JP2012208989A - Optical recording and reproducing method, and optical recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a transfer rate even with an increased number of recording/reproducing layers of an optical recording medium.SOLUTION: When recording information on an optical recording medium 10 having a plurality of recording/reproducing layers, a first recording operation of recording information by irradiating a first recording/reproducing layer 14 with a first recording/reproducing beam 170A and a second recording operation of recording information by irradiating a second recording/reproducing layer 34 with a second recording/reproducing beam 170B are simultaneously carried out, and thereby the recording or reproducing is simultaneously carried out on the first and second recording/reproducing layers 14 and 34 having the same lamination order from the center of the optical recording medium 10 in a direction of thickness.

Description

  The present invention relates to an optical recording / reproducing method and an optical recording / reproducing apparatus for an optical recording medium having a plurality of recording / reproducing layers.

  Conventionally, for viewing digital moving image contents and recording digital data, CD-DA, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-R, DVD +/- RW, DVD-RAM, Optical recording media such as Blu-ray Disc (BD) are widely used. Among them, BD, which is one of the next-generation DVD standards, has a wavelength of laser light used for recording and reproduction as short as 405 nm, and a numerical aperture of the objective lens is set to 0.85. On the optical recording medium side corresponding to the BD standard, tracks are formed at a pitch of 0.32 μm. In this way, recording / reproducing of 25 GB or more is possible with respect to one recording / reproducing layer of the optical recording medium.

  By the way, the capacity of moving images and data is expected to increase more and more in the future. Therefore, a method for increasing the capacity of the optical recording medium by increasing the number of recording / reproducing layers in the optical recording medium has been studied. In the BD standard optical recording medium, a technique for realizing a super-large capacity of 200 GB by providing six to eight recording / reproducing layers has been reported (see Non-Patent Documents 1 and 2).

  On the other hand, when the recording / reproducing layer is multilayered in the optical recording medium, if the recording / reproducing layer is formed with irregularities for tracking control such as grooves / lands, the medium configuration becomes complicated, and work such as eccentricity adjustment is performed. There is concern that it will be difficult. Further, each time a recording / reproducing layer is provided, a stamper as a mother die for forming irregularities is required, and the more layers are used, the more times the stamper is used and the higher the manufacturing cost.

  Therefore, in recent years, in an optical recording medium, a servo layer having irregularities and grooves and a recording / reproducing layer not having irregularities and grooves are provided separately, and tracking signals are obtained from the servo layer using a beam dedicated to tracking control. Techniques for recording information on a recording / reproducing layer using a recording / reproducing beam have been proposed (see Patent Documents 1, 2, and 3).

JP 2008-97693 A JP 2008-97694 A International Publication WO2008 / 099708

I. Ichimura et. Al., Appl. Opt, 45, 1974-1803 (2006) K. Mishima et.al., Proc. Of SPIE, 6282, 62820I (2006)

  When the number of recording / reproducing layers is increased as in the above technique, the recording / reproducing layers are arranged over a wide range in the thickness direction in the optical recording medium. As a result, the optical pickup for recording / reproducing needs to focus the beam in a wide range in the thickness direction, so the correction range of spherical aberration must be set wide. Therefore, the configuration of the optical pickup becomes complicated and large, and the seek time of the recording / reproducing layer by the optical pickup becomes long.

  Further, if the number of recording / reproducing layers is increased, the capacity of the optical recording medium increases, but this alone does not lead to an improvement in recording / reproducing speed. For example, when the recording capacity of the optical recording medium is increased, but the recording speed is not improved, the waiting time of the user in the recording work becomes long and the sensory convenience is lowered.

  Furthermore, when information is recorded on an optical recording medium having a plurality of recording / reproducing layers, it is necessary to perform OPC (Optimum Power Control) for optimizing the recording laser power and its output parameters for each recording / reproducing layer. The OPC records random data while changing the output power stepwise in the test writing area of each recording / reproducing layer, and reproduces and analyzes the recorded data, thereby recording the laser recording power level ( Pw), erase power level (Pe), etc. are optimized. By adopting OPC, the laser power can be optimized immediately before recording in consideration of the usage environment such as temperature, individual differences of lasers mounted in the drive, deterioration with time of each recording / reproducing layer, and the like. However, there is a problem that the preparation time before recording becomes longer by that much.

  In particular, when information is continuously recorded across a plurality of recording / reproducing layers, OPC is performed on all of the plurality of recording / reproducing layers to be recorded in order to maintain continuity of the information transfer rate. And a preparatory operation is required in which different output parameters are stored in the storage memory in each recording / reproducing layer. As a result, there was a problem that the preparation time before recording became longer and longer.

  In addition, since OPC changes the output power stepwise to record random data, the test writing area is irradiated with a high-power beam that cannot be normally formed to form an abnormal mark. For example, when OPC is performed in a test writing area of a specific recording / reproducing layer, if an abnormal mark is formed in the test writing area of the recording / reproducing layer adjacent thereto, reflection noise caused by the abnormal mark is generated. There was a problem that it became remarkable and accurate OPC could not be performed. In order to solve this problem, it is necessary to prepare a wide trial writing area and control so that random data recorded as OPC does not overlap between adjacent recording / reproducing layers. As a result, as the number of recording / reproducing layers is increased for the purpose of increasing the capacity of the optical recording medium, the test writing area of each recording / reproducing layer has to be expanded, and the user data area is reduced. .

  Further, in the optical recording medium in which the servo layer and the recording / reproducing layer are separately provided as in Patent Documents 1 to 3, the radial shift occurs in the recording mark formation position as the recording / reproducing layer is further away from the servo layer. Cheap. Therefore, in consideration of this shift, it is necessary to secure a wider test writing area, and there is a problem that the user data area is further reduced. Further, for example, when a plurality of servo layers are formed on one surface side of the optical recording medium in order to increase the recording / reproducing layer, the internal stress at the time of film formation tends to be shifted to one side of the optical recording medium. Warpage and distortion occur. Due to the warpage and distortion, the recording mark formation position is more likely to be displaced in the radial direction, and there is a problem that the test writing area must be secured wider.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical recording / reproducing technique capable of increasing a transfer rate even when a recording / reproducing layer is multilayered in an optical recording medium.

  The above-mentioned object is achieved by the following means by the inventors' extensive research.

  That is, the present invention that achieves the above-described object includes a plurality of first recording / reproducing layers that are preliminarily laminated on the first surface side or formed afterwards, and are preliminarily laminated on the second surface side opposite to the first surface. Or a recording / reproducing method for recording / reproducing information on / from an optical recording medium having a second recording / reproducing layer formed later and having the same number of layers as the first recording / reproducing layer. A first recording / reproducing operation for recording or reproducing information by irradiating the first recording / reproducing layer with a reproducing beam from the first surface, and a second recording / reproducing beam from the second surface to the second recording / reproducing layer. A second recording / reproducing operation for recording or reproducing information by irradiating is performed simultaneously, and the first and second recording / reproducing layers having the same stacking order from the center in the thickness direction of the optical recording medium, Optical recording of an optical recording medium, wherein recording or reproduction is performed simultaneously It is a raw way.

  In the optical recording / reproducing method for achieving the above object, the optical recording medium includes at least one servo layer having unevenness or grooves for tracking control, and the first recording / reproducing operation and the second recording / reproducing operation. Then, recording or reproduction is performed on the first recording / reproducing layer and the second recording / reproducing layer while performing tracking control by irradiating the servo layer with the tracking beam.

  In the optical recording / reproducing method for achieving the above object, in the first recording / reproducing operation and the second recording / reproducing operation, tracking control is performed using the common tracking beam and the servo layer.

  In the optical recording / reproducing method for achieving the above object, the servo layer is formed on at least one surface of the substrate of the optical recording medium, and the substrate is substantially transparent.

  In the optical recording / reproducing method for achieving the above object, when information is simultaneously recorded on the first and second recording / reproducing layers by the first recording / reproducing operation and the second recording / reproducing operation, Alternatively, the optimum recording power of both the first and second recording / reproducing beams can be obtained by performing the trial writing with the first or second recording / reproducing beam on one trial writing area of the second recording / reproducing layer. Is set.

  In the optical recording / reproducing method for achieving the object, the first recording / reproducing is performed when recording is simultaneously performed on the first and second recording / reproducing layers which are even-numbered from the center in the thickness direction of the optical recording medium. By performing trial writing with the first recording / reproducing beam on the trial writing area of the layer, optimum recording powers of both the first and second recording / reproducing beams are set, and the thickness of the optical recording medium is set. When recording is simultaneously performed on the first and second recording / reproducing layers that are odd-numbered from the center of the direction, trial writing is performed on the test writing area of the second recording / reproducing layer by the second recording / reproducing beam. By performing, the optimum recording power of both the first and second recording / reproducing beams is set.

  In the optical recording / reproducing method for achieving the above object, the first recording / reproducing layer and the second recording / reproducing layer of the optical recording medium are positioned symmetrically with respect to the center in the thickness direction of the optical recording medium. It is characterized by being arranged.

  The present invention that achieves the above object includes a plurality of first recording / reproducing layers that are previously laminated on the first surface side or formed later, and a second layer side that is opposite to the first surface and previously laminated or subsequent. A recording / reproducing apparatus for recording / reproducing information on / from an optical recording medium having a second recording / reproducing layer having the same number of layers as the first recording / reproducing layer, A first recording / reproducing optical system which is disposed on the first surface side and records or reproduces information by irradiating the first recording / reproducing layer with a first recording / reproducing beam from the first surface; and the optical recording medium And a second recording / reproducing optical system for recording or reproducing information by irradiating a second recording / reproducing beam from the second surface to the second recording / reproducing layer. The recording / reproducing optical system and the second recording / reproducing optical system have different thicknesses from the optical recording medium. To the the same stack order from the center of the first and second recording layer, and performing recording or reproduction at the same time, an optical recording and reproducing apparatus for an optical recording medium.

  The optical recording / reproducing apparatus that achieves the above-described object is further provided when information is simultaneously recorded on the first and second recording / reproducing layers by the first recording / reproducing optical system and the second recording / reproducing optical system. Both of the first and second recording / reproducing beams can be obtained by performing trial writing on the one test writing area of the first or second recording / reproducing layer with the first or second recording / reproducing beam. Output control means for setting the optimum recording power is provided.

  According to the present invention, the transfer rate can be increased even if the recording / reproducing layer is multilayered in the optical recording medium.

1 is a block diagram showing an overall configuration of an optical recording / reproducing apparatus and an optical recording medium for realizing an optical recording / reproducing method according to an embodiment of the present invention. It is a block diagram which shows the example of an internal structure of the 1st optical pick-up of the same optical recording / reproducing apparatus. It is a block diagram which shows the example of an internal structure of the 2nd optical pick-up of the same optical recording / reproducing apparatus. It is sectional drawing which shows the laminated structure of the same optical recording medium. It is sectional drawing which shows the manufacturing procedure of the optical recording medium. It is sectional drawing which shows the manufacturing procedure of the optical recording medium. It is sectional drawing which shows the manufacturing procedure of the optical recording medium. It is sectional drawing which shows the manufacturing procedure of the optical recording medium. It is a flowchart which shows the setting procedure of the recording power by the optical recording / reproducing apparatus. It is sectional drawing which expands and shows the execution procedure of OPC to the optical recording medium by the same optical recording / reproducing method. It is a graph which shows the change of the recording power at the time of performing OPC by the same optical recording / reproducing apparatus. It is sectional drawing which expands and shows the recording procedure to the optical recording medium by the same optical recording / reproducing method. It is sectional drawing which expands and shows the recording procedure to the optical recording medium by the same optical recording / reproducing method. It is sectional drawing which expands and shows the reproduction | regeneration procedure of the optical recording medium by the same optical recording / reproducing method. It is sectional drawing which shows the other laminated structure example of the optical recording medium with which the same optical recording / reproducing method is applied. It is sectional drawing which shows the other laminated structure example of the optical recording medium with which the same optical recording / reproducing method is applied. It is sectional drawing which shows the other laminated structure example of the optical recording medium with which the same optical recording / reproducing method is applied.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows an optical recording medium 10 to which an optical recording / reproducing method according to an embodiment of the present invention is applied, and an internal configuration of an optical recording / reproducing apparatus 70 that realizes the optical recording / reproducing method. The recording / reproducing apparatus 70 includes first and second optical pickups 90A and 90B, first and second linear motion mechanisms 75A and 75B that move the first and second optical pickups 90A and 90B in the tracking direction, A tracking control device 80 that controls the first and second linear motion mechanisms 75A and 75B and an output control device 86 that controls the output power of each beam of the first and second optical pickups 90A and 90B are configured. .

  The first and second linear motion mechanisms 75A and 75B are so-called linear motors, on which the first and second optical pickups 90A and 90B are mounted. As a result, the first optical pickup 90A is moved in the radial direction of the optical recording medium 10 by the first linear motion mechanism 75A. The second optical pickup 90B is moved in the radial direction of the optical recording medium 10 by the second linear motion mechanism 75B.

  The first optical pickup 90A irradiates a beam from one first surface 10A side of the optical recording medium 10. The second optical pickup 90B irradiates the beam from the other second surface 30A side of the optical recording medium 10. Although not particularly illustrated, the first optical pickup 90 </ b> A and the second optical pickup 90 </ b> B are arranged in a state shifted by a predetermined angular difference in the circumferential direction of the optical recording medium 10. In this way, it is possible to avoid a situation in which the beams interfere with each other. The angle difference is preferably within 20 degrees, for example.

  The internal configurations of the first and second optical pickups 90A and 90B are partially the same and partially different. Accordingly, with respect to parts / members that are common to each other, the first optical pickup 90A adds A to the end of each symbol in the drawing or text, and the second optical pickup 90B uses B at the end of the symbol in the drawing or text. And the same number except for the end. Here, the internal configuration of the first optical pickup 90A will be described in detail, and the second optical pickup 90B will be described focusing on differences from the first optical pickup 90A.

  As shown in FIG. 2, the first optical pickup 90A includes a recording / reproducing optical system 100A and a tracking optical system 200A. The recording / reproducing optical system 100A is an optical system that performs recording / reproduction with respect to the first recording / reproducing layer group 14 of the optical recording medium 10. The tracking optical system 200A is an optical system that performs tracking control using the servo layer 18 when information is recorded on the first recording / reproducing layer group 14 using the recording / reproducing optical system 100A.

  The divergent recording / reproducing beam 170A emitted from the light source 101A of the recording / reproducing optical system 100A is transmitted through the collimator lens 153A provided with the spherical aberration correcting means 193A and is incident on the polarization beam splitter 152A. The beam 170A has a blue wavelength of 380 to 450 nm (here, 405 nm). The beam 170A incident on the polarization beam splitter 152A is transmitted through the polarization beam splitter 152A and further converted into circularly polarized light by transmission through the quarter-wave plate 154A, and then enters the beam splitter 260A of the tracking optical system 200A. Incident. The beam splitter 260A is set to have a high transmittance and a low reflectance. Specifically, the ratio of the transmittance to the reflectance is set to 10 times or more. Accordingly, the beam 170A passes through the beam splitter 260A and is converted into a convergent beam by the objective lens 156A. The beam 170A is focused on either the first recording / reproducing layer group 14 or the servo layer 18 to be recorded / reproduced, which is formed inside the optical recording medium 10.

  The aperture of the objective lens 156A is limited by the aperture 155A, and the numerical aperture NA is 0.70 to 0.90 (here, 0.85). For example, the beam 170A reflected by the first recording / reproducing layer group 14 passes through the objective lens 156A, the beam splitter 260A, and the quarter-wave plate 154A and is converted into linearly polarized light that is 90 degrees different from the forward path. Reflected by the polarization beam splitter 152A.

  The beam 170A reflected by the polarization beam splitter 152A passes through the condenser lens 159A, is converted into convergent light, and enters the photodetector 132A through the cylindrical lens 157A. Astigmatism is given to the beam 170A when it passes through the cylindrical lens 157A.

  The photodetector 132A has four light receiving units (not shown) and outputs a current signal corresponding to the amount of light received. From these current signals, a focus error (hereinafter referred to as FE) signal by an astigmatism method, a tracking error (hereinafter referred to as TE) signal by a push-pull method limited at the time of reproduction, and reproduction of information recorded on the optical recording medium 10 A signal or the like is generated. The FE signal and the TE signal are amplified and phase compensated to a desired level, and then fed back to the actuators 191A and 192A. The actuators 191A and 192A perform tilt control, tracking control, focus control, and the like for the objective lens 156A. The tracking error signal from the recording / reproducing optical system 100A is used only during reproduction.

  A divergent tracking control beam 270A having a red wavelength of 630 to 680 nm (here, 650 nm) emitted from the light source 201A of the tracking optical system 200A is transmitted through a collimator lens 253A including a spherical aberration correction unit 293A. , And enters the polarizing beam splitter 252A. The beam 270A incident on the polarization beam splitter 252A is transmitted through the polarization beam splitter 252A, further transmitted through the quarter-wave plate 254A, converted into circularly polarized light, and then reflected by the beam splitter 260A. The beam 270A is further converted into a convergent beam by the objective lens 156A, and is focused on the servo layer 18 formed inside the optical recording medium 10. The beam 270A reflected by the servo layer 18 passes through the objective lens 156A, is reflected by the beam splitter 260A, is converted into linearly polarized light that is 90 degrees different from the forward path in the quarter-wave plate 254A, and then the polarized beam splitter. Further reflection at 252A. The beam 270A reflected by the polarizing beam splitter 252A passes through the condenser lens 259A, is converted into convergent light, and enters the photodetector 232A via the cylindrical lens 257A. Astigmatism is given to the beam 270A when passing through the cylindrical lens 257A.

  The photodetector 232A has four light receiving units (not shown), and outputs a current signal corresponding to the amount of light received. From these current signals, a tracking error (TE) signal is generated by the push-pull method. When information is also recorded on the servo layer 18, a reproduction signal may be generated from this current signal. On the photodetector 232A side, it is not necessary to generate a focus error (FE) signal. Of course, a focus error (FE) signal may be generated.

  As already described, the beam splitter 260A is set to have a high transmittance and a low reflectance. Accordingly, a part of the return light emitted from the light source 101A of the recording / reproducing optical system 100A and reflected by any of the first recording / reproducing layer group 14 is reflected by the beam splitter 260A and proceeds to the tracking optical system 200A side. . Conversely, most of the return light emitted from the light source 201A of the tracking optical system 200A and reflected by the servo layer 18 may pass through the beam splitter 260A and travel toward the recording / reproducing optical system 100A. In the recording / reproducing optical system 100A and the tracking optical system 200A, even if both return lights are mixed, the recording / reproducing optical system 100A and the tracking optical system 200A have different focal points in the optical recording medium 10. Because of the position, the spread angles of the beams 170A and 270A are different. Therefore, the influence of mixing is removed by extracting only one of the beams 170A and 270A using a slit or aperture having a fixed shape (not shown) and then entering the light detectors 132A and 232A. Of course, the beams 170A and 270A may be separated by a filter having wavelength selectivity.

  In particular, the difference between the focal position of the beam 170A in the optical recording medium 10 in the recording / reproducing optical system 100A and the focal position in the optical recording medium 10 of the beam 270A of the tracking optical system 200A is always within a certain range. By doing so, the above-mentioned slits and apertures can be made simple, so that the beam can be more easily separated. In order to stabilize the difference in focal length, it can be said that the closer the focal position of the recording / reproducing beam 170A and the focal position of the servo beam 270A are, the smaller the error is.

  As shown in FIG. 3, the second optical pickup 90B includes a recording / reproducing optical system 100B, but does not include a tracking optical system. The recording / reproducing optical system 100B is an optical system that performs recording / reproducing with respect to the second recording / reproducing layer group 34 of the optical recording medium 10. The recording / reproducing optical system 100B has substantially the same configuration as the recording / reproducing optical system 100A of the first optical pickup 90A.

  When information is recorded on the second recording / reproducing layer group 34 by the recording / reproducing optical system 100B of the second optical pickup 90B, it is obtained by irradiating the servo layer 18 with the tracking optical system 200A of the first optical pickup 90A. A tracking error (TE) signal is used. Specifically, the actuators 191B and 192B perform tilt control, tracking control, focus control, and the like on the objective lens 156B using the tracking error signal.

  Returning to FIG. 1, the tracking control device 80 includes an access controller 82, a first driver 84A, and a second driver 84B. The access controller 82 controls the actuators 191A, 191B, 192A, 192B of the first and second optical pickups 90A, 90B, and uses the first driver 84A and the second driver 84B to reach the target tracking position. The first linear motion mechanism 75A and the second linear motion mechanism 75B are controlled.

  Specifically, the access controller 82 controls the first and second optical pickups 90A and 90B as follows.

(1) Control at the time of recording The access controller 82 receives a tracking number to be recorded from a recording / reproducing control device (not shown), and the first optical pickup 90A with respect to the land / groove of the servo layer 18 corresponding to this tracking number. The beam 270A for tracking is irradiated. This is achieved by the access controller 82 receiving the tracking error (TE) signal from the beam 270A of the tracking optical system 200A and feedback-controlling the actuators 191A and 192A and the first linear motion mechanism 75A. In this state, the first optical pickup 90A records information by irradiating the first recording / reproducing layer group 14 with a recording / reproducing beam 170A.

  At the same time, the access controller 82 controls the actuators 191A and 192A and the second linear motion mechanism 75B using the tracking error (TE) signal of the first optical pickup 90A. That is, the actuators 191A, 191B, 192A, 192B, the first linear motion mechanism 75A, and the second linear motion mechanism 75B perform the same operation in the tracking direction. In this state, the second optical pickup 90B irradiates the second recording / reproducing layer group 34 with a recording / reproducing beam 170B to record information. As a result, in the present embodiment, the first and second optical pickups 90A and 90B are simultaneously tracking-controlled using the common servo layer 18, and information is simultaneously transmitted to the first and second recording / reproducing layer groups 14 and 34. Record.

(2) Control at the time of reproduction The first recording / reproducing layer group 14 is reproduced by irradiating the first recording / reproducing layer group 14 with the beam 170A of the recording / reproducing optical system 100A of the first optical pickup 90A. In this tracking control, the access controller 82 directly uses the tracking error (TE) signal of the recording / reproducing beam 170A without using the tracking beam 270A, and the actuators 191A, 192A and the first straight line are used. This is realized by feedback control of the moving mechanism 75A.

  The second recording / reproducing layer group 34 is reproduced by irradiating the second recording / reproducing layer group 34 with the beam 170B of the recording / reproducing optical system 100B of the second optical pickup 90B. In this tracking control, the access controller 82 feeds back the actuators 191B and 192B and the second linear motion mechanism 75B by directly using the tracking error (TE) signal of the recording / reproducing beam 170B of the second optical pickup 90B. Realized by controlling. That is, in the present embodiment, the first and second optical pickups 90A and 90B are separately subjected to tracking control, and information of the first and second recording / reproducing layer groups 14 and 34 is reproduced simultaneously.

  The output control device 86 includes test writing means 87, quality evaluation means 88, and recording power adjustment means 89.

  The test writing means 87 performs test data test writing on the test writing area of each recording / reproducing layer of the optical recording medium 10 before writing actual information in the user data area. Specifically, first, using a power setting pattern composed of random data or simple data that is a repetition of specific data, the power setting pattern is written while changing the laser power step by step. Thereafter, the power setting pattern is reproduced, and the optimum recording power is selected by using the signal quality determination result in the quality evaluation means 88. The selected optimum recording power is transmitted to the recording power adjusting means 89 and reflected in the actual output.

  The quality evaluation means 88 receives the reproduction data of the recording mark that has been trial-written in the trial writing area (OPC area) of the first or second recording / reproducing layer group 14, 34, and uses this data to obtain an error rate or SAM ( (Sequential Amplitude Margin) value is detected and transmitted to the test writing means 87. Therefore, the test writing means 87 uses the error rate and the SAM value obtained from the quality evaluation means 88 to determine whether these satisfy a certain standard or whether an uncorrectable error has occurred. Judge the quality of the playback data and select the optimum recording power that gives the best quality. For example, the optimum recording power that minimizes the error rate or the SAM value is selected. Although the error rate and the SAM value are exemplified here as the reference value, the present invention is not limited to this, and the signal quality may be determined using other methods.

  The recording power adjustment unit 89 receives an instruction from the test writing unit 87 and controls the recording power of the light source 101A of the first optical pickup 90A and the recording power of the light source 101B of the second optical pickup 90B. Specifically, the recording power Pw, the erasing power Pe, and the bias power Pb in each of the light sources 101A and 101B are set.

  FIG. 4 shows an enlarged cross-sectional structure of the optical recording medium 10 of the present embodiment.

  The optical recording medium 10 has a disk shape with an outer diameter of about 120 mm and a thickness of about 1.2 mm. The optical recording medium 10 includes a first cover layer 11, a first recording / reproducing layer group 14, a first intermediate layer group 16, a first buffer layer 17, a servo layer 18, and a support substrate 12 in order from the first surface 10A side. The second buffer layer 37, the second recording / reproducing layer group 34, the second intermediate layer group 36, the second cover layer 31, and the second surface 30A.

  Here, the first recording / reproducing layer group 14 includes L0 to L5 recording / reproducing layers 14A to 14F, and has a structure capable of recording information in each of them. The L0 to L5 recording / reproducing layers 14A to 14F have a planar structure having no unevenness or grooves for tracking control, and when a recording beam 170 having high energy is irradiated from the recording / reproducing optical system 100. A recording mark is formed. The types of the first recording / reproducing layer group 14 include a recordable recording / reproducing layer in which information can be additionally written but cannot be rewritten, and a rewritable recording / reproducing layer in which information can be rewritten.

  The support substrate 12 is a disk-shaped substrate having a thickness in the range of 10 μm to 1200 μm, preferably 10 μm to 600 μm, in order to ensure the thickness (about 1.2 mm) required for the optical recording medium. Specifically, in the present embodiment, the thickness of the support substrate 12 is set to 500 μm and the diameter is set to 120 mm. On the first surface 10A side of the support substrate 12, lands 18A and grooves 18B are formed in a spiral shape from the vicinity of the center toward the outer edge. The land 18A and the groove 18B become unevenness (groove) for tracking control. The unevenness on the support substrate 12 becomes the future servo layer 18.

  Note that various materials can be used as the material of the support substrate 12, and for example, glass, ceramics, and resins can be used. Of these, a resin is preferred from the viewpoint of ease of molding. Examples of the resin include polycarbonate resin, olefin resin, acrylic resin, epoxy resin, polystyrene resin, polyethylene resin, polypropylene resin, silicone resin, fluorine resin, ABS resin, and urethane resin. Among these, polycarbonate resin and olefin resin are particularly preferable from the viewpoint of processability.

  The servo layer 18 formed on the support substrate 12 includes tracking control irregularities (grooves and lands) formed on the surface of the support substrate 12 and a reflective layer formed thereon. . In particular, in the present embodiment, a metal film such as Al or Ag is formed as a reflective layer, and functions as a simple light reflecting film. The servo layer 18 is designed to have a transmittance of 10% or less when the tracking beam 270A of the first optical pickup 90A is irradiated. As a result, it is avoided that the beam 270A leaks out to the opposite side and becomes a noise component on the second optical pickup 90B side. In addition, when providing the recording film which can record information in addition to a reflective function, it is good also as a film | membrane structure substantially the same as recording-reproducing layers 14A-14F mentioned later.

  Here, the pitch P1 between adjacent lands 18A or grooves 18B in the servo layer 18 is set to be less than 0.74 μm. Specifically, the pitch P1 is desirably set in the range of 0.6 μm to 0.7 μm, and more preferably set in the vicinity of 0.64 μm. On the other hand, the track pitch P2 of the recording mark is set to half (1/2) of the pitch P1 of the land 18A and the groove 18B. That is, the track pitch P2 between the recording marks is set to be less than 0.37 μm, desirably set in the range of 0.26 μm to 0.35 μm, and more preferably set in the vicinity of 0.32 μm. As a result, the track pitch P2 between the recording marks is about 0.32 μm which is compatible with the BD standard.

  The pitch P1 (around 0.64 μm) between the lands 18A / grooves 18B of the servo layer 18 is large enough to allow sufficient tracking with the beam 270A in the relatively long red wavelength region. In the present embodiment, tracking is performed using both the land 18A and the groove 18B. As a result, with respect to the pitch P1 of the servo layer 18, the track pitch P2 of the recording mark is about 0.32 μm, which is a half thereof. Thus, by performing tracking control using the land 18A and the groove 18B, the track pitch P2 of the recording marks in the recording / reproducing layer group 14 can be reduced without reducing the pitch P2 of the servo layer 18.

  The first buffer layer 17 is made of a light-transmitting acrylic ultraviolet curable resin and has a film thickness of 238 μm. The first buffer layer 17 is made of a material that increases the amount of light absorption as the wavelength of the beam is shorter. By doing so, the light absorption amount of the blue wavelength beam 170A is large and the absorption amount of the red wavelength beam 270A is small. As a result, the first buffer layer 17 can suppress the amount of light that the blue wavelength beam 170A reaches the servo layer 18 and reflects, thereby reducing signal noise during reproduction. On the other hand, the first buffer layer 17 actively transmits the red wavelength beam 270A, thereby increasing the amount of the tracking signal.

  In the first recording / reproducing layer group 14 (L0 to L5 recording / reproducing layers 14A to 14F) laminated on the first surface 10A side of the first buffer layer 17, dielectric films are laminated on both outer sides of the write-once recording film, respectively. It has a three-layer structure (not shown). The L0 to L5 recording / reproducing layers 14A to 14F have a light reflectance, an absorptivity, a transmittance and the like for the beam 170A in the blue wavelength region (short wavelength) in the recording / reproducing optical system 100A of the first optical pickup 90A. Has been optimized.

  In addition to the basic function of protecting the write-once recording film, the dielectric film of each recording / reproducing layer also plays a role of expanding the difference in optical characteristics before and after the formation of the recording mark.

  When the beam 170A is irradiated, if the energy absorbed by the dielectric film is large, the recording sensitivity is likely to be lowered. Therefore, in order to prevent this, it is preferable to select a material having a low absorption coefficient (k) in the wavelength region of 380 nm to 450 nm (particularly 405 nm) as the material of these dielectric films. In the present embodiment, TiO 2 is used as the material for the dielectric film.

  The write-once recording film sandwiched between the dielectric films is a film on which an irreversible recording mark is formed, and the reflectance with respect to the beam 170A is greatly different between the portion where the recording mark is formed and the other portion (blank region). . As a result, data can be recorded / reproduced.

  The write-once recording film is formed mainly of a material containing Bi and O. This write-once recording film functions as an inorganic reaction film, and the reflectance is greatly different due to a chemical or physical change caused by the heat of laser light. Specific materials include Bi-O as the main component, or Bi-MO (where M is Mg, Ca, Y, Dy, Ce, Tb, Ti, Zr, V, Nb, Ta). , Mo, W, Mn, Fe, Zn, Al, In, Si, Ge, Sn, Sb, Li, Na, K, Sr, Ba, Sc, La, Nd, Sm, Gd, Ho, Cr, Co, Ni And at least one element selected from Cu, Ga, and Pb). In this embodiment, Bi—Ge—O is used as the material of the write-once recording film.

  Here, the case where the write-once recording film is employed in the L0 to L5 recording / reproducing layers 14A to 14F is shown, but a phase change recording film capable of repeated recording can also be employed. In this case, the phase change recording film preferably contains SbTeGe as a main component.

  The first intermediate layer group 16 includes L0 to L4 intermediate layers 16A to 16E in order from the side far from the first surface 10A, and is laminated between the L0 to L5 recording / reproducing layers 14A to 14F. Each of the intermediate layers 16A to 16E is made of an acrylic or epoxy ultraviolet curable resin. The film thicknesses of the L0 to L4 intermediate layers 16A to 16E are preferably set to 20 μm or less in order to increase the number of stacked layers, the L0 intermediate layer 16A is 16 μm, the L1 intermediate layer 16B is 12 μm, and the L2 intermediate layer 16C is 16 μm, the L3 intermediate layer 16D is 12 μm, and the L4 intermediate layer 16E is 16 μm. That is, intermediate layers having two kinds of film thicknesses (16 μm and 12 μm) are alternately stacked. As a result, as the interlayer distance between the L0 to L5 recording / reproducing layers 14A to 14F, the first distance (16 μm) and the second distance (12 μm) different from the first distance are alternately set in order from the light incident surface side. It will be. The difference between the first distance and the second distance is set to 4 μm. In this way, interlayer crosstalk is reduced. Of course, all the intermediate layer groups 16 may have the same film thickness.

  The first cover layer 11 is made of a light-transmitting acrylic ultraviolet curable resin, like the first intermediate layer group 16, and has a film thickness of 40 μm.

  The second buffer layer 37 formed on the second surface 30 </ b> A side of the support substrate 12 is made of a light-transmitting acrylic ultraviolet curable resin and has a thickness of 238 μm.

  In the second recording / reproducing layer group 34 (L0 to L5 recording / reproducing layers 34A to 34F) laminated on the second surface 30A side of the second buffer layer 37, dielectric films are laminated on both outer sides of the write-once recording film, respectively. It has a three-layer structure (not shown). The L0 to L5 recording / reproducing layers 34A to 34F have a light reflectance, absorptivity, transmittance, etc., for the blue wavelength region (short wavelength) beam 170B in the recording / reproducing optical system 100B of the second optical pickup 90B. Has been optimized.

  The second intermediate layer group 36 includes L0 to L4 intermediate layers 36A to 36E in order from the side far from the second surface 30A, and is laminated between the L0 to L5 recording / reproducing layers 34A to 34F. Each of the intermediate layers 36A to 36E is made of an acrylic or epoxy ultraviolet curable resin. The film thicknesses of the intermediate layers 36A to 36E are preferably set to 20 μm or less in order to increase the number of stacked layers. The L0 intermediate layer 36A is 16 μm, the L1 intermediate layer 36B is 12 μm, the L2 intermediate layer 36C is 16 μm, L3 The intermediate layer 36D is 12 μm, and the L4 intermediate layer 36E is 16 μm. That is, intermediate layers having two kinds of film thicknesses (16 μm and 12 μm) are alternately stacked. As a result, as the interlayer distance between the L0 to L5 recording / reproducing layers 34A to 34F, the first distance (16 μm) and the second distance (12 μm) different from the first distance are alternately set in order from the second surface 30A side. Will be. The difference between the first distance and the second distance is set to 4 μm. In this way, interlayer crosstalk is reduced. Of course, all the second intermediate layer groups 36 may have the same film thickness.

  The materials of the second recording / reproducing layer group 34 and the second intermediate layer group 36 are the same as those of the first recording / reproducing layer group 14 and the first intermediate layer group 16, and thus description thereof is omitted.

  The second cover layer 31 is made of a light-transmitting acrylic ultraviolet curable resin, like the second intermediate layer group 36, and has a thickness of 40 μm.

  As a result of the above configuration, the boundary (servo layer 18) between the support substrate 12 and the first buffer layer 17 in the optical recording medium 10 is located at a distance of 350 μm from the first surface 10A. The L0 recording / reproducing layer 14A farthest from the first surface 10A in the first recording / reproducing layer group 14 is located at a distance of 112 μm from the first surface 10A, and the L1 recording / reproducing layer 14B is the first surface 10A. To 96 μm, the L2 recording / reproducing layer 14C from the first surface 10A to 84 μm, the L3 recording / reproducing layer 14D from the first surface 10A to 68 μm, the L4 recording / reproducing layer 14E from the first surface 10A to 56 μm, and the most on the first surface 10A The near L5 recording / reproducing layer 14F is located at a distance of 40 μm from the first surface 10A. The overall thickness of the first recording / reproducing layer group 14 (distance between the L0 recording / reproducing layers 14A to L5 recording / reproducing layer 14F) is 72 μm. .

  In the second recording / reproducing layer group 34, the L0 recording / reproducing layer 34A farthest from the second surface 30A is located at a distance of 112 μm from the second surface 30A, and the L1 recording / reproducing layer 34B is the second surface 30A. To 96 μm, the L2 recording / reproducing layer 34C from the second surface 30A to 84 μm, the L3 recording / reproducing layer 34D from the second surface 30A to 68 μm, the L4 recording / reproducing layer 34E from the second surface 30A to 56 μm, and the second surface 30A The near L5 recording / reproducing layer 34F is located at a distance of 40 μm from the second surface 30A. The overall thickness of the second recording / reproducing layer group 34 (distance between the L0 recording / reproducing layers 34A to L5 recording / reproducing layer 34F) is 72 μm.

  That is, the optical recording medium 10 has a symmetrical structure in the thickness direction except that the servo layer 18 is asymmetrically arranged. As a result, since internal stress generated during the production of the optical recording medium 10 is generated symmetrically in the thickness direction, warpage and deformation can be reduced. In particular, even if the support substrate 12 is thinned to 700 μm or less, here 100 μm, it is possible to suppress warping and deformation of the optical recording medium 10.

  Next, a method for manufacturing the optical recording medium 10 of this embodiment will be described.

  As shown in FIG. 5A, first, a support substrate 12 in which grooves and lands are formed only on one side is manufactured by a polycarbonate resin injection molding method using a metal stamper. By using an injection mold, the support substrate 12 is provided with recording conditions including address information, recording / reproducing power, etc. of the first recording / reproducing layer group 14 and the second recording / reproducing layer group 34, and the position of each recording / reproducing layer. Alternatively, basic information that should be held in advance when the medium is manufactured, such as the distance between layers, is preformatted. Specifically, basic information is preformed using the wobble of the land 18A or the groove 18B. The production of the support substrate 12 is not limited to the injection molding method, and may be produced by the 2P method or other methods.

  Thereafter, the servo layer 18 is formed on the surface of the support substrate 12 on the side where the grooves and lands are provided. The servo layer 18 is formed by sputtering or the like a film that is reflective to the light source of the tracking optical system 200A (for example, a metal film such as Al or Ag).

  Next, as shown in FIG. 5B, the first buffer layer 17 and the second buffer layer 37 are simultaneously formed on both surfaces of the support substrate 12 on which the servo layer 18 is formed. For example, an acrylic or epoxy UV curable resin whose viscosity is adjusted is formed into a film on both surfaces of the support substrate 12 by a spin coat method or the like, and is cured by irradiating with ultraviolet rays. Buffer layers 17 and 37 are formed. Instead of the ultraviolet curable resin, a light transmissive sheet made of a light transmissive resin is attached to both surfaces of the support substrate 12 using an adhesive, an adhesive, or the like, and the first and second buffer layers 17 and 37 are attached. It can also be. In addition, the first and second buffer layers 17 and 37 can be formed on both surfaces of the support substrate 12 by spraying, DIP method, or the like.

  Next, as shown in FIG. 5C, the L0 recording / reproducing layer 14 </ b> A of the first recording / reproducing layer group 14 and the second recording / reproducing layer group 34 are respectively formed on the first buffer layer 17 and the second buffer layer 37. The L0 recording / reproducing layer 34A is simultaneously formed. Specifically, a dielectric film, a write-once recording film, and a dielectric film are formed in this order using a vapor phase growth method. Among these, it is preferable to use a sputtering method. Thereafter, the L0 intermediate layer 16A of the first intermediate layer group 16 is formed on the L0 recording / reproducing layer 14A of the first recording / reproducing layer group 14, and the L0 recording / reproducing layer 34A of the second recording / reproducing layer group 34 is formed. The L0 intermediate layer 36A of the second intermediate layer group 36 is formed. These formations are performed simultaneously. The L0 intermediate layers 16A and 34A are formed, for example, by forming a film of an ultraviolet curable resin whose viscosity has been adjusted by spin coating or the like, and then irradiating and curing the ultraviolet curable resin with ultraviolet rays. By repeating this procedure, the first recording / reproducing layer group 14 and the first intermediate layer group 16 are alternately stacked on the first buffer layer 17 side, and the second recording / reproducing layer group 34 on the second buffer layer 37 side. And the 2nd intermediate | middle layer group 36 is laminated | stacked alternately.

  When the formation of the L5 recording / reproducing layer 14F of the first recording / reproducing layer group 14 and the formation of the L5 recording / reproducing layer 34F of the second recording / reproducing layer group 34 are completed, as shown in FIG. The second cover layers 11 and 31 are simultaneously formed to complete the optical recording medium 10. The first and second cover layers 11 and 31 are formed by, for example, coating a viscosity-adjusted acrylic or epoxy UV curable resin by a spin coating method or the like, and irradiating the UV with respect to this to cure. To form. In addition, although the said manufacturing method was demonstrated in this embodiment, this invention is not specifically limited to the said manufacturing method, Another manufacturing technique can also be employ | adopted.

  Next, an optical recording / reproducing method for recording / reproducing information on / from the optical recording medium 10 using the optical recording / reproducing apparatus 70 of the present embodiment will be described. In the present embodiment, in each of the first recording / reproducing layer group 14 and the second recording / reproducing layer group 34, information is recorded for a pair of recording / reproducing layers having the same stacking order from the center in the thickness direction of the optical recording medium 10. At the same time.

<OPC control>
When recording information on the optical recording medium 10, first, the recording power of the optical recording / reproducing apparatus 70 is set according to the flowchart of FIG.

First, in step 300, the output control device 86 reproduces a DI (Disc Information) area of the optical recording medium 10 to read basic characteristic information of the optical recording medium 10. This DI area includes the type of medium (write-once type or rewritable type), recording speed (1X, 2X, etc.), recording strategy, servo layer 18 position, recording / reproducing layer position, recording / reproducing layer interlayer distance, etc. The recommended recording power P _K of the laser beam is also recorded. Therefore, setting this recommended recording power _{P K} as the initial recording conditions (Step 302). In this embodiment, this DI area is formed in the servo layer 18. Therefore, the information is read from the servo layer 18 by the beam 270A in the red wavelength region of the first optical pickup 90A.

  Next, in step 304, it is determined in which recording / reproducing layer of the first and second recording / reproducing layer groups 14 and 34 of the optical recording medium 10 information is recorded. Specifically, it is determined whether the pair of recording / reproducing layers to be recorded are in an even order or an odd order from the center in the thickness direction of the optical recording medium 10. For example, when the L0 recording / reproducing layer 14A of the first recording / reproducing layer group 14 and the L0 recording / reproducing layer 34A of the second recording / reproducing layer group 34 are simultaneously recorded, it is determined that these are in the odd order (first order). Therefore, the process proceeds to step 306. On the other hand, when the L1 recording / reproducing layer 14B of the first recording / reproducing layer group 14 and the L1 recording / reproducing layer 34B of the second recording / reproducing layer group 34 are simultaneously recorded, it is determined that they are in the even order (second order). Therefore, the process proceeds to step 310.

Here, assuming that information is simultaneously recorded on the L0 recording / reproducing layers 14A and 34A having an odd order, in step 306, the test writing area X of the L0 recording / reproducing layer 34A of the second recording / reproducing layer group 34 is recorded. Then, a power setting pattern (here, a random pattern) is recorded (see FIG. 7). In this case, as shown in FIG. 8, with respect to the recording power to be actually recorded, there are multiple stages (P _{K + 1} , P _{K + 2} , P _{K + 3} , P _K−1 , P _K) on both sides of the recommended recording power P _K as a reference. _-2 , P _K-3 ), and a power setting pattern writing operation is executed for each recording power. A specific method for recording the power setting pattern in the trial writing area X of the L0 recording / reproducing layer 34A will be described in detail in the second recording / reproducing operation described later. Omitted.

  Thereafter, in step 308, the recorded power setting pattern is reproduced using a PRML processing device (not shown). In step 314, the quality evaluation means 88 uses the error rate or SAM value to reproduce the reproduced signal. Evaluate the quality. This evaluation result is transmitted to the test writing means 87. In step 316, the test writing means 87 selects the recording power at which the highest quality recording was performed, and referring to this, both the light source 101A of the first optical pickup 90A and the light source 101B of the second optical pickup 90B are selected. Recording power Pw, erasing power Pe, and bias power Pb are determined, and the recording power adjusting means 89 is instructed. The recording power setting is completed by the above steps. The recording power adjusting unit 89 uses the recording power Pw, erasing power Pe, and bias power Pb that have been instructed to switch both the light source 101A of the first optical pickup 90A and the light source 101B of the second optical pickup 90B. Control.

  On the other hand, when returning to step 304 and recording the L1 recording / reproducing layers 14B and 34B in the even order at the same time, in step 310, with respect to the test writing area X of the L1 recording / reproducing layer 14B of the first recording / reproducing layer group 14. Then, a power setting pattern (here, a random pattern) is recorded (see FIG. 7). A specific method for recording the power setting pattern in the test writing area X of the L1 recording / reproducing layer 14B will be described in detail in the first recording / reproducing operation described later. Omitted.

  Thereafter, in step 312, the recorded power setting pattern is reproduced using a PRML processing device (not shown). Similar to the odd order, in step 314, the quality of the reproduction signal is evaluated by the quality evaluation means 88, and in step 316, the test writing means 87 is used for the light source 101A of the first optical pickup 90A and the second optical pickup 90B. The recording power Pw, erasing power Pe, and bias power Pb of both of the light sources 101B are determined, and the OPC is completed.

  <Simultaneous recording of information on the first and second recording / reproducing layer groups>

  As already described, in the present embodiment, in each of the first recording / reproducing layer group 14 and the second recording / reproducing layer group 34, the recording / reproducing layer having the same stacking order from the center in the thickness direction of the optical recording medium 10 is used. On the other hand, information is simultaneously recorded or reproduced. Specifically, in order to record information on the L0 recording / reproducing layer 14A of the first recording / reproducing layer group 14 as the first recording / reproducing operation, first, the red wavelength region of the tracking optical system 200A of the first optical pickup 90A is used. The servo layer 18 is irradiated with the beam 270A and tracking is performed. Specifically, as shown in FIG. 9, tracking is performed by irradiating both the groove 18B and the land 18A in the servo layer 18 with the spot of the beam 270A. Simultaneously with the tracking, the L0 recording / reproducing layer 14A is irradiated with a recording beam 170A in the blue wavelength region of the recording / reproducing optical system 100A of the first optical pickup 90A.

  As a result, information is recorded on the L0 recording / reproducing layer 14A along the groove 18B and land 18A while tracking the groove 18B and land 18A. As a result, the track pitch P2 of the recording marks formed on the L0 recording / reproducing layer 14A is half of the pitch P1 between the grooves 18B.

  When recording information on the L0 recording / reproducing layer 34A of the second recording / reproducing layer group 34 as the second recording / reproducing operation, the tracking error signal of the tracking optical system 200A of the first optical pickup 90A is used. Tracking control of the second optical pickup 90B is performed. As a result, the first optical pickup 90A and the second optical pickup 90B are always present at the same position in the tracking direction. Simultaneously with the tracking, the L0 recording / reproducing layer 34A is irradiated with the recording beam 170B in the blue wavelength region of the recording / reproducing optical system 100B of the second optical pickup 90B. As a result, information is recorded in the L0 recording / reproducing layer 34A. The track pitch P2 of the recording marks formed on the L0 recording / reproducing layer 34A is also half of the pitch P1 between the grooves of the servo layer 18.

  By simultaneously proceeding the first recording / reproducing operation and the second recording / reproducing operation as described above, simultaneous recording of information on the first and second recording / reproducing layer groups 14 and 34 is realized.

  Note that the recording power Pw, the erasing power Pe, and the bias power Pb when performing the simultaneous recording are set by OPC control using the L0 recording / reproducing layer 34A of the second recording / reproducing layer 34, as already described. It becomes.

  After the necessary information has been recorded on the L0 recording / reproducing layer 14A of the first recording / reproducing layer group 14 and the L0 recording / reproducing layer 34A of the second recording / reproducing layer group 34, this additional recording information (related to recording) Address information, content information, etc.) are simultaneously recorded in a management area reserved in advance in a part of the L0 recording / reproducing layers 14A, 34A.

  Thereafter, when recording information on the L0 recording / reproducing layers 14A, 34A is resumed, first, the management area of the L0 recording / reproducing layers 14A, 34A is reproduced, the position where the previous recording is completed is confirmed, and the recording is started from that position. Continue. In this way, the recording operation is continued at the same time until information recording is completed for all of the data areas in the L0 recording / reproducing layers 14A and 34A.

  When recording in the data area of the L0 recording / reproducing layers 14A, 34A is completed, recording is performed on the data areas of the L1 recording / reproducing layers 14B, 34B adjacent to the L0 recording / reproducing layers 14A, 34A as shown in FIG. Start. At this time, as already described, the OPC control is performed using the L1 recording / reproducing layer 14A of the first recording / reproducing layer 14, and the recording power Pw and the erasing power of both the beams 170A and 170B in simultaneous recording are performed. Pe and bias power Pb are set.

  After the necessary information has been recorded on the L1 recording / reproducing layer 14B, the current additional recording information (address information on recording, content information, etc.) is recorded in the management area of the L0 recording / reproducing layer 14A. deep. As a result of repeating this recording operation, in the first and second recording / reproducing layer groups 14 and 34, information is simultaneously given to the pair of recording / reproducing layers having the same stacking order from the center in the thickness direction of the optical recording medium 10. To be recorded. In the present embodiment, as shown by the arrow Q in FIG. 10, the case where information is recorded in order from the center side in the thickness direction of the optical recording medium 10 toward the outside is illustrated. May be recorded in order from the center toward the center, or may be recorded while randomly selecting the stacking order.

  Although the case where the management area is secured in the L0 recording / reproducing layers 14A and 34A is illustrated here, other recording / reproducing layers may be used. When the servo layer 18 includes a recording film, it is preferable to secure a management area in the servo layer 18 and record additional information there. This recording may be performed using the beam 270A for which tracking control is performed. By consolidating the management information in the servo layer 18, it becomes possible to simultaneously grasp the management information of both the first recording / reproducing layer group 14 and the second recording / reproducing layer group 34.

  Although not specifically illustrated here, when information is continuously recorded across the L1 recording / reproducing layers 14B, 34B from the L0 recording / reproducing layers 14A, 34A, the odd-numbered L0 recording / reproducing is performed. It is preferable to perform OPC control on both the layer 34A and the even-ordered L1 recording / reproducing layer 14B in advance and set the respective recording powers in the memory. In this way, the continuity of the information transfer rate can be maintained.

  <Simultaneous reproduction of information in first and second recording / reproducing layer groups>

  In the present embodiment, information simultaneously recorded on the first recording / reproducing layer group 14 and the second recording / reproducing layer group 34 is reproduced simultaneously. For example, as shown in FIG. 11, when information in the L0 recording / reproducing layer 14A of the first recording / reproducing layer group 14 is reproduced as the first reproducing operation, the beam of the recording / reproducing optical system 100A of the first optical pickup 90A is used. The L0 recording / reproducing layer 14A is irradiated with 170A, and reproduction is performed while performing tracking control and focus control.

  As the second reproduction operation, when reproducing the information in the L0 recording / reproducing layer 34A of the second recording / reproducing layer group 34, the beam 170B of the recording / reproducing optical system 100B of the second optical pickup 90B is irradiated with the L0 recording / reproducing layer 34A. And playback while performing tracking control and focus control. By simultaneously performing the first reproduction operation and the second reproduction operation in parallel, information reproduction in the first and second recording / reproducing layer groups 14 and 34 is realized. During recording, the servo control is used to perform tracking control. However, during simultaneous reproduction, the first and second optical pickups 90A, 90B are used by using the respective recording / reproducing optical systems 100A, 100B. Each of these is controlled separately.

  As described above, according to the optical recording / reproducing method of the present embodiment, the first recording / reproducing operation using the first optical pickup 90A and the second recording / reproducing operation using the second optical pickup 90B are performed at the same time. Information is simultaneously recorded on or reproduced from the first and second recording / reproducing layer groups 14 and 34. As a result, the transfer rate during recording or reproduction can be dramatically increased.

  In particular, in the present optical recording / reproducing method, a plurality of first recording / reproducing layer groups 14 and a plurality of second recording / reproducing layer groups 34 are set to the same number, and the same stacking order is obtained from the center in the thickness direction of the optical recording medium 10. Information is recorded or reproduced simultaneously on the pair of recording / reproducing layers. In this way, for the pair of recording / reproducing layers to be recorded / reproduced, the distances from the surfaces 10A, 30A of the optical recording medium 10 are close to each other, and the optical path of the beam is also symmetric. As a result, for example, the control signal obtained in the first optical pickup 90A, specifically, the control information such as the tilt and the surface shake of the optical recording medium 10, can be directly used in the second optical pickup 90B if the polarity of the information is reversed. Can be used as a control signal. As a result, in the second optical pickup 90B, it is possible to omit a photodiode mechanism or the like specially for obtaining this control signal.

  Furthermore, in the present embodiment, as the first recording / reproducing operation, the recording / reproducing of the first optical pickup 90A is performed on the first recording / reproducing layer group 14 while performing tracking control by irradiating the servo layer 18 with the tracking beam 270A. The information is recorded by irradiating the beam 170A. On the other hand, in the second recording / reproducing operation, the second optical pickup 90B is tracking-controlled with respect to the second recording / reproducing layer group 34 using the beam 270A and the servo layer 18 used in the first recording / reproducing operation. Information is recorded by irradiating a 90B recording / reproducing beam 170B. Therefore, in the second optical pickup 90B in the optical recording / reproducing apparatus 70, it is possible to omit the tracking optical system, and the structure can be simplified.

  In this embodiment, when moving to another recording / reproducing layer, the focal points of the beams 170A and 170B of the first and second optical pickups 90A and 90B are moved symmetrically with respect to the center of the optical recording medium 10. good. By controlling in this way, the optical recording medium 10 can be naturally moved from the center in the thickness direction to another pair of recording / reproducing layers having the same stacking order. As a result, interlayer jump control can be simplified.

  In the first and second recording / reproducing layer groups 14 and 34, information is simultaneously recorded on the recording / reproducing layers having the same stacking order from the center of the optical recording medium 10 in the thickness direction. The recording characteristics in the reproducing layer are approximate. Therefore, in this embodiment, when information is simultaneously recorded on a pair of recording / reproducing layers, OPC is performed using only one of the recording / reproducing layers. As a result, the time required for OPC can be halved as compared with the case where OPC is performed on both the first and second recording / reproducing layer groups 14 and 34.

  Further, in the present embodiment, as shown in FIG. 7, when recording is performed on the first and second recording / reproducing layer groups 14 and 34 that are even-numbered from the center side of the optical recording medium 10, the first recording / reproducing layer is used. When OPC is performed in the group 14 and recording is performed on the first and second recording / reproducing layer groups 14 and 34 having an odd order, the OPC is performed on the second recording / reproducing layer group 34. As a result, the test writing area X of the first recording / reproducing layer group 14 is formed only in the even-numbered recording / reproducing layers, and the test writing area X of the second recording / reproducing layer group 34 is formed only in the odd-numbered recording / reproducing layers. Is done. Accordingly, since the test writing area X does not overlap between adjacent recording / reproducing layers, generation of noise during OPC is suppressed, and the accuracy of OPC can be improved even if the interlayer distance between the recording / reproducing layers is reduced. . Further, since the test writing area X is not adjacent, the accuracy of OPC is hardly deteriorated even if the random data recorded as OPC is overlapped in the stacking direction, so that the test writing area X can be narrowed. As a result, the user data area of the first and second recording / reproducing layer groups 14 and 34 can be expanded.

  Further, according to this optical recording / reproducing method, information can be recorded on the first and second recording / reproducing layer groups 14 and 34 by using two independent recording / reproducing beams 170A and 170B. Accordingly, it is possible to share the focal movement range of the recording / reproducing beams 170A and 170B of the first and second optical pickups 90A and 90B in the thickness direction. As a result, even if the number of recording / reproducing layers is increased, it is possible to obtain an advantageous state with respect to coma aberration such as tilt.

  Specifically, in the present optical recording / reproducing method, the recording / reproducing beam 170A of the first optical pickup 90A used in the first recording / reproducing operation is made incident from the first surface 10A of the optical recording medium 10, and the second recording / reproducing operation is performed. The recording / reproducing beam 170B of the second optical pickup 90B used in is made incident from the second surface 30A of the optical recording medium 10. As a result, for example, in the first optical pickup 90A that performs the first recording / reproducing operation, recording is performed on the first recording / reproducing layer 14 disposed on one side with respect to the center in the thickness direction of the optical recording medium 10. In the second optical pickup 90B that performs the second recording / reproducing operation, recording is performed on the second recording / reproducing layer 34 disposed on the other side with respect to the center of the optical recording medium 10 in the thickness direction. As a result, like the optical recording medium 10, the first recording / reproducing layer 14 can be brought closer to the first surface 10A, and the second recording / reproducing layer group 34 can be brought closer to the second surface 30A. Therefore, this recording / reproducing method is advantageous for coma aberration in tilt and the like while increasing the number of recording / reproducing layers.

  Further, in the optical recording medium 10 used in the present embodiment, the first recording / reproducing layer group 14 and the second recording / reproducing layer group 34 are arranged at positions symmetrical with respect to the center in the thickness direction of the optical recording medium 10. ing. As a result, the optical design of the first and second optical pickups 90A and 90B of the optical recording / reproducing apparatus 70, the position recognition of the recording / reproducing layer, focus control, and the like can be shared, and the recording / reproducing speed can be increased. In addition, since the internal stress generated in the first and second recording / reproducing layer groups 14 and 34 in the optical recording medium 10 is also symmetric in the thickness direction, the warp of the optical recording medium 10 is also suppressed. As a result, even in the L5 recording / reproducing layers 14F and 34F farthest from the servo layer 18, a deviation in the radial direction is unlikely to occur with respect to formation of the recording mark. it can.

  Further, in this optical recording / reproducing method, the recording / reproducing beam 170A of the first optical pickup 90A and the recording / reproducing beam 170B of the second optical pickup 90B are shifted from each other in the circumferential direction with respect to the optical recording medium 10. Placed in. As a result, even if the beams 170A and 170B leak to the opposite surface, it is possible to avoid adversely affecting the reproduced waveform. If a large amount of the tracking beam 270A irradiated on the servo layer 18 passes through the servo layer 18, the second optical pickup 90B side tends to be adversely affected. Therefore, in the present optical recording medium 10, by setting the transmittance of the beam 270A to 10% or less in the servo layer 18, the adverse effect of the beam 270A on the second optical pickup 90B side can be suppressed.

  In the optical recording medium 10 to which the optical recording / reproducing method of this embodiment is applied, the servo layer 18 is formed only on one surface of the support substrate 12, and the first recording / reproduction layer is further formed on both surfaces of the support substrate 12. A group 14 and a second recording / reproducing layer group 34 are arranged. As a result, the internal stress at the time of forming the first and second recording / reproducing layer groups 14 and 34 is dispersed on both sides of the support substrate 12, so that the warp and deformation of the optical recording medium 10 can be suppressed. By dispersing the internal stress in this way, it is possible to suppress the warp of the optical recording medium 10 even if the thickness of the support substrate 12 is set within the range of 100 μm to 1000 μm.

  In addition, if it is going to form the unevenness | corrugation for tracking on both sides of the support substrate 12, the manufacturing process itself of this support substrate 12 will become complicated, and the precision of the support substrate 12 will deteriorate easily. Therefore, in the present embodiment, the unevenness for tracking is formed on one side of the support substrate 12 to improve the accuracy by simplifying the manufacture of the support substrate 12. Even if the servo layer 18 is unified as described above, the single beam 270A is used to perform the tracking control of the first and second optical pickups 90A and 90B arranged on both sides. The recording accuracy by can be sufficiently secured.

  Furthermore, in this optical recording medium 10, the thicknesses of the first buffer layer 17 and the second buffer layer 37 are set to be substantially the same. As a result, the warp of the support substrate 12 during the process of forming the first and second buffer layers 17 and 37 can be suppressed. This means that the support substrate 12 can be made thin or made of a material having low rigidity, and the space for forming the recording / reproducing layer can be increased accordingly.

  In particular, in the present embodiment, when the optical recording medium 10 is manufactured, the first buffer layer 17 and the second buffer layer 37, the first recording / reproducing layer group 14, the second recording / reproducing layer group 34, and the first intermediate layer group 16 are used. And the second intermediate layer group 36 are formed simultaneously on both sides. As a result, the internal stress generated during UV curing acts equally on both sides of the support substrate 12, so that the warp of the optical recording medium 10 can be further reduced.

  Further, in the optical recording medium 10, the reflectance of the servo layer 18 when irradiated with the tracking red wavelength beam 270 </ b> A is compared with the reflectance when the servo layer 18 is irradiated with the recording / reproducing beam 170 </ b> A. It is set large. In order to achieve this specifically, for the first buffer layer 17, a material is selected that has a greater light absorption as the beam wavelength is shorter. In this way, even if the recording / reproducing beam 170A having a blue wavelength is incident on the servo layer 18 side, it is easily absorbed by the first buffer layer 17, so that the amount of light reaching the servo layer 18 (from the servo layer 18) (Reflection amount) can be suppressed. On the other hand, the tracking beam 270A by the first optical pickup 90A can actively pass through the first buffer layer 17, so that the amount of light reaching the servo layer 18 (the amount of reflected light from the servo layer 18) can be increased. . As a result, it is possible to improve the quality of the reproduction signal and at the same time realize stable tracking control.

  In the present embodiment, the first buffer layer 17 is given a characteristic in which the light absorption rate differs between the red wavelength and the blue wavelength. As a result, the reflectance of the servo layer 18 is such that the tracking beam and the recording / reproducing beam are used. However, the present invention is not limited to this. For example, the reflective film itself formed on the servo layer 18 may be provided with wavelength selection characteristics such that the reflectance varies depending on the wavelength. In addition to the first buffer layer 17, a filter layer having wavelength selection characteristics of light transmittance and absorptance may be formed separately.

  Further, when a plurality of servo layers are formed in an optical recording medium as in the prior art, the arrangement of which servo layer is used and which recording / reproducing layer is recorded becomes complicated, and recording / reproducing control tends to be confused. Therefore, as in this embodiment, only the tracking beam 270A of the first optical pickup 90A is irradiated to one servo layer 18, and the tracking error signal is used to make the first recording / reproducing layer group 14 and the first recording layer 14 Recording all of the two recording / reproducing layer groups 34 simplifies the recording / reproducing control, so that recording / reproducing errors can be reduced.

  In the optical recording medium 10 of the above embodiment, the case where the thicknesses of the first cover layer 11 and the second cover layer 31 are the same is illustrated, but the present invention is not limited to this. For example, as in the optical recording medium 10 shown in FIG. 12, it is also preferable that the thicknesses of the first cover layer 11 and the second cover layer 31 are different. Specifically, the thickness of the first cover layer 11 is set to be larger by the thickness of the support substrate 12 than the thickness of the second cover layer 31. By doing so, the servo layer 18 is arranged at the center in the thickness direction of the optical recording medium 10. Note that when the optical recording medium 10 is manufactured, the first cover layer 11 and the second cover layer 31 having different thicknesses are preferably laminated separately. Even if they are not laminated at the same time, the support substrate 12, the first and second buffer layers 17, 37, the first recording / reproducing layer group 14, the first intermediate layer group 16, the second recording / reproducing layer group 34, and the second intermediate layer Since the layer group 36 has already secured a certain degree of rigidity, warping and deformation of the optical recording medium 10 are sufficiently suppressed.

  Further, in the above embodiment, the recording and reproducing layers of the first and second recording and reproducing layer groups 14 and 34 are shown only when the recording film is formed in advance, but the present invention is not limited to this. For example, like the optical recording medium 10 shown in FIG. 13, the first and second bulk layers 13 and 33 having a predetermined thickness are formed as a whole where the first and second recording / reproducing layer groups can be in the future. Can do. When the first and second bulk layers 13 and 33 are irradiated with the recording beams 170A and 170B, only the focal portion of the beam spot undergoes a state change to form a recording mark. That is, the optical recording medium in the present invention is not limited to the recording / reproducing layer on which the beam is irradiated, but a recording mark is formed in the planar area as needed. This includes the case where the two recording / reproducing layer groups 14 and 34 are formed in a multi-layer structure. By adopting the structure of the bulk layers 13 and 33 in the optical recording medium 10, the position of the recording / reproducing layer can be freely set within the range of the bulk layers 13 and 33. For example, even if the thickness and arrangement of the first bulk layer 13 and the second bulk layer 33 are different from each other, the distances from the first and second surfaces 10A and 30A of the first and second recording / reproducing layer groups 14 and 34 are different. , Can be matched to each other. In addition, although the structure which abbreviate | omits a cover layer was illustrated here when employ | adopting the 1st, 2nd bulk layers 13 and 33, a buffer layer can also be abbreviate | omitted besides this.

  In the present embodiment, the first and second recording / reproducing layer groups 14 and 34 are used for recording / reproducing while irradiating the servo layer 18 with the tracking beam 270A of the first optical pickup 90A. Although the case where information is recorded by irradiating the beams 170A and 170B of the laser beam is illustrated, the present invention is not limited to this. For example, as shown in FIG. 14, the second optical pickup 90B is also provided with a tracking beam 270B, and the servo layers 18 are irradiated with tracking beams 270A and 270B from both sides, whereby the first, It is also possible to perform tracking control independently by the second optical pickups 90A and 90B. In this way, it is possible to simultaneously record in different locations of the first and second recording / reproducing layer groups 14 and 34.

  Furthermore, in this embodiment, the case where the unevenness for tracking control is not formed in the first and second recording / reproducing layers 14 and 34 is shown, but the present invention is not limited to this. The tracking irregularities of the recording / reproducing layers of the first and second recording / reproducing layers 14 and 34 may be formed.

  In the present embodiment, the case where the wavelength of the tracking beam 270A and the wavelengths of the recording / reproducing beams 170A and 170B are different between red and blue is shown. However, the present invention is not limited to this, You may employ | adopt the beam of the same wavelength range between recording / reproducing.

  The optical recording medium and the like of the present invention can be applied to various optical recording media having a servo layer and a recording / reproducing layer.

DESCRIPTION OF SYMBOLS 10 Optical recording medium 11 1st cover layer 12 Support substrate 14 1st recording / reproducing layer group 16 1st intermediate | middle layer group 17 1st buffer layer 18 Servo layer 31 2nd cover layer 34 2nd recording / reproducing layer group 36 2nd intermediate | middle layer Group 37 Second buffer layer 86 Output control device 90A First optical pickup 90B Second optical pickup

Claims (9)

A plurality of first recording / reproducing layers previously laminated on the first surface side or formed later, and the first recording layer previously laminated or formed on the second surface side opposite to the first surface and the first recording A recording / reproducing method for recording / reproducing information on / from an optical recording medium having a second recording / reproducing layer having the same number of layers as a reproducing layer,
A first recording / reproducing operation for recording or reproducing information by irradiating a first recording / reproducing beam from the first surface to the first recording / reproducing layer, and a second recording / reproducing beam from the second surface to the second recording Simultaneously executing a second recording / reproducing operation for recording or reproducing information by irradiating the reproducing layer;
Recording or reproduction is performed simultaneously on the first and second recording / reproducing layers having the same stacking order from the center in the thickness direction of the optical recording medium,
An optical recording / reproducing method for an optical recording medium. The optical recording medium includes at least one servo layer having irregularities or grooves for tracking control,
In the first recording / reproducing operation and the second recording / reproducing operation, recording or recording is performed on the first recording / reproducing layer and the second recording / reproducing layer while performing tracking control by irradiating the servo layer with a tracking beam. Characterized by playing,
The optical recording / reproducing method of the optical recording medium according to claim 1. In the first recording / reproducing operation and the second recording / reproducing operation, tracking control is performed using the common tracking beam and the servo layer.
An optical recording / reproducing method for an optical recording medium according to claim 2. The servo layer is formed on at least one surface of the substrate of the optical recording medium,
The substrate is substantially transparent,
4. An optical recording / reproducing method for an optical recording medium according to claim 2 or 3. When information is simultaneously recorded on the first and second recording / reproducing layers by the first recording / reproducing operation and the second recording / reproducing operation, one test writing area of the first or second recording / reproducing layer is recorded. On the other hand, the optimum recording power of both the first and second recording / reproducing beams is set by performing trial writing with the first or second recording / reproducing beam,
5. An optical recording / reproducing method for an optical recording medium according to claim 1. When recording is simultaneously performed on the first and second recording / reproducing layers that are even-numbered from the center in the thickness direction of the optical recording medium, the first recording is performed on the test writing area of the first recording / reproducing layer. By performing trial writing with the reproducing beam, the optimum recording power of both the first and second recording / reproducing beams is set,
When recording is simultaneously performed on the first and second recording / reproducing layers that are odd-numbered from the center in the thickness direction of the optical recording medium, the second recording is performed on the test writing area of the second recording / reproducing layer. By performing trial writing with a reproducing beam, the optimum recording power of both the first and second recording / reproducing beams is set.
The optical recording / reproducing method of the optical recording medium according to claim 5. The first recording / reproducing layer and the second recording / reproducing layer of the optical recording medium are arranged at positions symmetrical with respect to the center in the thickness direction of the optical recording medium,
An optical recording / reproducing method for an optical recording medium according to claim 1. A plurality of first recording / reproducing layers previously laminated on the first surface side or formed later, and the first recording layer previously laminated or formed on the second surface side opposite to the first surface and the first recording A recording / reproducing apparatus for recording / reproducing information on / from an optical recording medium having a second recording / reproducing layer having the same number of layers as a reproducing layer,
A first recording / reproducing optical system that is disposed on the first surface side of the optical recording medium and that records or reproduces information by irradiating the first recording / reproducing layer with the first recording / reproducing beam from the first surface; ,
A second recording / reproducing optical system which is disposed on the second surface side of the optical recording medium and records or reproduces information by irradiating a second recording / reproducing beam from the second surface to the second recording / reproducing layer; ,
The first recording / reproducing optical system and the second recording / reproducing optical system simultaneously record or reproduce the first and second recording / reproducing layers having the same stacking order from the center in the thickness direction of the optical recording medium. Is characterized by
An optical recording / reproducing apparatus for an optical recording medium. When information is simultaneously recorded on the first and second recording / reproducing layers by the first recording / reproducing optical system and the second recording / reproducing optical system, one of the first and second recording / reproducing layers is tested. Output control means for setting optimum recording powers of both the first and second recording / reproducing beams by performing trial writing on the writing area by the first or second recording / reproducing beam. Features
9. An optical recording / reproducing apparatus for an optical recording medium according to claim 8.

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