JP2012064287A - Recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for reading a BCA formed by a stamper by performing tracking.SOLUTION: The recording medium includes a donut-shaped BCA102, and a donut-shaped recording area 120 provided outside of the BCA 102. In the BCA 102, a plurality of aggregates formed of a plurality of grooves aligned in a radial direction are aligned in the radial direction, and a plurality of pits are disposed discretely in a portion other than the plurality of the aggregates. The lengths of the respective pits in the radial direction are shorter than those of the respective grooves in the radial direction.

Description

  The present invention relates to a recording technique, and relates to a recording medium for recording predetermined information.

  Optical discs are widely used as optical information recording media on which information is recorded or reproduced by laser light irradiation. This type of optical disc includes reproduction-only CD-ROMs, DVD-ROMs, and BD-ROMs in which embossed pit rows are formed in advance, CD-Rs, DVD-Rs, and BD-s that can record data only once. R, rewritable CD-RW, DVD-RW, DVD-RAM, BD-RE, and the like. Each of these optical discs is configured to record or reproduce information by irradiating the information recording layer with a focused spot through a transparent substrate. In the information recording layer, pit rows and grooves are formed along a spiral recording track.

  In such an optical disc, in addition to the spiral recording track, there is a disc having an area called a burst cut area (BCA) as information reproducible by a focused spot of the optical disc apparatus. This BCA is a line segment that is arranged on the circumference with a predetermined interval and extends in the radial direction in the form of low reflectance, and the pattern is determined by the content of information to be recorded. The bar code is arranged in a circumferential shape. In the BCA, burst cut information such as the type of optical information recording medium (ROM, additional recording, or rewritable) and copyright management number is recorded. For example, in a read-only ROM optical disk, the BCA in the low reflectivity portion is created by removing the metal reflection film formed on the information recording layer by powerful laser irradiation.

  Apart from such a method using laser irradiation, proposals have been made to create BCA with stamper irregularities. More specifically, information is recorded by using glass whose surface is polished and washed as a master, applying a photoresist to the surface of the master, and exposing the surface with a laser beam or the like. Next, the exposed master is developed to form irregularities such as pits and groove grooves. Then, a stamper is created by plating the master. A resin-molded substrate is prepared by injection molding using the stamper as a mold. On the molded substrate thus produced, a recording layer and a reflective layer are formed in the case of a rewritable or write-once disc, and only a reflective layer is formed in the case of a read-only disc. Then, the shape of the optical disk is obtained by bonding the substrates (for example, see Patent Document 1).

JP 2006-155802 A

  In the method of forming BCA by laser irradiation, the interval between patterns that can be formed is considerably larger than that of pits. For example, the width of the low-reflectance portion is about 10 [μm], and the widest pattern interval is 100 [μm] or more. For example, with a Blu-ray disc, the time corresponding to 1T of the bit interval of 1 channel (radius = 21.6 mm, speed 4.917 m / s) is 5.8 μs at 2174 rpm, and its length is 28.5 μm. Used in combination with 5T signals. In addition, since the light reflection layer in the Blu-ray disc has a high reflectance with respect to blue laser light, an Ag-based reflection film containing Ag as a main component is used. Since the Ag-based reflective film has a high thermal conductivity, high laser power is required for marking, and damage to the protective layer and the cover layer may increase. Even in production, a special BCA code recording device removes a part of the reflection film of the optical disc in a rectangular shape along the radial direction or changes the phase while traversing the laser spot light in the radial direction with respect to the optical disc. Thus, a non-reflective portion or a highly reflective portion is formed. For this reason, since it takes time to write a barcode-shaped recording section, the productivity is inferior and the cost is increased.

On the other hand, in the method of forming a BCA with a stamper, a grooved stamper is obtained by recording the groove only once on the master, so that mass production of an optical disk on which the BCA has been recorded is easily reduced in cost. Therefore, it is desired to form BCA with a stamper.
In addition, when a modulation method that can detect control information without performing tracking is used, the BCA recorded on the inner periphery of the optical disc is often read without performing tracking. However, when tracking is not used for BCA reproduction, only BCA information, which is low-density information, is recorded in the mirror portion where there is no signal other than BCA. This limits the amount of information that can be recorded. Furthermore, BCAs other than the pit rows of the optical disc are suitable for recording security information and the like due to the feature that they are difficult to be replicated, but the amount of information is also limited. Therefore, in order to increase the amount of information that can be recorded, an optical disc that can be tracked in the BCA area is desired. In addition, since it is more stable to read BCA by tracking, an optical disc that can be tracked in the BCA area is desired in order to stably read BCA information.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique capable of reading a BCA formed by a stamper with tracking.

  In order to solve the above-described problems, a recording medium according to an aspect of the present invention includes a donut-shaped first region and a donut-shaped second region provided outside the first region. In the first region, a plurality of aggregates formed by a plurality of grooves arranged in the radial direction are arranged in the circumferential direction, and a plurality of pits are discretely arranged in portions other than the plurality of aggregates.

  According to this aspect, since a plurality of aggregates formed by a plurality of grooves arranged in the radial direction are arranged in the circumferential direction, it is possible to cope with execution of tracking, and a plurality of pits are provided in portions other than the plurality of aggregates. Since they are arranged discretely, the amount of information that can be recorded in the BCA can be increased.

  The circumferential length of each pit is shorter than the circumferential length of each groove. In this case, since the circumferential length of each pit is shorter than the circumferential length of each groove, each groove can be used as a BCA.

  In the first region, the depth of each groove is deeper than the depth of each pit. In this case, since the depth of each groove is deeper than the depth of each pit, the reflectance in the aggregate can be reduced.

  In the first region, the length between the pits adjacent in the circumferential direction is longer than the circumferential length of each pit. In this case, since the circumferential length between adjacent pits is longer than the circumferential length of each pit, the reflectance between adjacent pits can be increased.

  In the first region, the length between the grooves adjacent in the radial direction is shorter than the length between the pits adjacent in the radial direction. In this case, since the length in the radial direction between adjacent grooves is shorter than the length in the radial direction between adjacent pits, the reflectance of the portion provided with the groove can be reduced.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, the BCA formed by the stamper can be read with tracking.

It is a figure explaining the structure of the optical disk used as the comparison object of this invention. It is a figure explaining the structure of BCA of FIG. It is a figure explaining the structure of the BCA pattern of FIG. It is a figure explaining another structure of the BCA pattern of FIG. It is a figure which shows the structure of the reproducing | regenerating apparatus which concerns on Example 1 of this invention. It is a figure explaining the structure of the optical disk of FIG. It is a figure explaining the structure of BCA of FIG. It is a figure explaining the structure of the BCA pattern of FIG. It is a figure which shows the reproduction | regeneration waveform by the BCA pattern of FIG. It is a figure explaining another structure of the BCA pattern of FIG. It is a flowchart which shows the process of producing the stamper which concerns on Example 1 of this invention. It is a flowchart for demonstrating the manufacturing method of the optical disk based on Example 1 of this invention. FIGS. 13A to 13E are views showing a stamper manufacturing process according to Embodiment 2 of the present invention. It is a figure which shows the reproduction | regeneration waveform by the BCA pattern which concerns on Example 2 of this invention. It is a figure explaining the structure of the BCA pattern which concerns on Example 3 of this invention. It is a figure which shows the reproduction | regeneration waveform by the BCA pattern of FIG. It is a figure explaining the structure of the BCA pattern which concerns on Example 4 of this invention. FIG. 18 is a block diagram of an apparatus for recording the BCA pattern of FIG. 17 on a resist master. It is a figure which shows the reproduction | regeneration waveform by the BCA pattern used as the comparison object of this invention.

Example 1
Before describing the present invention specifically, an outline will be given first. Embodiment 1 of the present invention relates to an optical disc on which a BCA is created using a stamper, and the optical disc according to the present embodiment can perform tracking so that the BCA can be read stably. Composed. In order to be able to cope with tracking, the BCA is constituted by a plurality of grooves along the track. Here, an aggregate of a plurality of grooves forms a conventional BCA pattern. In order to stably read out the BCA information, it is desirable to be able to track in the BCA area. In order to cope with this, the BCA is provided with a pit row in addition to the groove. The pit row is configured along the track. The pit row only needs to be present to enable tracking, but additional information may be provided in the pit row.

  FIG. 1 is a diagram for explaining the configuration of an optical disc 200 to be compared with the present invention. The optical disc 200 includes a BCA 202 on the rotation center side, that is, on the inner diameter side, and a recording area 220 outside the BCA 202. Here, the BCA 202 is provided within a predetermined radius range. FIG. 2 is a diagram for explaining the configuration of the BCA 202. The horizontal direction in FIG. 2 corresponds to the circumferential direction in FIG. 1, and the vertical direction in FIG. 2 corresponds to the radial direction in FIG. In FIG. 2, a part of the BCA 202 shown in FIG. 1 corresponding to a part in the circumferential direction is shown. The BCA 202 includes a plurality of BCA patterns 204. One BCA pattern 204 is a low reflectance line segment. Hereinafter, a combination of one BCA pattern 204 and a plurality of BCA patterns 204 is referred to as “BCA pattern 204” without distinction. As shown in the figure, the BCA pattern 204 is arranged like a barcode in the BCA 202, and a plurality of the BCA patterns 204 are arranged on the same circumference and arranged in small increments on the same circumference with a uniform length in the radial direction. It has been. The arrangement pattern of the BCA pattern 204 in the circumferential direction corresponds to the aforementioned BCA information (hereinafter referred to as “basic control information”).

  FIG. 3 is a diagram for explaining the configuration of the BCA pattern 204. As in FIG. 2, the horizontal direction in FIG. 3 corresponds to the circumferential direction in FIG. 1, and the vertical direction in FIG. 3 corresponds to the radial direction in FIG. As illustrated, the BCA pattern 204 is a quadrangle surrounded by a line segment having a length in the radial direction of the BCA 202 and a line segment having a predetermined length in the circumferential direction. FIG. 4 is a diagram for explaining another configuration of the BCA pattern 204. As in FIG. 2, the horizontal direction in FIG. 4 corresponds to the circumferential direction in FIG. 1, and the vertical direction in FIG. 4 corresponds to the radial direction in FIG. As illustrated, the BCA pattern 204 includes a plurality of grooves that are long in the circumferential direction and short in the radial direction. Such a BCA pattern 204 is created by a stamper. Incidentally, the BCA mark portion formed by removing the reflective film has a very low reflectance of 5% or less, and the reflectance of a general BCA mark portion formed by a stamper is not sufficiently low. .

  FIG. 5 shows the configuration of the playback apparatus 100 according to the first embodiment of the present invention. The playback apparatus 100 includes an optical disk 10, a PUH 12, a laser driver 14, a matrix circuit 16, a Read circuit 18, a servo circuit 22, a demodulation circuit 24, a control circuit 28, a storage unit 30, a drive circuit 32, and a spindle motor 34. The control circuit 28 includes a control information processing unit 40.

  The optical disk 10 is held on a turntable (not shown), and is rotated together with the spindle motor 34 at a constant linear velocity by a control circuit 28 composed of a microcomputer and a drive circuit 32 controlled by a servo circuit 22. Here, the optical disk 10 is assumed to be a BD-ROM, and the configuration thereof will be described. In addition, the optical disk of each embodiment is applicable not only to BD-ROM but to various optical disks (especially ROM disk). FIG. 6 is a diagram for explaining the configuration of the optical disc 10. The optical disc 10 includes a BCA 102 and a recording area 120. Here, the optical disc 10 is created by a stamper ST (not shown). Similar to the BCA 202 in FIG. 1, the BCA 102 has a concentric donut-shaped area (first area), and records control information. The control information includes the basic control information described above and also includes additional basic information. The additional basic information will be described later. The recording area 120 is provided outside the BCA 102 and has a concentric donut-shaped area (second area). The recording area 120 records user data such as image data and audio data. It can be said that control information for reproducing user data is recorded in the BCA 102.

  More specifically, as an example, the optical disc 10 has an outer diameter of 120 mm and a light transmission layer thickness of 0.1 mm according to the BD-ROM. Also, in the optical disc 10, the track pitch of the recording area 120 is 0.32 μm, the channel bit length (1T) corresponding to DSV (Digital Sum Value) at RLL 17pp is 0.0745 μm, the shortest 2T mark length is 0.149 μm, and the longest 8T mark. The length is 0.6 μm. In the optical disc 10, a BCA 102 is provided in a radius range of 21 mm to 22 mm.

  FIG. 7 is a diagram for explaining the configuration of the BCA 102. The horizontal direction in FIG. 7 corresponds to the circumferential direction in FIG. 6, and the vertical direction in FIG. 7 corresponds to the radial direction in FIG. The BCA 102 is not created by removing the recording film with a laser beam for each sheet, but the unevenness of the BCA pattern 104 is created by a stamper. Hereinafter, a combination of one BCA pattern 104 and a plurality of BCA patterns 104 is referred to as “BCA pattern 104” without distinction. As described above, basic control information is recorded by the BCA pattern 104. Further, a row of pits 106 is provided in a portion of the BCA 102 other than the BCA pattern 104. Since the row of pits 106 is arranged along the track, tracking control is possible. The additional control information is recorded by the pattern of the pit 106 row.

  FIG. 8 is a diagram for explaining the configuration of the BCA pattern 104. FIG. 8 corresponds to an enlarged view of the circumferential direction of FIG. The BCA pattern 104 is formed as an aggregate of a plurality of grooves 108 arranged in the radial direction. The groove 108 is a general term for the first groove 108a, the second groove 108b, the third groove 108c, the fourth groove 108d, the fifth groove 108e, and the sixth groove 108f. Further, as shown in FIG. 7, a plurality of BCA patterns 104, which are aggregates of the grooves 108, are arranged in the circumferential direction. Here, a plurality of BCA patterns 104 arranged in the circumferential direction correspond to the basic control information. In other words, the BCA 102 includes a plurality of BCA patterns 104 arranged in the circumferential direction constituted by an assembly of a plurality of grooves 108 arranged in the radial direction. A plurality of BCA patterns 104 arranged in the circumferential direction constitute basic control information.

  In the BCA 102, in order to obtain a high reflectance between the BCA patterns 104, a track pitch wider than that of the recording area 120 in FIG. 6 is applied. Specifically, a range of 0.35 μm to 2.0 μm is selected as the track pitch. Here, it is 0.35 μm which is a range in which tracking control is possible in the BD-ROM. The groove 108 is 4 μm to 17 μm which is longer than the longest 8T signal having a length of about 0.6 μm in the track train having a pitch of 0.35 μm. Here, the length is 10 μm to 11 μm like a groove.

  The plurality of pits 106 are discretely arranged along the track in a portion of the BCA 102 other than the plurality of BCA patterns 104. The row of pits 106 includes a combination of 2T mark to 8T mark and 2T space to 8T space. That is, the circumferential length of each pit 106 is shorter than the circumferential length of each groove 108. Further, the depth of the pit 106 is in the range of 1/4 to 1/8, preferably 1/5 to 1/7 of the information reading wavelength λ. When the depth of the pit 106 is ¼ of the laser wavelength λ, the maximum is obtained, and when the depth of the pit 106 is ８, the amplitude of the push-pull signal is ¼ of the laser wavelength λ. It becomes the minimum at the time of, and becomes the maximum when it is 1/8. Therefore, the above range of the pit 106 corresponds to an optimum value for obtaining both tracking control by the push-pull signal and pit information. The depth of the groove 108 is set similarly to the depth of the pit 106. The row of pits 106 records management information and security information of the optical disc 10.

  FIG. 9 shows a reproduction waveform by the BCA pattern 104. FIG. 9 is a reproduction waveform of the lowermost track shown in FIG. 8, the horizontal axis indicates time, and the vertical axis is converted from reflectance to voltage. Upper row is RF waveform (RF-1) 2T mark, 4T space, 6T mark, 2T space, 2T mark, 7T space, 8T mark, 3T space, 4T mark, 4T space, 2T mark, 2T space, BCA mark, 2T Spaces, 3T marks, 2T spaces, 2T marks, 8T spaces, and 6T marks are subsequently reproduced. The reflectance of the 8T space is 35% or more, and the reflectance of the BCA mark is about 10%. The middle row is a 500 kHz L.P. P. The waveform (LPF-1) after passing through the filter, and the lower stage is a binary waveform (Comp-OUT) after passing through the comparator. Basic control information can be obtained by decoding the binary waveform. Note that the basic control information including basic information of the optical disc 10 is read even if tracking control is not necessarily performed.

  FIG. 10 is a diagram for explaining another configuration of the BCA pattern 104. The BCA pattern 104 shown in FIG. 10 is similar to FIG. 8, but the row of grooves 108 and pits 106 is wobbled. In addition, in the row of pits 106 having a track pitch of 0.35 μm, information relating to security such as management information of the optical disc 10 and encrypted descrambling information for protecting the copyright of video and music reproduced by the user. Information related to encryption is recorded.

  Returning to FIG. 5, the PUH 12 causes a laser diode (not shown) to emit light on the information reading surface of the optical disc 10 and uses an actuator such as a thread mechanism or an electromagnetic coil (not shown) to drive the optical disc 10 on the optical disc 10. Move in the radial direction. The laser reflected from the optical disk 10 is converted into an electrical signal by a photodetector (not shown) including a plurality of light receiving parts via an optical system (not shown) such as an objective lens in the PUH 12. The matrix circuit 16 generates a user information signal as a sum signal based on the electric signal, and generates a servo signal or the like as a difference signal. The servo signal includes a focus error signal, a tracking error signal, and disc information. The presence or absence of the recording layer, the reflectance, and the number of layers are confirmed by the focus error signal, the servo circuit 22 operates so that the reference recording layer on which DI is recorded is focused, and then the tracking error signal is used. Then, the servo circuit 22 is activated by feedback processing that reduces the error signal.

  The control information processing unit 40 included in the control circuit 28 acquires basic control information from the BCA pattern 104 in the BCA 102 of the optical disc 10 and acquires additional control information from the pit 106. Tracking control is executed to acquire basic control information and additional control information (hereinafter collectively referred to as “control information”). The control information processing unit 40 stores control information in the storage unit 30. The control circuit 28 specifies a processing method suitable for the optical disc 10 from the control information stored in the storage unit 30. The drive circuit 32 moves the PUH 12 to the address of the recording management information. The Read circuit 18 performs waveform equalization processing such as PRML on the sum signal output from the matrix circuit 16, and the demodulation circuit 24 demodulates the modulation signal and performs error correction and descrambling. The storage unit 30 stores the result.

  In order to reproduce the user information, the control circuit 28 reads the address and moves the PUH 12 by the driving circuit 32. The matrix circuit 16 outputs a sum signal, the Read circuit 18 binarizes the sum signal by waveform equalization processing such as PRML, and the demodulation circuit 24 demodulates the RLL (1-7) pp modulation signal, Perform error correction and descrambling, and output data such as video, audio, and program information.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it can be realized by a program loaded in the memory, but here it is realized by their cooperation. Draw functional blocks. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 11 is a flowchart showing a process of creating a stamper according to the first embodiment of the present invention. Polishing and cleaning step (S10) in which a glass master having a diameter of 130 mm to 220 mm and a thickness of 1 mm to 10 mm is prepared, and the glass master is processed using cerium oxide and ultrapure water to remove scratches, process the surface flatly, and perform cleaning. ), Applying a positive organic resist with a thickness corresponding to the depth of the pit to be formed by spin coating, or creating a resist disk in a resist coating step (S12) in which an inorganic resist is sputtered. Subsequently, an exposure step (S14) by an exposure apparatus that exposes the pit rows and the BCA pattern 104, a pit 106 exposed by an alkali developer or dry etching, a development step (S16) for developing the BCA pattern 104, and a sputter that sputters Ni or the like. Step (S18), a plating step (S20) for performing electroforming to form the stamper with a predetermined thickness, a glass peeling step (S22) for peeling the glass master from the stamper, the stamper surface is protected with a silicate, etc., and the back surface is protected The stamper ST in which the BCA 102 is formed is completed through the back surface polishing step (S24) for polishing, the inner and outer periphery cutting step (S26) for cutting the inner periphery and outer periphery of the stamper, and the like.

  FIG. 12 is a flowchart for explaining a method of manufacturing the optical disc 10 according to the first embodiment of the invention. The stamper ST formed with a portion corresponding to the BCA 102 is a disk having a thickness of 1.1 mm and an outer diameter of 120 mm made of a transparent resin such as polycarbonate resin or acrylic resin in a molding apparatus (S40) represented by an injection molding machine. The optical disk substrate is produced by transferring the pits 106 and the BCA pattern 104 formed on the stamper. Next, an Ag alloy containing 90% or more of Ag as a reflective film is formed in a film forming apparatus (S42) such as sputtering or a vacuum vapor deposition apparatus so as to have a thickness of about 40 nm. It is formed. A disc having a BCA mark is obtained after a cover layer having a thickness of about 100 μm is formed by a light transmission layer forming apparatus (S44) in which an ultraviolet curable resin is applied by spin coating and cured by ultraviolet rays.

  According to the embodiment of the present invention, since a plurality of BCA patterns formed by a plurality of grooves arranged in the radial direction are arranged in the circumferential direction, not only when tracking is not performed but also when tracking is performed. Yes. In addition, since a plurality of pits are discretely arranged in portions other than the BCA pattern, information recorded in the BCA can be read stably. In addition, since information is recorded in a plurality of pits, the amount of information that can be recorded in the BCA can be increased. In addition, since the amount of information that can be recorded in the BCA is increased, security information can be recorded. Moreover, since security information is recorded, the safety of information can be improved. In addition, since a stamper is used, productivity efficiency can be improved.

(Example 2)
As in the first embodiment, the second embodiment relates to an optical disc on which a BCA is created using a stamper, and the BCA includes a BCA pattern formed by a plurality of grooves and a pit row. In the optical disk according to the first embodiment, the depth of each groove is equal to the depth of each pit. More specifically, the depth of each groove and the depth of each pit are in the range of 1/5 to 1/7 of the information reading wavelength λ. On the other hand, Example 2 aims at further reducing the reflectance of the BCA pattern, and the depth of each groove is made deeper than the depth of each pit. The playback apparatus 100 according to the second embodiment is the same type as that shown in FIG. 5, the optical disc 10 is the same type as that shown in FIG. 6, the BCA 102 is the same type as that shown in FIG. 7, and the BCA pattern 104 is shown in FIG. It is the same type as 8. Here, the difference will be mainly described.

  7 and 8, the depth of each groove 108 is designed to be deeper than the depth of each pit 106. More specifically, the depth of each groove 108 is set to a quarter of the information reading wavelength λ. This is for making the reflectance of the BCA pattern 104 smaller. On the other hand, the depth of each pit 106 is set to a range of 1/5 to 1/7 with respect to the information reading wavelength λ. The grooves 108 and the pits 106 having different depths can be obtained by accurately performing etching and ashing steps so that the information reading wavelength λ is 1/3 to 1/4.

Next, the manufacturing process of the stamper of Example 2 will be described.
(Step 1: Manufacturing process of glass board with resist)
Prepare a glass plate that is sufficiently larger than the diameter of the optical disk to be created. One surface of the glass disk is polished by a wet polishing method using an abrasive such as cerium oxide so that the surface becomes sufficiently smooth. The surface of the glass plate that has been polished smoothly is washed with pure water. After washing the glass disk surface, the glass surface is dried, and an adhesive such as hexamethyldisilazane adheres to the glass disk surface within a controlled time. The glass disk covered with the adhesive is used for resist application. The resist coating is generally performed by a spinner, and the glass plate mounted on the spinner turntable is rotated with proper rotation, and the photoresist is applied to the glass plate surface. The glass plate coated with the photoresist is then dried at a temperature below the boiling point of the diluent at 60 ° C. to 120 ° C. in order to remove the diluent. This process is called post-baking or the like. The glass disk on which the photoresist is applied after step 1 is called a resist disk.

(Step 2: Cutting process)
In the cutting process, an exposure device is used to record a desired information signal on the resist board as a latent image on the resist, and the subsequent latent image on the resist is deposited on the resist as a shape change (resist shape). It is divided into a developing process. What is formed by intermittent laser light by the optical modulator is a series of intermittent micro grooves (holes) on the disk substrate and is called a pit. The intermittent period and the intermittent length are used as information signals. In this way, BCA mark grooves and pits are formed by the exposure apparatus. As for the recording power at the time of exposure, the BCA mark groove performs recording with a relatively large power compared to pit recording. As a result, it is possible to obtain recesses having different depths in the pit portion and the BCA mark portion, which are the basis of the pits, in a later step.

  After the exposure is completed, the resist disk is carried to a developing process, and a latent image in the resist is deposited as a shape change. The development process mainly uses an alkali developer made of an inorganic material or an alkali developer made of an organic material, and consists of a turntable mounted with a resist board and a developing liquid droplet outlet for discharging the developer. The developer is discharged while rotating the plate, the resist plate surface is developed at once, and the laser irradiation intensity change at the time of exposure is deposited as a change in the concave shape of the resist. FIGS. 13A to 13E show stamper manufacturing steps according to Embodiment 1 of the present invention. Here, FIG. 13A shows a glass substrate 110 in which a BCA mark groove BM ′ having a deep depth Re and a shallow pit portion PM ′ are formed in the photoresist 112.

(Step 3: Etching process (1))
The developed resist board is carried to an etching process. The shape of the pit portion having an appropriate depth according to the present invention and the shape of the BCA mark groove portion having a depth different from the pit portion can be obtained through this step. The etching process is a combination of an etching process using fluorine-based hydrocarbons for etching the glass disk of the resist disk and an ashing process using oxygen for removing unnecessary resist on the resist disk. Both of these steps are generally performed using a vacuum apparatus. A resist disk after development is mounted in a vacuum apparatus, and a glass disk having a desired shape from which the resist is removed is created by combining etching conditions and ashing conditions. A high voltage is applied to an atmosphere in which CF ₄ , CHF ₃ , C ₂ H ₄ F ₂ , CH ₃ F, etc., which are fluorine-based hydrocarbons, are introduced into a vacuum apparatus once set to a low pressure, and plasma is generated in the vacuum chamber This can be achieved by removing the SiO ₂ on the surface of the glass plate as a silicon fluoride compound by the fluorine plasma (FIG. 13B). FIG. 13B shows a state where the bottom surface of the BCA mark groove BM ′ is etched to the depth h3 beyond the surface of the glass substrate 110.

(Step 4: Ashing process (1))
In this process, as preparation for the etching of the pit part to be performed in the next process, while maintaining the pit shape obtained in the cutting process, the resist in the pit part is removed and the surface of the glass plate under the pit part is exposed. There is. This process is also performed in a vacuum apparatus as in step 3. It is desirable to use the vacuum apparatus used in step 3 as it is. After step 3 is completed, gas introduction into the vacuum apparatus is generally stopped, and the gas used in step 3 is discharged once at a low pressure of 10 ⁻³ Pa to 10 ⁻⁵ Pa. By only switching the gas introduction valve (operation for continuously switching the gas introduction), a high-quality glass master can be obtained even if the pressure is not once lowered. Thereafter, a gas for removing the resist on the resist board is introduced. When performing the first ashing step and the second ashing step, the ashing conditions are determined based on the result of measuring the heating temperature of the photoresist surface during ashing or the heating temperature of the glass substrate surface in advance. It is desirable to obtain the introduced oxygen concentration in advance. The oxygen concentration in the apparatus can be changed by changing the flow rate of oxygen introduced into the apparatus.

  In this ashing process, the BCA mark groove on the glass plate is etched in the etching process (1) described above, but the resist around the pit part is not etched. In the ashing in this ashing process, the ashing is performed by ashing. Since the shape of the resist around the pit portion also changes, the etching process that is reserved after this process is considered in consideration of the deformation caused by the etching of the BCA mark groove part due to the pit etching process that is reserved after this process. By managing the ashing process around the BCA mark groove part so that the best BCA mark groove part shape can be obtained, the good BCA mark groove part shape and the good pit shape described in the present invention can be obtained. The cross-sectional shape of the resist board after ashing is shown in FIG. FIG. 13C shows an etching state in which the bottom surfaces of the BCA mark groove portion BM ′ and the pit portion PM ′ having a smooth inner wall surface have reached the surface of the glass substrate 110.

(Step 5: Etching process (2))
Etching is desirably performed under the same conditions as in the etching step (1), and etching is performed until the etching depth reaches a desired depth (FIG. 13D). The flatness of the bottom surface of the recording groove is preferably 10 nm or less because the pit depth h2 is 1/5 to 1/7 of the recording wavelength.
(Step 6: Ashing process (2))
The resist remaining in step 5 is removed in this step. Therefore, the ashing conditions do not need to be set as fine as in step 4, and the glass that has achieved the object of the present invention by determining the oxygen concentration introduced into the apparatus so that efficient ashing is performed. A master can be created (FIG. 13 (e)).

  11 and the subsequent steps are the same as those in the first embodiment. An optical disk substrate is prepared by injection molding a polycarbonate resin or the like with a thickness of 1.1 mm. A disk finished product having a BCA pattern 104 after forming a cover layer with a thickness of about 100 μm by forming an Ag alloy containing 90% or more of Ag as a reflective film to a thickness of about 40 nm by sputtering. become. As in the first embodiment, the management information and security information of the optical disc 10 may be recorded in the columns of the pits 106 other than the BCA pattern 104.

  FIG. 14 shows a reproduction waveform by the BCA pattern 104 according to the second embodiment of the present invention. As shown in RF-2, the reflectance of the BCA mark is lower than about 10%. Specifically, the reflectance of the 8T space is 35% or more, and the reflectance of the BCA mark is about 6%. As a result, information based on the BCA pattern 104 can be read stably.

  According to the embodiment of the present invention, since the depth of each groove is deeper than the depth of each pit, the reflectance in the BCA pattern can be lowered. Further, since the reflectance in the BCA pattern can be lowered, the difference between the portion with high reflectance (pit row portion) and the portion with low reflectance (portion of BCA pattern 104) can be increased. In addition, since the difference between the high reflectance portion and the low reflectance portion becomes large, the error rate can be reduced.

Example 3
The third embodiment relates to an optical disc on which a BCA is created using a stamper as before, and the BCA includes a BCA pattern formed by a plurality of grooves and a pit row. Example 3 aims to increase the reflectance of the pit row portion, and the circumferential length of each pit is the length between adjacent pits (the end of a predetermined pit and the predetermined pit). The distance between the pit and the edge of the adjacent pit). The playback apparatus 100 according to the third embodiment is the same type as that shown in FIG. 5, the optical disc 10 is the same type as that shown in FIG. 6, and the BCA 102 is the same type as that shown in FIG. Here, the difference will be mainly described.

  FIG. 15 is a diagram illustrating the configuration of the BCA pattern 104 according to the third embodiment of the present invention. 15, as in FIG. 8, the horizontal direction corresponds to the circumferential direction of FIG. 6, and the vertical direction corresponds to the radial direction of FIG. 6. In FIG. 8, the circumferential length of the pit 106 is a signal corresponding to DSV in normal RLL 17 pp. In FIG. 15, in order to increase the reflectance other than the BCA pattern 104, 2T marks and 3T marks are used as the circumferential length of the pits 106, and the length between the pits 106 adjacent in the circumferential direction is used. 7T space and 8T space are used. That is, in the BCA 102, the circumferential length between adjacent pits 106 is longer than the circumferential length of each pit 106.

  FIG. 16 shows a reproduction waveform by the BCA pattern 104. As shown in RF-2 and LPF-2, the average reflectance other than the BCA mark is increased, and the reading error is reduced.

  According to the embodiment of the present invention, since the circumferential length between adjacent pits is longer than the circumferential length of each pit, the reflectance between adjacent pits can be increased. In addition, since the reflectance between adjacent pits is increased, the difference between the high reflectance portion and the low reflectance portion can be increased. In addition, since the difference between the high reflectance portion and the low reflectance portion becomes large, information based on the BCA pattern 104 can be read stably. It should be noted that, if at least the sum of the circumferential lengths between adjacent pits per round is longer than the sum of the circumferential lengths of the pits, a portion having a certain degree of reflectivity There is an effect of increasing the difference from the low part.

Example 4
The fourth embodiment relates to an optical disc on which a BCA is created using a stamper as before, and the BCA includes a BCA pattern formed by a plurality of grooves and a pit row. When a BCA is created using a stamper, the reflectance ratio between the BCA pattern and other portions tends to be smaller than in the BCA in which the reflection film is removed by a laser. As a result, the probability of error occurrence may be improved. Embodiment 4 aims to further reduce the reflectance of a BCA pattern in a BCA created using a stamper. In the optical disc according to the fourth embodiment, the track pitch of the plurality of grooves arranged in the radial direction is narrower than the track pitch of the plurality of pits arranged in the radial direction. For example, the former is halved from the latter. The playback apparatus 100 according to the fourth embodiment is the same type as that shown in FIG. 5, the optical disc 10 is the same type as that shown in FIG. 6, and the BCA 102 is the same type as that shown in FIG. Here, the difference will be mainly described.

  The optical disk 10 in Example 4 has an outer diameter of 120 mm, a light transmission layer thickness of 0.1 mm, which is the same as that of a BD-ROM, a track pitch of the recording area 120 excluding the vicinity of the BCA 102, and RLL of 17 pp. The optical disc 10 has a channel bit length (1T) corresponding to DSV of 0.0745 μm, the shortest 2T mark length of 0.149 μm, and the longest 8T mark length of 0.6 μm. Further, in the optical disc 10, in order to obtain a high reflectance between the BCA patterns 104, a track pitch slightly wider than the recording area 120 is applied to the row of pits 106, and a range of 0.35 μm to 2.0 μm is selected. It is. In particular, here, it is set to 0.4 μm which is a range in which tracking control is possible in the BD-ROM.

  The row of pits 106 is composed of a combination of 2T marks to 8T marks and 2T spaces to 8T spaces, and the depth of the pits 106 is 1/4 to 1/8, preferably 5 minutes, with respect to the information reading wavelength λ. The range is 1 to 1/7. This is the minimum when the depth of the pit 106 is ¼ of the maximum when the laser wavelength λ is ¼, and the amplitude of the push-pull signal is that the groove depth is ¼ of the laser wavelength λ. Since the maximum is sometimes at least 1/8, the optimum value is obtained for obtaining both tracking control by the push-pull signal and information on the pit 106. Further, in order to increase the average reflectivity of the pit 106 row other than the BCA pattern 104, the power during exposure is slightly lowered, and the modulation degree of the pit 106 is lowered to 50% or less. Although the signal quality of the row of pits 106 is deteriorated, since the track pitch is 10% or more wider than the recording area 120, the deterioration of the signal quality due to the decrease in the modulation degree is cancelled.

  FIG. 17 is a diagram illustrating the configuration of the BCA pattern 104 according to the fourth embodiment of the present invention. The BCA pattern 104 is 4 μm to 17 μm longer than the longest 8T signal having a length of about 0.6 μm in a track row having a pitch of 0.4 μm. Here, the BCA pattern 104 has a length of 10 μm to 11 μm, which is close to the groove. It is marked with. The track pitch of the grooves 108 is 0.2 μm, which is half of the track pitch 0.4 μm of the pits 106. That is, in the BCA 102, the radial length between adjacent grooves 108 is shorter than the radial length between adjacent pits 106. For example, the former may be ½ or less of the latter. Note that the BCA pattern 104 and the row of pits 106 may be wobbled. In addition, in the row of pits 106 having a track pitch of 0.4 μm, security information such as management information of the pits 106, encrypted descrambling information for protecting the copyright of video and music reproduced by the user, encryption Information related to may be recorded.

  FIG. 18 is a block diagram of an apparatus for recording the BCA pattern 104 on the resist master. The apparatus includes a laser light source 50, an ND filter 52, a translucent mirror 54, a mirror 56, an optical modulator 62, an optical polarizer 64, a beam expander 66, an optical modulator 68, a mirror 70, a beam expander 72, and a semitransparent. A mirror 74, a mirror 76, an objective lens 78, a registration board 80, a turntable 82, a motor 84, a rotation angle detector 86, a track feed control mechanism 88, and a control device 90 are included.

  The grooves 108 having a half pitch with respect to the rows of pits 106 are exposed by a beam A60 for recording the rows and grooves 108 of the pits 106 and a beam B58 for recording only the grooves 108. In the exposure process, the resist board 80 is placed on the turntable 82 and rotated by the motor 84 in accordance with an instruction from the controller 90. The laser emitted from the laser light source 50 becomes a beam A 60 that passes through the ND filter 52 and the semitransparent mirror 54 and is reflected by the mirror 56. The beam A60 is sequentially provided with an optical polarizer 64 for swinging the beam slightly to the left and right, an optical modulator 68 for changing the intensity of the beam, a mirror 70, and a beam expander 72.

  On the other hand, an optical modulator 62 and a beam expander 66 for changing the intensity of the beam are sequentially provided in the optical path of the other beam B58 reflected by the semitransparent mirror 54 described above. In addition, an optical polarizer may be provided in the optical path of the beam A60 in order to put a wobble on the resist board 80 in the same manner as the beam A60. The beam A 60 and the beam B 58 are incident on the semitransparent mirror 74, enter the objective lens 78 through the mirror 76. The beam A60 and the beam B58 emitted from the objective lens 78 are condensed at a predetermined position in the radial direction of the track recorded on the resist board 80. The grooves 108 and pits 106 formed by the beam A60 may be in the form of grooves or pits that are continuous by about 10 μm. The pit 106 by the beam B58 may be a groove shape or a pit row that is continuous by about 10 μm. The turntable 82 on which the resist board 80 is placed is moved by a track feed control mechanism 88 so that the objective lens 78 records a signal within a radius of 21 mm to 22 mm. Further, since the groove 108 is a mark on the barcode formed on the circumference, a signal of the rotation angle of the rotation angle detector 86 for grasping the rotation angle of the motor 84 is obtained, and the optical modulator 62, the light The modulator 68 is controlled via the control device 90.

  In Example 4, the depth of the BCA pattern 104 was in the range of 1/5 to 1/7 of the information reading wavelength λ. In order to reduce the reflectance of the BCA pattern 104, The depth of the BCA pattern 104 may be ¼ of the information reading wavelength λ. As a result, the reflectance in the BCA pattern 104 is lower than that in the fourth embodiment. For example, the reflectance of the 8T space is 35% or more, and the reflectance of the BCA pattern 104 is about 3%. The reflectance of the BCA pattern 104 after passing through the LPF is about 10% with respect to the reflectance between marks, and reading errors are reduced.

  FIG. 19 shows a reproduction waveform by the BCA pattern 204 to be compared with the present invention. As described above, there is no pit row in the area of the BCA pattern 204. The BCA pattern 204 is formed of a pit row or groove having a length of about 10 mm with a pitch of 0.35 μm, for example. Since there is no pit row, tracking control is not supported, and the reproduction waveform crosses a plurality of tracks as in RF-2, so that the output via the 500 KHz LPF becomes LPF-2. The reflectance of the BCA pattern 204 is about 15%, which is higher than those in Examples 1 to 4. Further, the reflectance of the BCA pattern 204 after passing through the LPF is as high as 60% with respect to the reflectance between marks, and an error is likely to occur. Also, since there is no pit row, security information cannot be entered in the pit row.

  According to an embodiment of the present invention, the length in the radial direction between adjacent grooves (the distance between the end of a predetermined groove in the radial direction and the end of the groove adjacent to the predetermined groove) Since it is shorter than the length in the radial direction, the reflectance of the BCA pattern can be reduced. Further, since the reflectance in the BCA pattern is reduced, the difference between the high reflectance portion and the low reflectance portion can be increased. Further, since the difference between the high reflectance portion and the low reflectance portion becomes large, information based on the BCA pattern 204 can be read stably.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  Any combination of Examples 1 to 4 is also effective. According to this modification, the effect of any combination of the first to fourth embodiments can be obtained.

  10 optical disk, 12 PUH, 14 laser driver, 16 matrix circuit, 18 read circuit, 22 servo circuit, 24 demodulation circuit, 28 control circuit, 30 storage unit, 32 drive circuit, 34 spindle motor, 40 control information processing unit, 100 playback Equipment: 102 BCA, 104 BCA pattern, 106 pits, 108 grooves, 110 glass substrate, 112 photoresist, 120 recording area.

Claims (5)

A doughnut-shaped first region;
A donut-shaped second region provided outside the first region,
In the first region, a plurality of aggregates formed by a plurality of grooves arranged in the radial direction are arranged in the circumferential direction, and a plurality of pits are discretely arranged in portions other than the plurality of aggregates. A recording medium characterized by the above.   The recording medium according to claim 1, wherein the circumferential length of each pit is shorter than the circumferential length of each groove.   The recording medium according to claim 1 or 2, wherein in the first region, the depth of each groove is deeper than the depth of each pit.   4. The recording medium according to claim 1, wherein, in the first region, a length between pits adjacent in the circumferential direction is longer than a length of each pit in the circumferential direction. 5.   5. The recording medium according to claim 1, wherein in the first region, a length between grooves adjacent in the radial direction is shorter than a length between pits adjacent in the radial direction.

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