JP2006066004A - Rom-type optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ROM-type optical recording medium by which a reproduction signal having satisfactory jitter characteristics can be obtained and data can be desirably reproduced and which has excellent wear resistance and scratch resistance on an incident surface side. <P>SOLUTION: In the ROM-type optical recording medium including a substrate 2 having a plurality of concave pits formed on a surface thereof, a light transmission layer 4, a reflective layer 3 formed between the substrate 2 and the light transmission layer 4 and a hard coat layer 5 formed on the surface of the light transmission layer 4, and irradiated with a laser beam through the light transmission layer 4 to reproduce data, the concave pits 2a has a length longer than a basic length BL to be determined according to data to be recorded, and spaces 2b between the concave pits adjacent to each other in a track direction has a length shorter than the basic length BL. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ROM type optical recording medium, and more specifically, a reproduction signal having good jitter characteristics can be obtained, and data can be reproduced as desired. The present invention relates to a ROM type optical recording medium having excellent wear resistance and scratch resistance.

  Conventionally, optical recording media represented by CDs and DVDs are widely used as recording media for recording digital data. In these optical recording media, a ROM type optical recording housing in which data cannot be additionally written or rewritten, such as a CD-ROM or DVD-ROM, and data can be additionally written like a CD-R or DVD-R. The write-once optical recording medium that cannot rewrite data and the rewriteable optical recording medium that can rewrite data, such as CD-RW and DVD-RW, can be broadly classified.

  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 playing back 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, and the difference in the surface shape of the substrate Data can be reproduced by reading.

  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.

で示されるように、光記録媒体に対するレーザビームの光軸の傾きに許される角度誤差、すなわち、チルトマージンＴが非常に狭くなるという問題が生じる。 However, when the numerical aperture NA of the objective lens for focusing the laser beam is increased, the following equation (1),

As shown in FIG. 2, there arises a problem that 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 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.

  Further, with the spread of next-generation ROM type optical recording media, it is expected that the number of reproduction errors due to scratches on the light incident surface side of the light transmission layer will increase in the same way as in the past optical recording media. .

  Accordingly, an object of the present invention is to obtain a reproduction signal having good jitter characteristics, to reproduce data as desired, and to be a ROM type excellent in wear resistance and scratch resistance on the incident surface side. It is to provide an optical recording medium.

  As a result of intensive studies to solve the above problems, the present inventors have developed a next-generation ROM type optical recording even when concave pits and spaces are formed on the substrate according to the data to be recorded. When the data recorded on the medium 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 the adjacent concave portion The length of the gap between them is longer than the space formed on the surface of the substrate, and the length of the gap between these reflection layers and the gap between the depressions is detected by the photodetector, so it is recognized by the data reproduction device It has been found that the length of the uneven pattern to be formed is caused by the fact that it does not match the length corresponding to the recorded data. In addition, the deterioration of the jitter characteristics of the reproduced signal seen when the convex pits and spaces are formed on the substrate was also recorded in the lengths of the convex pits and spaces detected by the photodetector, respectively. We found out that it is caused by the fact that it does not match the length corresponding to the data. Furthermore, it is effective to provide a hard coat layer on the surface of the light transmission layer in order to improve the wear resistance and scratch resistance on the light incident surface side of the light transmission layer without adversely affecting the jitter characteristics of the reproduced signal. I found out. The present invention has been completed based on this finding.

  That is, the ROM type optical recording medium of the present invention comprises a substrate having a plurality of concave pits formed on the surface thereof, a light transmission layer, a reflection layer formed between the substrate and the light transmission layer, and the light A ROM type optical recording medium comprising: a hard coat layer formed on a surface of a transmission layer; and a laser beam irradiated through the light transmission layer to reproduce data. The concave pit has a length longer 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 shorter than the basic length BL. It is characterized by having a thickness.

  Thereby, the length of the recess formed in the reflective layer and the length of the gap between the recesses can be made substantially coincident with the basic length BL which is the length corresponding to the data to be recorded, so that the data recorded on the optical recording medium The length of the concave pits and spaces detected by the photodetector is almost the same as the length corresponding to the recorded data, so that a reproduced signal having good jitter characteristics can be obtained. The data can be reproduced as desired. Further, by providing the hard coat layer, the wear resistance and scratch resistance on the incident surface side are improved, and the ROM type optical recording medium can be used without being housed in the cartridge.

  In addition, another ROM type optical recording medium of the present invention includes a substrate having a plurality of convex pits formed on the surface thereof, a light transmission layer, and a reflection layer formed between the substrate and the light transmission layer. And a hard coat layer formed on the surface of the light transmission layer, and a ROM type optical recording medium configured to reproduce data by being irradiated with a laser beam through the light transmission layer. The convex pit has a length shorter than the basic length BL determined according to data to be recorded, and the length of the space between the convex pits adjacent in the track direction is the basic length. It has a length longer than the length BL.

  As a result, the length of the protrusion formed on the reflective layer and the length of the gap between the protrusions can be substantially matched with the basic length BL, which is the length corresponding to the data to be recorded. When the recorded data is reproduced, the lengths of the convex pits and spaces detected by the photodetector are approximately 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. Further, by providing the hard coat layer, the wear resistance and scratch resistance on the incident surface side are improved, and the ROM type optical recording medium can be used without being housed in the cartridge.

  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 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, a reproduction signal having good jitter characteristics can be obtained, data can be reproduced as desired, and ROM-type light having excellent wear resistance and scratch resistance on the incident surface side. A recording medium can be provided.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a partially cutaway perspective view showing an outline of a ROM type optical recording medium having concave pits on a substrate according to a preferred embodiment of the present invention, and FIG. 2 is an outline of a portion indicated by A in FIG. It is an expanded sectional view.

  As shown in FIG. 1, the optical recording medium 1 has a disk shape, and a center hole 6 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 FIG. 1 and FIG. 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 indicated by the arrow in FIG. Data is configured to be played back.

  As shown in FIG. 2, the optical recording medium 1 according to this embodiment includes a substrate 2, a reflective layer 3 formed on the substrate 2, a light transmissive layer 4 formed on the reflective layer 3, and a light transmissive layer. A hard coat layer 5 formed on the layer 4.

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 elliptic 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 of the optical recording medium 1, and constitute a track. Further, 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 laser beam incident through the hard coat layer 5 and the light transmission layer 4 and emitting it again from the hard coat layer 5 side.

  In the present invention, 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, The reflective layer 3 can be formed of at least one metal selected from the group consisting of Ge, Ag, Pt, Au, Nd, In, and Sn, or an alloy thereof. Among these, when the reflective layer 3 is formed of Ag or an alloy containing Ag, the reflective layer 3 having high reflectivity and excellent surface flatness can be formed. It is possible to reduce noise included in the reproduction signal, 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 and a hard coat layer 5 are sequentially 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. . 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.

  The hard coat layer 5 has a function of protecting the optical recording medium 1 and making the optical recording medium 1 usable without being accommodated in a cartridge.

  In the present invention, the surface of the hard coat layer 5 preferably has a hardness of B or more in a pencil hardness test.

  As the resin material used for forming the hard coat layer 5, a known inorganic or organic compound can be used. As the organic compound, for example, an active energy ray-curable resin can be preferably exemplified. For example, the organic compound may be a compound having at least one active group selected from the group consisting of a (meth) acryloyl group, a vinyl group, and a mercapto group. For example, there is no particular limitation.

  In the present invention, the compound having a (meth) acryloyl group used to form a hard coat layer includes trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, urethane (meth) acrylate, and ester. Examples include (meth) acrylate.

  The film thickness of the hard coat layer 5 is preferably 0.5 to 5 μm. When a hard coat layer is formed on the light transmission layer 4, the total thickness is preferably 70 to 150 μm.

  The hard coat layer 5 includes inorganic fine particles such as silica fine particles having an average particle diameter of 5 nm or more and 100 nm or less, preferably inorganic fine particles having an average particle diameter of 5 nm or more and 20 nm or less in order to further improve the wear resistance. You can also

  The light transmissive layer 4 and the hard coat layer 5 may be formed of a non-polymerizable diluent solvent, an organic filler, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a leveling agent, or a lubrication as necessary. Agents, pigments, silicon compounds and the like may be included. Silicone compounds such as silicone can be used as the leveling agent or lubricant, and fluorine compounds can be used as the lubricant.

  Similarly to the light transmissive layer 4, the hard coat layer 5 can be formed by a method of applying by a spin coat method or a method of pasting a material formed in a sheet shape on the light transmissive layer 4.

  Moreover, when producing the hard-coat layer 5 using an inorganic compound, as this inorganic compound, silicon nitride, zinc oxide, etc. can be used, for example, and it can form by vapor phase growth methods, such as sputtering. The thickness is preferably 100 nm or less. It can also be formed by coating.

  FIG. 4 is a cross-sectional view in the substrate thickness direction along the line XX in 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 is formed on the reflective layer 3 corresponding to the concave pit 2a formed on the surface of the substrate 2. 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 this embodiment, the concave pit 2a formed on the surface of the substrate 2 is formed to be longer than the basic length BL by a length of (0.1 to 0.3) · D, On the other hand, the space 2b between the concave pits 2a adjacent 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 the 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 space 2b having a length of 596- (0.1 to 0.3) · Dnm at the longest are combined in a predetermined combination on the surface of the substrate 2. 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.

  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.

  In this embodiment, first, on the surface of the photoresist master, a concave pit having a length that is longer by (0.1 to 0.3) · D than the basic length BL, and the basic length BL. On the other hand, a space having a length shorter by (0.1 to 0.3) · D is formed. Next, using this photoresist master, on the surface of the stamper, a convex pit having a length (0.1 to 0.3) · D longer than the basic length BL and the basic length BL. , A space having a length shorter by (0.1 to 0.3) · D. Thereafter, the substrate 2 of the optical recording medium 1 is manufactured using the stamper 51.

FIG. 5 is a process diagram showing the manufacturing process of the optical recording medium 1.
First, as shown in FIG. 5A, 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. 5B, with respect to the basic length BL, a concave pit having a length of (0.1 to 0.3) · D and the basic length BL ( The substrate 2 in which a space having a length shorter by 0.1 to 0.3) · D is formed.

  Next, the substrate 2 is set in a sputtering apparatus, and as shown in FIG. 5B, the reflective layer 3 is formed on the surface of the substrate 2 by sputtering.

  Next, the substrate 2 on which the reflective layer 3 is formed is set in a spin coating apparatus, and as shown in FIG. 5C, the light transmission layer 4 is formed on the surface of the reflective layer 3 by spin coating. It is formed.

  Finally, the substrate 2 on which the light transmissive layer 4 is formed is set in a spin coating apparatus in the same manner as described above, and as shown in FIG. 5D, the surface of the light transmissive layer 4 is formed by spin coating. The hard coat layer 5 is formed, and 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.

  Further, by providing the hard coat layer 5 on the surface of the light transmission layer 4, the wear resistance and scratch resistance on the incident surface side are improved, and the optical recording medium 1 can be used without being housed in the cartridge.

  Next, FIG. 6 shows a schematic enlarged cross-sectional view of a ROM type optical recording medium having convex pits on a substrate according to another preferred embodiment of the present invention.

  As shown in FIG. 6, the optical recording medium 70 according to the present embodiment includes a substrate 72, a reflective layer 73 formed on the substrate 72, a light transmissive layer 74 formed on the reflective layer 73, and light transmission. And a hard coat layer 75 formed on the layer 74. The optical recording medium 70 is the same as the optical recording medium 1 according to the preferred embodiment shown in FIG. 2 except that convex pits 72a are formed on the surface of the substrate 72 and data is recorded. It has a configuration.

  FIG. 7 is a schematic perspective view of the surface of the substrate 72, and FIG. 8 is a cross-sectional view in the substrate thickness direction along the line YY of FIG. In FIGS. 7 and 8, both arrows L indicate the scanning direction of the laser beam.

  As shown in FIG. 7, 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 this embodiment, as shown in FIG. 8, the convex pits 72a on the surface of the substrate 72 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. .

  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.

  In manufacturing the optical recording medium 70, 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.

  On the surface, a concave pit having a length shorter by (0.1 to 0.3) · D than the basic length BL and only (0.1 to 0.3) · D with respect to the basic length BL After the mother stamper in which the space having a long length is formed is set in the mold, 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, in the same manner as in the preferred embodiment, the reflection layer 73, the light transmission layer 74, and the hard coat layer 75 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 embodiment, and various modifications can be made. For example, in the optical recording media 1 and 70 according to the preferred embodiments shown in FIGS. 2 and 6, the reflective layers 3 and 73 are formed on the surfaces of the substrates 2 and 72. It is not always necessary to form the reflective layers 3 and 73 on the surface, 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.

  In the optical recording media 1 and 70 according to the preferred embodiments shown in FIGS. 2 and 6, the light transmission layers 4 and 74 are formed on the surfaces of the reflection layers 3 and 73. , 73 is not necessarily formed on the surface of the light-transmitting layer 73, and one or more other layers are interposed between the reflective layers 3, 73 and the light-transmitting layers 4, 74. May be.

1 is a partially cutaway perspective view showing an outline of a ROM type optical recording medium according to a preferred embodiment of the present invention. It is a general | schematic expanded sectional view of the part shown by A of FIG. It is a schematic perspective view of the surface of a board | substrate. It is sectional drawing of the board | substrate thickness direction which follows the XX line | wire of FIG. 3, It is a general | schematic expanded sectional view which shows the cross-sectional shape of the surface of a board | substrate and the surface of a reflective layer. It is process drawing which shows the manufacturing process of an optical recording medium. It is a general | schematic expanded sectional view of the ROM type optical recording medium which concerns on the other preferable embodiment of this invention. It is a schematic perspective view of the surface of a board | substrate. It is sectional drawing of the board | substrate thickness direction which follows the YY line | wire of FIG. 7, and is a schematic expanded sectional view which shows the cross-sectional shape of the surface of a board | substrate and the surface of a reflection layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical recording medium 2 Substrate 2a Concave pit 2b Space 3 Reflective layer 3a Concave 3b Space between concave parts 4 Light transmission layer 5 Hard coat layer 51 Stamper 60 Mold 70 Optical recording medium 72 Substrate 72a Convex pit 72b Space 73 Reflective layer 73a Convex part 73b Interval between convex parts 74 Light transmission layer 75 Hard coat layer

Claims (6)

  A substrate having a plurality of concave pits formed on the surface thereof, a light transmission layer, a reflection layer formed between the substrate and the light transmission layer, and a hard coat layer formed on the surface of the light transmission layer; A ROM type optical recording medium configured to reproduce data by being irradiated with a laser beam through the light transmission layer, wherein the concave pit is determined according to data to be recorded The ROM has a length longer than the basic length BL, and the length of the space between the concave pits adjacent in the track direction is shorter than the basic length BL. Type optical recording medium.   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, having a length of (0.1 to 0.3) .D.   The ROM type optical recording medium according to claim 1, wherein the hard coat layer contains an active energy ray-curable resin.   A substrate having a plurality of convex pits formed on its surface, a light transmission layer, a reflection layer formed between the substrate and the light transmission layer, and a hard coat formed on the surface of the light transmission layer A ROM-type optical recording medium configured to reproduce data by being irradiated with a laser beam through the light transmission layer, wherein the convex pits are recorded on the data to be recorded. The length of the space between the convex pits adjacent to each other in the track direction is longer than the basic length BL. Characteristic ROM type optical recording medium.   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 5. The ROM type optical recording medium according to claim 4, wherein the ROM type optical recording medium has a length of BL + (0.1 to 0.3) .D.   The ROM type optical recording medium according to claim 4, wherein the hard coat layer contains an active energy ray-curable resin.

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