JP2001014684A - Optical disk and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the recording and reproducing by providing the embossment pit into which positional information of plural information recording layers is recorded so that one part of the embossment pit of the other layer is positioned within light beams when the light beams are focused on the embossment pit of a certain layer. SOLUTION: First and second embossments pits 3, 7 and first and second phase transition recording areas 4, 8 are respectively formed in first and second information recording layers 1, 5 respectively provided in one side surface of a first substrate and one side surface of the substrate 6 of a second information recording layer. The first and second substrates are stuck with an adhesive 9 in the state that respective information recording layers 1, 5 are faced each other. The light beams 30 focused on the first information recording layer 1 are provided with a spot diameter 33 at the focusing position on the first information recording layer 1 and are provided with the spot diameter 34 on the second information recording layer 5. The first and second embossments pits 3, 7 are arranged so as to exist within the range of the same optical beams 30 even when respective layers are provided with different spot diameters 33, 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a recordable and reproducible optical disk having a plurality of information recording layers.

[0002]

2. Description of the Related Art In recent years, with the advancement of information as represented by the rise and fall of multimedia technology, the demand for a recording / reproducing apparatus which records a large amount of information such as digital moving pictures and which can be randomly accessed has increased. I am doing it.

[0003] In response to such market demand, DVD-RAM has become a unified standard for optical disks having the characteristics of random access, large capacity and removable.
(Digital Versatile Disc for Random Access Memor
y) The standard has been established, commercialized under this unified standard, and distributed on the market.

[0004] However, there has been an increasing demand for further increasing the capacity of optical discs, for example, in fields dealing with vast amounts of information such as image databases.

In order to satisfy such an insatiable demand,
DVD-ROM (Digital Versatile Disc for Read On)
It has been reported by academic societies and the like that it is possible to increase the disk capacity almost twice by using a two-layer technology, which is one of the techniques used for increasing the capacity of a ly memory disk.

However, in order to realize a single-sided dual-layer RAM type optical disk as a system, a single-sided dual-layer RO is required.
There is a problem to be cleared by the element that did not cause a problem in M.

[0007] In the ROM type optical disk, all the information described on the optical disk is recorded only by the shape information of the information recording surface, that is, minute unevenness. In other words, information is recorded in a uniform manner in the information reproduction area of the optical disc.

However, in the case of a RAM type optical disk, even when all user information is not recorded on the disk, the header information indicating the position information of the track to which the beam of the reproduction light is currently irradiated and the linear velocity are kept constant. Information necessary for the operation of the optical disc, such as wobble signal information for the optical disc, is recorded. Since such information is treated not as erasable information but as non-erasable information, for example, in the case of a DVD-RAM disc, it is formed in advance as embossed pits or groove wobbles such as irregularities of a DVD-ROM disc. I have. This indicates that information recorded by a plurality of methods such as phase change recording marks, emboss pits, and groove wobbles are mixed in the recording / reproducing area of one optical disk.

FIG. 3 shows a state of a signal reproduced from the above-mentioned RAM type optical disk. FIG.
FIG. 3A shows a low-to-high medium in which a recording mark has a higher reflectivity than a space portion.
(B) shows a high-to-low (High to Low) medium in which the recording mark maintains a lower reflectance than the space portion. As shown in the figure, the intensity of the reflected light 12 from the header area due to the embossed pit is larger than the intensity of the reflected light 13 from the phase change recording area (that is, the land / groove area).

In a conventional optical disk having a multilayer information recording layer, when an optical disk is completed by laminating a plurality of layers, the lamination is performed without any particular restriction. Therefore, as shown in FIG. The embossed pits 3 of the phase change recording area 4 of the first information recording layer and the phase change recording area 8 of the second information recording layer which face each other
And 4 were stuck together in an arbitrary positional relationship.

In a single-sided, double-layer optical disc which records and reproduces information from one side of a single optical disc manufactured by bonding two substrates having such characteristics, the information recording on the near side as viewed from the light incident surface. The layer transmits light when recording / reproducing information on the information recording layer on the back side. However, as in the case of the reflectance, the transmittance also changes in the information recording / reproducing area by the phase change recording mark of the information recording layer to be dropped and the header area by the emboss pit. That is, with reference to FIG. 11, when reading the information of the first phase change recording area 4 located immediately below the emboss pit 7, the read signal reflected from the emboss pit 7 in the same light beam is read. You will be affected.

[0012]

That is, when information is recorded / reproduced on one information recording layer, an area irradiating the other information recording layer has an information recording / reproducing area using a phase change recording mark and an emboss pit. The following problems occur when the information reproducing areas are mixed.

(1) When information is recorded on the information recording layer on the back side as viewed from the light incident surface, the amount of light reaching the information recording layer on the back side changes, so that the stability of information recording is impaired. (2) When reproducing information from the information recording layer on the back side when viewed from the light incident surface, the amount of crosstalk to be superimposed changes with the layer on the near side, so that the stability of information reproduction is impaired. (3) When reproducing information from the information recording layer on the near side as viewed from the light incident surface, the amount of crosstalk superimposed by light reflected on the information recording layer on the back side changes, so that information reproduction stability. Is impaired.

The present invention relates to a single-sided multilayer optical disc,
An object of the present invention is to provide an optical disk and a method for manufacturing the same, which can stabilize the amount of crosstalk from an information recording layer in which recording and reproduction are not currently performed and can ensure stable recording and reproduction.

[0015]

In order to achieve the above object, an optical disc according to the basic structure of the present invention has a plurality of information recording layers, and information can be recorded independently on the plurality of information recording layers. In the one capable of storing and reproducing information from one surface, embossed pits provided for pre-recording at least control information relating to position information in each of the plurality of information recording layers are provided in one layer. When the light beam is focused on the embossed pit, at least a part of the embossed pit of another layer is provided in such a positional relationship as to be located in the light beam.

In the above-described basic configuration, at least one header area of each layer provided by emboss pits in the plurality of information recording layers and formed by being arranged in the radial direction of a track in the same zone is provided in the light spot. A part may be provided so as to be included.

In the above configuration, when the number of information recorded is N and the incident light for recording / reproduction is condensed on the n-th information recording layer from the light incident surface with a beam diameter _Bn , the distance from the light incident surface is m. The beam diameter of the incident light on the
_{m, n} , the length of the header area in the radial direction of the optical disk is R,
Assuming that the length of the header area in the optical disk rotation direction is L, the upper limit D in the radial direction of the optical disk between the header area of the mth layer from the light incident surface and the header area of the nth layer from the light incident surface. _{rad. m, n} and the proximity distance upper limit D _{tan. m and n} are _expressed by the following equations (1) and (2).

(Equation 2) May be configured as represented by

In the above configuration, at least a part of the header area of the plurality of information recording layers may be overlapped.

Further, the plurality of information recording layers are formed by bonding a first information recording layer and a second information recording layer, and the first information recording layer and the second information recording layer are bonded to each other. When attaching the recording layers, a positioning unit for adjusting the positions of the two information recording layers may be provided.

Further, in the above configuration, when the first information recording layer and the second information recording layer are bonded to each other, a positioning portion of the two information recording layers may be formed by a printed material or unevenness.

In the method of manufacturing an optical disk according to the basic structure of the present invention, a step of applying a resist film on a surface of a glass substrate to form a pattern including embossed pits and grooves; Forming a stamper, forming a predetermined pattern on the resin transparent substrate using the stamper, forming a multilayer recording film on a pattern forming surface of the resin transparent substrate on which the pattern is formed, and forming a first recording film. Forming a first substrate having an information recording layer, and forming a second recording medium having a second information recording layer by forming a multilayer recording film in reverse on the pattern forming surface of the separate resin transparent substrate having the pattern formed thereon Forming a first substrate and a light beam at an embossed pit of the first substrate for recording positional information and the like at predetermined positions of the first and second substrates. Forming respective alignment portions serving as markers of a positional relationship such that at least a part of the embossed pits of the second substrate is located in the light beam when in focus; Two substrates are opposed to each other so as to abut the first and second information recording layers, and the first and second substrates are bonded to each other by aligning the alignment portions. And

In view of the above-mentioned problems, the present inventors have made extensive studies and developments day and night, and as a result, the two recording layers have been manufactured by manufacturing a single disc satisfying a specific arrangement condition. They have found that it is possible to construct a single-sided, dual-layer optical disk system while keeping the amount of crosstalk constant. Therefore, by applying the optical disk according to the above basic configuration and the method of manufacturing the same, the amount of interlayer crosstalk of the single-side read multilayer optical disk as a product can be made constant, and stable reading can be ensured.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an optical disk and a method for manufacturing the same according to the present invention will be described below in detail with reference to the accompanying drawings. An optical disc according to the first embodiment of the present invention will be described with reference to FIGS. FIG.
Shows the basic configuration of the optical disc according to the first embodiment.

In FIG. 1, a first information recording layer 1 is provided on one surface of a first substrate 2, and the first information recording layer 1 has first embossed pits 3. A first phase change recording area 4 is formed. A second information recording layer 5 is provided on one surface of the second substrate 6, and the second information recording layer 6 has a second embossed pit 7 and a second phase change A recording area 8 is formed.

Reference numeral 30 denotes a light beam when the first information recording layer 1 is focused, and the spot diameter 33 at the focus position of the first information recording layer 1 is the second information recording layer. 6
Has a correspondence as shown in FIG. In the optical disk according to the present invention, even if the first embossed pits 3 and the second embossed pits 7 have the same relationship as the spot diameters 33 and 34 in each layer as described above, the same light beam 30 is used. It is characterized by being included in the range of.

FIG. 2 shows an optical disc which records and reproduces information on two information recording layers from one side of the optical disc. In FIG. 2, a first information recording layer 1 is formed on one surface of a first substrate 2 and has embossed pits 3 and a phase change recording area 4 in a predetermined area. The second information recording layer 5 is formed on one surface of the second substrate 6 and has embossed pits 7 and phase change recording areas 8 in predetermined areas. The first substrate 2 and the second substrate 6 are adhered by an adhesive 9 in a state where the information recording layers 1 and 5 are opposed to each other.

The header information used for operating the optical disk system is arranged, for example, in a DVD-RAM in the optical disk radial direction r in each zone as shown in FIG. In FIG. 4, reference numeral 14 denotes a recording / reproducing area by a phase change mark, and reference numeral 15 denotes a header area by emboss pits 3 or 7. In the single-side read dual-layer optical disc of the present invention shown in FIG. 2, at least a part of the header portion previously recorded by the emboss pits overlaps the first information recording layer and the second information recording layer. The specific state of the overlap is, as described above, when the light beam focused on one layer includes the embossed pits 3 or 7 of that layer and the diffused light beam of the other layer Include at least a portion of the embossed pit 7 or 3 of another layer.

With such an arrangement, when viewed from the light beam, the header area 3 of the first information recording layer 1 and the header area 7 of the second information recording layer 5 exist almost simultaneously in the light beam. You are doing. This specific effect is
(1) When recording on the second information recording layer (when the light beam scans the information recording area of the second information recording layer with the phase change mark), the first information recording through which the light beam passes Since most of the layer is an information recording area, the intensity of transmitted light that passes through the first information recording layer and reaches the second information recording layer is constant over a wide range, and the light is transmitted to the second information recording layer. (2) When reproducing the information recording layer of each layer,
Crosstalk from another layer when reproducing the header area is mainly crosstalk from the header area of another layer, and crosstalk from another layer when reproducing the information recording area by the phase change recording mark. The talk is mainly the crosstalk of the information recording area by the phase change recording mark of another layer, and the crosstalk amount is constant over a wide range.

Next, a method for manufacturing an optical disk according to the second embodiment of the present invention will be described. As described above, the method for manufacturing an optical disc according to the second embodiment includes the steps of applying a resist film on the surface of a glass substrate to form a pattern including embossed pits and grooves, and forming the glass substrate on which the pattern is formed. Forming a stamper, forming a predetermined pattern on the resin transparent substrate using the stamper, and forming a recording film composed of a plurality of layers on a pattern forming surface of the resin transparent substrate on which the pattern is formed. Forming a first substrate having a first information recording layer by applying a multi-layer recording film on the pattern forming surface of a separate resin transparent substrate having the pattern formed thereon, in a layer opposite to the first information recording layer. Forming a second substrate having a second information recording layer, and recording position information and the like at predetermined positions of the first and second substrates. When the light beam is focused on the emboss pit of the first substrate, at least a part of the emboss pit of the second substrate is formed as an alignment mark serving as a mark of a positional relationship such that the emboss pit is located in the light beam. And the step of causing the first substrate and the second substrate to face each other so that the first and second information recording layers abut each other. Laminating.

FIG. 5 shows an example of a method for manufacturing an optical disk according to the second embodiment. As shown in FIG. 5A, the optical disk of each layer is coated with a resist film 16 on an original plate 17 and recorded thereon to form a resist film 18 having a groove shape, as shown in FIG. 5B. So, the glass original plate 1
7, a stamper mold 19 is created. Resin molding is performed using the stamper mold 19 to produce a resin molded substrate 20 as shown in FIG.

Next, as shown in FIG. 5D, a recording film 21 composed of a plurality of layers is applied on the resin molded substrate by using a sputtering device or the like. In the manufacture of a normal single-sided readout single-layer optical disc, a protective film is applied thereafter to complete it. In the case of a single-sided double-layer optical disc, reverse stacking phase change recording in which the order of the layers to be applied such as a recording film is reversed. A substrate having the film 22 is prepared. Next, a medium in which recording films are stacked in a normal order is arranged on the light incident surface side, a medium in which a reversely stacked recording film is stacked is arranged on the other side, and two substrates are bonded together. Completed by

At the time of this bonding, it is necessary to align the header area within an appropriate range along the optical disk radial direction γ and the rotation direction θ. The optical disc according to the second embodiment has a symbol as the positioning unit 28 as shown in FIG. For example, in the optical disc of this embodiment,
In order not to impair the capacity of the optical disc, a mark serving as a mark is put in an area which is not usually used for system operation of the optical disc at the innermost circumference of the optical disc. Here, DVD-
Taking a RAM as an example, a place where symbols or structures for alignment are arranged will be described. DVD-RAM
The disc is a disc with a diameter of 120 ± [mm]

(Equation 3) The circular hole is penetrating. As a region for clamping, a diameter of 22 [mm] Max to a diameter of 33.0 mmMi is used.
n regions are used. Part of the information for system operation is the diameter on the optical disc.

(Equation 4) From diameter

(Equation 5) 115.2 m in diameter as a lead-in area between
m] to diameter

(Equation 6) Are recorded as embossed pits and phase change recording marks in a secured area. Excluding the shape and the portion used as the information recording area of the optical disk as described above, the diameter is 33.0 Mi.
Diameter from n [mm]

(Equation 7) Is an area not used in the current optical disk system. The symbol for alignment in this area is B
It is possible to record using a high-power laser in the same manner as recording information in a CA (Burst Cutting Area). A procedure for bonding two optical disks each having a multilayer recording film applied on a resin molded substrate independently will be described. An appropriate amount of an adhesive such as an ultraviolet curable resin is applied to one side of the two disks to be bonded. The appropriate amount means that the distance between the two information recording layers is a predetermined distance, such as 4
This is the amount of the adhesive that can be bonded so as to be about 0 μm. The other substrate is moved closer to the substrate on which the adhesive is applied, and the alignment marks of the first information recording layer and the alignment marks of the second information recording layer are overlapped as shown in FIG. The two substrates are bonded together while observing with an optical sensor or the like.

Next, the processing accuracy required for bonding will be described. Consider for example, an interlayer distance of two information recording layers are considered a two-layer optical disc d, the beam spot diameter W ₁ of the other information recording layer when the focal point in the beam spot size W ₀ in one of the information recording layer . Assuming that the wavelength of the light source is λ and the refractive index of the medium is n, W ₁ is expressed as follows.

[0034]

(Equation 8) A crosstalk signal from another information recording layer can be considered as an average of signals included in a beam spot on another information recording layer. Therefore, in order to improve the above-described problem from the header area due to the embossed pits of the other information recording layers, the header areas do not need to completely overlap, and at least a part of the header area is not included in the beam spot in the other information recording layer. It would be good if it was hanging. If the header area of each information recording layer is closer than the relationship between the position and length of the header area and the beam spot diameter in each information recording layer shown in FIG. 1, a part of the header area overlaps on the optical path of the light beam. Will be. That is, in the optical system where the beam spot diameter becomes B ₀ at the focal position by using a light source having a wavelength of lambda, the interlayer distance d between two information recording layers, in the tangential direction of the header region shown in FIG. 8 length 35 Considering the recording and reproduction of an optical disk having a length of 35 in the radial direction of the header area,
The tangential component D _{tan of the} allowable shift amount of the header position and the radial component D _rad are

(Equation 9) It is expressed as B _d in the equation is a beam spot diameter at a distance d from the focal position. For example, DVD-RA
Each value of M (ver.1.0) λ = 650 × 10 ⁻⁹ [m] (6) B ₀ = 930 × 10 ⁻⁹ [m] (7) d = 40 × 10 ⁻⁶ [m] (8) L = 419 × 10 ⁻⁶ [m] (9) R = 1.4 × 10 ⁻³ [m] (10) Here, in the DVD-RAM, since the header areas are aligned in the radial direction in the zone, R can be regarded as the length of one zone in the radial direction, and thus the optical disc obtained from the equations (4) and (5) Is the maximum allowable deviation amount between the radial direction and the rotational direction of D _tan = 444 × 10 ⁻⁶ [m] (11) D _rad = 1.42 × 10 ⁻³ [m] (12)

Here, in the current DVD-RAM standard, since the upper limit of the amount of eccentricity is 50 μm _pp , there is no problem regarding D _rad even when two substrates are bonded. On the other hand, regarding D _tan , in addition to the method described in the present embodiment, a mark for positioning is provided on the outer peripheral portion of the optical disk, a mark for positioning is recorded at the time of recording the master, The improvement can be achieved by a method of aligning the header position by regarding the area itself as a mark for alignment. Furthermore, it is needless to say that the smaller the amount of deviation is, the more the header area is overlapped by the embossed pits of the two information recording layers.

FIG. 9 shows an optical disk according to the third embodiment. The optical disc according to the third embodiment has the same configuration as the optical disc according to the first embodiment, but differs from the optical disc according to the second embodiment in which an alignment symbol is used for alignment, as an alignment unit for alignment. An uneven structure is used. In the second embodiment, symbols having exactly the same shape are used. However, in the optical disc of the third embodiment, the first information recording layer 3 is used.
8 and a convex portion 40 provided to the second information recording layer 39 are different from each other, and both have a shape and size that can be fitted.

More specifically, a pair of concave / convex structures 40 and 41 for alignment, which are located at the same position on the substrate of the first information recording layer 38 and the second information recording layer 39, are: First information recording layer 38 and second information recording layer 3
In FIG. 9, the relationship between the unevenness is reversed. For this reason, when the position of the header area existing in the recording area is previously adjusted in the first and second information recording layers, the unevenness of the alignment is matched. At the time of bonding, a predetermined amount of an adhesive such as an ultraviolet curable resin is applied to the surface of one of the substrates to be bonded, and the positions of the two substrates are adjusted so that the uneven structure for alignment is fitted. Match. When the alignment is confirmed, ultraviolet rays are irradiated to cure the ultraviolet curable resin, and one optical disc is completed.

The optical disks according to the first to third embodiments described above are applied to an optical disk device having a configuration as shown in FIG. 10, and the recording operation of the optical disk device will be described with reference to FIG. The following describes the reproduction operation.

At the time of recording, a recording data sequence, which is data to be recorded, is processed by a recording data processing unit 123, and then input to an LD driver 124, where the LD driver 12
4 modulates the intensity of the laser diode 125. The light beam thus intensity-modulated is irradiated onto the optical disc 100 through the collimator lens, the beam splitter 128 and the objective lens 120, so that data is recorded on the recording film of the optical disc 100 as a recording mark, for example, from crystalline to amorphous or It is recorded as a phase change mark from amorphous to crystalline.

Here, at the time of recording, the reflected light from the optical disc 100 is reflected by the objective lens 120 and the beam splitter 128.
Then, the light enters the photodetector 126 via the condenser lens 141, and the output of the photodetector 126 is input to the analog operation circuit 133, and a signal corresponding to the emboss pit 16 on the optical disc 100 (hereinafter, emboss pit) A wobble signal whose amplitude changes according to the wobble pattern of the land track and the groove track on the optical disc 100 is generated.

A timing extracting circuit (not shown) generates position information of a sector or an ECC block indicated by the emboss pit according to the emboss pit signal, and further generates a speed control signal according to the wobble signal. The speed control signal is input to the servo circuit 132, and based on the speed control signal, the servo circuit 132
The spindle motor 121 is controlled via the motor 22 to a predetermined rotational speed.

At the time of recording, a focus error signal and a tracking error signal are further generated by the analog arithmetic circuit 133, and the lens actuator 127 is generated by the servo circuit 132 based on these signals.
Is controlled, focus servo and tracking servo are performed.

At the time of reproduction, a light beam having a constant intensity emitted from the laser diode 125 is applied to the collimator lens 14.
0, the light is irradiated onto the optical disc 100 through the beam splitter 128 and the objective lens 120,
Reflected light from the objective lens 120 and the beam splitter 1
28 and the light detector 126 via the condenser lens 141.
Incident on. The output of the photodetector 126 is input to an analog operation circuit 133, and a change in reflectance depending on the presence or absence of a recording mark on the recording film is output as a reproduction signal.

During the reproduction, the analog arithmetic circuit 133 generates a wobble signal, a focus error signal, and a tracking error signal on the optical disk 100, and a timing control circuit (not shown) generates a speed control signal in accordance with the wobble signal. The motor driver 12 is driven by the servo circuit 132 based on the speed control signal.
2, the spindle motor 121 is controlled to a predetermined rotation speed. Further, by controlling the lens actuator 127 by the servo circuit 132 based on the focus error signal and the tracking error signal,
Focus servo and tracking servo are performed.

The reproduction signal corresponding to the recording mark output from the analog operation circuit 133 is converted into binary data by the binarization circuit 129, and then converted to binary data.
Is input to In the reproduction data processing unit 130, the recording data processing circuit 1
23, and outputs a reproduced data sequence by performing a process substantially opposite to that of the sequence 23. Reference numeral 131 denotes a memory for storing position information of the land and other rack partial areas required for the switching control.
Reference numeral 134 denotes a controller. Records like the above
Recording / reproducing with respect to the optical disc 100 is performed by the reproducing operation.

In the first to third embodiments described above, the case where an ultraviolet curable resin is used as a method for bonding two substrates has been described.
For example, the method of bonding two substrates with an adhesive sheet or the like does not impair the essence of the present invention,
Implementation of the present invention is possible. Also, the case where two substrates are bonded as the number of substrates has been described as an example, but the number of substrates to be laminated is not limited to two as long as the number of substrates is plural, and the present invention can be implemented with three or four substrates. However, the limit of the number of stacked layers is naturally limited due to the relationship of the light beam transmission ability.

[0047]

As is apparent from the above description, the optical disk of the present invention is provided with two or more information recording layers capable of recording and reproducing information by irradiating light from one side of the optical disk. It is possible to provide an optical disk system that can record and reproduce information stably on an optical disk.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a sectional configuration of an optical disc according to a first embodiment.

FIG. 2 is a partially cutaway perspective view showing the configuration of the optical disc of the first embodiment.

FIG. 3 is an output waveform diagram showing (a) a relationship between a reproduction signal of a recording mark of an H to L medium and an emboss pit reproduction signal, and (b) a relationship between a signal of a recording mark of an L to H medium and an emboss pit reproduction signal. .

FIG. 4 is a plan view showing embossed pits arranged in a group portion and a group division portion of the optical disc.

FIG. 5 is a sectional view showing an example of steps (a) to (e) of the method for manufacturing an optical disc according to the second embodiment.

FIG. 6 is an exemplary plan view showing positioning symbols arranged on an optical disc according to a second embodiment;

FIG. 7 is a plan view showing a state of alignment of a two-layer optical disc according to a second embodiment.

FIG. 8 is a sectional view showing the relationship between the length of the header area of the two-layer optical disc of the second embodiment and the beam spot diameter in each information recording layer.

FIG. 9 is an exemplary perspective view showing a positioning unit of an optical disc according to a third embodiment;

FIG. 10 is a block diagram for explaining an outline of a recording operation of an optical disk device to which the optical disk of the present invention is applied.

FIG. 11 is a sectional view showing a configuration of a conventional optical disc.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 1st information recording layer 2 1st information recording layer substrate 3 1st information recording layer embossed pit 4 Phase change recording area of 1st information recording layer 5 2nd information recording layer 6 2nd information Recording layer substrate 7 Emboss pits of second information recording layer 8 Phase change recording area of second information recording layer 9 Adhesive bonding first information recording layer and second information recording layer 10 First Light incident direction when information is recorded / reproduced on / from the information recording layer 11 Light incident direction when information is recorded / reproduced on / from the second information recording layer 12 Reflection from the header area due to embossed pits Light 13 Reflected light from phase change recording area 14 Recording / reproducing area by phase change mark 15 Header area by embossed pit 16 Resist film 17 Glass master 18 Resist film with group shape 19 Stamper mold 2 Resin molded substrate 21 Phase change recording film 22 Phase change recording film (reverse stacking) 23 Center hole 24 Clamp area 25 Lead-in area 26 User data area 27 Lead-out area 28 Alignment symbol 29 Alignment symbol for first information recording layer 30 alignment symbol of second information recording layer 31 area where alignment symbol of first information recording layer overlaps alignment symbol of second information recording layer 32 alignment symbol of first information recording layer The state in which the alignment marks of the second information recording layer are overlapped 33 The beam spot diameter BS _{o at the} focal position The beam spot diameter BS _d at the position separated by the gap d between the two information recording layers from the focal position Embossed tangential direction length _L tan 36 zone boundary 37 zone width _R z 38 first information header area by the pit Substrate 40 alignment protrusion structure 41 align recessed structures of the substrate 39 the second information recording layer of the recording layer

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yutaka Okamoto 1 Komukai Toshiba-cho, Kochi-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba R & D Center (72) Inventor Kazuo Watanabe Small, Kochi-ku, Kawasaki-shi, Kanagawa Mukotoshiba 1 F-term in Toshiba R & D Center (reference) CC12 CD08 5D121 AA01 AA02 BB02

Claims (6)

[Claims] 1. An optical disc having a plurality of information recording layers, capable of recording information independently of the plurality of information recording layers and capable of storing and reproducing information from one side, Emboss pits provided for pre-recording at least control information on position information in each layer of the information recording layer are at least one of the emboss pits of another layer when the light spot is focused on the emboss pit of one layer. An optical disc characterized in that a part of the optical disc is provided in such a positional relationship as to be located in the light spot. 2. When the number of recorded information is N and the incident light for recording and reproduction is focused on the n-th information recording layer from the light incident surface with a beam diameter _Bn , the m-th information recording from the light incident surface is performed. When the beam diameter of the incident light in the layer is B _{m, n} , the length of the header area in the radial direction of the optical disk is R, and the length of the header area in the rotational direction of the optical disk is L, the m-th layer from the light incident surface. Of the optical disk in the radial direction of the optical disk in the radial direction between the header region of the optical disk and the header region of the nth layer from the light incident surface _{. m, n} and the proximity distance upper limit D _tan. The optical disk according to claim 2 _{, wherein m and n} are represented by the following equations (1) and (2). (Equation 1) 3. The information recording layer of a plurality of layers is formed by bonding a first information recording layer and a second information recording layer, and the first information recording layer and the second information recording layer are bonded to each other. 3. The optical disc according to claim 1, further comprising a positioning unit for positioning the two information recording layers when the recording layers are bonded. 4. The optical disc according to claim 3, wherein when the first information recording layer and the second information recording layer are bonded to each other, the alignment portion between the two information recording layers is a printed material. 5. The optical disc according to claim 3, wherein a positioning portion of the two information recording layers is uneven when the first information recording layer and the second information recording layer are bonded. 6. A step of applying a resist film on a surface of a glass substrate to form a pattern including embossed pits and grooves, a step of forming a stamper from the glass substrate on which the pattern is formed, and using the stamper. Forming a predetermined pattern on a transparent resin substrate; forming a first information recording layer by forming a recording film composed of a plurality of layers on a pattern forming surface of the transparent resin substrate on which the pattern is formed; Forming a second information recording layer in which a recording film composed of a plurality of layers is formed on a pattern forming surface of the separate resin transparent substrate on which the pattern is formed, in a layer opposite to the first information recording layer The second with
Forming a substrate of the second substrate when a light beam is focused on the embossed pits of the first substrate for recording position information and the like at predetermined positions of the first and second substrates. Forming respective alignment portions serving as markers of a positional relationship such that at least a part of the emboss pit is located in the light beam; and forming the first substrate and the second substrate into the first and second substrates. A method of manufacturing an optical disc, comprising: opposing the information recording layers so as to abut each other, and attaching the first and second substrates so that the alignment portions are aligned.