a recording irradiation means for condensing and irradiating a light beam for recording information on each recording surface of the optical disk having the above-described configuration. Since the multi-layer optical disk having a small eccentricity of the track or pit having the above configuration is used, it is possible to provide an optical disk recording apparatus with a small tracking disturbance during recording and reproduction.

  Further, when the above-mentioned optical disk has a structure in which one of the adjacent disk sheets facing each other has a recording surface and the other does not have a recording surface, the interval between the adjacent recording surfaces is uniform. Therefore, it is possible to provide an optical disc recording apparatus capable of condensing and irradiating a recording surface with a light beam with little coma and spherical aberration.

  In addition, the optical disk reproducing apparatus according to the present invention includes reproducing irradiation means for condensing and irradiating a light beam for reproducing information on each recording surface of the optical disk having the above-described configuration. Since the multi-layer optical disk having a small eccentricity of the track or pit having the above-described configuration is used, it is possible to provide an optical disk reproducing apparatus with a small tracking disturbance during recording and reproduction.

  Further, when the above-mentioned optical disk has a structure in which one of the adjacent disk sheets facing each other has a recording surface and the other does not have a recording surface, the interval between the adjacent recording surfaces is uniform. Therefore, it is possible to provide an optical disk reproducing apparatus capable of condensing and irradiating a recording surface with a light beam with little coma and spherical aberration. Furthermore, in the above optical disc, when the interval between the recording surfaces is uniform, when moving the light collection irradiation point of the light beam from the recording surface on which the light beam is condensed and irradiated to a different recording surface, The distance to the target recording surface can be accurately predicted, and an interlayer access jump based on the predicted distance to the target recording surface can be performed.

  The optical disk playback device may have the function of the optical disk playback device.

  The method of manufacturing an optical disk according to the present invention also includes a disk sheet having a recording surface including spiral or concentric tracks or pits on one surface and having a positioning area. Since a plurality of layers are stacked on the substrate, the position of the spiral center or concentric circle center of the track or pit can be easily matched between the recording surfaces of the respective disk sheets at low cost. As a result, it is possible to easily and cost-effectively produce a multilayer optical disk with a small track or pit eccentricity (shift of the spiral center or concentric circle center of the track or pit with respect to the rotation center of the optical disk) and small tracking disturbance during recording and reproduction. Can do.

  In the above manufacturing method, the positioning region may be removed after the disk sheets are stacked on the disk substrate.

  In addition, since the method for manufacturing an optical disc according to the present invention stacks a plurality of disc sheets on the disc substrate at one time, the number of processes for stacking the plurality of disc sheets on the disc substrate can be reduced. Can be shortened, and throughput can be improved.

  In addition, you may combine the structure described as this invention arbitrarily with each structure described as said invention as needed.

  An embodiment of the present invention will be described below with reference to FIGS.

  First, the configuration of the optical disk of the present invention and the method for forming the optical disk will be described.

  1 and 2 are schematic views showing the configuration of an optical disc according to an embodiment of the present invention. The optical disc 1 has a configuration in which a plurality of disc sheets 6 are arranged on a disc substrate 5. The disk sheet 6 is provided with an information recording area 3 in which recording information consisting of an uneven pit pattern or an uneven track pattern is formed spirally or concentrically, and an area outside the information recording area 3. And a positioning region 4 for positioning between them. 1 and 2, the positioning area 4 is provided on the inner peripheral side of the information recording area 3. However, the present invention is not limited to this and is outside the range of the information recording area 3. It can be installed anywhere. That is, the positioning area 4 may be provided on the outer peripheral side of the information recording area 3, and may be provided on both the inner peripheral side and the outer peripheral side. The optical disc 1 has an inner peripheral hole 2 for centering when the optical disc 1 is rotationally driven.

  As shown in FIG. 2, a cross-sectional view of the optical disk 1 has a structure in which a plurality of disk sheets 6 are laminated on a disk substrate 5. The plurality of disc sheets 6 have two circular positioning areas 4 at the same position, and are stacked so that the positioning areas 4 overlap. Therefore, since the center positions of the respective disk sheets 6 can be specified by the positioning region 4, all the center positions of the plurality of disk sheets 6 can be matched. When the positioning area 4 is circular, it is preferable that a plurality of positioning areas 4 are provided so that the center positions of the plurality of disk sheets 6 can all coincide. On the other hand, if the positioning region 4 has a shape that is not point-symmetric, for example, a shape in which a plurality of circles are partially overlapped, even if only one is provided, the center positions of the plurality of disc sheets 6 are all matched. be able to. Here, the disk sheet 6 has spiral or concentric pits or tracks only on one surface thereof.

  Further, the disk substrate 5 has a positioning area 4 for positioning between the disk substrate 5 and the disk sheet 6 at a position corresponding to the positioning area 4 provided on the disk sheet 6. It is provided so as to have the same shape as the positioning region 4. As a result, the center position of the disk substrate 5 and the center positions of the plurality of disk sheets 6 can be matched.

  Next, an example of a method for forming the recording surface 14 of the disk sheet 6 will be described with reference to FIGS. In this example, an ultraviolet curable resin layer 8 (ultraviolet curable resin layer) is formed on the disk sheet substrate 9, and an uneven pattern is formed on the surface of the ultraviolet curable resin layer 8.

  The master 7 made of glass or metal has a shape corresponding to the pits or tracks of the disk sheet 6, that is, a concave or convex pattern 12 consisting of concave or convex pits or tracks. An ultraviolet curable resin layer 8 is formed by applying an ultraviolet curable resin on the master 7, and a disk sheet substrate 9 is disposed on the ultraviolet curable resin layer 8. A transparent pressing member 10 is disposed on the disk sheet substrate 9, the disk sheet substrate 9 is pressed against the master 7 by the transparent pressing member 10, and the disk sheet substrate 9 of the transparent pressing member 10 is in contact. By irradiating ultraviolet rays from a surface opposite to the surface, the ultraviolet curable resin layer 8 is cured, and a concave / convex pattern consisting of concave or convex pits or tracks is transferred. Thereafter, the transparent pressing member 10 is removed, and the cured ultraviolet curable resin layer 8 is peeled from the master disk 7 together with the disk sheet substrate 9, whereby the structure shown in FIG. 4, that is, the ultraviolet curable provided on the disk sheet substrate 9. A disc sheet 6 having a configuration in which an uneven pattern is formed on the surface of the resin layer 8 is formed.

  5 and 6 are cross-sectional perspective views of the disk sheet 6 formed by the above-described forming method. FIG. 5 shows an example in which concave or convex pits 13 are provided spirally or concentrically on the surface of the disk sheet 6 (ultraviolet curable resin layer 8). FIG. 6 shows an example in which concave or convex tracks 16 and 17 are provided spirally or concentrically on the surface of the disk sheet 6 (surface of the ultraviolet curable resin layer 8). In this specification, the surface of the disk sheet 6 on the side where the pits 13 or the tracks 16 and 17 are provided is referred to as a recording surface 14 of the disk sheet 6, and the surface opposite to the recording surface 14 is defined as a disk surface. Let it be the back surface 15 of the sheet 6. Here, the back surface 15 is a flat surface. The disk sheets 6 are laminated so that one of the opposed surfaces of the adjacent disk sheets 6 is the recording surface 14 and the other is the back surface 15. Therefore, the intervals between the plurality of recording surfaces 14 are all substantially equal to the thickness of the disk sheet 6. Here, it is desirable that the uneven steps of the pits 13 or the tracks 16 and 17 be in the range of 20 nm to 100 nm in order to perform accurate tracking. The width of the pit 13 and the widths of the tracks 16 and 17 should be determined by the size of the light beam spot for recording or reproduction, and should be about half the diameter of the light beam spot. Is desirable.

  Here, the method for forming the recording surface 14 using the ultraviolet curable resin layer 8 has been described, but the present invention is not limited to this. For example, it is possible to press a master having a concavo-convex pattern corresponding to the recording surface 14 on the surface of the disk sheet substrate 9 to directly form the concavo-convex pattern on the surface of the disk sheet substrate 9. Thereby, the optical disk 1 in which the uneven pattern is directly formed on the surface of the disk sheet substrate 9 is obtained. In this case, the recording surface 14 can be formed without using an ultraviolet curable resin, the formation process of the disk sheet 6 is simplified, and a multilayer optical disk can be formed at low cost.

  In the present invention, a recording surface may be provided on the surface of the disk substrate 5, but when the recording surface 14 is provided on the surface of the disk substrate 5, the recording differs from the process of providing the recording surface 14 on the disk sheet 6. A surface forming process is required, and it is desirable not to provide a recording surface on the surface of the disk substrate 5 in order to reduce the cost of the optical disk 1 by simplifying the disk manufacturing process.

Forming a concavo-convex pattern directly on the surface of the disk sheet substrate 9 means that the disk sheet substrate is pressed against a stamper having a concavo-convex pattern corresponding to a pit or track for an optical disk using a roller or a holding member, The concavo-convex pattern is transferred to the surface. A specific description will be given with reference to FIGS. 7 to 9 as follows.
FIG. 7 is a schematic cross-sectional view showing an embodiment of a disk sheet forming method for forming an uneven pattern using a stamper. The strip-shaped sheet material 44 m is disposed on the stamper 45 and pressed between the rotating roller 46 and the stamper 45. In the stamper 45, the rotating roller 46 moves in the direction of the arrow in the drawing while maintaining a pressed state with the belt-like sheet material 44m. Thereby, the concavo-convex pattern corresponding to the pits or tracks formed on the surface of the stamper 45 is mechanically transferred onto the belt-like sheet material 44m.

  In addition, the said strip | belt-shaped sheet material shown in FIG. 7 is a thing of the form by which the both ends of this strip | belt-shaped sheet material are wound up by the sheet roller 47 at roll shape. According to this, the belt-like disc sheet 44 is wound up by the sheet roller 47, and at the same time, a new belt-like sheet material 44m is sent to the stamper 45, and the above steps are repeated.

  According to the above method, it is possible to continuously form the belt-like disc sheet 44 having a plurality of recording surfaces 56 at intervals.

  As a result, the mass productivity of the belt-like disc sheet 44 and, consequently, the mass productivity of the optical disc 1 can be improved. Further, by winding the belt-like disk sheet 44 in a roll shape, the mass productivity of the belt-like disk sheet 44 is enhanced and its management is facilitated.

  Next, FIGS. 8A and 8B are cross-sectional views showing another method for forming a disk sheet. The belt-like sheet material 44m wound around the sheet roller 47 in a roll shape has a concavo-convex pattern corresponding to the recording surface 56 (pits or tracks), and the concavo-convex surface is sent out to a stamper 45 having a flat surface.

  Next, as shown in FIG. 8A, the belt-like sheet material 44m disposed on the stamper 45 at the initial position is pressed relatively weakly between the rotating roller 49 and the stamper 45, and the stamper 45 and the belt-like material are pressed. The sheet material 44m is brought into a close contact state. Here, the strip-shaped sheet material 44m and the stamper 45 do not move from the initial position, and the rotating roller 49 moves in the direction of the arrow x in the drawing while pressing the strip-shaped sheet material 44m against the stamper 45.

  Next, in a state where the above contact state is maintained, the belt-shaped sheet material 44m is transported together with the stamper 45 in the direction of the arrow y in the figure, and as shown in FIG. The pressing member 50 presses the stamper 45 relatively strongly.

  Thereby, the concavo-convex pattern corresponding to the pits or tracks on the surface of the stamper 45 is mechanically transferred onto the strip-shaped sheet material 44m.

  Next, the stamper 45 is peeled off from the belt-like disk sheet 44 and returned to the initial position. As a result, a belt-like disk sheet 44 having a recording surface 56 provided with the concave / convex pattern is formed.

  Then, the belt-like disk sheet 44 is wound up by a sheet roller 47, and at the same time, a new belt-like sheet material 44m is sent to the stamper 45, and the above steps are repeated.

  According to the above method, since the belt-shaped sheet material 44m is pressed by the stamper 45 having a flat surface and the pressing member 50 having a flat pressing portion, it is possible to apply a vertically symmetrical pressing force to the belt-shaped sheet material 44m. It is possible to suppress the occurrence of curling (bending) in the belt-like disk sheet 44 after pattern transfer.

  Further, the formation process of the recording surface 56 on the strip-shaped sheet material 44m by the stamper 45 and the rotating roller 46 is not limited to the above-described process, and the strip-shaped sheet material 44m is pressed against the stamper 45 by the rotating roller 49, Any process (method) for forming the recording surface 56 at 44 m may be used.

  FIG. 9 is a cross-sectional view showing another method for forming a disc sheet in the form of being wound around the sheet roller 47 in the same manner as described above.

  First, a belt-shaped sheet material 44m wound up in a roll shape around a sheet roller 47 is formed between a first rotating roller 51 having a stamper 45 disposed on the surface and a second rotating roller 52 having no uneven pattern on the surface. To send. Here, the stamper 45 has an uneven pattern corresponding to the recording surface 56 (pits or tracks). Further, the first rotating roller 51 and the second rotating roller 52 have substantially the same shape, and are opposed to each other with a gap corresponding to the thickness of the belt-like disk sheet 44.

  Next, the first rotating roller 51 and the second rotating roller 52 press the band-shaped sheet material 44m, and mechanically form a concavo-convex pattern corresponding to the pits or tracks formed on the surface of the stamper 45 on the band-shaped sheet material 44m. Transcript to. As a result, a belt-like disk sheet 44 having a recording surface 56 provided with the concave / convex pattern is formed.

  Thereafter, the belt-like disk sheet 44 is wound up by the sheet roller 47 in conjunction with the rotation of the first rotating roller 51 and the second rotating roller 52.

  In the above-described method, the belt-shaped sheet material 44m is disposed in the gap between the first rotating roller 51 and the second rotating roller 52 having substantially the same shape and arranged opposite to each other, and the belt-shaped sheet material 44m is disposed on the first rotating roller. 51 and the 2nd rotation roller 52 press.

  Therefore, a vertically symmetrical pressing force is applied to the belt-shaped sheet material 44m, and there is little possibility of curling the belt-shaped disk sheet 44 after pattern transfer.

  As a result, the uneven pattern on the stamper 45 can be more accurately transferred onto the belt-like sheet material 44m.

  In the method for creating a recording surface using the photosensitive curable resin described with reference to FIGS. 3 to 4, the disk sheet can be formed by winding the sheet roller as described above.

  As described above, as a disk sheet forming method using a photosensitive curable resin, a method as shown in FIG. 10 or 11 can be used. First, in FIG. 10, the belt-like sheet material 44 m wound up in a roll shape around the sheet roller 47 is sent out toward the stamper 45 having an uneven pattern corresponding to the recording surface 56 (pit or track).

  Next, a liquid ultraviolet curable resin is applied on the strip-shaped sheet material 44 m or the stamper 45, and the ultraviolet curable resin layer 53 is disposed between the strip-shaped sheet material 44 m and the stamper 45.

  Next, the belt-like disk sheet 44 is pressed against the stamper 45 by the rotating roller 54, and the layer thickness of the ultraviolet curable resin layer 53 is made uniform. Here, the belt-like sheet material 44m and the stamper 45 do not move in the transport direction of the belt-like sheet material 44m, and only the rotation roller 54 rotates in the arrow direction in the drawing while maintaining the pressing state with the belt-like sheet material 44m.

  Then, immediately after the rotational movement of the rotating roller 54, the ultraviolet light 11 is irradiated from the belt-like disk sheet 44 side to cure the ultraviolet curable resin 53. Thereby, the uneven pattern can be transferred to the ultraviolet curable resin layer 53.

  Thereafter, the cured ultraviolet curable resin 53 is peeled off from the stamper 45. As a result, a belt-like disk sheet 44 having a recording surface 56 made of an ultraviolet curable resin is formed.

  Then, the belt-like disc sheet 44 is wound up by the sheet roller 47, and at the same time, a new belt-like sheet material 44m is sent to the stamper 30, and the above steps are repeated.

  In the above formation method, the ultraviolet light 11 is irradiated from the side of the belt-like sheet material 44m. However, when a transparent stamper 45, for example, a glass stamper 45 having a concavo-convex pattern formed on the surface is used, the side of the stamper 45 It is also possible to irradiate with UV light.

  According to the above forming method, the pit or track pattern formed on the stamper 45 can be efficiently transferred to the ultraviolet curable resin layer 53, and a process for forming the optical disc 1 having excellent mass productivity can be provided. it can.

  Thereby, the miniaturization and cost reduction of the optical disk forming apparatus can be realized, and consequently the cost of the optical disk 1 can be reduced.

  Further, in the above forming method, only the rotating roller 54 is rotated in the direction of the arrow in the figure, but the rotating roller 54 is not moved in the transport direction of the strip-shaped sheet material 44m, and the stamper 45 While maintaining the pressed state, it is also possible to move in a direction opposite to the arrow in the figure by a predetermined distance from the initial position.

  Next, FIG. 11 shows an example of a disk sheet forming method in the case where the disk sheet forming method described in FIGS. 3 to 4 is wound around a sheet roller as described above.

  First, the belt-like sheet material 44m wound up in a roll shape around the sheet roller 47 is sent out toward a stamper 45 having an uneven pattern corresponding to the recording surface 56 (pits or tracks).

  Next, a liquid ultraviolet curable resin layer 53 is formed on the stamper 45 or the strip-shaped sheet material 44 m at the initial position, and the ultraviolet curable resin 53 is disposed between the strip-shaped sheet material 44 m and the stamper 45.

  Next, as shown in FIG. 11A, the belt-shaped sheet material 44 m is pressed against the stamper 45 relatively weakly by the rotating roller 55. Here, the belt-like sheet material 44m and the stamper 45 do not move in the conveying direction of the belt-like sheet material 44m, and the rotation roller 55 rotates and moves in the direction of the arrow x in the drawing while maintaining the pressing state with the belt-like sheet material 44m. Thereby, the layer thickness of the liquid ultraviolet curable resin layer 53 is made uniform.

  Next, the stamper 54 is moved together with the belt-like sheet material 44m in the direction of the arrow y in the above figure, the belt-like sheet material 44m is sandwiched between the stamper 54 and the pressing member 50, and the belt-like sheet material is pressed with a pressure stronger than the pressure by the rotating roller 55. Press 44m. Thereby, the layer thickness of the liquid ultraviolet curable resin layer 53 is further uniformized.

  Further, the ultraviolet light 11 is irradiated from the pressing member 50 side while the belt-shaped sheet material 44m is pressed, and the ultraviolet curable resin layer 53 is cured. Thereby, the uneven pattern can be transferred to the ultraviolet curable resin layer 53.

  Then, after the ultraviolet curable resin layer 53 is cured, the pressing by the pressing member 50 is released, and the stamper 45 is separated from the cured ultraviolet curable resin layer 53. As a result, a belt-like disk sheet 44 having a recording surface 56 made of an ultraviolet curable resin is formed.

  Thereafter, the belt-like disc sheet 44 is wound up by the sheet roller 47, and at the same time, a new belt-like sheet material 44m is sent to the stamper 45, and the above steps are repeated.

  In the above forming method, the ultraviolet light 11 is irradiated from the side of the belt-like disk sheet 44. However, when a transparent stamper 45, for example, a glass stamper 45 having a concavo-convex pattern formed on the surface is used, Ultraviolet light may be irradiated from the side.

  According to the above forming method, a forming process of the optical disc 1 excellent in mass productivity can be provided as in the forming method shown in FIG. Therefore, the optical disk forming apparatus can be reduced in size and cost, and as a result, the cost of the optical disk 1 can be reduced.

  Furthermore, in order to cure the ultraviolet curable resin layer 53 by irradiating the ultraviolet light 11 in a state where the liquid ultraviolet curable resin layer 53 is pressed by the stamper 45 and the pressing member 50, compared with the forming method shown in FIG. Thus, the layer thickness of the ultraviolet curable resin layer 53 can be made even more uniform.

  12 to 14 show a method of forming the positioning region 4 on the disc sheet 6. First, as shown in FIG. 12, the disc sheet 6 having the concavo-convex pattern 12 is disposed on the fixed mold 18. The fixed mold 18 is provided with a protective recess 20 for preventing the concave / convex pattern 12 from coming into contact with the fixed mold 18 and being damaged, and a receiving portion 19 corresponding to the positioning region 4. Further, the fixed mold 18 is provided with an inner diameter processed portion 26 that is a portion that contacts the inner peripheral hole 2 of the optical disc 1 and a center hole 28 through which the inner diameter processed portion 26 passes in order to produce the inner peripheral hole 2. Yes.

  After the disk sheet 6 is placed on the fixed mold 18, the movable support mold 21 moves in the direction of the fixed mold 18, and presses the disk sheet 6 against the fixed mold 18, so that the disk sheet 6 is fixed so as not to bend. The movable support die 21 is supported by a support rod 24 that passes through a penetrating portion provided in the movable machining die 23, and the movable support die 21 and the movable machining die 23 are movable independently. is there. Further, the movable support die 21 is provided with a processing part passage hole 22 at a position corresponding to the positioning region 4.

  Next, as shown in FIG. 13, the movable machining mold 23 moves in the direction of the fixed mold 18, and the positioning region machining section 25 of the movable machining mold 23 presses the disk sheet 6, and the disk sheet 6. The positioning region 4 is formed by deforming. In this case, the positioning region 4 has a convex portion formed on one side and a concave portion formed on the back surface thereof. At the same time, the inner diameter processing portion 26 and the outer diameter processing portion 27 cut the inner periphery and the outer periphery of the disc sheet 6.

  FIG. 14 shows a cross-sectional view of the disk sheet 6 taken out from the mold after the processing is completed. By the above method, a plurality of disc sheets 6 having the positioning region 4 and the inner peripheral hole 2 are completed. A plurality of disk sheets 6 having the positioning region 4 and the inner peripheral hole 2 at the same position are obtained by repeating the process of creating the disk sheet 6 described above.

  Next, the plurality of completed disk sheets 6 are carried into a vacuum apparatus such as a vapor deposition apparatus or a sputtering apparatus, and a reflective film is formed on the surface of each of the disk sheets 6 on which spiral or concentric pits or tracks are formed. Alternatively, a recording film is formed. Then, each said disk sheet 6 is carried out from a vacuum device, and the said disk sheet 6 which has the recording surface 14 in which the reflecting film or the recording film was formed is completed. Thereafter, the plurality of disk sheets 6 are laminated so that the positioning areas 4 of the overlapping disk sheets 6 coincide with each other, and then bonded together. At this time, the disc sheet 6 is laminated so that the surfaces on which the convex portions are formed are in the same direction. Therefore, on the surfaces of the adjacent disk sheets 6 facing each other, a convex portion is provided on one side and a concave portion is provided on the other side, so that lamination is performed so that the convex portion is fitted into the concave portion. Is called.

  The disc sheet 6 is attached using an adhesive. As the adhesive, in order to shorten the production time, it is preferable to use an adhesive made of an ultraviolet curable resin that can be cured by ultraviolet irradiation. The adhesive made of the ultraviolet curable resin is applied onto the disk sheet 6 by a spin coating method, and the ultraviolet curable resin is cured by irradiating the ultraviolet rays after the lamination, thereby enabling the bonding in a short time. Here, the adhesive made of an ultraviolet curable resin used for attaching the plurality of stacked disc sheets 6 is an adhesive having a much thinner thickness than the disc sheets 6, for example, approximately 1 μm, between the disc sheets 6. Used to form a layer. The shrinkage that occurs during curing by ultraviolet irradiation is not so large as to affect the smoothness of the disc sheet 6 after formation because the ultraviolet curable resin (adhesive layer) is thin.

  Moreover, a pressure sensitive adhesive film can be used instead of the adhesive which consists of ultraviolet curable resin. When a pressure-sensitive adhesive film is used, the pressure-sensitive adhesive film is laminated between a plurality of disk sheets 6, and pressure is applied from both sides of the plurality of stacked disk sheets 6, whereby the disk sheet 6 is Can be pasted together. In this case, it is possible to carry out the bonding of the disk sheet 6 only by applying pressure, and it becomes possible to perform bonding in a short time, as well as an apparatus for applying an ultraviolet curable resin and an ultraviolet light source. A device for curing is not required. As a result, a multilayer optical disk 1 having the configuration shown in FIGS. 1 and 2 in which adjacent disk sheets 6 are bonded together using a pressure-sensitive adhesive film is formed.

  Further, a heat-sensitive adhesive film that can be bonded at a temperature lower than the softening temperature of the disk sheet can be used. When a heat-sensitive adhesive film is used, the heat-sensitive adhesive film is laminated between a plurality of disk sheets 6, and is lower than the softening temperature of the plurality of disk sheets 6 stacked, and is equal to or higher than the operating temperature of the heat-sensitive adhesive film. The disk sheet 6 can be bonded together by raising the temperature to the temperature of. In this case, the disk sheet 6 can be bonded only by raising the temperature, and an apparatus for applying an ultraviolet curable resin and an apparatus for curing such as an ultraviolet light source become unnecessary. As a result, a multilayer optical disk 1 having the configuration shown in FIGS. 1 and 2 in which adjacent disk sheets 6 are bonded together using a pressure-sensitive adhesive film is formed. Here, when the temperature is raised for bonding with the heat-sensitive adhesive sheet, a flatter multilayer optical disk 1 is formed by applying pressure from both sides of the plurality of stacked disk sheets 6.

  Further, the positioning region 4 formed in accordance with the above-described process can uniquely specify the position of the spiral center or concentric circle center of the uneven pattern of each disk sheet 6. Therefore, by stacking the disk sheets 6 with the positioning region 4 as a reference, the spiral center or concentric circle center of each disk sheet 6 can be made coincident. Thereby, a multi-layer optical disk with small eccentricity can be formed in all the disk sheets 6.

  In the above forming method, as shown in FIG. 13, the inner and outer peripheries of the disk sheet are processed simultaneously with the formation of the positioning area 4, but only the positioning area 4 is formed and the recording film is formed. In addition, after the bonding of the disk sheet on the disk substrate is completed, the inner periphery and the outer periphery of the disk sheet can be processed.

  The optical disk recording / reproducing apparatus of the present invention will be described below with reference to FIGS.

  FIG. 15 shows an enlarged cross-sectional view of the multilayer optical disk 1 of the present invention. A plurality of disk sheets 6 having a recording surface 14 on one surface and a back surface 15 having a flat surface on the other side of the disk substrate 5 are opposed to the recording surface 14 of the disk substrate 5 and the recording surface 14 of the disk sheet 6. In addition, the recording sheets 14 and the back surface 15 of the disk sheets 6 adjacent to each other are stacked so as to face each other by stacking, and the disk substrate 5 and the plurality of disk sheets 6 stacked are attached by an adhesive 31. It has a combined structure.

  The light beam 29 is focused and irradiated on the recording surface 14 of each disk sheet 6 by the objective lens 30, and focusing is always performed so that the light beam is focused on the recording surface 14. The focused light beam 29 is tracked for recording or reproduction along the pits 13 or tracks 16 and 17 as the optical disk 1 rotates.

  FIG. 16 is a schematic diagram of a recording apparatus or reproducing apparatus for recording / reproducing information on the optical disc 1.

  The optical disk 1 is chucked by the spindle 36 and rotated while being centered by the inner peripheral hole 2. On the other hand, the light beam 33 is an optical pickup (recording light irradiation means, reproducing light) having a light beam light source, a photodetector, a focusing optical system, a tracking optical system, and an objective lens 34 for condensing the light beam. Control is performed by irradiation means) 35. The optical pickup 35 condenses and irradiates a light beam so that information can be recorded or reproduced on each recording surface 14 of the optical disc 1. That is, focusing is performed on the recording surface 14 of a specific disk sheet 6 among a plurality of disk sheets 32 stacked on the disk substrate 5, and tracking is performed on the pits 13 or the tracks 16 and 17. The recording apparatus or reproducing apparatus performs a drive control circuit 37 for performing rotation driving and access control, focusing control, and tracking control of the optical pickup 35, and for performing light beam intensity control, reproduction signal detection, or recording signal control. The recording control circuit 38 or the reproduction control circuit 38 is provided.

  By using the optical disc 1 described above and the optical disc playback device or optical disc recording device, it becomes possible to perform playback or recording on the multilayer optical disc 1 having a plurality of recording surfaces 14, and realize a large capacity optical disc device. can do.

  In FIG. 16, the configuration in which the light beam is incident from the plurality of disk sheets 32 is described. However, it is also possible to perform recording or reproduction by inputting the light beam from the disk substrate 5 side. However, when a higher-density optical disk is realized by using a high NA (NA: numerical aperture) objective lens 34 to reduce the diameter of the focused spot of the light beam 33, a slight tilt of the optical disk causes the light beam Therefore, it is desirable to make the disk sheet 6 thinner. For example, when the objective lens 34 having an NA of 0.70 or more is used, the influence of this coma aberration becomes very significant.

  As the thickness of the disk substrate 5 is relatively thick, the mechanical strength of the disk substrate 5 is increased. Thus, when the mechanical strength of the disk substrate 5 is increased, the flatness of the optical disk 1 can be maintained even when a plurality of relatively thin disk sheets 6 are stacked. It can be realized. The thickness of the disk substrate 5 is preferably larger than the thickness of the disk sheet 6, and more preferably 0.3 mm or more in order to maintain sufficient mechanical strength.

  In order to increase the number of stacked disk sheets 6 and increase the storage capacity, the thickness of the disk sheet 6 is desirably as thin as possible, but is preferably at least 15 μm. When the disk sheet is thinner than 15 μm, the mechanical strength of the disk sheet 6 becomes weak, and handling of the disk sheet becomes difficult. On the other hand, the thickness of the disk sheet 6 is preferably 50 μm or less, and therefore most preferably 20 μm or more and 50 μm or less. By setting the thickness of the disk sheet 6 to 50 μm or less, the storage capacity of the optical disk 1 can be increased by increasing the number of stacked disk sheets 6 without making the thickness of the optical disk 1 too thick.

  Further, if the position of the spiral center or concentric circle center of the concave-convex pattern 12 included in each disk sheet 6 is shifted, the state of occurrence of eccentricity differs in each disk sheet 6. In this case, it is necessary to track the collected light beam 29 corresponding to the different eccentricity of each disk sheet, and a powerful tracking device is required.

  However, in the multilayer optical disc according to the present invention, the positioning region 4 suppresses the deviation of the center position between the disc sheets 6, so that the tracking device can be simplified, that is, the tracking device can be downsized. it can.

  As a recording method of the optical disc 1, a ROM (Read Only Memory) method capable of reproduction only, a WO (Write Once) method capable of recording and reproduction, and a RE (Re-Writeable) method capable of recording, erasing and reproduction are provided. It is possible to apply.

  In the case of a ROM type optical disk, pits 13 as shown in FIG. 5 are recorded on the disk sheet 6, and a light beam is concentratedly irradiated on the pits 13, and the reflected light quantity is detected. Perform playback. As shown in FIG. 15, when the light beam 29 is condensed and applied to the recording surface 14 located at the interface between the disk sheet 6 and the adhesive 31, the refractive index of the disk sheet 6 and the refractive index of the adhesive 31 are obtained. Otherwise, a part of the light beam irradiated to the recording surface 14 which is the interface between them is reflected by the recording surface 14 to generate reflected light. The reflected light is detected by a photodetector in the optical pickup 35, and information is reproduced by reading the change in the amount of reflected light due to the presence or absence of the pits 13.

  For example, when the refractive index of the disk sheet 6 is n1 and the refractive index of the adhesive 31 is n2, the light reflectance R at the interface between the disk sheet 6 and the adhesive 31 is obtained by the following equation.

  For example, when a resin sheet made of a polycarbonate resin having a refractive index n1 of 1.58 is used as the disk sheet 6, and a fluororesin-containing acrylic ultraviolet curable resin having a refractive index n2 of 1.33 is used as the adhesive 31, The reflectance R at the interface between the disk sheet 6 and the adhesive 31 is 0.74%.

  For example, when laser light having an intensity of 30 mW is incident on the recording surface 14 on the light incident side, the reflected light intensity from the recording surface 14 is 221 μW. However, in this case, there are a plurality of the interfaces composed of a plurality of disk sheets, and the light beam intensity becomes weaker every time the interfaces are passed. Accordingly, the reflected light intensity from the recording surface 14 of the disc sheet that is away from the light incident side becomes weak, and the reflected light intensity changes by the recording surface 14. Here, the reproduction signal of the same level can be always sent to the reproduction control circuit 38 by changing the amplification factor of the reproduction signal detected by the photodetector of the optical pickup 35 according to the reflected light intensity.

  Here, the configuration example using the polycarbonate sheet and the acrylic ultraviolet curable resin has been described. However, the present invention is not limited to this, and the disk sheet 6 may be, for example, a polyethylene terephthalate (PET) film or a polyethylene naphthalate. Polyethylene resin sheets such as phthalate (PEN) films, polypropylene resin sheets, olefin resin sheets, and the like can also be used.

  In the embodiment described above, by increasing the difference in refractive index between the disk sheet 6 and the adhesive 31, the amount of reflected light from the recording surface located at the interface between them is increased, and a reproduction signal with sufficient strength is obtained. It is possible.

  In the optical disc according to the present invention, a reflective film can be formed on the recording surface 14 of the disc sheet. Since the amount of light reflected from the recording surface can be increased by forming the reflective film, it is possible to improve the reproduction signal quality. The material of the reflective film is preferably a material having a high reflectivity with respect to a light beam for reproduction, and includes, for example, a metal thin film such as Al, Au, Pt, Ti, Ag, or those metals. It is desirable to be an alloy. When the reflectivity of the reflective film is low, it is necessary to increase the thickness of the reflective film in order to obtain a desired amount of reflected light, and transmission through the reflective film due to an increase in light absorption accompanying an increase in the thickness of the reflective film. The amount of transmitted light decreases, and the number of stacked recording surfaces 14 decreases. The film thickness (reflectance) of the reflecting film should be determined by the number of recording surfaces 14 provided. The reflecting film formed on the recording surface 14 on the light incident side is made thinner, The thickness of the reflective film formed on each recording surface 14 is controlled so that the thickness of the reflective film is gradually increased toward the recording surface 14 on the opposite side so that the amount of reflected light from each recording surface becomes equal. To do.

  Further, in the optical disk 1 having the configuration using the reflective film, if the refractive index of the disk sheet 6 and the refractive index of the adhesive 31 are different, light is reflected only by the recording surface 14 on which the reflective film is formed. It does not occur, and light reflection occurs at the interface between the back surface 15 of the disk sheet 6 and the adhesive 31. In this case, the amount of reflected light to be reproduced is reduced by reflecting the light beam at the interface. Therefore, it is desirable that the refractive index of the disk sheet 6 and the refractive index of the adhesive 31 are substantially equal.

  In the optical disc according to the present invention, a recording film can be formed on the recording surface of the disc sheet. By using an amorphous material made of a phase change material as a recording film, information recording is performed by partially changing the phase to a polycrystal by irradiating the recording film with a light beam pulse, and an amorphous state. Information can be reproduced by detecting the difference in reflectance between the crystalline state and the polycrystalline state. Specifically, it is as follows.

  In the case of the WO optical disk 1, as shown in FIG. 6, tracks 16 and 17 provided in a concave or convex shape are formed on the disk sheet 6, and on the tracks 16 and 17, WO A recording film corresponding to the system is formed, and the light beam 29 focused and irradiated is tracked along the tracks 16 and 17. Information is recorded by irradiating a pulsed light beam with a relatively strong intensity, and information is reproduced by continuously irradiating a light beam with a relatively weak intensity and detecting the amount of reflected light. Is done. The recording and reproduction may be performed on either the track 16 or the track 17 or may be performed on both the track 16 and the track 17.

  The configuration of the WO optical disk 1 is basically the same as that of the ROM optical disk 1. The difference from the ROM type optical disc 1 is that a recording film is provided instead of the reflection film. In addition, in the WO type optical disc, recording is performed by the alteration of the recording film or the resin deformation in the vicinity of the recording film due to the temperature rise caused by the light beam being focused on the recording film. Therefore, the recording film needs to appropriately absorb the light beam in order to generate a desired temperature rise.

  As the recording film, a material having a relatively low reflectance and a high absorption coefficient is used as compared with the reflecting film used in the ROM type optical disc 1. As the recording film of the WO optical disk 1, a phase change material mainly composed of at least two elements selected from the group of Sb, Te, In, Ag, and Ge can be used. Information recording is performed by irradiating the amorphous recording film made of the phase change material with a light beam pulse to partially change the phase into polycrystalline, and the amorphous state and the polycrystalline are recorded. Information is reproduced by detecting the difference in reflectance in the state.

  Further, as another recording film of the WO optical disk 1, a metal film such as Ta or Si, or an alloy film containing them as a main component can be used. When these metal films and alloy films are irradiated with a light beam pulse, the temperature rises at the irradiation position, and the resin is deformed in the vicinity thereof. By detecting the change in reflectance due to the resin deformation, the recorded information can be reproduced.

  The RE optical disc 1 has the same configuration as the WO optical disc 1. As the recording film, it is possible to use a phase change material mainly composed of at least two elements selected from the group of Sb, Te, In, Ag, and Ge, as in the case of the WO optical disk 1. By irradiating the amorphous recording film made of the phase change material with a light beam pulse having a relatively strong intensity, a phase change is partially made into a polycrystal, thereby recording information. By irradiating a light beam with extremely low intensity, the phase is changed from polycrystalline to amorphous, thereby erasing information. Here, it is desirable that the composition of the phase change material is optimized so as to cause a phase change from amorphous to polycrystalline and a phase change from polycrystalline to amorphous. The recorded information is reproduced by detecting a difference in reflectance between the amorphous state and the polycrystalline state.

  With respect to the positioning area, in the multilayer optical disk 1 shown in FIGS. 1 and 2, the configuration in which the positioning areas 4 made of conical bends are provided at two locations in the inner peripheral area of the optical disk 1 has been described. For example, it may be a pyramid-shaped positioning region. Further, the number thereof may be three or more, and the positioning accuracy is improved by increasing the number of positioning regions 4.

  Next, FIG. 17 and FIG. 18 show a plan view and a cross-sectional view of a configuration in which a positioning region 39 formed by concentric bending is provided in the inner peripheral region of the optical disc 1. The positioning area 4 having the configuration shown in FIG. 1 has a conical bending structure, and after rotating the respective disk sheets 6 so that the positioning areas of the plurality of disk sheets 6 overlap, the disk sheets 6 are bonded together. As shown in FIGS. 17 and 18, it is necessary to perform positioning of the disc sheet 6 without performing alignment in the rotational direction of the optical disc 1 by forming a positioning region 39 consisting of concentric bends. It is possible to perform the alignment, and the process for bonding the disk sheets 6 can be simplified. As a result, the optical disc 1 can be provided at a lower cost.

  Further, the positioning region is not limited to the one having a bent structure, and a positioning method using another positioning region may be used. For example, in the steps shown in FIG. 12 to FIG. 14, a disk sheet having a concavo-convex pattern is placed on a mold to process a positioning area. This is shown in FIG. 3 except for the information recording area 3 of the master 7. A concentric positioning uneven pattern for positioning is formed in the inner peripheral area and / or outer peripheral area of the disk, and the concentric positioning uneven pattern for visual recognition is transferred to the disk sheet 6 by transferring the concentric positioning uneven pattern to the disk. It can be provided on the sheet 6. By laminating the disc sheet 6 with this concentric positioning uneven pattern as a reference, it is possible to provide the multilayer optical disc 1 with small eccentricity. According to this method, it is possible to perform positioning for stacking without providing a bent structure in the disk sheet 6, and it is possible to realize cost reduction by simplifying the optical disk forming process.

  Next, FIG. 19 is a multilayer having a configuration in which the recording surface 14 side of a plurality of disc sheets 6 is bonded together with an adhesive 31 so as to face the surface of the disc substrate 5 in the same manner as the optical disc 1 shown in FIG. In the optical disc, the configuration of an optical disc in which a protective layer 41 is provided on the surface opposite to the disc substrate of the optical disc formed by laminating a plurality of the disc sheets on the disc substrate is shown.

  In order to increase the storage capacity of the optical disk 1, it is desirable to reduce the layer thickness of each disk sheet 6 and to stack as many disk sheets 6 as possible. However, as shown in FIG. 15, the thickness of the disk sheet 40 on the surface opposite to the disk substrate of the optical disk, that is, the outermost surface in the configuration shown in FIG. Due to the accident, the damage generated on the outermost surface of the disk sheet reaches the recording surface 14 of the disk sheet located on the outermost surface, and the risk that information is lost is extremely increased.

  Further, when the light beam 29 is collected from the disk sheet side of the optical disk, if the thickness of the disk sheet 40 located on the outermost surface is thin, the spot diameter of the light beam 29 irradiated on the outermost surface of the disk sheet 40 is reduced. Thus, slight damage and small dust adhesion obstruct the optical path of the light beam 29, making it difficult to record or reproduce information.

  Here, in the case of the multilayer optical disc 1 shown in FIG. 19, a protective layer 41 is provided on the disc sheet 40 located on the outermost surface. That is, the protective layer 41 is provided on the surface of the disk sheet 6 farthest from the disk substrate 5 on the side opposite to the surface on the disk substrate 5 side. Thereby, it is possible to prevent damage or the like from reaching the recording surface 14. Further, since the distance between the recording surface 14 and the surface of the protective layer 41 is increased, the spot diameter of the light beam 29 irradiated on the surface of the protective layer 41 is relatively increased. As a result, when the light beam 29 is condensed from the disk sheet 6 side and recording or reproduction is performed, it is possible to reduce adverse effects on the recording / reproduction characteristics due to damage or dust generated on the surface of the protective layer 41. .

  As the protective layer 41, an acrylic ultraviolet curable resin or an epoxy ultraviolet curable resin can be used. Thereby, the protective layer 41 can be formed by a simple process and at a low cost. Further, as the protective layer 41, it is possible to use the same material as the adhesive 31, but in order to suppress the reflection of the light beam at the interface between the disk sheet 40 located on the outermost surface and the protective layer 41, It is desirable to make the refractive index of the protective layer 41 equal to that of the disk sheet 40.

  In the multilayer optical disc having the above-described configuration, by providing the same positioning region 4 as in FIG. 2, it is possible to reduce the variation in eccentricity of each disc sheet in the multilayer optical disc.

  Next, the optical disc 1 shown in FIG. 20 is an enlarged cross-sectional view showing a configuration example in which a protective sheet 43 is bonded with an adhesive 42 instead of the protective layer 41 of the second configuration example shown in FIG. As in the case of the configuration example shown in FIG. 19, by providing the protective sheet 43, it is possible to prevent the recording surface 14 from being damaged, and recording due to damage generated on the surface of the protective sheet 43, dust, or the like. The adverse effect on the reproduction characteristics can be reduced.

  The protective layer 41 shown in FIG. 19 is formed by applying a liquid ultraviolet curable resin by spin coating and irradiating and curing the ultraviolet light. The protective layer 41 is formed on the inner and outer circumferences of the optical disc 1. A difference in thickness occurs. On the other hand, the fluctuation | variation of layer thickness can be reduced by bonding the protective sheet 43 which has uniform layer thickness with the adhesive agent 42 of thin layer thickness.

  Further, when recording or reproducing is performed by irradiating a light beam from the protective layer 41 or the protective sheet 43 side, fluctuations in the layer thickness lead to an increase in coma aberration or spherical aberration of the light beam. Therefore, by suppressing the layer thickness variation using the protective sheet 43, a good light beam condensing state is maintained, and good recording characteristics or reproduction characteristics can be obtained.

  Also in the multilayer optical disk having the configuration shown in FIG. 20, it is possible to reduce the variation in the eccentricity of each disk sheet in the multilayer optical disk by providing the same positioning region 4 as in FIG.

  In the above description, a multilayer optical disk having a configuration in which the surface of the disk substrate 5 and the recording surface 14 of the disk sheet 6 face each other has been described, but it is also possible to have a structure in which all the disk sheets 6 are turned upside down. is there. In this case, since the recording surface 14 of the outermost disk sheet 6 is exposed, it is desirable to provide a protective layer 41 or a protective sheet 43 that protects the recording surface 14.

  Further, in the configuration of FIG. 15, it is not necessary to provide the protective layer 41 and the protective sheet 43 by making the thickness of the disk sheet 6 located on the outermost surface larger than the thickness of the other disk sheets 6. Thus, the configuration of the multilayer optical disk can be simplified and the cost can be reduced.

[Example 1]
As Example 1 of the present invention, an ultraviolet curable resin layer 8 having a recording surface 14 composed of concave pits 13 was formed on a disk sheet substrate 9 in accordance with the disk sheet 6 forming method shown in FIG. Specifically, it is as follows.

  Four types of masters 7 each having a pit pattern in which an ultraviolet curable resin layer 8 having a thickness of 1 μm is laminated on a disk sheet substrate 9 made of a polyethylene terephthalate (PET) film having a thickness of 30 μm and different information is recorded. Is used to form concave pits 13 having a depth of 20 nm and a width of 0.3 μm on the surface of the ultraviolet curable resin layer 8 in a spiral shape with a pitch of 0.5 μm, so that four types corresponding to the respective masters are formed. The disc sheet 6 was formed. Next, according to the process shown in FIGS. 12-14, the positioning area | region 4 was formed in each disc sheet | seat 6, and the inner periphery and the outer periphery were processed simultaneously.

  Next, a reflective film made of an AlTi alloy was formed on the recording surface 14 of the four types of disk sheets 6. The reflection film thickness of each disk sheet 6 was determined so that the reflected light intensities from the respective layers of the light beam for reproduction substantially coincide. When the disk sheets 6 are stacked by adjusting the film thickness so that the reflectance of each layer is 15%, 24%, 42%, and 94% from the light incident side, the reflection of the light beam from each layer All of the light intensities were able to be about 15%.

  Next, the four types of disk sheets 6 are laminated so that the positioning regions overlap with each other, and an adhesive 31 made of an acrylic ultraviolet curable resin is spun on the disk substrate 5 made of a polycarbonate resin having a thickness of 1.0 mm. Coating was performed by a coating method, and four types of disk sheets 6 were bonded together. Here, the disc sheets 6 were bonded so that the positioning regions 4 of the disc sheets 6 overlapped with the positioning regions provided on the disc substrate 5. Further, the recording surface 14 of each disk sheet 6 was oriented as shown in FIG. 15, and a ROM type four-layer optical disk in which a plurality of disk sheets 6 were bonded on the disk substrate 5 was formed.

A four-layer optical disk formed in accordance with the above method is attached to the optical disk reproducing apparatus shown in FIG. 16, a light beam is incident from the disk sheet 6 side, and the light beam is focused on each recording surface 14 to record as an uneven pit pattern. Replayed information. As a result, a bit error rate (BER) of 1.5 × 10 ⁻⁴ is obtained on the recording surface 14 on the light incident side, and 1 × 10 ⁻⁵ to 2 × 10 ^{−5 on} the other recording surfaces 14. A BER was obtained, and a practical BER could be realized on any recording surface 14 of the four-layer optical disc.

[Example 2]
With respect to the four-layer optical disk described in Example 1, the surface of the disk sheet 40 located on the outermost surface is spin-coated with an acrylic ultraviolet curable resin, and then irradiated with ultraviolet light to form an ultraviolet curable resin layer having a layer thickness of 20 μm. A protective layer 41 made of a four-layer optical disk having the structure shown in FIG. 19 was formed.

As a result of reproducing the above four-layer optical disc having the protective layer 41 in the same manner as in Example 1, it was confirmed that a BER of 4 × 10 ^{−5 to} 7 × 10 ⁻⁵ was obtained on all the recording surfaces 14. This result is because the light incident surface becomes the surface of the protective layer 41, so that the light beam spot on the light incident surface is enlarged, and the occurrence of errors due to the influence of scratches and dust existing on the light incident surface is suppressed. Is.

Example 3
For the four-layer optical disk described in Example 1, an adhesive 42 made of an acrylic ultraviolet curable resin was applied to the surface of the disk sheet 40 located on the outermost surface by a spin coating method, and the thickness made of PET resin was 20 μm. The protective sheet 43 was attached. Here, the layer thickness of the adhesive 42 (ultraviolet curable resin layer) was 1 μm.

As a result of reproducing the above four-layer optical disc having the protective sheet 43 in the same manner as in Example 1, it was confirmed that a BER of 1 × 10 ⁻⁵ to 2 × 10 ⁻⁵ was obtained on all recording surfaces 14. As a result, the light incident surface becomes the surface of the protective sheet 22, so that the light beam spot on the light incident surface is enlarged, and the occurrence of errors due to the influence of scratches and dust existing on the light incident surface is suppressed. Is.

  In Example 2, the BER of the recording surface 14 on the light incident surface side is improved, but the BER of other recording surfaces 14 is deteriorated. This is because the occurrence of errors increases due to fluctuations in the shape of the focused spot of the light beam in response to fluctuations in the thickness of the protective layer 41 applied by spin coating.

  On the other hand, in Example 3, since the layer thickness of the protective sheet 43 is uniform, the above-described fluctuation of the focused spot shape does not occur, and a good BER can be realized on all the recording surfaces 14. did it.

  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.

  For example, the present invention also includes an optical disc in which a plurality of disc sheets having a recording surface on one side are stacked with reference to a positioning area.

  Further, the present invention also includes an optical disc in which a plurality of the disc sheets are stacked so that the recording surfaces and back surfaces of the disc sheets adjacent to each other face each other.

  An optical disc in which a plurality of the disc sheets are provided on a disc substrate is also included in the present invention.

  Further, the present invention includes an optical disk in which the disk substrate has a positioning area, and the position of the positioning area of the disk sheet is specified based on the positioning area of the disk substrate.

  The present invention also includes an optical disc in which the recording surface is constituted by an uneven pattern formed on the surface of an ultraviolet curable resin layer provided on a disc sheet substrate.

  Further, the present invention also includes an optical disc in which the recording surface is constituted by a concavo-convex pattern formed on the surface of a disc sheet substrate.

  An optical disk in which a protective layer is provided on the outermost surface of a plurality of disk sheets provided on the disk substrate is also included in the present invention.

  An optical disk in which the protective layer is an ultraviolet curable resin layer is also included in the present invention.

  An optical disk in which the protective layer is a protective sheet bonded on the disk sheet is also included in the present invention.

  The present invention relates to a multi-layer optical disc that can be manufactured easily and at a low cost with little tracking disturbance during recording / reproduction, a method for producing the same, and an optical disc recording apparatus that realizes recording or reproduction of high-density information And an optical disk playback device. Accordingly, the present invention relates to a CD, a CD-ROM, a CD-R, a CD-RW, a DVD, a DVD-ROM, a DVD-R, a DVD-RW, a DVR, a DVR-ROM, a DVD-Blue, and a so-called Blu-ray Disc. In the manufacturing industry of optical discs such as these and devices for recording or reproducing them (optical disc recording device and optical disc playback device), the present invention can be suitably used.

It is a top view explaining the structure of the multilayer optical disk of this invention. It is sectional drawing explaining the structure of the multilayer optical disk of this invention. It is sectional drawing explaining the formation method of the disc sheet | seat of this invention. It is sectional drawing explaining the formation method of the disc sheet | seat of this invention. It is a section perspective view explaining composition of a disc sheet of the present invention. It is a section perspective view explaining composition of a disc sheet of the present invention. It is sectional drawing explaining the formation method of another disc sheet concerning this invention. It is sectional drawing explaining the formation method of another disc sheet concerning this invention. It is sectional drawing explaining the formation method of another disc sheet concerning this invention. It is sectional drawing explaining another formation method of the disc sheet | seat of this invention. It is sectional drawing explaining another formation method of the disc sheet | seat of this invention. It is sectional drawing explaining the formation method of the disc sheet | seat of this invention. It is sectional drawing explaining the formation method of the disc sheet | seat of this invention. It is sectional drawing explaining the formation method of the disc sheet | seat of this invention. It is sectional drawing explaining the structure of the multilayer optical disk of this invention. It is sectional drawing explaining the recording / reproducing apparatus of the multilayer optical disk of this invention. It is a top view explaining the other structure of the multilayer optical disk of this invention. It is sectional drawing explaining the other structure of the multilayer optical disk of this invention. It is sectional drawing explaining the further another structure of the multilayer optical disk of this invention. It is sectional drawing explaining the further another structure of the multilayer optical disk of this invention. (A)-(D) are sectional drawings explaining the formation method of the conventional multilayer optical disk.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk 2 Inner peripheral hole 3 Information recording area 4 Positioning area 5 Disc substrate 6 Disc sheet 7 Master disk 8 Ultraviolet curable resin layer 9 Disc sheet substrate 10 Transparent press member 11 Ultraviolet light 12 Uneven pattern 13 Pit 14 Recording surface 15 Back surface 16 Uneven track DESCRIPTION OF SYMBOLS 17 Concave-track 18 Fixed mold 19 Receiving part 20 Protection recessed part 21 Movable support mold 22 Processing part passage hole 23 Movable processing mold 24 Support rod 25 Positioning area processing part 26 Inner diameter processing part 27 Outer diameter processing part 28 Beam 30 Objective lens 31 Adhesive 32 Multiple disk sheets 33 Optical beam 34 Objective lens 35 Optical pickup 36 Spindle 37 Drive control circuit 38 Recording control circuit or reproduction control circuit 39 Positioning area 40 Disc sheet 41 Protective layer 42 Adhesive 43 Protective sheet 44 Strip belt sheet 44m Strip sheet material 45 Stamper 46 Rotating roller 47 Sheet roller 49 Rotating roller 50 Pressing member 51 First rotating roller 52 Second rotating roller 53 UV curable resin layer 54 Rotating roller 55 Rotating roller 56 Recording surface

Claims (15)

A plurality of disk sheets having a recording surface including spiral or concentric tracks or pits on one surface are laminated on a disk substrate,
An optical disc, wherein each of the disc sheets has a positioning area for positioning between the disc sheets.   The positioning region includes a convex portion provided on one of mutually facing surfaces of an adjacent disk sheet and a concave portion provided on the other, and the convex portion is fitted in the concave portion. Item 4. The optical disk according to Item 1.   2. The optical disk according to claim 1, wherein one of adjacent surfaces of the disk sheets has a recording surface, and the other has no recording surface.   2. The optical disk according to claim 1, wherein a thickness of the disk substrate is thicker than a plurality of the disk sheets.   2. The optical disk according to claim 1, wherein the disk substrate has a positioning region for positioning between the disk substrate and the disk sheet.   2. The optical disk according to claim 1, wherein adjacent disk sheets are bonded via a pressure-sensitive adhesive film.   2. The disk sheet according to claim 1, wherein the disk sheet includes a disk sheet substrate and an ultraviolet curable resin layer provided on the disk sheet substrate, and an uneven pattern is formed on the surface of the ultraviolet curable resin layer. Optical disc.   2. The optical disk according to claim 1, wherein the disk sheet is formed by directly forming an uneven pattern on the surface of a disk sheet substrate.   9. The optical disk according to claim 1, wherein a protective layer is provided on a surface of the disk sheet farthest from the disk substrate opposite to the disk substrate side surface.   The optical disk according to claim 9, wherein the protective layer is made of an ultraviolet curable resin.   The optical disk according to claim 9, wherein the protective layer is a protective sheet bonded on the disk sheet.   An optical disk recording apparatus comprising: a recording irradiation means for condensing and irradiating a light beam to record information on each recording surface of the optical disk according to claim 1.   2. An optical disc reproducing apparatus comprising: a reproducing irradiation means for condensing and irradiating a light beam for reproducing information on each recording surface of the optical disc according to claim 1.   An optical disk comprising a recording surface including spiral or concentric tracks or pits on one surface and a plurality of disk sheets having a positioning area stacked on a disk substrate based on the positioning area. Manufacturing method.   15. The method of manufacturing an optical disk according to claim 14, wherein a plurality of disk sheets are laminated on the disk substrate at a time.

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