JP2006012346A - Rom type optical recording medium and stamper for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ROM type optical recording medium which allows a reproduced signal having a good jitter characteristic to be obtained and allows data to be reproduced as desired. <P>SOLUTION: The ROM type optical recording medium is provided with a substrate 2 having a plurality of recessed pits 2a formed on the surface thereof, a light-transmissive layer 4, and a reflection layer 3 formed between the substrate 2 and the light-transmissive layer 4, and so configured that data are reproduced by being irradiated with a laser beam through the light-transmissive layer 4. In the ROM type optical recording medium, recessed pits 2a on the surface of the substrate 2 are longer than a fundamental length BL determined in accordance with data to be recorded, and spaces 2b between recessed pits 2a adjacent in a track direction are shorter in length than the fundamental length BL. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ROM type optical recording medium, and more particularly to a ROM type optical recording medium that can obtain a reproduction signal having good jitter characteristics and can reproduce data as desired. It is.

  The present invention also relates to a stamper for manufacturing a ROM type optical recording medium, and in particular, a reproduction signal having good jitter characteristics can be obtained and data can be reproduced as desired. The present invention relates to a stamper capable of producing a simple ROM type optical recording medium.

  Conventionally, optical recording media represented by CDs and DVDs are widely used as recording media for recording digital data. These optical recording media, such as CD-ROM and DVD-ROM, can add data to ROM-type optical recording media that cannot add or rewrite data, and CD-R or DVD-R. It can be roughly divided into a write-once type optical recording medium that cannot rewrite data and a rewritable type optical recording medium that can rewrite data, such as CD-RW and DVD-RW.

  Among these, in the ROM type optical recording medium, concave pits or convex pits are formed on the surface of the substrate, and data is recorded by such pits and spaces between adjacent pits. These pits and spaces are respectively associated with digital data “0” or “1”, and the lengths thereof are associated with the number of bits “0” or “1”. Therefore, desired data can be recorded by modulating the lengths of pits and spaces.

  On the other hand, when reproducing recorded data, a laser beam is irradiated along a track formed on the substrate, and the reflected light amount of the laser beam is detected by a photodetector, so that the difference in the surface shape of the substrate Data can be reproduced by reading.

  In manufacturing such a ROM type optical recording medium, first, a photoresist is uniformly applied by spin coating on a precisely polished and cleaned glass substrate to form a photoresist coating film on the glass substrate. Is done. Next, the photoresist coating film is irradiated with an exposure laser beam, and the photoresist coating film is exposed to form a latent image having an uneven pattern corresponding to the pits of the optical recording medium. Further, by immersing this glass substrate in a chemical solution and developing the exposed photoresist coating film, either the exposed portion or the unexposed portion is removed to correspond to the pits on the glass substrate. An uneven pattern is formed, and a photoresist master is produced.

  Next, an electroless plating process is performed on the surface of the photoresist master on which the concavo-convex pattern is formed, and after a thin film such as Ni is formed, a metal film is formed by the electrolytic plating process. Further, a thin film such as Ni and a metal film are peeled off together to produce a stamper to which the concavo-convex pattern is transferred. Finally, the stamper is set in a mold, and a disk-shaped substrate having a concave portion and a convex portion formed on its surface is manufactured by injection molding.

  On the other hand, in recent years, a next-generation ROM type optical recording medium having a larger capacity and a higher data transfer rate has been proposed. In such a next-generation ROM type optical recording medium, the recording density can be improved by increasing the numerical aperture NA of the objective lens for focusing the laser beam and shortening the wavelength λ of the laser beam. Yes.

  However, when the numerical aperture NA of the objective lens for focusing the laser beam is increased, as shown by the following equation (1), the angle error allowed for the tilt of the optical axis of the laser beam with respect to the optical recording medium, that is, the tilt There arises a problem that the margin T becomes very narrow.

  In Equation (1), d is the thickness of the layer through which the laser beam passes before reaching the pit formed on the surface of the substrate. As apparent from the equation (1), the tilt margin T decreases as the NA of the objective lens increases, and increases as the thickness d of the layer through which the laser beam is transmitted decreases.

  Therefore, in a next-generation ROM type optical recording medium, a thin light transmission layer having a thickness of about 100 μm is formed on a substrate, and data is reproduced by irradiating a laser beam from the light transmission layer side. With such a configuration, the tilt margin is expanded.

  In a ROM type optical recording medium, in order to obtain a reproduction signal having a high C / N ratio, a reflection layer is generally formed on a substrate to improve the reflectance with respect to a laser beam.

  However, unlike the conventional CD-ROM and DVD-ROM, the next-generation ROM type optical recording medium is configured to be irradiated with a laser beam from the light transmitting layer side. Is provided, the laser beam incident on the optical recording medium is reflected by the reflective layer before reaching the surface of the substrate. For this reason, the reproduction signal generated by the photodetector does not correspond to the surface shape of the substrate, but mainly corresponds to the surface shape of the reflective layer. As a result, when concave pits and spaces, or convex pits and spaces are formed on the substrate according to the data to be recorded, the jitter characteristics of the reproduced signal deteriorate, and the recorded data is In addition, there is a problem that it is extremely difficult to reproduce.

  Therefore, an object of the present invention is to provide a ROM type optical recording medium that can obtain a reproduction signal having good jitter characteristics and can reproduce data as desired.

  Another object of the present invention is to provide a stamper capable of obtaining a reproduction signal having good jitter characteristics and obtaining a ROM type optical recording medium capable of reproducing data as desired. There is.

  In order to achieve the above object, the present inventor has conducted extensive research, and as a result, even when concave pits and spaces are formed on the substrate in accordance with the data to be recorded, the next-generation ROM type optical recording medium When the data recorded on the disk is reproduced, the jitter characteristics of the reproduced signal are deteriorated because the length of the concave portion of the reflective layer is shorter than the concave pit formed on the surface of the substrate and between adjacent concave portions. The length of the gap of the reflective layer becomes longer than the space formed on the surface of the substrate, and the length of the gap between the reflection layers and the gap between the depressions is detected by the photodetector, so that it is recognized by the data reproducing device. It has been found that the length of the uneven pattern is caused by the fact that it does not match the length corresponding to the recorded data.

  The present invention is based on such knowledge, and the object of the present invention is formed between a substrate having a plurality of concave pits formed on the surface, a light transmission layer, and the substrate and the light transmission layer. A ROM type optical recording medium comprising a reflective layer and configured to reproduce data by irradiating a laser beam through the light transmitting layer, wherein the concave pits are data to be recorded The length of the space between the concave pits adjacent to each other in the track direction is shorter than the basic length BL. This is achieved by the characteristic ROM type optical recording medium.

  In the present invention, the basic length BL is a length determined according to the number of bits of “0” or “1” of data to be recorded. For example, in a next-generation ROM type optical recording medium, 1− When recording 2T to 8T data modulated by 7RLL with a recording capacity of 25 GB, 149 nm, 223.5 nm, 298 nm, 372.5 nm, 447 nm, 521.5 nm, 596 nm corresponding to 2T to 8T. There are seven types of lengths.

  According to the present invention, the length of the recess formed in the reflective layer and the gap between the recesses can be made substantially coincident with the basic length BL which is a length corresponding to the data to be recorded. When the recorded data is reproduced, the length of the concave / convex pattern detected by the photodetector is substantially the same as the length corresponding to the recorded data, and thus a reproduced signal having good jitter characteristics is obtained. And the data can be replayed as desired.

  In the present invention, when the distance from the surface of the reflective layer to the surface of the substrate is D, the concave pits have a length of BL + (0.1 to 0.3) · D, and the distance between the concave pits The space preferably has a length of BL− (0.1 to 0.3) · D, and the concave pit has a length of BL + (0.15 to 0.25) · D. More preferably, the space between the concave pits has a length of BL- (0.15 to 0.25) · D.

  When the concave pits have a length of BL + (0.1 to 0.3) · D, and the space between the concave pits has a length of BL− (0.1 to 0.3) · D Makes it possible to make the length of the recess formed in the reflective layer and the gap between the recesses substantially coincide with the basic length BL.

  In a further preferred embodiment of the present invention, the reflective layer is made of Ag or an alloy containing Ag. When the reflective layer is formed of Ag or an alloy containing Ag, it is possible to form a reflective layer with excellent surface properties, and therefore it is possible to reduce noise included in the reproduction signal.

  The object of the present invention includes a substrate having a plurality of convex pits formed on a surface thereof, a light transmission layer, and a reflection layer formed between the substrate and the light transmission layer. A ROM type optical recording medium configured to reproduce data by irradiating a laser beam through a layer, wherein the convex pits are determined according to data to be recorded ROM-type optical recording, characterized in that it has a length shorter than BL, and the length of the space between the convex pits adjacent in the track direction is longer than the basic length BL Achieved by the medium.

  According to the present invention, the length of the protrusions formed in the reflective layer and the gap between the protrusions can be made substantially coincident with the basic length BL which is the length corresponding to the data to be recorded. When the data recorded on the medium is reproduced, the length of the concavo-convex pattern detected by the photodetector is almost the same as the length corresponding to the recorded data, and thus a reproduced signal having good jitter characteristics And the data can be reproduced as desired.

  Another object of the present invention is a stamper for manufacturing a ROM-type optical recording medium, wherein a plurality of convex pits are formed on the surface, and the convex pits are formed in the ROM-type optical recording medium. A length that is longer than the basic length BL determined according to data to be recorded on the medium, and a length of a space between the convex pits adjacent in the track direction is shorter than the basic length BL. It is achieved by a stamper characterized by having

  Furthermore, another object of the present invention is a stamper for manufacturing a ROM type optical recording medium, wherein a plurality of concave pits are formed on the surface, and the concave pits are formed on the ROM type optical recording medium. The length is shorter than the basic length BL determined according to the data to be recorded, and the length of the space between the concave pits adjacent in the track direction is longer than the basic length BL. Achieved by a stamper characterized by

  According to the present invention, it is possible to provide a ROM type optical recording medium capable of obtaining a reproduction signal having good jitter characteristics and reproducing data as desired.

  Further, according to the present invention, it is possible to provide a stamper capable of producing a reproduction signal having good jitter characteristics and capable of producing a ROM type optical recording medium capable of reproducing data as desired. become.

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

  FIG. 1 is a schematic perspective view of a ROM type optical recording medium according to a preferred embodiment of the present invention, and FIG. 2 is a schematic enlarged cross-sectional view of a portion indicated by A in FIG.

  As shown in FIG. 1, the optical recording medium 1 has a disk shape, and a center hole 5 for setting the optical recording medium 1 in a data reproducing device is formed at the center thereof.

  The optical recording medium 1 shown in FIGS. 1 and 2 is irradiated with a laser beam having a wavelength of 380 nm to 450 nm through an objective lens (not shown) from the direction shown by the arrow in FIG. The data is reproduced.

  As shown in FIG. 2, the optical recording medium 1 according to the present embodiment includes a substrate 2, a reflective layer 3 formed on the substrate 2, and a light transmission layer 4 formed on the reflective layer 3. Yes.

  The substrate 2 functions as a mechanical support for the optical recording medium 1.

  The material for forming the substrate 2 is not particularly limited as long as it can function as a support for the optical recording medium 1. For example, a polycarbonate resin, an olefin resin, or the like can be used. The thickness of the substrate 2 is not particularly limited, but is preferably about 1.1 mm.

  FIG. 3 is a schematic perspective view of the surface of the substrate 2. In FIG. 3, an arrow L indicates the scanning direction of the laser beam.

  As shown in FIG. 3, a plurality of concave pits 2 a having a substantially elliptical shape are formed on the surface of the substrate 2. The plurality of concave pits 2a are formed in a spiral shape from the inner circumference side to the outer circumference side or from the outer circumference side to the inner circumference side to constitute a track. The areas other than the plurality of concave pits 2a are formed flat, and a space 2b is formed between the concave pits 2a adjacent in the track direction. These concave pits 2a and spaces 2b are respectively associated with digital data “0” or “1”, and data is recorded by the concave pits 2a and spaces 2b.

  As shown in FIG. 2, a reflective layer 3 is formed on the substrate 2.

  The reflection layer 3 has a function of reflecting the incident laser beam via the light transmission layer 4 and emitting it again from the light transmission layer 4 side.

  In this embodiment, the material for forming the reflective layer 3 is not particularly limited as long as it can reflect a laser beam. Mg, Al, Ti, Cr, Fe, Co, Ni, Cu, Zn , Ge, Ag, Pt, Au, Nd, In, Sn can be used to form the reflective layer 3 with at least one metal selected from the group consisting of Sn, In and Sn. Among these, when the reflective layer 3 is formed of Ag or an alloy containing Ag, the reflective layer 3 having high reflectance and excellent surface flatness can be formed, which is preferable. .

  The thickness of the reflective layer 3 is not particularly limited, but is preferably 5 nm to 100 nm, and more preferably 15 nm to 60 nm.

  The reflective layer 3 is formed on the substrate 2 by a vapor phase growth method such as sputtering. Vapor phase growth methods such as sputtering are intended to eject atoms from the target by colliding ions accelerated in an electric field with the target, and depositing the ejected atoms to form a thin film. The surface shape of the substrate serving as a base is transferred to the formed thin film. Therefore, the surface shape of the substrate 2 is transferred to the reflective layer 3, and the concave portion 3 a corresponding to the concave pit 2 a on the surface of the substrate 2 is formed in the reflective layer 3.

  As shown in FIG. 2, a light transmission layer 4 is formed on the reflection layer 3.

  The light transmission layer 4 is a layer through which the laser beam is transmitted, and at the same time, serves as a protective layer for protecting the surface of the reflection layer 3.

  The light transmission layer 4 is optically transparent, requires little optical absorption and reflection in the wavelength region of the laser beam used, 380 nm to 450 nm, and has a low birefringence. It is formed.

  The ultraviolet curable resin used to form the light transmission layer 4 contains a photopolymerizable monomer, a photopolymerizable oligomer, a photoinitiator, and other additives as required. As the photopolymerizable monomer, a monomer having a molecular weight of less than 2000 is suitable, and examples thereof include monofunctional (meth) acrylate and polyfunctional (meth) acrylate. Examples of the photopolymerizable oligomer include oligomers containing or introduced in the molecule a group that crosslinks or polymerizes upon irradiation with ultraviolet rays, such as an acrylic double bond, an allylic double bond, and an unsaturated double bond. it can. Moreover, as a photoinitiator, you may use any well-known thing, for example, a molecular cleavage type photoinitiator can be used.

  The light transmission layer 4 is formed by applying an ultraviolet curable resin to the surface of the reflective layer 3 by spin coating or the like to form a coating film, and irradiating the coating film with ultraviolet rays to cure the ultraviolet curable resin. Formed. Alternatively, the light transmissive layer 4 can be formed by adhering a sheet formed of a light transmissive resin to the surface of the reflective layer 3 using an adhesive.

  The thickness of the light transmission layer 4 is preferably 30 μm to 200 μm.

  4 is a cross-sectional view taken along the line XX of FIG. 3 and is a schematic enlarged cross-sectional view showing the cross-sectional shapes of the surface of the substrate 2 and the surface of the reflective layer 3. In FIG. 4, an arrow L indicates the scanning direction of the laser beam.

  As shown in FIG. 4, a concave pit 2a is formed on the surface of the substrate 2, and a concave portion 3a corresponding to the concave pit 2a formed on the surface of the substrate 2 is formed on the reflective layer 3. Is formed.

  According to the inventor's research, even when the concave pit 2a and the space 2b are formed on the substrate 2 according to the data to be recorded, the data recorded on the next generation ROM type optical recording medium is reproduced. In some cases, the jitter characteristic of the reproduced signal is deteriorated because the length of the concave portion 3a of the reflective layer 3 is shorter than the concave pit 2a formed on the surface of the substrate 2, and the gap 3b between the adjacent concave portions 3a. Is longer than the space 2b formed on the surface of the substrate 2, and the length of the recess 3a of the reflective layer 3 and the gap 3b between the adjacent recesses 3a is detected by the photodetector. Therefore, it has been found that the length of the concavo-convex pattern recognized by the data reproducing apparatus is caused to become inconsistent with the length corresponding to the recorded data.

  Therefore, as a result of further research based on such knowledge, the present inventor has determined that the concave pit 2a on the surface of the substrate 2 has a length of (0.1 to 0.3) · D with respect to the basic length BL. The space 2b between the concave pits 2a adjacent to each other in the track direction is formed so as to be shorter than the basic length BL by a length of (0.1 to 0.3) · D. In such a case, the length of the recess 3a formed in the reflective layer 3 and the gap 3b between the recesses 3a should be substantially the same as the basic length BL corresponding to the data to be recorded. Found that it would be possible.

  Therefore, in the present embodiment, the concave pit 2a formed on the surface of the substrate 2 is formed so as to be longer than the basic length BL by a length of (0.1 to 0.3) · D. In addition, the space 2b between the concave pits 2a adjacent to each other in the track direction is formed to be shorter than the basic length BL by a length of (0.1 to 0.3) · D.

  Here, D is the distance from the surface of the reflective layer 3 to the surface of the substrate 2, and is the thickness of the reflective layer 3 in this embodiment. The basic length BL is a length determined according to the number of bits “0” or “1” of data to be recorded. For example, 2T modulated on the optical recording medium 1 by 1-7 RLL modulation. When recording 8 to 8T data with a recording capacity of 25 GB, seven lengths of 149 nm, 223.5 nm, 298 nm, 372.5 nm, 447 nm, 521.5 nm, and 596 nm corresponding to 2T to 8T are available. have.

  Therefore, in this embodiment, when 2T to 8T data modulated by 1-7 RLL modulation is recorded on the optical recording medium 1, the length of 149+ (0.1 to 0.3) · Dnm is shortest. 7 types of concave pits 2a having a maximum length of 596+ (0.1 to 0.3) · Dnm and a minimum length of 149− (0.1 to 0.3) · Dnm. 7 types of spaces 2b having a maximum length of 596- (0.1 to 0.3) · Dnm are combined in a predetermined combination on the surface of the substrate 2. To be formed.

  In the present embodiment, the recess 3a of the reflective layer 3 and the gap 3b between the recesses 3a both have substantially the same length as the basic length BL, which is the length corresponding to the recorded data. When the data recorded on the optical recording medium 1 is reproduced, the length of the concavo-convex pattern detected by the photodetector is substantially the same as the length corresponding to the recorded data. Therefore, a reproduction signal having good jitter characteristics can be obtained, and data can be reproduced as desired.

  The optical recording medium 1 having the above configuration is manufactured as follows.

  In manufacturing the optical recording medium 1, first, a photoresist master for forming the substrate 2 is manufactured, and then a stamper is formed by a mastering process using the photoresist master.

  5A to 5D are process diagrams showing a manufacturing process of a photoresist master for forming the substrate 2.

  As shown in FIG. 5A, first, a precisely polished and cleaned glass substrate 20 is set in a spin coating apparatus, and a coupling agent such as hexamethyldisilazane is placed on the surface of the glass substrate 20. Applied.

  Next, the glass substrate 20 on which the coupling agent has been applied is set in a spin coating apparatus, and a coating solution containing a photoresist having a skeleton resin such as a novolac resin or polystyrene resin on the glass substrate 20 is spun. By a coating method, it is uniformly applied to form a coating film.

  Thereafter, the coating film is baked, and a photoresist layer 21 is formed on the glass substrate 20 as shown in FIG. The photoresist layer 21 is formed to a thickness corresponding to the depth of the concave pit 2a to be formed on the surface of the substrate 2.

  Next, the glass substrate 20 is set on a turntable in the exposure apparatus, and the glass substrate 20 is rotated. As shown in FIG. 5C, the exposure laser beam 22 is applied to the photoresist layer 21. Irradiated.

  The exposure laser beam 22 is irradiated while moving along the radial direction of the glass substrate 20 from the center to the outer edge of the glass substrate 20 while the glass substrate 20 is rotated, and data to be recorded. Accordingly, the irradiation time and the irradiation interval are controlled by switching on / off.

  Thus, the surface of the photoresist layer 21 is intermittently irradiated with the exposure laser beam 22, and as a result, the photoresist layer 21 is exposed to the exposure region 21 a corresponding to the concave pit 2 a on the surface of the substrate 2 and the substrate 2. Unexposed areas 21b corresponding to the surface space 2b are alternately formed.

  Next, the glass substrate 20 on which the photoresist layer 21 is formed is immersed in an alkaline solution, and the photoresist layer 21 is developed to remove the exposed region 21a. In the present embodiment, the glass substrate 20 on which the photoresist layer 21 is formed is immersed in an alkaline solution for a longer time than usual, and the size of the removal region that is removed by development processing is enlarged.

  Since the exposure laser beam 22 is a Gaussian beam, the intensity of the exposure laser beam 22 is the strongest at the center portion of the beam spot and becomes weaker toward the peripheral portion. Therefore, in the exposure region 21a of the photoresist layer 21, the exposure region exposed by the portion where the intensity of the exposure laser beam 22 is weak is formed at both ends thereof, and in the other region, the exposure laser beam 22 is exposed. An exposed area is formed by a portion having a high intensity.

  In the present embodiment, as described above, the glass substrate 20 on which the photoresist layer 21 is formed is immersed in an alkaline solution for a longer time than usual. The exposure area exposed by the portion where the intensity of the beam 22 is weak is also removed. As a result, the length of the recess formed on the surface of the photoresist master 30 is increased, and at the same time, the length of the gap between the adjacent recesses is reduced. As shown in FIG. A concave pit 23a having a length (0.1 to 0.3) · D longer than the length BL and a length (0.1 to 0.3) · D shorter than the basic length BL And a space 23b having a surface of the photoresist master 30 is formed.

  When the photoresist master 30 is manufactured, a stamper having a concavo-convex pattern formed on the surface of the photoresist master 30 is then transferred to the surface, and the substrate 2 of the optical recording medium 1 is used by using this stamper. Is produced.

  6A to 6C are process diagrams showing a stamper manufacturing process.

  In producing the stamper, first, a chemical solution containing Pd chloride and Sn chloride is applied so as to cover the entire concave pits 23a and spaces 23b formed on the surface of the photoresist master 30.

  Thereafter, the photoresist master 30 is dipped in a borohydrofluoric acid solution to remove Sn attached to the photoresist master 30, and the surface of the photoresist master 30 is washed with pure water. On top, a Pd underlayer is formed.

  Next, the photoresist master 30 on which the Pd base is formed is immersed in a solution containing Ni ions, and as shown in FIG. 6A, the photoresist master 30 is formed on the photoresist master 30 by an electroless plating method. Then, an electroless nickel layer 42 is formed, and thereafter, an electrolytic nickel layer 43 is formed on the electroless nickel layer 42 by an electrolytic plating process using the electroless nickel layer 42 as an electrode.

  Thus, when the electrolytic nickel layer 43 is formed, as shown in FIG. 6B, the laminate 50 composed of the photoresist, the electroless nickel layer 42 and the electrolytic nickel layer 43 is integrally formed on the glass substrate 20. Is peeled off. Thereafter, the laminate 50 is immersed in an alkaline solution, and the photoresist is dissolved and removed.

  Furthermore, the laminate 50 from which the photoresist has been removed is dried, and as shown in FIG. 6C, a stamper 51 having convex pits 51a and spaces 51b is produced.

  In the present embodiment, as described above, the concave pit 23a having a length longer than the basic length BL by (0.1 to 0.3) · D is formed on the surface of the photoresist master 30 as described above. And a space 23b having a length shorter than the basic length BL by a length of (0.1 to 0.3) · D, is formed on the surface of the stamper 51. In contrast, the convex pit 51a having a length longer by (0.1 to 0.3) · D, and a length shorter by (0.1 to 0.3) · D than the basic length BL. And a space 51b having the same.

  When the stamper 51 is formed, the substrate 2 of the optical recording medium 1 is manufactured using the stamper 51.

  FIG. 7 is a process chart showing the manufacturing process of the optical recording medium 1.

  First, as shown in FIG. 7A, the stamper 51 is set in the mold 60. Thereafter, the mold 60 is set in an injection molding machine, and the molten polycarbonate resin is injected into the mold 60 at a high pressure.

  Thereafter, the polycarbonate resin is cured through a predetermined cooling period.

  Thus, as shown in FIG. 7B, with respect to the basic length BL, the concave pit 2a having a length of (0.1 to 0.3) · D and the basic length BL. , (0.1 to 0.3) · D, the substrate 2 formed with the space 2b having a short length is produced.

  Next, the substrate 2 is set in a sputtering apparatus, and as shown in FIG. 7B, the reflective layer 3 is formed on the surface of the substrate 2 by sputtering.

  Finally, the substrate 2 on which the reflective layer 3 is formed is set in a spin coating apparatus. As shown in FIG. 7C, the light transmission layer 4 is formed on the surface of the reflective layer 3 by spin coating. Thus, the optical recording medium 1 is completed.

  According to this embodiment, the concave pits 2a formed on the surface of the substrate 2 are formed so as to be longer than the basic length BL by a length of (0.1 to 0.3) · D. Since the space 2b between the concave pits 2a adjacent to each other in the direction is shorter than the basic length BL by a length of (0.1 to 0.3) · D, it is formed in the reflective layer 3. It is possible to make the length of the recess 3a and the gap 3b between the recesses 3a substantially coincide with the basic length BL. Therefore, when the data recorded on the optical recording medium 1 is reproduced, the lengths of the concavo-convex patterns detected by the photodetector almost coincide with the length corresponding to the recorded data. Can be obtained, and data can be reproduced as desired.

  FIG. 8 is a schematic enlarged cross-sectional view of a ROM type optical recording medium according to another preferred embodiment of the present invention.

  As shown in FIG. 8, the optical recording medium 70 according to this embodiment includes a substrate 72, a reflective layer 73 formed on the substrate 72, and a light transmission layer 74 formed on the reflective layer 73. Except that convex pits 72a are formed on the surface of the substrate 72 and data is recorded, it has the same configuration as the optical recording medium 1 shown in FIG.

  FIG. 9 is a schematic perspective view of the surface of the substrate 72, and FIG. 10 is a cross-sectional view taken along the YY axis of FIG. 9 and 10, both arrows L indicate the scanning direction of the laser beam.

  As shown in FIG. 9, a plurality of convex pits 72 a having a substantially elliptical shape are formed on the surface of the substrate 72. The plurality of convex pits 72a are formed in a spiral shape from the inner circumference side to the outer circumference side or from the outer circumference side to the inner circumference side of the optical recording medium 70, and constitute a track. In addition, regions other than the plurality of convex pits 72a are formed flat, and spaces 72b are formed between the convex pits 72a adjacent in the track direction. These convex pits 72a and spaces 72b are respectively associated with digital data “0” or “1”, and data is recorded by the convex pits 72a and spaces 72b.

  In the present embodiment, as shown in FIG. 10, the convex pits 72a on the surface of the substrate 2 are shorter than the basic length BL by a length of (0.1 to 0.3) · D. On the other hand, the space 72b between the convex pits 72a adjacent to each other in the track direction is formed to be longer than the basic length BL by a length of (0.1 to 0.3) · D. Yes.

  Also in this embodiment, D is the distance from the surface of the reflective layer 73 to the surface of the substrate 72, and the basic length BL is determined according to the number of bits of “0” or “1” of data to be recorded. Length.

  When the convex pits 72a and the spaces 72b on the surface of the substrate 72 have such lengths, the length of the gap 73b between the convex portions 73a and the convex portions 73a formed on the reflective layer 73 is data to be recorded. The length of the concavo-convex pattern detected by the photodetector when the data recorded on the optical recording medium 70 is reproduced can be recorded in accordance with the basic length BL which is a length corresponding to the recording length. The length corresponding to the recorded data can be substantially matched. Therefore, a reproduction signal having good jitter characteristics can be obtained, and data can be reproduced as desired.

  The optical recording medium 70 having the above configuration is manufactured as follows.

  In manufacturing the optical recording medium 70, first, a photoresist master is manufactured.

  In this embodiment, when producing the photoresist master, the glass substrate on which the photoresist layer is formed is immersed in an alkaline solution for a shorter time than usual. As a result, on the surface of the photoresist master, a concave pit having a length shorter by (0.1 to 0.3) · D than the basic length BL and (0.1 relative to the basic length BL). To 0.3) .D, a space having a length longer than D is formed.

  When the photoresist master is produced, a master stamper is then produced by a mastering process.

  In the present embodiment, as described above, the surface of the photoresist master has a concave pit having a length shorter by (0.1 to 0.3) · D than the basic length BL, Since a space having a length (0.1 to 0.3) · D longer than the basic length BL is formed, the surface of the master stamper has a length relative to the basic length BL. , A convex pit having a length shorter by (0.1 to 0.3) · D, and a space having a length longer by (0.1 to 0.3) · D than the basic length BL. It is formed.

  Thus, when the master stamper is manufactured, the mother stamper is manufactured by the mastering process based on the master stamper.

  FIG. 11 is a process diagram showing a mother stamper manufacturing process according to a preferred embodiment of the present invention.

  First, the master stamper 80 is immersed in a potassium permanganate solution, and the surface of the master stamper 80 is subjected to oxidation treatment. Next, the oxidized master stamper 80 is immersed in an electrolytic nickel solution, and a metal film is formed by electrolytic plating. As shown in FIG. 11A, the electrolytic nickel is deposited on the surface of the master stamper 80. Layer 91 is formed.

  Next, as shown in FIG. 11 (b), the electrolytic nickel layer 91 is peeled from the master stamper 80, and thereafter, the central hole and the outer periphery of the peeled electrolytic nickel layer 91 are punched, and the mother stamper 90 is Produced.

  In the present embodiment, as described above, the surface of the master stamper 80 has a convex pit 80a having a length shorter by (0.1 to 0.3) · D than the basic length BL. And a space 80b having a length (0.1 to 0.3) · D longer than the basic length BL is formed. Therefore, the surface of the mother stamper 90 has a basic length. A concave pit 90a having a length shorter by (0.1 to 0.3) · D than BL, and a length longer by (0.1 to 0.3) · D than the basic length BL. And a space 90b is formed.

  When the mother stamper 90 is manufactured, the mother stamper 90 is set in a mold, and then the substrate 72 is formed by injection molding. Thus, the convex pit 72a having a length shorter by (0.1 to 0.3) · D than the basic length BL, and (0.1 to 0.3) · D with respect to the basic length BL. A substrate 72 having a space 72b having a length that is as long as possible is produced.

  Thereafter, the reflection layer 73 and the light transmission layer 74 are sequentially formed on the surface of the substrate 72, and the optical recording medium 70 is completed.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

  For example, in the optical recording media 1 and 70 shown in FIGS. 2 and 8, the reflective layers 3 and 73 are formed on the surfaces of the substrates 2 and 72, but on the surfaces of the substrates 2 and 72, It is not always necessary to form the reflective layers 3 and 73, and one or more other layers may be interposed between the substrates 2 and 72 and the reflective layers 3 and 73. In this case, the sum of the thickness of the layers interposed between the substrates 2 and 72 and the reflective layers 3 and 73 and the thickness of the reflective layers 3 and 73 is determined from the surface of the reflective layers 3 and 73 from the surface of the substrates 2 and 72. Distance D to the surface.

  Further, in the optical recording media 1 and 70 shown in FIGS. 2 and 8, the light transmission layers 4 and 74 are formed on the surfaces of the reflection layers 3 and 73. It is not always necessary to form the light transmission layers 4 and 74 on the top, and one or more other layers may be interposed between the reflection layers 3 and 73 and the light transmission layers 4 and 74. .

  Further, in the embodiment shown in FIGS. 5 to 7, the substrate 2 of the optical recording medium 1 is manufactured by setting the stamper 51 to which the surface shape of the photoresist master 30 is transferred in a mold. However, it is not always necessary to prepare the substrate 2 of the optical recording medium 1 by setting the stamper 51 to which the surface shape of the photoresist master 30 is transferred to a mold, and the stamper 51 is used as the master stamper. The mother stamper and the child stamper may be manufactured from the above, and the child stamper among them may be set in a mold to manufacture the substrate 2 of the optical recording medium 1.

  In the above embodiment, the length of the concave pits and spaces or the length of the convex pits and spaces is adjusted by controlling the time for immersing the glass substrate on which the photoresist layer is formed in the alkaline solution. However, instead of controlling the time to immerse the glass substrate with the photoresist layer in the alkaline solution, for example, the exposure laser beam irradiation time is controlled to adjust the length of the exposure area. By doing so, the lengths of the concave pits and spaces or the convex pits and spaces may be adjusted.

FIG. 1 is a schematic perspective view of an optical recording medium according to a preferred embodiment of the present invention. FIG. 2 is a schematic enlarged cross-sectional view of a portion indicated by A in FIG. FIG. 3 is a schematic perspective view of the surface of the substrate. 4 is a cross-sectional view taken along the line XX of FIG. 3, and is a schematic enlarged cross-sectional view showing the cross-sectional shapes of the surface of the substrate and the surface of the reflective layer. FIG. 5 is a process diagram showing a manufacturing process of a photoresist master. FIG. 6 is a process diagram showing a stamper manufacturing process. FIG. 7 is a process diagram showing the manufacturing process of the optical recording medium. FIG. 8 is a schematic enlarged cross-sectional view of an optical recording medium according to another preferred embodiment of the present invention. FIG. 9 is a schematic perspective view of the surface of the substrate. FIG. 10 is a cross-sectional view of the YY-axis cross section of FIG. 9, and is a substantially enlarged cross-sectional view showing the cross-sectional shapes of the surface of the substrate and the surface of the reflective layer. FIG. 11 is a process diagram showing a manufacturing process of the mother stamper.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Optical recording medium, 2 ... Substrate, 2a ... Concave pit, 2b ... Space, 3 ... Reflection layer, 3a ... Recess, 3b ... Gap between recesses, 4 ... Light transmission layer, 5 ... Center hole, 20 ... Glass substrate 21 ... Photoresist layer, 21a ... Exposed area, 21b ... Unexposed area, 22 ... Laser beam for exposure, 23a ... Concave pit, 23b ... Space, 30 ... Photo resist master, 42 ... Electroless nickel layer, 43 ... Electrolytic Nickel layer, 51 ... stamper, 51a ... convex pit, 51b ... space, 60 ... mold, 70 ... optical recording medium, 72 ... substrate, 72a ... convex pit, 72b ... space, 73 ... reflective layer, 73a ... convex Part, 73b ... gap between convex parts, 74 ... light transmission layer, 80 ... master stamper, 90 ... mother stamper, 90a ... concave pit, 90b ... space, 91 ... electrolytic nickel layer

Claims (9)

A substrate having a plurality of concave pits formed on the surface, a light transmissive layer, and a reflective layer formed between the substrate and the light transmissive layer, are irradiated with a laser beam through the light transmissive layer. A ROM-type optical recording medium configured to reproduce data, wherein the concave pit has a length longer than a basic length BL determined according to data to be recorded, and a track A ROM type optical recording medium, wherein a length of a space between the concave pits adjacent to each other in a direction is shorter than the basic length BL. When the distance from the surface of the reflective layer to the surface of the substrate is D, the concave pit has a length of BL + (0.1 to 0.3) · D, and the space is BL−. 2. The ROM type optical recording medium according to claim 1, which has a length of (0.1 to 0.3) · D. A substrate having a plurality of convex pits formed on the surface, a light transmission layer, and a reflection layer formed between the substrate and the light transmission layer, and being irradiated with a laser beam through the light transmission layer The ROM type optical recording medium is configured such that data is reproduced as a result of which the convex pits have a length shorter than the basic length BL determined according to the data to be recorded. A ROM type optical recording medium, wherein a length of a space between the convex pits adjacent to each other in a track direction is longer than the basic length BL. When the distance from the surface of the reflective layer to the surface of the substrate is D, the convex pit has a length of BL- (0.1 to 0.3) · D, and the space is 4. The ROM type optical recording medium according to claim 3, wherein the ROM type optical recording medium has a length of BL + (0.1 to 0.3) .D. 5. The ROM type optical recording medium according to claim 1, wherein the reflective layer is made of Ag or an alloy containing Ag. 6. A stamper for manufacturing a ROM type optical recording medium, wherein a plurality of convex pits are formed on the surface, and the convex pits are determined according to data to be recorded on the ROM type optical recording medium. A stamper characterized in that the length of the space between the convex pits adjacent to each other in the track direction is shorter than the basic length BL. . The ROM type optical recording medium includes a substrate, a light transmission layer, and a reflection layer formed between the substrate and the light transmission layer, and the distance from the surface of the reflection layer to the surface of the substrate is D The convex pit has a length of BL + (0.1 to 0.3) · D, and the length of the space between the convex pits adjacent in the track direction is BL− ( The stamper according to claim 6, wherein the stamper has a length of 0.1 to 0.3) · D. A stamper for manufacturing a ROM type optical recording medium, wherein a plurality of concave pits are formed on a surface thereof, and the concave pits are determined according to data to be recorded on the ROM type optical recording medium A stamper characterized in that it has a length shorter than the length BL, and the length of the space between the concave pits adjacent in the track direction is longer than the basic length BL. The ROM type optical recording medium includes a substrate, a light transmission layer, and a reflection layer formed between the substrate and the light transmission layer, and the distance from the surface of the reflection layer to the surface of the substrate is D The concave pits have a length of BL− (0.1 to 0.3) · D, and the length of the space between the concave pits adjacent in the track direction is BL + (0. 9. The stamper according to claim 8, which has a length of 1 to 0.3) · D.

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