JP4308117B2 - Information recording method and apparatus, and information recording medium - Google Patents

Description

  The present invention relates to an information recording medium and a method and apparatus for recording information on the information recording medium.

In recent years, with the increase in the amount of information that can be recorded on one optical recording medium, the distribution of software recorded on the optical recording medium, and the development of technology for preventing unauthorized copying, individual identification information for optical recording media has been developed as a so-called security technology. Is required to be recorded.
In response to this demand, for example, an additional recording area (Burst Cutting Area, hereinafter referred to as “BCA”) in which a barcode is overwritten is provided in the pit portion of a read-only optical recording medium as identification information for the optical recording medium. A technique for recording identification information (ID) that differs for each optical recording medium in the BCA area at the time of manufacturing the medium, and, if necessary, an encryption key and a decryption key is generally applied.

  On the other hand, a recordable optical information recording medium having an information layer capable of recording an information signal only once and having a single recording layer, or a rewritable optical information recording medium having an information layer capable of freely rewriting an information signal has been developed. The variety of media types is increasing (hereinafter referred to as “single-layer type optical disc” including recording type and rewritable type). Furthermore, an optical disc having a plurality of recording layers (hereinafter referred to as “multi-layer type optical disc” including a recording type and a rewritable type) capable of high-capacity recording such as high-definition video has been put into practical use.

In these single-layer type optical discs and multilayer type optical discs, information can be freely recorded. Therefore, handling of recorded information with respect to security is more and more important.
Correspondingly, as a method for recording an ID on an optical disk, for example, for a phase change optical disk, an amorphous part and a crystal part are alternately generated using a laser beam, and the difference in reflectance is used. An example of creating a BCA has been reported (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2001-243636 (page 16, FIG. 3)

  However, in the above conventional configuration, since the medium identification information is recorded by irradiating the laser beam from the normal information recording / reproducing surface side, the multilayer type optical disc can be used for the recording conditions of the medium identification information of the single layer type optical disc. The recording conditions when recording the medium identification information on the recording layer farthest from the laser irradiation side must be changed greatly in consideration of the effect of the previous layer, and the BCA preparation apparatus becomes complicated. In addition, in the case of recording materials that are generally highly wavelength-dependent, such as organic dyes, stable recording is difficult because the recording conditions differ due to slight changes in the recording wavelength and slight differences in the optical properties of the dye material. It had the problem that.

  Further, the recording medium in Patent Document 1 is a rewritable phase change recording medium, and the recording mode at the time of BCA processing is the same as that at the time of erasing in normal recording, and is relatively low temperature, so that the recording layer is damaged during processing. There are few things. On the other hand, the recording mode at the time of BCA processing of the write-once type phase change recording medium is the same as the normal recording, and a high temperature is required. Moreover, since recording is performed with a laser spot having a large area, recording is performed by applying energy several hundred times that of normal recording. For this reason, since a high temperature portion is formed on the recording layer in a very wide range, the recording layer is damaged, and there is a problem that the signal quality at the time of BCA reproduction is deteriorated.

  The present invention solves the above-described conventional problems. A method, an apparatus, and a device for realizing medium identification information recording easily and stably in a write-once recording medium and a recording material having a large wavelength dependency. An object is to provide an optical disk on which a BCA pattern is formed.

In order to solve the above problems, an information recording apparatus and method according to the present invention perform recording or reproduction of user data on a disc-shaped information recording medium having an information recording layer including a recording layer and a light absorption layer. An information recording apparatus and method for recording medium identification information by irradiating a laser beam from the opposite surface . The light absorption layer is disposed between the surface irradiated with the laser beam and the recording layer, the light absorption layer is heated by the laser beam, and medium identification information is indirectly recorded on the recording layer by heat propagation.
With this configuration, even when the information recording layer is a single layer or multiple layers, the path until the laser beam is incident and the medium identification information is recorded becomes the same, so that the medium identification information can be recorded under the same recording conditions.

With this configuration, the information recording layer is indirectly recorded through the light absorption layer, so that the medium identification information can be stably recorded while suppressing thermal deformation of the information recording layer.
In addition, the light absorption layer of the information recording medium used in the information recording method of the present invention functions as a reflective layer when recording or reproducing user data.

With this configuration, it is not necessary to newly provide a light absorption layer, and good medium identification information can be recorded at low cost .

In the information recording method of the present invention, the laser beam to be irradiated is in a defocused state with respect to the light absorption layer, and the information recording apparatus of the present invention includes a focus control means for realizing the defocused state. Yes.

With this configuration, the light is appropriately dispersed and the recording layer is not suddenly changed in temperature, so that there is little physical damage to the recording layer or the substrate.
If the defocus amount is too small, the effect is small, and if it is too large, a large laser power is required. Therefore, the defocus range is preferably from plus or minus 2 to 10 times the depth of focus.

In the information recording medium used in the information recording method of the present invention , the recording layer is preferably made of a phase change recording material.
With this configuration, it is possible to record good medium identification information using the difference in reflectance between the crystalline state and the amorphous state. The information recording layer is made of a write-once phase change recording material, and the medium identification information is recorded by changing the amorphous phase of the information recording layer to a crystalline phase. In this case, the information recording layer is in a high temperature state, but since the information recording layer is indirectly recorded via the light absorption layer, the medium identification information can be stably recorded while suppressing thermal deformation of the information recording layer. .

In the information recording medium used in the information recording method of the present invention , the recording layer is preferably made of an organic dye type recording material.
With this configuration, the organic dye recording material becomes a thermal recording that receives heat generated by the light absorption layer, and is not affected by the subtle light absorption characteristics unique to the dye material, so that stable recording can be performed.

In the information recording apparatus of the present invention, the disk mounting portion is provided with a centering mechanism for correcting the center position at the inner peripheral portion opposite to the laser beam incident side for recording the medium identification information from the optical pickup to the disk. ing.
With this configuration, when using a downward-facing laser pickup for safety reasons, centering can be performed on the opposite side of the pickup, making it efficient and suitable for mass production using air adsorption for disk mounting. An information recording apparatus can be realized.

  According to the information recording method of the present invention, the medium identification information is recorded by irradiating the laser beam from the surface opposite to the surface on which user data is recorded or reproduced. Regardless, even in the case of a recording material having a large wavelength dependency, the BCA pattern can be formed easily and stably.

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the case where the information recording layer is made of a write-once type phase change recording material is explained, but the same can be explained when the information recording layer is made of a rewritable phase change recording material or an organic dye type recording material. .
<Embodiment>
FIG. 1 is a cross-sectional view of an information recording layer single layer type optical disc 5 used in an information recording method according to an embodiment of the present invention.

In FIG. 1, 11a is a front side dielectric layer, 11c is a back side dielectric layer, 11b is a recording layer, 11d is a reflective layer, 1 is a substrate, and 2 is a cover layer. On a transparent substrate 1 made of polycarbonate having a thickness of 1.1 mm having a tracking groove, a reflective layer 11d made of Al alloy is 40 nm by vacuum sputtering, a back side dielectric layer 11c made of ZnS-SiO ₂ is 30 nm, Te A recording layer 11b made of —O—Pd and a front dielectric layer 11a made of ZnS—SiO ₂ were sequentially formed to 40 nm, and a transparent cover layer made of polycarbonate having a thickness of 0.1 mm by an adhesive not shown. A single-layer type optical disc 5 was prepared by bonding 2 to each other.

The reflective layer 11d also functions as a light absorption layer. In the present embodiment, the medium identification information recording laser beam 4 is irradiated from the substrate 1 side, and user data recording is performed by irradiating the laser beam from the cover layer 2 side.
FIG. 2 is a cross-sectional view of the information recording layer double-layer optical disc 6 used in the information recording method according to the embodiment of the present invention.

In FIG. 2, 12a is the second front dielectric layer, 12c is the second back dielectric layer, 12b is the second recording layer, 12d is the second reflective layer, and 1 is the substrate. 3 is an intermediate layer, and 2b is a cover layer. A reflective layer 11d, a back side dielectric layer 11c, a recording layer 11b, and a front side dielectric layer 11a are sequentially formed on a transparent substrate 1 by a vacuum sputtering method in the same manner as in a single-layer optical disk, and then UV-cured. The intermediate layer 3 made of resin is provided with a thickness of 25 μm, and the second reflective layer 12d made of Al alloy is 10 nm by vacuum sputtering, the second back side dielectric layer 12c made of ZnS—SiO ₂ is 15 nm, and the second reflective layer 12c made of Te—O—Pd is used. the layers th recording layer 12b 10 nm, and 20nm sequentially formed second layer front dielectric layer 12a due to ZnS-SiO _2, polycarbonate transparent cover layer having a thickness of 0.075mm by adhesive (not shown) By bonding 2b, a double-layered optical disk 6 was produced. In the present embodiment, the medium identification information recording laser beam 4 is irradiated from the substrate 1 side, and user data recording is performed by irradiating the laser beam from the cover layer 2 side.

FIG. 3 is a cross-sectional view of the information recording layer four-layer type optical disc 7 used in the information recording method according to the embodiment of the present invention.
In FIG. 3, 13a is the second front dielectric layer, 13c is the second back dielectric layer, 13b is the second recording layer, 14a is the third front dielectric layer, and 14c is the third layer. The back side dielectric layer, 14b is the third layer recording layer, 15a is the fourth layer front side dielectric layer, 15c is the fourth layer back side dielectric layer, 15b is the fourth layer recording layer, 1 is the substrate, 3b, 3c and 3d are intermediate layers, and 2c is a cover layer. A reflective layer 11d, a back side dielectric layer 11c, a recording layer 11b, and a front side dielectric layer 11a are sequentially formed on a transparent substrate 1 by a vacuum sputtering method in the same manner as in a single-layer optical disk, and then UV-cured. An intermediate layer 3b made of a resin is provided with a thickness of 15 μm, and a second back side dielectric layer 13c made of ZnS—SiO _{2 is formed} by vacuum sputtering to 10 nm, a second recording layer 13b made of Te—O—Pd is made 15 nm, and ZnS—SiO ₂ Next, the second front side dielectric layer 13a by 20 nm is sequentially formed, and then an intermediate layer 3c made of UV curable resin is provided by 15 μm. Further, the third back side dielectric layer 14c by ZnS-SiO _{2 is formed} by vacuum sputtering. the 5 nm, the third layer recording layer 14b by Te-O-Pd 10nm, a ZnS-SiO ₂ by the three-layer front dielectric layer 14a are sequentially formed 15 nm, then, It provided 15μm intermediate layer 3d by external curing resin, further 5nm a fourth layer inner side dielectric layer 15c by the ZnS-SiO ₂ by vacuum sputtering, Te-O-Pd 10nm four-layer recording layer 15b by, ZnS- A four-layer type optical disk is formed by sequentially depositing a 15 nm-thick dielectric layer 15a on the front side of SiO ₂ and bonding a transparent cover layer 2c made of polycarbonate having a thickness of 0.06 mm with an adhesive (not shown). 7 was created.

In the present embodiment, the medium identification information recording laser beam 4 is irradiated from the substrate 1 side, and user data recording is performed by irradiating the laser beam from the cover layer 2 side.
FIG. 4 is a cross-sectional view of the coated optical disk 8 used in the information recording method in the embodiment of the present invention.

  In FIG. 4, 16b is a recording layer, 16d is a reflective layer, 1b is a coating type substrate, and 2d is a dummy substrate. On the transparent coating type substrate 1b made of polycarbonate having a tracking groove having a thickness of 0.6 mm, an azo organic dye is applied in an average of 100 nm by a spin coating method, and a reflective layer 16d made of an Al alloy by vacuum sputtering. Was coated with a transparent dummy substrate 2d made of polycarbonate having a thickness of 0.6 mm by using an adhesive (not shown) to prepare a coated optical disk 8. In the present embodiment, the medium identification information recording laser beam 4 is irradiated from the dummy substrate 2d side, and the user data recording is performed by irradiating the laser beam from the coating type substrate 1b side.

FIG. 5 is a diagram showing an example of the information recording method in the embodiment of the present invention. However, some components are omitted for the sake of clarity.
The medium identification information is a signal corresponding to a unique serial number for each disc, and is recorded as a barcode-like signal in a part of the lead-in area of the disc. In FIG. 5, the incident side of the medium identification information recording laser beam with respect to the single layer type optical disc 5 and the double layer type optical disc 6 is the substrate 1 side opposite to the time of user data recording. With this configuration, in the double-layer optical disc 6, the medium identification information is recorded on the first recording layer 11b, but is not affected by the second recording layer 12b or the like. Therefore, the medium identification information can be recorded on the double-layer optical disk 6 under the same recording conditions as the single-layer optical disk 5.

FIG. 12 is a diagram showing an example of a conventional information recording method for comparison.
In FIG. 12, the incident side of the medium identification information recording laser beam with respect to the single-layer type optical disc 105 and the double-layer type optical disc 106 is the same as the cover layers 102 and 102b side during user data recording. In the two-layer optical disc 106, the medium identification information is recorded in the first recording phase 111b, but is affected by the second recording layer 112b and the like. Therefore, it is necessary to set a medium identification information recording condition different from the recording condition of the single-layer optical disk 105 in the dual-layer optical disk 106.

FIG. 6 is an explanatory diagram of the recording mechanism in the embodiment of the present invention.
In FIG. 6, (b) is a conventional medium identification information recording method. Since the laser beam 121a is focused directly on the recording layer 111b and heated, the recording layer 111b is thermally damaged and the recording mark 122a is deformed. It will be a thing. (A) illustrates indirect heating recording which is a feature of the recording method of the present invention. The medium identification information recording laser beam 21b first heats the reflective layer 11d, which is a light absorption layer, and heats the recording layer 11b by heat conduction or heat radiation. The advantage of this method is that it does not cause a sudden temperature change in the recording layer, so that there is little physical damage to the recording layer or the substrate. Further, this advantage can be further enhanced by expanding the beam spot of the medium identification information recording laser beam 21b on the reflecting layer 11d and lowering the power density.

FIG. 7 is an explanatory diagram of defocus recording in the embodiment of the present invention.
In FIG. 7, (b) shows a state where the reflection layer 11d is in focus, 23 is a medium identification information recording laser beam, 24 is a reflection layer heating unit, and 25 is a depth of focus. Further, (a) is a state where defocusing is performed on the front side, and 26a is a minus side defocus amount. (C) is a state of defocusing to the back side, and 26b is a plus side defocus amount. Although the reflective layer heating unit 24 is very narrow in the focused state (b), it is expanded in the defocused states (a) and (c), and the power density is lowered, so that it is more stable. The medium identification information can be recorded on the recording layer 11b. If the defocus amount is too small, the effect is small, and if it is too large, the recording power increases.

  In general, the depth of focus Δs is expressed by the following formula 1.

FIG. 8 is a characteristic diagram showing the effect of the defocus amount in the present embodiment. The sample uses two layers, and the laser incident side is the opposite side of the user data recording side.
From FIG. 8, when defocus is not added (defocus 0), the modulation factor min is 0.73, but when defocus is added, the modulation factor min is improved. However, when the defocus amount exceeds ± 10 × Δs, the energy is excessively dispersed, so that the temperature increase necessary for recording cannot be obtained and the modulation degree cannot be secured. From this result, the defocus amount exhibiting particularly good characteristics was ± 2 to 10 × Δs.

In addition, as a method for reducing the power density, the same effect can be obtained by reducing the NA of the lens or intentionally giving aberration to the lens.
However, the size (width) of the beam spot needs to be smaller than the size (width) of the minimum recording mark. This is to solve the tendency that the recording mark becomes larger than the beam spot because the recording is indirectly performed on the recording layer by heat propagation.

  Further, the recording method of the present invention has an advantage that the light absorption characteristics of the recording material of the recording layer can be ignored because the light absorption layer is heated and recorded indirectly. Therefore, in a recording layer using an organic dye, recording can be performed by thermal recording regardless of whether there is absorption at the recording wavelength.

FIG. 9 is a diagram for explaining an example of the information recording method in the embodiment of the present invention.
In FIG. 9, reference numeral 31 denotes a laser beam condensing spot, 32 denotes a radial length of the condensing spot, and 33 denotes an amount of movement of the optical pickup per one rotation of the disk. In the present embodiment, recording is performed by shifting from an amorphous state to a crystalline state using a laser focused spot 31 that is long in the radial direction of the disc, and recording is continued by 33 optical pickup movements per rotation of the disc. The BCA pattern will be completed.

FIG. 10 is a diagram showing a reproduction signal of medium identification information.
In FIG. 10, 41 is an unrecorded output, 42 is a modulation depth max indicating the recording depth when the unrecorded output 41 is 1, 43 is a modulation depth min, and the detection pickup is for recording / reproducing user data. Is used. The quality of the reproduced signal is better as the values of the modulation degree max42 and the modulation degree min43 are larger and the difference between the modulation degree max42 and the modulation degree min43 is smaller.

The signal quality when recording and reproducing the medium identification information using the single layer type optical disc 5, the double layer type optical disc 6, the four layer type optical disc 7, and the coating type optical disc 8 in FIGS. 1 to 4 is shown. Table 1 below.
The laser used for recording has a wavelength of 810 nm, the radial length of the condensing spot is 48 μm, the circumferential NA is 0.5, the radial movement amount per rotation of the disk is 6 μm, and the circumferential length of the recording mark. The length was 17 μm and the linear velocity was about 6 m / sec. Further, the laser wavelength of the reproduction pickup is 405 nm, and the NA is 0.85. The reproduction power is 0.35 mW.

  In Table 1, no. No. 1 is a result of recording medium identification information from the surface opposite to the user data recording side (Back) without defocusing. 2 is No.2. As a result of performing recording with the relative distance between the recording condensing lens and the optical disc being 5 × Δs apart (defocused) as compared with No. 1. 3 is the result of recording (defocusing) closer to 5 × Δs. 4 is a conventional example, and shows the result of recording medium identification information from the user data recording side (Front).

  In the conventional example, the recording power is different between a single layer, two layers, and four layers. Further, the modulation factor min is as small as about 0.4, and the difference from the modulation factor max is large. On the other hand, in the embodiment of the present invention, the recording power of the single layer, the double layer, and the four layers is the same. The modulation factor min is 0.6 or more, and the difference from the modulation factor max is small compared to the conventional example. Even in the coating type, the difference in the degree of modulation was small. No. with defocus added. 2, no. 3, the difference between the modulation factor min and the modulation factor max is further reduced, and stable medium identification information recording can be realized.

  As described above, in the embodiment of the present invention, the medium identification information recording laser beam for the optical disc is irradiated from the opposite side of the substrate as that during user data recording. With this configuration, a multilayer optical disc is not affected by the second and subsequent recording layers and the like, so that medium identification information can be recorded under the same recording conditions as a single-layer optical disc. In addition, the recording layer is recorded via the reflective layer, so that the deformation of the recording layer due to rapid temperature addition is alleviated and stable recording becomes possible. Furthermore, by defocusing the laser beam with respect to the recording layer within a certain range, there is an effect of mitigating rapid temperature application, and more stable recording is possible. In addition, since the organic dye recording material is heat-recorded in response to heat generated by the light absorption layer, it is not affected by the light absorption characteristics of the dye, so that the medium identification information can be recorded satisfactorily.

FIG. 11 is a sectional view showing the information recording apparatus of the present invention.
In FIG. 11, 51 is a medium identification information recording optical pickup, 52 is a turntable, 53 is a centering mechanism, 54 is a motor, and 55 is a focus control means. The optical disk 5 is fixed to the turntable 52 on the user data recording surface side by a method not shown, and is rotated by a motor 54 at a predetermined speed. Recording of the medium identification information is performed by irradiating a laser beam from the optical pickup 51 to the reflective layer side of the optical disc 5. Then, the optical pickup 51 is moved by feed means (not shown), the recording portion is expanded in the radial direction, and the BCA is completed. Further, the information recording apparatus of the present invention is provided with the centering mechanism 53 for correcting the center position on the inner peripheral portion opposite to the medium identification information recording laser beam incident side. When the optical pickup 51 is used, centering can be performed on the side opposite to the surface on which the optical pickup is performed, and information excellent in mass productivity, such as fixing the optical disk 5 to the turntable 52 using air adsorption, is provided. A recording apparatus can be realized. Further, the information recording apparatus of the present invention has a focus control means 55 and has a structure in which the defocus amount can be freely set up to ± 10 times or more of the focal depth, and the power density of the recording laser spot is adjusted. Since the deformation of the recording layer and the substrate due to a rapid heat change during recording can be suppressed, good and stable medium identification information recording can be performed.

  The above embodiment shows an embodiment of the present invention and does not limit the present invention. Various modifications can be made without departing from the scope of the present invention.

  The information recording method according to the present invention can easily and stably record medium identification information, and thus is useful as BCA recording on an optical disc. It can also be used for applications such as optical tapes and optical cards.

Sectional drawing of the information recording layer single layer type optical disk used for the information recording method in embodiment of this invention. 1 is a cross-sectional view of an information recording layer double-layer optical disc used in an information recording method according to an embodiment of the present invention. 1 is a cross-sectional view of an information recording layer four-layer optical disc used in an information recording method according to an embodiment of the present invention. Sectional drawing of the coating-type optical disk used for the information recording method in embodiment of this invention. The figure which shows an example of the information recording method in embodiment of this invention. (A) It is explanatory drawing of the recording mechanism in embodiment of this invention, (b) is explanatory drawing of a prior art. Explanatory drawing of the defocus recording in embodiment of this invention. The characteristic view which shows the effect of the defocus amount in embodiment of this invention. The figure explaining an example of the information recording method in embodiment of this invention. The figure which showed the reproduction | regeneration signal of medium identification information. Sectional drawing which showed the information recording device of this invention. The figure which showed an example of the conventional information recording method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 1b Coating type substrate 2, 2b, 2c Cover layer 2d Dummy substrate 3, 3b, 3c, 3d Intermediate layer 4 Medium identification information recording laser beam 5 Single layer type optical disc 6 Double layer type optical disc 7 Four layer type optical disc 8 Application Type optical disk 11a Front side dielectric layer 11b Recording layer 11c Back side dielectric layer 11d Reflective layer 12a Second layer near side dielectric layer 12b Second layer recording layer 12c Second layer back side dielectric layer 12d Second layer reflective layer 13a 4th layer 2nd layer front side dielectric layer 13b 4th layer 2nd layer recording layer 13c 4th layer 2nd layer back side dielectric layer 14a 4th layer 3rd layer front side dielectric layer 14b 4th layer 3rd layer recording layer 14c 4th layer 3rd layer back side dielectric layer 15a 4th layer 4th layer front side dielectric layer 15b 4th layer 4th layer recording layer 15c 4th layer 4th layer back side dielectric layer 16b coating type recording layer 16d reflective layer 21a, 21b Media identification information recording laser beam 22a, 22b Recording mark 23 Medium identification information recording laser beam 24 Reflection layer heating unit 25 Depth of focus 26a Negative defocus amount 26b Positive defocus amount 31 Condensing spot 32 Condensing spot radial length 33 Movement of optical pickup Amount (per disc rotation)
41 Unrecorded output 42 Modulation depth max
43 Degree of modulation min
51 Optical pickup for recording medium identification information 52 Turntable 53 Centering mechanism 54 Motor 55 Focus control means

Claims (15)

A disc-shaped information recording medium having an information recording layer including a recording layer and a light absorption layer is irradiated with a laser beam from a surface opposite to a surface on which user data is recorded or reproduced, thereby identifying medium identification information. An information recording method for recording,
The light absorption layer is disposed between the surface irradiated with the laser beam and the recording layer, the light absorption layer is heated by the laser beam, and the medium identification is indirectly performed on the recording layer by heat propagation. An information recording method, wherein information is recorded.   The information recording method according to claim 1, wherein there are a plurality of the information recording layers. The information recording method according to claim 1 , wherein the light absorption layer of the information recording medium functions as a reflection layer when recording or reproducing the user data. Laser beam irradiation, characterized in that it is a defocus with respect to said light absorbing layer, the information recording method according to any one of claims 1 to 3. 5. The information recording method according to claim 4 , wherein the defocusing range is 2 to 10 times the focal depth. Before type recording layer, characterized in that it consists of a phase-change recording material, information recording method according to any one of claims 1 to 5. Before type recording layer is made from a write-once phase-change recording material,
The medium identification information is recorded by changing the pre-Symbol amorphous phase of the recording layer in the crystalline phase, the information recording method according to claim 6. Before type recording layer, characterized in that it consists of an organic dye type recording material, the information recording method according to any one of claims 1 to 5. An information recording layer forming step of forming an information recording layer including a recording layer and a light absorption layer on a disk-shaped substrate;
An identification information recording step of recording medium identification information by irradiating the information recording layer with a laser beam from a surface opposite to a surface on which user data is recorded or reproduced;
A method for manufacturing an information recording medium comprising:
Further comprising a light absorption layer forming step of forming the light absorption layer between the surface irradiated with the laser beam and the recording layer;
In the identification information recording step, the light absorption layer is heated by the laser beam, and the medium identification information is recorded on the recording layer indirectly by heat propagation . The method for manufacturing an information recording medium according to claim 9 , wherein in the information recording layer forming step, a plurality of the information recording layers are formed. 10. The method of manufacturing an information recording medium according to claim 9 , wherein the light absorption layer of the information recording medium functions as a reflection layer when recording or reproducing the user data. A disc-shaped information recording medium having an information recording layer including a recording layer and a light absorbing layer is irradiated with a laser beam from a surface opposite to a surface on which user data is recorded or reproduced, thereby identifying medium identification information. An information recording apparatus having an optical pickup for recording,
The light absorbing layer is disposed between the surface irradiated with the laser beam and the recording layer, the light absorbing layer is heated by the laser beam, and the medium identification is indirectly performed on the recording layer by heat propagation. An information recording apparatus for recording information. 13. The information recording apparatus according to claim 12 , further comprising a centering mechanism for correcting a disk center position at an inner peripheral portion opposite to a light incident side from the optical pickup in the disk mounting portion. . Wherein the information recording medium, controls the focus of the relative position of the optical pickup, and further comprising a focus control means, the information recording apparatus according to claim 12 or claim 13. The information recording apparatus according to claim 14 , wherein the focus position of the focus control unit includes at least one point that is twice to ten times the depth of focus.

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